Study on influence of cosine-shaped subgrade settlement at different positions on the deformation and interlayer contact behavior of unit slab ballastless track

Abstract The influence of cosine-shaped subgrade settlement (CSSS) at different positions on the structure of unit slab ballastless track (USBT) of high-speed railway (HSR) is studied in this paper. The pre-developed general mapping model of the track structure deformation and interlayer contact behavior evolution of HSR is used, the CSSS description function is incorporated, and the deformation equations for each layer of the USBT structure under CSSS are derived. The incremental approach method is used to solve the statically indeterminate equation with contact nonlinearity, and then the influence of CSSS at different positions on the track structure deformation and interlayer contact behavior evolution is analyzed. The results show that the transfer pattern of track deformation is related to the position of settlement, and the structure deformation is more sensitive to the settlement at the position of the slab joint. Under the CSSS, the vertical deformation of the track structure remains synchronized and is transmitted upward layer by layer. The type of track irregularity differs between the subgrade settlement area and the area outside of it. In the area of uneven subgrade settlement and its small area on both sides, the debonding position of the track slab-base slab and track system-subgrade system mainly appears at the position of the slab joint, which presents the distribution law of “smaller at the near end, larger at the far end”.