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

Abstract

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.

Assesment of the Possibility of Foam Glass Application in the Sub-Ballast Layers

“…The numerical analysis of the modified structure of the sub-ballast layers (with built-in thermal insulation layer of foam glass) was conducted to assess the freezing of this structure and to determine the required dimensions of the individual sub-ballast layers depending on different climatic loads (air freezing index I F and the average annual air temperature θ m ). The numerical models of the modified design of the sub-ballast layers were developed based on the experience presented in Ižvolt et al (2021Ižvolt et al ( , 2022 using the SVHeat programme (Thode, 2012). These models feature 2D transition models of a double-track railway line (as the most common case) with an embankment height of 2.0 m.…”

“…The content of the paper is related to the publication (Ižvolt et al, 2021), focused on the verification of the possibilities of application of extruded polystyrene in the sub-ballast layers and to the publications discussing the possibility of application of composite foam concrete in the structural sub-ballast layers (Ižvolt et al, 2019(Ižvolt et al, , 2022 or as a protective (sub-ballast) layer (Vlček & Valašková, 2021). The primary objective of the paper is to assess the possibility of applying foam glass aggregate fr.…”

“…0/63 mm on the reduction of the structural thickness of the protective crushed aggregate layer in terms of climatic factor effects (water and frost). Considering the experience of the subgrade surface freezing into the active zone in the direction from the track bench surface and from the embankment slope presented in Ižvolt et al (2022), the numerical modelling of sub-ballast layers used a combination of two thermal insulation materials (foam glass aggregate and extruded polystyrene boards). The output of the numerical (mathematical) analysis is a design nomogram (mathematical relations) that enables to design the structural composition of the modified sub-ballast layers or the standard construction (structural layers) of the railway substructure.…”

Assessment of Dynamics of a Rail Vehicle in Terms of Running Properties While Moving on a Real Track Model

“…These works are conducted by many researchers to investigate rail vehicle dynamics as a key factor affecting their operational safety. It relates to the increasing running speed of railway vehicles and with the intent to ensure reliable and safe operation on railway lines as much as possible [29][30][31][32].…”

Experimental Verification of Modified Sub-Ballast Layers, Application of Foam Glass Boards

“…This field characterises both the standard and modified design of the sub-ballast layers. The modified design of the sub-ballast layers incorporates different thermal insulation materials (composite foam concrete [6], Liapor concrete, extruded polystyrene boards [7], foam glass). The deformation resistance of the individual structural sub-ballast layers was also monitored on an actual railway line in…”