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Comportement mécanique et dégradation d’une voie ferrée en tunnel

Abstract : Railways have been evolving since the onset of the first rail rolled iron (1789). Wooden sleepers now give way to concrete sleepers while in some countries and commonly in tunnels ballast is replaced by continuous concrete slabs. This type of track, however, requires the integration of rail supports systems to ensure passenger comfort. The "low vibration track" (LVT) system developed by the company Sonneville is such a system. It contains a concrete block based on a micro-cellular pad all integrated in a rubber boot embedded in the slab of unreinforced concrete. This system today covers more than 1100km of railway track around the world, including the Channel tunnel.This work takes place within the framework of joint research between Ecole des Ponts ParisTech and the Eurotunnel group, that investigates the railway dynamic behavior and the support system degradation in the Channel tunnel.The first part of this work presents existing models for ballasted tracks and proposes extended models for non-ballasted tracks. Using a periodic condition of the railway track in steady state it can be shown that the distribution of loads on the support systems is governed by a characteristic relation that does not depend on the support behavior. This result allows us to offer an equivalent system represented by a preloaded spring. This analytical model is then used to calculate the dynamic response of the track by combining with support behavior (linear or nonlinear). This model has been validated by comparison with measurement data in the Channel tunnel. Lastly, a model is presented for a track whose supports have different properties. This model allows rapid calculation of track leveling due to support damage and has been integrated into the new software "EuroAnalyse".The second part of this work deals with the degradation of the LVT concrete block. Firstly, the research focuses on the damage mechanism by calculating the block stress with the help of the finite element method. The result shows that the concrete experiences tension stresses which can lead to damage by fatigue loads. Secondly, a method of identification is developed to monitor the concrete blocks in a tunnel. We show that the eigen frequencies of the block depend on its damage level and this is demonstrated by data and simulations. The method of measuring the eigen frequencies based on modal analysis has been integrated into the software "EuroDetection" which will be part of the track monitoring system for Eurotunnel
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Tien Hoang. Comportement mécanique et dégradation d’une voie ferrée en tunnel. Mécanique des matériaux [physics.class-ph]. Université Paris-Est, 2017. Français. ⟨NNT : 2017PESC1104⟩. ⟨tel-02918108⟩

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