An approach for assessment of building failures in a part of Ilorin, Nigeria

Abstract

The aim of this study was to investigate the causes of building failures in a part of Ilorin. Vertical electrical sounding (VES) was conducted, and 1D inverted resistivity indicates four distinct layers. The first layer is top soil with resistivity values of 16.1 Ωm to 81.1 Ωm and a depth of 0.1 m to 0.3 m. The second layer is clay/silty clay with resistivity values between 12.6 Ωm and 59.6 Ωm and a depth of 1.1 m to 2.8 m. The third geoelectric layer is weathered basement with resistivity values between 5.9 Ωm and 38.4 Ωm and a depth of 1.3 m to 6.2 m, and the fourth layer is fresh basement layer. Four pits were dug to a depth of 1.5 m, and undisturbed soils were collected for geotechnical test. Maximum dry density of the soils falls between 1.73 and 1.84 with an average of 1.90 Mg/m. Dynamic cone penetration test (DCPT) was conducted, and the quantity of blows to achieve 1000 mm (1 m) penetration depth (n) was recorded. DCPT of the soils varies between 89.8 kN/m2 and 314.3 kN/m2, with low bearing capacity of 89.8 kN/m2 to 134.7 kN/m2 at a depth of 0.1 m to 0.3 m, which is below the recommended minimum value of 150 kN/m2, and this contributed to the building failures in the study area.