Study On CO Distribution In Single Inclined Shaft Construction Area Of Extra Long Highway Tunnel In Alpine Region

The construction environment of super long highway tunnel is bad.The main pollutant CO produced in the construction process seriously affects the safety of construction personnel.For extra long tunnels in alpine regions,the complex working conditions of single inclined shaft and multiple working faces are often used.It is very important to understand and master the distribution of CO.This paper takes a super long highway tunnel through Tianshan Mountain as the engineering background.Use network ventilation and computational fluid dynamics theory analysis.Based on the data collected in the field,the ventilation dynamic parameters,chamber parameters,blasting smoke parameters and air supply volume after altitude correction are calculated.Using ANSYS computational fluid dynamics simulation software,a 1:1 tunnel mesh model is established.K-epsilon turbulence model and component transport model are used.Under the typical working conditions in winter and summer,the construction is divided into single working face and multi working face,under 30 groups of boundary conditions.The co distribution in the construction environment of super long highway tunnel with single inclined shaft in alpine region is studied by numerical simulation.The results are as follows(1)It is found that CO adheres to the wall near the working face at high altitude.The adhesion of CO is affected by temperature.Below 20℃ the higher the temperature is,the more obvious the co adheres to the wall.In addition,it is easy to produce eddy current near the working face.It is easy to cause co accumulation and retention.(2)It is found that in the high altitude environment,when multiple working faces are constructed at the same time,the CO in the inclined shaft will appear layered distribution.And below 20℃,the higher the temperature,the more obvious the co stratification.The average concentration of CO is the lowest at the corner of inclined shaft.According to the concentration of CO,it can be divided into low concentration area,medium concentration area and high concentration area.In addition,the wind speed range corresponding to CO concentration was obtained(3)The air flow field near the working face and the bend of inclined shaft is studied.Based on the theory of air flow field,the cause of eddy current near the working face and co staying at the bend of inclined shaft are further explained.(4)According to the distribution law of CO,the ventilation scheme of single inclined shaft super long highway tunnel in alpine area is optimized.In order to dilute the co near the working face,jet fans are arranged on the tunnel side wall near the working face.In order to reduce the eddy current near the working face,the distance between the nozzle of the air duct laid on the wall and the working face is adjusted to 15m.In order to dilute and remove the trapped CO at the bend of inclined shaft and reduce the concentration dispersion of CO stratification,jet fans are arranged at the bend of inclined shaft.The research conclusion can provide reference for the construction ventilation design of extra long tunnel in alpine region.