CN104294802B - Down stream formula step plunge pool system - Google Patents

Abstract

The falling flow cascaded water cushion pond energy dissipation system of the present invention includes a multi-level stepped cushion pond arranged at different elevations on the side of the reservoir dam body, and an upstream water diversion channel leading out the water in the reservoir. The horizontal spillway corresponding to the water cushion ponds at all levels from the elevation to the lowest elevation and the bank diversion channel that introduces the water in the water cushion ponds at the lowest elevation into the downstream channel. The downstream ends of the water cushion ponds at all levels are located on the same side, and the downstream ends Overflow weirs are set on the side walls; the outlet of the upstream diversion channel is located above the upper reaches of the highest-elevation water cushion pond, and the horizontal spillway corresponding to the second-elevation water cushion pond is at the same elevation as the highest-elevation water cushion pond The overflow weir set in the pad pond is connected, and its water outlet is located above the upstream of the pad pond at the second elevation, ... . The energy dissipation system of the invention can avoid the damage of the pad pond, ensure the safety of the downstream river course, and improve the energy dissipation rate.

Description

Energy Dissipation System of Falling Flow Cascade Cushion Pond

technical field

The invention belongs to the technical field of flood discharge and energy dissipation in water conservancy and hydropower projects, and in particular relates to an energy dissipation system suitable for combining water cushion ponds and falling flow energy dissipation in narrow valleys and downstream rivers changing from narrow to wide in small flow and high head water conservancy projects .

Background technique

In the construction of high water head power stations, in order to ensure the safety of hydraulic projects in operation, a series of flood discharge and energy dissipation measures are required. Traditional energy dissipation measures include traditional underflow energy dissipation, deflected flow energy dissipation and surface flow energy dissipation. New energy dissipation facilities include vertical shaft swirl energy dissipation, wide end pier, ladder energy dissipation, hole plug orifice energy dissipation, etc. However, for projects with narrow river valleys, vertical mountains on both sides, rapid changes in downstream channels from narrow to wide, and complex geological conditions on the bank slope, it is difficult to arrange water cushion ponds and large single-width projects according to the existing technology due to obstacles caused by geological conditions. The flood discharge tunnel with large flow rate, or the arrangement of energy-dissipating facilities in the prior art, the project cost is high and the construction period is increased.

Contents of the invention

The purpose of the present invention is to address the deficiencies of the existing technology, and provide a cascading cascaded pad pond energy dissipation system suitable for narrow valleys and downstream rivers that change from narrow to wide and low-flow and high-head water conservancy projects, so as to improve the energy dissipation rate and project efficiency. Safety and economy, reducing the difficulty of hub layout.

The falling flow cascaded water cushion pond energy dissipation system of the present invention includes a multi-level stepped cushion pond arranged at different elevations on the side of the reservoir dam body, and an upstream water diversion channel leading out the water in the reservoir. The horizontal spillway corresponding to the water cushion ponds at all levels from the elevation to the lowest elevation and the bank diversion channel that introduces the water in the water cushion ponds at the lowest elevation to the downstream channel. Overflow weirs are set on the side walls of the downstream end of the pond; the outlet of the upstream diversion channel is located above the upper reaches of the highest elevation pond, and the horizontal spillway corresponding to the second elevation pond is at the same elevation as the highest elevation pond The overflow weir set in the highest elevation pond is connected, and its outlet is located above the upstream of the second elevation pond, and the horizontal spillway corresponding to the third elevation pond is at the same elevation as the second elevation pond and is the same as the second elevation pond. The overflow weir of the elevation paddle pond is connected, and its outlet is located above the upper reaches of the third elevation paddle pond, ..., the horizontal spillway corresponding to the lowest elevation paddle pond is the same as the elevation of the next lowest elevation paddle pond and is the same as the second lowest elevation paddle pond The overflow weir of the elevation pad pond is connected, and its water outlet is located above the upper reaches of the lowest elevation pad pond, and the water inlet end of the bank diversion channel is connected with the overflow weir provided on the downstream side wall of the lowest elevation pad pond, Its end is connected with the downstream channel, so that the water in the reservoir drops to the highest elevation cushion pond through the upstream diversion channel, and then drops through the horizontal spillways corresponding to the water cushion ponds at all levels from the second elevation to the lowest elevation from high to low. In the water cushion ponds at all levels, and flow into the downstream channel through the diversion channel on the bank. In this process, the falling flow is used to cause the water flow to collide, resulting in strong impact, turbulence, mixing and shearing, to eliminate part of the energy, so as to improve the energy dissipation rate and avoid engineering damage.

For the energy dissipation system of the above-mentioned falling-flow cascaded water cushion ponds, the axis of the water cushion ponds shall be arranged in the way with the least excavation amount. The axes of the pad ponds are partially parallel and partially intersected. If the axes of the pad ponds intersect, the intersection angle is an acute angle.

For the energy dissipation system of the above-mentioned cascaded water cushion ponds with falling flow, the elevation difference between two adjacent water cushion ponds is △x=30-45m, so as to prevent the water cushion ponds from being damaged by excessive falling velocity and ensure the minimum engineering quantity. The elevation difference between pad ponds at all levels is selected according to geological conditions, and can be equal or unequal.

For the energy dissipation system of the above-mentioned falling flow cascaded water cushion pond, the length of the water cushion pond is l=20-40m, the width b ₁ =15-30m, and the depth h ₁ =maximum water level height+fluctuation height+safe superelevation. The maximum water level height is the water level height in the pad pond corresponding to the maximum discharge flow, the fluctuation height is the water level change caused by the violent tumbling of the water flow, and the safe superelevation is the height required to ensure that the water flow will not turn out of the pad pond . In order to avoid the damage of the water cushion pond, the tensile stress of the concrete in the water cushion pond should be avoided. The water cushion pond should be built in the excavation to avoid filling as much as possible, and the water cushion pond should take anti-seepage measures to avoid energy dissipation caused by leakage System disruption. At the same time, a certain water depth should be guaranteed in the water cushion ponds at all levels to prevent the maximum flow of falling water from directly impacting the water cushion pond floor during flood discharge, causing damage to the water cushion ponds, and then scouring the mountains, causing irreparable damage and endangering the operation safety of the hub.

In the falling flow cascaded water cushion pond energy dissipation system, the width of the overflow weir b ₂ ≤ b ₁ , where b ₁ is the width of the water cushion pond. The width of the inlet of the horizontal spillway corresponding to the water cushion ponds at all levels from the second elevation to the lowest elevation = the overflow weir width of the water cushion pond of the previous level, so the horizontal spillway connected between the two-level water cushion ponds runs from upstream to downstream Can be constant width or progressive.

In the falling flow cascaded cushion pond energy dissipation system, the angle between the water flow direction at the end of the bank diversion channel and the water flow direction of the downstream channel is an acute angle, so as to ensure that the water flow smoothly enters the river channel and prevent scour.

Compared with the prior art, the present invention has the following beneficial effects:

1. The energy dissipation system of the present invention combines the energy dissipation of the falling flow and the water cushion pond for energy dissipation in sections, which increases the energy dissipation rate compared with the surface steep groove spillway (i>1), because it is arranged on the mountain side of the dam body , to avoid the construction of cushion ponds in narrow river valleys, the possible damage to the cushion ponds caused by low-flow and high-head water flow, or the erosion of downstream rivers when deflecting flow is used to dissipate energy, thus ensuring the safety of the hub, especially suitable for downstream The water conservancy project with small flow and high head that the river channel quickly changes from narrow to wide solves the problems of site conditions and topographic and geological conditions that are arranged in the existing energy dissipation method.

2. The energy dissipation system of the present invention is built in accordance with the engineering geological conditions and geomorphic conditions of the dam site where the hub is located. By adjusting the axes of the water cushion ponds and the size of the water cushion ponds at all levels, the amount of excavation and filling can be minimized, avoiding the need to When the spillway is built in the valley, a large amount of filling and excavation is usually required to reduce the slope of the spillway, which improves the economic benefits of the project.

3. The energy dissipation system of the present invention is built in accordance with the engineering geological conditions and topographical conditions of the dam site where the hub is located, and the elevation difference between adjacent two-stage pad ponds is flexibly designed according to the topographical and topographical conditions, and the layout is flexible, so it can avoid Unfavorable geological conditions greatly reduce the difficulty of hub layout.

Description of drawings

Fig. 1 is a top view of the first overall arrangement of the energy dissipation system of the falling flow cascaded cushion pond of the invention.

Fig. 2 is a top view of the second overall layout of the energy dissipation system of the falling-flow cascaded cushion pond described in the invention.

Fig. 3 is a top view of the third overall arrangement of the energy dissipation system of the falling flow cascaded cushion pond according to the invention.

Fig. 4 is a top view of the fourth general arrangement of the energy dissipation system of the falling-flow cascaded cushion pond according to the invention.

Fig. 5 is a top view of the fifth overall arrangement of the energy dissipation system of the falling-flow cascaded cushion pond according to the invention.

FIG. 6 is a cross-sectional view along line A-A of FIG. 1 .

Fig. 7 is a structural schematic diagram of a single cushion pond and the horizontal spillway connected thereto.

Fig. 8 is a B-B sectional view of Fig. 7 .

FIG. 9 is a C-C sectional view of FIG. 7 .

In the figure, 1—upstream diversion channel, 2—water cushion pond, 3—overflow weir, 4—horizontal spillway, 5—bank diversion channel, 6—downstream channel, 7—mountain, 8 ——original ground line, 9—water surface line, 10—dam, 11—upstream reservoir, h ₁ —depth of water cushion, h ₂ —height of overflow weir, Δx—distance between adjacent water cushions The elevation difference between them, l—the length of the water cushion pond, b ₁ ——the width of the water cushion pond, b ₂ ——the width of the overflow weir.

detailed description

The energy dissipation system of the falling flow cascaded cushion pond of the present invention will be further described through the examples below.

The engineering overview of embodiment 1 and comparative example 1 is as follows:

A power station is built in a narrow river valley, with steep mountains on both sides, and the downstream channel quickly changes from narrow to wide. The upstream water level elevation of the reservoir is 621.00m and the downstream water level elevation is 531.00m, the drop is 90m, and the discharge flow rate is 300m ³ /s. Aiming at the above projects, two energy dissipation systems of Example 1 and Comparative Example 1 were used to carry out hydraulic model tests.

Example 1

This implementation adopts the energy dissipation system of cascaded water cushion ponds of falling flow, including the water cushion ponds 2 arranged in three steps at different elevations on the side of the reservoir dam body, and the upstream diversion channel 1 that draws the water out of the reservoir. , the horizontal spillway 4 corresponding to the water cushion ponds at all levels of the second elevation and the lowest elevation and the bank diversion channel 5 that introduces the water in the water cushion ponds at the lowest elevation into the downstream channel 6, and the downstream ends of the water cushion ponds at all levels are located at the same On the side, overflow weirs 3 are set on the downstream end walls of the water cushion ponds at all levels; Above the upper reaches of the high-elevation pad, the horizontal spillway corresponding to the second-elevation pad is at the same elevation as the highest-elevation pad and connected to the overflow weir set in the highest-elevation pad, and its outlet is located at the second-elevation pad Above the upstream of the pond, the horizontal spillway corresponding to the lowest elevation pond has the same elevation as the second elevation pond and connects with the overflow weir of the second elevation pond, and its outlet is located above the upstream of the lowest elevation pond , the water inlet end of the bank diversion canal 5 is connected with the overflow weir 3 arranged on the side wall at the downstream end of the lowest elevation pad pond, and its end is connected with the downstream river channel 6, and the water flow direction at the bank diversion channel 5 end is in line with the downstream channel The angle at which the water flow directions of 6 intersect is 27.1°.

The structure of the water cushion pond is shown in Figure 7, Figure 8, and Figure 9. The dimensions of the three-stage cushion ponds are the same, their length l=20m, width b ₁ =15m, depth h ₁ =10m, their overflow weir height h ₂ =5m, width b ₂ =b ₁ , where b ₁ is the width of the pad, the elevation difference between the highest elevation pad and the second elevation pad = the elevation difference between the second elevation pad and the lowest elevation pad = 30m, and the second elevation pad The width of the inlet of the horizontal spillway corresponding to the pond is equal to the width of the overflow weir of the highest elevation pad pond, and the width of the inlet of the horizontal spillway corresponding to the lowest elevation pad pond is equal to the width of the overflow weir of the second elevation pad pond. The width of the water outlet is the same as that of the corresponding pad pond (see Figure 3).

Test results: When the discharge rate is 300m ³ /s, the water flow enters the downstream channel smoothly. The average velocity of the water flow in the diversion channel on the bank is measured to be 6.5m/s, and the energy dissipation rate of the cascade pond energy dissipation system reaches 95%. The fill volume is 17,000 m ³ .

Comparative example 1

The energy dissipation system is arranged with steep trough spillway and water cushion pond, and the slope of the steep trough spillway is 0.8.

Test results: when the discharge rate is 300m ³ /s, the measured average flow velocity at the end of the pad pond is 13.18m/s, and the maximum flow velocity in the pad pond reaches ^25.69m /s. The economic benefit and energy dissipation effect are lower than that of Example 1.

The engineering overview of embodiment 2 and comparative example 2 is as follows:

A power station is built in a narrow river valley, with steep mountains on both sides, and the downstream channel rapidly changes from narrow to wide. The elevation of the reservoir entrance is 2126.00m, the elevation of the exit is 2011.00m, the drop is 115m, and the discharge flow is 600m ³ /s. Aiming at the above projects, two energy dissipation systems of Example 2 and Comparative Example 2 were used to carry out hydraulic model tests.

Example 2

This implementation adopts the energy dissipation system of cascaded water cushion ponds of falling flow, including the water cushion ponds 2 arranged in three steps at different elevations on the side of the reservoir dam body, and the upstream diversion channel 1 that draws the water out of the reservoir. , the horizontal spillway 4 corresponding to the water cushion ponds at all levels of the second elevation and the lowest elevation and the bank diversion channel 5 that introduces the water in the water cushion ponds at the lowest elevation into the downstream channel 6, and the downstream ends of the water cushion ponds at all levels are located at the same On the other side, overflow weirs 3 are set on the downstream end walls of the pad ponds at all levels; the layout of the above-mentioned facilities is similar to that shown in Figure 4. The axis of the paddy pond intersects with the axis of the lowest elevation paddy pond to form an angle of 18.4°; the outlet of the upstream diversion channel 1 is located above the upstream of the highest elevation paddy pond, and the horizontal spillway corresponding to the second elevation paddle pond and the highest elevation paddy pond The same elevation and connected with the overflow weir set in the highest elevation pond, its outlet is located above the upstream of the second elevation pond, and the horizontal spillway corresponding to the lowest elevation pond is at the same elevation as the second elevation pond And it is connected with the overflow weir of the second elevation pad pond, and its water outlet is located above the upstream of the lowest elevation pad pond, and the water inlet end of the bank diversion channel 5 is set with the bottom side wall of the lowest elevation pad pond. The overflow weir 3 is connected, and its end is connected with the downstream channel 6, and the angle at which the flow direction at the end of the bank diversion channel 5 intersects with the flow direction of the downstream channel 6 is 26.7°.

The structure of the water cushion pond is shown in Figure 7, Figure 8, and Figure 9. The highest elevation water cushion pond has the same size as the second elevation water cushion pond, their length l=30m, width b ₁ =25m, depth h ₁ =15m, and the height h ₂ of the overflow weir 3 =5m, width b ₂ = 20m<b ₁ , where b ₁ is the width of the pad, and the elevation difference between the pad at the highest elevation and the pad at the second elevation = 45m. The lowest elevation water cushion pond has length l=40m, width b ₁ =30m, depth h ₁ =15m, height of overflow weir h ₂ =5m, width b ₂ =20m<b ₁ , where b ₁ is the water cushion pond Width, the difference in elevation between the lowest elevation pool and the second elevation pool = 35m. The width of the inlet of the horizontal spillway corresponding to the second elevation pad pond is equal to the width of the overflow weir of the highest elevation pad pond, and the width of the inlet of the horizontal spillway corresponding to the lowest elevation pad pond is equal to the width of the overflow weir of the second elevation pad pond Equal, the width of the outlet of each horizontal spillway is the same as the width of the corresponding pad (similar to Figure 2).

Test results: When the discharge rate is 600m ³ /s, the water flow enters the river smoothly, and there is no obvious erosion on the downstream bank slope and the bottom of the river. The measured flow velocity at the outlet of the bank diversion channel is 8.3m/s. 96.5%.

Comparative example 2

The upstream flood discharge tunnel is adopted, and the lower part is directly connected to the energy dissipation system of the downstream river channel.

Test results: When the discharge rate is 600m ³ /s, the drop point of the deflector is only 4.2m away from the opposite bank of the river, and the scour depth reaches 32.12m, which threatens the safety of the downstream river slope and the normal operation of the project.

The engineering overview of embodiment 3 and comparative example 3 is as follows:

A power station is built in a narrow river valley, with steep mountains on both sides, and the downstream channel quickly changes from narrow to wide. The elevation of the reservoir entrance is 1426.00m, the elevation of the exit is 1321.00m, the drop is 105m, and the discharge flow is 1200m ³ /s. Aiming at the above projects, two energy dissipation systems of Example 3 and Comparative Example 3 were used to carry out hydraulic model tests.

Example 3

This implementation adopts the energy dissipation system of cascaded water cushion ponds of falling flow, including the water cushion ponds 2 arranged in three steps at different elevations on the side of the reservoir dam body, and the upstream diversion channel 1 that draws the water out of the reservoir. , the horizontal spillway 4 corresponding to the water cushion ponds at all levels of the second elevation and the lowest elevation and the bank diversion channel 5 that introduces the water in the water cushion ponds at the lowest elevation into the downstream channel 6, and the downstream ends of the water cushion ponds at all levels are located at the same On the other side, overflow weirs 3 are set on the downstream end walls of the pad ponds at all levels; the layout of the above-mentioned facilities is similar to that shown in Figure 4. The axis of the paddy pond intersects with the axis of the lowest elevation paddle pond to form an angle of 39.5°; the outlet of the upstream diversion channel 1 is located above the upper reaches of the highest elevation paddy pond, and the horizontal spillway corresponding to the second elevation paddle pond and the highest elevation paddle pond The same elevation and connected with the overflow weir set in the highest elevation pond, its outlet is located above the upstream of the second elevation pond, and the horizontal spillway corresponding to the lowest elevation pond is at the same elevation as the second elevation pond And it is connected with the overflow weir of the second elevation pad pond, and its water outlet is located above the upstream of the lowest elevation pad pond, and the water inlet end of the bank diversion channel 5 is set with the bottom side wall of the lowest elevation pad pond. The overflow weir 3 is connected, and its end is connected with the downstream channel 6, and the angle at which the flow direction at the end of the bank diversion channel 5 intersects with the flow direction of the downstream channel 6 is 32°.

The structure of the water cushion pond is shown in Figure 7, Figure 8, and Figure 9. The dimensions of the three-stage cushion ponds are the same, their length l=30m, width b ₁ =25m, depth h ₁ =12m, their overflow weir height h ₂ =5m, width b ₂ =18m<b ₁ , where b ₁ is the width of the paddy pond, the elevation difference between the highest elevation paddle pond and the second elevation paddle pond = the elevation difference between the second elevation paddle pond and the lowest elevation paddle pond = 35m, the second elevation The width of the water inlet of the horizontal spillway corresponding to the water cushion pond is equal to the width of the overflow weir of the water cushion pond at the highest elevation, and the width of the water inlet of the horizontal spillway corresponding to the water cushion pond at the lowest elevation is equal to the width of the overflow weir of the water cushion pond at the second elevation. The width of the outlet of the horizontal spillway is equal to the width of the inlet (see Figure 4).

Test results: When the flood discharge flow rate is 1200m ³ /s, the water flow enters the river smoothly, and there is no obvious erosion on the downstream bank slope and the bottom of the river. 97.2%.

Comparative example 3

The upstream flood discharge tunnel is adopted, and the lower part is directly connected to the energy dissipation system of the downstream river channel.

Test results: When the flood discharge rate is 1200m ³ /s, the drop point of the deflector is only 10.2m away from the opposite bank of the river, and the downstream fogging is serious, and the scour depth reaches 32.12m, which threatens the safety of the downstream river slope and the normal operation of the project.

It should be noted that the "second elevation water cushion pond" in the above embodiments can also be called "second-lowest elevation water cushion pond".

Claims (10)

1. A drop-flow type cascaded water cushion pond energy dissipation system is characterized in that the system includes a multi-stage stepped water cushion pond (2) arranged at different elevations on the side of the reservoir dam body, and the water in the reservoir is The upstream aqueduct (1) drawn, the horizontal spillway (4) corresponding to the pad ponds at all levels from the second elevation to the lowest elevation, and the bank aqueduct ( 5), the downstream ends of the water cushion ponds at all levels are located on the same side, and overflow weirs (3) are arranged on the side walls of the downstream ends of the water cushion ponds at all levels; the outlet of the upstream diversion channel (1) is located at the highest elevation of the water cushion ponds The horizontal spillway corresponding to the second elevation pond is at the same elevation as the highest elevation pond and connects with the overflow weir set in the highest elevation pond, and its outlet is located above the upstream of the second elevation pond , the horizontal spillway corresponding to the third elevation pond is at the same elevation as the second elevation pond and connects with the overflow weir of the second elevation pond, and its outlet is located above the upstream of the third elevation pond, the lowest The horizontal spillway corresponding to the elevation pond is at the same elevation as the second-lowest elevation pond and connects with the overflow weir of the second-lowest elevation pond, and its outlet is located above the upper reaches of the lowest elevation pond. The water inlet end of the water channel (5) is connected with the overflow weir provided on the downstream side wall of the lowest elevation pad pond, and its end is connected with the downstream channel (6), so that the water in the reservoir is dropped to the highest elevation water through the upstream diversion channel. Dian ponds, and then through the horizontal spillways corresponding to the pad ponds at all levels from the second elevation to the lowest elevation, drop into the pad ponds at all levels in turn from high to low, and flow into the downstream channel through the bank diversion channel (5). 2. According to claim 1, the cascaded cascaded water cushion pond energy dissipation system is characterized in that the axes of the water cushion ponds at all levels are parallel to each other or intersect to form an acute angle. 3. According to claim 1 or 2, the cascade cascaded water cushion pond energy dissipation system is characterized in that the elevation difference between two adjacent water cushion ponds is Δx=30-45m. 4. According to claim 1 or 2, the falling flow cascaded water cushion pond energy dissipation system is characterized in that the length of the water cushion pond is l=20-40m, the width b ₁ =15-30m, and the depth h ₁ =maximum Water level height + fluctuation height + safety super high. 5. According to claim 3, the falling flow cascaded water cushion pond energy dissipation system is characterized in that the length of the water cushion pond is l=20-40m, the width b ₁ =15-30m, and the depth h ₁ =maximum water level +Swing height+Safe super high. 6. According to claim 1 or 2, the cascaded cascaded water cushion pond energy dissipation system is characterized in that the width of the overflow weir (3) b ₂ ≤ b ₁ , where b ₁ is the width of the water cushion pond . 7. The energy dissipation system of the cascading water cushion pond according to claim 3, characterized in that the width of the overflow weir (3) b ₂ ≤ b ₁ , where b ₁ is the width of the water cushion pond. 8. The energy dissipation system of the falling flow cascaded water cushion pond according to claim 4, characterized in that the width of the overflow weir (3) b ₂ ≤ b ₁ , where b ₁ is the width of the water cushion pond. 9. The energy dissipation system of falling flow cascaded water cushion ponds according to claim 5, characterized in that the width of the overflow weir (3) b ₂ ≤ b ₁ , where b ₁ is the width of the water cushion ponds. 10. According to claim 1 or 2, the falling flow cascaded water cushion pond energy dissipation system is characterized in that the angle at which the water flow direction at the end of the bank diversion channel (5) intersects with the water flow direction of the downstream channel (6) is acute angle.