Geophysical Investigation of the Subsurface Structural Competency Around College of Computing and Communication Studies, Bowen University, Iwo, Osun State, South West Nigeria

Abstract

Mapping of the subsurface structures within the environment is highly essential in engineering site characterization. The subsurface structure around the college of computing and communication studies, Bowen University Nigeria was studied using the very low frequency electromagnetic (VLF-EM) and the geo-electrical resistivity method. This was aimed with a view to investigate the weak and competent geological zones. In this study, five traverses were generated for both the VLF-EM and geoelectrical resistivity method, using the VLF-EM 16 equipment and OHMMEGA-Terrameter respectively. The results of the VLF-EM revealed the presence of positive and negative anomalies responses. The positive anomalies indicate the weak zones, which may be caused by geological structures such as faults/fractures, and contacts between rocks and the negative anomalies indicate the competent zones, which may be due to hard rock/laterite. The geo-electrical resistivity results revealed the vertical and lateral inverted resistivity values of the subsurface structure. The result revealed four layers such as top soil, weathered layer, fractured and fresh basement. From both the interpreted results, the weak/fractured zones mapped in the basement are points of interest in this research. The results of the investigation revealed that the probable cause(s) of the structural failures within the study area are evidence of geological features mapped as fracture and clayey formation that is present in the study area. Therefore, in order to evade future structural problems and minimize capitals used in restoring distressed structures in the University, a geophysicist services should be engaged for pre-foundation studies, which will act as a guide before and during construction.