Accounting for 2D Spatial Variation in Slope Reliability Analysis

Within the framework of the limit equilibrium method of slices, a slope reliability analysis accounting for two-dimensional (2D) spatial variation requires a model to discretize a random field into a finite number of random variables. A careful review of the existing models has revealed that the models originally developed for homogeneous slopes suffer from certain shortcomings when applied to nonhomogeneous slopes, which have been taken care of in the refined models recently proposed by the authors. Further, on the two approaches followed in accounting for spatial variability, the paper examines the consequences of adopting the simplified approach based on a specific slip surface in place of the rigorous approach based on the probabilistic critical slip surface. Analyses of illustrative examples have revealed that an analysis based on a combination of an inappropriate discretization model and a simplified approach might result in errors as much as 65% on the nonconservative side. The paper also addresses the issue of obtaining solutions in slope situations in which site-specific values of the 2D scale of fluctuation are either not available or are different layerwise.