ABSTRACT

This study is aimed at determining the suitability of laterite soil derived from granite-gneiss from the burrow pit along Km 4 Ologuneru-Eleyele Road as a subgrade or subbase material Three samples were collected at different height from a burrow pit in the study area and were subjected to soil tests such as natural moisture content, optimum moisture content, maximum dry density, specific gravity and Atterberg limit at its dry state. Engineering tests such as California bearing ratio, compaction and unconfined compressive strengths test were also carried out on the lateritic soil at their natural state and when water was added to the soil. These tests obtained for each pit were compared with one another and other existing standard specifications for highway subgrade or subbase soil. The result of the grain size analysis shows that sample JA and JB have fine grain particle slightly above 35% which is the required percentage for a subgrade material while JC was extremely higher than the required. The result of the liner shrinkage shows that the shrinkage level of the samples are less than 8%, making it a good soil in terms of the shrinkage level. The plasticity Index of the soil samples JA and JB shows that the constituency limit of the soils are good while that of JC is slightly above the required limit of 17%. The optimum moisture content of all soil samples analyzed was greater than the required value of 14.5%. The CBR results were less than the required value of 30% and 80% for both the soaked and unsoaked value for a subbase or subgrade material making the soil not so good for a subbase material. Due to the results gotten from the test carried out, it was concluded that the soil along Ologuneru-Eleyele, Ibadan will be a good subgrade or subbase material by adding chemicals such as cement, lime ash etc to reduce the plasticity and make it possible to carry loads forany construction in engineering.