ABSTRACT
The paper investigated the cumulative deformation characteristic and shakedown limit of ballast samples under cyclic loading by Discrete Element Method (DEM) simulations. Based on the representative photos of ballast particles with a certain gradation, a discrete element numerical model of ballast sample, reflecting the irregular shapes and breakage characteristics of real ballast particles, was built for cyclic loading simulations. By adopting the shakedown theory, the deformation characteristics and the mechanism of ballast samples under cyclic loading were analyzed, including the influences of confining pressure, loading frequency and axial stress amplitude, and thus the stress limits (i.e. maximum principal stress) for different deformation states (i.e. shakedown behaviors) were determined. Finally, an empirical mathematical model was built to express the relationship between the shakedown limit and the ratio of maximum to minimum principal stress, which provides a reference for the design, maintenance, and repair of railway ballast bed.
