Pump station front pool dendritic groove sand flushing structure and design method

Abstract

The application discloses a pump station front pool tree-shaped groove sand washing structure and a design method. The tree-shaped groove sand washing structure mainly comprises a plane and a longitudinal diffusion pump station front pool, a front pool tree-shaped groove and a terminal half-hemispherical funnel-shaped sand collecting groove. The diffusion-shaped front pool can increase the water section area, thereby reducing the water flow velocity, so that the silt can be deposited in the front pool and the sand collecting groove. When the silt is deposited to a certain degree, the silt early warning device in the sand collecting groove is triggered, and the deposited silt is efficiently cleaned. The application also provides a design method of the pump station front pool tree-shaped groove structure. By designing the tree-shaped groove at the bottom of the pump station front pool, the silt can be automatically deposited when the pump station is running, and a small amount of water is used to clean the bottom of the pump station front pool when the pump station is stopped, so that the deposited silt in the front pool is collected and discharged by an automatic machine. The method can avoid the deposited silt in front of the pump from blocking the water pump water inlet, reduce the pump station blade abrasion, prolong the service life of the pump station unit, and guarantee the water supply and delivery safety.

Description

Technical Field

[0001] This invention relates to the field of sand flushing engineering technology, specifically to a tree-like trench sand flushing structure and design method for a pump station forebay. Background Technology

[0002] Most rivers in my country have high sediment content, and sediment accumulation in the forebay of water intake pumping stations is an unavoidable and urgent problem that needs to be solved in the operation and management of pumping stations in rivers with high sediment content. The problems caused by sediment accumulation mainly include two aspects: First, sediment accumulation will deteriorate the water flow pattern in the forebay, worsen the water intake conditions of the pumping station, and reduce the efficiency of the pumping station. At the same time, the deterioration of the flow pattern will further aggravate the sediment accumulation in the forebay, and even block the pumping station inlet; Second, a large amount of sediment particles entering the pumping station will wear down the pump unit blades, affecting the safety and lifespan of the unit.

[0003] Large amounts of accumulated silt require periodic pump shutdowns for cleaning. Traditional methods mostly involve manual dredging or mechanical removal. However, both manual and mechanical methods are time-consuming and resource-intensive, and the dredging efficiency is low. Therefore, a forebay structure for water intake pump stations is needed that allows silt to settle automatically in the forebay and can automatically clean, collect, and discharge the silt within the forebay using a small amount of water in a short time. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a tree-shaped trench sand flushing structure and design method for a pump station forebay. It adopts the principle of "water constriction for sand flushing", which uses the trench to reduce the cross-section of the water flow, increase the water flow velocity, and enhance the sand flushing capacity of the water flow. The water flow carries the silt into the sand collection ditch and is automatically cleaned by the mud pump, which can greatly save manpower and material resources and improve dredging efficiency.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A tree-shaped trench flushing structure for a pump station forebay includes an inlet, a forebay, a tree-shaped trench, and a sand collection ditch; the inlet and the sand collection ditch are connected through the forebay, with the inlet located upstream and the sand collection ditch located downstream.

[0007] Vertical water-binding walls are installed on both sides of the forebay, and tree-shaped trenches are installed at the bottom of the forebay.

[0008] The forebay has a slope from upstream to downstream, and the bottom width of the forebay gradually spreads out to both sides from upstream to downstream.

[0009] The downstream section of the sand collection ditch connects to the pumping station unit, which is used to extract water from the forebay.

[0010] More preferably, the inlet is arranged horizontally, and the inlet is equipped with a maintenance gate and a working gate in sequence, which are used to shut off and open the inlet during maintenance and normal operation.

[0011] More preferably, the inner side of the water-binding wall is lined with concrete, and the arrangement is in the form of a folded slope that spreads to both sides, with the diffusion trend being the same as the original side wall line; the water-binding wall is composed of alternating diffusion sections and vertical sections, which are connected by an arc surface to make the water flow smoother.

[0012] More preferably, the tree-shaped trench is arranged at the bottom of the forebay, with the starting elevation of the tree-shaped trench being lower than that of the horizontal section of the inlet, and connected to the inlet by a slope.

[0013] More preferably, the bottom surface of the tree-shaped trench excavated at the bottom of the forebay is parallel to the original slope line of the forebay bottom; the tree-shaped trench has the same outward diffusion trend as the forebay and the water-binding wall, and the tree-shaped trench branches downstream at intervals.

[0014] More preferably, after excavating a tree-shaped trench at the bottom of the forebay, the unexcavated portion protrudes to form a water-binding mound. The water-binding mound is high in the middle and low on both sides, and the top has a slope that slopes from the central axis to both sides, so that silt does not easily accumulate on the top of the water-binding mound.

[0015] More preferably, several groups of tree-shaped trenches are arranged along the upstream to downstream direction, namely, primary tree-shaped trenches, secondary tree-shaped trenches...N-level tree-shaped trenches. After the width between the primary tree-shaped trench and the water-binding wall is determined, the width between the subsequent tree-shaped trenches and the width between the tree-shaped trenches and the water-binding wall gradually decreases, but the sum of the widths of each level of tree-shaped trench remains unchanged and is equal to the width of the primary tree-shaped trench.

[0016] More preferably, the sand collection ditch is semi-funnel-shaped, with the upper half of the side wall connecting the sand collection ditch and the forepool inclined to form a slope, and the lower half vertical; the bottom of the sand collection ditch is a rectangular trough, with the bottom of the trough being high in the middle and low at both ends.

[0017] Mud pumps are installed at both ends of the bottom ditch of the sand collection ditch to extract the mud and sand from the bottom ditch.

[0018] More preferably, a sediment warning device is installed on the slope of the sediment collection ditch. When the sediment accumulation thickness in the sediment collection ditch exceeds the limit set by the sediment warning device, the sediment in the sediment collection ditch is cleaned up.

[0019] A design method for a tree-like trench sand-flushing structure in a pump station forebay includes the following steps:

[0020] Step 1: During the normal operation of the pumping station and the siltation period, the structure of the forebay is designed to allow the silt to settle automatically.

[0021] S1-1. Determine the maximum particle size of the sediment entering the pumping station;

[0022] S1-2. Calculate the sediment initiation velocity at the corresponding water depth in the forebay of the pumping station using the sediment initiation formula.

[0023] S1-3. Determine the planar and longitudinal diffusion angles of the pump station forebay;

[0024] Step 2: During the short-term shutdown of the pump station for sand flushing, the silt can be automatically cleaned by designing a tree-like trench structure at the bottom of the forebay.

[0025] S2-1. Determine the design flow rate for sand flushing;

[0026] S2-2. Determine the depth of the tree-shaped trench based on the sediment content of the river where the pumping station is located;

[0027] S2-3. The classic formula for uniform flow in open channels is used to calculate the width and depth of the channel using a trial-and-error method.

[0028] S2-4. Calculate the sediment initiation velocity at the corresponding water depth in the tree-shaped trench using the sediment initiation formula.

[0029] S2-5. Calculate the water flow velocity in trenches of different widths and compare it with the sediment initiation velocity calculated in S2-4. If the water flow velocity is less than the sediment initiation velocity, the silted sediment cannot be smoothly initiated and carried away by the water flow. Then, re-determine the design flow rate or trench width and depth.

[0030] S2-6. Construct a three-dimensional hydrodynamic mathematical model, conduct hydrodynamic numerical simulation, and verify the sand flushing capacity of the designed tree-shaped trench.

[0031] The present invention has the following beneficial effects:

[0032] 1. The tree-like trench sand-flushing structure of the pump station forebay adopted in this invention mainly includes a planar and longitudinally diffused pump station forebay, a tree-like trench in the forebay, and a half-funnel-shaped sand-collecting ditch at the end. The diffused forebay can increase the cross-sectional area of ​​water flow, thereby reducing the water flow velocity and allowing silt to accumulate in the forebay and the sand-collecting ditch. After the silt accumulates to a certain extent, the silt early warning device in the sand-collecting ditch is triggered to efficiently clean the accumulated silt.

[0033] 2. This invention designs tree-shaped trenches at the bottom of the pump station forebay, which can promote the automatic deposition of silt and sand when the pump station is running. When the pump station is stopped, a small amount of water is used to clean the bottom of the pump station forebay, collect the silt and sand in the forebay, and discharge it automatically.

[0034] 3. This invention can prevent the accumulation of silt and sand in front of the pump from clogging the water pump intake, reduce the wear of pump station blades, improve the service life of pump station units, and ensure the safety of water supply. Attached Figure Description

[0035] Figure 1This is a plan view of the tree-shaped trench in the forebay of the pump station according to the present invention.

[0036] Figure 2 This is a longitudinal cross-sectional view of the tree-shaped trench in the forebay of the pump station according to the present invention.

[0037] Figure 3 This is a diagram showing the arrangement of the water-binding wall in this invention.

[0038] Figure 4 This is a schematic diagram of the water-binding pier structure of the present invention.

[0039] Figure 5 This is a 3D rendering of the tree-like trench section of the forebay in the numerical simulation.

[0040] The components include: 1. Inlet; 2. Forebay; 3. Tree-shaped trench; 4. Sediment collection trench; 5. Mud pump; 6. Pumping station unit; 7. Maintenance gate; 8. Working gate; 9. Water-binding wall; 10. Slope; 11. Original forebay bottom slope line; 12. Diffusion section; 13. Vertical section; 14. Original sidewall line; 15. Water-binding pier; 16. Primary tree-shaped trench; 17. Sediment early warning device. Detailed Implementation

[0041] In the description of this invention, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of this invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of this invention.

[0042] like Figure 1 and Figure 2 As shown, a tree-shaped trench flushing structure for a pump station forebay is mainly suitable for water intake pump station projects, especially for water intake pump station projects in rivers with a lot of silt.

[0043] The tree-like trench flushing structure includes an inlet 1, a forebay 2, a tree-like trench 3, and a sand collection ditch 4; the inlet 1 and the sand collection ditch 4 are connected through the forebay 2, and the inlet 1 is defined to be located in the upstream direction, while the sand collection ditch 4 is located in the downstream direction.

[0044] Water-binding walls 9 are vertically arranged on both sides of the front pool 2, and tree-shaped trenches 3 are arranged at the bottom of the front pool 2.

[0045] The forebay 2 has a 1:10 slope from upstream to downstream, and the bottom width of the forebay 2 gradually spreads and extends to both sides from upstream to downstream.

[0046] Downstream of the sand collection ditch, pump station unit 6 is connected to pump water from the forebay 2.

[0047] The inlet 1 is arranged horizontally, and the inlet 1 is equipped with a maintenance gate 7 and a working gate 8 in sequence, which are used to shut off and open the inlet 1 during maintenance and normal operation.

[0048] The inner side of the water-binding wall 9 is lined with concrete and arranged in a zigzag shape that spreads to both sides, with the same diffusion trend as the original side wall line 14. The water-binding wall 9 is composed of alternating diffusion sections 12 and vertical sections 13, which are connected by an arc surface to make the water flow smoother.

[0049] Tree-shaped trench 3 is arranged at the bottom of the forepool 2. The starting elevation of the tree-shaped trench 3 is lower than that of the horizontal section inlet 1, and it is connected to the inlet 1 through a slope 10 with a gradient of 1:3.

[0050] The bottom surface of the tree-shaped trench 3 excavated at the bottom of the forebay 2 is parallel to the original slope line 11 of the forebay bottom; the tree-shaped trench 3 has the same outward diffusion trend as the forebay 2 and the water-binding wall 9, and the tree-shaped trench 3 branches downstream at intervals.

[0051] After excavating a tree-shaped trench 3 at the bottom of the forebay 2, the unexcavated part protrudes to form a water-binding mound 15. The water-binding mound 15 is high in the middle and low on both sides, and the top has a slope from the central axis to both sides with a slope of 1:10, which makes it difficult for silt to accumulate on the top of the water-binding mound 15.

[0052] Several groups of tree-shaped trenches 3 are arranged from upstream to downstream, namely, first-level tree-shaped trenches 16 and second-level tree-shaped trenches... N-level tree-shaped trenches. After the width between the first-level tree-shaped trenches 16 and the water-binding wall 9 is determined, the width between the subsequent tree-shaped trenches and the width between the tree-shaped trenches and the water-binding wall gradually decreases, but the sum of the widths of each level of tree-shaped trenches remains unchanged and is equal to the width of the first-level tree-shaped trenches 16.

[0053] The sand collection ditch 4 is semi-funnel shaped. The upper half of the side wall connecting the sand collection ditch 4 and the forepool 2 is inclined to form a slope with a gradient of 1:1, while the lower half is vertical. The bottom of the sand collection ditch 4 is a rectangular ditch with a high middle and low ends. Mud pumps 5 are installed at both ends of the bottom ditch to pump out the mud and sand in the bottom ditch.

[0054] A sediment warning device 17 is installed on the slope of the sediment collection ditch 4. When the sediment accumulation thickness in the sediment collection ditch exceeds the limit set by the sediment warning device, the sediment in the sediment collection ditch is cleaned up.

[0055] Based on the above device, there is a design method for a tree-shaped groove flushing structure in the forebay of a pumping station. By designing tree-shaped grooves at the bottom of the forebay, the pumping station can promote the automatic deposition of silt and sand during operation. When the pumping station is stopped, a small amount of water is used to clean the bottom of the forebay, collect the silt and sand in the forebay, and discharge it automatically.

[0056] The specific steps are as follows:

[0057] Step 1: During the siltation period of normal operation of the pumping station, the silt is automatically settled by designing the structure of the forebay of the pumping station.

[0058] S1-1. By collecting water and sediment samples from the project area on-site and conducting sieve tests, the maximum particle size of sediment that can enter the pumping station is determined.

[0059] S1-2. Calculate the sediment initiation velocity at the corresponding water depth using Academician Dou Guoren's sediment initiation formula. The formula is as follows:

[0060]

[0061] D: Sediment particle size

[0062] γ s : Bulk density of a single grain of sediment

[0063] γ: water specific weight

[0064] δ: Thickness of water molecules (taken as 3×10) -10 m)

[0065] H: Water depth

[0066] H a Atmospheric pressure (water column height)

[0067] S1-3. Determine the planar and longitudinal diffusion angles of the pump station forebay;

[0068] During normal operation of the pumping station, the flow rate at each cross-section of the pumping station's forebay has the following relationship with the average flow velocity and cross-sectional area of ​​the water flow:

[0069] Q 常 =v1A1

[0070] When the pump station's water intake flow rate Q 常 When determined, the average flow velocity across a cross-section is inversely proportional to the cross-sectional area; the larger the cross-sectional area, the lower the average flow velocity and the weaker the sediment-carrying capacity.

[0071] Q 常 =v1A1=v1BH

[0072] Because the forebay exhibits a downstream and upstream diffusion trend at its bottom and banks respectively, the cross-sectional area of ​​the forebay increases with its depth H and width B, thus reducing the average flow velocity v1. When the flow velocity is less than the sediment initiation velocity, sediment begins to settle. As the flow velocity decreases, the particle size of the settleable sediment also gradually decreases. Based on specifications or specific circumstances, the minimum allowable sediment particle size leaving the forebay is determined, and the corresponding initiation velocity is calculated to determine the planar and longitudinal diffusion angles of the pump station's forebay.

[0073] Step 2: During the short-term shutdown of the pump station for sand flushing, the silt can be automatically cleaned by designing a tree-like trench structure at the bottom of the forebay.

[0074] S2-1. Determine the design flow rate for sand flushing;

[0075] S2-2. The depth of the tree-shaped trench is determined based on the sediment content and siltation level of the river where the pumping station is located.

[0076] S2-3. Using the classic formula for uniform flow in open channels, the width and depth of the channel are calculated using a trial-and-error method. The formula is as follows:

[0077] Formula for uniform flow in open channels:

[0078]

[0079] Q 冲沙 Design flow rate for sand flushing

[0080] i: Slope of the bottom slope

[0081] C: Xie Cai coefficient

[0082] A: Cross-sectional area of ​​water passage

[0083] R: hydraulic radius

[0084] The Chezy coefficient is obtained from the Chezy formula:

[0085]

[0086] χ=2h+b

[0087]

[0088] b: Trench width

[0089] h: Trench water depth

[0090] n: Surface roughness of the trench

[0091] χ: Wet perimeter (the boundary line of the fluid contact with the solid wall on the cross-section of the water passage)

[0092] A: Cross-sectional area of ​​water passage

[0093] R: hydraulic radius

[0094] S2-4. Calculate the sediment initiation velocity at the corresponding water depth in the tree-shaped trench using Academician Dou Guoren's sediment initiation formula.

[0095] S2-5. Calculate the water flow velocity in trenches of different widths; and compare it with the sediment initiation velocity calculated in S2-4. If the water flow velocity is less than the sediment initiation velocity, then re-determine the design flow rate or trench width and depth.

[0096] S2-6. Construct a three-dimensional hydrodynamic mathematical model, conduct hydrodynamic numerical simulation, and verify the sand flushing capacity of the designed tree-shaped trench.

[0097] The present invention will now be described in further detail with reference to the accompanying drawings and specific preferred embodiments.

[0098] Screening tests determined that the maximum particle size of sediment entering the pumping station was 4.0 mm.

[0099] According to the "Design Code for Pumping Stations (GB 50265-2010)," the particle size of the silt discharged from the reservoir should not exceed 0.05 mm, meaning the average flow velocity at the outlet section should be less than the starting velocity corresponding to a 0.05 mm silt particle size. Based on the formula in S1-2, under normal operating conditions (water depth 3.0 m), the starting velocity of 0.05 mm silt is calculated to be 0.213 m / s.

[0100] Q during normal operation of the pumping station 常 =20m 3 / s, width of the forebay inlet B 进 =5m, the proposed forebay length l = 22m, the bottom slope gradient i = 0.0175, and the sidewall diffusion angle θ = 30°. That is, the forebay outlet cross-section width B 出 = 30.40m, water depth H 出 =3.38m, the average flow velocity at the outlet section is v1 = 0.195m / s, which is less than the starting velocity of sediment with a particle size of 0.05mm.

[0101] Therefore, the width B of the inlet of the pump station forebay is determined. 进 =5m, forebay length l = 22m, sidewall diffusion angle θ = 30°, forebay outlet cross-sectional width B 出 =30.40m, slope of the front pool bottom i=0.0175.

[0102] Based on the above dimensions, the proposed trench width is 1.0m to 4.0m, the concrete channel roughness coefficient n = 0.02, and the bottom slope i = 0.0175. Specific calculation results are shown in Table 1.

[0103]

[0104] Table 1

[0105] The sediment initiation velocity at the corresponding water depth in the dendritic channel was calculated using Academician Dou Guoren's sediment initiation formula, as shown in Table 2.

[0106]

[0107] Table 2

[0108] Calculate the water flow velocity in trenches of different widths and compare it with the sediment initiation velocity in Table 2. If the water flow velocity is less than the sediment initiation velocity, the design flow rate or trench width and depth should be re-determined. Detailed data comparison results are shown in Table 3.

[0109]

[0110] Table 3

[0111] The calculation results show that the water flow velocity in the trenches is greater than the initial velocity of the sediment. Considering both the trench depth and the amount of excavation, the final selection is a primary trench width of 3m, a secondary trench width of 2m, and a tertiary trench width of 1.5m, with a depth of 0.2m and a design flushing flow rate of 1.5m. 3 / s.

[0112] 3D rendering of the tree-like trench section of the forebay in numerical simulation calculations, as shown below. Figure 5 As shown.

[0113] The pump station's forebay inlet is equipped with maintenance gates and working gates arranged sequentially, with the inlet ends connecting to the main body of the forebay. Because the forebay exhibits a tendency to diffuse in both plan and elevation, the cross-sectional area of ​​the water body continuously increases, leading to a decrease in water flow velocity. This allows most of the sediment carried by the water to settle in the forebay and the half-funnel-shaped sediment collection ditch at the tail end.

[0114] When the thickness of the silt accumulation in the semi-funnel-shaped sand collection ditch exceeds the limit set by the silt warning device, the inlet gate is closed and the mud pump is turned on to clean the silt in the semi-funnel-shaped sand collection ditch. When draining the remaining water in the forebay, due to the slope of the top of the water-binding piers, the silt accumulated on the top of the water-binding piers will be flushed first during the water level drop. After the water in the forebay is basically drained, the inlet gate is opened to allow the designed flushing flow rate. The introduced flow rate first flushes the remaining silt at the bottom of the forebay and the top of the water-binding piers. Then, under the constraint of the water-binding piers and the water-binding walls on both banks, the water flow will continuously flush the remaining silt in the ditch. As the silt in the ditch is continuously flushed, the water flow will eventually be able to completely enter the ditch and flush the remaining silt.

[0115] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the protection scope of the present invention.

Claims

1. A tree-like trench sand-flushing structure for a pump station forebay, characterized in that: It includes an inlet (1), a forebay (2), a tree-like ditch (3), and a sand collection ditch (4); the inlet (1) and the sand collection ditch (4) are connected through the forebay (2), and the inlet (1) is defined to be located in the upstream direction and the sand collection ditch (4) is located in the downstream direction; Water-binding walls (9) are vertically arranged on both sides of the forepool (2), and tree-shaped trenches (3) are arranged at the bottom of the forepool (2); The bottom surface of the tree-shaped trench (3) excavated at the bottom of the forepool (2) is parallel to the original slope line (11) of the forepool bottom; the tree-shaped trench (3) has the same outward diffusion trend as the forepool (2) and the water-binding wall (9), and the tree-shaped trench (3) branches downstream at intervals; After excavating a tree-shaped trench (3) at the bottom of the forepool (2), the unexcavated part protrudes to form a water-binding mound (15). The water-binding mound (15) is high in the middle and low on both sides, and the top has a slope that slopes from the central axis to both sides, so that silt does not easily accumulate on the top of the water-binding mound (15). The forepool (2) has a slope from upstream to downstream, and the bottom width of the forepool (2) gradually spreads and extends to both sides from upstream to downstream. The downstream of the sand collection ditch is connected to the pump station unit (6), which is used to extract water from the forebay (2).

2. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: The inlet (1) is arranged horizontally. The inlet (1) is equipped with a maintenance gate (7) and a working gate (8) in sequence, which are used to shut off and open the inlet (1) during maintenance and normal operation.

3. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: The inner side of the water-binding wall (9) is lined with concrete and arranged in a folded slope shape that spreads to both sides. The diffusion trend is the same as that of the original side wall line (14). The water-binding wall (9) is composed of alternating diffusion sections (12) and vertical sections (13). The diffusion sections (12) and vertical sections (13) are connected by an arc surface, so that the water flow can be smoother.

4. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: Tree-shaped trench (3) is arranged at the bottom of the forepool (2). The starting elevation of the tree-shaped trench (3) is lower than that of the horizontal section inlet (1), and it is connected to the inlet (1) through a slope (10).

5. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: Several groups of tree-shaped trenches (3) are arranged from upstream to downstream, namely, first-level tree-shaped trenches (16) and second-level tree-shaped trenches... N-level tree-shaped trenches. After the width between the first-level tree-shaped trench (16) and the water-binding wall (9) is determined, the width between the subsequent tree-shaped trenches and the width between the tree-shaped trenches and the water-binding wall gradually decreases, but the sum of the widths of each tree-shaped trench remains unchanged and is equal to the width of the first-level tree-shaped trench (16).

6. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: The sand collection ditch (4) is semi-funnel-shaped. The upper half of the side wall connecting the sand collection ditch (4) and the forepool (2) is inclined to form a slope, and the lower half is vertical. The bottom of the sand collection ditch (4) is a rectangular ditch with a high middle and low ends. Mud pumps (5) are installed at both ends of the bottom ditch of the sand collection ditch to extract the mud and sand in the bottom ditch.

7. The tree-like trench sand-flushing structure for a pump station forebay according to claim 1, characterized in that: A sediment warning device (17) is installed on the slope of the sediment collection ditch (4). When the sediment accumulation thickness in the sediment collection ditch exceeds the limit set by the sediment warning device, the sediment in the sediment collection ditch is cleaned up.

8. A design method for a tree-like trench flushing structure in a pump station forebay according to any one of claims 1-7, characterized in that: Specifically, the steps include the following: Step 1: During the normal operation of the pumping station and the siltation period, the structure of the forebay is designed to allow the silt to settle automatically. S1-1. Determine the maximum particle size of the sediment entering the pumping station; S1-2. Calculate the sediment initiation velocity at the corresponding water depth in the forebay of the pumping station using the sediment initiation formula. S1-3. Determine the planar and longitudinal diffusion angles of the pump station forebay; Step 2: During the short-term shutdown of the pump station for sand flushing, the silt can be automatically washed away by designing a tree-like trench structure at the bottom of the forebay. S2-1. Determine the design flow rate for sand flushing; S2-2. Determine the depth of the tree-shaped trench based on the sediment content of the river where the pumping station is located; S2-3. The classic formula for uniform flow in open channels is used to calculate the width and depth of the channel using a trial-and-error method. S2-4. Calculate the sediment initiation velocity at the corresponding water depth in the tree-shaped trench using the sediment initiation formula. S2-5. Calculate the water flow velocity in trenches of different widths and compare it with the sediment initiation velocity calculated in S2-4. If the water flow velocity is less than the sediment initiation velocity, the silted sediment cannot be smoothly initiated and carried away by the water flow. Then, re-determine the design flow rate or trench width and depth. S2-6. Construct a three-dimensional hydrodynamic mathematical model, conduct hydrodynamic numerical simulation, and verify the sand flushing capacity of the designed tree-shaped trench.

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