倾斜煤层采动卸压瓦斯运移优势通道多尺度演化时效性机理研究

The evolution of mining overburden fractures and the migration of pressure relief gas in inclined seamare of time-dependent effects. Due to the effects of coal seam inclination angle and working face advancing speed, it is difficult to determine the dominant passage of pressure relief gas migration. Therefore, the extraction effects of pressure relief gas will be influenced. Aiming at the key scientific problem about the evolutionary time-effectiveness of mining pressure relief gas migration dominant channel, which will be researched by the theoretical analysis, laboratory experiments,numerical simulation and field industrial test. By the self-developed true triaxial coal-rock damage-seepage test system, the relationship between damage characteristic and seepage characteristic will be analyzed. Then the coupling model between them will be constructed and their interaction characteristics will be identified.Based on the three-dimensional solid-gas coupling physical similarity simulation test,the relationship between fracture characteristic parameters and overburden strata permeability will be studied. The criterion for determining dominant passage of pressure relief gas migration will be put forward, and the evolution laws of pressure relief gas migration caused by overburden fracture were studied under different advancing velocities. Further more, the time-dependent coupling model about dominant passage of pressure relief gas migration will be built. Through numerical simulation and field industrial test, the laws of pressure relief gas migration during the overburden stratum damage-fracture-failure process will be illustrated by combining with the laboratory experiments and physical simulation. Eventually, the multi-scaletime-dependent mechanism of pressure relief gas migration dominant passage will be revealed, which will provide theoretical basis for efficient gas drainage under pressure relief.

倾斜煤层采动覆岩裂隙演化和卸压瓦斯运移具有一定时间效应，受煤层倾角和工作面推进速度影响，确定卸压瓦斯运移优势通道较为困难，影响瓦斯抽采效果。针对采动卸压瓦斯运移优势通道演化时效性的关键科学问题，项目拟采用理论分析、实验室实验、数值模拟及现场工业性试验展开研究。运用自主研发的真三轴煤岩损伤-渗流试验系统，测试分析煤岩体损伤特征参数和渗流特征参数间的关系，构建两者之间耦合模型，明确两者相互作用；应用三维固气耦合物理相似模拟实验，分析采动覆岩裂隙特征参数和渗透率相互关系，提出卸压瓦斯运移优势通道判定准则，研究不同推进速度下覆岩破裂与卸压瓦斯运移演化规律；构建卸压瓦斯及其运移通道的时效演化耦合模型，应用数值模拟及现场工业性试验，分析时间效应下采动覆岩损伤-破裂-破断过程中卸压瓦斯运移规律，揭示倾斜煤层采动卸压瓦斯运移优势通道多尺度演化时效性机理，为卸压瓦斯高效抽采提供一定理论依据。

工作面采动后覆岩采动裂隙网络是卸压瓦斯的运移通道和储集场所，因此，卸压瓦斯抽采的关键是掌握覆岩采动裂隙和卸压瓦斯运移演化规律，但受倾斜煤层角度影响，上述两者时效性演化规律将与水平煤层发生明显不同。针对此，项目采用理论分析、实验室实验、数值模拟及现场工业性试验等相结合研究方法开展研究。运用煤岩损伤-渗流试验系统，分析了在不同加载速率下含裂隙岩石应力应变特征、损伤特征和渗流特性，建立实验过程中应力应变、声发射信号特征参数及渗透特征参数间关系，发现裂隙岩体的压实过程可分为初始压密、弹性压实及塑性压固三个阶段，建立了裂隙岩体侧向约束压缩过程中能量耗散-分形方程，并得到了能量耗散与空隙变化路径。采用数值模拟和理论分析，分析时间效应影响下覆岩采动应力变化、裂隙演化规律、瓦斯运移特征，掌握了不同推进速度下覆岩破裂演化规律，利用裂隙迂曲度对立方定律进行修正，得到了卸压瓦斯在单一裂隙中流动的流量计算方程，并结合分形理论构建了裂隙网络的渗透-分形方程，建立了以裂隙开度计算瓦斯流态的控制方程，提出了卸压瓦斯运储区的量化判别准则，并将裂隙网络划分为破断裂隙瓦斯运移优势区、破断裂隙压实瓦斯微渗区、离层裂隙瓦斯运移优势区、离层裂隙压实瓦斯微渗区及离层裂隙瓦斯富集区，明晰了低位岩层中卸压瓦斯的运移模式以渗流与升浮为主，高位岩层中以扩散为主，进一步揭示卸压瓦斯运储区应力-裂隙-瓦斯运移的联动演化机理，明确了开采速度影响采动覆岩离层与破断裂隙开度，从而减缓卸压瓦斯向上富集速度，依据此确定了卸压瓦斯抽采系统布置原则，指出工作面推进速度的增加，需要适当增设低层位瓦斯抽采钻孔。最后进行了现场工业性试验，取得了良好的工程效果。项目研究深化了倾斜煤层采动卸压瓦斯运移优势通道多尺度演化时效性机理，完善了煤与瓦斯共采理论体系，以及提高瓦斯灾害防治水平等具有一定的科学价值。