Slope Displacement Analyses Using Force Equilibrium-Based Finite Displacement Method and Circular Failure Surface

Abstract

Conventional methods of slope stability provide a constant value for the safety factor of the slope, without information of slope displacements and possible variations of safety margins along the potential failure surface. To overcome this shortcoming, a force-equilibrium-based finite displacement method (FFDM) is proposed. Two well known slice methods for circular failure surfaces, namely, the simplified Bishop's and Fellenius' methods are considered in the proposed procedure. The FFDM takes into account all limit equilibrium requirements originally adopted in the slice method with additional displacement compatibility functions and hyperbolic shear stress-displacement relationships. The FFDM provides incremental slope displacements induced by internal or external stress (or safety status) variations. The FFDM also provides local stress-based and displacement-based safety factors as parts of analytical outputs. A monitored highway slope during a rainstorm is used in a preliminary verification of FFDM. Results of the comparative study shows that the slope displacements computed using Fellenius' approach tend to be over-conservative, regardless of different considerations on the influence of groundwater pressures, due partially to its less realistic assumption on the inter-slice forces. The simplified Bishop's method provides acceptable analytical slope displacement results comparable with that measured for the studied slope caused by an elevated groundwater, and is recommended for further applications.