Numerical Modelling of Track Behavior Capturing Particle Breakage under Dynamic Loading

Abstract

This paper presents a study on ballasted track behavior, capturing particle breakage under dynamic loading using large-scale laboratory testing, supplemented with computational modeling approaches. Four large-scale triaxial tests are conducted to investigate the ballast breakage responses subjected to cyclic loading subjected to varying frequencies, f=10-40Hz. Measured laboratory observations show that an increase in loading frequency and magnitude results in significantly increased degradation (breakage) and deformation of ballast. Computational modeling using a coupled discrete-continuum approach (coupled DEM-FEM) is introduced to provide insightful understanding of the deformation and breaking of ballast under cyclic loading. Discrete ballast grains are simulated by bonding of many cylinders together at appropriate sizes and locations. Selected elements located at corners, surfaces and sharp edges of the simulated particles are connected by parallel bonds; and when those bonds are broken, they are considered to represent ballast breakage. The predicted axial strain a, volumetric strain v obtained from the coupled DEM-FEM model agree reasonably well with those observed experimentally. The coupled model is then used to investigate micromechanical aspects of ballast aggregates including the evolution of particle breakage, contact force distributions and orientation of contacts during cyclic loading.

Mechanical behavior and particle crushing of irregular granular material under high pressure using discrete element method

“…The crushable granular materials were modelled using DEM methods 24 , 25 . Some coupling methods were also used to study the particle crushing of granular materials, such as DEM-FEM, DEM-XFEM and DEM-SBFEM 26 – 28 . The numerical method has brought the investigation of particle breakage into a grain scale and provided several new insights.…”