Field Validated Discrete Element Model for Railroad Ballast

This paper presents field validation results of a realistic railroad ballast model, developed recently at the University of Illinois based on the Discrete Element Method (DEM), with ballast settlement data collected from the Facility for Accelerated Service Testing (FAST) for Heavy Axle Load (HAL) applications at Transportation Technology Center (TTC) in Pueblo, Colorado. By addressing adequately the particulate nature of different sized and shaped ballast aggregate particles and their interactions with each other at contact points, the ballast DEM model provides a quantitative track performance simulation capability to conduct field applications and investigate various aspects of railroad ballast designs and behavior. For the field validation, four 100-ft test sections were constructed in early 2010 with four different aggregate materials used as the new ballast layer installations on a curve at the TTC FAST test track. During the ballast layer construction, settlement plates were also installed on top of subgrade in the middle and outside rail locations in order to measure deformations within the ballast. In particular, ballast layer settlements due to train loadings were measured to assess track surface degradation, track stiffness, and ballast breakdown. Each aggregate material, donated by one partnering US railroad