Abstract:The channel between the Three Gorges and Gezhouba is a mountain gorge river with the dual characteristics of“reservoir+natural river”.The water flow condition deteriorates sharply in flood season,and the most prominent flood rapids such as Shuitianjiao,Xitan,Shizinao,and Piannao are the most prominent,which affects the navigation safety of ships.To solve the problem of obstructing navigation by flood rapids between the Three Gorges and Gezhouba dams,this paper analyzes the evolution characteristics of riverbed between the dams based on the measured topography for many years.Taking Shuitianjiao Rapids Beach as an example,it adopts the methods of hydrologic prototype observation,actual ship seaworthiness test and theoretical calculation to study and analyze its obstructing characteristics.Then the fixed-bed normal physical model and remote-controlled self-propelled ship model test are used to optimize and compare the regulation plans of the beach,and the regulation plan of “reef blasting+slag cleaning+tank filling” is determined.The research results show that the maximum gradient decreases from 0.75‰ to 0.2‰ at the flow level of 35,000 m3/s after regulation,and the surface velocity of the upstream route decreases from 3.3-3.7 m/s to 2.0-2.9 m/s.The navigation obstruction flow patterns such as cyclone and backflow are significantly improved,and the test ships can sail autonomously andreach the beach safely,achieving the regulation goal.The research results can provide technical guidance and demonstration for the regulation design of the flood rapids between the two dams,and can also be used as reference for other similar beach regulation studies.
