Equivalent Stress Tensor and Anisotropic Failure Criterion of Soils

Experimental evidence shows that the strength of geomaterials is significantly influenced by the inherent anisotropy, the intermediate principal stress and the stress direction. To measure the joint effect of the fabric tensor and the stress tensor, a second-order tensor named the equivalent stress tensor is extracted from the equilibrium equation of the soil-skeleton. As the magnitude and direction of the effective stress together with the microscopic characteristics of anisotropy are enrolled in the equivalent stress tensor, the modelling process of anisotropic failure criterion with the application of the equivalent stress tensor is proposed. On this basis, a general 3D failure criterion of anisotropic geomaterials is formulated based on the SMP criterion, of which all introduced parameters can be conveniently determined by conventional laboratory tests. Comparison with experimental results of various stress paths from literatures claims that the anisotropic failure criterion is able to capture the strength anisotropy in torsional shear tests. Further discussion is done on the possible application of the equivalent stress and the probable improvement of the new criterion to address other models.