Analysis of ballast tamping and stone-blowing processes on railway track behaviour: the influence of using USPs

Railroads have played a significant role in the development of modern society, particularly during recent decades. In order to ensure that these structures provide an adequate quality of service, maintenance works are needed. In spite of the fact that ballast tamping is the most common maintenance task carried out on railway tracks, its application causes ballast degradation while the track returns to its previous position. As a result, other techniques such as stone blowing, or the use of under-sleeper pads, have been developed as an alternative solution to reduce the frequency of maintenance works. Nevertheless, despite the potential benefits of these techniques, the efficacy of their widespread application needs to be confirmed by more in-depth study, in order to understand their effects on the mechanical performance of railway tracks. This paper therefore focuses on analysing in the laboratory the effects of tamping and stone-blowing processes on the mechanical performance of railway tracks (settlement, stiffness, capacity to dissipate energy, pressure under the ballast layer and ballast degradation); the influence of under-sleeper pads is also assessed. The results show that not only is the stone-blowing process more effective than tamping in maintaining the track geometry and reducing the frequency of maintenance tasks, but it also allows for more stable short- and long-term mechanical performance of the section, as well as obtaining lower degradation of ballast and substructure. In addition, it was found that the use of under-sleeper pads in tracks could improve the effectiveness of maintenance tasks and the behaviour of the track after these processes, particularly in the case of tamping.