Influence of Particle Packing, Size, and Gradation on Crushing Strength of Ballast Using Discrete Element Method

This paper presents effect of ballast form and packing on its crushing strength and fragmentation behavior using the discrete element method (DEM). Bubblepack algorithm was chosen for this study to generate the ballast with different forms and packing conditions. Two key parameters, namely the bubblepack ratio ( \(\rho \) $\rho$ ) and overlapping distance ( \(\Phi \) $\mathrm{\Phi }$ ), which govern the form and packing of individual ballast, were examined through single-particle crushing tests. The findings revealed that ballast models generated at low \(\rho \) $\rho$ and high \(\Phi \) $\mathrm{\Phi }$ values exhibit suitable crushing strength. Moreover, the strength and coordination number of the ballast assembly were assessed through one-dimensional compression tests in DEM, conducted on gradations from four countries. It is observed from the results that these parameters are contingent upon the packing conditions. Additionally, the impact of the degree of compaction of the ballast assembly was investigated across various porosity levels, which revealed that there was a decrease in both strength and coordination number with increasing porosity.