Study on the characteristics of compression wave propagating through high-speed railway tunnel with side branches

When a high-speed train enters into the tunnel, the compression wave will be generated. When the compression wave arrives at the tunnel exit, it will be radiated as the impulse wave to the surrounding environment, and when its energy is large enough, the micro-pressure wave will be produced with its magnitude proportional to the changing rate of the exiting compression wave. Based on the method of characteristics for one-dimensional unsteady compressible non-isentropic flow model and the relation of the pressures before and after constructing side branches derived from the acoustics theory, the computational method and program for the propagation of compression waves in the slab tunnel with side branches are proposed. It is found that the results obtained in the present study have good agreement with the existing results, validating the effectiveness of the proposed method. By using the initial compression wave of the Japanese Shinkansen tunnel, the characteristics of the compression wave propagating in tunnel with side branches are studied for the train speed of 200~400 km/h and the tunnel length of 0~24 km. The effects of the number, the location and the spacing of the side branches on the pressure and the pressure changing rate of the exiting compression wave are observed. Furthermore, the influences of non-linearity and friction on the propagating characteristics of the compression wave are achieved, and the worst tunnel lengths for different train speed are then determined. ©, 2015, Editorial Office of China Civil Engineering Journal. All right reserved.