Correlation of California bearing ratio with Geotechnical Properties of Selected Lateritic Soils

Abstract

This work presents the correlation of CBR with index and compaction properties of selected lateritic soil in Minna, Niger State. Twenty-seven (27) samples were collected from 3 locations in Minna metropolis. Classification tests, British Standard Heavy and Light compaction tests, Consistency limit test as well as CBR test were carried out on the samples. Microsoft Excel tool was used to analyze the results. From the tests results, the samples are classified in AASHTO and USCS system as A–2, A–4, CL–ML, CL and ML respectively. Samples from Maikunkele are majorly granular, while those from Maitumbi and LapaiGwari are mainly Silty-clay materials with reddish, grey or brown patches. The Average Liquid Limit (LL), Plastic Limit (PL), Plastic Index (PI) and specific Gravity (Gs) of test samples are 20. 40 – 33.40%, 12.6 – 30.0%, 8.4 – 30.6% and 2.52 – 2.71 respectively. The British Standard Heavy compaction test result produced average MDD and OMC values 1.97– 2.52 g/cm3 and 7.20 – 13.5%, while the British Standard Light compaction test result produced average 1.89 – 2.92 g/cm3 and 10.28 – 16.00 % as MDD and OMC values respectively. The average CBR values range from 11.90 – 109.9 %. Using the Microsoft Excel tool, the study further established a regression equation for the CBR value of lateritic soils. The performance of the regression model was assessed in terms of correlation coefficients, F-statistics and residuals pattern. Using the developed model, the regression equations developed indicated strong correlation of CBR and PL, LL, PI, and Gs (with R2 = 0.89 – 0.99). However, the work revealed a poor and moderate correlation of CBR with MDD and OMC with R2 = 0.45 and R2= 0.73 respectively at BSL compaction energy level.