Numerical Simulation On Construction Ventilation Of Single Head Tunnel

The status quo of China's construction about the ventilation can not be optimistic. With the accelerating rate of tunneling and the increasing length of the tunnel,the problem of ventilation has become a "bottleneck." In terms of the safety and the schedule of the construction,or from the economic point of view, the scattered smoke and ventilation problems in the long and large single head tunnel construction, are realistic problems placed before engineering design personnel, project construction and project management personnel. In this paper, according to the Yalong River 1 # highway tunnel,the author try to do the basic theoretical calculations and numerical analysis about single head tunnel construction under the forced ventilation conditions. The main conclusions and findings are as follows:1) Summarize several major applications in the tunnel ventilation construction at the present stage, the calculation theory required in the air flow for the tunnel longitudinal ventilation, and the layout in all aspects of the ventilation. According to the characteristics of single head tunnel construction,combined with the summarized theory,the author makes the calculation of the required air volume, and elaborates the exposition of the ventilation system, the daily management and maintenance measures, and the safety measures in a more systematic way.2)In terms of single head tunnel construction, the longer the distance, the greater the degree of difficulty. The author makes the numerical analysis about the tunnel flow field and pollutant concentration under the forced ventilation conditions. This numerical analysis provides a reasonable theoretical basis for the security of the tunnel construction, changes the rough and empirical estimate ways in the past.Therefore, it has practical significance in avoiding the uncertainty factors of the construction, ensuring the safety of the normal production,improving labor productivity, and promoting the efficient conduct construction progress.3) Achieve the numerical simulation of the wind structure in a three-dimensional space inside the tunnel and the spread of harmful gas concentrations through large-scale finite element software ADINA. Single head tunnel forced ventilation belongs to the limited wall jet fluicids. The working face area makes the formation of the jet airflow area, back area and the turbulent area. The simulation results show that, due to the concentration proliferation effects of eddy current, there are high concentrations of harmful gases in the vortex center, and the eddy current has obvious residual effect on the proliferation. The concentration of harmful gases within the working range has a negative index of changes in ventilation time, and has been verified by the formula.4) In order to speed up the speed of reducing emissions of harmful gases under the forced ventilation conditions,the author makes the the numerical simulation of the jet fans positions and the distances between fans. The calculation results show that, under the forced ventilation conditions, the tunnel jet fans placed in a central location of the recirculation zone can significantly speed up the pace of harmful gas emission reduction; The jet fans working distance is about 120m,which can be used as a reference when we place the tunnel jet fans, thus reducing the blindness during the installation process.