Railway track substructure: Recent research and future directions

Abstract

Rail has a vital role to play in the decarbonisation of transportation, both now and in the future. It has the potential to mitigate, but also suffers from the effects of climate change, with the ageing infrastructure on historic networks increasingly vulnerable to more frequent extremes of temperature, rainfall and storminess. If rail is to remain affordable, it is essential that we target resources where they are most needed, avoiding unnecessary maintenance and over-engineered reconstruction or renewal. This requires an improved understanding of the engineering behaviour of railway infrastructure, especially the track and its supporting substructures, so that we have the confidence to adopt new approaches to construction, maintenance, refurbishment and repair. This paper is a written version of the 3rd International Society for Soil Mechanics and Geotechnical Engineering Ralph Roscoe Proctor Lecture, delivered at the 4th International Conference on Transportation Geotechnics on 25 May 2021. It summarises some of the research carried out at the University of Southampton (UK) over the past decade or so to develop a better understanding of the loading applied to, and the response of, the railway track and substructures; and more cost- and carbon-effective ways of preventing deterioration or restoring performance. The importance of trackbed or rail support system stiffness, track vertical alignment and train speed are demonstrated and discussed, and practical ways of reducing the ongoing settlement of railway track are presented. It is argued that, to facilitate future development and improvement, more rigorous but practically usable models for the evolution of track settlement are needed, validated with reference to high quality field data; together with a better understanding of material and system damping.