采动影响下煤岩力学特性及瓦斯运移规律研究(1).pdf

采动影响下煤岩力学特性及 瓦斯运移规律研究 重庆大学博士学位论文 学生姓名李文璞 指导教师尹光志 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 一四年十月 国家重点基础研究发展计划（973 计划）项目（2011CB201203） 国家自然科学基金资助项目51374256、51204217、51174241 国家科技重大专项课题2011ZX05034-004 万方数据 万方数据 Research on Mechanical Characteristics and Gas Migration Law of Coal influenced by Mining   A Thesis ted to Chongqing University in Partial Fulfillment of the Requirement for the Doctor’s Degree of Engineering By Li Wenpu Supervised by Prof. Yin Guangzhi SpecialtyMining Engineering College of Resource and Environmental Science of Chongqing University October， 2014 National Basic Research Program of China 973 Program 2011CB201203 National Natural Science Foundation of China 51374256、51204217、51174241 National Science and Technology Major Projects of China 2011ZX05034-004 万方数据 万方数据 中文摘要 I 摘 要 随着煤矿开采深度的增加，地应力、瓦斯压力增大，煤层的渗透性降低，瓦 斯灾害事故频繁发生。由于采动的影响，煤岩应力发生重新分布，经历了加载和 卸载共同作用的复杂应力途径。以往多采用常规的加载方式对煤岩的力学和渗透 特性进行研究，这与实际情况有较大的差异。为此，本文采用试验研究、理论分 析、数值模拟等相结合的方法，利用自行研制的“含瓦斯煤热流固耦合三轴伺服 渗流实验装置” ，对常规加载条件和不同加卸载条件下含瓦斯煤的力学特性和渗透 规律进行试验研究，揭示不同加卸载条件下含瓦斯煤的变形模量、泊松比、强度 以及渗透特性等变化规律； 研制了 “多场多相耦合下多孔介质压裂-渗流实验系统” 并进行了煤岩不同开采条件下力学特性及渗透率变化规律的试验研究；利用“多 场耦合煤矿动力灾害大型模拟试验系统”对真三轴应力状态下大尺度煤岩在常规 加载及不同开采条件下的力学及渗流特性进行研究；建立了常规加载及不同加卸 载条件下含瓦斯煤的有效应力计算公式及渗透率与有效应力关系的公式；采用数 值计算的方法，对煤层瓦斯在采动影响条件下工作面前方和采空区上方采动裂隙 场中瓦斯运移规律进行数值模拟分析。本文主要研究成果如下 ①采动应力影响下煤岩的应力路径表现为轴向应力加载和围压卸载的共同作 用。含瓦斯煤的承载强度与不同的加卸载条件有如下关系加卸载煤样的承载强 度随初始轴力的升高呈指数关系降低，随围压卸载速度的增加呈指数函数关系降 低，随初始围压的升高呈指数关系降低，随瓦斯压力的升高呈线性关系降低。变 形模量随轴向应变的增加均呈先迅速减小然后缓慢减小直至破坏后保持基本稳定 的趋势；不同加卸载条件下含瓦斯煤的泊松比均表现出随着轴向应变的增加先逐 渐减小后迅速增加最后基本保持稳定。 ②常规加载与加卸载条件下煤样渗透率与应变的关系在屈服前规律有所不 同，屈服前常规加载渗透率与应变呈二次曲线关系减小；而加卸载渗透率随应变 首先呈线性关系增加然后呈二次曲线关系减小。煤样屈服后两种条件下渗透率与 应变的关系规律基本相同，即呈指数关系增大，且与轴向应变呈正指数关系增大， 与径向应变和体积应变呈负指数关系增大。 ③三轴加载及加卸载条件下含瓦斯煤变形破坏过程中弹性应变能的变化趋势 与轴向应力的变化趋势相对应。围压卸载过程中，含瓦斯煤单元耗散能随着卸载 位置轴向压力的增加而增加，且其占单元总能量增加量的比例增大。 ④自行研制了“多场多相耦合下多孔介质压裂–渗流实验系统” ，并利用该系 统进行了常规加载及不同开采条件下煤岩的试验研究。常规加载条件含瓦斯煤的 万方数据 重庆大学博士学位论文 II 峰值强度远远大于开采条件下含瓦斯煤的峰值强度，无煤柱开采、放顶煤开采、 保护层开采三种开采条件下含瓦斯煤及不含瓦斯煤的峰值强度依次降低。 ⑤真三轴应力状态下大尺度煤岩渗透率变化曲线与体积应变变化曲线有较好 的对应关系，渗透率均首先随着体积应变的增加而减小，然后随着体积应变的减 小而有不同程度的增加。无煤柱开采、放顶煤开采、保护层开采煤岩渗透率在减 小阶段其减小量依次减小，渗透率在增加阶段其增加量逐渐增加。一定瓦斯压力 范围内，瓦斯压力越大，大尺度煤岩渗透率减小量越小，渗透率增加量增加。 ⑥考虑瓦斯力学作用和瓦斯吸附作用两个方面对有效应力系数的影响，建立 了单调加载及加卸载条件下原煤的有效应力计算公式及渗透率与有效应力关系的 公式。含瓦斯煤的有效应力系数随着围压的增加而线性减小，含瓦斯煤的有效应 力系数随着瓦斯压力的增加而线性增加，加卸载条件下的有效应力系数小于单调 加载条件下的有效应力系数。 ⑦基于采动影响下煤层瓦斯运移的数学模型，利用 UDEC 软件模拟开采过程 中裂隙场的演化形态，随着工作面的不断推进，采空区上方上覆岩层形成采动裂 隙梯形台，并进行了煤层瓦斯在采动裂隙场中瓦斯运移动态演化规律的 COMSOL 数值模拟研究，采动裂隙场中的离层裂隙和竖向破断裂隙具有瓦斯流动导向性。 ⑧利用COMSOL软件模拟分析工作面前方三种开采条件下煤层瓦斯渗透率变 化规律与支承压力分布规律，两者有较好的对应关系。随着工作面推进距离的增 加，三种开采条件下煤层支承压力对应的应力集中系数增加，且增加的趋势逐渐 变缓；当工作面推进距离相同时，无煤柱开采、放顶煤开采、保护层开采三种开 采条件下应力集中系数依次降低。 关键词关键词含瓦斯煤岩，采动，加卸载，有效应力，瓦斯运移 万方数据 英文摘要 III ABSTRACT With the increasing of the mining depth, crustal stress and gas pressure increase and the coal seam permeability decreases, the gas disaster accidents frequently occur. Because of the influence of mining, stress of coal or rock redistributes and goes through the interaction of complex loading and unloading stress paths. erly the conventional loading s were used on the study of mechanics and seepage characteristics of coal or rock，but they are quite different from the actual situation. Therefore, combining the experimental research with theoretical analysis and numerical simulation s, based on “domestic-developed triaxial servo-controlled seepage equipment for thermal-hydrological-mechanical coupling of coal containing methane”, the experimental study on mechanical properties and seepage law of coal containing methane under conventional loading and different loading-unloading conditions are pered. It reveals the change regularity of deation modulus and Poissons ratio and strength and permeability of coal containing methane under different loading-unloading conditions. Then “fracturing and seepage experimental system for multi-physical field and multiphase coupling of porous media” was self-developed, the experimental study of mechanical property and permeability evolution law was pered on coal containing methane under different mining conditions. Based on “multifield coupling test system for dynamic disaster in coal mine”, the experimental study of large size coal sample at the true triaxial stress situation under conventional loading and loading-unloading conditions was carried out. The effective stress calculation and the permeability with effective stress equation under loading-unloading conditions were established. What’s more, gas migration law influenced by mining in the front of working face and at mining fracture field above goaf was analyzed using the of numerical calculation.The main results are as follows ① The interaction of loading and unloading represents stress path of coal or rock under the effect of disturbance stress. There was the relationship between bearing strength of coal containing methane and different loading-unloading conditions. Bearing strength of loading-unloading coal decreased exponentially with the increasing of initial axial force, bearing strength decreased with increasing in confining pressure unloading speed which presented the exponential function relationship, it decreased exponentially with the increasing of initial confining pressure, it decreased with increasing in gas 万方数据 重庆大学博士学位论文 IV pressure which showed the linear relationship. With the increasing of axial strain, deation modulus under different conditions presented the trend which decreased rapidly first then decreases slowly until to remain approximate stable after failure, the Poissons ratio exhibited the tendency that first decreased then increased and maintain stability at last. ② The relationship between permeability and strain of coal containing methane under loading and loading-unloading conditions before yielded was different. There is a quadratic curve relation between permeability and strain under conventional loading. Under loading-unloading conditions permeability increased as linear relation at first, then decreased as quadratic curve relation. After coal yielded the relationship between permeability and strain under two conditions were basically same, permeability both increased as exponential functions relation, permeability increased positive exponentially with the increasing of axial strain, and it increased with radial strain and volumetric strain which presented a negative exponential function relation. ③ The variation trend of elastic strain energy corresponded to the variation trend of axial pressure under two conditions in the process of deation failure. With the increasing of axial pressure of the unloading locations, dissipation energy of coal unit containing methane increased in the process of unloading confining pressure, and the proportion of unit dissipation energy increment of total energy increment increased. ④ Fracturing and seepage experimental system for multi-physical field and multiphase coupling of porous media was self-developed. The experimental study of mechanical property and permeability evolution law was pered on coal containing methane under conventional loading and different mining conditions. The peak strength of coal containing methane under conventional loading conditions was much greater than the peak strength under different mining conditions. The peak strength of coal reduced under three kinds of mining conditions including non-pillar mining and top-coal caving and protective coal seam mining. ⑤ The evolution curve of permeability of large size coal at the true triaxial stress situation had a good corresponding relationship with volumetric strain. Permeability reduced with the increasing of volumetric strain at first, and then permeability increased in different levels with the reduction of volumetric strain. According to the sequence of non-pillar mining and top-coal caving and protective coal seam mining, permeability of coal influenced by mining reduced less and permeability increased more. In the certain gas pressure scope, with the increasing of gas pressure, permeability decreased less and 万方数据 英文摘要 V increased more. ⑥ Combined effects of gas mechanism and gas adsorption on the effective stress coefficient, the effective stress calculation and the permeability with effective stress equation under monotonic loading and loading-unloading conditions were established. The effective stress coefficient of coal containing methane decreased linearly with the increase of confining pressure, and linearly increased with the increasing of gas pressure, and the effective stress coefficient under loading-unloading conditions is less than under monotonic loading condition. ⑦ Based on the mathematical model of gas migration of coal seam influenced by mining, the evolution of the fracture field was simulated using UDEC software in the process of coal seam mining. As the working face advancing, overburden above goaf ed mining fracture field which was the ladder station. Then gas migration dynamic evolution law of coal seam in the mining fracture field was analyzed by COMSOL numerical simulation, it was found that delamination fracture and vertical fracture fissure in the mining fracture field had the guidance of gas flow. ⑧ Using COMSOL numerical simulation , permeability evolution law had a good corresponding relation to abutment pressure distribution law in the front of working face under three kinds of mining conditions. With the increasing of working face, stress concentration coefficient corresponding to abutment pressure increased under three kinds of mining conditions, and the increase trend gradually slowed. As at the same advancing distance, in the turn of non-pillar mining and top-coal caving and protective coal seam mining, the stress concentration coefficient gradually reduced. Keywords coal containing methane, mining, loading-unloading, effective stress, gas migration 万方数据 目 录 VII 目 录 中文摘要中文摘要 .......................................................................................................................................... I 英文摘要英文摘要 ....................................................................................................................................... III 1 绪论绪论 .............................................................................................................................................. 1 1.1 引言引言 ....................................................................................................................................... 1 1.2 国内外研究现状国内外研究现状 .................................................................................................................... 1 1.2.1 不同加卸载应力路径下岩石力学特性的研究现状.................................................. 2 1.2.2 含瓦斯煤的力学特性研究现状 ............................................................................... 10 1.2.3 含瓦斯煤的渗流特性研究现状 ............................................................................... 12 1.3 论文主要研究内容及技术路线论文主要研究内容及技术路线 .......................................................................................... 22 1.3.1 主要研究内容 ........................................................................................................... 22 1.3.2 技术路线 ................................................................................................................... 23 2 含瓦斯煤物理力学性质研究含瓦斯煤物理力学性质研究 ........................................................................................ 25 2.1 矿井背景矿井背景概况概况 ...................................................................................................................... 25 2.2 含瓦斯煤物理力学性质研究含瓦斯煤物理力学性质研究 .............................................................................................. 29 2.2.1 工业分析 ................................................................................................................... 29 2.2.2 比表面积分析 ........................................................................................................... 30 2.2.3 压汞试验 ................................................................................................................... 35 2.2.4 等温吸附瓦斯试验 ................................................................................................... 38 2.2.4 吸附膨胀变形测定试验 ........................................................................................... 39 2.3 本章小结本章小结 ............................................................................................................................. 42 3 地应力场中含瓦斯煤力学及渗流特性试验研究地应力场中含瓦斯煤力学及渗流特性试验研究 ............................................. 45 3.1 含瓦斯煤单轴压缩力学特性试验研究含瓦斯煤单轴压缩力学特性试验研究 .............................................................................. 45 3.1.1 试验煤样 ................................................................................................................... 45 3.1.2 试验装置 ................................................................................................................... 45 3.1.3 单轴压缩应力-应变曲线及裂纹扩展演化分析 ...................................................... 47 3.2 含瓦斯煤常规三轴压缩力学特性及渗流特性试验研究含瓦斯煤常规三轴压缩力学特性及渗流特性试验研究 .................................................. 49 3.2.1 试验装置 ................................................................................................................... 49 3.2.2 试验方案 ................................................................................................................... 51 3.2.3 含瓦斯煤常规三轴压缩力学特性试验研究 ........................................................... 51 3.2.4 含瓦斯煤常规三轴压缩渗流特性试验研究 ........................................................... 56 万方数据 重庆大学博士学位论文 VIII 3.3 本章小结本章小结 .............................................................................................................................. 60 4 采动应力场中含瓦斯煤力学特性及渗流特性试采动应力场中含瓦斯煤力学特性及渗流特性试验研究验研究 ............................. 63 4.1 概述概述 ...................................................................................................................................... 63 4.2 加卸载应力路径的确定加卸载应力路径的确定 ...................................................................................................... 63 4.3 常规加载及加卸载条件下含瓦斯煤力学特性及渗流特性试验结果及分析常规加载及加卸载条件下含瓦斯煤力学特性及渗流特性试验结果及分析 .................. 69 4.3.1 常规加载及加卸载条件下含瓦斯煤力学特性试验研究 ....................................... 69 4.3.2 不同初始围压条件下加卸载煤样力学特性 ........................................................... 72 4.3.3 不同瓦斯压力条件下加卸载煤样力学特性及渗流特性试验研究 ....................... 74 4.3.4 不同初始应力状态条件下加卸载煤样力学特性试验研究 ................................... 84 4.3.5 不同围压卸载速度条件下加卸载煤样力学特性试验研究 ................................... 86 4.3.6 不同瓦斯压力条件下峰前加卸载煤样力学特性及渗流特性试验研究 ............... 88 4.4 常规加载及加卸载条件下含瓦斯煤岩能量变化分析常规加载及加卸载条件下含瓦斯煤岩能量变化分析 ....................