Analysis of Effect Parameters of Track Settlement in Heavy Haul Railways
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Abstract:
Ballast bed in heavy haul railway will accumulate residual deformation and lead to track accumulative settlement under the repeatedly influence of the dynamic load of train. Studying on rule LU Ye s of track settlement of heavy haul railway is the premise of variant design and maintenance management, the effects of transportation conditions and track structure parameters on ballast settlement were analyzed by improving the existing track settlement calculation model and building track structural finite element analysis model. The results show that vehicle running speed, axle load and railway traffic are main factors of controlling track deformation; it benefits to decrease track settlement by adopting heavy rail, increasing bottom area of sleeper, reducing space of sleeper; track settlement reduces by 12.3% when thickness of ballast increases from 30 cm to 40 cm, and track settlement increases by 25% when elastic modulus of ballast increases from 90 MPa to 150 MPa, however, increasing thickness of ballast leads to more maintenance work and small elastic modulus reduces the capacity of structure, therefore, it is important to select track structural parameters reasonably.Keywords:
Ballast
Settlement (finance)
Track geometry
Axle load
Ballast and subgrade play major roles in the maintenance life of track structures because they are the source of the cumulative permanent deformation associated with the deterioration of surface and line. Ballast is also the principal means of correcting for this deterioration, which is caused by traffic and environmental factors. Better methods are still needed for the prediction of the effects of the controlling parameters on track performance for more rational track design and maintenance planning. The purpose of this paper is to provide a better understanding of these problems and describe progress being made toward their solution. The functions of ballast and subgrade are briefly discussed, and the mechanisms of permanent deformation are described. Newly developed or improved methods to measure the in situ physical state of ballast are presented, and examples of results from field tests are given. The capabilities of existing analytical track structure models for the prediction of track deterioration are assessed. New instrumentation techniques used for measuring the dynamic and permanent strains and deformations in ballast and subgrade are described. Finally, the characteristics of the stress, strain, and deformation in ballast and subgrade are illustrated with results of both analytical and experimental studies.
Ballast
Track geometry
Instrumentation
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Ballast
Track geometry
Railway line
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Abstract The ability to predict track geometry degradation is of critical importance in planning of track maintenance operations. This paper presents results of an FRA sponsored study on the relationship between track geometry degradation and ballast condition as measured by Ground Penetrating Radar (GPR). The study examined six different sites on a major Class 1 freight Railroad, with a range of ballast conditions and tie types, and developed a relationship between the rate of degradation of key track geometry parameters, profile (surface), and cross-level, as a function of two GPR measured ballast parameters: Ballast Fouling Index and Fouling Depth Layer (depth of clean ballast layer). The study sites included both fouled and clean ballast conditions that were monitored for track geometry on a very frequent basis (every two to four weeks) and also experienced multiple GPR measurements during that same period. Data analytic techniques were applied to this large data set to develop a relationship between rate of geometry degradation and ballast fouling condition and depth of ballast. The results showed a statistically significant relationship between high rates of geometry degradation and poor subsurface conditions as defined by the GPR parameters. A predictive model was developed to project and forecast geometry degradation as a function of ballast conditions.
Ballast
Track geometry
Ground-Penetrating Radar
Degradation
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The article discusses the importance of various components to make an effective subgrade and ballast. Soil types, drainage, ballast types and sizes, and the problems of dynamic forces are briefly described. Nine references are listed for further information of the various aspects of the track.
Ballast
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A program to obtain more nearly definitive measures of ballast pressure distribution utilizing modern types of earth pressure cells and laboratory simulation of a well-compacted subgrade under the ballast was undertaken in the Civil Engineering Department of the University of Illinois during the period of February 1965 through June 1996. The study was given financial sponsorship by the Railway Maintenance Corporation of Pittsburg, Pennsylvania, pressure cells were loaned by the Research Center, Association of American Railroads, Chicago, Illinois and rails, ties, ballast and subgrade materials were donated by the Illinois Central Railroad, The hydraulic loading jacks, 12-channel pressure cell recorder and working site were provided by the Civil Engineering Department of the University of Illinois. The ballast section in its primary functions of distributing wheel load from the cross ties, anchoring the track, providing immediate drainage, and contributing resilience is one of the most important elements in a railroad track structure. A suitable depth of ballast is needed in order to get a uniform pressure distribution on the subgrade under the rail and a unit pressure distribution imposed on the subgrade within the allowable limits of the subgrade bearing capacity. If ballast pressures are not uniformly distributed on the subgrade, some of the ballast particles will be forced into the subgrade leading to instabilities and formation of ballast pockets.
Ballast
Lateral earth pressure
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Ballast
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British Rail is proposing to purchase a fleet of stoneblowing machines to maintain its track geometry. After a lengthy research and development program, B.R. is now convinced of the economic case for the move to this revolutionary method of track maintenance. Stoneblowing is a method of track surfacing that aims to correct geometrical deterioration by injecting a measured quantity of stone directly under the sleeper (tie) to raise the level of the track. Track that is maintained in this way has a more durable geometry than track maintained by conventional surfacing techniques. Far less make up ballast is required than with conventional surfacing, reducing ballast distribution and regulating costs. This paper describes how these benefits are achieved and shows results directly from the prototype equipment.
Ballast
Track geometry
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Ballast
Track geometry
Visual inspection
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This paper presents the results of a study on the relationship between missing ballast and the development of track geometry defects. More specifically, this paper looks at the relationship between missing crib and shoulder ballast, as identified by automated ballast profile measurement systems, and the development of ballast related track geometry defects. The missing ballast data was obtained from a hy-rail mounted light detection and ranging (LIDAR) based ballast profile measurement system (1) and then correlated to track geometry defects that developed along the inspected track locations on a major US Class 1 railroad. The focus was on those track geometry defects that have been traditionally considered ballast-related, which is then compared with the calculated volume of missing ballast to see if there is a correlation. Further analyses looked at the effect of curve vs. tangent track as well as that of individual geometry defect classes. The results of this analysis showed that there was in fact a direct relationship between volume of missing ballast and the development of track geometry defects.
Ballast
Track geometry
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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.
Ballast
Track geometry
Identification
Degradation
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