Traditional and Advanced Probabilistic Slope Stability Analysis

The paper contrasts results obtained by the traditional First Order Reliability Method (FORM) and a more advanced Random Finite Element Method (RFEM) in a benchmark problem of slope stability analysis with random shear strength parameters. The key difference between the methods is that RFEM takes into account spatial correlation in a rigorous way allowing slope failure to occur naturally along the path of least resistance. Both methods lead to predictions of the "probability of slope failure" as opposed to the more traditional "factor of safety" measure of slope safety, however they give significant different results depending on the value of the correlation length. For small correlation lengths FORM is generally conservative, however it is shown that there is a "worst case" correlation length for which FORM leads to unconservative predictions of slope reliability.