الفهرس 
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Abstract
Earthfill dams are constructed to stand safe and stable against the acting force, inparticular, that based on pervious foundation. Two basic problems are found due toseepage flow beneath earth dams; the first pertains to estimation of the amount ofunderseepage while the other is concerned with the resulting effects caused by theseepage force that may affect the stability of such structures. Loss of water throughunderseepage is of a great economic concern for storage dams. Excessive seepagegradients may washout the soil particles along the seepage surface on the downstreamslope of dam and can threaten its stability. The pore water pressure in the saturated zone,below the free surface in the dam embankment increases the probability of sliding of damfaces.To avoid the above dangerous effect, caused by the underseepage, measures of seepagecontrol must be provided. One of the most efficient control methods is providing the damwith drainage filter, specially based on pervious foundation of finite depth.In the present work, the control of seepage beneath an earth dam using a filter isinvestigated. The effect of the main parameters, involved in the problem, on the seepagecharacteristics is studied. Thus, the effect of the filter position, and dimensions, as well asthe foundation depth on the seepage quantity, and the coordinate of seepage surface areanalyzed.In the present study the problem of seepage through and beneath an earth dam, based onlayer of finite depth, with trapezoidal filter is experimentally studied using Hele-Shawmodel. Experimental work is divided into five groups; the first is to study effect of the upstream angle of the filter (α=10.5PᵒP, 16PᵒP, 30PᵒP, 45PᵒP, 60PᵒP, and 75PᵒP) on each discharge enteringthe filter and that seeps to the soil. In the second group; permeability of the dam body ischanged four times for constant angle of the upstream face of the filter (α= 75PᵒP), dischargeentering the filter and that seeps to the soil are recorded and drawn in dimensionlessform. Dye is used in group three to find the horizontal length of the filter resulting fromα=45 and 75PᵒP. In group four, phreatic surface is drawn and photographed for allexperiments. Heights of the trapezoidal filter are recorded from experiments (group five)and Matlab program is used to find a general equation represents height of the filter.Effect of the layer of finite depth on the height of the filter is experimentally studiedusing the same model (Hele-Shaw) based on an impervious base for (α=45PᵒP, and 75PᵒP).Three equations are mathematically derived to deduce filter height-.13 -Comparison between the deduced equations and experimental work is done. For the case of dam based on an impervious base; results of Casagrande, Van Iterson and experimental work are compared and presented.