SPECIFIC ASSESSMENT METHOD OF RAILWAY BALLAST PARTICLE DEGRADATION BASED ON UNIQUE LABORATORY TEST

Abstract

Purpose. There are specific, standardized laboratory test methods to assess railway ballast particle degradation; they are the Los Angeles (EN 1097-2) and the Micro-Deval abrasion (EN 1097-1) tests. These testing methods can’t take into consideration the real railway stress-strain circumstances of ballast materials, and they particles. In this paper the authors represent a specific laboratory fatigue breakage test of railway ballast materials. With this kind of testing method, the deterioration process of railway ballast particles can be assessed more realistic and precisely. Methodology. A special layer structure is built-up with elastic sublayer system and 30 cm thick ballast samples (from two different type andesite base rocks) that is loaded by dynamic, pulsating forces. Particle size distribution functions have to be recorded before and after a more million cycle fatigue test, but intermediate measurements are also executed. The measured data should be processed, and different parameters have to be calculated that are offered by international literature and researches. The test doesn’t consider the particle breakage due to hand-made and machine-made tamping, but it can simulate particle degradation due to more years’ railway traffic in laboratory circumstances. Findings. There is a development after the R&D work made and published in 2014: in 2017 and 2018 years the ballast particle deterioration process is given according to more intermediate fatigue cycles with individual measurements, that show more precise «picture» about the full particle degradation, i.e. breakage process. The authors give more precise correlation functions between the calculated parameters and load cycles during fatigue. Originality. The paper summed up the results of a specific developed laboratory test method for assessment of the breakage process of railway ballast particles according to two different railway ballast materials from andesite base rocks. Practical value. The results help with the calculation of approximate time interval of required ballast screening (cleaning) work in the future. This research is supported by the ÚNKP-17-4 New National Excellence Program of Ministry of Human Capacities.