Ige, O.O.Kuforiji, S.O.Olaleye, I.M.2023-06-072023-06-072020https://uilspace.unilorin.edu.ng/handle/20.500.12484/11045The rate of road fai lure and elevated cost of quality materials used in civil engineering construction has led to the need for investigation of naturally occurring local soils as alternative material in construction industries. This research used geophysical, geotechnical and mineralogical approaches to investigate the condition of soils from failed portions along Ilorin-Lokoja Federal Highway with respect to identifying causes of failure and assessing the natural neighbouring soils as suitable base/sub-base course material. Results of five Vertical Electrical Soundings conducted on critically failed portions of the road show low resistivity values near the surface, suggesting the presence of clay and elevated moisture resulting in oversaturation of the top soil thus leading to failure of that portion of the road. Mineralogical and chemical analyses revealed the absence of high-level swelling clays, dominance of "true laterite" with high concentration of Fe203 as cementing agent. Low plasticity from geotechnical stud ies revealed the presence and influence of clay on the integrity of the samples. The samples possess low linear shrinkage values which suggest little potential to shrink or swell when exposed to alternating weather condition . They are poorly graded soils, suggesting un iform grain sizes. The samples generally present parabol ic shape during compaction which is an ind ication of "workability" if used as in-situ construction material. The California Bearing Ratio (CBR) values ind icate good ratings and are fairly suitable as base and sub-base material in road construction . Overall, geotechnical evaluations revealed that the sample can only function effectively as subgrade material except in few (~30%) where the soils can serve as sub-base course i n pavement construction. Generally, the tested soils possess properties which make them fairly suitable for road construction. However, changes in climatic factor and state of drainage system must be critically considered to ensure a better road network.enGeophysical, Geotechn ical, M ineralogy , Lokoja, CBRArticle