GEO SPATIAL INVESTIGATION OF UNDERGROUND SOIL TEXTURE AND THE NATURE OF SOIL’S ENTRAPPED GAS AT SOUTH CAMPUS FEDERAL POLYTECHNIC EDE

Abstract

This study investigated the spatial distribution of underground soil texture and the nature of entrapped soil gases within the Federal Polytechnic Ede (South Campus), Osun State, Nigeria, using geospatial and geotechnical approaches. Twenty geo-referenced soil samples were collected and subjected to sieve analysis to determine particle-size distribution and soil textural classification, while field excavation was used to assess the nature of entrapped soil gases. The results revealed considerable spatial variability in soil colour, texture, and engineering characteristics. Sandy loam was the dominant soil type, occurring at eighteen sampling locations, whereas clay, loamy sand, and silt loam were identified at one location each. The predominance of sandy loam indicates generally good drainage, moderate moisture retention, and favourable thermal properties, while localized clay- and silt-rich soils exhibited higher water-retention capacity and greater heat-storage potential. The investigation of entrapped gases showed that acidic gases predominated across the study area, with neutral gases occurring at a few locations and alkaline gas detected only at one location. These variations reflect differences in subsurface geochemical, biological, hydrological, and thermal processes that influence soil thermal conductivity, gas migration, and engineering performance. The integration of geospatial mapping with soil texture and gas characterization provides valuable information for foundation design, road construction, land-use planning, and environmental monitoring. The findings emphasize the importance of detailed site-specific geotechnical investigations to improve infrastructure durability and sustainable engineering development.