Introduction

Stability by strength reduction is a procedure where the factor of safety is obtained by weakening the soil in steps in an elastic-plastic finite element analysis until the slope fails. Specifically, an analysis is performed with the mobilized strength properties for the friction angle (φ) and cohesion (c') followed by an incremental decrease of 𝑡𝑎𝑛𝜑' and 𝑐'.

This results in stress states that violate the strength criteria, which are resolved by employing the same iterative stress update algorithm used in SIGMA/W for standard elastic-plastic  analysis. This example verifies the Strength Reduction stability procedure in SIGMA/W by comparison to Dawson et al. (1999). In addition, the results are discussed in the context of an alternate procedure known as a stress-based stability analysis.