A Simplified Multiple Yield Surface Plasticity Model and Numerical Implementation into FLAC

摘要

This paper present a simplified multiple yield surface (MYS) plasticity model. For each yield surface, the Drucker-Prager type of yield function is used to represent the stress states for which plastic flow occurs. To simplify the formulation, the plastic potential function is selected such that pure shear results in pure shear deformation and a hyperbolic relation is used to represent the stress-strain backbone curve. In the development of numerical algorithm for the model, the concept of "virtual surfaces" is applied to locating which yield surface is activated after plastic flow occurs. The numerical algorithm is implemented into the finite difference computer program FLAC through a FISH (a special language) subroutine. To evaluate the model performance, numerical simulation of triaxial tests, and numerical prediction of the bearing capacity for a shallow footing are performed and the numerical results are compared with the test results and the closed-form solution or other method, respectively. The comparison indicates that the simplified MYS plasticity model can represent the soil material behavior reasonably well.