A hydro-mechanical elastoplastic model for unsaturated soils under isotropic loading conditions

This paper presents an elastoplastic constitutive model for the coupling of hydraulic and stress–strain behavior of unsaturated soils under isotropic loading conditions. The proposed model is capable of considering the influence of irrecoverable changes in water volume fraction on stress–strain behavior and plastic strain on hydraulic behavior. Bounding surface and subloading surface plasticity frameworks are employed to describe hydraulic and mechanical behavior, respectively. The appropriate coupled hardening rules are introduced to fully describe the coupling effects between hydraulic and stress–strain behavior. Model predictions for unsaturated highly expansive and collapsible soils are compared with test data, and reasonable agreement is achieved.