A cap model for soils featuring a smooth transition from partially to fully saturated state

Abstract

AbstractSoils consist of a porous soil skeleton filled by fluids like air and water. The accurate description of their mechanical behaviour requires a coupled solid‐fluid approach. The analysis is based on a set of balance equations, kinematic equations and constitutive equations, the latter including a material model for the soil. Depending on the degree of saturation, the soil behaviour has to be modelled in both, partially and fully saturated state. We present a constitutive model for soils developed from the cap model proposed by Kohler and Hofstetter. The elasto‐plastic model is formulated in terms of two independent stress variables, generalised effective stress σij☆ and matric suction pc. It is applicable to partially and fully saturated state. The yield surface includes a shear failure envelope and a hardening cap surface. Its evolution in terms of matric suction is controlled by the load collapse (LC) yield curve and parameters defining the suction‐dependent intersection of the shear failure envelope with the 1☆‐pc‐plane, where 1☆ = tr(σij☆). Our extension of the model includes an improved LC yield curve to enable a better representation of wetting/drying paths and to allow a smooth transition from partially to fully saturated state. Numerical results for a low to medium plasticity clay are in good agreement with experimental data. (© 2013 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)