Highway Geotechnical Properties Of Quartzite-Derived Lateritic Soil From Ijebu-Ijesa, Southwestern Nigeria

The highway geotechnical properties of quartzite-derived lateritic soil from Ijebu-Ijesa were investigated with a view to determining the suitability or otherwise for flexible highway construction.The field investigations included the study of the geological and geotechnical settings of the area and collection of four bulk samples within the study area. The laboratory investigation procedures involved the use of air dried sample which were subjected to laboratory classification tests including; grain size distribution and consistency limits (liquid limit and plasticity limit). Other engineering tests often employed in evaluating highway sub-grade material which include Compaction test, California Bearing Ratio (CBR) and Unconfined Compression test (UCS), in accordance with British Standard 1377 (1990) with some modification where necessary were also conducted. Results of engineering tests revealed that the specific gravity of the soil ranges from 2.32 to 3.10. The results of grain size distribution analysis revealed that the soil is well graded. The amount of fines of the soil samples range from 28.7% to 35.55%.The liquid limit for the soil samples ranges from 28.5% to 35.40%.Casagrande chart classification showed that the soil samples have low to medium plasticity. The maximum dry density ranges from 1850Kg/m3 to 1890Kg/m3 with their optimum moisture contents ranging from 13.08% to 17.98%. Unsoaked California Bearing Ratio of the soil ranges from 0.75% to5.3%.Unconfined Compressive Strength of the soil ranges from 132.18KN/m2 to 135.00KN/m2 and 1200.50KN/m2 to 1640.92KN/m2for uncured and cured respectively. Findings from this study indicate that the soil is suitable to be used as subgrade material in the construction of flexible pavement.