Swelling characteristics of GMZ bentonite and its mixtures with sand

• Void ratio vs swelling pressure at saturation is independent of initial condition.
• Mt void ratio vs swelling pressure is independent of bentonite/sand ratios.
• Mt void ratio vs swelling pressure at saturation is dependent on type of Mt.
• A method is proposed to predict the swelling characteristics of the mixtures.

Gaomiaozi (GMZ) bentonite produced in Inner Mongolia has been chosen as a matrix material of buffer/backfill materials in the deep geological disposal to isolate the high level radioactive waste in China. Swelling characteristics of GMZ bentonite and bentonite–sand mixtures inundated with distilled water were studied by experimental methods. The test result shows that the relation between the void ratio and the swelling pressure of compacted GMZ bentonite–sand mixtures at full saturation is independent of the initial conditions such as the initial dry density and initial water content, and dependent on bentonite/sand ratio. An empirical equation is proposed to predict the swelling deformation and swelling pressure of the mixtures with different densities and bentonite/sand ratios. Finally, the swelling capacities of GMZ, Kunigel-V1 and MX-80 bentonites are compared.