Investigation of road failure at Ogun-Osun-Alabata Road, Nigeria, using vertical electrical sounding technique

Abstract

Electrical resistivity survey was carried out around Abeokuta area of Ogun State, Nigeria, to study the subsurface geologic layer with a view to investigating the failure in Alabata road that stretches about 1000 m. Vertical electrical sounding (VES) data were acquired with ABEM Terameter using Schlumberger electrode configuration at five (5) stations along the profile. The field data obtained was analysed using computer software (IPI2WIN) which gives an automatic interpretation of the observed apparent resistivity. The major lithologic units delineated beneath the study area are topsoil, sandy/sandy clay, and weathered basement layer. The resistivity of the topsoil layer varies from 120.7 to 392.4 ?m with thickness ranging from 1.1 -3.1 m. The sandy/sandy clay has resistivity values ranging from 22.3 - 206.0 ?m and thickness between 3.7 -20.6 m. The weathered basement has resistivity values ranging from 50.7 -1163.9 ?m with infinite depth. However, the depth from the earth's surface to the bedrock surface varies between 1.1-21.7 m. Results of the study have shown that the cause of road failure may be attributed to the sandy/sandy clay nature of the first layer.

Keywords: Electrical resistivity, Vertical Electrical Sounding, Lithologic units, Road failure, Apparent resistivity