Theoretical Analysis of Seepage through Homogeneous and Non-homogeneous Saturated-Unsaturated Soil

In this research, the program SEEP / W was used to compute the value of seepage through the homogenous and non-homogeneous earth dam with known dimensions. The results show that the relationship between the seepage and water height in upstream of the dam to its length for saturated soil was nonlinear when the dam is homogenous. For the non-homogeneous dam, the relationship was linear and the amount of seepage increase with the height of water in upstream to its length. Also the quantity of seepage was calculated using the method of (Fredlund and Xing, 1994) and (Van Genuchten, 1980) when the soil is saturated – unsaturated, the results referred to that the higher value of seepage when the soil is saturated and the lowest value of seepage when using Van Genuchten method for both homogeneous and non-homogeneous earth fill dams. Also relationship for the seepage (Q) with the curve fitting parameter (a) for sand, silt and clay soil was nonlinear when the dam is homogenous with constant variables (n, m) and the amount of seepage increase with increasing value of (a). The amount of seepage for a nonhomogeneous dam with a different value of (Kshell to Kcore) was calculated and then compared with the value of (K equivalent) which was equal to average (Kshell and Kcore) for the homogenous dam. The results show that when the average between (Kshell and Kcore) is ≤ 100 the difference was small between the quantity of the seepage calculated. For simplicity of the solution process, it can be replaced non-homogeneous dam by a homogenous dam with (K eq) when the values of Kshell and Kcore are less than or equal to 100