Numerical Investigation of HMA Effect on Dynamic Behavoiur of Railway Track Transition Zone

There are many structures along the railway tracks such bridges and culverts. The track vertical stiffness suddenly changes where the track passes over these structures. Therefore, these locations are called transition zones. Sudden track stiffness changes in these locations can lead to the asymmetric deformations, railway roughness, damage to the components of superstructure system. Studies shown that changing of the track stiffness along the railway lines is one of the main sources of tracks geometric damages. One of the most common places that the railway track stiffness changed along the railway lines are the culverts and bridges. The vertical stiffness change in these area causes the asymmetric deformations, rail roughness, damage of the components and as a result increasing the maintenance costs. One of the methods to solve the above problems is used to the hot mix asphalt (HMA) layer in adjacent of the culverts and bridges. In the present study, the behaviour of railway track in adjacent of culverts with HMA layer has been evaluated. For this purpose, a 3D finite element model of railway track culvert with HMA layer was built, and then different sensitivities on the geometric dimensions of HMA layer (including thickness and length) were analysed. Also based on analyse with exist a optimized layer of hot mixed asphalt around bridges structures the rail vertical displacement, ballasted layer vertical displacement and the normal stress in the middle of the subsgrade layer decreased approximately 19%, 22% and 36% respectively.