Moving forward with Track to the Future
Source: RTM Aug/Sep 16
Professor William Powrie, dean of the Faculty of Engineering at the University of Southampton, gives RTM and update on the innovative Track to the Future project.
Last year, RTM reported on the announcement of a major new programme grant known as Track to the Future (T2F), aimed at improving the understanding of the underlying science and developing new analytical tools for the design of long-life, low-noise railway track systems.
The value of the award, to the universities of Southampton, Birmingham, Huddersfield and Nottingham, is £5m from the Engineering and Physical Sciences Research Council (EPSRC), with a further £3.5m in cash and in kind from collaborating industry partners including Network Rail and from the universities for postgraduate studentships associated with the research programme.
This article is a brief update and review of progress during the programme’s first year. T2F is addressing three major research challenges:
- Track life: track maintenance is costly in cash and carbon terms, and interferes with railway operations. T2F will explore new, low-maintenance track forms. It will develop an understanding of the relationships between track stiffness and settlement, which can be measured, and differential movement of the track, which causes performance to deteriorate. It will extend ballast life by understanding and eliminating or mitigating causes of deterioration and developing designs that will continue to perform well after deterioration has set in; and will facilitate ballast re-use rather than downcycling or disposal.
- Switches (points) and transitions: where trains change direction and cross tracks or other infrastructure there is a complex interaction of geometry, support, wheel profile and vehicle dynamics. This is not sufficiently understood, and frequent costly and disruptive maintenance is required. T2F will draw together the key areas of ground support, switch or transition zone geometry, and vehicle dynamics for the reliable assessment of crossing and transition zone behaviour, life and maintenance needs.
- Noise and vibration: public tolerance of vibration and noise from railways is decreasing as use intensifies, yet these are traditionally regarded as secondary in design. T2F will develop and demonstrate, through modelling and full-scale testing, a low-noise, low-vibration track consistent with reduced whole-life costs and low maintenance.
Over the past year, in terms of understanding the science, we have developed two complementary approaches to the discrete element modelling of ballast, both of which capture how the stress-strain behaviour of ballast changes with load cycling over a range of confining pressures. This work has been published in the journal ‘Granular Matter’ as two companion papers.
We have also demonstrated the utility of an innovative theoretical framework for understanding and quantifying the behaviour of fibre-reinforced ballast; carried out and published an initial review of current models linking trackbed stiffness to geometry deterioration rates; and carried out measurements of S&C condition and behaviour at two locations on the UK railway network, which is giving some new insights into how the detail of the crossing design affects its performance .
The project team has also analysed a range of vehicle and track configurations, and a variety of geometrical shapes of crossing (wing and nose), to determine the best performing shape for installation on UK infrastructure in the near future, and support stiffness. Optimisation has taken current manufacturing capabilities into account but has also evaluated more radical shapes that will become feasible in the future through advanced manufacturing technology. And we have developed a large microphone array for the quantitative measurement of airborne noise from railways in different environments under different operating conditions.
In terms of modelling, tools and outputs for more direct use by industry, we have also edited and lead authored the new Guide to Track Stiffness, on behalf of the Cross-Industry Track Stiffness Working Group.
The team has carried out whole-life social cost modelling of the impacts of under sleeper pads and random fibre ballast reinforcement for two case study routes. This work has shown that the indirect economic impacts of these interventions, generated by changes in factors such as lineside noise, can be greater than the direct financial impacts for the rail infrastructure operator. However, it has also emphasised the complexity of estimating such indirect impacts; for example, under sleeper pads lead to a reduction in groundborne noise but an increase in airborne noise.
The coming year promises to be an exciting one, as we gear up for further laboratory tests; field trials of innovative ballast solutions, such as random fibre reinforcement; and we welcome our first cohort of PhD research students.
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