Parameter analysis of jet tunnel ventilation for long distance construction tunnels at high altitude

With the advancement of railroad tunnel construction work in the high-altitude areas of southwest China, the jet tunnel ventilation technology is used more frequently in long-distance tunnel. In this paper, a tunnel under construction at an altitude of 3500m in the Sichuan-Tibet Railway was taken as the background, and the key parameters of jet tunnel ventilation technology were simulated numerically and analyzed by combining the response surface method, while taking the altitude factor into consideration. The obtained results demonstrate that: Two jet fans with the air volume of 2250 m3/min could boost the tunnel air pressure by 12.85 Pa, making the air flow smoother in the tunnel. When the jet fan interval was 350m and the air volume reached 2250 m3/min, the polluted air circulation disappeared. When fans were installed at the effective spacing, wind speed and turbulence intensity were stable and fan comprehensive influence coefficient k was the highest on the center control line, which the ventilation effect was the best. The effective spacing under different air-volume conditions was analyzed to fit the effective spacing as a function of fan air volume change: y = 0.00560214x1.71734. Finally, the key parameters of jet tunnel ventilation technology were optimized by response surface method. [Display omitted] •Simulation of ventilation effect considering high altitude factors.•Analysis of longitudinal ventilation parameters in long-distance construction tunnels.•Optimal fan air volume analysis by fluid movement conditions in the tunnel.•Function for fitting the effective spacing of the jet fans by the variation of velocity, turbulence intensity and lifting-pressure of the flow field.•Optimal design of ventilation parameters by response surface method.