2D ballast particle contour generation based on the random midpoint displacement algorithm

Ballast particles are an important part of the railway ballast bed. Ballast particles with irregular shapes and strong randomness are not only of significance for ensuring track stability, but also provide good elasticity to absorb the impact and vibration of wheel–rail interaction. However, it is obviously unrealistic to import the contour of every real ballast particle when using the discrete element method (DEM) simulation. Therefore, this paper developed a new algorithm, the random midpoint displacement method (RMDM), for the fast reconstruction and random generation of 2D ballast particle contour. Seven morphological parameters are proposed to describe the surface characteristics of ballast particles based on the analysis of the contour samples of three typical ballast particles using MATLAB. This method was verified by comparison with the real ballast particle based on particle morphology analysis and DEM simulation. The results show that the reconstructed ballast contour by RMDM is consistent with the field ballast contours in the view of the fractal dimensions and has an improvement in the view of the computational efficiency.