ABSTRACT
Ballasted railway tracks are conventionally found on compacted ballast platforms, which are laid on natural or improved subgrade. The ballast is responsible for limiting the vertical stress magnitudes applied to the weaker subgrade and preventing train-induced sleeper movement. Under heavy cyclic train loads, the ballast particles degrade and deteriorate progressively, resulting in track misalignment and leading to more frequent and costly maintenance cycles. In this paper, the mechanical behaviour of ballast including the effect of particle size distribution, confining pressure, and particle deformation and breakage, is studied. The important factors affecting the mechanical behaviour of ballast, including the various characteristics of individual ballast grains, are illustrated. A new ballast particle size distribution that is recommended to the Australian railway industry, and a new constitutive model for ballast that incorporates the effect of particle breakage during shearing, are presented and discussed.
