In soft coal seams with low permeability, when using hydraulic punching to enhance the gas drainage, the phenomena of plugging holes and sticking often occur.To solve this problem, the technology of hydraulic punc-hing by multi-stage coal breaking was proposed.Based on the analysis on the causes of plugging holes, the multi-stage coal breaking system device was developed.The 1st level coal breaking device is to crush the original coal in-itially, the 2nd level coal breaking device is to clear the cinder or slime wrapping the drill and it's surroundings, and the 3rd level coal breaking device is to grind small pieces of coal again.Based on the distribution characteris-tics of submerged jet velocity field, the attenuation laws of axial velocity on the 2nd level coal breaking device were analyzed, and the optimal distance of the 2nd level coal breaking device and the 1st level coal breaking device was determined.The multi-stage hydraulic punching process was developed, and was applied in gas pre-drainage of the-655 horizontal roadway rock cross-cut coal uncovering in the No.8 Hebi Coal Mine.The application result showed that using the multi-stage hydraulic punching can realize the smooth slagging and avoid the holes plugging.The coal output of single hole was 3 tons to 8 tons, the concentration and flow of gas drainage increased 3~15 times after punching, and the pre-drainage time up to the standard was shortened to 3 months, which provides a good basis for uncovering coal safe and quickly.%在松软低透煤层中应用水力冲孔强化瓦斯抽采时，经常出现堵孔、卡钻等现象。针对这一问题，提出多级破煤水力冲孔技术。在分析堵孔发生原因的基础上，研制了多级破煤系统装置：一级破煤装置对原始煤体进行初始破碎；二级破煤装置对包裹在钻头及钻杆周边的煤渣、煤泥进行破碎、清除；三级破煤装置对小块煤体再次研磨。基于淹没射流速度场分布特征，分析了二级破煤装置射流轴向流速衰减规律，确定了二级破煤装置与一级破煤装置的最佳距离。在此基础上研发了多级破煤水力冲孔工艺，并应用于鹤煤八矿－655轨道石门揭煤瓦斯预抽，应用结果表明采用多级破煤水力冲孔工艺能够实现排渣顺畅，避免堵孔等现象的发生，单孔出煤量为3～8吨，冲孔后瓦斯抽采浓度及抽采流量均提高了3～15倍，石门预抽达标时间缩短至三个月以内，为安全快速揭煤提供了良好基础。
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