California bearing ratio (CBR). A simple test that compares the bearing capacity of a material with that of a well-graded crushed stone (thus, a high quality crushed stone material should have a CBR 100%). CBR is basically a measure of strength. It is primarily intended for, but not limited to, evaluating the strength of cohesive materials having maximum particle sizes less than 0.75 inches (AASHTO, 2000). It was developed by the California Division of Highways around 1930 and was subsequently adopted by numerous states, counties, U.S. federal agencies and internationally. Most agency and commercial geotechnical laboratories in the U.S. are equipped to perform CBR tests. Resistance value (R-Value). A test that expresses a material's resistance to deformation as a function of the ratio of transmitted lateral pressure to applied vertical pressure. It is essentially a modified triaxial compression test. Materials tested are assigned an ...