Analysis To Influence Factors To Constituents Of Blasting Fume And Its Dispersion Law At Stope And Heading And Control In Metal Mine

Blasting fume poisoning is one of the most common accident types happening during underground mining activities at metal mines in China.Its occurrence not only has negative impact on the normal production,but also exposes miners to the dangerous situation.In this dissertation,triggering mechanism between blasting conditions at heading and stope and the generation of hazardous constituents of blasting fume as well as its alteration were analyzed under the background of blasting fume poisoning event in subsurface metal mine.Through introducing a series of research methods,such as theoretical analysis,mathematical modeling,simulative method,field tests,the author carried out research to the dispersion law of hazardous constituent in the blasting fume,time-space migration and distribution law of CO in heading and stope,as well as the optimizing analysis to the local ventilation parameters,and finally put forward the control strategy of blasting fume in the heading and stope.Based on the conducted research,the following conclusions can be formulated:(1)Under the condition of short-hole blasting at heading and mediate-deep hole blasting at stope,the oxygen balances of blasting reaction of 2#rock emulsion explosive and porous granular ANFO explosive are influenced by various blasting circumstances,such as explosive charge mass,cutting mode,bolehole sizes,chargre structure,way of ignition,condtion of borehole stemming,property of rock,which triggering the generation of toxic gases such as CO,NOx,as well as their changing constituents.(2)Spatio-temporal features of dust,NOx and CO in the blasting fume are characterized by sedimentatary decrease and disappearance,or descending concentration.CO concentration distribution presents Gaussian distribution in stope and heading space under the condition of natural ventilation and forced local ventilation.And the CO concentration in the tailgate cross-section of both heading and stope demonstrates exponential attenuation law in the cross-section of the heading.(3)The gas cloud of carbon monoxide presents the integrated effects of removal and dilution.The peak concentration of CO demonstrates exponential attenuation law with the distance between test position and the heading face.Concentration of CO in the cross-section of heading and stope is lower at down side and higher at upper side".The formula of dispersion coefficient of CO was deduced.And obtained dispersion coefficient of CO is 0.055 m2/s derived from the formula.(4)When the ventilation distance reaches 795 m,the peak concentration of CO decreases below the occupational exposure limit.By optimizing the ventilation parameters including position of outlet of duct and intake airflow of ventilator,the optimum ventilation scheme for blasting fume control at heading is that the distance between the duct outlet and the heading face is no longer than 12.5 m,and the intake airflow ought to be 3.5 m3/s.The ventilation time formula involving ventilation distance,distance between duct outlet and heading face,and intake airflow is deduced.(5)It is found that areas with weak air flow consistently exist at up-left,up-right corners,and the right-middle part in the stope.Concentration of CO remains there in high level and low decreasing rate.Concentration of CO in the cross-section of the tail gate of stope is lower at the down and left sides,while is higher at the up and right sides".Both volumetric concentration and concentration gradient of carbon monoxide decrease with the ventilation time.Volumetric concentration of carbon monoxide shows exponential attenuation law in the tail gate cross-section.(6)Thorough optimizing ventilation parameters like average air speed intake airway and intake airflow of ventilator,the optimum ventilation scheme for blasting fume control at stope is that the airflow of a ventilator is not less than the 3.0 m3/s,and average air speed in the intake airway is not less the 0.6 m/s.The prediction model of the ventilation time of the stope was established by using BP modeling with the network structure of(8,10,1).The above findings could provide an accordance for blasting fume monitoring and control,a reference for drainage of blasting fume and calculation of ventilation time of stope and heading,as well as technical support for prevention of blasting fume poisoning accident.