The properties of railway ballast material are affected by the local geologies and climatic environments from which the parent rock is sourced. These factors can make it challenging to select the most appropriate material for railway applications. To address this issue, this paper first reviews the means of ballast selection in complex environments across the world. The selection criteria for ballast materials are compared and test methods for ballast quality quantification are summarised. Next, ballast parent rock types and the implications of mining approaches are discussed, before analysing ballast morphology with respect to ballast size and shape. Then ballast petrography is reviewed with a focus on the effect of mineral composition on performance. Finally, some promising future ballast technologies are discussed with a focus on environmental performance. These include recycled ballast, asphaltic materials, steel slag and ballast gluing. The review shows that regarding ballast selection means and criteria, the number and type of quantitative indicators varies greatly between countries. In particular there are divergences in test methods and quantitative indicators for ballast quality considering material types and local geologies. Suggested future research directions are proposed, such as the effect of tamping and dynamic track stabilisation on ballast properties.@en

Railway track transition zones are areas where there is a sudden change in the track-ground structure. They include changes between ballasted and slab track, bridge approaches, and tunnel entry/exits. They are often the location of rapid track deterioration, and therefore this paper investigates the use of auxiliary rails and soil improvement to minimise train-track-ground dynamic effects. To do so, a 3D finite element model is developed using eight-node solid elements and a perfectly matched layer absorbing boundary condition. A moving train load is simulated using a sprung mass model to represent train-track interaction. After presenting the model, it is validated against field data collected on both a plain line and at a transition zone. Once validated, a sensitivity study is performed into auxiliary rails and soil improvement. It is found that auxiliary rails can improve the dynamic characteristics of the track across the transition, and that more widely spaced auxiliary rails provide greater benefit compared to closely spaced ones. Regarding soil improvement, a large benefit is found, and for the material properties under investigation, the effect of soil stiffening is greater than using auxiliary rails.

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