Integrated Geophysical Techniques: A Viable Tool for Accentuating the Needed Importance of Side-Drains to Paved Road Networks

Abstract

Subsurface Geo-electrical surveys were carried out along the Uteh-Aduwawa road (popularly called the Upper Mission road extension), a suburb of Benin City but in Ikpoba-Okha Local Government Area of Edo State, in order to assess the integrity of a portion of the road that was being unused by motorists and commuters at a point in time, and to know the possible cause(s) of the seeming road failure leading to its disuse. The methodology involved the combined use of the Dipole-Dipole profiling and Vertical Electrical Sounding (VES) as well as the Electromagnetic Very Low Frequency (VLF) and the data obtained were subjected to standard best procedures involving the use of manual curve matching and further enhancement interpretations using WINRESIST and DIPROfWIN inversions software for the resistivity survey, while the EM-VLF was interpreted using the Fraser and Karous-Hjielt filtering software. The interpreted field data showed high resistivity-value subsoil and layers of competent sub-grade soil as agreed by the local geology of the area despite the fact that the entire portion of the road was submerged in flood. These strongly suggested that the road under study seemingly ‘failed’, not because of the earth materials used in its construction or the in-situ subsoil on which the road was constructed but basically due to the non-functionality of the side drains, either as a result of its design in terms of size, depth and elevation to cater for the volume of adjoining floods from the off-lanes or proper lack of self de-silting mechanism in its construction thereby leading to huge floods and standing ‘pool of water’ on the road even long after the rains were over. The resultant effect of this on the roadway is a continuous micro-detachment of bituminous overlay on the pavement.