ABSTRACT
The morphological features of railway ballast, especially the edges and corners, have a great impact on the additional stress on the subgrade surface induced by train loads. In this paper, a novel shape reconstruction method was adopted to generate an arbitrary number of ballast particles. Then, a three-dimensional Discrete element-Finite element method (DEM-FEM) coupling model of the ballasted track-subgrade, in which the ballasted track was simulated by DEM and the subgrade soil was simulated by FEM, was established to analyze the contact stress at the ballast-subgrade interface. In this work, 150 groups of ballasted track-subgrade numerical models composed of irregular particles with randomly reconstructed shapes were applied to investigate the stress distributions on the subgrade surface under various train axle loads. Besides, the average stress of a 10 cm diameter circular area on the subgrade surface directly under the wheel load was calculated. The results indicated that both the peak and average additional stresses induced by train loads followed normal distributions for various numerical models (i.e., various groups of random ballast particle morphology). Compared with field testing data of the additional stress on the subgrade surface under train loads acquired by earth pressure cell, the larger average stresses were obtained in numerical models, because of direct contact between ballast particles and the subgrade along with stress homogenization by the pressure cell.
