Quantifying Degradation of Railway Ballast Using Numerical Simulations of Micro-deval Test and In-situ Conditions

Abstract

Throughout the life of the track, ballast grains wear as a result of both the trains passing over the track and the maintenance operations (tamping). The morphology of the grains is changed: they lose angularity and fine particles are produced, causing a gradual loss of track performance. Eventually ballast renewal becomes necessary. In order to predict the evolution of this degradation, a multi-scale study is proposed. A comparison between discrete element method (DEM) simulations of Micro-Deval attrition test and of the passage of trains over a sleeper is performed in order to both detect the different loading and wearing mechanisms involved and quantify the amount of friction work produced, which is directly related to friction wear. The same numerical approach is also used with the simulations of the track to detect families of contacts in order to determine characteristic loading paths at the micro-scale. Loads and displacements of both systems are then compared in order to discuss the relevance of the Micro-Deval test.