Geophysical Assessment of Subsurface Conditions and Their Impact on Building Foundations at Alamo community, Gbongan, Osun State, Nigeria
Résumé
This study assesses subsurface conditions for building foundation suitability in Alamo, Gbongan, Osun State, Nigeria, using an integrated geophysical approach. Vertical Electrical Sounding (VES) and 2D Electrical Resistivity Tomography (ERT) were conducted with ABEM SAS 300C Terrameter along three traverses. Data were processed using DIPROfWIN and WinRESIST software to generate 1D and 2D resistivity profiles. The results delineated four subsurface layers: topsoil, weathered layer, fractured basement, and fresh basement. Low-resistivity zones (6–60 Ωm), associated with clay-rich and saturated materials, were deemed geotechnically weak. In contrast, zones with resistivity values above 200 Ωm indicated competent basement rock suitable for structural foundations. The alignment between VES and ERT findings validates the interpretations and emphasizes the effectiveness of combining these methods. The study underscores the value of detailed geophysical surveys in foundation planning, particularly in geologically complex terrains, to reduce structural failure risks.