Pseudo-static Stability Analysis of Multilayered Slopes Using Sarma’s Method of Non-vertical Slices

Stability analysis of multi-layered slopes with complex geometry and pore pressure conditions has always been a topic of immense interest to both the researchers and the practitioners in the field of geotechnical engineering. Over the decades, within the framework of limit equilibrium methods of slices, a number of rigorous methods have been proposed which are valid for general non-circular slip surfaces, satisfy all conditions of equilibrium, and take full account of the interslice forces. Among these, the Sarma method is the only method in which the slices are not necessarily vertical, and the critical inclinations of the slices are found as part of the solution and use the internal strength of material for the solution of the problem. Because of the number of iterations involved in finding the critical set of slice inclinations, Sarma method is not suitable for finding the critical slip surface. In order to compare the results obtained by using the other rigorous methods with those using Sarma’s method, the latter can be used to re-analyze the critical slip surfaces determined for the other methods. In this study involving three complex slope stability problems, the critical slip surfaces determined using the Morgenstern and Price method and the Spencer method are re-evaluated using the Sarma method. The GEO5 software is utilized for the purpose. The comparison of results has brought out that compared to the Sarma method, both the Morgenstern and Price and the Spencer method consistently yields conservative values of factor of safety for each of the three example problems.