Probabilistic Post-Liquefaction Slope Stability Analysis for Risk Assessment of Trout Lake Dam

Probabilistic slope stability analyses allow uncertainty to be quantified and incorporated rationally into a Potential Failure Mode Analysis (PFMA) by providing a range of factors of safety with their associated probability. In deterministic slope stability analysis, the engineer or the engineering team select arbitrary material properties for the slope stability model based on their experience and their engineering judgment. The probabilistic analysis is a risk tool to allow the PFMA team collectively decide on how the uncertainties in the slope stability analysis be addressed. This paper presents a case study of a probabilistic post-liquefaction slope stability analysis for the Trout Lake earthen dam. A PFMA workshop was held to evaluate the seismic risk to the dam using the results of this study. There were uncertainties in characterizing the strength of potentially liquefiable heterogeneous foundation soils that were composed of silty and sandy gravel and cobbles. A finite element model of the earthen dam was developed to perform the probabilistic analysis.