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Abstract
Purpose. There are special, standardized laboratory test methods to evaluate railway ballast particle breakage; they are the Los Angeles and the Micro-Deval abrasion test. The authors opine that these methods aren’t the most adequate methods to assess the real ballast particle degradation because in reality never occurs these kinds of stresses and strains (i.e. particles in a rotating drum with or without steel balls and with or without water). A new laboratory test procedure is needed. The authors attempted to configure an adequate one in 2014, it is detailed in the paper, as well as the initial results and improvement possibility. This test method is related to dynamic pulsating test, the particle size distributions (PSD) had to be determined before and after fatigue. In 2017-2018 the research is supported by ÚNKP-17-4 program. Methodology. Multi-level steel box is utilized with a special layer structure, detailed in the paper. Five different types of railway ballast samples were tested. PSDs were defined, and regarding to the results relationship between ballast particle degradation values (according to Los Angeles and Micro-Deval abrasion tests, as well as this newly developed laboratory test method) was searched, as well as time interval between necessity railway ballast cleaning work was also calculated. Findings. The authors sentenced the results regarding to the self-developed laboratory test method that is able to assess the particle degradation and time interval between railway ballast cleaning work more precisely related to the real railway operation circumstances. Relationship was determined between particle breakage according to standardized and unique (non-standardized) laboratory test methods. Originality. The paper summarized the results a newly developed laboratory test method for evaluation of the degradation of railway ballast particles. Practical value. It sentenced the possibility to improve the measurements and assessments regarding to the research phase supported by the ÚNKP-17-4 project.
Highlights
There are special, standardized laboratory test methods to evaluate railway ballast particle breakage; they are the Los Angeles and the Micro-Deval abrasion test
It has to be noticed that bitumen stabilised ballast material is able to be applied [13]
– confining stress plays a relevant role in the particle degradation, the larger the confining stress, the larger the breakage [37]
Summary
There are special, standardized laboratory test methods to evaluate railway ballast particle breakage; they are the Los Angeles and the Micro-Deval abrasion test. PSDs were defined, and regarding to the results relationship between ballast particle degradation values (according to Los Angeles and Micro-Deval abrasion tests, as well as this newly developed laboratory test method) was searched, as well as time interval between necessity railway ballast cleaning work was calculated. Ii)it has to have uniform grading according to points b) and d) because the proportionately lot of void between grains guarantees the rapid flowing through of water in the structure, as well as the larger energy damping [60], iii) it has to contain sharp edge grains according to points a) and c) because the largest inner particle friction is able to be expanded, durable track geometry (e.g. against vertical deformation) is able to be obtained, iv) grains with less deterioration (breakage) characteristics have to be applied according to point b), it can be obtained by usage of railway ballast with low Los Angeles and Micro-Deval abrasion values, or by recycled ballast material (perchance by rounded grain material, i.e. river grains) [16, 46], v) it has to have required and adequate layer width. It has to be noticed that bitumen stabilised ballast material is able to be applied [13]
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