Comparison of laboratory testing using smartrock and discrete element modeling of ballast particle movement

Track performance is largely dependent on ballast performance. Unfavorable ballast conditions cause track geometry roughness and can contribute to increased rates of damage and deterioration to the rail, tie, and fastening components. Recent discrete element modeling (DEM) studies demonstrated a strong relationship between individual ballast particle movement and overall ballast performance. This paper presents a laboratory and numerical study on ballast particle movement under cyclic loading. In the laboratory test, a wireless device called SmartRock was embedded in a ballast box to monitor individual ballast particle movement beneath a crosstie under cyclic loading. In the numerical study, an image-aided DEM approach was utilized to generate DEM particles with a realistic shape of ballast particles and simulate the ballast box test. The laboratory test results recorded by the SmartRock and DEM simulations results were compared. Good agreement was observed between the simulated and recorded particle motion in terms of peak vertical, horizontal, and angular accelerations during ballast deformation. The results indicate that horizontal movement and rotation are important modes of motion for ballast particles under cyclic loading. The SmartRock is also shown to be capable of recording real-time particle movement including translation and rotation and, thus, can be used as a fundamental research and monitoring tool in railroads.