Effect of the Sheet Piles on Seepage Under the Earth Dam at Various Reservoir Water Levels

Seepage in earth dams is one of the most challenging issues in geotechnical and hydraulic engineering, as it directly impacts dam safety and reservoir performance. Seepage may lead to internal erosion, piping, and structural failure if not effectively handled. This paper aims to study the effect of sheet pile installation at the dam body and foundation on seepage reduction at the proposed earth dam located in the Al-Khoser seasonal river basin, Mosul city, northern Iraq. The study also compares the effectiveness of sheet piles with other seepage control methods. Seepage analysis was performed using the SEEP/W submodel within the Geo-Studio package. Different Scenarios were analyzed. The first (12) Scenarios involved a homogeneous dam body without a core, exploring different configurations of blankets and foundation treatments. The final Scenario No. 13 incorporated a central impervious core. The results demonstrated that sheet piles, due to the low hydraulic conductivity of the foundation, had minimal effect on reducing seepage rates. However, an improvement was observed in Scenario No. 12, where an extended upstream blanket was used, which reduced seepage to (1.1 × 10⁻⁷ m³/s) through the dam and (1.44 × 10⁻¹⁰ m³/s) through the foundation. In Scenario No. 13, the usage of a core reduces the seepage considerably, where the seepage rate was reduced to (8.45 × 10⁻⁸ m³/s) through the dam body and to (1.35 × 10⁻¹⁰ m³/s) through the foundation, which mean that seepage decreased by 35% in the dam body and 18% in the foundation compared to the first Scenario.