Abstract:
Electrical resistivity measurement and geotechnical tests were undertaken along Akure-Alade
Owena road, Southwestern Nigeria with a view to determining the possible causes of the pavement
failure along the studied road. Four traverses were established in the study area, the dipole-dipole
measurement was taken at 5 m electrode interval and a total of twenty three (23) vertical electrical
sounding (VES) were obtained along the traverses. The geotechnical tests were carried out on 15
soil samples obtained at depths not exceeding 1 m. In the four studied locations, the geoelectric
section revealed that the locations were underlain by four geoelectric layers namely; the topsoil,
subsoil, weathered/fractured layer, and fresh basement rock. The major part of the topsoil was
characterized by relatively low resistivity values (<100 Ωm) suggestive of weak zones that are
capable of causing failure of the road. It was observed that the uppermost layer (0-6 m) exhibits
very low resistivity values (<24 Ωm) along traverse 3, these suggests the presence of plastic clay
as observed in the study area which can lead to reduction in the bearing capacity of the soil. The
2D resistivity model depicts the presence of linear features / fractures and shallow water table that
could be inimical to the road pavement. The Susceptibility classification showed that the road
could be rated as poorly to moderately susceptible to failure with location 3 being the most
susceptible to failure. The geotechnical results revealed that most of the investigated soil samples
are clayey in nature and have properties below Federal Ministry of Works specification. Finally,
it was established from the results that the geophysical results correlates with the geotechnical
results showing the clayey nature of the soil samples and thus are weak engineering materials
