Abstract: To comprehensively evaluate the pavement performance and the particle breaking behavior of carbonaceous shale, the gradation change of carbonaceous shale during cyclic compaction is tested. According to the indoor compaction test, the influence of particle breakage on filler is described, and the best filling gradation is determined. The best gradation is selected for the wetting deformation test, and the variation law of the wetting deformation is analyzed from the perspective of particle breakage. Finally, the field filling effect of carbonaceous shale is verified. Three stages, i.e., structure adjustment, particle breakage, and compression deformation, are identified during the cyclic compaction of carbonaceous shale. The relatively stable gradation structure formed provides the basis for its use as filler. The formation mechanism of the maximum dry density of fillers is greatly affected by the changes in the contents of 20-40 mm and below 2 mm particles during the particle crushing process. The relative breakage rate of the sample increases linearly with the increase of the coarse grain content, the maximum dry density increases first and then decreases, and the optimal coarse grain content is about 70%. The wetting deformation is the macro embodiment of the fillers particle crushing. The relative breakage rate Br can be used to predict the wetting deformation of fillers when encountering water, and the strength decreases by about 40% after wetting deformation. The mathematical relationships between the relative breakage rate and the confining pressure, stress level are established. The on-site compaction test and settlement observation show that the best loose paving thickness of carbonaceous shale embankment is about 40 cm.

Key words: carbonaceous shale, pavement performance, particle breakage, compaction characteristics, wetting deformation, field compaction test