Abstract:

In order to well optimize the mineral gradation,a method to numerically test the compactness and the California bearing ratio ( CBR) of aggregates via PFC^2D was proposed. Then,based on the reliability analysis,the variation laws of the compactness and the CBR were analyzed respectively for synthetic coarse aggregates,synthetic fine aggregates and coarse-fine combined aggregates,and a close-grained gradation of aggregates skeleton under strong interlocked force was proposed. Moreover,the mechanical performances of the aggregates skeleton were verified through laboratory tests. The results show that the optimal mass ratios of the coarse aggregates with the diameters of 19~31.5mm,9.5~19mm and 4.75~9.5mm are respectively 0 ∶ 20 ∶ 10,60 ∶ 30 ∶ 10,60 ∶ 20 ∶ 20 and 50 ∶ 30 ∶ 20,while those of the fine aggregates with the diameters of 2.36~4.75mm,0.6~2.36mm and less than 0.6mm are respectively 38.5 ∶ 16.5 ∶ 45、33 ∶ 22 ∶ 45,36 ∶ 24 ∶ 40 and 30 ∶ 30 ∶ 40,and that the optimal mass ratio of coarse-fine combined aggregates is 65 ∶ 35. It is also found that the graded broken stone composed of the aggregates skeleton with close-grained gradation under strong interlocked force is of excellent mechanical properties because its CBR and compressive strength are respectively 1.16 and 1.12 times those of the standard gradation.

Key words: road engineering, aggregates skeleton, gradation, particle flow, numerical test, California bearing ratio, compactness