Non-orthogonal elastoplastic constitutive model of transversely isotropic clay

In order to describe the influence of soil anisotropy on stress-strain relationship,a non-orthogonal elastoplastic constitutive model of transversely isotropic clays is established based on the concept of the modified characteristic stress. Modelling procedures are as follows:(1) By referring to the modified stress method,the fabric tensor is introduced into the characteristic stress formula to incorporate the influence of anisotropic fabric. (2) Based on the frictional rule on the octahedral plane in the modified characteristic stress space,a transversely isotropic β-strength criterion reflecting the effects of soil anisotropy and intermediate principal stress is established. (3) In the modified characteristic stress space,the inclined yield surface is adopted to describe the influence of the initial anisotropic consolidation stress condition on the yield characteristics of soil by introducing the volumetric associated hardening parameter,and (4) the incremental direction of the plastic strain of transversely isotropic clays is determined by the three-dimensional non-orthogonal plastic flow rule based on the fractional partial derivative. Only six material parameters are needed in the non-orthogonal elastoplastic model,which can be determined by conventional triaxial tests,and three model parameters are concerned in the proposed model,which can all be easily determined by the determined material parameters. The comparison between model predictions and experimental results shows that the model can reasonably capture the strength and deformation properties of transversely isotropic clays. © 2020, Science Press. All right reserved.