巴基斯坦N-J水电站引水隧洞地应力估算

Estimation of the In-situ Stress in Rock Mass in the Tunnel of N-J Hydropower Station Excavated with TBM

巴基斯坦N-J水电站TBM隧道所处区域构造复杂,埋深大,隧道开挖过程中岩爆频繁。现场地应力是影响岩爆等级和范围的重要因素。依据钻孔饼化岩芯的断面形态和岩饼厚度,对现场地应力方向和量值进行了估算。结果表明岩芯钻孔轴线方向近似平行于其中一个主应力方位;假设岩体自重应力为其中一个主应力,则TBM隧洞轴线方向为第三个主应力方位。对应于水平侧压力系数0.8-1.5,最大主应力量值在80MPa-110MPa。开挖拱顶和拱底部位有强岩爆倾向,需要做好防护措施。

For The geological condition is very complex for the N-J hydropower station in Pakistan.The maximum overburden depth of the N-J TBM tunnel reaches 1900 m.Rock burst occurs frequently during tunnel excavation.In-situ stress is one of the most important factors that influence the tendency of rock burst.The shape and thickness of the core discing are analyzed to estimate the principal stress direction and magnitude of the in-situ stress of the TBM tunnel.The analyzed results show that the axis of the borehole is almost parallel to one of the principal stress directions.If the gravity stress is one of the principal stress,TBM tunnel axis is the third principal stress direction.The relationship between the two principal stresses in the horizontal plane is obtained.For lateral stress coefficient between 0.8-1.5,the magnitude of the other stress is 80 MPa-110 MPa.During tunnel excavation,strong rock burst is likely to occur in regions around the arch bottom and vault.