含瓦斯煤体气固耦合渗流机理及应用研究

发布时间：2018-03-07 09:47

本文选题：含瓦斯煤体　切入点：瓦斯渗流理论　出处：《中国矿业大学》2013年博士论文　论文类型：学位论文

【摘要】：含瓦斯煤层的动力灾害主要包括煤与瓦斯突出和冲击地压，动力灾害发生后会摧毁巷道等采掘空间，并伴随着瓦斯涌出异常，严重威胁着煤矿安全高效生产和矿山工作人员的生命安全。含瓦斯煤层动力灾害发生时应力场和瓦斯渗流场是相互影响的，因此研究含瓦斯煤层应力场和瓦斯场的气固耦合效应对进一步揭示动力灾害机理及预防动力灾害发生有着十分重要的作用。本文利用理论建模和数值模拟手段系统研究了煤层应力与瓦斯渗流的耦合规律，，主要得到以下结论：（1）根据煤体结构特点，采用双重孔隙结构模型描述煤体的多孔基质和裂隙结构特征。分析了煤体基质在应力作用下的压缩变形规律，得到了基质系统孔隙率、渗透率与应力的变化关系；分析了裂隙受压缩而闭合和受剪切而张开的规律，并采用分形理论建立了裂隙开度与应力的变化模型，在此基础上建立了三维空间裂隙系统的孔隙率、渗透率与复杂应力场的关系。（2）分析了受裂隙作用形成的煤体部分分割和部分连接的特殊结构，得到了瓦斯吸附膨胀或解吸收缩应变对煤体连接部分的有效应力的影响，并在此基础上建立了在瓦斯吸附膨胀或解吸收缩应力作用下的含瓦斯煤体有效应力方程。采用体积应变量衡量裂隙煤体的损伤程度，建立了煤体的损伤演化方程；采用Mohr-Coulomb屈服准则作为判断破坏的依据，并分别对剪切破坏和拉伸破坏后的应变量进行塑性修正；同时分析了煤体粘聚力随应变增加而降低的特征，采用煤体粘聚力应变软化模型表征煤体的应变软化特征。（3）根据瓦斯气体的渗流规律和状态方程，分别建立了基质系统和裂隙系统内瓦斯气体的质量守恒方程。基于TOUGH2多相流模拟软件开发了TOUGH2(CH4)瓦斯渗流模拟软件，模拟分析了煤样内瓦斯渗流过程，验证了本软件的合理性；采用C++语言编写了煤体损伤本构模型的dll库文件，通过FLAC3D软件对煤体单轴压缩过程进行了模拟，其结果准确的反映了煤体的损伤破坏过程。应力场对渗流参数产生影响，同时瓦斯渗流场对煤体有效应力产生影响，结合渗流参数与应力关系和煤体有效应力方程即构成了气固耦合模型。根据建立的气固耦合模型，开发了TOUGH2(CH4)-FLAC气固耦合数值模拟软件，并模拟分析了有围压加载时煤体内瓦斯渗流规律，模拟结果与理论结果相符。根据模拟结果可以证明本文提出的气固耦合模型和数值计算方法具有一定的可靠性。（4）以鹤岗南山矿为工程背景，将开发的TOUGH2(CH4)-FLAC软件应用于现场，对巷道围岩损伤演化和瓦斯渗流情况进行了模拟研究，得到了围岩受冲击扰动前后的损伤特征和瓦斯渗流规律，揭示了冲击扰动造成瓦斯涌出异常的机理。研究成果对深入认识含瓦斯煤层动力灾害机理、制定预防措施等具有重要的意义，同时煤层气固耦合程序的应用为进行煤层瓦斯渗流规律分析提供了一种研究方法。
[Abstract]:Dynamic disaster of coal seams mainly include coal and gas outburst and rock burst, power after the disaster will destroy the roadway excavation space, and accompanied by abnormal gas emission, a serious threat to the safe and efficient production of coal mine and mine safety of staff. Gas containing coal layer dynamic disaster stress field and seepage field of gas is the mutual influence, so the study of gas bearing coal seam stress field and gas field gas solid coupling effect to further reveal the mechanism of dynamic disaster prevention and disaster power generation plays a very important role. This paper studies the coupling of seepage force should be coal and gas by using simulation model and numerical method to build theoretical system, mainly by the following conclusion:
(1) according to the structural characteristics of coal, porous matrix and fracture structure with dual pore structure model of coal was analyzed. The coal matrix in deformation under the action of stress, the porosity of the matrix system, change the relationship between permeability and stress; analysis of fracture under compression and shear closure open the law, and the open degree of crack model and the change of stress is established based on the fractal theory, the three-dimensional fracture system of porosity, permeability and complex stress field.
(2) analyzed by coal body part segmentation and part fracture formation of special structure connection, the expansion of gas adsorption or absorption solution of shrinkage strain of coal body connecting part of the effective stress effect is established based on the solution absorption expansion or shrinkage stress under the action of coal containing gas effectively stress equation in gas. The adsorption volume should damage variable to measure the fissures of coal, a coal damage evolution equation; Mohr-Coulomb yield criterion is used to estimate the failure as the basis, and the shear failure and tensile failure strain after plastic correction; and analyzes the coal cohesion with strain increase and reduce the strain characteristics, coal cohesion strain softening model characterization of coal softening characteristics.
(3) according to the seepage and gas state equation, mass conservation equation of gas matrix system and fracture system were established respectively. TOUGH2 multiphase flow simulation software is developed based on TOUGH2 (CH4) software to simulate the gas seepage, gas coal samples in the simulation analysis of infiltration process, verify the rationality of the software the use of C++ language; coal damage constitutive model of the DLL library, through the FLAC3D software of coal under uniaxial compression is simulated, the results reflect the failure process of coal damage. The stress field on the seepage parameters influence at the same time, gas flow field on the effective stress of coal production effect of combination of seepage parameters and stress and effective stress of coal gas equation constitutes a solid coupling model. According to the established gas solid coupling model, the development of TOUGH2 (CH4) numerical -FLAC gas solid coupling simulation software and simulation The law of gas seepage in coal is analyzed under the condition of confining pressure. The simulation results are consistent with the theoretical results. According to the simulation results, it is proved that the gas solid coupling model and numerical calculation method proposed in this paper are reliable.
(4) in Hegang Nanshan coal mine as the engineering background, the development of TOUGH2 (CH4) -FLAC software is applied to the scene, on the surrounding rock damage evolution and gas seepage simulation studies have been carried out, obtained by rock impact damage characteristics and gas seepage law before and after the disturbance, reveals the impact of disturbance caused by the abnormal gas emission mechanism. Research on understanding the mechanism of dynamic disaster of coal seams, is of great significance to develop preventive measures at the same time, application of coalbed gas solid coupling procedure for the analysis of seepage law of coal seam gas provides a kind of research method.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TD712

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