Seepage analysis is an important design aspect of the floodwall in South Louisiana for assessing its hydraulic stability. Estimating subsurface flow through the floodwall requires a thorough understanding of pore pressure characteristics in foundation soils under hurricane storm surge condition. During a surge period, the seepage flow is far from the steady-state due to the low permeability of the local soft soil foundation and is influenced by the surge-induced water surcharge load on the flood side of the floodwall. The active pore pressures on the floodwall under surge conditions result from both the transient flow and excess pore pressure resulting from soil volume changes induced by the water surcharge and structural deformation. Prediction of such subsurface flow is beyond the capability of conventional seepage analyses. This paper presents a finite element seepage analysis to investigate active pore pressures on the floodwall with the consideration of soil-structure interaction effects. The results of the finite element seepage analysis are used to evaluate the gap formation and the seepage cut-off of the floodwall based on seepage design criteria.
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