【作者】 刘正和；

【导师】 赵阳升；

【作者基本信息】 太原理工大学 ， 采矿工程， 2012， 博士

【摘要】 在开采煤炭过程中,为了保护巷道和管理采场顶板,常常留下各类煤柱,这些煤柱是造成地下资源损大的主要根源。特别是近些年来,在煤层顶板中存在一层或者数层较坚硬的岩层地质条件下,随着矿井机械化程度的提高,工作面采高的增加,采动影响范围越来越大,回采巷道煤柱上集中应力增加,分布范围增大,导致回采巷道护巷煤柱很大。对于高瓦斯矿井,为了满足安全生产的需要,工作面采用“两进两回”或“三进两回”的布置方式,为了减少巷道掘进率,其中一条或者两条回采巷道保留下来为下个工作面利用,免受工作面采动影响,一侧护巷煤柱宽度达到50m,这样导致回采巷道煤柱宽度问题更为突出,而这些煤柱又难以回收,导致采区回采率大幅下降,煤炭资源损失严重。因此,开展减小回采巷道护巷煤柱宽度的技术基础研究,是国民经济和社会发展中迫切需要解决的关键科学问题,有着重要的科学意义和广泛的应用前景。护巷煤柱能否减小,取决于开采时工作面侧向应力集中的程度,而集中应力大小又取决于开采煤层的厚度、强度、煤层顶、底板岩层结构及其力学特性以及垮落后顶板形成的结构等因素。随着采高的增大,冒落的矸石难以充满采空区,顶板以一定角度向采空区倾斜,侧向集中应力增大,煤柱边缘煤体破坏,集中应力向煤体转移,导致煤柱宽度大幅增加；因此,能够保证安全、有效的减小煤柱的宽度,侧向集中应力控制尤为关键。根据开采引起集中应力分布规律,提出用预裂爆破切缝的方法转移开采引起煤柱集中应力(沿靠近工作面回采巷道顶板上方边缘垂直顶板切缝),即预裂爆破切缝弱化采动影响应力传递减小护巷煤柱宽度。本文针对赵庄煤矿的地质条件,采用理论分析、实验室模型试验、数值模拟计算的综合研究方法,对切缝前、后侧向顶板形成结构、垮落移动变形特征、围岩、侧向煤体应力分布规律等进行研究,获得如下主要结论：(1)当顶板未切缝时,垮落的矸石未能充满采空区,侧向顶板处于悬臂状态,此时顶板结构可简化为悬臂梁结构；当回采巷道顶板切缝并且垮落矸石充满采空区时,侧向顶板在矸石的支撑作用下可简化为多跨梁结构。(2)根据侧向顶板的结构形式,通过受力分析,建立了侧向附加集中应力的力学模型,得出切缝前、后工作面侧向顶板运动在煤体中产生的集中应力计算公式：未切缝时：切缝后(垮落的矸石充满采空区)：(3)基于赵庄矿地质条件,采用相似模拟试验和数值模拟研究了不同切缝深度下顶板垮落特征,煤柱及上覆岩层应力分布变化规律。模拟结果表明,以切缝深度作为垮落角顶点,随着切缝深度的增加,垮落角逐渐减小。不切缝时,垮落角为61°,当切缝深度为15m时,垮落角为37°,切缝深度为20m时,垮落角为33°；随着切缝深度的增加,煤柱应力峰值和平均应力逐渐减小,峰值位置越靠近采空区边缘。与不切缝相比,当切缝深度为15m时,煤柱应力峰值与平均应力减小幅度最大,分别减小了46.5%和48.3%,之后随着切缝深度的增加,减小幅度较小随着切缝深度的增加,煤柱应力峰值位置与回采巷道煤壁距离呈负指数规律减小,与工作面后方距离呈负对数规律减小；与煤柱平均应力呈负对数规律减小(4)在煤柱上覆岩层,随着切缝深度的增加,应力峰值逐渐减小,岩层层位越低,应力峰值越大；在采空区上覆岩层靠近切缝边缘,其应力逐渐增加,岩层层位越高,应力越大。与不切缝相比,切缝深度为15m时,岩层应力峰值减小幅度较大,10m高处岩层应力峰值为15.8MPa,20m高处为14MPa,之后减小幅度较小；切缝深度达到30m时,1Om高处岩层应力峰值为15MPa,20m高处岩层应力峰值为12.98MPa。(5)根据理论研究、试验研究得出侧向顶板垮落引起集中应力分布规律,采用极限平衡法推导出切缝前、后塑性区宽度的计算公式,研究表明,在赵庄矿地质条件下,顶板切缝深度为15m时,护巷煤柱宽度可减小60%。更多还原

【Abstract】 During the coal mining, in order to protect the road and manage the roof, all kinds of coal pillar are always left which are the major source losses of underground resources. Especially in recent years, in the geological conditions of the coal seam with one or several hard rock stratums, and with the improvement of mechanization, and the increase of mining height in working place, the expansion of the mining area and the increase of the concentrated stress in the coal pillar with the mining roadway, and the larger distribution, it leads to the big coal pillar in the mining lanes. As for the high gas mine, in order to meet the safety requirement, the working face is decorated by the way of "two into two out" or "three into and two out". In order to reduce the rate of tunneling, one or two mining lanes are reserved for the next working face in case the mining face is influenced—the width of the one side for the protection lane coal pillar is up to50m, which caused the width problem of the coal pillar in the mining lane to be more obvious. Besides, these coal pillars are difficult to be recovered, which leads to the decline of the rate recovery in mining and the great losses of coal resources. Therefore, the technical basic research of reducing the width of the coal pillar is a scientific problem and urgent need of the national economic and social development, which has important scientific significance and wide application.The decrease of the coal pillar of protected lane depends on the lateral stress concentration during the mining. At the same time, the stress concentration depends on the thickness and strength of the coal seam mining, and the structure of and mechanical properties of the roof and floor in the coal seam rock and the structure of the roof after collapse, and other factors. With the increase of the mining height, the fall coal gangue is difficult to fill the goaf, so the roof with a certain Angle tilt to the gob side. Then the lateral stress concentration increases, the coal pillar edge is damaged, and the concentrated stress transfers to the coal seam side, and at last the width of the coal pillar increases. Therefore, to ensure the safety and effectiveness of reducing the coal pillar width, the control of the lateral concentrated stress is very important. According to the stress distribution caused by the mining, we advises that the pre-split blasting cut seam method is used to transfer the concentrated stress (near mining face roadway the roof along the edge of roof to cutting the vertical seam), that is, pre-split blasting cut seam mining method is used to weaken the effect of the stress to transfer and reduce the width of the coal pillar. According to the geological conditions of ZhaoZhuang Coal Mine, the theoretical analysis, the laboratory model test and the numerical simulation have been adopted. The formation structure of the roof breaks, the fall deformation characteristics, the surrounding rock and the lateral stress distribution law of coal before sewing and back also have been studied. At last the main conclusions as follows:(1) When the roof is not cut and the collapse coal gangue does not fill the goaf, the lateral roof is in a state of cantilever, which can be simplified as a cantilever beam structure. When the mining roof is cut and the collapse coal gangue fills the goaf, the lateral roof under the support of the coal gangue can be simplified as a cross beam structure.(2) According to the structure of the lateral roof, through the force analysis, the mechanical model of the lateral additional stress concentration is established and the concentration stress formula which made by the movement of the lateral roof, and before&after the seam is cut in the coal mining face is acquired: When it is not cut: After it is cut (the collapse coal gangue fills the goaf):(3) Based on the geological conditions of ZhaoZhuang Coal Mine, the similar simulation experiment and numerical simulation have been adopted to study carving characteristics of the roof under the different cutting seam depth, the stress distribution on the coal pillar and overlaying strata. The results showed that, the cutting seam depth is used as vertex of the fall Angle, with the increased depth of the cut seam, the fall Angle gradually reduces. When the seam is not cut, the fall Angle is61°. When the cutting depth is15m, the fall Angle is37°. When the cutting depth is20m, the fall Angle is33°. With the increased depth of the cut seam, the peak stress of the coal pillar and the average stress decrease, and the peak stress position is gradually nearer to the edge of the goaf. Compared with no cutting, when the cutting depth is15m, the peak stress and average stress reduce most, that is, reduce by46.5%and48.3%respectively. After that, with the increased depth of the cutting, the reduce scale is small.With the increased depth of the cutting seam, the position of the peak stress for the coal pillar and the distance of the mining roadway wall reduce in a way of negative exponent. The distance to the back of working face decreases in a way of negative logarithm and the average stress for the coal pillar reduces in a way of negative logarithm.(4) On the overlaying strata of the coal pillar, with the increased depth of the cut seam, the peak stress gradually reduces. When the strata horizon is lower, the peak stress is greater. The gaof strata which is near to the edge of the cutting seam, the stress gradually increases. When the rock layer is higher, the stress is greater. Compared with no cutting, when the depth of the cut seam is15m, the peak stress of the rock decreases to a larger extent. When it is at10m high, the peak stress is15.8MPa. When it is20m high, the peak stress is14MPa. After that the reduce scale is small. When the depth of the cut seam is up to30m, at the depth of10m, the peak stress of the rock is15MPa, and at the height of20m, the peak stress is12.98MPa. (5) According to the theoretical and the experimental study, the stress distribution is caused by fall-down of the roof on the lateral side, the calculation formula of the width of the plastic zone before and after the seam cutting is deduced based on the limit equilibrium method. It is showed that, under the geological conditions of ZhaoZhuang Coal Mine, the depth of the roof cutting seam is15m; the width of the protection coal pillar can be reduced by60%.更多还原