Deformation mechanism of surrounding rocks and key control technology for a roadway driven along goaf in fully mechanized top-coal caving face

The variation of the stress in the bolted surrounding rocks structure of the roadway driven along goaf in a fully mechanized top coal caving face with moderate stable conditions are studied by using numerical calculation. The essential deformation characteristics of the surrounding rocks in this kind of roadway are obtained and the key technology of bolting support used under these conditions is put forward.

Statistic constitutive equation of top-coal damage for fully mechanized coal face with sublevel caving

Under the action of abutment pressure in front of fully mechanized coal face with sublevel caving(CFSC),top-coal over CFSC deformed.In the process of whole de- formation of top-coal,it changed from continuum elastic mass to non-continuum plastic mass contained fissures,become a loose body.According to its bearing characteristics and mechanical properties,top-coal mass can be divided into four deformation zones along the winning direction of CFSC,i.e.initial stress zone,elastic zone,plastic zone and loose zone.Top-coal in plastic zone located in the post-peak zone of the stress-strain curve for top-coal.With equivalent strain principle of damage mechanics and mathemati- cal theory of statistic,combining the movement law of top-coal,set up a constitutive equa- tion with damage statistics for top-coal in different position in CFSC.The equation illus- trated the mathematical relationship among top-coal bearing capacity,horizontal confining pressure along the winning direction of CFSC and mechanical properties of top-coal mate- rial.The conclusions not only provide a basis for numerical computer simulations on damage deformation and failure mechanism for top-coal,but also further promote the ap- plication of damage mechanics in CFSC.

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.

Analysis and key control technologies to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines

In order to prevent spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines in China, we have analyzed the characteristics of spontaneous coal combustion and explain theoretically the factors affecting spontaneous coal combustion, such as rock bursts, high temperatures, high ventilation resistance, slow advancing speed and large obliquity mining. Key technologies to prevent spontaneous combustion occurring in sharply inclined seams in deep mines are pro- posed; these include pouring water, stopping leakage in upper and lower comers of the working face, choking off the goaf and cov- eting the coal. CO concentrations were controlled within two years to less than 15×10^-6 at the upper comer by applying these tech- nologies at the 1410 working face of the Huafeng coal mine. Our method has significant theoretical value and is of practical impor- tance in controlling spontaneous coal combustion occurring at a fully mechanized caving face with large obliquity in deep mines.

Investigation on the stress field characteristic of top coal at FMTC faces under the influence of caving thickness

In the background of the technology condition and the geological condition of the 1151（3） fully mechanized top-coal caving face （FMTC face）, and by means of taking nonlinear 3D numerical simulation, the stress redistribution rules of top coal with different thick coal seam were obtained by investigation on the numerical simulation of the redistributions of the stress with different coal seam＇s thickness. The research showes that there exists a certain difference on the stress distributions of the top coal at face, the maximum principal stress is located near to the tailentry＇s corner. The vertical stress＇s peak of the top coal decreases and the distance ahead of face position increases as the once mining thickness of the coal seam increases. At the same coal seam, the vertical stresses＇ peak of top coal gradually decreases from the top to the bottom, the peak＇s position is basically the same and its changes are gradually obvious with the thickness of coal seam increas- ing. The vertical stress of top coal places in a low stress state at a certain range ahead of face and over the face, which reveals the essence that the support loads are generally low under the condition of FMTC. The study supplies the theoretical foundation for the support design and selection, the theory of top coal＇s fragmentation, the movement rules of top coal and improving the recovery of top coal.

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.

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.

Study of mechanical principle of floor heave of roadway driving along next goaf in fully mechanized sub-level caving face

Abstract On the basis of analyzing floor strata mechanical circumstance of the roadway, the mechanical model was established. The relative displacement of roadway floor, narrow pillar floor coal mass and floor strata was calculated, the results showed that the high abutment pressure on coal mass beside the roadway was the main reason to lead to relative displacement of floor strata. And the roadway floor heave come mainly from three aspects. Firstly, the roadway floor strata is easily fractured by the stretch stress. Secondly, because the high abutment pressure is greater than the uniaxial compressive strength of floor strata, when the roadway floor strata are fractured, the coal mass floor strata at the same depth will be fractured, and broken rock will fluid into the open roadway. Thirdly, comparing with the coal mass floor, the roadway floor is relative ascending.

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.

综放工作面围岩控制与智能化放煤技术现状及展望

分析了厚及特厚煤层智能化综放工作面围岩控制技术与智能化放顶煤技术发展现状及存在的问题,从巷道围岩高效支护、工作面超前支护、坚硬特厚顶煤冒放性、液压支架位姿监测及智能化放顶煤5个方面提出了工程实际需求。针对综放工作面实现安全、高效、智能化开采存在的技术难题与工程需求,对综放工作面围岩控制技术、智能化放煤技术进行了研究:构建了坚硬特厚煤层顶煤悬臂梁力学模型,研发了提高顶煤冒放性及放出率关键技术,实现了坚硬特厚煤层超大采高综放开采;研发了单元式超前液压支架顶梁可旋转自复位装置,实现了液压支架顶梁根据巷道顶板倾斜角度自动旋转支护,有效提高了单元式超前液压支架对巷道顶底板的适应性;提出了采用巷道支护液压支架替代传统锚网支护结构的思路,具有支护效率高、成本低、节省工作面超前支护等优点;开发了基于立柱与尾梁千斤顶行程的综放液压支架支护姿态监测装置与算法,提高了液压支架支护姿态解算效率与精度;提出了基于透明地质模型、煤量监测装置与煤矸识别装置融合的智能放煤控制方法,可有效解决多夹矸层特厚顶煤智能化放煤技术难题。提出智能地质保障技术、机器视觉精准测量与智能感知技术、综放工作面设备智能精准自适应控制技术、综放工作面数字孪生技术等是智能化综放开采技术与装备的发展趋势。

两次采动影响下小煤柱巷道切顶卸压围岩控制技术

为解决多次采动影响下留小煤柱巷道矿压显现剧烈、围岩变形量大的问题,提出了“切顶卸压+顶、帮锚索补强”联合控制技术。以贾家沟煤矿10115运输巷为工程背景,分析了切顶卸压位置、高度与巷道围岩垂直应力分布的关系,给出切顶卸压关键参数,并研究了留小煤柱巷道在切顶卸压后受两次采动影响下的矿压显现规律。结果表明:切顶卸压后,煤柱上的应力峰值随切顶深度的增加呈指数降低;10115运输巷在邻近工作面一次采动过程中巷道围岩变形依次呈现出无变形、缓慢变形、快速变形和围岩稳定的变化规律,本工作面二次采动过程中巷道围岩变形依次呈现出明显变形和剧烈变形的规律;巷道围岩在受二次采动影响时变形更加剧烈,巷道变形量为一次采动时的3.0~7.5倍。

基于DeepLab v3+的综放工作面含矸率预测研究

针对综放工作面真实煤矸堆叠状态下的体积含矸率很难获取的问题,提出一种基于DeepLab v3+的综放工作面含矸率预测方法。构建了煤矸堆积体图像数据集,采用半自动的数据标注方法和限制对比度自适应直方图均衡化法对煤矸图像进行预处理。运用DeepLab v3+模型进行煤矸图像语义分割,进而计算煤矸图像的投影面积含矸率。利用PFC3D数值模拟软件,基于重建的三维煤矸块体建立数值模型,模拟顶煤放落和刮板输送机运煤过程,通过fish语言读取每个矸石或煤的体积,计算得到煤矸堆积体体积含矸率。通过分析不同顶煤厚度条件下刮板输送机上煤矸堆积体的投影面积含矸率与体积含矸率的量化关系,建立了煤流的体积含矸率预测模型。实验结果表明:DeepLab v3+模型的准确率、平均像素准确率和平均交并比分别为97.68%,97.72%,95.33%,均高于经典语义分割模型FCN8s和PSPNet,实现了煤矸堆积体投影面积含矸率的精准快速识别;体积含矸率预测模型的决定系数R^(2)为0.9828,预测效果较好。

近距离煤层采空区下综放工作面巷道合理位置研究

近距离煤层综放工作面开采空间大,采动强度高,下位煤层回采巷道受上煤层采动影响存在应力集中、巷道支护困难等问题,因此近距离煤层综放工作面巷道合理位置的选取对后期支护控制起到关键性作用。以西露天煤矿2煤层和1煤层1分层为研究对象,综合考虑了上煤层开采时的底板应力降低区域和下煤层开采时的极限平衡区域,确定了下煤层巷道的合理位置应在距离实体煤柱内错22.79 m以上的区域。基于上述理论计算结果,分析了上煤层开采后底板应力分布规律及不同内错距下巷道围岩变形破坏特征及规律,结果表明:①距离采空区底板越近,应力最大值与最小值相差越明显;②随着内错距不断增大,围岩应力和应力集中系数呈现急剧降低-缓慢增大-稳定的趋势,在内错距20~25 m内应力及应力集中系数相对较小;③巷道围岩塑性区范围呈现先减小后增大的趋势,当巷道处于内错20,25 m时巷道围岩破坏相对较小;④巷道变形量随着内错距增大而逐渐减小,当内错距增加至25 m时,巷道围岩移进量基本保持不变;⑤确定巷道合理内错距为20~25 m。工程应用结果表明:巷道采用内错距24 m布置时,巷道围岩松动破坏深度及变形量均在可控范围内,进一步证明了该内错距的合理性。

注氮条件下大采高综放工作面采空区自燃“三带”的分布规律

为解决大采高综放工作面因采高大、回采率低、开采扰动强等造成采空区遗煤自燃危险性增大的问题,以宁夏某煤矿大采高综放工作面为研究对象,应用渗透率演变方程和气体流动模型,分析注氮前后氧浓度时空演化规律及采空区自燃“三带”分布特征。结果表明:采空区氧浓度在注氮条件下呈现出中部大,两侧小的倒“U”型分布;在氧浓度划分下,氧化带范围呈现出先增大后减小的半月形,最大宽度由未注氮时的100 m缩小到50 m;在风速划分下,氧化带较未注氮时整体向工作面方向前移了15 m左右,有效降低了自燃危险区范围。

双临空综放面巷道变形能量时空演化机理及防治技术研究

以塔山矿8204-2特厚煤层综放不规则双临空工作面工程地质条件为背景,基于数值模拟揭示了不同煤柱宽度下采动应力及煤柱应变能密度分布特征。结果表明,双临空工作面回采期间,30~60 m宽的煤柱处于高应力状态,峰值超过25.96 MPa,为原岩应力的2.09倍;当煤柱宽度在30~60 m时,煤柱表现出高应力、高应变能密度的“两高”特点,发生强动压的危险性高。为防止三角变宽煤柱动力失稳,现场成功实践了“超深高密大直径卸压钻孔+补丁锚索加强支护”的强动压治理技术,使得巷道掘进和回采期间均未发生冲击地压及显著动压事故,实现了不规则综放面的安全回采。

煤矿大倾角综放工作面采煤参数及采煤工艺优化分析

以A煤矿26514工作面为例,介绍了一种基于有限元分析的煤矿大倾角综放工作面采煤参数及采煤工艺优化方法。该方法根据煤矿大倾角综放工作面参数构建相应的有限元模型,通过有限元模型的分析寻找现有工作面采煤参数与采煤工艺的缺陷,进而以此为基础制定工作面采煤参数与采煤工艺优化方案。研究对大倾角综放工作面的开采具有重要意义。

大倾角综放采场遗留顶煤运移规律及防灭火技术

为研究大倾角综放采场遗留顶煤运移规律及裂隙扩展情况,以王家山煤矿中二401工作面为研究对象,采用物理相似模拟实验与数值模拟实验相结合的方法,深入分析大倾角综放采场遗留顶煤运移及裂隙发育规律。结果表明,大倾角综放采场遗留顶煤破碎和运移具有非对称性,工作面倾斜中下部应力与位移量均大于倾斜上部。遗留顶煤在采空区内沿倾斜方向呈现“顶煤—直接顶—顶煤”交替堆积形态,倾斜下部堆积量大于倾斜中上部。围岩裂隙发育范围广,随工作面推进最终可扩展至3号煤层。针对遗煤特征综合提出此类采场的“两阶段”防灭火技术措施,达到良好的防灭火效果,确保工作面安全高效生产。

大水易淤综放工作面泄水巷煤泥淤积物临界流速研究

高家堡煤矿综放工作面面前淋水,水源主要来自采煤工作面顶板,矿井涌水量达到4000~5000 m^(3)/h。结合开采工作面泄水巷煤泥淤积的特点,利用罗宾诺维奇—莫纳方程和哈根—泊肃叶(Hagen-Poiseuille)等公式,确定了煤泥混合物的流变类型和本构方程;采用大型环管实验法建立了煤—泥—水混合物的流动模型,理论分析了工作面泄水巷煤泥淤积物分别在高低压段和不同剪切速率下的沉降特性;计算得到动水条件下煤泥淤积物发生流动的临界流速为1.1~1.5 m/s,从而得出煤泥淤积物的临界流速。研究煤泥在矿井水流动过程中的淤积机理,可为科学合理的清淤工作提供理论依据。

基于工艺引擎的规划放煤控制系统

目前对综放智能化的研究主要聚焦于感知方面,对放煤过程智能化的研究较少,自动放煤控制技术存在自适应性不足、效率较低、放煤质量难以把控等问题。为了提升放煤过程的智能化水平与运行效率,设计了一种基于工艺引擎的规划放煤控制系统。该系统由放煤管控单元和窗口决策单元组成:规划放煤管控单元通过异步递进的放煤调度策略、柔性切换技术及规划放煤工艺编辑引擎,实现采煤机位置弱关联的自动顺序放煤及工艺在线编辑,通过关联后部刮板输送机负载,动态调整工艺启停,保障刮板输送机安全作业;窗口决策单元通过PID控制算法动态调节尾梁角度,实现放煤窗口反馈控制,采用遗传算法优化BP神经网络对放煤窗口大小进行智能决策,以适应不同工况,提高放煤质量。现场应用结果表明:基于异步递进的放煤调度策略与柔性切换技术提升了单刀自动运行效率,无需再手动接管;每一班组自动化运行刀数提升了33.3%;系统关联的后部刮板输送机负载、泵站等设备可动态调整工艺启停,每班后部刮板输送机平均停止次数下降了61.1%,可保障作业安全;工艺编辑引擎能适应多种场景下的应用,工艺调整用时大幅度降低;后部动作与前部动作相互叠加,使得单刀平均用时缩短了9.3%,提升了开采效率;倾角传感关联控制与规划放煤窗口智能决策将每日发热量提升了10.3%,改善了放煤质量。