Integrated geoelectrical and geotechnical characterization of subsurface conditions responsible for foundation failures at the former Shagari housing estate, Numan, Adamawa State, Nigeria

Beatrice Bomki Humphrey; Jamu Benson Yerima; Emmanuel Ike; Adetola Sunday Oniku

Authors

Beatrice Bomki Humphrey
Department of Physics, Faculty of Physical Sciences, Modibbo Adama University, Yola, Nigeria
Jamu Benson Yerima
Department of Physics, Faculty of Physical Sciences, Modibbo Adama University, Yola, Nigeria
Emmanuel Ike
[email protected]

Department of Physics, Faculty of Physical Sciences, Modibbo Adama University, Yola, Nigeria
Adetola Sunday Oniku
Department of Physics, Faculty of Physical Sciences, Modibbo Adama University, Yola, Nigeria

Keywords:

Foundation failure, Electrical resistivity tomography, Geotechnical characterization, Differential settlement

Abstract

Foundation failures remain a persistent challenge within heterogeneous basement-complex terrains of northeastern Nigeria. This study presents an integrated geoelectrical--geotechnical investigation of foundation failures at the former Shagari Housing Estate, Numan, Adamawa State, Nigeria, aimed at delineating subsurface conditions responsible for structural distress and differential settlement. Two-dimensional electrical resistivity tomography (ERT), acquired with the Wenner configuration and interpreted using RES2DINV inversion software, was combined with laboratory geotechnical analyses to develop a robust subsurface failure model. Geoelectrical results reveal very low resistivity values (2.67--24.7 Ω m), indicating water-saturated, weak clayey subsoils, with corrosivity conditions ranging from very strongly to moderately corrosive. Particle-size distribution shows high fines content (79.48%), exceeding the recommended 35% threshold. Atterberg limits confirm expansive behavior, with liquid limits of 49.00--56.80% and plasticity indices of 31.07--41.15%, while natural moisture contents (18.99--23.08%) exceed acceptable ranges. Undrained triaxial tests show low shear strength (cohesion: 7--22 kN/m²; friction angle: 1.5⁰--5⁰) and low bearing capacity (maximum 55.16 kN/m²). Consolidation results indicate medium to high compressibility and low permeability. The strong spatial correlation between low-resistivity zones and poor geotechnical properties confirms that the observed failures are associated with highly plastic, compressible, and moisture-sensitive soil layers. The findings demonstrate that integrating ERT with laboratory analyses provides a reliable predictive framework for identifying geotechnically vulnerable zones before construction.

Dimensions

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