Shear strength of granular soil under saturated and unsaturated conditions

Abstract

The shear strength of soils depends on various factors such as the stress level, soil density, and degree of saturation. Capillary forces in unsaturated soils feature an increased strength against shear loading, and influence stress, deformation, and flow phenomena. Thus it is crucial to incorporate the bonding effect of unsaturated soils to numerical models addressing the behaviour of unsaturated soils. The presented experimental campaign of triaxial compression tests aims to investigate the effect of capillarity on the mechanical behaviour of granular soil. The experimental programme consists of consolidated-drained tests on saturated soils and equivalent constant suction tests on unsaturated soils with matric suction of 10 kPa. The results of the experimental campaign reflect the higher resistance of unsaturated soils against shear loading manifested by an additional apparent cohesion term and by suction-induced hardening.