An anisotropic unified nonlinear strength criterion (AUNS) for geomaterials

Abstract

Due to depositional processes and other factors, such as shear banding and the intermediate principal stress, soils and rocks are typically cross-anisotropic. Strength anisotropy should be described by the proper anisotropic strength criterion. This paper presents an anisotropic unified nonlinear strength criterion to accurately characterize the strength anisotropy of geomaterials based on a unified nonlinear strength criterion (UNS). The anisotropic state variable in terms of a joint invariant and a unit stress tensor is brought into the UNS criterion to characterize the effect of the anisotropy. The new criterion had been illustrated in both the meridian and octahedral planes, leading it the oversimplification to describe strength anisotropy behaviors of soils and rocks under different loading conditions. Moreover, only conventional triaxial test is employed to calibrate the parameters of the new criterion. The results demonstrated the ability of the anisotropic strength criterion to be applied to a wide range of soils and rocks for true triaxial tests along with the complex stress condition in torsion shear tests. By comparing the predictions to test results reported in the literature, the new criterion proposed in this paper is able to provide excellent traits of the strength anisotropy for various geomaterials.