Studies On The Changes In River Sedimentation Under The Influence Of Inverted Siphon And Its Improving Measures

The sediment concentration of Yellow River, Haihe River and some other rivers in our country is very higher, the annual average sediment concentration is more than 5 kg/m3,belong to sediment-laden river. To build hydraulic structures on these rivers, the sediment problem will be a key technical problem. The problems mainly can be divided into two categories, one is the impact of sediment-laden river on the proposed project, the other is the impact of the proposed project on these rivers. If there is no any research, the deposition will easily occur on the proposed project, which will affect the project benefit and safety; once the river sedimentation changes near the project, which will also affect the project safety, the flood capacity problem is particularly prominent. At present, the earlier stage demonstration work by model test is necessary, and we should select the most reasonable arrangement plan. In the long-term practice of the river renovation project, our water conservancy workers have done a lot of research on the river sediment transport, river evolution and regulation, etc. We achieved a number? of important results, solved many sediment problems successfully, such as Gezhouba Dam, Three Gorges Project, Xiaolangdi Project, etc. Since the 90’s, in terms of numerical calculation,2d and 3d sediment mathematical model have got a lot of development and engineering application.The Abandoned Yellow River is a muddy river, it has a large sediment in the flood season, but in the non-flood season, the rate of flow is small, the sediment concentration is also the same. In this paper, taking the upstream river under the influence of inverted siphon as an example, analyze the sediment deposition causes after running control for many years and the changes in river sedimentation which affected by the existing gate control mode. To ensure project safety, we put forward some improvement measures.The main research contents and results are as follows:1. According to the requirements of the relevant regulations, some model tests are conducted, they are divided into fixed bed water, fixed bed of muddy water and local movable bed three parts. The experimental results basically reflect the real river flow;2. The river reached has characteristic of bend flow, under the condition of no measure, in the operation mode of two gates with symmetrical opening, a low-speed recirculation zone obvious on the left bank, it easily to cause sediment deposition.3. After adding two spur dikes rectification measures, the water flow can be adjusted, the flow velocity increases significantly by contracting river bed, the velocity distribution is more reasonable, that is conducive to reduce sediment deposition. Through the fixed bed of muddy water test, the deposition phenomenon appears both on the left and right sides of the river, the left bank is more serious. After two spur dikes are added, the left bank accumulation is weakened, the remediation effect is ideal. Through the local dynamic bed test, the erosion is generated near the head area of the first spur dike, some reinforcement treatments are necessary;4. By using UG software, the 3D model of the culvert engineering is established. The Flow-3D software is used to simulate the project on the prototype scale, the volume of fluid (VOF) approach is adopted to deal with the free surface. The calculation results and experimental conclusions are basically the same;5. The sediment content of the Ancient Yellow River is analyzed, and the sediment deposition is calculated under the design and the improvement measure conditions, we basically understand the causes of sediment deposition. With mainstream, the sediment moves forward constantly, the lateral diffusion occurs, the sediment deposits in the lower velocity zone finally. As the extension of time, the left bank deposition is more serious, the river mainstream towards the right bank, with the contraction of the water cross section, the silt on the right bank is taken away, and even cause erosion, that is consistent with the actual erosion and deposition;6. Through the two spur dikes rectification measures, we successfully resolve the left low velocity zone where is likely to cause sedimentation problems, it shows that the improvement effect is relatively ideal, the improvement measures can also provide some reference for the similar projects.