Abstract
It has recently been reported that under sleeper pads (USPs) could improve ballasted rail track by decreasing the sleeper settlement and reducing particle breakage. In order to find out what happens at the particle–pad interface, discrete element modelling (DEM) is used to provide micro mechanical insight. The same positive effects of USP are found in the DEM simulations. The evidence provided by DEM shows that application of a USP allows more particles to be in contact with the pad, and causes these particles to transfer a larger lateral load to the adjacent ballast but a smaller vertical load beneath the sleeper. This could be used to explain why the USP helps to reduce the track settlement. In terms of particle breakage, it is found that most breakage occurs at the particle–sleeper interface and along the main contact force chains between particles under the sleeper. The use of USPs could effectively reduce particle abrasion that occurs in both of these regions.
Highlights
In recent years, under sleeper pads (USPs) have become popular in newly-built high speed railway tracks in central Europe
discrete element modelling (DEM) of a box test on ballast has been used to give micro mechanical insight into how Under Sleeper Pads improve the performance of ballasted railway track
This was modelled by representing the USP using three layers of small bonded spheres, and using a realistically shaped clump to represent the ballast particle
Summary
Under sleeper pads (USPs) have become popular in newly-built high speed railway tracks in central Europe. Bolmsvik [2] showed that track misalignment could be reduced by the use of USPs. USPs have been found to reduce both inter-particle abrasion and sleeper– ballast attrition [3,4]. USPs have been found to reduce both inter-particle abrasion and sleeper– ballast attrition [3,4] Both Riessberger [5] and Abadi et al [6] observed that the use of a USP increases the ballast– sleeper contact area which leads to a reduced contact pressure in experimental tests. This was presumed to be the reason. The improvement of using geogrid-reinforced ballast has been successfully
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