Geophysical Investigation of Building Foundation in Part of Ilorin, North Central Nigeria Using Electrical Resistivity Method

Abstract

Electrical resistivity method has been performed using Vertical Electrical Sounding (VES) technique at a Bishop Smith Memorial College, Ilorin, Kwara State to examine the geophysical parameters that can be used to evaluate the subsurface competency. Eight VES stations were sounded, using Schlumberger configuration for data acquisition with current electrode spacing varying from 1.0 to 140.0 m. The VES data obtained were interpreted using ipi2win+ip Software. The field data acquired was presented as geoelectric sounding curves and geoelectric section. The interpretation of the field results revealed heterogeneous subsurface geologic sequence probed to 34.6 m and beyond. It also showed presence of near surface linear geologic structures of varying lengths, depths and attitude which suggest the competent zones for foundation laying. The major subsurface layers are the top soil which consists of interlocking and concretional lateritic stones and clayey sand, weathered basement, fractured basement and fresh basement. For building development in the study area, the topsoil must be excavated to at least the Fresh basement (competent layer) to avoid building deformation.