張小樓煤礦1.2Mta新井設(shè)計(jì)【含CAD圖紙+文檔】,含CAD圖紙+文檔,張小樓,煤礦,mta,設(shè)計(jì),cad,圖紙,文檔 翻 譯 部 分 英文原文 Methane moving law with long gas extraction holes in goaf Yong ZHANG, Xibin ZHANG*,Chunyuan LI, Chuanan LIU, Zufa WANG Faculty of Resources and Safety Engineering, China University of Ming & Technology, Beijing 100083, China Abstract In order to grasp the methane moving law in goaf and provide 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 of 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 near 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. 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of China Academy of Safety Science and Technology, China University of Mining and Technology(Beijing), McGill University and University of Wollongong. Keywords: gas in goaf; gas movement;gas extraction holes; position of extraction holes; expe riment 1 Introduction The roof strata above the goaf will fracture and form the caving, fracture and bending 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 along 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 structure characteristics of roof strata’s movement [2]. * Corresponding author. Tel.: +86-15210567715. E-mail address: zhangxibin627246@126.com. 1877-7058 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.11.21793558 Yong ZHANG et al. / Procedia Engineering 26 (2011) 357 – 365 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 Hydrodynamics equations of gas movement With 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 category, 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. Consequently, the gas movement in the fractured rock of goaf is taken for continuum medium movement in pore medium [5]. 2.1. Gas Seepage characteristics Goaf 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 source of momentum equation of the number i (x, y or z ), μ is the viscosity of molecular, D and C are predefined matrices, |v| is vectors module of velocity, and v J 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 laminar 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, α is the permeability for expressing the space and the function of preventing the viscosity, m2. 1.2. Gas diffusion characteristics There are two 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 equation [4]. Yong ZHANG et al. / Procedia Engineering 26 (2011) 357 – 365 In equation 3, Ji is the gas flow caused by the concentration and thermal gradient; D Im is the diffusion coefficient of mixed gas; Xi is the mass fraction of i gas;TiD is the thermal diffusion coefficient; and T is the temperature. When the gas concentration is much higher, equation 7 could be 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. 1.3. Control equations of gas The gas emission and 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, ρ is mixture density, g/m; T is time variable; ui and uj are velocity, m/s; δij is “Kronecker delta”(when i=j, δij =1; if not, δij =0); P is pressure, Pa; τij is shear stress tensor of molecular; Si is the source item of momentum loss to express pore medium; E is the energy in per volume, J; H is total enthalpy in per volume, J/mol; k is the heat transfer coefficient of fluid; T is static temperature, K; ns is the sum of components; Ru is universal constant, and it is 8.3145 J/(mol·K); if the component is s, Ms is its molecular weight, Ys is its mass concentration; Ds is its mass diffusion coefficient, and hs is its absolute enthalpy value of unit mass. In control equations, equation 5 is the continuum equation of each component, equation 6 is the momentum equation of mixtures, equation 7 is the energy equation of mixtures, and equation 8 is the state equation of ideal gas of mixtures. 3. Field observation 3.1. Working face situation Synthetic mechanized longwall mining technology and fully caving method for managing mined areas are used in Chengshan mine. The main coal seam is the No.3B coal seam, and it’s average thickness is 3.0m, average dip angle is 8°. And the coal reserves are 600,000t. No.3202 working face of Chengshan mine is 600m along the mining direction and 240m along sloping direction. During drifting the headentry of No.3202 working face, the highest absolute gas emission is even 9.3m 3/min, and it is 41.6m 3/min during mining the working face. Therefore, gas emission is much higher in this coal mine. It is difficult to solve the problem only by ventilation measures. Gas extraction technology is one of the best measures for controlling gas content in the goaf. According to the “O” circle theory of fracture distribution in the stope, gas will move and gather up in the fractures of “O” circle in the goaf. In order to study the range of roof strata and provide the reasonable parameters for gas extraction, the height of roof-falling and fractured zones in the stope is calculated according to the experiential formula [8]. In equation 9 and 10, H1 and H2 are the height of roof-falling and fractured zones along the normal direction of the coal seam separately; M is the height of the mining coal seam; K is the broken coefficient of rock in roof-falling zones which is 1.2; and θ is the dip angle of the coal seam. Then H1 is equal to 15.15m, and H2 is 30.11-40.31m. 3.2. Observation method Sensors are used to monitor and observe gas distribution in goaf and extraction holes respectively. When the working face advances about 80m from the interconnection, the first head of sensors are installed along the tailentry and headentry, which are numbered T1and T4 separately, and it is the first field. Then, the working face goes on advancing 200m and 300m from the interconnection, four sensors are installed along the tailentry and headentry respectively, which they are respectively numbered T2, T3, T5, T6. Sensors of extraction holes are installed in the number 1, 3, 6 holes of the second and third holes field, and they are numbered T2-1, T2-3, T2-6 and T3-1, T3-3, T3-6. Besides, T2-1 and T3-1 are inserted into 120m along the holes; T2-3 and T3-3 are inserted into 80m along the holes; and T2-6 and T3-6 are inserted into 40m along the holes. Figure 1 shows a sketch of the arrangement of gas monitor sensor in No.3202 working face. In figure 1, only the first head of sensors and the second field are indicated. Fig.1 Arrangement of gas monitor sensor in No.3202 working face Yong ZHANG et al. / Procedia Engineering 26 (2011) 357 – 365 3.3. Observation results Observation results are shown in figure 2. Gas concentration increases in the goaf with the rising of distance from working face. When the distance from the working face is less than 150m, the change of gas concentration will relatively stable. For example, when the distance from the working face to the observation point is 10m, 50m, 100m and 150m, the average gas concentration is 2.6%, 3.9%, 4.1% and 5.9% separately. But if the distance is more than 150m, gas concentration increases sharply. Gas concentration reaches 10.55% if the distance from the working face is 170m; it is even much more than 16.9% when the distance is far more than 200m. Sensors monitoring result indicates that there exists a huge gas storeroom in the goaf, and the farther the distance from the working face to observation points, the higher the gas concentration gathering up. Fig.2 Changing curve of goaf gas average concentration 4. Laboratory experiment With the influence of construction technology, the monitoring effect of gas distribution near tailentry is much better by using sensors monitoring system in the goaf. But it is difficult to monitor the middle and bottom of the goaf, particularly, it is difficult to know gas distribution well in different holes position. Therefore, the equivalent material simulation is done in the laboratory. The experiment has been done by using integrated simulation table on gas and rock movement which was developed by China University of Mining & Technology, Beijing. The experimental model is shown in figure 3. Fig.3 Integrated simulation table on gas transporting and rock moving 4.1. Experimental details The geometry similarity ratio of the model is 1:100, and the integrated simulation table has four reticular test systems in which there are 320 sampling points. Meanwhile, every sampling point links to a suction pump. Long holes are used to simulate gas extraction in the field, which are also arranged above the tailentry. Besides, the vertical distance above the tailentry is 20cm, 30cm and 40cm respectively, and the horizontal interior distance from the tailentry to holes is 10cm when the vertical distance is 20cm, and it is 10cm, 20cm and 30cm respectively when the vertical distance is 30cm. The extraction flow of holes is 0.4ml/min, the dry bulb temperature is 15.2℃, the wet bulb temperature is 14.2℃, the relative humidity is 90％, and the velocity pressure of return air is 2.192mm water column. According to the position of extraction holes, there are six testing programs, and experimental results are shown in figure 4. In figure 4, H stands for the horizontal interior distance from the tailentry to gas extraction holes, and V stands for the vertical distance abo ve the tailentry between gas extraction holes and the tailentry. I: The experiment does not use gas extraction in goaf, and its distribution of gas concentration is shown in figure 4(a). II: The experiment uses gas extraction holes in goaf. The vertical distance is 40cm, and holes are parallel with the tailentry. The distribution of gas concentration is shown in figure 4(b). III: The vertical distance above the tailentry is 20cm, and the horizontal interior distance is 10cm. The distribution of gas concentration is shown in figure 4(c). IV: Gas extraction holes are over the tailentry, and the vertical distance is 30cm. The distribution of gas concentration is shown in figure 4(d). V: The vertical distance is 30cm, and the horizontal interior distance is 10cm. The distribution of gas concentration is shown in figure 4(e). VI: The vertical distance is 30cm, and the horizontal interior distance is 20cm. The distribution of gas concentration is shown in figure 4(f). Fig.4 Gas distribution in goaf with different extraction parameters 4.2. Experimental results When the experiment does not use gas extraction in the goaf, the gas concentration is less than 1% near the intake side or even lower, but there is gas of high concentration flowing into the working face near the tailentry side, and the distribution of gas concentration is veined shape in the middle of the goaf. When the experiment is taken II program, the gas concentration reduces integrally in the goaf, but the gas concentration is more than 1% in the upper corner of the tailentry. When the experiment is taken III program, the change of gas concentration is not obvious integrally in the goaf, but the concentration near the tailentry decreases. When the vertical distance above the tailentry is 30cm, the gas concentration all reduces in goaf. When the program is IV, the reduction is obvious near the intake side and gas concentration is less than 0.5%, but it still maybe beyond 1% near the tailentry. When the experiment is taken V program, gas concentration obviously decreases near both intake and tailentry side, but gas concentration is around 1% in the middle of goaf, which is much higher. When the experiment is taken VI program, the whole gas concentration in the goaf reduces obviously; it is around 0.5% in the middle of intake and goaf, but gas gathers up in the upper corner of the woking face. Comparing with all experiments, it is easy to know the follwing views. The position of gas extraction holes has a great effect on gas concentration in the goaf. In the vertical direction above the tailentry, the lower the position of holes, the worse gas extraction results, and gas concentration is limited in return air side of working face. But when the gas extraction holes lay out in high position, gas concentration obviously reduces in return air side. And the extraction result is the best when the vertical distace above the tailentry is 30cm. Besides, if gas is extracted in the top of tailentry, gas concentration will reduce on a large scale. But it is still high in the upper boundary of goaf and it is possible to gas up in the upper corner of working face. With the same vertical distance and same gas extraction volume, holes are moved little distance into working face when the horizontal interior distance over the working face is 10cm and 20cm respectively, while the controlling range changes largely. If holes are too close to the tailentry, though the whole gas concentration reduces obviously in the back of goaf, gas concentration is high near the tailentry, and it is possible to gas up in the upper corner of working face. And if the horizontal interior distance is too far, it is also apt to gas up. In order to reduce the whole gas concentration in the goaf and near the tailentry, and deal with gas in the upper corner of working face, gas extraction holesshould be located over the working face and the reasonable horizontal interior distance from tailentry to holes is 10-20m. Therefore, gas extraction holes should be located above the rock-falling zones and at the bottom of fracture zones as much as possible according to the collapsed state of roof strata. And it is fanshaped for all holes. The height of final holes is different in different position. The height of final holes near the tailentry is about 20m above the regular rock-falling zone; the height of final holes near the middle of goaf is about 30m at the bottom of fracture zone. And the reasonable horizontal interior distance from tailentry to gas extraction holes is 10-20m. 5. Conclusions Gas movement in the fractured rock of goaf can be regarded as the incompressible flow in the pore medium, and its moving state is closely related to the airflow. The molecular diffusion and viscous flow (or mass flow) are two main forms of the gas movement in the goaf. And the control equations of flow field can be replaced by the Navier-Stocks equation. Field observation indicates that gas concentration increases in the goaf as the distance from the working face to observation point rises. When the distance from the back of goaf to the working face is far beyond 150m, its gas concentration is much higher than near the working face. And there exists a huge gas storeroom in the goaf, in which gas has extraction value. In order to reduce the gas concentration in the goaf and the upper corner of working face, gas extraction holes should be loacted according to the collapsed state of roof strata, which is based on the experimental results. Therefore, holes should be arranged to fanshaped pattern as much as possible. The height of final holes near the tailentry is about 20m above the regular rock-falling zone; the height of holes near the middle of goaf is about 30m at the bottom of the fractured zone. And the reasonable horizontal interior distance from tailentry to observation point is 10-20m. Acknowledgements This work has been supported by a grant from the Major State Basic Research Development Program of China (973 Program) (No.2011CB201200) and National Natural Science Foundation of China (No.50834005). 中文譯文 采空區(qū)瓦斯移動(dòng)規(guī)律與瓦斯抽放孔位置關(guān)系 張勇，張錫斌，李春園，劉傳安，王族發(fā) 資源與安全工程學(xué)院，中國礦業(yè)大學(xué)，北京100083，中國 摘要 為了掌握采空區(qū)中的瓦斯移動(dòng)規(guī)律和為瓦斯抽放鉆孔提供理論數(shù)據(jù)，放頂煤和工作面垮落區(qū)的高度根據(jù)已驗(yàn)證的公式已經(jīng)計(jì)算出來，通過現(xiàn)場(chǎng)和實(shí)驗(yàn)室的實(shí)驗(yàn)已經(jīng)觀察到了瓦斯的運(yùn)動(dòng)規(guī)律。它同時(shí)也得出了瓦斯運(yùn)動(dòng)特征和瓦斯抽放孔不同位置的關(guān)系。當(dāng)最終的抽放孔安排在煤層上方30米和水平偏東10-20米的地方它具有最佳的瓦斯抽放結(jié)果。此外，最終抽放孔的高度應(yīng)該根據(jù)覆巖地層結(jié)構(gòu)調(diào)整。當(dāng)最終抽放孔靠近東翼的時(shí)候抽放孔的高度應(yīng)該控制在定期放頂煤上部； 當(dāng)抽放孔靠近工作面中心的時(shí)候，抽放孔的高度應(yīng)該控制在斷裂帶下部。 2011年Elsevier 公司發(fā)布。中國科學(xué)技術(shù)安全學(xué)院責(zé)任選擇和同行評(píng)議，中國礦業(yè)大學(xué)（北京校區(qū)），麥吉爾大學(xué)，臥龍崗大學(xué)。 關(guān)鍵詞：采空區(qū)瓦斯；瓦斯運(yùn)動(dòng)規(guī)律；瓦斯抽放孔；瓦斯抽放孔位置；實(shí)驗(yàn) 1簡(jiǎn)介 采空區(qū)頂板巖層將破斷并將形成放頂煤，煤層采出后在垂直方向上會(huì)形成裂隙帶和彎曲帶。還有很多斷裂和裂紋的放頂煤和斷裂區(qū)，地層滲透率也很高。根據(jù)回踩工作面裂隙O型理論分布規(guī)律，采空區(qū)的瓦斯將會(huì)沿著這些裂隙裂縫流動(dòng)并且聚集。然后，很容易導(dǎo)致瓦斯?jié)舛瘸瑯?biāo)，這就需要采取措施減少瓦斯含量。為了解決這個(gè)問題并且得到最佳的抽放效果，應(yīng)該根據(jù)巖石結(jié)構(gòu)的變化調(diào)整抽放鉆孔的分布根據(jù)拱形結(jié)構(gòu)頂板巖層運(yùn)動(dòng)的特點(diǎn)。采空區(qū)的瓦斯在經(jīng)過抽放鉆孔抽放之后將會(huì)重新分布。因此，應(yīng)該研究瓦斯移動(dòng)規(guī)律和瓦斯抽放鉆孔位置之間的關(guān)系以使得工作面角落和采空區(qū)角落的瓦斯能夠被有效的控制。 2瓦斯運(yùn)動(dòng)的流體動(dòng)力學(xué)方程 隨著巷道通風(fēng)的壓力梯度，瓦斯從煤層中擴(kuò)散或滲透到采空區(qū)然后再到巷道中，并且它的流速非常的緩慢，平均流速小于10-5m/s。因此，采空區(qū)中流動(dòng)的瓦斯和空氣屬于低速類別流動(dòng)，它很難對(duì)巷道通風(fēng)產(chǎn)生影響。雖然壓力梯度很高，采空區(qū)和巷道中的瓦斯和空氣流量仍然被視為不可壓縮流體。另外，巖層的分布，采空區(qū)中的裂隙和裂縫是不規(guī)則的。因此，在采空區(qū)裂隙巖體中流動(dòng)的瓦斯是在空隙介質(zhì)中的連續(xù)介質(zhì)運(yùn)動(dòng)。 2.1瓦斯涌出特征 采空區(qū)被認(rèn)為是在研究中被認(rèn)為是多孔介質(zhì)；流體動(dòng)力損失由以下公式求得： 方程式中 Si--流體動(dòng)力損失 U--分子粘度 D、C--預(yù)定義矩陣 |v|--速度絕對(duì)值 Vj--速度的分向量 一般情況下，在多孔介質(zhì)中流動(dòng)的低流層的壓力降于其流速成正比。在液體慣性損失忽略不計(jì)的情況下，多孔介質(zhì)模型可以簡(jiǎn)化應(yīng)用于達(dá)西特征中。 方程式中： a--滲透性表達(dá)的空間和防止粘度的功能 m2 2.2瓦斯擴(kuò)散特征 采空區(qū)中瓦斯的運(yùn)動(dòng)有兩個(gè)主要控制因素，一個(gè)是濃度和溫度變化引起的分子擴(kuò)散。另一個(gè)是粘性流動(dòng)或質(zhì)量流量壓力變化的作用。根據(jù)菲克特點(diǎn)，得出下面的擴(kuò)散方程公式。 方程式中：Jj--濃度和溫度變化引起的瓦斯流動(dòng) Dim--混合氣體擴(kuò)散系數(shù) Xi--瓦斯的質(zhì)量分?jǐn)?shù) DiT--熱擴(kuò)散系數(shù) T--溫度 當(dāng)氣體濃度過高時(shí)，就可能發(fā)生的方程 7 方程式中：如果瓦斯是i或者j，那么Mj就是它的分子量，Dij是瓦斯中第i號(hào)瓦斯組分的擴(kuò)散系數(shù)；Mmix是混合氣體的分子量。 1.3 瓦斯控制方程 采空區(qū)瓦斯涌出量與運(yùn)動(dòng)已與空氣流動(dòng)狀況關(guān)系密切，它屬于典型的滲透擴(kuò)散過程。因?yàn)樵诓煽諈^(qū)中的氣體流量被視為不可壓縮流體，流場(chǎng)控制方程可以替換為Navier-Stocks方程。 公式中，ρ是混合物的密度，單位是g/m ；T是時(shí)間變量；Ui和Uj是速度（m/s）；δij是當(dāng)i=j時(shí)候δij=1；如果i不等于j則δij=0 ；P是壓力（Pa）；τij是剪應(yīng)力分子的張量；Si是流體動(dòng)力損失；E是單位體積內(nèi)的能量（J）；H是單位體積內(nèi)總焓的能量（J/mol）；k是流體的傳熱系數(shù)；T是靜態(tài)溫度（k）；ns是組合成分總和；Ru是通用常數(shù)（8.3145 J/(mol·K)）；如果組分是s，Ms是它的分子量，Ys是它的質(zhì)量濃度；Ds是它的大量擴(kuò)散系數(shù)，hs是它的焓的絕對(duì)值的單位質(zhì)量。 在控制方程中，方程式5是每個(gè)組分的連續(xù)性方程，方