Assessment of subsoil corrosivity using geoelectric layer parameters at Ilere community near Akure, southwestern Nigeria

Abstract

Fifty-nine (59) vertical electrical sounding (VES) data were acquired within Ilere community, near Akure southwestern Nigeria to characterize the area into different corrosivity zones at different depth surfaces. The acquired field data were interpreted using manual curve matching technique and the initial layer parameters (resistivity and thickness) were iterated to produce the final geoelectric parameters (resistivity and thickness). Since metallic utilities are installed at different depths depending on their purpose, the VES results were presented as table, topsoil and iso-resistivity depths slice maps (0.5, 0.75, 1.0 and 3.0 m) in order to make the research work relevant for different uses. The 0.5 m depth slice isoresistivity map shows that about 75% of this depth surface are of higher resistivity (above 201 Ωm) suggesting negligible corrosivity. The 0.75 m depth slice isoresistivity map indicated that about 70% of this depth surface are of higher resistivity (above 201 Ωm) suggesting negligible corrosivity. Likewise, the 1.0 m depth slice isoresistivity map shows that about 60% of this depth surface are of higher resistivity (above 201 Ωm) suggesting negligible corrosivity. Finally, the 3.0 m depth slice isoresistivity map shows that about 35% of this depth surface are of higher resistivity (above 201 Ωm) suggesting negligible corrosivity. There is a reduction in the percentage of the portion delineated to be of negligible corrosivity in each depth slices of the study area as we move deeper into the subsurface.