Application of Electrical Method for Geophysical Assessment of Subsurface Structures Contributing to Road Failures in Shao-Malete Road, Kwara State

Abstract

This study applies the Electrical Resistivity Method using the Vertical Electrical Sounding (VES) technique to investigate and evaluate subsurface structures contributing to recurrent road failures along the Shao-Malete Road in Kwara State, Nigeria. A total of seventy-one (71) VES stations were conducted using the Schlumberger array to delineate the subsurface lithological variations and assess their influence on pavement stability. The interpretation resistivity data revealed a different subsurface layer’s sequence consisting of lateritic topsoil, clayey-sand, sandy-clay, weathered basement and fresh basement. The reveal that the lateritic topsoil was found to be thin or discontinuous in several failed segments of VES 6-10, 12, 14, 16 and 21 locations, making these areas vulnerable to deformation under vehicular loads. The clayey and sandy-clay layers is also characterized by low to moderate resistivity values identified at shallow depths in VES 5, 11, 22, 35, 42, 51, 52, 58, and 62 locations, which indicate high moisture retention and swelling potential that further contribute to pavement weakening during the wet season. In addition, a thick and poorly consolidated weathered basement layer was delineated beneath some failed segments, contributing to reduced subgrade strength and the development of pavement distress such as cracks and potholes. This study demonstrates that subsurface heterogeneity and moisture-sensitive materials play significant roles in the observed road failures. It recommends integrating geophysical surveys in preconstruction assessments to guide subgrade stabilization and drainage design for sustainable road infrastructure.