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This paper investigates an environmentally-friendly approach to improve railway ballast performance and reduce ballast degradation by using elastic under sleeper pad (USP). Large-scale track process simulation apparatus (TPSA) tests were conducted on ballast assemblies under 25 and 35-ton axle loads, with and without USP. A coupled discrete-continuum modelling was developed to study the USP's effectiveness in minimizing ballast deformation and breakage. Hybrid coupled discrete-continuum modelling was also performed. Ballast grains with varying shapes were modeled in the discrete element method (DEM) as bonded cylinders, while the capping and subgrade were treated as a continuum media via finite difference method (FDM). Interface elements were created to facilitate force and displacement transfer between discrete and continuum domains. The USP, with a 10 mm thickness, was also simulated in DEM. Model parameters were meticulously calibrated through triaxial and cyclic compression tests, and the coupled model was validated against TPSA test data. The study further examines the micromechanical changes in ballast in the presence of USPs under cyclic loading, focusing on contact force distribution, particle connectivity and breakage. These insights provide a deeper understanding of how USPs mitigate ballast breakage from a microstructural perspective.

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Mitigating Ballast Degradation Using Under Sleeper Pads: Laboratory and Coupled DEM-FDM Modeling

  • 会议论文

  • 发表日期：

    2026年

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  • Trung Ngo,
  • Buddhima Indraratna,
  • Jing Chen

摘要

This paper investigates an environmentally-friendly approach to improve railway ballast performance and reduce ballast degradation by using elastic under sleeper pad (USP). Large-scale track process simulation apparatus (TPSA) tests were conducted on ballast assemblies under 25 and 35-ton axle loads, with and without USP. A coupled discrete-continuum modelling was developed to study the USP's effectiveness in minimizing ballast deformation and breakage. Hybrid coupled discrete-continuum modelling was also performed. Ballast grains with varying shapes were modeled in the discrete element method (DEM) as bonded cylinders, while the capping and subgrade were treated as a continuum media via finite difference method (FDM). Interface elements were created to facilitate force and displacement transfer between discrete and continuum domains. The USP, with a 10 mm thickness, was also simulated in DEM. Model parameters were meticulously calibrated through triaxial and cyclic compression tests, and the coupled model was validated against TPSA test data. The study further examines the micromechanical changes in ballast in the presence of USPs under cyclic loading, focusing on contact force distribution, particle connectivity and breakage. These insights provide a deeper understanding of how USPs mitigate ballast breakage from a microstructural perspective.