Elastoplastic model for hydro-mechanical behavior of unsaturated soils

A coupled elastoplastic constitutive model is presented for describing the hydraulic and mechanical behaviors of unsaturated soils. The model is capable of considering the influence of the irreversible changes in water saturation on the mechanical behavior and in plastic deformation on the hydraulic behavior. The mechanical and hydraulic behaviors are captured using the subloading surface and bounding surface plasticity frameworks, respectively. The coupling between hydraulic and mechanical behaviors is established using the intergranular stress concept in addition to appropriate coupled hardening rules. Attention is also given to the movement of the soil water characteristic curve due to the plastic deformation. Model predictions for some unsaturated soil samples are compared with experimental data, and a reasonable agreement is achieved.