“三软”单一煤层水力冲孔卸压增透机理及现场试验

The mechanism and field test of permeability improvement by hydraulic flushing in three-soft and single coal seam

水力冲孔是实现"三软"煤层瓦斯高效抽采的有效途径之一。通过应力应变–煤体结构–渗透率的耦合实验,揭示了"三软"煤层渗透率随煤体结构和应力变化的演化规律,发现软煤在卸压后渗透率得到大规模提升。以Hoek-Brown准则为理论依据,通过数值模拟,发现水力冲孔出煤后的卸压增透范围显著增加。采用自主研发的"瓦斯抽采孔水力作业机",在郑煤集团大平煤矿21141底板抽放巷进行了水力冲孔试验,使得水力冲孔更加安全、高效,并使得老孔的修复成为现实。现场试验充分检验了装备的可靠性和理论分析的准确性,显著提高了煤层瓦斯的抽采效率。

Hydraulic flushing is the most effective way for high-efficient extraction in three-soft coal seam. In thispaper, the mechanism was studied by laboratory experiment, theoretical analysis and field test for pressure reliefand permeability improvement in three-soft coal seam after hydraulic flushing. The coupling experiment of stressand strain-coal structure-permeability revealed the evolution of permeability along with the change of the structureand stress, and found that permeability of soft coal was improved on a large scale after pressure relief. Based onHoek-Brown criterion theory, the numerical simulation results show that the relief range increased significantly afterhydraulic flushing in coal. The hydraulic flushing tests using self-developed machine for gas drainage boreholein 21141 floor drainage tunnel of Daping Mine shows, the machine made hydraulic flushing more secure and efficient,and made it possible to repair the old drainage borehole . The field tests fully tested the reliability of theequipment and the accuracy of the above theoretical analysis, and improved the extraction efficiency significantly.