Abstract
Shear strength of engineered clay barriers is one of the essential parameters for the design for waste containment facilities. Liquids leaching through these facilities have chemical composition that differ from distilled water typically used in laboratory characterization of clay barriers. There are limited studies in the technical literature that investigate the shear strength behavior of clayey materials subjected to liquids of different concentrations. This paper summarizes the findings of a series of direct shear tests performed to evaluate the effect of brine solution (BRS) concentration on the volume change and shear strength behavior. The testing program covered a wide range of applied normal stress (7-200 kPa) and inundation liquids including distilled water and brine solutions with 1.0 and 4.0 M concentrations. Experimental observations showed that inundation with 1.0 M brine solution concentration had a negligible effect on net vertical strain, swelling pressure, peak shear strength and volumetric shear during shearing, whereas inundation with 4.0 M BRS resulted in a significant decrease in net swell strain, swelling pressure, volumetric strain during shearing and increase in peak shear strength. The interpretation of observed trends was provided in light of different mechanisms, namely osmotic flow (on the clay fabric scale) and diffused double-layer change (on the clay particle scale).