Experiment Study of the Relationship Between the CBR Strength and Degree of Compaction of Subgrade Soil

California Bearing Ratio (CBR) has been commonly accepted and used as an indication of resistance and stability of subgrade all over the world. Although CBR and degree of compaction are both used as the indication of resistance of subgrade, the relationship between the two still requires further investigation. The formula showing the relationship between the CBR strength and degree of compaction of subgrade soil is obtained through an improved experiment method, in which soil samples with five predetermined degrees of compaction are produced and their CBR strengths are tested. Also some useful conclusions are obtained regarding the relationship between the swelling characteristic of subgrade soil and degree of compaction, which can serve as reference for road engineers.