Optimizing cut off wall depth in Gurdian dam of Julfa based on the seepage analysis by Seep/W

Gurdian dam with 1450 meters length is including out of the axis of the dam that receives water from the Aras River. Based on geological studies and drilling investigation, river bed in dam site made up of layers of marl and sandstone with interlayer of loose conglomerate of Miocene. Permeability of this sediments vary between 10-11 and 10-3 m/sec. Regarding to dam site specifications is used cut off wall with plastic concrete for over the wall 850 meters length. In fact cut off wall is an impediment under the axis of the dam that caused decrease the seepage amount. Of course the amount of acceptable seepage reduction for this depends on the local geology and characteristics economic value water in the region and the cost all every cubic meters of water. With regard to the conditions of the dam water reservoir of Gurdian, will provide by pumping from Aras river, the cost of each cubic meter water is high, therefore is willing to reduce the seepage amount below 90 percent compared to without cut off wall. Due to this and the underground conditions depth of cut off wall in different parts has been set. The results of seepage analysis indicate that the optimal depth of cut off wall is varied between 5 to 12 meters in different parts. The seepage value from foundation of dam without cut off wall will be 1,898,200 m3/yr and with a cut off wall will decrease to 208,500 m3/yr.