Thermo-Hydro-Mechanical Behaviour of Deep Argillaceous Rocks

ABSTRACT: The argilites from Meuse/Haute-Marne is a material studied by ANDRA, as a potential host rock for radioactive waste disposal. Numerous tests were performed in order to determine the thermo-hydro- mechanical behaviour of this rock. First, physical properties like density, porosity, water content, permeability and mineralogy were determined on all the stratum on core samples (research laboratories) and in boreholes (in-situ). Some uniaxial and triaxial compression tests were performed on samples coming from different depths. Mechanical behaviour is determined as elasto-visco-plastic with an induced anisotropic damage. The material appears stiffer when calcite content increases, and when clay or water content decreases. Biot's coefficient decreases when axial stress increases and the material is able to swell. These phenomena can be explained at the microlevel. Finally, some creep tests were performed under temperature from 20 to 120°C. Viscoplastic strains appear to be very low under hydrostatic stress but increase with deviatoric stress and temperature.