采动裂隙-变形-瓦斯渗流增透耦合机理及逾渗演化研究

Mining-induced mechanical behavior of coal and rock provides theoretical basis of the quantitative calculation and accurate explanation on coupling of cracks and enhanced permeability of coal and rock. Based on percolation theory, the evolution law and nonlinear catastrophe of connectivity between generated and initial cracks can be studied. The coupling mechanism between cracks and enhanced permeability is obtained from the deformation of coal as a key bond. The relationship established between geometric characterization and physical parameter make quantitative evaluation of enhanced permeability coupling with crack growth feasible in the percolation model. To obtain the law of gas flowing, the following tests need to be carried out including reconstruction of crack growth in coal samples and the coupling test of mining-induced stress and gas flowing under various mining layouts. The numerical simulation for coupling mechanism of mining-induced cracks, deformation and gas flowing is further developed considering pressure relief induced by dilatation. The theoretical coupling model is then obtained. The results provide new theory for simultaneous exploitation of coal and gas in deep coal mining, and prevention from disasters induced by gas.

煤岩体采动力学行为、采动裂隙量化表征及增透耦合机理研究对于增透低渗透煤岩层具有重要的科学意义。本项目以采动裂隙作为研究对象，基于逾渗理论研究裂隙联通的非线性突变及演化规律；以变形为桥梁，研究采动裂隙场与瓦斯渗流场耦合机制。开展相似材料模型实验及数值模拟实验，揭示典型开采条件下采场裂隙时-空演化规律，建立裂隙几何表征到物理特性的关联，得到定量评价裂隙场增透效果的逾渗理论模型。开展不同开采条件下煤岩体试样裂隙发育拓展规律实验和含瓦斯煤体渗流耦合实验，揭示煤体瓦斯渗流规律。开展采动裂隙场、变形场及瓦斯渗流场耦合数值实验，获得不同采动条件下三场演化分布特征；进一步建立三场耦合增透理论模型。项目成果将为煤与瓦斯共采及瓦斯灾害防治提供新的增透理论。

深部煤炭开采过程中，采动裂隙的定量表征是研究变形与渗流的基础。项目针对采场裂隙演化过程中的核心科学问题：裂隙几何-变形-渗流相互作用开展研究，取得了积极进展。揭示了采动裂隙场的时-空演化规律，建立几何表征到物理特性的关联，得到定量评价采动裂隙场增透效果的逾渗理论模型。揭示了不同采动卸压条件下变形场瓦斯渗流场耦合规律，获得了含瓦斯煤岩体细观力学结构。建立了采动裂隙场、变形场、瓦斯渗流场三场耦合增透理论模型。解决了两个关键科学问题：裂纹联通突变的逾渗模型及演化定量描述，采动条件下煤岩体增透机理及评价指标。取得了重要结果：1）基于MXFEM开源程序建立了单裂隙扩展演化数值模型；2）建立了三轴条件下基于应变的渗透率演化逾渗模型；3）开展了基于应力降的非连续支承压力强扰动特征研究；4）建立了低渗煤岩气液两相流分形运动方程；5）开展了单轴压缩煤体裂隙结构-力学相互作用研究；6）分析了不同加载速率下煤岩采动力学响应及破坏机制。因此采动裂隙-变形-瓦斯渗流增透耦合机理及逾渗演化研究为煤与瓦斯共采增透理论体系地完善奠定了基础。