Discrete Element Modeling of Permanent Deformation Accumulation in Railroad Ballast Considering Particle Breakage

Abstract

Particle shape and mineralogy have been found to greatly affect railroad ballast response under train loading. In this research effort, the effect of particle breakage on ballast permanent deformation behavior was studied using the Discrete Element Method (DEM). Real ballast particle shapes were digitized using an inexpensive imaging tool, and agglomerates of spheres were used to regenerate those complex shapes. Particle crushing tests were carried out in the laboratory, and discrete element models simulating the crushing test were calibrated based on the laboratory test results. Model parameters established through this calibration process were subsequently used to study the permanent deformation response of ballast layers comprising complex-shaped breakable ballast particles under repeated loading. The effect of particle shape was studied by comparing the permanent deformation behavior for ballast layers comprising simplified ellipsoid particles to those comprising the complex-shaped particles simulated using agglomerates of spheres. The simulation results clearly highlighted the significance of particle breakage in ballast permanent deformation accumulation under cyclic loading. Most particle breakage was observed to occur under the initial load cycles, which also corresponded to the highest rate of permanent strain accumulation. The particle breakage as well as the rate of strain accumulation gradually decreased with increasing load cycles.

Discrete element modelling of track ballast capturing the true shape of ballast stones

“…The study showed promising results using aggregate shapes rather than sphere-shaped ballast stones. [18] simulated ballast particle breakage by calibrating the crushing criteria in the DEM simulation by particle crushing laboratory test. Polyhedral ballast shapes were compared with spherical shaped ballast stones.…”

“…Tutumluer and Hashash [17], represented the ballast as 3D Polyhedrons, using 3D-scannings of lime-stone, obtaining realistic shaped ballast. [18] used a ballast model similar to the "3D -scanned ballast" model presented in this study, where overlapping spheres represents the ballast stone, here 3 real stones were scanned and modelled by overlapping spheres. Another study representing ballast stones by overlapping spheres is the study conducted Zhou et al [19], here the main interest was to simulate the tamping procedure.…”

Dynamic Behavior in Transition Zones and Long-Term Railway Track Performance

“…Although very robust numerical approaches have been proposed to simulate railway tracks and the complex degradation behavior of the particulate media of the ballast layer, such as the Discrete Element Modeling (Dahal and Mishra, 2020), its application is still limited to very small stretches of track (models with only a few sleepers long) (Chen and McDowell, 2016) because of the extreme computational effort that is required to simulate structures such as transition zones.…”