The Study On Optimization Of Middle Vent Shaft In Subway Tunnel Ventilation System

With its great achievements in the field of economic development, our country has become the second biggest economic community in the world. Meanwhile the city is expanding and the population is increasing, which bring huge pressure to the transportation of the city. Subway is the best choice to relieve the pressure of the city’s transportation, and many big cities around the world have built the underground railway. As it is rapid, punctual and comfortable, metro has earned the citizen’s trust and has become the best way to travel for the citizens.Since the first subway that was built in1863running, the development of underground railway lasted for150years and the related technologies of metro construction had made a further promotion. With the progress of world’s technology, the ventilation of metro has obtained great development. The modern subway has much higher speed, much bigger density of departure and much more passengers, and the urban metro has higher requirement in the ventilation, so it is the preliminary task of the engineer to design the ventilation system which is safe, economic and suitable.All the7th line of Chengdu metro uses the system of platform shed door, which causes the tunnel absolutely apart from the station platform. In the meantime that the trackway exhaust system is set in the station tunnel and all the stations adopt the single-piston vent shaft. That is to say, only one vent shaft is assembled at the end of the exit of the station. According to the primary design documents of7th line of Chengdu metro, the paper sets up the metro’s geometric model which is used in the SES program and also does the simulation analysis of the biggest transportation capacity in the7th line. The simulation mainly analyzes the adoption of the middle vent shaft which is located in the running tunnel between the station of LiuLichang and KeHua Road. Meanwhile it also analyzes the influence of middle vent shaft on the nearby piston vent shaft, the wall surface temperature and the air temperature in the tunnel. Finally it takes temperature as the estimated index, analyzes the advantages and disadvantages of the middle vent shaft and makes the theoretic accounts for the design.By the paper’s studying, it indicates that the middle vent shaft has two important influences on the tunnel’s wall and air temperature:first, after the middle vent shaft is assembled, the temperature of running tunnel will slightly promote and the temperature of the tunnel which is located in the station will promote in a large scale; the temperature of the tunnel which is behind of the station will decrease, and the farer from the station, the smaller scale of temperature’s decreasing. In addition, the assembled of middle vent shaft will decrease the air’s quantity of the running tunnel that the middle vent shaft locates, but it has little influence over the nearby running tunnel. The comprehensive analysis is that the middle vent shaft which is in the running tunnel between the station of LiuLichang and KeHua Road could be canceled by the index of temperature.