Numerical investigation of the effectiveness of radon control measures in cave mines
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摘要
Ventilation is one of the radon control measures in an underground working environment. However, the dynamics related to the cave mining methods particularly in block/panel cave mines, complicate the design of effective ventilation system, and implementation. Events such as hang ups(in the drawbells),leakage from old workings, and changes in cave porosity lead to differing response of an existing ventilation designs. However, it is difficult to investigate these conditions at the mine or with a laboratory scale study. Therefore, this study develops a discrete model to investigate the impact of different radon control measures in cave mines using computational fluid dynamics techniques. We considered two ventilation conditions for a fully developed cave: with and without the undercut ventilation. For each of the two conditions, we studied four parameters: airflow distribution through the production drifts, radon distribution through the production drifts, the effect of increasing airflow on radon concentration, and the effect of a cave top negative pressure on radon distribution. The results show that: the undercut ventilation significantly increases the radon concentration in the production drift; the growth of radon concentration through the production drift is nonlinear(oscillating pattern); maintaining a negative pressure on top of the cave is more effective at mitigating radon exposure, when the undercut ventilation is active;and increase in air volume flow rate decreases radon concentration in most regions, however, there might be regions with significant radon accumulation due to pressure variation across the drifts. These findings provide vital information for designing an effective ventilation system and for proactive implementation of radon control measures in cave mines.
Ventilation is one of the radon control measures in an underground working environment. However, the dynamics related to the cave mining methods particularly in block/panel cave mines, complicate the design of effective ventilation system, and implementation. Events such as hang ups(in the drawbells),leakage from old workings, and changes in cave porosity lead to differing response of an existing ventilation designs. However, it is difficult to investigate these conditions at the mine or with a laboratory scale study. Therefore, this study develops a discrete model to investigate the impact of different radon control measures in cave mines using computational fluid dynamics techniques. We considered two ventilation conditions for a fully developed cave: with and without the undercut ventilation. For each of the two conditions, we studied four parameters: airflow distribution through the production drifts, radon distribution through the production drifts, the effect of increasing airflow on radon concentration, and the effect of a cave top negative pressure on radon distribution. The results show that: the undercut ventilation significantly increases the radon concentration in the production drift; the growth of radon concentration through the production drift is nonlinear(oscillating pattern); maintaining a negative pressure on top of the cave is more effective at mitigating radon exposure, when the undercut ventilation is active;and increase in air volume flow rate decreases radon concentration in most regions, however, there might be regions with significant radon accumulation due to pressure variation across the drifts. These findings provide vital information for designing an effective ventilation system and for proactive implementation of radon control measures in cave mines.
Ventilation is one of the radon control measures in an underground working environment. However, the dynamics related to the cave mining methods particularly in block/panel cave mines, complicate the design of effective ventilation system, and implementation. Events such as hang ups(in the drawbells),leakage from old workings, and changes in cave porosity lead to differing response of an existing ventilation designs. However, it is difficult to investigate these conditions at the mine or with a laboratory scale study. Therefore, this study develops a discrete model to investigate the impact of different radon control measures in cave mines using computational fluid dynamics techniques. We considered two ventilation conditions for a fully developed cave: with and without the undercut ventilation. For each of the two conditions, we studied four parameters: airflow distribution through the production drifts, radon distribution through the production drifts, the effect of increasing airflow on radon concentration, and the effect of a cave top negative pressure on radon distribution. The results show that: the undercut ventilation significantly increases the radon concentration in the production drift; the growth of radon concentration through the production drift is nonlinear(oscillating pattern); maintaining a negative pressure on top of the cave is more effective at mitigating radon exposure, when the undercut ventilation is active;and increase in air volume flow rate decreases radon concentration in most regions, however, there might be regions with significant radon accumulation due to pressure variation across the drifts. These findings provide vital information for designing an effective ventilation system and for proactive implementation of radon control measures in cave mines.
引文
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[2]McNearny RL,Abel JF.Large-scale two-dimensional block caving model tests.Int.J.rock Mech.Min.Sci.Geomech.Abstr.,vol.30.Elsevier;1993.p.93-109.
[3]Loring DM,Meisburger IV EP.A discussion of radon and the mitigation strategy at the.Henderson Mine 2010.
[4]El-Fawal MM.Mathematical modelling for radon prediction and ventilation air cleaning system requirements in underground mines.J Am Sci2011;7:389-402.
[5]Holford DJ,Schery SD,Wilson JL,Phillips FM.Modeling radon transport in dry,cracked soil.J Geophys Res Solid Earth 1993;98:567-80.
[6]Mc Pherson MJ.Subsurface ventilation and environmental engineering.Springer Science&Business Media;2012.
[7]HPA.Radon and Public Health:Report prepared by the subgroup on radon epidemiology of the independent advisory group on ionising radiation,documents of the health protection agency.UK:Health Protection Agency;2009.
[8]Sainsbury B.Sensitivities in the numerical assessment of cave propagation.In:Potvin Y,editor.Proc.2nd Int.Symp.Block Sublevel Caving(Caving 2010);2010.p.20-22.
[9]Hartman HL,Mutmansky JM.Introductory mining engineering.John Wiley&Sons;2002.
[10]Fuenzalida MA,Pierce M,Andrieux P,TG-C.Application of a methodology for secondary fragmentation prediction in cave mines,Santiago,Chile;2014.
[11]Dorador L,Eberhardt E,Elmo D,Aguayo A.Assessment of broken ore density variations in a block cave draw column as a function of fragment size distributions and fines migration;2014.
[12]Schafrik S,Millar DL.Verification of a CFD code use for air flow simulations of fractured and broken rock.Appl Therm Eng 2015;90:1131-43.
[13]Clover P.Petrophysics MSc course note.Imp Coll London 2008:10-20.
[14]Mac?as-Garc?a A,Cuerda-Correa EM,D?az-D?ez MA.Application of the RosinRammler and Gates-Gaudin-Schuhmann models to the particle size distribution analysis of agglomerated cork.Mater Charact 2004;52:159-64.
[15]Fan LS,Zhu C.Size and properties of particles.In:Princ.gas-solid flows.Cambridge:Cambridge University Press;1998.p.3-45.
[16]González-Tello P,Camacho F,Vicaria JM,González PA.A modified NukiyamaTanasawa distribution function and a Rosin-Rammler model for the particlesize-distribution analysis.Powder Technol 2008;186:278-81.
[17]RosIN P.The laws governing the fineness of powdered coal.J Inst Fuel1933;7:29-36.
[18]Djordjevic N.A two-component model of blast fragmentation.In:AusIMMProceedings(Australia),vol.304;1999.p.9-13.
[19]Botha J,Arkadius T,Samosir E.Simulation applications at PT Freeport Indonesia’s DOZ/ESZ block cave mine,Lulea,Sweden;2008.
[20]Mudd GM.Radon releases from Australian uranium mining and milling projects:assessing the UNSCEAR approach.J Environ Radioact2008;99:288-315.
[21]Software Cradle Co.L.User’s guide:basics of CFD analysis;2013.
[22]Hager WH.Losses in flow.Wastewater Hydraul.:Springer;2010.p.17-54.
[23]Liu H.Pipeline engineering.CRC Press;2003.
[24]Kotrappa P,Frederick MD.Difficult to digest myths and mysteries of radon.In:2002 Int.Radon Symp.Proc.;2002.
[25]Singh AV,Sharma L,Gupta-Bhaya P.Studies on falling ball viscometry.ArXiv Prepr ArXiv12021400;2012.
[26]Yamada Y,Fukutsu K,Tokonami S,Ishikawa T,Zhuo W,Furukawa M,et al.Size measurements of radon decay products by diffusion method.In:Proc.4th Eur.Conf.Prot.against radon home Work,Czech Republic;2004.