GEOPHYSICAL POST-FOUNDATION STUDIES OF MINISRTY OF JUSTICE BUILDING, EKITI-STATE SECRETARIAT, ADO-EKITI, EKITI-STATE, NIGERIA

Abstract

Geophysical investigations were carried out around the ministry of Justice building, Ekiti State Secretariat, Ado-Ekiti, with the aim of investigating the possible cause(s) of failures from the foundation of the building in the government Secretariat. The Electromagnetic and Electrical Resistivity methods were used for the investigation. The Electrical Resistivity method involves Vertical Electrical Sounding (VES) and 2D Electrical Resistivity Tomography using Schlumberger and dipole-dipole configuration. Three (3) VES points were conducted along the traverse within the investigated area with half current electrode separation (AB/2) varying from 2 m to a maximum of 65 m. The electromagnetic measurements were taken at distance separation of 10 m along the traverse line in the SE-NW direction. The VES curve types obtained in the area are H and HKH. Four geoelectric layers were delineated within the investigated area which includes the topsoil, lateritic clay, clay, and partly weathered basement which is a quartzite rock with resistivity values ranging from 47-280 ohm-m, 383-435 ohm-m, 47-78 ohm-m, and 239-4999 ohm-m and the thickness ranges from 1-1.6 m, 2.8-4.2 m, and 9.1-27.9 m respectively. The dipole-dipole results also delineate four geologic formations that revealed the differential settlement within the clayey zone of the building foundations. The electromagnetic method also delineated seven subsurface geologic formations which revealed that most of the materials characterizing the subsurface are of clayey composition. The integration of the results showed that the possible cause(s) of failures in part of the building is due to the presence of clayey formations and geologic fractures within the foundation of the studied area.