REVIEW OF THE MODERN BALLASTED RAILWAY TRACKS’ SUBSTRUCTURE AND FURTHER INVESTIGATIONS

ISSN 2307–3489 (Print), ІSSN 2307–6666 (Online) Наука та прогрес транспорту. Вісник Дніпропетровського національного університету залізничного транспорту, 2019, № 6 (84) ЗАЛІЗНИЧНА КОЛІЯ ТА АВТОМОБІЛЬНІ ДОРОГИ UDC 625.12:625.173 B. ELLER1*, S. FISCHER2* 1*Dep. «Transport Infrastructure and Water Resources Engineering», Szechenyi Istvan University, Egyetem Sq., 1, Gyor, Hungary, 9026, tel. + 36 (96) 613 544, e-mail , ORCID 0000-0001-7253-1757 2*Dep. «Transport Infrastructure and Water Resources Engineering», Szechenyi Istvan University, Egyetem Sq., 1, Gyor, Hungary, 9026, tel. + 36 (96) 613 544, e-mail , ORCID 0000-0001-7298-9960 REVIEW OF THE MODERN BALLASTED RAILWAY TRACKS’ SUBSTRUCTURE AND FURTHER INVESTIGATIONS Purpose. The authors’ aim is to summarize the results of relevant international publications and, based on these, to give a comprehensive review about the modern ballasted tracks’ substructure. Methodology. This article is a start of a PhD research, which means it was proceeded by a secondary research. At first, the substructure and its protection layers were summarized, after that the geosynthetic cementious composite mat materials, especially the Concrete Canvas are discussed. Findings. The experiences of the geosynthetics’ and other protection layers’ functions, show that a possible using of the GCCM (geosynthetic cementious composite mat) under the ballast can be a good solution for renewing short sections in the railway tracks. Originality. One of the authors – namely Balázs Eller – is a PhD student at Szechenyi Istvan University in Gyor (Hungary). His research topic is the reinforcement possibilities of railway substructure with the usage of special (mainly cement-bonded) layers. This article was written to collect and summarize the up to date knowledge related to modern ballasted railway tracks’ substructure to be able to determine the following research ways and possibilities at this topic. The research plan will be sentenced in the near future, as well as the required laboratory and field tests will be prepared. Practical value. As expectation, after having executed the related research, the advantages and disadvantages of GCCM layers in the railway substructure will be able to defined, as well as factual deterioration process can be determined related to the ballasted tracks and their geometrical stability. Keywords: substructure; subgrade; ballasted track; protection layer; concrete canvas Purpose The aim of this paper to summarize the experiences about the connection between the substructure and superstructure, and the railway protection layers at relevant international publications to make a comprehensive review about the adequate technologies of nowadays. After that a new possibility is being showed, which could help to reduce future maintenance costs. This paper deals with the ballasted tracks, because this is what was established almost in Hungary, and because of the weaker and flexible base, the substructure fouling is more significant here. Creative Commons Attribution 4.0 International doi: https://doi.org/10.15802/stp2019/195831 72 Methodology The basis of this paper is the research in science education, and study current state-of-the-art technologies. The authors studied the different materials, the investigations with them and their behaviour from usability aspect. Both laboratory and in situ tests are being studied. The different technologies are being compared, for study the better and cost effective ways to use. The railway substructure In general The degradation process of the railway track is a natural process. The ageing of the different types and different materials of elements is not the same. For example, from a bad (insufficient) rail welding or rail joint, there can be increased dynamical ef© B. Eller, S. Fischer, 2019 ISSN 2307–3489 (Print), ІSSN 2307–6666 (Online) Наука та прогрес транспорту. Вісник Дніпропетровського національного університету залізничного транспорту, 2019, № 6 (84) ЗАЛІЗНИЧНА КОЛІЯ ТА АВТОМОБІЛЬНІ ДОРОГИ fect which leads to more pumping effect and contaminated ballast. From another aspect, the consequence is the same if the problem comes from the weak soil properties or inadequate drainage. In this complex system, all the elements influence all the other elements. The degradation has to be maintained, but while a welding or a rail can be changed relative easily, the subgrade could only be renewed after the established of the whole superstructure. So the superstructure of the railway needs permanently and adequate support from the subballast, subgrade. If the substructure has not got enough bearing capacity or it has got weak soil mechanical properties, a new protection layer is needed. Otherwise, the many speed limits that caused by the obsoleted faults, need more excess energy that could cost billions in every year [15], furthermore the maintaining of these faults also costs a lot. If the axle load is increased by 2.5 tons, the total maintenance cost increased by 4.2% too [28]. If the substructure has not got enough bearing capacity and other appropriate soil mechanical properties, soil replacement or new protection layer is needed. That improves the bearing capacity, drainage and other significant tasks that are indispensable. On the other hand, the ballast layer is the other important element because it connects to the substructure and distributes the load to there. Ballast and subballast contribute to protect the subgrade from overstressing [39]. However, subballast, which is always needed, is preferred for completing the total granular layer thickness beyond the minimum ballast layer thickness required for fulfilling the other ballast functions. Thanks to this, the track deformation is closely related to the quality of ballast. Fouling causes accumulation of fines between ballast particles and consequently increases the permanent deformation within the ballast layer and results in increased surface deviation of railway track [8]. Fouling can also inhibit drainage and may lead to deterioration in the mechanical properties of the medium. In the worst case, mud pumping effect occurs. If the fine particles from the subgrade is mixed with the ballast, the way out of the water is ended (Fig. 1). This can be a straight way for a water pocket (or in other words: ballast pocket or water bag) to being formed. This problem can be hard to solve, beCreative Commons Attribution 4.0 International doi: https://doi.org/10.15802/stp2019/195831 cause the simple ballast exchange is not enough, very ineffective [36]. Fouling The major causes that may contribute to the development of subgrade problems can be categorized into three groups [29]:  load factor,  soil factor,  environmental factor (soil moisture, soil temperature). There are two types of loads in the railways:  the deadweight of the railway structure,  the dynamic loads of the traffic. The deadweight occurs less problem than the dynamical ef (...truncated)