采动影响下损伤破裂煤岩体渗透性演化规律研究

发布时间：2018-06-30 17:48

本文选题：煤与瓦斯共采 + 损伤　；参考：《中国矿业大学》2017年博士论文

【摘要】：在煤矿地下开采历程中,瓦斯事故始终是煤矿安全生产的最大威胁,对煤层实施人工增透,提高煤层瓦斯抽采效果,实现煤与瓦斯共采,不仅能提高煤矿的安全生产水平,还将改善我国的能源结构,对保障我国的能源安全有着重要意义。因此,采动影响下煤岩体损伤破裂及渗透演化机理一直是我国煤矿安全研究领域的重点和难点。为进一步揭示采动影响下破裂煤岩体渗透性演化规律,本文采用试验研究、理论分析、数值模拟等方法,根据无煤柱、放顶煤与保护层三种开采方式,开展采动煤岩体渗流-应力耦合试验研究;在考虑煤岩损伤对渗透率影响的基础上,建立了采动煤岩体渗流-应力-损伤耦合模型;基于此模型对不同开采条件下煤岩的损伤破裂与渗流演化规律进行了探讨分析。主要研究内容如下:(1)根据不同开采条件下的采动应力演化特征,开展了真实采动应力路径下的煤岩三轴渗流实验,通过声发射、能量演化、分形等手段对煤岩的力学行为及渗流特征进行了分析,研究了不同开采方式对煤岩的强度、体应变、弹性能、耗散能、渗透率、声发射累计能量、分形维数、裂隙网络演化等参数的影响,并综合探讨了不同开采方式对煤层瓦斯突出危险性的影响。(2)考虑损伤对煤岩渗透率的影响,基于平板流体理论建立了考虑损伤的峰后渗透率模型,并通过实验数据对比检验了模型的合理性。在表征单元体的基础上,引入Weibull分布函数来描述煤岩材料力学属性在空间上的非均匀分布;采用最大拉应力准则及摩尔-库伦准则来判断煤岩细观单元的破裂,建立强度退化方程来描述破裂煤岩细观单元的力学行为;基于连续介质有限元的基本原理,在MATLAB和COMSOL软件平台上,开发描述煤岩破裂演化过程的渗流-应力-损伤耦合程序;将建立的模型分别应用于煤岩压缩-渗流耦合和含孔煤岩加载破坏过程等数值试验中,来验证模型对于模拟渗流-应力-损伤耦合环境下煤岩破裂演化过程的有效性。(3)在考虑弹性压密与峰后破坏的基础上,通过弹塑性理论推导了钻孔开挖后围岩的应力应变分布特征,结合损伤煤岩体渗透率演化模型,分析了体积压密系数、初始地应力、损伤影响系数、钻孔尺寸、煤岩强度等多种因素对围岩应力应变分布及瓦斯渗流规律的影响,综合应力应变、渗透率、瓦斯压力等特征的分布差异对钻孔围岩分区进行了讨论。并利用煤岩体渗流-应力-损伤耦合模型对开挖后瓦斯抽采钻孔围岩的损伤破坏及渗流特征进行模拟分析,分析了侧压力系数对钻孔围岩的损伤分布及增透效应的影响。(4)以乌兰矿突出煤层的工程地质条件为背景,建立沿工作面走向的长壁开采三维数值模型,研究分析了工作面支承压力演化、被保护煤层不同位置处的卸压角分布、被保护煤层的应力演化等特征,对保护层开采过程中上覆煤层的卸压效果进行评价。基于考虑损伤影响的煤层渗透率演化模型和被保护煤层的应力演化特征,得到了保护层开采过程中上覆煤层渗透率的分布演化特征,并根据渗透率的分布差异对上覆煤层划分了不同区域,最后通过乌兰矿的现场工程实践对数值计算结果进行验证。(5)基于考虑损伤影响的渗透率模型,对保护层开采、放顶煤开采和无煤柱开采三种不同开采方式下工作面前方煤岩的渗透率分布特征进行了分析,探讨了三种典型开采方式下煤岩渗透率分布的差异,并根据渗透率分布的差异进行了围岩分区。基于损伤煤体增透率模型和渗透率-损伤演化规律,利用损伤有限元计算程序,以单一煤层开采为例对煤岩体渗透率及增透率演化进行定量描述,分析了采动对煤岩体的增透效果。
[Abstract]:In the course of underground mining, gas accidents are always the greatest threat to safety production in coal mines. Artificial penetration of coal seams, improvement of coal seam gas extraction effect, and co mining of coal and gas can not only improve the safety production level of the coal mine, but also improve the energy structure of our country, which is of great significance for the security of energy in China. This is the key and difficult point in the field of coal mine safety research in China. In order to further reveal the law of permeability evolution of fractured coal and rock mass under the influence of mining, this paper uses three methods, such as experimental research, theoretical analysis, numerical simulation and other square methods, according to the non coal pillar, top coal and protective layer. On the basis of the influence of coal rock damage to permeability, the seepage stress damage coupling model of coal rock and rock is established on the basis of the effect of coal rock damage to permeability. Based on this model, the damage fracture and seepage evolution rules of coal and rock under different mining conditions are discussed and analyzed. (1 According to the characteristics of the evolutional stress evolution under different mining conditions, the three axis seepage experiment of coal and rock under the real mining stress path is carried out. The mechanical behavior and seepage characteristics of coal rock are analyzed by means of acoustic emission, energy evolution and fractal, and the strength, body strain, elastic energy, dissipative energy and seepage of different mining formulas are studied. The influence of the permeability, the cumulative energy of acoustic emission, the fractal dimension, the evolution of the fracture network and so on, and the influence of the different mining methods on the coal seam gas outburst risk. (2) considering the effect of damage on the permeability of coal and rock, based on the plate fluid theory, the model of the post peak permeability is established to consider the damage and the experimental data is compared. The rationality of the model is tested. On the basis of the characterization unit, the Weibull distribution function is introduced to describe the nonuniform distribution of the mechanical properties of coal and rock materials in space, and the maximum tensile stress criterion and the Moore Kulun criterion are used to determine the fracture of the meso element of the coal and rock, and the strength degradation equation is established to describe the mechanics of the meso element of the broken coal and rock. Behavior; based on the basic principle of continuous medium finite element, the seepage stress damage coupling program is developed to describe the fracture and evolution process of coal rock on the MATLAB and COMSOL software platform, and the model is applied to the numerical experiments of coal rock compression seepage coupling and pore bearing rock loading failure process to verify the model for simulated seepage. The effectiveness of the fracture and evolution process of coal and rock under stress damage coupling environment. (3) on the basis of elastic compression and post peak failure, the stress and strain distribution characteristics of surrounding rock after borehole excavation are derived by elastoplastic theory, and combined with the permeability evolution model of damaged coal and rock mass, the volume compression coefficient, initial ground stress and damage influence system are analyzed. Number, drilling size, coal rock strength and other factors affect the distribution of stress and strain of surrounding rock and the law of gas seepage, the distribution difference of comprehensive stress, strain, permeability, gas pressure and other characteristics on the partition of borehole surrounding rock, and the damage of surrounding rock after excavation by the seepage stress damage coupling model of coal rock mass The damage and seepage characteristics are simulated and analyzed, and the influence of side pressure coefficient on the damage distribution and penetration effect of borehole surrounding rock is analyzed. (4) a three-dimensional numerical model of long wall mining along the working face is established on the background of the engineering geological conditions of the outburst coal seam in Ulan mine, and the evolution of supporting pressure in the working face and the different coal seam are divided and analyzed. The pressure relief angle distribution at the position and the stress evolution of the protected coal seam are used to evaluate the pressure relief effect of the overlying coal seam during the mining process. Based on the evolution model of coal seam permeability and the characteristics of the stress evolution of the protected coal seam, the distribution and evolution of the overlying coal seam permeability during the mining process are obtained. Characteristics are divided into different regions according to the distribution difference of permeability. Finally, the numerical results are verified through the field engineering practice of Ulan mine. (5) based on the permeability model considering the damage effect, three different mining methods are used for the protection layer mining, the top coal mining and the non pillar mining. The permeability distribution characteristics are analyzed, the difference of permeability distribution in three typical mining methods is discussed, and the surrounding rock partition is carried out according to the difference of permeability distribution. Based on the damage coal body penetration rate model and the permeability damage evolution law, the damage finite element calculation program is used to take the single coal seam mining as an example to the coal rock. The permeability and permeability evolution are quantitatively described, and the effect of mining on coal and rock mass is analyzed.
【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TD712

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