The influence of variation in track level and support system stiffness over longer lengths of track for track performance and vehicle track interaction

Abstract

Differential settlement leading to the development of track geometry irregularity drives the need for maintenance of ballasted railway tracks. Predicting the development of differential settlement requires an understanding of how train loading and the resulting stresses vary along the track and are distributed into the track bed and subgrade, and how the track bed and subgrade respond to these stresses. Irregularity of the rail level influences the wheel-rail contact force applied along the track. Irregularity in loaded level results from a combination of differences in the unloaded level and differences in the deflection under load associated with variations in the track support system stiffness and the applied load. The track support system stiffness will also influence how the stresses are distributed into the ground. To investigate the relative significance of variations in the initial (unloaded) track level and support system stiffness along a railway, stiffness and track deflection surveys were carried out along a 200 m length of track. Measurements were taken at every sleeper using a precise total station for unloaded level and accelerometers together with a frequency-based analysis to calculate the deflection and the track support system stiffness under train passage. A simple 2D lumped mass vehicle track interaction model was used to assess the significance of the unloaded sleeper level, the variation in track stiffness and any identified voiding on the loaded level, the track deflection and the wheel / rail contact forces. The simulations showed that, over the ranges considered, the unloaded track level had a more significant influence on the loaded level and the wheel / rail contact forces than the variation in track stiffness, whereas the variation in track stiffness was of most importance in calculating the measured track deflections under load

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Identifiers

ORCID for David Milne: orcid.org/0000-0001-6702-3918

ORCID for John Harkness: orcid.org/0000-0003-0908-0791

ORCID for Louis Le Pen: orcid.org/0000-0002-4362-3895

ORCID for William Powrie: orcid.org/0000-0002-2271-0826

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