الفهرس 
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Abstract
Reducing seepage quantities and increasing earth dam stability are important environmental and economical design goals. Therefore, earth dams based on pervious foundations must be provided with seepage control measures. An upstream impervious blanket, tied to dam core, may provide an adequate measure to control seepage through such dams. A vertical cut-off connected to the dam core may be added to increase its effectiveness. In the present study, analytical, experimental, and numerical solutions are presented to analyze the effect of blanket with cut-off on seepage discharge, head loss due to the blanket, maximum exit gradient, height of seepage surface, and location of the free surface. The main involved parameters are; embankment dimensions, foundation depth, effective head, blanket length, and cut-off depth. The analytical solution is based on combining confined and unconfined seepage zones. Equations are derived for seepage discharge, head loss along the blanket, and the free surface location. Comparison with other analytical solutions; (Bennet, 1946), (USBR, 2014) and (Noori et al., 1987), showed a good agreement with 8.0% maximum deviation. The experimental analysis is based on the viscous flow (Hele-Show) model. The numerical solution is based on finite element method, using the software (GMS). Throughout the work, two cases have been investigated; a dam with U/S blanket only and a dam with U/S blanket and cut-off, in addition to the case of a dam without seepage control measures (the reference case). Different values of blanket length, cut-off depth and foundation layer depth were tested. Shiwashok earth dam in Iraq is considered as a case study. Results show that existence of blanket with cut-off reduces both seepage discharge and exit gradient, increases the head loss, and lowers the free surface to a great extent. A blanket of length equals 0.75 of the dam base width is sufficient to reduce seepage discharge and maximum exit gradient by about 60% and 35%, respectively. Considering Shiwashok earth dam, comparisons between results of the three solutions revealed a very good agreement with an overall deviation within 10.0%. Results are presented in charts and regression equations to determine the seepage discharge, the head loss and the maximum exit gradient, in dimensionless forms, were given.