Effect of Geometry and Foundation Conditions on the Accuracy of the Steady State Seepage Analysis Results for Rockfill Dams

One of the most important concerns in designing an embankment dam is seepage analysis. Conventional seepage analyses of embankment dams are performed in two-dimensional (2D) space, in which the impacts of water flow lines seeping from the side abutments are ignored. This fact is especially important if the dam is constructed in a narrow valley. In addition, if the effects of existing underlain faults in the reservoir water discharge rate, under different loading conditions, are to be scrutinized, three-dimensional (3D) modeling of the dam for seepage analysis is inevitable. In this paper, the significance of three-dimensional seepage analyses is emphasized by making a 3D model of a real dam site. The assumed 3D model contains all details of the rock fill dam body and its foundation and abutments. Also, all ground improving methods for the water tightening of the underlain faults have been considered. The 3D steady state seepage analysis results were compared to those of a 2D analysis, from different points of view, indicating that when a dam is designed for a narrow valley, performing a 3D seepage analysis is vital, due to the widthwise water flow from the side abutments. Several sensitivity analyses were also performed to show the effect of uncertainty in evaluating the characteristics of side abutment grouting curtains in seepage analysis result.