Integration of 2D geoelectrical resistivity imaging and boreholes as rapid tools for geotechnical characterization of construction sites: A case study of New Akhmim city, Sohag, Egypt

Abstract

Due to the increasing in the population density, the restriction of the agricultural areas and the scarcity of building's lands and their highly costs in Egypt, especially in Sohag province which led the officials and decision-markers to search for alternatives in the desert places to solve this problems. Therefore, New Akhmim area was proposed as a new site for constructing a new city. The main aim of this research is to delineate the engineering characteristic of the soil, identify of the bedrock depth and determine the subsurface structures and lithology of the investigated site. Great effort should be done to determine the depth to competent layer (bedrock) within the proposed site and correlate the results with the available boreholes. Complementary geophysical tool was implemented for the engineering designs in order to ensure stability of building construction and evade the shocking effects of building collapse later. Thus, electrical resistivity tomography (ERT) was undertaken on the present site for monitoring these subsurface engineering issues. The field geometry was made up of eight profiles using Wenner configuration. The data of the 2D resistivity tomography along these profiles with smallest electrode separation of 5 m were interpreted using Res2dinv software. The subsurface is characterized by three different resistivity zones, which were interpreted as gravel intercalated with coarse sands at the top, sand beneath it and shale beneath the sand layer. The ERT results were in consistent with the results of ten engineering boreholes drilling in the study area. The presence of shale was correlated to the cause of chronic differential settlements of some engineering structures like slickensides due to drying and wetting within the area. No serious structural features were detected as faults, karstification phenomena or caving. So the area is valid for construction proposes.