ABSTRACT
In general, the mechanical response of ballast is governed by four main factors: (a) characteristics of constituting particles, (e.g. size, shape, surface roughness, particle crushing strength, resistance to attrition etc.), (b) bulk properties of the granular assembly including particle size distribution, void ratio or density and degree of saturation, (c) loading characteristics including current state of stress, previous stress history and applied stress path, and (d) particle degradation, which is a combined effect of grain properties, aggregate characteristics and loading. These factors are discussed in the following Sections.
