不同开采条件下煤岩损伤演化与煤层瓦斯渗透机理研究

发布时间：2018-07-15 07:27

【摘要】：煤矿开采历程中，长期以来将煤层瓦斯视作煤矿井下安全生产第一灾害，提高煤层渗透率，从而增强煤层瓦斯抽采效果，减少安全生产隐患，并抽采出来作为清洁能源加以利用，因此，，煤岩损伤演化及其渗透机理一直是我国煤矿安全研究领域的重点和难点。为增强对煤岩损伤演化及渗透性的认识，本文以重庆松藻煤电有限责任公司松藻煤矿K1煤层、K2煤层和山西晋城无烟煤业集团有限责任公司赵庄矿3#煤层的煤为研究对象，从煤岩三轴应力状态、周期性采掘扰动及煤层降压瓦斯抽采等条件出发，采用实验室测试和理论研究结合的方法，系统地开展了煤岩孔裂隙特征及其吸附解吸特性、三轴应力状态下煤岩损伤演化与渗透机理、周期性采掘扰动下煤岩损伤演化与渗透机理、煤层降压瓦斯抽采过程中煤岩损伤演化与渗透机理、多场耦合渗透率模型及渗透率敏感性分析等方面的研究，并结合岩石力学、渗流力学及损伤力学从理论层面上进行了一系列有益的探讨。通过本文研究，在以下方面取得了一些进展： 1)分析了煤岩原生孔裂隙结构特征，并利用HCA型高压容量法吸附装置对其吸附瓦斯特性进行了试验研究，得到了不同温度下的等温吸附曲线及吸附常数a、b值随温度的变化规律。 2)开展了三轴应力状态下不同温度、不同粒径、不同瓦斯压力条件下(温度)的力学特性及渗流特性试验研究，并在不同开采方式下的加卸载试验中进行了三种不同卸载速率条件下的试验研究，分别探讨了煤岩的变形特性、渗透特性等损伤演化规律及其煤岩变形与渗透率关系。 3)利用统计损伤的概念和方法，建立了考虑三轴应力状态及温度的煤岩统计损伤本构模型，并通过试验所测得数据对其实用性及合理性进行了验证，结果表明，考虑温度的煤岩统计损伤本构模型的理论曲线能够较好地反映实测煤岩损伤演化趋势，其统计损伤本构模型理论计算数据能够较好与实验测定曲线吻合。 4)通过不同温度、不同粒径和不同稳定时间条件下的煤岩周期性荷载试验研究了周期性采掘扰动下煤岩损伤演化与渗透机理，系统地探讨了煤岩加、卸载阶段的主应力差、渗透率与轴向应变关系，并分析了3种条件下的单次循环变形及渗透特性，变形、渗透率随时间和循环次数关系等变化规律；探讨了不同稳定时间条件下煤岩渗透率变化滞后于体积应变。 5)通过不同温度条件下周期性荷载试验，探讨了煤变形的能量演化机制，从能量角度出发，突出了煤在不同温度条件下循环荷载作用过程中的能量转化关系及应变能转化速率的研究，分析了吸收能、弹性应变能、耗散能随循环次数及温度的变化规律；基于能量耗散分析建立的煤岩损伤演化方程进行了验证，测定了相关参数指标，较好地描述煤岩在压缩时的损伤演化过程，探讨了能量耗散与损伤的关系。 6)通过不同应力、不同温度条件下(CH4、He)的气体压力降低渗流试验，分析了煤层降压瓦斯抽采过程中煤岩变形特性和渗透特性，并探讨了不同应力条件下煤岩的吸附膨胀、解吸基质收缩变形和有效应力对渗透率影响、不同温度下煤岩应变随气体压力和温度的变化趋势、煤岩渗透率随气体压力下降呈先减小后增大的趋势、煤岩渗透率随温度的升高呈现先减小后增大的趋势以及渗透率和体积应变关系，研究了煤岩割理压缩系数的可变性。 7)基于Jishan Liu模型、Shi-Durucan模型以及煤岩多孔介质均质、各向同性热弹性的有效应力与应变关系，在考虑应力、温度和瓦斯的吸附解吸等因素以及改进其算法和条件的基础上，建立了多场耦合渗透率模型，通过试验数据验证和及其与PM模型和SD模型的对比分析，证明所构建的渗透率模型能够较好地反映实测渗透率的变化趋势；通过定义气体压力敏感性系数和温度敏感性系数，推导了基于敏感性系数的煤岩渗透率与气体压力、温度的函数关系式开展了不同气体压力和不同温度条件下煤层渗透性的敏感性分析。
[Abstract]:In the course of coal mining, coal seam gas is considered as the first disaster of safety production in coal mine for a long time, improving the permeability of coal seam, thus enhancing the effect of coal seam gas extraction, reducing the hidden danger of safety production and exploiting it as clean energy. Therefore, the evolution of coal rock damage and its permeation mechanism have always been the research of coal mine safety in China. In order to enhance the understanding of the evolution and permeability of coal and rock damage, this paper takes Chongqing song alga coal and electricity limited liability company, K1 coal seam in pines coal mine, K2 coal seam and Shanxi Jincheng smokeless coal industry Refco Group Ltd Zhao Zhuangkuang 3# coal seam as the research object, from coal rock three axis stress state, periodic mining disturbance and coal seam Based on the conditions of gas extraction and gas extraction, the characteristics and adsorption desorption characteristics of the coal and rock holes, the mechanism of coal rock damage evolution and infiltration under the three axis stress state, the mechanism of coal rock damage evolution and infiltration under the periodic excavation disturbance, the coal seam depressurization in the process of gas extraction in the coal seam are carried out in a combination of laboratory test and theoretical research. The study of rock damage evolution and permeability mechanism, multi field coupling permeability model and permeability sensitivity analysis, and a series of beneficial discussions on the theoretical level of rock mechanics, seepage mechanics and damage mechanics. Some progress has been made in the following aspects:
1) the characteristics of the fracture structure of the primary pore of the coal and rock are analyzed. The adsorption gas characteristics of the adsorption gas are studied by the HCA high pressure capacity adsorption device. The isothermal adsorption curve and the adsorption constant a and the b value with the temperature are obtained at different temperatures.
2) the mechanical properties and percolation characteristics of different temperatures, different particle sizes and different gas pressure conditions (temperature) were carried out under the three axis stress state, and three different unloading rates were carried out in the loading and unloading tests under different mining methods, and the deformation characteristics and permeability characteristics of the coal and rock were discussed respectively. The evolution law of damage and the relationship between coal and rock deformation and permeability.
3) by using the concept and method of statistical damage, a statistical damage constitutive model of coal and rock with three axis stress state and temperature is established and verified by the data measured by the test. The results show that the theoretical curve of the constitutive model of the statistical damage of coal and rock considering the temperature can better reflect the measured coal and rock loss. The theoretical calculation data of the statistical damage constitutive model agree well with the experimental curve.
4) through the cyclic loading test of coal and rock under different temperature, different particle size and different stable time, the damage evolution and permeability mechanism of coal and rock under periodic excavation disturbance are studied. The main stress difference, permeability and axial strain of coal rock adding and unloading stage are systematically discussed, and the single cyclic deformation and seepage under 3 conditions are analyzed. The permeability of coal and rock is lagged behind the volume strain under the conditions of different time and time.
5) through the periodic load test under different temperature conditions, the energy evolution mechanism of coal deformation is discussed. From the point of view of energy, the energy conversion relation and the strain energy conversion rate of coal in the process of cyclic loading under different temperatures are studied. The absorption energy, elastic strain energy and dissipative energy are analyzed with the cycle times and temperature. The evolution equation of coal rock damage based on energy dissipation is verified and the related parameters are measured. The damage evolution process of coal and rock in compression is described well, and the relationship between energy dissipation and damage is discussed.
6) through the seepage test of gas pressure reduction under different stress and different temperature conditions (CH4, He), the deformation characteristics and permeability characteristics of coal and rock in the process of coal seam lowering gas extraction are analyzed, and the adsorption expansion of coal and rock under different stress conditions, the effect of the shrinkage deformation of the desorption matrix and the effective stress on the permeability, and the coal rock under different temperatures are discussed. With the change trend of gas pressure and temperature, the permeability of coal and rock decreases first and then increases with the decrease of gas pressure. The permeability of coal rock decreases first and then increases, and the relationship between permeability and volume strain, and the variability of the compression coefficient of coal and rock cleats is studied.
7) based on the Jishan Liu model, the Shi-Durucan model and the homogeneous porous medium of coal and rock, the relationship between the effective stress and strain of isotropic thermoelastic. On the basis of considering the factors such as stress, temperature and gas adsorption and desorption, and improving the algorithm and conditions, the multi field coupling permeability model is established, which is verified by the test data and with the PM. The contrast analysis of the model and the SD model proves that the permeability model can reflect the change trend of the measured permeability better. By defining the sensitivity coefficient of gas pressure and the temperature sensitivity coefficient, the permeability and gas pressure based on the sensitivity coefficient are derived, and the function of temperature is carried out with different gas pressure. Sensitivity analysis of coal seam permeability under different temperature conditions.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TD712.6

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