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.