Investigations on water escape causes of Arbatan Dam in Azerbaijan-e-Sharghi

Investigation on the causes of the water escape from Arbatan Dam is the main objective of this paper. The dam is located 50 km of North-East Tabriz in Azerbaijan-e-Sharghi province. The maximum capacity of the dam reservoir is about 27 millions m3 and is feeding by an artificial channel with 26 km length from Talkh-e-Roud River. The dam is constructed in 2005 and it is dewatered four years later due to water escaping. Geothechnial and field investigations show that Gypsifeerous marls with intercalations of Gypsum crystals are the main lithology of the site. A Salt layer has also been recognized in 35m under the reservoir. It seems the water has been reached to salt layer by dissolution of gypsum layers. The salt layer dissolution has been caused the underground channels and sinkholes, consequently. Roof falling of the underground channels caused the ground subsidence and the dam axis has broken. The same tendency of sinkholes and land subsidence with layers strike in the study area confirms the obtained result.