Study Of Dust Diffusion Law In A Construction Tunnel Under Far-Pressing-Near-Absorption Ventilation

A large amount of dust will be generated during the construction of highway tunnels which causing dust pollution in the tunnel space.It will cause great harm to the human body when a lot of dust is sucked into the body and the pneumoconiosis will occur.if severe cases which is currently an incurable occupational disease.At the same time,the high concentration of dust environment not only reduces the production efficiency of the enterprise but also causes various safety production problems.The Far-Pressing-Near-Absorption ventilation is used as an efficient ventilation and dust removal measure in tunnel construction.Therefore,it is very important to study the law of dust movement during the construction of highway tunnels under Far-Pressing-Near-Absorption ventilation.The research object of this paper is the Nanshan Highway Tunnel.A model of the tunnel is established under Far-Pressing-Near-Absorption ventilation in using ICEM and Fluent software on the basis of computational fluid mechanics and theory of dust transport.And set the meshing and related parameters of the numerical model.It is obtained about the distribution of flow field and dust distribution in the tunnel under various influencing factors through numerical simulation,and the relative position are obtained which is the distance between the pressure and suction duct from the working surface and the influence of the pressure and suction ratio on the dust movement.Finally,the relevant conclusions are drawn by combining the similarity theory to verify the accuracy of the simulated data in the field test.(1)There have a great influence on the distribution of the dust concentration in the tunnel which contain the distance between the pressing and the absorption duct from the working face.It is obtained after analysis of the numerical simulation results that the reasonable relative position of pressure and suction duct from the working surface:the distance of the pressure duct from the working surface L_y=16m,the distance of the suction duct from the working surface L_c=4m.The working surface is exactly at the edge of the effective range of the pressure duct and the edge of the effective suction of suction duct under this ventilation parameter.The air flow emitted by the pressure duct reaches the working surface and carries high-concentration dust into the negative pressure area of the suction duct.The dust coverage area is less than 5m from the working surface with a concentration of more than 10mg/m~3,and The effect of ventilation and dust removal is the best.(2)When the position of the air duct is fixed,and the ratio of the pressure and suction duct ratio r<1,a large vortex will be generated between the pressure and the air extraction cylinder which resulting in the accumulation of dust.When r>1,the flow field in the tunnel moves towards the working surface as a whole.The negative pressure area is not enough to capture high-speed dust of the air inlet of the pressure duct,and the diffusion distance of the dust exceeds 30 meters.The ratio of pressure and suction duct air volume is appropriate when r=1.2.The dust is effectively controlled in the vicinity of the working surface,and the effect of the dust control and remove is maximized under the Far-Pressing-Near-Absorption ventilation.(3)Based on the similarity theory of fluid flow,it find that the reasonable ventilation parameters of the Far-Pressing-Near-Absorption in the actual construction process of the Nanshan tunnel.The accuracy of the numerical simulation results was verified by comparing the agreement between the measured and simulated values while an experiment was established on the spot.The comparison shows that the two data are basically the same,which proves that it is credible that the reasonable ventilation parameters obtained by the numerical simulation and the system of long-pressure short-draft ventilation of Nanshan Highway Tunnel.(4)In the construction of the Nanshan Highway Tunnel,the same reasonable ventilation parameters is obtained similarly from the actual measurement and numerical simulation.The appropriate distance about Nanshan Highway Tunnel between the pressing dust from the working face is 16m.The appropriate distance between the absorption dust from the working face is 4m.The dust concentration in the tunnel is lower than the standard allowable concentration,which provides theoretical and data support for the ventilation design during the tunnel construction.The above research It provides theoretical and data support for the ventilation design during the construction of Nanshan Highway Tunnel with the above research which has positive significance for the development of reasonable ventilation and dust removal measures for highway tunnel construction.Figure[33]table[3]reference[59]...