Mixed Ventilation System For Tunnel Small Air Duct Construction

With the continuous advancement of transportation construction in China,the construction of highway tunnels has entered the stage of tackling difficulties,and the number of high-elevation and extra-long tunnels are also increasing.Tunnel construction ventilation affects the tunnel construction cycle and is related to the physical and mental health of the construction personnel.High-altitude super-long tunnels are different from ordinary highway tunnels.The problems of tunnel construction ventilation are constantly emerging.Faced with the problems of insufficient air supply,long ventilation distance,serious air duct leakage,difficult fan layout,and large occupation of tunnel construction space,how to ensure the safety of the construction period ventilation design has positive practical significance for promoting the construction of highway tunnels.Therefore,this article relies on the Xinjiang East Tianshan Super Long Highway Tunnel to develop a new type of small duct construction ventilation system,the main research contents are as follows:(1)A new type of small duct mixed construction ventilation system is proposed,which derives and calculates the air demand,the pressure in the pipeline and the pressure at the pressure reducing valve.Combined with the reliance on the project,the tunnel construction phases are divided.According to the wind demand of the construction face and the second lining,four small air duct hybrid tunnel ventilation modes are designed.Fans are compared for model selection.(2)The typical ventilation conditions of the construction of the four palms are selected,and the computational fluid dynamics software FLUENT is used to simulate and verify the rationality of te new construction ventilation system’s supply.Simultaneously,numerically simulate the ventilation effect of 10 typical working conditions,analyze the construction airflow field characteristics and velocity distribution,and obtain the relationship between the wind speed and wind pressure in the pipeline when the air demand is constant and changes.(3)Developed a small duct mixed ventilation construction control system,designed various stages of construction ventilation control plans,clarified the system functions,built a system framework,and completed the small duct mixed ventilation system control design.In summary,the small-pipe mixed construction ventilation system can solve theproblems of high air leakage rate,insufficient air supply,and large tunnel construction space in the construction of extra-long tunnel ventilation ducts.The development of ventilation technology has important theoretical significance and application value.