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Aims: This study entails the geophysical approach for the post foundation investigation using magnetic prospecting and impact method of electromagnetism.
Study Design: Traverses and GPS stations of the area were taken.
Place and Duration of Study: The former Faculty of Arts building at Ekiti State University. Ekiti State University is located along Ado-Iworoko road in Ado-Ekiti, Ekiti State which is located in southwestern Nigeria. The work was on 3rd of October 2019.
Methodology: The instrument used in the ground magnetic data acquisition was the proton precession magnetometer. The study area was divided into four traverses that are 100 m long perpendicular to the strike line i.e. the traverse runs from east to west of the study area. A spacing of 5 m serving as stations were maintained on each traverse making a total of eighty stations was accumulated for the four traverses. The impact method of electromagnetics was carried out immediately after the ground magnetic method, the only alteration was the establishment of sub-stations immediately after each station at 2.5 m away from the main station at each traverse. The creation of sub-stations is to comb the study area and obtain a concise data so as to delineate each of the subsurface structures.
Results: The generated geomagnetic contour map of the study area indicates that the central region with high magnetic value implies competent formation, while the extreme North West has low magnetic values suggesting unstable formation. Electromagnetic Profiles of Traverse EFA-1 is a very conductive zone from top to bottom and can be classified as a very weak zone. It cannot bear the load of the structure that was placed on it and thus not a safe site. The weakness of the zone may lead to differential settlement. Traverse EFA-2 defines a fairly competent zone of weathered or a fractured bedrock typically a weathered zone of intermediate value; it can still bear the load of a structure. Traverse EFA-3 is a zone of weathered/fractured bedrock. It has an intermediate potential and evidence of a linear fracture. In traverse EFA-4 is not a competent zone of low to intermediate value. The low value zones may be seasonally wet and dry which can affect the stability of the foundation.
Conclusion: Data analysis delineated suspected fractured, shear or faulted zones and also revealed that the collapsed Faculty of Arts building was sited within the incompetent clayey weathered layer; these weak zones were detrimental to the integrity and stability of the structure.
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