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

人们普遍认为，火车每位付费乘客的碳排放量低于航空乘客的碳排放量。这导致铁路在世界各地复兴，成为主要的大众交通工具。为了使铁路可行，从旅行时间和经济角度来看，提高列车速度和轴重的需求已变得至关重要。除了时速186英里的英吉利海峡隧道铁路线(CTRL)外，英国火车的最高时速一般为125英里。在法国，TGV现在以每小时200英里的速度运行，但最近在巴黎到斯特拉斯堡的线路上创造了每小时356英里的陆地速度纪录。因此，对更高列车速度的需求日益增长是显而易见的。然而，在世界各地的铁路网中引入高速系统带来了铁路岩土工程方面的新问题，即在高速列车速度下列车-轨道振动显著放大。造成这种现象的主要原因是轨道的特征波速，它主要取决于路基、下垫层的瑞利波速度和钢轨的自然弯曲波速。当列车速度接近这一临界速度时，轨道结构和支撑地面会经历过大的动力运动。这些运动会导致轨道、道碴和道碴的快速损坏，包括可能的脱轨和地面故障。这可能会威胁到列车的稳定性和安全性，从而导致严重的线路速度限制，导致网络严重延误。因此，很明显，为了提高英国(和海外)的线路速度，不仅需要能够对临界速度影响进行建模和预测，而且还需要能够稳定它们。然而，需要有针对性的研究，以确定稳定技术对铁路轨道动力响应的影响。轨道的动力特性是一个非常复杂的三维问题，车轮、钢轨、垫层、轨枕、道碴、编组和路基之间存在瞬时相互作用。为了提供安全可靠的高速铁路，必须能够正确地建模和预测轨道响应，包括达到并包含临界轨道速度的速度。此外，关键的轨道速度问题会导致地面振动向邻近结构传递。这项工作的主要目的是使用先进的三维有限元轨道模型D.A.R.T.3D(铁路轨道动力分析，3维)，通过使用特制的试验道床观察应力波模式，研究达到或包括临界轨道速度的轨道的三维动态行为。这项研究的次要目标是研究现有的轨道稳定方法，以便了解局部刚度增加对瑞利应力波、临界轨道速度以及轨道动态行为的整体改善的影响。这项工作与英国铁路行业和世界铁路行业未来的战略发展高度相关。

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.