Modeling and analysis of the combined hardening response of fully coupled multi-phase porous media in relation to partially saturated soils

This paper investigates the hydro-mechanical response of multi-phase porous media using a coupled flow-deformation theory that accounts for nonlinear constitutive behaviours. A nonlinear, coupled hydro-mechanical formulation is developed using the three-phase extended poroelasticity, equations. A novel combined volumetric-deviatoric hardening law is proposed, enabling the model to evaluate the stress–strain relationship and volume change behaviour. The formulation is then applied to partially saturated soils, whose constitutive relations are governed by an extended elastoplastic model for the mechanical part, a water retention curve, and a hydraulic conductivity function for the hydraulic part. Soil volume change is incorporated into the water retention behaviour, thereby satisfying the hydro-mechanical coupling. Following the finite element formulation of the fully coupled equations, the proposed model is verified with elemental-level experimental results and validated with model-level numerical problems. Parametric studies indicate the importance of hydraulic conductivity and suction changes on the hydro-mechanical response of partially saturated soils.