Thermodynamic modeling of accumulated deformation of saturated clays under pure principal stress rotation

In contrast with elasto-plastic and empirically regressed models for soils, a novel thermodynamic constitutive model is proposed based on the granular solid hydrodynamics. Two energy dissipation mechanisms of elastic relaxation and granular entropy movement are mathematically described, which allows for the modeling of non-linear hardening and softening behaviors of soils and the modeling of accumulated plastic deformation due to the pure rotation of principal stresses in particular. The simulated results for Hangzhou clay indicate that the pure principal stress rotation can also cause inelastic deformation accumulation without any changes of principal stresses. During the rotation of principal stresses, the directions of principal strains do not coincide with the ones of the principal stresses, which is a typically non-coaxial behavior. The strain peaks fall behind the stress peaks. There exists a stress-strain hysteresis loop during the rotation of principal stresses, and the energy dissipation and non-elastic process should happen. All model results fairly fit the laboratory data.