| In the Medium and Long-Term Railway Network Plan(2016-2025)approved by the State Council,the railway construction in the western region has been strengthened.There are more mountains in the western region.With the rapid construction of the railway network in the western region,the number of super long tunnels will gradually increase.The high altitude,low pressure,and cold climate in the western region cause certain differences between the ventilation of the tunnel construction in the high altitude area and the plain area,especially the characteristics of the airflow field and the diffusion and migration of CO in the tunnel.Therefore,the ventilation of the tunnel construction has become an urgent problem to be solved.Based on the urgent need for research on construction ventilation for high altitude and super long railway tunnels,using the numerical simulation software Fluent and selecting the RNG k-?turbulence model,this paper uses a finite-rate model to simulate the coupling of CO and air in the tunnel based on the construction of high-altitude single-hole single-track super long railway tunnels(DangJin Mountain tunnel).Considering the influence of atmospheric pressure and buoyancy,the distribution and diffusion law of gun smoke produced blasting during ventilation exhaustion in high-altitude super long railway tunnel during construction is studied and analyzed.At the same time,dynamic grid technology is applied to simulate and analyze the distribution and distribution of exhaust gas(CO)along the outflow during the outflow process.The main research work and research results are:(1)Perform multiple on-site measurements,monitor various parameters such as CO,NO_X,TSP concentration and ventilation speed on different working surfaces in the tunnel,and evaluate the tunnel environment based on the collected data.According to the relevant regulations,the tunnel ventilation volume is theoretically calculated,and the ventilation volume of high altitude tunnels is revised on the basis of the revised theory.(2)Taking the first stage ventilation design as an example,a full-scale 3D simulation model is established to simulate and study the movement and diffusion law of gun smoke in the tunnel under three different blasting conditions:single blasting,positive hole and flat blasting at the same hole(flat guide).The simulation results show that,compared with the wind effect before blasting,considering the influence of wind current before blasting,the diffusion and dilution of CO in the tunnel is more obvious,and the concentration peak declines faster;the attenuation of CO concentration in the tunnel conforms to the e-index law.(3)Establishing a three-dimensional transport model of the slag-out car,the diffusion distribution law of the exhaust along the slag-out car is analyzed and studied.The simulation results show that the greater the driving speed of the slag-out car,the greater the pressure and speed at the front and rear end of the car,the greater the gap speed of the piston air ring,the larger the area affected by the eddy currents at the tail,and the stronger the dilution and diffusion of CO,the lower the CO concentration at the rear end.During the driving process of the slag-out car,the CO diffusion process conforms to the one-dimensional diffusion basic solution of the instantaneous point source,that is,the CO concentration decays according to the e-index.The article systematically analyzes the distribution and diffusion of pollutants during tunnel construction,which providing reference for the construction organization and ventilation system changes in high altitude tunnels. |
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