Development of Design Guidelines for High-speed Railway Track Including Critical Track Velocities and Track Mitigation Strategies

It is generally understood that the carbon foot-print of trains, per paying passenger, is less than that of an airline passenger. This has led to a resurgence of railways across the world as a principal means of mass transport. In order for railways to be viable, in terms of journey times and economics, the need for increased train speed and axle weight has become of paramount importance. Apart from the 186mph Channel Tunnel Railway Line (CTRL) the maximum speed of trains in the UK is generally 125mph. In France the TGV now operates at 200mph, but a land speed record of 356mph was recently set on the Paris to Strasbourg line. An increasing demand for higher train speeds is therefore clearly evident. Introduction of high-speed systems to the railway network across the world has however brought new problems in terms of railway geotechnics, namely the significant amplification of train-track vibrations at high train speeds. This phenomenon has been attributed to the characteristic wave speeds of the track, which mainly depend on the Rayleigh wave velocity of the subgrade, underlying embankments, and the natural flexural wave velocity of the rail. When train speeds approach this critical speed the track structure and supporting ground experiences excessive dynamic motions. These motions cause rapid deterioration of the track, ballast and subballast, including possible derailment and ground failure. These may threaten the stability and safety of the train and hence lead to significant line speed restrictions, causing significant delays to the network. It is therefore evident that in order to increase line speeds in the UK (and overseas) it is necessary to not only be able to model and predict critical velocity affects, but also how to stabilize them. However research needs to be targeted to determine what affects stabilization technologies have on the dynamic response of the railway track. The dynamic behaviour of railway track is a very complex 3-dimensional problem with instantaneous interactions occurring between the wheel, rail, pad, sleeper, ballast, formation and subgrade. In order to provide a safe and reliable high-speed railway it is necessary to be able to correctly model and predict the track response, including speeds leading up to and including critical track velocities. In addition critical track velocity issues lead to significant ground vibration transmission to adjacent structures. The principal objective of the proposed work is to investigate the 3-dimensional dynamic behaviour of railway track up to and including critical track velocities using the advanced 3-dimenional finite element railway track model D.A.R.T.3D (Dynamic Analysis of Railway Track, 3-dimensional) and by looking at the stress wave patterns using a purpose built test track bed. The secondary objective of the research is to look at the available methods for track stabilization in order to access the affect of localized stiffness increases on the Rayleigh stress wave, the critical track velocity and hence the overall improvement in the dynamic track behaviour. The work is highly relevant to the future strategic development of both the UK rail industry and the rail industry world wide.

As climate change continues to generate significant concerns across the world a dichotomy exists in terms of the need to reduce carbon emissions , but still allow the economic development of nations. At the centre of a country's economic development is transportation, both in terms of its people and saleable goods (freight). It is well understood that the carbon footprint of trains per paying passenger is a less than that of an airline passenger. This has led to a significant investment in railways across the world; one only has to look at the UK to see that a dramatic rise in rail passenger numbers has occurred over the last decade. There is also a desire to transport more freight by rail rather than road, again to reduce carbon emissions and free up the road network. It is clear that in order for countries to proper they need to have a robust, efficient and fast rail network. This philosophy is at the very heart of this proposal and therefore its Impact Factor on the future strategic development of high-speed railway networks is very high. The UK and international rail industry will benefit greatly from this research proposal, including railway track engineers, track design consultants and contractors. Secondary beneficiaries will be policy making organisations, such as Governments. Specifically it will allow the development of strategies for increasing line speeds over difficult soil conditions, often present when constructing new track or renewing existing railway track. To ensure that the UK rail industry directly benefits from this proposal, Network Rail are forming an active part of the Advisory Board and can therefore directly influence the quality of the results obtained and how they are presented, for example the results can be incorporated directly into the UK Network Rail standards. Through Network Rail the results will also be presented to the European Rail consortiums. Internationally one of the main dissemination routes is through international conferences and seminars (such as the Railway Engineering Conference and the AREMA conference). Where appropriate, seminars will be given to all interested parties, particularly to the PWI and the railway engineering consultants, who are often tasked with finding solutions to CTV issues. The PI of this proposal has an excellent track record in knowledge transfer to industry having previously developed and spun out research work in railway engineering. In addition, a new web site will be created where all results and publications will be displayed for the international community to access. Professor Forde also has strong links with the TRB (USA Transport Research Board) another excellent avenue for research dissemination and engagement. Professor Forde is also the organiser for the International Railway Engineering conference and hence the opportunity to present Keynote Papers on the research results to a wide international audience, both during the research programme and on completion of the work is a principal mechanism of engaging the railway community worldwide in the work. The BBC will also be approached during the project to gauge interest in the making of a documentary on the challenges faced by high-speed trains since it would clearly gain the interest of the public. This is an excellent mechanism to promote the EPSRC and the research work performed within UK universities. Combined with the links with industry, this proposal can be used as a catalyst to spark research collaboration both nationally and internationally between academia and industry.