Natural Ventilation of a High-Altitude Super-Long Railway Tunnel

Most railway tunnels meet the requirement of operation ventilation by the piston effect of trains, but studies of operation ventilation for super-long railway tunnels at high altitude are relatively infrequent. The new Guanjiao tunnel, which is located on the Xining-Golmud railway, is relied on in conducting research on the natural ventilation of super-long railway tunnels during operations at high altitudes. Based on:(1) the meteorological data of the Guanjiao tunnel region, and according to the calculation principles of fluid dynamics and constant flow theory and (2) getting the velocity of the natural wind and piston wind of the train, combined with the traffic forecast and traffic organizational planning, the natural wind exchange frequency of the Guanjiao tunnel is finally determined. This paper shows that the wind velocity in the Guanjiao tunnel is between 1.5 to 4 m/s and the natural wind direction is mainly from Golmud to Xining. The average piston wind velocity in tunnel I is 8.38 m/s and 8.1 m/s in tunnel II. Once inside the tunnel, to make the air exchange, theoretically it needs 5.3 trains to go through tunnel I and 5.5 trains through tunnel II.