Limit equilibrium slope stability analysis using rigid finite elements

This paper revisits the interslice force assumptions associated with the method-of-slices approach to slope stability analysis. A brief review is presented on analysis procedures for this class of problem and a comparison is made between the factor of safety equations derived by Fellenius and a modified form of Bishop’s equation. A simplified rigid finite element method that takes into account progressive yielding through a sliding law is proposed, eliminating the need to provide constraint equations for the variation of interslice forces required by more advanced procedures, such as that developed by Morgenstern and Price. An example is given to demonstrate the proposed procedure and to investigate the sensitivity of the global and local factors of safety to the interslice and basal shear forces. It is demonstrated that the global factor of safety tends not to be sensitive to interslice shear forces when dealing with circular slip. For the slip circles that were analyzed, the Morgenstern and Price procedure yielded slice forces that were similar to those predicted by the proposed method, which takes into account the deformation and failure characteristics of the material comprising the slope.