A thermodynamic constitutive model for structured and destructured clays: Fid-Bau Portal

A thermodynamic constitutive model for structured and destructured clays

Zhang, Zhichao / Feng, Mingfei / Zhou, Guangshuo / Xu, Zhenglong

Abstract A thermodynamic constitutive model for structured and destructured clays is proposed in this paper based on thermodynamic principles on the energy storages and dissipations. The model includes state-dependent relations of hyperelasticity and plasticity without the concept of yielding surface. The proposed nonlinear hyperelasticity is dependent on the sates of soil stress, density, and structure and leads to the limit state surface that varies with the bonding structure from a curved surface for structured clays to a plane surface for destructured clays. The plastic and destructure laws are subjected to the second thermodynamic law and expressed in the elastic-strain space instead of the stress space, which naturally account for the couplings between elasticity and plasticity with the Lode-angle and structure effects. The model is well validated by the predictions of drained/undrained conventional and true triaxial shearing tests for both structured and destructured clays, which well capture the K0 effect, the non-coaxiality between stress and strain, and the structure/destructure effects on the elastic-stiffness and strain-softening of clays. For both structured and destructured clays, the critical-state elastic strain is unique under a fixed Lode angle and hence the critical state only relies on the critical-state density and the direction of shearing path.