The influential parameters affecting the vibration intensities in the vicinity of railway tracks

Abstract

Railways and other sources of environmentally induced vibrations often lead to annoyance and sometimes property damage. In this framework, transition zones are deemed as the most sensitive locations on the railway track, especially to high vibrations and impact loads. This causes high maintenance costs and is often very annoying, as the availability of the track gets limited during maintenance processes. One of the main reasons of this problem is the stiffness change of the railway supporting structure which is sometimes abrupt. This thesis will shed some light on the factors playing roles in altering the vibration intensities in level crossings. Moreover, the effects of these factors on ground vibrations will be highlighted. Further on, a model is presented which incorporates all these parameters. This model can be used to predict the change in ground vibrations in level crossings. The objective of this thesis is to determine the influential parameters in terms of the response vibrations in the surroundings of railway tracks. On that account, following an in-depth literature study, and based on the analysis of the measurements performed at Movares, it was suggested to investigate three factors being the ambient temperature effect, the hanging sleeper scenario and the inhomogeneity of foundation and analyze their impacts. The in-situ measurements illustrated a correlation with temperature, where the vibrations are amplified during hot periods and in the summer season. Besides that, the reports indicated the presence of the hanging sleeper scenario, where the suspension between the rails and the foundation is no longer active. It was also reported that locations with inhomogeneous foundations experience higher vibrations than those with quasi-homogeneous foundations. On those grounds, it was decided to study the effects of the hanging sleeper scenario, the ambient temperature and the presence of a slab-track crossing on the track. A complete vehicle/track/soil numerical model has been used in the parametric study in order to assess the factors affecting the response vibrations induced by trains and to quantify their impacts. Along with that, the numerical results have been validated, to some extent, with analytical results. More specifically, the steady-state response obtained with both approaches are compared present a good agreement. The results exhibit that the hanging sleeper phenomenon has a substantial effect on the vibrations. Furthermore, the existence of a level crossing (representing a foundation inhomogeneity) proved to be of significance as well. Lastly, the ambient temperature possesses a limited impact which could turn severe in extreme conditions.