孟底沟水电站导流洞堵头全工况稳定性分析及长度优化

Stability Analysis and Length Optimization of Diversion Tunnel Plug in Mengdigou Hydropower Station

孟底沟水电站导流洞堵头段断层、节理裂隙发育,地质条件较差,堵头挡水水头高,边界条件复杂,且封堵工期紧张,急需对导流洞开挖、施工及运行全过程稳定性进行研究。采用三维非线性有限元法,模拟导流洞洞室开挖、衬砌施工、堵头施工以及堵头运行全过程,得出以下结论:①洞室开挖过程中,围岩基本稳定,局部围岩较差的部位存在局部失稳的可能,建议局部采取锚固、灌浆等措施;②运行期围岩、堵头整体稳定,衬砌结构满足抗压强度要求,局部衬砌拉应力超过抗拉强度,需加强配筋;③长度40 m与50 m的堵头上游段推力分担比基本一致,建议堵头长度在40 m以上。研究成果可为孟底沟水电站导流洞堵头的设计施工提供参考。

In Mengdigou Hydropower Station,faults and joint fissures are developed in the plug section of diversion tunnel.The geological conditions are poor,the water head of the plug is high,the boundary conditions are complex,and the plugging period is short.Therefore,it is urgent to study the stability of the whole process of diversion tunnel excavation,construction and operation.Thus,a three-dimensional nonlinear finite element method was used to simulate the whole process of diversion tunnel excavation,lining construction,plug construction and plug operation.The following conclusions are got from the research.During the excavation process of the tunnel,the surrounding rock is basically stable,and local instability may exist in the parts with poor surrounding rock.It is suggested to take measures such as anchoring and grouting locally.During the operation period,the surrounding rock and plug are overall stable,the lining structure meets the requirements of compressive strength,and the tensile stress of partial lining exceeds the tensile strength,so reinforcement should be strengthened.The thrust sharing ratio of upstream section of plug with length of 40 m and 50 m is basically the same,and the length of the plug is recommended to be more than 40 m.The research results can provide reference for the design and construction of diversion tunnel plug of Mengdigou Hydropower Station.