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.

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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The article describes the preliminary results and conclusions of experimental monitoring of the thermal regime of railway track structure performed on the experimental stands (railway track models in 1:1). The purpose of this study was to optimize the structural thickness of the protective layer in the subgrade structure. The first part of the study describes the experimental stand design and methodology for monitoring the heat and humidity variations in the railway track structure. The following parts describe the results of verification of the thermal characteristics of the material incorporated into the model of the railway track and of its subgrade.

Extruded polystyrene (XPS) and its excellent thermal insulation properties have been known for over 60 years. Due to its thermal, mechanical, but also deformation properties, XPS has a universal application, not only in the construction industry. This paper presents the results of the first series of experimental measurements of the deformation resistance of the sub-ballast layers with a built-in XPS thermal insulation layer and the sub-ballast layers with a standard structure (crushed aggregate sub-ballast layer). The aim of the first series of experimental measurements was to determine the impact of placing the XPS layer at the subgrade surface level (deformation resistance of subgrade surface E0 = approx. 10MPa or 30MPa) on the deformation resistance of the sub-ballast layers and then to determine the necessary thickness of the sub-ballast layer in relation to the required deformation resistance at the sub-ballast upper surface. Experimental measurements carried out so far show that the application of XPS boards in the sub-ballast layers has almost no or minimal effect on its deformation resistance. Since XPS boards have significantly better thermal technical properties compared to crushed aggregate, considerable savings of this material can be achieved in areas with unfavorable climatic conditions (high values of air frost index).

In addition to other topics on railway engineering, the Department of Railway Engineering and Track Management is permanently paying attention to the issue of the non-traffic load of railway track (track load of climatic impacts) for the purpose of verification and possible adjustments of the existing methodology of the railway subgrade structure design to the adverse effects of frost used on the Slovak railways. For this purpose, the model of a railway track structure was built -Experimental Stand DRETM I -with an inbuilt thermometer in its individual structural layers and their interfaces, connected to recording equipment. This paper presents the characterized results of individual winter periods observed since 2003, its partial analysis is made and it states some fundamental knowledge necessary to be taken into account in the design and assessment of the railway track structure to the adverse effects of frost. Based on the evaluation of experimental measurements and knowledge obtained so far, a draft design nomogram for the design of the structure of a railway track on a non-traffic load was made, which greatly simplifies this whole process of design and assessment, compared with the current methodology in TNŽ 73 6312 "The design of structural layers of subgrade structure".

The paper describes experimental activity carried out at the Department of Railway Engineering and Track Management of the Faculty of Civil Engineering, University of Žilina. It focuses on assessing the suitability of the application of thermal insulation material (the reinforced foam concrete layer) in the track bed structure. Within the experimental measurements, the traffic load (static load component) and non-traffic load (the effect of climatic factors) were monitored. The experimental measurements were carried out on individual segments of the experimental field, differing in thickness of reinforced foam concrete layer and deformation resistance of the subgrade sub-surface.