Technological requirements and influence factors of California bearing ratio of expressway subgrade materials

The similarities and differences of California bearing ratio(CBR) test requirements in America,Britain,Japan and China are analyzed;The test technology and proceeding are emphasized.The CBR denotes the potential strength of subgrade material and it is the important index of evaluating its using performance in expressway.In order to study the main influence factors of the CBR value of clay,the physics and chemistry tests of fifteen groups of subgrade materials,taking from the Qingdao-Yinchuan Expressway in Hebei Province,are done.Based on the result of tests,which there are obvious difference between CBR value with the same plastic index clay,the influence factors of CBR of expressway subgrade materials,such as distribution of particle sizes in soils,mineral component and clay mineral component,are studied.The useful conclusions are drawn as follows: the main influence factors of CBR of expressway subgrade material are the type of mineral component and its content;secondly are the distribution curve shape of particle sizes in soils.