【作者】 刘星光；

【导师】 高峰；

【作者基本信息】 中国矿业大学 ， 工程力学， 2013， 博士

【摘要】 瓦斯既是煤与瓦斯突出和瓦斯爆炸等煤矿灾害的主要诱因，同时又是一种不可再生的清洁能源，实现煤与瓦斯共采，不仅能提高煤矿安全生产水平，还将改善我国的能源结构，对保障我国的能源安全有重要意义。而我国煤层普遍具有高瓦斯、低渗透、强吸附的特点，其中煤层渗透率比美国低2～3个数量级，瓦斯抽采难度极大，对煤层进行人工增透成为实现煤与瓦斯共采的有效途径。因此，充分认识含瓦斯煤岩体变形破坏及其渗透性演化规律，定量描述煤层增透效果，对于实现煤与瓦斯共采具有极其重要的意义。本文针对含瓦斯煤变形破坏特征及其渗透行为，开展了实验室试验、理论分析和数值模拟研究。主要研究内容如下：（1）利用MTS815和高压瓦斯渗透试验系统分别对型煤和原煤试样进行了单轴、三轴压缩试验以及瓦斯渗透试验，发现原煤的单轴和三轴抗压强度分别为型煤的10.3倍和3.7倍，单轴和三轴弹性模量分别为型煤的75.1倍和12.7倍，型煤的塑性破坏形式和原煤的脆性破坏形式截然不同。型煤的初始渗透率是原煤的20倍，而破坏后型煤渗透率为原煤的90%。试验研究结果表明目前以型煤试验结果指导煤矿瓦斯抽采设计与施工极易造成重大安全隐患。（2）利用三轴压缩试验研究了不同瓦斯压力下原煤的力学性质，结果表明：随着瓦斯压力的增加，原煤刚度和强度逐渐降低，峰值破坏剧烈程度逐渐减弱，煤样逐渐由脆性劈裂破坏向延性剪切破坏转变。针对不同瓦斯压力下煤岩体损伤破坏特征，定义了煤岩体双标量损伤模型，同时考虑孔隙瓦斯压力和吸附膨胀应力作用，建立了新的含瓦斯煤弹性损伤本构模型。（3）利用三轴瓦斯渗透试验研究了原煤损伤破坏过程中的渗透特征，结果表明：随着瓦斯压力的增加，原煤渗透率逐渐减小；渗透率与体积应变呈良好的线性关系。基于平板裂隙流动方程建立了煤体渗透率与裂隙体积应变的关系，考虑了瓦斯压力和吸附瓦斯对裂隙体积应变的影响，并首次引入了表征裂隙面粗糙度和裂隙迂曲度对渗透率影响的比例系数，建立了新的渗透率演化模型。（4）基于所建立的损伤本构和渗透率演化模型，自行开发了相应的三维弹性损伤和渗透性耦合分析有限元程序，实现了对采动煤岩体的损伤及渗透率演化的定量描述。并以单一煤层开采为例，对不同瓦斯压力下采动煤岩体损伤和渗透率演化特征进行数值模拟。计算结果表明：随工作面从30m推进到150m，工作面前方煤体损伤范围也由5m增加到30m左右，损伤区内渗透率最大可增加2-3个量级，且相对于煤层瓦斯压力1MPa的计算结果，煤层瓦斯压力6MPa情况下工作面前方煤体损伤度最大增加19%，渗透率比率最大可增加85%。计算结果与工程实际基本吻合，可为煤矿瓦斯抽采设计提供科学指导。更多还原

【Abstract】 Methane is not only the major cause of gas disasters, such as coal and gasoutburst, gas explosion, but also a clean, efficient and non-renewable energy. Thesimultaneous extraction of coal and gas can not only heighten the level of safeproduction of coal mine, and also improve the energy structure in China, which has aimportant significance for the energy security. However, the characteristics of coalseams in china generally are high gas content, low permeability and strongadsorptions, in which the permeability of the coal seams is2-3orders of magnitudelower than that in American. So the gas extraction is extremely difficult and themining-enhanced permeability of coal seams is an effective way to realizesimultaneous extraction of coal and gas. Therefore, it is so important for thesimultaneous extraction of coal and gas to fully understand the deformation, failureand permeability evolution law of gas-saturated coal and to describe the effect ofmining-enhanced permeability quantitatively. In order to study characteristics ofdeformation, failure and permeability evolution of gas-saturated coal, the laboratorytest, theoretical analysis and numerical simulation research were conducted. The maincontents are as follows.(1) By using MTS815and high pressure gas permeability test systems, theuniaxial, triaxial compression tests and gas permeability tests for raw coal andbriquette coal were carried out. The tests results show that the uniaxial compressionstrength and triaxial compression strength of the raw coal is respectively10.3timesand3.7times of the briquette. The elastic modulus of raw coal is respectively75.1times and12.7times of briquette coal in uniaxial and triaxial compression. The plasticfailure model of briquette coal is distinct from the brittle failure model of raw coal.The initial permeability of briquette is20times of raw coal, but after failure, thepermeability of briquette is about90%of the raw coal. Experimental research resultsshow that using the test results of briquette coal to guide the design and constructionof coal mine gas drainage is easy to cause significant safety risks.（2）With the use of triaxial compression test, mechanical properties of the rawcoal under different gas pressures were studied. Results show that as the gas pressureincreases, the strength and stiffness of the raw coal decrease gradually and the failureintensity at the peak stress weaken gradually, in addition, the failure modes of thesamples transform from brittle splitting failure into ductile shear failure. So, according to the damage and failure features of the coal and rock under different gas pressures, adouble-scale damage model was presented. Considering the pore gas pressure andadsorption expansion stresss, a new elastic damage constitutive equation forgas-saturated coal was established.（3）The permeation properties of raw coal during damage and failure wereresearched by gas permeability test under triaxial compression. The test results showthat the permeability of raw coal decreases with increasing gas pressure. Thepermeability and volumetric strain present well linear relationship. Based on flatfracture flow equations, relationship between fracture volumetric strain andpermeability was established. Considering the effects of gas pressure and adsorbedgas on fracture volumetric strain, and for the first time, by introducing a ratiocoefficient to characterize the effect of fracture surface roughness and fracturetortuosity on permeability, a new permeability evolution model was established.（4）Based on the established damage constitutive model and permeabilityevolution model, a3D finite element analysis program coupling the elastic damageand permeability was developed. Using this program, the quantitative description ofthe damage and permeability evolution law of the mining coal and rock was achieved.Take a single coal seam mining for example, a numerical simulation was performed,in which the damage characteristics and permeability evolution law of the mining coaland rock were studied under different gas pressures. The results show that as theworking face moves forward from30meters to150meters, the damage regionextends from5meters to30meters accordingly, and the permeability in the damageregion may increase likely by2-3orders of magnitude. Besides, compared with thecase under a1MPa gas pressure, a6MPa gas pressure may lead to a damage increaseby19%and a permeability ratio increase by85%in front of the working face.Calculation results coincide basically with the engineering practice and can be used asa scientific guidance for coal mine gas extraction design.更多还原