ControllingMechanismofRockBurstbyCO...

Research ArticleControllingMechanism of Rock Burst by CO2 Fracturing BlastingBased on Rock Burst System

Tianwei Lan12 Chaojun Fan 1 Jun Han1 Hongwei Zhang1 and Jiawei Sun1

1College of Mining Liaoning Technical University Fuxin 123000 China2Key Laboratory of Mining Disaster Prevention and Control Qingdao 266590 China

Correspondence should be addressed to Chaojun Fan chaojunfan139com

Received 27 April 2020 Revised 28 July 2020 Accepted 5 August 2020 Published 27 August 2020

Academic Editor Caiping Lu

Copyright copy 2020 Tianwei Lan et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Rock burst induced by mining is one of the most serious dynamic disasters in the process of coal miningemechanism of a rockburst is similar to that of a natural earthquake It is difficult to accurately predict the ldquotime space and strengthrdquo of rock burst butthe possibility of rock burst can be predicted based on the results of microseismic monitoring In this paper the rock burst systemunder the tectonic stress field is established based on the practice of coal mining and the result of mine ground crustal stressmeasurement According to the magnitude of microseismic monitoring the amount of the energy and spatial position of the rockburst are determined Based on the theory of explosion mechanics aiming at the prevention and control of rock burst in the coalmine the technique of liquid CO2 fracturing blasting is put forward By the experiment of blasting mechanics the blastingparameters are determined and the controlling mechanism of rock burst of liquid CO2 fracturing blasting is revealed eapplication of liquid CO2 fissure blasting technology in the prevention and control of rock burst in Jixian Coal Mine shows thatCO2 fracturing blasting reduces the stress concentration of the rock burst system and transfers energy to the deeper part and thereis no open fire in the blasting It is a new safe and efficient method to prevent and control rock burst which can be applied widely

1 Introduction

Rock burst is one of the most serious dynamic disasters incoal mining Both rock burst and natural earthquake aredynamic disasters caused by the crack and instability ofcrustal rock mass resulting in the release of energy eoccurrence mechanisms of the two are similar and they aredifficult to be predicted [1ndash4] e research on the mech-anism of rock burst has always been an unsolved scientificproblem that has been discussed for a long time in the fieldsof mining engineering and rock mechanics [5ndash10] eapplication of CT scanning 3D printing big data cloudcomputing Internet of things and other emerging tech-nologies in the study of coal mine rock burst has become ahot topic in mining research [11ndash14] e monitoring andwarning methods of rock burst mainly include microseismicmonitoring method electromagnetic radiation method AEmethod mining stress monitoring method and drillingcuttings method rough the analysis of monitoring data

the possibility of rock burst can be predicted but the ac-curacy still needs to be further improved [15ndash19] For theprevention of rock burst there are two aspects regionalprevention and local risk relief including protection layermining borehole pressure relief coal seam water injectionpressure relief blasting liquid CO2 fracturing blasting hy-draulic fracturing and other methods [20ndash23] rough theimplementation of risk relief measures the risk of rock burstis reduced But the exact location of the rock burst cannot bedetermined it leads to the heavy workload and materialconsumption If the structure and energy characteristics ofcoal and rock mass can be predicted and preventive mea-sures can be taken according to the predicted results theprevention level of rock burst will be improved and the costof risk relief will be reduced

e gestation and generation of rock burst can be af-fected by the stress concentration degree and energy storagesize of the regional coal-rock mass structure system and thecoal-rock mass system should have a certain scale range

HindawiShock and VibrationVolume 2020 Article ID 8876905 9 pageshttpsdoiorg10115520208876905

[24 25] In order to study the structure system and energycharacteristics of rock mass under rock burst a rock burstsystem based on the tectonic stress field is established eenergy magnitude and spatial location of rock burst systemare determined by microseismic monitoring technologyBased on the established rock burst system the liquid CO2fracturing blasting technology is put forwarde practice ofpreventing and controlling rock burst in coal mine showsthat the CO2 fracturing blasting reduces the stress con-centration of the rock burst system and transfers the energyto the deeper part It is a new safe and efficient technologyto prevent rock burst

2 Analysis of Energy in Rock Burst System

21 Establishment of Rock Burst System e complexity ofrock burst is related to the heterogeneity anisotropy anddiversity of influencing factors of the structure system of coaland rock mass e stress and energy of coal and rock masssystem are the basic conditions and the mining engineeringactivities are the induced conditions More than 85 of theenergy causing rock burst comes from surrounding rocke coal mainly provides the medium condition for rockburst e space of energy storage-exchange-release of coaland rock mass system with rock burst should have a certainscale which cannot be infinitely great or infinitely small andshould be related to the structure stress and energy level inthe coal and rockmass system Amodel of rock burst systemwhich reflects the relation of the coal and rock mass systemand rock burst is established e shape of the model isassumed to be spherical hereinafter referred to as the rockburst system (Figure 1)

22Analysis ofEnergy inRockBurst System According to thetheory of elasticity a representative element of rock mass atthe depth H in the crustal rock mass is subjected to three-dimensional stress and the unit body is in the state of elasticdeformation (Figure 2) e elastic energy of unit volumeaccumulation under in situ stress field can be expressed bythe following formula

U0 12E

σ21 + σ22 + σ23 minus 2μ σ1σ2 + σ2σ3 + σ1σ3( 11138571113960 1113961 (1)

where U0 represents elastic energy accumulated in unitvolume J σ1 σ2 and σ3 represent principal stress in threedirections of any unit MPa E represents modulus ofelasticity MPa μ represents Poissonrsquos ratio

en the energy for the spherical rock burst system canbe expressed

U 12E

σ21 + σ22 + σ23 minus 2μ σ1σ2 + σ2σ3 + σ1σ3( 11138571113960 111396143πR

3

(2)

where U represents the energy of rock burst system J Rrepresents the radius of rock burst system m

According to the in situ stress measurement results ofsome rock burst mines in China the stress fields in most(almost all) areas are horizontal compressive tectonic stress

fields e change of maximum principal stress direction andmagnitude in most parts of China is due to the collision of theChinese mainland plate by the India plate and Eurasian plateand the subduction of the eastern Pacific plate and thePhilippines plate to Eurasia In the vast majority of areas thein situ stress is a three-dimensional unequal compressivestress field dominated by horizontal stress e magnitudeand direction of the three principal stresses vary with spaceand time so they are unstable stress fields e measured datashow that the vertical stress is basically equal to the weight ofoverlying strata e deviation between the vertical stressdirection and the vertical direction is generally no more than20deg e measured data show that there are two principalstresses in the horizontal or nearly horizontal plane in most(almost all) regions and the angle between the two principalstresses and the horizontal plane is generally nomore than 30deg

e dip angles of the maximum and minimum principalstresses σ1 and σ3 are near horizontal direction e max-imum horizontal stress σ1 is generally larger than the verticalstress σ2 and there are certain linear relationships betweenσ1 σ2 and σ3 and self-weight stress cH and they are usuallyσ1asymp 2cH σ2asymp cH and σ1asymp 07cH e energy of rock burstsystem related to self-weight stress can be obtained bysubstituting them into formula (2)

U 2π3E

(549 minus 82μ)c2H

2R3 (3)

Radius

Boundaryof the system

Core of rockburst system

Figure 1 Schematic diagram of ldquosphericalrdquo type rock burst system

σ2

σ3

σ1

σ2

σ3

σ1

y

z

xO

H

M

Representativeelement

Ground level

Figure 2 Representative element under the action of three-di-mensional stress

2 Shock and Vibration

23 Analysis of Scale in Rock Burst System When the energystored in the rock burst system reaches the critical state ofthe energy required for the occurrence of the rock burstmining engineering activities induce the instability of therock burst system and the instantaneous release of energycauses the rock burst So the rock burst is a nonlineardynamic process of energy accumulation in steady state andenergy release in a nonsteady state in the deformationprocess of rock burst system

e energy of rock burstU is provided by the rock burstsystem which is usually determined by the difference betweenthe energy of tectonic stress field UG and the energy of gravitystress field UZ By calculation

UZ 2π3E

1 minus 2μ2 minus μ1 minus μ

1113888 1113889c2H

2R3

UG 2π3E

(549 minus 82μ)c2H

2R3

⎧⎪⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎪⎩

(4)

en

ΔU UG minus UZ 2π 102μ2 minus 1269μ + 4491113872 1113873c

2H

2R3

3E(1 minus μ)

(5)

erefore we can obtain the radius of the rock burstsystem as

R

3E(1 minus μ)ΔU

2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

31113971

(6)

Rock burst and natural earthquake are both dynamicdisasters caused by the crack and instability of crustal rockmass It can also be considered that rock burst is anearthquake induced by mining In seismology the energy toproduce an earthquake can be determined by Gutenbergrsquosand Kanamorirsquos empirical formulas of energy magnitudee principle of microseismic monitoring is similar to thatof earthquake prediction and has been widely used in themonitoring of rock burst in coal mines By analyzing seismicwave signals the position magnitude and energy of the rockburst can be determined erefore according to themagnitude of microseismic monitoring the relationshipbetween energy and magnitude can be established and thescale range of rock burst system can be determined

ΔU 101695ML+318 (7)

U is the energy released by a rock burst JML is magnitude

R

3E(1 minus μ) middot 101695ML+318

2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

3

11139741113972

(8)

3 The Working Principle of Liquid CO2

Fracturing Blasting

31 Structure of CO2 Cracker Liquid CO2 fracturingblasting technology is mainly used in coal mines to increasethe permeability of coal seams and gas extraction efficiency[26 27] It is rare to apply liquid CO2 fracturing blastingtechnology to rock burst prevention and control Comparedwith the traditional explosive technology the liquid CO2fracturing technology has no open fire and can be relativelysafe in the process of blasting and the pressure relief effect isremarkable e CO2 cracker is mainly composed of a fillingvalve a heating pipe the main pipe a sealing gasket ashearing piece and an energy release head (Figure 3)

32 6e Working Principle of Liquid CO2 Fracturing BlastingWhen the temperature of liquid CO2 is lower than 31degC orthe pressure is greater than 735MPa it usually exists inliquid form When the temperature of liquid CO2 is higherthan 31degC it begins to gasify Taking advantage of the phasetransition characteristics of CO2 liquid CO2 was filled in themain pipe of the cracker and the heat pipe was rapidlyexcited by the detonator Liquid CO2 was instantly gasifiedand expanded to generate high pressure When the pressurereached the ultimate strength of the constant pressureshearing piece the shearing piece was broken and the high-pressure gas was released from the energy release head andthen acts on the coal and rock mass thus realizing thedirectional fracturing blasting on the coal and rock mass(Figure 4) e crushing zone fracture zone and vibrationzone were formed successively from the center of the ex-plosion position so as to complete the pressure relief(Figure 5)

4 Test and Research on Liquid CO2

Fracturing Blasting

41 Test Purpose and Determination of Parameters Based onthe theory of explosion mechanics in order to determine theblasting effect of liquid CO2 fracturing device reasonableblasting parameters were determined through the experimentalresearch of blasting mechanics Pressure tests were carried outon the basic parameters of the fracturing blasting in the labo-ratory to determine the matching relationship between thecrackers and borehole diameters the stress at different positionsin the boreholes during the blastings and the impact on theblasting effect after hole sealing so as to reveal the controllingmechanism of rock burst of liquid CO2 fracturing blasting andprovide a basis for the prevention and control of rock burst

e parameters and specifications of liquid CO2 frac-turing blasting test devices are shown in Tables 1 and 2Different crackers are placed in three different specificationsof test devices for blasting test YE5853-4CH signal amplifierand YE6231 data collector are used in the experiment tocollect the pressure of CO2 released during blasting on thepipe wall and YE7600 software is used to process the dataFinally the blasting parameters are determined by com-paring and analyzing the pressure data

Shock and Vibration 3

42 Experiment Scheme and Design According to thepurpose of the experiment different specifications ofcrackers were selected and put into three different spec-ifications of test devices for blasting test Six experimentschemes were designed and each scheme was tested threetimes e design of the experiment scheme is shown inTable 3

Before blasting all the small holes in the pipe wall wereopened and the blasting power was controlled by con-trolling the strength of the shearing pieces Sampling

frequency was set to 96 kHz and pure cotton cloth was usedto seal holes when the holes needed to be sealed Force testsat different positions of the test device are shown in Figure 6

43 Analysis of Experiment Data According to the experi-mental schemes of liquid CO2 fracturing blasting ZLQ-38300 was selected to blast in CSZZ-822500 and the strengthof shearing piece in the cracker was 300MPa Four sensorswere installed to test the force at different positions thepressure sensor at point A is about 21mm away from theenergy release head of the cracker which keeps level with theventing of the energy release head the measuring points Band C were located at the top of the testing device and themeasuring point D was located at the tail of the testingdevice e stress test data of different positions after liquidCO2 blasting are shown in Figure 7

rough the liquid CO2 fracturing blasting test it can beseen that the pressure at point A was the largest and thepressure was above 200MPa which could meet the re-quirement of coal failure the pressure at measuring points B

1 2 3 4 64 5

Figure 3 Structure of CO2 cracker 1 filling valve 2 heating pipe 3 main pipe 4 sealing gasket 5 shearing piece 6 energy release head

Figure 4 Sketch map of working principle of CO2 cracker

Cracking hole

Crushingzone

Fracturezone

Cracker

Hoop tensile

Gas outletbrvbarEgrave

Coal seam

Vibrationzone

Radial tensile

Figure 5 Sketch map of damage range of CO2 cracker

Table 1 Specifications and parameters of test devices

Bore (mm) Length (mm) Tube thickness (mm)CSZZ-822500 82 2500 65

CSZZ-682500 68 2500 45

CSZZ-482500 48 2500 140


Table 3 Experiment schemes design

Schemes Specifications of testdevices

Specifications ofcrackers

Sealed or notsealed

Number ofsensors

Strength of shearingpiece (MPa)

Spacing between hole wall andenergy release head (mm)

No 1 CSZZ-822500 ZLQ-38300 Sealed 4 300 21No 2 CSZZ-822500 ZLQ-38300 Sealed 2 300 21No 3 CSZZ-822500 ZLQ-38300 No 2 300 21No 4 CSZZ-822500 ZLQ-38300 Sealed 2 200 21No 5 CSZZ-682500 ZLQ-38300 Sealed 2 200 17No 6 CSZZ-482500 ZLQ-38300 Sealed 2 200 10

Table 2 Specifications and parameters of liquid CO2 crackers

Bore(mm)

Length of main pipe(mm)

Cartridge length(mm)

Material of shearingpiece

Strength of shearing piece(MPa)

CO2 capacity(kg)

ZLQ-38300 38 300 15 High strength alloy steel 200300 0234ZLQ-38600 38 600 15 High strength alloy steel 200300 0468

A

B C

Cracker

Measure unitPressure sensor

D

Hole sealing

82

38

100

300

500

500

300

2500

I

I

(a)

A

B

Measure unit

CrackerSensor

19

38

65

4482 95

34561deg

6

(b)

Figure 6 Diagram of force tests at different positions (length unit mm)

Magnitude (105 Pa)

Time (s)64350 64400 64450 64500 64550 64600 64650 64700

ndash2000

2000

0

(a)

Magnitude (105 Pa)

Time (s)64200 64250 64300 64350 64400 64450 64500 64600

50

0

64550

(b)

Figure 7 Continued


C and D was no more than 10MPa which did not meet therequirement of coal failure erefore in the practice theenergy release head of the cracker should be directed to therisk relief area and the radial level of the energy release headof the cracker must be maintained It is suggested that thedistance between the hole wall and the energy release headshould be between 10mm and 15mm For the area with alonger blasting range multisection series blasting can beimplemented

5 Analysis of CO2 Fracturing Blasting of RockBurst System in Jixian Coal Mine

51 Analysis of Rock Burst System in Jixian Coal Minee rock burst in Jixian Coal Mine is serious especially inthe syncline axis of the No 2 mining area in the deep miningarea where gas content is high and multiple rock burstsoccur continuously e magnitude of rock burst monitoredby microseism in the mine is mostly within the range ofML 05ndash25 On March 11 2013 a rock burst with themagnitude of 15 occurred in the lower roadway of the leftfirst working face inWest No 2 Mining Areae rock burstcaused the floor heave of the 15 m roadway outward fromthe coal wall of the working face e range of 210m to270m of the lower roadway was seriously damaged by theimpact and the adjacent working faces were all shockederock burst location was vertically depth of h 700m fromthe surface and the lithology of the floor was sandstoneE 21700MPa and μ 024 According to formulas (5) and(6) the energy released by the ldquo311rdquo rock burst system inJixian Coal Mine was ΔU 53times105 J and the radius of therock burst system is 259m (Figure 8)

When a rock burst occurs after a period of energytransfer exchange supplement and storage of the rock burstsystem the energy reaches the critical energy of the next rockburst and the rock burst will occur again under the influenceof mining engineering erefore in view of the ldquo311rdquo rockburst system of Jixian Coal Mine the liquid CO2 fracturingblasting method is chosen as the priority to relieve thepressure of rock burst system

52 Analysis of CO2 Fracturing Blasting Technology for RockBurst System According to the theoretical analysis ofliquid CO2 fracturing blasting and laboratory experimentresults multiple series blasting was carried out withcrackers with specifications of ZLQ-38300 and ZLQ-38600 e weight of injected CO2 was 017 kg and 026 kgrespectively the diameter of the borehole was 50mm atotal of 5 boreholes were constructed the drilling spacingwas 10 m and the distance between the cracker and theborehole wall was 12mm Hole collapse occurred in theborehole after blasting ere were many broken coalblocks and the hole wall was rough which contributed tothe pressure relief for the rock burst pressure system(Figure 9)

e application of liquid CO2 fracturing blastingtechnology in the prevention and control of rock burstin Jixian Coal Mine shows that CO2 fracturingblasting reduces the stress concentration of rock burstsystem and transfers energy to the deeper part and thereis no open fire in blasting It is a new safe and efficienttechnology to prevent rock burst which can be appliedwidely

Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)

Figure 7Waveforms of stress in different positions of CO2 fracturing blasting (a)e waveform of measuring point A (2013MPa) (b)ewaveform of measuring point B (66MPa) (c) e waveform of measuring point C (26MPa) (d) e waveform of measuring point D(94MPa)


6 Conclusions

(1) It is difficult to accurately predict the ldquotime spaceand intensityrdquo of rock burst but the possibility ofrock burst can be predicted according to the resultsof microseismic monitoring e relationship be-tween rock burst and monitoring data of minemicroseism is established

(2) e stress field of rock burst mine is mostly hori-zontal compression tectonic stress field e rockburst system under the tectonic stress field is

established e energy criterion related to miningdepth system size and medium properties of coaland rock mass is analyzed and the critical energycondition is proposed

(3) According to the magnitude of microseismic mon-itoring the relationship between the energy of rockburst and the radius of rock burst system is deter-mined It is revealed that the failure process of rockburst system is a nonlinear dynamic process of ac-cumulating energy in stable state and releasing en-ergy in unstable state

(a) (b)

Figure 9 Borehole surface before and after liquid CO2 fracturing blasting (a) Before blasting (b) After blasting

37579600

F 12 H = 3m

Le no1 working face

4441

000

Dynamic system for ldquo311rdquo rock burst

1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259

Figure 8 Dynamic system for ldquo311rdquo rock burst in Jixian Coal Mine


(4) e application of liquid CO2 fracturing blastingtechnology in the prevention and control of ldquo311rdquorock burst in Jixian Coal Mine shows that the ap-plication of liquid CO2 fracturing blasting in the rockburst system reduces the stress concentration of therock burst system and makes the energy transfer tothe deeper part and there is no open fire in theblasting process which has a good pressure reliefeffect It can be applied widely in the prevention andcontrol of rock burst in coal mines

Data Availability

e experimental data used to support the findings of thisstudy are included within the article

Conflicts of Interest

e authors declare no potential conflicts of interest withrespect to the research authorship andor publication ofthis article

Acknowledgments

is research was funded by the Research Fund of KeyLaboratory of Mining Disaster Prevention and Control(MDPC201926) the State Key Research DevelopmentProgram of China (2017YFC0804209) and the NationalNatural Science Foundation of China (51604139)

References

[1] H Xie J Wang G Wang et al ldquoNew ideas of coal revolutionand layout of coal science and technology developmentrdquoJournal of China Coal Society vol 43 no 5 pp 1187ndash11972018

[2] C Fan S Li D Elsworth J Han and Z Yang ldquoExperimentalinvestigation on dynamic strength and energy dissipationcharacteristics of gas outburst-prone coalrdquo Energy Science ampEngineering vol 8 no 4 pp 1015ndash1028 2020

[3] Q Qi H Li Z Deng S Zhao et al ldquoStudying of standardsystem and theory and technology of rock burst in domesticrdquoCoal Mining Technology vol 22 no 01 pp 1ndash5 2017

[4] L Dou ldquoInduced shock and control of hard roofrdquo in Pro-ceedings of the 37th International Conference on GroundControl in Ming China Xuzhou July 2018

[5] T Lan C Fan H Zhang et al ldquoSeepage law of injected waterin the coal seam to prevent rock burst based on coal and rocksystem energyrdquo Advances in Civil Engineering vol 2018Article ID 8687108 9 pages 2018

[6] Y Pan ldquoIntegrated study on compound dynamic disaster ofcoal-gas outburst and rockburstrdquo Journal of China Coal So-ciety vol 41 no 01 pp 105ndash112 2016

[7] Y Jiang Y Pan F Jiang L Dou and Ju Yang ldquoState of the artreview on mechanism and prevention of coal bumps inChinardquo Journal of China Coal Society vol 39 no 2pp 205ndash213 2014

[8] Q Qi Z Ouyang H Shankun H Li X Li and N ZhangldquoStudy on types of rock burst mine and preventionmethods inChinardquo Coal Science and Technology vol 42 no 10 pp 1ndash52014

[9] Y Jiang and Y Zhao ldquoState of the art investigation onmechanism forecast and control of coal bumps in Chinardquo

Chinese Journal of Rock Mechanics and Engineering vol 34no 11 pp 2188ndash2204 2015

[10] T Lan H Zhang J Han and W Song ldquoStudy on therockburst mechanism based on geo-stress and rock massenergy principlerdquo Journal of Mining amp Safety Engineeringvol 29 no 06 pp 840ndash844 2012

[11] Z Ma R Gu Z Huang G Peng L Zhang and D MaldquoExperimental study on creep behavior of saturated dis-aggregated sandstonerdquo International Journal of Rock Me-chanics and Mining Sciences vol 66 pp 76ndash83 2014

[12] M Birk R Dapp N V Ruiter and J Becker ldquoGPU-basediterative transmission reconstruction in 3D ultrasoundcomputer tomographyrdquo Journal of Parallel and DistributedComputing vol 74 no 1 pp 1730ndash1743 2014

[13] Y Ju J Zheng M Epstein L Sudak J Wang and X Zhaoldquo3D numerical reconstruction of well-connected porousstructure of rock using fractal algorithmsrdquo ComputerMethods in Applied Mechanics and Engineering vol 279pp 212ndash226 2014

[14] H Zhao L Yang Li Kun and Y Zhao ldquoDesign and ex-perimental research of a multifunctional loading system basedon industrial CTrdquoMachine Tool and Hydraulics vol 46 no 4pp 109ndash115 2018

[15] L Dong J Wesseloo Y Potvin and X Li ldquoDiscriminationof mine seismic events and blasts using the Fisher classifiernaive bayesian classifier and logistic regressionrdquo Rock Me-chanics and Rock Engineering vol 49 no 1 pp 183ndash2112016

[16] F Gan X Wang M Wang and Y Kang ldquoExperimental in-vestigation of thermal cycling effect on fracture characteristicsof granite in a geothermal-energy reservoirrdquo EngineeringFracture Mechanics vol 235 Article ID 107180 2020

[17] G Bai X Zeng X Li X Zhou Y Cheng and J LinghuldquoInfluence of carbon dioxide on the adsorption of methane bycoal using low-field nuclear magnetic resonancerdquo Energy ampFuels vol 34 no 5 pp 6113ndash6123 2006

[18] V Frid ldquoRockburst hazard forecast by electromagnetic ra-diation excited by rock fracturerdquo Rock Mechanics and RockEngineering vol 30 no 4 pp 229ndash236 1997

[19] M Alber R Fritschen M Bischoff and T Meier ldquoRockmechanical investigations of seismic events in a deep longwallcoal minerdquo International Journal of Rock Mechanics andMining Sciences vol 46 no 2 pp 408ndash420 2009

[20] M Geng Z Ma P Gong et al ldquoAnalysis of the effect onpressure relief by the pressure relieving hole layouts on highstress coal roadwayrdquo Journal of Safety Science and Technologyvol 11 pp 5ndash10 2012

[21] C Fan M Luo S Li H Zhang Z Yang and Z Liu ldquoAthermo-hydro-mechanical-chemical coupling model and itsapplication in acid fracturing enhanced coalbed methanerecovery simulationrdquo Energies vol 12 no 4 p 626 2019

[22] Z Ouyang ldquoApplication and mechanism of mine stratapressure pumping prevention with multi-stage blastingpressure releasing technologyrdquo Coal Science and Technologyvol 10 pp 32ndash36 2014

[23] P Konicek K Soucek L Stas and R Singh ldquoLong-holedestress blasting for rockburst control during deep under-ground coal miningrdquo International Journal of Rock Mechanicsand Mining Sciences vol 61 pp 141ndash153 2013

[24] T Lan C Fan S Li et al ldquoProbabilistic prediction of minedynamic disaster risk based on multiple factor pattern rec-ognitionrdquo Advances in Civil Engineering vol 2018 Article ID7813931 6 pages 2018


[25] J Liu L Xie Y Yao Q Gan P Zhao and L Du ldquoPreliminarystudy of influence factors and estimation model of the en-hanced gas recovery stimulated by carbon dioxide utilizationin shalerdquo ACS Sustainable Chemistry amp Engineering vol 7no 24 pp 20114ndash20125 2019

[26] C Fan D Elsworth S Li L Zhou Z Yang and Y Songldquoermo-hydro-mechanical-chemical couplings controllingCH4 production and CO2 sequestration in enhanced coalbedmethane recoveryrdquo Energy vol 173 pp 1054ndash1077 2019

[27] X Zhou J Men D Song et al ldquoResearch on increasing coalseam permeability and promoting gas drainage with liquidCO2 blastingrdquoChina Safety Science Journal vol 02 pp 60ndash652015


[24 25] In order to study the structure system and energycharacteristics of rock mass under rock burst a rock burstsystem based on the tectonic stress field is established eenergy magnitude and spatial location of rock burst systemare determined by microseismic monitoring technologyBased on the established rock burst system the liquid CO2fracturing blasting technology is put forwarde practice ofpreventing and controlling rock burst in coal mine showsthat the CO2 fracturing blasting reduces the stress con-centration of the rock burst system and transfers the energyto the deeper part It is a new safe and efficient technologyto prevent rock burst

2 Analysis of Energy in Rock Burst System

21 Establishment of Rock Burst System e complexity ofrock burst is related to the heterogeneity anisotropy anddiversity of influencing factors of the structure system of coaland rock mass e stress and energy of coal and rock masssystem are the basic conditions and the mining engineeringactivities are the induced conditions More than 85 of theenergy causing rock burst comes from surrounding rocke coal mainly provides the medium condition for rockburst e space of energy storage-exchange-release of coaland rock mass system with rock burst should have a certainscale which cannot be infinitely great or infinitely small andshould be related to the structure stress and energy level inthe coal and rockmass system Amodel of rock burst systemwhich reflects the relation of the coal and rock mass systemand rock burst is established e shape of the model isassumed to be spherical hereinafter referred to as the rockburst system (Figure 1)

22Analysis ofEnergy inRockBurst System According to thetheory of elasticity a representative element of rock mass atthe depth H in the crustal rock mass is subjected to three-dimensional stress and the unit body is in the state of elasticdeformation (Figure 2) e elastic energy of unit volumeaccumulation under in situ stress field can be expressed bythe following formula

U0 12E

σ21 + σ22 + σ23 minus 2μ σ1σ2 + σ2σ3 + σ1σ3( 11138571113960 1113961 (1)

where U0 represents elastic energy accumulated in unitvolume J σ1 σ2 and σ3 represent principal stress in threedirections of any unit MPa E represents modulus ofelasticity MPa μ represents Poissonrsquos ratio

en the energy for the spherical rock burst system canbe expressed

U 12E

σ21 + σ22 + σ23 minus 2μ σ1σ2 + σ2σ3 + σ1σ3( 11138571113960 111396143πR

3

(2)

where U represents the energy of rock burst system J Rrepresents the radius of rock burst system m

According to the in situ stress measurement results ofsome rock burst mines in China the stress fields in most(almost all) areas are horizontal compressive tectonic stress

fields e change of maximum principal stress direction andmagnitude in most parts of China is due to the collision of theChinese mainland plate by the India plate and Eurasian plateand the subduction of the eastern Pacific plate and thePhilippines plate to Eurasia In the vast majority of areas thein situ stress is a three-dimensional unequal compressivestress field dominated by horizontal stress e magnitudeand direction of the three principal stresses vary with spaceand time so they are unstable stress fields e measured datashow that the vertical stress is basically equal to the weight ofoverlying strata e deviation between the vertical stressdirection and the vertical direction is generally no more than20deg e measured data show that there are two principalstresses in the horizontal or nearly horizontal plane in most(almost all) regions and the angle between the two principalstresses and the horizontal plane is generally nomore than 30deg

e dip angles of the maximum and minimum principalstresses σ1 and σ3 are near horizontal direction e max-imum horizontal stress σ1 is generally larger than the verticalstress σ2 and there are certain linear relationships betweenσ1 σ2 and σ3 and self-weight stress cH and they are usuallyσ1asymp 2cH σ2asymp cH and σ1asymp 07cH e energy of rock burstsystem related to self-weight stress can be obtained bysubstituting them into formula (2)

U 2π3E

(549 minus 82μ)c2H

2R3 (3)

Radius

Boundaryof the system

Core of rockburst system

Figure 1 Schematic diagram of ldquosphericalrdquo type rock burst system

σ2

σ3

σ1

σ2

σ3

σ1

y

z

xO

H

M

Representativeelement

Ground level

Figure 2 Representative element under the action of three-di-mensional stress




UZ 2π3E


1113888 1113889c2H

2R3

UG 2π3E

(549 minus 82μ)c2H

2R3

⎧⎪⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎪⎩

(4)

en


2H

2R3

3E(1 minus μ)

(5)


R

3E(1 minus μ)ΔU

2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

31113971

(6)


ΔU 101695ML+318 (7)


R


2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

3

11139741113972

(8)


Fracturing Blasting




Fracturing Blasting









1 2 3 4 64 5



Cracking hole

Crushingzone

Fracturezone

Cracker

Hoop tensile


Coal seam

Vibrationzone

Radial tensile




CSZZ-682500 68 2500 45

CSZZ-482500 48 2500 140





Sealed or notsealed

Number ofsensors





Bore(mm)





CO2 capacity(kg)


A

B C

Cracker


D

Hole sealing

82

38

100

300

500

500

300

2500

I

I

(a)

A

B

Measure unit

CrackerSensor

19

38

65

4482 95

34561deg

6

(b)


Magnitude (105 Pa)

Time (s)64350 64400 64450 64500 64550 64600 64650 64700

ndash2000

2000

0

(a)

Magnitude (105 Pa)

Time (s)64200 64250 64300 64350 64400 64450 64500 64600

50

0

64550

(b)

Figure 7 Continued








Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)



6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References

































UZ 2π3E


1113888 1113889c2H

2R3

UG 2π3E

(549 minus 82μ)c2H

2R3

⎧⎪⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎪⎩

(4)

en


2H

2R3

3E(1 minus μ)

(5)


R

3E(1 minus μ)ΔU

2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

31113971

(6)


ΔU 101695ML+318 (7)


R


2π 102μ2 minus 1269μ + 4491113872 1113873c2h2

3

11139741113972

(8)


Fracturing Blasting




Fracturing Blasting









1 2 3 4 64 5



Cracking hole

Crushingzone

Fracturezone

Cracker

Hoop tensile


Coal seam

Vibrationzone

Radial tensile




CSZZ-682500 68 2500 45

CSZZ-482500 48 2500 140





Sealed or notsealed

Number ofsensors





Bore(mm)





CO2 capacity(kg)


A

B C

Cracker


D

Hole sealing

82

38

100

300

500

500

300

2500

I

I

(a)

A

B

Measure unit

CrackerSensor

19

38

65

4482 95

34561deg

6

(b)


Magnitude (105 Pa)

Time (s)64350 64400 64450 64500 64550 64600 64650 64700

ndash2000

2000

0

(a)

Magnitude (105 Pa)

Time (s)64200 64250 64300 64350 64400 64450 64500 64600

50

0

64550

(b)

Figure 7 Continued








Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)



6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References




































1 2 3 4 64 5



Cracking hole

Crushingzone

Fracturezone

Cracker

Hoop tensile


Coal seam

Vibrationzone

Radial tensile




CSZZ-682500 68 2500 45

CSZZ-482500 48 2500 140





Sealed or notsealed

Number ofsensors





Bore(mm)





CO2 capacity(kg)


A

B C

Cracker


D

Hole sealing

82

38

100

300

500

500

300

2500

I

I

(a)

A

B

Measure unit

CrackerSensor

19

38

65

4482 95

34561deg

6

(b)


Magnitude (105 Pa)

Time (s)64350 64400 64450 64500 64550 64600 64650 64700

ndash2000

2000

0

(a)

Magnitude (105 Pa)

Time (s)64200 64250 64300 64350 64400 64450 64500 64600

50

0

64550

(b)

Figure 7 Continued








Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)



6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References


































Sealed or notsealed

Number ofsensors





Bore(mm)





CO2 capacity(kg)


A

B C

Cracker


D

Hole sealing

82

38

100

300

500

500

300

2500

I

I

(a)

A

B

Measure unit

CrackerSensor

19

38

65

4482 95

34561deg

6

(b)


Magnitude (105 Pa)

Time (s)64350 64400 64450 64500 64550 64600 64650 64700

ndash2000

2000

0

(a)

Magnitude (105 Pa)

Time (s)64200 64250 64300 64350 64400 64450 64500 64600

50

0

64550

(b)

Figure 7 Continued








Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)



6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References





































Time (s)75900 75950 76000 76050 76100 76150 76200 76250

0

20

10

76300

Magnitude (105 Pa)

(c)

Time (s)64335 64340 64345 64350 64355 64360 64365 64380

0

100

50

Magnitude (105 Pa)

64370 64375

(d)



6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References































6 Conclusions





(a) (b)


37579600

F 12 H = 3m

Le no1 working face

4441

000


1

37579600 37580000 444100037580400

4440

600

234678

9

5

Le no2 working face

Le no3 working face

F 11 H=18m

4440600 37580000 37580400

259




Data Availability




Acknowledgments


References
































Data Availability




Acknowledgments


References































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