Geotechnical Investigation of Foundation Soils for Building Construction in Abuja FCT

Rapid urban expansion across the Federal Capital Territory of Abuja has generated increased demand for reliable geotechnical characterisation of foundation soils to prevent structural failures in residential and commercial buildings. This study investigates the geotechnical properties of soils at three construction sites in different districts of Abuja FCT, with the objective of assessing subsoil bearing capacity and recommending appropriate foundation types. Standard penetration tests and shallow test pits were used to characterise subsurface conditions, supplemented by laboratory analyses of collected samples. Geotechnical parameters determined include particle size distribution, Atterberg limits, compaction characteristics, unconfined compressive strength, and shear strength from consolidated undrained triaxial tests. The bearing capacity at shallow and intermediate depths was estimated using the Terzaghi general bearing capacity equation and correlated with SPT N-values. Settlement predictions were performed to evaluate the adequacy of proposed strip and pad foundation configurations. The study identifies lateritic gravel layers within the upper 1.5 metres at two sites as competent bearing strata, while one site exhibits expansive clay subsoil requiring ground improvement. Results are presented in geotechnical reports formatted according to Nigerian Building and Road Research Institute guidelines. This research supports the culture of evidence-based geotechnical design in the FCT construction sector and provides a practical undergraduate reference for geotechnical site investigation. Keywords: geotechnical investigation, foundation soils, bearing capacity, Abuja FCT, SPT.