1. School of Science,Xi’an University of Science and Technology,Xi’an　 710054,China; 2. College of Safety Science and Engineering,Xi’an University of Science and Technology,Xi’an　 710054,China

裂隙产状是影响瓦斯抽采钻孔孔周煤体渗流状态的重要因素之一。为探究裂隙的不同产状对煤体渗流特性的影响，分别制作了含有1，2，3条裂隙共5种产状的煤样;利用自主设计的三轴渗流试验系统，采用稳态渗透法对煤样进行渗流试验研究，得到了三轴应力下裂隙煤体的渗流雷诺数、渗透率和Forchheimer数变化趋势，并分析了裂隙煤体非Darcy渗流的演化规律。结果表明:① 渗流试验过程中，42%的渗流雷诺数分布在10~100，且渗流趋势符合非线性渗流特点;说明随着裂隙面面积的增大，流动过程中黏滞阻力和惯性力对流速的影响越来越大，其发生非Darcy渗流的可能性就越高;② 通过分析裂隙煤体受力状况，得到裂隙煤样渗透率k随着有效应力σ的增加呈下降趋势，且符合k=aσ-b关系;说明随着应力水平的增加，煤样内部部分裂隙发生闭合、渗流通道数目和宽度的减少，最终导致渗透率急剧降低;③ 通过计算各个阶段的Forchheimer数Fo，得到Fo与渗流速度v符合二次曲线规律增长，且随着Fo的增加非Darcy渗流效应也越来越显著，说明裂隙煤样渗透性的增强是导致发生高速非Darcy渗流的根本原因。结合以上结论，可在煤层瓦斯预抽工作中，依据钻孔孔周煤体瓦斯流动规律准确确定抽采钻孔影响范围，从而为钻孔布孔方式的设计提供重要的理论依据。

The fracture occurrence is one of the important factors affecting the seepage state of the coal around the borehole. In order to explore the influence of different occurrences of fissures on the seepage characteristics of coal,five coal samples containing one,two and three fractures were prepared. The self-designed tri-axial seepage test system was used to observe the steady-state infiltration method. The seepage test of the coal sample was carried out,and the regres- sive Reynolds number,permeability and Forchheimer number of the fractured coal under tri-axial stress were obtained, and the evolution of non-Darcy seepage in the fractured coal was analyzed. The results show that ① During the seepage test,42% of the seepage Reynolds number is distributed in the range of 10 ~ 100. The seepage trend accords with the nonlinear seepage characteristics;it shows that the viscous drag and the flow process increase with the increase of the fracture surface area. The influence of inertial force on the flow velocity is getting larger and larger,and the possibility of non-Darcy seepage is higher. ② By analyzing the stress state of the fractured coal,the permeability k of the fractured coal sample decreases with the increase of the effective stress σ. Trend,and in line with the k = aσ-b relationship;indi- cating that as the stress level increases,the internal crack of the coal sample closes,the number and width of the seep- age channel decrease, and finally the permeability decreases sharply. ③ Through the calculation of each stage of Forchheimer the number Fo and the seepage velocity v are in accordance with the regular curve growth,and the non- Darcy seepage effect is more and more obvious with the increase of Fo . It indicates that the increase of the permeability of the fractured coal sample is the root cause of the high-speed non-Darcy seepage. Combined with the above conclu- sions,in the pre-extraction work of coal seam gas,the influence range of the extraction drilling hole can be accurately determined according to the gas flow law of the coal body around the borehole hole,which provides an important theo- retical basis for the design of the borehole pattern.

ZHANG Tianjun,PANG Mingkun,PENG Wenqing,et al. Non-Darcy percolation characteristics of cracked coal samples with different occurrences under three-bearing compression[J]. Journal of China Coal Society,2019,44(1):246-253.