This paper presents the results of numerical modelling of the influence of various factors (geometrical layout of the structural layers of the railway track, climatic factors and ballast fouling) on the freezing of railway track structure with a built-in thermal insulation layer of extruded polystyrene (Styrodur). At the same time, the suitability and expediency of incorporating the thermal insulation layer at the sub-ballast upper surface level (i.e. below the rail ballast construction layer), or at the level of subgrade surface are discussed. Numerical modelling results in the main factors that should be taken into account in the dimensioning of the sub-ballast layers with a built-in thermal insulation layer. Based on the data on the depth of freezing of the railway track structure obtained from numerical modelling, a design nomogram for dimensioning was created and subsequently the influence of the changes of climatic characteristics on the freezing of the railway track structure was then mathematically expressed.
In the first part, the paper deals with the origin and reasons to construct an unconventional type of the structure of railway superstructure, which is referred to as a slab track, it is shortly characterized by its development and the possible application of the railway tracks. The second part of the paper deals with the historical development of unconventional structure of railway superstructure in the Slovak Republic, characteristics of the developed and tested structures, and then in the third part of this paper, there are characterized specific structures of slab track applied in the ongoing modernization of the railway infrastructure in the Slovak Republic
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.
The paper characterizes the existing results and preliminary conclusions of mathematical modelling of the thermal regime of railway track structure carried out on the experimental stand and optimizes the structural thickness of the protective layer in the subgrade structure by the SVHEAT SoilVision software. SoilVision system is a modelling software based on the finite element method developed for geotechnical engineers. The first part describes the experimental stand design and methodology for monitoring the heat and humidity variations in the railway track structure [1]. This paper section characterizes the results of mathematical modelling of the thermal regime of the railway track model and subsequently carries out a comparison of results of experimental measurements and mathematical modelling by the SVHEAT [2]. The paper enables mathematical modelling of various combinations of material compositions of railway track structure after entering all the relevant input data of the winter periods. In this way, conditions for drawing up the relevant design nomograms for various types of subgrade structure or railway body types are created.
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