Hydro junction is a complex of different types of hydraulic structures built in suitable sections of rivers or channels to meet the goal of promoting benefits and eliminating disadvantages of various hydraulic projects.A water conservancy project is usually a reservoir or main project formed by it——dam, the name of the hydropower station, such asThree Gorges Dam、Miyun reservoir 、Luogong Dam、Xin'anjiang Hydropower StationEtc;Some are also directly called water conservancy hubs, such asGezhouba DamHydro junction.
Water conservancy hubs can be divided into flood control hubs, irrigation (or water supply) hubs, hydropower generation hubs and shipping hubs according to their different tasks.Most water conservancy projects[1]It undertakes multiple tasks and is called a comprehensive water conservancy project.The main factors affecting the functions of water conservancy projects are to select reasonable locations and optimal layout schemes.The location of the hydro junction project generally passes through the riverWatershed planningorRegional water conservancy planningdetermine.The specific location must fully consider the terrain and geological conditions, so that all hydraulic structures can be arranged on a safe and reliable foundation[1]And can meet the requirements of building dimensions and layout, as well as the necessary conditions for construction.The layout of hydro junction projects is generally determined through feasibility study and preliminary design.The hydroproject layout must enable buildings with different functions to have their own positions, coordinate with each other in use, and fully and effectively complete their tasks;When each hydraulic structure is used alone or in combination, the flow condition is good, and the upstream and downstream flow and scouring and silting changes will not affect or less affect the normal operation of the hub. In short, it should be safe and reliable technically;On the premise of meeting the basic requirements, it is necessary to strive for compact layout of buildings, one building can play multiple roles, reduce the amount of work and land occupation of the project, so as to reduce investment;At the same time, the requirements of management and operation, construction convenience and short construction period shall be fully considered.The general layout of a large-scale water conservancy project is a complex system engineering, which needs to be demonstrated and determined according to the analysis and research methods of system engineering.
In the water intake hub and water storage hub, the river crossing structures designed to intercept water flow, raise water level and regulate and store water volume are divided intoSpillwayAndNon overflow damTwo types.Overflow dam (gate)Water release structure。
Water release structure
It is designed for releasing flood and emptying reservoir.The forms areside spillway 、Spillway(gate), sluice tunnel, gate bodyDrain holeOr culvert pipes under the dam.
Water intake structure
It is designed for irrigation, power generation, water supply and water intake for special purposes.The forms areIntake sluice、Headrace tunnelAnd water diversion culvert pipes.
Specialized buildings
For power generation plantSurge chamber, is the pump room and flow channel for water lifting, and is used for navigation, wood and fishnavigation lock、Ship lift、Raft path, fishway, etc.
Hub location selection
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stayWatershed planningOr in the regional planning, the general location of a water conservancy project in the river has been basically determined, but its specific location needs to be within this range through different schemestechnical economyCompare and choose.The location of a hydro junction is often based on its main body dam（Water retaining structure）The position of is representative.Therefore, the selection of hydro junction location is often referred to asDam site selection。Some water conservancy projects only need to select dam sites in a narrow range;For some water conservancy projects, it is necessary to select the dam section within a wide range and then select the dam site within the dam section.for exampleThree Gorges Project, once at the exit of the Three GorgesNanjin PassThe dam section and Meirentuo dam section 30~40km upstream are compared.The dam axis of the former is shorter, the work amount of the bar is smaller, and the power generation is slightly larger.However, there are many underground works, especially the geological conditions, hydraulic layout and construction conditions are far worse than the latter, so Meirentuo dam section was selected.In this dam section, Taipingxi and Sanduping dam sites are selected for comparison.The geological conditions of the two are basically the same, the formerdam bodyThe quantities are small, but the latter is convenient for the layout of the hydroproject, especially for the construction. Finally, Sanduping dam site is selected.[2]
Grade
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Water conservancy hubs are often classified according to their scale, benefits and economic and social impacts, and the buildings in the hubs are classified according to their importance.For buildings with high level, the requirements are higher in terms of flood resistance, strength and stability, building materials, reliability of operation, and vice versa, so as to achieve the goal of both safety and economy.
Division basis: project scale, benefit and importance in national economy.Divided into five grades (GB50201-94)
Engineering grade
reservoir
hydropower station
Project scale
Total storage capacity（tenm）
Installed capacity（tenkW）
Ⅰ
Large (1) type
>10
>120
Ⅱ
Large (2) type
10～1.0
120~30
Ⅲ
medium-sized
1.0～0.1
30~5
Ⅳ
Small (1) type
0.1～0.01
5~1
Ⅴ
Small (2) type
0.01～0.001
<1
See Table 1 and Table 2 for the classification indicators of China's water conservancy and hydropower projects (mountainous and hilly areas), as well as the classification of hydraulic structures. However, according to the specific situation and after full demonstration, their levels are allowed to be increased or decreased.
Hydro junction
Water conservancy project
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It refers to the hydro junction buildings (including the water source project in the water diversion project) and other large independent buildings.Including water retaining works, flood discharge works, water diversion works, power plant worksStep up substationEngineering, shipping engineering, fishway engineering, traffic engineering, housing construction engineering and other construction projects.The first seven items, such as water retaining works, are the main building works.
1. Water retaining works.Including various dam (sluice) works for water retaining.
2. Flood discharge works.Including spillway, spillway tunnel, sand flushing hole (tunnel), emptying tunnel and other works.
3. Diversion works.Including power generation diversion channel, water inlet, tunnel, surge shaft, high-pressure pipeline and other projects.
4. Power plant project.Including ground and underground power plant projects.
5. Step up substation project.Including step-up substation[3]、SwitchyardEtc.
6. Shipping engineering.Including upstream and downstream approach channelsnavigation lock、Ship liftEtc.
7. Fishway works.It can be listed separately according to the layout of the hydroproject buildings.Combined with the barrage, it can also be a part of the barrage project.
8. Traffic engineering.Including permanent roads, bridges and culverts, railways, wharves and other traffic projects inside and outside the site, such as dam access, plant access and external.
9. Housing construction works.It includes permanent auxiliary production buildings, warehouses, offices, living and cultural welfare buildings and outdoor works serving production and operation.
10. Other construction works.It includes internal and external observation works, power lines (plant dam area), lighting lines, communication lines, water supply, heat supply, drainage and other public facilities works in the plant dam area and living quarters, environmental construction works in the plant dam area, automatic hydrological forecasting works and others.
