Impact of pore fluid salinity on the mechanical behavior of unsaturated bentonite-sand mixture

High salinity of local groundwater and the thermal gradient present within the deep geological repository environment make it necessary to investigate the effect of the pore fluid salinity on the hydro-mechanical behavior engineered barriers at different degrees of saturation. This study examines the impact of CaCl2 salt solution at two concentrations, i.e., 100 and 250 g/L on the compressibility and shear strength behavior of the bentonite-sand buffer (BSB) within a range of saturations. Both as-compacted and desiccated BSB specimens were studied. Desiccated specimens were prepared in a constant-suction environment using the vapor equilibrium technique, and high-pressure cells were used to carry out the triaxial shear experiments. Experimental results were compared with the available data from the literature for BSB materials prepared with distilled water in order to get a better understanding of the impact of the salinity. The comparison shows that the existence of salt in the specimens has notable effect on the total suction levels, compressibility and shear strength of the material.