Effect of Width, Length and Position of Cutoff Wall on the Seepage Characteristics of Earth Dam

Abstract

Seepage is one of the main causes of failure of earthen dam. To encounter the seepage through the foundation of dam, construction of cutoff wall is a frequently used and a conventional technique. In this study, several numbers of numerical analysis are performed against different widths and lengths of the cutoff wall for different positions along the cross section of the dam to find out the appropriate one. All these analyses are performed for a homogeneous dam with foundation soil being clay and silty clay. Numerical analyses are conducted by SEEP/W (a sub program of Geo studio). The numerical results depict that the best possible position of the cutoff wall is at the downstream toe of the dam. This is because, in this position, most number of flow lines get encountered by cutoff wall. It is also observed that the effect of the width of cutoff wall on the total head and pore water pressure (PWP) is negligible but it affects the velocity of seepage and total discharge. On the other hand, the length of the cutoff wall controls all these flow properties. Clay foundation provided a better result than silty clay foundation for all the cases to control the seepage through the foundation of the earth dam.