Vertical Electrical Sounding to Determine Fracture Distribution At Adumasun Area, Oniye, Southwestern Nigeria.

Abstract

People living in Ibadan, Southwestern Nigeria have started shifting their focus on construction of buildings towards villages that are close to the metropolis. It is therefore imperative to carry out this research in order to recommend the types of structures to be erected at Adumasun area, Oniye, Southwestern Nigeria when the time comes in order to avoid catastrophic failure that might have happened thereafter. The aim of this research is to carry out vertical electrical sounding geophysical survey at Adumasun area, Oniye, Southwestern Nigeria with a view to determining the fracture distribution within the study area. The study area is located between latitude 07037′55.37″to 07038′00″North and longitude 0030 11′10.2″to 003011′16.8″East. Schlumberger electrode array was employed for the study using R 50 Resistivity meter for the data acquisition. The geoelectric survey comprised of ten depth soundings, with maximum current electrode spacing (AB) of 200m. 40% of the modeled curves are A-type, 50% are H-type, and 10% are KH-type. The geoelectric sections obtained from the sounding curves revealed 3-layer and 4-layer earth models respectively. The models showed that the subsurface layers were categorized into the topsoil, the second layer, and the third layer (where it is present). One-third of the study area showed fresh bedrock while two-third showed fractured bedrock. Areas underlying with fresh bedrock and thin overburden thickness are recommended for the construction of high-rise buildings while areas with fractured basement and thick overburden thickness are recommended for the construction of low-rise buildings. It is concluded that the study area is averagely competent for the construction of high-rise buildings and low-rise buildings depending on where individual builders are located.