REDUCTION OF A MICRO-PRESSURE WAVE BY INSTALLING POROUS BUFFERING PLATES IN A BRANCHED OUTLET TUNNEL OF A HIGH-SPEED RAILWAY

Abstract

 When a high-speed train moves into a tunnel, a compression wave forms in the tunnel and propagates towards the tunnel exit. A part of the compression wave is diverged from the main tunnel route to the side branch tunnel, and then a micro-pressure wave, a low frequency noise, is discharged from the portal of the branch end. To reduce a micro-pressure wave, we propose a porous absorber attached to the wall of a wind path in the side branch. The effect of the absorber is studied with a scale-model experiment, where a model train moves into a model tunnel with a side branch. The result shows that a micro-pressure wave is reduced by up to half, and that the reduction increases with the area of the porous wall of the absorber. Then, a porous absorber is constructed in the test railway line in Yamanashi, and the field measurement result also shows the reduction of a micro-pressure wave by the absorber.