ENGINEERING SITE INVESTIGATION USING 2D ELELCTRICAL RESISTIVITY TOMOGRAPHY AT THE SIKTAN PROPOSED DAM SITE AT ERBIL GOVERNORATE, IRAQI KURDISTAN REGION

Abstract

2D Electrical Resistivity Tomography (ERT) was carried out at the proposed Siktan Dam site, Erbil Governorate, NE Iraq. The aim of this study is to evaluating the geo-structural setting of the concealed bedrock along the proposed dam axis and the flanks of the proposed dam site. A comprehensive geotechnical investigation consisting of borehole drilling works and electrical resistivity data were carried out to investigate the subsurface formation. Geologically the proposed dam site is located on the Shiranish Formation consisting of dark gray claystone alternating with limestone marlstone and sandstone. Three profiles were taken by Wenner array with 48 electrodes along of each profile which equal 235m, the space between electrodes is 5m. The SYSCAL PRO instrument is used to collect resistivity data and (SYSCAL Switch) were used with 48 electrodes along one line, and which carries out an automatic switching of these electrodes for acquiring profiling data. The data were processed and interpreted by applying 2D inversions TomoLab software. The using of geophysical prospecting in geotechnical investigation is sometimes looked at as a probable rather than certain method when it comes to construct a detailed subsurface layer profiles. The correlation between borehole information and electrical resistivity ranges was done. The combination of geophysical and geotechnical data may greatly improve the quality of buildings construction in civil engineering. From the structural point of view there is no faults have been detected in this location from ERT and boreholes data as well as there is no evidence of the existence of cavities or any other risky resources. The results indicate that the proposed site is suitable for construction of the dam. Boreholes and geotechnical investigations successfully used to verify the results of the resistivity measurements results.