水射流切槽诱导高瓦斯煤体失稳喷出机制与应用

针对钻孔内水射流切槽诱发煤体失稳喷出问题，探讨了在水射流破煤与瓦斯压力作用下的煤体切槽诱导失稳喷出机制，并推导了诱导失稳发生的判据公式。基于古汉山矿10631运输巷二1煤层，采用ANSYS软件数值模拟分析了切槽煤体应力分布及演化特征；并基于裂纹扩展试验分析了水射流冲击煤岩断裂特性；最后，进行了现场试验与应用。数值模拟和实验室试验结果表明：围压条件下，切槽煤体周围会形成应力显著变化区，且随切槽深度的增加而扩大和增强；大直径水射流冲击破断煤岩分为初期响应、稳定破坏和断裂突变3个阶段，煤岩破裂具有瞬时性。现场试验应用表明，水射流切槽会诱发煤体失稳移动，失稳喷出现象与理论分析较吻合，切槽诱导失稳钻孔的累计和瞬时瓦斯排放量是常规钻孔的3~4倍，有利于提高钻孔瓦斯抽采能力和防治矿井煤与瓦斯突出。

Mechanism and application of inducing high-gas coal outburst from borehole by waterjet slotting

In terms of the waterjet slotting induced phenomenon of coal and gas outburst from the borehole，the mechanism of coal and gas outburst induced by waterjet slotting was discussed，and the criterion formula of inducing instability was deduced.Based on the 2-1 coal seam in No.10631 transportation roadway at Guhanshan Mine，the ANSYS numerical simulation software was used to analyze the stress distribution and evolution of the slotted coal.In addition，based on the crack extension theory，the waterjet impacted coal and fracture characteristics were analyzed by testing.Also，the field test and application were conducted.Numerical simulation and testing results show that under the condition of confining pressure，a significant stress change area around the slot was formed，which was enhanced with the increase of slot depth.Three phases were divided when a large diameter waterjet impacted coal seam，including early response，stability disruption and abrupt failure.The coal fracture was instantaneous.Field test and application show that the waterjet slotting induced the coal to be instable and moved，which could explain the outburst phenomenon.The accumulated and transient gas emissions in slotting borehole were three to four times higher than that in conventional boreholes，which improved the ability of borehole gas extraction and the prevention of coal and gas outburst.