Describing inherently anisotropic behaviours of natural clay by a hypoplastic model.

The purpose of this paper is to model the loading direction‐dependent behaviours of inherently anisotropic intact clay by means of the hypoplastic framework. The basic hypoplastic model for clays proposed by Mašín (2013) is enhanced by incorporating a predefined anisotropic asymptotic state boundary surface formulation which is based on an anisotropic variable by projecting the microstructure tensor onto the normal of the spatially mobilized plane. The capability of the proposed hypoplastic model is first illustrated by simulations of intact Wenzhou soft clay under drained torsional shear tests using the hollow cylinder apparatus. The model is then used to predict undrained shear results on San Francisco Bay mud. Comparisons between the predicted and measured results demonstrate that the proposed hypoplastic model is capable of modelling the combined effect of the principal stress direction and intermediate principal stress on the stress‐strain behaviour of natural soft clay with inherent anisotropy. This paper proposes an improved hypoplastic model for inherently anisotropic clays by incorporating a novel anisotropic asymptotic state boundary surface formulation. [ABSTRACT FROM AUTHOR]