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.@en

Railway track transitions are zones where there is an abrupt change in the track-ground structure. They are often the location of rapid track deterioration, which means more frequent track maintenance is needed compared to plain line tracks. With the aim of reducing maintenance, modern transition zone designs use tapered stiffness earthwork profiles to minimise train-track dynamics. However, there has been limited comparison regarding the effect of different tapered profiles on dynamic behaviour. Therefore, this paper's novelty is the investigation of the performance of different earthwork designs in smoothing stiffness transition's considering different types of improvement and also train speed. To do so, first a 3D finite element track model is developed, with support conditions transitioning from an earth embankment onto a concrete bridge. A dynamic moving train load is simulated using a rigid multi-body approach capable of accounting for train-track interaction. The model is used to study the effect of four earthwork solutions with differing stiffness tapers. For each scenario, two different track structure types (ballast and concrete slab) are considered, along with different magnitudes of ground improvement. Lastly, the effects of train speed are explored. It is found tapered earthwork solutions for ballasted tracks show greater dynamic improvement compared to slabs due to their reduced bending stiffness. Further, the more complex improvement geometries such as double trapezoid shapes offer some additional improvement at locations within 3 m of the bridge. However, when considering such tapered stiffness-based earthwork solutions, additional factors such as constructability must also be considered.@en