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ABSTRACT
Many tunnels in the UK are ballasted as the need for fixed geometry was not required when the tunnel was first constructed (i.e. they are currently floating geometry). However, with the need for the electrification of tunnels, which often requires track lowering and changes in freight train kinematics, the desire for fixed geometry is becoming more prevalent. Given the problems with concrete track tunnels, especially the time requirements for installation, the need for a method of providing fixed geometry conditions very rapidly is clearly required. The XiTRACK reinforcement system is currently being used/considered for tunnels in the UK to provide such track restraint. In the XiTRACK system the ballast tunnel track (whether a virgin ballast track or a removed PACT system) is treated using specially designed polymers that cure within minutes of application. The polymers are designed to be energy absorbing and the formed GeoComposite allows for track drainage. In effect the track can be converted from floating geometry to fixed geometry in a very short period of time, typically 24 hours for one of the tunnels being considered.
This paper describes the process of tunnel track reinforcement using XiTRACK. It shows the development of stress concentrations around the railhead and demonstrates how these induced stresses result in settlement in normal ballasted tunnels (i.e. track faults). The paper shows how these stresses are managed within the formed XiTRACK GeoComposite, significantly reducing the likelihood of future track movement. In short, the paper describes how the fixed geometry condition is achieved and discusses the predicted longevity of the system. The paper also discusses the benefits of the system in terms of construction time reduction and the ability of the track to be rapidly repaired should any potential future problems develop.
Proceedings of 9th International Conference on Railway Engineering, London June 2007