An internally installed multi-chamber buffer structure for micro-pressure wave mitigation in 400km/h high-speed railway tunnels

Journal article, 2026

The initial compression wave, induced by the train tunnel entry, generates rapidly expanding high-pressure air at the tunnel exit, which causes micro-pressure waves (MPWs) and triggers sonic booms. MPWs cause vibrations in nearby structures and induce auditory discomfort. Inspired by the configuration of a multi-chamber reactive muffler, this study developed a novel buffer structure installed inside a tunnel near the portals. Using the sliding mesh technique and a quasi-three-dimensional axisymmetric approach, the performances of buffer structures with different configurations, positions, numbers of chambers, and chamber depths were compared. The results indicated that the connected buffer structure reduced the amplitude and pressure gradient of the tunnel exit MPWs by 38.7% and 52.1%, respectively, demonstrating significantly superior performance compared to the closed buffer structure. The entrance buffer structure contributed most to the mitigation effects, whereas the exit buffer structure exacerbated the MPWs. Increasing the chamber number and depth enhanced the mitigation effectiveness, but when these parameters exceeded certain thresholds, the mitigation effectiveness reached a plateau.