A numerical modeling study on the seepage under embankment dams

Abstract

The present study focuses on the flow discharge under the embankment dams with clay core. Using numerical analysis, the effect of the cutoff wall and horizontal drain on the flow discharge, hydraulic gradient and uplift pressure beneath the dam was examined. The finite element program of SEEP/W was applied for modeling embankment dam. Comparing the results of numerical modeling of the embankment dam with the results of physical modeling demonstrated the acceptable accuracy of the numerical method in the flow evaluation. The effect of the position and depth of the cutoff wall on the seepage under embankment dam was also investigated. The seepage discharge was evaluated in terms of using horizontal drain and a combination of the cutoff wall and horizontal drain. The effect of dam’s layering foundation on the flow was investigated. The results indicated that the placement of the cutoff wall under the clay core would have the most reduction of seepage under the embankment dam. By increasing the cutoff wall depth, uplift pressure under the embankment dam was decreased and the hydraulic gradient was increased. The maximum hydraulic gradient occurred at the location of the cutoff wall. The effect of the cutoff wall on the seepage reduction under the embankment dam was decreased through decreasing permeability of the dam foundation. Increased horizontal drain length resulted in uplift pressure decrease. The results of modeling of embankment dam constructed on layering soil foundation suggested that the amount of hydraulic gradient, uplift pressure and seepage flow would change significantly when the cutoff wall depth ratio equals to the two-layer boundary depth.