采矿英文文献.doc

英文原文Numerical simulation of coal seam joints and stiffness effects on coal bumpsYangdongjiang, yixinzhao, jiezhuChina University of Mining and Technology (beijing)Beijing, PRC 100083 yixin_AbstractThe numerical approach to translatory coal bumps analysis is used to examine the effects of joint and coal seam stiffness on the outburst velocity, deformation magnitude of the opening wall and plastic zone length in the coal seam. A series of tests are performed by varying the joint dip angles, spacing normal to joint tracks, joint block size and coal seam stiffness ratio to the surrounding rock. Results of joint and coal seam stiffness effects analysis indicate that joint dip angle, interval spacing, block size and coal seam stiffness ratio have profound influences on coal bumps. The increasing of interval spacing and joint block size can generate larger roadway deformation, lower roadway deformation velocity and longer plastic region in the coal seam. Higher stiffness ratio can also result in larger deformation, higher deformation velocity of opening wall. Coal bumps conditions deteriorate as the dip angle rotated to 90 degree or the elastic zones disappear in the whole active zone of coal seam for different spacing distributions. Keywords: Coal bumps, numerical simulation, joint, translatory 1、INTRODUCTIONUnderground coal bumps is one of the catastrophic mine failures result from sudden releases of energy. With the enormous amounts of released energy, coal bumps may cast several tons of coal mas openings horizontally, which always result in destruction and collapse of roadways, damage of facility even death and injury to the miners. The phenomenon of coal bumps can be found in various kin roadway shape. Coal bumps throws out large quantity of coal from the wall and then the roadway will be closed over hundreds of meters. The research is financially supported by Research Fund for the Doctoral Program of Higher Education under grant No. 20030290001.2、MECHANISM OF COAL BUMPS Generally speaking, coal bumps can be classified (Rice, 1935) into two types: One is pressure bumps which are caused when strong and brittle coal pillars or portions of pillars and loaded beyond their load-carrying capacity resulting in sudden and violent failure. The other is shock bumps, which are attributed to rupturing of strong strata above the coal seam. 34In fact, most coal bumps occurred like translatory rock bursts (Lippmann, 1989), which result in coal seam projecting dynamically into the excavation and the excavation can be closed over hundreds of meters. The qualitative description of the mechanism of coal bumps is shown in Figure 1.At pre-excavation state, the primitive overburden pressure q acting on the coal seam can be assumed to be at static friction elastic state, shown in Figure 2(a). However, after the roadway is mined out, the primitive vertical pressure exerted on the seam over the width of the excavation should be transferred onto the seam adjacent to the excavation 5.The vertical pressure distribution after excavation is shown in Figure 2(b). Perturbations in the original litho static stress field caused by the excavation can, therefore, result in coal/joint failure on the seam horizons. Thus, the coal seam can be divided into three distinct zones: the pressure relief zone A, maximum static equilibrium zone B and the primitive overburden pressure zone C.The mining induced seismic, detonations or other activities may cause waves and unstable crack propagation in the coal seam and surrounding rock. This will cause decrease of normal stress and increase of shearing stress to the interfaces between the coal seam and the adjacent overlying and underlying rock layers. The effects may convert the sticking friction into a sliding friction. Moreover, at the active zones, the coal seam near the excavation will be an active plastic region. Only when the whole active zones are transferred to be one active plastic region at some condition, the coal bumps are more likely to occur. Once the coal bumps occur, coal at A zone and portion of B zone will translatory eject to the roadways. 3、NUMERICAL SIMULATION TECHNIQUE 3.1 Numerical Modeling Numerical modeling using UDEC version 3.0 (ITASCA, 1996) has been carried out for Tangshan coal mine in order to investigate stability of 12 coal seam on 14th level. Numerical models were developed for analyzing the effects of three main parameters of joint on coal bumps. The geometry of the two-dimensional 40m40m model studied is shown in Figure 3. According to the mining depth and overlying strata situation, the original litho static stress of 21 Mpa is imposed on the top boundary of the mechanical model. Moreover, the tectonic stress is 25 Mpa loaded on the left and right boundary horizontally.3.2 Geo-Material Properties In current numerical modeling, the Mohr-Coulomb model was adopted. For all cases, the mechanical properties for coal seam and both the roof and floor rock are listed as the following, coal seam: elastic modulus 5.9 Gpa, passions ratio 0.34; the roof and floor rock: elastic modulus 36 Gpa and passions ratio 0.28. 4、ANALYSIS OF THE RESULTSWhen joints with straight joint traces are developed parallel to one another they form a set. The simulation focuses on analyzing the multiple joint set and coal seam stiffness ratio K (E/E) effects on coal bumps.The modeling was performed in two stages. Firstly, the effects of joint dip angle and joint spacing d were simulated by fixing the stiffness ratio K. Secondly, the effect of K was evaluated4.1 Joint effects on coal bumps 4.1.1 Joint dip angle effects Firstly, the effect of joint dip angle is simulated by changing from 0o to 90o in increments of 15o as counter clockwise. It is found that in all cases the coal bumps conditions deteriorate when the joint dip angle is rotated to the 90 degree. This means that at the same joint spacing condition the steeper joints make the coal seam grow easier unstable or outburst. It can be explained that the slender layers parallel to the wall of roadway in coal seam will easily buckle or rupture as compressed by the surrounding rocks or influenced by seismic events. The wall deformation and velocity toward the roadway are recorded by monitoring middle point of opening wall. With the dip angle of joint increasing, the deformation and the average deformation velocity of the opening wall increase. The distribution of simulation results is almost symmetry to=90o. The alterations of spacing distribution could not change the effect tendency of joint dip angle on the deformation and deformation velocity of roadway. The joint dip angle effects on both deformation and velocity at 1.0 m joint spacing are shown in Figure 4(a), Figure 4(b) and Figure4(c) respectively. 4.1.2 Joint spacing effects The simulation was performed by adopting joint spacing d with various values from 0.25 to 5.0 m in the dip angle of 45 degree. It is found that larger joint spacing can give rise to larger deformation of the roadway and lower outburst velocity of the coal seam, as shown in Figure 5. Moreover, the larger joint spacing leads to longer active plastic region in the coal seam.4.1.3 Joint block size effects Randomly sized polygonal blocks were created in the coal seam and the average edge length of block specified. The simulation results indicate that the size of joint blocks can affect deformation of roadway greatly. Bigger joint blocks leads to larger convergence deformation of roadway. This is because intact coal seam or larger coal blocks can store more strain energy easily, which will result in deformation of roadway and longer unstable process of roadway after excavation. However, to small blocks, more strain energy was consumed by joint sets, which leads to smaller deformation of road faster deformation velocity. 4.2 Stiffness ratio effects Considering the relative stiffness of coal seam and surrounding rock, the simulation was performed by changing the stiffness ratio K (E/E from 1 to 15 in increments of 2.5. Moreover, there is a joint set consisting of multiple joints, which has=45o and d=1.0m, in the coal seam. It is assumed in the present study that the reduced “competence” of the coal seam is directly associated with reduced stiffness coal. The translatory bumps seem to occur only where the rock in the roof and floor layers adjacent to the seam are about 10 times stiffer and stronger than the coal (Lip man, 1989). The simulation results also show that whether the joint spacing is large or small, the deformation of the roadway and the initial deformation velocity of the roadway wall after excavation increase along with the increasing of stiffness ratio, as shown in Figure 7.5 CONCLUSIONS Result of joint and stiffness ratio effects analysis indicate that joint dip angle, interval spacing, join block size and stiffness of coal seam and surrounding rock have profound influences on coal bumps. The increasing of interval spacing can generate larger deformation, lower initial outburst velocity of the opening wall and longer active plastic region in the coal seam. Higher stiffness ratio can also result in larger roadway deformation, higher initial outburst velocity of coal seam. Coal bumps conditions deteriorate as the dip angle rotated to 90 degree or the elastic zones disappear in the whole active zone of coal seam for different spacing distributions. The simulation gives the proof to the techniques of preventing coal bumps, such as relief blasting or relief drilling which can cause many small fractures/joints in the coal seam adjacent to excavation. This study also indicates that joint spacing, joint dip angles, joint block size and the stiffness ratio play an important role on coal bumps or coal seam translatory deformation to the roadway. 中文翻译数值模拟煤层节点和刚度影响煤层突出江杨冬 赵义新 朱杰 中国矿业大学（北京） yixin_摘 要这种数值计算方法转变煤层突出分析是用来研究影响煤层联合和刚度的突出速度，开放性隔离墙和塑性区长度煤层的变形量。一系列测试是在不同的节理倾向，间距正常的联合轨道，结合块大小和煤层刚度比的围岩来进行的。结果显示，节点和煤层刚度影响的分析表明，节理倾向，间距，块大小和煤层刚度深层影响了煤层突出。间距和联合块大小的增加可以产生较大的巷道变形。降低巷道变形速度和更长的塑行区煤炭煤层。高等的刚度比也可造成较大的变形以及开孔墙的高变形速率。煤炭突出恶化的条件是随着倾角以90度旋转或者弹性区消失在煤层整个活动区的不同间距分布。关键词：煤层突出； 数值模拟； 节点； 平动1导言地下煤层突出是矿井事故其中一个导致地雷突然释放巨大能源。随着大量能源释放，煤层突出也许能铸造几顿煤多智能体开孔的水平，这样通常是造成道路的破坏和坍塌，损坏设备甚至是矿工的受伤和死亡。煤层突出这种结构能在各种类似的巷道形状中被找到。煤炭突出从壁面抛出大量的煤炭，然后巷道被关闭了几百米。2煤炭突出的原理一般而言，煤层突出可（水稻，1935年）分为两类：其一是颠簸的压力时造成强大和脆性煤柱或部分支柱和负荷超过其承载能力导致突然和暴力失败。另一种是冲击碰撞，这是由于（3-4）断裂。事实上，大多数煤层突出发生就像平动的岩石暴发强有力的阶层以上的煤层。（李普曼，1989年） ，这导致煤层突出的动态预测的挖掘及挖掘能被关闭几百米。煤突出的定性描述的机制如图1所示：图1.定性描述的煤层突出机理1.平动区域 2.突出外的区域 3原始巷道壁体 在先前挖掘区域内，覆盖层的原始压力q代表煤层可假定在静摩擦弹性状态下，如图2 （a）所示。然而，在巷道被开采后，原始的垂直压力的焊缝宽度的挖掘应该转移到（5）. 垂直开挖后压力分布图显示的煤层附近是挖掘处2（b） 。在原始的地压力扰动下造成的应力场可以挖掘，因此，导致煤或节点失败的煤层视野。因此，煤层可分为三个不同的区域： 减压A区，最大静态平衡区B和原始覆压区C.图2.垂直压力分布(a)预挖阶段 （b）开挖阶段采矿诱发地震，爆炸或其他活动可能引起海啸和在煤层与围岩里不稳定裂纹扩展。这将导致减少了正应力和剪应力增加的接口之间的煤层和邻近的上覆岩层和根本。这种影响可能会将粘性摩擦转换为滑动摩擦。此外，在活跃区，煤层附近的挖掘将是一个活跃的塑性区。只有当整个活动区在一些条件下，转移到一个积极的塑性区，煤层突出更可能发生。一旦煤层突出发生，A区的煤和B区一部分的煤将转移喷射到巷道。3数值模拟技术3.1数值模拟为了研究稳定的12煤层的第14水平，数值模拟利用UDEC 3.0版（艾塔斯卡， 1996年）已经在唐山矿被使用。数值模式被开发用于分析煤层突出中三个主要参数的联合的影响力。几何形状的二维模型研究如图3所示。根据开采深度和上覆岩层的情况下，21mpa的原始地压应力是力学模型边界的顶端。此外，构造应力为25mpa被水平地载荷在左边和右边界。图3 数值模型原来示意图3.2地质材料属性目前的数值模拟，在莫尔库仑模型被接纳。在所有情况下，机械特性和煤层的顶底板岩石被列为如下，煤层：弹性模量5.9Gpa泊松！ S比值0.34；顶底板岩石：弹性模量36千兆泊松！ S比值0.28 。4分析测试结果当节点和直节点轨迹与另个相平行时进行，它们形成一个体系。模拟仿真重点分析了多个节点装置体系和影响煤层突出的煤层刚度比K(E2/E1)。(a)突出变形曲线 (b)起初突出速度曲线 (c)平均变形速度曲线图4 节理倾角影响的曲线 (a)突出变形曲线 (b)平均变形速度曲线 (c)塑性区长度曲线图5节理间距影响的曲线这个建模在两个阶段实行。首先，联合倾角和联合间距D区的影响是通过定位刚度比K来进行模拟的。其次，对K