The EUROBALT project has led to the advancement of knowledge in the behaviour of ballasted track in several different areas.
The measurements have shown the importance of the track stiffness in the whole process of the track degradation. Even though a complete understanding has not been achieved in this particular area, this concept will be now considered by the railways companies. Different tools have also been improved or developed in order to measure the track stiffness, under traffic or by separate investigation (STEDEF measurement technique or PANDROL double integration).
Modelling the ballast has been investigated with first studies with new approaches (ENPC). Moreover, two models have been developed, with the same goal of predicting track geometry deterioration. Even though the validation has been limited, it is a big step forward in the study of the phenomena (INRETS "VOCO + BALTAS" and TUB SIRaGe).
As for the models of track damage modelling, different problems were studied and models were developed or improved. These models will also allow a better understanding of the phenomena of track deterioration and the prediction of maintenance and renewal requirement and costs (BRR models).
The monitoring studies led to :
the development of a prototype able to recover in real time the long wave faults on a track, using versine based measurement cars (MAN technique),
the development of a calculation method to define the forces applied on a track section when a train passes, using the data obtained from the new piezofoil sensors developed within the project (MAN method and TUB piezofoil sensors applications).
What is also important is the knowledge gained by the different participants, particularly the railways companies. The different approaches used to characterise the behaviour of the ballast showed that the parameters are numerous and not easy to resolve. It can be stated, however, that the concepts of track elasticity or track elasticity variation is one of the key factors in track geometry deterioration. Further studies must be led now to describe more precisely its importance, define means of measurement, and develop the track specifications necessary to realise the benefits that are possible.
The EUROBALT project is a big step forward in providing a more precise knowledge of the ballasted track. A complete understanding, however, remains elusive, and is likely to require significant further investigations.
Standard railway tracks use ballast as a support, on very high speed lines as well. Compared with track laying on concrete slabs,this system is generally speaking advantageous in terms of cost-performance trade-off (roughly 75% saving on investments) maintainability and environmental compatibility (alleviation of noise and vibrations). Nevertheless the mechanical behaviour of the socalled track-ballast-subgrade system, which is very intricate, remains poorly explained.Making full use of the qualities of this technique at the highest speeds (300 to 350Km/h) requires an improvement of the knowledge of this material, as well as of the dynamic and long-term behaviour of ballasted track by means of experimental and theoretical research. This will allow an optimisation of the ballasted track system with regard to such parameters as the nature of subgrade and the category of traffic, and with an objective of keeping low infrastructure costs. This will also make possible a predictive approach of the evolution of ballasted tracks, upon which automated monitoring systems will be developed in order to facilitate and reduce the cost of diagnosis and maintenance.
The research programme intends to establish an experimental designation of the ballasted track and of its interactions with trains and subgrade and to build on this base, if necessary using unconventional analysis methods, a model of the track-ballast-subgrade system, describing its static and dynamic behaviour and its long-term evolution.
The simulation model will allow to design an optimal conformation of the system and to alleviate its wear. Included in the programme is the development of automated monitoring systems based upon the previously defined model.
Funding SchemeCSC - Cost-sharing contracts
DE2 8YB Derby
KT15 2AR Weybridge