受载含瓦斯水合物煤体渗透特性试验研究

基于三轴渗流试验、X-CT扫描等手段，研究瓦斯水合物合成及加卸载应力条件对煤体-瓦斯-水合物体系渗透率影响规律。首先，开展恒有效应力下煤体中不同饱和度瓦斯水合物合成及渗透率测试，识别水合物在煤体中微观分布，确定煤体孔径分布、饱和度和分布模式对渗透率影响；进而，开展不同瓦斯压力下含水合物煤体渗透率试验，基于Klinkenberg方程，计算绝对渗透率和滑脱因子，揭示水合物饱和度-煤样孔径分布-渗透率-滑脱因子相互作用关系；继而，基于加卸载下含瓦斯水合物煤体渗流试验，探讨有效应力对体系渗透率作用规律，引入加载过程渗透率损失率及卸载过程渗透率损伤率，定量评价加卸载对试样渗透率影响；最后，结合水合物微观分布模式、有效应力-水合物饱和度函数等，建立关联有效应力-体积应变-孔隙率-饱和度变化的渗透率计算模型。研究成果对于瓦斯固化防突技术与理论体系构建具有重要科学意义和工程价值。

The effects of gas hydrate formation and loading-unloading condition on permeability are studied for coal-gas-hydrate system, based on triaxial seepage test and X-CT scanning. Firstly, the gas hydrates with different saturations are formed in coal under constant effective stress and the permeability tests of hydrate-bearing coal are carried out by using integrated gas hydration-triaxial seepage test device. Meanwhile, the micro-distribution of hydrate in briquette coal is identified by X-CT scanning. The effects of pore diameter distribution, hydrate saturation and distribution on permeability are determined. Secondly, the permeability tests of hydrate-bearing coal under different gas pressures are conducted, with the absolute permeability, slippage factor calculated based on Klinkenberg Equation. Moreover, the impact of pore size distribution of coal sample and hydrate saturation are evaluated on permeability and slippage effect. Thirdly, the seepage tests of gas hydrate-bearing coal are implemented under loading and unloading conditions to illustrate the variation laws of permeability with effective stress. Additionally, loss rate of loading permeability, as well as damage rate of unloading permeability are introduced to quantitatively evaluate loading and unloading condition on permeability. Finally, the permeability calculation model related to effective stress-volume strain-porosity-hydrate saturation is established through incorporating the micro-distribution of hydrate and effective stress-hydrate saturation relation. Therefore, the research is expected to provide important scientific significance and engineering value for establishing technical and theoretical system aiming at coal and gas outburst prevention based on hydrate method.