Regression Analysis on California Bearing Ratio of Selected Soft Soils in Osun State for Pavement Construction

Abstract

This paper presents a regression analysis on the California Bearing Ratio (CBR) of selected soft soils in Osun State for pavement construction. The lateritic soil used, obtained along Osogbo-Ikirun road, Osogbo-Ilesha road, and West By-Pass Okebale in Osogbo, Osun State, is labeled as locations P, Q, and R, respectively, for easy identification. Geotechnical tests were carried out in line with British Standard (1990), encompassing parameters such as moisture content, specific gravity, particle size analysis, Atterberg limits, Compaction, and California Bearing Ratio. A correlation relationship between CBR and LL, PL, PI, OMC, and MDD was developed using multiple linear regression analysis. Standard Minitab 13 and Microsoft Excel 2013 software packages were utilized for the analysis. The comparison between experimental and predicted CBR values from the derived model yielded R² values of 1, 1, and 0.9741 for locations P, Q, and R, respectively. The analysis underscores that geotechnical properties, including percentage fines for Osogbo-Ikirun road, optimum moisture content for Osogbo-Ilesha road, and specific gravity for West By-Pass soils, can be employed to reliably predict CBR values. The regression analysis indicates a robust quality control measure for the variables PF, OMC, and SG during field compaction. The inclusion of these variables into a comprehensive quality control and specification framework is recommended to enhance the longevity and durability of road pavements.