Study On Ventilation System For Asphalt Pavement Construction Of Extra-long Tunnel

During the asphalt pavement of extra-long tunnel,the performance of ventilation system affects the construction environment directly.Therefore,the efficiency of tunnel ventilation system is a key point restricting the construction.At present,the existing research on tunnel ventilation mainly focuses on operative ventilation,and the study on construction ventilation is relatively scarce.This paper analyzes the environmental factors of the ventilation system in the construction of asphalt pavement in extra-long tunnel,and studies its ventilation mode,ventilation equipment and method of controlling wind volume.The pollutants in paving are generated from high temperature asphalt mixture and construction machinery exhaust gas.According to the test results on tunnel construction site and laboratory test data,it is determined that the main pollutants are CO,NO_X,asphalt smoke,benzene soluble matter and benzo[a]pyrene.The temperature of asphalt mixture has great influence on the emission of harmful substances,when using warm asphalt mixture on construction,the emission of harmful substances can be significantly reduced.By analyzing the factors influencing the effective ventilation distance of jet fan in tunnel,the mathematical model of effective ventilation distance is established.The effective ventilation distance of SDS-12.5 jet fan is 245.25m in MCS tunnel according to the calculation;based on the structural characteristics of the extra-long tunnel and referring to the operative ventilation mode of the extra-long tunnel,the existing construction ventilation mode is optimized,which effectively improves the construction environment of the tunnel.By FLUENT software,the parallel operation condition of axial fans in tunnel ventilation system is simulated and analyzed,which proposes to use stall factor to evaluate the possibility of stall occurring under different wind pressure ratio.The simulation results show that the larger the wind pressure ratio,the smaller the stall factor and the more stable the fan operation,and there is an optimal installation position to keep the fan running smoothly;the characteristic curves of general axial fan and diesel engine are analyzed jointly,which determines an stable and energy-saving method of match the power between axial flow fan and diesel engine.Based on the fuzzy control theory,the ventilation fuzzy control system of asphalt construction in extra-long tunnel is established,and the wind volume of the ventilation system is adjusted automatically along with the pollutant concentration.The system is simulated by using the Simulink module.The simulation results show that the system is stable and rapid relatively.In this paper,the ventilation system of asphalt pavement in extra-long tunnel is studied theoretically,and the simulation test is carried out relying on MCS extra-long tunnel project.The research results provide reference for the practical tunnel engineering application.