深部岩体大变形规律:金川二矿巷道变形与破坏现场综合观测研究

针对深部高应力下硐室和巷道时效大变形问题,重点开展了金川二矿深部巷道大变形破坏调查、多手段原位综合观察、大变形灾害安全管理标准等方面研究工作。首先针对不同围岩支护类型下大变形巷道破坏问题,从破坏表现形式的角度总结提炼了金川二矿巷道10种典型变形破坏模式并阐明其形成机制;进而依托1150m水平大巷的大变形试验研究段,采用巷道表面的三维激光扫描测量、岩体内部开裂的钻孔摄像观测、围岩不同深度变形的位移计自动量测相结合的方式,揭示了深部巷道表面变形的空间非对称性、围岩内部浅层与深层变形的非均匀性、时效变形增长的跳跃递进性等不同于浅部岩体变形特点和破坏方式的新特征,表明了金川二矿碎裂围岩时效大变形本质是高应力下巷道开挖诱发表层围岩开裂,并在重分布应力驱动下围岩开裂深度逐步向深部转移进而导致巷道围岩自身承载性能逐步劣化的机制,从而表现出持续的时效大变形;最后提出基于功能失效和结构失稳原则的深部巷道大变形安全管理标准,并在现场反馈分析与应用实践基础上总结出了控制二矿深部巷道变形灾害的“双层喷锚网+锚注”和“喷锚网注+单筋砼”复合支护技术,充分利用喷网混凝土的表面柔性支撑与围压效应、锚杆对围岩内部的抑制开裂效应、水泥浆的充填并粘合开裂缝效应、钢筋混凝土的强刚性抗压和恢复围压效应等组合功能,从而形成一种“由表及里、表里结合”改善围岩受力状态、重构围岩承载圈的支护理念。

In-situ observation on large deformation and failure of deep tunnel:Case study for the Jinchuan No.2 mine

In view of the large deformation behaviors in the deep tunnel of Jinchuan No.2 mine,this paper focuses on the tunnel failure modes induced by the large deformation,the multi-means on-situ testing and the safety management standard for tunnel’s large deformation.Firstly,ten kinds of typical deformation and failure modes of the tunnel’s large deformation were summarized and the mechanism was clarified considering different support types of tunnels.Secondly,a complicated on-situ test,i.e.3D dimensional laser scanning,borehole imaging observation and automatic multipoint extensometer,had been carried out to investigate the spatial asymmetry of deformation of deep tunnel,the non-uniformity deformation of the shallow and deep surrounding rock,and the jumping progressiveness of the rock’s time-dependent deformation.The observation data indicated that the large deformation mechanism of the fragmented surrounding rock in Jinchuan No.2 mine is that the excavation induces the cracking of the shallow surrounding rock under high stress,and the cracking extension of the surrounding rock gradually develops to the deep,which deteriorates the bearing capacity of the surrounding rock and performances as continuous time-dependent large deformation,which is different from the traditional deformation and failure performance in shallow tunneling engineering.Finally,the safety management standard of large deformation of deep tunnel,which is based on the principle of functional failure and structural instability,was proposed.Based on the feedback analysis of the field application,the support methods of “double-layer spray anchor net+anchor injection” and “spray anchor net+single reinforced concrete” were proposed for controlling the large deformation of deep tunnels in Jinchuan No.2 mine,based on the supporting principal of improving the stress environment and reconstructing the bearing ring for the surrounding,by utilizing composite effect between the flexible and pressure effect of shorcrete,reinforcement function of rock bolt and bonding role of cement paste.