A flood discharge system and method for a pumped-storage power station

Abstract

The present invention relates to the technical field of water conservancy and hydropower engineering, and particularly relates to a flood discharge system and a flood discharge method for a pumped-storage power station. The flood discharge system of the pumped-storage power station includes a flood discharge tunnel, an energy dissipation structure, a stilling basin, and a protection facility. The flood discharge tunnel includes a gentle slope base layer and a steep slope base layer. A dissipation section is arranged within the calibrated range at the outlet of the flood discharge tunnel in the steep slope base layer. The dissipation section includes a diffusion area and a widening area. The energy dissipation structure includes multiple energy dissipation steps. The multiple energy dissipation steps in the diffusion area are used to gradually change the flow velocity of the water flow. The stilling basin is connected to the outlet of the flood discharge tunnel, and the protection facility is connected between the outlet of the stilling basin and the original riverbed covering layer. The present invention utilizes the upstream water flow to pass through multiple energy dissipation steps and the stilling basin to dissipate the energy of the water flow, and the water flow after energy dissipation passes through the protection facility and transitions to the original riverbed covering layer, reducing the impact on the downstream environment and protecting the original riverbed covering layer.

Description

Technical Field

[0001] The present invention relates to the technical field of water conservancy and hydropower engineering, and particularly to a flood drainage system and a flood drainage method for a pumped-storage power station. Background Art

[0002] With the continuous advancement of water conservancy and hydropower projects, the pumped-storage power station project has become an important part of the new power system, and has important functions of peak shaving, valley filling, energy storage frequency modulation and power grid stabilization. Although the construction of the pumped-storage power station project blocks the original flood discharge route of mountain torrents, due to the high sediment content of mountain torrents, it will affect the stable operation of the pumped-storage power station system and cause general natural floods not to enter the reservoir. Therefore, it is often necessary to build a supporting flood drainage system to discharge mountain torrents downstream through this system.

[0003] At present, the main characteristics of pumped-storage power station projects are high water heads and a large amount of sediment. According to engineering design experience, the water heads are often as high as 100m or even close to 200m. Therefore, the following problems need to be urgently solved in such projects: (1) The energy dissipation problem, that is, while discharging floods through engineering measures, it is necessary to reduce the flood flow velocity to reduce the huge kinetic energy in order to reduce the damage to the terrain and buildings downstream of the outlet; (2) The problem of a large amount of sediment, because the sediment content in mountain torrents is relatively high, and sometimes even accompanied by debris flows, and the flood contains large-sized stones, which will cause sediment deposition and damage to buildings; (3) The length of the flood discharge tunnel is nearly one kilometer, and the engineering quantity of arranging energy dissipation facilities throughout the whole process is large and the cycle is long, resulting in high project investment and high later operation and maintenance costs. Summary of the Invention

[0004] The technical problem to be solved by the embodiments of the present invention is to provide a flood drainage system and a flood drainage method for a pumped-storage power station to solve the above-mentioned deficiencies existing in pumped-storage power station projects in the prior art.

[0005] The present invention discloses a flood drainage system for a pumped-storage power station, including:

[0006] A flood discharge tunnel, including a gentle slope base layer and a steep slope base layer arranged in sequence along the water flow direction, and an energy dissipation section is arranged within the calibration range at the outlet of the flood discharge tunnel, and the energy dissipation section includes a diffusion area with a gradually increasing horizontal width along the water flow direction, and a widened area with a constant horizontal width starting from the end of the diffusion area;

[0007] The energy dissipation structure includes multiple energy dissipation steps arranged in sequence along the energy dissipation section, and the width of the energy dissipation steps is consistent with the horizontal width at the corresponding position of the energy dissipation section. The energy dissipation steps include a step plane for primary energy dissipation of the upstream water flow and a step vertical surface for guiding sediment in the water flow to the downstream. In the diffusion area, the step height and step length of multiple energy dissipation steps increase in sequence along the water flow direction, so as to gradually transition the upstream water flow to the multiple energy dissipation steps in the widened area through the change of flow velocity;

[0008] The stilling basin is connected to the outlet of the flood discharge tunnel and is used for secondary energy dissipation of the water flow flowing out of the flood discharge tunnel;

[0009] The protection facility is connected between the outlet of the stilling basin and the original riverbed covering layer and is used for transitional buffering of the water flow flowing out of the stilling basin.

[0010] Optionally, the slope of the gentle slope base layer is less than that of the steep slope base layer. The flood discharge tunnel further includes several turning sections, and several turning sections are all arranged through the gentle slope base layer.

[0011] Optionally, the steep slope base layer further includes a smooth section connected between the gentle slope base layer and the energy dissipation section. The layer surface of the steep slope base layer at the smooth section constitutes a smooth diversion surface for guiding sediment in the water flow to the downstream. The position where the energy dissipation section is connected to the smooth section is at a calibration distance n from the outlet of the flood discharge tunnel, and the range of the calibration distance n is 70m ≤ n ≤ 100m.

[0012] Optionally, the step plane is an inclined plane formed by rotating the horizontal plane clockwise by a preset angle along the water flow direction, and the step vertical surface is an inclined plane formed by rotating the vertical plane counterclockwise by a preset angle along the water flow direction. And the step vertical surface of the energy dissipation step and the step plane of the next-level energy dissipation step form a scouring concave angle with an angle greater than 90° at the connection.

[0013] Optionally, the corresponding widths, step lengths, and step heights between any two energy dissipation steps in the widened area are all the same, and the step length and step height of the top-level energy dissipation step in the widened area are both greater than the step length and step height of the bottom-level energy dissipation step in the diffusion area.

[0014] Optionally, the pumped-storage power station flood discharge system further includes side walls arranged oppositely. The flood discharge tunnel is arranged between the two side walls. The connection line of the outer sides of multiple energy dissipation steps is collinear with the corresponding side wall, and the connection line of the central axes of multiple energy dissipation steps along the water flow direction is a straight line.

[0015] Optionally, the stilling basin includes a basin body and a stilling component disposed on the bottom plate of the basin body. The bottom plate of the basin body is flush with the outlet of the flood discharge tunnel. The stilling component includes multiple rows of stilling piers arranged along the direction perpendicular to the water flow, and the stilling piers between adjacent two rows are arranged in a staggered manner. The stilling pier is a trapezoidal prism structure parallel to the water flow direction, and the side surface of the stilling pier facing the upstream water flow is obliquely arranged.

[0016] Optionally, the protection facilities include a concrete apron layer, a gabion mattress layer, and a gravel layer that are sequentially connected and arranged at the outlet of the stilling basin, so that the water flow at the outlet of the stilling basin is gradually buffered through the concrete apron layer, the gabion mattress layer, and the gravel layer in sequence.

[0017] Optionally, the gabion mattress layer includes multiple interconnected hexahedral gabions. The hexahedral gabion includes a cage body and multiple filling stones filled in the cage body. The cage body is a six-sided double-twisted wire mesh structure formed by weaving low-carbon steel wires. A resin protective film is coated on the wires of the cage body, and the mesh holes of the cage body are smaller than the particle size of the filling stones. Gravel fillers are also arranged in the cage body, and the gravel fillers are filled in the stone gaps between adjacent two filling stones in the cage body.

[0018] The present invention also discloses a flood discharge method, which adopts the above-mentioned flood discharge system of the pumped-storage power station, including:

[0019] Laying the flood discharge tunnel, the energy dissipation structure, the stilling basin, and the protection facilities in the target watershed. When a flood occurs in the target watershed, the flood carrying sediment in the target watershed is introduced into the flood discharge tunnel and flows sequentially along the gentle slope base layer and the steep slope base layer;

[0020] When the water flow flows along the steep slope base layer to the energy dissipation section, the water flow first undergoes energy dissipation through multiple energy dissipation steps in the diffusion area, and at the same time gradually reduces the unit width discharge until it transitions to multiple energy dissipation steps in the widened area and continues to dissipate energy while keeping the unit width discharge unchanged. The sediment in the water flow is diverted to the downstream along with the multiple energy dissipation steps;

[0021] After the water flow undergoes primary energy dissipation through multiple energy dissipation steps, it carries sediment and is introduced into the stilling basin along the outlet of the flood discharge tunnel, and rolls in the stilling basin for secondary energy dissipation. The sediment is discharged from the stilling basin along with the water flow;

[0022] The water flow flowing out of the stilling basin gradually loses energy through the protection facilities until it flows into the original riverbed overburden layer to complete flood discharge.

[0023] Compared with the prior art, the beneficial effects of the flood discharge system and the flood discharge method of the pumped-storage power station provided by the embodiments of the present invention are as follows:

[0024] By arranging flood discharge tunnels, energy dissipation buildings, stilling basins and protective facilities, and using the settings of gentle slope bases and steep slope bases, the gentle slope base can reduce the water flow velocity at the entrance of the flood discharge tunnel to reduce the scouring of the inner wall of the flood discharge tunnel. And by arranging an energy dissipation section within the calibrated range at the exit of the flood discharge tunnel and arranging the energy dissipation building only at the energy dissipation section, compared with the full-tunnel arrangement scheme, the project quantity is greatly saved. At the same time, by using the gradually changing setting of the horizontal width of the energy dissipation section within the diffusion area, only the calibrated range at the exit of the flood discharge tunnel is widened, so that under the condition of increasing less excavation volume, the unit discharge is effectively reduced, and the energy dissipation effect of the energy dissipation building is significantly improved. Furthermore, through the scheme of gradually transitioning the multi-stage energy dissipation steps from small size to large size, the phenomenon of water flow splashing on the energy dissipation steps is avoided, the water flow connection is made smoother, and the water flow pattern is improved. In addition, the stilling basin and protective facilities are used to further improve the energy dissipation and buffering of the water flow, effectively solving the problem of the damage of high-head floods to the downstream terrain and buildings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The technical solutions of the present invention will be further described in detail below in conjunction with the drawings and embodiments. In the drawings:

[0026] Figure 1 is a schematic diagram of the overall structure of the flood discharge system of the pumped-storage power station provided by the embodiment of the present invention;

[0027] Figure 2 is a top view of the steep slope base provided by the embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of the distribution of the multi-stage energy dissipation steps provided by the embodiment of the present invention;

[0029] Figure 4 is a side view of the connection of the flood discharge tunnel, the stilling basin and the protective facilities provided by the embodiment of the present invention;

[0030] Figure 5 is a side view of the connection of the multi-stage energy dissipation steps provided by the embodiment of the present invention;

[0031] Figure 6 is a top view of the connection of the flood discharge tunnel, the stilling basin and the protective facilities provided by the embodiment of the present invention;

[0032] Figure 7 is a schematic diagram of the structure of the hexahedron steel reinforcement cage provided by the embodiment of the present invention;

[0033] Figure 8 is a schematic diagram of the connection of two adjacent hexahedron steel reinforcement cages provided by the embodiment of the present invention.

[0034] The reference numerals in the drawings are:

[0035] 1. Flood discharge tunnel; 11. Gentle slope base layer; 12. Steep slope base layer; 121. Energy dissipation section; 1211. Diffusion area; 1212. Widening area; 122. Smooth section; 2. Energy dissipation steps; 21. Step plane; 22. Step vertical surface; 3. Stilling basin; 31. Stilling pier; 4. Protection facilities; 41. Concrete apron layer; 42. Reinforced gabion layer; 421. Hexahedron steel cage; 43. Gravel layer; 5. Original riverbed covering layer; 6. Side wall. Detailed implementation manners

[0036] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Now, with reference to the accompanying drawings, the preferred embodiments of the present invention will be described in detail.

[0037] The present invention discloses a flood discharge system for a pumped-storage power station, as Figures 1-4 shown, which includes a flood discharge tunnel 1, an energy dissipation building, a stilling basin 3 and protection facilities 4. The flood discharge tunnel 1 includes a gentle slope base layer 11 and a steep slope base layer 12 arranged in sequence along the water flow direction, and an energy dissipation section 121 is arranged within the calibration range at the outlet of the flood discharge tunnel 1. The energy dissipation section 121 includes a diffusion area 1211 with a gradually increasing horizontal width along the water flow direction, and a widening area 1212 with a constant horizontal width starting from the end of the diffusion area 1211. The energy dissipation building includes a multi-stage energy dissipation step 2 arranged in sequence along the energy dissipation section 121, and the width of the energy dissipation step 2 is consistent with the horizontal width at the corresponding position of the energy dissipation section 121. The energy dissipation step 2 includes a step plane 21 for primary energy dissipation of the upstream water flow, and a step vertical surface 22 for guiding the sediment in the water flow to the downstream. The step height and step length of the multi-stage energy dissipation steps 2 in the diffusion area 1211 increase in sequence along the water flow direction, and are used to gradually transition the upstream water flow to the multi-stage energy dissipation steps 2 in the widening area 1212 through a change in flow velocity. The stilling basin 3 is connected to the outlet of the flood discharge tunnel 1 and is used for secondary energy dissipation of the water flow flowing out of the flood discharge tunnel 1. The protection facilities 4 are connected between the outlet of the stilling basin 3 and the original riverbed covering layer 5, and are used for transitional buffering of the water flow flowing out of the stilling basin 3.

[0038] Through the implementation of the flood discharge system of the above-mentioned pumped-storage power station, a flood discharge tunnel 1, an energy dissipation structure, a stilling basin 3 and a protection facility 4 are arranged. By means of the arrangement of the gentle slope base layer 11 and the steep slope base layer 12, the gentle slope base layer 11 can reduce the water flow velocity at the entrance of the flood discharge tunnel 1, so as to reduce the scouring of the inner wall of the flood discharge tunnel 1. And by arranging an energy dissipation section 121 within the calibrated range at the outlet of the flood discharge tunnel 1 and arranging the energy dissipation structure only at the energy dissipation section 121, compared with the full-tunnel arrangement scheme, the project quantity is greatly saved. At the same time, by means of the gradually changing setting of the horizontal width of the energy dissipation section 121 within the diffusion area 1211, only the calibrated range at the outlet of the flood discharge tunnel 1 is widened, so that under the condition of increasing less excavation quantity, the unit-width discharge is effectively reduced, and the energy dissipation effect of the energy dissipation structure is significantly improved. Furthermore, through the scheme that the multi-stage energy dissipation steps 2 gradually transition from small size to large size, the phenomenon that water splashes on the energy dissipation steps 2 is avoided, the water flow connection is made smoother, and the water flow pattern is improved. In addition, by means of the stilling basin 3 and the protection facility 4, the energy dissipation and buffering of the water flow are further improved, the problem of the damage of high-head floods to the downstream terrain and buildings is effectively solved, and the siltation and damage of multi-sediment floods in the flood discharge structure are reduced. Preferably, for the convenience of construction, the bottom slope (referring to the vertical distance H when passing through the horizontal length L) of the flood discharge tunnel 1 generally does not exceed 20%. The flood discharge system of the pumped-storage power station of the present invention can be applied to water conservancy and hydropower engineering fields such as dam flood discharge, hydropower station water diversion and irrigation channels.

[0039] As described above, by means of the arrangement of the diffusion area 1211 and the widened area 1212, the width of the flood discharge tunnel 1 at the energy dissipation section 121 gradually diffuses from a small width to a large width. The principle is that: the energy dissipation effect of the stepped energy dissipation structure is most affected by the unit-width discharge (discharge / width of the tunnel). The larger the unit-width discharge, the worse the energy dissipation effect. For example, the width of the flood discharge tunnel of a certain power station is 3.5 m, and the unit-width discharge is about 29 m 2 / s, and the energy dissipation effect is not good. Therefore, it is necessary to increase the width to 6 m, and the unit-width discharge is about 17 m 2 / s. Increasing the width of the nearly 1000-meter-long flood discharge tunnel 1 requires a large investment cost, while the multi-stage energy dissipation steps 2 of the embodiment of the present invention are only arranged within the calibrated range at the outlet of the flood discharge tunnel 1, and can greatly improve the energy dissipation effect on the premise of increasing the least project quantity.

[0040] In addition, the step height and step length of the multi-stage energy dissipation steps 2 in the diffusion region 1211 increase successively along the water flow direction. For example, the bottom slope of the steep slope base layer 12 is 20%, the step length of each energy dissipation step 2 in the widening region 1212 is 5 m, and the step height is 1 m. Then, along the water flow direction in the diffusion region 1211, the step length of the first-stage energy dissipation step 2 is 1 m and the step height is 0.2 m, the step length of the second-stage energy dissipation step 2 is 2 m and the step height is 0.4 m, the step length of the third-stage energy dissipation step 2 is 3 m and the step height is 0.6 m... until the step length of the energy dissipation step 2 at the connection increases to 5 m and the step height is 1 m. At this time, it enters the widening region 1212, and the sizes of the subsequent energy dissipation steps 2 remain unchanged. The principle is as follows: Based on the hydraulic model test, it is found that when the high-speed water flow on the steep slope base layer 12 directly encounters the large-sized energy dissipation steps 2 in the widening region 1212, water splashing will occur. Therefore, in the embodiment of the present invention, by setting the multi-stage energy dissipation steps 2 with sizes increasing successively along the water flow direction in the diffusion region 1211, when the high-speed water flow passes through the multi-stage energy dissipation steps 2 in the diffusion region 1211, the flow velocity is reduced, and it gradually changes to the large-sized energy dissipation steps 2 in the widening region 1212, thereby ensuring a stable water flow pattern and no water droplet splashing.

[0041] Furthermore, the slope of the gentle slope base layer 11 is smaller than that of the steep slope base layer 12. The flood discharge tunnel 1 further includes several turning sections, and all the several turning sections are arranged through the gentle slope base layer 11.

[0042] Through the implementation of the above-mentioned flood discharge system of the pumped-storage power station, during the excavation of the flood discharge tunnel 1, there are situations where the terrain is complex or obstacles need to be avoided. Therefore, by setting turning sections in the flood discharge tunnel 1, the flood discharge tunnel 1 can better adapt to the undulations of the terrain and can effectively shorten the total length of the flood discharge tunnel 1. And the turning sections can change the direction and velocity distribution of the water flow, which helps to evenly distribute the water flow. At the same time, all the several turning sections are arranged through the gentle slope base layer 11. By using the smaller slope of the gentle slope base layer 11, since the water flow velocity at the turning sections is usually large, the situation of excessive water surface difference between the inner and outer sides of the turning sections caused by centrifugal force can be avoided, thereby ensuring a stable water flow pattern.

[0043] Furthermore, the steep slope base layer 12 further includes a smooth section 122 connected between the gentle slope base layer 11 and the energy dissipation section 121. The layer surface of the steep slope base layer 12 located at the smooth section 122 constitutes a smooth diversion surface for guiding the sediment in the water flow to the downstream. The distance from the connection position of the energy dissipation section 121 and the smooth section 122 to the outlet of the flood discharge tunnel 1 is a calibrated distance n, and the range of the calibrated distance n is 70 m ≤ n ≤ 100 m.

[0044] Through the implementation of the flood discharge system of the above-mentioned pumped-storage power station, the smooth section 122 of the steep slope base layer 12 is the area where no energy dissipation structure is provided. Since the energy dissipation structure is arranged at the outlet of the flood discharge tunnel 1, the length of the smooth section 122 on the steep slope base layer 12 is much greater than the length of the energy dissipation section 121. Allowing the water flow to maintain a relatively high speed on the smooth section 122 helps to improve the flood discharge efficiency and facilitates the rapid diversion of sediment in the water flow to the downstream, so as to reduce the sedimentation of sediment-laden floods in the flood discharge structure. In addition, in the embodiment of the present invention, the energy dissipation structure is only arranged within a range of 100 m from the outlet of the flood discharge tunnel 1. The principle different from the full-length arrangement of the existing conventional stepped overflow dam and stepped spillway is as follows: First, the flood discharge tunnel 1 is usually nearly one kilometer long and is arranged as a stepped section along the whole process, with a quite large amount of work and a long cycle. While in the embodiment of the present invention, it is arranged within a range of 100 m from the outlet of the flood discharge tunnel 1, effectively saving the amount of work and facilitating the later maintenance; Second, verified by model tests, the water flow within 100 m from the outlet of the flood discharge tunnel 1 can form an aerated uniform flow, and the aerated uniform flow means that the flow velocity tends to be stable and cannot be further reduced. Therefore, arranging the energy dissipation structure only within a range of 100 m from the outlet of the flood discharge tunnel 1 has the same outlet flow velocity as that of the flood discharge tunnel 1 with a full-length stepped section.

[0045] Preferably, an energy dissipation section 121 is arranged on the steep slope base layer 12, and the position where the energy dissipation section 121 is connected to the smooth section 122 is 100 m from the outlet of the flood discharge tunnel 1, so that the arrangement of the multi-stage energy dissipation steps 2 can ensure the formation of an aerated uniform flow of the water flow and effectively save the amount of work.

[0046] Preferably, an energy dissipation section 121 is arranged on the steep slope base layer 12, and the position where the energy dissipation section 121 is connected to the smooth section 122 is 70 m from the outlet of the flood discharge tunnel 1, so that the arrangement of the multi-stage energy dissipation steps 2 can ensure the formation of an aerated uniform flow of the water flow and greatly save the amount of work.

[0047] Preferably, an energy dissipation section 121 is arranged on the steep slope base layer 12, and the position where the energy dissipation section 121 is connected to the smooth section 122 is 80 m from the outlet of the flood discharge tunnel 1, so that the arrangement of the multi-stage energy dissipation steps 2 can ensure sufficient energy dissipation degree and save the amount of work.

[0048] Furthermore, as shown in Figure 5 The step plane 21 is an inclined plane formed by rotating the horizontal plane clockwise by a preset angle along the water flow direction, the step vertical surface 22 is an inclined plane formed by rotating the vertical plane counterclockwise by a preset angle along the water flow direction, and the step vertical surface 22 of the energy dissipation step 2 and the step plane 21 of the next-stage energy dissipation step 2 form a scouring concave angle with an angle greater than 90° at the connection position.

[0049] Through the implementation of the flood discharge system of the above-mentioned pumped-storage power station, the step plane 21 of the energy dissipation step 2 provides opportunities for the water flow to collide, shear, entrain air, and friction, enabling the dissipation of the energy in the water flow. Furthermore, the design of the multi-stage energy dissipation step 2 provides multiple energy dissipation stages, allowing the water flow to gradually decelerate when passing through the flood discharge tunnel 1, reducing energy transfer, effectively reducing the speed and impact force of the water flow, and achieving the purpose of energy dissipation. On this basis, by using the inclined setting of the step plane 21, a slope for sediment diversion can be formed, enabling the sediment to pass smoothly, thereby reducing the stagnation and accumulation of sediment on the step plane 21. In addition, by using the step elevation 22 with the same inclined setting, when the water flow encounters the step elevation 22, the direction of the water flow will change along the step elevation 22, and the change in the water flow direction will lead to an increase in the turbulence intensity of the water flow. Turbulence will increase the friction and mixing between the water flow and the surrounding medium, thereby further consuming the energy of the water flow to improve the energy dissipation effect. And due to the relatively large slope of the step elevation 22, the sediment in the water flow can be quickly diverted to the downstream. In addition, by using the step elevation 22 of the energy dissipation step 2 and the step plane 21 of the next-level energy dissipation step 2 to form a scour concave angle with an angle greater than 90° at the connection, sediment deposition concave angles can be prevented from appearing between two adjacent energy dissipation steps 2, enabling the sediment carried by the water flow to pass smoothly, reducing the stagnation and accumulation of sediment, avoiding the collision and abrasion of the sediment on the energy dissipation step 2, improving the sediment discharge effect, increasing the service life of the energy dissipation structure, reducing the maintenance cost, and preventing the influence of long-term sedimentation on the performance of the tunnel. Preferably, to achieve the best sediment discharge and anti-sediment deposition effects, the step plane 21 is rotated clockwise by an inclination angle of 3-5° with respect to the horizontal plane of a conventional step, and the step elevation 22 is rotated counterclockwise by an inclination angle of 15-30° with respect to the vertical plane of a conventional step.

[0050] Furthermore, looking back Figure 2 , the widths, step lengths, and step heights corresponding to any two energy dissipation steps 2 within the widened area 1212 are all the same, and the step length and step height of the uppermost energy dissipation step 2 within the widened area 1212 are both greater than the step length and step height of the lowermost energy dissipation step 2 within the diffusion area 1211.

[0051] Through the implementation of the flood discharge system of the above-mentioned pumped-storage power station, the sizes of the energy dissipation steps 2 at all levels are not exactly the same. The widths, step lengths, and step heights corresponding to the multi-stage energy dissipation steps 2 within the diffusion area 1211 increase sequentially along the water flow direction, while the widths, step lengths, and step heights corresponding to the multi-stage energy dissipation steps 2 within the widened area 1212 are all the same. This enables the multi-stage energy dissipation steps 2 within the diffusion area 1211 to gradually reduce the water flow speed during flood discharge and improve the energy dissipation efficiency. At this time, the water flow has been reduced from a high speed to a certain low speed state, and then the multi-stage energy dissipation steps 2 within the widened area 1212 ensure that the water flow dissipates energy evenly, reducing the change in the local water flow speed, which helps prevent water flow impact and erosion.

[0052] Furthermore, the flood discharge system of the pumped-storage power station further includes side walls 6 arranged oppositely, and the flood discharge tunnel 1 is arranged between the two side walls 6. The connection line of the outer sides of the multi-stage energy dissipation steps 2 and the corresponding side wall 6 are collinear, and the connection line of the central axes of the multi-stage energy dissipation steps 2 along the water flow direction is a straight line.

[0053] Through the implementation of the above-mentioned flood discharge system of the pumped-storage power station, by making the outer sides of the multi-stage energy dissipation steps 2 collinear with the corresponding side wall 6, it can ensure that the water flow maintains a stable flow direction when passing through the multi-stage energy dissipation steps 2, and avoid the scouring of the inner wall of the flood discharge tunnel 1 by the water flow. At the same time, by using the connection line of the central axes of the multi-stage energy dissipation steps 2 along the water flow direction as a straight line, when the water flow passes through any energy dissipation step 2, it can uniformly diffuse to both sides at the middle position of the step plane 21 of the energy dissipation step 2 to form a transverse vortex, and shear and friction with the water body flowing normally downstream above, achieving the energy dissipation effect, so that the multi-stage energy dissipation steps 2 form a complete energy dissipation system, and through different energy dissipation mechanisms, such as resistance, turbulence, collision, etc., improve the energy dissipation efficiency.

[0054] Furthermore, in combination Figure 4 with Figure 6 as shown, the stilling basin 3 includes a basin body and energy dissipation components arranged on the bottom plate of the basin body. The bottom plate of the basin body is flush with the outlet of the flood discharge tunnel 1. The energy dissipation components include multiple rows of energy dissipation piers 31 arranged along the vertical water flow direction, and the energy dissipation piers 31 between adjacent two rows are arranged in a staggered manner. The energy dissipation pier 31 is a trapezoidal prism structure parallel to the water flow direction, and the side surface of the energy dissipation pier 31 facing the upstream water flow is obliquely arranged.

[0055] Through the implementation of the above-mentioned flood discharge system of the pumped-storage power station, by making the bottom plate of the stilling basin 3 flush with the outlet of the flood discharge tunnel 1, it helps to carry away the sediment when the water flow passes through the stilling basin 3, so that there is no need to set a tail sill in the stilling basin 3 and no need to dig deeply downward, and the sediment can be prevented from accumulating in the stilling basin 3. At the same time, by using the trapezoidal prism-shaped energy dissipation piers 31, compared with other shaped energy dissipation piers 31, it has better structural stability and can better withstand the thrust and tensile force of the water flow, so that the water level in the stilling basin 3 can be raised to form a hydraulic jump, making the water flow roll in the stilling basin 3 and performing secondary energy dissipation on the water flow flowing out of the flood discharge tunnel 1. When the water flow is of large flow rate, the oblique side surface of the energy dissipation pier 31 facing the upstream water flow is used to collide with the water flow and dissipate energy, and can divert the sediment flowing through to avoid sediment deposition at the energy dissipation pier 31. And by multiple rows of energy dissipation piers 31, the contact and collision opportunities between the water flow and the energy dissipation piers 31 are increased, so as to improve the energy dissipation effect. In addition, by arranging the energy dissipation piers 31 of adjacent two rows in a staggered manner, the water flow can be subjected to the energy dissipation effect of the energy dissipation piers 31 at different positions in the stilling basin 3, avoiding the water flow from concentrating in certain areas, thereby reducing local scouring and stress concentration, and increasing the uniformity and comprehensiveness of energy dissipation.

[0056] Furthermore, the protection facility 4 includes a concrete apron layer 41, a reinforced gabion layer 42, and a gravel layer 43 that are sequentially connected and arranged at the outlet of the stilling basin 3, so that the water flow at the outlet of the stilling basin 3 is sequentially transitioned and buffered through the concrete apron layer 41, the reinforced gabion layer 42, and the gravel layer 43.

[0057] Through the implementation of the above-mentioned flood discharge system of the pumped-storage power station, three protective layers with different structures are sequentially connected and arranged between the stilling basin 3 and the original riverbed overburden layer 5, so that the surfaces of the concrete apron layer 41, the reinforced gabion layer 42, the gravel layer 43, and the original riverbed overburden layer 5 are all flush with the bottom plate of the stilling basin 3. When the water flow flowing out of the flood discharge tunnel 1 undergoes secondary energy dissipation in the stilling basin 3, it flows sequentially along the surfaces of the concrete apron layer 41, the reinforced gabion layer 42, and the gravel layer 43, and part of the water flow infiltrates from the surfaces of the concrete apron layer 41, the reinforced gabion layer 42, and the gravel layer 43 respectively. That is, the concrete apron layer 41 directly bears the impact of the high-speed water flow first, and reduces the direct impact force of the water flow on the downstream through its thick structure to protect the original riverbed overburden layer 5 downstream. And it can evenly disperse the water flow, reduce the eddy current and pulsation in the water flow, and improve the smoothness of the water flow. Then, the reinforced gabion layer provides additional structural strength, can withstand greater water pressure and impact, and can resist a certain degree of erosion and impact, so the long-term maintenance requirements may be reduced. Further, the gravel layer 43 absorbs and disperses the water flow energy, reducing the continuous impact of the water flow on the original riverbed overburden layer 5. The porosity of the gravel layer 43 enables it to adapt to different water flow velocities and flows, providing a flexible buffering and protection effect. Thus, the gradually transitional protection form of the concrete apron layer 41, the reinforced gabion layer 42, and the gravel layer 43 is adopted, so that the energy of the water flow coming out of the stilling basin 3 is further dissipated in different regions in sequence, avoiding the situation that the concrete apron layer 41 or the reinforced gabion layer 42 is directly connected to the original riverbed overburden layer 5, which may easily cause scour pits at the junction and threaten the stability of the protection structure.

[0058] Furthermore, as shown in Figure 7 Figure 10, the reinforced gabion layer 42 includes a plurality of interconnected hexahedral steel cages 421. The hexahedral steel cage 421 includes a cage body and a plurality of filling stones filled in the cage body. The cage body is a six-sided double-twisted wire mesh structure formed by weaving low-carbon steel wires. The wires of the cage body are coated with a resin protective film, and the mesh holes of the cage body are smaller than the particle size of the filling stones. Gravel fillers are also arranged in the cage body and filled in the stone seams between adjacent two filling stones in the cage body.

[0059] Through the implementation of the flood discharge system of the above-mentioned pumped-storage power station, a gabion layer 42 is formed by using a plurality of interconnected hexahedral gabion cages 421. The hexahedral structure has good structural stability and can adapt to different terrain changes. Whether it is flat or sloping terrain, it can provide stable protection. And through the six-sided double-twisted wire mesh structure formed by weaving low-carbon steel wires and filling the cage body with stones, the entire hexahedral gabion cage 421 forms a strong protective layer, which can withstand large impacts and erosions of water flow and helps to protect the downstream structure. Among them, the mesh holes of the cage body are set to be smaller than the particle size of the filled stones, which can prevent the filled stones from flowing out during filling or flood control, so as to improve the stability of the gabion layer 42. In addition, by coating the resin protective film on the steel wires of the cage body, the corrosion resistance of the steel wire structure of the cage body can be increased, and the service life of the gabion layer 42 can be extended. And by setting crushed stone fillers in the stone seams between adjacent filled stones, the structure can be further strengthened, the gaps between the filled stones can be reduced, and the compactness and stability inside the hexahedral gabion cage 421 can be improved. Preferably, the low-carbon steel wires are woven into a hexagonal double-twisted wire mesh by a special machine to assemble a cage body with a size of 2m×1m×1m (length×width×height). The particle size of the stones filled in the cage body is between 150mm and 300mm, and the stone seams are filled with crushed stone fillers. The particle size of the crushed stone fillers is selected to be 50mm to 100mm to increase the filling density. However, the crushed stone fillers smaller than the mesh size of the cage body shall not exceed 15%, and the porosity shall not be greater than 20%. And different hexahedral gabion cages 421 are connected to each other by steel wires to improve the overall stability (reference Figure 8 ).

[0060] The flood discharge system of the pumped-storage power station of the present invention arranges the energy dissipation building only within a range of 100m from the outlet of the flood discharge tunnel 1. Compared with the full-tunnel arrangement scheme, the project quantity is saved, and the later-stage step maintenance is more convenient. And by using the gradual change of the horizontal width of the energy dissipation section 121 in the diffusion area 1211, only the calibrated range of the outlet of the flood discharge tunnel 1 is widened. Thus, under the condition of increasing less excavation volume, the unit-width flow rate is effectively reduced, and the energy dissipation effect of the energy dissipation building is significantly improved. Then, through the scheme of gradually transitioning from small-sized to large-sized multi-stage energy dissipation steps 2, the phenomenon of water splashing on the energy dissipation steps 2 is avoided, the water flow connection is made smoother, and the water flow pattern is improved. The stilling basin 3 neither sets a traditional tail sill nor digs deeply downward. The bottom plate of the stilling basin 3 is flush with the outlet of the flood discharge tunnel 1. By arranging the energy dissipation piers 31 with a trapezoidal structure to raise the water depth to form hydraulic jump energy dissipation, the sediment can be discharged into the river through the gaps of the energy dissipation piers 31, avoiding sediment deposition in the stilling basin 3. Finally, a concrete apron layer 41, a gabion layer 42 and a crushed stone layer 43 are successively connected and arranged between the stilling basin 3 and the original riverbed covering layer 5, avoiding the situation that the connection between the stilling basin 3 and the original riverbed covering layer 5 is likely to cause scour pits at the junction, thus threatening the stability of the protective structure.

[0061] The present invention also discloses a flood drainage method, which adopts the above-mentioned flood drainage system of a pumped-storage power station, and includes:

[0062] A flood drainage tunnel 1, an energy dissipation structure, a stilling basin 3 and a protection facility 4 are arranged in the target basin. When a flood occurs in the target basin, the flood carrying sediment in the target basin is introduced into the flood drainage tunnel 1 and flows successively along the gentle slope base layer 11 and the steep slope base layer 12;

[0063] When the water flow flows along the steep slope base layer 12 to the energy dissipation section 121, the water flow first dissipates energy through the multi-level energy dissipation steps 2 in the diffusion area 1211, and at the same time gradually reduces the unit discharge until it transitions to the multi-level energy dissipation steps 2 in the widened area 1212, and continues to dissipate energy while keeping the unit discharge unchanged. The sediment in the water flow is diverted to the downstream along with the multi-level energy dissipation steps 2;

[0064] After the water flow dissipates energy once through the multi-level energy dissipation steps 2, it carries sediment and is introduced into the stilling basin 3 along the outlet of the flood drainage tunnel 1, and rolls in the stilling basin 3 for secondary energy dissipation, and the sediment is discharged from the stilling basin 3 along with the water flow;

[0065] The water flow flowing out of the stilling basin 3 gradually loses energy through the protection facility 4 until it flows into the original riverbed covering layer 5 to complete flood drainage.

[0066] Through the implementation of the above flood drainage method, when rainfall occurs in the basin, the flood carrying sediment particles enters the flood drainage tunnel 1, and first passes through the gentle slope base layer 11 and the smooth section 122 of the steep slope base layer 12. The smooth section 122 is most conducive to drainage and sediment discharge while reducing abrasion. Before flowing out of the tunnel, the water flow consumes the kinetic energy of the water flow through the multi-level energy dissipation steps of the energy dissipation section 121. Among them, the water flow diffuses from the diffusion area 1211 to the widened area 1212, the water passing width becomes larger, and the unit discharge decreases, significantly improving the effect of air entrainment and energy dissipation of the steps. At the same time, when the water flow flows from the smooth section 122 through the diffusion area 1211 of the energy dissipation section 121, it first passes through the multi-level energy dissipation steps 2 with gradually increasing sizes for transition, effectively avoiding the splashing phenomenon of water flow and sediment particles caused by the water flow directly flowing into the large-size energy dissipation steps 2 through the smooth section 122. And the step elevation 22 and the step plane 21 are rotated by a certain angle on the basis of the traditional conventional steps, increasing the flow velocity at the scouring concave angle where the adjacent two energy dissipation steps 2 are connected, and completely avoiding the sediment deposition at the scouring concave angle.

[0067] Based on the hydraulic model test, it is found that for the energy dissipation of the water flow passing through the multi-stage energy dissipation steps 2, in a specific working condition, the original flow velocity of 23 m / s can be reduced to 12 m / s. Subsequently, the potential energy effect that increases the flow velocity and the aeration and friction effects that decrease the flow velocity reach an equilibrium, and the flow velocity will not continue to decrease with the increase of the length of the energy dissipation section 121 and the number of energy dissipation steps 2. Therefore, the present invention arranges the multi-stage energy dissipation steps 2 only within the calibrated range from the outlet of the flood discharge tunnel 1, greatly saving the project quantity. The water flow enters the stilling basin 3 through the outlet of the flood discharge tunnel 1. Affected by the stilling basin piers 31, the water flow rolls twice in the stilling basin 3 for secondary energy dissipation, reducing the flow velocity from 12 m / s to about 5 m / s. And the sediment can gradually flow out of the stilling basin 3 from the gaps between two adjacent rows of stilling basin piers 31.

[0068] The water flow flowing out of the stilling basin 3 successively passes through the concrete apron layer 41, the gabion layer 42, and the gravel layer 43, and the energy is gradually dissipated. The flow velocity when reaching the original riverbed covering layer 5 is < 3 m / s. Such a gradually transitional protection facility completely has no scour pit generated, effectively protecting the stability of the structure foundation of the stilling basin 3 and the riverbed bank slope.

[0069] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it. For those skilled in the art, the technical solutions recorded in the above embodiments can be modified, or some of the technical features can be equivalently replaced; and all such modifications and replacements should fall within the protection scope of the appended claims of the present invention.

Claims

1. A flood discharge system for a pumped storage power station, characterized in that: The pumped storage power station flood discharge system comprises: A flood discharge tunnel, comprising a gentle slope base and a steep slope base arranged in sequence along a water flow direction, wherein an energy dissipation section is arranged within a calibrated range of the steep slope base at the outlet of the flood discharge tunnel, wherein the steep slope base also comprises a smooth section connected between the gentle slope base and the energy dissipation section, wherein the surface of the layer of the steep slope base located at the smooth section constitutes a smooth diversion surface for diverting sediment in the water flow to a downstream, wherein the position where the energy dissipation section is connected to the smooth section is a calibrated distance n from the outlet of the flood discharge tunnel, and the calibrated distance n ranges from 70m≤n≤100m, and wherein the energy dissipation section comprises a diffusion area whose horizontal width increases in sequence along the water flow direction, and a widening area whose horizontal width remains unchanged from the end of the diffusion area; An energy dissipation building, comprising a plurality of energy dissipation steps arranged in sequence along the energy dissipation section, and the width of the energy dissipation steps is consistent with the horizontal width of the corresponding position of the energy dissipation section, the energy dissipation steps include a step plane for dissipating energy of the upstream water flow, and a step facade for diverting sediment in the water flow to the downstream, the step height and step length of the plurality of energy dissipation steps in the diffusion area are increased in sequence along the water flow direction, and are used to gradually transition the upstream water flow to the plurality of energy dissipation steps in the widening area through a flow velocity gradient, the corresponding width, step length and step height between any two energy dissipation steps in the widening area are consistent, and the step length and step height of the uppermost energy dissipation step in the widening area are greater than the step length and step height of the lowermost energy dissipation step in the diffusion area; The central axis line of the multiple energy dissipation steps along the water flow direction is a straight line, the step plane is an inclined plane formed by rotating the horizontal plane clockwise along the water flow direction at a preset angle of 3-5°, the step elevation is an inclined plane formed by rotating the vertical plane counterclockwise along the water flow direction at a preset angle of 15-30°, and the step elevation of the energy dissipation step and the step plane of the next energy dissipation step at the junction form a scouring concave angle greater than 90°; An energy dissipation pool is connected to the outlet of the flood discharge tunnel and is used for secondary energy dissipation of water flowing out of the flood discharge tunnel; The protective facility is connected between the outlet of the energy dissipation pool and the original riverbed cover layer, and is used for transition buffering of the water flow out of the energy dissipation pool.

2. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The slope of the gently sloping base layer is smaller than the slope of the steeply sloping base layer. The flood discharge tunnel further comprises a plurality of turning sections, and the plurality of turning sections are arranged through the gently sloping base layer.

3. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The flood discharge system of the pumped storage power station also includes side walls arranged opposite to each other, the flood discharge tunnel is arranged between the two side walls, and the connecting line of the outer sides of the multiple levels of the energy dissipation steps is collinear with the side walls on the corresponding sides.

4. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The energy dissipation pool includes a pool body and an energy dissipation assembly arranged on the bottom plate of the pool body. The bottom plate of the pool body is flush with the outlet of the flood discharge tunnel. The energy dissipation assembly includes a plurality of rows of energy dissipation piers arranged along a direction perpendicular to the water flow, and the energy dissipation piers between two adjacent rows are staggered. The energy dissipation piers are trapezoidal structures parallel to the water flow direction, and the side surfaces of the energy dissipation piers facing the upstream water flow are obliquely arranged.

5. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The protective facilities include a concrete apron layer, a reinforced gabion layer and a crushed stone layer which are arranged in sequence at the outlet of the energy dissipation pool, so that the water flow at the outlet of the energy dissipation pool can be transitionally buffered through the concrete apron layer, the reinforced gabion layer and the crushed stone layer in sequence.

6. The flood discharge system of a pumped storage power station according to claim 5, characterized in that: The reinforced gabion layer includes a plurality of interconnected hexahedral reinforced cages, each of which includes a cage body and a plurality of filling stones filled in the cage body. The cage body is a six-sided double-twisted steel wire mesh structure woven from low-carbon steel wires. The steel wires of the cage body are coated with a resin protective film, and the mesh of the cage body is smaller than the particle size of the filling stones. Crushed stone filler is also provided in the cage body, and the crushed stone filler is filled in the stone gaps between two adjacent filling stones in the cage body.

7. A flood discharge method, using the pumped storage power station flood discharge system according to any one of claims 1 to 6, characterized in that: The flood discharge method comprises: The flood discharge tunnel, the energy dissipation building, the energy dissipation pool and the protective facilities are arranged in the target watershed, and when a flood occurs in the target watershed, the flood in the target watershed carries sediment and is introduced into the flood discharge tunnel, and flows in sequence along the gentle slope base and the steep slope base; When the water flows along the steep slope base to the energy dissipation section, the water first passes through the multi-level energy dissipation steps in the diffusion area to dissipate energy, and gradually reduces the single-width flow until it transitions to the multi-level energy dissipation steps in the widening area, and continues to dissipate energy while keeping the single-width flow unchanged, and the sediment in the water flow is diverted to the downstream along the multi-level energy dissipation steps; After the water flows through the energy dissipation steps for the first time, it carries the sediment along the outlet of the flood discharge tunnel and is introduced into the energy dissipation pool, and swirls in the energy dissipation pool for the second time, and the sediment is discharged from the energy dissipation pool along with the water flow; The water flowing out of the energy dissipation pool flows through the protection facilities and gradually loses energy until it flows into the original riverbed cover layer to complete flood discharge.

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