A combined energy dissipation structure of a diversion tunnel body and an outlet thereof

Abstract

The application provides a combined energy dissipation structure of a diversion tunnel body and an outlet of the diversion tunnel, and relates to the technical field of water conservancy and hydropower engineering, comprising a diversion tunnel, wherein the diversion tunnel comprises a pressure slope section, the tail end of the pressure slope section is connected with an expansion section, the tail end of the expansion section is connected with a stilling basin, the tail end of the stilling basin is connected with an energy dissipation baffle, the tail end of the expansion section is provided with a guide wall, the guide wall comprises a left guide wall and a right guide wall, and the stilling basin and the energy dissipation baffle are arranged in the guide wall. The application effectively reduces the flow velocity of the outlet water flow through the expansion section of the tunnel body, realizes the partial energy dissipation of the water flow in the tunnel, and further improves the energy dissipation effect in cooperation with the stilling basin and the energy dissipation baffle. The application has low construction difficulty, excellent energy dissipation effect, and provides a novel and efficient energy dissipation structure for the diversion tunnel structure of water conservancy and hydropower engineering.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering technology, and in particular to an outlet energy dissipation structure outside the combined diversion tunnel. Background Technology

[0002] With the continuous expansion of high-dam and large-reservoir hydropower development in my country, the complexity of diversion tunnel projects in narrow river valleys and the technical challenges they face are becoming increasingly prominent. These areas have complex topographical and geological conditions, limited space at the outlet, restrictive energy dissipation facility placement, and weak erosion resistance on riverbanks, with numerous deposits, landslides, and other adverse geological hazards. During flood season, diversion tunnels in narrow river valleys exhibit high flow velocities and large total discharge power, making the need to dissipate the enormous energy of the outlet flow a critical technical challenge. Therefore, it is imperative to develop innovative energy dissipation structures to overcome the bottlenecks in energy dissipation at the diversion tunnel outlet under multiple constraints, effectively ensuring energy dissipation performance, thereby guaranteeing the safety of the diversion tunnel flow and providing reliable support for power station construction. Summary of the Invention

[0003] This invention provides an outlet energy dissipation structure outside the combined diversion tunnel, which aims to solve the outlet energy dissipation problem under complex conditions such as excessively high flow velocity at the diversion tunnel outlet, narrow terrain conditions, limited energy dissipation space, and weak erosion resistance of the riverbanks, thereby ensuring smooth flow through the diversion tunnel and guaranteeing the smooth implementation of power station construction.

[0004] The present invention provides the following technical solution to achieve the above objectives: An energy dissipation structure at the outlet outside the main body of a combined diversion tunnel includes a diversion tunnel, which includes a slope section at its end, connected to an enlargement section at its end; an energy dissipation pool at its end, and an energy dissipation sill at its end; a guide wall at the end of the enlargement section, including a left guide wall and a right guide wall; the energy dissipation pool and the energy dissipation sill are located within the guide wall; the cross-sectional dimensions of the enlargement section of the diversion tunnel are larger than those of the slope section.

[0005] Furthermore, the slope ratio of the slope compression section is 1:10.

[0006] Furthermore, the left and right guide walls are arranged at a 5° angle towards the energy dissipation sill.

[0007] Furthermore, the length of the energy dissipation pool is greater than the energy dissipation sill.

[0008] Furthermore, the elevation of the energy dissipation sill is higher than that of the stilling pool, and the energy dissipation sill and the stilling pool are connected by a slope with a slope ratio of 1:1.

[0009] Furthermore, the length of the guide wall is set to be equal to the sum of the lengths of the stilling pool and the energy dissipation sill.

[0010] Furthermore, the energy dissipation sill is a wide platform structure.

[0011] Furthermore, the elevation of the first end of the guide wall is set higher than that of the last end, and the elevation of the last end of the guide wall is consistent with that of the energy dissipation sill.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by the present invention changes the mainstream direction of the water flow in the tunnel by using the slope section of the normal cross-section of the diversion tunnel, so that the mainstream direction changes from the top of the tunnel to the bottom of the tunnel and then enters the outlet expansion section. 2. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by this invention effectively reduces the flow velocity of the outlet water by expanding the outlet section of the tunnel body, thereby dissipating part of the energy of the water flow within the tunnel. 3. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by the present invention further reduces the flow velocity through a diffusion-type stilling pool, so that the water flow can fully diffuse and dissipate energy in front of the energy dissipation sill, thereby improving the energy dissipation rate of the water flow in front of the sill. 4. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by the present invention increases the water depth and adjusts the flow state by increasing the energy dissipation sill, so that the water flow is dispersed again and the flow velocity is more uniform, and the flow velocity is reduced again, thereby achieving the energy dissipation effect at the outlet. 5. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by this invention eliminates the need for any anti-scour facilities downstream of the energy dissipation sill. As the outlet expansion section and stilling basin reduce some energy and flow velocity, the energy dissipation sill further reduces the flow velocity, allowing the main stream to flow close to the right bank and into the downstream channel after passing the tail sill, ensuring smooth connection with the downstream river surface and a relatively stable river surface.

[0013] 6. The energy dissipation and scour prevention structure at the outlet of the diversion tunnel provided by this invention allows the water flow to be closer to the right bank and flow into the downstream channel through the left guide wall, reducing the impact of the water flow back to the left bank riverbed on the slope toe structure.

[0014] 7. The energy dissipation and anti-scour structure at the outlet of the diversion tunnel provided by this invention has a diffusion angle of only 5° on both sides of the stilling pool. The small diffusion angle allows for the arrangement of energy dissipation-related facilities under conditions of narrow outlet site and limited energy dissipation space, thereby achieving an effective energy dissipation effect.

[0015] 8. The energy dissipation and scour prevention structure at the outlet of the diversion tunnel provided by this invention is more suitable with a 10m difference between the elevation of the energy dissipation sill and the stilling pool. The energy dissipation sill and the stilling pool are connected with a 1:1 slope. The energy dissipation sill structure is designed as a wide platform structure in combination with the topographic conditions of the outlet area to ensure a smoother connection between the water flow over the sill and the downstream river surface, effectively reducing the scour and siltation of the downstream riverbed. Attached Figure Description

[0016] Figure 1 This is a top view of the energy dissipation and scour protection structure at the outlet of the diversion tunnel; Figure 2 This is a front view of the energy dissipation and scour protection structure at the outlet of the diversion tunnel; Figure 3 This is a downstream river channel scour and sedimentation distribution map of Example 1; Figure 4 This is a map showing the distribution of scour and sedimentation in the downstream channel of Comparative Example 1; Figure 5 This is a downstream river velocity distribution map of Comparative Example 1; Figure 6 This is a downstream river velocity distribution map of Example 1; Figure 7 This is a schematic diagram of the flow pattern at the outlet of the diversion tunnel and the downstream river channel in Comparative Example 2; Figure 8 This is a diagram showing the velocity distribution along the axis of the guide tunnel in Comparative Example 2. Figure 9 This is a diagram showing the distribution of the water surface line along the axis of the diversion tunnel in Comparative Example 2. Figure 10 This is a schematic diagram of the flow pattern at the outlet of the diversion tunnel and the downstream river channel in Example 1; Figure 11 This is a flow velocity distribution diagram along the axis of the guide tunnel in Example 1; Figure 12 This is a diagram showing the distribution of the water surface line along the axis of the diversion tunnel in Example 1.

[0017] Attached diagram labels: 1- Normal dimensional slope section of tunnel body; 2- Enlarged cross-section section of tunnel exit; 3- Left guide wall; 4- Right guide wall; 5- Stilling basin; 6- Energy dissipation sill. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0019] It should be noted that the terms "vertical," "horizontal," "up," "down," "left," "right," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] Example 1. An energy dissipation structure at the outlet outside the combined diversion tunnel, the structure is referenced. Figure 1 and Figure 2 The system includes a diversion tunnel, which comprises a slope section 1, the end of which is connected to an enlargement section 2. The end of the enlargement section 2 is connected to a stilling basin 5, and the end of the stilling basin 5 is connected to an energy dissipation sill 6. A guide wall is provided at the end of the enlargement section 2, including a left guide wall 3 and a right guide wall 4. The stilling basin 5 and the energy dissipation sill 6 are located within the guide wall. The cross-sectional dimensions of the enlargement section 2 of the diversion tunnel are larger than those of the slope section 1. The dimensions of the enlargement section 2 are 17m × 24m (width × height), and the dimensions of the slope section 1 are 15m × 17m (width × height). By setting up the enlargement section 2 of the diversion tunnel, the outlet water velocity is effectively reduced, and some of the energy of the water flow is dissipated within the tunnel. By setting up the energy dissipation sill 6, the water depth is increased and the flow pattern is adjusted, so that the water flow is dispersed again and the flow velocity is more uniform, and the flow velocity is reduced again, achieving the outlet energy dissipation effect. The elevation of the top of the outlet of the enlargement section 2 of the diversion tunnel is slightly higher than the downstream water surface elevation under design conditions. The slope ratio of the slope section 1 is 1:10; the left guide wall 3 and the right guide wall 4 are arranged at a 5° angle towards the energy dissipation sill 6; as Figure 1 As shown, by setting the left guide wall 3 and right guide wall 4 at a 5° angle, the stilling basin 5 is arranged in a diffused manner, which improves the energy dissipation effect of the stilling basin 5. The diffused stilling basin further reduces the flow velocity, allowing the water flow to fully diffuse and dissipate energy in front of the energy dissipation sill, thus increasing the energy dissipation rate of the water flow in front of the sill. The length of the stilling basin 5 is greater than that of the energy dissipation sill 6. The elevation of the energy dissipation sill 6 is higher than that of the stilling basin 5. The energy dissipation sill 6 and the stilling basin 5 are connected by a slope with a slope ratio of 1:1. The elevation of the energy dissipation sill 6 is higher than that of the stilling basin 5. The stilling basin 5 is set at a depth of 10 meters, and the energy dissipation sill 6 is connected to the stilling basin 5 with a 1:1 slope. The energy dissipation sill 6 is a wide platform structure, which ensures a smoother connection between the water flow over the sill and the downstream river surface, effectively reducing the scouring and silting of the downstream riverbed. The length of the guide wall is equal to the sum of the lengths of the stilling basin 5 and the energy dissipation sill 6. The elevation of the first end of the guide wall is higher than the elevation of the last end, and the elevation of the last end of the guide wall is consistent with that of the energy dissipation sill 6. The aforementioned arrangement facilitates excavation along the terrain surface to the energy dissipation sill 6 during engineering practice, reducing the amount of work and the investment.

[0022] Comparative Example 1. A diversion tunnel without any energy dissipation devices, the dimensions of which are 15m × 17m (width × height).

[0023] Comparative Example 2. An energy dissipation structure at the outlet outside the combined diversion tunnel, with structural reference... Figure 1 and Figure 2The system includes a diversion tunnel, which comprises a slope section 1, the end of which is connected to an enlargement section 2; the end of the enlargement section 2 is connected to a stilling basin 5, and the end of the stilling basin 5 is connected to an energy dissipation sill 6; a guide wall is provided at the end of the enlargement section 2, including a left guide wall 3 and a right guide wall 4; the stilling basin 5 and the energy dissipation sill 6 are located within the guide wall; the cross-sectional dimensions of the enlargement section 2 are larger than those of the slope section 1, and the dimensions of the enlargement section 2 are 17m × 22m (width × height), while the dimensions of the slope section 1 are larger than those of the slope section 1. The dimensions are 15m × 17m (width × height); the slope ratio of the slope section 1 is 1:10; the left guide wall 3 and the right guide wall 4 are arranged at a 5° angle towards the energy dissipation sill 6; the elevation of the energy dissipation sill 6 is 10 meters higher than that of the stilling basin 5, and the energy dissipation sill 6 and the stilling basin 5 are connected by a slope with a slope ratio of 1:1; the length of the guide wall is equal to the sum of the lengths of the stilling basin 5 and the energy dissipation sill 6; the elevation of the first end of the guide wall is higher than that of the last end, and the elevation of the last end of the guide wall is consistent with that of the energy dissipation sill 6.

[0024] Experimental Example. A comparative experiment was conducted using equal-length models of the diversion tunnels described in Example 1 and Comparative Example 1 to determine their energy dissipation effects: The river flow velocity distribution and downstream scouring and deposition distribution in Example 1 are as follows: Figure 6 and Figure 3 As shown in the diagram, the main currents are all along the right bank. Tests were conducted under a 20-year flood event. After exiting the tunnel ( Figure 6 The minimum water flow velocity on the right bank (between 0+700 and 0+750) is 4.811 m / s, and the maximum water flow velocity is 14.834 m / s; Figure 6 The minimum backflow velocity on the left bank (between 0+750 and 0+800) was 4.550 m / s, and the maximum was 5.701 m / s. Due to the relatively high backflow velocity on the left bank, sedimentation occurred, resulting in slight scouring at the toe of the slope. The scouring cover layer was approximately 2 m thick. The scouring depth was relatively deeper near the main flow on the right bank, with the lowest point elevation around 3428 m. When the diversion flow decreased, the scouring depth and extent on the right side of the riverbed lessened. Under a 5-year flood event, the lowest point elevation of the scour pit was approximately 3433 m. Under a frequent flood event, the scour pit depth did not change significantly, but the scouring extent decreased. The scouring and sedimentation test results show that although there was a large backflow velocity on the left bank during high-flow diversion, the scouring at the toe of the slope was relatively slight, consisting mainly of the surface cover layer of the riverbed.

[0025] The distribution of river flow velocity and downstream scouring and deposition in Comparative Example 1 are as follows: Figure 5 and Figure 4 As shown, a test was conducted under a 20-year flood condition. Because no energy dissipation measures were implemented, after exiting the tunnel ( Figure 5The minimum water flow velocity on the right bank (between 0+700 and 0+750) is 11.664 m / s, and the maximum water flow velocity is 19.683 m / s. Figure 5 The minimum backflow velocity on the left bank (between 0+750 and 0+800) is 4.485 m / s, and the maximum is 7.731 m / s. The outflow from the tunnel rushes directly to the left bank, forming a large backflow area behind the downstream cofferdam. Due to this backflow, scour zones form at the toe of the left bank slope between 0+650 and 0+700 and between 0+850 and 0+950, ​​with the lowest point of the scour pit being less than 3435 meters. Sedimentation occurs between 0+700 and 0+850, with the highest point of sedimentation at approximately 3452 meters. The experimental results show that the diversion tunnel in Comparative Example 1 has a flow rate of approximately 4700 m³ / s, a unit width discharge capacity of approximately 310 m³ / s, a unit width flood discharge power of approximately 14,000 kW, and an outlet velocity of approximately 20 m / s. Therefore, relying solely on the downstream river water cannot achieve the purpose of energy dissipation.

[0026] A comparative test of equal-length models using the diversion tunnels described in Example 1 and Comparative Example 2 was conducted to determine the energy dissipation effects of Example 1 and Comparative Example 1: Comparative Example 2. The overall flow pattern of this type of structure under a 5-year flood event is as follows: Figure 7 As shown, the incoming flow forms a submerged hydraulic jump in the abrupt expansion section, and the tail sill plays a certain role in energy dissipation due to water accumulation. However, a secondary drop occurs after the tail sill. To understand the flow velocity distribution at the outlet of Comparative Example 2, a longitudinal section at the central axis of the diversion tunnel was selected. The velocity distribution and water surface line are shown in the figure. Figure 8 and Figure 9 As shown in the figure, analysis of its flow velocity reveals that the mainstream remains at the bottom after the hydraulic jump, and the energy dissipation effect is good.

[0027] Example 1. The overall water flow pattern under a 5-year flood event is as follows: Figure 10 As shown, the incoming flow forms a hydraulic jump in the abrupt expansion section. The energy dissipation effect of the tail sill is slightly weaker compared to the first type, and a secondary drop also occurs after the tail sill. Simultaneously, the flow velocity distribution at the outlet is observed by selecting the central axis of the diversion tunnel. The velocity distribution and water surface profile are shown below. Figure 11 and Figure 12 As shown in the diagram, when the cross-section is enlarged to 17m x 22m, the outlet flow is completely submerged because the height of the tunnel top is less than the second conjugate depth of the hydraulic jump. This does not meet the requirement of the second conjugate depth of the hydraulic jump and reduces the energy dissipation effect. Therefore, a cross-section of 17m x 24m is recommended to ensure the energy dissipation effect.

[0028] Obviously, the above description is only a part of the embodiments of the present invention, and not all of the embodiments. The above embodiments are not intended to limit the present invention, and various modifications and variations can be made to the present invention by those skilled in the art. Any combination, modification, equivalent substitution, improvement, and all other embodiments that can be made by those skilled in the art within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. An outlet energy dissipation structure outside the combined diversion tunnel, comprising a diversion tunnel, characterized in that: The diversion tunnel includes a slope section (1), the end of which is connected to an enlargement section (2); the end of the enlargement section (2) is connected to a stilling basin (5), and the end of the stilling basin (5) is connected to an energy dissipation sill (6); a guide wall is provided at the end of the enlargement section (2), including a left guide wall (3) and a right guide wall (4); the stilling basin (5) and the energy dissipation sill (6) are located inside the guide wall; the cross-sectional width and height of the enlargement section (2) of the diversion tunnel are both greater than those of the slope section (1), and the elevation of the top of the outlet tunnel of the enlargement section (2) is higher than the downstream water surface elevation under the design conditions.

2. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 1, characterized in that: The slope ratio of the slope section (1) is 1:

10.

3. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 1, characterized in that: The left guide wall (3) and the right guide wall (4) are arranged at a 5° angle towards the energy dissipation sill (6).

4. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 1, characterized in that: The length of the stilling pool (5) is greater than that of the energy dissipation sill (6).

5. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 1, characterized in that: The elevation of the energy dissipation sill (6) is higher than that of the stilling pool (5), and the energy dissipation sill (6) and the stilling pool (5) are connected by a slope with a slope ratio of 1:

1.

6. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 1, characterized in that: The length of the guide wall is set to be equal to the sum of the lengths of the stilling pool (5) and the energy dissipation sill (6).

7. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 3, characterized in that: The energy dissipation sill (6) is a wide platform structure.

8. The outlet energy dissipation structure outside the combined diversion tunnel as described in claim 3, characterized in that: The elevation of the first end of the guide wall is set higher than that of the last end, and the elevation of the last end of the guide wall is consistent with that of the energy dissipation sill (6).

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