深部瓦斯抽采钻孔稳定性与成孔控制数值分析

Numerical analysis of stability and hole-forming control of gas drainage borehole in deep mine

为了提高瓦斯抽采钻孔成孔率,以丁集煤矿11-2回风巷地质条件为背景,采用FLAC3D数值模拟软件和理论分析,研究了抽采钻孔稳定性影响因素,并对成孔控制技术进行了数值分析。研究结果表明,影响钻孔稳定性的因素有:侧压系数、岩体力学强度、初始应力(埋深)、钻孔围压和围岩力学强度;钻孔稳定性随着侧压系数增大、岩体力学强度降低、采深加大和钻孔围岩力学强度减小而降低;抽采负压对钻孔稳定性的影响很小;随着钻孔围压的增大、围岩强度强化区范围的增加,钻孔的二次应力影响范围反而减小,塑性区半径减小,孔壁径向位移减小,钻孔更容易处于稳定平衡状态。

In order to enhance the hole-forming ratio of gas drainage boreholes,the influencing factors of stability of drainage borehole were investigated by FLAC3Dsoftware on the basis of geological conditions of No.11-2 return airway in Dingji coal mine,besides the numerical analysis on the hole-forming control techniques.The results show that the stability of drainage borehole is related to side pressure coefficient,mechanical strength of rock mass,initial stress（mining depth）,confining pressure of borehole and mechanical strength of surrounding rock.The stability of drainage borehole decreases with increased side pressure coefficient,mining depth,and decreased mechanical strength of rock mass and surrounding rock.The influence of drainage negative pressure is very small.Conversely,with the increase of mechanical strength of surrounding rock and confining pressure of borehole,the drainage borehole is easy in a stable situation due to the decrease of secondary stress distribution zone,plastic area radius and the radial displacement of borehole wall.