Three-dimensional reliability analysis of earth slopes

Reliability of cohesive soil slopes is assessed using a three-dimensional (3D) probabilistic stability analysis algorithm. Spatial variability of soil properties is represented by an anisotropic random field. Parametric studies are performed for a typical earth structure. The influence of the model parameters, including expected value, variance and correlation distance of soil shear strength, on the reliability associated to particular failure mechanisms is evaluated. The effect on reliability of the dimensions and shape of potential slip surfaces for a given random field is also assessed. It is shown that the mechanisms that contribute most significantly to global probability of failure of the slope may be quite different from those identified as critical by standard deterministic evaluations assuming soil homogeneity. Some practical implications of this fact are discussed.