Pressurisation thermique dans l'argile de Boom

The phenomenon of thermal pressurization has been investigated in the Boom clay, the potential host rock presently considered in Belgium for radioactive waste disposal at great depth. Samples from the Mol underground research laboratory (-223 m) have been used. Tests were conducted in a new hollow cylinder triaxial apparatus specifically developed. This device allows a short drainage length (10 mm) favourable in testing low permeability clays and claystones. A thermal pressurization test was carried out by increasing temperature very slowly (from 25 to 65°C at 1°C/h) in undrained conditions while measuring the changes in pore pressure in a sample submitted to in-situ stress conditions. The thermal coefficient measured decreased from 0.04 to 0.02 MPa/°C, in accordance with literature data. The drained cooling phase carried out afterwards provided a value of the drained thermoelastic coefficient in good agreement with that obtained by Sultan et al. (2000).