Research On System Reliability Of Deep Anti-sliding Stability Of Gravity Dam Bedrock Considering Stochastic Fracture Network

The deep anti-sliding stability of gravity dam has always been a key issue on dam safety assessment.At present,the research on the reliability of deep anti-sliding stability of gravity dam is mostly based on the engineering experience of industry experts to draw up the sliding planes with a certain position.On this basis,calculation and evaluation of the reliability of deep anti-sliding stability of the dam foundation are carried out after considering the statistical characteristics of the physical and mechanical parameters of the sliding planes,loads and other random factors.However,in practical projections,the geological conditions of the bedrock are often extremely complicated.A large number of randomly distributed fractures appear in the bedrock of many major projects.Up to now,traditional gravity dam anti-sliding stability research methods have not focused on the effect of fractures in the bedrock of gravity dams.Full consideration of the influence on the uncertainty of stability has led to a deviation from the actual situation in the reliability analysis of the deep anti-sliding stability of the gravity dam,and the research results have certain limitations.Therefore,a random fracture network model is set up for the fractures in the bedrock,and then the deep slip paths of the dam foundation,based on meso-mechanical analysis,are identified.Finally,within the framework of the reliability analysis of the engineering structure system,a quantitative analysis of the reliability of the deep anti-sliding stability of a gravity dam with random fractures bedrock is performed.The main research contents and conclusions are as follows:First,according to the statistical data of engineering geological fractures,combined with the proved long and large structural planes,study the method of constructing the foundation rock model of the gravity dam based on Monte-Carlo fractures network simulation.Based on the randomly generated fractures network model and the principle of meso-mechanical analysis,genetic algorithms are used to search for dangerous slip paths in the bedrock fractures network,and to identify the deep anti-slip and stable slip channels of the dam foundation.Then to determine the slip mode that meets the calculation requirements of the current norms,and provide a calculation model basis for the next step of the deep anti-sliding stability calculation of the dam foundation.Second,combined with the engineering example of a gravity dam with fractures in the bedrock,the primary reliability algorithm commonly used in engineering structure reliability analysis is used to calculate and analyze the reliability of the deep anti-sliding stability of the gravity dam,and the Monte Carlo reliability algorithm is used as the benchmark algorithm to verify the feasibility of the method.Analyze the statistical characteristics of the shear friction coefficient f’ and the cohesive force c’ that affect the reliability of the dam foundation’s deep anti-sliding stability,the influence of different distribution types and negative correlations of two random variables on the reliability of dam foundation’s deep anti-sliding stability is studied in detail.The calculation results show that when the shear resistance parameters obey the lognormal distribution and the random variables are not correlated,the reliability results obtained are more conservative.Then,based on the system reliability theory,the general correlation coefficient method is used to consider the correlation between different slip channels in bedrock,and analyze the reliability of the multi-slip channel system.At the same time,the influence of the distribution characteristics and correlation of the random variable shear friction coefficient f’ and cohesive force c’ on the reliability calculation results of the gravity dam foundation rock deep system is studied.The calculation results show that the system reliability index value calculated by the limit method is close to the Monte Carlo method,but the calculation efficiency of the limit method is much higher than that of the Monte Carlo method.Compared with the wide and narrow limit method,the range calculated by the narrow limit method is smaller than the range calculated by the wide limit method,and the accuracy is higher.This paper combines theoretical analysis with actual engineering,and fully considers the randomness of the dam foundation fractures network distribution and the randomness of physical and mechanical parameters.A method for calculating the reliability of the deep anti-sliding stability system of gravity dams with random fractures is proposed,which solves the problem of calculating the reliability of the deep anti-sliding stability of gravity dams in actual engineering.It is of guiding significance for studying the anti-sliding stability analysis of gravity dams with random fractures in the bedrock.