Study On Prediction Method Of Service Life Of Riprap Spur Dike Under Unsteady Flow

The spur dike is one of the commonly used waterway regulation buildings in the river channel,it has the function of narrow riverbed,backwater high water level and adjustment ratio drop,and plays an irreplaceable role in waterway regulation field.At present,the theory of reliability design is very mature in the field of mechanical engineering and structure project,but the theory of design of navigation structure is still lagging behind.Therefore,it is necessary to study the reliability and life of the Riprap spur dike under unsteady flow condition,to enrich the research content of the waterway regulation building and to provide the technical reference for the future engineering.This paper is based on the National Natural Science Foundation Project "Study on water damage mechanism and calculation simulation of spur dike in mountainous navigable river under unsteady flow"(51079165)"and national Key research and Development program Project" Channel Beach Groove Regulation technology and demonstration in complex multi-branch reach(2016YFC0402106),With the help of laboratory test data,the most commonly used waterway regulation structures in the upper reaches of the Yangtze River are studied,and on the basis of sufficient research on hydraulic characteristics and water destruction mechanism of riprap spur dikes,Based on the theory of unsteady flow and fatigue reliability analysis,the research on the reliability and service life of the Riprap Spur dike is carried out,and the service life of the cast dikes is discussed and the suggestions for the design use time are given.The conclusions of this paper are summarized as follows:(1)Based on the theory of basic statistics,this paper,by means of hypothesis testing knowledge in probability theory,tests the model flow process,the average daily flow rate of 55,the pulsating pressure and the longitudinal instantaneous velocity through various hypotheses,and finally thinks that the flow of the model flow obeys the logarithmic normal distribution,and the average daily flow of the,the pulsating pressure obeys the logarithmic normal distribution,the longitudinal instantaneous velocity obeys the normal distribution,and the probability density function of the model flow process and the fluctuating pressure is given,which provides the research basis for the future to simulate the structure reliability theory.(2)According to the actual engineering needs,the reliability of the Riprap dike and the "service life" are defined to make it more convenient to be applied in the engineering practice;Considering the present situation of the design of the waterway regulation building and the method of determining the working life of the structure engineering,This paper gives the design life of the widely used waterway regulation building with Riprap Spur dike.(3)From the angle of "maximum depth",the standard of "manual intervention" maintenance management for the riprap dikes is given,which is used as the criterion for the failure of Spur dike;Based on the flow process and the maximum depth,the frequency of the flow process with unsteady flow is taken as the evaluation criterion of reliability.(4)Based on the theory of fatigue reliability analysis in the fields of structural engineering and mechanical engineering,the life of spur dike is studied according to logarithmic normal distribution,and the calculation formula of reliability of spur dike and calculation formula of service life are deduced.