Key technologies and equipment for a fully mechanized top-coal caving operation with a large mining height at ultra-thick coal seams

Thick and ultra-thick coal seams are main coal seams for high production rate and high efficiency in Chinese coal mines, which accounts for 44 % of the total minable coal reserve. A fully mechanized top-coal caving mining method is a main underground coal extraction method for ultra-thick coal seams. The coal extraction technologies for coal seams less than 14 m thick were extensively used in China. However, for coal seams with thickness greater than 14 m, there have been no reported cases in the world for underground mechanical extraction with safe performance, high efficiency and high coal recovery ratio. To deal with this case, China Coal Technology ＆ Engineering Group, Datong Coal Mine Group, and other 15 organizations in China launched a fundamental and big project to develop coal mining technologies and equipment for coal seams with thicknesses greater than 14 m. After the completion of the project, a coal extraction method was developed for top-coal caving with a large mining height, as well as a ground control theory for ultra-thick coal seams. In addition, the mining technology for top-coal caving with a large mining height, the ground support technology for roadway in coal seams with a large cross-section, and the prevention and control technology for gas and fire hazards were developed and applied. Furthermore, a hydraulic support with a mining height of 5.2 m, a shearer with high reliability, and auxiliary equipment were developed and manufactured. Practical implication on the technologies and equipment developed was successfully completed at the No. 8105 coal face in the Tashan coal mine, Datong, China. The major achievements of the project are summarized as follows： 1. A top-coal caving method for ultra-thick coal seams is proposed with a cutting height of 5 m and a top-coal caving height of 15 m. A structural mechanical model of overlying strata called cantilever beam-articulated rock beam is established. Based on the model, the load resistance of the hydraulic support with a large mining height for top-coal caving method is determined. With the analysis, the movement characteristics of the top coal and above strata are evaluated during top-coal caving operation at the coal face with a large mining height. Furthermore, there is successful development of comprehensive technologies for preventing and controlling spalling of the coal wall, and the top-coal caving technology with high efficiency and high recovery at the top-coal caving face with a large mining height. This means that the technologies developed have overcome the difficulties in strata control, top-coal caving with high efficiency and high coal recovery, and enabled to achieve a production rate of more than 10 Mtpa at a single top-coal caving face with a large mining height in ultra-thick coal seams; 2. A hydraulic support with 5.2 m supporting height and anti-rockburst capacity, a shearer with high reliability, a scraper conveyor with a large power at the back of face, and a large load and long distance headgate belt conveyor have been successfully developed for a top-coal caving face with large mining height. The study has developed the key technologies for improving the reliability of equipment at the coal face and has overcome the challenges in equipping the top-coal caving face with a large mining height in ultra-thick coal seams; 3. The deformation characteristics of a large cross-section roadway in ultra-thick coal seams are discovered. Based on the findings above, a series of bolt materials with a high yielding strength of 500-830 MPa and a high extension ratio, and cable bolt material with a 1 × 19 structure, large tonnage and high extension ratio are developed. In addition, in order to achieve a safe roadway and a fast face advance, installation equipment for high pre-tension bolt is developed to solve the problems with the support of roadway in coal seams for top-coal caving operation with a large mining height; 4. The characteristics of gas distribution and uneven emission at top-coal caving face with large mining height in ultra-thick coal seams are evaluated. With the application of the technologies of gas drainage in the roof, the difficulties in gas control for high intensive top-coal caving mining operations, known as ＂low gas content, high gas emission＂, are solved. In addition, large flow-rate underground mobile equipment for making nitrogen are developed to solve the problems with fire prevention and safe mining at a top-coal caving face with large mining height and production rate of more than 10 Mtpa. A case study to apply the developed technologies has been conducted at the No. 8105 face, the Tashan coal mine in Datong, China. The case study demonstrates that the three units of equipment, i.e., the support, shearer and scraper conveyor, are rationally equipped. Average equipment usage at the coal face is 92.1%. The coal recovery ratio at the coal face is up to 88.9 %. In 2011, the coal production at the No. 8105 face reached 10.849 Mtpa, exceeding the target of 10 Mtpa for a topcoal caving operation with large mining height performed by Chinese-made mining equipment. The technologies and equipment developed provide a way for extracting ultra-thick coal seams. Currently, the technologies and equipment are used in 13 mining areas in China including Datong, Pingshuo, Shendong and Xinjiang. With the exploitation of coal resources in Western China, there is great potential for the application of the technologies and equipment developed.

Development and prospect on fully mechanized mining in Chinese coal mines

Fully mechanized mining(FMM)technology has been applied in Chinese coal mines for more than 40 years.At present,the output of a FMM face has reached 10-million tons with Chinese-made equipment.In this study,the new developments in FMM technology and equipment in Chinese coal mines during past decades are introduced.The automatic FMM technology for thin seams,complete sets of FMM technology with ultra large shear height of 7 m for thick seams,complete sets of fully mechanized top coal caving technology with large shear height for ultra-thick seams of 20 m,complete sets of FMM technology for complex and difficult seams,including steeply inclined seams,soft coal seams with large inclination angle,and the mechanized filling mining technology and equipment are presented.Some typical case studies are also introduced.Finally,the existing problems with the FMM technology are discussed,and prospect of FMM technology and equipment applied in Chinese coal mines is put forward.

Demonstration Project of Safe and Efficient Mining Operations in Extra-thick Coal Seam

Mineable coal reserves in thick and extra-thick seams account for 44% of the total deposit in China. Fullymechanized top-coal caving technology is a new mining method of safe and efficient underground operations in extra-thick seams in China. The development of fullymechanized top-coal caving technology in China, which was successfully applied in Face 8105 in Tashan Coal Mine, Datong, Shanxi, China, is analyzed in this paper.Studies on movement pattern of top-coal and roof from fully-mechanized top caving face in 14–20 m extra-thick seams have been carried out. A series of key technologies were successfully developed, including strata control technology, equipment for high-efficient and high-recovery top caving operations, and safety guarantee technology for low gas occurrence and high gas emission. As a result, the fully-mechanized top-coal caving Face 8105, with large mining height in Tashan Coal Mine, has achieved a recovery rate of 88.9% and an average equipment operation rate of 92.1%. With coal production of 10.84 Mt in 2011,the demonstration project is a technology and equipment breakthrough for fully-mechanized top-coal caving face in extra-thick coal seams with large mining height.

松软煤层大采高工作面煤壁片帮机理及深浅孔交替超前预注浆加固技术研究

目的为探究松软煤层大采高工作面煤壁片帮机理,并对片帮严重的松软煤层大采高工作面煤壁进行有效控制,方法利用材料力学理论得到煤壁片帮的频发位置,引入煤壁剪切破坏准则,得出松软煤体煤壁片帮的主控因素。并以李村煤矿1305工作面为例,通过FLAC3D建立数值模型,以煤壁最大位移、煤体破坏深度、支承压力大小和支承压力峰值位置4个因素作为参考比较对象,通过引入正交试验法,研究了煤层埋深、内摩擦角、黏聚力、抗拉强度以及支护强度对煤壁片帮的影响程度。结果结果表明:煤体自身的物理力学性质(内摩擦角和黏聚力)是影响煤壁片帮的主要因素,其次煤体的赋存条件(埋深)也是一个较为关键的影响因素。结论工业性试验基于正交试验结果提出了大采高综采工作面深浅孔交替超前预注浆加固技术,有效控制了李村煤矿1305工作面煤壁片帮严重情况,为其他类似地质条件大采高综采工作面煤壁片帮控制提供了借鉴。

6~10 m厚煤层超大采高液压支架及其工作面系统自适应智能耦合控制

厚煤层储量及产量占我国原煤总储量及产量的一半,通过梳理厚煤层开采历史沿革,总结了我国厚煤层开采40年来的技术及装备研发实践,系统分析了以高端大采高液压支架及围岩智能耦合理论为代表的6~10 m大采高综采高效智能化综采技术及装备研究进展,提出了大采高支护理论及围岩智能耦合控制的突破是厚煤层一次开采高度突破的首要因素,完善的感知体系建立是液压支架自适应支护的前提,数字技术的应用为大采高工作面高效推进及装备智能协同控制提供了新的技术途径;阐明了大采高综放液压支架与围岩耦合关系,剖析了采高增加对硬煤层冒放性的有利影响,提出了基于煤矸识别、放煤机构控制的“纯煤段记忆放煤+煤岩分界模糊段人工反馈式干预放煤”的智能放煤控制策略;分析了大采高开采“采–运”协同智能耦合控制关键技术,构建了基于采煤机牵引速度与刮板输送机链速间联动调节的工作面装备间多机异构耦合自适应协同控制模型;研发了厚煤层开采中10 m超大采高液压支架,分析了厚煤层开采不断突破开采高度极限的新认识,从开采装备、控制系统等方面提出厚煤层一次开采高度的突破的研发方向。

基于MATLAB大采高液压支架稳定性仿真研究

针对液压支架存在失稳等重大安全隐患,以某型大采高液压支架为研究对象,对支架前倾、后仰、侧翻、滑移4种失稳进行分析,运用MATLAB仿真的方法对不同采高、底座宽度、极限倾角、煤层倾角、加载载荷下的支架重心高度等进行仿真分析和研究。研究结果表明:随着支架极限倾角的增加,支架重心高度呈现逐渐减小的趋势;随着支架底座宽度增加,支架重心高度呈现逐渐增加的趋势;随着采高高度的增加,最大、最小煤层倾角呈现逐渐减小的趋势;随着支架底座宽度增加,最大、最小煤层倾角呈现逐渐增加的趋势;随着加载载荷增加,煤层倾角呈现逐渐减小的趋势。该研究为液压支架稳定性、安全可靠性提高等方面提供理论基础。

河流下多煤层开采安全性及保护技术

我国新疆地区干旱缺水,艾维尔沟河作为新疆一条具有重要地理特征和环境影响的河流,其对于流经区域的经济、生态都具有重要意义,因此在艾维尔沟河下进行煤炭开采时,既要保证矿井安全也要保证河流的正常使用。采用理论分析、数值模拟等方法对河流下多煤层开采安全性及河流保护技术进行研究,通过理论计算得到多煤层开采条件下,覆岩导水裂隙带发育高度(11401工作面为41.9 m、1502工作面为110 m、11401工作面为113.8 m)并绘制剖面示意图;同时,采用数值模拟方法对覆岩导水裂缝发育形态及高度进行确定,最终基于导水裂隙带高度(117.8 m)与最小煤层埋藏深度(191.5 m)的相互关系,确定河流下开采是安全的可行的。在保证河流下煤层安全开采的前提下,通过分析离层注浆原理,并结合采动影响特征参数及工程现场,提出了以离层注浆为主,河道防渗及优化开采设计为辅的多手段对采动影响范围内地表特定目标的精准保护技术。根据实际采矿地质条件,采用概率积分法计算试采工作面开采前后河道位置处地表移动变形,计算结果显示:采用离层注浆精准保护技术后,河道的最大水平变形值(2 mm/m)未超出允许坝体的极限变形值(2.5 mm/m),所以采用离层注浆精准保护技术可以实现,井下安全开采的同时,保证河道的正常使用。通过对河流下多煤层开采的安全性及保护技术的分析研究,为矿山绿色开采提供参考和借鉴。

大采高工作面顶板结构模型及液压支架支护阻力计算

针对大采高工作面覆岩垮落范围大,易出现液压支架稳定性差、损坏率高以及支架压死的问题,采用物理模拟、理论分析以及工程实践的方法,对大采高工作面顶板破断结构模型与支架合理支护阻力计算方法进行了研究。结果表明:随着大采高工作面推进,受采空区空间大的影响,顶板将呈现“组合悬梁-非铰接顶板-铰接顶板”结构特征;支架与围岩相互作用体系由支架-组合悬梁结构-非铰接顶板结构-铰接顶板结构组成,揭示了各结构间的相互作用关系并确定了大采高工作面支架工作阻力的计算公式,支架支护阻力应适应覆岩结构失稳运动的变化,承载结构自身重量以及运动产生的附加载荷;结合大同矿区晋华宫煤矿大采高工作面开采条件,计算了工作面支架合理支护阻力并进行了支架选型,矿压监测显示,选择的ZZ13000/28/60型支撑掩护式液压支架能满足顶板控制的要求,保障了大采高工作面的安全回采。

深部特厚煤层综放沿空掘巷煤柱优化及巷道支护

为研究深部大采高综放工作面窄煤柱沿空掘巷巷道矿压控制问题,以国能宁煤集团枣泉煤矿2^(-2)特厚煤层130203大采高综放工作面回风巷道为背景,基于实用矿山压力理论,建立了巷道围岩内、外应力场动态结构力学模型,运用理论计算和数值计算针对不同尺寸煤柱煤体应力对比分析,将原留设15 m护巷煤柱缩小至5 m进行了煤柱优化。结果表明:在稳定的内应力场掘巷有利于巷道的稳定性,避免了顶板事故及冲击地压相关灾害的发生,现场5 m小煤柱护巷工程应用中,130203回风巷道小煤柱侧变形量为1050 mm,实体煤帮变形量为400 mm,两帮呈现不对称性变形,底板局部底鼓量为1400 mm;深部特厚煤层综放开采沿空掘巷采用5 m小煤柱护巷方案设计正确,极大改善了巷道围岩的应力环境,整体设计满足生产要求,现场应用良好。130203工作面小煤柱沿空掘巷技术成功应用,为矿井开采提供了可靠的科学依据。

10m超大采高智能化开采关键技术及装备研究

通过调研陕西陕煤曹家滩煤矿业有限公司22煤层赋存条件,探究了超大开采空间矿压显现规律及超高煤壁片帮特点,总结了超大采高综采工作面围岩控制关键技术,分析了超大采高综采工作面端头区支护特点,提出“大梯度+小台阶”端头区过渡模式,实现了综采工作面中部到两端头巷道6 m高差的短缓过渡及端头区三角煤高回收率支护;基于综采工作面智能化成套开采装备选型配套,研发了适应10 m超大采高综采工作面的成套开采装备,实现了超大开采空间安全防护、特厚煤层高效截割、超大运量煤流顺畅运输;搭建工作面“采支运”一体化智能协同作业控制系统及多源系统集成与数据融合分析平台,支撑10 m超大采高综采工作面安全高效开采。

大倾角大采高软弱顶底板工作面分区矿压规律研究

为研究内蒙古长城二矿大倾角大采高软弱顶底板复杂开采地质条件下,1305S工作面正常区、过渡区、卸压区的矿压显现规律及特征,建立了倾斜煤层采空区冒落矸石滑移充填数值模拟模型,采用数值模拟和现场实测相结合的研究方法进行研究。研究结果表明:沿倾斜方向,1305S工作面中上部所受垂直应力呈现出过渡区>正常区>卸压区的特点,工作面下部呈现出卸压区>过渡区>正常区的特点;1305S工作面推进过程中,平均周期来压步距为13.3 m,周期来压时支架工作阻力在26.75~33.05 MPa之间,沿工作面倾斜方向顶板所受垂直应力总体呈现出工作面上部>中部>下部的特点;巷道工作面一侧的边帮变形量较大。现场实测结果表明,回风巷顶板监测最大移进量为860.18 mm,运输巷顶板监测最大移进量为367.84 mm,两巷围岩移进量呈现出回风巷>运输巷的特点。

大采高综采覆岩“两带”高度综合探测研究

为获取大采高综采“两带”高度,促进煤炭资源安全、高效开采,以斜沟煤矿为工程背景,综合运用经验公式预估、现场试验探测和数值仿真计算,对18102工作面8#煤综采时的覆岩“两带”高度演化开展研究。结果表明:拟合得到的经验公式仅考虑了采厚因素影响,用于预测“两带”发育高度存在一定的局限性;现场钻探压水试验和瞬变电磁探测综合探测得到覆岩垮落带高度34.6 m,导水裂隙带高度74.8 m;分析了大采高综采时覆岩破坏高度、围岩应力场变化和位移场变化,“两带”高度数值计算结果与试验探测结果吻合良好。研究结果可为类似条件矿山的顶板管理、露头防(隔)水煤岩柱留设等提供参考。

浅埋近距煤层群开采覆岩三带发育特征分析

研究浅埋近距离煤层群开采的覆岩三带规律对于指导矿井下行安全开采有着至关重要的作用。为了研究上、下煤层开采过程中覆岩层的破坏规律,根据韩家湾煤矿现场实际情况,通过物理相似模拟实验研究浅埋近距离煤层过上层煤的采空区时上覆岩层结构失稳特征。研究浅埋近距离煤层群条件下开采4-2煤层后的覆岩移动变形规律、裂隙发育规律、矿压变化规律及其随工作面推进的变化情况及地表岩层的运移规律,发现浅埋近距离煤层下组煤层回采过程中,上覆岩层下沉量呈现三阶段变化,即下沉量上升阶段、下沉量恒定不变阶段、下沉量减小阶段。距离下组煤层越近,覆岩下沉量越大,距离下组煤层越远,覆岩下沉量越小。明确覆岩三带发育特征,能够为浅埋近距离煤层群开采水害防治提供依据,为榆神府矿区类似重复采动时工作面的安全回采提供指导和借鉴。

特厚煤层开采覆岩断裂带发育高度测试研究

宽沟煤矿为特厚、高瓦斯煤层开采,工作面回采期间经常发生上隅角瓦斯超限现象。在采动覆岩裂隙内布置水平定向长钻孔抽采卸压瓦斯是一种有效的治理措施,钻孔布置于断裂带内上部区域可取得较好的抽采效果。因此,亟需对矿井特厚煤层开采断裂带发育高度进行测试研究。以矿井B2特厚煤层I010206工作面开采为原型,利用经验公式对断裂带发育高度进行了计算,得到断裂带发育高度范围为104.3~125.1m。在此基础上,通过布置两个顶板仰孔,采用注水漏失量测试的方法对工作面开采断裂带发育高度进行了实测研究,得出断裂带上边界为距离煤层底板108.3~109.4 m;结合ZK401号钻孔柱状,判断I010206工作面特厚煤层开采断裂带发育至煤层上方13.5 m的细粒砂岩层位,发育高度106.2 m。研究成果可为矿井确定特厚煤层开采断裂带发育高度,进而设计布置钻孔抽采卸压瓦斯提供技术参考。

煤矿大采高工作面片帮冒顶诱因分析及控制技术研究

厚煤层大采高工作面回采过程中时常发生片帮冒顶事故,在周期来压期间更为严重。以沙曲矿24208大采高工作面为工程背景,综合运用现场监测、理论分析和数值模拟等方法,分析造成工作面片帮冒顶的主要诱因,提出相应的防范和控制措施。结果表明,直接顶的垮落对工作面影响明显,支架载荷增大,与基本顶来压时的支架载荷相近,引起工作面不同程度的片帮冒顶;支架支护强度、截深和推进速度是造成大采高工作面片帮冒顶的主要影响因素,提出了增大支架支护强度和初撑力、控制截深和加快推进速度的防治措施,同时将劳动制度由原来的‘六—六—十二制’改为‘四—六制’,有效改善了工作面的顶板下沉和片帮冒顶情况。

倾斜厚煤层覆岩瓦斯高渗区应力场-渗流场联动演化采高效应

倾斜煤层开采后覆岩应力场分布特征与水平、近水平煤层存在着较多的不同点,其上覆岩层瓦斯高渗区域及其裂隙演化规律也有所差异,同时受煤层采高的影响较为明显。为掌握倾斜厚煤层覆岩瓦斯高渗区应力场-渗流场联动演化规律,基于数值模拟方法,以新疆昌吉硫磺沟煤矿的主采工作面为原型,研究倾斜厚煤层采动覆岩裂隙演化规律的采高效应,揭示不同采高条件下覆岩裂隙高渗区的时空演化规律。结果表明:倾斜煤层的覆岩应力场总体上呈采空区下端应力高、上端应力低的非对称“蝶形”分布,采空区下端瓦斯高渗区以横向延展为主,采空区上端瓦斯高渗区以纵向扩大为主;此外,煤层开采引起的瓦斯渗流场变化和应力破坏形成更多瓦斯运移通道的耦合作用是采动瓦斯渗压改变的原因,而瓦斯高渗区为阻断瓦斯并且控制瓦斯贯通的重点区域。因此,将瓦斯抽采系统布置于瓦斯高渗区内可从最大程度上降低整个采动裂隙场的瓦斯浓度,有效地控制生产期间瓦斯浓度异常的风险。

浅埋煤层大采高工作面地表裂隙漏风研究

为了掌握浅埋煤层大采高工作面采空区上方地表裂隙漏风规律,通过地表裂隙考察、SF 6示踪气体现场测试、数据拟合分析等方法进行地表漏风特征分析,并制定专项漏风防控措施进行治理。结果表明:大采高工作面采空区上方距离工作面20 m以上的粘土层地表区域,容易发育形成长期稳定的张开型和塌陷型裂隙;不同区域地表裂隙漏风风速呈现回风侧塌陷型裂隙>中部张开型裂隙>进风侧塌陷型裂隙,且分别距离工作面584、539、487 m后漏风风速基本为零;通过对地表裂隙回填压实和井下回风侧采空区注浆堵漏,在降低上隅角CO浓度的同时增加了O_(2)浓度,有效抑制了采空区的遗煤自燃,减少了采空区惰性气体的涌出。

倾斜煤层放煤工艺参数的选择分析

倾斜煤层在我国具有较大得到储量,如何对倾斜煤层进行有效的开采,提高开采效果对我国煤炭资源的使用具有重要的影响。针对倾斜煤层放煤工艺参数的选择设置,采用PFC仿真模拟的形式进行分析。结果表明,随着放煤步距的增加,顶煤的放出量呈逐渐增加的趋势,经过分析,选择合理的放煤参数为采高4m时进行两采一放的放煤方式。

大采高工作面压裂煤层开采工艺优化设计与研究

根据23101工作面大采高煤层硬度高,裂缝发育不完善,截割体积块度小的缺点,结合割煤形式和压裂煤层模型,建立压裂煤层数值模型,对不同煤层下切割深度、割落煤体的影响进行模拟仿真,基于现场实验数据表明:压裂后,工作面煤壁裂缝显著增加,每次切割的时间缩短了11.3%,牵引速度提升了12%,粉尘质量浓度减少了46%,同时,块煤率增加了19.7%。

综放回采关键工艺参数的确定

为进一步提升工作面厚及特厚煤层的开采效率,降低其开采成本,提高煤矿的竞争力。以88203综采工作面为例,在对煤层以及顶底板条件分析的基础上,初步确定适用于该工作面的最佳采高为3.5 m;然后,重点对放煤口数目和割煤速度进行确定,最终确定放煤口数目为3个,对应的最佳割煤速度为6.54 m/min,为指导实践生产具有重要意义。