Integrated Geotechnical and Geophysical Assessment of Topsoil Competency and Aquifer Vulnerability in Gwarinpa, Abuja

Abstract

This study presents an integrated geophysical and geotechnical assessment of the subsurface in the Gwarinpa area, aiming to characterize soil competency and aquifer vulnerability to guide sustainable urban development. The investigation, employing vertical electrical sounding (VES) techniques and geotechnical analysis, reveals a subsurface dominated by a weathered basement complex with shallow, unconfined aquifers. Findings indicate that the sandy topsoil offers good drainage but exhibits low unconfined compressive strength (55-78 kPa), rendering it incompetent for supporting heavy structures without stabilization. Furthermore, the aquifer protective capacity is rated as moderate to poor across most of the area, with critically vulnerable zones identified in the western and eastern sectors where the overburden is thin and fractured. Based on these results, the study concludes that soil stabilization is imperative for any significant construction. It provides critical recommendations for urban planning, including the use of generated zoning maps to direct infrastructure away from vulnerable areas, the enforcement of land-use regulations to protect groundwater, and the necessity for site-specific geotechnical investigations. This research underscores the efficacy of combining geophysical and geotechnical methods to de-risk urban development and ensure long-term environmental and structural integrity.