GEOPHYSICAL INVESTIGATION OF PRE-BUILDING FOUNDATION OF KWARA STATE UNIVERSITY QUARTER USING ELECTRICAL RESISTIVITY METHOD

Abstract

Incessant increase of collapsed buildings has raised alarm in our society. Many buildings collapsed due to many factors, in which the foundation is major. If the foundation is weak, the structure placed is in danger. In this research, the foundation of Kwara State University Staff Quarters was investigated before laying the structure on the site location. The electrical resistivity method was used to investigate the subsurface geologic layer with a view to determining the depth to the bedrock and thickness of the geologic layers. Vertical Electrical Sounding (VES) using Schlumberger array was carried out. ABEM terrameter (SAS 300) was used for the data acquisition. The field data obtained was analyzed using computer iterative modeling using the WinResist software. The VES results revealed the heterogeneous nature of the subsurface geological sequence: hardpan topsoil (clayey and sandy-lateritic), weathered layer, partly weathered or fractured basement, and fresh basement. The resistivity value for the topsoil layer varies from 40 Ωm to 450 Ωm with thickness ranging from 1.25 m to 7.5 m. The weathered basement has resistivity values ranging from 50 Ωm to 593 Ωm and thickness of between 1.37 to 20.1 m. The fractured basement has resistivity values ranging from 218Ωm to 520Ωm and thickness of between 12.9 to 26.3 m. The fresh basement (bedrock) has resistivity values ranging from 1215 Ωm to 2150 Ωm with infinite depth. However, the depth from the earth’s surface to the bedrock surface varies between 2.63 to 34.99 m. The study stressed the importance of the findings in civil engineering structures