Numerical Simulation of Big Bay Lake Dam Breach

The Big Bay Lake Dam is located in south Mississippi. The earth fill dam was 2000 feet long and 57 feet high with a 3H:1V slope. It was built in 1990-1991, and failed catastrophically on March 12, 2004. The original failure investigation was conducted by the owner’s engineer, henceforth referred to as Engineer, concluding the dam failed by piping under the cutoff wall. After being re-evaluated in 2013 by Ferguson et al., it was determined the failure occurred due to piping events along the conduit. Using available data, the failure was modeled using Plaxis 3D to analyze the stages and progression of the failure in comparison to the real-life event and previous investigations. Plaxis 3D is an advanced finite element analysis software program that can be used to concurrently model seepage and the stability of geo-structures. 3D finite element analysis of the breach at Big Bay Lake Dam was performed in two phases; in the first phase, flow analysis was performed using a normal pool steady state seepage condition to simulate the pore water pressure distribution within the dam. Based on these steady-state seepage conditions within the embankment, a deformation and stability analysis was performed and analyzed about the reported failure modes. The 3D numerical analysis results are in good agreement with the failure mechanism determined by Ferguson, et. al. as well as a report made by Eustiss Engineering for trial purposes.