AbstractThe rotational failure mechanism with a log-spiral is most efficient in upper-bound limit analysis for homogenous slopes, but it cannot work well in regard to layered slopes. In this study, the log-spiral rotational mechanism is extended for layered slopes by a multicenter method that focuses on the variations of slip surfaces between adjacent soil layers. There are multiple rigid blocks, each of which rotates around a separate center, in the proposed mechanism, and the additional rupture surface is between the adjacent blocks. Several typical examples are analyzed by the proposed method and other published mechanisms based on the limit equilibrium method or limit analysis method. Benefiting from the log-spiral, the proposed mechanism has fewer rigid blocks than that in other published mechanisms based on the limit equilibrium method or upper-bound limit analysis. The factors of safety obtained by the proposed method are smaller than existing upper-bound mechanisms, and the slip surfaces lie well in the plastic zones obtained by the finite element method (FEM). These comparisons demonstrate the applicability and advantages of the proposed failure mechanism. Furthermore, the influence of nonassociated flow rule on a two-layer slope is considered, and associated effect charts are given.