Anisotropic Undrained Stress-Strain Behavior of Clays

A general analytical model that describes the anisotropic, elasto-plastic path-dependent stress-strain-strength properties of inviscid saturated clays under undrained loading conditions is presented. The model combines properties of isotropic and kinematic plasticity by introducing the concept of a field of shear moduli. This field is defined in stress space by the relative configuration of yield surfaces. For any loading history, the instantaneous configuration is determined by calculating the translation and contraction (or expansion) of each yield surface. The material behavior can thus be determined for complex loading paths. The model parameters can be derived entirely from the results of conventional triaxial tests. The model predictions agree very well with experimental test results from triaxial, plane strain, and simple shear laboratory tests and account for stress induced anisotropy in a simple manner.