Maintenance vs total renewal – a methodology for assessing track ballast condition

Take any train journey and it is guaranteed there is one thing that everyone will notice. Stones. Without those stones – or the ballast – you are not going anywhere. By supporting the rails and sleepers, ballast holds all the components safely in place. Maintaining the ballast and ensuring it stays in optimum condition is, therefore, critically important. It’s on this area of expertise which track maintenance expert Johannes Neuhold will be sharing some of his innovative thinking at RailTech Europe 2017 – now just a few days away.

Based at the renowned Institute of Railway Engineering and Transport Economy at Graz University of Technology in Austria, Neuhold’s main research topics include the complex mechanics of track maintenance, so few are better placed to give an overview of the key issues which govern the maintenance of ballast and the implications for the railway sector.

His presentation, Network-wide Ballast Strategy, will give delegates an overview of how new methods which combine cost-savings with technology are showing promising results on the rail network across Austria, as he told RailTech. “My area of expertise is what you might call a very good combination of technical and economical issues,” said Neuhold, who is due to speak on Day Three of the three day conference, which focuses on Predictive Maintenance of Rail Infrastructure. RailTech Europe 2017 takes place on 28, 29 and 30 March in the Jaarbeurs in Utrecht.

Life-cycle-cost

“On the one hand I am working on analysing measuring signals from the measurement signals from the measuring cars to make a prognosis of track condition for the future,” he added. “On the other hand I am combining this technical knowledge with life-cycle-cost approaches, so that it is possible to plan the right maintenance actions at the right time, in advance.”

Can you outline some some of the technical, commercial and organisational challenges in working with track ballast? Ballast is a very important component within the track construction, as it has to fulfil some essential tasks for operating train traffic. This includes distributing stresses, dewatering and keeping the track in its required position. During the service life, the ballast bed wears and therefore has to be maintained so that the operation of a safe, reliable and capable train traffic is possible. The consequence of heavy loads produced by railway traffic means track quality deteriorates very quickly. The most common maintenance action for the ballast bed is tamping, which restores the correct position of the track. But if the ballast has reached a specific ‘fouling-limit’, tamping no longer has any effect and so the ballast has to be cleaned. This is a very complex undertaking, both from a technical and – in particular –  an economical sense because of its high costs.”

What is your current methodology and how is it carried out? Our methodology uses fractal analyses of vertical track geometry in order to ascertain the condition of the ballast. Fractal analysis is a mathematical method that splits up a measuring signal – in this case the signal of the track geometry – into different wavelength ranges. By analysing which wavelength range dominates the irregularities within the signal, it is possible to evaluate the reason for track geometry problems. For example, this can indicate ‘fouled’, or clogged, ballast. Within our method, fractal analysis is used for describing the ballast condition.

Total renewal

Is it preferable to clean the ballast as a ‘standalone’ action or should it always be done as part of a comprehensive infrastructure package? Ballast cleaning is a very complex and costly measure. Therefore, I believe it is very important to evaluate in detail whether it is reasonable to execute ballast cleaning as a maintenance action, whereby the rest of the superstructure, such as rails, sleepers, fastenings, is not renewed, or it is executed as part of a total renewal package. It is only reasonable to carry out ballast cleaning in the form of a maintenance action if the remaining service life of the other superstructure-components is high enough. Analyses show that ballast cleaning makes sense from an economic standpoint until three-quarters of its service life has been reached. So it is vital to investigate if ballast cleaning purely as a maintenance action is both technically viable and cost-effective.

What are the key benefits of this approach? I think the main advantage of my approach is that it is very easy to define a ballast strategy. Only three parameters are needed: the age of the track, the current fractal figure (this is the result of fractal analysis as I have explained, which describes the ballast condition) and the strategic service life of the track. Furthermore, it is possible to detect track sections where problems with the ballast are likely to appear and so the most reasonable (maintenance) actions can be planned for early.

‘System-optimum’

Is the Life-Cycle-Cost issue being fully appreciated by infrastructure managers? Is it factored in as part of the ‘bigger picture’ when planning and carrying out renewal works? I think there has been a huge development in the last few years with considerations of life-cycle-management becoming more and more important for infrastructure managers. This is an ongoing development and there are still many areas within the railway infrastructure system which can be optimised by sophisticated life-cycle-considerations to reach a ‘system-optimum’.

If there was one key message that delegates at RailTech could take away from your presentation, what would it be? I would say it is essential to make all decisions based on a combination of technical and economical facts to find the best solution for the entire system. Regarding track maintenance, this can only by reached by predicting which measure has to be executed at which point in time.

Johannes Neuhold will give a presentation on 30 March at the RailTech Europe 2017 conference. Visit the conference website for more information: https://www.railtech.com/railtech-2017/conference/

Author: Simon Weedy

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