Application of 3D electrical resistivity tomography to building foundation – A case study of Ahmadu Bello University

Abstract

The recent failure of building foundations such as cracks, structural differential settlements and collapse has now become a great concern to geoscientists. A new site at Ahmadu Bello University, Nigeria, was investigated to explore the suitability of the subsurface material for the foundations of buildings, identify weak zones that may be prone to subsidence and the competence to support massive structures. This investigation was achieved with 3D electrical resistivity tomography (ERT). The data were obtained using Terrameter SAS 4000 and ES 464 electrode selector equipment and processed using the RES3DINV software. Dipole-dipole configuration at electrode spacing of 5 m was used to acquire the data along six profiles laid in the study area. The results in correlation with borehole data showed that the subsurface has a minimum of three geo-electric sections. It can be concluded that the competent layer with high resistivity values (746 to 1206 Ωm) is recommended for building or high rising building foundations due to its fresh basement rock. In the topsoil, clay formation should be avoided, this is because the clay materials are subject to differential settlement or flow under pressure.