Abstract: To accurately predict the amplitude of the micropressure wave at the exit of a high-speed railway tunnel, Fluent software is used to simulate a scenario in which a train with an average speed of 400 km/h enters a double-track tunnel with an endwall area of 100 m². The impacts of buffer structures at the side openings of the tunnel entrance and exit, as well as the slope gradient at the tunnel exit on the micropressure wave are analyzed. Furthermore, the combined mitigation effect of the micropressure wave is examined in conjunction with the entrance and exit buffer structures. The results indicate the following: (1) The correlation between the peak value of the exit micropressure wave, buffer structure, and slope gradient of tunnel exit as well as the variation trend of the solid angle linearly fitted by radiation solid angle formula demonstrates that the solid angle exhibits a twostage ascending curve transitioning from sharp to gradual with increasing opening ratio of the buffer structure and slope gradient. (2) The numerical analysis reveals the variation law of the initial compression wave pressure gradient and the mitigation efficiency law of the exit micropressure wave under different opening ratios of the entrance buffer structure. A prediction formula for the combined mitigation efficiency of the micropressure wave is proposed, based on the buffer structure and the slope gradient of tunnel exit, to predict the variation trend under different combinations of multiple working conditions. (3) Following the error analysis between the prediction results and numerical simulation verification, the exit solid angle can be integrated with the mitigation law of the entrance buffer structure.

Key words: high-speed railway tunnel, buffer structures, solid angle of radiation, micropressure wave, mitigation efficiency