Geophysical Investigation of Pavement Failure on a Portion of Okene-Lokoja Highway, North Central Nigeria

Abstract

Non-destructive geophysical methods involving electrical resistivity sounding and very low frequency electromagnetic profiling were used in investigating the cause of pavement failure on a portion of Okene-Lokoja highway North Central Nigeria. Seventeen (17) soundings were acquired and very low frequency electromagnetic profiling data were taken at 10m intervals along 2 traverses. The geoelectric section shows that the unstable portion of the highway is characterized by thin topsoil and low resistivity weathered layer(clay) between 58?m-125?m and partly weathered/fractured bedrock with resistivity between 69?m-140?, while the VLF-EM profile and 2-D VLF-EM pseudosection indicate the presence of conducting bodies with  (> 50%) positive peak of the filtered real amplitude (anomalous high current density) which is indicating clayey material or linear geological structures such as faults, fractures, joints and lithological contacts . Low resistivity weathered layer (clay), partly fractured bedrock and linear geological structures have been identified as the cause of pavement failure in the study area.

Keywords: Geological structures, Geophysical method, Pseudosection, Non-destructive, fractured bedrock.