Effect of press-in ventilation technology on pollutant transport in a railway tunnel under construction

Press-in ventilation technology is an important method to ensure the effective control of pollutants concentration and production safety during the drilling and blasting construction of railway tunnels. In this work, carbon monoxide was employed as the tracer gas used in simulating the characteristics of pollutant transport. Influences of blocking ratio and distance between air vent and working face on ventilation performance were investigated in a subscale tunnel model. Moreover, the effects of tunnel geometry, including included angle between inclined shaft and construction section, slope of inclined shaft, tunneling length, and air vent position, on fan energy consumption were discussed. Experimental results show that press-in ventilation effectiveness gradually deteriorates with the increase of blocking ratio and the distance between air vent and working face. Fan energy consumption is strongly dependent on included angle between inclined shaft and construction section, tunneling length and air vent position, in which energy consumption varies linearly with included angle and tunneling length and increases exponentially with the distance between air vent and working face. Finally, a new empirical expression was proposed to calculate the required air supply volume. The results can enrich the researches of pollutant dispersion using press-in ventilation technology during tunnel construction, and provide a significant reference for the optimization design of press-in ventilation.