Study On Numerical Simulation Of Blasting Fume Migration Law And Control In Tunnel With Drilling And Blasting Construction

In the blasting stage of tunnel construction by drilling and blasting method,a lot of smoke and dust will be produced and causes the pollution of tunnel space,which contains a lot of poisonous and harmful gas and dust.The dust not only affects the construction period,but also seriously threatens the safety and health of tunnel workers.Therefore,it plays an important role in ensuring the safety of construction personnel to master the spatial distribution and migration rule of blasting smoke in the tunnel and determine the time when the smoke reduces to the allowable concentration.At present,there are few research achievements on the migration law of toxic and harmful gas in tunnel blasting smoke.In this paper,combined with the actual site situation of Pingdingshan tunnel in Henan province,FLUENT software was used to simulate and analyze the migration rule of CO and dust in the smoke and dust,so as to obtain the distribution rule of air field in the tunnel and the change rule of CO concentration and dust concentration.According to the simulation results,the influence on the air flow and smoke movement in tunnels of the distance from the outlet of the air duct to the tunnel surface,the wind speed at the inlet of the air duct,add dust collector and the location of the dust collector is further analyzed.And the time when CO concentration and dust concentration reach the permitted concentration is determined from the variation of soot concentration with time.The results show that:(1)Under the construction condition of pingdingshan tunnel site,the time when CO concentration and dust concentration decrease below the permissible concentration is 1500s,1200s respectively;(2)The time for CO concentration and dust concentration to decrease below the allowable concentration is1100 S under the condition that only the compressed ventilator is included,the distance from the nozzle to the palm is 60m,and the wind speed at the inlet of the ventilator is 20m/s;(3)The best smoke extraction effect is achieved when the inlet wind speed is 14m/s,the suction air volume of the dust remover is 600m~3/min,the installation position of the dust remover at Y section of the tunnel is Y=0 m and the optimal distance between the air duct mouth and the metacarp is 50m after adding a dust remover.At this time,the CO concentration and dust concentration in the tunnel reach the permissible concentration of 1100s and 900s.