Engineering geological assessment of some lateritic soils in Ibadan, south-western Nigeria using bivariate and regression analyses
Bivariate correlation and regression techniques were employed to evaluate the relationship between pairs of geotechnical variables for residual lateritic soils derived from three genetic crystalline rocks in Ibadan metropolis, south-western Nigeria. The significance of mean group differences (parent-rock and level of compactive effort) at 5% level of significance was determined using paired t-test analysis. This is with a view to ascertaining the influence of the pedogenic factor of parent rock, percentage fines, and energy of compaction on engineering index properties of the lateritic soils. The clay-size contents had positive correlations with both Optimum Moisture Content (OMC) and plasticity index, and a negative correlation with the Maximum Dry Density (MDD). The MDD and OMC had significant negative and positive correlations respectively with the amount of fines. The amount of fines and Unconfined Compressive Strength (UCS) had significant negative and positive correlations respectively with the California Bearing Ratio (CBR). The study shows significant parent-rock group differences in most engineering properties. The bandedgneiss-derived soils were found to be better engineering soils than the migmatite-gneiss- and quartzite/quartz- schist-derived soils. The modified AASHTO level of compactive effort which produced better compacted soils than the West African level is recommended for the soils.
Keywords: Regression analysis, engineering properties, lateritic soils, pedogenic factors