The mechanical behaviour of an unsaturated compacted silty clay

Abstract

A comprehensive experimental study has been carried out to investigate the volumetric and shear strength behaviour of a compacted silty clay, which exhibited collapse-on-wetting behaviour. The experiments consisted mainly of suction-monitored triaxial tests, carried out in a new apparatus. The test results are interpreted on the basis of an elasto-plastic framework using the conventional stress variable approach (net stress and suction) as well as an approach that takes into account the degree of saturation within two modified stress variables. The evidence for critical states was examined, based on the stress–dilatancy relationships. It was found that a critical state was observed experimentally in cases where the samples contracted over much of their stress paths, but was not truly established in other cases. Relationships between the shear strength and specific volume at the ultimate state were established for samples over a wide range of degrees of saturation (from fully saturated to the air-dried state). A comprehensive experimental study has been carried out to investigate the volumetric and shear strength behaviour of a compacted silty clay, which exhibited collapse-on-wetting behaviour. The experiments consisted mainly of suction-monitored triaxial tests, carried out in a new apparatus. The test results are interpreted on the basis of an elasto-plastic framework using the conventional stress variable approach (net stress and suction) as well as an approach that takes into account the degree of saturation within two modified stress variables. The evidence for critical states was examined, based on the stress–dilatancy relationships. It was found that a critical state was observed experimentally in cases where the samples contracted over much of their stress paths, but was not truly established in other cases. Relationships between the shear strength and specific volume at the ultimate state were established for samples over a wide range of degrees of saturation (from fully saturated to the air-dried state).