Analysis Model And Impact Study Of Complex Sliding Surface Of Gravity Dam Foundation

Gravity dam is an important part of hydraulic engineering and widely used.From the point of view of material strength and sliding stability,the stability of foundation surface and weak bedrock surface is often referred to as the control factor of the overall safety of gravity dam.Especially since the Wenchuan earthquake in 2008 and the Fukushima nuclear accident in 2011,the attention on the ultimate bearing capacity of hydraulic and nuclear power plants has been raised to a new level,which promotes the in-depth study of the analysis model.Accordingly,the hydraulic and nuclear power codes represented by seismic safety evaluation have been revised,and the models are becoming more and more detailed.For example,the multi-sliding surface stability analysis model of bedrock has been added in the new design code for concrete gravity dams.The detailed analysis model also brought some problems,such as coordination with the conclusion of the traditional model in the specification.Based on the analysis of the anti-sliding stability and the influence of parameters on the complex interface of gravity dams,such as the deep anti-sliding of multi-sliding of bedrock added in the code,stepped foundation and folding slope foundation of the three dimensional slope section the following research work is carried out in this paper:1.The analysis method of multi-sliding surface and double-sliding surface of deep bedrock is put forward in design code for concrete gravity dams(NB/T 35026-2014).The calculation of double-sliding surface continues the old code.In this paper,the stability of double-sliding surface is calculated by the method of multi-sliding surface analysis in the new code,and the control conditions of the two calculation models are compared from the point of view of load calculation.The code for seismic design of hydraulic structures of hydropower project(NB 35407-2015)makes adjustments to the design response spectrum,dynamic modulus and other parameters.In this paper,the deep anti-sliding stability of bedrock in the new and old codes under seismic conditions is compared and analyzed,and the influence of parameter changes on the tail-rock skid angle under the minimum resistance ratio coefficient is discussed.2.The multi-sliding surface stability equation based on rigid-body limit equilibrium method proposed in the newly design code for concrete gravity dams(NB/T35026-2014)is a one-dimensional high-order equation about the ratio of resistance coefficient.In previous literatures,the deep anti-sliding stability equation of bedrock sliding surface was regarded as a global optimization problem and its function function was assumed to change monotonously.Iterative trial method is often used to solve the equation.In this paper,the enumerationmethod is used to analyze the monotonic interval of the function,point out the discontinuity points,discuss the monotonicity of the local interval,and select the optimal solution which is in conformity with the actual project.On this basis,the genetic algorithm GA with high efficiency is applied to find the optimal solution of local interval of multi-sliding surface.Finally,the finite element method is used to validate the two methods in this paper,and the influence of parameters of each slip surface is analyzed.3.The three-dimensional rigid body limit equilibrium method for gravity dam bank slope is developed based on the equilibrium equation of force and moment and the equal resistance ratio coefficient method.First,the three-dimensional external loads of the dam are calculated by the layered interpolation method combined with the dam block model,which realized the full-automatic numerical analysis of three-dimensional external loads of different dam models.Secondly,the original solution method of three dimensional anti-sliding stability of gravity dam bank section is solved by enumeration method.In this paper,an efficient mathematical optimization method genetic algorithm is introduced to solve the problem.Thirdly,on this basis,the influence of the change of parameters of horizontal section and slope section on the analysis of anti-sliding stability of bank slope section is discussed.The research in this paper is realized numerically of GravDamDC gravity dam material mechanics method static and dynamic analysis software compiled by the research group and good results have been achieved in practical engineering applications.