On some mechanical characteristics of the ballast in assessing the stress-strain behaviour of railway tracks

Abstract

On the basis of recent research, a review has been carried out on the experimental determination of the mechanical parameters of the materials used as ballast material. Considerable attention is given to the well-founded selection of input data for the calculation, i. e. quantitative characteristics of the elastic properties of the materials used to form the ballast layer, which is treated as a continuous medium. It appears that this approach makes it possible to assess correctly the influence of grain (grain size distribution) distribution, ballast layer thickness and material type on the stability of a railway track to vertical and horizontal disturbances. The data of this review show that material properties and particle size have a signifi cant impact on elastic moduli and in finite-element modelling of static strength problems, grain-size distribution and material properties are only taken into account through these moduli. Experimental results show a non-linear dependence of the elastic moduli on the stress behaviour of the ballast prism, which is related to a densifi cation of the medium in compression. However, it is established that, after a suffi ciently large number of loading cycles, the medium can be treated as linearly elastic. In general, the results of the research allow establishing requirements for damping, geometric and granulometric parameters of the ballast prism.