Abstract: The calculation method of the internal and external pressure of the vehicle passing through the long and large tunnels with the altitude difference between the tunnel entrance and exit in the western mountainous areas in China is of great significance. As a result, the theoretical analysis method is used to modify the singledimensional calculation model of the internal and external pressure of the vehicle in the plain area to make it suitable for the tunnel with a difference in elevation between the entrance and exit. The feasibility of the calculation method is verified by comparing with the measured data in the train of the QinghaiTibet Railway, and the calculation method is applied to actual design. The main conclusions are drawn as follows: (1) According to the variation law of the atmospheric pressure with the altitude, the calculation of the internal and external pressure of a train in an altitude difference tunnel can be realized through adjusting the reference pressure, temperature, density and sound speed corresponding to each time in the original calculation model. (2) The calculation results show that the clearance area of the singletrack tunnel of a highaltitude mountain rail transit is 19.5 m2, that of the doubletrack tunnel is 41.5 m2, and the minimum requirement of the dynamic sealing index of the train is 2.5 s.

Key words: cold and highaltitude areas, railway tunnel, entrance and exit, elevation difference, internal and external pressure of train, calculation method