A study on variation of test conditions on CBR determination

Abstract

The California Bearing Ratio Test (CBR Test) is a test first developed by California State Highway Department (U.S.A.) for evaluating the bearing capacity of sub grade soil for design of flexible pavement. The CBR value of the sub grade soil is being used widely since a long time in design of pavement structure and is critical in deciding the overall thickness of the pavement. Additionally, for good drainage, a typical specification for the pavement foundation design requires the value of permeability coefficient of the sub grade material to be specified. Thus, permeability and CBR constitute two important parameters in the design and assessment of long-term performance of the pavement. In this project only strength aspects of pavement subgrade have been considered. In this study, laboratory investigations have been carried out on a number of soil samples procured from different roadwork sites. Preliminary tests, such as index tests and particle size distribution tests, used for soil classification, have been taken up followed by Proctor compaction and CBR tests. CBR tests have been conducted for same samples under various conditions of soaking, with due emphasis on moisture content parameters in the soil sample. In this study for the purpose of comparison two different types of soils have been considered to study the variations