European Research for An Optimised Ballasted Tracks
Granular materials such as ballast have been used for a long time to build the majority railway tracks throughout the world. Although ballast presents specific interesting properties, degradations can be observed on ballasted tracks loaded with high speed and/or freight trains, thus leading to significant amount of maintenance or track renewal. Understanding which parameters in the train/track interaction are responsible for this untimely degradation and being able to set criteria and limit values for these parameters are therefore necessary conditions for reducing maintenance costs and for increasing the global efficiency and the interoperability of the Trans-European railway network. The Eurobalt II project started on September 1997 with the aim to establish an understanding of the relationships between track design parameters and long term maintenance requirements, to produce an optimised ballasted track design and to justify decisions on ballasted track versus other non-ballasted track types upon objective criteria. A partnership has been formed comprising European railway administrations, universities and railway industry participants. The project has been supported by the European Commission Brite-Euram framework. The approach followed during the Eurobalt II project was specifically oriented towards very practical application. It relied on the hypothesis that track geometry deterioration is a direct consequence of ballast settlement and therefore a better understanding of the role of the track stiffness was clearly required. Track assessment and monitoring requirements have been considered during the project. Banverket developed the Track Loading Vehicle into a valuable prototype assessment vehicle capable of measuring track stiffness on the move. Preliminary surveys with the new equipment have impressively confirmed the relationship between the track stiffness profile and track geometry quality. The modelling activity has been supported by the experimental results and advanced models have been proposed to investigate a parametric study for optimising the track design and maintenance. Concluding specifications have been proposed for new construction situations but the case of most existing tracks remains open. Thus EUROBALT has advanced the understanding of ballasted track behaviour in some potentially very productive areas. The particular objective has been achieved, in that it is now possible to relate the various vehicle and track design parameters to the long term maintenance requirements and life cycle costs. Strategic decisions on the optimum solution for particular requirements, including the choice between slab track and ballasted track, can now be made based upon much more objective criteria. What is most encouraging is that large opportunities have been identified for improving the performance of many current ballasted tracks.