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Ballast fouling and associated degradation of track geometry is a serious problem for railway systems in general and high-speed passenger rail systems in particular. This paper presents the results of a field test on Amtrak's Nort...
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Ballast fouling and associated degradation of track geometry is a serious problem for railway systems in general and high-speed passenger rail systems in particular. This paper presents the results of a field test on Amtrak's Northeast Corridor where a long-term problem area existed near Oakington Road, Havre de Grace, Maryland, near MP 63.7 between Philadelphia and Washington DC. This test looked at the application of a new generation of three-dimensional cellular confinement systems (geocells) in reducing the rate of track geometry degradation, particularly in poor subgrade and ballast locations which require frequent, expensive, track surface maintenance. The field test compared two distinct sets of rebuilt track conditions, to j include zones with and without a layer of geocell material. Both zones were rebuilt with improved drainage and a good, well-defined track structure and substructure (to include a well-defined depth of clean ballast). The test measurements included pre-maintenance and post-maintenance track geometry measurements together with comparative sub-grade pressure measurements inside and outside the geocell cell zones. The pressure cell measurements, which looked at subgrade pressure under left and right rails in both the geocell zone and the control (non-geocell) zones, included measurements under both Acela high-speed trains and lower speed regional trains. In all cases, the subgrade pressures in the geocell zone were approximately half of those for the cells in the control zone (no geocell). Track geometry measurements were made using Amtrak's track geometry vehicle which measures key track geometry parameters at 1-ft intervals along the track. There were several well-defined locations in the overall test zone that experienced significant track geometry degradation; these were all corrected during reconstruction. In the zones with no geocell material, these geometry variations reappeared within 6 to 7 months with the same if not greater amplitudes. By contract, in the geocell zone, the "after" geometry variations were significantly smaller than the pre-reconstruction geometry variations. Furthermore, the rate of geometry degradation was signficantly less for the geocell zones compared to the pre-geocell time periods for the exact same track. This indicated the effectiveness of the geocell material in reducing the rate of track geometry degradation and extending the surfacing maintenance cycles. Analysis of the rate of degradation showed that the effect of installing the geocell material was to significantly reduce the rate of degradation (and thus increase the surfacing cycle) by a factor of 6.7 times the pre-geocell installation surfacing cycle.
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The railway track geometry condition is a key factor influencing the safety and comfort of train operations, and controlling the tamping cycles of railway tracks. For the scientific disposition of limited maintenance resources, ra...
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The railway track geometry condition is a key factor influencing the safety and comfort of train operations, and controlling the tamping cycles of railway tracks. For the scientific disposition of limited maintenance resources, railway infrastructure managers need to predict the tamping cycles based on an accurate grasp of track geometry degradation rules. Taking each 200-m track segment as a research object, the authors analyze the uncertainty and heterogeneity of track geometry degradation based on the discrete evaluation of the track geometry condition. On this basis, an improved track geometry degradation model using Weibull distributions is proposed to accurately estimate the tamping cycle of each track segment. By considering several heterogeneous factors in the model, individualized modeling for different track segments is realized. The developed model was verified by a case study of 100 track segments of the Chinese Lanxin railway line within the jurisdiction of the Lanzhou Railway Bureau. The estimation results of model parameters reflect the influence of various heterogeneity factors on the track geometry deterioration processes and the tamping cycles of track segments. The accuracy of the tamping cycle estimation results indicates that the proposed approach has significance for guiding the management of tamping maintenance of railway track segments.
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This paper studies the effect of railway track design parameters on the expected long-term degradation of track geometry. The study assumes a geometrically perfect and straight track along with spatial invariability, except for th...
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This paper studies the effect of railway track design parameters on the expected long-term degradation of track geometry. The study assumes a geometrically perfect and straight track along with spatial invariability, except for the presence of discrete sleepers. A frequency-domain two-layer model is used of a discretely supported rail coupled with a moving unsprung mass. The susceptibility of the track to degradation is objectively quantified by calculating the mechanical energy dissipated in the substructure under a moving train axle for variations of different track parameters. Results show that, apart from the operational train speed, the ballast/substructure stiffness is the most significant parameter influencing energy dissipation. Generally, the degradation increases with the train speed and with softer substructures. However, stiff subgrades appear more sensitive to particular train velocities, in a regime which is mostly relevant for conventional trains (100-200 km/h) and less for high-speed operation, where a stiff subgrade is always favorable and can reduce the sensitivity to degradation substantially, with roughly a factor up to 7. Also railpad stiffness, sleeper distance and rail cross-sectional properties are found to have considerable effect, with higher expected degradation rates for increasing railpad stiffness, increasing sleeper distance and decreasing rail profile bending stiffness. Unsprung vehicle mass and sleeper mass have no significant influence, however, only against the background of the assumption of an idealized (invariant and straight) track. Apart from dissipated mechanical energy, the suitability of the dynamic track stiffness is explored as an engineering parameter to assess the sensitivity to degradation. It is found that this quantity is inappropriate to assess the design of an idealized track. (c) 2018 Elsevier Ltd. All rights reserved.
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This study addresses the contribution of spatial variance in the railway track support stiffness to the expected long-term track degradation. Hereto, a novel frequency-domain model is developed with a double periodicity 'layer', c...
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This study addresses the contribution of spatial variance in the railway track support stiffness to the expected long-term track degradation. Hereto, a novel frequency-domain model is developed with a double periodicity 'layer', capable of dealing with both sleeper periodicity and arbitrary non-uniformity in track properties. The model application focuses on a locally reduced support stiffness (hanging sleeper) along the track. The resulting susceptibility to degradation is assessed by quantifying the mechanical energy dissipated over the influence length under a moving train axle. Different descriptions of this energy amount are benchmarked with respect to their predictive value. In the presence of a degraded sleeper support, hanging sleepers are found to develop faster with increasing train speed; the speed effect may be estimated as roughly linear. Moreover, degradation increases progressively with an increasing local relative stiffness reduction. Coincidence of the train speed corresponding to the sleeper passing frequency with the first resonance peak of the system leads to severely increased degradation; increased damping however attenuates dissipation peaks at resonant speeds and shifts their position upwards. The effect of a degraded support is most significant on soft subgrades. The effect of multiple degraded sleeper supports increases up to three sleepers, for any train speed. With respect to the system parameters, particularly the railpad stiffness has significant effect; especially for high-speed tracks a high pad stiffness is very unfavorable. Other effective control parameters in the case of degraded sleeper supports are the sleeper spacing and the rail cross-sectional properties; for example replacing a 54E1 with a 60E1 rail profile may reduce energy dissipation with roughly 30% on high-speed track. An increasing unsprung vehicle mass is unfavorable for track degradation, again with the effect increasing with the train speed. The developed methodolog
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The measurement and improvement of track quality are key issues in determining both the time and cost of railway maintenance. Efficient track geometry maintenance ensures optimum allocation of limited maintenance resources and has...
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The measurement and improvement of track quality are key issues in determining both the time and cost of railway maintenance. Efficient track geometry maintenance ensures optimum allocation of limited maintenance resources and has an enormous effect on maintenance efficiency. Applying the appropriate tamping strategy also helps reduce maintenance costs, making operations more cost effective and leading to increased safety and passenger comfort. In this paper, track geometry data from the iron ore line in northern Sweden, which handles both passenger and freight trains, are used to calculate track quality degradation trend in a cold climate. The paper describes Trafikverket's (Swedish Transport Administration) tamping strategy and illustrates the distribution of safety failures in different seasons. It also analyses the track geometry degradation and discuss about the possible reasons for distribution of failures over a year and along the track.
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Variations in dynamic stiffness along railway tracks are at the basis of long-term degradation problems under train operation. For a spatially invariant and straight track, the dynamic response to constant axle loading at a consta...
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Variations in dynamic stiffness along railway tracks are at the basis of long-term degradation problems under train operation. For a spatially invariant and straight track, the dynamic response to constant axle loading at a constant velocity is stationary in a convective reference system. This is no longer true if geometrical and/or constitutive track properties are non-uniform over the length. Such discontinuities appear on many scales; the sleeper bay is an example with a periodical character, whereas examples with an incidental character are level crossings, bridges, tunnels, abutments, culverts but also switch panels and ballast and foundation stiffness variations. Also track irregularities may be considered as a non-uniformity. Any longitudinal variation in system properties causes a transient disturbance in the convective, stationary response field. A local and often strong amplification of the stress and strain field in the structure is the result. In terms of mechanical energy: the energy state varies continuously in a convective reference system due to transition radiation. Depending on its intensity it is accompanied by dissipation of mechanical energy. For repeating axle and train loading, such process is cyclic and a long-term degradation mechanism is established. For the running train, the inherent time- and position-dependent energy loss function could be described as 'dynamic drag', in analogy to the well-known 'viscous drag'. The present paper exposes in more detail the physical backgrounds of track degradation, with a focus on soft soils, where transition problems concentrate. Some propositions are made, on a conceptual level, for modelling and an improved design of track transitions with a reduced maintenance need.
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Ballasted railway tracks, despite their benefits, present some limitations and drawbacks, mainly associated with geometry degradation due to ballast settlement and particle breakage. Periodic maintenance interventions are thus req...
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Ballasted railway tracks, despite their benefits, present some limitations and drawbacks, mainly associated with geometry degradation due to ballast settlement and particle breakage. Periodic maintenance interventions are thus required as well as renewal processes, which lead to the significant consumption of natural materials and energy whilst causing frequent interruptions to traffic. This is made more problematic when aggregates with appropriate characteristics for ballast are not available in the proximity of the construction/maintenance site, which is becoming increasingly common due to restrictive environmental guidelines. In this context, this paper presents a review of the effectiveness of the major conventional techniques/materials for track design and maintenance as well as innovative solutions that are being developed to reduce track degradation, whilst also analysing their main parameters to optimize track behaviour and durability, depending on its design and the required changes in its mechanical performance. The aim is to then provide a set of recommendations and guidelines for the use of such technologies to improve track response and durability as well as highlighting possible further research associated with both the development of innovative solutions and the improvement of conventional techniques. (C) 2017 Published by Elsevier Ltd.
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Particle tracking codes such as MAD-X or TRANSPORT commonly use a matrix formalism to propagate beams through magnetic elements as it simplifies the analysis of particle behavior, facilitates beam optimization and component design...
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Particle tracking codes such as MAD-X or TRANSPORT commonly use a matrix formalism to propagate beams through magnetic elements as it simplifies the analysis of particle behavior, facilitates beam optimization and component design, and enables accurate particle accelerator simulations. However, these codes are inefficient when tracking many particles or accounting for energy degradation along the beamline. To overcome these limitations, we introduce Georges, a Python library used in the field of particle accelerators for medical applications comprising two modules: Manzoni and Fermi. Manzoni is an efficient particle tracking code that can track many particles while calculating beam losses and energy degradation using the Fermi–Eyges formalism implemented in the Fermi module. In this paper, we present the implementation details of Georges, which includes a verification conducted against other software tools such as MAD-X and BDSIM, along with a documentation on computational time.
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ABSTRACT Ballast layer defects are the primary cause for rapid track geometry degradation. Detecting these defects in real-time during track inspections is urgently needed to ensure safe train operations. To achieve this, an indic...
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ABSTRACT Ballast layer defects are the primary cause for rapid track geometry degradation. Detecting these defects in real-time during track inspections is urgently needed to ensure safe train operations. To achieve this, an indicator, the track degradation rate (TDR) was proposed. This rate is calculated using track geometry inspection data to locate and predict railway-line sections with ballast layer defects. The TDR is determined by the monthly standard deviation of the rail longitudinal level, which is one aspect of track geometry. The Ballast Layer Health Classification (BLHC) is designed by assessing the two successive TDRs before and after track geometry maintenance actions. The BLHC is used to categorize the conditions of the ballast layer, including normal periodic deterioration, abrupt deterioration, effective maintenance, rising deterioration, and severe deterioration. Both the TDR and BLHC were validated through field assessments of ballast layer conditions, where the two indicators were found to be effective in revealing defects. The results indicate that the TDR is sensitive to ballast layer defects, while the BLHC can quickly identify the location of these defects. Consequently, the BLHC can provide real-time guidance for ballast layer maintenance.
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