Investigation of Building Failure in A Typical Basement Complex Environment Using Integrated Approach – A Case Study in Ile-Ife, Nigeria

A building located within the Basement Complex of the ancient town of Ile – Ife, Osun State, Southwestern Nigeria was observed to have failed due to excessive total and differential settlement. The failure was investigated using the electrical resistivity and geotechnical methods The electrical resistivity method involved the 2-D electrical resistivity imaging (ERI) technique using the dipole-dipole array along four traverses of 30 – 60 m in lengths. The geotechnical method involved the cone penetration test (CPT) using the 2.5-ton static penetrometer machine. Quantitative and qualitative analysis of the ERI data were made using the DIPROfWIN software for the pseudo-inversion while the CPT data were interpreted for lithology using standard chart. The results show that the topsoil, about 1.0 m thick, is composed of sandy clay/clay that is characterized by cone resistance (q c ) of 0.2 – 2.0 MPa and resistivity of 75 - 200 Ωmm. The underlying clayey weathered layer, which constitute the shallow foundation soil is characterized by thickness of 4 - >10 m, q c of 0.2 – 1.0 MPa, resistivity of 25 - 75 Ωmm and estimated consolidation settlement of 200 – 500 mm. The basal layer is the saprock/fresh bedrock characterized by q c of > 8.0 MPa and resistivity of 100 - 1000 Ωmm. The subsoil is thus characterized by variably thick incompetent clayey weathered layer within which the shallow foundation was placed; hence the excessive total and differential settlements. Keywords: Basement Complex, Building Failure, Electrical Resistivity Imaging, CPT, Excessive Settlement DOI: 10.7176/JEES/14-2-01 Publication date: March 31 st 2024