Study On The Influence Of The Abandoned Yellow River Culvert Engineering On The Evolution Of The Upper And Lower Channel

The riverbed evolution is aroused by the interaction between current and riverbed as well as engineering structure.On one hand,the fluvial process can be studied by the dynamic method including mathematic model calculation and engineering structure model test;on the other hand,it also can be studied by thegeomorphology method which analyses the data we measured.But this method has some defects in application,such as poor spatial analysis ability,inadequate calculation accuracy and low efficiency which can not pick up the riverbed evolution information fully from the channel data.By means of combining riverbed evolution analysis and numerical simulation of GIS platform,this paper uses the data input and spatial data analysis functions of GIS software to digitize the topographic map of upper and lower reaches of the Yancheng Abandoned Yellow River culvert project based on the topographic data of upper and lower reaches of the Yancheng Abandoned Yellow River culvert project.Through comparison and analysis,this paper obtained the typical cross sectional drawing,the change of characteristics of sections,the change of plane talweg and the change of volume of scour and fill of riverbed of the river and summarized the recent characteristics of scouring and silting evolution of the river channel.This paper obtained the characteristics of flow field of different schemes and analyzed the causes of river sediment deposition since the project has been running for many years and the impact of existing schemes of controlling and running the gate on the changes of erosion and siltation of the river channel by using FLOW-3D software to simulate the upper and lower reaches of the Yancheng Abandoned Yellow River culvert project based on the analysis of riverbed topographic data.The main achievements of the research are as follows:(1)The analysis of changes of the shape and characteristic parameters of river channel shows that:the sedimentation method of the upstream is the channel being narrowed,and the width of the bottom of the channel is severely narrowed between each years in channel CS4-CS6.The form of scouring and silting is the left bank of the upstream river deposited and the right bank was scoured.Sedimentation is the main characteristic in front of the gate.The section siltation of downstream of the river is less serious than that of the upstream.On the contrary,the scour appeared on the left bank of the downstream of river and the sedimentation appeared on the other bank.Take the upstream and downstream as a whole,the riverbed section was narrowed,and the main groove has shifted from the left bank to the right bank in the upper reaches,while shifted to the right bank in the lower reaches.(2)The analysis of changes of plane scouring and silting shows that during 2011 to 2013 after the renovation,the areas with high siltation intensity are mainly located on the left bank of the river and both sides of downstream of irrigation and drainage sluice,the maximum deposition intensity reached 3.5m.There are different degrees of erosion in the main channel and the right bank of the river channel.The most severe scour occurs at the downstream location of the irrigation and drainage gate,with the maximum scour intensity reaching 2.5m.Calculation of regional sediment volume shows that:taking the upstream and downstream of river channels in each year as the research object,and select the area between the two sections and calculating the amount of sedimentation.According to the calculation results,the unit sedimentation volume of the upstream in each year is larger than the amount of unit sedimentation of the downstream,and the total amount of sedimentation after the flooding has a small increase than that before the flood,and the upper and lower reaches of the culvert had generally deposited in 2008-2012.(3)Through the hydrodynamic simulation and calculation of four schemes in the operation period of the culvert project,it shows that the calculated results are basically is consistent with the experimental results.The calculation results show that the average velocity in the tunnel is lager than that in the culvert without silting.The study shows that no silting will occur in the culvert for the three schemes during the normal operation period through the gate control.Water movement exists low speed raceway on the left bank of the upstream channel,at the downstream of the gate used for irrigation and drainage and on both sides of the lower reaches.Sediment is easier to deposit after a long period of operation.The fourth scheme used during the design flood can meet the requirements of flood discharge after dredging,and the flow field information obtained by numerical calculation is more comprehensive,which provides an effective means to analyze the flow characteristics of the river.