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TIMODAZ – Modelling the Excavated Damage Zone around an underground
gallery - Coupling mechanical, thermal and hydraulical aspects
Summary
Robert Charlier 1 , René Chambon 2 , Xiang-Ling Li 3 , Arnaud Dizier 1,4 ,
Yannick Sieffert 2 , Frédéric Collin 1,4 , Séverine Levasseur 1,4
1 ArGEnCo, Université de Liège, Belgium
2 Laboratoire 3S-R, Université Joseph Fourier – Grenoble I, France
3 EURIDICE, Belgium
4 FRIA - FRS-FNRS, Belgium
A zone with significant irreversible deformations and significant changes in flow and transport
properties is expected to be formed in clay around underground excavations. The stress
perturbation around the excavation could lead to a significant increase of the permeability, related
to diffuse and/or localized crack propagation in the material. Further the drainage and
the heating of disposal will modified the size and the structure of the damage zone. The main
objective of the study is to model these processes at small and large scale in order to assess
their impacts on the performance of radioactive waste geological repositories. This paper concerns
more particularly the thermo-hydro-mechanical modelling of a hollow cylinder experiment
performed in Boom Clay and the hydro-mechanical modelling of a long term dilatometer
experiment performed in Opalinus Clay at Mont Terri Rock Laboratory in Switzerland. This
study shows that simple models already permit to reproduce the behaviours observed experimentally.
1. Introduction
The aim of the TIMODAZ project is to investigate the effect of thermal changes on the excavated
damaged zone (EDZ) around nuclear deep disposals in clay host rocks. During the disposal construction,
rock mass around the gallery is damaged and its permeability may be modified. Further
the drainage and later the heating will modified the size and the structure of the damage zone. In the
framework of the TIMODAZ project, it is intended to develop constitutive models and numerical
tools. A series of benchmark modelling with different constitutive laws and numerical tools are performed.
From now, two benchmarks have started. The first one, described in section 2, concerns a
small scale laboratory experiment on a hollow cylinder clay sample submitted to thermo-hydromechanical
loadings. The second one, described in section 3, is an in-situ experiment which studies
the axial water transmissivity evolution through the EDZ.
2. Laboratory experiment
To study the thermal impacts on damaged zone, a small scale laboratory experiments tests is modelled
and submitted to a benchmark exercise. As illustrated on Figure 1, heating/cooling cycles are
applied on a hollow cylinder performed in Boom Clay which is modelled with in 1D radial axisymmetric
conditions. The clay is supposed to be isotropic and homogeneous and is assumed to be
fully saturated. The internal confining pressure in the central hole is decreased from the initial in
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