Research on Railway Ballast With the Optimal Sphere Filling by Using Discrete Element Model

DEM (discrete element method) is an effective method to study the dynamics of ballast track. The DEM assumes that the ballast is composed of spheres and the optimal combination of spheres in single ballast is the key to study ballast tracks by using DEM. A track ballast model using DEM is established with accurate ballast profile that is filled with spheres obtained by using a binocular 3D scanner and the Bubble Pack algorithm; In this paper, a direct shear test is adopted to study mechanical properties of the track ballast filled differently. The optimal sphere filling method is chosen using a ballast model based on DEM. The results show that: the volume filling rate ω of the ballast is negatively correlated with the radius ratio r of the small ball and the large ball that are adjacent, and positively correlated with the overlap angle ϕ of the two adjacent balls; with the same volume filling rate, the smaller ratio r is, the greater number of spheres is, and the closer the maximum shear stress of numerical calculation is to the measured level; for general engineering calculations, the optimal combination with a volume filling rate of 0.8 should be used for calculation.