Thermo-hydro-mechanical behaviour of two deep Belgian clay formations: Boom and Ypresian Clays

The coupled thermo-hydro-mechanical behaviour of Boom clay taken from HADES at 220m depth and Ypresian clay taken from 370 m depth were thoroughly studied in laboratory using advanced techniques, such as odometer cells specifically adapted to control vapor pressure at different temperatures, isotropic cells with local axial and radial measurements especially adapted for vapor transfer, and constant volume cells in thermal baths to capture the thermal sensitivity of water permeability. Particularly, testing protocols have received special attention; Their initial geotechnical properties and main microstructural features were extensively characterized. Water retention curves and saturated water permeability (at two orientations) were determined at different temperatures. Their yield and compressibility at different temperatures and suctions were characterized. In the case of Ypresian clay, special attention was given to the volume change response at different orientations. The impact of relatively fast thermal pulses on the pore pressure build-up and dissipation features of these low permeability materials was investigated using a constant volume and fully-instrumented heating cell under different hydraulic boundary conditions. Thermal pulses were analysed by numerical simulations performed with the finite element code CODE_BRIGHT.