Subsurface structural characterization of the Chooman Dam site using geoelectric method

A recent evaluation of Chooman Dam highlighted the potential for dam failure due to either seepage or an earthquake on nearby faults. Unfortunately, this dam suffers from infiltration or leakage problems related mainly to different geological and tectonic factors. In response to these concerns, electrical resistivity surveys employing vertical electric sounding (VES) method were carried out at the dam site, located in Kurdistan Province in the west of Iran in order to delineate potential pathways of leakage occurring thorough the subsurface structure close to the dam body, bed rock depth and lateral discontinuities in the study area. The VES surveys were conducted using the Schlumberger electrode array in 400 points or stations along 28 profiles at a station interval of 20 to 50 m in up- and downstream sides of the dam embankment. For data acquisition, a terrameter SAS 4000 resistivity system, made by Swedish ABEM Company, was used. Maximum separation of current electrodes in the Schlumberger VES surveys was considered 430 m. These geoelectrical studies revealed a thick package of andesite basement in the eastern part and vitriform tuff basement in the western part of the study area. Considering the results and the detection of a strike-slip fault on the downstream side of the dam embankment, it is evident that fractures are the main causative factor responsible for the leakage in the Chooman Dam.