为研究时速400 km隧道洞口增设不同型式及参数的等截面缓冲结构时，初始压缩波气压及压力梯度峰值、洞口微气压波的气压峰值变化规律，采用三维CFD数值仿真方法进行分析，结果显示： 1）洞口增设缓冲结构使初始压缩波气压峰值小幅上升，峰值增长率为0.26%~7.74%。2）正切型缓冲结构相较于直切及倒切型缓冲结构对微气压波的缓解性能更优，且微气压波气压峰值缓解率随着缓冲结构斜切段的切削斜率k减小而提升。倒切型缓冲结构微气压波缓解率R_micro为17.1%，直切型缓冲结构微气压波缓解率R_micro为23.0%，A-6正切型缓冲结构微气压波缓解率R_micro可达45.1%。3）缓冲结构增设开孔能有效提升微气压波缓解率，且顶部开孔相较于侧面开孔的缓解性能更优。不开孔B-1型缓冲结构微气压波缓解率R_micro为44.1%，侧面开孔B-2型缓冲结构微气压波缓解率R_micro为58.5%，顶部开孔B-8型缓冲结构微气压波缓解率R_micro为64.4%。4）顶部开孔缓冲结构的缓解性能与开孔型式无明显关联，与开孔面积呈正相关性。5）隧道进出口增设长度为25 m的B、C、D组开孔型缓冲结构时，微气压波缓解率达55%以上。

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%.