Geology and Geotechnical Characterization of Subsurface Conditions for Building Construction at Federal University Gusau

Abstract

This study presents a comprehensive geological and geotechnical characterization of subsurface conditions at Federal University Gusau, Zamfara State, and Northwestern Nigeria, to evaluate the suitability of the campus for sustainable building construction. The research employed integrated field geological mapping, vertical electrical sounding (VES), and geotechnical laboratory testing to delineate subsurface stratigraphy and assess engineering properties of foundation materials. Twenty (20) VES stations were surveyed across the campus using the ADMT ZN300 instrument to determine resistivity variations and subsurface layering. Results reveal a three-to-four layer geo-electric sequence comprising: (1) topsoil/lateritic overburden (0.5–6 m thickness; resistivity 24–394 Ωm); (2) weathered basement (8–15 m thickness; 150–735 Ωm); (3) fractured basement (variable thickness; 200–750 Ωm); and (4) fresh basement bedrock (>15 m depth; 750–1200 Ωm). Geotechnical analysis indicates that the lateritic overburden exhibits variable engineering properties, with some zones showing low shear strength (cu = 15–35 kPa) and high compressibility, rendering them unsuitable for shallow foundations without improvement. Conversely, the fresh basement bedrock demonstrates high bearing capacity (>500 kPa) and competence for foundation support. Structural measurements from 17 outcrops indicate an average dip of 19.2°, with dominant structural trends oriented NE–SE, which may influence foundation alignment and groundwater flow patterns. The study recommends deep foundation systems (piled or raft foundations) extending to the fresh basement layer for multi-story structures, comprehensive site-specific investigations prior to construction, and avoidance of foundations on uncompact lateritic clay zones. This research provides critical baseline data for infrastructure development at Federal University Gusau and similar basement complex terrains in Northwestern Nigeria.