Compaction behavior of fine-grained soils, lateritic soils and crushed rocks

This paper studies compaction characteristics and California Bearing Ratio, CBR values of fine-grained soils, lateritic soils and crushed rocks. All test data were collated from the Bureau of Rural Road 6, the Department of Rural Roads, Thailand. The Ohio's and the modified Ohio's curves can predict satisfactorily the compaction curves of the fine-grained soils, and lateritic soils and crushed rocks consistent with the grade B of the American Association of State Highway and Transportation Officials (AASHTO) requirement. The CBR value of a specific soil is directly related to the relative dry unit weight (the ratio of dry unit weight to maximum dry unit weight, γd/γd,max). The field compaction result of a fine-grained soil at the optimum water content, OWC, shows that initially the dry unit weight increases rapidly with the number of roller passes and the relationship between dry unit weight and number of roller passes is represented by the logarithm function. Finally, the dry unit weight reaches a constant value, which is close to the laboratory maximum dry unit weight. Even with a large number of roller passes (compaction energy), the dry unit weight cannot be enhanced further because the soil state approaches the zero air void state. In practice, the excess roller pass is thus not economic. Based on the analysis of the test data, the field compaction procedure for road embankment and pavement constructions, which includes the material selection and the construction control, is suggested. It is useful in terms of both engineering and economic viewpoints.