Three-Dimensional Finite Element Analysis of Levee Through-Seepage Considering End-Around Effects

The current state-of-practice for seepage analyses of levees is to perform two-dimensional steady-state analyses for a transverse cross section. However, evaluation of levees adjacent to urban development can be significantly complicated by the presence of three-dimensional complexities that cannot be explicitly captured using commonly accepted two-dimensional analyses. Variations in landside toe elevation, levee geometry, landside improvements, or the presence of remediations are inherently three-dimensional and therefore can lead to significant differences when conditions are assumed to be two-dimensional. Based on the authors' experience, the presence of one or more of these complexities at levees in the California Central Valley is not uncommon, especially in urban areas. This paper presents the results of three-dimensional seepage steady-state analyses to evaluate three-dimensional effects arising from end-around flow at the upstream limit of a cutoff wall within a uniform coarse-grained levee cross section. Analysis results of three-dimensional, steady-state seepage analyses for four cases are presented, including one case without a cutoff wall and three cutoff wall cases with varying levee geometries. These analyses are then compared against simplified techniques with two-dimensional seepage analyses, commonly used by practicing engineers, to assess their accuracy and reliability for capturing three-dimensional effects. Finally, the results and comparison are used to provide insight on the significance of three-dimensional effects