Temperature effect on shear behavior of ore-backfill couplingspecimens at various shear directions

JIANG Fei-fei(江飞飞)1 2 ZHOU Hui(周辉)1 2 SHENG Jia(盛佳)3 4

LI Xiang-dong(李向东)3 KOU Yong-yuan(寇永渊)5

1 State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock andSoil Mechanics Chinese Academy of Sciences Wuhan 430071 China2 University of Chinese Academy of Sciences Beijing 100049 China

3 National Engineering Research Center for Metal Mining Changsha Institute of Mining Research Co LtdChangsha 410012 China

4 School of Resource amp Environment and Safety Engineering Hunan University of Science and TechnologyXiangtan 411201 China

5 Jinchuan Group Co Ltd Jinchang 737104 China

copy Central South University Press and Springer-Verlag GmbH Germany part of Springer Nature 2021

Abstract Understanding the temperature effect on shear behavior of the ore-backfill coupling structure is critical for thesafety and stability of backfill stope under the condition of high horizontal stress in deep mining Direct shear tests werecarried out on the cemented rod-mill sand backfill (CRB) and ore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 degC) The shear behavior and AE characteristic parameters of OCRB at different sheardirections were compared and analyzed The results show that the temperature effect on the shear performance of CRBmainly depends on the characteristics of microstructures and main mineral phases the performance of CRB at 40 degC isrelatively good the shear deformation of OCRB has one more ldquopeak fluctuation stagerdquo than CRB and has a goodcorrelation with AE characteristic parameters The temperature can positively or negatively impact the shear strength ofOCRB depending on the temperature and shear direction the shear performance of OCRB along the axis direction (D1)is significantly better than that perpendicular to the axis direction (D2) The co-bearing capacity of the ore-backfillcoupling structure (ie stopes) is closely related to the ambient temperature and principal stress orientation

Key words cemented backfill ore-backfill temperature shear direction shear strength AE energy

Cite this article as JIANG Fei-fei ZHOU Hui SHENG Jia LI Xiang-dong KOU Yong-yuan Temperature effect onshear behavior of ore-backfill coupling specimens at various shear directions [J] Journal of Central South University2021 28(10) 3173minus3189 DOI httpsdoiorg101007s11771-021-4841-4

1 Introduction

The backfill mining method has been widely

applied in underground mines due to its advantagesin surface subsidence control mined-out voidstreatment high recovery ratio solid waste disposaland environmental protection [1minus 3] Cemented

DOI httpsdoiorg101007s11771-021-4841-4

Foundation item Project(KFJ-STS-QYZD-174) supported by the Science and Technology Service Network Initiative of the ChineseAcademy of Sciences Projects(41941018 42077251) supported by the National Natural Science Foundation of ChinaProject(P2018G045) supported by the Science amp Technology Research and Development Program of China RailwayProject(2018CFA013) supported by the Hubei Provincial Natural Science Foundation Innovation Group China

Received date 2020-04-17 Accepted date 2021-01-12Corresponding author JIANG Fei-fei PhD Research Assistant Tel +86-17607189836 E-mail ffjiangwhrsmaccn ORCID https

orcidorg0000-0002-3453-2510

J Cent South Univ (2021) 28 3173－3189

J Cent South Univ (2021) 28 3173－3189

backfill is a homogeneous mixture of aggregatebinder and water and its physico-mechanicalproperties have always been one of the criticalresearch contents of many scholars [4minus7]

For the deep backfill mines under the conditionof high horizontal stress the backfill andsurrounding rock will bond to form a couplingco-bearing structure after the filling slurry istransported to the stopes The ambient temperatureand principal stress orientation of deep mining oftendirectly affect the physico-mechanical properties ofbackfill and rock-backfill coupling structure thus toaffect the safety and stability of backfill stopes Atpresent many studies have been carried out toinvestigate the influence of temperature onmechanical properties of backfill and somevaluable results have been obtained Previousstudies have revealed that the temperature cansignificantly affect the process and rate of cementhydration of backfill as well as the pore structuresinside the backfill thus affecting the strengthdevelopment of backfill [8 minus 10] ALDHAFEERIet al [11] confirmed that the reactivity of cementedpaste backfill (CPB) is temperature-dependent bylaboratory tests and the numerical model proposedby NASIR et al [12] also proved that the strengthdevelopment of CPB is closely related to thetemperature and the degree of hydration Laboratorytests have been performed by FALL et al [13 14] toexplore the mechanical properties of cementedtailings backfill (CTB) at various temperatures WUet al [15] simulated the influence of temperature onthe hydraulic behavior of CTB based on COMSOLmultiphysics Although the temperature has asignificant influence on the mechanical performanceof backfill the existing researches have proved thatthe effect of temperature on the mechanicalbehaviors of rock can be ignored within acertain range of temperature (generally below 100 degC)[16 17] Due to the different sensitivity of rock andbackfill to temperature the mechanical behaviors ofrock and backfill are different at varioustemperatures thus affecting the overall mechanicalresponse of rock-backfill coupling structureTherefore it is of great significance to conductrelevant experimental studies for understanding themechanical properties of rock-backfill couplingstructure under the deep high-temperature

environmentThis experimental study takes the deep backfill

mining of Jinchuan No 2 mine as the researchbackground and the current mining depth hasreached more than 800 m [18 19] With the increaseof mining depth the mine is facing the unfavorableconditions of continuously increasing temperatureand high horizontal stress According to thestatistics the average geothermal gradient of themining area is 284 deg C100 m which is located inthe Hexi Corridor of Gansu province in NorthwestChina [20] It can be predicted that the deep rockand backfill in the mine will be inevitably exposedto the ambient temperatures of 20minus60 degC in the nextfew decades Furthermore the maximum principalstress is the horizontal tectonic stress which is closeto 50 MPa at the levels of 1000 and 850 and theratio of the horizontal stress to vertical stress can beup to 2 The interval stoping technology is adoptedand the backfill of the primary stope and theorebody of the secondary stope are interlaced Theaxial direction of designed backfill stopes is mostlyparallel or perpendicular to the orientation ofmaximum horizontal principal stress due to the needfor stoping cycles Therefore high horizontal stresswill exert transverse shear stress on the backfillstope and it is necessary to conduct shear tests atvarious temperatures and shear directions Howeverthere is a lack of understanding the temperatureeffect on the shear behavior of the rock-backfillcoupling structure in the deep backfill miningconditions and the relevant research findings arescarce as far as we know Besides there is no reporton the influence of shear direction on the shearbehavior of the rock-backfill coupling structure

In this paper direct shear tests were carried outon the cemented rod-mill sand backfill (CRB) andore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 ordmC) A PAC-DISPsystem was used to record the acoustic emission(AE) signals during the whole shearing processBased on the shear test results of CRB at varioustemperatures the temperature effect on the shearbehavior and AE characteristic parameters of OCRBat three different shear directions were comparedand analyzed Two aspects of novelty arehighlighted in this paper 1) The revelation of thetemperature effect on shear behaviors of backfill

3174

J Cent South Univ (2021) 28 3173－3189

and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes

2 Experimental set-up

21 MaterialsThe rod-mill sand (RMS) was used in this

study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was

used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278

22 Specimen preparationTwo types of cube specimens CRB and OCRB

coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box

A total of 45 specimens including 36 CRB

Table 1 Physical properties of RMS

Parameter

Particle density(g∙cmminus3)

Porosity

D10mm

D30mm

D50mm

D60mm

D90mm

Cu

Cc

RMS

267

4064

0124

0560

1434

2136

2771

17226

1184

Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2

30(D10timesD60)

Table 2 Main chemical compositions of RMS and JPC(wt)

Sample

RMS

JPC

SiO2

7147

25

Al2O3

105

758

CaO

441

4992

Na2O

344

057

Sample

RMS

JPC

K2O

297

098

Fe2O3

28

314

MgO

202

234

SO3

113

457

Figure 1 Particle size sieving results of RMS

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J Cent South Univ (2021) 28 3173－3189

specimens and 9 OCRB specimens were prepared

using the procedures mentioned above Thereinto

the CRB specimens were continuously cured for

28 d in a constant temperature (20plusmn05) degC and

constant humidity of (95plusmn1) while the OCRB

specimens were continuously cured for 28 d in a

constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program

23 Testing programThe testing program is shown in Table 3 The

CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3

24 Testing methodsA RJST-616 shear tester (Developed by

Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the

Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail

Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions

Specimen type

CRB

OCRB

Age timed

28

28

28

28

28

28

TemperaturedegC

20

40

60

20

40

60

Normal stresskPa

200 300 400 500

200 300 400 500

200 300 400 500

500

500

500

Shear direction

mdash

mdash

mdash

D1D2D3

Parameter

PSSRSS

AE Signal

PSSAE Signal

Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane

3176

J Cent South Univ (2021) 28 3173－3189

pre-amplification was set to 40 dB and the AE

detection threshold was fixed at 45 dB and the

acquisition rate of AE signals was set to 1 MSPS

The direct shear tester and AE acquisition system

are shown in Figure 4

As a common non-destructive testing (NDT)

technology in the field of geotechnical engineering

the AE technology can be used to analyze the

cracking process of rock [23minus26] Cracking process

analysis based on AE technology involves a variety

of related characteristic parameters such as hit

event rate count frequency and energy among

which the hitevent rate and AE energy rate are

often considered as the critical parameters in

the shear failure process analysis [27minus29] The AE

energy released during the shear failure process can

Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3

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J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

3178

J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

3179

J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

3180

J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

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J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

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trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

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entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

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Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

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initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

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[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

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[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

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[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

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1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

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848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

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[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

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[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

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[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

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International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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backfill is a homogeneous mixture of aggregatebinder and water and its physico-mechanicalproperties have always been one of the criticalresearch contents of many scholars [4minus7]

For the deep backfill mines under the conditionof high horizontal stress the backfill andsurrounding rock will bond to form a couplingco-bearing structure after the filling slurry istransported to the stopes The ambient temperatureand principal stress orientation of deep mining oftendirectly affect the physico-mechanical properties ofbackfill and rock-backfill coupling structure thus toaffect the safety and stability of backfill stopes Atpresent many studies have been carried out toinvestigate the influence of temperature onmechanical properties of backfill and somevaluable results have been obtained Previousstudies have revealed that the temperature cansignificantly affect the process and rate of cementhydration of backfill as well as the pore structuresinside the backfill thus affecting the strengthdevelopment of backfill [8 minus 10] ALDHAFEERIet al [11] confirmed that the reactivity of cementedpaste backfill (CPB) is temperature-dependent bylaboratory tests and the numerical model proposedby NASIR et al [12] also proved that the strengthdevelopment of CPB is closely related to thetemperature and the degree of hydration Laboratorytests have been performed by FALL et al [13 14] toexplore the mechanical properties of cementedtailings backfill (CTB) at various temperatures WUet al [15] simulated the influence of temperature onthe hydraulic behavior of CTB based on COMSOLmultiphysics Although the temperature has asignificant influence on the mechanical performanceof backfill the existing researches have proved thatthe effect of temperature on the mechanicalbehaviors of rock can be ignored within acertain range of temperature (generally below 100 degC)[16 17] Due to the different sensitivity of rock andbackfill to temperature the mechanical behaviors ofrock and backfill are different at varioustemperatures thus affecting the overall mechanicalresponse of rock-backfill coupling structureTherefore it is of great significance to conductrelevant experimental studies for understanding themechanical properties of rock-backfill couplingstructure under the deep high-temperature

environmentThis experimental study takes the deep backfill

mining of Jinchuan No 2 mine as the researchbackground and the current mining depth hasreached more than 800 m [18 19] With the increaseof mining depth the mine is facing the unfavorableconditions of continuously increasing temperatureand high horizontal stress According to thestatistics the average geothermal gradient of themining area is 284 deg C100 m which is located inthe Hexi Corridor of Gansu province in NorthwestChina [20] It can be predicted that the deep rockand backfill in the mine will be inevitably exposedto the ambient temperatures of 20minus60 degC in the nextfew decades Furthermore the maximum principalstress is the horizontal tectonic stress which is closeto 50 MPa at the levels of 1000 and 850 and theratio of the horizontal stress to vertical stress can beup to 2 The interval stoping technology is adoptedand the backfill of the primary stope and theorebody of the secondary stope are interlaced Theaxial direction of designed backfill stopes is mostlyparallel or perpendicular to the orientation ofmaximum horizontal principal stress due to the needfor stoping cycles Therefore high horizontal stresswill exert transverse shear stress on the backfillstope and it is necessary to conduct shear tests atvarious temperatures and shear directions Howeverthere is a lack of understanding the temperatureeffect on the shear behavior of the rock-backfillcoupling structure in the deep backfill miningconditions and the relevant research findings arescarce as far as we know Besides there is no reporton the influence of shear direction on the shearbehavior of the rock-backfill coupling structure

In this paper direct shear tests were carried outon the cemented rod-mill sand backfill (CRB) andore-CRB (OCRB) coupling specimens at varioustemperatures (20 40 and 60 ordmC) A PAC-DISPsystem was used to record the acoustic emission(AE) signals during the whole shearing processBased on the shear test results of CRB at varioustemperatures the temperature effect on the shearbehavior and AE characteristic parameters of OCRBat three different shear directions were comparedand analyzed Two aspects of novelty arehighlighted in this paper 1) The revelation of thetemperature effect on shear behaviors of backfill

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and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes

2 Experimental set-up

21 MaterialsThe rod-mill sand (RMS) was used in this

study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was

used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278

22 Specimen preparationTwo types of cube specimens CRB and OCRB

coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box

A total of 45 specimens including 36 CRB

Table 1 Physical properties of RMS

Parameter

Particle density(g∙cmminus3)

Porosity

D10mm

D30mm

D50mm

D60mm

D90mm

Cu

Cc

RMS

267

4064

0124

0560

1434

2136

2771

17226

1184

Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2

30(D10timesD60)

Table 2 Main chemical compositions of RMS and JPC(wt)

Sample

RMS

JPC

SiO2

7147

25

Al2O3

105

758

CaO

441

4992

Na2O

344

057

Sample

RMS

JPC

K2O

297

098

Fe2O3

28

314

MgO

202

234

SO3

113

457

Figure 1 Particle size sieving results of RMS

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J Cent South Univ (2021) 28 3173－3189

specimens and 9 OCRB specimens were prepared

using the procedures mentioned above Thereinto

the CRB specimens were continuously cured for

28 d in a constant temperature (20plusmn05) degC and

constant humidity of (95plusmn1) while the OCRB

specimens were continuously cured for 28 d in a

constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program

23 Testing programThe testing program is shown in Table 3 The

CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3

24 Testing methodsA RJST-616 shear tester (Developed by

Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the

Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail

Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions

Specimen type

CRB

OCRB

Age timed

28

28

28

28

28

28

TemperaturedegC

20

40

60

20

40

60

Normal stresskPa

200 300 400 500

200 300 400 500

200 300 400 500

500

500

500

Shear direction

mdash

mdash

mdash

D1D2D3

Parameter

PSSRSS

AE Signal

PSSAE Signal

Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane

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J Cent South Univ (2021) 28 3173－3189

pre-amplification was set to 40 dB and the AE

detection threshold was fixed at 45 dB and the

acquisition rate of AE signals was set to 1 MSPS

The direct shear tester and AE acquisition system

are shown in Figure 4

As a common non-destructive testing (NDT)

technology in the field of geotechnical engineering

the AE technology can be used to analyze the

cracking process of rock [23minus26] Cracking process

analysis based on AE technology involves a variety

of related characteristic parameters such as hit

event rate count frequency and energy among

which the hitevent rate and AE energy rate are

often considered as the critical parameters in

the shear failure process analysis [27minus29] The AE

energy released during the shear failure process can

Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3

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J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

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J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

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J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

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J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

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J Cent South Univ (2021) 28 3173－3189

and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

and ore-backfill coupling structure under highhorizontal stress and 2) The exploration of theinfluence of shear direction on the shearperformance of ore-backfill coupling structure Thefindings presented in this paper provide some basisfor safety evaluation and design of deep backfillstopes

2 Experimental set-up

21 MaterialsThe rod-mill sand (RMS) was used in this

study derived from the sand silo of the backfillplant on the surface in Jinchuan No 2 mineAccording to the main physicochemical propertiesof test results as shown in Tables 1 2 and Figure 1the coefficient of uniformity and coefficient ofcurvature of RMS are 17226 and 1184respectively indicating that the RMS is well-gradedThe RMS contains high silica content (exceed 70)and low sulfur content which is conducive toimproving the strength of cemented backfill[21 22] The Jinchang Portland cement (JPC)produced by a local cement plant in Jinchang was

used as the hydraulic binder in the experimentalinvestigations The JPC and RMS were blended in aratio of 2080 Tap water in the laboratory was usedto mix the solid mass (total mass of dry RMS andJPC) the pH value of mixing water was 763 andthe mass ratio of water to total solid was 2278

22 Specimen preparationTwo types of cube specimens CRB and OCRB

coupling specimens with a side length of 50 mmwere involved in the experimental study Figure 2shows the specimen preparation procedures indetail 1) The ore was taken from the 1000 m levelof Jinchuan No 2 mine and the average uniaxialcompressive strength (UCS) of intact ore sampleswas 129 MPa The intact ore specimens withdimensions of 50 mmtimes50 mmtimes50 mm wereobtained by using the techniques of cutting andpolishing Then to minimize the processing damageto the ore specimens a computer numerical control(CNC) router was used to carve the square hole (25mmtimes 25 mmtimes50 mm) in the middle of intact orespecimens 2) In the preparation of backfill slurryput the required amount of dry RMS and JPC into amixing container and the solid mass was well-mixed after being stirred for 5 min Then therequired amount of water was added to the containerand stirred for another 10 min until the slurry wasmixed homogeneously Next the slurry can bepoured into the cube dismountable transparentacrylic molds and the hollow section of orespecimens The molds can be removed after waitingfor 12 h for the initial setting at room temperature(20 degC) and then the CRB and OCRB specimenswere cured in a programmable constant temperatureand humidity curing box

A total of 45 specimens including 36 CRB

Table 1 Physical properties of RMS

Parameter

Particle density(g∙cmminus3)

Porosity

D10mm

D30mm

D50mm

D60mm

D90mm

Cu

Cc

RMS

267

4064

0124

0560

1434

2136

2771

17226

1184

Note Di is the particle size at i passing Cu is the coefficient ofuniformity Cu=D60D10 Cc is the coefficient of curvature Cc=D2

30(D10timesD60)

Table 2 Main chemical compositions of RMS and JPC(wt)

Sample

RMS

JPC

SiO2

7147

25

Al2O3

105

758

CaO

441

4992

Na2O

344

057

Sample

RMS

JPC

K2O

297

098

Fe2O3

28

314

MgO

202

234

SO3

113

457

Figure 1 Particle size sieving results of RMS

3175

J Cent South Univ (2021) 28 3173－3189

specimens and 9 OCRB specimens were prepared

using the procedures mentioned above Thereinto

the CRB specimens were continuously cured for

28 d in a constant temperature (20plusmn05) degC and

constant humidity of (95plusmn1) while the OCRB

specimens were continuously cured for 28 d in a

constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program

23 Testing programThe testing program is shown in Table 3 The

CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3

24 Testing methodsA RJST-616 shear tester (Developed by

Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the

Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail

Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions

Specimen type

CRB

OCRB

Age timed

28

28

28

28

28

28

TemperaturedegC

20

40

60

20

40

60

Normal stresskPa

200 300 400 500

200 300 400 500

200 300 400 500

500

500

500

Shear direction

mdash

mdash

mdash

D1D2D3

Parameter

PSSRSS

AE Signal

PSSAE Signal

Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane

3176

J Cent South Univ (2021) 28 3173－3189

pre-amplification was set to 40 dB and the AE

detection threshold was fixed at 45 dB and the

acquisition rate of AE signals was set to 1 MSPS

The direct shear tester and AE acquisition system

are shown in Figure 4

As a common non-destructive testing (NDT)

technology in the field of geotechnical engineering

the AE technology can be used to analyze the

cracking process of rock [23minus26] Cracking process

analysis based on AE technology involves a variety

of related characteristic parameters such as hit

event rate count frequency and energy among

which the hitevent rate and AE energy rate are

often considered as the critical parameters in

the shear failure process analysis [27minus29] The AE

energy released during the shear failure process can

Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3

3177

J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

3178

J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

3179

J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

3180

J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

3181

J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge

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[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

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[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

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[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

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[9] CUI Liang FALL M Mechanical and thermal properties of

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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

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[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

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Underground Space Technology 2010 25(1) 9 minus 20 DOI

101016jtust200907008

[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

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397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

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[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

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and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

specimens and 9 OCRB specimens were prepared

using the procedures mentioned above Thereinto

the CRB specimens were continuously cured for

28 d in a constant temperature (20plusmn05) degC and

constant humidity of (95plusmn1) while the OCRB

specimens were continuously cured for 28 d in a

constant humidity of (95plusmn1) at varioustemperatures (20 40 and 60 deg C) After the curingprocess was completed the laboratory tests can beperformed according to the testing program

23 Testing programThe testing program is shown in Table 3 The

CRB specimens were tested at four various normalstresses (200 300 400 and 500 kPa) while theOCRB specimens were tested at three differentshear directions (D1 along the axis D2perpendicular to the axis D3 perpendicular to theaxial plane) The shear planes of OCRB at differentshear directions consist of ore and backfill (i eCRB) in which D1 and D2 have the same shearplane area (i e the backfill and ore accounted for50 each) while the backfill and ore account for25 and 75 of the shear plane area at D3respectively as shown in Figure 3

24 Testing methodsA RJST-616 shear tester (Developed by

Institute of Rock and Soil Mechanics ChineseAcademy of Sciences China) was employed tostudy the shear behavior of CRB and OCRBspecimens In the shear test the force-control modewas first used to load the normal force to a specifiedvalue and keep it constant Then the displacement-control mode was adopted to load the shear force ata rate of 03 mmmin and the test was stoppedautomatically when the shear displacement reached8 mm During the shear tests a PAC-DISP systemwas adopted to collect the AE signals and at leastone Nano-30 miniature AE sensor was mounted atthe surface of the lower part of the tested specimens(as shown in Figure 4(d)) The coupling agent wasapplied between the sensor and the specimen the

Figure 2 Specimen preparation procedures of CRB andOCRB specimensin detail

Table 3 Laboratory testing program of CRB and OCRB specimens under different conditions

Specimen type

CRB

OCRB

Age timed

28

28

28

28

28

28

TemperaturedegC

20

40

60

20

40

60

Normal stresskPa

200 300 400 500

200 300 400 500

200 300 400 500

500

500

500

Shear direction

mdash

mdash

mdash

D1D2D3

Parameter

PSSRSS

AE Signal

PSSAE Signal

Note All specimens were cured at constant humility of (95plusmn1) D1 is the direction along the axis D2 is the direction perpendicular to theaxis D3 is the direction perpendicular to the axial plane

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J Cent South Univ (2021) 28 3173－3189

pre-amplification was set to 40 dB and the AE

detection threshold was fixed at 45 dB and the

acquisition rate of AE signals was set to 1 MSPS

The direct shear tester and AE acquisition system

are shown in Figure 4

As a common non-destructive testing (NDT)

technology in the field of geotechnical engineering

the AE technology can be used to analyze the

cracking process of rock [23minus26] Cracking process

analysis based on AE technology involves a variety

of related characteristic parameters such as hit

event rate count frequency and energy among

which the hitevent rate and AE energy rate are

often considered as the critical parameters in

the shear failure process analysis [27minus29] The AE

energy released during the shear failure process can

Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3

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J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

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J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

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J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

3181

J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

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J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

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J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

pre-amplification was set to 40 dB and the AE

detection threshold was fixed at 45 dB and the

acquisition rate of AE signals was set to 1 MSPS

The direct shear tester and AE acquisition system

are shown in Figure 4

As a common non-destructive testing (NDT)

technology in the field of geotechnical engineering

the AE technology can be used to analyze the

cracking process of rock [23minus26] Cracking process

analysis based on AE technology involves a variety

of related characteristic parameters such as hit

event rate count frequency and energy among

which the hitevent rate and AE energy rate are

often considered as the critical parameters in

the shear failure process analysis [27minus29] The AE

energy released during the shear failure process can

Figure 3 Schematic diagram of shear planes of OCRB specimens at different shear directions (a) D1 (b) D2 (c) D3

3177

J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

3178

J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

3179

J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

3180

J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

3181

J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

3183

J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

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[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

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1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

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[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

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conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

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06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

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in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

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isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

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International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

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Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

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Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

be calculated with the following equations [30 31]

Ei =1R intti

tj

U 2 ( t )dt (1)

E =sumEi (2)

where R is the input impedance of voltage

measurement ti and tj are the beginning and ending

time of AE event segment respectively Ei is the

absolute energy obtained by the AE probe during

the time of tj minus ti U(t) is the voltage value of AE

event related to the time t E is the total absolute

energy during the whole shearing process

3 Experimental results and analysis

31 Temperature effect on shear mechanical and

microstructure properties of CRB

311 Shear cracking processes

Figure 5 shows the relationship between shear

stress and shear displacement of CRB at various

temperatures The results indicate that the shear

deformation behaviors at different temperatures are

consistent and in general they can be divided into

four stages initial compaction stage (I) pre-peak

elastic deformation stage (II) post-peak plastic

deformation stage (III) residual deformation

stage (IV) In stage I the shear stress increases

slowly with the shear displacement due to the

contact gap between specimen and shear box and

voids inside the CRB In stage II the shear stress

increases rapidly and linearly with the shear

displacement until it reaches the peak shear strength

(PSS) and in general the PSS can be achieved

within the range of 1minus3 mm shear displacement The

shear stress decreases gently with the shear

displacement in stage III and tends to be stable after

Figure 4 Direct shear tester and AE acquisition system

Figure 5 Relationship between shear stress and sheardisplacement of CRB at various temperatures

3178

J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

3179

J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

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J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[9] CUI Liang FALL M Mechanical and thermal properties of

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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

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[12] NASIR O FALL M Coupling binder hydration temperature

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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

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[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

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and Concrete Composites 2010 32(10) 819minus828 DOI 10

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[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

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1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

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224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

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and fatigue loading [J] International Journal of Rock

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[18] YANG Zhi-qiang Key technology research on the efficient

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559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

entering stage IV With the increase of temperature

(e g from 20 to 40 ordmC) the PSS and peak shear

displacement of CRB tend to increase indicatingthat appropriate increasing temperature is conduciveto improving the maximum allowable deformationand capacity to resist shear deformation of theelastic deformation stage The underlying of thisphenomenon is that the temperature can promote thepositive changes of mineral composition andinternal cementation structure of CRB Therelatively high temperature can accelerate thehydration process and generate more beneficialproducts (such as portlandite) and the minerals areprone to thermal expansion under the environmentof high-temperature so that the internal cementationand pore structure of backfill can be refined [32 33]

To investigate the shear cracking process ofCRB specimens at different stages this paperfocuses on the AE hit and energy responses duringthe shear process and the results are shown inFigures 6 and 7 respectively The experimentalresults show that the AE hit rate is generallymaintained at a low level at the beginning of thetest and no AE energy is released indicating thatthere is no damage to the tested specimen at theinitial loading stage After entering the elasticdeformation stage the hit rate and energy rageincrease significantly with shear displacement Atthis stage the elastic strain energy accumulates inthe specimen until the peak strength is reachedThen the hit rate and energy rate in the plasticdeformation stage continue to increase and themaximum hit rate and energy rate appear during thepost-peak stage At this stage the internalmicrocracks of the specimen continue to grow untila shear fracture surface is formed Finally the

residual deformation stage is achieved the upperand lower shear planes continue to rub and slideunder the action of normal stress and shear stressand the AE hit rate remains at a high level Incontrast the AE energy rate gradually decreases andtends to be zero after entering the residual stage

Furthermore by comparing the characteristicparameters of AE energy during the shear test atvarious temperatures it can be known that thevariation of cumulative AE energy with sheardisplacement will go through three periods namelythe initial quiet period rising period and stableperiod Temperature can significantly affect thedisplacement range and magnitude of AE energyrelease of CRB during the shearing process The

Figure 6 AE hit response during shear test of CRB at20 degC

Figure 7 AE energy response during shear tests of CRBat various temperatures (a) 20 ordmC (b) 40 ordmC (c) 60 ordmC

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J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

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J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

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J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

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J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

higher the temperature the more concentrated theenergy release For example the interval length of

shear displacement of AE energy released at 20 ordmC

is 54 mm while those at 40 and 60 ordmC are 35 and

23 mm respectively After entering the stable

period the cumulative AE energy of 20 40 and

60 ordmC are 1592times106 857times106 and 2218times106 aJ

respectively indicating that the energy release of

CRB during the shear failure process at 40 ordmC is

gentle while that at 60 ordmC is stronger

312 Shear strength parameters

Figure 8 shows the test results of shear strength

parameters of CRB at various temperatures

indicating that the temperature has a significant

influence on both peak shear strength (PSS) and

residual shear strength (RSS) of CRB The

temperature can have a positive effect on the PSS

while it may have a negative impact on RSS For

example the RSS at 40 and 60 ordmC is lower than that

at 20 ordmC The ratio of PSS to RSS ranges from 3 to 8

under the same conditions Besides the shear

strength and normal stress at various temperatures

are in a good linear relationship and the correlation

coefficient R2 of linear fitting is all greater than

092 Therefore it can be considered that the shear

failure of CRB at various temperatures meets

the Mohr-Coulomb criterion [34minus36] and strength

criterion formulas are as follows

τp = cp + σn tanϕp (3)

τr = cr + σn tanϕr (4)

where τp and τr are peak shear strength and residual

shear strength respectively cp and cr are peak

cohesion and residual cohesion respectively ϕp and

ϕr are peak angle of internal friction and residual

angle of internal friction respectively σn is the

normal stress

Table 4 shows the calculation results of the

peak shear strength and shear strength parameters at

various temperatures according to Eqs (3) and (4)

The peak cohesion cp ranges from 145012 to

155821 kPa and it is positively correlated with the

temperature The peak angle of internal friction ϕp is

between 4924deg (at 60 deg C) and 4640deg (at 40 deg C)

The residual cohesion cr ranges from 8053 to

4048 kPa and the maximum cr value is at 40 ordmC

The residual angle of internal friction ϕr is between

Table 4 Linear fitting results of shear strength parameters of CRB

Group

I

II

III

TemperaturedegC

20

40

60

Peak strength parameter

Fitting formula

y1= 145012+115x1

y2= 154614+105x2

y3= 155821+116x3

Correlationcoefficient

R2

0923

0952

0990

CohesioncpkPa

145012

154614

155821

Internalfrictionangleϕp(deg)

4899

4640

4924

Residual strength parameter

Fitting formula

y1=4602+102x1

y2=8053+075x2

y3=4048+096x3

Correlationcoefficient

R2

0999

0978

0975

CohesioncrkPa

4602

8053

4048

Internalfrictionangleϕr(deg)

4557

3687

4383

Figure 8 Relationship between shear stress and normalstress of CRB at various temperatures (a) PSS (b) RSS

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

3181

J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

3687deg and 4557deg and the minimum value of ϕr isat 40 ordmC It is clear that the ϕp is greater than ϕr andthe ratio of cp to cr ranges from 31 to 42313 Microstructures

To analyze the reasons for the differences inshear performance of CRB at various temperaturesthe X-ray diffraction (XRD) test and scanningelectron microscopy (SEM) observation wereconducted in the laboratory An FEI Quanta 250 wasemployed to observe and compare the cementationstructures and a Bruker D8 Advance was adopted toexam the phase composition of hydration productsFigure 9 shows the SEM micrographs of CRB atvarious temperatures (at 50 μm) According to themorphological and microstructure features ofmineral phases the hydration products of CRBmainly include flocculation hydrated calciumsilicate (C-S-H) and acicular ettringite (AFt) Moreimportantly the increase of temperature caneffectively reduce the internal air voids of CRBthus increasing the compactness and improving theshear strength of CRB [37 38] It should be notedthat there is a small amount of micro-crack insidethe CRB at 60 deg C as shown in Figure 9(c)indicating that a higher temperature can cause somedamage to the internal structure of CRB after curingfor a long-term (eg 28 d) Table 5 shows the phasequantitative analysis results of CRB at differenttemperatures with the XRD test The results showthat the main phase compositions of CRB at varioustemperatures include quartz microcline albite andillite which account for more than 85 Thecontent of portlandite increased and the content ofettringite decreased with the temperature increasedfrom 20 to 40 and 60 ordmC which are beneficial toimproving the strength of CRB [39minus41] The aboveanalysis indicates that the increase of temperature isconducive to improving the microstructure of theCRB and the cementation structure and shearperformance of CRB at 40 ordmC are relatively good

32 Temperature effect on coupling shear

behavior of OCRB

321 Coupling shear deformation and strength

Figure 10 shows the relationship between shear

stress and shear displacement of OCRB at various

temperatures The results show that the shear

deformation behaviors of OCRB at various

temperatures are consistent and can be roughly

Table 5 Phase quantitative analysis results of CRB at different temperatures with XRD test

TemperaturedegC

20

40

60

Mass fraction

Quartz

4037

3284

3864

Microcline maximum

1923

2298

1079

Albite

1765

2217

2523

Illite

1052

771

1182

Portlandite

137

555

206

Calcite

626

515

586

Ettringite

409

289

399

Dolomite

051

07

16

Figure 9 SEM micrographs of CRB at varioustemperature after curing for 28 d (at 50 μm) (a) 20 degC(b) 40 degC (c) 60 degC

3181

J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

divided into five stages initial compaction stage(Iʹ) pre-peak elastic deformation stage (IIʹ) peakfluctuation stage (IIIʹ) post-peak plasticdeformation stage (IVʹ) and residual deformation

stage (Vʹ) The OCRB has one more stage IIIʹ (peakfluctuation stage) compared with CRB there are atleast twice the peak shear stress in stage IIIʹ and thefirst peak stress is generally higher than the rest Inthe process of shear stress load the ore and backfillare in a state of bearing shear load together Thereare differences in the sequence of deformation andfailure during the shearing process due to thedifferences between ore and backfill in the strengthbearing capacity of load and deformation and thefirst and second peak stresses are caused by thefailure of ore and backfill respectively

Table 6 shows the specific test results of shearstrength parameters of OCRB indicating that bothtemperature and shear direction significantly affectthe shear performance of OCRB specimens andtemperature effects on the PSS and RSS aresignificantly different For the PSS the temperaturecan have a positive or negative impact and isclosely related to the temperature value and sheardirection as shown in Figure 11(a) In the directionof D1 the PSS of OCRB is greatly improved andincreased by 4524 with the temperature increasedfrom 20 to 40 degC and notably decreased by 2921as the temperature increases from 40 to 60 deg Cwhich shows that the shear resistance in D1 ofOCRB is better at 40 degC In the direction of D3 thePSS of OCRB first decreases then increases withincreasing temperature and its shear resistance isbetter at 60 degC For the RSS the residual strength ofOCRB always increases with the rising temperatureregardless of the shear direction as shown inFigure 11(b) which is consistent with the variation

Figure 10 Relationship between shear stress and sheardisplacement of OCRB (a) At various temperatures(b) In the same direction (D1)

Table 6 Test results of shear strength and AE parameters of OCRB

Specimen ID

OCRB-20-1

OCRB-40-1

OCRB-60-1

OCRB-20-2

OCRB-40-2

OCRB-60-2

OCRB-20-3

OCRB-40-3

OCRB-60-3

TemperatureordmC

20

40

60

20

40

60

20

40

60

Sheardirection

D1

D1

D1

D2

D2

D2

D3

D3

D3

Shear planesize(mmtimesmm)

5080times5068

5040times5090

5088times5060

5020times5030

5062times5100

5082times5060

5070times5090

5060times5060

5038times5072

Peak sheardisplacement

mm

18167

21619

19039

23104

20686

14476

20741

20902

24096

Peak shearstrengthkPa

531279

771627

546236

333220

374339

328642

563351

487432

925967

Residualshear strength

kPa

40124

50909

61021

62929

91144

95898

72075

72334

74708

AE signaldurations

1388

1650

1643

1886

1498

1560

1938

1488

1435

CumulativeAE energy

106 aJ

1881

80306

22545

6890

1757

12321

3704

12351

87744

3182

J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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and Concrete Composites 2010 32(10) 819minus828 DOI 10

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1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

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224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

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Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

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559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

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Jinchuan Mine 2 China [J] Environmental Earth Sciences

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[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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J Cent South Univ (2021) 28 3173－3189

trend of CRB but the RSS of OCRB is higher thanthat of CRB under the same conditions322 AE characteristics during shear process

Figure 12 shows the evolutions of AE hit ratecount and peak frequency with shear displacementfor the direction of D1 The results show that thevariation laws of different AE characteristic

parameters with temperature during the shear

process are similar With the increase of

temperature the response of AE hit rate and count

rate is significantly enhanced and peak frequency

gradually develops from low frequency to high

frequency Besides the cumulative AE hit and AE

count during the shear process at 20 degC are generally

at a low level and the values are significantly

increased with the temperature increased to 40 or

60 deg C indicating that the temperature can

substantially intensify AE activity during the shear

process The main reason is that the temperature canaffect the mechanical properties of backfill and the

structural characteristics of ore-backfill coupling

specimens (e g ore-backfill interface parameters)

thus affecting the mechanical response of the shear

process

Figure 13 shows the experimental curves of the

temperature effect on the AE energy characteristic

parameters during the shear failure process of

OCRB The results suggest that the AE energy has a

good correlation with the shear deformation of

OCRB and the variation characteristics are similar

to that of CRB that is it will also go through three

periods of the initial quiet period rising period and

stable period Compared with CRB the AE energy

Figure 11 Relationship between shear strengthparameters of OCRB and temperature (a) PSS (b) RSS

Figure 12 Temperature effect on AE hit (a) AE count(b) and average frequency (c) during shear failureprocess of OCRB in direction of D1

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J Cent South Univ (2021) 28 3173－3189

of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

3184

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

References

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[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208

[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025

[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge

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[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

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[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical

behaviour of cemented paste backfill [C] Proc of 53rd

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[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

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[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

dependence of strength development and self-desiccation in

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[9] CUI Liang FALL M Mechanical and thermal properties of

cemented tailings materials at early ages Influence of initial

temperature curing stress and drainage conditions [J]

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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

QIU Jing-ping Ultrasonic evaluation of strength properties

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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

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DOI 101016japgeochem201606005

[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

temperature on the mechanical properties of mine cemented

tailings backfill [J] Engineering Geology 2010 114(3 4)

397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

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and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

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of OCRB is characterized by ldquolocal paroxysmaland jumpingrdquo within a small range of sheardisplacement during the rising period Theextremum of the AE energy rate appears mostly inthe peak fluctuation stage IIIʹ and it tends to be zeroduring the post-peak stages and the correspondingcumulative AE energy gradually tends to be stableFurthermore the cumulative AE energy is closelyrelated to the temperature value and the shearingdirection In the direction of D1 the cumulative AEenergy at various temperatures after entering thestable period is 1880times106 aJ (at 20 ordmC) 80306times106 aJ (at 40 ordmC) and 22545times106 aJ (at 60 ordmC)

displaying a trend of rising first and then fallingwith the increasing temperature In the direction ofD2 the final cumulative AE energy is 6890times106 aJ(at 20 ordmC) 1757times106 aJ (at 40 ordmC) and 12321times106 aJ (at 60 ordmC) showing an opposite trend to D1By comparison the final cumulative AE energy inD3 always increases with the increasingtemperature In addition there is no clearcorrelation between the PSS and the cumulative AEenergy at various temperatures For example thePSSs of OCRB at 20 and 60 degC in D1 are nearly thesame but the cumulative AE energy at 20 degC is lessthan that at 60 degC In contrast the PSS at 40 degC inD2 is the highest while its final cumulative AEenergy is the lowest

33 Shear direction effect on coupling shearbehavior of OCRBFigure 14 shows the experimental curves of the

shear direction effect on the AE energycharacteristic parameters during the shear failureprocess of OCRB It is obvious that the sheardirection has a significant influence on the shearstrength of OCRB at the same temperature and thePSSs of OCRB in D1 and D3 are significantlyhigher than that in D2 while the RSSs in D1 and D3are lower than that in D2 By comparing the intervallength of shear displacement of peak fluctuationstage IIIʹ at different shear directions we can knowthat the interval length of displacement in D2 isgreater than that in D1 and D3 In the direction ofD2 the ore and backfill will directly contact witheach other for sliding shear after the first and secondpeak stresses are reached and the strengthdifference between ore and backfill leads tocontinuous damage and energy release on the shearsurface

The experimental results also indicate that theAE variation laws of OCRB with sheardisplacement are generally consistent and it willalso experience three periods During the risingperiod the AE energy increases rapidly within asmall interval of displacement and the extremum ofthe AE energy rate appears mostly in the peakfluctuation stage IIIʹ The influence of sheardirection on the AE energy of OCRB during theshearing process could be either enhanced orweakened and the final cumulative AE energy after

Figure 13 Temperature effect on AE energy releaseduring shear failure process of OCRB (a) D1 (b) D2(c) D3

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J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

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J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

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J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

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[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

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[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

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[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

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[9] CUI Liang FALL M Mechanical and thermal properties of

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[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

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[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

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[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

cemented paste backfill at early ages [J] Tunnelling and

Underground Space Technology 2010 25(1) 9 minus 20 DOI

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[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

temperature on the mechanical properties of mine cemented

tailings backfill [J] Engineering Geology 2010 114(3 4)

397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

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and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

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rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

entering the stable period depends on thetemperature For example the cumulative AEenergy in D2 at 20 degC is higher than that in D1 andlower than that in D3 while the cumulative AEenergy in D2 at 40 deg C is relatively lower Besidesthe PSS of OCRB in different shear directions ismostly positively correlated with the cumulative AEenergy that is the higher the PSS the greater thecumulative AE energy except for a few cases (egthe cumulative AE energy in D2 is higher than thatin D1 and D3 at 20 degC)

Furthermore the shear direction also has asignificant influence on the failure mode of OCRBTaking the shear failure mode of OCRB at 40 degC asan example as shown in Figure 14(b) the shearfailure planes of the specimens in D1 and D3 arerelatively flat and the ore-backfill in the upper and

lower shear parts are in a good coupling state Incontrast the integrity of the upper and lower shearparts is poor in D2 and the ore along the sheardirection even was broken into several small piecesindicating that the resistance to shear deformationand overall performance of OCRB in D2 is weakerthan that in D1 and D3

4 Discussion

Based on the above analysis of the test resultsthe temperature is a crucial factor affecting the shearbehavior and AE characteristic parameters of bothCRB and OCRB and the mechanism underlying thetemperature effect between CRB and OCRB isclosely related 1) For CRB the temperature affectsthe shear mechanical properties of CRB bychanging its internal cementation and porestructures as well as the production of main mineralphases For example the air voids inside the CRBare refined the content of portlandite increased andthe content of ettringite decreased with thetemperature increasing from 20 to 40 degC which areconducive to improving the shear performance ofCRB At 60 deg C although the air voids inside theCRB are also refined a small amount of micro-crack appeared inside the CRB the content of themain mineral phases also changed unfavorablycompared with 40 deg C resulting in the mechanicalproperties of CRB at 60 degC are worse than those at40 deg C Therefore the overall cementation structureand shear performance of CRB at 40 ordmC arerelatively good The temperature effect on thestructure and mechanical properties of CRB can beadequately evaluated utilizing SEM XRD andother microstructure testing methods 2) For OCRBthe effect of temperature on its mechanicalproperties is influenced by the characteristics ofcoupling structure components and structuralfactors When the coupling structure is in a high-temperature environment (below 100 degC) a series ofhydration reactions and thermal expansion occur inthe backfill specimens of the coupling structure Incontrast the temperature effect on the mechanicalproperties of the rock can be ignored due to its high-temperature resistance The different sensitivity ofrock and backfill to temperature will directly affectthe mechanical properties of the coupling structure

Figure 14 Shear direction effect on AE energy releaseduring shear failure process of OCRB (a) 20 degC (b) 40 degC(c) 60 degC

3185

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

References

[1] SUN Wei WANG Hong-jiang HOU Ke-peng Control ofwaste rock-tailings paste backfill for active miningsubsidence areas [J] Journal of Cleaner Production 2018171 567minus579 DOI 101016jjclepro201709253

[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208

[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025

[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge

201803005

[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

of underground cemented tailings backfill [J] Tunnelling and

Underground Space Technology 2008 23(1) 80minus 90 DOI

101016jtust200608005

[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical

behaviour of cemented paste backfill [C] Proc of 53rd

Canadian Geotechnical Conference Montreal 2000

373minus380

[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

Quantitative investigation on micro-parameters of cemented

paste backfill and its sensitivity analysis [J] Journal of

Central South University 2020 27(1) 267 minus 276 DOI

101007s11771-020-4294-1

[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

dependence of strength development and self-desiccation in

cemented paste backfill that contains sodium silicate [J]

Cement and Concrete Composites 2016 67 101minus110 DOI

101016jcemconcomp201601005

[9] CUI Liang FALL M Mechanical and thermal properties of

cemented tailings materials at early ages Influence of initial

temperature curing stress and drainage conditions [J]

Construction and Building Materials 2016 125 553 minus 563

DOI 101016jconbuildmat201608080

[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

QIU Jing-ping Ultrasonic evaluation of strength properties

of cemented paste backfill Effects of mineral admixture and

curing temperature [J] Ultrasonics 2020 100 105983 DOI

101016jultras2019105983

[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

paste backfill [J] Applied Geochemistry 2016 72 10minus 19

DOI 101016japgeochem201606005

[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

cemented paste backfill at early ages [J] Tunnelling and

Underground Space Technology 2010 25(1) 9 minus 20 DOI

101016jtust200907008

[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

temperature on the mechanical properties of mine cemented

tailings backfill [J] Engineering Geology 2010 114(3 4)

397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

3187

J Cent South Univ (2021) 28 3173－3189

and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

Besides the structural characteristics (e g rock-backfill interface parameters) of OCRB will alsoaffect its shear mechanical behavior The shear testof OCRB is essentially a process in which the rockand backfill are in a state of bearing shear loadtogether In addition under the same shear directionthe temperature effect on the mechanical propertiesof the coupling structure can be well characterizedby the AE parameters (e g AE hit rate and AEenergy)

Furthermore the co-bearing mechanism ofOCRB is closely related to the shear direction Inthe direction of D1 two peak stresses appeared inthe shearing process the PSSs are higher than thatof CRB and the cumulative AE energy of OCRB ishigher than that of CRB at the same temperatureFor example at 40 deg C the first peak strength andsecond peak strength of OCRB are 771627 and532557 kPa respectively which are far higher thanthe PSS value (205052 kPa) of CRB thecumulative AE energy of OCRB and CRB are80306times106 and 857times106 aJ respectively Theresults indicate that the ore and backfill are in agood coupling state of bearing shear load together inD1 In the direction of D2 the PSSs of OCRB atvarious temperatures are approximately the sameand the PSS improvement is not significantcompared with that of CRB The variationcharacteristics of AE energy of OCRB is similar tothose of CRB the difference of cumulative AEenergy between OCRB in D2 and CRB at the sametemperature is insignificant indicating that thebearing capacity of ore in D2 is limited and thebackfill is mainly subjected to the shear load In theshear direction of D3 the PSS of OCRB is greatlyimproved compared with that of CRB at the sametemperature and the released AE energy notablyincreases compared with that of CRB indicatingthat the ore-backfill is in a good state of bearingshear load together Since the ore area accounts for75 of the shear plane in D3 (as shown in Figure3) it can be inferred that the ore plays a moresignificant role in bearing the shear load than thebackfill in the shear direction Based on the analysismentioned above it can be concluded that the shearperformance of OCRB along the axis direction (D1)is better than that of perpendicular to the axisdirection (D2) The influence of principal stress

orientation should be taken into consideration in thebackfill mining and stope design

In this paper a large number of laboratoryshear tests were conducted and some useful resultsare obtained on the mechanical properties of ore-backfill coupling structure under differenttemperatures and shear directions The researchresults can provide some basis for understanding theshear behavior of ore-backfill coupling structuresunder the deep high-temperature miningenvironment However the tests carried out in thelaboratory are small-scale and the shear boundarycondition applied is constant normal load (CNL)For real underground engineering the constantnormal stiffness (CNS) boundary condition is moreappropriate to describe the mechanical response ofunderground excavation since the CNS is morerealistic than CNL [42 43] Therefore a large-scalephysical model constructed to simulate the realstress environment and CNS boundary conditionswill be a topic worthy of follow-up research

5 Conclusions

1) The shear deformation of CRB can bedivided into four stages and the AE energy releasehas a good correlation with the shear deformationThe AE energy releases at the beginning of the pre-peak elastic deformation stage (II) and increasesrapidly in the post-peak plastic deformation stage(III) The higher the temperature the moreconcentrated the energy release The shear failure ofCRB at various temperatures meets the Mohr-Coulomb criterion The influence of temperature onthe shear behavior of CRB mainly depends on thecharacteristics of cementation and pore structuresand the production of main mineral phases Thecementation structure and shear performance ofCRB at 40 ordmC are relatively good

2) The shear failure process of OCRB has onemore stage IIIʹ (peak fluctuation stage) comparedwith CRB and the extremum of the AE energy ratemostly appears in this stage The temperature effecton the PSS and AE energy of OCRB can be eitherenhanced or weakened depending on thetemperature value and shear direction The variationof cumulative AE energy of OCRB with sheardisplacement will go through three periods of the

3186

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

References

[1] SUN Wei WANG Hong-jiang HOU Ke-peng Control ofwaste rock-tailings paste backfill for active miningsubsidence areas [J] Journal of Cleaner Production 2018171 567minus579 DOI 101016jjclepro201709253

[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208

[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025

[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge

201803005

[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

of underground cemented tailings backfill [J] Tunnelling and

Underground Space Technology 2008 23(1) 80minus 90 DOI

101016jtust200608005

[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical

behaviour of cemented paste backfill [C] Proc of 53rd

Canadian Geotechnical Conference Montreal 2000

373minus380

[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

Quantitative investigation on micro-parameters of cemented

paste backfill and its sensitivity analysis [J] Journal of

Central South University 2020 27(1) 267 minus 276 DOI

101007s11771-020-4294-1

[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

dependence of strength development and self-desiccation in

cemented paste backfill that contains sodium silicate [J]

Cement and Concrete Composites 2016 67 101minus110 DOI

101016jcemconcomp201601005

[9] CUI Liang FALL M Mechanical and thermal properties of

cemented tailings materials at early ages Influence of initial

temperature curing stress and drainage conditions [J]

Construction and Building Materials 2016 125 553 minus 563

DOI 101016jconbuildmat201608080

[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

QIU Jing-ping Ultrasonic evaluation of strength properties

of cemented paste backfill Effects of mineral admixture and

curing temperature [J] Ultrasonics 2020 100 105983 DOI

101016jultras2019105983

[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

paste backfill [J] Applied Geochemistry 2016 72 10minus 19

DOI 101016japgeochem201606005

[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

cemented paste backfill at early ages [J] Tunnelling and

Underground Space Technology 2010 25(1) 9 minus 20 DOI

101016jtust200907008

[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

temperature on the mechanical properties of mine cemented

tailings backfill [J] Engineering Geology 2010 114(3 4)

397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

3187

J Cent South Univ (2021) 28 3173－3189

and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

initial quiet period rising period and stable periodThe mechanism underlying the temperature effect ofOCRB is closely related to the characteristics ofcoupling structure components and structural factors

3) The shear direction has a significantinfluence on the shear strength and shear capacity ofOCRB and the shear performance of OCRB in D1and D3 is significantly higher than that in D2 Thecorrelation between peak strength and cumulativeAE energy of OCRB is more sensitive to sheardirection than temperature The ore-backfill is in agood coupling state of bearing shear load together inD1 and D3 while the bearing capacity of ore in D2is limited and the backfill is mainly subjected to theshear load Therefore the influence of principalstress orientation should be considered in thebackfill mining and stope design

ContributorsThe overarching research goals were

developed by JIANG Fei-fei and ZHOU HuiJIANG Fei-fei SHENG Jia and KOU Yong-yuanconducted the laboratory tests and analyzed theexperimental results JIANG Fei-fei ZHOU Huiand LI Xiang-dong conducted the literature reviewand wrote the first draft of the manuscript All theauthors replied to reviewers 1049011 comments and revisedthe final version

Conflict of interestJIANG Fei-fei ZHOU Hui SHENG Jia LI

Xiang-dong and KOU Yong-yuan declare that theyhave no conflict of interest

References

[1] SUN Wei WANG Hong-jiang HOU Ke-peng Control ofwaste rock-tailings paste backfill for active miningsubsidence areas [J] Journal of Cleaner Production 2018171 567minus579 DOI 101016jjclepro201709253

[2] SHESHPARI M A review of underground mine backfillingmethods with emphasis on cemented paste backfill [J]Electronic Journal of Geotechnical Engineering 201520(13) 5183minus5208

[3] QI Chong-chong FOURIE A Cemented paste backfill formineral tailings management Review and futureperspectives [J] Minerals Engineering 2019 144 106025DOI 101016jmineng2019106025

[4] LINGGA B A APEL D B Shear properties of cementedrockfills [J] Journal of Rock Mechanics and GeotechnicalEngineering 2018 10(4) 635minus 644 DOI 101016j jrmge

201803005

[5] FALL M BENZAAZOUA M SAA E G Mix proportioning

of underground cemented tailings backfill [J] Tunnelling and

Underground Space Technology 2008 23(1) 80minus 90 DOI

101016jtust200608005

[6] BELEM T BENZAAZOUA M BUSSIEgraveRE B Mechanical

behaviour of cemented paste backfill [C] Proc of 53rd

Canadian Geotechnical Conference Montreal 2000

373minus380

[7] LIU Lang ZHOU Peng FENG Yan ZHANG Bo SONG K I

Quantitative investigation on micro-parameters of cemented

paste backfill and its sensitivity analysis [J] Journal of

Central South University 2020 27(1) 267 minus 276 DOI

101007s11771-020-4294-1

[8] WANG Yong FALL M WU Ai-xiang Initial temperature-

dependence of strength development and self-desiccation in

cemented paste backfill that contains sodium silicate [J]

Cement and Concrete Composites 2016 67 101minus110 DOI

101016jcemconcomp201601005

[9] CUI Liang FALL M Mechanical and thermal properties of

cemented tailings materials at early ages Influence of initial

temperature curing stress and drainage conditions [J]

Construction and Building Materials 2016 125 553 minus 563

DOI 101016jconbuildmat201608080

[10] JIANG Hai-qiang YI Hong-shun YILMAZ E LIU Shi-wei

QIU Jing-ping Ultrasonic evaluation of strength properties

of cemented paste backfill Effects of mineral admixture and

curing temperature [J] Ultrasonics 2020 100 105983 DOI

101016jultras2019105983

[11] ALDHAFEERI Z FALL M POKHAREL M POURAMINI

Z Temperature dependence of the reactivity of cemented

paste backfill [J] Applied Geochemistry 2016 72 10minus 19

DOI 101016japgeochem201606005

[12] NASIR O FALL M Coupling binder hydration temperature

and compressive strength development of underground

cemented paste backfill at early ages [J] Tunnelling and

Underground Space Technology 2010 25(1) 9 minus 20 DOI

101016jtust200907008

[13] FALL M CEacuteLESTIN J C POKHAREL M TOUREacute M A

contribution to understanding the effects of curing

temperature on the mechanical properties of mine cemented

tailings backfill [J] Engineering Geology 2010 114(3 4)

397minus413 DOI 101016jenggeo201005016

[14] FALL M POKHAREL M Coupled effects of sulphate and

temperature on the strength development of cemented

tailings backfills Portland cement-paste backfill [J] Cement

and Concrete Composites 2010 32(10) 819minus828 DOI 10

1016jcemconcomp201008002

[15] WU Di CAI Si-jing Coupled effect of cement hydration and

temperature on hydraulic behavior of cemented tailings

backfill [J] Journal of Central South University 2015 22(5)

1956minus1964 DOI 101007s11771-015-2715-3

[16] ZHOU Xiao-ping LI Guo-qing MA Hai-chun Real-time

experiment investigations on the coupled thermomechanical

and cracking behaviors in granite containing three pre-

existing fissures [J] Engineering Fracture Mechanics 2020

224 106797 DOI 101016jengfracmech2019106797

[17] CHEN You-liang NI Jing SHAO Wei AZZAM R

Experimental study on the influence of temperature on the

mechanical properties of granite under uni-axial compression

3187

J Cent South Univ (2021) 28 3173－3189

and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

and fatigue loading [J] International Journal of Rock

Mechanics and Mining Sciences 2012 56 62minus66 DOI

101016jijrmms201207026

[18] YANG Zhi-qiang Key technology research on the efficient

exploitation and comprehensive utilization of resources in

the deep Jinchuan nickel deposit [J] Engineering 2017 3(4)

559minus566 DOI 101016JENG201704021

[19] ZHAO Hai-jun MA Feng-shan ZHANG Ya-min GUO Jie

Monitoring and mechanisms of ground deformation and

ground fissures induced by cut-and-fill mining in the

Jinchuan Mine 2 China [J] Environmental Earth Sciences

2013 68(7) 1903minus1911 DOI 101007s12665-012-1877-7

[20] WANG Jun HUANG Shang-yao HUANG Ge-shan WANG

Ji-yang Basic characteristics of the earth1049011s temperature

distribution in Southern China [J] Acta Geologica Sinica-

English 1986 60(3) 91minus106 DOI 101111j1755-6724

1986mp60003008x

[21] ERCIKDI B CIHANGIR F KESIMAL A DEVECI H ALP

İ Utilization of industrial waste products as pozzolanic

material in cemented paste backfill of high sulphide mill

tailings [J] Journal of Hazardous Materials 2009 168(2 3)

848minus856 DOI 101016jjhazmat200902100

[22] DONG Qing LIANG Bing JIA Li-feng JIANG Li-guo

Effect of sulfide on the long-term strength of lead-zinc

tailings cemented paste backfill [J] Construction and

Building Materials 2019 200 436 minus 446 DOI 101016j

conbuildmat201812069

[23] ZHOU Xiao-ping ZHANG Jian-zhi QIAN Qi-hu NIU

Yong Experimental investigation of progressive cracking

processes in granite under uniaxial loading using digital

imaging and AE techniques [J] Journal of Structural

Geology 2019 126 129minus 145 DOI 101016j jsg 2019

06003

[24] ZHOU Xiao-ping ZHANG Jian-zhi BERTO F Fracture

analysis in brittle sandstone by digital imaging and AE

techniques Role of flaw length ratio [J] Journal of Materials

in Civil Engineering 2020 32(5) 04020085 DOI 101061

(asce)mt1943-55330003151

[25] ZHANG Jian-zhi ZHOU Xiao-ping ZHOU Lun-shi

BERTO F Progressive failure of brittle rocks with non-

isometric flaws Insights from acousto-optic-mechanical

(AOM) data [J] Fatigue amp Fracture of Engineering Materials

amp Structures 2019 42(8) 1787minus1802 DOI 101111ffe

13019

[26] ZHANG Jian-zhi ZHOU Xiao-ping AE event rate

characteristics of flawed granite From damage stress to

ultimate failure [J] Geophysical Journal International 2020

222(2) 795minus814 DOI 101093gjiggaa207

[27] KESHAVARZ M PELLET F L HOSSEINI K A Comparing

the effectiveness of energy and hit rate parameters of

acoustic emission for prediction of rock failure [C] ISRM

International Symposium on Rock Mechanics-SINOROCK

2009 Hong Kong China 2009 ISRM-SINOROCK-

2009-044

[28] MENG Fan-zhen WONG L N Y ZHOU Hui YU Jin

CHENG Guang-tan Shear rate effects on the post-peak shear

behaviour and acoustic emission characteristics of artificially

split granite joints [J] Rock Mechanics and Rock

Engineering 2019 52(7) 2155minus2174 DOI 101007s00603-

018-1722-8

[29] ZHANG Jian-zhi ZHOU Xiao-ping Forecasting

catastrophic rupture in brittle rocks using precursory AE time

series [J] Journal of Geophysical Research Solid Earth

2020 125(8) e2019JB019276 DOI 1010292019JB019276

[30] WU Di ZHAO Run-kang QU Chun-lai Effect of curing

temperature on mechanical performance and acoustic

emission properties of cemented coal gangue-fly ash backfill

[J] Geotechnical and Geological Engineering 2019 37(4)

3241minus3253 DOI 101007s10706-019-00839-8

[31] KIM J S LEE K S CHO W J CHOI H J CHO G C A

comparative evaluation of stress-strain and acoustic emission

methods for quantitative damage assessments of brittle rock

[J] Rock Mechanics and Rock Engineering 2015 48(2)

495minus508 DOI 101007s00603-014-0590-0

[32] JIANG Fei-fei ZHOU Hui SHENG Jia KOU Yong-yuan

LI Xiang-dong Effects of temperature and age on physico-

mechanical properties of cemented gravel sand backfills [J]

Journal of Central South University 2020 27(10) 2999 minus3012 DOI 101007s11771-020-4524-6

[33] BARTON N A review of mechanical over-closure and

thermal over-closure of rock joints Potential consequences

for coupled modelling of nuclear waste disposal and

geothermal energy development [J] Tunnelling and

Underground Space Technology 2020 99 103379 DOI

101016jtust2020103379

[34] BAREITHER C A BENSON C H EDIL T B Comparison

of shear strength of sand backfills measured in small-scale

and large-scale direct shear tests [J] Canadian Geotechnical

Journal 2008 45(9) 1224minus1236 DOI 101139t08-058

[35] SUITS L D SHEAHAN T C NAKAO T FITYUS S Direct

shear testing of a marginal material using a large shear box

[J] Geotechnical Testing Journal 2008 31(5) 101237 DOI

101520gtj101237

[36] LI Li Generalized solution for mining backfill design [J]

International Journal of Geomechanics 2014 14(3)

04014006 DOI 101061(asce)gm1943-56220000329

[37] XU Wen-bin LI Qian-long ZHANG Ya-lun Influence of

temperature on compressive strength microstructure

properties and failure pattern of fiber-reinforced cemented

tailings backfill [J] Construction and Building Materials

2019 222 776minus785 DOI 101016jconbuildmat2019 06203

[38] HAN Bin ZHANG Sheng-you SUN Wei Impact of

temperature on the strength development of the tailing-waste

rock backfill of a gold mine [J] Advances in Civil

Engineering 2019 2019 1minus9 DOI 10115520194379606

[39] BERNIER R L LI M G MOERMAN A Effects of tailings

and binder geochemistry on the physical strength of paste

backfill [C] Proceeding of Sudburry99 Sudbury Canada

1999 1113minus1122

[40] LIU Lang FANG Zhi-yu QI Chong-chong ZHANG Bo

GUO Li-jie SONG K I Experimental investigation on the

relationship between pore characteristics and unconfined

compressive strength of cemented paste backfill [J]

Construction and Building Materials 2018 179 254minus264

DOI 101016jconbuildmat201805224

[41] LI Wen-chen FALL M Sulphate effect on the early age

strength and self-desiccation of cemented paste backfill [J]

Construction and Building Materials 2016 106 296 minus 304

DOI 101016jconbuildmat201512124

[42] SHANG J ZHAO Z MA S On the shear failure of incipient

3188

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189

J Cent South Univ (2021) 28 3173－3189

rock discontinuities under CNL and CNS boundaryconditions Insights from DEM modelling [J] EngineeringGeology 2018 234 153minus166 DOI 101016jenggeo201801012

[43] THIRUKUMARAN S INDRARATNA B A review of shear

strength models for rock joints subjected to constant normalstiffness [J] Journal of Rock Mechanics and GeotechnicalEngineering 2016 8(3) 405minus414 DOI 101016j jrmge201510006

(Edited by FANG Jing-hua)

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

摘要摘要为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应分别对不

同温度(204060 degC)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验并对

不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析结果表明温度对CRB剪切性

能的影响主要取决于其微观结构和主要矿物相特性且在40 degC时的性能相对较优OCRB的剪切变形

较CRB增加了ldquo峰值波动阶段rdquo且与AE特征参数有良好的相关性温度对OCRB的剪切强度既可以

是正面影响也可以是负面影响这取决于温度值大小和剪切作用方向沿轴向(D1)方向OCRB的剪切

性能明显优于垂直于轴向(D2)方向的矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主

应力方向密切相关

关键词关键词胶结充填体岩石-充填体温度剪切方向剪切强度AE能量

中文导读中文导读

3189