Feasibility of using unsaturated zone models on the seepage through embankment dams

Seepage through embankment dam body is determined by a phreatic surface that separates the lower saturated zone from the upper dry zone. in fact,there is a partially saturated zone that acts as a transition zone between the two regions. in this research,seepage in the partially saturated zone will be examined using different models to simulate this zone to take the decision when it must be taken into account or may be neglected. comparison between the results in cases of steady,and transient seepage using seep/w,plaxflow softwares is carried out for different embankment dam types. the comparison is carried out for the position of phreatic surface,exit point,seepage losses,and hydraulic gradient al-basel dam is chosen as a case study. the study showed that the unsaturated zone can be neglected in case of homogenous dam,but it has to be considered in case of zoned dams.