锦屏二级水电站深埋隧洞开挖损伤区特征分析

EXCAVATION DAMAGED ZONE CHARACTERISTICS IN DEEP TUNNEL OF JINPING II HYDROPOWER STATION

在高应力条件下,岩体强度和应力之间的尖锐矛盾将导致围岩出现损伤,损伤是不同应力条件下围岩状态的直接体现。利用声波检测和钻孔电视对锦屏二级深埋引水隧洞的一典型断面进行全断面测试,声波测试结果显示,断面上低波速带断面形态呈不对称状,与断面应力分布也并不完全对应。在每个声波钻孔中补充钻孔电视,对破裂发育深度和围岩内部实际构造特征有了更直观的认识。为对损伤区特性进行更加准确的描述,利用FLAC3D计算在洞周不同位置处关键点的应力路径,对关键点的应力状态进行分析。在UDEC泰森多边形离散的基础上增加对于节理的描述,分析节理对损伤区分布的影响,模拟结果表明,节理的存在改变了隧洞开挖后洞周的应力分布,从而导致围岩破损和破坏区域的差异。最后,借助于颗粒流程序PFC对隧洞开挖后围岩的损伤区进行模拟,所揭示出的损伤局部化特征和损伤区、破裂区分布特征与现场实际具有很好的一致性。

In high stress condition, the sharp conflict between rock mass strength and stress will lead to damage to surrounding rock. Damage is the direct embodiment of the state of surrounding rock. The acoustic detection and borehole television are used to test a whole section in Jinping II deep diversion tunnel. The acoustic test results show that the section shape of low wave velocity zone is not symmetrical; and stress distribution is not completely corresponding. The borehole television was added in each acoustic drilling, a more intuitive understanding on fracture development depth and internal actual structure features of surrounding rock is obtained. In order to describe the damage zone characteristics more accurately, FLAC3D is used to calculate the stress path of the key points in different positions and analyze the stress states of the key points. Based on the discretization by UDEC voronoi polygons, adding the joint description, the influence of joint on excavation damaged zone（EDZ） is analyzed. The simulation results show that the presence of joint changes the stress distribution after excavation and leads to the difference in damage and fracture zones. With the help of particle flow code（PFC） in advantage of describing microscopic fracture characteristics, the damage zone is simulated. It is revealed the damage localization characteristics and damage zone, fracture zone distribution characteristics have the very good consistency with actual ones.