Geophysical Assessment of Pavement Failure Along the Ikere-Iju Road, Southwestern Nigeria, Using 2D Electrical Resistivity Imaging

Background and Objective: Pavement failure along the Ikere-Iju road in Southwestern Nigeria has become a persistent issue, affecting transportation and safety. Subsurface geological conditions are suspected to be a major contributing factor. This study aims to investigate the causes of the failure using 2D electrical resistivity imaging. The objective is to delineate weak zones and provide geophysical insights for effective road rehabilitation. Materials and Methods: A geophysical investigation was conducted to analyze the causes of persistent pavement failure along the Ikere-Iju road, Southwestern Nigeria, and propose mitigation measures. Using 2D electrical resistivity imaging (ERI) with a dipole-dipole array, subsurface geological structures were examined. Resistivity data were collected along four 200 m long traverses with a target depth of 15 m. Results: The lateral and vertical variations in subsurface lithology, distinguishing failed and stable road segments. The presence of extensive clayey topsoil, cavities, and faulted zones contributed significantly to road failure. Notably, traverse 1 exhibited low to moderate resistivity (48-200 ohm-m), indicating clay, sandy clay, and lateritic formations, while competent layers were found below 5 m. Traverse 2 showed lithological transitions at 5 m, with weak clayey sections extending between 20-130 m. Traverse 3 revealed a low resistivity clay zone extending to 7 m, with stable formations deeper. Traverse 4 highlighted a major fault/cavity below 5 m, contributing to road subsidence. Conclusion: The study concludes that poor drainage, clayey topsoil, and subsurface cavities are the primary causes of road failure. To enhance pavement durability, proper drainage systems, excavation of weak clay layers, and mitigation of cavities are recommended for future road construction projects.