A fully coupled flow-deformation model for time-dependent analysis of unsaturated soils

抄録

A fully coupled flow-deformation model for describing time-dependent behaviour of unsaturated soil is presented. The proposed hydro-mechanical model is formulated based on the theory of multiphase mixtures using the effective stress approach and the bounding surface viscoplastic constitutive model. The governing equations for the flow model are derived using the conservation equations of mass and momentum. The deformation of the solid skeleton is described using the bounding surface viscoplasticity framework to capture the time-dependent stress-strain behaviour of geomaterials. The constitutive model is based on the viscoplastic consistency theory and the bounding surface plasticity model. The proposed viscoplasticity model allows a smooth transition from rate-independent plasticity to rate-dependent viscoplasticity. The hardening parameter representing the size of the bounding surface is defined as a function of viscoplastic strain, viscoplastic strain rate, and suction. For unsaturated soils, the suction hardening effect is described using the coupled influence approach where suction has a multiplicative effect to the viscoplastic volumetric hardening. The numerical results are then presented demonstrating the capability of the proposed model in describing time-dependent behaviour of unsaturated soils.