Investigation of Electrical Resistivity of Lateritic Soils in Benue State for Geotechnical Applications

Electrical resistivity measurements of soils provide non-invasive geophysical information useful for foundation assessment, groundwater depth estimation, and corrosion risk evaluation in civil engineering projects. This study investigates the electrical resistivity of lateritic soils at ten sites across Makurdi, Gboko, and Otukpo local government areas in Benue State, North Central Nigeria, using the Wenner array resistivity technique. Resistivity surveys were conducted to depths of 20 meters using a digital resistivity meter, and vertical electrical sounding data were processed using iterative forward modeling to derive subsurface resistivity profiles. Laboratory measurement of resistivity, moisture content, and particle size distribution were performed on disturbed samples from each site to validate field results. Results indicate surface resistivity values ranging from 45 ohm-m to 890 ohm-m, reflecting strong dependence on clay content, moisture, and iron oxide cementing. The study identifies zones of low resistivity below 8 m depth at three sites in Makurdi that correspond to potential groundwater-saturated horizons. High resistivity zones near the surface at Gboko sites correlate with laterite hardpan layers confirmed by shallow trial pit excavation. The study provides resistivity benchmarks for lateritic soil types in the Benue State middle belt region and recommends integration of resistivity surveys into standard geotechnical investigations for construction projects in the area. Keywords: electrical resistivity, lateritic soil, Benue State, Wenner array, geotechnical application