Study On The Stability Reliability Analysis Method Of Three-dimensional Slope Of Concrete Faced Rockfill Dam Based On Copula Function

Concrete faced rockfill dam(CFRD)has become one of the most promising dam types because of its advantages such as high adaptability to natural environment,convenient construction,low cost,good seismic performance and so on.In recent years,in order to solve the high imbalance between economic development and resource distribution,realize economic development and resource sharing in the east and west,China has built a large number of CFRDs in the western region.With the rapid development of economy,science and technology,construction technology and equipment,the CFRDs has gradually realized the leap from 100m to 200m or even 300m.However,the hydropower engineering in the western region are mostly located in the Mediterranean-Himalayan earthquake zone,and the geological conditions are complex,with frequent and strong earthquakes.Once a dam break occurs,it will lead to disastrous consequences.Therefore,to ensure the seismic safety of the dam is the most important thing for the success of the project construction.There are a lot of uncertainties in the construction and operation of the CFRDs,mainly including the uncertainty of dam material parameters and ground motion.With the continuous development of reliability theory,reliability analysis method has become the important methods for analyzing various uncertain factors in the field of geotechnical engineering.Therefore,at present,there are following questions in the study of the stability and reliability of the CFRDs slope:1)Traditional dam slope stability and reliability analysis is mostly carried out based on 2D models.However,the high dam is built between high mountains and canyons,which has obvious 3D valley effect.It is not reasonable to use 2D method to analyze the stability of the dam slope,and it is difficult to determine the effective reinforcement scope.2)The strength of rockfill is a key index that affects the slope stability of of CFRDs.Some studies have pointed out the correlation between the strength parameters,so it is very necessary to establish the joint probability distribution model of rockfill strength.However,the test data of CFRDs project is limited.Based on the limited data,only the correlation coefficient and edge distribution function of the strength parameters of rockfill can be obtained,and the joint probability distribution function of rockfill strength cannot be uniquely determined.3)Dam materials has strong nonlinearity and the traditional probabilistic analysis method is no longer applicable.Therefore,it is of great significance to establish a probabilistic analysis method suitable for uncertain problems in CFRDs project to improve the accuracy and efficiency of static and dynamic reliability analysis of CFRD slopes,and to study the safety of CFRD slopes.In view of the above problems,this paper is based on the 3D static and dynamic stability analysis of slope,combined with Copula theory to reasonably characterize the correlated non-normal characteristics of the strength parameters of rockfill,and adopts the power spectrum and random function method to generate random ground motion,so as to develop the static and dynamic probabilistic analysis method suitable for CFRD projects.Based on random strength parameters of rockfill,coupled random strength parameters and ground motion,the reliability of static and dynamic stability of 3D slope of CFRDs is studied,which provides scientific basis and theoretical guidance for rational evaluation of stability and seismic performance design of dam slope.The main work of this paper is as follows:(1)A reliability analysis method for static and dynamic stability of 3D slope is presented,which takes into account the randomness of parameters and ground motion.Based on RBF neural network,an intelligent response surface method for static reliability analysis of 3D slope systems with random parameters is established.Based on the generalized probability density evolution theory,a 3D slope dynamic stability reliability analysis method with random ground motions is established.The applicability of the two methods in the reliability analysis of geotechnical engineering structures is verified,which lays the foundation for the analysis of the stability of the 3D slope of CFRDs with random parameters and random coupling of parameters and ground motions.(2)Based on Copula theory,the strength joint distribution model of dam materials is proposed.Collected and summarized the strength parameters of 1257 groups of rockfill materials for 124 rockfill dam projects at home and abroad.The data is classified.The strength parameter distribution model and correlation characterization are studied systematically.The influence of edge distribution function and Copula function on the joint distribution model of dam material strength is analyzed.(3)A static stability reliability analysis method for 3D slope of CFRDs based on intelligent response surface is presented.Under the condition of incomplete probability information,a joint probability distribution model conforming to the strength of rockfill materials is established based on Copula theory,and the static stability reliability of dam slope is defined.The calculation formula of slope failure probability based on Monte-Carlo method(MCS)is introduced,and the intelligent response surface method for static stability reliability analysis of 3D dam slope of CFRDs is proposed.Then,the feasibility and effectiveness of the proposed method are verified.Based on the built intelligent response surface,the influence law of Copula function type and sample size on static stability reliability of dam slope is revealed.(4)Dynamic stability reliability analysis method for 3D slope of CFRDs is constructed considering the randomness of the strength parameters of rockfill.Three-dimensional CFRDs as an example verifies the effectiveness of the method.The influence of the joint probability distribution function of different rockfill strength on the dynamic stability reliability of dam slope is revealed.The effect of Copula function type on the dynamic stability reliability of dam slope of CFRDs is analyzed.(5)Dynamic stability reliability analysis method for 3D slope of CFRDs considering the rockfill strength parameters and the coupling randomness of ground motions is developed.The effectiveness of the proposed method is verified by an example of 3D CFRDs.The influence law of the joint probability distribution function of different rockfill strength on the dynamic stability reliability of dam slope stability is revealed.The effects of Copula function types on the dynamic stability reliability of dam slope stability are analyzed.The system compares the randomness of parameters,randomness of ground motions,and the differences in the dynamic stability reliability of dam slope stability with random coupling of parameters and ground motions.