Deterioration of Track Geometry in Ballasted High Speed Line

Modeling Approach and Parametric Study

Résumé

In the context of environmental sustainability and increasing traffic volume, the emergence and modernization of public transportation are encouraged. As regards to High Speed Line (HSL), this leads to an increase of operating speeds which seems to be responsible for unusual fast evolving geometrical disorders observed in ballasted tracks. To tackle this problem, a study is launched dealing with the understanding of such disorders and the analysis of the influence of some structural parameters. For this purpose, we have developed a numerical program based on continuum mechanics that consists in computing the dynamic response of a railway structure under loads moving at constant speed. The developed method relies on the adaptation of the quasi-stationary technique to railway tracks. Moreover it allows taking into account the viscoelastic behavior of possible bituminous layers through the Huet-Sayegh model for asphalt materials. Using this developed numerical tool, the impact of the train speed on the ballast layer is studied by looking at the evolution of the vertical acceleration within this layer. A parametric study is then performed to determine which parameters make it possible to mitigate the computed accelerations. The considered parameters are the pad stiffness, the moment of inertia of the rail and the contrast of layer moduli. The results of the numerical simulations are discussed in the aim of proposing realistic solutions to minimize geometrical disorders in the ballast layer.