Etude des ouvrages de stockage
souterrain de déchets de haute
activité
ULg – équipe de géomécanique
SCK – CEN / ULg 02/09/10
ULg Geomechanics team
• R. Charlier, Pr. O, chairman SAC Praclay
• F. Collin, Chercheur Qualifié FNRS
• S. Levasseur et B. François, Chargés de
Recherche FNRS
• A. Dizier (FRIA), P. Gérard, S. Delvoie, B.
Cerfontaine, doctorants
• JP Radu, F. Pascon, ingénieurs de
recherche
• Lab’s team 4 people.
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Research themes
• Geomechanics
• Rupture
• Thermo-hydro-mechanical coupling
• Numerical modelling : LAGAMINE code
• Experimental investigations
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Stockage géologique profond: différents concepts
 2 options
 Forages profonds creusés à partir de la surface
 Enfouissement dans des mines
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The PRACLAY in-situ experiment comprises
three tests:
the “Gallery&Crossing Test”, the “Seal Test”
and the “Heater Test”
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Underground nuclear waste disposals
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Rock behaviour around disposals
Mechanical behaviour
Fluid transfers
Heating / cooling effect
• Numerical simulation
• Clayey rocks : URL Mol, Bure, Mont Terri
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Fractures observed at
Bure and HADES
COX
Slickenside
BC
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Fracture traces observed on the
excavation walls
COX
BC
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Fractures pattern observed along
borehole cores in COX and BC
COX
BC
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Typical herringbone pattern observed during
excavation in COX and BC
~4 m
COX
BC
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DZ as a preferential transport
pathway
• DZ : damaged zone, i.e. zone strongly
modified by the mechanical loading
• Mechanical loading : excavation, heating,
gas generation
• Transport pathway : fluid (liquid and gas)
flow as radionuclide advective transport
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Geomechanics coupled to fluid flow :
geomechanics know-how
• Fluid pressure direct influence on mechanical
state of stress : Terzaghi / Bishop effective
stress, net stress + suction
• But few effect of geomechanics on fluid flow,
unless changes in permeability
• Damage, permeability and stress distribution
studies in Excavation Damaged Zone needed
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DZ as a preferential transport
pathway
• Describe the Damaged Zone
• Damage as a rather general concept
• Transport pathway : considered based
solely on fluid flow
• Basic question : what is the permeability
evolution related to “damage”
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Chip formation :
experimental results (LML)
and numerical modelling (ULg)
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Essais sur cylindre creux – LMR EPFL
– V. Labiouse
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Essais sur cylindre creux – LMR EPFL
– V. Labiouse
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MODÈLE NUMÉRIQUE / EXPÉRIMENTAL
Comparison between experimental data and modelling (at the end of the
second phase):
Experimental data show anisotropy
Radial evolution of the radial displacement
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Modélisation de la localisation des
déformations – ¼ de cylindre creux
Localisation des déformations
de cisaillement
Déplacements
7 mm
42 mm
Déplacement maximum = 3.2 mm
avec
et
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EDZ permeability distribution
Coupling : Mechanic – Permeability
Changes of permeability : 5 order of magnitude
Vertical drilling
Horizontal drilling
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(Andra, G. Armand)
EDZ permeability distribution
Structural and hydrogeological
characterisation of the excavationdisturbed zone in the Opalinus Clay (Mont
Terri Project, Switzerland)
Paul Bossart, Thomas Trick, Peter M.
Meier, Juan-Carlos Mayor
Applied Clay Science 26 (2004) 429– 448
Changes of permeability : 2 order of magnitude
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Research structure
1.
2.
3.
4.
Damage zone observations
Damage zone simulations
Evidences of permeability evolution in DZ
Constitutive equations for permeability
evolution
5. Anisotropy considerations
6. Numerical simulations of coupled HM
problems with permeability evolution
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Conclusions
• Permeability may be strongly modified in
EDZ : in situ evidences.
• Some models relating permeability to
strain or damage exist or are in
development.
• Numerical modelling is complex but
possible. Few simulations have been
done.
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Conclusions : Open questions
• Lab evaluation of permeability evolution
with strain / damage remains difficult.
Nevertheless progresses are ongoing.
• Strain and micro fissure localisation effect
on permeability needs to be better
understood.
• Strong need of model validation both on
lab and in situ experiments.
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Collaborations
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Euridice
SCK CEN
ONDRAF
ANDRA
NAGRA
University : Barcelona, Lausanne, Paris,
Grenoble, Lille, etc…
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European projects
• CATSIUS CLAY (benchmarks : clay
modelling)
• TIMODAZ (thermal effects and Excavated
Damage Zone)
• FORGE (gas transfers)
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Future cooperation with SCK-CEN
• FORGE project : numerical simulation of
gas flow – Mol in situ test
• Gas flow in EDZ …
• Anisotropy and elastoplastic behaviour
• Mol geological history and fracture
prediction
• Doctoral thesis ?
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