FINITE ELEMENT ANALYSES OF ISOTROPIC AND ANISOTROPIC COHESIVE SOILS WITH A VIEW TO CORRECTLY PREDICTING IMPENDING COLLAPSE

SUMMARY One major problem encountered when using the finite element method to simulate the load-deformation behaviour of an elasto-plastic soil mass is that the theoretical collapse load is generally exceeded, and in some cases the numerical solution fails to exhibit a collapse load. A mixed variational principle is used as the basis for developing the governing equations of deformation and the results from this are compared with those obtained from the use of the virtual power equation. The former is found to give improved results and is generalized to include description of finite deformation. An Eulerian frame of reference is used. The method of approximating configuration changes in the numerical solution procedure is found to determine the shape of the load-deformation curve. Finally, a simple method of accounting for anisotropy of yield is presented. 1. INTRODUCTION Although a wealth of literature exists on finite element studies of elasto-plastic continua, few have examined the ability of the method to correctly predict .collapse load solutions. Comparison of numerical results with analytically obtained values has, generally speaking, been restricted to trivial cases. Commonly quoted examples include the expansion of a thick-wall cylinder and the loading of a ‘V’-notched tensile block. These problems, because