Abstract: Packing characteristics are the comprehensive embodiment of particle shape, size and other factors. It also reflects the mechanical properties of particle aggregates to an extent. Round gravels of river alluvial gravel soil with size range of 10-50 mm is used as research objects. By using the digital image technology and analyzing the morphology of large quantities of round gravels, aspect ratios of round gravels are taken as the shape parameters and the method to build the ellipsoid models is formed. Based on the above, the ellipsoid model database is established with the same distribution in shape and size as the actual round gravels, and the models are used to numerically simulate the packing tests of single set round gravels. By comparing with the physical packing experiments, the following conclusions are made: The morphological features of the round gravels are mainly reflected in the macroscopic contour shape, and the angular characteristics are not obvious. The numerical simulation results show that the void ratios of packing test in different size groups vary little. The coefficient of interparticle friction has significant effect on the void ratios. The void ratio increases rapidly when the friction coefficient is 0.0-0.4 and then becomes flat. The physical experiments results verify the validity of the ellipsoid model simulation, and the coefficient of interparticle friction under gravity is calibrated to be approximately 0.3.

Key words: round gravel, packing property, particle morphology, ellipsoid model, identical distribution, void ratio