Effect of confining pressure on shear strength and dilatancy responses of saturated sands

A series of consolidated-drained triaxial tests were performed on saturated sand using a high-pressure apparatus to investigate the influence of initial effective confining pressure and intrinsic soil properties on strength and deformation behavior. Under conventional triaxial compression, samples exhibited strain-softening behavior accompanied by progressive dilatancy at low to medium confining pressures, transitioning to strain-hardening behavior with sustained contraction at high pressures. All reduced triaxial compression tests showed strain-softening response, characterized by initial contraction followed by dilatancy. The peak friction angle demonstrated a strong linear correlation with initial effective confining pressure. A stress–dilatancy relationship was employed to determine the critical state friction angle, and correlations were established among the shear dilatancy index, relative density, and initial effective confining pressure. This paper offers validated methodologies for predicting key strength parameters in stability assessments of sand foundations under high confining pressures.