Application of geophysical approach to highway pavement failure: a case study from basement complex terrain southwestern Nigeria

Geophysical survey involving Schlumberger Vertical Electrical Sounding, 2-D imaging dipole–dipole technique and ground magnetic method were carried out along Ibadan-Ife Highway located in the Precambrian Basement Complex of Southwestern, Nigeria to examine the geological factors responsible for Highway pavement failure. This was with the view to detailing the subsurface geoelectric sequence, mapping the subsurface structural features within the sub-grade soil and delineating the bedrock relief as a means of establishing the cause(s) of the road pavement failure. The geoelectric sections, 2-D resistivity structures and modeled magnetic profiles revealed that the stable segments were founded on a shallow/outcropping basement near homogeneous substratum devoid of major geological features while linear features suspected to be fault/fractured zones, buried stream channels, bedrock depressions and lithological contacts were identified beneath the failed segments of the highway pavement. The geoelectric sections generally identified four geologic layers comprising the topsoil, weathered layer, partly weathered/fractured basement and fresh bedrock. Thus, the failed portions of the road are probably precipitated by very thick and low resistive substratum (clay) beneath the highway pavement and the identified suspected linear features are the major geological factors responsible for the highway pavement failure.