Study On Risk Assessment Of Earth-rock Dam System Considering Time-varying Effect

The earth-rock dams built from 1950s to 1970s are approaching the design reference period with many hidden dangers and aging problems.The factors that affect the normal operation of earth-rock dams are uncertain and have obvious time-varying characteristics.However,the current reliability management of earth-rock dams mainly relies on monitoring data for static detection and evaluation,focusing less on the risk decision-making of the whole process of structural service,which has obvious shortcomings.Therefore,based on the National Natural Science Foundation of China(51679222,51709239),this study carried out the risk assessment of earth-rock dam system considering time-varying effect.The main research work and results are as follows:(1)Through the risk identification of earth-rock dam system,the level of risk factors is evaluated.The risk identification index system of earth-rock dam is constructed by exploring risk factors.GA-AHP method is used to calculate the weight of risk factors and obtain the relative importance order of risk factors,which are helpful to identify the main failure modes and paths.DBN model is introduced to consider the time-varying effect of risk factors and quantify the risk level of each risk factor.(2)Risk assessment of the single failure mode and comprehensive risk rate of earth-rock dam without considering time-varying effect.According to the principle of reliability,the risk rate calculation model of single failure mode of earth-rock dam is established,which is solved by Monte-Carlo method.Based on the tomographic analysis system,a Static Bayesian Network is transformed by introducing the Leaky Noisy-or gate extended model,so as to improve the conditional probability system and evaluate the comprehensive risk rate of earth-rock dam at a certain time.(3)Risk assessment of earth-rock dam system considering time-varying effect.The Dynamic Bayesian Network is used to build the risk assessment model of earth-rock dam system considering the time-varying effect.The Markov State Transition Model is introduced to obtain the effective network parameters.Taking the risk rate without considering the time-varying effect as evidence,the time-varying risk probability considering the general operation law of earth-rock dam and the objective detection data is obtained.(4)Example application.Taking Longxingsi reservoir dam as an example,the law of risk probability of factors,single failure mode and comprehensive risk rate of earth-rock dam changing with time are obtained on the basis of assessment on risk rate of single failure mode and considering the general rules of earth-rock dam operation.Compared with the static assessment method,the risk level of the earth-rock dam is quantified,which is more consistent with the actual operation.