混凝土喷射机说明书2

中国矿业大学 2007 届本科生毕业设计 第 66 页 Where , is the length of bolted end ; is the length of outer part.1l 2lBolt 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 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.1. Bolting of the gateway and its assessment 1.1 Support assessment by discrete element method We consider two case in order to compare , firstcase: 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).中国矿业大学 2007 届本科生毕业设计 第 67 页 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.1.2 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( of National Bureau of 5patenChina) 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 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.1.3 Measurement of gateway closureIn 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. 中国矿业大学 2007 届本科生毕业设计 第 68 页 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 23 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 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.2. 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.中国矿业大学 2007 届本科生毕业设计 第 69 页 References1. 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。70792. 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）：1131183. 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（34）： 67704. 陶连金.宝山煤矿巷道围岩松动范围测试.建井技术,1993(34):67705. 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中文译文关于倾角煤层挖掘巷道的锚杆支护的研究摘要 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 倾斜地层 巷道 地层运动 锚杆支护 离散元素法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1.1 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，煤层厚度中国矿业大学 2007 届本科生毕业设计 第 70 页 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。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，锚喷支护内有一中国矿业大学 2007 届本科生毕业设计 第 71 页 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。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：（1）21l这里 是锚杆的长度； 是伸出部分的长度1l中国矿业大学 2007 届本科生毕业设计 第 72 页 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4.1 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护，在初期顶板明显要承受更高的应力，只有轻微的偏差发生。然而随着边墙煤的掉落和开采，顶板的自由跨距在增加，顶板逐渐进入不稳定阶段，下沉和基床的分离如图 5 所示。同无支撑的巷道相比，经过锚杆支护的顶板的巷道可以在一个比较长的时间内保持稳定，甚至到它最终动摇。在第二种情形，边墙煤层的变形和失效被边墙的锚杆严格控制，边墙是稳定的。顶板只偏转了一个很小的角度。在如图 6 所示的岩层图表中几乎看不到位移。整个周围的地层处在稳定的条件下，哪怕受到开采的影响，巷道只会局部的失效，顶板还是相当稳定。因此采用一种全面的包括边墙锚杆支护形式是非常重要的。图 5 当只有顶板被锚杆支护时的周围地层的运动中国矿业大学 2007 届本科生毕业设计 第 73 页 图 6 当采用全面支护时顶板的稳定性4.2 锚杆支护的方案及其应用基于倾斜的组合横梁理论，巷道松动区域的测量和离散元素分析，在顶板上安装四根 1.6 米长的锚杆。在每一根锚杆外部的末端，安装了一种测试装置（中国国家专利局的专利）来确保锚杆最少能承受 20kN 的负载。锚杆间距是0.75 米，排列斜度是 1.0 米。对于已经形成的裂缝，钢结构同锚杆顶板一起使用，来保证支撑应力和预防局部顶板掉落。钢板是 0.01 米厚，0.89 米长和 0.1米宽。边墙的煤层被间距是 1.0 米的木料锚杆加固，木料锚杆对于上方边墙是 2.0米长，下方边墙是 1.0 米长。木料锚杆安装好后，则不会少于 7.5kN 的负载。对于前面的邻接压力所影响的区域，增加了加固支护。有木料盖的金属磨擦支撑被作为临时加固。加固的距离是在工作面前方 25 米。加固物被排列在巷道的中心线上。更多的关注应该投向巷道的挖掘过程。顶板的锚杆支护要在顶板露出后马上完成，接着是边墙支护。最多延迟时间不