Abstract
Differential settlement and development of track geometry irregularity drives the need for maintenance of ballasted railway tracks. Predicting this requires an understanding of how train loading and the resulting stresses vary and are distributed along the track and how the track responds. Irregularities, from differences in the unloaded level and deflection under load (from variation in stiffness and load) influence the wheel-rail contact force along the track. The stiffness will also influence the distribution of stress into the ground. To investigate variation in the (unloaded) track level and support system stiffness along a railway, stiffness, track deflection and sleeper level surveys were carried out along a 200 m length of track. Measurements were taken at every sleeper using total station for track level and accelerometers to calculate deflection, together with a frequency-based analysis for the track support system stiffness. A simple 2D vehicle track interaction model was used to study the influence of the unloaded sleeper level, the variation in track stiffness and any identified voiding for the performance of the track. Here, the unloaded level was more significant for the loaded level and the wheel / rail contact forces than the variation in track stiffness, which was most importance for the deflections under load.
Highlights
An ambition of the rail industry in the UK and elsewhere is to use ever-advancing monitoring and modelling techniques to manage the performance of railway track and inform maintenance planning as part of a strategy to improve reliability, increase capacity, reduce delays, enhance safety and drive down costs [1]
These will be influenced by variations in both track stiffness and unloaded track geometry, which are likely to change over the life of a track owing to the development of differential settlement and maintenance
The objective of this research was to assess the significance of real variations in track support system stiffness, unloaded track level and non-linearity due to voiding on the modelled behaviour of a long length of track, through simulations using data obtained from large scale trackside measurements
Summary
An ambition of the rail industry in the UK and elsewhere is to use ever-advancing monitoring and modelling techniques to manage the performance of railway track and inform maintenance planning as part of a strategy to improve reliability, increase capacity, reduce delays, enhance safety and drive down costs [1] This might include forecasting attributes of the physical behaviour of the track, such as track deflection and changes in track level through differential settlement as functions of train loading, along an entire route to better understand maintenance needs. To understand and predict the development of differential settlement, it is necessary to understand how train loads and resulting stresses are distributed into the trackbed and subgrade and how they vary along a track length These will be influenced by variations in both track stiffness and unloaded track geometry (level), which are likely to change over the life of a track owing to the development of differential settlement and maintenance. Absolute sleeper levels can be measured from the side of the track by conventional surveying
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