两柱掩护式综放支架对端面顶煤稳定性的控制作用

采用数值计算方法,分析在软煤、中硬煤和硬煤不同煤层硬度力学条件下,由改变两柱式液压支架立柱前倾角得到的不同水平支护阻力对端面顶煤控制的效果。模拟结果表明：合理的支架水平力可以有效的控制工作面端面冒顶,但顶煤硬度不同时,控制效果有很大差异,主要表现为：不同的顶煤硬度条件下存在一个合理的立柱前倾角度,硬煤条件时需75°~80°的前倾角度,中硬煤条件时需70°~75°的前倾角度。一般情况下,煤层硬度越小,立柱前倾角应越小;当煤层较软时,两柱掩护式综放支架需采取减小端面距等措施进行支护。

综放面端面顶煤稳定性分析及控制

采用现场观测及计算机数值模拟计算方法,研究综放面端面顶煤冒漏机理,得出端面顶煤冒漏的主要影响因素是端面距大小、片帮范围和支架的初撑力,控制端面煤壁片帮是控制顶煤冒漏的有效措施。现场应用实践表明,在综放面向端面煤体打木锚杆是控制煤壁片帮的有效手段,通过实施本措施,端面煤岩体平均冒落高度由3.5m下降到0.8m,取得了显著的经济技术效益。

综放面端面顶煤稳定性分析及控制研究

采用现场观测及计算机数值模拟计算方法,研究综放面端面顶煤冒漏机理,得出端面顶煤冒漏的主要影响因素是端面距大小、片帮范围和支架的初撑力,控制端面煤壁片帮是控制顶煤冒漏的有效措施,具有显著的经济技术效益。

综放面端面顶煤稳定性数值模拟

采用数值模拟计算的方法，对综放面端面顶煤失稳因素进行了模拟分析。模拟结果表明：顶煤稳定取决于顶煤本身的力学性质及老顶、直接顶运动对它的影响，同时也受工作面支架工况的影响，其中，端面距是影响综放面端面顶煤失稳的一个重要因素。

综放面端面顶煤稳定性控制的实践

综放开采煤作为一种高产高效的采煤途径被众多煤炭企业所运用,但由于面端头及巷道悬顶面积大以及设备过于集中等问题,综放采煤过程中工作面事故多发,其中顶煤破碎问题尤为突出,如何保证综放面端面顶煤的完整性和稳定性就成为了综放采煤成功的关键技术。本文对综方面端面冒顶的原因进行了分析,通过实践对端面顶煤稳定性控制的新技术进行了分析研究,得出了新的稳定性实践控制结论。

综放沿空掘巷顶煤稳定性及不对称支护

针对综放沿空掘巷顶煤稳定性差这一问题,建立了顶煤稳定性力学模型,研究了巷道顶煤破裂的判别条件及巷道上覆岩层的运动规律,在此基础上提出了综放沿空掘巷不对称支护的理念,结果表明:综放沿空掘巷巷道顶煤稳定性存在3种类型:即顶煤几乎不开裂、开裂比较频繁和开裂频率很高。顶煤开裂位置在巷道顶板中心偏煤柱侧,裂缝处的巷道顶板经历着"冒漏-回转挤压-冒漏"的往复过程,巷道顶板的支护设计应是适当靠近煤柱侧的偏心设计。工业性试验表明不对称支护对综放沿空掘巷有较好的控制效果。

分层开采下分层大断面开切眼顶板稳定性评估

为了研究分层开采下分层工作面大断面开切眼顶煤稳定性问题,以大柳塔煤矿活鸡兔井1-2煤层下分层203开切眼顶煤的14个钻孔为研究背景,采用理论分析、数值模拟和现场钻孔窥视分析了上分层开采与下分层开切眼掘进对开切眼顶煤塑性区的影响,并通过岩体完整性指数对顶板结构稳定性进行评价。从顶煤结构形态来看,由于上分层开采造成开切眼顶煤局部超挖或欠挖现象,开切眼的最大超挖量为1.2 m,最大欠挖量为0.8 m,顶煤不平整率为27.7%。理论分析结果表明:受上分层开切眼顶煤采动影响,底煤塑性区深度为2.02 m;受下分层开切眼掘进扰动影响,顶煤塑性区深度为1.50 m。钻孔窥视结果表明:将开切眼顶煤塑性区分别按理论计算和钻孔窥视划分为理论塑性区与实测塑性区,上分层采动影响造成的底板实测塑性区深度范围为1.06~2.04 m,下分层开切眼掘进扰动影响造成的顶煤实测塑性区深度范围为0.34~1.50 m,上分层采动影响造成的底板实测塑性区比理论塑性区平均小17.63%,下分层开切眼掘进扰动造成的顶煤实测塑性区比理论塑性区平均小25.82%。数值模拟分析结果表明:上分层采动影响造成的底煤塑性区深度范围为1~2 m,下分层开切眼掘进扰动影响造成的顶煤塑性区深度为1 m。上述3者所得结果一致性程度较高。开切眼顶煤稳定性评价结果表明:顶煤完整性指数范围为42.9%~87.9%,顶煤厚度与完整性指数呈正相关,与裂隙发育呈负相关,顶煤完整性评价为良好以上的占比超过1/2,说明顶煤整体结构基本完整。该研究结果可为分层开采下分层大断面开切眼同类工矿条件的顶煤厚度留设及支护方案设计提供参考。

综放工作面端面顶煤破坏机理及冒顶治理

采用现场观测及计算机数值模拟计算方法,研究综放工作面端面顶煤冒顶机理,得出后端面顶煤冒顶的主要影响因素是端面距大小、片帮范围和支架的初撑力,控制端面煤壁片帮是控制顶煤冒顶的有效措施。现场应用表明,在综放面向端面煤体打木锚杆是控制煤壁片帮的有效手段,通过实施该措施,端面煤岩体平均冒落高度由3.5 m下降到0.8 m,取得了显著的经济技术效益。

两柱掩护式综放支架工艺适应性研究

为研究两柱掩护式综放支架的工作特性及对工作面条件的适应性,掌握支架工作阻力的循环变化规律,针对现场工作面端面顶板的控制效果以及支架的工艺性能进行了数据实测。研究表明:两柱式支架工作阻力以增阻状态为主,支撑效率大幅提高;能够阻止顶梁的低头运动,保持支架的稳定;可以提供更高的工作阻力和水平力,取得更好的端面控顶效果;控制结构简单、后部放煤空间大、移架和放煤速度快,为进一步提高工作面回采效率创造了条件。

Caving thickness effects of surrounding rocks macro stress shell evolving characteristics

In order to explore the influence of different caving thicknesses on the MSS distributionand evolving characteristics of surrounding rocks in unsymmetrical disposal andfully mechanized top-coal caving (FMTC),based on unsymmetrical disposal characteristics,the analyses of numerical simulation,material simulation and in-situ observation weresynthetically applied according to the geological and technical conditions of the 1151(3)working face in Xieqiao Mine.The results show that the stress peak value of the MSS-baseand the ratio of MSS-body height to caving thickness are nonlinear and inverselyproportional to the caving thickness.The MSS-base width,the MSS-body height,theMSS-base distance to working face wall and the rise distance of MSS-base beside coalpillar are nonlinear and directly proportional to the caving thickness.The characteristics ofMSS distribution and its evolving rules of surrounding rocks and the integrated cavingthickness effects are obtained.The investigations will provide lots of theoretic referencesto the surrounding rocks' stability control of the working face and roadway,roadway layout,gas extraction and exploitation,and efficiency of caving,etc.

Analysis of stability of support and surrounding rock in mining top coa of inclined coal seam

The study analyzes the characteristics of roof movement in mining top coal of inclined coal seam,and establishes the mechanical model of support and surrounding-rock stability in inclined coal seam.Besides,this study carries out the numerical calculation and field observation of roof movement and support stability,and provides the critical control measures.The results show that the fracture firstly appears in middle-upper roof and extends upwards in top coal caving in inclined coal seam;regular and irregular caving zones appear in middle-upper stress concentration region,and the asymmetric caving arch is finally formed.Support load of middle-upper working face is larger than that of the middle-lower face;dynamic load coefficient of upper support is large,and the load on the front of support is larger than that on the rear of it,which leads to poor support stability.Stability of support and surrounding-rock system depends mainly on upper-support stability.

Stability of roof structure and its control in steeply inclined coal seams

To improve the effectiveness of control of surrounding rock and the stability of supports on longwall topcoal caving faces in steeply inclined coal seams, the stability of the roof structure and hydraulic supports was studied with physical simulation and theoretical analysis. The results show that roof strata in the vicinity of the tail gate subside extensively with small cutting height, while roof subsidence near the main gate is relatively assuasive. With increase of the mining space, the caving angle of the roof strata above the main gate increases. The characteristics of the vertical and horizontal displacement of the roof strata demonstrate that caved blocks rotate around the lower hinged point of the roof structure, which may lead to sliding instability. Large dip angle of the coal seam makes sliding instability of the roof structure easier.A three-hinged arch can be easily formed above both the tail and main gates in steeply inclined coal seams. With the growth in the dip angle, subsidence of the arch foot formed above the main gate decreases significantly, which reduces the probability of the roof structure becoming unstable as a result of large deformation, while the potential of the roof structure's sliding instability above the tail gate increases dramatically.

Stability control of water-enriched roofs of coal drifts

Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured.The development and connection of cracks provide new water channels which may result in water loss,seriously affecting the in-tegrity and stability of roofs,leading to incidents of roof fall.Control of water-enriched rocks surrounding coal drifts is quite diffi-cult in China.Based on the practical situation of a water-enriched roof of a coal drift in working face 112201 of the Meihuajing coal mine,we studied the deformation features of surrounding rocks and the development of fractured areas and analyzed the major reasons for the decrease in load-carrying capacity,indicating that the key to maintain roof stability of this kind of coal drift is water retention.In addition,we proposed a staged control technology consisting of:1) surface grouting;2) cable anchor strengthening and 3) roof grouting,which has proven to be successful in this practical application.Our study indicates that,after the problem of water loss from the water-enriched roof had been effectively solved,a combined support system with high performance bolts can maintain the stability of the bearing structure,resulting in the control of roof stability in this kind of coal drift.

Failure mechanism and control technology of longwall coalface in large-cutting-height mining method

The stability control of longwall coalface is the key technology of large-cutting-height mining method.Therefore,a systematic study of the factors that affect coalface stability and its control technology is required in the development of large-cutting-height mining method in China. After the practical field observation and years of study,it was found that the more than 95% of failures in coalface are shear failure. The shear failure analysis model of coalface has been established,that can perform systematic study among factors such as mining height,coal mass strength,roof load,support resistance,and face flipper protecting plate horizontal force. Meanwhile,sensitivity analysis of factors influencing coalface stability showed that improving support capacity,cohesion of coal mass and decreasing roof load of coalface are the key to improve coalface stability. Numerical simulation of the factors affecting coalface stability has been performed using UDEC software and the results are consistent with the theoretical analysis. The coalface reinforcement technology of large-cutting-height mining method using the grouting combined with coir rope is presented. Laboratory tests have been carried out to verify its reinforcement effect and practical application has been implemented in several coal mines with good results.It has now become the main technology to reduce longwall coalface failure of large-cutting-height mining method.

Numerical study of rock bolting parameter variation effect on stability of stratified, composite roof structure of drift in a coal mine

Described the outcomes of a comprehensive numerical modeling on the rock bolting performance for preventing the deformation of stratified, composite roof structure of drift in a coal mine. The investigation was undertaken in the adverse geological condi- tions, with variation of bolt parameters, including length, density, distribution, pretension, as well as the geometry of opening,so as to determine the effect of bolting parameter variation on roof deformation and stability. The outcomes clearly demonstrated that a sig- nificant improvement of roof stability can be achieved associating with bolting parameters optimization, and indicated the importance of flexible geotechnical designation of rock bolting reinforcement in mining practice.

Influence of Lithological Characters of Coal Bearing Formation on Stability of Roof of Coal Seams

Lithology is one of the important factors influencing the stability of roof of coal seams. In order to investigate this, the phenomenon of underground pressure and distribution of pressure were studied by using the local observation and simulation test with similar materials. The observation results show that the distance of initial weighting and periodic weighting of the mudstone roof is shorter than that of sandstone roofs. The sandstone roof with a high strength has a longer distance of initial weighting and periodic weighting, the abutment stress on the working face is big and the height of caving and fracture zone is high. The peak point of abutment stress in the sandstone roof is near to the working face and the pressure bump is inclined to occur. The result is contrary to that in case of the mudstone roof with a low strength. While in the transition zone of nipped sandstone, roof rock-mass is broken and is poor in stability, therefore, it is difficult to hold the roof.

两柱掩护式综放支架与围岩相互作用相似模拟研究

基于两柱掩护式综放支架新架型,采用大比例相似模拟实验,研究了工作面顶煤的变形破坏特征及支架与围岩相互作用规律,分析了顶梁前后比和支架工作阻力对支架位态和端面顶煤稳定性的影响规律.结果表明:随顶煤硬度减小,控顶区顶煤和两柱掩护式综放支架位态稳定性同时下降;顶煤较软时,放煤区和端面区顶煤的失稳并不断扩大直至贯通是导致支架-围岩系统失稳的原因,提出了顶煤双区失稳的概念;在软煤条件下,支护的关键是通过控制放煤量限制放煤区顶煤的垮落线前移,提高支架支护质量,控制端面冒顶,实验工作阻力设定值由2.7MN增加到5.5MN,端面冒顶高度由2.13m减小到1.66m,顶梁前后比设定值由2.38减小到1.49时,端面冒顶高度由1.75m减小到0.915m,同时顶梁回转角度变化由16.8°减小到1.2°.