A new approach to interpret the mechanical behaviour of unsaturated soil using effective stress and degree of saturation

Abstract

Unsaturated soil shows complex mechanical behaviours compared to saturated soil. A number of constitutive models for unsaturated soil have been proposed. However, these models suffer limitations. In this paper, a new constitutive model has been proposed in terms of effective stress and degree of saturation based on the modelling assumption about the relationship between hardening effect and degree of saturation. The proposed volume change equation gives a new explanation for the volume change of unsaturated soil. Then, an alternative approach to simulate coupled hydraulic hysteresis and the influence of the volume change on soil–water characteristic curves is suggested. Finally, this paper presents comparisons between the model simulations and experimental data. It is shown that the proposed model represents great ability to reproduce the mechanical and hydraulic response of unsaturated soil.