Model experiments on the influence of tunnel hood cross-sectional area on the reduction of the pressure gradient of the compression wavefront in high-speed railways

Abstract

Micro-pressure wave emission from tunnel portals in high-speed railways causes environmental issues. Tunnel hoods installed in the tunnel portals reduce the micro-pressure wave emission by reducing the pressure gradient of the compression wavefront generated in the tunnels. This study investigated the influence of the hood cross-sectional area on reducing the pressure gradient of the compression wavefront under the conditions in the current Shinkansen specifications, assuming that train running speeds would increase in the future. Scale model experiments were conducted using axisymmetric cross-section models of the tunnel, hoods, and trains; the high-speed train model was launched into the tunnel and hood models. The effect of the hood on the reduction of the micro-pressure wave was estimated by measuring the pressure gradient of the compression wavefront generated in the tunnel model. The experimental results show that the effect of the hoods depends on their length and cross-sectional area, even if there are apertures on the sidewall of the hoods. Furthermore, when there are no side apertures on the hoods and the cross-section is longitudinally uniform, the optimum hood cross-sectional area at which the maximum pressure gradient of the compression wavefront is the lowest depends on the train speed and nose length. The findings of this study will provide useful insights into the structural design of tunnel hoods in high-speed railways.

Keywords

• micro-pressure wave
• compression wave
• pressure gradient
• railway
• tunnel hood
• shinkansen