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Monitoring and Substructure Condition Assessment of Existing Railway Linesfor Upgrading to Higher Axle Loads and Speeds
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2006 (English)In: 7th World Congress on Railway Research, 2006Conference paper, Published paper (Refereed)
Abstract [en]

Many of the European railways have been designed for completely different traffic conditions than thoserequired today. Upgrading of existing railway lines for higher axle loads and speeds requires new modernmethods for in situ investigation of the railway ballast and substructure. Combination of continuousmeasurements of track geometry quality and non-destructive methods like dynamic track stiffness and Ground Penetrating Radar (GPR) can be a good example of obtaining the important information about theconditions of existing railways. A new methodology for evaluation of all available measurementscompleted with results from geotechnical investigations is proposed to study problems dealing with railway structure and subgrade in case upgrading or maintenance work is required.

Railway investigations using Banverket´s Rolling Stiffness Measurement Vehicle (RSMV) equipped withGPR, and a methodology of comprehensive evaluation of all relevant available information have beentested on a few railway lines in Sweden since 2002. Results from these investigations are used forassessment of the root cause of existing or possible future problems with repeated track maintenance,settlement and stability when upgrading a track for higher axle load and/or speed.

The paper presents practical results of investigations and a new methodology to evaluate several types ofmeasurements in comparison with real track – substructure conditions. Suggestions on upgradingactivities are given for a case study of 25 km of track with a planned increase of axle load from 22.5 to 25metric tons. The goal is to minimize the upgrading and maintenance cost in a Life Cycle Cost (LCC)perspective.

Place, publisher, year, edition, pages
2006.
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10351OAI: oai:DiVA.org:kth-10351DiVA: diva2:216188
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-20Bibliographically approved
In thesis
1. Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance
Open this publication in new window or tab >>Railway Track Stiffness: Dynamic Measurements and Evaluation for Efficient Maintenance
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Railway track stiffness (vertical track load divided by track deflection) is a basic parameter oftrack design which influences the bearing capacity, the dynamic behaviour of passing vehiclesand, in particular, track geometry quality and the life of track components. Track stiffness is abroad topic and in this thesis some aspects are treated comprehensively. In the introductionpart of the thesis, track stiffness and track stiffness measurements are put in their propercontext of track maintenance and condition assessment.

The first aspect is measurement of track stiffness. During the course of this project, Banverkethas developed a new device for measurement of dynamic track stiffness called RSMV(Rolling Stiffness Measurement Vehicle). The RSMV is capable of exciting the trackdynamically through two oscillating masses above one wheelset. The dynamic stiffness is acomplex-valued quantity where magnitude is the direct relation between applied load anddeflection (kN/mm) and phase is a measure of deflection-delay by comparison with force. Thephase has partial relationship with damping properties and ground vibration. The RSMVrepeatability is convincing and both overall measurements at higher speeds (up to 50 km/h)and detailed investigations (below 10 km/h) can be performed. The measurement systemdevelopment is described in Paper A and B.

The second aspect is evaluation of track stiffness measurements along the track from a trackengineering perspective. Actual values of stiffness as well as variations along the track areimportant, but cannot always answer maintenance and design related questions alone. InPaper D track stiffness is studied in combination with measurements of track geometryquality (longitudinal level) and ground penetrating radar (GPR). The different measurementsare complementary and a more reliable condition assessment is possible by the combinedanalysis. The relation between soft soils and dynamic track stiffness measurements is studiedin Paper C. Soft soils are easily found and quantified by stiffness measurements, in particularif the soft layer is in the upper part of the substructure. There are also possibilities to directlyrelate substructure properties to track stiffness measurements. Environmental vibrations areoften related to soft soils and partly covered in Paper C. One explanation of the excitationmechanism of train induced environmental vibrations is short waved irregular supportconditions. This is described in Paper E, where track stiffness was evinced to have normalvariations of 2 – 10 % between adjacent sleepers and variations up to 30 % were found. Anindicative way of finding irregular support conditions is by means of filtering longitudinallevel, which is also described in the paper. Train-track interaction simulation is used in PaperH to study track stiffness influence on track performance. Various parameters of trackperformance are considered, e.g. rail sectional moment, rail displacement, forces at wheel-railinterface and on sleepers, and vehicle accelerations. Determining optimal track stiffness froman engineering perspective is an important task as it impacts all listed parameters.

The third aspect, efficient maintenance, is only partially covered. As track stiffness relates toother condition data when studied from a maintenance perspective, vertical geometricaldefects (longitudinal level and corrugation/roughness) are studied in paper F. The generalmagnitude dependency of wavelength is revealed and ways of handling this in conditionassessment are proposed. Also a methodology for automated analysis of a large set ofcondition data is proposed in Paper G. A case study where dynamic track stiffness,longitudinal level and ground penetrating radar are considered manifests the importance oftrack stiffness measurements, particularly for soil/embankment related issues.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xii, 31 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:17
Keyword
Railway track stiffness, maintenance, soil dynamics, measurement, simulation, vibration
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-10360 (URN)
Public defence
2009-05-08, Sal D3, KTH, Lindstedtsvägen 5, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100623Available from: 2009-05-07 Created: 2009-05-07 Last updated: 2010-07-19Bibliographically approved

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