Estimation of Effective Stress by Geo-electric Characterization at a Proposed Solar Power Installation Site in Ajowa Akoko, Nigeria

Abstract

Geo-electrical resistivity survey has been used for geotechnical investigation at a site proposed for solar power installations in Ajowa Akoko, Nigeria, to assist its foundation prognosis. Vertical electrical soundings (VES) were conducted in 24 locations spaced 50 meters apart with maximum AB/2 spread of 160 meters covering an area of 2km². Electrical characterization of subsurface layers was done to identify a maximum of four geo-electric subsurface layers comprising the top soil (clayey sand and laterite), weathered layer (zone of capillary rise), and highly weathered (saturated) layer and fresh basement. The concept of electrical resistivity variation with subsurface formations - related to degree of saturation, specific gravity of solids, void ratio and unit weight of water - has been used to calculate the effective stress of each soil layer obtained from pore water pressure and total stress data. The effective stress estimated over the surveyed area for the various depths of 1.5m, 4.0m and 19m corresponding to the base of each characterized subsurface were 26.13kN/m² - 44.00kN/m², 73.80kN/m² and 181.19kN/m² respectively. The effective stress plot shows that the soil stability increases with depth in the surveyed location. The study demonstrates the usefulness of VES method in estimating geotechnical attributes for efficient and precise information.