A type of retaining wall used for flood discharge in gravity dams

Abstract

This invention belongs to the field of water conservancy and hydropower engineering technology, specifically relating to a spillway for flood discharge in a gravity dam. It includes sidewalls, a reverse-curved section, the spillway body, and a base plate. There are two sets of sidewalls arranged in parallel. The reverse-curved section and the base plate are both located between the two sets of sidewalls, sequentially connecting to the outlet end of the gravity dam. The working surface of the spillway body is trapezoidal in shape, located in the middle of the base plate, with its larger end connecting to the outlet end of the reverse-curved section. The working surface of the spillway body is a downwardly concave arc surface. This spillway body allows for good diffusion of the water jet in both the longitudinal and lateral directions. Furthermore, the water jet ejected from the base plate and the water jet ejected from the spillway body towards the far end form an approximately rectangular area, increasing the water jet's impact range and effectively eliminating the energy carried by the downstream flow in the spillway structure, thereby reducing the threat to the stability of the spillway structure.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy and hydropower engineering technology, specifically relating to a spillway for flood discharge in gravity dams. Background Technology

[0002] To prevent the enormous energy carried by the downstream water flow in water conservancy and hydropower projects from causing severe scouring of the downstream river channel and affecting the stability of the slope and the safe operation of the structure itself, energy dissipation measures are generally adopted in engineering to dissipate or disperse the excess energy during the flood discharge process as much as possible. This is also a key point and difficulty in engineering construction. Due to its advantages such as simple structure, convenient construction, high economic benefits and high energy dissipation rate, the jet flow energy dissipation method is the most widely used in high dam spillway structures.

[0003] Among them, jet flow energy dissipation involves installing a jet sill at the end of the spillway structure, causing the water flow to be jetted downstream. The energy in the water flow is dissipated through the diffusion, turbulence, and aeration of the water jet in the air, before it falls into the channel farther from the spillway structure, where it dissipates energy in the scour pit and the water cushion formed by a certain tailrace depth. With the widespread application of jet flow energy dissipation in high dam spillway structures, researching jet sill forms with good energy dissipation effects and applicability to different hydraulic, topographical, and geological conditions has become a key technical issue. Currently, commonly used jet sills can generally be divided into the following three categories:

[0004] The first type is a continuous arc-shaped curb, which is the most traditional and simplest type.

[0005] The second type is the longitudinal diffusion of water tongues to create a sill, such as a narrow slit sill;

[0006] The third type is the horizontal diffusion of water tongues to create a ridge, such as a slanted ridge and a twisted ridge;

[0007] The underlying principle of various irregularly shaped retaining walls is to disperse the water jet as much as possible into the water to reduce the energy of water entering the water per unit area, thereby reducing the scouring of the downstream river channel.

[0008] However, gravity dams are generally steep with large water drop, resulting in fast water flow and high centrifugal force during flood discharge. If a gravity dam uses continuous sills, the outflowing water is concentrated during flood discharge, with no longitudinal spread of the water tongue, a small drop area, and a large depth of submersion in the water cushion. When the riverbed bedrock is weak, it can easily form deep scour pits, which may even threaten the stability of the foundation of the structure.

[0009] If a gravity dam body uses a narrow slotted sill, during flood discharge, the outgoing water flow will be stretched longitudinally along the axis of the spillway, and the water tongues on both sides will turn inward, with the water drop area distributed in a straight line. However, narrow slotted sills are not suitable for gravity dams with a wide discharge width. Furthermore, this water droplet entry form, with a large distance between the two sides and a small distance in the middle, is greatly restricted by the terrain. In order to avoid the far ends of the water tongues on both sides touching the bank slope, the size of the angle of attack must be controlled, sacrificing the degree of diffusion, which affects its energy dissipation effect.

[0010] If a gravity dam body uses a sloping sill, the sloping sill will increase the width of the water jet during flood discharge, and may even require space several times the width of the discharge structure. In gravity dams, where the discharge channel axis is parallel to the downstream river channel, the space on both banks is limited, and lateral diffusion can easily cause the water jet to impact both banks, resulting in severe scouring damage.

[0011] Furthermore, the traditional spillway distance varies significantly under different flood discharge rates, making it unable to flexibly adapt to various flood frequencies. This greatly increases the downstream protection area required and consequently, the engineering costs. Therefore, existing spillway designs are insufficient to meet the flood discharge requirements of gravity dams. Designing a spillway type that can effectively disperse the water jet, dissipate energy in the air as much as possible, and is highly adaptable is an urgent technical challenge. Summary of the Invention

[0012] In order to solve the above-mentioned problems in the prior art, the present invention provides a spillway for flood discharge in gravity dams, so as to solve the technical problem that the spillway in the prior art is difficult to meet the flood discharge requirements of gravity dams.

[0013] This invention is specifically implemented through the following technical solutions:

[0014] A cantilever sill for flood discharge in a gravity dam includes a sidewall, a reverse-curved section, the sill body, and a base plate;

[0015] There are two sets of sidewalls, and the two sets of sidewalls are arranged in parallel.

[0016] The reverse arc curve segment and the bottom plate are both set between the two sets of sidewalls. The reverse arc curve segment and the bottom plate are connected in sequence to the outlet end of the straight section of the gravity dam's spillway, and the outlet end of the bottom plate extends away from the center of the reverse arc curve segment.

[0017] The working surface of the sill body is trapezoidal in shape. The sill body is located in the middle of the base plate. The large end of the sill body is connected to the water outlet end of the reverse arc curve segment, and the working surface of the sill body is a downwardly concave arc surface.

[0018] To better realize the present invention, further optimizations are made to the above structure: the radius of the working surface of the sill body is equal to the radius of the working surface of the reverse arc curve segment, and the center of the working surface of the sill body coincides with the center of the working surface of the reverse arc curve segment.

[0019] To better realize the present invention, further optimization is made to the above structure. The radius of the working surface of the reverse arc curve segment is R = (6~12)h, where h is the water depth at the lowest point of the reverse arc curve segment when the gravity dam discharges water at the highest water level.

[0020] To better realize the present invention, further optimization is made to the above structure, wherein the included angle θ1 formed by the line connecting the water inlet end of the bottom plate to the center of the working surface of the reverse arc curve segment and the line connecting the lowest point of the reverse arc curve segment to the center of the working surface of the reverse arc curve segment is 5° to 10°.

[0021] To better realize the present invention, the above structure is further optimized, and the central angle θ2 of the lifting frame body is 30° to 40°.

[0022] To better realize the present invention, the above structure is further optimized by including a diversion pier, which is set between the two sets of side walls. The length direction of the diversion pier is parallel to the length direction of the side walls, and the diversion pier extends from the water inlet end of the reverse arc curve segment to the small end of the sill body.

[0023] To better realize the present invention, further optimization is made to the above structure. The distance between the end point of the diversion pier and the small end of the cantilever body is d, where d is 0~(θ1-θ2)R / 2m.

[0024] To better realize the present invention, further optimization is made to the above structure, wherein the distance Hd between the end point of the diversion pier and the cantilever body is h+Hc, and Hc=2~3m.

[0025] To better realize the present invention, the above structure is further optimized. The number of the cantilever body is multiple, and the multiple cantilever bodies are arranged sequentially along the width direction of the base plate.

[0026] To better realize the present invention, the above structure is further optimized, and the working surface of the sill body is an isosceles trapezoid.

[0027] In summary, the present invention has the following technical effects:

[0028] The trapezoidal working face of the cantilever structure allows the water jet to have good diffusion not only in the longitudinal direction but also in the lateral direction. Furthermore, the water jet ejected in advance from the bottom plate and the water jet ejected from the cantilever structure to the far end form an approximately rectangular area, increasing the water jet's landing range. This effectively eliminates the energy carried by the downstream water flow in the spillway structure, reducing the depth of the water jet's penetration. Consequently, it weakens the impact of the water jet on the downstream water cushion and reduces the threat to the stability of the downstream bank slope and spillway structure, enabling the cantilever structure to better meet the flood discharge requirements of the gravity dam. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of a spillway for flood discharge in a gravity dam, according to the present invention.

[0031] Figure 2 This is a longitudinal cross-sectional view of a spillway for flood discharge in a gravity dam, according to the present invention.

[0032] Figure 3 This is a top view of a spillway for flood discharge in a gravity dam, according to the present invention.

[0033] Figure 4 This is a cross-sectional view of a spillway for flood discharge in a gravity dam, as described in this invention, in its working state.

[0034] Figure 5 This is a top view of the spillway of a gravity dam body in operation, according to the present invention.

[0035] Figure label:

[0036] 1. Side wall;

[0037] 2. Reverse arc curve segment;

[0038] 3. Challenge the body;

[0039] 4. Base plate;

[0040] 5. Diversion pier. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," 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 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, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] Example:

[0045] like Figures 1 to 5 As shown:

[0046] A spillway for flood discharge in a gravity dam includes a sidewall 1, a reverse-curved section 2, the spillway body 3, and a base plate 4; wherein,

[0047] There are two sets of sidewalls 1, which are set in parallel. One end of each set of sidewalls 1 is connected to the two sides of the straight section of the gravity dam's spillway.

[0048] The reverse arc curve segment 2 and the bottom plate 4 are both set between the two sets of sidewalls 1. The reverse arc curve segment 2 and the bottom plate 4 are connected in sequence to the outlet end of the straight section of the gravity dam's spillway, and the outlet end of the bottom plate 4 extends away from the center of the reverse arc curve segment 2.

[0049] The working surface of the sill body 3 is trapezoidal in shape. The sill body 3 is located in the middle of the base plate 4. The large end of the sill body 3 is connected to the water outlet end of the reverse arc curve section 2, and the working surface of the sill body 3 is a downward concave arc surface.

[0050] The trapezoidal working face of the sill body 3 in the sill allows the water tongue to have a good diffusion effect not only in the longitudinal direction, but also in the lateral direction, so that the water tongue can diffuse fully in the air to eliminate some of the energy in the water flow.

[0051] Furthermore, the water jet ejected in advance from the bottom plate 4 and the water jet ejected from the cantilever body 3 to the far end form an approximately rectangular area, increasing the water jet's landing range. This effectively eliminates the energy carried by the downstream water flow in the spillway structure, reducing the depth of the water jet's penetration. Consequently, it weakens the impact of the water jet on the downstream water cushion and reduces the threat to the stability of the downstream bank slope and spillway structure, enabling the cantilever to better meet the flood discharge requirements of the gravity dam.

[0052] Preferably, the working surface of the aforementioned cantilever body 3 is an isosceles trapezoid, so that the water jet emitted from the cantilever body 3 is more uniform and the water jet can spread gradually in the longitudinal and transverse directions to increase the diffusion area of ​​the water jet, thereby further reducing the threat of the water jet to the stability of the downstream bank slope and the spillway structure.

[0053] In the optimized form, the radius of the working surface of the aforementioned sill body 3 is equal to the radius of the working surface of the reverse arc curve segment 2, and the center of the working surface of the sill body 3 coincides with the center of the working surface of the reverse arc curve segment 2, so that the water flow through the reverse arc curve segment 2 and the sill body 3 is smoother.

[0054] It should be noted that the working surface of the reverse curve segment 2 and the working surface of the sill body 3 mentioned above refer to the surface that the water flows through when it passes through the reverse curve segment 2 or the sill body 3.

[0055] The optimized radius of the working surface of the aforementioned reverse arc curve segment 2 is R; where,

[0056] R = (6~12)h, where h is the water depth at the lowest point of the reverse arc curve segment 2 when the gravity dam is releasing water at its highest water level.

[0057] The optimized angle θ1 formed by the line connecting the water inlet end of the base plate 4 to the center of the working surface of the reverse arc curve segment 2 and the line connecting the lowest point of the reverse arc curve segment 2 to the center of the working surface of the reverse arc curve segment 2 is 5° to 10°.

[0058] In an optimized configuration, the central angle θ2 of the aforementioned sill body 3 is 30° to 40° to control the ejection angle of the water tongue, allowing the water tongue sufficient time to diffuse, turbulentize, and aerate in the air to eliminate some of the energy in the water flow.

[0059] In the optimized version, there are multiple cantilever bodies 3, which are arranged sequentially along the width of the bottom plate 4. The multiple cantilever bodies 3 dissipate or disperse excess energy during the flood discharge process as much as possible, thereby improving the energy dissipation effect of the cantilever.

[0060] The optimized design also includes a diversion pier 5; among which,

[0061] Diversion pier 5 is set between two sets of sidewalls 1. The length direction of diversion pier 5 is parallel to the length direction of sidewall 1. Diversion pier 5 extends from the water inlet end of the reverse arc curve section 2 to the small end of the cantilever body 3. Diversion pier 5 can divide the space between the two sets of sidewalls 1 into multiple flow channels to adapt to gravity dams with multiple overflow orifices.

[0062] For example, the overflow weir of a gravity dam is equipped with three overflow orifices. Two overflow bodies 3 and two diversion piers 5 can be installed in the sill. The two diversion piers 5 can divide the space between the two sets of sidewalls 1 into three flow channels, which are respectively connected to the three overflow orifices.

[0063] During the flood discharge process, staff can determine the number of overflow outlets to be opened based on the amount of water that the gravity dam needs to discharge, which means selecting the number of flow channels that need to be operated, making the use of the spillway more convenient.

[0064] In the optimized configuration, the distance between the end point of the aforementioned diversion pier 5 and the small end of the cantilever body 3 is d, where,

[0065] d is 0 to (θ1-θ2)R / 2m. The specific length of d can be selected according to the actual engineering of the gravity dam. The narrower the terrain downstream, the smaller the length of d.

[0066] Optimized, the distance H between the end point of the aforementioned diversion pier 5 and the cantilever body 3 is... d h+H c , where H c =2~3m.

[0067] To better illustrate the function and effect of this retaining wall, the following provides the hydraulic model test content of this retaining wall:

[0068] The spillway structure is a gravity dam with an overflow outlet. The spillway is 60m wide and the crest elevation of the overflow dam is 2970.00m. The upper part of the upstream face is vertical. To utilize part of the water weight to increase the stability of the dam body and thus reduce the amount of concrete in the dam body, the lower part is a slope with an elevation of 2909.00m and a slope ratio of 1:0.30. The downstream face of the weir crest connects with a straight line of 1:0.75 and a reverse arc curve segment 2 with a diameter of 35.0m through the WES curve to form the spillway surface.

[0069] After the reverse curve segment 2 reaches its lowest point, it smoothly connects to two cantilever bodies 3. The two cantilever bodies 3 are arranged along the width direction of the reverse curve segment 2. The working surface of the cantilever body 3 is an isosceles trapezoid, and the large end of the cantilever body 3 connects to the reverse curve segment 2. The central angle θ of the reverse curve segment 2 is 53°. The angle θ1 formed by the starting point of the base plate 4 and the lowest point of the reverse curve segment 2 is 5°. The exit angle of the cantilever body 3 is 35°. The small end of the cantilever body 3... The width of the cantilever body 3 is 10m, the width of the hypotenuse of the cantilever body 3 is 3.75m, the distance between the end of the cantilever body 3 closest to the side wall 1 and the side wall 1 is 10m, the distance between the close points of the two cantilever bodies 3 is 5m, the radius of the arc of the top surface of the diversion pier 5 is 17.5m, the central angle is 40°, the height of the diversion pier 5 is 8m, the distance from the end of the diversion pier 5 to the small end of the cantilever body 3 is 5m, and the length of the straight section of the diversion pier 5 is 15.7m.

[0070] A systematic hydraulic model test was conducted on this structure. The test results showed that, with the upstream reservoir water level at the check level of 2991.62m, the discharge capacity of all three overflow orifices fully open was 8994.32m. 3 / s, in terms of the shape of the water tongue, it presents a three-dimensional spatial shape that diffuses both horizontally and vertically. The water flow that is ejected from the bottom plate 4 falls to the near point, and the water flow that is ejected from the inclined side of the sill body 3 gradually becomes farther away. The water flow that is ejected from the small end of the sill body 3 falls the farthest. The entire water tongue falling area is approximately rectangular.

[0071] From the perspective of hydraulic parameters, the far and near distances of the water tongue are 106.8m and 25.8m respectively, the longitudinal extension length of the water tongue is 81m, and the width of the water tongue is 65m, indicating a good diffusion effect. The entry angles of the far and near ends of the water tongue are 33° and 16° respectively. The downstream water surface fluctuations are small, with the maximum fluctuation in the downstream impact zone not exceeding 3.0m. The flow velocity at the bank is below 5m / s. The scour pits in the cushion pond are relatively flat and shallow, with a maximum depth of less than 10m. Moreover, the water flow in the cushion pond forms a backflow, so the sediment will not be washed downstream to form large scour pits. Instead, it will move upstream to the dam toe and settle back down, forming a stable mound, which is conducive to the stability of the dam.

[0072] When the downstream reservoir water level drops and the gate is fully open, the lateral width of the water tongue does not change much. Due to the reduced flow rate, the far-reaching distance of the water tongue decreases slightly, while the near-reaching distance increases slightly. The longitudinal separation distance decreases slightly, but the overall shape does not change significantly. The water tongue's drop range is stable at different water levels, and the rectangular areas entering the water approximately overlap.

[0073] When the flow rate decreases further and the gate is partially open, the thickness of the jet water tongue is thinner, the far-reaching distance of the water tongue increases slightly, the near-reaching distance remains approximately unchanged, the longitudinal extension length of the water tongue increases, and the diffusion effect is good.

[0074] In summary, under the action of this sill, the outgoing water jet has an excellent diffusion effect, with varying degrees of diffusion in both the lateral and longitudinal directions, resulting in good energy dissipation. Furthermore, the water flow in the downstream stilling basin has a good channel return effect, a small downstream impact area, minimal water surface fluctuations, and low flow velocity. This minimizes scouring of the bank slope and bottom, which is highly beneficial to bank slope stability and dam stability. It significantly reduces the protection costs required by traditional methods and is highly beneficial in terms of energy dissipation effect, engineering safety, and economic indicators, making it of great promotional value.

[0075] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A spillway for flood discharge in a gravity dam, characterized in that... The structure includes a side wall (1), a reverse arc curve section (2), a cantilever sill body (3), and a base plate (4); there are two sets of side walls (1), which are arranged in parallel; the reverse arc curve section (2) and the base plate (4) are both located between the two sets of side walls (1), and the reverse arc curve section (2) and the base plate (4) are connected sequentially to the outlet end of the straight section of the gravity dam's spillway, and the outlet end of the base plate (4) extends away from the center of the reverse arc curve section (2); the cantilever sill body... The working surface of the body (3) is trapezoidal in shape. The body (3) is located in the middle of the bottom plate (4). The large end of the body (3) is connected to the water outlet end of the reverse arc curve segment (2). The working surface of the body (3) is a downward concave arc surface. The radius of the working surface of the body (3) is equal to the radius of the working surface of the reverse arc curve segment (2). The center of the working surface of the body (3) coincides with the center of the working surface of the reverse arc curve segment (2). The angle formed by the line connecting the water inlet end of the base plate (4) to the center of the working surface of the reverse arc curve segment (2) and the line connecting the lowest point of the reverse arc curve segment (2) to the center of the working surface of the reverse arc curve segment (2) is 5° to 10°. It also includes a diversion pier (5), which is set between the two sets of side walls (1). The length direction of the diversion pier (5) is parallel to the length direction of the side wall (1), and the diversion pier (5) extends from the water inlet end of the reverse arc curve segment (2) to the small end of the sill body (3). The distance between the end point of the diversion pier (5) and the small end of the cantilever body (3) is d, where d is 0~(θ1-θ2)R / 2m.

2. The embankment according to claim 1, characterized in that... The radius of the working surface of the reverse arc curve segment (2) is R = (6~12)h, where h is the water depth at the lowest point of the reverse arc curve segment (2) when the gravity dam discharges water at the highest water level.

3. The embankment according to claim 2, characterized in that... The central angle θ2 of the body (3) of the sill is 30° to 40°.

4. The embankment according to claim 3, characterized in that... The distance H between the end point of the diversion pier (5) and the cantilever body (3) d h+H c H c =2~3m.

5. The embankment according to any one of claims 1 to 4, characterized in that... The number of the cantilever body (3) is multiple, and the multiple cantilever bodies (3) are arranged sequentially along the width direction of the base plate (4).

6. The embankment according to claim 5, characterized in that... The working surface of the sloping body (3) is an isosceles trapezoid.

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