Coupling plasticity and energy-conserving elasticity models for clays

A class of two-invariant stored energy functions describing the hyperelastic characteristics of soils is coupled with a critical-state plasticity model. The functions include constant as well as pressure-dependent elastic shear modulus models, and automatically satisfy the requirement that the elastic response for any loading path be energy conserving. The elastic responses predicted by the hyperelastic model are compared with measured undrained elastic responses of an overconsolidated clay in order to assess, both qualitatively and quantitatively, the predictive capability of the hyperelastic model. The importance of the pressure-dependent nature of the elastic shear modulus is assessed within the context of elastic and plastic responses. An energy-conserving model provides a fundamentally correct description of elastic material behavior even in the regime of plastic responses.