【作者】 魏锦平；

【导师】 靳钟铭；

【作者基本信息】 太原理工大学 ， 采矿工程， 2004， 博士

【摘要】 采动岩体裂隙演化规律的定量描述是岩石力学的重要课题之一。通过模拟支承压力对硬煤、软煤和中硬煤300mm×300mm×300mm大煤样的动态连续压裂过程，运用分形几何理论，研究了顶煤在支承压力峰值前后作用下裂隙的演化规律：硬煤的裂隙演化一般经历两次加密、两次扩展，否则垮落块度大，顶煤放出率低，相应的弱化处理技术是完成这种演化过程的必要措施。中硬煤的裂隙演化一般经历两次加密、一次扩展，是以加密为主的演化规律；而软煤裂隙则是一次扩展、一次加密，以扩展为主的演化规律。研究表明，裂隙分维和支承压力具有良好的多项式定量关系；同时，通过顶煤压裂试验得出了基于损伤力学的顶煤压裂本构方程，损伤变量的变化验证了裂隙演化规律的正确性。根据现场实测和300mm×300mm×300mm大煤样的压裂实验，得出了顶煤块度的分布特征，为块体顶煤的相似模拟放煤试验设计奠定了基础。 通过块体顶煤的相似模拟放煤试验得出了顶煤块径大小、分布层位对顶煤回收率的影响规律，并得出了放煤工艺对顶煤分布特征的适应性规律。研究表明，顶煤块体大小是影响顶煤回收效果的主要因素，在顶煤块径一定的条件下，块体层位分布不同是造成顶煤回收率差异的主要原因，研究表明各级块度均匀混合时顶煤回收效果最好，块度从下向上增大分布次之，大块为中位顶煤时回收效果最差；各种放煤方式的适应性不同，各级块度均匀混合的顶煤适合用间隔放煤；块度从下向上增大适合用顺序放煤；大块在顶煤中位分布时，中硬煤以下适合用间隔放煤，硬煤应采用顺序放煤方式。对于中硬以上煤层，采取适当的顶煤弱化措施是大幅度提高顶煤回收率的前提。 在块体顶煤放煤相似模拟试验基础上，通过理论分析，研究了顶煤放出过程中的成拱机理，揭示了顶煤块径、支架掩护梁角度、摩擦系数及架后煤矸堆积角等因素对成拱参数的影响规律，得出支架掩护梁的临界角度为40°，架后岩堆的临界堆积角为45°～50°，低于临界角度，则顶煤成拱部位高，甚至演化为支架上的稳定半拱，影响顶煤放出、甚至丢煤；通过推导放煤成拱的极限跨距，证明块度越大，拱高跨比越大，成拱部位越高，破拱难度越大，顶煤损失越多。因此，对中硬以上顶煤，必须采取弱化措施，对坚硬顶板，必须采取采前预处理弱化措施，以增大支架后岩堆坡面的角度和高度，从而避免放煤成拱，影响放煤效率和顶煤回收率。综放面顶煤压裂规律及成拱机理研究 针对“两硬”综放工作面顶板来压强烈，存在冲击危害，而顶煤压裂效果差，回收率低的现象，在顶煤压裂规律研究的基础上，展开“两硬”综放面顶煤压裂控制的研究。通过对岩层移动的现场观测，建立了“两硬”条件综放采场台阶悬臂一悬臂梁.组合的煤岩组合结构力学模型，并以此煤岩结构为基础，建立“两硬”条件综放采场顶煤压裂的有限元数值模型，分析了坚硬顶板不同来压步距对坚硬顶煤的压裂效应，并确定了合理的支架阻力，从而对坚硬顶板进行有效的控制，消除坚硬顶板对采场的冲击隐患，同时保证采场矿压对坚硬顶煤的有效压裂，达到提高顶煤回收率之目的，由此形成了坚硬顶煤、坚硬顶板条件下综放采场围岩控制的基本理论和方法。 在有效控制坚硬顶板的基础上，利用数值模拟正交试验法，研究了采高、采放比、支架阻力、放煤步距等工艺参数对顶煤压裂效果的影响规律，从而对工作面工艺参数进行优化;并根据实验所得放煤方式对块体顶煤的适应性规律，选择“两硬”综放面的放煤工艺，从而形成了系统、完善的“两硬”条件综放工艺。以上顶煤控制压裂及放煤理论在“两硬”综放采场的应用，提高顶煤回收率的效果明显。更多还原

【Abstract】 Quantitative description for the evolution of crack in rock is one of the fundamental problems of rock mechanics. Based on the field observation of the abutment pressure, the cracking process of top coal is dynamically simulated, and the coal sample ,whose size is 300mm X 300mm X 300mm, is press cracking by the simulated abutment pressure. The cracks are measured continuously. Through the fractal geometry, the evolution of crack is described quantitatively. The variety of crack fractal dimension reveals the crack propagation. The complete fracture of hard coal comes through two stages of crack density increment and two stages of crack expansion. The complete fracture of medium-hard coal undergoes two stages of crack density increment and one stage of crack expansion, and the denseness of crack is the key for medium-hard coal to fracture. To the soft coal, there are once crack density increment and once crack expansion, and the expansion is import to fracture.It is found that the relation between the fractal dimension of crack and the abutment pressure is polynomial expression. According to the damage mechanics, the constitutive equation of top-coal fracturing is obtained. The propagation law of crack is proved to be correct by the changing of damage variable. Based on the spot measure and coal sample fracture experiment, the distribution of the top-coal block is found. Coal block distribution is the foundation of simulation test for coal block drawing.Through similar simulation test of block top-coal drawing, the influence of coal block size and block position in top coal on the recovery ratio and drawing manner is studied. It is found that the drawing manner has the different adaptation to the top coal which has different block distribution. The caving capacity is mainly decided by the block size. The top-coal which has layer difference of block with the same size has different recovery ratio. It is shown, that, to the given top-coal blocks, the recovery ratio of uniformly mixed blocks is maximal in the manner of drawing at interval of one support. When top coal has increasing block size from the underside to the upside, the recovery ratio is medium, andthe best drawing manner is in order. When the big blocks are in the middle part of top coal, the recovery ratio will be minimum, in this case, drawing at interval is needed for medium-hard coal and soft coal, and drawing in order suits with hard top coal. The top-coal block distribution needs corresponding drawing manner. In order to increase the recovery ratio, the pre-treated measures are needed to soften the hard top coal.The arching mechanism is studied in this paper. The relation of arching parameters to top-coal block, shield girder angle, friction coefficient, and angle of waste rock after support is found, which shows that the limit angle of shield girder is 40, and the limit angle of waster rock in gob is 45 ~50. If the angle is less than the limit angle, the arch, formed by top coal blocks will be in high position or a half arch comes into being. It is difficulty to destroy the balance of high arch or half arch, as a result, the top coal will be lost. The ratio of arch height to arch span increases with the coal bock size increment and the waste rock pile angle decrease. Reduce the arch height is helpful to improve the top coal recovery.The longwll top coal caving with hard roof and hard coal faces two troubles: One is the impact of roof, the other is that the hard top-coal is difficulty to be drawn. On basis of the law of coal fracture, the control of top coal fracture is studied. It is important to reduce the span of the hard roof to avoid its impact load on supports. However, at longwall top coal caving face, the periodical weight of roof is a main factor that crushes the top coal, which is beneficial to the top coal recovery. How to use the roof pressure safely is of crucial importance in top coal caving. Based on field monitoring, theoretical analysis of strata movement, the numerical model of compound structure of hard roof stepped cantileve更多还原