无煤柱开采保护层覆岩裂隙发育及瓦斯抽采技术

发布时间：2018-06-08 02:51

本文选题：错层位 + 无煤柱　；参考：《中国矿业大学(北京)》2015年博士论文

【摘要】：论文针对错层位开采覆岩采动裂隙的生成与发育、被保护层的卸压效果及煤与瓦斯共采技术体系的建立与回采工艺的优化展开研究,采用理论分析、数值模拟、相似模拟实验以及现场实测等内容综合展开。首先,对厚煤层一次全高开采以及错层位单个工作面开采覆岩稳定与破坏展开研究,取得如下主要研究结论：(1)工作面回采对上覆岩层破坏高度是关系到瓦斯抽采的关键间题,因此首先对厚煤层一次全高开采覆岩的破坏高度进行确定,提出了基于关键层理论的覆岩三带划分方法,并对实际情况进行计算,通过与现场实测成果进行对比分析,认为新方法的判定结果更接近实测值。(2)在确定一次全高开采覆岩三带划分的基础上,针对错层位无煤柱开采多个搭接工作面体现出单一超长工作面的特点,首次提出错层位无煤柱搭接工作面覆岩三带划分的方法。(3)对于工作面开采倾斜方向覆岩采动裂隙的生成研究,首先采用破断梁理论进行,将首采工作面倾斜方向覆岩视为两端固支梁,给出了固支端的弯矩表达式以及破断准则,并认为工作面倾斜方向两端覆岩采动裂隙的高度基本相同,其内部任意一点应力表达式为：σ=Mh//J7/q/12(6Lx-6x2-L2)h'/J7并给出生成裂隙的准则为：6x2-6Lx+L2+/2(σ-X)h2/qtgφ≤0由于首采工作面沿倾斜方向两端均处于固支,因此认为首采工作面两端出现裂隙高度相同且基本对称。当开采错层位内错式无煤柱接续工作面时,由于两工作面之间无煤柱,岩梁相当于处于一端固支、一端悬臂的状态,其内部应力为：σ=3ql2/h2(l/h+3ql4/2Eh4-1)得到顶板出现裂隙的准则为：3ql2/h(l/h+3ql4/2Eh4-1)≥(σ-C)ctgφ在此基础上进一步给出顶板产生裂隙的位置,即岩层出现位移S,且S满足：S=hε=3ql2/Eh(l/h+3ql4/2Eh4-1)为了进一步反映随着工作面采动对覆岩稳定性的影响及裂隙的发育特点,采用弹性薄板力学模型重点对工作面两侧进行建模,分析其内部的应力与尺寸对裂隙发育的影响,得到如下结论：(1)首采工作面两侧实体煤侧对称出现裂隙,且应力大小基本相同,顶板初次断裂前两侧最大应力为：σ=-0.3qa2/h2相应的出现裂隙的工作面回采参数为：顶板发生断裂后,沿工作面倾向两侧最大应力为：σ=0.3378qa2/h2相应的出现裂隙的工作面回采参数为：基本顶发生断裂前后应力出现较小的变化,认为工作面倾斜方向两侧环形裂隙发育变化不大,当接续工作面开采后,由于两工作面之间无煤柱搭接,因此搭接处上方顶板不再出现新的裂隙,且随着上覆岩层的压实,部分裂隙会闭合,两个工作面体现单一工作面的特点,即在形成搭接的多个工作面的两侧出现裂隙区,其应力分布为：σ=1.854qa2/h2相应的出现裂隙的工作面回采参数为：接续工作面的基本顶发生初次断裂后,其应力分布为：σ=1.962qa2/h2相应的出现裂隙的工作面回采参数为：对比两工作面发现,接续工作面开采后,靠实体煤一侧的应力是首采工作面的6倍,因此认为错层位开采首采工作面与传统采煤方法相同,而由于取消区段护巷煤柱,接续工作面靠实体煤一侧的应力大,因此裂隙发育更加充分。(2)进一步对采场横向裂隙的发育规律展开研究,发现首采工作面开采期间,覆岩垮落压实,形成“O”型圈,接续工作面开采期间,由于无煤柱,覆岩垮落带与首采工作面形成一个整体,且随着工作面开采范围的增加而逐渐增大,整个采空区的形态表现为“O-L-O”型。在前述研究基础上,进一步对留煤柱与无煤柱开采保护层对被保护层的卸压效果进行研究,得到如下研究结论：(1)传统留煤柱护巷开采保护层,煤柱尺寸直接影响到与保护层对应的被保护层区域,煤柱中部存在原岩应力区的前提下,被保护层相应存在四个区：原岩应力区、应力增高区、部分卸压区及充分卸压区。(2)在采用错层位巷道布置开采保护层,由于相邻工作面之间实现完全无煤柱搭接,因此多个相邻工作面体现出单一工作面特点,被保护层中相应位置仅仅存在充分卸压区,且被保护层经历多次采动影响,卸压更充分。(3)进一步结合留煤柱护巷开采保护层,借鉴突变理论对留煤柱巷煤柱的合理尺寸进行公式推导,认为当留设煤柱的屈服区超过煤柱的88%就会有发生突变的可能性,在此,从实现被保护层充分卸压的角度出发,确定留设煤柱发生突变、破坏对于被保护层的连续、充分卸压有利,给出煤柱留设的合理尺寸为：a=[25mξ/22flnfR+kt/kt[1+f(1/ξ-1)ctgφ]|煤柱发生失稳的相应时间为：t=η/ElnE+λKdHaL=25mξL/22flnfR+kt/kt[1+f(1/ξ-1)ctgφ]η/ElnE+λ/Kdm工作面的推进速度需要满足：v≥÷22fE/25mξη/lnfR+kt/kt[1+f(1/ξ-1)ctgφlnE+λ/Kdm在此基础上,确定相应的开采顺序依次为：工作面1→工作面4→工作面2→工作面5→工作面3,相应的卸压区域包括在保护层开采工作面1时,被保护层仅仅形成卸压区域1,当保护层开采完工作面4与开采完工作面2后,形成卸压区域2,当保护层开采工作面5时,由于保护层工作面1与工作面2之间的煤柱发生破坏,在被保护层中形成卸压区域1-2。同理,在开采完保护层工作面3,将会形成被保护层卸压区域1-2-3,这样,考虑保护层工作面4与保护层工作面5的卸压效果,将在被保护层形成连续卸压区域。相应的保护范围,与传统护巷煤柱向比,充分卸压区域随着保护层工作面1的开采,被保护层的卸压范围由1'=L-2hctg6增加到保护层工作面2开采后的1"=2L+a-2hctgδ。(4)如采用错层位开采,与留煤柱相比,第一,可提高回采率；第二,不存在煤柱失稳带来的支护上的难题；第三,可避免煤柱不能及时垮落而影响被保护层的卸压效果。为了验证前述理论研究成果,先后对保护层开采进行了相似模拟实验与计算机数值模拟实验研究,研究中得到如下结论：(1)保护层开采过程中,随着倾斜工作面长度的增加,覆岩破坏的范围无论是横向还是纵向均增长；(2)采用错层位内错式无煤柱布置对上覆被保护层实现连续卸压有利,增加了倾斜方向的卸压范围,同时,被保护范围升高；(3)采用留煤柱护巷,煤柱造成上方被保护层存在应力升高区域,整个被保护层倾斜方向出现充分卸压范围、部分卸压区、应力增高区；(4)错层位内错式无煤柱布置接续工作面开采时,相当于增加了倾斜方向的开采范围,覆岩裂隙带发育高度增加,被保护煤层在裂隙带内的相对层位降低,认为采用错层位巷道布置对上覆被保护层的卸压更有利；(5)计算机数值模拟中,发现首采工作面开采过程中,纵向上,工作面两端巷道上方出现环形裂隙圈；横向上,工作面覆岩破坏范围为”O”型圈；(6)采用错层位内错式无煤柱布置时,接续工作面回采过程中,两工作面搭接部分裂隙逐渐压实,而在形成搭接工作面的两端出现纵向环形裂隙圈,且裂隙发育高度较单个工作面要高；横向上,接续工作面开采过程中,覆岩破坏范围经历“O-L-O"型；(7)为了进行对比,对工作面之间留设20m护巷煤柱进行数值模拟,发现两个工作面均在两端出现纵向上的环形裂隙圈,裂隙发育高度相同,小于错层位开采。结合错层位进行对比,认为留煤柱开采保护层需要每个工作面单独设置,而错层位巷道布置无煤柱开采可考虑搭接的多个工作面统一布置。最后,通过对错层位巷道布置覆岩纵向与横向裂隙及垮落特点进行总结概述,综合考虑形成无煤柱内错式搭接的多个工作面,建立了地面钻孔抽采瓦斯系统、U+L型+上向钻孔抽采瓦斯系统以及高抽巷抽采瓦斯系统,总体来看,错层位内错式无煤柱开采抽采瓦斯系统较传统留煤柱开采要简单,可大幅度节省巷道工程量。最后,结合实际工程背景开采下伏8#煤层保护上方2#被保护煤层,为了改善设计中存在的巷道工程量大、卸压范围小以及工作面瓦斯涌出量大的间题,首先提出采用错层位内错式巷道布置实现上覆2#被保护煤层,具有巷道工程量小、实现被保护层的连续卸压的特点,进一步结合工作面瓦斯涌出受日产量与推进速度的影响,进一步提出缩小保护层工作面倾斜长度(原设计长度250m,优化后125m)、增加日推进量(日进尺4.2m)的技术优化措施。
[Abstract]:The paper aims at the formation and development of the fractured mining fracture of the overlying strata, the pressure relief effect of the protected layer, the establishment of the coal and gas CO production technology system and the optimization of the recovery process, and the comprehensive expansion of the theoretical analysis, numerical simulation, similar simulation experiment and the field measurement. First, a full high mining of the thick coal seam is made. The main research conclusions are as follows: (1) the failure height of overlying strata in working face is the key problem related to the gas extraction, so first of all, the failure height of overlying rock in thick coal seam is determined, and based on the theory of key layer, the theory of key layer is put forward. The three zones of overlying rock are divided and the actual situation is calculated. By comparing with the field measured results, it is considered that the results of the new method are closer to the measured values. (2) on the basis of the determination of the three zone division of a full high mining overlying rock, a single super long working face is embodied in the fault layer without coal pillar mining. For the first time, the method of dividing the three zones of overlying strata overlying strata is proposed for the first time. (3) in the study of the formation of the fractured mining fracture in the inclined direction of the working face mining, first of all, the fracture beam theory is adopted to take the overlying overburden of the first mining face as a two end fixed beam, which gives the expression of the bending moment and the breaking criterion of the fixed end. It is considered that the height of the mining fissures at both ends of the working face is basically the same, and the stress expression of any point in it is: Sigma =Mh//J7/q/12 (6Lx-6x2-L2) h'/J7 and the criterion for the formation of crevice is: 6x2-6Lx+L2+/2 (sigma -X) h2/qtg Phi < 0 because the first working face is fixed at both ends of the inclined direction, so the first working face is considered. At the two ends, the fracture height is the same and basically symmetrical. When the wrong pillar is mined in the wrong layer, because there is no pillar in the two working face, the rock beam is equivalent to the state at one end and at the end of the cantilever. The internal stress is: 3ql2/h (l/h+3ql4/2Eh4-) the criterion for the fracture of the roof is 3ql2/h (l/h+3ql4/2Eh4- 1) on the basis of above (sigma -C) CTG phi, the position of the crack in the roof is further given, that is, the displacement S of the rock stratum and the S satisfy: S=h e =3ql2/Eh (l/h+3ql4/2Eh4-1), in order to further reflect the influence of the working face to the stability of the overlying rock and the characteristics of the fracture development, the mechanical model of the elastic thin plate is used to build on both sides of the working face. The influence of the internal stress and size on the fracture development is analyzed. The following conclusions are obtained: (1) the solid coal side cracks on both sides of the first mining face are symmetrical, and the stress size is basically the same, and the maximum stress on both sides of the roof before the initial fracture is: the working face recovery parameters of the corresponding crack gap of the corresponding Sigma =-0.3qa2/h2 are: after the roof breaks, the fracture of the roof is broken, The maximum stress along the side of the working face is: the mining parameters of the working face of the corresponding fracture of the sigma =0.3378qa2/h2 are as follows: the stress appears little change before and after the fracture of the basic top, and it is considered that the annular fissure on both sides of the inclined direction of the working face has little change. When the continuous working face is mined, there is no coal pillar lap between the two working faces. There is no new crack in the top roof of the lap, and with the compaction of the overlying strata, some cracks will be closed, and the two working faces reflect the characteristics of the single working face, that is, there is a fracture zone on both sides of the overlapped working face, and the stress distribution is: the working face recovery parameters of the corresponding fracture surface of sigma =1.854qa2/h2 are: After the first fracture of the basic top of the continued working face, its stress distribution is: the working face recovery parameters of the corresponding fracture surface of sigma =1.962qa2/h2 are as follows: compared with the two working face, it is found that the stress on the side of the solid coal is 6 times that of the first mining face after the continuous working face is mined. Therefore, it is considered that the first mining face and the traditional coal mining method in the wrong layer mining are considered. In the same way, due to the cancellation of the coal pillar of the roadway, the stress on the side of the solid coal is great, so the fracture development is more fully. (2) further research on the development law of the transverse fissure of the stope. It is found that during the mining of the first mining face, the overlying rock collapsed and compacted and formed a "O" type ring. The rock collapse zone and the first mining face form a whole, and gradually increase with the increase of the mining scope of the working face, the form of the whole goaf is "O-L-O" type. On the basis of the previous research, further research on the pressure relief effect of the protection layer of the retained coal pillar and the coal pillar mining protection layer is carried out, and the following conclusions are obtained: (1) The traditional coal pillar protecting roadway mining protection layer, the size of coal pillar directly affects the protected layer corresponding to the protective layer, under the premise of the central rock stress zone in the middle of the coal pillar, there are four areas in the protected layer: the original rock stress area, the stress increase area, the partial pressure relief area and the full pressure relief zone. (2) the mining protection with the staggered level roadway is used. Layer, due to the realization of completely no coal pillar overlap between adjacent working faces, so a number of adjacent working faces embody a single working face, and the corresponding position in the protected layer only has sufficient pressure relief area, and the protective layer has experienced multiple mining effects, and the unloading pressure is more fully. (3) further combining the mining protection layer of retaining coal pillar to protect the roadway and draw on the catastrophe theory for reference. The reasonable size of coal pillar in the pillar of the coal pillar is deduced, and it is believed that when the yield area of the coal pillar exceeds the 88% of the coal pillar, it will have the possibility of sudden change. In this way, the sudden change of the retained coal pillar is determined from the angle of realizing the full pressure relief of the protected layer, which is favorable to the continuity of the protected layer and the full pressure discharge is favorable, and the coal pillar is set aside. The reasonable size is: a=[25m /22flnfR+kt/kt[1+f (1/ -1) CTG [CTG]. The corresponding time for the instability of coal pillar is: t= ETA /ElnE+ lambda KdHaL=25m L/22flnfR+kt/kt[1+f (1/ zeta -1) CTG [CTG]] The order of mining is as follows: working face 1, working face 4, working face 2, working face 5 and working face 3. The corresponding pressure relief area, including 1 of protective layer mining face, only forms the pressure relief area 1. When the protection layer is finished mining face 4 and after the mining face 2, the pressure relief area 2 is formed, and when the protection layer mining face is 5, because the protection layer mining face is 5, because the protection layer is mining face 5 The coal pillar between the working face 1 and the working face 2 is damaged, and the pressure relief area 1-2. is formed in the protected layer. The pressure relief area of the protected layer will be formed after the protection layer 3 is mined, so that the pressure relief fruit of the protection layer 4 and the protection layer 5 will be considered, and the corresponding pressure relief area will be formed in the protected layer. Correspondingly, the pressure relief area will be formed in the protected layer. The protection range, compared with the traditional coal pillar coal pillar, the full pressure relief area with 1 of the working face of the protective layer, the pressure relief range of the protected layer is increased from 1'=L-2hctg6 to the 1 "=2L+a-2hctg Delta" (4) after the protection layer working face (4), such as using the wrong layer mining, compared with the coal pillar, the first, can improve the recovery rate; second, there is no coal pillar instability. In order to verify the previous theoretical research results, the similar simulation experiments and computer numerical simulation experiments have been carried out on the protection layer mining, and the following conclusions are obtained: (1) in the process of protection layer mining, the following conclusions are obtained: (third) With the increase of the length of the inclined working face, the scope of the overburden failure is increased both horizontally and vertically; (2) the placement of the wrong layer of the internal and wrong pillar is advantageous to the continuous pressure relief in the overlying protective layer, increases the pressure relief range in the inclined direction, and increases the protection range; (3) the coal pillar is used to protect the roadway, and the coal pillar causes the upper protection layer. There is a region of stress rising, the full range of pressure in the inclined direction of the whole protected layer, partial pressure relief area, high stress area; (4) when the wrong layer of internal and wrong pillar arrangement of the continuous working face, it is equivalent to the increase of the mining range in the direction of inclination, the increase of the height of the fissures in the overlying rock, the relative layer of the protected seam in the fracture zone. It is considered that the layout of the staggered layer roadway is more favorable to the pressure unloading of the overlying protective layer; (5) in the numerical simulation of computer, the annular fissure ring appears on the top of the working face during the mining process of the first working face; on the horizontal side, the overlying area of the working face is "O" type ring, and (6) the wrong type internal and error type is adopted. During the coal pillar layout, during the recovery process of the continuous working face, the overlapping part of the two working face is gradually compacted, and the longitudinal annular fissure ring appears at the two ends of the overlapping working face, and the height of the crack development is higher than that of the single working face; in the course of mining the continuous working face, the overlying rock failure range goes through the "O-L-O" type; (7) in order to carry on it, In contrast, the numerical simulation of the coal pillar with 20m retaining wall between the working face has been carried out. It is found that the annular fissure ring on both ends of the two working faces appears on both ends. The height of the crack development is the same and less than the wrong layer mining. The coal pillar mining can consider the unified layout of multiple working faces. Finally, through the summary and summary of the characteristics of the longitudinal and lateral cracks and the collapse of the overlying strata in the wrong layered laneway, comprehensive consideration is made on the formation of the multiple working faces of the fault free lap joint without the pillar, and the ground drilling vassal system and the U+L + updirection drilling gas extraction system are established. As a whole, the gas extraction system of high pumping roadway, in general, it is simpler than the traditional coal pillar to mine the gas drainage system with the wrong type of internal and wrong pillar mining. In the end, the 8# coal seam under the actual engineering background is protected by the protection of the coal seam above the 2# coal seam protection, in order to improve the large amount of roadway engineering and pressure unloading in the design. With small scope and large amount of gas emission in the working face, first of all, it is proposed to use the staggered layer internal and wrong roadway layout to realize the overlying 2# protected coal seam, which has the characteristics of small roadway engineering and continuous pressure relief of the protected layer, and further combined with the influence of the daily output and propulsion speed of gas emission in the working face, the reduction of protection is further proposed. The length of the inclined face of the working face (the original design length is 250m, after optimization 125m), and the technical optimization measures to increase the daily pushing volume (daily footage 4.2m).
【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TD712

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