Probabilistic Slope Stability Analysis: A Case Study

Probabilistic slope stability analyses are becoming more and more popular to evaluate the safety level of slopes and associated risk and reliability, especially in the recent years. The probabilistic approach can take into account the uncertainties and natural variability in material properties, as well as in environmental factors, by using various statistical distribution functions (such as normal, lognormal etc.) for random variables. It is already noted by various researchers that, a slope with a deterministic factor of safety larger than 1.00 using average values of soil parameters may have a significant level of probability of failure, if the material properties are unknown, or contain significant uncertainty/variability. In this study, a well-documented landslide case study is used to demonstrate the importance of probabilistic approach in slope stability; to investigate the effects of considering variability in material properties; and to compare deterministic and probabilistic slope stability analyses results. Deterministic limit equilibrium, probabilistic limit equilibrium, and probabilistic finite element analyses are conducted for Lodalen landslide in Oslo, Norway and the results are compared with each other. The factor of safety, the probability of failure and the most critical failure surface are investigated with and without statistical cross-correlation of soil’s shear strength parameters. The results of this study can provide further insights into the comparison of deterministic and probabilistic approaches in slope safety.

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