Investigation of the compaction behaviour of sand-gravel mixtures via DEM: Effect of the sand particle shape under vibration loading

In simulations of granular mixtures with real-shaped particles, fine particles are mostly simplified to spheres to improve computational efficiency. The basis for simplification is that the shape effect of fine particles is negligible when compared with coarse particles. However, existing simplifications are usually arbitrary without considering the size ratio between coarse and fine particles, causing fine shapes to be ignored unreasonably. Therefore, what size ratio can simplify the shape of fine particles? To solve this problem, the real model with real-shaped fines and the simplified model with simplified-shaped fines were established to explore the difference between the two models affected by size ratios. The real-shaped particles were constructed based on representative sand and gravel grains, and contact parameters were calibrated by a series of physical tests. The simulation results show that the permanent deformation of real models can be reproduced by simplified models with a large SR, while the resilient deformation cannot be reproduced no matter what SR is. Although there are some differences between the two models at macro- and mesoscales, the fine shapes can be simplified under the condition of SR ≥ 11, the computational efficiency of which can be greatly improved compared with real models. This study aims to provide a quantitative basis for the shape simplification of fine particles from the perspective of simulation accuracy and computational efficiency.