Pressure fluctuation and a micro-pressure wave in a high-speed railway tunnel with large branch shaft

Abstract

In the future, long tunnels for high-speed railways will be constructed for efficient urban space utilization. In these tunnels, branch shafts larger than the main tunnel would be installed as passenger evacuation routes. Although the effect of micro-pressure waves (MPWs) radiated from a branch portal are not be negligible, the effect of MPWs in tunnels with large branch shafts have not been investigated. In this study, we investigate the effect of MPWs radiated from a branch shaft and the pressure wave fluctuations for the branch shaft. The train speed is set to 260–360 km/h, and the ratio of the cross-sectional area of the branch to that of the tunnel Rb is set to 0.5–3.6, which is larger than those of branch shafts installed in conventional Japanese high-speed railway tunnels. The experimental results show that the pressure rise in the main tunnel due to the train nose passing through the branch junction (passing wave) increases with Rb, and that value converges to the pressure rise of entry wave (the pressure wave generated when the train nose enters the tunnel) in the infinite case Rb→∞. Furthermore, the MPW generated by the passing wave would be the largest MPW radiated from the tunnel portal when Rb > 1.0.