Expansion and application of the principle of effective stress in anisotropic saturated soils

The principal of effective stress is the foundation of soil mechanics. In this paper, two typical methods are used to analyze the inner stress of anisotropic soils in order to characterize the inhomogeneity of the internal stress and anisotropic mechanical behaviors of soil caused by the irregular shape and distribution of soil particles. The results show that, for anisotropic soils, the effective stress without considering the contact area of soil particles cannot describe the nonuniformity of the internal stress while the skeleton stress as a real stress can do. For ease of application, and referring to the physical connotation of the effective stress, an equivalent stress tensor is proposed to characterize the skeleton stress produced by all other external forces except for pore water pressure. The specific expression of the equivalent stress tensor is given with the fabric tensor, and the two-to-two conversion relations among effective stress, skeleton stress and equivalent stress are established. Moreover, using the equivalent stress to describe the soil skeleton stress and adopting existing constitutive model to simulate mechanical behaviors of soil skeleton, constitutive models of isotropic soils can be "anisotropized" without additional modification of the basic mechanical law of soils to realize the expansion of the principal of effective stress to anisotropic soils. Finally, as an example, the Lade's failure criterion is transformed into the equivalent Lade's failure criterion. Comparison with the existing experimental results proves that the expanded principle of effective stress is applicable to anisotropic geomaterials. © 2020, Science Press. All right reserved.