2D Electrical Resistivity Imaging (ERI) for Subsurface Evaluation of a Pre-engineering Construction Site in Akure, Southwestern Nigeria

Abstract

2D electrical resistivity imaging (ERI) and vertical electrical sounding (VES) were integrated to map the subsurface lithology at a pre-engineering construction site in Akure, southwestern Nigeria, in order to ascertain the competence and suitability of the site for engineering structures. Four 2D horizontal profiling (Wenner array) was used to qualitatively study and interprete the geoinformation of the lithological nature of each geoelectric layer within the study site. Four vertical electrical sounding were also conducted using Schlunberger configuration. The VES data were processed and inverted using master curves and WinResist computer software, while the 2D inversion was done using Diprowin. The results of the 2D horizontal profiling revealed that the study area is composed of four subsurface geo-electric layers with resistivities ranging between 6.91Ωm to 93.6Ωm. These results revealed an expansive clay formation to the depth probed. While the VES results showed a three subsurface geo-electric layers with resistivities ranging between 8.4Ωm to 640Ωm with the second layers where the foundation is supposed to be laid confirmed the presence of clay with resistivities ranging between 8.4Ωm to 13.0Ωm with depth ranging between 4.9m to 7.9m. The results revealed the site to be an expansive clay formation and showed that shallow foundation may not be feasible or advisable for massive engineering structures because of the presence of clay materials in the area. But small or light engineering structures may be recommended.