Digital Simulation Of Discharging Blasted Fume And Dust For Large Underground Chamber During Construction

Abstract:During construction of large underground chambers in China, the main method of excavation is blasting. Bblasting produces plenty of gas fume and dust. After blasting, slag transport car such as vehicles work can produce automobile exhaust and air-borne dust. Gas fume, dust and automobile exhaust are harmful substances, if our body inhaled can damage health, and cause occupational disease, etc. So the ventilation after bursting of the chambers is necessary. Ventilation can eliminate gas fume, dust and automobile tail gas. At the same time to provide required airflow for personnel breathing and machine operation is important significance to safeguard workers’health.On the basis of collecting and reading a lot of domestic and foreign literature, this paper analyzes the basic theory of designing the ventilation systems for large underground camber. Combined with the design method of numerical experimental, the software of FLUENT was used to simulate the process of discharging gas fume, dust and vehicle running. By analyzing the simulation results and studying the impact of various factors on the efficiency of ventilation, there are some suggestions for designing ventilation. The main contents and conclusions are as follows:(1) Sum up the research status and major research methods of excavation ventilation for large underground camber domestic and foreign. Use the fundamental design theory and ventilation safety standards of large underground chamber during construction to analyze the major sources of pollution during construction. All of the above provide theoretical support for numerical experiments.(2) Analysis the equations and principle, which were based on different models. Selecting different experiments corresponding model according to the needs, and setting the boundary conditions and initial conditions based on engineering examples, which to lay the foundation for the experiments.(3) FLUENT software was used to simulate ventilation in different cross sectional area and lengths chamber. In this paper, by analyzing the morphology of ventilation airflow in chamber, the chamber area is divided into air flow jet area, turbulent zone, recirculation zone and advection region. (4) This article statistic the time and required air volume for eliminating the blasting gas fume in different cross sectional area and lengths, use the method of formula correction and static analysis to analyse the required air volume, and respectively drawing a formula to calculate the required air volume for eliminating the blasting gas fume. The method of formula correction is more accurate, and the method of static analysis is relatively simple.(5) In this paper, the cross sectional area and the air quantity in ventilation tube, respectively being the variable to design of experiment for ventilation dust simulation. Draw a conclusion that dust settling to the ground under gravity, and mainly in the3m from the ground, dust in the horizontal plane is mainly distributed in the turbulent region and the recirculation zone, rarely distributed in the air flow jet area.(6) When the dust of the type and size of blasting parameters determined, the greater impact on the spread of dust are cross sectional area and the air quantity in ventilation tube. After blasting, the cross sectional area is directly related to the maximum concentration of dust. Both the diffusion rate of dust and the time to exclude dust have linear correlation with the cross sectional area and the air quantity in ventilation tube.(7) Through calculate the automobile exhaust concentration of slag transport car in the chamber, the article draw the conclusion that car exhaust has little influence on the concentration of harmful gas and it can be ignored. The moving vehicle in the chamber has a greater influence on the morphology of ventilation airflow, especially the two car crossing or the distance of the two cars is small, it will form the backflow whirlpool and affect the ventilation effect.