Characterization of THM Behaviour of Compacted MX-80 Granular Bentonite Using an Advanced Double-wall Triaxial Cell

This paper aims at characterization of thermo-hydro-mechanical behaviour of MX-80 granular bentonite obtained from an innovative double-cell triaxial system. The system has been mainly developed to perform suction controlled tests on unsaturated geomaterials under wide ranges of temperature and confining pressure applied to nuclear waste storage. The device was provided with two innovative features; the double-wall system which allows precise measurement of volume variation of the sample, and the hydraulic and pneumatic circuits, which provide several testing layouts to apply on saturated and unsaturated soil conditions. The system has been calibrated for the mechanical loading and the inner-cell evolutions upon high temperature and pressure applications. Drained triaxial compression tests were performed on saturated and unsaturated MX-80 granular bentonite compacted at different water contents and target dry densities. In case of testing in unsaturated conditions, the total suction was controlled by means of the vapor equilibrium technique. The influence of total suction and confining stress on the compression index and the shear strength of bentonite samples were investigated in this paper. The influence of temperature on the deviatoric response of normally consolidated bentonite at high confining stress was also investigated.