Exploring the effects of size ratio and fine content on vibration compaction behaviors of gap-graded granular mixtures via calibrated DEM models

Gap-graded granular mixtures, consisting of two different sizes with a great range gap, are widely used as filling materials in subgrade engineering. The mixtures usually bear vibration loads in the construction stage to meet the compaction requirement, yet surprisingly few studies have focused on its compaction behaviors under vibration loads. To enrich relevant research, this study explores the effects of size ratio (SR) and fine content (FC) on the macro- and mesoscopic compaction behaviors of gap-graded mixtures via calibrated DEM models. Firstly, spherical brown corundum grains, a rock-liked granular material, were used to calibrate contact parameters in the DEM model. Furtherly, the model was verified by comparing with the corresponding physical test using brown corundum mixtures. The study found that the DEM model is reliable in simulating compaction behaviors of gap-graded mixtures, and the calibrated contact parameters can be referenced in the simulation of rock-liked granular materials. Based on simulation results of DEM models, the intense particle motion does not necessarily cause a significant change in permanent deformation, while it would cause an unstable resilient deformation. Limited by the strong internal stability in overfilled assemblies, fine particles remain stable among coarse particles and the contact structure is almost unchanged after vibration compaction.