Prediction of CBR of Different Groups of Alluvial Soils for Design of Flexible Pavements

In practice, determination of California bearing ratio (CBR) value in laboratory is laborious, time-consuming and costly. Furthermore, the results sometimes are not accurate due to poor quality of skill of the technicians testing the soil samples in the laboratory. In many case results, a limited number of prescribed tests may not be sufficient to map the field variation, and they may have very negative impact on the quality of the construction. Similarly enormous time is required to evaluate directly the CBR of constructed subgrade during checking for quality control. So evaluation of CBR of subgrade soils on the basis of simple, cheap and less time-consuming tests may be necessary. In the present investigation, an attempt has been made to develop a framework for prediction of CBR value of alluvial clayey soils which cover a large part of Indo-Gangetic plain and coastal area of Indian peninsula. For this purpose, a very large number of test results on soil samples collected from different sites in West Bengal have been used as the generalized parameter to characterize the clayey soil. The correlation is established in the form of an equation of CBR as a function of consistency limits by the method of regression analysis. The reliability of the proposed method has been studied for large number of tested values.