浅埋煤层短壁开采关键层破断及控制研究.pdf

博士学位论文 浅埋煤层短壁开采关键层破断及控制研究 Study on the Breaking and Control of Key Strata under Short-Wall Mining in Shallow Seam 作 者姜海军 导 师曹胜根 教授 中国矿业大学 二○一六年十二月 国家重点基础研究发展计划（973）项目（2015CB251603） 国家自然科学基金项目（51374197） 煤炭资源与安全开采国家重点实验室自主课题项目（SKLCRSM12X06） 万方数据 中图分类号 TD323 学校代码 10290 UDC 622 密 级 公开 国家重点基础研究发展计划资助（973）项目（2015CB251603） 国家自然科学基金项目资助（51374197） 煤炭资源与安全开采国家重点实验室自主课题资助（SKLCRSM12X06） 中国矿业大学 博士学位论文 浅埋煤层短壁开采关键层破断及控制研究 Study on the Breaking and Control of Key Strata under Short-Wall Mining in Shallow Seam 作 者 姜海军 导 师 曹胜根 教授 申请学位 工学博士学位 培养单位 矿业学院 学科专业 采矿工程 研究方向 采场围岩控制 答辩委员会主席 屠世浩 评 阅 人 盲审 二○一六年十二月 万方数据 学位论文使用授权声明学位论文使用授权声明 本人完全了解中国矿业大学有关保留、使用学位论文的规定，同意本人所撰 写的学位论文的使用授权按照学校的管理规定处理 作为申请学位的条件之一， 学位论文著作权拥有者须授权所在学校拥有学位 论文的部分使用权，即①学校档案馆和图书馆有权保留学位论文的纸质版和电 子版，可以使用影印、缩印或扫描等复制手段保存和汇编学位论文；②为教学和 科研目的，学校档案馆和图书馆可以将公开的学位论文作为资料在档案馆、图书 馆等场所或在校园网上供校内师生阅读、浏览。另外，根据有关法规，同意中国 国家图书馆保存研究生学位论文。 （保密的学位论文在解密后适用本授权书） 。 作者签名 导师签名 年 月 日 年 月 日 万方数据 论文审阅认定书论文审阅认定书 研究生 姜海军 在规定的学习年限内， 按照研究生培养方案的要 求，完成了研究生课程的学习，成绩合格；在我的指导下完成本学位 论文,经审阅，论文中的观点、数据、表述和结构为我所认同，论文 撰写格式符合学校的相关规定， 同意将本论文作为学位申请论文送专 家评审。 导师签字 年 月 日 万方数据 致谢致谢 当完成论文的最后写作，我的情绪久久不能平静回首过去，思绪万千。二 十多年的寒窗苦读，有过成功的喜悦，亦有过失败的沮丧。在这里，首先衷心感 谢我的恩师曹胜根教授，自步入师门的那一刻起，恩师在生活方面给予了无微不 至的关心和帮助， 在为人处世方面， 以身为范教会了诸多道理， 在学习和科研中， 教会我了我严谨的治学态度，求实创新的学术思想从论文选题一直到论文的撰 写与修改，每一个环节中都凝聚着恩师的汗水和心血。在恩师谆谆教诲下，我经 历了人生中最重要的阶段，懂得了做人做事的方式，学会了许多专业知识和相关 技能，我的每一点进步都是从恩师身上得到的最宝贵的财富这么多年来，恩师 做学的严谨、做人的淳朴、做事的认真将是我一生学习的榜样在此我谨向恩师 及母校表达最崇高的敬意和最诚挚的感谢 论文的完成离不开诸多同门师兄弟以及同学的帮助。在此，感谢姚强岭副教 授、巨峰副研究员、武进忠讲师，赵宏超讲师等在我研究生学习阶段的指导；感 谢周茂普研究员、江小军副研究员和张蓓博士等在现场实践期间的帮助；感谢程 正刚硕士、张厚江硕士、咸宇超硕士、张云博士、王琛硕士等在实验室试验、数 值分析、物理模拟以及论文翻译中的提供的帮助，没有你们无私的帮助，博士论 文难以完成；感谢多年来课题组已经毕业的和在读的师兄弟们，真诚相待，互帮 互助，兄弟情义永不变 特别感谢刘曙光教授、 闫长旺教授、 刘全龙博士、 邓雪杰博士、 刘杰刚博士、 时如意博士、 王希鹏博士和张华博士等在我学习和生活方面给予的巨大帮助和支 持 特别感谢神东集团的张叔叔、徐阿姨、孙哥、闫敏师弟和张宏旭等在我博士 论文资料收集方面给予的巨大帮助 感谢母校，她用“勤奋、求实、进取、奉献”的精神一直感染和鼓励着我，感 谢矿业工程学院的各位老师对我的培养、指导和帮助 感谢我的父母、姐姐、弟弟及所有家人，有你们在生活上悉心的照顾及对我 的宽容和鼓励，才使我得以全身心的投入到博士期间的学习和论文写作当中。 最后， 由衷的感谢评审和答辩本论文的各位专家、 教授， 希望得到您的指导、 建议和修改意见，同时感谢百忙之中参加我论文答辩工作的各位专家评委 姜海军 2016 年 12 月于中国矿业大学南湖校区 万方数据 I 摘摘 要要 如何通过合理方案设计实现短壁回采过程中留设的支巷间煤柱实现自身的 稳定屈服，从而缓解或消除浅埋煤层坚硬顶板破断大面积来压所产生的动力灾 害问题，同时最大程度提高煤炭回收率，对神东地区短壁回采工艺的应用以及 实现边角煤的最大程度回收尤为重要。本文从决定浅埋煤层顶板稳定的关键层 着手，综合利用理论分析、物理模拟和数值模拟等研究方法，分析关键层开裂 前的变形和能量分布以及开裂后形成砌体梁结构的稳定机理；系统分析相邻区 段开采过程中关键层及其上覆岩层的变形和破断规律；结合局部刚度理论和屈 服煤柱理论对“关键层-屈服煤柱”系统安全破坏进行了工程方案设计和优化。 取得以下创新性成果 （1）建立了包含煤壁屈服区在内的复合地基梁力学模型，研究了煤壁屈服 区宽度与超前支承压力分布、关键层的初次开裂和周期开裂之间的关系，系统分 析关键层的开裂位置、能量分布和变形等情况；建立了包含原岩水平应力作用的 砌体梁稳定计算方法和判据； 结合神东浅埋煤层覆岩特点分析了关键层及其上覆 岩层的开裂过程、变形、应力分布和整体垮落机理。 （2）根据短壁连采工作面布置特点和尺寸，利用物理相似模拟和数值模 拟，研究了相邻区段开采对上覆关键层稳定的影响。结果表明，本区段支巷回 收过程加剧了相邻已采区段关键层的变形，影响程度随已采区段关键层跨度增 加而越加明显；而已采区段关键层是否稳定直接决定了相邻在采区段关键层的 变形、极限跨距和垮落模式；通过位于相邻两侧区段上方所形成的双压力拱结 构相互作用机理分析了产生上述影响的原因。 （3）在进一步完善围岩局部刚度计算方法的基础上，并结合屈服煤柱理论 提出了“关键层-屈服煤柱”系统安全破坏理论，在系统分析区段支巷宽度、支 巷回收顺序、末采支巷 （区段内最后回收的支巷） 位置、屈服煤柱 （支巷间煤柱） 位置和数量等参数对围岩局部刚度影响的基础上，将屈服煤柱设计方案简化为6 个最基本的刚度单元，通过数值模拟和理论计算确定了适合每个局部刚度单元 的合理屈服煤柱宽度；在综合考虑区段内支巷安全回收和关键层安全破坏以及 增加区段可采面积和区段煤炭回收率的基础上对屈服煤柱设计方案进行了筛选 和优化，并进一步给出了“关键层-屈服煤柱”系统安全破坏工程方案优化设计 流程。 该论文有图 145 幅，表 9 个，参考文献 229 篇。 关键词关键词浅埋煤层；短壁开采；动力灾害；关键层；屈服煤柱 万方数据 II Abstract How to realize the stable yield of pillar left in the panel between branch entry through the rational project design, and then relieve or eliminate the dynamic disaster caused by the hard roof caving under shallow depth, meanwhile maximize the coal recovery are very important for application of short-wall mining technology and maximize the corner coal recovery in Shendong mines. This dissertation comprehensively utilizes the theoretical analysis, physical modeling, numerical simulation s to analyze the deation and energy distribution before cracking and the stable mechanism of voussoir beam structure after cracking of the key strata that determines the stabilization of roof in shallow seam, and further study the deation and cracking law of key strata above the two adjacent panels when one of them is being mined, and optimize the engineering design plans of “key strata - yield pillar” system safe failure. The main innovative points are listed as follows 1 This dissertation estabilishes the compound foundations beam model with consideration of coal rib yield zone to analyze the relationship between yield zone width and the first cracking, periodic cracking of key strata, and the cracking position, energy distribution and deation distribution. The criterion and calculation s for voussoir beam under the action of original horizontal stress, and the cracking process, deation, stress distribution and caving mechanism of key strata and other roofs above it have been systematically researched. 2 According to the characteristics of panel layouts of short-wall continuous mining, this dissertation studies the influence of adjacent panel mining to key strata stabilization above them. The relavent results show that the the recovery of the mining panel can increae the deation of key strata above the adjacent mined out panel seriously, especially when the mined out panel’s size is large, and meanwhile the key strata stabilization above the mined out pan can determine the deation, maximum span and caving mode of key strata above adjacent mining panel, those influence can be explained through the two compression arches interaction above two panels. 3 This dissertation proposes a theory of “key strata-yield pillar” safe failure based on the yield pillar theory and the local masses stiffness theory after improving its calculating s, and simplifies the yield pillar design plans into six foundamental stiffness nuits under systematically research on the effects of branch 万方数据 III entry width, branch entry mining sequence, the position of last mined branch entry in panel, the position and number of yield pillar between two branch entries to local masses stiffnes, and determine the rational yield pillar width corresponding to each local stiffness unit, and optimize the yield pillar design plans through comprehensive considerations of the safe mining of the last branch entry in the panel, key strata safe failure, increasing recovery area and recovery ratio in one panel, and further give the flowchart of engineering plan optimization design for “key strata-yield pillar” system safe failure. There are 145 figures, 9 tables and 229 references in this paper. Keywords shallow seam; short-wall mining; dynamic disater; key strata; yield pillar 万方数据 IV Extended Abstract This thesis mainly focus on the stable failure of “key strata – yield pillar” system. Based on the elastic foundation beam model and the abutment distribution characteristics when the advance distance access to the key strata maximum span, the dissertation analyses the deation, moment, energy distribution and energy storage of key strata under different yield zone width. Based on the deeply study on the relationship between original horizontal stress and compression arch balance, we establish the voussoir beam stable calculation flowchart that includes the consideration of original horizontal stress effects through language programming, and further improve the voussoir beam theory, and conduct the parameters analysis based on the characteristics of overlying strata in Shendong shallow seam. We utilize the numerical model software to study the cracking process, stress distribution and caving mechanisms of key strata. According to the size and panel layout of short-wall continual mining in Shendong, this dissertation analyze the influence of branch entry recovery in mining panel to key strata stabilization in adjacent mined out panel, and study the effects of key strata state stable or caved above mined out panel to roof stabilization in adjacent mining panel, and realize the “key strata – yield pillar” system stable failure based on local stiffness theory and yield pillar theory. The main conclusions are listed as follows 1 Based on the deation and loading state of key strata before first and periodic weighting, we can know that, as the yield zone width increase, the front abutment peak value moving further, the distance between the peak value position and rib is equal to the yield zone width, which is coincident to the characteristics of front abutment distribution, meanwhile the peak value also increase, and the front abutment vanished when the distance to face is more than 45m. The peak value of key strata moment increase with the yield zone width increase, at the same time its peak value position move further away from face, and the deflection of key strata at face and midspan also increase. When the yield zone width is zero, the whole coal foundation can be considered as elastic foundation, and the front abutment peak value position will occur at face. 2 The peak bending strain energy density increases with increase in yield zone width, and its peak point move far away from the faceline, and the distance between them is equal to the distance between peak bending moment and faceline for a given 万方数据 V yield zone width. before first cracking and periodic cracking of key strata. Its distribution scope is less than that of the front abutment pressure. As the yield zone width increase continuously, the core of the accumulated elastic energy moves away from the face, and the accumulated elastic energy increases rapidly, resulting in more elastic energy being released during first caving. 3 Based on the deeply study on the relationship between original horizontal stress and compression arch balance, we establish the voussoir beam stable calculation flowchart that includes the consideration of original horizontal stress effects through language programming, and further improve the voussoir beam theory, and conduct the parameters analysis based on the characteristics of overlying strata in Shendong shallow seam. The theoretical research shows that the key strata with relative large thickness will failure in the crushing mode, while the overlay roof above it may be failure in buckling mode. The ratio of deflection in key strata midspan to its thickness ranges from 10 to 35 when the key strata deation accesses to the critical failure state. As the original horizontal stress increase, the voussoir beam midspan deflection decrease at the critical failure state, its maximum span increase, and it is more likely failure in crushing mode. When the mined space is larger than the maximum span of key strata, with the increase of mined out span, the key strata bearing capacity decrease, the time between its cracking and failure decrease, and the key strata caving will produce more dynamic disaster. 4 According to surrounding rock feature in the Shendong shallow seam, the dissertation establish the three dimension numerical model to analyze the cracking and caving mechanism of key strata and other roofs above it. The results of the numerical model shows that when the face advance to 28m, the crack occur in the key strata bottom at midspan under tension stress; when the span reaches 44m, the key strata will yield at its upper in front the face under tension stress; as the face advance to 52m, the key strata tension yield zone located its bottom at midspan will gradually extend to four corners above the gob and “X” type yield zone, meanwhile the yield zone located at its upper part surrounding rib will extend further along the rib and link each other to “O” type yield zone, and the final failure mode of “O-X” in key strata with the combination of two parts tension yield zone, at the same time, the shear yield zone in overlay strata above it will extend further to surface and other horizontal directions. The final failure mode of key strata is same as that of the elastic plate. When the face advance to 56m, with the deflection of key strata in 万方数据 VI midspan, the yield zone in key strata and roof above it extend to the surface, and the key strata is closed to its critical stable state. As the face further advance, the key strata and overlay rock until to surface above it caved together. 5 According to the tension and shear failure criterion in Mohr-Coulomb constitutive model of FLAC3D and the relationship between micro-seismic events and cracking in hard roof, the cracking zone and its number is recorded and shows in three-dimension by FISH language programme. As shown in modeling results, the failure process of key strata from integrated state to exhaustive caving is divided into three stages stable stage, the face advance length is less than 40 percent of key strata maximum span in this stage, its main characteristics are that the deflection of key strata is relative low and no micro-seismic events occur. The stable cracking stage, the face advance length ranges from 40 percent to 87 percent of key strata maximum span in this stage, as the face continue advance, the micro-seismic events appear and increase with roof cracking, the key strata midspan deflection increase, micro-seismic activities mainly concentrate on key strata bottom at center gob and lower parts of overlay roof above it, however, these changes are under relative stable state. The accelerated failure stage, as the face advance length reaches 87 percent of key strata maximum span, cracks appear in key strata upper part in front rib, and the energy released by micro-seismic actives suddenly increase, as the face advance further, the “O-X” type yield zone s around goaf and the micro-seismic events number and key strata midspan deflection increase substantially, the roof will cave in this stage. 6 We have constructed the corresponding physical model according to the entry layout and engineering geology. The modeling results show that the key strata is critical factor for large area caving of roofs in shallow seam; As the mined out panel have mined out in a certain dimension, the adjacent panel mining activities can influence the deation and stress distribution in key strata above two panel and barrier pillar between them; As the key strata above mined out panel have caved, the key strata above adjacent panel will cave in suddenly after er cave when the span of it is less than its maximum stable span, the later cave in a manner of sliding along rib and have relatively large dynamic load. 7 The numerical modeling for single panel’s continuously branch entry mining shows that as the number of mining entry increase, the deflection of key strata in rib and midspan all increase, the vertical load distribution on key strata transfer from gentle distribution to concentrating in front of rib, and the load on