Etude des ouvrages de stockage souterrain de déchets de haute

activitéULg – équipe de géomécanique

SCK – CEN / ULg 02/09/10

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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

• 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

BC

Slickenside

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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

COX BC

~4 m

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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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Comparison between experimental data and modelling (at the end of the second phase):Experimental data show anisotropy

MODÈLE NUMÉRIQUE / EXPÉRIMENTAL

Radial evolution of the radial displacement

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Modélisation de la localisation des déformations – ¼ de cylindre creux

avec et

DéplacementsLocalisation des déformations de cisaillement

Déplacement maximum = 3.2 mm

7 mm

42 mm

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EDZ permeability distribution

Horizontal drilling Vertical drilling

Coupling : Mechanic – Permeability

(Andra, G. Armand)

Changes of permeability : 5 order of magnitude

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EDZ permeability distributionStructural and hydrogeological characterisation of the excavation-disturbed zone in the Opalinus Clay (Mont Terri Project, Switzerland)Paul Bossart, Thomas Trick, Peter M. Meier, Juan-Carlos MayorApplied Clay Science 26 (2004) 429– 448

Changes of permeability : 2 order of magnitude

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Research structure

1. Damage zone observations

2. Damage zone simulations

3. Evidences of permeability evolution in DZ

4. 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

• 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 ?