Stability Analysis of a Layered Slope with Failure Mechanism of a Composite Slip Surface

Abstract

A great significance should be given to layered slope stability, because the actual slope is often heterogeneous with a composition of multilayer soils due to natural formation and artificial filling. Previous research has theoretically investigated the limit-equilibrium (LE) stability of layered slopes using the single slip surface (SSS) with a circular curve, which may be inconsistent with engineering facts. Hence, this work established the failure mechanism of a composite slip surface (CSS) for a layered slope. The CSS was adopted with a circular curve and noncircular curve. Similar to the SSS, the CSS is also a smooth curve. To simplify the analysis process of slope stability and avoid the influence of the difference of material in the interior of the sliding body on the slope stability, a new LE stress method was proposed on the basis of the global mechanical-equilibrium conditions of the whole sliding body without the divided slice. Compared to the traditional LE methods, the LE stress method had a high calculation speed by avoiding the iterative calculation of slope factor of safety (FOS). Then, both the failed and stable slope examples were listed, and the limit-analysis method (LAM), the finite-element (FE) LAM, and the traditional LE Morgenstern-Price (M-P) method were adopted to analyze the slope stability. Thus, by comparison and analysis of the results in various examples, the feasibility of the present study was verified. Furthermore, the stability charts of a horizontally layered subgrade slope with two soil layers were drawn to facilitate the safety design of the slope. Moreover, the study demonstrated that the failure mechanism of SSS with a noncircular curve or the CSS with a circular curve is suggested to analyze the layered slope stability.