CHENILLE: the fault-heating experiment in the URL Tournemire (France)

The understanding of the coupled thermo-hydro-mechanical behavior of fault zones in naturally fractured rocks is essential both for fundamental and applied sciences and in particular for the safety assessment of radioactive waste disposal facilities. An international research program called CHENILLE was built to address key questions related to the impact of high temperatures (up to 120°C) on shear zones as well as fault reactivation processes in shale formations. Here, we report on an ongoing thermally controlled in-situ fluid injection experiment on a strike-slip fault zone outcropping at IRSN’s Tournemire Underground Research Laboratory (URL). This includes a series of laboratory experiments to understand the mechanical, hydraulic, structural and thermal evolution occurring within the fault zones during the thermal and hydraulic loading. Reported preliminary results comprise acoustic emission activity and active seismic monitoring results, the thermal diffusion and the temperature evolution measured in-situ with DTS in and around the fault and the corresponding numerical thermal simulation of the experimental setup.