Traditional tunnel construction ventilation is atmospheric pressure ventilation, long-distance tunnel construction ventilation duct is larger, limited by the construction space, the amount of air intake and exhaust is limited. To change this situation, the ventilation system of small air duct mixed supercharged tunnel is proposed. Through the analysis of the air demand of typical drilling and blasting method, the ventilation system of small air duct mixed tunnel construction is designed. The multi-outlet pipeline model is established by numerical simulation, and then the pressure and temperature losses in the transmission of compressed gas in the system pipeline are studied, and the wind pressure control parameters of the key operation of the system are calibrated. The ventilation system was tested by the ventilation example of the Dongtianshan tunnel, and the validity of the wind pressure control parameters was verified, which provided a scientific basis for the optimal design and application of the construction ventilation system. Key words：Air duct ； Compressible flow ；Numerical simulation；Ventilation system;

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