Study On Classification Index And Method Of Gas Work Area In Highway Tunnel

The classification standard of gas working area is the most important and the most important standard for the prevention and control of gas in tunnels.The construction organization plan of ventilation,monitoring,electrical equipment,operating machinery and blasting shall be determined according to the classification of the working area in gas tunnel construction,which directly affects project investment and construction efficiency.At present,there are flaws in the theoretical calculation method of the classification index of the gas work area,which makes the classification standard of the gas work area of the highway tunnel may be higher or lower,which directly affects the safety of the gas prevention and control in the tunnel work area,which causes the gas prevention and control management standards to not match the actual conditions of the work area.This leads to frequent construction safety hazards and serious waste of construction funds.In this paper,the Tongzi Tunnel on the Zhongzun Double Line is used as a supporting project.First,through theoretical analysis,the calculation parameters of the classification index of the tunnel gas area are studied.Then,Fluent is used to establish a three-dimensional simulation model of tunnel ventilation to study the distribution of ventilation air flow and gas in time and space.Finally,the on-site measurement method of gas concentration and wind speed is optimized by combining on-site measurement and analysis.The main research work and results are as follows:1)According to theoretical analysis,it is proposed that the unbalanced coefficientα of gas emission in traffic tunnels,taking into account the turbulence of tunnel ventilation and the unbalanced gas diffusion,as well as the deviations from the actual measurement of gas concentration and wind speed.The safety factors K1 and K2 related to gas concentration are revised to the calculation method of the absolute gas emission volume,the classification index of the tunnel gas working area.2)Through theoretical analysis,it is concluded that the airflow and gas distribution have temporal and spatial characteristics,combined with the actual situation of the project,and a ventilation model of tunnel 200 m away from the excavation face is established by using Fluent.The tunnel ventilation flow field and gas distribution law are analyzed from two dimensions of time and space,and it is concluded that the wind speed and gas concentration at 120 m away from the tunnel face tend to be stable.3)Analyzing the uneven distribution of gas and wind flow along the space of the tunnel after the ventilation is stabilized by Fluent,the safety factors reflecting the unbalanced spatial distribution of wind speed and gas concentration along the space of the tunnel under stable conditions are obtained as 1.20 respectively.And 1.10,thus giving the multi-lane tunnel gas area suggested value of classification index.4)On the basis of the above-mentioned gas temporal and spatial distribution research,combined with on-site gas monitoring,a comprehensive analysis puts forward the test location of gas concentration in the calculation of absolute gas emission in the gas working area: 30 minutes after the tunnel is vented and ventilated,the gas is carried out at a distance of 120 m from the tunnel face.Determination.5)Based on the above-mentioned research on the temporal and spatial distribution of ventilation wind speed,combined with on-site wind speed monitoring,the analysis and analysis puts forward the test location of the ventilation wind speed in the calculation of absolute gas emission in the gas work area: 120 m away from the tunnel face;at the same time,Fluent is used to lay out the wind speed measurement surface The wind speed is calculated at 29 measuring points,and the wind speed measuring method is optimized by MATLAB,and an optimization suggestion is proposed to reduce the wind speed measuring points from 29 to 5.This paper studies the recommended values of the classification index of the gas working area,the on-site measurement method of gas concentration and wind speed,etc,which provides technical support for the reasonable determination of the classification standard of the gas tunnel and gas working area,and is of great significance to the safety and economy of the gas tunnel construction.