热带地区高地温隧道施工时,冰块因其经济性和易获取等优点常被用作辅助降温手段。为解决在使用冰块降温时冰块用量和布置参数的选取问题,以海南五指山特长公路隧道工程为背景,使用Fluent软件模拟通风和冰块降温下隧道温度场的变化规律,...热带地区高地温隧道施工时,冰块因其经济性和易获取等优点常被用作辅助降温手段。为解决在使用冰块降温时冰块用量和布置参数的选取问题,以海南五指山特长公路隧道工程为背景,使用Fluent软件模拟通风和冰块降温下隧道温度场的变化规律,分析冰块用量和布设位置2个因素对隧道纵向和掌子面温度场的影响。得出以下结论:1)冰块布设位置前后5 m左右范围内温度下降较为明显,且降温的范围随时间推移逐渐增大。2)双侧各布置1.5 m 3冰块时,掌子面5 m范围内温度最低为18℃,较未布置冰块时下降了10℃左右;稍远位置温度为23℃左右,较未布置冰块时下降了5~8℃。3)与只有通风降温的工况相比,1 m 3的冰块(双侧各布置0.5 m 3)可以降低掌子面温度6℃左右,在此基础上每增加1 m 3冰块用量,可多降低掌子面温度3℃左右。4)相同冰块用量时,将冰块布设于风管出风口轴线上比双侧布置可多降低掌子面温度3~5℃,且持续降温效果更强。展开更多
In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochem...In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.展开更多
文摘热带地区高地温隧道施工时,冰块因其经济性和易获取等优点常被用作辅助降温手段。为解决在使用冰块降温时冰块用量和布置参数的选取问题,以海南五指山特长公路隧道工程为背景,使用Fluent软件模拟通风和冰块降温下隧道温度场的变化规律,分析冰块用量和布设位置2个因素对隧道纵向和掌子面温度场的影响。得出以下结论:1)冰块布设位置前后5 m左右范围内温度下降较为明显,且降温的范围随时间推移逐渐增大。2)双侧各布置1.5 m 3冰块时,掌子面5 m范围内温度最低为18℃,较未布置冰块时下降了10℃左右;稍远位置温度为23℃左右,较未布置冰块时下降了5~8℃。3)与只有通风降温的工况相比,1 m 3的冰块(双侧各布置0.5 m 3)可以降低掌子面温度6℃左右,在此基础上每增加1 m 3冰块用量,可多降低掌子面温度3℃左右。4)相同冰块用量时,将冰块布设于风管出风口轴线上比双侧布置可多降低掌子面温度3~5℃,且持续降温效果更强。
文摘In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.
