Predicting california bearing ratio (cbr) value of a selected subgrade material

Abstract

The subgrade bearing capacity is an important parameter in flexible pavement design, and it is largely influenced by the variation of subgrade moisture. California Bearing Ratio (CBR) is the most popular method of assessing the subgrade bearing capacity. It compares the load required to make a particular penetration on a given subgrade with the load to make the same penetration on standard material. Although it would be beneficial to perform CBR tests at more frequent intervals on a road section to design, it would not be practical in certain instances owing to the laborious and time-consuming CBR test process. In that case, developing a method to predict the subgrade CBR based on the variation of moisture would be an advantage. Accordingly, this study aims to assess the influence of moisture content and the compacted density on the subgrade CBR value. Hence, the possibility of developing a model to predict subgrade CBR was investigated. A series of standard CBR tests were performed for different combinations of moisture and compaction densities, and standard CBR values were estimated. Thereafter, a statistical model was developed to predict the CBR value for the selected clay material and validated with laboratory test results.