Technique of coal mining and gas extraction without coal pillar in multi-seam with low permeability

Aimed at the low mining efficiency in deep multi-seams because of high crustalstress,high gas content,low permeability,the compound 'three soft' roof and the trouble-somesafety situation encountered in deep level coal exploitation,proposed a new idea ofgob-side retaining without a coal-pillar and Y-style ventilation in the first-mined key pressure-relieved coal seam and a new method of coal mining and gas extraction.The followingwere discovered:the dynamic evolution law of the crannies in the roof is influenced bymining,the formative rule of 'the vertical cranny-abundant area' along the gob-side,thedistribution of air pressure field in the gob,and the flowing rule of pressure-relieved gas ina Y-style ventilation system.The study also established a theoretic basis for a new miningmethod of coal mining and gas extraction which is used to extract the pressure-relievedgas by roadway retaining boreholes instead of roadway boreholes.Studied and resolvedmany difficult key problems,such as,fast roadway retaining at the gob-side without a coalpillar,Y-style ventilation and extraction of pressure-relieved gas by roadway retainingboreholes,and so on.The study innovated and integrated a whole set of technical systemsfor coal and pressure relief gas extraction.The method of the pressure-relieved gasextraction by roadway retaining had been successfully applied in 6 typical working faces inthe Huainan and Huaibei mining areas.The research can provide a scientific and reliabletechnical support and a demonstration for coal mining and gas extraction in gaseous deepmulti-seams with low permeability.

Theory and practice of integrated coal production and gas extraction

The integrated extraction of coal and gas combines coal mining with gas capture. Taking into account the gas deposition and flow conditions in the Chinese coal basins, this paper describes the status of the theory and key technologies of this integrated extraction system, and presents its application and practice in the Shaqu, Zhongxing, Fenghuangshan and Pingmei mines. Areas for further improvements in future studies are discussed, focusing in particular on the fundamentals of the extraction system to make it greener, more scientific, and more advanced in both the exploitation and utilization of coal and the gas in coal.

Definition, theory, methods, and applications of the safe and efficient simultaneous extraction of coal and gas

Simultaneous extraction of the coal and gas is an effective method of eliminating coal mine gas disasters while safely exploiting the coal and achieving efficient gas drainage in China, which is widely accepted by the main coal-producing countries around the world. However, the concrete definition of simultaneous extraction is vague and there is little accurate theoretical support for the simultaneous extraction of coal and gas, which makes it difficult to determine an efficient gas drainage method appropriate to the features of coal seams. Based on theoretical analysis, laboratory tests and field observations, a specific definition of simultaneous extraction of coal and gas is proposed after analyzing the characteristics of coal seam occurrences in China, and we developed the mechanism of mining-enhanced permeability and established the corresponding theoretical model. This comprises a process of fracture network formation, in which the original fractures are opened and new fractures are produced by unloading damage. According to the theoretical model, the engineering approaches and their quantitative parameters of ＇unloading by borehole drilling＇ for single coal seams and ＇unloading by protective seam mining＇ for groups of coal seams are proposed, and the construction principles for coal exploitation and gas-drainage systems for different conditions are given. These methods were applied successfully in the Tunlan Coal Mine in Shanxi Province and the Panyi Coal Mine in Anhui Province and could assure safe and efficient simultaneous extraction of coal and gas in these outburst coal mines.

Characteristics and applications of gas desorption with excavation disturbances in coal mining

According to the deficiency of experiment system for gas adsorption and desorption in coal mass, a large scale experiment system is developed independently by researchers. This experiment system is composed of primary and auxiliary boxes, power transmission system, mining system, loading system, gas charging system, data monitoring and intelligent acquisition system. The maximum experiment coal consumption is 1200 kg, the mining system is developed to conduct experiment for gas desorption under excavating disturbance, and the plane-charging cribriform ventilation device is developed to realize uniform ventilation for experiment coal sample, which is accord with the actual gas source situation of coal bed. The desorption characteristics of gas in coal are experimentally studied under the conditions of nature and mining using the experiment system. The results show that, compare with nature condition, the permeability of coal and the velocity of gas desorption could significantly increase under the influence of coal pressure relief and destruction caused by mining, and the degree of gas desorption could somewhat increase too. Finally, pressure relief gas extraction of current seam and adjacent seams after mining in a certain coal mine of Yangquan mining area are introduced, and the gas desorption experiment results is verified by analyzing the effect of gas extraction.

Application of deep borehole blasting on fully mechanized hard top-coal pre-splitting and gas extraction in the special thick seam

In order to solve the problems of top-coal inadequate destruction and large amounts of gas emission in mining extra thick and hard coal seam,this study investigated the pre-splitting for deep borehole blasting and gas pre-draining technologies on top coal.The mechanism of the technologies was systematically expounded based on hard top-coal cracks development obtained by numerical simulation and theoretical analysis.The results show that explosive blasting in the hard rock results in a large number of cracks and large displacement in the rock mass due to the effect of explosion stress.Meanwhile,the thick top-coal caves,and desorbing gas flows along the cracks improve gas extraction.Finally,the pre-splitting for deep borehole blasting and gas pre-draining technologies was applied in No.3802 working face of Shui Liandong Coal Mine,which increases monthly output in the face to 67.34 kt and the drained gas concentration to 86.2%.The drained gas average concentration from each borehole reaches 40%,and the effect is remarkable.

Study on comprehensive gas control techniques and practice in coal mines

The origins and main control methods of gas in coal seams were introduced cursorily, and the processes that need to be done in controlling gas, which includes prediction of gas emissions, drainage systems, the means of prevention of gas outbursts, and some suggestions were put forward. The characteristic of different gas emissions and the corresponding counter measures were presented, and ＆ case study of simultaneous extraction of coal and gas in Xieyi Coal Mine was carried out by coal mining and gas extraction without coal-pillar. The field application shows that gas drainage ratio in panel 5121（0） averages about 90% and reaches as high as 95~/0, which will give beneficial references to gas control in coal mines.

Experimental investigation into stress-relief characteristics with upward large height and upward mining under hard thick roof

According to geological conditions of No. 3 and No. 4 coal seams （namely A3 and B4） of the Pan＇er coal mine and the parameters of panels 11223, 11224, and 11124 with fully-mechanical coal mining, we built 2D similar material simulation and FLAC3D numerical simulation models to investigate the development of mining-induced stress and the extraction effect of pressure-relief gas with large height and upward mining. Based on a comprehensive analysis of experimental data and observations, we obtained the deformation and breakage characteristics of strata overlying the coal seam, the development patterns of the mining-induced stress and fracture, and the size of the stress-relief area. The stress-relief effect was investigated and analyzed in consideration with mining height and three thick hard strata. Because of the group of three hard thick strata located in the main roof and the residual stress of mined panel 11124, the deformation, breakage, mining-induced stress and fracture development, and the stress-relief coefficient were discontinuous and asymmetrical. The breakage angle of the overlying strata, and the compressive and expansive zones of coal deformation were mainly controlled by the number, thickness, and strength of the hard stratum. Compared with the value of breakage angle derived by the traditional empirical method, the experimental value was lower than the traditional results by 3°-4°below the hard thick strata group, and by 13°-19° above the hard thick strata group. The amount of gas extracted from floor drainage roadway of B4 over 17 months was variable and the amount of gas per month differed considerably, being much smaller when panel 11223 influenced the area of the three hard thick strata. Generally, the stress-relief zone of No. 4 coal seam was small under the influence of the hard thick strata located in the main roof, which played an important role in delaying the breakage time and increasing the breakage space. In this study we gained understanding of the stress-relief mechanism influenced by the hard thick roof. The research results and engineering practice show that the main roof of the multiple hard thick strata is a critical factor in the design of panel layout and roadways for integrated coal exploitation and gas extraction, provides a theoretical basis for safe and high-efficient mining of coal resources.

Study on Critical,Modern Technology for Mining in Gassy Deep Mines

To achieve safe and highly efficient mining in the gassy, deep mines of the Huainan collieries simultaneous coal and gas extraction, and the corresponding ventilation methods were developed. This includes a set of mining procedures and principles which help insure safe and efficient production. Furthermore, green mining, meaning the comprehensive use of emitted gas, proper treatment of the environment and appropriate mine temperature control, is now standard. The concepts of modem mining and the principles of pressure relief are described. Coal-gas simultaneous ex- traction and multi-pressure relief techniques were developed which require a combination of surface and underground gas extraction. The application of Y-ventilation systems, of roadways retained along goafs, of stress control techniques for highly fragile mine roofs and of powerful, automatic and reliable mining equipment contributes to safe operation of modem deep mines. Operating parameters for these techniques are described and the results of their use discussed.

保护层开采条件下卸压瓦斯治理技术实践

针对下峪口煤矿保护层开采条件下上保护层工作面回采过程中瓦斯超限问题,以及被保护层3号煤层回采工作面瓦斯治理难题,通过对工作面瓦斯涌出预测及分析瓦斯来源,确定合理的瓦斯抽采方案。结合中近距离煤层条件下煤与瓦斯共采技术,确定采用合理布置穿层钻孔抽放卸压瓦斯、采空区埋管抽放瓦斯、顺层钻孔预抽、边抽边采等综合瓦斯治理方案。试验结果表明,4216工作面回采期间未发生瓦斯超限问题;上保护层回采初期(15~35 m)卸压瓦斯抽采进入活跃期,钻孔施工应当超前工作面35 m施工;也表明该综合瓦斯治理方案有效可行,研究成果对韩城矿区突出矿井瓦斯防治具有一定的借鉴意义。

基于岩层移动的“煤与煤层气共采”技术研究

研究了岩层移动对煤层气卸压运移的影响,结果证明,覆岩关键层的破断运动对邻近层煤层气涌出的动态过程起控制作用;覆岩主关键层位置将决定下保护层可能的最大卸压高度.

高瓦斯综放工作面的均衡开采技术研究

针对综放工作面正常开采期内经常发生瓦斯超限的问题,提出了"均衡开采"的概念。根据综放工作面的瓦斯涌出特征,采用分源法建立了综放工作面瓦斯涌出量的预测模型,并给出了回风巷及尾巷的瓦斯浓度方程和工作面产量方程;根据均衡开采的概念内涵,提出了综放工作面均衡开采的目标函数及其约束条件,从而建立了综放工作面均衡开采的理论模型。结合阳泉矿区某矿9804综放工作面的开采技术条件,开展了该工作面均衡开采的理论分析与实测研究,并对其应用效果进行了监测。结果表明:9804综放工作面采煤机的均衡割煤速度的理论计算结果和实测结果分别为1.9和1.7m/min,两者基本一致;在9804综放工作面的后续开采中应用均衡开采技术后,回风巷和尾巷均未出现瓦斯超限而断电停产,且工作面日产量比原生产能力增加了18%。

三维采动应力条件下覆岩裂隙演化规律试验研究

利用自行研制的"多场耦合煤矿动力灾害大型模拟试验系统",根据中国平煤神马集团十矿己15煤层24080工作面的地质资料,在三向不等应力条件下进行了三维模拟开采试验。通过应力监测、色素示踪、照相素描等手段,统计了各水平、垂直切面的裂隙形态、数量与分布特征,并建立了采空区覆岩裂隙网络数值模型。研究结果表明:三维应力条件下,采空区覆岩裂隙在空间上呈"类梯形台"形态,在低位岩层中呈"圆角矩形"形态,在中高位岩层则呈"O型"形态。按瓦斯运移难易程度可将覆岩裂隙分为以"纵向贯通裂隙"为主的直接流动通道和以"层内破断裂隙-层间离层裂隙-层内破断裂隙"方式延伸的间接流动通道。

中国煤炭资源绿色开采研究现状与展望

中国是世界上少有的以煤炭作为主要能源的国家之一,煤炭产量已经超过了世界总产量的三分之一,与煤炭生产相关的资源破坏、环境损害以及生产事故现象十分突出,因而我国学者率先提出了实现煤炭资源绿色开采的理念和科学研究与技术框架,继而又提出了实现科学采矿的学术观点.本文从煤炭资源绿色开采的内涵与框架、采动岩体结构理论和采动岩体渗流理论等方面较为系统地论述了煤炭资源绿色开采基础研究方面取得的主要进展;以煤与瓦斯共采、保水采煤和矸石直接充填采煤等技术开发成果,综述了在突破传统采煤技术理念上的煤炭资源绿色开采技术方面取得的重要进展;从实现煤炭资源绿色开采应重视的基础科学研究、重点技术攻关、政府应履行的职能以及国家立法等方面对今后相关研究与技术开发工作作了简单展望.

晋城矿区煤与煤层气共采研究进展及急需研究的基本问题

晋城矿区是我国最大的无烟煤生产矿区,自投产以来,受制于矿井煤层高瓦斯含量,常规井下抽采难以满足矿井安全高效生产的需要。晋煤集团通过探索地面抽采技术、井下抽采技术和地面与井下联合抽采技术,形成了"采煤采气一体化"的立体抽采模式,称为"晋城模式",并在国内推广应用,取得了好的效果。基于晋城矿区实际,提出了煤与煤层气共采的基本概念,分析了煤与煤层气共采研究现状,介绍了"采煤采气一体化"的煤矿瓦斯治理模式、地面抽采关键技术和井下抽采关键技术,并提出了今后一段时间内的努力方向和急需研究的几个基本问题。

复杂矿井绿色安全开采体系设计探讨

信湖矿井为淮北矿区首个千米新井,开采技术条件极其复杂,因此科学先进的设计定位是确保其绿色、安全开采的关键。设计在研究现有资料的基础上,分析了煤矿建设与开采对职工健康和生命的威胁,以及排放的"三废"、共伴生资源是否利用、高能耗、岩层移动对生态环境的破坏;据此从设计源头把关,建立了绿色安全开采体系,包括回风乏热利用、煤与瓦斯共采、矿山环境恢复与治理、节能减排和围岩综合控制等关键技术,力争把信湖矿井建设为节能环保的安全高效现代化矿井。

煤与瓦斯共采在错层位巷道布置中的机理研究及应用构想

为了完善现有煤与瓦斯共采技术,创新煤与瓦斯共采方法,对错层位巷道布置下的煤与瓦斯共采系统展开研究,利用相似模拟试验,分析错层位巷道布置覆岩运动情况,预测其开采围岩裂隙发育和瓦斯运移形式,提出了创新煤与瓦斯共采技术构想。研究结果表明:采空区覆岩三带高度随接续工作面的增加而增大,相邻采空区垮落矸石压实区呈现"O-L-O"形变化,多个相邻采空区覆岩出现大"O"形圈裂隙带;相邻采空区内瓦斯可实现相互运移,大"O"形圈裂隙带内赋存大量瓦斯气体;研究提出了地面钻井抽采瓦斯、走向高位瓦斯抽采巷和外错尾巷穿层钻孔3种煤与瓦斯共采技术,比传统巷道布置情况下的煤与瓦斯共采技术在安全、经济等方面更具优势。

高瓦斯矿区复杂地质条件安全高效开采关键技术

为解决高瓦斯矿区复杂地质条件安全高效开采技术难题,根据淮南矿区实际,通过理论研究和工程实践,提出并研究了煤与瓦斯共采技术、极易离层煤岩支护工程技术、复杂地质条件下采矿工程地质保障技术、以及绿色开采等高瓦斯矿区复杂地质条件安全高效开采关键技术,确定了关键技术参数,全面考察了现场应用效果.

淮南矿区现代采矿关键技术

为实现高瓦斯矿井安全高效开采,根据淮南矿区的实际情况,研究了高瓦斯煤层群煤与瓦斯共采技术及通风方式、开采程序技术原则、安全高效采煤技术,探索实践了瓦斯综合利用、环境治理、矿井降温技术等绿色开采技术.确定了关键技术参数,全面考察了现场应用效果.根据研究结果,确立了现代采矿的基本内涵.

近距离突出煤层上保护层坚硬煤岩开采治灾技术

针对白皎矿近距离突出煤层保护层开采时,保护层煤体硬度高、夹矸厚且硬、开采范围内断层密集、直接顶坚硬、下覆被保护层卸压瓦斯涌出量大、瓦斯超限频发等复杂技术难题,提出了坚硬煤岩综采装备合理选型、综合立体式卸压瓦斯抽采系统、切顶卸压沿空留巷、Y型通风、均压防灭火等为一体的综合治灾与防灾技术。该综合技术在2421首采面进行了保护层开采试验,结果表明:下覆煤层透气性系数增加1300多倍,瓦斯抽采量提高173倍,大幅降低突出危险性;掘进和回采期间瓦斯均未超限,安全和经济效益显著。

我国煤层气抽采方法及在晋城矿区的应用

瓦斯是煤矿安全生产的最大威胁之一,同时也是人类生存环境的破坏者,因此,有效地进行采前预抽和利用已受到人们的重视。针对中国煤层气赋存的低压、低渗、低饱和等复杂地质特征,探讨了现有煤层气的开采方法及优缺点,包括:井下瓦斯抽放、地面垂直井抽采、煤与瓦斯共采和废弃矿井抽采等,并结合晋城矿区具体条件研究了各种抽采方法的适用性。研究结果可为中国煤层气的有效开采和利用提供参考。