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Preventive condition-based tamping for railway tracks: a decision support model
Published in Jaap Bakker, Dan M. Frangopol, Klaas van Breugel, Life-Cycle of Engineering Systems, 2017
R. Li, K.B. Salling, A. Zoeteman, A.R.M. Wolfert
Tamping is a complex and critical task particularly difficult to plan and execute (Chu & Chen 2012). There exist mainly three challenges: 1) the prediction of track degradation over time. It is important to ensure the track condition below the thresholds in the planning horizon. But it is challenging because it is impacted by many factors, such as geographical factors like topographical, subsoil condition; track structure, for example rail, sleeper and ballast component type; and other factors such as rolling stocks, previous maintenance history, and climatic conditions etc. There have been several research studies conducted within track degradation however there is no method widely implemented. 2) Budget and the track possession for tamping. They are important and challenging as to ensure the feasibility of the tamping schedule as well as the train operation during the tamping process. 3) The operational limitations. The tamping machine has several limitations among other things it is not allowed to start/stop in a transition curve, which basically is a mathematically calculated curve on the railway track designed to prevent sudden changes in lateral acceleration. Figure 2 show such a transition curve which links a straight section to a curve with constant radius. If a tamping section stops inside a transition curve, it requires the tamping operation to extend to the next section, as illustrated in Figure 2.
Allocation of effective maintenance limit for railway track geometry
Published in Structure and Infrastructure Engineering, 2019
Hamid Khajehei, Alireza Ahmadi, Iman Soleimanmeigouni, Arne Nissen
Obviously, the allocation of an inappropriate maintenance limit may result in an ineffective tamping regime, which will ultimately negatively affect the overall quality of the track, the train punctuality and serviceability, the train safety, the ride quality, the passenger comfort and the total related maintenance costs. Performing over-tamping imposes higher maintenance costs and it should also be noted that while a tamping action improves the quality of the track geometry, the tines of the tamping machine break the ballast particles under the sleeper and reduce the life cycle of the ballast (Andrews, 2013). In addition, performing fewer tamping actions than required increases the time that the track spends in a bad condition, which may lead to a higher risk of train derailment. Summing up, the allocation of an effective maintenance limit for the performance of tamping is of crucial importance.
Modelling the evolution of ballasted railway track geometry by a two-level piecewise model
Published in Structure and Infrastructure Engineering, 2018
Iman Soleimanmeigouni, Xun Xiao, Alireza Ahmadi, Min Xie, Arne Nissen, Uday Kumar
The track geometry degradation characteristics should be kept within specific limits. The European Standard EN 13848-5 (2008) defines three limits for maintenance. (1) Intermediate Action Limit (IAL): this is the safety limit. If the IAL is exceeded, there is a risk of derailment; the risk can be reduced by speed reduction, line closure, or corrective maintenance. Different indicators are mentioned in EN 14363 (2016) for evaluation of safety against derailment such as the ratio of guiding force and vertical wheel force on the outer wheel . The readers are referred to EN 14363 (2016) for more information about the factors influencing the safety against derailment of vehicles. (2) Intervention Limit (IL): this is the corrective maintenance limit. If the IL is exceeded, corrective maintenance should be conducted before the IAL is reached. (3) Alert Limit (AL): this is the preventive maintenance limit. If the AL is exceeded, the track geometry condition should be analysed and considered in regularly planned maintenance operations. Tamping is the main maintenance action used to remedy the track geometry condition and keep it within the required limits. Nowadays, tamping machines are equipped with special devices that provide this opportunity to do tamping, levelling and lining actions, simultaneously. Therefore, in addition to vertical geometry defects, the horizontal track geometry defects will be maintained by tamping action. Tamping machine lifts the track to a specific level and the tamping tines pack the ballast under the sleepers. The tamping tines penetrate the ballast and compact the ballast under the sleeper with a squeezing movement to provide a stable sleeper bed.