Analysis of dynamic stresses in ballasted railway track due to train passages at high speeds
Jing Hu, Xue-cheng Bian
Abstract
Repeated train passages bring detrimental effects on train operations, especially at high speeds. In this study, a computational model consisting of moving train vehicles, track structure, and track foundation is used to investigate the stress distribution in the track substructure and underlying soil, particularly when the train speed approaches the critical speed via 2.5D finite element method. The numerical model has been validated by in-situ test results from a ballasted high-speed railway. The computational results reveal that the substructure is shown to be effective in reducing the stresses transmitted to the ground; however, a simple Boussinesq approximation is proved to be inaccurate because it cannot properly take account of the effect of multi-layered substructures and train speeds. It is acceptable to assume a simplified smooth track in the analysis model for determining the maximum stresses and displacements for a low-speed railway (⩽100 km/h) but, for a high-speed one, the dynamic amplification effect of track irregularities must also be considered in subgrade design. Analysis of the stress paths revealed that the load speed and track irregularity increase the likelihood of failure for the subgrade; track irregularity can induce many times of principal stress rotations even under a simple single moving load.