Micro-mechanics of Railway Ballast - The effect of particle shape
This project is part of Track21, a wider EPSRC programme grant focussed on the mechanics of ballasted railway track, and investigates the effect different particle shapes have on the mechanical properties of railway ballast (and granular materials in general).
The aim of the project is to improve the longevity of ballast and reduce the amount of maintenance work needed to keep railway track in a usable state. This can be done by controlling ballast shapes to reduce deformations under repeated loading.
Commonly shape can be characterised at three different levels, namely Form, Angularity and Surface Roughness. Each category describes shape at a different scale of observation. Understanding shape is essential for understanding how micro-structures form and evolve in a granular material subjected to loads.
To study these micro-structures, we use the Discrete Element Method (DEM) which models each particle individually, using Newton's laws of motion, as well as particle interactions through a frictional contact law, to simulate the behaviour of a granular material. The micro-mechanical data from each particle, such as displacement, rotation, interparticle contacts and forces etc, provide insights into the fundamental reasons behind differences in mechanical behaviour and can allow the targeted use of specific shapes for specific desired behaviour.