To investigate the impact of sand particle size on the mechanical properties of the ballast bed, this study employed a "layered sand spreading and layer-by-layer compaction" method to construct six multi-scale ballasted track discrete element simulation models with different particle size distributions. By controlling the void volume between ballast particles, the mass conservation of the particle system is ensured before and after the change in sand particle size. Static and dynamic tests of the railway track structure in sandy areas were conducted to calibrate the mesoscopic parameters of the contact model and verify the accuracy of the discrete element model. Based on this, the effects of sand particle size on the computational efficiency of the discrete element model, the microscopic movement patterns of particles within the ballast bed, and the macroscopic quality state are systematically analyzed. The results show that the computational efficiency of the discrete element model decreases exponentially with the reduction of sand particle size. The average contact force and movement characteristics of the ballast gradually decrease with the reduction of sand particle size. And the effect of sand particle size on the normal contact force is more significant. The high-stress area in the ballast bed is positively correlated with sand particle size, while the dynamic stiffness of the ballast bed and the dynamic displacement of the sleeper are negatively correlated. Comprehensive research indicates that in the study of sandy ballast beds, the reasonable scale of sand particle size should be between 0.225 mm and 3 mm.
 

Sandy railway,Ballast bed,Sand particle size,Discrete element method,Microscopic contact,Quality state