Angle of repose in the numerical modeling of ballast particles focusing on particle-dependent specifications: Parametric study

The discrete element method (DEM) is widely used in the realistic simulation of the shapes of particles. Researchers have considered the simplification of particle shapes owing to the high computational cost of such simulation. In this regard, the modeling of calibrated particles is a major challenge owing to the simultaneous effects of particle properties. The angle-of-repose test is a standard test method used to calibrate the bulk behavior of simulated particles. In the present study, the hollow-cylinder (slump) test was modeled for the verification of discrete element simulations. In this regard, a sensitivity analysis was conducted for all effective parameters, namely the static friction, rolling friction, restitution coefficient, sphericity, roundness, particle size distribution, and number of ballast particles. The results indicate that the rolling friction, roundness, number of particles, and size of particles are the most important parameters in the determination of the angle of repose (AOR). For particles in the range of ballast (20–60 mm), the effect of the number of particles on the angle of repose is reduced when the number is greater than 426. Additionally, it is concluded that angular particles can be replaced with sub-angular particles (R ≈ 0.2–0.45) with a higher rolling friction coefficient (μ_r > 0.14).