Results of Subsoil Investigation on a Collapsed Building Site in Lagos, Nigeria

Abstract

Geotechnical properties of the subsoil of a collapsed building site at Ebute-Metta, Lagos were evaluated by drilling a borehole from the ground level to a depth of 25.50m. The subsoil is heterogeneous vertically. The liquid limits vary from 27.0% to 28.5%. The plastic limits are of the order of 15.0% to 21.0%. The plasticity index ranges from 6.0% to 13.5%. The shrinkage potential is low to medium. The means of the empirical compression index, moisture content and bulk density are 0.16%, 17.62% and 1.92 kg/m3 respectively. The coefficient of volume of compressibility varies from 0.104 m2/MN to 0.156 m2/MN. The coefficient of consolidation ranges from 2.72 m2/yr to 58.40 m2/yr. The existence of stiff, silty clay layer from the surface to 10.50m depth, presence of compressible refuse materials at foundation level, unfavourable geotechnical properties and adoption of shallow foundation contributed to the collapse of the building.