Discrete element modelling of railway ballast under triaxial conditions

Abstract

Railway ballast is a granular material with a complex stress–strain relationship under monotonic loading. The discrete element method has been widely used to investigate the mechanical behaviour for the behaviour of granular materials. In this paper, discrete element modelling has been used to capture the essential mechanical features of railway ballast. The effects of particle shape and interparticle friction have been studied. Parallel bonds have also been introduced in the simulations to simulate the interlocking of small-scale asperities, so that the correct stress–strain relationship for ballast can be modelled. Asperity breakage has been modelled by using small balls bonded at the edges of the main body of a particle. A range of confining pressures have been applied to the assembly of particles. The simulations demonstrate the validity of numerical modelling of railway ballast. In particular, the unique contribution of this paper is to show that the monotonic shearing behaviour of railway ballast can be correctly modelled under a range of confining pressures, providing micromechanical insight into the behaviour.

Keywords:

• numerical modelling
• ballast
• particle abrasion
• shear strength

Acknowledgements

The authors would like to thank Rail Research UK for funding this work.