Study On The Experimental Simulation Technology Of Silt Transport Under Great Water Depth Conditions In Reservoir

Since the impoundment of the three gorges reservoir, the sediment deposition distribution of about 90% in the reservoir, median size of the sediment is silt of 0.01 mm. Serious sediment deposition of the river are mainly in Meixi estuary, Huanghuacheng, Lanzhuba, Fengweiba, Tunaozi etc, particularly Huanghuacheng River appeared position changing of channel, the poor visibility of ship route, security risks of navigation. To insure high grade channel continuity in Yangtze River and constructing grade channel, the proplem of sediment deposition in the reservoir are urgent need to solve. But the simulation technique about cohesive fine sand transport in reservoir is lacking in the current situation, therefore this paper research the key technology about the test simulation technology of silt transport under conditions of great depth reservoir.This paper puts forward silt transportation rule and erosion or deposition characteristics of sediment in the three gorges reservoir, and then puts forward model similarity about silt transport under conditions of great depth reservoir, main content summary is as follows:In the first place, Suspended load flocculation is existing in the three gorges reservoir, sediment incipient motion is influenced by water depth, therefore sediment-carrying capacity is not suitable for distinguishing erosion or deposition of sediment. This paper put forward the concept of erosion area, transport area and deposition area about silty-sand,and then distinguishing erosion or deposition of sediment and amending the sediment movement equation and riverbed deformation equation depends on this concept. It is laid the substantial foundation for physical model design.In the second place, silt transportation velocity is hard to determine by incipient velocity formula, so this paper put forward calculating velocity scale by incipient velocity of field measurement and flume experiment. Flocculation settlement scale and incipient velocity scale is hard to determine on account of lacking of developed similarity theory. Therefore, this paper uses prototype sand for model testing,and then silt flocculation settlement scale and silt incipient velocity scale equals one.Because the corrected riverbed deformation equation can be deduced λZλγ=λSλH in this paper, deeming the time scale of erosion and deposition can’t be determined by riverbed deformation equation, and it should equal the time scale of water flow. Therefore, it is necessary to adjust time scale by similarity of riverbed change in the model test insure erosion and deposition similarity of riverbed.In the third place, in order to prove suggested similarity scale, this paper innovative designs model contraposing winding, wider and braided river in the reservoir area. Eventually, determining the velocity scale is 5 by comparison test. On the basis of comparison test, author run long sequence test of erosion and deposition. The test results prove velocity distribution, flow characteristics, sedimentation area and sedimentation thickness of model is similar to the prototype, technology of silt transport under conditions of great depth reservoir basing on prototype sand is feasible, innovative and practical.