高应力区“三软”突出煤层群上保护层开采下伏煤岩瓦斯非线性动力学行为研究

Upper protective layer mining is a preference for regional outburst prevention measures in outburst coal seam group mining. Under the influences of occurrence conditions and exploiting environment of coal-rock seam gas, such as high stress, high gas and soft coal-rock seam, upper protective layer mining is encountering difficulties, e.g. how to improve the outburst prevention effect of the underlying layer and prevent gas abnormal effusing of the protective layer working face as well as many other problems. The project, with the background of the research on the upper protective layer mining of ‘Three Soft’ outburst coal seam group in the high-stress area, and combining the methods of theoretical analysis, numerical simulation, similar simulation test, field test, etc., aims to establish a viscoelastic damage model for the underlying coal-rock seam and a pore-fissure-gas solid-fluid coupling dynamic model, to reveal the evolution laws for the movement of the underlying coal-rock seam, pore-fracture system and its permeability under upper protective layer mining, and the space-time evolution laws for the desorption-diffusion-seepage flow in the underlying coal-rock seam gas under the combined effect of upper protective layer mining and gas extraction, to build a quantitative model of technical parameters and a space-time collaborative design project for outburst prevention of upper protective layer mining and gas extraction during mining upper protective layers of ‘Three Soft’ outburst coal seam group in the high stress area, to optimize technical parameters and to enhance the outburst prevention effect in upper protective layer mining and gas extraction. This research would provide theoretical foundations for improving the regional outburst prevention technology for upper protective layer mining in outburst coal seam group.

开采上保护层是突出煤层群开采优先选择的区域防突措施，受高应力、高瓦斯和煤岩松软等煤岩瓦斯赋存状况和开采环境影响，上保护层开采面临如何提高下伏被保护层防突效果和预防保护层工作面瓦斯异常涌出等诸多难题。本项目以高应力区“三软”突出煤层群上保护层开采为研究背景，采用理论分析、数值模拟、相似试验和现场测试等手段，建立高应力区“三软”突出煤层群上保护层开采下伏煤岩粘弹塑性损伤模型、孔裂隙瓦斯流固耦合动力学模型，揭示上保护层开采下伏煤岩层移动、孔裂隙及透气性时空演化规律，以及上保护层开采和瓦斯抽采共同作用的下伏煤岩瓦斯解吸-扩散-渗流流动时空演化规律；构建高应力区“三软”突出煤层群上保护层开采和瓦斯抽采技术参数量化关系模型及时空协同设计防突方案，优化上保护层开采和瓦斯抽采技术参数，提高上保护层开采和瓦斯抽采防突效果。该研究成果可为完善突出煤层群上保护层开采防突技术提供理论基础。

高应力区“三软”突出煤层群开采时极易发生煤与瓦斯突出灾害事故。在煤与瓦斯突出预防措施中，开采保护层是优先选择的区域防突措施，而开采上保护层又是开采保护层区域防突措施的优先选择；上保护层开采诱导的下伏煤岩层应力场、裂隙场、渗流场演化等非线性动力学是合理确定瓦斯抽采方式和抽采设计的重要依据。本项目以平煤四矿和皖北朱集西矿为研究对象，采用相似模拟试验、理论分析、数值模拟及试验验证等相结合的方法，对高应力区“三软”突出煤层群上保护层开采下伏煤岩变形及瓦斯流动等非线性动力学行为进行了研究。搭建了高应力区“三软”突出煤层群上保护层开采相似模拟试验系统，试验研究了高应力区“三软”突出煤层群上保护层开采下伏煤岩围岩破坏、孔裂隙分布及透气性演化规律；应用FLAC3D软件分析了上保护层不同推进距离、不同保护层厚度、不同煤层间距等条件下，下伏煤岩层垂直位移、塑性区、卸压范围及卸压角的变化规律；基于Poyting-Thomson体蠕变力学模型，建立了“三软”煤层采动煤岩体变形与卸压瓦斯流动气固耦合动力学模型（包括：采动煤岩体变形控制方程、采动煤岩体瓦斯流动控制方程、气固耦合变量和定解条件），并借助COMSOL Multiphysics软件分析了不同层间距上保护层开采卸压防突效果，研究了顺层抽采和穿层抽采两种方式的抽采效果，揭示了高应力区“三软”突出煤层上保护层开采和瓦斯抽采共同作用的下伏煤岩层瓦斯解吸-扩散-渗流时空演化规律；基于不同抽采方式防突效果与煤层开采布置假设条件，优化设计了不同层间距煤层群上保护层开采和被保护层瓦斯抽采防突设计方案，并进行了数值模拟分析和试验验证。研究结果对丰富开采突出煤层群防突技术具有重要的理论指导意义。