Influence of Inertial Effect of Compression Wave on Waveform Evolution

In order to accurately assess the micro-pressure wave outside tunnel exits, a theoretical formula of pressure gradient of wavefronts was deduced based on the one-dimensional plane wave equation and the flow characteristics of compression wave. The effects of propagation distance, and the amplitude and wavefront length of the initial compression wave on pressure gradient at different positions were analyzed using this theoretical formula. The results indicate that the pressure gradients significantly increase with propagation distance. When the propagation distance is close to the critical length, the pressure gradients show an abrupt change. With the same propagation distance, the pressure gradients increase along with the amplitude of the initial compression wave and decrease with the length of wavefront. When the propagation distance does not exceed the critical length, the relative error between the theoretical formula and numerical calculation is less than 6%, and the numerical results agrees well with measurements reported in literature.