Three-dimensional ecological regulating weir with curved surface and design method thereof

Abstract

The present application changes the traditional weir structure with smooth concrete bottom and steep hydraulic fall, and designs a three-dimensional curved surface ecological regulation weir with ecological regulation function. The weir body side profile is a V-shaped side profile rising to both sides of the weir body, a relatively gentle water flow area is generated in the edge area, and a low flow channel is generated to the center. The design flow of the downstream weir surface meets the fish channel design flow, and ensures that the target fish in the river section passes through the river section. The fish swimming speed equation is used to determine the design flow velocity and weir surface length. The weir body surface is rough, which forms a boundary layer suitable for fish movement and is beneficial to reduce the average flow velocity.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection technology, and in particular to a three-dimensional curved ecological regulating weir and a design method thereof. Background Art

[0002] In river management, weirs or submerged T-shaped weirs are often constructed across rivers to meet the needs of flood control, water storage, irrigation, navigation, landscape, and livelihoods. However, traditional weir designs rarely consider their adverse ecological impacts. Weirs, essentially interrupting the riverbed slope, create multiple obstacles for upstream and downstream organisms. These include: the difference in upstream and downstream elevation prevents swimming species from migrating upstream; the shape of the weir crest affects climbing species; shallow water depth upstream or downstream alters flow velocity; and backwater inundation from upstream weirs alters riverbed habitats, causing aquatic organisms to shift to slower-flowing, deeper habitats. Weir construction blocks the movement of aquatic organisms, affecting fish migration and even causing the extinction of migratory fish. Increased sediment deposition upstream leads to changes in water quality, while increased water depth and reduced flow velocity also lead to decreased dissolved oxygen and increased water temperature. Weirs also alter downstream flow and sediment conditions, impacting downstream habitats and water quality. River channel structural features that hinder the movement of fish and other aquatic life include large vertical drops, high water velocities, excessive turbulence, sharp corners, and smooth bottoms. There is an urgent need for a weir structure that meets the requirements of river channel regulation and has ecological regulation functions to minimize the impact on fish and other aquatic life. Summary of the Invention

[0003] The present invention overcomes the problem that the existing weir structure has structural characteristics that are unfavorable to water ecology. It changes the traditional weir structure with a smooth concrete bottom and a steep hydraulic drop, and designs a three-dimensional curved ecological regulation weir with ecological regulation function and its design method.

[0004] In order to solve the above problems, the present invention adopts the following design scheme:

[0005] A three-dimensional curved ecological regulation weir, comprising a weir body spanning a river channel, wherein the weir body is located at a lower position in the middle of the river channel and at higher positions at both ends of the river channel. The weir body is divided into an upstream section, a middle section, and a downstream section along the river channel. The top cross-section of the middle section is circular. The weir surface slope of the upstream section is 18-30°, and the weir surface slope of the downstream section is less than 1:10.

[0006] Preferably, the top of the cross section of the weir body across the river channel is V-shaped, thereby generating a relatively gentle water flow area at the edge area of ​​the weir body and a low flow channel towards the center of the weir.

[0007] Preferably, the V-shaped angle is 5-10°, and a suitable V-shaped angle is designed by referring to the requirements of local migratory fish for water flow velocity during migration.

[0008] Preferably, the cross-section of the weir body along the river channel is spindle-shaped.

[0009] Preferably, when the drop is ≤ 1 meter, the slope of the downstream section is less than 1:10; when the drop is 1-4 meters, the slope of the downstream section is less than 1:15. The design flow rate of the weir surface in the downstream section meets the design flow rate of the fish passage, ensuring that the target fish in the river section can pass through this section. The fish swimming speed equation is used to determine the design water flow velocity and weir surface length.

[0010] Preferably, the surface of the weir body is rough, forming a boundary layer suitable for fish movement and facilitating reduction of average water flow velocity.

[0011] Preferably, the weir surface is covered with mixed rocks of 150 to 200 mm in diameter, arranged at intervals of 70 to 90 mm and at irregular intervals, to form a hydraulically diverse flow structure on the weir.

[0012] Preferably, the long axis of the rock is perpendicular to the weir face and is at least 50% embedded, with the widest axis of the rock facing the water flow.

[0013] The present invention further provides a design method for the above-mentioned ecological regulation weir, the method comprising the following steps:

[0014] (1) Determine the appropriate V-angle based on the water velocity requirements of local migratory fish during migration;

[0015] (2) Determine the slope and length of the downstream weir using the fish swimming speed equation;

[0016] (3) Determine the weir surface roughness based on the critical shear stress method.

[0017] Compared with the prior art, the present invention has significant improvements:

[0018] In order to overcome the problem that the existing weir structure has structural characteristics that are unfavorable to the water ecology, the present invention changes the traditional weir structure with a smooth concrete bottom and a steep hydraulic drop, and designs a three-dimensional curved ecological regulation weir with ecological regulation function. The side profile of the weir body is a V-shaped side profile that rises to both sides of the weir body, which produces a relatively gentle water flow area in the edge area and a low-flow channel toward the center. The design flow of the weir surface in the downstream section meets the design flow of the fish channel, ensuring that the target fish in the river section pass through the river section. The fish swimming speed equation is used to determine the design water flow velocity and the weir surface length. The surface of the weir body is rough, forming a boundary layer suitable for fish movement, and is conducive to reducing the average water flow velocity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1Schematic diagram of the planar layout of the weir structure according to an embodiment of the present invention.

[0020] Figure 2 : is a cross section of the weir structure across the river channel according to the embodiment of the present invention.

[0021] Figure 3 3 is a cross section of the weir structure according to an embodiment of the present invention along the river channel.

[0022] Figure 4 This is a rock placement diagram according to an embodiment of the present invention.

[0023] The reference numerals are as follows: weir body-1, upstream section-2, middle section-3, downstream section-4, rock-5. DETAILED DESCRIPTION

[0024] The following is a further detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0025] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] like Figure 1 FIG. 1 shows an embodiment of the weir structure of the present invention.

[0028] The weir structure of this embodiment includes a weir body. The weir top is circular while meeting the requirements of head and river channel regulation. The weir body is located at a low position in the middle of the river channel and at a high position at both ends of the river channel. The weir body is divided into an upstream section, a middle section and a downstream section along the river channel. The top cross-section of the middle section is circular. The weir surface slope of the upstream section is 18-30°, and the weir surface slope of the downstream section is less than 1:10.

[0029] like Figure 2 As shown, the top of the weir, spanning the river channel, is V-shaped, creating a gentler flow at the edge of the weir and a low-flow channel toward the center of the weir. The V-shaped angle is 5-10°, designed based on the water velocity requirements of local migratory fish during migration.

[0030] like Figure 3 As shown, the weir has a fusiform cross-section along the river channel. When the drop is ≤ 1 meter, the slope of the downstream section is less than 1:10; when the drop is 1-4 meters, the slope of the downstream section is less than 1:15. The design flow rate of the downstream weir meets the design flow rate for fish passage, ensuring that target fish species in the river section can pass through this section.

[0031] The rough surface of the weir forms a boundary layer suitable for fish movement and helps to reduce the average water flow velocity. Figure 4 As shown, the present invention uses mixed rocks with diameters of 150 to 200 mm to cover the weir face. The rocks are spaced 70 to 90 mm apart and irregularly spaced to create a hydraulically diverse flow structure across the weir. The long axis of the rocks is perpendicular to the weir face and is at least 50% embedded. The widest axis of the rocks faces the water flow.

[0032] The present invention also provides embodiments of a weir design method.

[0033] The method comprises the following steps:

[0034] (1) Determine the shape of the weir crest based on the water velocity requirements of local migratory fish during migration;

[0035] (2) Determine the slope and length of the downstream weir using the fish swimming speed equation;

[0036] (3) Determine the weir surface roughness based on the critical shear stress method.

[0037] In the step (1), while meeting the requirements of water head and river regulation, the weir top design adopts a wide-top weir design to avoid a pointed-top design. The wide-top design reduces the possibility of generating a falling water flow, which will hinder the passage of fish. The downstream edge of the crest should be rounded rather than sharp to allow climbing fish to cross the top edge and continue upstream. The weir top notch is designed to be V-shaped, which is more conducive to the passage of fish than a semicircular or rectangular notch. The appropriate V-shaped angle is designed by simulating the requirements of local migratory fish for water flow speed during migration.

[0038] In step (2), when designing the downstream weir surface, vertical weir surfaces and steps or lips on the weir surface should be avoided. The slope design of the downstream weir surface follows the principle of minimizing the slope. When the drop is ≤1 meter, the slope should be less than 1:10; when the drop is 1-4 meters, the slope should be less than 1:15. The design speed of the downstream weir surface meets the design flow of the fish passage to ensure that the target fish in the designed river section pass through the river section. The key principle of the downstream weir surface design is to determine the minimum size of the channel provided by the target fish species, life stage and on-site river section of the river.

[0039] The design water velocity and weir length can be determined by the fish swimming velocity equation. The hydraulic performance standard of the structure is determined by simulating the local river characteristics based on the known swimming ability of the target species. Design flow: The design flow range of the fish passage during the migratory period of the target fish species determined in the initial assessment, the flow range that meets the hydraulic performance standard of the structure. The low flow of the fish passage (Q L ) is the minimum flow rate that provides fish passage. According to experience, Q L Set to 95% of the maximum critical flow rate (i.e. the flow rate that exceeds 95% of the time period). H is the highest flow rate that meets the hydraulic performance standards for fish passages. A rule of thumb is Q H Use 20% of the maximum critical flow rate.

[0040] To progress upstream through a weir, a species must swim faster than the current. The lower the current, the slower the species' upward swimming speed, and the greater the distance they can travel before exhaustion. The maximum permissible current speed is chosen so that the species can pass the length of the weir without exhaustion within the design flow range. The relationship between current speed, fish swimming speed, and weir length (L) can be calculated using the biodynamic equation:

[0041] U w =U f -(L / t)

[0042] U w is the design water flow velocity, U f is the swimming speed of the fish, L is the length of the weir surface, and t is the speed at which fFatigue time (i.e. the time taken for a fish to reach exhaustion when swimming continuously at a given speed). This is determined for different U f values. The resulting curves can be used to determine the appropriate weir length that would theoretically allow the species to pass through a given design flow velocity. It should be noted that this relationship is not only species dependent, but also dependent on the size of the target species, and environmental conditions (e.g. water temperature). Therefore, the species, life stage, and environmental conditions of the target river reach are also taken into account when determining U f .

[0043] After determining the maximum passable flow velocity, the hydraulic design equation is used to determine the slope of this velocity within the design flow range of the fish pass, taking into account the geometry of the weir (i.e. the width, shape, and substrate on the downstream face). For a given head drop, the slope determines the length of the weir. After determining the design velocity, the associated water depth is calculated to determine whether this depth would impede the target species from passing through.

[0044] Upstream weir face slope In the design process, the upstream face of the weir is generally made vertical. The upstream face of the weir can also be made inclined due to weir stability or layout requirements. Since the flow over the weir is influenced by the shape of the upstream face boundary, the hydraulic characteristics of an inclined overflow weir are not exactly the same as those of a vertical upstream face. A 30° slope helps to reduce the maximum flow velocity on the top of the weir and through the top of the weir, creating better conditions for downstream passage. In this design, a design considering 18-30° slope of the upstream weir face is considered.

[0045] In the step (3), when designing the overall weir roughness, it is noted that the weir face should avoid using smooth concrete, and the roughness of the weir face should be increased to form a boundary layer suitable for fish movement and to help reduce the average flow velocity. There is no established method to determine the stability of artificial rough substrate, but the critical shear stress method can be used to guide the design of the substrate size of the design flow, and the maximum shear stress on the riverbed should not exceed the critical shear stress of the particles constituting the matrix. For mixed particle size matrix, the critical bed shear stress method is also applicable. As shown in Figure 4 , the design selects to cover the weir face with mixed rocks of 150 to 200 millimeters. The rocks are closely spaced (70-90 millimeters) and irregularly spaced to form a hydraulic variety of flow structures on the weir. The long axis of the rock should be perpendicular to the weir face and at least 50% embedded. The widest axis of the rock should be oriented towards the flow. Such a design not only reduces the flow velocity on the surface in front of the weir, but also provides a wetted edge in front of the weir.

[0046] The weir structure of the present embodiment can be retrofitted on an existing weir body on a river, or can be constructed and built on a new river.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A method for designing a three-dimensional curved ecological regulation weir, the weir comprising a weir body spanning a river channel, the weir body being lower in the middle of the river channel and higher at both ends of the river channel. The top of the weir body, where it spans the river channel, is V-shaped. The weir body is divided into an upstream section, a middle section, and a downstream section along the river channel. The top cross-section of the middle section is circular. The weir surface slope of the upstream section is 18-30°, and the weir surface slope of the downstream section is less than 1:

10. The method comprises the following steps: (1) Determine the appropriate V-angle based on the water velocity requirements of local migratory fish during migration. The V-angle is in the range of 5-10°. (2) The slope and length of the downstream weir are determined by the fish swimming speed equation. The slope design of the downstream weir follows the principle of slope minimization. When the drop is ≤ 1 meter, the slope should be less than 1:10; when the drop is greater than 1 meter and less than 4 meters, the slope should be less than 1:

15. The fish swimming speed equation is: U w =U f -(L / t), where U w is the design water flow velocity, U f is the swimming speed of the fish, L is the length of the weir surface, and t is the speed at which f Fatigue time is the time required for fish to reach exhaustion when swimming continuously at a given speed. f The obtained curve can be used to determine the appropriate weir face length that theoretically allows species to pass through a given design water velocity; (3) Determine the weir surface roughness based on the critical shear stress method.

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