含瓦斯煤渗透特性影响因素与煤层瓦斯抽采模拟研究

发布时间：2018-05-19 18:43

本文选题：含瓦斯煤 + 力学属性　；参考：《重庆大学》2014年博士论文

【摘要】：随着我国煤炭需求量的逐年攀升,煤矿开采不断地向深部延伸,面对“三高一低”(高地应力、高地温、高瓦斯压力和低渗透性)的煤炭资源,瓦斯灾害日益严重,煤与瓦斯共采技术已成为了开采深部煤炭资源的首选和必然。人工采掘活动,改变了煤体的应力场和温度场,进而又引起了煤体中的瓦斯运移,因此研究应力和温度耦合作用下含瓦斯煤的变形特性和渗透特性、含瓦斯煤渗透特性的影响因素及煤层瓦斯抽采过程中的瓦斯渗流规律都是深部煤炭资源开采的重点和难点。本文以贵州矿区玉舍煤矿1#煤层为主,兼有其他6个煤层煤样为研究对象,采用实验室测定、理论研究、数值模拟及工程应用相结合的方法,从含瓦斯煤的变形及渗流特性、渗透特性影响因素、煤层瓦斯抽采的物理模拟等角度出发,系统开展了含瓦斯煤的基本物理力学属性、热流固耦合作用下煤的变形特性和渗透特性、含瓦斯煤渗透特性影响因素及瓦斯抽采条件下的物理模拟等试验研究和理论分析,同时进行了煤层瓦斯抽采数值模拟分析,并结合渗流力学、岩石力学及弹性力学从理论层面上进行了一系列有益的探讨。通过本文的研究,在以下方面取得了一些进展:1)分析了含瓦斯煤的内外部孔隙特征,并开展单轴抗压强度、三轴抗压强度及变形特性试验,得到了煤的变质程度与其内外部孔、裂隙发育程度均呈正相关关系,煤层粒径、坚固性系数和其基本力学参数的关系。对煤的吸附解吸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随温度的变化规律,与煤的内部孔隙特征关系。2)改进了现有伪三轴渗流设备,开展了不同温度和围压条件下含瓦斯煤的三轴压缩试验,分析了温度和围压对含瓦斯煤力学参数的影响。探讨了含瓦斯煤破坏前的围压、温度对渗透率及轴向应变的影响规律,含瓦斯煤在破坏过程中围压和温度与渗透率特征值之间量化关系及随其变化的趋势,全面阐述了渗透率滞后效应的作用机理。3)开展了应力、温度、含水率和粒径条件下的三轴渗流试验,分析了热力多因素耦合作用下含瓦斯煤渗透特性的变化规律,推导了含水率和温度、含水率和有效应力耦合作用下含瓦斯煤渗透率关系式,探讨了渗透率的影响机理。开展了不同变质程度和不同坚固性系数含瓦斯煤的三轴渗流试验,分析了煤的变质程度与其外部孔、裂隙发育程度关系,煤的坚固性系数与瓦斯放散初速度、三轴抗压强度及渗透率关系。4)对三轴渗流设备的出口端增设了正压调节阀,开展了出口正压条件下的孔隙压力试验,得到含瓦斯煤渗透率与孔隙压力关系,分析了孔隙压力与温度耦合作用下对含瓦斯煤渗透率的影响规律。定义了孔隙压力敏感系数,推导了孔隙压力敏感系数与孔隙压力之间关系,探讨孔隙压力对含瓦斯煤渗透率的响应程度。5)改进了现有的三轴渗流设备,开展出口正压、出口大气压和出口负压的三轴渗流试验,分析了不同有效应力、温度条件下含瓦斯煤的渗流规律,探讨了含瓦斯煤瓦斯流速与热应力、外荷载作用、孔隙压力和煤骨架变形及吸附作用之间作用机理。6)开展了出口负压的三轴渗流试验,对比分析了三种出口负压对瓦斯流速的影响,揭示了适当减小出口负压有利于瓦斯流动的机理。在最佳出口负压的基础上,研究了抽采管径和抽采管路长度对含瓦斯煤瓦斯流速影响,含瓦斯煤瓦斯流速随管径的增加而增大,随温度的增加而减小及随管路长度的延长而降低的变化规律。7)建立了含瓦斯煤系统总应变方程,考虑滑脱效应的渗透率变化模型,并结合气体流动的连续性方程、含瓦斯煤变形平衡方程及几何方程,构建了包含应力场和渗流场并考虑气体滑脱效应的含瓦斯煤系统流固耦合方程。通过数值模拟分析和物理模拟试验对比,验证了模型的正确性和适用性,对比分析了煤体内气体压力沿径向分布和煤体内气相渗透率的变化规律。以贵州玉舍煤矿1#煤层穿层钻孔为工程计算实例,分析了计算区域、截面上瓦斯压力随抽采时间的变化规律,对比了计算区域在相同抽采时刻不同位置的瓦斯压力变化趋势,揭示了不同抽采负压条件下计算模型瓦斯流量的演化规律,并就不同阶段最佳抽采负压进行了探讨。
[Abstract]:With the increasing demand of coal in China, coal mining continues to extend to the deep. In the face of the coal resources of "three high and one low" (high ground stress, high ground temperature, high gas pressure and low permeability), the gas disaster is becoming more and more serious. Coal and Gas Co mining technology has become the first choice and necessity of mining deep coal resources. The stress field and temperature field of coal body are changed, and then the gas migration in coal body is caused. Therefore, the research on the deformation characteristics and permeability characteristics of coal containing gas under the coupling of stress and temperature, the influencing factors of the permeability characteristics of gas coal and the law of gas seepage in the process of coal seam gas extraction are the key points in the mining of deep coal resources. In this paper, based on the 1# coal seam in the Guizhou mining area of Yu she coal mine, and with 6 other coal seam samples as the research object, the method of combining the laboratory testing, theoretical research, numerical simulation and engineering application is used, from the angle of the deformation and seepage characteristics of the coal gas, the influence factors of the permeability, the physical simulation of the coal seam gas extraction, etc. The system has carried out the basic physical and mechanical properties of coal bearing coal, the deformation characteristics and permeability characteristics of the coal, the influence factors of the permeability of coal and the physical simulation under the condition of gas extraction, and the numerical simulation analysis of the coal seam gas extraction. A series of beneficial discussions have been carried out on the theoretical level of mechanics and elasticity. Through this study, some progress has been made in the following aspects: 1) the characteristics of the inner and outer pores of the coal containing gas are analyzed, and the uniaxial compression strength, the three axis compressive strength and the deformation characteristics are tested, and the metamorphism of coal and the holes in the inner and outer parts of the coal are obtained. The relationship between the gap development degree is positive correlation, the coal seam particle size, the strength coefficient and its basic mechanical parameters. The adsorption desorption characteristics of coal are studied. The isothermal adsorption curve and the adsorption constant a at different temperatures, the variation of B with the temperature and the internal pore characteristics of coal.2) have been obtained. The existing pseudo three axis seepage is improved. Three axial compression tests of coal containing gas under different temperature and confining pressure were carried out. The influence of temperature and confining pressure on the mechanical parameters of coal bearing coal was analyzed. The influence of confining pressure on coal bearing coal before failure, the influence of temperature on permeability and axial strain, and the characteristic value of peri pressure, temperature and permeability during the failure process were discussed. The quantitative relationship and the trend of its variation, the mechanism.3 of the permeability lag effect is fully expounded. The three axis seepage tests under the conditions of stress, temperature, water content and particle size are carried out. The variation rules of the permeability characteristics of gas coal under the coupling effect of thermal factors are analyzed, and water content and temperature, water content and effect are derived. The influence mechanism of permeability is discussed and the influence mechanism of permeability is discussed. The three axis percolation test of gas coal with different degree of metamorphism and different sturdy coefficient is carried out. The relationship between the degree of metamorphism of coal and its external pore, the degree of fracture development, the solid coefficient of coal and the initial velocity of gas discharge, and the anti pressure of the three axis are analyzed. A positive pressure regulating valve is added to the outlet of the three axis percolation equipment, and the pore pressure test under the positive pressure of the outlet is carried out. The relationship between the permeability of the gas coal and the pore pressure is obtained. The influence of the pore pressure and the temperature on the permeability of the coal bearing coal under the coupling of the pore pressure and the temperature is analyzed. The pore pressure sensitivity system is defined, and the pore pressure sensitivity system is defined. The relationship between pore pressure sensitivity coefficient and pore pressure is deduced, and the response degree of pore pressure to gas bearing coal permeability.5 is discussed. The existing three axis percolation equipment is improved, and the three axis seepage test of positive pressure, outlet pressure and outlet negative pressure is carried out, and the seepage flow of gas coal with different effective stress and temperature is analyzed. Law, the gas flow velocity and thermal stress, external load, pore pressure and coal skeleton deformation and adsorption mechanism.6) are discussed. The three axis seepage test of negative pressure of export is carried out. The effect of three kinds of negative pressure on gas flow velocity is compared and analyzed, and the mechanism to reduce the negative pressure of the outlet to the gas flow is revealed. On the basis of the optimum negative pressure of the outlet, the influence of the extraction pipe diameter and the length of the extraction pipe on the gas flow velocity of the gas coal is studied. The gas flow velocity of the gas coal increases with the increase of the pipe diameter. With the increase of the temperature and the change law.7 decreasing with the length of the pipeline, the total strain equation of the coal bearing coal system is established, and the slippage is considered. The permeability change model of the effect is combined with the continuity equation of gas flow, the equation of the gas coal deformation balance and the geometric equation. The fluid solid coupling equation containing the stress field and the seepage field and the gas slipping effect is constructed. The correctness of the model is verified by the comparison between the numerical simulation analysis and the physical simulation test. The variation law of gas pressure along the radial distribution and gas phase permeability in coal is compared and analyzed. The drilling of 1# coal seam in the 1# coal seam of Yu she coal mine is a practical example. The variation of gas pressure with the extraction time in the calculated area is analyzed, and the different position of the calculation area is different in the same pumping time. The change trend of gas pressure is revealed, and the evolution law of gas flow in the calculated model under different pumping negative pressure is revealed, and the optimum extraction negative pressure in different stages is discussed.
【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

【参考文献】