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situ stress to model the gallery excavation. During this step, a damaged (plastic) zone is expected to
develop around the hole. Temperature is increased at the inner wall, resulting in a radial gradient.
For the modelling of this experiment, a frictional elasto-plastic Drücker-Prager model [4] is proposed
as mechanical law and the thermo-mechanical couplings are based on thermo-elasticity with
different constitutive laws [3]. The modelling is decomposed into several phases. The two first
phases concern the decrease of the internal confining pressure from the initial value. The third
phase is related to a heating/cooling cycle applied at the inner radius of the cylinder.
Figure 1: Representation of the hollow cylinder and boundary conditions
Figure 2: Description of the thermo-hydro-mechanical loadings applied during the modelling
Figure 3 shows profiles of the pore pressure with the radial distance at different time of the experiment.
The two first phases is represented in Figure 3 (a). The decrease of the internal pressure induces
a drawdown of the pore water pressure. Figure 3 (b) describes the evolution of the pore water
pressure with heating/cooling cycle at different times. A rise in temperature induces an increase of
pore water pressure caused by the difference between the thermal coefficient expansion of the water
and of the solid. When the temperature decreases, the viscosity increases resulting in a rise in pore
water pressure. Figure 4 exhibits stress paths for different combinations of the Drücker-Prager criterion.
The plasticity appears at a lower stress state according the hardening rules [3]. Considering a
basic thermo-mechanical model, these stress paths show that the thermal aspects are small comparing
to the hydro-mechanical part of this modelling.
3. In situ experiment
To study the hydraulical impacts on damaged zone, a long term dilatometer experiment is performed
in Opalinus clay. This experiment is developed to test the influence of bentonite swelling
pressure on the transmissivity of the Excavation Damage Zone [1,2]. Its concept is the combination
of dilatometer tests and numerous hydraulic tests with multi-packer system in a newly drilled borehole
(Figure 5). The pressure in the dilatometer probe is increased stepwise and hydraulic tests are
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