A Study of Seepage through Oba Dam Using Finite Element Method

Abstract

Dams are constructed to impound water for flood control, water supply, irrigation, energy generation, recreation as well as pollution control. Yet destructive effects of water on them are enormous. Seepage has been implicated as a major cause of dam failure due to its potential to cause internal eruption of soil. Different methods have been identified to study the extent of seepage in earth dams.  Of the methods, flow net is commonly used due to its relative simplicity. However, it becomes more complex with zoned earthfill dams.  In this paper, Finite Element Method (FEM) is employed to study seepage behaviour in Oba dam. Though the method was developed for the analysis of aircraft structural problems, due to its versatility, it is found as tool to solve variety of other practical problems. Finite Element formulation of the governing equation was established and computer programme was written to solve it. The bottom of the dam was meshed using rectangular element mesh while the piezometric heads at nodal points were determined. Also, determine was the coordinates that define the phreatic surface of the seepage. The results obtained were compared with those obtained from flow net approach which served as control using t-Test technique. It was observed that there was no significant difference (p > 0.0005) between the results. Thus, the method is appropriate for the study. The added advantage of the FEM is that simulation of the seepage problem of the dam becomes easy.

Keywords: Finite Element, seepage, Oba dam, piezometric head, phreatic surface.