Thermo-hydro-mechanical behaviour of compacted MX80 bentonite at 150°C

This paper presents the behaviour of compacted MX80 bentonite specimens when they are subjected at thermal and thermohydraulic gradients. The purpose of this work is to develop an improved understanding of heat and moisture movement in unsaturated clay barriers at temperatures above 100°C. Each specimen was statically compacted at 1.65 Mg/m3 and has dimensions of 300mm height and 100mm diameter. With the aid of a thermohydraulic column cell it was possible to apply boundary conditions that imitate the conditions in an underground repository. For the two on going tests undertaken in this study the applied temperatures were 25°C and 150°C at the top and bottom of each specimen. For applying the hydraulic gradient, water injected from the top of the specimen at a pressure of 600kPa. The test results show that, the temperature along the depth of the specimen stabilized in about 3-10 days whereas the relative humidity did not equilibrate. The exposure of the specimen at thermohydraulic gradient manifested a greater axial stress than that of the thermal gradient.