Analysis And Research On Decommissioning Evaluation Of Small-sized Earth Dam

Most of the reservoir dams in China were built in the 1960s and 1970s,most of them were small earth dams,which had been in operation for several decades.Limited by the technical and historical conditions at that time,there were many problems,such as low flood control standards,poor quality of projects and many hidden dangers of diseases,which led to the long-term operation of some reservoirs with dangers and aging problems,and the reservoir function have gradually shrink,the benefits have been seriously attenuated,and even caused serious consequences of dam break.The 21st century will be the peak period for strengthening small earth dams and eliminating dangerous dams.Therefore,it is of great practical significance to study the operational risks and failure rules of earth dams in service,and it is of great theoretical and practical value to study the way out of earth dams with hidden safety hazards and lost original functions.The main contents of this paper are as follows:(1)Based on many years’statistical data,the main causes and failure rules of small earth dams are studied.,and the main reasons for decommissioning of small earth dams are analyzed and summarized.The main influencing factors of decommissioning of small earth dams are determined from the aspects of engineering safety,ecological environment and social and economic benefits.The evaluation index system of small earth dam decommissioning is constructed,and the method of index quantification is put forward.(2)The weighting method of earth dam decommissioning evaluation index and the evaluation model of earth dam decommissioning are studied in this paper.Four weighting methods,namely three-scale method,unique reference object comparison judgment method,mean square deviation weight method and anti-entropy weight method are studied.The importance of each index factor is analyzed,the weight of each index factor is determined,and the decommissioning evaluation model of small earth dam based on harmony degree equation is put forward,and the grade of decommissioning evaluation of small earth dam is determined.(3)Based on the object-oriented programming method,the development of the decommissioning evaluation system based on Visual Basic software is studied A simple and convenient evaluation system with accurate and reliable calculation results is established,which provides an effective calculation tool for the decommissioning evaluation of small earth dams.(4)The main effects of demolition of decommissioned dams are studied,and the impacts of demolition on river ecosystem,economy and society are analyzed and summarized.The influences of flow velocity,water temperature,sediment and pollution after dam demolition are analyzed from the perspectives of short-term impact and long-term impact.The advantages and disadvantages of dam demolition are considered in combination with the positive and negative effects.