A precise numerical method for dynamic analysis of metro turnout transition zones

The prefabricated rubber mat floating slab track (PRMFST) has been increasingly applied in metro turnout areas in recent years due to its high construction efficiency and superior vibration damping performance. However, the significant stiffness disparity between PRMFST and conventional monolithic track beds (CMTB) may induce severe vehicle-track coupling vibrations. To investigate dynamics responses of various stiffness homogenization measures between PRMFST in turnouts and CMTB in mainline sections, and to explore reasonable stiffness distributions in transition zones, it established a coupled vehicle-turnout-transition zone dynamic model. The model considers both the inter-layer interface constraint effects of the PRMFST and the refined wheel-rail contact relationships in turnouts. A self-developed dynamics program was employed to analyze the impacts of transition stiffness ratio, the quantity of transition stages, and the length on the train, track, and tunnel. Results indicate that higher stiffness ratio improves train stability and reduces rail deflection variation rate, but tunnel vibration intensity approaches that without transition zones when the ratio exceeds 3.0. Compared to no transition, stiffness homogenization significantly reduces vibrations above 40 Hz. Multi-stage transition zones reduce low-frequency vibrations of the 1 ~ 12.5 Hz more than single-stage transition, but the difference in tunnel source strength between two and three-stage transitions is minimal. The proposed method can precisely reflect the distribution of vibration acceleration levels across different frequencies and characterize the wheel-rail two-point contact force and nonlinear mechanical components in the turnout area. The findings provide a basis for applying the novel track structures in metro turnout areas and offer theoretical reference for improving their dynamic adaptability in turnout transition zones.