| In the wide plain area of the river,the use of open channel diversion is a common method of diversion,which has many advantages such as convenient construction,high efficiency low cost and so on.In the design of the diversion channel,not only the cost,schedule,safety and other factors need to be considered,but also the construction safety and the navigation flow conditions during the diversion are often considered.The dam site of this project is a typical branching section,with a long construction period.Constructing a diversion channel on the river center,not only needs to consider the appeal factor,but also needs to consider the diversion ratio of the supporting river;the diversion channel is not only It is necessary to undertake the task of discharge,and it is also necessary to serve as a navigation problem.The internal flow conditions of the open channel are complicated.Therefore,the split ratio and navigation analysis of the open channel are essential for the normal and safe construction of the project.In view of the above problems,this paper uses a combination of numerical analysis methods and physical model tests to analyze the split ratio of the diversion channel on the braided reach river and the analysis of the navigation flow conditions in the open channel.The main research contents and results of this paper are as follows:(1)Calculating the split ratio on the branching channel is a multi-factor coupling process,including the original riverbed form,elevation,sediment concentration and precipitation.When calculating the diversion of the open channel,it is necessary to consider the section form of the open channel.Dip angle,etc.Based on the previous researches,this paper establishes the relevant mathematical model by using the original topographic data,and verifies the correctness and reliability of the model through the observation data of the hydrological station near the dam site.(2)The mathematical model is used to calculate the upstream and downstream water levels under the design flow of each period,and the water flow characteristics such as the discharge capacity and the split ratio of the east and west rivers under different working conditions are calculated and reviewed.According to the calculation results,the track line ratio is determined.The variation law of the main flow position and its vertical and horizontal flow velocity,flow state and navigation water depth are proposed.The maximum navigation flow rate of the navigation flow rate ≤3.5m/s in each construction stage is proposed,and the reasonable navigation channel range and the water level and flow range suitable for navigation are determined.Verify whether there are undesirable fluid flows such as bubbles and turbulence in the gate area of the open channel.(3)Verify the platform flow rate after the demolition of the cofferdam to the12.0m elevation during the flood season;during the first and third flood seasons,the east and west rivers are navigable,and the velocity and flow state of the chamber are measured.Determine a reasonable range of navigation and water and flow ranges suitable for navigation.(4)The calculation and analysis results show that the primary selection scheme can basically meet the discharge requirements,but the river channel diversion on both sides is larger than the original natural river channel.The improved "one-word" diversion scheme is adopted to ensure safe construction in the foundation pit and meet the navigation requirements under different working conditions.During the construction period,it is basically capable of self-propelled navigation.In special conditions,such as the demolition of the cofferdam to the 12 m elevation during the flood season and the large-flow flood during the dry season,relevant navigational measures are required to ensure the normal passage of the vessels in the diversion channel. |
