Insights into particle breakage induced macroscopic and microscopic behavior of ballast materials under repeated load triaxial compression via DEM

Abstract

Ballast particles undergo breakage under the load of trains, which greatly affects the stability and safe operation of ballasted railway. Existing discrete element methods for simulating particle breakage have shortcomings, such as unclear breakage mechanisms and low computational efficiency, making it difficult to reveal the mechanisms of particle breakage and the related deformation processes under cyclic loading. To address this challenge, this paper first simulated the particle breakage by adopting the particle cutting method and then studied the evolution law of particle breakage under repeated triaxial compressive loading. The breakage-related macroscopic and microscopic behaviors including the stress-strain relation, particle rotation, and fabric anisotropy were analyzed accordingly. The results show that the accumulative plastic strain increases with load amplitude, decreases with confining pressure, and increases with load frequency, and that particle breakage exacerbates accumulative plastic strain. Particle breakage primarily occurs in the early stage of cyclic loading, and the ballast breakage index (BBI) is most influenced by load amplitude, followed by load frequency. Particle breakage reduces the magnitudes of internal contact forces and the anisotropy of normal contact forces within the specimens. Increasing load amplitude and frequency promote particle rotation and sliding, while increasing confining pressure suppresses them. When the frequency exceeds 10 Hz, the responses of the particles, such as vibrational acceleration, rotation, and sliding, increase rapidly. These findings provide effective particle-scale indicators for the study of ballasted track.