A generalized anisotropic failure criterion for geomaterials

Experimental evidence shows that the strength of geomaterials, such as soils and rocks, is significantly influenced by inherent anisotropy and other factors such as shear banding and the intermediate principal stress, which cannot be properly described by an isotropic failure criterion. This paper presents a generalized failure criterion for geomaterials with cross-anisotropy. To account for the influence of cross-anisotropy, we introduce an anisotropic variable in terms of the invariants and joint invariants of the stress tensor and the fabric tensor into the frictional coefficient of the failure criterion. The anisotropic failure criterion is formulated in both the deviatoric plane and the meridian plane which collectively offer a general three-dimensional description of strength anisotropy. All the parameters introduced in the criterion can be conveniently determined by conventional laboratory tests. We demonstrate that the new criterion is general and robust in describing the variation of strength with loading direction for a wide range of materials. The failure criterion has been applied to the prediction of strength for several clays, sands and rocks reported in the literature. The predictions compare favorably with available experimental data. Further discussion is made on possible improvement of the new criterion to address other materials with complex strength characteristics, as well as its potential usefulness for constitutive modeling of anisotropic geomaterials.