超大型地下洞室拱圈围岩变形、破坏特性研究

Deformation and failure characteristics of top arch surrounding rock of super large underground caverns

白鹤滩左岸地下厂房南端墙至^#3机组洞段受层内错动带发育影响,拱圈围岩破坏现象突出。结合地质、物探、监测、施工资料对拱圈围岩的变形破坏模式、空间分布特征、演化机制进行分析,结果表明：变形＂负增长＂表征了洞周环向剪切变形的破坏模式,围岩＂弯曲折断＂、＂鼓出塌落＂破坏现象主要发生于剪切变形加速阶段;＂台阶状＂锚杆应力变化与相应部位＂应力控制型＂围岩变形步调一致,且沿孔深逐渐衰减。＂一拉一压＂型锚杆应力主要受结构面的局部控制作用,＂荷载陡降＂型锚杆应力变化伴随锚固系统介质界面间的非协调变形出现。研究成果可为工程后续加固设计提供重要支撑。

Due to the effect of the internal staggered zones at the left bank of Baihetan Hydropower Station, the destruction phenomenon of the surrounding rock at the top arch between the southern wall and the units No. 3 is obvious. The deformation evolution mechanisms, spatial distribution patterns and failure modes of the surrounding rock are analyzed based on the geological conditions, geophysical prospecting, monitoring data and constrution documents. The results show that the circumferential shear deformation and failure mode of tunnel is characterized by the ＂negative growth＂ of displacement, and the ＂bending breakage＂ as well as ＂drum collapse＂ failure phenomenon occurs mainly in the acceleration phase of shear deformation. According to the stress-time curves, the variations of ＂step type＂ stress of bolts keep in step with the ＂stress-controling type＂ deformation of the surrounding rock at the corresponding position, and gradually decay with the increase of the depth. The variations of stress of ＂tension-compression＂ type bolts are mainly affected by the local control of structural planes. The variations of stress of ＂stress steep drop＂ type bolts are associated with the incompatible deformation of anchorage system. This study may provide important supports for future reinforcement designs.