Ballast, rails and sleepers form a quasi‐elastic track system. When the deformations exceed the elastic limit of the system and the track is no longer lying in its correct position, precautions have to be taken. During a technical track examination several parameters are measured. Should the operational tolerance values of these parameters be exceeded, track maintenance needs to be conducted. Track maintenance includes levelling, lifting, lining and tamping of the track, which is performed by a tamping machine, where the tamping tines penetrate the ballast and compact it beneath the sleeper. For the purpose of this research project, a tamping machine was equipped with a number of strategically positioned sensors in order to perform the in‐situ measurements required to describe the interaction of the tamping tines with the ballast and its compaction beneath the sleeper. With a special emphasis on the energy transferred into the ballast and alteration of ballast stiffness during compaction, conclusions concerning efficiency of the tamping process in different ballast conditions are made and presented.
Der Zustand des Gleisschotterbetts ist einer der wichtigsten Faktoren für den sicheren und ökonomischen Betrieb von Gleisanlagen. Um den idealen Zeitpunkt für die Schotterreinigung oder die Erneuerung des Schotters zu finden bzw. auch um die Gebrauchstauglichkeit und Leistung über den gesamten Lebenszyklus zu erhöhen, ist die Kenntnis über den Schotterzustand bzw. über die Abnutzung des Schotters von größter Wichtigkeit. Das Gleisstopfen als zentraler Prozess der Gleisinstandhaltungsarbeiten beeinflusst die Instandhaltungsintervalle maßgeblich und ist notwendig für die Wiederherstellung der korrekten Gleislage. Während des Stopfvorgangs bilden die Stopfpickel ein dynamisches Interaktionssystem mit dem Gleisschotter. Die translatorische Beistellbewegung wird durch die dynamische Anregung der Pickel überlagert, um den Gleisschotter unterhalb der Schwellen bestmöglich zu verdichten. Die genannte Interaktion wurde an verschiedenen Standorten in Österreich messtechnisch erfasst und dient als Grundlage für einen Vergleich mit den Ergebnissen eines neu entwickelten, semi‐analytischen mechanischen Modells. Schlussfolgerungen bzgl. des unterschiedlichen Verhaltens und Widerstands gegen weitere Verdichtung von abgenutztem und neuem Schotter werden getroffen und im vorliegenden Beitrag diskutiert.
The condition of the ballast bed is one of the most important parameters to be determined in order to assure a safe and economical operation of railway systems. Better knowledge of ballast condition provides an advantage in defining the optimum time for ballast bed cleaning or renewal. State of the art ballast condition quantification methods all require in-situ ballast sampling followed by laboratory tests, reducing track availability and making additional track closure necessary, thus making the determination of ballast condition a time-consuming and challenging task. The tamping process is the core maintenance activity in ballasted track and it is crucial for the economical service life of the track and essential in restoring the track geometry for safe train operations. During the tamping process, the tamping tines interact with the ballast matrix, transferring the displacement caused by the dynamic excitation to the ballast, compacting it under the sleeper. This interaction is observed and measured in-situ within the framework of a research project presented in this paper. Lateral forces and compaction energy, together with the loading and unloading response of the ballast matrix during compaction are used to determine the ballast condition. Serving as a confirmation of the ballast condition definitions made based on the in-situ measurements, a semi-analytical model of the tamping unit-ballast matrix interaction has been developed. The mechanical model is used to simulate different ballast conditions in order to optimize the ballast life cycle and improve the understanding of ballast behaviour under cyclic loading.
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