Characteristics of Gas Emission at Super-Length Fully-Mechanized Top Coal Caving Face

Characteristics of gas emission at the K8206 working face in the Third mine of the Yangquan Coal Group were investigated. The effects of strata movement,advancing velocity of working face,production capacity of working face and gas extraction capability of strike high-level entry on gas emission at K8206 working face were analyzed. A regression equation,reflecting the relationship between relative gas emission rate and the production capacity of work-ing faces,was established. Another regression equation showing the relationship between the gas emission rate from adjacent layers when the working face was advancing for one metre and advancing velocity was derived. It can be con-cluded that,1) the amount of gas emitted at the K8206 working face is far greater than that of ordinary top coal caving faces with a dip length of 180-190 m; 2) the dynamic process of gas emission from adjacent layers during the initial mining stage is controlled by the movement of key strata; 3) the amount of gas emitted that needs to be forced out by air is greatly affected by the capability of gas extraction; 4) when the advancing velocity is between 3.5-5.5 m/d or when the output is up to 8-12 kt/d,the gas emission from adjacent layers is almost constant.

Study on gob-side entry retaining in fully-mechanized longwall with top-coal caving and its application

Based on the engineering background of gob-side entry retaining in fully-mechanized longwall with top coal caving(GER-FLTC) on N2105 working face of Yuwu coal mine, by adopting the methods of theoretical analysis and numerical calculation, the control techniques of surrounding rocks in GER-FLTC working face are studied in this paper. The two main difficulties of stability of surrounding rocks at gob-side retained entry in fully-mechanized longwall working face are the stability control of top coal and control of large deformation of GER-FLTC working face. Interaction mechanical model between roofing and roadside backfilling in GER-FLTC is established and the equations for the calculation of roof-cutting resistance of roadside backfilling are derived. Results of numerical calculation show that the damage zones of top coal can be categorized into the delaminating zone of top coal above the backfilling, tensile damage zone of top coal above the retained roadway and shear damage zone of the upper rib of the solid coal. Stability control of top coal is the critical part to success of GER-FLTC. With consideration of large deformation of surrounding rocks of gob-side retained entry in fully-mechanized longwall, the support technique of‘‘roofing control and wall strengthening'' is proposed where high strength and highly prestressed anchor rods and diagonal tensile anchor cables support are used for top coal, high strength and highly prestressed yielding anchor rod support is used for solid coal and roadside prestressed load-carrying backfilling is constructed by high-water material, in order to maintain the integrity of the top coal, transfer load, high resistance yielding load-carrying of solid coal, roof-cutting of roadside backfilling and support,and to achieve GER-FLTC. Results from this study are successfully applied in engineering practice.

SAFETY PROBLEMS IN FULLY-MECHANIZED TOP-COAL CAVING LONGWALL FACES

The thick-san top-ctal catrig technology has been in use in China for over a decade,and has given rise to siguscant economic efficiendes. Eftorts in reeent years to extend its applica tion to more complex mining conditions, mostly high-gas seams , with or without proneness ofspontaneous combustion. have brought about new safety problems This paper will highlight thefcatures and problems retared with thick-seam top-coal caving systems, compared with conventionai, fully-mecbanized longwall systems , particularly issues retated to methane, spontaneous combustion and dust,and disam the methods and measures to ded with them.

Study on safe thickness of overlying thin bedrock in fully-mechanized top-coal caving face with thick coal seam

To prevent support crush, the overlying strata safe thickness and its influential elements were studied by the adoption of theoretical analysis, numerical simulation and in-situ measurement. According to the production and geological condition of first face in Sima coal mine, the results indicate that the clay contains large permissible bearing ability and has better arching force. After mining destruction, stable structure is formed in bedrock to ensure face safety. The clay thickness ＆ bedrock thickness are the key influential elements to stable structure. The minimal bedrock thickness is about 40 m to ensure safe mining under loose surface soil condition. When surface soil contains mainly thick clay, it forms steady structure with the composition of thin bedrock, so that it can reduce minimal thickness of bedrock and to ensure safe mining. When clay thickness is 40 m, minimal bedrock thickness is 20 m. When clay thickness is 30 m, minimal bedrock thickness is 30 m. Bearing pressure peak ranges from 5 to 15 m in the front face under thin bedrock condition. The bearing pressure distribution range is 15 m. Main roof break distance is small, and initial weighting of main roof is not distinctive, while first periodic weighting of main roof is quite distinctive.

Analysis on distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face

The three-dimensional damage constitutive relationship of coal is established and distribution law of the abutment pressure of the integrated coal beside the road-in packing for gob-side entry retaining in fully-mechanized caving face under the effect of given deformation of the main roof is analyzed by the damage mechanics theory. And the relationship between distribution of the abutment pressure and thickness of coal seam is explored. The presented result is of great theoretical significance and practical value to the study on stability control of the surrounding rock of road-in packing for gob-side entry retaining in fully-mechanized caving face.

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.

Theoretical analysis on the deformation characteristics of coal wall in a longwall top coal caving face

Against the background of analyzing coal wall stability in 14101 fully mechanized longwall top coal caving face in Majialiang coal mine,based on the torque equilibrium of the coal wall,shield support and the roof strata,an elastic mechanics model was established to calculate the stress applied on the coal wall.The displacement method was used to obtain the stress and deformation distributions of the coal wall.This study also researched the influence of support resistance,protective pressure to the coal wall,fracture position of the main roof and mining height on the coal wall deformation.The following conclusions are drawn:(1) The shorter the distance from the longwall face,the greater the vertical compressive stress and horizontal tensile stress borne by the coal wall.The coal wall is prone to failure in the form of compressive-shear and tension;(2) With increasing support resistance,the revolution angle of the main roof decreases linearly.As the support resistance and protective force supplied by the face guard increases,the maximum deformation of the coal wall decreases linearly;(3) As the face approaches the fracture position of the main roof,coal wall horizontal deformation increases significantly,and the coal wall is prone to instability;and(4) The best mining height of 14101 longwall face is 3.0 m.

Control on mine pressure of thick and strong roof stratum movement in long wall thick coal caving face

The caving of thick and strong roof stratum causes tremendous rock pressure in mine.The results of the analysis on dynamic natures of actual measurements of some fields,of which the roof pressure can be caused by thick and strong stratum in long wall thick coal caving face,could present the relation between the collapse and movement of thick and strong roof strata and surrounding rock pressure.In order to control the roof pressure effectively,the thick and strong roof strata,can be fractured and softened previ- ously by hydraulic fracturing and low-high pressure water infusion,fracturing and softening method.The results of study can provide basis for strata control and safe management in long wall thick coal caving face.

Analysis of factors of top coal caving in fully mechanized sublevel caving face in soft coal and control

According to the analysis of the mechanism of top coal caving, the caving condition was pointed out, and many factors of caving were also determined. Then the relationship between factors and caving was studied. Based on the above research, one effective method by using field monitoring was brought forward to determine the controlling factor. Then some related key technologies were provided, such as keeping the integrality of the top-coal, raising the horizontal resistance of supports and decreasing the real end-face distance etc.. At last one application of this method was presented, and it was proved to be an effective method.

急倾斜中厚煤层单一巷道放顶煤采煤方法研究与应用

为解决某矿急倾斜中厚煤层倾角及厚度变化大的开采问题,提出了“急倾斜中厚煤层单一巷道放顶煤采煤方法”。该采煤方法是沿急倾斜煤层倾斜方向划分为若干区段,每个区段沿急倾斜煤层走向仅布置1条巷道。此巷道服务于1个采煤区段,担负工作面通风、运输和行人等任务。对单一巷道放顶煤采煤方法的巷道布置、综放工艺和沿空留巷方法进行了探讨。实践表明,该采煤方法使采煤工作面形成全负压通风,避免了巷道与采空区窜风,杜绝了采空区瓦斯积聚和遗煤自燃,实现了采煤机械化,提高了急倾斜中厚煤层的开采效率和煤炭回收率。单一巷道放顶煤采煤法为类似急倾斜煤层安全、高效开采提供了技术支撑。

基于光滑粒子动力学顶煤放落与输送过程仿真研究

目前针对综放开采中顶煤放出规律的数值模拟研究中,对于顶煤运动的连续-非连续性问题需复杂的耦合算法,必须解决煤岩界面信息精确交互问题,且忽略了刮板输送机输送过程。针对该问题,基于光滑粒子动力学构建了无网格数值计算模型,通过建立连续介质力学控制方程的光滑粒子动力学离散方程,并引入弹塑性土体本构模型和Drucker-Prager屈服准则,实现了顶煤坍塌、运移、放出过程的动态模拟。考虑采场实际放煤和输煤过程,构建了刮板输送机模型,模拟沿工作面水平方向顶煤放出和底煤输送过程,得到不同刮板输送机运行速度(0~1.5 m/s)下的煤岩界面和煤流速度变化规律。仿真结果表明:弹塑性土体本构模型可有效模拟颗粒的流动行为,通过设定摩擦角、弹性模量等材料参数,避免了传统离散元法模型的参数不定问题;煤流速度稳定后,放煤口附近的顶煤应力分布呈“双峰”形态;刮板输送机运行速度对放煤时间影响较大,但对终止的煤岩界面和放出体形状影响较小;多支架同时放煤需考虑刮板输送机的输送能力,不同支架之间的底煤输送干涉可能导致放煤口的堵塞效应;“见矸关门”准则导致不同放煤口放煤量存在差异,40个放煤口顶煤放出量的标准差(7.52 m^(2))高于自动放煤的标准差(1.93 m^(2))。

基于FLAC3D与无人机航测的全部垮落法采煤塌陷分析

内蒙古串草圪旦煤矿位于黄河中游上段,其全部垮落法采煤导致大面积塌陷,地表生态和环境问题频发。为研究采空区地表裂缝发育规律及塌陷应力与位移场演化特征以串草圪旦煤矿6102工作面为研究对象,利用无人机航测查清了地表裂缝分布范围及规律,构建了FLAC3D数值模型并计算分析了采空区围岩应力及位移变化,将分析结果与无人机航测结果进行了相互验证。结果表明:(1)塌陷主要以地裂缝为表现形式,主要分布于矿区西北部及中西部。工作面发育2类地裂缝,一类为弧形阶梯式裂缝群,呈平行分布且以间隔5~20 m出现,大部分形成阶梯式高度为15~130 cm的错台,裂缝以3°~5°的偏角垂直工作面推进方向发育;另一类为直线型边缘裂缝带,拉张破坏严重,平行工作面外围呈带状发育,少数可展布于工作面内部,最外围裂缝至工作面的距离分别为38,53 m。(2)由于地下煤层开挖,采空区顶板出现明显的“马鞍状”拉应力集中区,且随着开挖的推进地表集中区拉应力先增大后减小,最大值为0.181 MPa;(3)采空区顶部完全垮塌,地表垂直位移最大值在采空区正中间,最大值约5.5 m;地表水平位移最大值位于采空区煤柱正上方,最大值1.93 m。(4)数值模拟计算的沉降量、裂缝角与无人机航测数据基本一致。研究成果可为煤层开采带来的生态环境问题解决方案提供参考依据。

放顶煤综合工况智能识别及自动控制方法研究

在研究综放开采自动化放煤中,由于放顶放煤过程中突变工况对煤矸石识别准确度的影响,根据煤和煤矸石中γ射线的辐射强度不同,采用自然γ射线法对煤矸石混合物进行识别,监测放煤过程中γ射线辐射强度变化,判断顶煤放落状态。最后基于自然γ射线法设计一种放煤自动控制系统指导液压支架尾梁动作,实现放煤控制自动化。

厚煤层工作面多种放煤方式的选择

我国大部分煤炭以厚煤层的形式埋藏于地下深处,综放开采是主要的开采工艺方式。在综采过程中,不同的放煤方式对煤层的采出具有重要影响。针对不同放煤方式的影响作用进行仿真分析,可为厚煤层放煤方式的选择提供一定参考。结果表明,单轮间隔放煤具有较好的开采效果,是更适合厚煤层开采的放煤方式。

龙岩市非煤矿山顶板事故分析与管理措施

顶板事故在非煤地下矿山事故中占比最多,顶板管理是非煤地下矿山安全管理的重点和难点。统计分析龙岩市2008—2023年共15a的顶板事故情况,总结非煤矿山顶板事故的特点。研究得出,矿井爆破工艺技术水平低及在大暴露空间下进行作业是顶板事故原因。提出改善措施,将中深孔爆破分段崩落采矿法代替空场法,但受到矿石价格影响,该方法成本高,当前可行性低;通过推广应用凿岩台车、撬毛台车等机械工具,严格控制井下采掘作业空间宽度和高度等措施,加强顶板管理,努力实现顶板零事故。

低位综放工作面提高顶煤回采率的放煤方式优化

针对古城煤矿低位综放工作面顶煤回采率低的问题,以S1306低位综放工作面为背景,分析了现有放煤方式。首先,通过建立不同放煤方式与放煤口长度的PFC数值计算模型,分析了不同放煤口长度以及相同放煤口长度、不同放煤方式下顶煤回采率;其次,提出了双口间隔动态放煤方式,对比分析了单口顺序放煤、双口顺序放煤以及双口间隔动态放煤的顶煤回采率;最后,研究了不同采放比对3种放煤方式顶煤回采率的影响。研究表明:低位综放工作面顶煤回采率随着放煤口长度的增大而逐渐减小;放煤口长度一定时,单口顺序放煤顶煤回采率大于双口顺序放煤的顶煤回采率;双口间隔动态放煤顶煤回采率相较于单口顺序放煤提高了约8.44%,放煤时间节省了46%,且放煤均衡性优于单口顺序放煤与双口顺序放煤;双口间隔动态放煤和单口顺序放煤的顶煤回采率均随着采放比的增大而增大,当采放比小于1∶1时,双口间隔动态放煤顶煤回采率大于单口顺序放煤方式,当采放比大于1∶1时,两者之间差距明显减小,但双口间隔动态放煤的时间大大缩短。因此,双口间隔动态放煤方式结合了低位综放工作面条件下单口放煤方式顶煤回采率高和双口放煤方式放煤时间短的优势。

Experiment Research of Application of FMCCT in Complex-Condition Coal Seams

The fully-mechanized caving coal technique (FMCCT) is a great technique progress of mining method in thick coal seams in China, and it has succeeded in some suitable condition mines. This paper introduces some technical measures and achieved outcomes in gas and fire precaution and support selection for the use of the fully-mechanized caving coal technique in the complex-condition coal seams based on the practice of Weijiadi Coal Mine, in which the technique is used in the gently inclined extremelythick soft coal seam with the dangers of coal and gas outburst and spontaneous combustion.

巨厚砾岩层下综放工作面冲击地压危险性评价和矿震发生特征分析

为有效监测和防治综采工作面冲击地压事故,以耿村煤矿巨厚砾岩层下综放工作面为工程背景,采用综合指数法评价综放工作面冲击地压危险性,利用微震监测结果研究综放工作面回采期间矿震特征。结果表明:(1)13230综放工作面冲击危险性指数为0.65,属于中等冲击地压类型;(2)综放工作面回采期间矿震主要发生在工作面前方顶底板煤岩体中,工作面处于“见方区”时发生矿震的频次、最大能量和总能量均明显高于“非见方区”的,“见方区”矿震的震源主要位于工作面前方中部顶底板煤岩体和运输平巷上帮顶板煤岩体中;(3)综放工作面顶板周期来压期间通常伴随大能量的矿震事件。研究结果可为耿村煤矿综放开采冲击地压监测和防治提供参考。

综放工作面局部采空区浆体充填试验研究

以桑树坪二号井3307工作面局部采空区为研究对象,通过采空区残留空洞理论公式和地表瞬变电磁采空区勘探技术预计采空区残余空间大小;利用工作面顶板“三带”发育规律和物理相似模拟试验确定冒落带高度,为浆体充填钻孔布置提供依据;开展井下浆体充填现场试验,在3307回风联巷中布置充填试验系统,3308进风顺槽内穿过煤柱向采空区打充填钻孔,试验按照一定的工艺流程通过充填管路进行料浆充填。试验分析了影响充填因素,同时从料浆浓度、钻孔布置方式、钻孔直径和相关工艺等方面提出进一步优化建议,可为充分利用井下采空区开展充填工程,合理处理煤矿矸石等固废提供理论依据。

特厚煤层分叉合并区放煤方式适用性分析与优选

针对复杂结构特厚煤层分叉合并区域放煤方式选择困难的问题,通过顶煤厚度探测、GDEM数值仿真分析和工作面实测综放开采指标,得到特厚煤层分叉区和合并区的2个煤层赋存地质模型,建立颗粒动力学数值模型,实测不同放煤方式的顶煤放出率。研究结果表明:不同放煤方式条件下的含矸率相差较小,但是顶煤放出率差异较大;顶煤厚度不大于5m时单轮间隔1架的放煤效果最优,顶煤放出率为63.5%,较其他2种放煤方式高2.2%;顶煤厚度大于5m时多轮顺序放煤效果最优,顶煤放出率为74.9%,较其他2种放煤方式分别高5.0%和1.4%;现场试验中多轮顺序放煤较多轮间隔放煤的顶煤放出率高约7%,数值模拟和工程试验的结果一致性较好。优化后的放煤方式提高了顶煤放出率,为沙坪矿后续综放工作面和周边矿井提供了放煤方式优化模型。