Geophysical Approach in the Geological Characterization of Chebabta Dam, Northeast-Algeria

Abstract

Meskiana Area is characterized by a semi-arid climate, where water supply for irrigation and industry is not sufficient as the priority goes for domestic use. To meet the increasing population growth and development, the authorities have considered building a new water retaining structure on some major temporary water streams. For this purpose, Chebabta Site on Meskiana Wadi was chosen as the future dam site. It is large enough to store the desired volume of water.

This study investigates the conditions of the site and the adequacy of the ground as a foundation for the projected dam. The conditions of the site include the geological structure and mainly the presence of discontinuities in the formation on which the dam will be built, the nature of the lithologies under the foundation and the future lake, and the presence of any hazard. This site characterization is usually carried out using different methods in order to highlight any underground buried problematic structure. In this context, the different geophysical techniques remain the most used ones. Four geophysical methods were used in the case of Chebabta dam site, namely seismic refraction, constant separation traversing (CST), vertical electric sounding (VES) and electric resistivity tomography (ERT). The choice of the techniques and the location of the survey lines was made on the basis of the available geological data. In this sense, profiles were established on both banks of Meskiana Wadi.

The obtained results allowed a better characterization of the geological structure, defining the limit between the surface cover and the bedrock, which is, in other words, the limit between the weathered zone and the bedrock. Their respective thicknesses were also determined by seismic refraction and VES. However, ERT succeeded in estimating the thickness of alluvial deposits in the left bank of the Wadi and positioning a fault structure passing at the east of the study area.