Geophysical Evaluation of Road Failure Along Km 5, Ado-Ikere Ekiti Road, Southwestern Nigeria.

ABSTRACT This study employs electrical resistivity method to investigate the causes of road failure along Km 5, Ado-Ikere Ekiti Road, aiming to uncover the subsurface dynamics contributing to road deterioration, extend its implications beyond immediate problem-solving, offering valuable insights for geotechnical engineering and infrastructure development. The vertical sounding technique of schlumberger array coupled with combined VES and HP using Dipole-Dipole field arrangements were employed to the investigation. A total number of five (5) VES were conducted along a single 210m length traverse line established beside some failed portions of the road. This was used to generate the geoelectric section of the study area. Also, 2D Resistivity image of the subsurface was developed using Dipole-Dipole configuration. The subsurface formations delineated are topsoil, weathered formation, fractured basement and fresh basement with resistivity values 118-685, 62-145, 268-422, 506-2855 ohm-meter with thickness range of 0.6-12.8, 1.7-31, infinity, 16-infinity respectively. Clay was identified to constitute the main material characterizing the weathered formations due to very low resistivity values. Also, fractured zone delineated in VES 4 and 5 at great depth shows it contribution to the failure of the road. It is concluded from the study that, the possible causes of road failure along the studied highway are: the presence of weathered/clayey zone at a very shallow depth to the sub-surface; the presence of fractured zones beneath the studied area; lack of proper drainage at the road embankment; and poor construction material. Keyword: Basement, fracture, geoelectric, resistivity, schlumberger