Research on new ventilation technology for long tunnel construction based on air curtain dust suppression and dust diffusion law

Ventilation during the construction of long tunnels represents a core factor impacting the safety of tunnel engineering projects. Taking Yuanbao Tunnel as the case study, this paper proposed a novel ventilation approach utilizing air curtain machines. By establishing a theoretical model of the barrier efficiency of air curtain machines installed on both sides of the tunnel, the optimal jet parameter (c) of the air curtain machine was determined. A mathematical model was then constructed to describe the diffusion of explosive dust concentration at the tunnel face, aiming to reveal the dynamic distribution law of dust within the tunnel. Additionally, a three-dimensional numerical simulation method was employed to conduct a comparative analysis of the dust removal efficiency between traditional forced ventilation and the new air curtain machine ventilation at varying tunnel depths. Research results reveal that the air curtain barrier efficiency reaches 100% and optimal energy performance is achieved under the working condition with jet thickness of 0.1 m and jet velocity of no less than 10.3 times the polluted air velocity; the ventilation system efficiency of the novel air curtain machine is significantly higher than that of the traditional forced ventilation, and its performance is less susceptible to tunnel depth. Within 15 min of activation, the system reduces dust concentration in the operation area to 2 mg/m3, which is 50% of the traditional forced ventilation time. Leveraging air curtain barrier technology, this mode offers advantages such as good cleaning effect, high ventilation efficiency, and low energy consumption, providing a novel method reference for the ventilation design in long tunnel construction.