Sub-soil Water and Structural Foundation Study in Ilaje Community School and United Grammar School, Irele, Ondo State, Nigeria

Abstract

Geotechnical Soil Correlation and Potential Investigation of Trial Pits at Structural Foundation Sites across the Ilaje Community School and United Grammar School, Irele in Ondo State, Nigeria, were conducted. The purpose was to correlate and assess the potential effects of sub-soil water on depth to bedrock, foundation conditions, and possible geological structures within the proposed construction area. The study evaluated the engineering properties of soil samples collected from the site using the Atterberg limit, grain size analysis, and compaction test. The geophysical results revealed five geoelectric layers: topsoil, sandy layer, sandy/sandy clay layer, sandy/sand clay layer, and sand basement layer.  Analysis of the Atterberg limit indicated a dominance of inorganic clay-size particles with high plasticity and moisture content. The grain size analysis revealed the presence of well-graded gravelly clay silty sand. The classification of soil types and the compaction values obtained showed significant consistency across soil samples. Four subsurface soil layers were identified in the topsoil (mixture of sand, silt, and clay), coarse sand, clayey sand, and sand. These findings correlated well with the sub-soil investigation. The Geotechnical Trial pit data revealed that the soil condition in both communities generally required deep foundations. However, the foundation conditions of United Grammar School in Irele were more favourable than those in the Ilaje community, based on the computed values from the trial investigation.