Prediction of California Bearing Ratio (CBR-Value) from Index properties of soil for Modjo Dry Port Sub grade soil

Abstract

Abstract The most classical parameter that is used to measure quality of subgrade material in constructing dry port infrastructure and container terminals is CBR, but routinely testing for this parameter is both costly and time taking. Therefore, seeking other less costly and quick method of test that characterizes subgrade and material property will be a logical approach. This study attempted to present the results of the correlation between soaked CBR and index properties of soils. Laboratory tests were carried out to determine soaked CBR, LL, PL, MDD and OMC on soil samples collected from Modjo dry Port construction site. A correlation between CBR and the soil index properties was developed for single and multiple linear regression analysis using SPSS software. The laboratory test results indicated that soils around the study area lie in groups A-7-5 and A-7-6 based on the AASHTO classification system. Single and multiple linear regression analysis were performed on experimental data and correlations were developed to predict the CBR in terms of the index properties of the samples. Among the various parameters, MDD, OMC and the LL were found to be the most effective predictors. From the regression analysis, better result was found when CBR is combined with MDD, OMC and LL and the value of R2 in the combination was 0.909. This implies that 90.9% variation of CBR depends on the variation of those predictors. The validation of the correlation result was checked using eight generated CBR test results and the result obtained is good when compared to other works. It reveals that the correlation of CBR value with soil index properties is more applicable for preliminary characterization of the strength of subgrade soils.