2D electrical resistivity tomography (ERT) and GPR methods for soil characterization near Tiaret, northwest of Algeria—a case study

The aim of the current study is to characterize the shallow subsurface soil along the new railway high-speed linked province of Tiaret to Saida of northwestern Algeria. Possible cavities and fractures present in the subsoil are identified by combining two geophysical tools: electrical resistivity tomography (ERT) and ground penetrating radar (GPR). The dipole–dipole electrode array was adopted along two parallel lines to obtain the two-dimensional (2D) resistivity tomography dataset. The spacing electrodes and the total length of each line were 2.5 m and 357.5 m, respectively. The obtained results revealed several anomalies, which were located at depths ranging from 1 to 2.5 m. The higher resistivity values ranging from about 400 to 600 Ωm corresponded in fact to the possible existence of cavities and hard limestone. The background low resistivities (5–20 Ωm) corresponded to saturated materials. The analyzed inverse models were compared and calibrated by taking into account available boreholes. Twenty-four profiles in all were performed for the GPR measurements. The GPR profiles’ results were obtained using two antennas of 200 MHz and 400 MHz. These exposed the presence of several anomalies that could be attributed to cavities and fractures at the bottom of several excavations, at depths ranging from 1 to 2.2 m. The analyzed 2D resistivity tomography results were calibrated by geotechnical investigations data.