欠挖条件下导流隧洞衬砌结构应力应变分析

针对功果桥水电站导流隧洞欠挖情况,根据进口段欠挖典型断面建立了数值仿真分析模型,比较了不同欠挖程度下衬砌结构的受力特征,分析了衬砌和围岩间粘结强度对衬砌结构的影响,并采用内力法对衬砌内的配筋进行了复核。结果表明,随欠挖程度的增加,衬砌实际厚度减小;在外水压力作用下,衬砌变形逐渐增大,应力也随之增加,衬砌安全度逐渐减小;在衬砌与围岩间粘结强度为0.4MPa,且欠挖深度在衬砌厚度的40%(欠挖92cm)及其以上时,衬砌结构的安全将得不到保证;同时衬砌与围岩间粘结强度对边墙和底板的变形和应力影响较大,而对顶拱位置影响较小。

Stress and Strain Analysis of Concrete Lining of Diversion Tunnel under Condition of Underbreak

Combined with the diversion tunnel of Gongguoqiao Hydropower Project, the numerical model of typical section near tunnel intake is built. And the mechanic characteristics of concrete lining structure are compared under different underbreak conditions. Then the sensitivity of cohesive strength between concrete lining and surrounding rock is analyzed and the reinforcement is checked with internal force method. The results show that under action of external water pressure, the deformation and stress of concrete lining increase with the thickness of lining decreasing; the safety of lining structure can not be guaranteed when the thickness of lining is 40% reduced and the cohesive strength between rock and lining is 0.4 MPa. It is also found that the cohesive strength is critical to the deformation and stress distribution of the lining side wall and bottom while it has little impact on the vault.