Stress-Rotation Response of a Parallel Iwan Model for Sand

摘要

A plasticity model for simulating three-dimensional (3-D) hysteretic behavior of frictional materials is presented. The target application of the model is 3-D nonlinear seismic analyses involving simultaneous cyclic loading in multiple directions. The model, implemented in the program FLAC3D, is a generalization of the one-dimensional (1-D) parallel Iwan model, in which a number of components are connected in parallel, each component consisting of a linear elastic spring in series with a perfectly plastic slider. This simple arrangement produces nonlinear stress-strain curves and hysteretic, Masing behavior for 1 -D cyclic loading. Remarkably, this approach can also be used for simulation of 3-D cyclic loading. For generalization to 3-D, the constitutive model consists of a number of 3-D linear-elastic, perfectly-plastic components with Mohr-Coulomb yield conditions. All components are subjected to the same strain, with the global stress defined as the average of the component stresses. This simple framework is straightforward to implement numerically, leading to a robust tool for analysis of general 3-D stress paths. The model's performance for a complex non-proportional loading path is demonstrated through simulations of drained true triaxial tests involving stress rotation in the deviatoric plane.