Abstract
Particle friction in railway ballast influences strongly the behaviour of ballasted tracks. New challenges posed on railway infrastructure increase the requirement for simulations, which need the friction coefficient as an input parameter. Measured friction coefficients of ballast stone contacts were found only in two studies, both under constant loads. In this work, two types of ballast were investigated in cyclic friction tests with incremental increase of the applied load after several cycles. Before each load increase, 3D-scans of some ballast stones allowed to calculate the contact area. Estimating the stress in the contact, the stress-dependency of the friction coefficient and wear were investigated. These experimental observations are discussed regarding their impact for friction modelling in the simulation of railway ballast.
Highlights
In railways, ballasted tracks are the most common form of track systems
The Discrete Element Method (DEM), introduced in [1], is a widely used tool for the simulation of railway ballast and/or ballasted tracks, as it takes into account directly the granular nature of the material and provides insight into different phenomena occurring at the particle scale
In most of the experiments, lower CoF values were measured during the first cycles at a given vertical load
Summary
One of the main tasks of the ballast is to transfer forces (both in the vertical and lateral directions) from the wheel–rail contact to the ground. How these forces spread within the ballast for different types of operational conditions (e.g. speeds and axle loads, tangent vs curved track) is still not fully understood. The DEM simulation method allows the effect of new track components being introduced to be predicted, e.g. different sleepers types, [2]; under sleeper pads, [3,4]; under ballast mats, [4,5]; or geogrids, [5,6,7,8]. Compare [4,9,10,11,12] for DEM modelling of the mentioned aspects
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