1、翻译部分英文原文Methane moving law with long gas extraction holes in goafYong ZHANG, Xibin ZHANG* , Chunyuan LI, Chuanan LIU, Zufa WANGFaculty of Resources and Safety Engineering, China University of Ming & Technology, Beijing 100083, ChinaAbstract：In order to grasp the methane moving law in goaf and provid
2、e a theoretical data for gas extraction holes, the height of caving and fractured zones in the stope has been calculated according to the experiential formula and gas movement law has been observed by field and laboratory experiment. It also gives gas moving characteristics with different position o
3、f extraction holes. And it has the best gas extraction result when the final holes are arranged around 30m above the coal seam and 10-20m away from the tailentry in horizontal direction. Besides, the height of final holes should be adjusted to the overburden strata structure. When final holes are ne
4、ar the tailentry, their height should be controlled in the upper of regular caving zone; when they are close to the center of face, their height should be controlled at the bottom of fracture zones.1. IntroductionThe roof strata above the goaf will fracture and form the caving, fracture and bending
5、zones in the vertical direction after mining the coal seam. And there are lots of fractures and cracks in caving and fracture zones, the permeability of the stratum are also high. According to the “O” circle theory of fracture distribution in the stope 1, the gas of goaf will move and gather up alon
6、g those fractures and cracks. Then it is easier to cause the gas exceeding the limit, which need to take measures to reduce gas content. In order to solve this problem and get the best extraction effect, the layout of holes should be adjusted to the rock structure changes according to the arch struc
7、ture characteristics of roof stratas movement 2.Gas in goaf will distribute after holes extraction. Therefore, the relationship between gas moving law and position of gas extraction holes should be studied so that gas in the corner of working face and goaf could be effectively controlled.2. Hydrodyn
8、amics equations of gas movementWith the pressure gradient of roadways ventilation, gas penetrates or diffuses to the goaf and then to roadways from the coal seam, and its flow velocity is very low which usually less than 10-5m/s 3. Therefore, the flow of gas and air in goaf belongs to low-speed cate
9、gory, and it hardly has an effect on the roadways ventilation. Despite the pressure gradient is very high, the gas and air flow in the mined-out area and roadways can still be regarded as the incompressible flow 4. Besides, the distribution of rock, fractures and cracks in goaf are irregular. Conseq
10、uently, the gas movement in the fractured rock of goaf is taken for continuum medium movement in pore medium 5.2.1. Gas Seepage characteristicsGoaf is regarded as porous medium in the research; the source item of fluid momentum loss is described as the following equation 5.In equation 1, Si is the s
11、ource of momentum equation of the number i (x, y or z ), is the viscosity of molecular, D and C are predefined matrices, |v| is vectors module of velocity, and vj is the velocity component of the source in x, y or z direction.Generally, the pressure drop is proportional to the velocity in the low la
12、minar flow of porous medium. The porous medium model could be simplified by using Darcy characteristics when the liquid inertial loss is ignored.In equation 2, is the permeability for expressing the space and the function of preventing the viscosity, m2.2.2. Gas diffusion characteristicsThere are tw
13、o main controlling factors for the gas movement in the goaf. One is the molecular diffusion caused by the concentration and thermal gradient. Another is viscous flow or mass flow on the action of pressure gradient. According to the Fick characteristics, the following formula is the diffusion equatio
14、n 4.In equation 3, Ji is the gas flow caused by the concentration and thermal gradient; Dim is the diffusion coefficient of mixed gas; Xi is the mass fraction of i gas; DiT is the thermal diffusion coefficient; and T is the temperature. When the gas concentration is much higher, equation 7 could be
15、taken place by the diffusion formula of multicomponent.In equation 4, if the gas is i or j, Mi is its molecular weight, Dij is the multicomponent diffusion coefficient of the No. i gas component in the gas, and Mmix is the molecular weight of mixed gas.2.3. Control equations of gasThe gas emission a
16、nd movement has close relationship with the air flow condition in gob, and it belongs to the typical permeation-diffusion process. Because the gas flow in goaf is regarded as the incompressible flow, control equations of flow field can be replaced by the Navier-Stocks equation 6, 7.In formulas, is mixture density, g/m; T is time variable; ui and uj are velocity, m/s; ij is “Kronecker delta”(when i=j, ij=
