Development of three-dimensional failure mechanisms and genetic algorithm for limit analysis of two-layer slopes

This paper develops general three-dimensional kinematically rotational failure mechanisms for two-layer soil slopes, which not only considers the back slope angle but also involves the face-failure, toe-failure and base-failure mechanisms. Although the failure mechanisms are developed for two-layer soil slopes, it is easy to extend for multilayer soil slopes with the framework proposed in this study. Genetic algorithm (GA), which poses the advantages of highly computational efficiency over the traditional loop searching method, is developed to search for the upper bound of the critical height of slope. The proposed mechanisms could perfectly reduce to the failure mechanism of single-layer slopes, and the results generated from the GA algorithm are more critical than those of other available approaches, which indirectly identifies the validity of the current analysis and shows the advantage of the GA algorithm. Parametric studies, which cover a wide range of soil slope angle, back slope angle, relative layer thickness and soil strength as well as the width of restriction, are performed to investigate the transformation of the failure mechanism and the corresponding the critical height of two-layer slopes.