二次沿空留巷围岩变形机理及支护技术研究.pdf

二次沿空留巷围岩变形机理及 支护技术研究 重庆大学博士学位论文 学生姓名李国栋 指导教师曹树刚 教 授 专 业矿业工程 学科门类工 学 重庆大学资源及环境科学学院 二 O 一六年四月 万方数据 万方数据 The Deation Mechanics of Surrounding Rock and Supportive Technology of Secondary Gob-Side Entry Retaining A Thesis ted to Chongqing University in Partial Fulfillment of the Requirement for the Doctor’s Degree of Engineering By Guodong Li Supervised by Prof. Cao Shugang Specialty Mining Engineering College of Resources and Environmental Science Chongqing University, Chongqing, China April, 2016 万方数据 万方数据 中文摘要 I 摘 要 本论文针对两层近距离薄煤层开采二次沿空留巷开展研究，对二次留巷全过 程中，采场围岩内应力和裂隙的分布、演化规律进行了分析。根据覆岩的破断规 律和结构特征，揭示了不同开采阶段采场顶板结构的稳定性及巷道围岩的压力显 现规律。分析了顶板内力、应力、块度分布规律和破断特征，建立了二次留巷关 键块稳定性模型，分析了不同支护条件下关键块的稳定性。此外，还对散体矸石 的力学性能进行了测试和研究。通过本论文的研究，主要获得以下成果和进展 （1）对二次留巷全过程中，采场卸压区形态、支承压、巷旁支护阻力以及裂 隙的动态分布和演化规律进行了分析。通过定义颗粒间破断粘结与初始粘结数量 的比值关系，建立了描述覆岩破坏状态的损伤因子，研究了不同开采时期采场围 岩内的损伤演化规律。 （2）基于变形和破断判据，对覆岩关键层位进行了判定。建立了基于能量守 恒定律的裂隙带高度力学模型，根据韦家沟煤矿地质及开采条件，计算了裂隙带 发育高度。根据分形理论，对采动覆岩在二次留巷不同阶段内裂隙的分形盒维数 变化规律进行了分析，获得了二次留巷全过程中顶板破断及结构稳定性的变化规 律。 （3）基于颗粒流理论，选取颗粒和粘结的弹性模量、刚度比以及粒间摩擦系 数为变量，对宏观强度、峰值应变和弹性模量的变化规律开展研究，获得了颗粒 和粘结的细观参数变化时模型的宏观力学响应规律。基于参数敏感性分析及校验 结果，分析了二次留巷裂隙场发育及演化规律。 （4）建立了四边固支顶板模型，通过施加梯度载荷和均布载荷模拟不同煤层 赋存条件。采用加权残数法，获得了基于挠度函数的顶板内力和应力分布函数。 通过数值计算，获得了顶板在均布和梯度载荷作用下的破断规律，进而建立了破 断岩块的铰接面平面桁架结构模型。采用机动法对破断岩块的尺寸特征函数进行 了推导，并求解了各影响因素的敏感性。结果显示，在各因素中，岩层厚度对于 关键块的破断尺度影响最大，其次为覆岩载荷，顶板的抗拉强度在较小的取值区 间内影响较明显，工作面长度的影响最小。 （5）基于二次沿空留巷顶板的变形及破断规律，建立了一次采动滞后段、二 次采动超前段及二次采动滞后段沿空巷道关键块稳定性力学模型，分析了不同留 巷时期， 关键块的受力特征及平衡条件。 建立了表征关键块稳定性的判断函数和 ，对不同开采阶段关键块在支护参数变化下的稳定性进行了分析，并模拟了不 同端部条件下巷旁支护体的承载、变形及破坏规律。 1 K 2 K 万方数据 重庆大学博士学位论文 （6）针对矸石在自由压缩条件下的力学响应规律开展了颗粒流模拟和物理实 验研究。在自由压缩下，小粒径矸石的增阻速率在前期比大粒径矸石小，后期增 阻速率明显提升并大于大粒径矸石。 符合 Talbot级配的矸石前期变形量明显减小， 增阻速率块，且施加锚固后的散体矸石承载性明显提升。矸石的自由压缩从时间 上可分为三个阶段自组织平衡阶段（I 阶段） ，破碎压密阶段（II 阶段）和固结 增阻阶段（III 阶段） 。对处于 II、III 阶段的矸石而言，按受力状态的差异，从空间 上可划分为I 区域，自组织平衡区；II 区域，咬合破碎区；III 区域，固结区。各 区域呈近似同心圆形分布。其中，固结区是主要承载体，其受载变形规律将直接 影响矸石的压缩性能。 （7）根据二次沿空留巷顶板覆岩的运动规律，提出“合理选型支护材料，充 分发挥围岩自承能力，支护系统力学性能耦合，合理设计支护工艺和全过程控制 原则”的留巷支护思路。探索了采用“锚固矸石袋沿空留巷”方案进行二次留巷施工 的可行性。针对矿井生产实际，形成了完整的支护方案。通过工程实践，获得了 较好的巷道支护效果。 关键关键词词二次沿空留巷，应力及裂隙演化，覆岩结构，顶板垮落，围岩控制 万方数据 英文摘要 III ABSTRACT This thesis was done with the aimed of researching the secondary gob-side entry retaining under the mining situation of inclined close range thin coal seams. Based on above conditions, the distribution and evolution of mining induced stress and fracture in surrounding rock during the whole process of mining were analyzed. According to the charactertics of damage and structure of overlying rock stratum, the stability of roof in stope and mechanical behavior of surrounding rock in different mining stages were discussed. The internal force, stress, fragmentation and damage characteristics of roof were analyzed. Furthermore, the stability analysis model for key block in secondary gob-side entry retaining was established. Accordingly, the stability of the key block was calculated under series of supportive situation. In addition, the experiments and research on the mechanical properities of gangue were conducted. Through the above work in this thesis, the main research results and progresses were as follows 1 During the whole process of secondary gob-side entry retaining, the dynamic distribution and evolution of the distressed zone, abutment stress, stress in gob-side support and fracture in stope were measured and studyed. The new defination of damage factor was proposed in this thesis. It was based on the ratio between the numbers of interparticle breaking bond and the initial bond. Then it was used to analyze the damage evolution of surrounding rock in different mining processes. 2 According to the deation and fracture criterions, the key stratum above stope was determind. The mechanical model for calculating the hight of fracture zone was also established. This model was based on energy conservation theory. Based on the mining and geological situation of Weijiagou coal mine, the hight of fracture zone was calculated. Through the use of fractal theory, the varation of fractal box dimention in surrounding rock during different mining strages was analyzed. Such stages included the whole process of secondary gob-side entry retaining. 3 Based on the particle flow theory, the elastic modulus, stiffness ratio of particle and bond and the interparticle friction coefficient were selected as variables. The relationship betwee these paramaters and peak strength, peak strain, elastic modulus was calculated. The macroscopic mechanical response with the changes of microscopic parameters of particle and bond was acquired. According to the results of sensitivity analysis and calibration, the development and evolution of fracture field in stope were 万方数据 重庆大学博士学位论文 IV analyzed. 4 The simplified plate model with the boundary condation of four edges clamped was establish in this thesis. By applying gradient and uni load to simulat the stress boundary condation of inclined and horizontal coal seam. The weighted residual was used to deduce the ular of the deflection function and the distribution function of internal force and stress in roof. According to the result of numerical simulation, the breakage of roof under uni and gradient load were studied. Moreover, the plain truss structure model of rock block result from roof breaking was established. According to the motor , the calculating function of rock block size was deduced. The sensitivity analisis of the influence factors was also conducted. It suggested that the thickness of strata had the greastest impact on the size of key block, load of overburden strata followed, the influence of roof tensile strength was relative distinct in smaller range of value, the length of working face had the least influence amoung all paramaters. 5 Based on the deation and breakage of roof during secondary gob-side entry retaining, the stability mechanical model of key-block was constructed. This model could be used to describe the equilibrium state of key block behind mining face in the first and second mining and in frount of mining face in secondary mining. The stability decision functions and were proposed. The stability of key block was analyzed in different mining stages with the changing of support paramaters. Additionally， the deation, load-bearing capacity and breakage of gob-side support was simulated. 6 In order to test the bearing capacity of gangue under free compaction, the particle flow simulation and physical experiments were carried out. The results indicated that when the particle size of the gangue was small, the load-increasing rate was less than larger particle at first, but it increased faster larger ones. If the gradation of gangue was coned to Talbot’s gradation, the early compressing displacement of gangue was much smaller than single gradation ones and the loading-increasing rate repaidly rised. Moreover, the anchored gangue had better mechanical properity. The compaction of gangue could be divided into three stages in times rearranging stage stage I; breaking stage stage II and consolidating stage stage III. According to the force state in stage II and III, the spoils can be divided into three zones rearranging zone zone I; interlocking zone zone II and consolidating zone zone III from outside 1 K 2 K 万方数据 英文摘要 V to inside. Among them, the consolidating zone was the main part to bear the weight of overlying strata which had greatest impact on the compaction properity. 7 According to the deation of roof during the secondary gob-side entry retaining, supporting polices are proposed as follow adopt mechanical reasonable supportive material; utilize the sef-bearing properity of surround rock sufficently; couple the mechanical behavior of system; design the technology reasonablly; regard the project as an extremely complex system engineering. This thesis also explored adopting the scheme of “anchored gangue bags” to conduct secondary gob-side entry retaining. Accordingly, the complete supportive technology was ed based on the industrial situation. Finially, by using the supportive design in this thesis, a better supporting effect was acquired through industry test. Key words secondary gob entry retaining; stress and fracture evolution; the structure of overlying stratum; roof caving; surrounding rock control 万方数据 重庆大学博士学位论文 VI 万方数据 目 录 VII 目 录 中文中文摘要摘要 .......................................................................................................................................... I 英文摘要英文摘要 ....................................................................................................................................... III 1 绪绪 论论 ......................................................................................................................................... 1 1.1 研究背景及意义研究背景及意义 ....................................................................................................................... 1 1.2 国内外研究现状国内外研究现状 ....................................................................................................................... 3 1.2.1 采动应力演化及覆岩活动规律研究综述 ........................................................................ 3 1.2.2 沿空留巷覆岩活动规律研究综述 .................................................................................... 6 1.2.3 沿空留巷支护工艺及支护材料研究 ................................................................................ 7 1.3 近距离薄煤层二沿空留巷难点与关键近距离薄煤层二沿空留巷难点与关键 ................................................................................... 9 1.4 需进一步研究的内容需进一步研究的内容 ............................................................................................................... 9 1.5 论文主要研究内容论文主要研究内容 ................................................................................................................. 11 1.6 技术路线和研究方法技术路线和研究方法 ............................................................................................................. 12 2 二次沿空留巷采动应力分布及演化规律二次沿空留巷采动应力分布及演化规律 ............................................................ 13 2.1 引言引言 ......................................................................................................................................... 13 2.2 数值模型的建立数值模型的建立 ..................................................................................................................... 13 2.2.1 地质及开采条件 .............................................................................................................. 13 2.2.2 数值模型的建立 .............................................................................................................. 14 2.3 7 号煤层采动应力动态分布及演化规律号煤层采动应力动态分布及演化规律 ............................................................................... 16 2.3.1 开挖空间应力及塑性区演化机理 .................................................................................. 16 2.3.2 超前支承压力分布演化规律 .......................................................................................... 18 2.3.3 采场倾向应力分布及演化规律 ...................................................................................... 20 2.4 8 号煤层开采采场围岩应力分布及演化规律号煤层开采采场围岩应力分布及演化规律 ....................................................................... 22 2.4.1 工作面支承压力分布及演化规律 .................................................................................. 22 2.4.2 沿煤层倾向应力分布及演化规律 .................................................................................. 25 2.5 本章小结本章小结 ................................................................................................................................. 26 3 二次沿空留巷采场裂隙发育规律及覆岩破坏特征二次沿空留巷采场裂隙发育规律及覆岩破坏特征 ....................................... 29 3.1 颗粒流宏颗粒流宏-细观参数校验细观参数校验 ........................................................................................................ 29 3.1.1 细观参数的宏观响应机理 .............................................................................................. 29 3.1.2 采场煤岩力学性能测试 .................................................................................................. 30 3.1.3 细观参数校验模型的建立 .............................................................................................. 31 3.1.4 细观参数对模型宏观力学响应的影响 .......................................................................... 32 万方数据 重庆大学博士学位论文 VIII 3.1.5 细观参数对裂隙发育及宏观破坏规律的影响 .............................................................. 35 3.1.6 采场模型细观参数校验 .................................................................................................. 36 3.2 二次留巷采动覆岩裂隙和损伤演化规律二次留巷采动覆岩裂隙和损伤演化规律 ............................................................................. 37 3.2.1 采场裂隙分析模型的建立 .............................................................................................. 37 3.2.2 7 号煤层开采覆岩裂隙场发育规律 ................................................................................ 38 3.2.3 二次沿空留巷覆岩裂隙发育规律 .................................................................................. 39 3.2.4 基于裂隙发育状态的损伤因子定义 .............................................................................. 40 3.2.5 二次留巷全过程采场覆岩损伤演化特征 ...................................................................... 41 3.3 本章小节本章小节 ................................................................................................................................. 43 4 沿空留巷采场覆岩破断规律及结构特征沿空留巷采场覆岩破断规律及结构特征 ............................................................ 45 4.1 相似材料模型实验建模相似材料模型实验建模 ......................................................................................................... 45 4.2 相似材料配比实验及模型的建立相似材料配比实验及模型的建立 ......................................................................................... 46 4.2.1 配比材料选型及试件制作 .............................................................................................. 46 4.2.2 相似材料配比实验结果分析 .......................................................................................... 47 4.2.3 二次采动相似材料模型实验设计 .................................................................................. 48 4.3 7 号煤层开采覆岩破断规律及结构特征号煤层开采覆岩破断规律及结构特征 ............................................................................... 51 4.3.1 关键层判定 ....................................................................................................................... 51 4.3.2 7 号煤层开采覆岩破断规律 ............................................................................................ 53 4.4 基于能量转移的裂隙带高度力学模型基于能量转移的裂隙带高度力学模型 ................................................................................. 56 4.4.1 采场围岩能量转移模型 .................................................................................................. 57 4.4.2 求解 Um ............................................................................................................................ 58 4.4.3 求解 Ud ............................................