Hydro-mechanical behaviour of unsaturated GMZ bentonite-sand mixture under undrained condition

The hydro-mechanical behaviour of a compacted unsaturated Gaomiaozi bentonite-sand mixture is studied by conducting a series of isotropic compression tests and triaxial shear tests under constant water content. The tests are designed to simulate undrained loading response of the buffer/backfill materials for high level radioactive waste repository. It is found that the increase in consolidation stress and shearing stress induces the decrease in void ratio and suction and the increase in the degree of saturation. From results of triaxial shear tests on unsaturated specimens under constant water content, the outer convex stress-strain curve and contractive volumetric deformation and lateral expansion deformation are observed. Moreover, the net mean stress affects the initial stiffness, undrained shear strength and deformation of the specimen during undrained shear testing.