THREE-DIMENSIONAL DISCRETE ELEMENT ANALYSIS OF RAILWAY BALLAST’S SHEAR PROCESS BASED ON PARTICLES’ REAL GEOMETRY

Ballast beds are made up of particles with diverse sizes and shapes. Particle shape plays a fairly important role in affecting ballast aggregate’s mechanical behaviors; however, conventional grading curves indicating particle unidirectional size distribution cannot describe ballast particle shape characteristics comprehensively. Computer-vision technology is applied to obtaining three orthogonal views of a ballast particle, then extracting outlines of these three views to compute particle shape characteristic parameters. Three dimensional discrete element numerical simulations of ballast aggregate are processed by a self-developed program using elements which are built based on a particle’s three orthogonal views and identical in shape characteristics to realistic ballast particles. The computer-vision based discrete element method is validated with predictions from discrete element simulations matching closely with laboratory direct shear test results. Ballast aggregate’s deformation features and micro-scale mechanical behaviors in direct shear tests are investigated in depth based on the validated discrete element method