Study On Three-Dimensional Nonlinear Overall Safety Evaluation Standard Of Super-High Arch Dams

Super-high arch dams that are under constructionand have been built in China have huge amount of work,huge cost,huge water pressure,high ground stress and complex geological conditions,long construction period.Study on stress analysis and safety evaluation of super-high arch dams has been an important problemgradually concerned by people,and becoming a research hot.Although a large number of nonlinear finite element studies on arch dam safety evaluation are carried out at home and abroad,they lack of a system of standardization process and a control index system.In this dissertation,based on analysis and comparasion of results of three super-high arch dams including Xiluodu,Jinping(I),Xiaowan,consideringoutlets detail structure,a super-high arch dam three-dimensional nonlinear finite element method stress analysis and safety evaluation research is conducted in order to thoroughly analyse the main stress control area and the corresponding stress,deformation and overload safety,and establish a reasonable control standards,a super-high arch dam integral safety evaluation index system.The main contents are as follows:(1)The theories and methods of super-high arch dam stress analysis and safety evaluationare summaried and compared.The basic content,the advantages and disadvantages,and research progressof the main research methods are summaried.In the comparison of multiple super-high arch dam safety evaluation theory research,analysis of the meaning of super-high arch dam integral safetyis proposed.(2)By using three-dimensional nonlinear finite element method,theclose size of grid models,the same constitutive relation,the same analysis path,the same evaluationindex are adopted,the calculation results of nonlinear finite element program are comparedsystematically.A set of three dimensional nonlinear finite element standardization process for the super-high arch dam integral stability is put forward,the selection of the boundary conditions,material constitutive modeland yield conditionsaresuggested.(3)The outlets were not taken into consideration in the past methods,but in this paper,by comparing analytical results of threesuper-higharch dams employing FEM includingnormal working condition and overload conditions,the displacement and stress change rules are discussed.The main stress control area and the corresponding stress,deformation of super-high arch dams that consider outletsare proposed.(4)The partial and the overall yield cracking rules of super-high arch damsin different overload ratios are summarized,a set of considerable failure modes are discussed.Three safety factors includingfracturesafety factor,nonlinear deformation safety factor and limiting overload safety factor are reasoningly defined and furtherclarified.The quantitative study on deformation,stress,safetyfactorof super-high arch dams is carried out,the suggested values of three safety factorsaregiven based on three super-high arch dams analysis results.Finally,the considerable values of three safety factors K1,K2 and K3 are proposd as control criteria of the integral security evaluation of super-high arch dams.