Modeling Stress-Dilatancy Behavior of Compacted Silty Sand Under Suction-Controlled Axisymmetric Shearing

A thorough stress-dilatancy analysis of statically compacted silty sand is presented based on results from a comprehensive suction-controlled (drained) triaxial test program. Induced soil suction values, via axis-translation and relative humidity techniques, ranged between 0.05 to 300MPa, with net confining pressures varying from 100 to 300kPa. A first companion paper documented the strength, stiffness, and stress-induced anisotropy of the same soil under similar test conditions and variables. This paper focuses on the dilatancy rate, stress-strain and volume change responses, shear band formations, and peak as well as critical strength characteristics of isotropically consolidated silty sand under suction-controlled axisymmetric shearing. Augmentation in the peak stress ratio is found to be heavily dependent on the level of matric or total suction imposed, the maximum induced dilatancy, and the critical stress ratio. Experimental observations are also used to substantiate, or further refine, existing stress-dilatancy theories, which has led to the postulation of a simplified new formulation for predicting peak friction angle over the entire test suction range applied.