不同开采方式下煤岩应力场-裂隙场-渗流场行为研究

煤岩的采动力学行为与常规的煤岩材料力学行为有本质不同,传统的岩石力学实验研究没能体现开采方式和工程扰动的真实影响。深部煤与瓦斯共采实践中,不同开采方式扰动下的煤岩应力场、裂隙场和渗流场行为有显著差异,但煤岩采动力学行为特征尚缺乏科学的、定量化的分析和表达。通过开展不同开采方式下煤岩采动力学实验,分析3种典型开采方式下煤岩采动力学行为、采动裂隙展布及增透率演化规律,探索不同开采方式下煤岩真实采动应力场、裂隙场和渗流场的特征差异。研究表明:不同开采方式产生不同的采动应力场,并导致不同的煤岩裂隙场和渗流场行为特征差异;不同开采方式条件下煤岩峰值应力、峰值应力对应轴向应变和环向应变按照无煤柱开采、放顶煤开采和保护层开采的顺序降低,而体积应变绝对值则依次升高;不同开采方式下煤岩采动裂隙尺度分维D及煤层增透率激增点与工作面之间的距离(L_(rise))均按照保护层开采、无煤柱开采、放顶煤开采的顺序依次下降,确定煤层L_(rise)范围和增透率空间分布可为煤瓦斯共采工程提供理论指导。

Stress-fracture-seepage field behavior of coal under different mining layouts

There are essential differences between the mining-induced mechanical behavior and the material behavior of coal，but the significant influences of mining layouts and mining-induced disturbance are not reflected and considered in traditional rock mechanics researches.In deep underground coal and gas simultaneous extraction practices，the stress-fracture-seepage field behavior of coal under different mining layouts are of significant difference，and there is still a lack of scientific and quantitative analysis and expression on the mining-induced mechanical behavior of coal.To investigate the stress-fracture-seepage field behavior of coal under different mining layouts，the mining-induced mechanical behavior，mining-induced fracture distribution and mining-induced coal permeability change ratio(MPCR) evolution process of coal have been quantitatively analyzed by conducting mining-influenced coal mechanical experiments under three typical mining layouts，i.e.，non-pillar mining(NM)，top-coal caving mining(TCM) and protective coal-seam mining(PCM).The testing results have shown that the different mining layouts lead to various mining-induced stress fields，which further induce diverse fracture field and seepage field of coal.The peak stress，axial strain and circumferential stain corresponding to peak stress of coal under different mining layouts decrease in the order of NM，TCM and PCM，while，the absolute value of volumetric strain increase in that order.The diameter scale fractal dimensions，the distance (Lrise) between the inflection point of the MPCR evolution process and the mining face of typical coal specimens decrease in the order of PCM，NM and TCM.The coal and gas simultaneous extraction can be optimized by determining the range and spatial distribution of coal seam MPCR and Lrise.