keywords: Competence, foundation, VLF-EM, magnetics, electrical resistivity methods
Integrated Geophysical investigation involving the Very Low Frequency Electromagnetics (VLF-EM), Magnetics and Electrical Resistivity methods were carried out around the proposed Theatre and Media Arts Complex within the Federal University Oye-Ekiti. The study is aimed at assessing the competence of the subsurface materials for the proposed building. Six (6) traverses were established in the area in the W-E and N-S directions along which the VLF-EM, Magnetics and Vertical Electrical Sounding (VES) data were acquired. The dipole-dipole data were acquired along four separate traverses. Nineteen (19) Schlumberger Vertical Electrical Sounding (VES) stations were occupied within the study area. VLF-EM filtered real positive peak anomalies were identified in the area with the highest amplitude observed along traverse 2 at 82.5 m. The magnetic profiles identified high and low magnetic anomalies in the area with the major EM anomaly in traverse 2 revealed as high magnetic intensity. KH curve type is the dominant in the area and four major geoelectric layers were delineated in the area namely the topsoil (composed of clay, sandy clay, clayey sand and laterite), laterite, weathered layer (composed mainly of clay and sand) and fractured/fresh basement bedrock. The depth to bedrock ranges from 1.9-26.4 m. The lateritic layer below the topsoil is very thick beneath VES 6 (12.1 m). The Dipole-Dipole inverted 2-D resistivity image shows suspected basement depressions, fractures or lithological boundary which correlates with the results obtained from the other geophysical techniques. The resistivity and thickness maps of the area show that the topsoil is weak (clayey) in the northern and southern parts, lateritic in the central part, although generally thin (<1.5 m) and that the materials above the weathered layer (where they are lateritic) should be able to bear the load of the building even though it is rarely greater than 4 m in thickness. It could be deduced however, that the central portion of the study area which is expected to host the foundation of the proposed building is competent for the building construction purpose.