【作者】 林海飞；

【导师】 李树刚；

【作者基本信息】 西安科技大学 ， 安全技术及工程， 2009， 博士

【摘要】 我国大部分矿区煤层瓦斯赋存具有“三高三低”特征,使得煤层瓦斯采前预抽效果不甚理想,而利用采动覆岩移动影响及裂隙动态演化特征抽采卸压瓦斯,应是我国煤矿瓦斯治理的重要方向。论文系统评述了采动覆岩移动与结构演化、煤层瓦斯运移及瓦斯抽采方法的诸多成果,认为覆岩裂隙分布形态及其中瓦斯运移规律是实现煤与瓦斯安全共采的理论基础,也是今后研究重点之一。论文选择典型高瓦斯矿井煤样,用扫描电镜观察了煤样的微观结构,分析了其影响因素,基于MTS数控电液伺服渗流试验,分析了全应力应变过程中煤样的渗透特性,得到矿山压力是影响煤层瓦斯渗透性的主导因素。应用弹性薄板理论推导了覆岩破断时的初次及周期来压步距,得到基于薄板理论的关键层判别方法,并编写了相应的计算机自动判别程序。通过物理相似模拟实验及FLAC3D数值模拟,分析了煤层开采后覆岩裂隙产生、发展的时空规律和分布形态以及充分卸压范围与特征。基于前人研究成果,结合岩层控制的关键层理论,提出了采动裂隙带的工程简化模型,即采动覆岩中的穿层破断裂隙和层面离层裂隙贯通后,空间分布形状是一个动态变化的采动裂隙圆矩梯台带,分析了采动裂隙带动态演化特征、力学机理及影响因素,并得到切眼侧带宽大约为初次来压步距,工作面侧带宽在2~3倍周期来压步距间变化,进风巷及回风巷附近带宽约为0.7~0.8倍初次来压步距,内外梯台面的高度受制于关键层层位及所形成砌体梁结构的变形、破断和失稳形态。在分析采动裂隙带中卸压瓦斯来源及流态的基础上,运用多孔介质流体动力学、渗流力学等理论建立了瓦斯运移数学模型,并分析了卸压瓦斯运移与采动裂隙动态演化关系。通过FLUENT软件对U型、U+L型、U型+走向高抽巷及U+L型+走向高抽巷等通风条件下采动裂隙带中的瓦斯运移规律进行了数值模拟,得到联络巷间距约1.35倍工作面侧裂隙带带宽时尾巷排放瓦斯效果最好,高抽巷在回风巷附近与倾向断裂线边界0.46倍回风巷侧裂隙带带宽且与垮落带边界垂高2.8倍采高位置时,瓦斯抽采效果最好。通过现场观测,分析了日推进距、产量、配风量、开采工序、抽采量、矿山压力及覆岩移动等工作面瓦斯涌出的影响因素,得出初次来压时绝对及相对瓦斯涌出量是来压前的1.25倍,周期来压时绝对瓦斯涌出量是来压前的1.22倍,相对瓦斯涌出量是来压前的1.39倍,瓦斯涌出量呈周期性变化,其步距与周期来压步距基本相等,并分析了瓦斯涌出随关键层运动的7个阶段规律。通过山西和顺天池能源有限责任公司103综放面的现场实验,说明所得到的卸压瓦斯抽采布置参数较为合理,保证了工作面的安全生产,为优化卸压瓦斯抽采系统、实现煤与瓦斯安全共采提供了一定的理论依据和技术支持。更多还原

【Abstract】 The pre-degasification effect is less in China, because most of coal-bed methane existing "three high-low" features. It is an important tackling methane direction that using moving influence and mining-induced fracture evolution features of mining overburden rock to degas. The paper systematically summarized and reviewed plenty of achievements of rock strata movement and structure evolution, the migration laws of coal-bed methane and degasification methods, it can get that the mining overburden rock fissure patterns and distribution of methane migration law are the theoretical foundation of safety and simultaneous extracting of coal and gas, which are one of the study key points for the future.The micro-structural characteristics and influencing factors of coal sample is studied with scanning electron microscope, the whole process of stress and strain of the permeability of coal samples is analyzed through the electro-hydraulic servo seepage test. It is got that ground pressure is the main controlling factor. The first weighting step and period weighting step were derived by elastic thin plate theory when overburden rock was broken, the distinguishing method of key strata based on thin plate theory was obtained, and the corresponding distinguishing procedure was compiled.Based on simulation experiment and FLAC3D numerical simulation, the space-time law and distribution pattern of mining overburden rock and scopes and features of relieved pressure are analyzed. On the basis of the predecessors’research achievement, combined the key strata theory, it is proposed a simple engineering model which a dynamic mining-induced fracture round-rectangle trapezoidal zone would be formed if the bed-separated fissure and broken fissure were connected. It is analyzed that the dynamic evolution characteristics, mechanical mechanism and influencing factors of mining-induced fracture zone. It is obtained that the zone width of starting cut is about the first weighting step, the zone width of face is changing between 2~3 times of period weighting step, the zone width near intake entry and return entry is about 0.7~0.8 times of the first weighting step, the height of trapezoidal surface is basically subject to the location of the key strata and the deformation, breaking and instability form of the voussoir beams structure.On the basis of analyzing the relieved methane source and flow pattern in mining-induced fracture zone, the relieved methane delivery mathematical model is established by the theory of porous media fluid dynamics and mechanics of porous flow, and the relationship between relieved methane migration and dynamic evolution of mining-induced fracture is obtained. FLUENT software was applied to stimulate the methane delivery laws in the mining-induced fracture zone, which were in the ventilate condition of U, U+L, U and strike high roadway, and U+L and high roadway pattern. It is obtained that the discharge methane effect of tail roadway is best when the connection roadway interval is 1.35 times zone width of mining-induced fissure zone near face, and the degasification effect of strike high roadway is best where locate near the return entry, which the parallel distance from dip breaking line is 0.46 times zone width of mining-induced fracture zone near return entry, the vertical distance from caving zone boundary is 2.8 times mining height.Based on field observation, the influence factors of methane outflow were analyzed such as daily mining distance, daily coal output, air distribution, mining production processes, degasification quantity, ground pressure and overlying strata moving. It was obtained that the absolute and relative methane outflow of the first weighting are 1.25 times, the absolute methane outflow of the period weighting is 1.22 times, and relative methane outflow of the period weighting is 1.39 times than before weighting. The methane outflow is periodic changing which the step basically equity to period weighting. The seven stage laws of methane outflow with the key strata moving are analyzed. Through the field test in the 103 working face of Shanxi Heshun Tianchi Energy Co.,Ltd., it is showed that the degasification parameter of relieved methane is reasonable. The paper can provide a certain theoretical and technological foundation for optimizing achieving degasification system of relieved methane and safety and simultaneous extracting of coal and methane.更多还原