锦屏高拱坝整体安全度评估

锦屏高拱坝是目前世界上拟建的最高的双曲薄拱坝,水压力巨大,其设计和分析都超出现行规范。锦屏一级拱坝的环境条件存在明显的不对称特点：一是两岸地形不对称;二是两岸地质条件明显不对称;三是坝体的坝面受日照时间不对称。这些不对称性和高水压使锦屏高拱坝的安全性成为锦屏拱坝建设中最重要的关键技术问题之一。运用三维非线性有限元数值分析方法,研究锦屏拱坝在多种工况下的应力场和位移场以及左、右岸不利地质构造对拱坝工作性态的影响。坝体的应力和位移分布存在比较明显的左右不对称,引起不对称的原因除两岸地基刚度不对称外,拱坝坝体的不对称也是重要原因,因此应进一步优化拱坝体型。确定锦屏拱坝地基系统在不同破坏模式下的整体安全度：上游水压力超载引起系统失效的整体安全度约为5.0;坝基岩体抗剪强度降低使系统失效的整体安全度约为3.0;地震灾害引起系统失效的整体安全度约为6.0。根据屈服破坏区的分布,指出坝基加固处理的重点部位为左拱端下游侧1 800 m高程以上和右拱端上游侧1 630～1 800 m高程之间。

EVALUATION OF GLOBAL SAFETY DEGREE OF JINPING HIGH ARCH DAM

Jinping High Arch Dam is the highest double-curvature thin arch dam in the world at present.The water pressure is huge,and the design is beyond the present criterion.The asymmetric characteristics of Jinping High Arch Dam include the landform of two banks,the geological conditions of two banks and the sunlight time of dam surface.For the asymmetries and high water pressure,the safety of Jinping High Arch Dam is one of key issues in the design and construction of Jinping High Arch Dam.With 3D nonlinear finite element method,the stress field and displacement field of Jinping High Arch Dam under some working conditions are studied;and the effects of the geologic formation of two banks on working behavior of arch dam are investigated.The stresses and displacements of dam body are apparently asymmetric for the left and the right banks.The reasons of the asymmetry are not only the asymmetric stiffness of two banks of foundation,but also the asymmetry of dam shape.So the shape of arch dam should be further optimized.The global safety degree(GSD) of Jinping High Arch Dam for natural foundation is studied under different failure modes:GSD that caused by upstream overloading water pressure is about 5.0;GSD that caused by shear strength reduction of rock in dam foundation is about 3.0;GSD that caused by earthquake is about 6.0.According to the distribution of failure zone,the important parts of reinforcing treatment are proposed,i.e.the part above elevation 1 800 m of downstream side of the left arch and that between the elevation 1 630 m and elevation 1 800 m of upstream side of the right arch end.