Research on the mechanism of the influence of geothermal distribution on pressure fluctuation in the middle of the tunnel

Due to the influence of geological conditions, various complex environments exist in high-speed railway tunnels in some areas. Many tunnels along the plateau railway have high geothermal extreme environment, which leads to drastic changes in the temperature distribution along the length of the tunnel. When trains are driven into it at high speed will produce relatively complex aerodynamic effects. In this paper, the mechanism of pressure wave propagation and variation under different temperature conditions is investigated by using composite curves to simulate pressure waves at the tunnel entrance. The tunnel area is chosen for the study because the train isn’t involved in the calculations and the larger air domains at both ends of the tunnel has no significant effect on the flow field. When the tunnel geothermal zone is located in the middle and front section of the tunnel (80-160m), the amplitude of pressure fluctuation under geothermal conditions appears to increase in a certain region, and the mechanism of pressure wave change in this geothermal region is studied by different composite curves simulation methods, and the law of pressure fluctuation change when high geothermal exists in the middle and front section of the tunnel is obtained. The simulation method provides a research programme for further exploring the mechanism of pressure wave variation under different geothermal distribution conditions.