Correlation of geotechnical parameters with geological formations in a basement complex and its implications on civil structure foundation

Geotechnical tests were carried out on twenty subsoil samples obtained from ten locations at the depth of 1 and 2 m within Federal University of Technology, Akure, Nigeria. The area is typical of basement complex. The test include; Natural Moisture Content, Grain Size Analyses, Specific Gravity, Atterberg Limits, Compaction, California Bearing Ratio (CBR), and Unconfined Compression Tests. The ten locations where the soil samples were collected were selected across the geological classification of the area. ArcGIS 10.1 software was used to generate maps showing the geotechnical parameters distribution across four geological formations within the area at 1 and 2 m depth. It was observed that the distribution of each geotechnical parameter correlates with the composition of the weathering end-product of the geology. The rocks underlain the area includes; Migimatite Gneiss, Quartzite, Charnockite and Biotite Granite. The poorest geotechnical parameters were obtained within subsoil underlain by Charnockite, hence are most unsuitable soil to host the foundation of civil engineering structures, while the area underlie by weathering end-product of quartzite rock is of good geotechnical parameters and most suitable soil to host the foundation of civil engineering structures. The weathering end-products of Charnockite, Migimatite and Granite rocks give relatively high shear strength than that of quartzite, indicating low cohesive nature of the weathering end-product of quartzite.   Key words: Geological classification, geotechnical parameter, weathering, road base.