This paper demonstrates the results in the research topic of the railway ballast particles’ breakage test with unique laboratory test. The most railway lines in the world have so called traditional superstructure (ballasted tracks). In the past few years there were a lot of railway rehabilitation projects in Hungary, as well as abroad. Nowadays cannot be expected that there is enough quantity of railway ballast in adequate quality, because of the modifications and restrictions in the related regulations in Hungary since 2010. In Hungary there are only a few quarries which are able to ensure adequate railway ballast material for construction and maintenance projects for speed values between 120 and 160 km/h. This may cause supply and quality risk in production of railway ballast. The authors’ research’s main goal is to be able to simulate the stress-strain effect of ballast particles in real and objective way in laboratory conditions as well as in discrete element modelling.

Purpose. It is a very important issue to be able to determine the accurate particle degradation of railway ballast material. There are three differentbut connectingmethodology for that: 1) full scale field tests, 2) full scale or reduced scale laboratory tests, 3) computer modelling, mainly with discrete element method (DEM). Options no. 1 and no. 2 need a lot of time and money, but for option no. 3 sophisticated software is needed that can consider the accurate micromechanical characteristics of ballast bed material. Methodology. In this paper the authors summarize their results related to modelling, having applied a software that uses DEM for calculation, as well as laboratory tests, namely uniaxial compression tests with reduced scale and computer tomography. Findings. The authors obtained the results that the uniaxial compression test in laboratory was able to be modelled by DEM software with an initial precision but in the future should be specified. The results are certified by measurements performed by computer tomography method. Originality. It is a very complicated issue to model the particle breakage of railway ballast not only particle movements in DEM software. There are many available software packages at the 'market', e.g. PFC, EDEM, YADE. Some of them are quite expensive, the others can be controlled by significantly difficult manner (special programming technique is needed, command line, etc.) The authors applied not only laboratory loading tests, but sophisticated computer tomography for their research. Practical value The results can be useful for railway engineering area. This article is a part of a PhD research at Szechenyi Istvan University, the PhD student is Erika Juhász. Her aim is to develop a method to be able to determine the more accurate ballast breakage, as well as develop assessment methodology related to special measurement techniques (e.g. GOM techniques, computer tomography, etc.). The publishing of this paper was supported by ÚNKP-19-3-I-SZE-13 project.

This paper summarizes the authors' up-to-date results in the research topic of railway ballast particles' breakage test with individual laboratory test. In the past few years there were a lot of railway rehabilitation and maintenance project in Hungary, as well as abroad. The largest part of world's railways has traditional superstructure, i.e. they are so called ballasted tracks. The railway ballast is the highest mass in the railways' superstructure. Nowadays, it is a naturally fact that there is enough quantity of railway ballast in adequate quality. However, due to the modifications and restrictions in the related regulations since 2010, there are only few quarries in Hungary, which are able to ensure adequate railway ballast material for railway construction and maintenance projects for speed values between 120 and 160 km/h. Quarrying industry is stricken by aggravated environmental, heritage and conservation regulations year by year, it limits the accessibility of mineral wealth in significant manner. This fact with quality requirements means supply and quality risk in production of railway ballast in medium term. The main goal of authors' research is to be able to simulate the stress-strain effect of ballast particles in real and objective manner in laboratory circumstances, as well as in discrete element method modeling. This paper introduces the exact assembly of executed laboratory test and newest test results. The authors summarize the up-to-date international literature review, using that they give short outlook to the planned research with research directions in near future.

This paper presents a short literature review related to the fragmentation of the railway crushed ballast particles. With the help of the processed articles with the main topic of discrete element modelling (DEM) we aim to provide some insight into the international achievements and forward progress of the subject. Rock materials as granular elements can be investigated from several perspectives. The elements can be examined in laboratory conditions purely from the quarry, or even by obtaining already fragmented particles from the real railway tracks. In addition, DEM models can be created by using computer software. This article tackles only a small segment of the literature. Though each DEM topic was unique, they all involved examination of degradation of particles in some way. This review focuses on model building, including particle construction and calibration. The selected publications do not cover the current state of the entire DEM research related to ballast degradation.

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