To enhance gas drainage in the soft and hard interbedded (SHI) coal seam, it’s necessary to unload the in-situ stress and improve its gas migration performance. In this research, a directional hydraulic flushing (DHF) technology was carried out. The stress-unloading and gas migration improvement mechanism was analyzed through numerical simulation, and systematic engineering tests were conducted to verify the gas drainage effect. The results show that the improvement of gas migration performance in the SHI coal seam is caused by a combined effect of seepage-improving and diffusion-improving. After DHF, stress-unloading and plastic failure could be achieved both in the soft coal (SC) sublayer and in the hard coal (HC) sublayer. However, the gas diffusion capacity improves significantly in the SC sublayer, while the gas seepage capacity improves notably in the HC sublayer. Meanwhile, the stress-unloading and gas migration improvement effect improves with the flushing radius and the thickness of the SC sublayer. Besides, after adopting the DHF technology, the gas drainage effect improved markedly. The borehole number dropped by 49%, the gas drainage ratio increased from 26.0% to 48.2%, and the average coal roadway excavation speed increased from 2.4 to 5.6 m/d.

软硬互层煤层瓦斯抽采需要卸载地应力、改善煤层瓦斯运移性能。在这项研究中，开展了定向液压冲洗（DHF）技术。通过数值模拟分析应力卸载和瓦斯运移改善机理，并进行系统工程试验验证瓦斯抽采效果。结果表明，SHI煤层瓦斯运移性能的改善是促渗和促扩散共同作用的结果。DHF 后，烟煤 (SC) 亚层和硬煤 (HC) 亚层均可实现应力卸载和塑性破坏。然而，SC 亚层中的气体扩散能力显着提高，而 HC 亚层中的气体渗流能力显着提高。同时，应力卸载和气体运移改善效果随着冲刷半径和SC亚层厚度的增加而提高。此外，采用DHF技术后，瓦斯抽采效果明显改善。钻孔数下降49%，瓦斯抽放率由26.0%提高到48.2%，煤巷平均掘进速度由2.4m/d提高到5.6m/d。