A discrete element study on the deformation and degradation of coal-fouled ballast

Abstract

This paper presents the results of Discrete Element Modelling (DEM) which quantitively examine the effect of coal fouling on the deformation and degradation of ballast upon cyclic loading. The degradation model described herein considers the Weibull distribution effects in tandem with a granular medium hardening law that incorporates the maximum contact criterion to capture surface abrasion and corner breakage of angular ballast. The DEM model had been calibrated initially with laboratory data obtained from large-scale direct shear testing. Subsequently, a series of cubical shear test simulations have been carried out using DEM to understand the behaviour of fouled ballast whereby the numerical particle degradation modelling could simulate the experimental response of the ballast assembly at various fouling levels. The results show that the increased level of fouling exacerbates the sleeper settlement, while decreasing the resilient modulus and the particle breakage. Ballast beneath the sleeper experiences significant breakage compared to the crib ballast, and not surprisingly, the extent of damage decreases with depth. Rigorous microscopic analysis is also presented in relation to inter-particle contacts, particle velocity and anisotropy of the ballast assembly. This micromechanical examination highlights that the decrease in ballast breakage for fouled assemblies is predominantly attributed to the inevitable decrease in inter-particle contact pressures as effected by the coating of ballast aggregates by the coal fines.

Effect of rock strength on the degradation of ballast equipped with under sleeper pad using discrete element method

“…These findings provide an optimal design for a two-layer ballast system, which may effectively reduce track maintenance costs. Chen et al [26] employ DEM to precisely analyze the influence of coal fouling on the deformation and deterioration of ballast material when subjected to repeated loads. This study provides a detailed analysis of the mechanical behavior of fouled ballast, demonstrating that higher degrees of fouling intensify sleeper settlement, reduce the resilient modulus, and result in particle breakage.…”

The Discrete and Continuum Behaviour of Railway Ballast

“…The complex particle shapes of ballast and rockfill may also be derived from image analysis, typically from CT. These shapes have already been modelled with overlapping discs in 2D [12] or spheres in 3D [19], non-overlapping clumps of spheres (e.g. [48,38]), polyhedrons [53,30] and potential particles [4].…”