高压水射流环切割缝自卸压机制与应用

为解决深部矿井低透气性煤层瓦斯抽采难题，针对穿层钻孔提出了高压水射流环切割缝煤层自卸压增透技术。通过瓦斯流动理论分析普通钻孔及环割钻孔瓦斯流动模式，分别建立了普通钻孔及环割钻孔瓦斯流动微分方程，获得了高压水射流环切割缝自卸压技术改善煤层瓦斯流动机制;采用FLAC3D软件建模分析高压水射流割缝后钻孔周边煤体应力演化规律，基于煤体卸压程度及塑性区分布特征，确定了穿层钻孔合理化割缝参数;通过底板穿层钻孔高压水射流环切割缝技术现场考察，环切割缝后煤层变形量达到0.136%，煤层透气性系数较原始状态提高了42倍，瓦斯抽采纯量相较普通钻孔提高3.44~5.32倍，同等条件下煤层抽采半径提高了1倍以上。理论研究与现场试验均表明，采用高压水射流切割在煤层内部形成环形缝槽，能有效改善钻孔煤体应力状态，增加煤层渗透性，提高瓦斯抽采效率。

Investigationandapplicationofhighpressurewaterjetannularityslottingselfpressurereleasemechanism

In order to overcome the difficulty of gas extraction in low permeability coal seams in deep mines,a technology of high pressure water jet annularity slotting self pressure release is put forward.The gas flow pattern of normal boreholes and slotting boreholes is analyzed based on the gas flow theory.The differential equations of gas flow in the normal boreholes and slotting boreholes are established.The mechanism of improving coal seam gas extraction ability by the high pressure water jet annularity slotting self pressure release technology is obtained.The stress performance of the coal seam surrounding the borehole after the high pressure water jet slotting is modeled and analyzed by the FLAC3D software.The optimum slotting parameters are determined based on the coal seam pressure release and the distribution characteristics of the plastic zone.Through the field test of high pressure water jet annularity slotting selfpressure release technology,the BC 1 deformation inspecting instrument is used to measure the deformation amount of 0.136% of the coal seam in the borehole,and the natural gas emission of the coal seam borehole is tested.The gas permeability coefficient of the coal seam increases 42 times,and the measured gas extraction rate is 3.44-5.32 times higher than that of the ordinary borehole.Both the theoretical and field tests show that the high pressure water jet annularity slotting self pressure technology can effectively improve the stress state of the coal seam,increase the gas permeability of the coal seam and improve the gas extraction efficiency.