GEOPHYSICAL INVESTIGATION FOR ROAD PAVEMENT FAILURES ON NEW EKU ROAD SAPELE, DELTA STATE, SOUTHERN NIGERIA

Abstract

Road transportation greatly enhances the economic growth of a country, especially developing countries like Nigeria where other forms of transportation are still underdeveloped. However, the deplorable state of roads and the rampant road failures has caused amongst other things, road accidents leading to the loss of valuable properties and even human lives. This study employs geophysical investigation into road pavement failures along New Eku road, Sapele, Delta State, Nigeria, to determine the nature and integrity of the subsurface beneath which the road pavement lies. The two-dimensional electrical resistivity tomography (ERT) method involving the Wenner-Schlumberger configuration was used on three (3) different failed sections of the road covering a distance of approximately 70m. Three (3) profiles, each parallel to the failed sections of the road pavements were established. Data sets were collected using the Petro Zenith Earth Resistivity meter. The observed resistivity data from the field measurements were processed and then inverted with the aid of an electrical resistivity interpretation software (RES2DINV). The results show low resistivity values typical of, and suspected to be expansive clay and clayey materials at different portions of each profile. In profile 1, resistivity values of less than 30.5Ωm to about 130Ωm was observed down to a depth of about 13.4m from the top soil, while resistivity values ranging from 47.7Ωm to 128Ωm and 7.94Ωm to 45Ωm were observed in profiles 2 and 3 respectively. These values indicates that the presence of unsuitable road pavement subgrade possibly clayey soil, which expands and contracts under varying weather conditions, could be mostly responsible for the road pavement failures in the study area