Etude de la carbonatation des dispositifs du drainage profond de l'infrastructure ferroviaire

Abstract : This thesis focuses on the clogging phenomenon linked to the precipitation of calcite in high-speed line drainage systems (HSL). Indeed, the clogging of these drains can affect the geometric behavior of the track. Maintaining hydraulic devices in its optimal operating condition is a major challenge for SNCF Réseau. The objective of this research is to determine the processes and causes of calcite formation and its kinetics, by integrating the natural environment (geology) and railway context (anthropogenic materials) as well as the types of drainage devices. The purpose of this research has double industrial goals: preventive and curative. The dysfunction of the devices of the HSL drainage systems, whether along the track or in the tunnel, cause the presence of water in the foundation of the tracks, which can lead to a degradation of their mechanical characteristics, and in the long term induce rail levelling that can lead to impacts on traffic. The clogging of drainage devices by precipitated carbonate deposits is a major cause of reducing the functionality of these devices on the French Railway Networks (RFN): 546.8 km of HSL (Line 1 to 6) are potentially under this impact. In some ways, this impact is essential. For example, it has been estimated that over 78 km (HSL 2) of HSL equipped with draining collector, that the clogging of the devices related to the precipitation of carbonate deposits could represent up to 80% of cases of drainage dysfunction. The curent techniques used are the hydrocuring or the jackhammer for very hardened deposits but both of low profitability in view of the potentially clogged kilometers. In order to propose innovative design or treatment solutions adapted to the different site contexts, the study of the mechanisms involved was the subject of a site monitoring lasting more than two years at a HSL pilot site (Chauconin, 77) instrumented for this purpose allowing the analysis of the physico-chemical parameters of the drained water as well as that of precipitated deposits in their geological, geotechnical and hydrometeorological context. This approach was complemented by the study of 8 other complementary sites selected in full-scale of RFN including tunnels under variant geology as well as covering all existing drainage devices in the railway infrastructure.The hydrogeochemical model developed on this basis offers the possibility of reproducing the processes observed on the Chauconin site: the physical process (Rain-Flow) and the physicochemical process (Transfer-Reaction Model) according to their context in order to quantify predictably the deposits in the drainages devices. This conceptual model is based on an empirical hydrology model of two ground reservoir by coupling the processes of transfer and reaction (dissolution - precipitation). The first analysis of water and surrounding materials on the Chauconin site show that, in the absence of a drained aquifer, this drained water is rich in calcium and sulphates. The detailed analysis of the materials shows that some of the reported materials used in the foundation of the railway platform contain gypsum whose dissolution by infiltration water could explain the composition of the drained water. The waters on the additional sites with a presence of permanent or temporal aquifer are essentially calcium carbonate. These drained waters are consistent with their calcareous or Gypsums geology.The developed conceptual model could be expanded to other railway sites as tunnel. At this stage of our research work, we propose a conceptual decision-making tool with two objectives: diagnosis the calcite precipitation and justification of the choice of typologies of solutions
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Neng Jia. Etude de la carbonatation des dispositifs du drainage profond de l'infrastructure ferroviaire. Génie civil. Université Paris-Est, 2018. Français. ⟨NNT : 2018PESC1153⟩. ⟨tel-02304550⟩

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