Research On Uncertainty Of Earth-rock Dam Safety Evaluation

As of 2017,China has built more than 98,000 dams,most of which are earth-rock dams,and more than 95% of the earth-rock dams are old dams constructed before the 1980 s.In China,we have carried out large-scale reinforcement of dangerous and dangerous reservoirs.However,due to the large number of earth and rock dams and the large base number,the probability of out of danger is high,and we must not take the safety risks lightly.Therefore,it is necessary to carry out scientific and reliable evaluation of the safety status of earth-rock dams.At the same time,due to the characteristics of the spatial variability of the physical parameters of the dam and its foundation rock and soil and the dynamic change with time,as well as the natural environmental conditions of the dam and the trigger factors,the time of occurrence and the dynamic processes that may cause its destruction.Randomness,meanwhile,using natural language to represent the process and result of dam safety discovery,but the various properties described by natural language have strong uncertainty.These reasons lead to the inevitable uncertainty of the process and results of the safety monitoring and evaluation of earth-rock dams.Traditional safety evaluation methods do not or do not fully consider this uncertainty,which makes it unable to accurately reflect the operation status of earth-rock dams.In order to solve the above problems,this paper intends to use fuzzy set theory,gray system theory,cloud theory and other theories to describe uncertainty,explore new methods for safety evaluation of earth-rock dams,and have achieved the following main results:1.The traditional safety monitoring model is used for preliminary analysis of the safety status of earth-rock dams,and the mathematical model of multiple regression analysis is mainly used to establish statistical models.At the same time,in view of the shortcomings of the least square method,the improved method of the least square method is also discussed.The M estimation in the robust regression is introduced,and it is applied to the analysis of the observed data of the earth-rock dam.2.A safety evaluation model of earth-rock dam based on FBWM(Fuzzy best-worst multi-criteria decision-making method)method and gray clustering method.The FBWM method was introduced to calculate the weights of indexes.The best index and the worst index in the evaluation indexes were determined by consulting the data and the relevant experts.The relevant safety monitoring instrument measured data was analyzed,and the gray clustering weight matrix was constructed.Then the evaluation index weight matrix was combined with the gray cluster weight matrix to acquire the safety evaluation results of the earth-rock dam.3.Based on the cloud theory and the ideal point combination weighting method,the ideal point-cloud theory model for earth and rockfill dam safety evaluation is established.Real and reliable weights of indexes were determined using the combination weighting method based on the ideal point.Then,the safety evaluation grade ranges of each evaluation index were divided on the basis of the measured data.These grade ranges were “softened” by combining cloud theory;finally,the cloud membership function is used to generate the membership cloud of the security evaluation level state characteristic value,and compare it with the evaluation level concept cloud model map to obtain the evaluation result.The above three methods,especially the safety evaluation model considering uncertainty,have more reasonable calculation results.The proposed models could provide references in the diagnosis and decision making in the earth-rock dam management department.