Study On High-Intensive Construction Ventilation Technology Of Large Section And Long Tunnel

With China’s tunnel construction technology has entered the level of developed countries, while the status quo of ventilation technology for tunnel construction is relatively backward, the strong explration and further research need to be done. On the basis of’large scale complex conditions of super-long tunnels group construction collaborative ventilation technology application research’, this paper analyed Jinping II Hydropower Station diversion tunnels group complex ventilation environment and the variable construction organization schemes, and comprehensive studied overall ventilation scheme and local ventilation layout optimization of high pollution period’s tunnel trunk by making use of theoretical analysis, numerical simulation and field test. The main contents and conclusions are as follows:1,With analysis of hygienic standards of China’s existing tunnel construction norms and several ventilation methods of tunnel construction, and been combining with Jinping project’reality, stadied for several period ventilation with difficult problem, especially the period of height polluted tunnel trunk, chose which path for fresh air to come in and used air to exhaust from the entrance of tunnel or nearby tunnels supplying sufficient fresh airs, analyed the ventilation scheme, to determine the ventilation scheme is reasonable and effective. A theoretical analysis of ventilation scheme and ventilation system parameters, got the optimal parameters, and selected fans according to the calculation of parameters. And for the high polluted section of tunnel trunk, it must adopt measures to increase ventilation intensity and purify dust, as well as the more jet fans arrangement can be enough to overcome problems of tunnel’s worse air figure.2, Established RNG κ-ε turbulent model by using Fluent software, numerically simulated4diversion tunnel’s region, working face, in high pollution period. The results of4sets of models show that when adopted the high-intensive ventilation scheme, ventilation effect in working face regions within100m could achieve safety standards of pollutants within30minutes, ensured the safety of construction workers. And the ventilation simulation results obtained the following conclusions:(1) which position the ventiduct fixs up, top or side, has a great influence on working face regions’ pollution emission effect. The tunnel’s air condition is better and the formation of tunnel airflow field is more reasonable, when the ventiduct was fixed up in the top in the section of Jinping project which tunnel section’s transverse width is greater than the vertical height.(2) The distance between ventiduct outlet and tunnels working face will influence tunnel ventilation effect.The closer ventiduct outlet with the working face, the better ventilation effect will be, but must pay attention to the safe distance about them.(3) when the ventiducts symmetrically arranged on both sides of the tunnel’s wall could reduce bigger eddy current than the unilateral arrangement, and improve the working face ventilation effect to a certain extent, but the pollution emission effect of tunnel trunk had not been significantly improved.3,In view of the4diversion tunnel high pollution period, arranged monitoring points about the ventilation parameters and air quality in tunnel’s working face and its trunk, monitored at different time and space. Test results show that:(1) when4diversion tunnel adopted high-intensive ventilation scheme, ventilation parameters of working face and tunnel trunk both could meet construction ventilation’s requirements as well as personnel health needs.(2) The concentrations of harmful gases, included CO, SO2, CO2, NO2and dust, were all higher than the standards in the time of just after blasting and transporting,but with the continuous action of fans the air condition gradually restored to the specification requirements. The high-intensive ventilation scheme this paper studied effectively solved the construction status of high pollution, ensure the construction of the tunnel project and the staffs health successfully.