Experimental investigation of the relationship between the critical state shear strength of unsaturated soils and the soil-water characteristic curve

Abstract

This paper presents the comparison of experimental results of the critical state shear strength of an unsaturated glacial till and the predicted shear strength using the Soil-Water Characteristic Curve (SWCC), determined following three different techniques, namely: (i) the conventional SWCC without application of any consolidation stress; (ii) the SWCC measured on a specimen subjected to a net stress equal to the net normal stress of experimental shear tests; (iii) the SWCC derived from the degree of saturation and matric suction of the sheared specimen under critical state conditions. The results of the study suggest that the best predictions of the shear strength are possible using the experimental SWCC information expressed as an apparent SWCC. The study also suggests that the relationship between the apparent degree of saturation and the matric suction of a specimen sheared to critical state is unique, and is not influenced by the shearing mode, or compaction water content (i.e. soil structure).