Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Numerical simulation of coal wall cutting and lump coal formation in a fully mechanized mining face

It is difficult to accurately calculate the lump coal rate in a fully mechanized mining face.Therefore,a numerical simulation of the coal wall cutting process,which revealed the crack expansion,development,evolution in the coal body and the corresponding lump coal formation mechanism,was performed in PFC2D.Moreover,a correlation was established between the cutting force and lump coal formation,and a statistical analysis method was proposed to determine the lump coal rate.The following conclusions are drawn from the results:(1)Based on a soft ball model,a coal wall cutting model is established.By setting the roller parameters based on linear bonding and simulating the roller cutting process of the coal body,the coal wall cutting process is effectively simulated,and accurate lump coal rate statistics are provided.(2)Under the cutting stress,the coal body in the working face underwent three stages—microfracture generation,fracture expansion,and fracture penetration—to form lump coal,in which the fracture direction is orthogonal to the cutting pressure chain.Within a certain range from the roller,as the cutting depth of the roller increased,the number of new fractures in the coal body first increases and then stabilizes.(3)Under the cutting stress,the fractured coal body is locally compressed,thereby forming a compact core.The formation and destruction of the compact core causes fluctuations in the cutting force.The fluctuation amplitude is positively related to the coal mass.(4)Because the simulation does not consider secondary damage in the coal,the simulated lump coal rate is larger than the actual lump coal rate in the working face;this deviation is mainly concentrated in large lump coal with a diameter greater than 300 mm.

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.

Study on Filling Cross-Roadway in Fully-Mechanized Coal Faces with High Water-Content Material

A new method using high water content material to mechanically fill cross roadways to form artificial bottom for coal faces was introduced. The reasonable determination of filling range, the optimization of the compounding ratio of high water content material, and the filling technique were discussed in detail. This new method has been spread after industrial testing in Baodian Colliery. Compared with the traditional method, the manual wooden chock method, the new one decreases about 40% of the filling range and cost in dealing every one set of cross roadway in the testing condition.

Back-and-forth mining for hard and thick coal seams—research about the mining technology for fully mechanized caving working face of Datong Mine

The article introduced the key technology, mining process, and back-and-forth mining method for the caving working face of hard-thick coal seams in Datong mine, and researched this innovations process, optimized the systemic design and working face out-play, tried to perfect the caving mining technology of hard-thick coal seams further.

Reliability analysis of the velocity matching of coal cutting and caving in fully mechanized top-coal caving face

The matching relationship between coal cutting and caving in fully mechanized top-coal caving face is analyzed in detail from the angle of reliability. The coupling equation of reliability is established correspondingly, and the mathematical equation of the coefficient of velocity matching of coal cutting and caving is obtained, which meets a certain reliability demand for making the working procedure of coal caving not influence coal cutting of coal-cutter. The results show that the relationship between the coefficient of the velocity matching and the reliability of coal cutting and caving system is linear on the whole when R <0.9. It is pointed out that different numerical value should be selected for different coal face according to different demand for reliability.

Fracture mechanics model of fully mechanized top coal caving of shallow coal seams and its application

Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using the fracture mechanics theory. The relationships between the fracture length of the roof and the working resistance of the supports were discovered, and the correlations between the load on the overlying strata and the ratio of the crack's length to the thickness of the roof were obtained. Using a working face of Jindi Coal Mine, Xing county Shanxi province as an example, the relationships between the fracture length of the roof and the working resistance of the supports were analysed in detail. The results give a design basis in hydraulic top coal caving supports, which could provide useful references in the practical application. On-site experiment proves that the periodic weighting step interval of the caving face is 15–16 m, which is basically consistent with the theoretical analysis results, and indicates that the mechanized caving hydraulic support is capable of meeting the support requirements in the mining of a super-thick but shallowly buried coal seam.

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.

Vertical transportation system of solid material for backfilling coal mining technology

For transportation of solid backfill material such as waste and fly ash from the surface to the bottom of the shaft in a fully mechanized backfilling coal backfilling coal mining technology, we developed a new vertical transportation system to transport this type of solid backfill material. Given the demands imposed on safely in feeding this material, we also investigated the structure and basic parameter of this system. For a mine in the Xingtai mining area the results show that: (1) a vertical transportation system should include three main parts, i.e., a feeding borehole, a maintenance chamber and a storage silo; (2) we determined that 486 mm is a suitable diameter for bore holes, the diameter of the storage silo is 6 m and its height 30 m in this vertical transportation system; (3) a conical buffer was developed to absorb the impact during the feeding process. To ensure normal implementation of fully mechanized backfilling coal mining technology and the safety of underground personnel, we propose a series of security technologies for anti-blockage, storage silo cleaning, high pressure air release and aspiration. This vertical transporting system has been applied in one this particular mine, which has fed about 4 million tons solid material with a feeding depth of 350 m and safely exploited 3 million tons of coal.

Ground pressure and overlying strata structure for a repeated mining face of residual coal after room and pillar mining

To investigate the abnormal ground pressures and roof control problem in fully mechanized repeated mining of residual coal after room and pillar mining, the roof fracture structural model and mechanical model were developed using numerical simulation and theoretical analysis. The roof fracture characteristics of a repeated mining face were revealed and the ground pressure law and roof supporting condi- tions of the repeated mining face were obtained. The results indicate that when the repeated mining face passes the residual pillars, the sudden instability causes fracturing in the main roof above the old goal and forms an extra-large rock block above the mining face. A relatively stable ＂Voussoir beam＂ structure is formed after the advance fracturing of the main roof. When the repeated mining face passes the old goaf, as the large rock block revolves and touches gangue, the rock block will break secondarily under overburden rock loads. An example calculation was performed involving an integrated mine in Shanxi province, results showed that minimum working resistance values of support determined to be reason- able were respectively 11,412 kN and 10,743 kN when repeated mining face passed through residual pillar and goaf. On-site ground pressure monitoring results indicated that the mechanical model and support resistance calculation were reasonable.

Mating model on production capacity for the system of cutting coal and drawing top-coal in FMMSC

Being a safe and highly-efficient mining method, fully mechanized mining with sublevel caving （FMMSC） was extensively employed in Chinese coal mines with thick seam. In order to make drawing top-coal furthest to parallel work with shearer cutting coal, decrease failure ratio of rear scraper conveyor and increase safe production capacity of equipments, based on production technology, set up the mating model of safe production capacity of equipments for the system of drawing top-coal and shearer cutting coal in coal face with sublevel caving. It is mean capability of drawing top-coal adapted to the capability of shearer cutting coal in a working circle in the coal face that was deduced. The type selection of equipment of rear scraper conveyor can be tackled with this mating model. The model was applied in FMMSC in Yangcun Coal Mine, Yima Coal Group of China. With the mating light-equipments, the coal output in coal face attained 1.05 Mt in 2004. It gained better technical-economic benefit.

我国大倾角煤层开采技术变革与展望

大倾角煤层是我国煤炭资源的主要赋存样式之一。在地域分布上呈现出广泛性与区域性,据不完全统计,全国25个省、自治区、直辖市均涉及该类煤层开采,在中西部地区储量丰富、产量大、生产集中程度高。在赋存条件上呈现出多样性与复杂性,不同区域成煤时期不一,构造控煤过程迥异,形成了多样且复杂的开采条件,催生了不同的开采技术要求。大倾角煤层开采的技术难度大。煤层倾角导致采场围岩运动破坏呈现非对称性显现特征,支护系统稳定性控制与“三机”配套与协同、采准巷道布置与支护、工作面“人-机”环境安全保障等工作的难度显著加剧,严重制约了矿井安全高效开采。大倾角煤层开采的区域经济需求强,该类煤层赋存与生产较集中的区域多见以煤炭工业为主的资源型城市,经济结构相对单一,煤炭资源安全高效开发利用对区域能源保供、民生保障、经济保稳具有兜底作用。长期以来,大倾角煤层开采技术变革聚焦于解决“难”与“需”的矛盾,在采煤方法与工艺、岩层控制理论与技术、成套装备研制与应用3个方面不断完善、创新、发展,实现了由非机械化向机械化开采的转变,安全产效水平大幅提升,人员劳动强度大幅下降,作业环境显著改善。20世纪90年代中期,川煤集团绿水洞煤矿首次成功实现了大倾角中厚煤层长壁综采,冲破了大倾角煤层机械化开采技术“禁区”。在此示范作用下,大倾角厚煤层长壁综放开采、大采高综采、薄煤层伪俯斜长壁综采三项首创性工程实践先后取得成功。这一过程中创新了工作面非线性限位布置与调斜方式,确立了“支架-围岩”系统稳定性多维交互控制模式,研发了工作面成套装备,取得良好收效,综合机械化开采技术适用范围进一步拓宽。与此同时,大倾角煤层开采仍存在许多亟待突破的关键科学问题与技术瓶颈,导致自动化、智能化水平提升与近水平/缓倾斜煤层相较仍存在较大差距。需进一步强化倾斜层状煤系地层煤岩体采动力学行为研究,揭示其对采场围岩灾变的控制机制,并实现量化表征;需进一步阐明岩体承载结构-采场装备群组系统间的多维动态作用过程与规律,完善装备与围岩多维动态多目标协同控制理论与技术基础,实现技术转化应用。在科学问题取得突破的基础上进行采煤方法、回采工艺、岩层控制、成套装备的系统性技术创新与研发,破解大倾角煤层开采安全-产效双提升的制约技术瓶颈,使大倾角煤层综合机械化开采倾角上限在有可靠技术保障的前提下向上延伸(扩展),为实现自动化、智能化开采奠定基础。

煤矿井下非均匀照度图像去噪研究

煤矿综采工作面空间小、照明环境复杂多变,采煤过程中伴随着大量的粉尘、大雾,导致采集的图像出现曝光、细节特征减弱等问题,难以对井下照明区域光照强度过大的图像进行有效的特征提取。针对上述问题,提出了一种煤矿井下非均匀照度图像去噪算法。首先,将视频截取为图像,判断图像是否需要进行光照抑制,将需要进行光照抑制的RGB图像拆分通道,并计算每个通道的光照调节因子,实现图像的整体光照调节;然后,将未进行整体光照抑制的图像和经整体光照抑制的图像进行反射分量提取,即将输入的图像转换为HSV空间图像,使用单尺度Retinex(SSR)算法对V通道图像中的光照分量进行单独处理,将V分量中的入射分量去除,保留反射分量,并对反射分量使用直方图均衡算法实现光照均衡化处理;最后,使用基于引导滤波的暗通道先验算法对经过光照处理后的图像进行去雾处理,并使用伽马校正函数重新调节亮度不均的图像。主观评价结果表明:提出的煤矿井下非均匀照度图像去噪算法有效抑制了因光照导致整体亮度较高的问题,且由于大雾、粉尘等因素导致图像模糊的部分更加清晰,图像的细节特征更加突出。采用信息熵、均值、标准差、空间频率4种评价指标对提出的算法效果进行客观评价,结果表明,提出的算法在信息熵、均值、标准差、空间频率上较多尺度Retinex(MSR)算法分别平均提升了21.87%,-56.06%,153.43%,294.45%,较基于颜色保持的多尺度视网膜增强(MSRCP)算法分别平均提升了1.18%,-39.56%,33.29%,-4.71%,较带色彩恢复的多尺度视网膜增强(MSRCR)算法分别平均提升了38.06%,-55.27%,462.10%,300.96%,说明提出的算法能更有效地增加图像信息量、抑制光照强度、提升边缘信息及图像清晰度。

极近距离煤层开采无煤柱自成巷控制方法研究

极近距离煤层传统长壁开采,受上层遗留煤柱和采空区垮落等因素的影响,下煤层开采过程中应力环境复杂、矿压显现剧烈,易诱发巷道围岩大变形。为解决上述问题,提出了极近距离条件下巷道定向切顶–约束高强支护无煤柱自成巷控制方法。通过顶板定向预裂切顶,主动改变顶板悬臂结构,切断采空区向巷道顶板的应力传递。充分利用矿山压力和岩体碎胀特性,取消煤柱留设,结合高强支护加强巷道顶板整体性,共同实现切顶自成巷。建立了极近距离煤层开采覆岩结构模型,计算了下煤层切顶自成巷巷旁支护阻力。以典型极近距离煤层为工程背景,开展了不同开采方法的数值试验对比研究,结果表明,提出的自成巷控制方法使巷道围岩应力降低59.8%,巷道顶板变形减少70.8%,并明确了极近距离煤层开采无煤柱自成巷控制机理。在此基础上,开展了典型极近距离煤层工程设计及现场应用研究,结果表明该方法有效降低了矿压显现程度,保证了自成巷的安全稳定控制。

基于残差优化的综采工作面煤壁点云补全方法

煤矿综采工作面巷道的数字化三维重建过程中需要完整且密集的煤壁点云数据。受遮挡、视角限制等因素影响,采集的综采工作面煤壁点云数据往往不完整且稀疏,影响下游任务,需进行煤壁点云修复和补全。目前缺少针对井下点云补全任务的数据集和网络模型,现有模型用于煤壁点云补全时存在点云密度分布不均匀、点云特征信息丢失等情况。针对上述问题,设计了一种基于残差优化的煤壁点云补全网络模型,采用监督学习方式学习点云特征信息,通过最小化密度采样和残差网络迭代优化输出完整点云。采集煤矿井下真实综采工作面煤壁点云数据,预处理后筛选可用数据,通过模拟随机空洞制作煤壁点云缺失数据集,并用缺失数据集训练基于残差优化的煤壁点云补全网络模型。实验结果表明:与经典的FoldingNet,TopNet,AtlasNet,PCN,3D-Capsule点云补全网络模型相比,基于残差优化的煤壁点云补全网络模型针对构造的缺失煤壁点云和稀疏煤壁点云补全的倒角距离、地移距离及F1分数均能达到最优水平,整体补全效果最佳;针对实际缺失的煤壁点云,该模型能够实现有效补全。

特厚煤层工作面煤厚变化电磁波透视响应特征

目的为掌握煤厚变化对特厚煤层工作面电磁波透视探测的影响,以准确圈定地质异常区,保障工作面安全高效生产。方法根据煤层工作面地质条件,利用三维仿真软件,对煤厚变化进行了电磁波透视数值模拟,并结合工作面探查实例进行了分析。结果0~20m煤厚范围,随煤厚减小,电磁波透视场强值呈抛物线下降趋势,可分为缓慢降低(煤厚≥9m)、明显降低(9m>煤厚≥5m)和快速降低(煤厚<5m)3个范围。煤厚10m以上的工作面适合于依据相对煤层变薄程度和变薄区煤厚来分析透视电磁波响应:变薄程度>1/3正常煤厚且煤厚<8m的薄煤区有明显响应,变薄区煤厚越小,透视电磁波场强降低越显著。煤厚10m以下的工作面,可以仅依据相对煤层变薄程度分析透视电磁波响应:变薄程度>1/4正常煤厚的薄煤区有明显响应,变薄程度越大,透视电磁波场强降低越显著。陕西金源招贤矿业有限公司特厚煤层1304工作面探测实例表明:正常煤厚变化及薄煤区的电磁波响应特征与数值模拟结果一致;工作面物探圈定的落差1m以上断层及薄煤区范围,与实际揭露范围相吻合。结论利用煤厚变化电磁波响应特征能够可靠地探查特厚煤层工作面地质异常区范围。

多频雷达融合的顶煤结构精准探测技术

顶煤结构的准确探测是实现综放智能化开采的重要依据,然而我国煤层结构复杂且内部常含多层夹矸,易影响综放智能化开采的水平。为此,提出一种多频雷达融合的顶煤结构精准探测方法,可提高雷达天线探测深度内的浅部探测精度,同时对顶煤内部的结构信息进行解释。主要研究步骤如下:首先,对不同频率的雷达数据进行预处理和空间对齐,建立不同频率雷达数据之间的空间对应关系;其次,利用滑动窗口与小波变换加权融合方法对多频率雷达数据进行处理,根据窗口内各分段小波信号的能量占比确定各频率信号的时变权重值,并引入边缘检测算法来提高小波变换对雷达数据的融合效率,实现多频雷达数据有效融合;最后,根据煤-矸-岩的介电常数差异和电磁波传播的衰减特性,建立顶煤内部回波强度模型,并利用分层识别方法计算出顶煤内部煤-矸-岩之间的界面信息,进而反演出顶煤内部结构(包括顶煤厚度、夹矸厚度及层数、夹矸层间距等)。试验结果表明:所提出的方法能有效地将不同频率雷达数据进行融合,并能有效地探测出顶煤内部结构特征,且顶煤厚度、夹矸厚度和夹矸层间距的探测误差均小于10%。该方法有助于实现顶煤结构的精准探测,为综放智能化开采提供理论技术支撑。

厚煤层大采高综放工作面覆岩断裂演化规律研究

大采高综放开采易形成强烈的矿压显现,上覆岩层的断裂演化规律对工作面安全生产至关重要。以羊场湾煤矿160206工作面为工程背景,运用相似模拟试验、数值模拟和理论分析的综合研究方法,对大采高综放工作面覆岩的断裂过程与覆岩运移规律进行系统研究。研究表明:导水裂隙带内岩层随工作面推进表现为“台阶下沉”,同层岩层下沉趋势沿走向表现为“急剧下降—稳定(最大值)—快速上升—稳定(最小值)”。工作面覆岩运动场由两区分布(加速下沉区、缓慢下沉区)演化为三区分布(加速下沉区、缓慢下沉区、稳定区)。对离层演化与地表下沉规律进行了定量描述,运用理论计算表达式深入地剖析了地表的动态下沉机理及其相关因素。结合相似模拟与数值模拟的试验结果,提出了覆岩断裂演化的形态变化特征:覆岩断裂形态由“单等腰梯形”演化为“双等腰梯形”,表土层影响区由“矩形”演化为“倒梯形”。分析了覆岩中垮落区、离层区、压实区、裂隙富集区的动态演化过程:垮落区逐渐增大至一定程度,高度小幅度降低并趋于稳定,离层区由下至上逐渐发育并随工作面向前移动,离层区逐渐闭合形成压实区,且压实区逐渐增大并最终保持稳定,裂隙富集区位于采空区前后端部并随工作面向前移动。

大采高综采工作面矿压显现及顶板活动特征研究

为了得到唐山某煤矿综采工作面的矿压显现及顶板活动特征,基于关键层理论、“悬臂梁-砌体梁”力学模型,通过现场观测、理论分析、数值模拟的方法对9煤层矿压显现特征、顶板结构、支架工作阻力开展了深入研究,建立了覆岩结构力学模型,得到了工作面支架工作阻力的合理计算式。研究结果表明:工作面来压步距和来压大小均有一定的规律性,呈现一大一小的周期来压现象,来压期间中部测区支架荷载最大,两边偏小;通过直接顶关键层判别方法,确定了第2层岩层和第7层岩层分别为亚关键层1和亚关键层2。亚关键层1破断后以“悬臂梁”结构形态垮落进入采空区,亚关键层2破断后形成了稳定的“砌体梁”结构,此时亚关键层1与亚关键层2共同组成了“悬臂梁-砌体梁”结构;第2层岩层和第7层岩层组成的双关键层结构的破断运移规律导致了工作面呈现一大一小的周期来压现象。当双关键层同步破断时,支架工作阻力为13 688 kN。

黄土梁峁地形大采高煤层开采地表移动规律数值模拟研究

相较于平原地区,黄土梁峁地形下的煤层开采地表移动特征存在明显不同。为分析并揭示梁峁地形下煤层开采地表沉陷异常形变机理,结合现场实测与数值模拟手段,以山西某矿1313工作面为研究对象,对黄土梁峁地形大采高综放开采引起的地表沉陷进行了现场实测,分析了地表移动特征及相关参数取值;利用Rhino软件建立考虑地形的三维模型,导入离散单元法软件3DEC进行数值模拟计算,分析了开采过程中的岩层移动以及梁峁内部塑性破坏演变。研究表明:1313工作面地表移动剧烈,地表下沉起动距小于30 m,超前影响距为73 m,超前影响角为68.7°,走向边界角与上山边界角为40.3°,走向移动角与上山移动角为37.8°,以水平拉伸变形2 mm/m为移动边界的危险移动范围明显大于以下沉值10 mm确定的地表移动盆地范围;利用数值模拟分析黄土梁峁采动滑移过程发现,当工作面自开切眼沿走向回采30 m时,采空区周围岩体应力平衡被打破,顶板在自重以及上覆岩层的载荷作用下产生剪切破坏,采空区周边岩体发生塑性屈服,当工作面回采到120 m时,煤层处于非充分开采阶段,梁峁底部岩体剪切破坏带出现贯通现象,坡体在重力作用下发生向邻空侧的剪切滑移,相较于地表坡度15°的截面,地表坡度18°和22°的截面X轴负方向最大水平移动提升了107.3%与246.5%。