Anti-silt backflow water intake structure for multi-silt river

Abstract

The application discloses a backflow water intake structure for preventing bed load in a multi-sediment river, comprising a water intake hub arranged in a water intake section of a river channel, the water intake hub comprising a flow separation dike, a water intake structure and an intake building; the flow separation dike separates the river channel into a main flow area and a backflow area at the upstream of the water intake section, and the water intake structure is arranged in the backflow area; the water intake hub takes water from the river channel through a water intake side, and the water flow direction of the water intake hub is opposite to that of the main flow area; and the water intake structure is communicated with a water diversion tunnel through the intake building. The application can separate high-sand-content water flow in flood season from water intake flow, and the high-sand-content water flow is separated into the main flow area of the river channel, and the water intake hub takes water from the backflow area with low sand content; and through the synergistic effect of backflow water intake and multi-stage sedimentation, the application can greatly improve the problem of bed load in the water diversion flow, and significantly improve the safety of the operation of the hydropower station.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering technology, and in particular to a water intake structure for preventing bedload backflow in rivers with high sediment content. Background Technology

[0002] In the power generation operation of hydropower stations, especially high-head hydropower stations, the requirements for controlling sediment passing through the turbines are extremely high. Debris from debris flows and riverbed sand in the intake section of the hydropower station may enter the water diversion and power generation system with the water flow. If bedloads such as sand and gravel enter the water diversion system of the hydropower station, it will directly cause serious wear on the turbine's flow components, affecting the safety and operating efficiency of the unit.

[0003] Currently, the most common layout for water diversion hubs is the dam-type water diversion hub, which consists of three parts: a dam and spillway, a hydroelectric power station intake on the bank, and a riverbed flushing structure. It adopts the working principle of "forward flood discharge and flushing, and lateral water intake". Under this layout, the transport direction of bedload is basically consistent with the water diversion direction. However, the sand-blocking sill set at the intake has limited protection against large-diameter bedload, which can easily cause bedload to cross the sand-blocking sill set at the intake and enter the intake. Therefore, the unit still has safety risks.

[0004] For example, Chinese invention patent CN113202065A discloses a water intake structure for rivers with high sediment content. Its technical solution includes an overflow dam and a sedimentation and intake composite system. Water flowing from the reservoir upstream of the overflow dam is filtered of sediment by the sedimentation and intake composite system before being fed into a downstream power station. By adding a sedimentation and intake composite system, the water flowing from the reservoir upstream of the overflow dam is filtered of sediment before being fed into the downstream power station. When the water contains a large amount of sediment, especially during flood season, as mountain streams carrying large amounts of sediment enter the river channel and subsequently flow into the power station's intake area, the sedimentation and intake composite system first filters and settles the sediment in the water before it is fed into the downstream power station for power generation.

[0005] The above-mentioned patent's technical solution filters the water intake flow by setting up a sedimentation and water intake composite system. Its layout is still the common dam-type layout, and the water flow direction is consistent with the water intake direction. Therefore, there is still a risk that the bedload may cross the overflow dam and enter the power plant unit. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a bedload backflow prevention water intake structure for rivers with high sediment content, which can effectively separate sediment-laden water flow from water intake flow and reduce the risk of bedload entering hydropower station units.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a backflow water intake structure for preventing bedload transport in rivers with high sediment content, comprising a water intake hub set in the water intake section of the river channel, one side of the water intake hub being the water intake side for drawing water from the river channel, and the other side of the water intake hub being the water outlet side connected to a water diversion tunnel. The water intake hub includes a diversion dike, a water intake structure, and an inlet structure. The diversion dike divides the river channel upstream of the water intake section into a main flow area and a backflow area, and the water intake structure is set in the backflow area. The water intake direction of the water intake hub drawing water from the river channel through the water intake side is opposite to the water flow direction of the main flow area. The water intake structure is connected to the water diversion tunnel through the inlet structure. This invention diverts the river flow by setting up a diversion dike in the water intake section, thereby creating a backflow zone in the intake section. This achieves the separation of the high-sediment-laden water flow during the flood season from the water intake flow. The high-sediment-laden water flow is diverted to the main flow area of ​​the river, while the water intake hub draws water from the backflow zone with lower sediment content. In the prior art, the transport direction of bedload is consistent with the water intake direction. Coarse-grained sediment is easily carried by the water flow over the sediment barrier and enters the intake. However, this invention diverts the main flow with high sediment content during the flood season to the downstream opposite bank of the river by setting up a diversion dike, while creating a stable backflow zone on the water intake bank. Only surface water with low sediment content is drawn for water intake. In addition, the water intake flow direction of this invention is opposite to the main flow direction of the river, which reduces the probability of bedload entering the water intake hub from the principle of water flow movement. This can effectively ensure the safe and stable operation of the unit and is suitable for water intake conditions in mountainous rivers with high sediment content.

[0008] As an improvement to the above scheme: the water intake structure includes a sand guide sill, a gravel sedimentation pond, a sand retaining sill, and a sedimentation pond arranged sequentially along the water intake direction of the water intake hub; the sand guide sill is located on the water intake side of the water intake hub, and the diversion dike extends from the upstream of the water intake section to connect with the sand guide sill; the bottom elevations of the sand guide sill, the gravel sedimentation pond, and the sedimentation pond decrease sequentially, and the top elevation of the sand retaining sill is higher than the bottom elevation of the gravel sedimentation pond. This invention defines the layout of the water intake structure to form a multi-level protection structure for bedload, achieving a progressive purification effect of guiding sand, settling gravel, intercepting sand, and settling sand. By connecting the dike and the sand guide, the invention achieves continuous guidance of river flow, preventing high-sediment-laden water from the main flow zone from entering the backflow zone. Through a gradient layout that limits the bottom elevation of the sand guide, gravel settling pond, and sedimentation pond to decrease sequentially, and the high-level interception of the sand interception embankment, a water intake structure is formed that can gradually decelerate bedload and perform graded sand control. After entering the water intake structure, the flow velocity of the water will gradually decrease, enabling stratified settling and interception of large-diameter bedload, residual coarse-grained silt, and fine-grained suspended sediment, effectively improving the protection effect of bedload in the water intake flow.

[0009] As an improvement to the above scheme: the guide embankment is set across the backflow zone of the river channel; the top elevation of the guide embankment is more than 3m higher than the average elevation of the riverbed, and the top elevation of the guide embankment is higher than the thickness of the bedload transport layer below the design flood level. This invention, by limiting the arrangement of the guide embankment, enables it to cover the water flow cross-section on the intake side, preventing high-sediment-laden water from the main flow zone from bypassing the intake structure. Simultaneously, by limiting the elevation of the guide embankment, this invention can block the bedload transport channels within the river channel. When the flood season water flow carries bedload along the riverbed, it can be completely blocked by the guide embankment and guided downstream, effectively preventing large-diameter bedload from entering the intake structure.

[0010] As an improvement to the above scheme: the guide sill located on both sides of the water intake flow at the water intake hub is inclined, and the thickness of the guide sill gradually increases from top to bottom. This invention, by defining the structural form of the guide sill, utilizes the inclined sides to guide bedload in the upstream and downstream water flows in different directions. While preventing high-sediment-laden water flow in the main flow zone from crossing the guide sill, it also promotes the sliding of bedload in the return flow zone along the inclined surface into the sedimentation tank. Simultaneously, the inclined surface of the guide sill also smoothly guides the upstream and downstream water flows, reducing the probability of turbulence, eddies, and localized scouring, effectively stabilizing the water flow in the water intake area and preventing sediment from being stirred up due to water flow disturbance. Furthermore, the structural feature of the guide sill's thickness increasing from top to bottom effectively improves the overall structural strength of the guide sill, enabling it to withstand the long-term scouring of high-speed water flow and sediment particles during the flood season, thus extending the service life of the guide sill.

[0011] As an improvement to the above scheme: the bottom elevation of the sedimentation tank is lower than the average elevation of the riverbed; the bottom of the sedimentation tank is flat, and there is a vertical transition between the sedimentation tank and the sand-trapping embankment. This invention, by limiting the elevation and structural form of the sedimentation tank, can create an independent settling space downstream of the sand-trapping embankment, significantly expanding the cross-sectional area of ​​the intake water flow and rapidly reducing the flow velocity of the intake water flow. This ensures that the flow velocity within the tank is lower than the initiation velocity of the target particle size of the bedload, guaranteeing rapid settling of the bedload. Simultaneously, the flat-bottomed structure of the sedimentation tank avoids localized turbulence, ensuring uniform bedload settling and preventing localized accumulation of bedload within the tank. Furthermore, by limiting the vertical transition between the sedimentation tank and the sand-trapping embankment, this invention prevents bedload from flowing across the embankment with the water flow, preventing settled bedload from being re-lifted by the water flow and entering subsequent tank chambers.

[0012] As an improvement to the above solution: the top elevation of the sand-retaining embankment is more than 5m higher than the bottom elevation of the sedimentation tank; the sand-retaining embankment and the sedimentation tank have a sloping transition. This invention, by limiting the top elevation of the sand-retaining embankment, can cover the water flow depth of the sedimentation tank, effectively preventing settled bedload from crossing the embankment under the action of water flow. Simultaneously, by limiting the sloping transition between the sand-retaining embankment and the sedimentation tank, this invention can achieve a smooth connection of water flow between the two, avoiding abrupt changes in cross-section that cause water flow turbulence. This ensures both the sand-retaining effect and stabilizes the downstream flow field, creating stable water flow conditions for the sedimentation of suspended matter in the sedimentation tank, effectively improving the overall water purification effect and efficiency.

[0013] As an improvement to the above solution: both the gravel settling tank and the sand settling tank are equipped with a sand discharge structure extending to the outside of the water intake structure; the sand discharge structure is a sand discharge hole or a sand flushing channel. This invention, by configuring a sand discharge structure for the gravel settling tank and the sand settling tank, enables the periodic cleaning of the sediment deposited in the gravel settling tank and the sand settling tank.

[0014] As an improvement to the above scheme, the diversion dike is an arc-shaped dike structure with its central section curving and bulging towards the main flow area of ​​the river. The diversion dike in this invention can adopt a straight dike structure or an arc-shaped dike structure, with the arc-shaped dike structure being the preferred option. Using an arc-shaped dike structure as the diversion dike conforms to the natural flow direction of the main river channel, providing smooth guidance and diversion for the high-speed main flow during the flood season, resulting in higher diversion efficiency. It also effectively reduces the impact force of the high-speed water flow, decreases the scouring force on the diversion dike, and improves the structural stability of the diversion dike. Furthermore, it can regulate the backflow area, making the backflow on the local bank more uniform and stable, avoiding sediment entrapment problems caused by turbulent backflow. As an improvement to the above scheme: the water intake structure includes a trash rack section, an intake gate chamber section, a bottom plate, an emergency gate, and a maintenance gate; the trash rack section and the intake gate chamber section are arranged sequentially along the water intake flow direction of the water intake hub; the bottom plate is connected to the sedimentation tank, and the bottom elevation of the trash rack section is higher than the bottom elevation of the sedimentation tank; the emergency gate and the maintenance gate are located at the lower part of the intake gate chamber section, and multiple ventilation holes are provided at the upper part of the intake gate chamber section.

[0015] As an improvement to the above scheme: the water diversion tunnel includes a transition section and a standard section; the transition section connects the intake gate chamber section and the standard section.

[0016] The beneficial effects of this invention are as follows: By setting up a diversion dike in the water intake section of the river to divert the river flow, a backflow zone is formed in the water intake section, thus separating the high-sediment-laden water flow during the flood season from the water intake flow. The high-sediment-laden water flow is diverted to the main flow area of ​​the river, and the water intake hub draws water from the backflow zone with lower sediment content. In the prior art, the transport direction of bedload is consistent with the water diversion direction, and coarse-grained sediment is easily carried by the water flow over the sediment barrier and enters the intake. However, this invention uses a diversion dike to divert the high-sediment-laden main flow during the flood season. The water flow is diverted downstream to the opposite bank of the river, while a stable backflow zone is formed on the intake bank. Only surface water with low sediment content is extracted for water intake. Furthermore, the water intake flow direction of this invention is opposite to the mainstream flow direction of the river, which reduces the probability of bedload entering the water intake hub from the perspective of water flow movement principles. This can effectively ensure the safe and stable operation of the unit and is suitable for water intake conditions in mountainous rivers with high sediment content. Through the synergistic effect of backflow water intake and multi-stage sedimentation, this invention can significantly improve the bedload problem in the water intake flow and significantly enhance the safety of hydropower station operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the planar layout of the present invention; Figure 2 for Figure 1 Sectional view at point AA.

[0018] The markings on the map are as follows: 100-River channel, 200-Diversion dike, 310-Sedimentation embankment, 320-Sedimentation basin, 330-Sedimentation embankment, 340-Sedimentation basin, 400-Intake structure, 410-Trash screen section, 420-Intake gate chamber section, 430-Bottom slab, 440-Emergency gate, 450-Maintenance gate, 460-Ventilation hole, 500-Water diversion tunnel, 510-Water diversion tunnel transition section, 520-Water diversion tunnel standard section, 610-River flow direction, 620-Water intake flow direction. Detailed Implementation

[0019] To facilitate understanding of the present invention, the invention will be further described below with reference to the accompanying drawings.

[0020] In the description of this invention, it should be noted that the terms "front", "rear", "left", "right", "up", "down", "inner", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0021] like Figure 1 and Figure 2As shown, the proposed invention discloses a backflow intake structure for preventing bedload transport in sediment-laden rivers, comprising an intake hub and a water diversion tunnel 500. The intake hub includes a dike 200, an intake structure, and an inlet structure 400. The intake hub is located in the intake section of the river channel 100. One side of the intake hub is the intake side for drawing water from the river channel 100, and the other side is the outlet side connected to the water diversion tunnel 500. The intake structure is connected to the water diversion tunnel 500 via the inlet structure 400. In this invention, the intake hub guides and diverts the water flow within the river channel 100 through the dike 200, diverting the main current with high sediment content during the flood season downstream to form a main current zone on the opposite bank, and forming a backflow zone with lower sediment content on the local bank. The intake structure located in the backflow zone directly draws water from the surface clear water of the backflow zone. After the water is drawn and graded for sedimentation, it is transported to the hydropower station generating units through the water diversion tunnel 500.

[0022] like Figure 1 As shown, in this invention, after the river channel 100 is diverted by the diversion dike 200, the water intake structure draws water from the downstream of the river channel 100, and the water intake flow direction 620 is opposite to the river channel flow direction 610. The diversion dike 200 is configured as an arc-shaped dike structure with its middle part curving and protruding towards the main flow area of ​​the river channel 100, so as to improve the diversion and guiding effect of the diversion dike 200 on the water flow in the river channel 100, which is conducive to diverting the main flow with high sediment content to the opposite bank.

[0023] Specifically, such as Figure 1 and Figure 2 As shown, the water intake structure used in this invention includes a sand guide sill 310, a gravel settling pond 320, a sand retaining sill 330, and a sedimentation pond 340. The sand guide sill 310 is located on the water intake side of the water intake hub, and the diversion dike 200 extends from the upstream of the water intake section to connect with the sand guide sill 310. The bottom elevations of the sand guide sill 310, the gravel settling pond 320, and the sedimentation pond 340 decrease sequentially, thereby enabling the water intake structure to achieve multi-stage sedimentation of the water intake flow. The top elevation of the sand retaining sill 330 is higher than the bottom elevation of the gravel settling pond 320.

[0024] like Figure 2As shown, in this invention, a guide embankment 310 is set across the backflow zone of the river channel 100, and the top elevation of the guide embankment 310 is limited to be more than 3m higher than the average elevation of the riverbed of the river channel 100. The top elevation of the guide embankment 310 is also higher than the thickness of the bedload transport layer below the design flood level. The guide embankment 310 and the end of the dike 200 are connected to form a smooth connection. By setting the guide embankment 310, this invention can further guide the high sediment load of the main flow to the downstream of the river channel 100, so as to prevent the backflow of the main flow into the sedimentation basin 320 behind. Furthermore, the present invention optimizes the structure of the sand guide sill 310 by setting both sides of the sand guide sill 310 on the water intake flow direction at the water intake hub as inclined surfaces, and limiting the thickness of the sand guide sill 310 to gradually increase from the top to the bottom, so that the sand guide sill 310 forms a longitudinal cross-sectional shape that is narrow at the top and wide at the bottom. This allows the two sides of the sand guide sill 310 to guide the bedload in the upstream and downstream water flows in different directions, and improves the scour resistance and overall strength of the sand guide sill 310.

[0025] like Figure 2 As shown, in this invention, the bottom of the sedimentation tank 320 is set as a plane. The sedimentation tank 320 and the sand-trapping embankment 330 are connected by a vertical step structure to form a vertical transition, and the bottom elevation of the sedimentation tank 320 is limited to be lower than the average elevation of the riverbed by 100 meters. This invention places the sedimentation tank 320 downstream of the sand-trapping embankment 310. The sedimentation tank 320 reduces the flow velocity of the intake water, making it lower than the starting velocity of the target particle size of the bedload. The reduced flow velocity prevents the bedload of these target particle sizes from continuing to move downstream, thus causing larger bedload particles, including gravel and small pebbles, to settle in the sedimentation tank 320. A sand-discharging structure can be installed in the sedimentation tank 320, using sand-discharging holes or flushing channels. This structure allows the bedload settled in the sedimentation tank 320 to be discharged outside the water intake structure, achieving periodic removal of the bedload settled in the sedimentation tank 320.

[0026] like Figure 2As shown, in this invention, a sand-retaining embankment 330 is set at the end of the sedimentation tank 320. The height of the sand-retaining embankment 330 is set according to the initiation velocity of the sediment at the target particle size to ensure that the settled sediment will not be restarted when the water intake flows through the sand-retaining embankment 330. The top elevation of the sand-retaining embankment 330 is at least 5m higher than the bottom elevation of the sedimentation tank 320. The sand-retaining embankment 330 and the sedimentation tank 340 are connected by a slope to form a slope transition. The sedimentation tank 340 is set downstream of the sand-retaining embankment 330. The bottom elevation of the sedimentation tank 340 is lower than the bottom elevation of the sedimentation tank 320. The sedimentation tank 340 extends to connect with the inlet structure 400. This invention uses a sand-blocking sill 330 to block the settled sediment in the gravel settling tank 320, preventing the bedload already settled in the settling tank 320 from being reactivated by the water intake flow and entering subsequent tank chambers. The invention further reduces the flow velocity of the water intake through the settling tank 340, allowing smaller-diameter bedloads, i.e., suspended sediment, to settle within the settling tank 340. A sand discharge structure, employing sand discharge holes or flushing channels, can be installed in the settling tank 340 to discharge the settled bedload outside the water intake structure, thus achieving periodic removal of the settled bedload from the settling tank 340.

[0027] like Figure 1 and Figure 2 As shown, the intake structure 400 of this invention includes a trash rack section 410, an intake gate chamber section 420, a base plate 430, an emergency gate 440, and a maintenance gate 450. The trash rack section 410 and the intake gate chamber section 420 are arranged sequentially along the water intake direction of the water intake hub. The base plate 430 is connected to the sedimentation tank 340, and the bottom elevation of the trash rack section 410 is higher than the bottom elevation of the sedimentation tank 340. The emergency gate 440 and the maintenance gate 450 are located at the lower part of the intake gate chamber section 420, and the upper part of the intake gate chamber section 420 is provided with multiple ventilation holes 460. The water diversion tunnel 500 includes a water diversion tunnel transition section 510 and a water diversion tunnel standard section 520. The water diversion tunnel transition section 510 connects the intake gate chamber section 420 and the water diversion tunnel standard section 520.

[0028] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water intake structure for preventing bedload backflow in sediment-laden rivers, comprising a water intake hub located in the water intake section of a river channel (100), one side of the water intake hub being a water intake side for drawing water from the river channel (100), and the other side of the water intake hub being a water outlet side connected to a water diversion tunnel (500), characterized in that: The water intake hub includes a diversion dike (200), a water intake structure, and an inlet structure (400); the diversion dike (200) divides the river channel (100) into a main flow area and a backflow area upstream of the water intake section, and the water intake structure is located in the backflow area; the water intake hub draws water from the river channel (100) through the water intake side in the opposite direction to the water flow direction of the main flow area; the water intake structure is connected to the water diversion tunnel (500) through the inlet structure (400).

2. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 1, characterized in that: The water intake structure includes a sand guide sill (310), a gravel sedimentation pond (320), a sand retaining sill (330), and a sedimentation pond (340) arranged sequentially along the water intake direction of the water intake hub. The sand guide sill (310) is located on the water intake side of the water intake hub, and the diversion dike (200) extends from the upstream of the water intake section to connect with the sand guide sill (310). The bottom elevations of the sand guide sill (310), the gravel sedimentation pond (320), and the sedimentation pond (340) decrease sequentially, and the top elevation of the sand retaining sill (330) is higher than the bottom elevation of the gravel sedimentation pond (320).

3. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 2, characterized in that: The sand guide (310) is set across the backflow zone of the river channel (100); the top elevation of the sand guide (310) is more than 3m higher than the average elevation of the riverbed of the river channel (100), and the top elevation of the sand guide (310) is higher than the thickness of the bedload transport layer below the design flood level.

4. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 3, characterized in that: The sand guide (310) is located on both sides of the water intake flow direction of the water intake hub, and the thickness of the sand guide (310) gradually increases from the top to the bottom.

5. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 2, characterized in that: The bottom elevation of the sedimentation basin (320) is lower than the average elevation of the riverbed of the river channel (100); the bottom of the sedimentation basin (320) is flat, and there is a vertical transition between the sedimentation basin (320) and the sand-blocking embankment (330).

6. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 2, characterized in that: The top elevation of the sand-blocking embankment (330) is more than 5m higher than the bottom elevation of the sedimentation pond (320); the sand-blocking embankment (330) and the sedimentation pond (340) are connected by a slope.

7. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 2, characterized in that: Both the gravel settling tank (320) and the sand settling tank (340) are provided with sand discharge structures extending to the outside of the water intake structure; the sand discharge structures are sand discharge holes or sand flushing corridors.

8. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 1, characterized in that: The dike (200) is an arc-shaped dike structure with a curved protrusion in the middle facing the main channel (100) of the river.

9. The anti-dumping sediment recirculation water intake structure for sediment-laden rivers as described in claim 2, characterized in that: The intake structure (400) includes a trash rack section (410), an intake gate chamber section (420), a base plate (430), an emergency gate (440), and a maintenance gate (450); the trash rack section (410) and the intake gate chamber section (420) are arranged sequentially along the water intake direction of the water intake hub; the base plate (430) is connected to the sedimentation tank (340), and the bottom elevation of the trash rack section (410) is higher than the bottom elevation of the sedimentation tank (340); the emergency gate (440) and the maintenance gate (450) are located at the lower part of the intake gate chamber section (420), and the upper part of the intake gate chamber section (420) is provided with multiple ventilation holes (460).

10. The anti-bed sediment backflow water intake structure for sediment-laden rivers as described in claim 9, characterized in that: The water diversion tunnel (500) includes a water diversion tunnel transition section (510) and a water diversion tunnel standard section (520); the water diversion tunnel transition section (510) is connected between the water intake gate chamber section (420) and the water diversion tunnel standard section (520).

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