Plasticity Theory for Soil Stress-Strain Behavior

A general analytical model that describes both drained and undrained, anisotropic, elastoplastic, path-dependent stress-strain-strength properties of inviscid saturated soils is presented. For any loading (or unloading) history, the instantaneous configuration of the field of yield surfaces is determined by calculating the translation and contraction (or expansion) of each yield surface during successive changes in load. The material behavior can thus be determined for complex, and, in particular, for cyclic loading paths. The inverse stress-strain relations always exist and are uniquely defined if and only if the yield surfaces do not overlap. In order to avoid such overlappings, a new isotropic/kinematic hardening rule is introduced which couples the simultaneous translation of consecutive surfaces. The isotropic/kinematic hardening of the outer surfaces is thus made compatible with any isotropic/kinematic hardening rule assumed for the inner surfaces.