A Simple Method for Calculating the Seepage at the Foundation of Embankment Dams with Blanket and Clay Trench

Abstract

Controlling the seepage at the foundation of embankment dams is of great importance. In order to reduce the seepage, various approaches are available any of which can be selected based on the condition of the foundation. The correlations recommended in the design codes for calculating the seepage, have been derived for critical conditions and mostly provide conservative values. On the other hand, some effective parameters in seepage at the foundation have not been taken into account in those correlations and thus sometimes the values obtained from them differ a lot with the real values. In this paper, a simple correlation is proposed for calculating the reduction in seepage at the foundation of embankment dams due to construction of clay trench, clay blanket or a system composed of both clay blanket and trench. In order to derive these correlations, the results from 1382 numerical analyses performed by the SEEP/W program have been used. The effect of physical and geometrical factors related to the clay blanket and trench such as the coefficient of permeability, slope of trench, width of the bottom of trench, length and thickness of the blanket have also been considered. Eventually, with regard to the effect of the mentioned factors, the results of numerical analyses have been analyzed with the SPSS 18 software. The results obtained from the suggested correlation have been compared with those obtained from the software analyses as well as internationally recommended formulas. This comparison reveals that in some cases, the values obtained from the equations proposed in those references show a considerable difference with the results of numerical modeling. However, the difference between the results of the suggested formula in this study is shown to be very small with those of numerical analyses.