复杂条件下大倾角对放顶煤冒放规律的影响研究

根据申家庄煤矿2208工作面具体的工程地质条件，理论分析了大倾角对顶煤冒放性的影响，指出大倾角将使工作面上、中、下部产生三种性质不同的力学结构，并通过RFPA有限元软件分别对这三种结构的冒放特征进行了数值模拟，揭示了大倾角煤层顶煤的冒放规律，对该矿优化采煤工艺、提高煤炭采出率有重要指导意义。     

放顶煤工作面顶煤冒落形态

对含节理裂隙煤体的强度与破坏特征进行了分析，导出裂隙倾角对煤体强度的影响范围。在此基础上论证了放顶煤工作面顶煤冒落形态可分为倒台阶、柱形、散体三种基本形态。     

大倾角煤层综放俯斜开采采煤机工作状态分析与改进

以理论分析、现场实测为基础,研究了大倾角煤层综放俯斜开采采煤机的受力及工作状态;提出了加高滑靴,调整摇臂摆动范围的采煤机防斜试验设计方案,并进行了现场试验与测试.结果表明,该方案简单易行,便于安装更换,工作稳定可靠.     

大倾角煤层综放俯斜开采采煤机工作状态分析与改进

以理论分析、现场实测为基础,研究了大倾角煤层综放俯斜开采采煤机的受力及工作状态;提出了加高滑靴,调整摇臂摆动范围的采煤机防斜试验设计方案,并进行了现场试验与测试．结果表明,该方案简单易行,便于安装更换,工作稳定可靠．     

放顶煤开采顶煤冒放性影响规律研究

从地质因素出发,用理论分析、现场实测研究和数值模拟方法详细探讨了开采深度、煤层的厚度和强度、煤层中的夹石层厚度及强度、直接顶的岩性及厚度、老顶的岩性及厚度、煤体的裂隙发育程度等因素对顶煤冒放性的影响规律,并给出了影响因素的临界值。     

综采放顶煤地表移动规律特殊性

调查分析了兖州矿区鲍店矿综采放顶煤工作面和普通综采工作面地表移动观测站实测资料．研究结果表明：综放开采时地表移动更加剧烈,地表危险移动范围增大,超前影响范围超过常规分层开采约４０％,下沉活跃期占总移动时间的７１．４％,活跃期下沉量约占总下沉量的９５％．研究还表明,采厚是控制超前影响角和最大下沉速度滞后角的重要因素之一,地表充分采动区存在的残余变形现象更加明显     

厚煤层综采放顶煤工艺研究初探

本文用现场实测与观察法在三河尖矿对厚煤层综放工艺进行了现场研究，以回收率为衡量指标对放煤工艺方式及参数进行了研究，获得了满意的结果。同时结合采区合理巷道布置及生产管理，阐述了实现综放面高产高效的途径，最后论述了防尘及防灭火措施。这些研究结果对同类综放面设计提供了工艺方面的经验及参数。     

放顶煤开采顶煤移动与破坏规律的数值分析

结合现场实际采用数值模拟的方法，研究了放顶煤开采的支承压力形成规律，分析了采高和支架阻力对顶煤应力和位移分布的影响，为顶煤破碎机理的分析和顶煤移动，运动规律的研究提供了依据。     

两硬综放面顶煤顶板冒放结构探讨

用深基点观测和理论分析的方法揭示坚硬顶板、坚硬煤层条件下综放开采顶煤顶板活动规律及其冒放结构，结论对生产有现实的指导意义。     

Top coal flows in an excavation disturbed zone of high section top coal caving of an extremely steep and thick seam

Compared with gentle dip long-wall caving, the length of a working face in fully-mechanized top-coal caving for extremely steep and thick seams is short, while its horizontal section is high with increasing production. But the caving ratio is low, which might result in some disasters, such as roof falls, induced by local and large area collapse of the top coal in a working face and dangers induced by gas accumulation. After the development of cracks and weakening of the coal body, the tall, broken section of the top coal (a granular medium) of an extremely steep seam (over 60°) shows clear characteristics of nonlinear movement, We have thoroughly analyzed the geological environment and mining conditions of an excavation disturbed zone. Based on the results from a physical experiment of large-scale 3D modeling and coupling simulation of top coal-water-gas, we conclude that the weakened top coal can be regarded as a non-continuous medium. We used a particle flow code program to compare and analyze migration processes and the movements of a 30 m high section top coal over time before and after weakening of an extremely steep seam in the Weihuliang coal mine. The results of our simulation,experiment and monitoring show that pre-injection of water and pre-splitting blasting improve caving ability and symmetrical caving, relieve space for large area dynamic collapse of top coal, prolong migration time of noxious gases and release them from the mined out area and so achieve safety in mining.     

A review of cavability evaluation in longwall top coal caving

Longwall Top Coal Caving has been considered as one of the most effective technologies for the extraction of underground thick coal seams. A large number of studies on the applicability of Longwall Top Coal Caving into new mine sites have linked the success of its application to the geo mechanical understanding of the cavability of the top coal. The paper aims to improve the knowledge of the top coal cavability evaluation. A range of parameters that affect the top coal cavability were first identified. Afterward, a number of cavability assessment methods and classifications were reviewed. The result is important in that it assists researchers in developing an advanced and reliable tool for the top coal cavability evaluation.     

Top coal caving mining technique in thick coal seam beneath the earth dam

It is important to study the mining technology under structures for raising the coal resources recovery ratio. Based on the geological and mining conditions, the top coal caving harmonic mining technique in thick coal seam beneath the earth dam was put forward and studied. The 5 factors such as the panel mining direction, panel size, panel location, panel mining sequence and panel advance velocity were taken into account in this technique. The dam movement and deformation were predicted after the thick coal seam mining and the effects of mining on the dam were studied. By setting up the surveying stations on the dam, the movement and deformation of the dam were observed during mining. By taking some protective measures on the dam, the top coal caving mining technique in thick coal seam beneath the earth dam was carried out successfully. The study demonstrates that harmonic mining in thick coal seam is feasible under the dam. The safety of the earth dam after mining was ensured and the coal resources recovery ratio was improved.     

Technical parameters of drawing and coal-gangue field movements of a fully mechanized large mining height top coal caving working face

Under fully mechanized, large mining height top coal caving conditions, the shield beam slope angle of the support increases due to the enlargement of the top coal breaking and caving space. This results in a change of the caving window location and dimensions and, therefore, the granular coal-gangue movement and flows provide new characteristics during top coal caving. The main inferences we draw are as follows. Firstly, after shifting the supports, the caved top coal layer line and the coal gangue boundary line become steeper and are clearly larger than those under common mining heights. Secondly, during the top coal caving procedure, the speed of the coal-gangue flow increases and at the same drawing interval, the distance between the coal-gangue boundary line and the top beam end is reduced. Thirdly, affected by the drawing ratio, the slope angle of the shield beam and the dimensions of the caving window, it is easy to mix the gangue. A rational drawing interval will cause the coal-gangue boundary line to be slightly behind the down tail boom lower boundary. This rational drawing interval under conditions of large mining heights has been analyzed and determined.     

Simulation of recovery of upper remnant coal pillar while mining the ultra-close lower panel using longwall top coal caving

With the depletion of easily minable coal seams, less favorable reserves under adverse conditions have to be mined out to meet the market demand. Due to some historical reasons, large amount of remnant coal was left unrecovered. One such case history occurred with the remnant rectangular stripe coal pillars using partial extraction method at Guandi Mine, Shanxi Province, China. The challenge that the coal mine was facing was that there is an ultra-close coal seam right under it with an only 0.8–1.5 m sandstone dirt band in between. The simulation study was carried out to investigate the simultaneous recovery of upper remnant coal pillars while mining the ultra-close lower panel using longwall top coal caving(LTCC). The remnant coal pillar was induced to cave in as top coal in LTCC system. Physical modelling shows that the coal pillars are the abutments of the stress arch structure formed within the overburden strata. The stability of overhanging roof strata highly depends on the stability of the remnant coal pillars. And the gob development(roof strata cave-in) is intermittent with the cave-in of these coal pillars and the sandstone dirt band. FLAC3 D numerical modelling shows that the multi-seam interaction has a significant influence on mining-induced stress environment for mining of lower panels. The pattern of the stress evolution on the coal pillars with the advance of the lower working face was found. It is demonstrated that the stress relief of a remnant coal pillar enhances the caveability of the pillars and sandstone dirt band below.     

演马庄煤矿突出煤层炮采放顶煤工作面防治煤与瓦斯突出的方法和措施

介绍了演马庄煤矿 2 70 2工作面突出煤层炮采放顶煤效果检验的方法和防止煤与瓦斯突出所采取的措施 ,提出突出煤层炮采放顶煤工作面瓦斯抽放是防止煤与瓦斯突出的有效手段 ,当工作面有煤与瓦斯突出危险时 ,采取恰当的防突措施 ,能够降低煤与瓦斯突出的危险程度 ,可供同类工作面回采时借鉴     

Numerical investigation on the caving mechanism with different standard deviations of top coal block size in LTCC

The size distribution of the broken top coal blocks is an important factor, affecting the recovery ratio and the efficiency of drawing top coal in longwall top coal caving(LTCC) mining panel. The standard deviation of top coal block size(dt) is one of the main parameters to reflect the size distribution of top coal. To find the effect of dton the caving mechanism, this study simulates experiments with 9 different dtby using discrete element software PFC. The dtis divided into two stages: uniform distribution stage(UDS) whose dtis less than 0.1(Schemes 1–5), and nonuniform distribution stage(NDS) whose dtis more than 0.1(Schemes 6–9). This research mainly investigates the variation of recovery ratio, drawing body shape,boundary of top coal, and contact force between particles in the two stages, respectively. The results showed that with the increasing dt, the recovery ratio of the panel increases first and then decreases in UDS. It is the largest in Scheme 3, which mainly increases the drawing volume at the side of starting drawing end. However, the recovery ratio decreases first and then increases quickly in NDS, and it is the largest in Scheme 9, where the drawing volume at the side of finishing drawing end are relatively higher. In UDS, the major size of top coal is basically medium, while in NDS, the size varies from medium to small, and then to large, with a distinct difference in shape and volume of the drawing body. When the major size of top coal is medium and small, the cross-section width of the initial boundary of top coal at each height is relatively small. Conversely, when the top coal size is large, the initial boundary of top coal has a larger opening range, the rotating angle of lower boundary is relatively small in the normal drawing stage, which is conducive to the development of drawing body and reduces the residual top coal, and the maximum particle velocity and the particles movement angle are both larger. This study lays a foundation for the prediction of recovery ratio, and suggests that the uniform top coal is more manageable and has a larger recovery ratio.