The concept of effective stress in unsaturated soils

Abstract

Very small to large strain properties of a silty sand were measured at several water contents ranging from a few percentage points to saturation level by the use of three triaxial devices with different types of transducers. In the analysis of the data, attention was paid to the influence of the water content on the maximum (Young's) modulus and the effect of the confining stress, etc. Isotropic and triaxial tests, with the measurement of capillary pressure (suction), were also performed on the same material. The effective stress concept was used to interpret the results. The predictions of a rnicromechanical model were compared with the experimental data in the elastic domain and on the failure criterion. The method highlights a simple way to relate the strength and stiffness of the soil to its capillary pressure.