The rock physics properties of the crushed railway ballast include resistance against breakage and wear. The qualification of such materials and their compliance with requirements is mainly considered by two standard tests: The Los Angeles abrasion and Micro-Deval wear resistance tests. These tests are indispensable for the legally mandatory qualification of aggregates, but several measurement methods have been developed that better simulate operating conditions and provide an even more accurate classification of these materials. A Proctor compactor machine was applied to induce a top impact load more similar to the operating conditions of ballast. Pre-screened, sorted, washed, and dried samples of andesite aggregate from four quarries with different rock physics characteristics were used to conduct the test series. The impact load was applied with increasing numbers of blows, i.e., 64, 128, 256 and 1024. Several parameters and indexes were calculated to reveal different relationships, which had to be modified in some cases to obtain estimates as close as possible to those obtained in individual tests. The original Ballast Breakage Index seemed to be an appropriate measure of the change in ballast material quality during deterioration for over a decade. The original calculation method was not consistent with the newly introduced test method. Keeping the principle, however, a modified BBI index calculation method has been developed that fundamentally simplifies the calculation of ballast fragmentation. The whole series of measurements aimed to provide, by material and number of impacts, a series of fragmentation and degradation curves for each of the three repeated measurements, which would give the degradation of samples with different rock physics and grain sizes.

The physical classification of crushed stone and gravel used in railway construction is based on their strength and endurance and is performed by a laboratory test method using a rotating drum or a mortar method. The values of fracture resistance calculated using the Los Angeles method and abrasion calculated using the Micro-Deval method show a corresponding correlation and require further investigation. Purpose. The development of a new method for measuring rock material fracture that is consistent with widely used standards while also being more comparable to real-world railway operating conditions. Certainly, both standard tests are essential for ensuring product homogeneity during production, so the new recommended method is only a supplement. Methodology. The Proctor device was used to induce so-called shock loads from above, similar to railway loading conditions. Unlike the standard method, the andesite material was placed in a standard cylinder in these tests. The samples were pre-screened and sorted; the specified weight was approximately 1,300 g, and the specified sizes of the individual particles were 6.3, 8.0 and 11.2 mm. Only prewashed and dried materials of NZ (fine crushed stone) or KZ (special crushed stone) from four different quarries (Tállya, Szob, Nógrádkövesd, Recsk) with different rock physics characteristics were considered. The Proctor compactor machine was used because of its calculable labor (19.86 J/impact) and the crushing effect of the calculable impacts (64, 128, 256 and 1,028 blows). Even after loading different numbers of impacts, homogeneous samples from different quarries were sieved to measure the masses of fragments per fraction. Findings. The set of measurements made it possible to establish a series of fragmentation and degradation curves for each of the three repeated measurements based on the composition of the material and the number of blows, which showed the degradation of samples with different physical and mechanical properties of the rock material and particle sizes. With an increasing number of impacts, the amount of crushed material in the sample increased, but the distribution of crushed material did not decrease evenly and proportionally as the number of impacts increased. Parameters and indices were also computed to identify various correlations (i. e., FV, d < 22.4, d < 0.5, d < 0.063 mm, CU, M ratio, λ ratio). Some of them (e. g., FV) needed to be changed, but they were predefined due to the nature of the tests. Originality. While many standard and alternative railway track ballast fragmentation test methods and measurement tools are available, this paper proposes a new laboratory method and demonstrates the specific measurement and application effectiveness. Practical value. In addition to standard tests that are already widely used, the new method for measuring the fractional composition of railway ballast can help simulate real-world operating conditions of a railroad track in the laboratory. This method will improve the safety of railway operations.

This paper summarizes the results of laboratory tests in which the authors investigated the effects of extremely high vertical load to a railway track segment. The segment consisted of a cut concrete sleeper (contact area: 290×390 mm) with a pair of direct-elastic rail fasteners; the sleeper pieces had a standard, full height; the structure had a typical 350 mm depth railway ballast, underneath approx. 200 mm sandy gravel supplementary layer. The whole assembly was built in a 2.00×2.20 m area wooden rack. The deformations due to the approx. 150 kN static concentrated vertical force were measured and recorded by Digital Image Correlation Method (DICM), ensuring the GOM ATOS technology. The 150 kN peak load meant 1326 kPa vertical stress at the sleeper-ballast interface. The 3D geometry was scanned before the loading and after the collapse. In this way, the comparison was able to be executed. The maximum vertical deformation was 115 mm. The DICM technique is a relatively new methodology in civil engineering; however, it has been applied for more than ten years in mechanical engineering. Therefore, the authors investigated the applicability of DICM in this field. As a result, the pre and the post-states were determined in 3D. The displacement of the ballast particles was able to be defined with the possibility of drawing the displacement trajectories of given points. The DICM can be a valuable methodology in railway engineering, e.g., laboratory tests and field test applications.

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.

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 worlds 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.