采矿专业中英文文献翻译关于倾角煤层挖掘巷道的锚杆支护的研究.pdf

本科毕业设计 论文 通过答辩 原文 study on gateway bolting excavated in inclined coal seam tao lianjin 陶连金 wang yongjia 王永嘉 zhan zhuoyuan 张倬元 northeastern university shenyang 110006 chengdu university of technology chengdu 610059 abstract a typical gateway is analyzed using fully deformable discrete element method the fractured zone around the gateway is measured in field based on the measurement results and theoretical analysis a comprehensive support scheme adopting bolt and steel belt is proposed discrete element method is used to asses the bolting scheme and displacement monitoring in field is also carried out having been put into practice it is proved that the scheme is both successful and rational according to theoretical analysis and monitoring in filed some important keynotes that should be noticed in gateway bolting practice are presented as well keywords inclined seam gateway strata behavior bolting discrete element method introduction inclined coal seam is generally regarded as seam with a dip single 25 45 o which occupies a considerable proportion in both production and reserves in china problems related to strata control are however seldom studied and researches on in seam gateway are even 1 less the maintenance expense of gateway in inclined seam is generally 30 higher than that in nearly flat and gently inclined seam the reason why there exists a such phenomenon is complicated itself another possible reason is the lack of the inherent strata behavior law at present problems related to in seam gateway maintenance are highly emphasized and many studies on strata behavior and support of gateway are carried 2 4 out such researches play a positive role in gateway maintenance however most of the researches are carried out in flat or gently inclined seams due to their locating in remarkably anisotropic media and environment gateways in inclined seams are often subjected to unfavorable loads and deform unevenly strata move more intensively than that in gently inclined seam and the broken region is also large which makes gateway support even more difficult in view of the above mentioned facts we use fully deformable discrete element method in simulating strata behavior of gateway in inclined seam and the loosed zone around the gateway is also monitored in field based on the results a bolting scheme is proposed after putting into practice the scheme is proved to be effective and rational 1 deform and fail features of gateway without any support 本科毕业设计 论文 通过答辩 1 1 geologic conditions the study object is the no 36 seam in baoshan coal mine the dip angle of the seam is 35 and thickness is 1 0m the geologic conditions are rather simple the average buried depth is 440m the immediate roof is 2 meters thick of fine sandstone and shale the overall strength is low above the immediate roof is comparatively hard main roof the floor is fine sandstone the gateway width is 2 2m and the gateway is excavated in irregular shape in order to keep the roof intact the sidewall coal is however rather soft and loose and easily fails the surrounding rocks of the gateway are not stable roof and sidewall are apt to fall or break which is dangerous to both production and human safety the working face often stopped due to difficult maintenance of the gateways 1 2 simulation of gateway deformation and failure with discrete element method the joint statistical results show that the surrounding rocks of the gateway are cut by two orthogonal joints one group is the bedding plane of the coal measures another group is normal to the bedding plane mainly developed in the immediate roof because of the low strength of immediate roof there often exist long joints that cross through the immediate roof such long joints play a dominant part in roof falling according to the spatial distribution of joints a discrete element model is built as shown in fig 1 thecomputing parameters required are mainly based on measurement in field and some back analysis the load applied to the model are gravitational stress field the discrete elements are fully deformable so that he deformation of block can be involved after the gateway is excavated under the action of initial stresses the upper sidewall coal firstly breaks then the surface of the lower sidewall coal begins to yield the abutments of the roof at the two sidewall transfer to deep solid coal in consequence the immediate roof at the surface of the gateway begins to bend bedding separate fail and fall see fig 2 as a result large area of the roof falls until up to the main roof some broken blocks may collapse when a small disturbance occurs in the practical face it is very difficult to deal with the fallen rocks sometimes a chain collapse of upper immediate roof may occur if special attention is not paid which makes the fallen rock disposal a difficult and dangerous task 本科毕业设计 论文 通过答辩 the results indicate that two sidewall coals fail differently the upper coal breaks more intensively than the lower sidewall coal according to the above mentioned analysis it can be seen that in middle to lowly hard thin inclined seam the stability of the two sidewall coals is very important to the overall stability of the gateway if the sidewall fails then the abutments of the roof will transfer to deep solid coal as a result the free span of the roof increases which aggravates the unstable condition of the whole gateway such failure of surrounding rocks is even serious when it is subjected to mining influence it is thus the key to keep the sidewall solid and intact in order to keep the overall stability of gateway in inclined seams 2 measurement of loosed zone around gateway based on loosed zone theory of excavation a loosed zone is generally formed around the excavation if which the stress is lower than the initial stress owing to irregular shape of gateway in inclined seam and anisotropic media the loosed zone around gateway is certainly in irregular shape we use an ultrasonic joint detector type sc ii by fushun institute of coal science and technology to measure the loosed zone of the gateway the test results are shown in fig 3 the gateway was supported by two roof bolts 1 6m long with very slightly prestressed the measured loosed zone is upper sidewall coal more than 1 8m lower sidewall coal 1 4 1 5m and the roof is 0 95 1 1m 本科毕业设计 论文 通过答辩 the gateway can be stable without mining influence but as long as being subjected to mining activity the gateway will collapse wit sidewall failing and roof falling in extreme case the maximum caving height can reach as high as 4 0m as a result the gateway in the seam is very difficult to be maintained and the maintenance cost is thus rather high the test results are coincided with the numerical calculation so it is therefore necessary to reinforce the gateway including the sidewall comprehensively 3 inclined combined beam model for roofbolts in inclined seam roofbolts combine roof together when bolt length is shorter than the soft and loose roof of course if the bolt can be bolted at a competent stratum then the bolting mechanism will become hanging over a typical inclined combined beam model is illustrated in fif 4 the beam is composed by several total numbers of layers are k different kinds of strata with length l and thickness it is assumed that 1 each layer of the beam is homogeneous continuous and isotropic 2 the beam conforms to small deformation and 3 each layer deforms together and no slip along bedding occurs according to strength criteria of the beam the minimum thickness can be derived and then the total length of a bolt can be easily determined as follows 12 lll 1 where 1 l is the length of bolted end 2 l is the length of outer part bolt spacing a can be derived by the criteria that no slip occurs along bedding planes besides the above mentioned conditions the safety of the combined beam must be checked to prevent it from longitudinal instability when all the conditions are satisfied roof bolt parameters can ready be 本科毕业设计 论文 通过答辩 determined as for sidewall bolts their length and spacing can be derived by soil bracing theory in soil mechanics it should be noticed when roof is composed of weak and loose strata some bracing measures must be taken to protect the integrity of the fragile roof 4 bolting of the gateway and its assessment 4 1 support assessment by discrete element method we consider two case in order to compare first case only the roof is bolted second case both roof and sidewall are bolted having been bolted in the first case the roof has a obvious higher stiffness and strength in the initial stage only slight deflection occurs however with the sidewall coal failing and caving the free span of the roof increases the roof gradually enters unstable stage subsiding and bedding separating as shown in fig 5 compared with the unsupported gateway the gateway with roof bolted can keep stability for much longer time even it destabilizes finally in the second case the sidewall coal deformation and failure are strictly controlled by the sidewall bolts the sidewalls are stable roof deflects only a small amount displacement can be hardly seen in the block diagram fig 6 the overall surrounding strata are in stable conditions even influenced by mining activity the gateway only fails locally the roof is however rather stable it is thus important to adopt a comprehensive bolt support pattern including the sidewalls 4 2 bolting scheme and its implementation based on the inclined combined beam theory gateway loosed zone measurement and discrete element analysis four bolts 1 6m long are installed in the roof at the outer end of each bolt a testing device is installed 5 patent of national bureau of china to ensure that at least 20kn pretension is exerted bolt spacing is 0 75m array pitch is 1 0m due to rather developed joints steel bends are used together with roof bolt to ensure support effectiveness and prevent local roof caving the steel plate is 本科毕业设计 论文 通过答辩 0 01m thick 0 89m long and 0 1m wide the coal sidewall is reinforced by timber bolt with spacing 1 0m timer bolt for upper sidewall is 2 0m long and 1 0m for the lower sidewall the timber bolt is installed with no less 7 5kn pretension in the influence zone of front abutment pressure strengthened supports are added metal frictional prop with timber cap is set as temporary reinforcement the reinforcement distance is 25m ahead of the working face the reinforced props are arranged in the center line of the gateway more attentions should be paid to gateway excavation procedure the roof bolts should be installed as soon as possible after the roof is exposed then the sidewall bolt the maximum delayed time should be less than 6 hours which can make the roof deform exceedingly and integrity worsening after each construction cycle the bolts near the driving face should be refastened to assure their anchorage force 4 3 measurement of gateway closure in order to assess the effectiveness of the support scheme the gateway closure is monitored during its driving and working face retreating the closure of roof vs floor sidewalls and roof subsiding velocity are shown in fig 7 it can be seen that when the working face is far away from the monitoring area the deformation of the surrounding rocks is very small indicating that the gateway is not influenced by face dynamic pressure the support system can easily bear the static load of gateway itself with the working face advancing the gateway begin to sense the dynamic action of the working face when the distance between the face and monitoring area is around 20 meters the deforming velocity of surrounding is increasing obviously and the strata is moving remarkably such response of the gateway is the dynamic action of the working face the testing results show that the reinforced distance should be more than 20 meters however from the overall status of the surrounding rock the gateway is in stable conditions and can satisfy the demand of coal transportation air intake and other engineering function in spite of the fact that there are 2 3 groups of joints distinctively shown if the roof the roof is however stable under the combined action of roof bolts and steel bens the upper sidewall coal fails and falls in some places but the depth is limited 本科毕业设计 论文 通过答辩 within 0 6m based on the facts in field in brief the support scheme is rational and effective good economic and rechnical benefit were obtained 5 conclusion the failure pattern of gateway in inclined seam is remarkably anisotropic the failure zone is not only related to the mechanical properties of strata but also closely to the stability of sidewall coal body the sidewall coal failure causes the abutment points to transfer into deep solid coal increase the free span of the roof and therefore worsen the roof integrity it is thus a key task to keep the gateway sidewall sound in gateway maintenance by gateway loosed zone testing combined with the inclined combined beam model bolt parameters can be readily determined discrete element method can be adopted to verify the rationality and make some amendment as for the roof with multiple soft and loose layers ensuring bolt pretension and installing roof bolts as early as possible are the keys to make the roof stable meanwhile to keep roof integrity with steel bends sometimes metal net is needed is another important measure it is proved that bolting can be use in gateway with fragile and weak roof as long as necessary measures are taken considerable economic benefit can be obtained references 1 陶连金 大倾角煤层开采矿山压力显现及其控制 学位论文 沈阳 东北大 学 1996 70 79 2 候朝烔 郭宏亮 我国煤巷锚杆动手术的发展方向 煤炭学报 1996 21 2 113 118 3 陈炎光主编 中国煤矿巷道围岩控制 徐州 中国矿业大学出版社 1995 3 4 67 70 4 陶连金 宝山煤矿巷道围岩松动范围测试 建井技术 1993 3 4 67 70 5 刘明远 陶连金 李芳成等 锚杆预紧力标示圈 1993 国家专利号 93208997 6 本科毕业设计 论文 通过答辩 中文译文 关于倾角煤层挖掘巷道的锚杆支护的研究 关于倾角煤层挖掘巷道的锚杆支护的研究 摘要摘要 一种典型的巷道是使用完全可变形的离散元素法 巷道周围的断裂区 域是有规则的 在测量结果和理论分析的基础上 一种全新的使用锚杆和铁板的 支护方案被提出 离散元素法被用于评估锚杆支护方案 并且取代了在现场上经 常采用的监测手段 自从投入到实际应用以来 这种方案被证实是成功的和正确 的 对于理论分析和现场的监测 一些在巷道螺栓连接的实践中必须被注意的关 键点最好还是总结一下 关键词关键词 倾斜地层 巷道 地层运动 锚杆支护 离散元素法 概述概述 倾角煤层一般是指煤层有一个 25 到 45 的下沉角度 这种煤层在中国的产量 和储存量中占有相当大的比例 涉及到地层控制的问题 很少被研究 并且研究 地层巷道的学者就更少了 维护倾斜煤层巷道的费用一般来说比近似平直和逐渐倾斜的煤层巷道的费 用要高百分之三十 导致出现这种现象的原因一是自身的复杂情况 另一个是基 本的地层运动理论 目前 关于煤层巷道的维护问题已经引起关注 并且许多关于地层运动和巷 道的支撑的研究已经展开了 这些研究在巷道的维护过程中 起到了积极的作用 然而 大多数研究是围绕平直或者是逐渐倾斜的煤层展开的 由于他们是定 位在非常特殊的各有异性的媒介和环境中的 而在倾斜煤层的巷道通常受到不利 的载荷并且不均衡的产生变形 地层运动比逐渐倾斜的煤层要强烈 另外遭到破 坏的区域也是很大的 这就造成了巷道的支撑更加困难 从以上提到的情况来看 我们在仿真倾斜煤层巷道的地层运动中使用了完全 可变形离散元素法 并且在巷道的承载小的区域也被监控起来 基于这些监控结 果 一种螺栓连接的方法被提出 等到付诸实践以后 这种方法被证明是有效的 并且是合理的 1 没有任何支撑的巷道的变形和实效特征没有任何支撑的巷道的变形和实效特征 1 1 地质条件地质条件 研究对象是宝山煤矿的第 36 号煤层 煤层的向下倾角是 35 度 煤层厚度是 1 米 地质条件是相当简单的 平均的埋藏深度是 440 米 巷道上紧接着的顶 是 2 米厚的沙岩和页岩 施加全部的载荷是低的 再一层是比较硬的重要的顶 这一层是沙岩 巷道的宽度是 2 2 米并且为了保持顶不被改变 巷道被以不规则 的形状挖掘 边墙的煤却是又软又松 很容易掉下来 巷道周围的岩石不是很稳 定 顶和边墙易于倒下或者断裂 这对于煤炭生产和矿工的安全都是一个隐患 工作进程经常由于巷道的困难得维护而停止 1 2 用离散元素法来仿真巷道的变形和失效用离散元素法来仿真巷道的变形和失效 接缝的统计结果表明巷道的围岩是被两个垂直的接缝破坏的 一条是煤矿测 量的基床 另一条是垂直于基床的 主要发生在紧邻的顶 由于紧邻顶的低强度 常常会出现穿透紧邻顶的长裂缝 这么长的裂缝是冒顶事故发生的主要原因 按 照裂缝的空间分布 建立起一个如图 1 的离散元素模型 计算所需要的参数主要 基于现场的测量和一些后续的分析 模型实际的负载是重力 这些离散元素是完 全可变的 因此岩石的变形可以被考虑在内 本科毕业设计 论文 通过答辩 当巷道被挖掘好以后 在处应力的作用下 上方边墙的煤层首先破裂 接着 下方边墙的煤层的表面开始屈服变形 结果两个边墙的间的顶的支撑变成深层的 坚实的煤层 在巷道表面的紧邻的顶开始弯曲变形 基床分离 失效并且掉落 如 图 2 结果大面积的顶掉落 直到到主顶 当一个小震动发生时 一些破碎的 岩石可能倒塌 实际上 掉落的岩石很难处理 有时如果没有特别关注 上方紧 邻顶可能会发生一系列倒塌 那会使掉落岩石的处理成为一项困难并且危险的任 务 图 1 离散元素模型的岩石分割 图 2 巷道周围围岩的状况 结果表明两个边墙煤层的失效是不同的 上方的煤层比下方煤层更容易破 裂 按照上面提到的分析 可以看出在中间对于低的薄硬倾斜煤层 两个边墙煤 层的稳定性对于整个巷道的稳定性是非常重要的 如果边墙失效 接着顶的支撑 将会变成深层的坚实的煤层 结果顶的自由跨距增加 这样会加大整个巷道的不 稳定性 当受到采煤的影响时 围岩的失效会更严重 这样保证整个倾斜煤层巷 道的稳定性的关键就是保证边墙的坚实和完整 2 巷道周围的松动区域的测量巷道周围的松动区域的测量 基于松动区域的挖掘理论 一个松动区域通常在挖掘的洞的周围形成 因为 那的应力比初应力低 由于倾斜煤层巷道的不规则形状和各向异性的媒介 在巷 道周围的松动区域也是不规则的形状 我们使用一种超声波裂缝探测仪 抚顺煤 炭科学和技术学院研发的型号为 sc ii 来测量巷道的松动区域 测试结果如图 3 所示 巷道被两个到顶的 1 6 米的锚喷支护支撑 锚喷支护内有一点混凝土预 应力 被测量的松动区域是上方边墙煤层高 1 8 米 下方边墙煤层低 1 4 到 1 5 米 并且顶的高度是 0 95 到 1 1 米 本科毕业设计 论文 通过答辩 图 3 倾斜煤层巷道周围松动区域的结果 巷道在没有开采影响下可以是稳定的 但是只要受到开采的影响 巷道将会 由于边墙的失效和顶的掉落而倒塌 在最终的情况下 最大的采矿高度可以达到 4 0 米 因此倾斜煤层的巷道很难维护 而且维护费用非常高 测试的结果是符合数 值计算的 所以加固包括边墙在内的巷道是非常必要的 3 锚杆顶的倾斜组合横梁的模型锚杆顶的倾斜组合横梁的模型 在倾斜煤层中 当锚杆的长度小于软且松动的顶时 锚杆顶将倾斜的顶联合 起来 当然如果锚杆可以支撑到一个合适的地层 那么锚杆装置将会挂在上面 一种典型的倾斜组合横梁模型如图 4 所示 横梁是由几个 层的总数为 k 不同 性质的长度为 l 且厚度 为地层组成的 有如下假设 1 每一层的横梁是均匀 的 连续的 各向同性的 2 横梁屈服于小的变形 3 每一层同时变形 且 没有在基面上的滑动 图 4 倾斜组合横梁的锚杆顶模型 按照横梁的标准强度 组合横梁最小的厚度 可以被得出 并且锚杆的 总长度可以被容易的确定如下 2 1 l l l 1 这里 1 l 是锚杆的长度 2 l 是伸出部分的长度 由锚杆不会沿着基床滑动的规律 锚杆间距 a 可以得出 除了以上提到的条 本科毕业设计 论文 通过答辩 件 组合横梁的安全性一定要被检查 以保证它的纵向的稳定性 当所有的条件都具备了 锚杆顶参数就可以被确定了 至于边墙的锚杆 它 们的长度和间距可以由岩土力学中的岩土支撑理论得出 当顶是由不牢固和松软的地层构成时 一定要实施一些支撑的措施 来保护 易碎顶的完整性 4 巷道的锚杆支护及其评定巷道的锚杆支护及其评定 4 1 离散元素法的支撑评定离散元素法的支撑评定 我们考虑到两种情形来比较 一种是只有顶被锚杆支护 另一种是顶和边墙 都被支护 使用第一种情形的支