| Xinjiang is located in the western part of China.It has unique topographic and geomorphological characteristics.Most of the rivers belong to mountain and stream rivers.The inflow of the rivers is small and the sediment content is high.Sometimes,the phenomenon of less water and more sediment occurs,which forms the characteristics of water and sediment of rivers different from other areas in the mainland.As long as water is diverted from rivers,the problem of sediment is inevitable,especially on sandy rivers in Xinjiang.Whether the diversion hub can play its due role,whether the water intake quantity and water quality can meet the requirements,the key factors for success or failure are the proper treatment of sediment in rivers.Only by fully grasping and understanding the law of sediment transport in diversion hubs can the structure layout and management of diversion hubs be reasonable and scientific.How to reduce the harm of sediment to diversion hubs is a thorny problem faced by the construction and management of water conservancy projects in Xinjiang over the years.In this paper,the principle of water diversion and sediment control at the head of the original bend channel(Fergan type)of Jingou River and the main existing problems of the junction are elaborated.At the same time,taking the reconstruction project of Jingou River diversion junction as an example,relevant research results are obtained.The contents and achievements of graduate students are as follows:(1)The three-stage sand control system of Jingou Channel Head Junction adopts the combination of multi-level sand control and sediment discharge facilities on the elevation and multi-level sand control and sediment discharge facilities on the plane,which has good effect of water diversion and sediment control,high sediment discharge rate and flexible operation.(2)The main problems faced by Jingou Channel Head Project are aging of buildings and metal structures,wide bends in front of sluices,weak circulation in bends and silt deposition.(3)By comparing the location of the gate,the type of diversion hub,the type of upper dam and the type of lower dam,the project location is selected at the original gate site,the type of diversion hub is internal and external reservoir diversion,the type of upper dam is buttressed retaining wall+internal reservoir inlet gate is flat gate,and the type of lower dam is inclined geomembrane dam.(4)The discharge capacity of the sluice gate with full opening is measured in the experiment.When the pre-sluice water level reaches 821.87m,the measured discharge is 642.0m~3/s.When the pre-sluice water level reaches 821.40m,the measured discharge is 521.5m~3/s,which meets the discharge capacity requirements.Internal reservoir intake gate:when the normal intake level is821.00 m,the intake gate diversion flow is 45 m~3/s,and when the flood level is 821.87 m,the intake gate diversion flow is 113.5 m~3/s,which meets the design requirements.Inner Reservoir Diversion Gate:When the water level of the inner reservoir reaches 815.66 m and the opening of the diversion gate is 3/4,the diversion flow can reach the design flow of 45 m~3/s.When the water level of the inner reservoir reaches 817.35 m and the opening of the diversion gate is 1/2,the diversion flow can reach the design flow of 45 m~3/s,which meets the design requirements.(5)Through the numerical simulation of the upstream and downstream of the spillway and sediment sluice of the Jingou River Gate and Dam Intake Project in Xinjiang,the flow velocity of the water passing through the gate pier increases obviously,resulting in the sudden increase of the flow velocity in the channel,the flow field in the original channel also changes,the flow field is disordered,and the flow behind the gate appears eddy and circumfluence phenomenon.After the water flows out of the gate,the flow on the apron shows a jet state,and the maximum flow velocity on the apron reaches 40.5m/s.Under checking conditions,the flow pattern of upstream and downstream of the gate is similar to that of the design flood,but the flow velocity of each section increases correspondingly.After the water flows out of the gate,the flow appears a jet state on the apron,and the maximum flow velocity on the apron reaches 54.4m/s.Comparing the simulated and experimental flow velocities under different working conditions,the simulated and experimental flow velocities under design and check conditions are basically in agreement with each other,and the error is less than 5%.(6)According to the results of numerical simulation,the layout of the hub is further optimized:before optimization,the reverse arc radius and arc length of the left bank slope of the diversion dike downstream of the flood-discharge and sand-washing sluice are smaller,and after the flow in the channel passes through the flood-discharge and sand-washing sluice,the area of the cross-section decreases,the flow velocity increases,and the flow in the channel appears eddy and recirculation phenomenon.After optimization,the discharge capacity and energy dissipation capacity of the flood discharge sluice are enhanced,and the main flow in the channel is directed to the middle of the channel,so as to alleviate the erosion of the left bank slope by the main stream.The flow pattern in the channel is stable,and the phenomenon of backflow after the sluice disappears. |
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