Importance of lower-bound shear strength in the assessment of the probability of failure of spatially random clayey slopes -

Abstract

The stability of a soil slope is traditionally evaluated by adopting a deterministic approach that is based on a target global factor of safety that is calculated either through limit equilibrium methods or through finite element analyses. Due to the uncertainties that affect the risk of slope failures, recent studies have attempted to solve slope stability problems using reliability theory. Recently, probabilistic geotechnical analyses in which nonlinear finite-element methods are combined with random field generation techniques have been adopted to quantify the effect of spatial variability in soil properties on the risk of failure of slopes. This approach is currently referred to in the literature as the Random Finite Element Method (RFEM). In this study, a robust probabilistic slope stability analysis using the RFEM is conducted to investigate the effect of including a lower-bound shear strength in the probabilistic model describing the uncertainty in the undrained shear strength of clayey slopes. Another objective of this study is to investigate the sensitivity of the reliability of clayey slopes to the random field generated in the analysis. Finally, the results obtained from the simulated analyses are used to recommend design factors of safety that would result in acceptable probabilities of failure for undrained clayey slopes.