Keywords: railway transition zones, ballast-slab track, differential track stiffness, 3D numerical railway model, auxiliary rail application, dynamic track responses.

Railway track transition zones are problematic areas with rapid track deterioration and frequent track maintenance due to a sudden change in the track-soil structure, corresponding to differential track stiffness. Changes can be related to the connection between ballasted and slab track, bridge approaches, and tunnel entry/exits. To deal with this dynamic effect, the usage of auxiliary rails between the running rails is one of the well-known and effective techniques for railway transition zones. However, there is some shortage of knowledge about the influence of the spacing between auxiliary rails. Therefore, this paper develop a 3D finite element transition zones model of ballast-slab track with auxiliary rails, using eight-node solid elements and a perfectly matched layer (PML) for absorbing boundary conditions. The material properties for all track-soil components are defined as the isotropic and linear elastic. A moving train load is modelled using a sprung mass model to represent train-track interaction. After the simulation, the numerical results is validated against field data at a transition zone. Once validated, the model analysis of transition zones with auxiliary rails indicates that using two auxiliary rails is sufficient to improve the dynamic track characteristics across the transition. Further, the effect of three different spacing between two auxiliary rails is investigated and compared. It is found that the widely spaced auxiliary rails provide a more significant advantage on dynamic performance than closely-spaced ones, considering on receptance responses, rail displacements and stress distributions from ballast to natural soil layer.

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