Feb 14, 2014 - in Opalinus Clay and Similar Claystones». Frederic L. PELLET. University of ... Eric Boidy, Géraldine Fabre, Attila Hajdu, Mohamad Keshavarz.
February14th ,2014,Zürich
Symposium«RockMechanicsandRockEngineeringofGeologicalRepositories inOpalinus ClayandSimilarClaystones»
LabExperimentsforDeterminingtheMechanical BehaviorofShales andClaystones FredericL.PELLET University ofLyon,Department ofCivilandEnvironmentalEngineering,Villeurbanne, France frederic.pellet@cfmrͲroches.org
Outlines
• Introduction and Objectives • Petrophysics of Shales and Claystones • Tests for Mechanical Behavior Characterization • MicroͲStructural Analysis of Cracking in Shale • Concluding Remarks
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Acknowledgement • Institut deRadioprotectionetdeSûreté Nucléaire (IRSN) • Agence Nationale pourleStockage etlaGestiondesDéchets Radioactifs (ANDRA) • FrenchRailwaysCompany(SNCF) • PhDStudents: EricBoidy,GéraldineFabre,AttilaHajdu,Mohamad Keshavarz
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IntroductionandObjectives Why:
Predictionofthemechanicalbehaviour ofunderground radioactivewasterepositories
What:
AssessmentoftheextensionoftheExcavationDamageZone(EDZ) accountingfortimedependency
EDZ
MontͲTerryLab
ExtensionoftheEDZ300yearsafterthe 4 excavation(fromnumericalmodelling
IntroductionandObjectives DamageParameter,D
How:
ConstitutivemodelaccountingfortimeͲ dependentdamage (ratedependentmodel) 10years 1year 100years 300years İ vp
w: wıij
N
º S ı eq 3 1 ª « » 2 1 D « 1 D K p 1M » ı eq ¬ ¼
where: istheviscoplastic potential,K,NandMare theviscoplastic parameters oftherock,Veq isthevon Mises stressandS isthestressdeviator.
Parametersidentification andcalibration??? Pellet, F.L. et al. A viscoplastic constitutive model including anisotropic damage for the timeͲdependent mechanical behaviour of rock, Int. J. Numer. Anal. Meth. Geomech. (2005)
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Petrophysics SpecificitiesofShales andClaystones
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Petrophysics SpecificitiesofShales andClaystones •
Highcontentofclayparticles: വ
Kaolinite,Chlorite,Illite,Smectite (swellingͲshrinkage)
• MicrotonanoͲporosity: വ
Hugesurfaceeffectsstrongmolecularbond (doublelayertheory)
വ
Almostnofreewater (extremelylowhydraulic conductivity#10Ͳ20m2 )
magnified
Pitfallstoavoid: വ
HͲMcouplingwithBiot theory(few Hertzian contacts)
വ
Littlesuctionbecauseofcavitation
10 to 20 ȝm
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Petrophysics SpecificitiesofShales andClaystones •
PetroͲFabric:
വ
Heterogeneities (polycrystal)
വ
Crystallattice:strongatomicbond(coͲ valent,ionic…),dislocation
•
Anisotropy bothintermsofstrengthand deformabilityproperties(transverseisotropy)
Pitfalltoavoid :
BureArgillite
Carbonate
Quartz
Mica
Discrete Element Method:notsuitable 8
TestsforMechanicalBehaviorCharacterization
9
Rocksunder Study:Mineral ContentandPhysical Properties Rock Formations
Geological Periods
Others minerals
Quartz
Carbonates
(SiO2)
(CaCO3)
%
%
(Feldspars, micas, pyrite)
Clay
Particles Kaolinite Chlorite
Illite
Smectite
Interlayers Illite/ Smectite
BureArgillite
CallovoͲ Oxfordian
20Ͳ30
20Ͳ33
5
40Ͳ45
10
20
40
Ͳ
30
Tournemire Shale
Toarcian
19
15
11
55
28
3
16
Ͳ
8
Montd’Or Claystone
Jurassic
10
65
Ͳ
25
30
15
40
15
Ͳ
Density 3
Porosity
Water content
Saturation degree
%
%
UCS MPa
Average Moduli
Sonicvelocity PwaveMax
GPa
m.sͲ1
(PͲwave velocity)
Anisotropy
kN/m
%
BureArgillite
23.7
15.5
5.9
87%
27Ͳ29
5Ͳ6
3820
10%
Tournemire Shale
24.0
8.9
3.4
95%
35Ͳ38
21Ͳ27
4225
30%
Montd’Or Claystone
25.3
6.4
1.6
63%
50Ͳ80
18Ͳ25
4300
16%
Fabre, G., Pellet, F., Creep and timeͲdependent damage in argillaceous rocks, Int. J. Rock Mech. Mining Sci,. (2006) 10
MechanicalTestsforRocksBehaviorCharacterization DeterminetheoveralltimeͲdependentmechanicalpropertiesatthe scaleofarockspecimen
•
– Compressiontestswithdifferentratesofloadings – Creepcompressiontests – Relaxationtests
H =80mm I=40mm
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Intrumentation forTransverseIsotropic Specimens Specimendeformation(straintensor): T=0°
n
n t
t
t
t
t
t
s
s
s
H
T =90°
n
§ H ss ¨ ¨0 ¨0 ©
0
H ss 0
Transversal:parallel totheplane
0 · ¸ 0 ¸ H nn ¸¹ s ,t ,n Axial
H
§ H ss ¨ ¨0 ¨0 ©
0
H tt 0
0 · ¸ 0 ¸ H nn ¸¹ s ,t ,n
Transversal:perpenͲ dicular totheplane
Distorsion
H
Hvol
§ H ss ¨ ¨0 ¨0 ©
0
H tt H nt
0 · ¸ H tn ¸ H nn ¸¹ s ,t ,n
H ss Htt H nn
N.Gatelier,F.Pellet,B.Loret(2002),Mechanicaldamageofananisotropicrockundercyclictriaxialtests,Int.J.RockMech.Min.Sc.
TimeͲdependentbehaviorofrocks Theeffect oftherateofloading incompressiontests H1
H
V
Hs Creep
H !! H
HR
o
H VR
o
Tunnelconstruction with support
H
HR
Time
V1
o
H H
Vs
Creep failure Damage (creep failure) (damage)
VR Relaxation Vs
Hs Time
Monotonic CompressionTestonBureArgillite InfluenceoftheStructrural Anisotropy (loading rate:10Ͳ6.sͲ1) Late volumetric dilation
AxialStress[MPa ]
30 25
Hvol
Htt
n
Hnn
Hss
T v3
20
s
t
15
v2 10
Orientations,T Orientation 0° : 0° 45° 45° 90° 90°
5 0 -5000
-3000
-1000
1000
3000 5000 7000 MicroͲstrains (Pm/m)
9000
G.Fabre,F.Pellet(2006),Creepandtimedependentdamageinargillaceousrocks,Int.J.ofRockMech.andMini.Sci.
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Monotonic CompressionTestonBureArgillite Influenceoftherateofloading (T=0°) 10Ͳ4sͲ1
30
AxialStress[MPa ]
25
Hvol
Hss
Hnn
20 15 10
Loading Rates: 10Ͳ4 sͲ1 10Ͳ6 sͲ1 10Ͳ8sͲ1
2minutes
5
222hours (9days)
0 -4000
-2000
0
2000
4000
6000
8000
10000 10Ͳ6sͲ1
MicroͲStrains (Pm/m)
LongDuration Creep TestsinCompression BureArgillite (T T=0°) q=25.8MPa #0.9UCS(27Ͳ29MPa) 30.0
16000
q
14000
25.0
12000
Hnn
10000
MicroͲStrain[Pm/m]
6000
Dilationtrend
4000
Hvol
15.0
2000 10.0
0 -2000
Hss
-4000 -6000
5.0
-8000
0.0 0
16
50
100
150
200
Time[days]
250
300
350
Stress[MPa]
20.0
8000
15
MonotonicCompressionTestandRelaxationStageon Bure argillite 40
V 1 [MPa] Axial Stress, AxialStress,s 1V1[MPa] Contrainte, [MPa]
36 36
Relaxationstage
ReͲLoading
Axialstressvstime
32
32 28 28
28 26
20 20
n
24
Loading
Relaxation
16 16
Ec2 = 5230 MPa
12 12
Ec1 = 3620 MPa
Contrainte V1 [Mpa]
24 24
88
s
22
t
20 18 16 14 12 10 8
Ed = 5175 MPa
44
6
Unloading
4 0
5
00
10
15
20
25
Temps [jours]
Time[days]
0,00E+0 2,50E--33 5,00E--3 3 7,50E--3 3 1,00E--2 2 1,25E--2 2 1,50E--2 2 1,75E--2 2
H1 Déformation, Strains [Pm/m] 17
MultiͲStageCreep TestsinCompressionon TournemireShale
Pwave velocity [m.sͲ1] MicroͲstrain[P P m] PWave[m/s]
6000
30
Hnn
4400 4000
20
2000
10
43000
0
Htt
Ͳ2000
UCS=35Ͳ38MPa;T=90°
40
q
Ͳ10
Hvol
4200 Ͳ4000
Stress,q[MPa]
8000 4500
Ͳ20
Hss
Ͳ6000
Ͳ30
4100 Ͳ8000
Ͳ40 0
50
100
150
200
250
Time[day] Time[day]
F.Pellet,G.Fabre(2007),DamageevaluationwithPͲwavevelocitymeasurementsduringuniaxial compressiontestson argillaceousrocks,Int.J.Geomechanics,(ASCE)
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Oligocyclic Creep TestonMontd’OrClaystone 6 Loading Stages:from 30to55MPa: Unloading downto 20MPa 4000
200
Hnn
3500
175 150
Hvol
2500
125 100
2000
q
1500
75
1000
50
500
25
Hss
0
0 Ͳ25
Ͳ500
Ͳ50
Ͳ1000 0 19
Stress[MPa]
MicroͲstrain[μm/m]
3000
50
100
150
200
250
300
350
Time[days]
MicroͲStructuralAnalysisofCrackinginShale
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MicroͲStructuralAnalysisofTimeͲDependentCracking inBure Argillite 10Ͳ8sͲ1
10Ͳ4sͲ1
5000ʅm
10mm
10mm F.L.Pellet(2013),MicroͲstructuralanalysisoftimeͲdependentcrackinginshale,Env.Geotechnics
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SEMPhotographs MacroͲcrackin clay matrix and debonding of quartzand carbonategrain TransͲgranular microͲcrackina carbonategrain 100Pm
Shearing of pyritegrain
500P Pm
5Pm
50Pm
MicroͲcrackinclay matrix with reͲ orientation oftheclay platelet along microͲ shear planes 22
ConcludingRemarks •
Petrophysics consequences: – Shales andclaystones areheterogeneous polyͲcrystallinerocks,havingahigh contentofclaywithmicroͲpores. – AtamesoͲscale,theyareanisotropic (transverseisotropic)andexhibita markedtimeͲdependent behaviour.
•
MechanicalTests : – Creeptestswithrelaxationtestsandstrainratecontrolledcompressiontests arenecessarytodeterminetheparametersofany ratedependentmodels – Priortesting,physicalpropertiesneedtobeaccuratelydetermined(including sonicvelocities)
•
MicroͲStructuralAnalysisofCrackinginShale – Microcrackingpatternsdependontherateofloading(energydissipation) – MicrocrackingpatternsarealsodrivenbytherockpetroͲfabric. SEManalysis onthinsectionarerequiredevenifothersmeanscouldalsoprovidegood insights(XRayTomography) 23
FinalRemarks • Keepinmind! വ Lab testsresultsobtainedonspecimensgiveyouanorderofmagnitude (upperbound)ofthemechanicalpropertiesoftherockmass(scaleeffect, discontinuities,otherheterogeneities) വ In situ tests (including geophysics) and monitoring of the underground opening help to better constrain the mechanical properties of the rock mass for the numerical analysis (inverse analysis, uncertainties assessment)
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February14th ,2014,Zürich
Symposium«RockMechanicsandRockEngineeringofGeologicalRepositories inOpalinus ClayandSimilarClaystones»
Thankyouforyourattention!
frederic.pellet@cfmrͲroches.org
Simplified FlowChart fortheDesignof Project Lab Tests
InSituTests
ConstitutiveParameters Identification
Design
Numerical modelling
Realization
Monitoring InverseAnalysis: Scale effect;Heterogeneities… 26
ShearStrengthofClayRockDiscontinuities BCR3D:ServoͲControlledDirectShearEquipment BureArgillite Specimen
Z
X
Y
Vn V n
VVnn
Stressand displacementservoͲ Us UU controlledinthe3 ss directions,Fluid injection:Control PressureVolume Conventional shear box:rotation
UU s/2/2 U /2
s/2 U UssU/2 /2
ss
BCR3Dshear box:norotation
27
Shear testondryandsaturateddiscontinuities ConstantNormalLoad (CNL),shearingrateof0.05mm/s Normaldisplacement Ͳ shear displacement
ShearstressͲ sheardisplacement 8
0.0 Vn =16MPa
Dry
4
ShearStress[MPa]
Vn =2MPa
Vn =10MPa
Normaldisplacement[mm]
6
Vn =5MPa Vn =2MPa
2 0 Ͳ2 Ͳ4
Ͳ2
Ͳ1
0
4
Saturated
2
Vn =2MPa
1
2
3
4
5
6
7
Ͳ0.4 Vn =10MPa Vn =16MPa
Ͳ0.6
Ͳ0.8
Ͳ1
0
Vn =16MPa
Sheardisplacement[mm]
1 Vn
2
3
4
5
6
7
8
Vn =5MPa Sheardisplacement[mm] =2MPa
Ͳ0.5
Vn =10MPa
Vn =5MPa
0.0 Ͳ2
8
Normaldisplacement[mm]
Shearstress[MPa]
Vn =5MPa
Ͳ1.0
Ͳ6 6
Ͳ0.2
0 Ͳ2 Ͳ4 Ͳ6
Vn =10MPa
Ͳ1.0 Vn =16MPa
Ͳ1.5 Ͳ2.0 Ͳ2.5 Ͳ3.0
Ͳ8 Ͳ1
0
1
2
3
4
Sheardisplacement[mm]
5
6
7
8
Ͳ2
Ͳ1
0
1
2
3
4
Sheardisplacement[mm]
5
6
7 28
8
Photosofthe discontinuitiesafter testing
Drydiscontinuity
Saturated discontinuity
Left:lowerpart
Right:upperpart
29
Normalstressversusmaximumshearstress
Drydiscontinuities
Saturateddiscontinuities
8
8 Mohr-Coulomb TD-CNL-03
Maximumshearstress[MPa]
Maximumshearstress [MPa]
7
TD-CNL-04
6
TD-CV-06 TD-CV-02
5
TD-CV-17 TD-CV-05
4 3 2
Cohesion = 0.41 MPa Friction angle = 22°
1
Mohr-Coulomb
7
TW-CNL-07 TW-CV-21
6
TW-CV-23
5 4 3 2 Cohesion = 0.32 MPa Friction angle = 12 °
1
0
0
0
2
4
6
8
10
Normalstress[MPa]
12
14
16
18
0
2
4
6
8
10
12
14
16
Normalstress[MPa]
F.L.Pellet,M.Keshavarz,M.Boulon(2013),Influenceofhumidityconditionsonshearstrengthofclayrockdiscontinuities, EngineeringGeology.
30
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