Study On Scouring Simulation Technology Improvement Of Gravel-pebble Bed In Doujiangyan

The contradiction between Zipingpu and Doujiangyan is widely concerned bythe government and experts, and it is one of the relative science problems that studyon the improvement of scouring simulation technology for gravel-pebble beds inDoujiangyan. Based on the existing results of sediment incipient research and thehistory and status quo of Doujiangyan river, according to the actual conditions ofgravel-pebble beds, combined theory research, prototype observation and flumeexperiment, the problem of pebble incipient is systematically studied. The maincontents are as follows: The mechanism, criteria and different influence factors of sediment incipient, isfurther researched. As a result, transport for non-uniform sediment is an unsteadyand random process, the main influence factors of sediment incipient are shape,non-homogeneity, location in bed and flow condition. Based on the pebble and the incipient characteristic of pebble, considering theinfluence of pebble shape to the equivalent grain size, introducing the parameters ofshape and relative exposure degree, based on the equivalent grain size of pebble,adopting rolling incipient mode, the formula of calculating the incipient velocity forpebbles is deduced. Aiming at feature of mountain river, the incipient condition of incoherentnon-uniform sediment on different bed slopes with complete exposure and relativeexposure, is deduced. As a result, under the same bed slopes and fluid conditions, the -iii-四川大学硕士学位论文 岷江都江堰卵石河道冲刷模拟技术改进研究incipient velocity of the same sediment in complete concealment is 2.7 to 2.8 timesof the one in complete exposure; the applicability with different bed slopes and grainsizes, the incipient condition of incoherent non-uniform sediment on different bedslopes with relative exposure, is studied. According to some previous results, the relationships among three commonincipient motion conditions are deduced. Considering these relationships, dozens ofincipient motion conditions are united, K of all kinds of formulas is in common from3.37 to 7.86, the result is helpful to select appropriate incipient equation. Results above mentioned are verified by observed data in Doujiangyan riverand factual data in flume.