深部围岩遇弱结构瓦斯抽采钻孔失稳分析与成孔方法

Analysis on gas extraction drilling instability and control method of pore-forming in deep surrounding-rock with weak structure

针对煤岩长钻孔过泥岩、构造带和软煤层成孔难的实际问题,根据现场实测煤岩力学参数,采用大变形FLAC3D软件对丁集煤矿-910 m水平11-2回风平巷抽采钻孔进行计算机数值模拟,解算出钻孔的应力场、位移场和塑性破坏区变化规律,得到的钻孔围岩二次应力弹、塑性分布特征与理论计算结果完全一致。当侧压系数不等于1时瓦斯钻孔二次应力分布、塑性区、钻孔径向位移不再呈圆环状分布,钻孔顶、底部孔壁位移量约为两侧孔壁位移量的2倍,随着岩体侧压系数的升高,钻孔围岩应力集中程度升高,钻孔径向位移增大,围岩塑性区半径增大,钻孔稳定性降低。随钻孔围岩强度强化区范围的增加,钻孔二次应力影响范围减小,塑性区半径减小,孔壁径向位移减小,钻孔更容易达到稳定平衡状态。基于注浆固化成孔新理论,对丁集煤矿1412(1)工作面巷道抽采钻孔围岩弱结构破坏失稳进行了有效控制,并用工程实例进行了验证。

According to difficult pore-forming when long drilling through mudstone,structural belt and soft seam,studied return airway 11-2 level-910 m Dingji Coal Mine using FLAC3D computer numerical simulation with fact mechanical parameters of rock mass,calculated drilling stress field,displacement filed and change of plastic failure zone,and concluded that secondary stress elastic-plastic distribution map of drilling was consistent with the theoretical calculation.The distribution of secondary stress elastic-plastic was no longer a ring when side pressure coefficient was not equal 1,the roof and floor radial displacement of drilling was two times of two sides.The stress concentration degree of surrounding rock becomes higher,the displacement of drilling increases,the plastic radius of surrounding rock decreases,and the drilling becomes more instable with the increase of side pressure coefficient.When strengthening area of surrounding rock increases,the secondary stress influence scope of drilling reduces,the radius of plastic area decreases,the radial displacement of drilling decreases,and the drilling is easier to be stable.Based on the theory of drilling creating by solidification technology,the gas extraction drilling instability was controlled effectively in deep surrounding-rock with weak structure crossheading 1421（1） Dingji Coal Mine,and verified with case.