谷幅收缩变形对溪洛渡拱坝的安全影响分析

摘要

溪洛渡拱坝蓄水初期谷幅收缩现象较为明显,截止2017年5月19日,坝顶VDL04测线谷幅变形达到6.245 cm,量值远超同类工程.在对谷幅变形进行函数拟合和收敛预测的基础上,对两岸谷幅应用非线性有限元边界位移超载法,研究拱坝及基础应力 、变形及塑性区变化规律,分析坝体-基础破坏的薄弱部位及破坏方式,进行大坝在谷幅收缩极限状态下的安全评价.结果表明,随着谷幅变形超载倍数的增大,死水位工况下游坝面420 m以下强约束区产生拉剪破坏区,并在下游坝面420 m以上生成左右两个分支,沿左右拱端附近向上部高程发展,并向拱冠梁和坝体内部扩展;同时上游面以拱冠梁550 m高程为中心发展出上游拉剪破坏区,并呈现对称扩展.正常蓄水工况,当谷幅超载倍数达到Kcz=3.0时(VDL04谷幅位移-22.436 cm),谷幅位移导致坝体塑性体积显著增长;而死水位工况,当谷幅超载系数达到Kcz=2.0时(VDL04谷幅位移-14.972 cm),谷幅位移导致坝体塑性体积快速增长.%Xiluodu arch dam valley shrinkage deformation phenomenon is more obvious than other similar arch dams dur-ing initial impoundment.By the end of May 192017,the VDL04 line of Valley width deformation has reached6.245 cm in dam crest,which far exceed similar projects.On the basis of the function fitting and convergence prediction of valley deformation,nonlinear finite element boundary displacement overloading method is applied to simulate developing valley deformation,deformation and plastic zone change of arch dam and foundation and to analyze the weak parts and failure modes of dam and foundation.The safety evaluation of dam under the condition of valley shrinkage deformation limit is carried out.The results show that with the valley width deformation overload factor increases,downstream dam surface under 420 m constraint region produces tensile and shear failure zone under dead water level condition,and generates the left and right two plastic branches in the downstream surface,which expand along the left and right side of the arch abut-ment to the upper elevation.At the same time,the upstream dam surface has developed shear and tensile failure zone at the 550 m elevation arch crown.Research shows that the valley displacement results in a significant increase in the plas-tic volume of the dam body under the normal water condition when the valley width overload factor reaches Kcz = 3.0 (VDL04 Valley width line displacement is - 22.436 cm).When under the dead water condition,Kcz = 2.0 (VDL04 Valley width line displacement is - 14.972 cm) will result in significant increase in the plastic volume of the dam body.