1、 Layout form of hydropower stations
The typical layout forms of hydropower stations mainly include dam type hydropower stations, riverbed type hydropower stations, and diversion type hydropower stations.
Dam type hydropower station: Utilizing a barrage to raise the water level in the river, in order to concentrate the water head. Often built in high mountain canyons in the middle and upper reaches of rivers, it is generally a medium to high head hydropower station. The most common layout method is a hydroelectric power plant located downstream of the retaining dam near the dam site, which is a hydroelectric power plant behind the dam.
River bed type hydropower station: A hydropower station where the power plant, water retaining gate, and dam are arranged in a row on the riverbed to jointly retain water. Often built in the middle and lower reaches of rivers, it is generally a low head, high flow hydropower station.
Diversion type hydropower station: A hydropower station that uses a diversion channel to concentrate the drop of a river section to form a power generation head. It is often built in the middle and upper reaches of rivers with low flow and large longitudinal slope of the river.
2、 Composition of Hydroelectric Hub Buildings
The main buildings of the hydropower station hub project include: water retaining structures, discharge structures, inlet structures, diversion and tailrace structures, level water structures, power generation, transformation, and distribution buildings, etc.
1. Water retaining structures: Water retaining structures are used to intercept rivers, concentrate drops, and form reservoirs, such as dams, gates, etc.
2. Water release structures: Water release structures are used to release floods, or release water for downstream use, or release water to lower the water level of reservoirs, such as spillway, spillway tunnel, bottom outlet, etc.
3. Water intake structure of a hydropower station: The water intake structure of a hydropower station is used to introduce water into the diversion channel, such as deep and shallow inlet with pressure or open inlet without pressure.
4. Water diversion and tailrace structures of hydropower stations: The water diversion structures of hydropower stations are used to transport power generation water from the reservoir to the turbine generator unit; The tailwater structure is used to discharge the water used for power generation into the downstream river channel. Common buildings include channels, tunnels, pressure pipelines, etc., as well as cross buildings such as aqueducts, culverts, inverted siphons, etc.
5. Hydroelectric flat water structures: Hydroelectric flat water structures are used to stabilize changes in flow and pressure (water depth) caused by changes in the load of the hydropower station in the diversion or tailwater structures, such as the surge chamber in the pressurized diversion channel and the pressure forebay at the end of the non pressurized diversion channel.
6. Power generation, transformation, and distribution buildings: including the main power house (including installation site) for installing hydraulic turbine generator units and its control, auxiliary equipment auxiliary power house, transformer yard for installing transformers, and high-voltage switchgear for installing high-voltage distribution devices.
7. Other buildings: such as ships, trees, fish, sand blocking, sand flushing, etc.
Common classification of dams
A dam refers to a dam that intercepts rivers and blocks water, as well as a dam that blocks water in reservoirs, rivers, etc. According to different classification criteria, there can be different classification methods. Engineering is mainly divided into the following types:
1. Gravity Dam
A gravity dam is a dam constructed with materials such as concrete or stone, which mainly relies on the self weight of the dam body to maintain stability.
The working principle of gravity dams
Under the action of water pressure and other loads, gravity dams mainly rely on the anti slip force generated by the dam’s own weight to meet the stability requirements; At the same time, the compressive stress generated by the self weight of the dam body is used to offset the tensile stress caused by water pressure, in order to meet the strength requirements. The basic profile of the gravity dam is triangular. On the plane, the axis of the dam is usually straight, and sometimes in order to adapt to terrain, geological conditions, or to meet the requirements of hub layout, it can also be arranged as a broken line or arch with small curvature towards the upstream.
Advantages of gravity dams
(1) The structural function is clear, the design method is simple, and it is safe and reliable. According to statistics, the failure rate of gravity dams is relatively low among various types of dams.
(2) Strong adaptability to terrain and geological conditions. Gravity dams can be built in any shape of river valley.
(3) The problem of flood discharge at the hub is easy to solve. Gravity dams can be made into overflow structures, or drainage holes can be set up at different heights of the dam body. Generally, there is no need to install another spillway or drainage tunnel, and the hub layout is compact.
(4) Convenient for construction diversion. During the construction period, the dam body can be used for diversion, and generally no additional diversion tunnel is required.
(5) Convenient construction.
Disadvantages of gravity dams
(1) The cross-section size of the dam body is large, and there is a large amount of material used.
(2) The stress of the dam body is low, and the material strength cannot be fully utilized.
(3) The large contact area between the dam body and the foundation results in high uplift pressure at the dam bottom, which is unfavorable for stability.
(4) The volume of the dam body is large, and due to the hydration heat and hardening shrinkage of the concrete during the construction period, adverse temperature and shrinkage stresses will be generated. Therefore, strict temperature control measures are required when pouring concrete.
2. Arch Dam
An arch dam is a spatial shell structure fixed to the bedrock, forming a convex arch shape on the plane towards the upstream, and its arch crown profile presents a vertical or convex curve shape towards the upstream.
Working principle of arch dams
The structure of an arch dam has both arch and beam effects, and the load it bears is partially compressed towards both banks through the action of the arch, while the other part is transmitted to the bedrock at the bottom of the dam through the action of vertical beams.
Characteristics of arch dams
(1) Stable characteristics. The stability of arch dams mainly relies on the reaction force at the arch ends on both sides, unlike gravity dams that rely on self weight to maintain stability. Therefore, arch dams have high requirements for the terrain and geological conditions of the dam site, as well as strict requirements for foundation treatment.
(2) Structural characteristics. Arch dams belong to high order statically indeterminate structures, with strong overload capacity and high safety. When external loads increase or a part of the dam experiences local cracking, the arch and beam actions of the dam body will adjust themselves, causing stress redistribution in the dam body. The arch dam is an overall spatial structure, with a lightweight and resilient body. Engineering practice has shown that its seismic resistance is also strong. In addition, as an arch is a thrust structure that mainly bears axial pressure, the bending moment inside the arch is relatively small, and the stress distribution is relatively uniform, which is conducive to exerting the strength of the material. From an economic perspective, arch dams are a very superior type of dam.
(3) Load characteristics. The arch dam body does not have permanent expansion joints, and temperature changes and bedrock deformation have a significant impact on the stress of the dam body. When designing, it is necessary to consider bedrock deformation and include temperature as a main load.
Due to the thin profile and complex geometric shape of the arch dam, the construction quality, dam material strength, and anti-seepage requirements are stricter than those of gravity dams.
3. Earth-rock dam
Earth-rock dams refer to dams made of local materials such as soil and stone, and are the oldest type of dam in history. Earth-rock dams are the most widely used and rapidly developing type of dam construction in the world.
The reasons for the widespread application and development of earth rock dams
(1) It is possible to obtain materials locally and nearby, saving a large amount of cement, wood, and steel, and reducing the external transportation volume on the construction site. Almost any earth and stone material can be used to build dams.
(2) Able to adapt to various terrain, geological, and climatic conditions. Especially in harsh climates, complex engineering geological conditions, and high-intensity earthquake areas, earth-rock dams are actually the only feasible dam type.
(3) The development of large-capacity, multifunctional, and high-efficiency construction machinery has increased the compaction density of earth-rock dams, reduced the cross-section of earth-rock dams, accelerated construction progress, reduced costs, and promoted the development of high earth-rock dam construction.
(4) Due to the development of geotechnical mechanics theory, experimental methods, and computational techniques, the level of analysis and calculation has been improved, the design progress has been accelerated, and the safety and reliability of dam design have been further guaranteed.
(5) The comprehensive development of design and construction technology for supporting engineering projects such as high slopes, underground engineering structures, and high-speed water flow energy dissipation and erosion prevention of earth rock dams has also played an important promoting role in accelerating the construction and promotion of earth rock dams.
4. Rockfill dam
Rockfill dam generally refers to a type of dam constructed using methods such as throwing, filling, and rolling of stone materials. Because the rockfill is permeable, it is necessary to use materials such as soil, concrete, or asphalt concrete as impermeable materials.
Characteristics of Rockfill Dams
(1) Structural characteristics. The density of compacted rockfill is high, the shear strength is high, and the dam slope can be made relatively steep. This not only saves the filling amount of the dam, but also reduces the width of the dam bottom. The length of the water conveyance and discharge structures can be correspondingly reduced, and the layout of the hub is compact, further reducing the engineering quantity.
(2) Construction characteristics. According to the stress situation of each part of the dam body, the rockfill body can be divided into different zones, and different requirements for the stone materials and compactness of each zone can be met. The excavated stone materials during the construction of drainage structures in the hub can be fully and reasonably applied, reducing the cost. The construction of concrete faced rockfill dams is less affected by climatic conditions such as rainy season and severe cold, and can be carried out in a relatively balanced and normal manner.
(3) Operation and maintenance characteristics. The settlement deformation of the compacted rockfill is very small.
pumping station
1、 Basic components of pump station engineering
The pump station project mainly consists of pump rooms, pipelines, water inlet and outlet buildings, and substations, as shown in the figure. A unit consisting of a water pump, transmission device, and power unit is installed in the pump room, as well as auxiliary equipment and electrical equipment. The main water inlet and outlet structures include water intake and diversion facilities, as well as inlet and outlet pools (or water towers).
The pipelines of the pump station include inlet and outlet pipes. The inlet pipe connects the water source to the inlet of the water pump, while the outlet pipe is a pipeline connecting the outlet of the water pump and the outlet edge.
After the pump station is put into operation, the water flow can enter the water pump through the inlet building and inlet pipe. After being pressurized by the water pump, the water flow will be sent to the outlet pool (or water tower) or pipeline network, thereby achieving the purpose of lifting or transporting water.
2、 Layout of pump station hub
The hub layout of pumping station engineering is to comprehensively consider various conditions and requirements, determine the types of buildings, reasonably arrange their relative positions, and handle their interrelationships. The layout of the hub is mainly considered based on the tasks undertaken by the pumping station. Different pumping stations should have different arrangements for their main works, such as pump rooms, inlet and outlet pipelines, and inlet and outlet buildings.
Corresponding auxiliary buildings such as culverts and control gates should be compatible with the main project. In addition, considering the requirements for comprehensive utilization, if there are requirements for roads, shipping, and fish passage within the station area, the relationship between the layout of road bridges, ship locks, fish paths, etc. and the main project should be considered.
According to the different tasks undertaken by pumping stations, the layout of pumping station hubs generally includes several typical forms, such as irrigation pumping stations, drainage pumping stations, and drainage irrigation combination stations.
A water gate is a low head hydraulic structure that uses gates to retain water and control discharge. It is often built on the banks of rivers, canals, reservoirs, and lakes.
1、 Classification of commonly used water gates
Classification by tasks undertaken by water gates
1. Control gate: built on a river or channel to block floods, regulate water levels, or control discharge flow. The control gate located on the river channel is also known as a river blocking gate.
2. Intake gate: Built on the bank of a river, reservoir, or lake to control the flow of water. The intake gate is also known as the intake gate or canal head gate.
3. Flood diversion gate: Often built on one side of a river, it is used to discharge flood exceeding the safe discharge capacity of the downstream river into the flood diversion area (flood storage or detention area) or spillway. The flood diversion gate passes through water in both directions, and after the flood, the water is stored and discharged into the river channel from here.
4. Drainage gate: often built along the banks of rivers to remove waterlogging that is harmful to crops in inland or low-lying areas. The drainage gate is also bidirectional. When the water level of the river is higher than that of the inner lake or depression, the drainage gate mainly blocks water to prevent the river from flooding farmland or residential buildings; When the water level of the river is lower than that of the inner lake or depression, the drainage gate is mainly used for waterlogging and drainage.
5. Tidal gate: built near the estuary of the sea, closed during high tide to prevent seawater from flowing back; Opening the gate to release water at low tide has the characteristic of bidirectional water blocking. Tidal gates are similar to drainage gates, but they are operated more frequently. When the tide in the outer sea is higher than that in the inner river, close the gate to prevent seawater from flowing back into the inner river; When the tide in the open sea is lower than the river water in the inner sea, open the gate to release water.
6. Sand flushing gate (sand discharge gate): Built on a muddy river flow, it is used to discharge sediment deposited in front of the inlet gate, control gate, or channel system.
7. In addition, there are ice discharge gates and sewage gates set up to remove ice blocks, floating objects, etc.
According to the structural form of the gate chamber, it can be divided into open type, breast wall type, and culvert type, etc
1. Open type: The surface of the water flow through the gate is not obstructed, and the discharge capacity is large.
2. Breast wall type: There is a breast wall above the gate, which can reduce the force on the gate during water blocking and increase the amplitude of water blocking.
3. Culvert type: In front of the gate, there is a pressurized or non pressurized tunnel body, and the top of the tunnel is covered with filling soil. Mainly used for small water gates.
According to the size of the gate flow, it can be divided into three forms: large, medium, and small.
Large water gates with a flow rate of over 1000m3/s;
A medium sized water gate with a capacity of 100-1000m3/s;
Small sluices with a capacity of less than 100m3/s.
2、 Composition of water gates
The water gate mainly includes three parts: upstream connection section, gate chamber, and downstream connection section,
Upstream connection section: The upstream connection section is used to guide water flow smoothly into the gate chamber, protect both banks and riverbed from erosion, and together with the chamber, form an anti-seepage underground contour to ensure the anti-seepage stability of both banks and gate foundation under seepage. Generally, it includes upstream wing walls, bedding, upstream anti erosion grooves, and slope protection on both sides.
Gate chamber: It is the main part of the water gate, and its function is to control water level and flow, as well as to prevent seepage and erosion.
The structure of the gate chamber section includes: gate, gate pier, side pier (shore wall), bottom plate, breast wall, working bridge, traffic bridge, hoist, etc.
The gate is used to control the flow through the gate; The gate is placed on the bottom plate of the gate, spanning the orifice and supported by the gate pier. The gate is divided into maintenance gate and service gate.
The working gate is used for blocking water during normal operation and controlling the discharge flow;
The maintenance gate is used for temporary water retention during maintenance.
The gate pier is used to separate the bay hole and support the gate, breast wall, working bridge, and traffic bridge.
The gate pier transmits the water pressure borne by the gate, breast wall, and the water retaining capacity of the gate pier itself to the bottom plate;
The breast wall is installed above the working gate to help retain water and greatly reduce the size of the gate.
The breast wall can also be made into a movable type, and when encountering catastrophic floods, the breast wall can be opened to increase the discharge flow.
The bottom plate is the foundation of the chamber, used to transmit the weight and load of the upper structure of the chamber to the foundation. The chamber built on a soft foundation is mainly stabilized by the friction between the bottom plate and the foundation, and the bottom plate also has the functions of anti-seepage and anti-scour.
Work bridges and traffic bridges are used to install lifting equipment, operate gates, and connect cross-strait traffic.
Downstream connection section: used to eliminate the remaining energy of the water flow passing through the gate, guide the uniform diffusion of the water flow out of the gate, adjust the flow velocity distribution and slow down the flow velocity, and prevent downstream erosion after the water flow out of the gate.
Generally, it includes a stilling pool, apron, apron, downstream anti-scour channel, downstream wing walls, and slope protection on both sides.
Post time: Nov-21-2023
