Parametric Sensitivity of Shaft Buffer Structures on Train-induced Pressure Fluctuations in High-speed Railway Tunnels

When a train enters a tunnel, rapid pressure fluctuations occur within the tunnel, which induce significant pressure transients inside the vehicle and compromise passenger comfort. This study analyzes the effects of the shaft’s radial distance (L), cross-sectional diameter (D), and height (H) on the train surface pressure load. The pressure distribution characteristics ahead of the train are examined, the three-dimensional propagation of characteristics pressure waves is visualized through iso-surface analysis, and their underlying propagation mechanisms are investigated in depth. The results indicate that optimized values of L, D, and H for the shaft buffer structure can mitigate pressure fluctuations on the train surface. Regarding internal carriage pressure, greater relief is achieved with larger L and D, and smaller H. A response surface model was constructed using the Box-Behnken design with L, D, and H as design variables. Subsequently, global sensitivity analysis was performed using the Sobol method to quantify the influence of each parameter. The results show that L exerts the most significant influence on the train surface pressure, whereas D is the dominant factor influencing the internal carriage pressure. By contrast, the coupling effects among L, D, and H are relatively weak. These sensitivity findings indicate that targeted optimization of shaft parameters can effectively enhance passenger comfort during tunnel transits. Moreover, this study provides valuable insights for guiding the design and construction of tunnel ventilation shafts.