A sand blocking ridge for preventing the deposition of bed load sediment at the tail water outlet of a hydropower station
By setting up an arc-shaped transition section and a straight wall section of sand-retaining embankment at the tailrace outlet of the hydropower station, the problem of sediment accumulation at the tailrace outlet was solved, ensuring the safe and stable operation and economic benefits of the power station, and reducing construction costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SICHUAN UNIV
- Filing Date
- 2026-04-29
- Publication Date
- 2026-06-09
AI Technical Summary
Siltation at the tailrace outlet of the hydropower station has caused the tailrace water level to rise, affecting the safe and stable operation and economic benefits of the hydropower station. The existing silt-trapping facilities have failed to effectively solve this problem.
At the confluence of the power station's tailrace outlet and the river channel, a sand-retaining embankment with an arc-shaped transition section and a straight wall section is set up. The starting end of the sand-retaining embankment is smoothly connected to the riverbank, and the straight wall section extends along the direction of water flow. The length and height of the sand-retaining embankment are reasonably controlled to ensure smooth water flow and avoid siltation.
It effectively prevents sediment from entering the tailrace outlet, prevents siltation, ensures the normal operation of the power station, reduces construction costs, improves the impact capacity of water flow, and reduces sediment accumulation.
Smart Images
Figure CN122169477A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water conservancy and hydropower engineering, and specifically relates to a sand-blocking facility to prevent the deposition of bedload sediment at the tailrace outlet of a hydropower station. Background Technology
[0002] During the operation of hydropower projects, when the sediment content in the water is high and the tailrace outlet is located in a sediment deposition area, a large amount of bedload sediment will accumulate at the tailrace outlet, causing the tailrace level to rise and seriously affecting the safe and stable operation and economic benefits of the hydropower station. Currently, the solutions to the sediment deposition problem at the tailrace outlet can be mainly divided into two categories: active sediment prevention and passive dredging. The first is to use engineering structural design to block or guide bedload sediment away from the tailrace outlet; the second is to remove the deposited sediment manually or mechanically. Although existing methods can alleviate the sediment deposition problem to some extent, they all have significant limitations. Therefore, a more efficient, reliable, and economical sediment prevention solution is urgently needed. Existing sediment barriers are all located at the upstream water intake, generally built upstream of the reservoir inlet, at the water diversion hub entrance, or downstream of flash flood and debris flow gullies. These methods largely ignore or fail to recognize the sediment deposition risks and problems at some project tailrace outlets. Summary of the Invention
[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a sand-blocking dam to prevent the accumulation of bedload sediment at the tailrace outlet of a hydropower station, thereby preventing sediment from entering the tailrace outlet and causing siltation, and ensuring the normal operation of the power station.
[0004] The present invention provides a sediment-blocking embankment for preventing the deposition of silt from the tailrace outlet of a hydropower station. This embankment is installed in the river channel at the confluence of the tailrace outlet and the river channel. It includes an arc-shaped transition section and a straight wall section. The upstream end of the arc-shaped transition section smoothly connects to the upstream bank wall of the river channel to avoid obstructing the water flow. The downstream end of the arc-shaped transition section smoothly connects to the straight wall section. The straight wall section extends along the river flow direction and is erected in the river channel at the confluence of the tailrace outlet and the river channel. A tailrace flow passage is reserved between the downstream end of the straight wall section and the bank wall.
[0005] In the above technical solution of the present invention, the overall length of the sand-retaining sill is determined based on the overall length L4 of the tailrace outlet of the power station. The vertical distances between the starting end and the downstream end of the straight wall section of the sand-retaining sill and the tailrace outlet of the power station are L1 and L2, respectively. The cross-sectional length of the tailrace flow channel reserved between the downstream end of the straight wall section and the bank wall is L3 (i.e., the vertical distance between the end of the sand-retaining sill and the bank wall). The values of L1, L2, and L3 directly affect the flow capacity of the water in the sill. If they are too short, the water level will rise, directly affecting the power generation efficiency of the power station. This is the primary problem to be avoided by the sand-retaining sill. If they are too large, the construction position of the sand-retaining sill will deviate from the foundation and the connection with the slope will become more difficult, increasing construction costs and reducing the water-blocking capacity. By controlling the distances of L1, L2, and L3, the cross-sectional area of the water flow in the sand-retaining sill is controlled, thereby minimizing the impact of the sand-retaining sill on the tailrace elevation of the power station.
[0006] Furthermore, for the aforementioned sand-trapping embankment, the vertical distance L1 between the starting end of the straight wall section and the tailrace outlet of the power station is (0.8~1.5)H, where H is the height of the sand-trapping embankment.
[0007] Furthermore, the height H of the aforementioned silt-retaining sill is influenced by both the tailwater elevation h1 within the sill and the highest siltation level h2 outside the sill. This ensures that silt does not overflow the sill while minimizing its impact on the tailwater. Preferably, the silt-retaining sill height H = (0.8~1.5)h1, where h1 is the tailwater elevation of the power station, and the silt-retaining sill elevation is not lower than h2, where h2 is the highest siltation level outside the sill.
[0008] Furthermore, for the aforementioned sand-trapping embankment, the vertical distance from the downstream end of the straight wall section to the tailrace outlet of the power station is L2, where L2 = L1 + 0.2L1(n-1), and n is the number of tailrace outlets of the power station. Since the outflow rate of the power station at location L2 downstream is greater than that at location L1, the value of L2 must be greater than L1 to increase the flow capacity. Furthermore, the downstream end of the aforementioned sand-blocking embankment (i.e., the end of the sand-blocking embankment) and the length of the tailwater flow channel reserved in the side wall are L3, where L3 = (1~1.5)L2.
[0009] Furthermore, in the aforementioned sand-retaining embankment, the arc-shaped transition section is a circular arc with a radius of R. The size of R is such that the river water flows smoothly over the sand-retaining embankment, avoiding direct impact of the water flow on the embankment, which could cause the water to overflow and accumulate sediment within the embankment. Preferably, the radius of the circular arc section R = (2.5~3.5)L1.
[0010] Furthermore, the overall length L of the straight wall section of the aforementioned sand-retaining embankment satisfies L=(0.5~1)L4, where L4 is the overall length of the tailrace outlet of the power station.
[0011] The present invention also provides a method for preventing the deposition of bedload sediment at the tailwater outlet of a hydropower station, which involves setting up a sediment-blocking embankment in the river channel at the confluence of the tailwater outlet of the power station and the river channel. The structure of the sediment-blocking embankment is as described above for preventing the deposition of bedload sediment at the tailwater outlet of a hydropower station.
[0012] The sand-retaining embankment of this invention features an arc-shaped starting end that extends along the sidewall. The radius R of this arc allows for a smoother flow of water across the embankment, preventing direct impact and siltation. The distances L1 and L2 between the starting and downstream ends of the straight-wall section of the embankment and the power station outlet narrow the cross-sectional area of the intermediate river channel, increasing the flow velocity and enhancing the impact of the water flow on silt in the middle channel. This reduces the silt elevation within the channel and prevents silt from overflowing the embankment. When siltation occurs within the embankment, its presence compresses the tailrace, increasing its velocity and allowing the tailrace to flush away the silt.
[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a sediment-trapping embankment installed at the tailrace outlet of a power station. This embankment effectively blocks bedload sediment, preventing it from accumulating at the tailrace outlet and ensuring the normal operation of the power station. Existing sediment-trapping embankments are typically installed upstream of the water intake, usually at the reservoir inlet, the entrance to a water diversion hub, or downstream of a flash flood / debris flow gully. These embankments largely ignore or fail to address the sedimentation risks and problems that may arise at the tailrace outlet of some engineering projects.
[0014] This sediment trap provides a preventative and solution to the risks and problems associated with the accumulation of large amounts of bedload sediment at the tailrace outlet of a power station, filling a gap in existing technologies. Attached Figure Description
[0015] Figure 1 A schematic diagram of sediment accumulation at the tailrace outlet of the power station on the left bank of the river before the installation of the sand-blocking sill of this invention (the water flow direction is perpendicular to the paper). Figure 2 This is a schematic diagram of the sand-trapping embankment arrangement at the tailrace outlet of the power station on the left bank of the river in Example 1. Figure 3 This is a schematic diagram of siltation at the tailrace outlet of the power station on the left bank of the river in Example 1 after the installation of the silt retaining wall; Figure 4 This is a top-down view of the water flow pattern at the tailrace outlet of the power station on the left bank of the river in Example 1 after the installation of the sand-trapping barrier.
[0016] Legend: 1- Sand-blocking embankment; 2- Power station tailrace outlet; 3- Bank walls on both banks; 4- Right bank slope; 5- Gate; 6- Natural riverbed; 7- Siltation. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0018] Example 1 This embodiment uses a sediment-trapping sill to prevent siltation at the tailrace outlet of a hydropower station. It is located on the left bank of the river at the confluence of the power station's tailrace outlet and the river channel, and its structure is as follows: Figure 2 As shown, the structure includes an arc-shaped transition section and a straight wall section. The upstream end of the arc-shaped transition section smoothly connects to the upstream bank wall of the river channel to avoid obstructing the water flow. The downstream end of the arc-shaped transition section smoothly connects to the straight wall section (i.e., the tangent at the connection point is on the same straight line as the straight wall section). The arc-shaped transition section is a circular arc with a radius of R. The size of R is sufficient to allow the river water to flow smoothly over the sediment trap, avoiding direct impact of the water flow on the sediment trap, which could cause the water to overflow the sediment trap and accumulate sediment inside. The straight wall section extends along the direction of the river flow and is arranged in the direction of the river flow. It is erected in the river channel at the confluence of the power station's tailrace outlet and the river channel. A tailrace passage is reserved between the downstream end of the straight wall section and the bank wall.
[0019] The overall length of the sand-retaining sill is determined based on the overall length L4 of the power station's tailrace outlet. The vertical distances between the starting end and the downstream end of the straight wall section of the sand-retaining sill and the power station's tailrace outlet are L1 and L2, respectively. The cross-sectional length of the tailrace flow channel reserved between the downstream end of the straight wall section and the bank sidewall is L3 (i.e., the vertical distance between the end of the sand-retaining sill and the bank sidewall). The values of L1, L2, and L3 directly affect the flow capacity of the water within the sill. If they are too short, the water level will rise, directly affecting the power station's power generation efficiency, which is the primary problem to avoid with this sand-retaining sill. If they are too large, the construction location of the sand-retaining sill will deviate from the foundation and the connection with the slope will become more difficult, increasing construction costs and reducing the water-retaining capacity. This embodiment, through specific engineering conditions, reasonably controls the distances of L1, L2, and L3 to control the cross-sectional area of the water flow within the sand-retaining sill, thereby minimizing the impact of the sand-retaining sill on the power station's tailrace elevation. The height of the sand-blocking embankment is H. The height of the sand-blocking embankment is affected by the tailwater elevation h1 inside the embankment and the siltation height h2 outside the embankment. While ensuring that the silt will not overflow the embankment, the impact of the embankment on the tailwater is minimized.
[0020] Through extensive experimental research, it was finally determined that in this embodiment, the tailwater elevation h1=45m, the outer silt height h2=35m, the radius of the arc segment R=100m, the vertical distance L1=30m between the starting end of the straight wall segment and the tailwater outlet of the power station, the vertical distance L2=42m between the downstream end of the straight wall segment and the tailwater outlet of the power station, the cross-sectional length L3=42m between the downstream end of the straight wall segment (i.e., the end of the sand-blocking sill) and the tailwater flow channel reserved in the side wall, the overall length L4=159m of the tailwater outlet of the power station, the number of tailwater outlets of the power station n=3, the height of the sand-blocking sill H=40m, and the overall length of the sand-blocking sill L=101m.
[0021] The aforementioned sand-retaining embankment, situated in the river, features an arc-shaped starting end that extends along the sidewall. The radius R of this arc allows for a smoother flow of water across the embankment, preventing direct impact and siltation. The carefully designed distances L1 and L2 between the starting and downstream ends of the embankment's straight wall section and the power station outlet narrow the cross-sectional area of the intermediate river channel, increasing the flow velocity and enhancing the impact on siltation. This reduces the siltation elevation within the channel, preventing silt from overflowing the embankment. When siltation occurs within the embankment, its presence compresses the tailrace, increasing its velocity and allowing it to flush away the silt. Figure 4 The diagram shows the flow pattern inside and outside the sediment trap after the installation of this embodiment. It can be seen that the sediment trap prevents sediment from the river outside from accumulating at the tailwater outlet, and no significant tailwater elevation is observed. Figure 1 The image shows the topographic map of siltation under flood discharge conditions before the installation of the silt barrier. As clearly shown in the image, severe siltation has formed in front of the power station's outlet gate, causing the power station to be unable to operate normally. Figure 3 The image shows the siltation topography after the installation of the silt barrier. The amount of silt in front of the gate is significantly reduced after the installation of the silt barrier, indicating that the silt barrier designed in this invention can prevent sediment from entering the tailrace outlet of the power station and forming silt, thereby ensuring the normal operation of the power station.
Claims
1. A sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station, characterized in that, It is located in the river channel at the confluence of the power station's tailwater outlet and the river channel, and consists of an arc-shaped transition section and a straight wall section. The upstream end of the arc-shaped transition section is smoothly connected to the side wall of the upstream river channel, and the downstream end is smoothly connected to the straight wall section. The straight wall section extends along the direction of the river flow, and the downstream end of the straight wall section has a tailwater passage reserved with the side wall of the river channel.
2. The sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station according to claim 1, characterized in that, The vertical distance between the starting end of the straight wall section and the tailrace outlet of the power station is L1, where L1 = (0.8~1.5)H, and H is the height of the sand-trapping sill.
3. The sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station according to claim 1, characterized in that, The height of the sand-retaining embankment is H, where H = (0.8~1.5)h1, h1 is the elevation of the tailwater of the power station, and the elevation of the sand-retaining embankment is not lower than h2, where h2 is the highest elevation of silt outside the embankment.
4. The sediment-trapping sill for preventing siltation of bedload sediment at the tailrace outlet of a hydropower station according to claim 2 or 3, characterized in that, The vertical distance from the downstream end of the straight wall section to the tailwater outlet of the power station is L2, where L2 = L1 + 0.2L1(n-1), and n is the number of tailwater outlets of the power station.
5. The sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station according to claim 4, characterized in that, The length of the tailwater flow channel reserved between the downstream end of the straight wall section (i.e. the end of the sand-blocking embankment) and the side wall is L3, where L3 = (1~1.5)L2.
6. The sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station according to claim 4, characterized in that, The arc-shaped transition section is a circular arc with a radius of R, where R = (2.5~3.5)L1.
7. The sediment-trapping sill for preventing siltation at the tailrace outlet of a hydropower station according to claim 1, characterized in that, The overall length L of the straight wall section of the sand-retaining embankment satisfies the length L = (0.5~1)L4, where L4 is the overall length of the tailrace outlet of the power station.
8. A method for preventing bedload sediment deposition at the tailrace outlet of a hydropower station, characterized in that, A sand-blocking embankment is installed in the river channel at the confluence of the power station's tailwater outlet and the river channel. The structure of the sand-blocking embankment is as described in claims 1 to 8, which is a sand-blocking embankment to prevent the deposition of bedload sediment at the tailwater outlet of the hydropower station.