Abstract: In this study, a three-dimensional computational fluid dynamics numerical simulation method is employed to examine the variation patterns of the aerodynamic pressure and pressure gradient peak of initial compression waves (ICWs) as well as the pressure peak of micro-pressure waves (MPWs) for different types and parameters of equal section buffer structures at the tunnel entrance at 400 km/h. The major findings are as follows: (1) Adding buffer structures at the entrance slightly increases the ICW aerodynamic pressure peak, with a peak increase range of 0.26%－7.74%. (2) A tangent-type buffer structure outperforms straight- and inverted-cut-type buffer structures in terms of relief performance, and the peak relief rate of MPWs increases as the cutting slope of the buffer structure decreases. The relief rates of MPWs for inverted shear, straight shear, and A－6 tangent types reach 17.1%, 23.0%, and 45.1%, respectively. (3) Perforating the buffer structures effectively improves the relief rate of MPWs, and the top perforations achieve better relief performance than side perforations. The relief rates of MPWs for nonperforated B-1, side-perforated B-2, and top-perforated B-8 types are 44.1%, 58.5%, and 64.4%, respectively. (4) The relief performance of the top-perforated buffer structures does not significantly correlate with the perforation type but positively correlates with the perforation area. (5) When adding 25-m-long B, C, and D group perforated buffer structures at the tunnel entrance and exit, the relief rate of MPWs reaches over 55%.

Key words: high-speed railway tunnels, tunnel entrance, equal cross-section buffer structure, aerodynamic pressure of initial compression waves, pressure gradient, micro pressure waves, response rate