长平三矿1.80Mta新井设计【含CAD图纸+文档】
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附录A1 通过多孔介质气体的属性多孔介质饱和流体具有比纯流体介质的不同属性（见图1）。多孔域组成，由煤和岩石中的瓦斯、固体和液体组成。如果是刚性的固体中，气体流量仅依赖于由许多各种形状和不同大小的孔洞形成的流体区域。虽然N-S方程能计算通过多孔介质的有效流动，但对流体流经这些小区域的模拟是不切实际，远远超出了现今计算的能力。 图1 多孔介质的模型为了确定在多孔介质中气体的流动性能，就必须使用平均速率。在平均速率程序中，引进多孔介质渗透率这个重要的概念，。在图1中，我们考虑一个简单的例子，由于受到的压力作用，气体通过微循环孔流量不断下降。气体流量公式可以得到：其中，v是在孔洞里的气体流速。在光滑孔壁条件压力作用下，可以得到精确解：通过统计沿孔截面，我们可以计算透过该孔洞的平均流速：考虑到位于多孔介质孔隙中这样的孔洞非常少，则平均速率为：系数被称为相对饱和区，在多孔介质渗透率的形状各不相同。此外，透气性不可能是各向同性的。然而，气体通过多孔介质的流动更普遍的形式可以表示为：其中，k是渗透量，为k=kEE，f是气体流量的自身张力。公式（1）称为达西定律。它是通过多孔介质气体流动动量守恒，及在各个阶段的连续性方程，得到多孔介质气体流质量守恒有效，从而得到平均流速。换句话说，假设气体流量可以被压缩。比热常数Cp和Cv是在气体流动状态下的模拟。大多数情况下，依赖于特定的加热温度和气体内部压力，及可压缩流动的气体压力，且温度和密度的相互依存。一个动量、能量方程都强耦合的可信结果，并给出了高度非线性的方案。为了获得一个平均温度的解决方案，及材料性能均使用液体和固体性质：达西定律和能量连续性方程形式，是通过多孔煤层瓦斯流动控制方程系统。达西方程有不同于的Navier Stokes方程。例如，有没有衍生速度。一些传统的光滑壁面边界条件可能不适合多孔介质的流量。还需要注意的是达西定律没有衍生时间。目前，假如自身张力f是常数，它是不必要的瞬态分析。许多气体在多孔介质流动问题能与使用的Boussinesq近似的引力温度耦合。达西定律可以适用的压力泊松方程的多孔介质质量守恒。很明显，渗透压力一个快速度的潜力。多孔介质的压力有时也被称为孔隙压力。认为当煤层变形时，在达西方程速度必须相应的相对速度，其中v是该结构的取代速度。2 多孔介质气体流动的数学模拟2.1 控制方程通过多孔介质流动的连续性方程，是能量方程和达西方程气体组成的控制方程。连续性方程为：达西定律是：能量方程为：2.2 数值模拟方法动量方程是由加权与虚拟的数量和速度组成，在计算综合域中，分歧定理是用来降低的压力衍生物，表示导致自然边界条件。变分形式写为：其中，h是速度虚拟值。使用相关功能，离散方程如下：3 数值分析3.1普遍模型观点在平顶山矿区有从顶部向下有四个煤层。这些煤层被命名为E煤层，D煤层，C煤层和B煤层。它们被用作解放层是因为有丰富的碳二叠纪煤和瓦斯资源。其中主要煤层命名为D15的平均厚度为3.5米，煤层中的瓦斯相对压力非常高，煤层被划分为严重的煤瓦斯突出煤层。上层煤层（D16-17）的平均厚度为1.5米，煤层瓦斯得到抽采，从而没有煤瓦斯突出倾向。两者之间的缝隙空间范围从1到16米，主要空间为1-6米，两者之间的缝隙空间范围是1.3-4.0米。在煤层（D16-17）间隙空间作为解放层，这两个煤层被划分为极短距离解放层。为了简化数值模拟模型，只是把图2煤层位置布局出来。把煤层的物理参数列于表1。在图2中D15煤层厚1.1米，属于薄煤层。煤层（D16-17）是主要开采煤层厚4.6米。接缝D15是解放层和煤层（D16-17）是被解放的煤层，沙是两个煤层之间的泥岩。这两者之间接缝距离为5米，属于极近距离解放层。表1 煤和岩层的参数层位薄砂岩泥砂岩D15煤层泥砂岩D16-17煤层泥砂岩密度267026001750230015002400渗透系数（达西）气体压力（MPa）000.502.70杨氏模量（GPa）16.74.00.3818.80.368.3图2 煤和岩层的模型其目的是为了模拟解放层一步一步的挖掘。瓦斯流量和瓦斯分析，对被解放的煤层变化进行了分析。解放层开挖有六个步骤。每个步骤距离为5米，总长度为30米，把最初的瓦斯压力和煤层的瓦斯条件设为第一位。3.2 结果分析图3表示了初步瓦斯的压力。图4表示从第一开采瓦斯压力到第六位的变化。煤层瓦斯压力二维初始为0.5 MPa和中缝（D16-17）初步瓦斯压力为2.7MPa。瓦斯流量和瓦斯压力变化的诱导采掘。瓦斯流向开采区和瓦斯压力减少的解放层。以开采区瓦斯流量和瓦斯压力降低为中心，气体压力梯度是非常高的。开采后的第一个5米，煤层（D16-17）瓦斯压力转变为0.87 MPa。经过采掘10米，压力转化为0.78 MPa。经过采掘15米，压力为0.71 MPa。经过采掘20米，压力为0.66 MPa。当开采长度为25米，压力为0.61 MPa。截至第六步开采结束，压力为0.57 MPa。图3 初始瓦斯压力当没有任何采掘，瓦斯流量没有变化，。一旦开采扰动的实施，导致围岩应力场的改变，并有底板和解放层顶板一定的变形。随着岩石和煤层破坏，瓦斯内部开始流动，并且该流程融合到采掘区。随着采掘的推移，气流不断扩大，但解放层气体量减少。图4 瓦斯压力分别在10，15，20，30米处的状态图4 瓦斯压力分别在10，15，20，30米处的状态4 结论通过对流体流经多孔介质有限元分析，可以用来模拟在岩石和煤层瓦斯的初始状态。它也可以用来模拟诱导的采掘以及与瓦斯的压力和瓦斯流动的波动过程。解放围岩应力场是排放瓦斯的重要方法。同时，导致现有的瓦斯解放层条件也改变。这部分瓦斯融合到采掘区，瓦斯压力梯度变化较大。在被解放的煤层瓦斯压力逐渐减少。从而低渗透煤层和瓦斯突出危险煤层被解放，高渗透性煤层没有瓦斯突出危害。对解放层的开采，是建立安全及高效率矿井的条件。附录B1 The properties of the gas flow through porous mediaA porous medium saturated with a fluid has more different properties than a pure fluid medium （see Fig.1）. The porous domain consists of both fluid of the coal gas and solid such as coal seam and rock. In case the solid is rigid, the gas flows depend only on the properties of the fluid region that is formed by many all holes of possibly different shapes and sizes. Although the Navier-Stokes equations are valid for flows through porous media, the simulation of fluid flows through these regions of small scales is impractical and far beyond the capacity of present day computers if a large domain is considered.In order to determine the gas flow properties in porous media, the mean velocity must be used. During the averaging procedure, an important property of the porous media, called permeability, is introduced. Let us consider a simple example as shown in Fig.1, where the gas flows through a micro-circular hole are subjected to a constant pressure drop. The equation that governs the gas flow can be obtained：where, v is the velocity of gas flow in the hole. By imposing the no-slip condition on the wall, the exact solution can be obtained：Integrating the solution along the cross section of the hole, we can obtain the average velocity through the hole：Consider that such holes are sparsely located in a porous media that has a porosity , the averaged velocity is：The coefficient is called the permeability of pends on the shapes of the saturated region that differ from each other even in the porous medium. Furthermore, the permeability may not be isotropic. Nevertheless, a more general form that governs the gas flows through porous media can be expressed as：here, k is the permeability tensor, k=kEE;f is the body force of the gas flow. Eq.（1） is called the Darcys law. It governs the momentum conservation of the gas flow through the porous media. The continuity equations obtained in all sections are valid for the averaged velocity, which controls the mass conservation of the gas flow in the porous media considered. In other words, the gas flows can be assumed as compressible.The ideal compressible gas law：with constants specific heats Cp and Cv is used in the simulation of gas flows. Under most conditions, the specific heats depend on temperature and gas pressure.The compressible flows have the interdependence of gas pressure, temperature and density. The dependence results in a strong coupling of the momentum and energy equations, and presents a highly nonlinear be-havior in solutions.In order to obtain an averaged temperature solution, the material properties are averaged using the fluid and solid properties：The continuity equation, Darcys law and the energy equation form the governing equation system for the gas flow through the porous seam. The Darcys aw equation is different from Navier-Stokes equation.For instance, there is no derivative of the velocity.Some conventional no-slip wall boundary conditions may not be appropriate for porous media flows. Also note that Darcys law has no time derivatives. There- fore, if the body force f is constant, it is unnecessary to perform the transient analysis. Many gas flow problems in porous medium are in fact coupled with temperature using the Boussinesq approximation to the gravitational force. The Darcys law could apply the mass conservation by the pressure Poisson equation, the porous medium. It is clear that the permeability the pressure is very much like a velocity potential.The pressure in porous media is sometimes called pore pressure. When the deformability of the seam is considered, the velocity in Darcys equation must be replaced by the relative velocity v, where w is the velocity of the structure.2 Mathematic for mulation of the gas flow through porous media2.1 Governing equationsThe governing equations of the gas flows through porous media are the continuity equation, energy equation and Darcys equation. Where the continuity equation is：where the Darcys law is：where the energy equation is：2.2 Numerical methodThe momentum equation is weighted with virtual quantity of velocity and is integrated over the computational domain V. The divergence theorem is used to lower the order of the derivatives of the pressure, resulting in the expression of natural boundary conditions. The variational form is written as： where, his the virtual quantity of velocity. Using the related interpolation functions, the discretized equations are：3 Numeric alanalysis example3.1 General view of the modelThere are four coal groups from the top to the down underground in Pingdingshan coal district. The groups are named as E Coal Group, D Coal Group, C Coal Group and B Coal Group. They have the reasons to employ the mining technology of protective strata. There are rich Carbon-Permian coal and gas resources in Pingdingshan Coal District. Among those coal ores, the primary coal seam is named as D16-17 with the average thickness of 3.5 m. The gas pressure in the coal seam is relatively very high, the seam is clarified into the seam severely prone to coal-gas outburst. The average thickness of the upper coal seam（D15） is 1.5 m, the seam is clarified into little gas and no proneness to coal-gas outburst. The space between the two seams ranged from 1 to 16 m, the space mainly ranged from 1 to 6 m, the space scale between the two seams is 1.34.0 m. The seam （D15） is acted asprotective stratum, the seam （D16-17） is protected seam, the two seams were clarified into extremeshort-range strata.In order to simplify the numerical model, single layout is put out on the location among the coal seams as Fig.2. The physical and mechanical parameters of the coal seams are listed in Table 1. In Fig.2, the seam D15is 1.1 m thick, and is belong to thin seam. The seam （D16-17） is the primary mining seam and is 4.6 m thick. The seam D15is the protective stratum and the seam （D16-17） is the protected seam. There is sand mudstone between the two coal seams. The distance between the two seams is 5 m and the clarification is the extreme short-range protective stratumTable 1 Mechanical parameters of the coal and rock seams.StratumThin sandstoneSand mudstoneD15coal seamSand mudstoneD16-17coal seamSand mudstoneDensity（）267026001750230015002400Permeability coefficient（Darcy）Gas pressure（MPa）000.502.70Young modulus（GPa）16.74.00.3818.80.368.3The purpose is to simulate the excavation of protective strata step by step. The gas flow and gas pres sure variation in the protected stratum are analyzed.The protective stratum is excavated with six steps. The footage of each step is 5 m and the total length is 30 m. The initial gas pressure and the flow condition of the coal seams are set firstly. 3.2 Results analysisFig.3 displayes the initial gas pressure. Fig.4 displayes the gas pressure variation from the first excavation step to the sixth. The initial gas pressure in the seam D15 is 0.5 MPa and the initial gas pressure in the seam（D16-17） is 2.7 MPa. The gas flow and the gas pressure variation are induced by excavation. The gas flows from the protected stratum to the excavation zone and the gas pressure dissipates. The excavated zone becomes into the focus of gas flow and dissipation of gas pressure, the gas pressure gradient is very high. After excavating the first five meters, the gas pressure in the seam（D16-17） is changed into 0.87 MPa.After excavating 10 m, the pressure is changed into 0.78 MPa. After excavating 15 m, the pressure is 0.71 MPa. After excavating 20 m, the pressure is 0.66 MPa. When the excavating length is 25 m, the pressure is 0.61 MPa. At the end of the sixth excavating step, the pressure is 0.57 Mpa.Over the view of gas flow, the coal gas is still without any excavation. Once the motion of excavation disturbed, the stress field in the surrounding rock is changed, and there is certain deformation in the floor and roof of the protective stratum. Fracture
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