| With the steady advance of"The development of the western region in China"and"One Belt One Road"strategy,China’s infrastructure construction has been extended to the western region.In the western part of China,the terrain is very undulating.Roads and railways are faced with the construction of a large number of tunnels,some of which are long tunnels and spiral tunnels.When the altitude difference between the two places is large,the spiral tunnel can be used to reduce the slope of the highway between the two places and improve driving safety.At the same time,the spiral tunnel can also climb a larger height within a shorter distance,effectively shortening the distance between the two places and providing convenience for the economic development of mountainous areas.However,the special line of the spiral tunnel makes the diffusion and transport of pollutants in the construction area different from the existing tunnels,and the ventilation resistance is also different from the existing tunnels.Only by mastering the law of pollutant diffusion and migration and resistance of air flow in the construction area of spiral tunnel,can put forward effective pollutant control technology,provide a good construction environment for the construction area of tunnel,and ensure the physical and mental health of the construction personnel and the safety of tunnel construction.Therefore,the diffusion and prevention of pollutants in spiral tunnel construction area are noticed,and explores an efficient,convenient and low-energy pollutant control technology in tunnel construction area through model experiment,numerical calculation and theoretical derivation.The spiral tunnel ventilation air resistance,pollutant distribution and migration characteristics in the spiral tunnel construction area,ventilation system based on spiral tunnel construction area pollutant parameters control,tunnel construction ventilation intelligent control system based on the pollutant parameters analysis and shock bubble dust removal technology are studied.The Midecun spiral tunnel of the Jiangeyuan Expressway is the research object.The main research contents and achievements are as follows:（1）An experimental system of spiral tunnel similarity model is established.According to the flow state inside the tunnel and the experimental requirements,the similarity criterion of the model experiment,froude similarity criterion,is determined.The tunnel construction experimental platform was built according to similarity criterion.The model similarity ratio is 1:20.The model is composed of pipes with a diameter of 64.5 cm and a length of 55.5 cm.The length of the tunnel model is 7 m.According to the dust motion control equation,the dust similarity criterion in the model experiment was derived,and the dust particle size satisfying the similar condition in the model experiment is calculated according to the dust similarity criterion.The model experiment platform is composed of model tunnel,model ventilation system,pollutant generation system and test system.（2）The basic equation of uniform flow in spiral pipe and the formula of spiral resistance are derived.According to the uniform flow equation of spiral pipe,the flow resistance in regular shape spiral pipe is composed of both the on-way resistance along the pipe and the spiral resistance.According to the uniform flow equation of spiral pipe,the calculation formula of spiral resistance is derived,and the result is verified by numerical calculation.The resistance coefficient of Midecun Tunnel is 0.0443calculated by the ventilation resistance experiment of Midecun Tunnel,which is higher than the 0.02 recommended by the code.The spiral resistance of the operation period and the construction period of the Midecun Tunnel are calculated,and it is found that the spiral resistance in the construction period of the tunnel has a great influence on the ventilation resistance.（3）According to the distribution of dust,the model of heavy dust pollution zone and light dust pollution zone in tunnel are put forward.The distribution and transport characteristics of blasting dust in tunnel ventilation and without ventilation are studied by model experiment.The study found that in the absence of ventilation,the heavy dust pollution zone has a large volume and high dust concentration,while the light dust pollution zone gradually decreases with the extension direction of the tunnel.After the ventilation,the original pollution zone is broken.When air velocity of duct outlet reaches to 8.8 m/s（corresponding prototype duct export air velocity is 40 m/s,conversion in the tunnel air velocity is 1.56 m/s）,the minimum volume of heavy dust pollution zone appears.Under the action of air flow,between heavy pollution zone and light pollution zone formed a dust outlet,make the dust in heavy pollution zone can enter light pollution zone.（4）A ventilation intelligent control system（TVIC）which can intelligently control the operation state of the fan according to the pollutant parameters of the tunnel is proposed.The ventilation system of spiral tunnel construction is optimized based on pollutant control in construction area.Different from the linear tunnel,the section is symmetrical along the central axis,while the spiral tunnel appears inside and outside because of bending.It is found that compared with other air duct outlets,when the air duct outlets are arranged in the outside waist of the tunnel,the CO concentration generated by blasting can be reduced to within the allowable value in the shortest time of tunnel.The numerical results are also verified by field experiments.An intelligent control system for ventilation in tunnel construction（TVIC）is proposed,which can analyze the environmental parameters in the tunnel and calculate the optimal fan operating frequency,so as to reduce the energy consumption of ventilation system while ensuring the environmental demand of tunnel construction.（5）The shock bubble dust removal technology which can rapidly reduce the dust concentration in the construction area after blasting is proposed.The shock bubble is produced by a chemical reaction between acidic and alkaline reagents in a sealed chamber to produce CO2,which is released in an instant.The structure analysis and stability test of shock bubble generated under different pressure were carried out,and the optimal pressure was obtained through model experiment,and the dust removal effect of shock bubble was confirmed by field experiment. |
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