CGS Cross Canada Presentation Spring Tour 2013 and De… · Syncrude Geotechnical Engineering...

Syncrude Geotechnical Engineering

Securing Canada’s Energy Future

CGS Cross Canada Presentation Spring Tour 2013

Compaction & Design Tips for Construction of Dam Fills Year‐Round at rates up to 25 Million m3/year

Bob Cameron, B.A.Sc., M.A.Sc., P. Eng.Principal Geotechnical Engineer, Syncrude Canada Ltd.

Prepared with assistance from Ana Pastolero, E.I.T.

Tailings Storage

Plant Site

SouthWest Dam•Construction: 1996 to 2009 (13 years)•Maximum Rate: 25 Mm3/year•114 million m3 of engineered fill and 37 million m3 of existing uncontrolled fill•Dimensions: Length‐2.5km, Height‐75m

Highway #63 Berm•Construction: 1992 to 1994 (2.5 years)•Maximum Rate: 17 Mm3/year•42 million m3 of engineered fill and 40 million m3 of existing uncontrolled fill•Dimensions: Length‐2.5km, Height‐63m

2

Future Tailings Storage

Plant Site

NorthSouth Dyke•Construction: 2007 to 2012 (5 years)•Maximum Rate: 15 Mm3/year•76 million m3 of engineered fill •Dimensions: Length‐2.7km, Height‐37m

EastWest Dyke•Construction: 2007 to 2017 (10 years)•Maximum Rate: needs to be 50 Mm3/year•180 million m3 of engineered fill •Dimensions: Length‐4km, Height‐61m

3



Presentation IntentTo describe the iterative processes involved with balancing the Design of Earth Dam Structures with year‐round Construction

rates of up to 25 Mm3/year due to Business Needs.

(No tailings sand dykes will be discussed in this presentation)

2) DesignDam Geometries Dam Footprint

Abutment ConsiderationsMaterial Parameters

4) Quality Control / Quality AssuranceMonitoring Processes

Regulatory DocumentationDesign Tolerances

Construction SpecificationsConfirmatory Testing

Geotechnical Review Board

3) Year‐Round ConstructionSummer ConstructionWinter Construction

Material Selection / AvailableClean‐up Requirements

Settlement Considerations

5) Testing / AnalysisField testing to confirm Design Assumptions

Lab testing to confirm Field ValuesAnalysis of Material Parameters for Dam

Geometries to meet Design Intent

1) Business NeedsTime Sensitive Tailings ManagementOverburden Material Availability

Large Scale Mining Operations Equipment

4



Business NeedDesign and Construct large fill volume, time‐critical tailings retaining structures considering:

‐ site conditions (e.g. foundation treatment / base preparations, and abutment considerations)

and

‐ minable ore requirements (e.g. dig limits)

~80m high Mining Pitwall Dam AbutmentDam Foundation Treatment ‐ Base of Feed In‐Situ 2H:1V sloping of the Dam Abutment

5Foundation and Abutment Treatment



Foundation Treatment/Base PreparationBase Preparation is not as elaborate as most industry‐standard dams since SCL dams are generally designed: •To be very wide quasi‐homogenous earthen dams with no grout curtains or grouted abutments

•To have relatively short operational lives (~ 10 years)•With multiple lines of defense:

– With large (100s of meters) external downstream or upstream sand filters

– With large (15 to 20 meters) internal filters

– Or other 2nd lines of defense

Foundation Treatment 6



Foundation Treatment/Base PreparationBase Preparation generally involves:

•De‐watering / De‐slopping / De‐icing to ensure the design pore pressure parameters are met• Removal of softened pond muds and softened paleosol/limestone which could cause

instability due to pore water pressure above design•Further construction considerations for:– management of expanded rich feed which could cause low density zones by:

• removal of all rich feed• bulk cleaning the softest rich feed away with re‐cleaning the foundation in front of the

advancing 2 to 3m of lifts to prevent gas exsolution• elaborate gravel weighting with venting pipes with later grouting for civil foundation

work (e.g. manhole bases) • NOTE:mud slabs do not work

– evaluation of limestone fractures/fissures or watersands which may require design considerations such as:

• upstream engineered fills to seal• generous widths

– existing dump fills:• incorporated into the design when applicable

Foundation Treatment 7



Foundation Treatment /Base Preparation QA/QC

Geotechnical Construction Monitor approves the dam foundation quality

Foundation Treatment QA/QC

Geotechnical Construction Monitor documents:•GPS coordinates of the approved area•Elevation of the approved base•Material type at the approved base (in‐situ or fill, type of fill, geology of in‐situ)•Material type of first constructed lift•Date of approval•Monitor approving•Pictures•Summary Base Preparation drawing

8



Pit Wall Abutment Considerations• Low stress zones in the abutment due to movement along In‐Situ pond muds or rich

feed addressed by:• Delayed & Segmental mining with staged construction of compacted lifts

• Continuous In‐Situ units with preferential seepage paths and/or continuous joint issues addressed by:

• Flaring out compacted fills to increase the seepage path length and/or blind off the permeable units

• Key‐in In‐Situ sloping of the abutment tie‐in to change joint seepage paths • Differential settlement of In‐situ units vs. engineered fills

• Abutment fill geometry designed to be overloaded and so taking into consideration settlement parameters

EW Dyke

NS Dyke

Mining Pitwall

Abutment

Mining Pitwall

Abutment

Abutment Treatment

2km

9



Pit Wall Abutment Considerations

Abutment Treatment

Abutment In‐situ sloping key‐in of mining pitwall for a longer seepage path length

SI 110071

10




Abutment Treatment

KccKcb

KcaKcw

F15

F9WF21F10F12

F1211W

F12F11F7

F6

F11F25F63F61F63

41WF34F32F33

HO1 0.0

32.8

65.6

98.4

131.2

164.0

196.9

229.7

262.5

-1312 -1148 -984 -820 -656 -492 -328 -164 0 164 328 492 656 820 984 1148 13120

10

20

30

40

50

60

70

80-40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40

Dept

h (ft

)

Incremental Displacement From Set 1 (August 16, 2011) in mm

Dept

h (m

)

Incremental Displacement From Set 1 (August 16, 2011) in SI units

SI VP 110071 - A EW Dyke 1 East Abutment SI - Incremental Displacement52938.84N, 48052.56E, 296.5m Elevation A(-ve) Azimuth = 262o

16-Aug-1123-Aug-1131-Aug-116-Sep-1113-Sep-1114-Sep-1115-Sep-1116-Sep-1118-Sep-1121-Sep-1124-Sep-1127-Sep-1130-Sep-113-Oct-117-Oct-119-Oct-1112-Oct-1115-Oct-1118-Oct-1124-Oct-1127-Oct-1130-Oct-113-Nov-116-Nov-119-Nov-1112-Nov-1115-Nov-1120-Nov-1123-Nov-1126-Nov-111-Dec-118-Dec-1120-Dec-113-Jan-1226-Jan-12

Downslope Upslope

286.5m

226.5m

236.5m

246.5m

256.5m

266.5m

276.5m

displacement & v elocityv elocity & acceleration

lowmedhighconcern lev el: highest

Marine Oil Sands

Estuarine Oil Sands

Devonian

Clearwater

Fluvial

3 to

7.5

mm

7.5

to 1

5mm

15 to

18m

m

(> 1

8mm

)

100

to 2

50 U

nits

250

to 5

00 U

nits

500

to 6

00 U

nits

(>60

0) U

nits

0 to

100

Uni

ts0

to 3

mm

11


Securing Canada’s Energy Future Abutment Treatment


KccKcb

KcaKcw

F15

F9WF21F10F12

F1211W

F12F11F7

F6

F11F25F63F61F63

41WF34F32F33

HO1 0.0

32.8

65.6

98.4

131.2

164.0

196.9

229.7

262.5

-1804 -1640 -1476 -1312 -1148 -984 -820 -656 -492 -328 -164 0 165 329 493 657 821 985 11490

10

20

30

40

50

60

70

80-55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40

Dept

h (ft

)

Cmulative Displacement From Set 1 (August 16, 2011) in mm

Dept

h (m

)

Culumative Displacement From Set 1 (August 16, 2011) in SI units

SI VP 110071 - A EW Dyke 1 East Abutment SI - Cumulative Displacement52938.84N, 48052.56E, 296.5m Elevation A(-ve) Azimuth = 262o

Downslope Upslope

286.5m

226.5m

236.5m

246.5m

256.5m

266.5m

276.5m Marine Oil Sands

Estuarine Oil Sands

Devonian

Clearwater

Fluvial

24mm on Marine at 94.3mfrom mined pitwall face

28.2mm on PM at 231m from mined pitwall toe

Pond Mud slickensides in core

12



For construction of large volume dams at rates of 25 Mm3/year:

Foundation treatment involves:•Cleaning the base to meet design intent by removal of slop and softened In‐situ units (critical areas reserved for premium construction conditions – summer)•Management of low density zones (e.g. rich feed)•Design against preferential seepage paths (e.g. limestone fractures/fissures, watersands) with generous widths or sealing with upstream engineered fills •QA/QC Documentation

Foundation and Abutment Treatment

Summary ‐ Foundation and Abutment Treatment

Abutment treatment involves:•Designing for long seepage path lengths with In‐situ cut‐only key‐ins (critical area reserved for premium construction conditions – summer)•Designing for differential settlement of In‐situ units vs. engineered fills•Management of low stress zones due to movement along weak units (e.g. pond muds) and gas exsolution of rich feed oil sand

In‐situ sloping key‐in of mining pitwall for improved abutment tie‐in

13



Business NeedDesign and Construct large fill volume, time‐critical tailings retaining structures by using readily available overburden materials above ore.

Overburden Materials for Engineered Fill

Oil Sand Ore

Materials ‐ Availability 14



Mining Construction Material

Materials ‐ Selection

The intent is to split the pitwall benches such that the mined material for engineered fill is of similar SPD, ductility, and compatibility.

15

*


Securing Canada’s Energy Future Materials ‐ Selection

Possible Contamination At the Shovel Face

Base of Feed

Oil Sand Ore

Ponded Water

Material for Engineered

Fill

Large Icicles

Regrowth Brush

Frozen Face

Frozen Cap

Padded non‐spec material

Berm of non‐spec material

Slop filled ditch

Siltstones

16



Possible Contamination At the Shovel Face


White 1‐2mm thick vein ice is a sign of frozen ground.

Black micro‐thin discontinuousice <1mm is a sign of frozen ground.

Icicles on the face is unacceptable and must be removed.

17



QA/QC: Checking for Frost in Shovel Faces

Materials – Selection QA/QC

Mining fill material during winter that meets the design intent of the structure is required when constructing at rates of 25Mm3/year.

Some checks:•A ledge under the shovel face (an "overhang” of frozen material) is a good indication of frost thickness•Comparing the frozen material above with the non‐frozen material below if similar materials•Asking the shovel operator if they "feel" it as they dig•Looking for black ice (very thin film) or ice crystals/flakes.

• These melt (sublimate) very fast so it is important to look at a fresh face

•Feeling how cold the material is ‐ The Pain Test•Using thermometers

• Salinity can affect readings

A mining shovel pit in winter

• Taking bag samples from the fresh face and melting on a truck heater/defrosting• Fresh test‐pitting above the shovel with a backhoe to determine frost depth and catching ice crystals before sublimation

18



Material Tolerances for 25 Mm3/year Construction

Allowable material tolerances at the borrow source for compacted 1m lifts (SC‐SM)


Allowable material tolerances at the borrow source for compacted 0.75m lifts (CH)

• To deliver on such high construction rates, a zero tolerance method concerning engineered fill is not feasible.

• The tolerances may need review with respect to critical areas in the dam design.• The dam designs use generous widths to accommodate non‐premium material

conditions.

19



Material Selection – QA/QC ConsiderationsGeotechnical Construction Monitors activities:

• Inspection at the shovel face is required every 2 to 6 hours due to the changing geology and changing site conditions• Considerations during summer – safety berms, regrowth brush, etc.• Considerations during winter – frozen soil, etc.

• Providing input to the mining of the face so the mined material meets the design intent at the structure such as:• Utilizing the engineered fill tolerance tables• Full face raking with electric shovels for blending the material• Top and bottom cuts to selectively mine with hydraulic shovels• Etc.

• Documentation of material quality at the borrow source highlight:• What is seen (e.g. shovel mining a 10m high face with no ponded water on the bench

above)

• The quality (e.g. good quality CH for compacted 0.75m lifts in face)

• Where the fills are going (e.g. engineered fill going to the appropriate structure)

Materials – Selection QA/QC 20



Compacted 1m Lifts (SC‐SM)

Materials – Properties and Selection

2010 Data

21

35 of 43 samples are non‐plastic



2011 DataEast West Dyke 1650 Interior Shell

3/4m lift Mid-Bench Kc Clays (Kcc)"1650 kg/m

3" Material - Proctor Data (April 12, 2011 to Nov 7, 2011)

Moisture Content (%)0 5 10 15 20 25 30 35

Dry

Den

sity

(kg/

m3 )

1400

1500

1600

1700

1800

1900

2000

2100

2200

% C

ompa

ctio

n

90

100

110

120

130

Zero Air Void LineGs=2.75 S=1.00

Troxler Data (Kcc) n=612Troxler Data (Kcc) - Moisture Corrected (+4.9%)Standard Proctor - (Kcc) n=11Avg SPDD & OMCAvg Troxler Data - Moisture Corrected

Syncrude Canada Ltd. Geotechnical Engineering Geotech Lab Prepared By : Kent Wong Date : March 26, 2012

Average CorrectedField Dry Density1718 kg/m3 (104.1%)

Avg O

pt Mo

istur

e : 20

.5%

Avg Std Proctor : 1610 kg/m3, n=11

Avg A

ll Lab

Nat

Moist

ure :

16.2%

4.3%

Dry

of Op

timum

115% SPDD = 1897 kg/m3

Spec > 105% ( 1732 kg/m3)

100% SPDD = 1650 kg/m3 (Oct 2008)

Average Correction:Troxler Sample Natural Lab Moisture Content - Troxler Measured Field Moisture Content = 4.9%

% Corrected Field SPDD>115% : 1.6%+

+(>5% Review)% Corrected Field SPDD<105% : 55.9%% Corrected Field SPDD<100% : 13.9%* *(10% or less allowable)

Materials – Properties and Selection 22

Compacted 0.75m Lifts –Kcc (CH)

2011 Data


Securing Canada’s Energy Future Materials – Properties and Selection 23

Compacted 0.75m Lifts –Kca/Kcb (CH)

2011 Data



1300

1400

1500

1600

1700

1800

1900

10 15 20 25 30

Moisture Content (%)

07289 Mod.07289 Std09620 Mod.21767 Mod.21771 Mod.21771 Std.21772 Mod.22205 Mod.22205 Std.22460 Std.Field DataS i 12

Air Content 5%

10%

0%

Mid‐Bench Kc Clays (CH) – Lab and Field DataField Testing Intent:•To determine what Standard Proctor Dry Density (SPD) value to use for the well dry‐of‐optimum high plastic dispersive clays

Findings:• Modified Standard Proctor

Densities (MSPD) = 1.15xSPD for high plastic clays= 1.08xSPD for sandy fill

• 105% SPD was chosen because:• The chunky, blocky fill had to

be broken down• To address the dispersive

nature of the material• Troxler/Nuclear densiometer

average field fluid correction of approximately 5%

• Material is dry of optimum

Field and Lab Testing – Placement and Compaction

SPDD

24



Loose 2m or 5m Lifts – Pl, Kc‐clays, Kcw, Marine Oilsand

Fills used for buttressing stability support rather than seepage control.

Density controlled in the field through placement specifications.

Considerations on settlement further discussed in this presentation.

Materials – Properties and Semi‐Selection 25



Engineered Fills

Materials – Properties 26



Testing/Analysis for Design/Construction

Materials – Lab and Field Testing 27

Many of the papers can be found in the 38th, 48th, and 54th Canadian Geotechnical Conference publications (Canadian Geotechnical Society)



Testing/Analysis for Design/Construction

Materials – Lab and Field Testing 28



Summary – Material Selection

Material Selection

For construction of large volume dams at rates of 25 Mm3/year:

Mine for engineered fills of similar density, ductility, and compatibility:•Compacted 1m lifts of clayey sand – silty sand (SC‐SM) for seepage control•Compacted 0.75m lifts of high plastic clay (CH) for seepage control•Loose, semi‐select 5m lifts (moving towards 2m lifts) of readily available mine overburden fills for buttressing support•Still confirm that the fill is suitable

• Not too wet/dry/sandy/clayey/ chunky/indurated

Robust dam design to accommodate reasonable material tolerance.•Loose snow, Frozen soil, Siltstones

Knowledgeable Geotechnical Construction monitors, Dam Design Engineers, and Operations Representatives working together to optimize mining especially during challenging winter conditions.

29



Business NeedDesign and Construct large fill volume, time‐critical tailings retaining structures by using readily available large scale mining equipment.

Dozer cleaning the lift

High plastic chunky clay fills (CH)

Grader cleaning in front of the advancing lift

Placement and Compaction 30



Highway Berm – Single Thick Lift Test Strips

Field Testing Intent:•To determine the possibilities with constructing lifts ranging from 1.0m to 2.5m thick with mostly clayey sand and silty sand based fills.•Further testing (e.g. seepage test pits, slug tests) discussed later

Field Testing – Material Selection and Placement and Compaction

Answer:

31

Answer: To a depth of 1.0mand 2 passes with a D11 dozer or

equivalent to spread the lift


Securing Canada’s Energy Future Field Testing – Placement and Compaction

Compaction Equipment – Haul Trucks

Compacted lift with almost no rut and roll

240T haul truck

Field Testing Intent:•To determine what truck type worked best for the compaction performance required•Rut and Roll is useful for self‐proofing bad fills out but is not useful for monitoring densityFindings:

• Mechanical drive works well• DC‐drive truck motors would

burn out• DC‐drive trucks could not get

out of ruts• AC‐drive trucks converted from

DC‐drive trucks could not all drive the 5km/hr required compaction speed for extended periods

• Some truck steering would heat up• It was necessary to have trucks pulled out of the truck‐and‐shovel ore mining fleet or rental

trucks for dedicated uniform compaction activities on the dam structures

32



Field and Lab Testing Intent:•To determine the possibilities with constructing multiple lifts ranging from 0.75m to 1.5m thick with clayey sand and silty sand fills.•To review achievable density, compaction methodology, lift fabric quality, determine the impact of allowable defects, and measure hydraulic conductivity. •Other tests: field falling head tests in standpipes and slug tests

Permeability and Seepage Studies on 1m Compacted Lifts of Clayey Sand and Silty Sand (SC‐SM)

1.6m wide, 8.0m long, 2.5m deep

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

90.0 91.0 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 101.0 102.0 103.0 104.0 105.0

Per

mea

bilit

y (c

m/s

ec)

Percentage of Selected Standard Proctor Density (1800 Kg/m3)

2011 East West Dyke 1 Main Shell Permeability Testing

EW Historic Data

2011 Data

Trend Line

Min

imum

Spe

c fo

r Mai

n Sh

ell D

ensi

ty =

95.

0% S

PD .

Mai

n Sh

ell A

vg F

ield

den

sity

for 2

011

= 1

02.3

% S

PD

5x10-6 cm/sec Main Shell Design

1.0x10-6 cm/sec Main Shell

1.0x10-7 cm/sec Main Shell Design Low End

Permeability vs. % SPDD for Compacted 1m LiftsAt 95% design compaction - k = 5 x 10E-8 cm/sec

At average field density ~102% - k = 1 x 10E-7 cm/secTrend shows higher compaction then lower permeability

Compacted 1m Lifts

Field Testing – Material Selection and Placement and Compaction : Design Consideration – Permeability

Field Testing: Lab Testing:

Answer:

33

Answer: Design Kh

Vertical Kv

Likely Kh



Kc‐clay Fill Placement

Field Testing Intent:•To determine the possibilities with constructing with high plastic clay fills•To review achievable density, compaction methodology, lift fabric quality, …

Compacted 0.75m Lifts

Chunky, blocky Kc‐clay

D10, D11, or other dozer of equivalent

size

Placement and Compaction

Answer:

34



Field and Lab Testing Intent:•To determine the possibilities with constructing multiple lifts ranging from 0.75m to 1.5m thick with high plastic clay fills and with clayey sand and silty sand fills.•To review achievable density, compaction methodology, lift fabric quality, measure hydraulic conductivity, …

Permeability and Seepage Studies on dry‐of‐optimum high plastic (CH) Compacted Lifts

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.40 6 12 18 24 30 36 42 48

Time since filling (hours)

Test Pit #1 (1.5m lifts)Test Pit #3 (1.0m lifts)Test Pit #4 (1.0m lifts)Test Pit #8 (1.0m lifts)Test Pit #5 (0.75m lifts)Test Pit #6 (0.75m lifts)Test Pit #7 (0.75m lifts)

Field Testing – Material Selection and Placement and Compaction : Design Consideration – Permeability

Answer:Less than or equal

to 0.75m

35

Compacted 0.75m CH lifts shown to swell and plug up if flow is stopped.Designed to be backed with the compacted 1.0m SC‐SM lifts to act as a quasi‐filter.



Lab Testing Intent:•To determine the potential dispersive qualities of the readily available fill materials when exposed to tailings fluid•Considerations applied to design of future tailings retaining structures

Dispersive vs. Erosive

Design Considerations – Piping 36

Answer:

Kc‐clay fills (CH) shown to be dispersive.

Designed to have a high density in the field and usually backed with the compacted 1.0m SC‐SM lifts to act as a quasi‐filter to any defects in the clays.



Lab Testing Intent:•To determine potential strength characteristics for varying Kc fills mixed at varying ratios of dry chunks and wet clay•Parameters applied to analysis for future similar structures

Design Considerations – Shear Strength 37

Total Stress:

SLIDING

CROSS‐BEDDED

Effective Stress:Strength Parameters for Kc‐clay (CH) Fill

How will chunky partially saturated dry of optimum fills act?



Loose 5m thick lifts Placement


Field Testing Intent:•To determine the possibilities with constructing with loose, semi‐select Pl, Kc‐clays, Kcw, Marine Oilsand pushed in 5m thick lifts used for stability support/buttressing•To review achievable density, compaction methodology, and lift fabric quality•Design: used to support the compacted engineered lifts when the foundation consists of weak In‐situ units such as pond muds (construction optimization: reduces costs)

Haul truck dumping semi‐select fill Dozer pushing a 5m lift

38



Field and Lab Testing Intent:•Loose 5m lifts are not compaction tested during construction•The chunky fabric observed from 2 to 5m provides evidence towards dropping the lift thickness to 2m (still untested during construction)

2m Compacted zone at the surface of the previously constructed 5m lift (top 2

meters).

3m Loose, uncompacted zone at the base of the 5m

lift (bottom 3 meters).

2m Compacted zone not shown due to trench bench

Field Testing ‐ Placement and Compaction

Loose 5m Lift Profiles

39

(Buttressing Fills, Truck Traffic Only)



Lab Testing Intent:•To determine the maximum dry density and optimum fluid content for various bitumen grades for reject oil sand fills ‐ soils with two fluids•Basis of the single value 1800 kg/m3 for the maximum SPDD for compacted 1m lift fills to accommodate monitoring for construction rates of 25 Mm3/year

Compaction with Respect to Bitumen%

Lab Testing – Materials – Selection 40



Lab vs. Field (Troxler) Fluid Content Correlation

Field Monitoring and Lab Testing Intent:•To determine the moisture content difference and the impact to the actual density•Basis of the 105% of SPDD construction specification to account for the 3.6% lower moisture content reading of the field vs. the lab which is tracked over time (currently about 5% lower for Kc clays) Do not correct when the corrections are small

For soils with no bitumen like Kc clays

QA/QC on Field Monitoring 41



Corrections to Nuclear Densometers for dry density

Element

Hydrogen (H) 19 .0 0 .33Boron (B) 109 .2 750 .0Carbon (C) 120 .6 0 .34Nitrogen (N) 139 .5 1 .9Oxygen (O) 158 .5 0 .2Sodium (Na) 224 .9 0 .53Magnesium (Mg) 237 .4 0 .63Aluminum (Al) 262 .8 0 .23Silicon (Si) 273 .3 0 .16Phosphorous (P) 300 .8 0 .19Sulfur (S) 311 .1 0 .51Chlorine (Cl) 343 .3 33 .0Potassium (K) 378 .0 2 .1Calcium (Ca) 387 .3 0 .43Titanium (Ti) 461 .6 6 .1Manganese (Mn) 528 .5 13 .3Iron (Fe) 537 .2 2 .53Cadmium (Cd) 1074 .6 2390 .0Lead (Pb) 1975 .5 0 .17Uranium (U) 2268 .6 4 .2

Absorption Cross Section

# of Collisions to Thermalize a neutron

QA/QC on Field Monitoring

Field Monitoring and Lab Testing Intent:•To determine the source for the fluid content discrepancy between field and lab

• Iowa Dept. of Transportation (1999)• gauge reading higher: materials containing hydrogen other than free water such as bitumen, asphalt• gauge reading lower: materials absorbing thermalized neutrons such as iron and chlorine

• Box Test of Plant 5 Rejects : bulk/wet density error (ρw:‐0.03% to ‐1.8%) (ρd:+0.4% to +2.1%) • Bulb Test: bulk/wet density correction• Standardizing: If testing many materials throughout the day, it is critical to use a neutral site

to standardize

Possible Sources for Fluid Content Error:

42

Box Test



1995 to 2007 9632 troxlers 85 proctors

200954 troxlers 5 proctors

QA/QC on Field Monitoring

Field Monitoring and Lab Testing Intent:•To confirm that the current construction season data with the continued use of the single density value for the maximum SPDD for compacted lift fills still applies versus the historical data

Confirmation of Design % SPD

43

Compacted 1.0m lifts (SC‐SM) Compacted 1.0m lifts (SC‐SM)



Frozen Fill Compaction

Lab Testing Intent:•To determine the influence of various combinations of bitumen and water contents on the compacted density for oil sand fill that is at a temperature below 0°C•All frozen fills do not compact regardless of bitumen content, water content, or grain size.

95% SPD

Density for soil samples at temperatures below 0°C before compaction

Materials – Selection 44



Lab and Field Testing Intent:•To establish the compaction characteristics of fills constructed at below 0°C

• Useful for extending the construction season through October/November/December and even later if frozen ground is stripped off at the borrow source/shovel face

•Basis of the construction specification on max time to begin compacting 1.0m thick SC‐SM lifts at varying ambient air temperatures

Materials – Selection, Placement, and Compaction

Lab Testing: Field Testing:

45

Tim

e (h

ours

)

Below 0°C Construction in Lab Testing to Field Application



Field Testing Intent:•To measure the rate of thawing in the fill placed during the winter months•To determine the effect on settlement and hydraulic fracture potential caused by placing fills in the winter

Rate of Thaw of Winter Construction

• Most fill that was placed in winter thawed within 8 to 20 months after winter placement had occurred• 10m of fill placed in winter had thawed through the summer construction season upon measurement that October

• Largest winter fill section constructed, after thawing for 12 months, still had 13m of frozen fill out of the original 32m

Design Consideration – Settlement After Thaw 46



Summary ‐Winter Construction of Compacted SoilsFor construction of large volume dams at rates of 25 Mm3/year accounts for year long construction in both summer and winter (‐30C) conditions.Base Prep:

• Focus on non‐critical dam areas and save critical areas for optimal construction conditions (summer)

Material Selection:• Non‐frozen fill (<2% frozen fill allowed) from

a large mining face• Frozen layer of the top of the bench is

stripped off with dozers or backhoes • Frozen layer at the face of the bench is

stripped with a shovel• Appropriate monitoring to determine

the depth of frost (e.g. test pits done above shovel)

Winter Construction

Placement: • Do not use thin lifts. The full 1m lift thickness is required for heat

Compaction:• Time‐frame between mining from the face to compaction on the site is narrow with cooler temperatures• Dozers must keep all sides sloped and packed other than advancing lift to minimize frozen rubble contamination• Dry‐of‐optimum high plastic clays stop compacting at around ‐5C. During cooler temperatures, optimization with respect to

packing (e.g. at the end of fall only pack mid‐afternoon)

Inter‐lift Clean‐up:• Snow, ice, and frozen rubble defect tolerances to be applied

QA/QC:• Additional checks to confirm no slop on the lift surface prior to placement (e.g. chipping, thawing bag samples)

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Odometer Test Results with first-time wetting occurring at 800kPa for fills at 89% MSPDD

Odometer Test Results without soaking for fills at 89% MSPDD

Consolidation & Inundation Settlement

Lab Testing Intent:•To determine the potential first‐time wetting settlement of compacted fills•Settlement designed into freeboard geometries of future similar structures

Wetting

Design Consideration – Settlement – Consolidation and Inundation 48




Design Consideration – Settlement – Consolidation and Inundation

Compacted 1m lifts (SC-SM)

Loose 5m lifts

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Field Monitoring Intent:•To check the post‐construction performance of the design based on lab consolidation testing•To understand the timing of consolidation and inundation settlement•Settlement (estimated/recommended) designed into freeboard geometries of future similar structures


Design Consideration – Settlement – Consolidation and Inundation

Answer:Some looser 5m thick lift fills settled less than compacted fills due to suspected matrix suction and so will settle more during inundation

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GPS Monitoring – Settlement and Stability

Design Consideration – Settlement

Field Monitoring Intent:•To check the post‐construction performance of the design•To check the agreement between GPS monument stations and settlement gauges•To check the quality of the GPS monument stations with respect to other survey methods or slope inclinometers

• SIs are hard to use in thick compressing/settling fills where the effect of compression has to be weeded out of the data

Answer:Good agreement between the GPS monuments and settlement gauges.The deformation performance of the dam was very good considering the thick fills, winter construction, 1m lifts, and 2.5 year construction period.

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Pore Pressure Ratios (ru)

Field Monitoring Intent:•To determine potential pore pressure ratios for fills with similar grain size, fluid contents, compaction, and clean‐up specifications•Parameters applied to analysis for future similar structures

Design Consideration

Answer:•For a conservative slope stability analysis, higher ru.•For a conservative hydraulic fracture analysis, lower ru.•Dissipation of silty fine sands very slow.

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Slope Stability

Analysis:•To act as an undrained saturated fill, Total Stresses, the fills should not show a stress dependency in UU triaxial testing. If the fills show a stress dependency in UU triaxial testing and/or are dilative (not contractive), then Effective Stresses parameters could be used in the design.•For slope stability analysis, a higher ru provides more conservative results.

Design Consideration – Slope Stability

Compacted 1m lift of SC‐SM (ru~0) Effective Stress Analysis for Compacted 0.75m lift of CH

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Piezo elevation

ru



Hydraulic Fracture

Analysis:•Parameters applied to analysis for future similar structures•Dry of optimum fills with low ru Core – more prone to hydraulic fracture vs. wetted Core and cohesionless filters•For hydraulic fracture analysis, a lower ru gives more conservative results.•Crack Analysis also performed for seepage if there is a risk of hydraulic fracture•Breakout Pressure (Pb) and Propagation Pressure (Pp) adds to factor of safety

Compacted 0.75m Lifts – ru=0 Compacted 1.0m SC-SM Lifts – ru=0

Design Consideration – Hydraulic Fracture 54



Summary ‐ Placement and Compaction For construction of large volume dams at rates of 25Mm3/year requires year‐round construction:

Field and Lab Testing with Continued Monitoring is required to determine the construction and monitoring boundaries of construction during both summer and winter conditions for the engineered fill thick lifts being used for seepage control, deformation control, stability control, and settlement control.

•Determine how thick a lift can be to achieve design density and meet required lift fabric quality.

•Determine which compaction methodology (which equipment, how many passes) achieves design density and meet required lift fabric quality.

•Determine which Standard Proctor Value applies.

•Determine which field effects (fluid content corrections) to account for.

•Confirm in the field during construction and with continued monitoring post‐construction that the design parameters of density, permeability, strength, and ru are still applicable and that the structure continues to perform.

Placement and Compaction 55

Dozer advancing a compacted 0.75m lift



BUSINESS NEEDDesign and Construct large fill volume, time‐critical tailings retaining structures considering:

‐ mining operations field staff abilities

‐ construction monitoring field staff abilities

‐ governmental documentation requirements

1m compacted lift winter clean‐up with a flat‐bar

attachment to the backhoe bucket

0.75m compacted lift density full depth test (0.3m from bottom of the lift) with a drill to get

the probe through the compacted fill

Inter‐lift Clean‐up, Field Monitoring, and QA/QC 56



Construction Specifications




Defects – Compacted Lifts

Field Monitoring Intent: Clean‐up Terminology•Communicative tool to gauge the amount and degree of defects allowed.•Maintains consistency between and within all field personnel and the office design engineers.




Example: Defect Tolerance for 90% Seepage Clean – Compacted Lifts

Field Monitoring Intent: 90% Seepage Clean•Maximum defect size of 5m by 5m in discontinuous pockets amounting to less than 10% of the cumulative area•Gridding method shown as a monitoring process to confirm tolerance is being met




Inter‐lift Clean‐up – Compacted Lifts

Winter – deep groves left from spinning dozer with ice cleats to clean is unacceptable to leave so spin a dozer without ice

cleats and grade to finish

Winter – rubber tire loader removing siltstones from in front of an advancing lift , tires minimize rubble and grader clean-up

Winter –frozen slop checked by

chipping and thawing a bag

sample

Winter and Summer – no scarifying due to the grooves in the very dry

compacted lifts fill with loose rubble



Securing Canada’s Energy Future 61

Inter‐lift Clean‐up – Freeze‐Thaw

Inter‐lift Clean‐up, Field Monitoring, and QA/QC

Compacted dam components (1.0m SC‐SM lifts, 0.75m CH lifts) left over winter for continued construction in the following spring require freeze‐thaw removal:

• Test pitting to determine the total depth of freeze‐thaw affected material

• Removal of freeze‐thaw affected material to firm, compacted ground

• Re‐compaction

If constructed dam components are built through the winter (year‐round construction), freeze‐thaw clean‐up is not required.

Loose 2m to 5m fills for buttressing, even if left over winter for continued construction in the following spring, do not require freeze‐thaw removal but do require:

• Slop removal• Proof‐rolling / Re‐compaction

Dry and brittle

Heavily layered and

soft

Minor layering and soft




Placement and Compaction, Field Monitoring, and QA/QC

Note:•Allowable rut and roll is for visual monitoring on material quality rather than compaction and placement.•The 240T hauler uniform compaction speed < 5km/hr is so packing gets to the full depth of the lift.•Packing trucks are separated out from Truck‐Shovel Mine Fleet.•The uniform compaction discussed above assumes at least 2 passes by equivalent trucks during placement.•Lift thickness is dropped by half if packing on a slope.

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Priorities of QA/QC when building at 25Mm3/year1. Right material at the borrow‐pit and at the dam structure.

2. Base or previous lift cleanup is approved prior to placement (limits of approved areas delineated by cross‐staking in the field).

3. Appropriate lift thickness and material type for the equipment placing (e.g. D9/D10/D11 for 1m SC‐SM lifts in summer only).

4. Observing field performance (e.g. rut and roll as a self‐correction for wet‐of‐optimum) and highlighting material concerns if appropriate.

5. Observing uniform compaction by a minimum 240 ton (often 400 ton) heavy hauler going at less than 5km/hr with a minimum 4 passes with a careful front‐wheel or rear‐wheel stagger and highlighting technique concerns if appropriate.

6. Confirmatory nuclear density testing done of each lift to full depth (0.3m from surface, 0.3m from bottom of the lift).

7. Soil samples for lab confirmation taken as per the structure schedule (e.g. every Wednesday and Friday: SPD, GSD, Atterberg, and moisture content ; testing for SPD corrections at every 200000m3 of material ; permeability testing every 1 Mm3).

8. Document all in daily journal and density test sheets.

9. Information reviewed by the Engineer of Record (may need to be an in‐house geotechnical engineer making final approvals with input from consultant designers/technical resources and in‐house operations representatives).

NOTE: Non‐negotiable on the interpretation of adherence to construction specifications; a hierarchy of design/construction issue escalation may be required for field problem resolution

Field Monitoring 63



Licensing and Long Term Monitoring • Dam License – supporting documentation and analysis on the dam design for

governmental approval

• Dam As‐Built – supporting documentation and confirmatory testing that the construction met the design intent

• Annual Performance Review – supporting documentation and instrumentation monitoring (slope inclinometers, vibrating wire piezometers, standpipes, GPS monuments, etc.) that the dam structure is performing as designed

• Dam Safety Review – “cold eyes” reviews of the site conditions, dam documentation, analysis, and testing by qualified external consultant

Monitoring – Government Reporting 64



Compaction & Design Tips for constructing fills at rates up to 25 Million m3/year

Successfully balancing the Design Intent for Earth Dam Structures with Business Need and Construction Optimizations

EW Dyke•180 million m3 of engineered fill •Will need a construction rate of 50 Mm3/year

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NS Dyke•76 million m3 of engineered fill •At a maximum construction rate of 15 Mm3/year

Hwy63 Berm•42 million m3 of engineered fill •At a maximum construction rate of 17 Mm3/year

SW Dam•114 million m3 of engineered fill •At a maximum construction rate of 25 Mm3/year

Sponsors For Cross Canada Lecture Tour, Spring 2013

The Canadian Foundation for GeotechniqueLa Fondation canadienne de géotechnique

The Canadian Geotechnical SocietyLa Société canadienne de géotechnique

Sponsors For Cross Canada Lecture Tour, Spring 2013

Organization:

Funding:

CGS Cross Canada Presentation Spring Tour 2013 and De… · Syncrude Geotechnical Engineering...

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Transcript of CGS Cross Canada Presentation Spring Tour 2013 and De… · Syncrude Geotechnical Engineering...