Passive Control of Micro-Pressure Wave from High-Speed Railway Tunnel

靠近隧道出口的简单膨胀室可以显著降低隧道外传播的微压力波的振幅。1.这种腔室的最佳形状取决于反射波阵面的陡度。最大的百分比减少实现了最陡的波前。2.当预期入射波前的陡度范围时，应针对被认为可行的最陡情况优化腔室形状。这将在最需要的时候提供最大的好处。在大多数情况下，这种形状也将表现良好，不太陡峭的波前，即使它不是最佳的。3.对于任何特定的入射波前陡度，腔室的最佳形状取决于腔室尺寸。然而，对于本文中最相关的陡峭波前，相关性并不强。通常，具有单位体积隧道的良好设计的腔室可以导致微压力波的幅度减小约30%。这是除其他修改（例如，隧道入口处）。

Simple expansion chambers close to a tunnel exit portal can cause significant reductions in the amplitudes of micro-pressure waves propagating outside the tunnel.1. The optimum shape of such chambers depends upon the steepness of the reflecting wavefront. Greatest percentage reductions are achieved for the steepest wavefronts.2. When a range of steepnesses of incident wavefronts is expected, the chamber shape should be optimized for the steepest case that is considered feasible. This will provide greatest benefit when it is most needed. In most cases, this shape will also perform well with less steep wavefronts even though it is not optimum.3. For any particular incident wavefront steepness, the optimum shape of the chambers is dependent on the chamber size. For the steep wavefronts of greatest relevance herein, however, the dependence is not strong.4. Typically, a well-designed chamber with a unit volume of tunnel may cause a reduction of about 30% in the magnitudes of micro-pressure waves. This is in addition to reductions resulting from other modifications (e.g., at the tunnel entry).