Study on a control method of ventilation dead zone in gas tunnel construction with multiple working faces
To explore the best way to control the ventilation dead zone in the gas tunnel,this paper takes the Yangzong Tunnel as the engineering support and uses the method of combining numerical simulation and field to first study the optimal layout of the air duct in the press-in ventilation scheme,determine the optimal distance from the outlet of the air duct to the face and the optimal diameter of the air duct,and determine the optimal layout distance and spacing distance of the jet fan on this basis.Furthermore,the optimal layout scheme of jet fans for controlling the ventilation dead zone in the multi-working face ventilation system of the gas tunnel is explored.The research results show that:in the press-in ventilation scheme meeting the minimum required air volume,different duct diameters,and the distance between the duct outlet and the tunnel face not only leads to different gas dilution effects in the tunnel but also leads to large changes in the volume of the ventilation dead zone.To better control the ventilation dead zone and ensure the best gas dilution effect,the duct diameter should not be too large and the duct outlet should not be too far from the tunnel face.With the increase of tunnel excavation distance,a fixed range of non-ventilated dead zone will be formed in front of the tunnel.The dead zone range is a certain distance in front of the cross passage.Considering the economy of the construction scheme,jet fans need to be arranged in the tunnel to ensure construction safety;The arrangement of jet fans can effectively eliminate the dead zone of ventilation,but its effective range is limited.When the tunnel distance is too long,jet fans should be arranged in sequence.In this case,the effective range of jet fans is 150 m from the tunnel face.
safety engineeringgas tunnelventilation dead zonenumerical simulationgas distribution