An anisotropic failure criterion for geomaterials

The strength of geomaterials is strongly influenced by their fabric anisotropy, which can not be characterized by the isotropic failure criterion reasonably. A general anisotropic failure criterion is proposed. To characterize relative orientation between the loading direction and material fabric, an anisotropic variable expressed by the joint invariants of the stress tensor and fabric tensor is introduced. The failure criterion is developed based on the failure characteristics of geomaterials in both the meridian plane and deviatoric plane, which leads to a general three-dimensional description of strength anisotropy. Compared with the isotropic failure criterion, only two new parameters are introduced in the anisotropic one. All the model parameters can be readily calibrated based on the conventional laboratory tests. Comparison between the model predictions with the test results on sand, clay, natural clay as well as rock demonstrates that the new criterion can characterize the strength anisotropy of geomaterials in a reasonable manner.