Slope stability analysis based on a multigrid method using a nonlinear 3D finite element model

Abstract

The rigid-body limit equilibrium method cannot reflect the actual stress distribution in a rock mass, and the finite-element-based strength reduction method also has some problems with respect to convergence. To address these problems, a multi-grid method was adopted in this study to establish a structural grid for finite element computation and a slip surface grid for computing slope stability safety factors. This method can be used to determine the stability safety factor for any slip surface or slide block through a combination of nonlinear finite element analysis and limit equilibrium analysis. An ideal elastic-plastic incremental analysis method based on the Drucker-Prager yield criterion was adopted in the nonlinear finite element computation. Elasto-plastic computation achieves good convergence for both small load steps and large load steps and can increase computation precision to a certain extent. To increase the scale and accuracy of the computation, TFINE, a finite element parallel computation program, was used to analyze the influence of grid density on the accuracy of the computation results and was then applied to analysis of the stability of the Jinping high slope. A comparison of the results with results obtained using the rigid-body limit equilibrium method showed that the slope stability safety factors determined using finite element analysis were greater than those obtained using the rigid-body limit equilibrium method and were in better agreement with actual values because nonlinear stress adjustment was considered in the calculation.