Using the results from thousands of parametric numerical simulations, simplified equations were developed for predicting the deformations of embankment dams and levees when the underlying foundation soil liquefies. These tools were developed to support the U.S. Army Corps of Engineers' Portfolio Risk Analysis (PRA), which is being used to probabilistically quantify failure risks at over 600 dam and levee projects. During major earthquakes, many of these facilities are subject to liquefaction of saturated alluvial soils beneath the embankment. Given the resources and site specific data available in the PRA process, the Corps needs simple tools for identifying projects where liquefaction-induced deformations might jeopardize the impoundment. In this study, an explicit finite difference code, capable of tracking large deformations in soil structures, was employed to model a simplified embankment cross section. The embankment height, side slopes, embankment soil strength, headwater pool level, liquefied soil thickness, and residual liquefied soil strength were parametrically varied to represent the conditions typically found in the Corps' projects. The full parametric matrix involved 20,000 numerical simulations, which were run in a batch analysis on a network of desktop computers. Many of the simulations attempted for the weaker liquefied soil strengths could not be completed, due to severe distortions and large deformations within the solution grid. Results were compiled from 8,612 analyses that converged to a stable solution. Using linear regression, simplified algebraic equations were then fit to this simulated data set. Equations were developed to predict (a) the loss of freeboard and (b) a characteristic displacement (defined as the 99.8th percentile displacement magnitude within the embankment cross section). The fitted equations and associated guidelines are suitable for use as screening tools to identify earth structures that warrant more detailed analysis and study for liquefaction risks.
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