Cyclic behavior of semi-rigid recovered plastic blends in railway track substructure

Falling weight deflectometer (FWD) testing was conducted along with embankment and subgrade sampling over 210 km (130 miles) of Canadian National Railway’s Lac La Biche Subdivision, which runs between Edmonton and Fort McMurray, as a part of a larger investigation of the line for increased axle loads. The resulting measurements were evaluated for their ability to identify soft subgrades. Two analyses were conducted to this end. First, the statistical distribution of peak deflections recorded by the FWD was investigated for different types of subgrade material. Second, the properties of track substructure were studied by characterizing the deflection time histories using a dynamic model of a single mass on a viscoelastic foundation and least-squares curve fitting. Four characteristic types of deflection time histories were identified for differing substructure conditions. Simplified dynamic modelling of railway track substructure showed that where relatively thick embankment exists over subgrade, the response of track is overdamped behavior.

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Ground-penetrating radar evaluation of railway track substructure conditions

10.1117/12.462264 ◽

2002 ◽

Cited By ~ 19

Author(s):

Gary R. Olhoeft ◽

Ernest T. Selig

Keyword(s):

Ground Penetrating Radar ◽

Railway Track ◽

Track Substructure ◽

Ground Penetrating

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Track Substructure Design Methodology and Data

2010 Joint Rail Conference, Volume 1 ◽

10.1115/jrc2010-36232 ◽

2010 ◽

Cited By ~ 1

Author(s):

Theodore R. Sussmann ◽

James P. Hyslip

Keyword(s):

Material Properties ◽

High Speed ◽

Progressive Failure ◽

Failure Process ◽

Structure Design ◽

Design Methods ◽

Railway Track ◽

Track Structure ◽

Design Data ◽

Track Substructure

Track substructure design is an often overlooked step in the design of railroad track. The lack of consideration for the substructure when designing track results in greater maintenance demands due to inadequate track substructure performance. Railway track is a stable structure with a progressive failure process that allows track engineers to manage the degradation of the track through maintenance. However, increasing demands for track availability from high traffic volumes require that track maintenance be minimized while ensuring safety. Additionally, developing high speed rail and intercity passenger rail on existing corridors necessitates higher levels of substructure performance due to tighter track roughness tolerances. Reduction in maintenance needs can be achieved by ensuring that new construction and rehabilitation projects be designed to provide a stable track structure throughout the design life. Lack of readily available data for substructure materials is a drawback to the use of track design methods. This paper provides a summary of several available substructure track design methods along with the required data for design. The track design data is related to track measurements that could be used to determine much of the information necessary for design of track rehabilitation. Track load-deflection data could be used to develop much of the needed design data while ground penetrating radar could support delineation of similar track segments. Benefits of track structure design include knowledge of expected life, reduced maintenance, material properties for quality control, and development of material properties that could permit application of performance based contract specifications.

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Verification of boundary conditions of numerical modeling of the track substructure thermal regime – influence of the snow cover

Archives of Transport ◽

10.5604/01.3001.0012.8365 ◽

2018 ◽

Vol 4 (48) ◽

pp. 51-60 ◽

Cited By ~ 1

Author(s):

Libor IŽVOLT ◽

Peter DOBEŠ ◽

Juraj PIEŠ

Keyword(s):

Numerical Modeling ◽

Boundary Conditions ◽

Snow Cover ◽

Air Temperature ◽

Protective Layer ◽

Railway Track ◽

Experimental Stand ◽

Crushed Aggregate ◽

Railway Engineering ◽

Track Substructure

The initial part of the paper briefly characterizes a long-term experimental activity at the Department of Railway Engineering and Track Management (DRETM). The research of the DRETM focuses, besides other research activities and specific problems in the field of railway engineering (application of new structures and construction materials in conventional and modernized railway tracks, modernisation and rehabilitation of existing railway tracks for higher speeds, track diagnostics, influence of track operation on noise emissions and design of structural measures, possibility of application of recycled ballast bed material in the track substructure, ballast recycling technologies, ecological assessment of recycled material of the track substructure), on various factors affecting track substructure freezing. In 2012-2017, in the campus of the University of Žilina (UNIZA), an Experimental stand DRETM was built for the research purposes. The experimental stand DRETM consists of 6 types of track substructure placed in an embankment or a cut, in the 1:1 scale. Besides conventional building materials (crushed aggregate), these structures also include various thermal insulation materials (Liapor concrete, Styrodur, foam concrete). A significant part of the paper deals with numerical modeling of the freezing process of track substructure (an embankment with the embedded protective layer of crushed aggregate, fr. 0/31.5 mm) for various boundary conditions (air frost index, average annual air temperature), using SoilVision software. The aim of this research is to identify the thermal insulation effects of different thicknesses of snow cover on the depth of penetration of the zero isotherm into the track substructure (railway track). The paper conclusion specifies the influence of different snow cover thicknesses, or nf factor (factor expressing the dependency between the mean daily air temperature and the temperature on the ballast bed surface) and various climatic conditions (frost indexes and average annual air temperatures), affecting the railway infrastructure, on the resulting depth of freezing of the track substructure (railway track). These outputs will be in the further research used for the design of nomogram for determining the thickness of the protective layer of the frost-susceptible subgrade surface of the track substructure.

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Experimental and Numerical Verification of the Railway Track Substructure with Innovative Thermal Insulation Materials

Materials ◽

10.3390/ma15010160 ◽

2021 ◽

Vol 15 (1) ◽

pp. 160

Author(s):

Libor Izvolt ◽

Peter Dobes ◽

Marian Drusa ◽

Marta Kadela ◽

Michaela Holesova

Keyword(s):

Thermal Insulation ◽

Railway Track ◽

Numerical Analyses ◽

Numerical Verification ◽

Railway Line ◽

Static Modulus ◽

Thermal Insulating ◽

Foamed Concrete ◽

Track Substructure ◽

Railway Substructure

The article aims to present the modified structural composition of the sub-ballast layers of the railway substructure, in which a part of the natural materials for the establishment of sub-ballast or protective layers of crushed aggregate is replaced by thermal insulation and reinforcing material (layer of composite foamed concrete and extruded polystyrene board). In this purpose, the experimental field test was constructed and the bearing capacity of the modified sub-ballast layers’ structure and temperature parameters were analyzed. A significant increase in the original static modulus of deformation on the surface of composite foamed concrete was obtained (3.5 times and 18 times for weaker and strengthen subsoil, respectively). Based on real temperature measurement, it was determined the high consistency of the results of numerical analyses and experimental test (0.002 m for the maximum freezing depth of the railway line layers and maximum ±0.5 °C for temperature in the railway track substructure–subsoil system). Based on results of numerical analyses, modified railway substructure with built-in thermal insulating extruded materials (foamed concrete and extruded polystyrene) were considered. A nomogram for the implementation of the design of thicknesses of individual structural layers of a modified railway sub-ballast layers dependent on climate load, and a mathematical model suitable for the design of thicknesses of structural sub-ballast layers of railway line were created.

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