A high-speed train entering or leaving a tunnel generates pressure waves inside the tunnel, which travel through it back and forth, reflecting repeatedly at both end portals. At each reflection, a part of pressure wave energy is radiated as an impulsive wave from the portal toward the surrounding area. The impulsive wave is called a "micro-pressure wave" and has become one of the most serious environmental problems occurring in high-speed railways. When the tunnel length is less than a few hundred meters, the micro-pressure waves at each reflection are emitted successively during a rather short time period of several seconds, with the result that an oscillatory pressure waveform is observed outside the tunnel. In addition, pressure waves are directly radiated from the portal toward the outside at the entry or exit of the train, which are called a "tunnel entry/exit wave," to make the outside waveform more complex, overlapping with the micro-pressure waves. This paper reports the results of field measurement at a Shinkansen tunnel of about 100 m in length performed to clarify the pressure waves generated at portals of a short tunnel.

Copyright (c) 2003 Railway Technical Research Institute