Flood drainage system and method for pumped storage power station

Abstract

The invention relates to the technical field of water conservancy and hydropower engineering, in particular to a flood drainage system and method for a pumped storage power station. The flood drainage system of the pumped storage power station comprises a flood drainage tunnel, an energy dissipation building, a stilling pool and a protection facility, the flood drainage tunnel comprises a gentle slope base layer and an abrupt slope base layer, the abrupt slope base layer is provided with an energy dissipation section in a calibration range of an outlet of the flood drainage tunnel, the energy dissipation section comprises a diffusion area and a broadening area, and the energy dissipation building comprises multiple energy dissipation steps. The multi-stage energy dissipation steps in the diffusion area are used for gradually changing the water flow velocity, the stilling pool is connected to an outlet of the flood drainage tunnel, and the protection facility is connected between an outlet of the stilling pool and an original riverbed covering layer. The upstream water flow passes through the multi-stage energy dissipation steps and the stilling pool to dissipate the energy of the water flow, and the energy-dissipated water flow is transited to the original riverbed covering layer through the protection facility, so that the influence on the downstream environment is reduced, and the original riverbed covering layer is protected.

Description

Technical Field

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

[0002] With the continuous advancement of water conservancy and hydropower projects, pumped storage power station projects have become an important part of the new power system, and have important functions such as peak shaving, energy storage and frequency regulation, and grid stability. Although the construction of pumped storage power station projects blocks the original flooding route of mountain torrents, the high sand content of mountain torrents will affect the stable operation of the pumped storage power station system, resulting in general natural floods not entering the reservoir. Therefore, it is often necessary to build a supporting flood discharge system to discharge the mountain torrents downstream through the system.

[0003] At present, the main characteristics of pumped storage power station projects are high head and high sediment content. According to engineering design experience, the head is often as high as 100m or even close to 200m. Therefore, this type of project has the following problems that need to be solved urgently: (1) Energy dissipation problem, that is, while discharging flood water through engineering measures, it is necessary to reduce the flow rate of flood water and reduce the huge kinetic energy to reduce the damage to the terrain and buildings downstream of the outlet; (2) High sediment content problem. Due to the high sediment content in mountain torrents, sometimes even accompanied by debris flow, the flood contains large-sized stones, which will cause sediment accumulation and damage buildings; (3) The discharge tunnel is nearly a kilometer long, and the whole process of energy dissipation facilities is large in engineering volume and long in period, resulting in high engineering investment and subsequent 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 discharge system and a flood discharge method for a pumped storage power station to solve the above-mentioned deficiencies in pumped storage power station projects in the prior art.

[0005] The invention discloses a flood discharge system for a pumped storage power station, comprising: A flood discharge tunnel, comprising a gentle slope base and a steep slope base arranged in sequence along a water flow direction, wherein the steep slope base is provided with an energy dissipation section within a calibrated range of an outlet of the flood discharge tunnel, and the energy dissipation section comprises a diffusion area whose horizontal width increases in sequence along a water flow direction, and a widening area whose horizontal width remains unchanged from the end of the diffusion area; The energy dissipation structure comprises a plurality of energy dissipation steps which are sequentially connected and arranged 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 comprise a step plane for dissipating the energy of the upstream water flow, and a step facade for diverting the 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 sequentially increased along the water flow direction, and are used for gradually transitioning the upstream water flow to the plurality of energy dissipation steps in the widening area through a gradual change in flow velocity. 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.

[0006] Optionally, the slope of the gently sloping base layer is smaller than the slope of the steeply sloping base layer, and the flood discharge tunnel further includes a plurality of turning sections, and the plurality of turning sections are arranged through the gently sloping base layer.

[0007] Optionally, the steep slope base layer also includes a smooth section connected between the gentle slope base layer and the energy dissipation section. The steep slope base layer is located on the layer surface of the smooth section to form a smooth diversion surface for diverting sediment in the water flow to the downstream. 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 range of the calibrated distance n is 70m≤n≤100m.

[0008] Optionally, the step plane is an inclined plane formed by rotating a horizontal plane clockwise at a preset angle along the water flow direction, and the step facade is an inclined plane formed by rotating a vertical plane counterclockwise at a preset angle along the water flow direction, and the step facade of the energy dissipation step and the step plane of the next level of the energy dissipation step are located at the connection point to form a scouring angle greater than 90°.

[0009] Optionally, the corresponding widths, step lengths and step heights 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.

[0010] Optionally, the flood discharge system of the pumped-storage power station also includes relatively arranged side walls, the flood discharge tunnel is arranged between the two side walls, the line connecting the outer sides of the multiple-level energy dissipation steps and the side walls on the corresponding sides are collinear, and the line connecting the central axes of the multiple-level energy dissipation steps along the water flow direction is a straight line.

[0011] Optionally, 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.

[0012] Optionally, 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 passes through the concrete apron layer, the reinforced gabion layer and the crushed stone layer in sequence for transition buffering.

[0013] Optionally, the reinforced gabion layer includes a plurality of interconnected hexahedral reinforced cages, the hexahedral reinforced cages including 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, and crushed stone filler is also arranged in the cage body, and the crushed stone filler is filled in the stone gaps between two adjacent filling stones in the cage body.

[0014] The present invention also discloses a flood discharge method, which adopts the above-mentioned pumped storage power station flood discharge system, comprising: 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 multiple energy dissipation steps in the diffusion area to dissipate energy, and gradually reduces the single-width flow until it transitions to the multiple 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 multiple 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.

[0015] Compared with the prior art, the flood discharge system and flood discharge method of the pumped storage power station provided by the embodiment of the present invention have the following beneficial effects: By arranging flood discharge tunnels, energy dissipation buildings, energy dissipation pools and protective facilities, and using the setting of gentle slope base and steep slope base, 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. By arranging the energy dissipation section within the calibration range of the flood discharge tunnel outlet, the energy dissipation building is only arranged at the energy dissipation section, which greatly saves the engineering workload compared with the full tunnel arrangement scheme. At the same time, by using the gradual setting of the horizontal width of the energy dissipation section in the diffusion area, only the calibration range of the flood discharge tunnel outlet is widened, thereby effectively reducing the single-width flow with less excavation, and significantly improving the energy dissipation effect of the energy dissipation building. Then, through the scheme of gradually transitioning from small to large sizes of multi-level energy dissipation steps, the phenomenon of water splashing on the energy dissipation steps is avoided, the water flow connection is more stable, and the flow state of the water flow is improved. In addition, the energy dissipation pool and protective facilities are used to further improve the energy dissipation and buffering of the water flow, effectively solving the problem of damage to downstream terrain and buildings caused by high head floods. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which: Figure 1 A schematic diagram of the overall structure of a flood discharge system for a pumped storage power station provided by an embodiment of the present invention; Figure 2 A top view of a steep slope base provided by an embodiment of the present invention; Figure 3 A schematic diagram of the structure of the multi-level energy dissipation step distribution provided in an embodiment of the present invention; Figure 4 A side view of the connection between the flood discharge tunnel, the energy dissipation basin and the protective facilities provided in the embodiment of the present invention; Figure 5 A side view of a multi-stage energy dissipation step connection provided by an embodiment of the present invention; Figure 6 A top view of the connection between the flood discharge tunnel, the energy dissipation basin and the protective facilities provided in the embodiment of the present invention; Figure 7 A schematic diagram of the structure of a hexahedral reinforcement cage provided by an embodiment of the present invention; Figure 8 A schematic structural diagram of the connection of two adjacent hexahedral reinforcement cages provided in an embodiment of the present invention.

[0017] The reference numerals in the figures are: 1. Flood discharge tunnel; 11. Gentle slope base; 12. Steep slope base; 121. Energy dissipation section; 1211. Diffusion area; 1212. Widening area; 122. Smooth section; 2. Energy dissipation step; 21. Step plane; 22. Step facade; 3. Energy dissipation pool; 31. Energy dissipation pier; 4. Protection facilities; 41. Concrete tank layer; 42. Steel cage layer; 421. Hexahedral steel cage; 43. Gravel layer; 5. Original riverbed cover layer; 6. Side wall. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a preferred embodiment of the present invention is described in detail.

[0019] The present invention discloses a flood discharge system for a pumped storage power station, such as Figure 1-Figure 4 As shown, it includes a flood discharge tunnel 1, an energy dissipation building, an energy dissipation pool 3 and protective facilities 4. The flood discharge tunnel 1 includes a gentle slope base 11 and a steep slope base 12 arranged in sequence along the water flow direction. The steep slope base 12 is provided with an energy dissipation section 121 within the calibration range of the outlet of the flood discharge tunnel 1. The energy dissipation section 121 includes a diffusion area 1211 whose horizontal width increases in sequence along the water flow direction, and a widening area 1212 whose horizontal width remains unchanged from the end of the diffusion area 1211. The energy dissipation building includes a plurality of energy dissipation steps 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 of the corresponding position of the energy dissipation section 121. The energy dissipation step 2 includes a step plane 21 for dissipating the upstream water flow once, and a step facade 22 for diverting the sediment in the water flow to the downstream. The step height and step length of the multi-level energy dissipation steps 2 in the diffusion area 1211 increase successively along the water flow direction, and are used to gradually transition the upstream water flow to the multi-level energy dissipation steps 2 in the widening area 1212 through the flow velocity gradient. The energy dissipation pool 3 is connected at the outlet of the flood discharge tunnel 1, and is used for secondary energy dissipation of the water flowing out of the flood discharge tunnel 1. The protective facility 4 is connected between the outlet of the energy dissipation pool 3 and the original riverbed cover 5, and is used for transition buffering of the water flowing out of the energy dissipation pool 3.

[0020] Through the implementation of the above-mentioned pumped storage power station flood discharge system, the flood discharge tunnel 1, energy dissipation buildings, energy dissipation pool 3 and protective facilities 4 are arranged. By using the setting of the gentle slope base 11 and the steep slope base 12, the gentle slope base 11 can reduce the water flow velocity at the entrance of the flood discharge tunnel 1 to reduce the scouring of the inner wall of the flood discharge tunnel 1. And by arranging the energy dissipation section 121 within the calibration range of the outlet of the flood discharge tunnel 1, the energy dissipation building is only arranged at the energy dissipation section 121, which greatly saves the engineering volume compared with the full tunnel arrangement scheme. At the same time, by using the horizontal width gradient setting of the energy dissipation section 121 in the diffusion area 1211, only the calibration range of the outlet of the flood discharge tunnel 1 is widened, thereby effectively reducing the single width flow rate while increasing less excavation volume, and significantly improving the energy dissipation effect of the energy dissipation building. Then, through the scheme of gradually transitioning the multi-level energy dissipation step 2 from small size to large size, the phenomenon of water splashing on the energy dissipation step 2 is avoided, the water flow connection is more stable, and the water flow state is improved. In addition, the energy dissipation and buffering of the water flow are further improved by using the stilling pool 3 and the protective facilities 4, effectively solving the problem of damage to the downstream terrain and buildings caused by high-head floods, and reducing the siltation and damage of the flood with a lot of sediment in the flood discharge structure. Preferably, for the convenience of construction, the bottom slope of the flood discharge tunnel 1 (referring to the vertical distance H when passing through the horizontal length L) generally does not exceed 20%. The pumped storage power station flood discharge system 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.

[0021] As described above, by setting the diffusion area 1211 and the widening area 1212, the width of the flood discharge tunnel 1 at the energy dissipation section 121 is gradually diffused from a small width to a large width. The principle is: the energy dissipation effect of the step-type energy dissipation structure is most affected by the single-width flow (flow / tunnel width). The larger the single-width flow, the worse the energy dissipation effect. For example, the width of a flood discharge tunnel of a power station is 3.5m, and the single-width flow is about 29m 2 / s, the energy dissipation effect is not good, so the width needs to be increased to 6m, and the single-width flow rate is about 17 m 2 Increasing the width of the nearly 1,000-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 of the outlet of the flood discharge tunnel 1, which can greatly improve the energy dissipation effect while increasing the minimum amount of engineering work.

[0022] In addition, the step height and step length of the multi-level energy dissipation steps 2 in the diffusion area 1211 increase successively along the water flow direction. For example, the steep slope base 12 is a 20% bottom slope, and the step length of each energy dissipation step 2 in the widening area 1212 is 5m, and the step height is 1m. Then, along the water flow direction in the diffusion area 1211, the first-level energy dissipation step 2 has a step length of 1m and a step height of 0.2m, the second-level energy dissipation step 2 has a step length of 2m and a step height of 0.4m, and the third-level energy dissipation step 2 has a step length of 3m and a step height of 0.6m... until the connected energy dissipation step 2 increases to a step length of 5m and a step height of 1m. At this time, it enters the widening area 1212, and the size of the subsequent energy dissipation steps 2 remains unchanged. The principle is: based on the hydraulic model test, it is found that when the high-speed water flow on the steep slope base 12 directly encounters the large-size energy dissipation step 2 in the widening area 1212, water splashing will occur. Therefore, in the embodiment of the present invention, a multi-stage energy dissipation step 2 whose size increases successively along the water flow direction is set in the diffusion area 1211, so that when the high-speed water flows through the multi-stage energy dissipation step 2 in the diffusion area 1211, the flow velocity is reduced and gradually changes to the large-sized energy dissipation step 2 in the widening area 1212, thereby ensuring a smooth flow of water without splashing of water droplets.

[0023] Furthermore, the slope of the gently sloping base layer 11 is smaller than the slope of the steeply sloping base layer 12. The flood discharge tunnel 1 further includes a plurality of turning sections, and the plurality of turning sections are arranged through the gently sloping base layer 11.

[0024] Through the implementation of the above-mentioned pumped storage power station flood discharge system, in the process of excavating the flood discharge tunnel 1, there are situations where the terrain is complex or obstacles need to be avoided. Therefore, by setting a turning section in the flood discharge tunnel 1, the flood discharge tunnel 1 can better adapt to the undulating changes in the terrain, and the total length of the flood discharge tunnel 1 can be effectively shortened. And the turning section can change the direction and speed distribution of the water flow, which is helpful to evenly distribute the water flow. At the same time, several turning sections are arranged through the gentle slope base 11, and the smaller slope of the gentle slope base 11 is utilized. Since the water flow velocity at the turning section is usually larger, the situation where the water surface difference inside and outside the turning section is too large due to centrifugal force can be avoided, thereby ensuring a stable water flow state.

[0025] Furthermore, the steep slope base 12 also includes a smooth section 122 connected between the gentle slope base 11 and the energy dissipation section 121. The layer surface of the steep slope base 12 located at the smooth section 122 constitutes a smooth diversion surface for diverting sediment in the water flow to the downstream. The position where the energy dissipation section 121 and the smooth section 122 are connected is a calibrated distance n from the outlet of the flood discharge tunnel 1, and the range of the calibrated distance n is 70m≤n≤100m.

[0026] Through the implementation of the above-mentioned pumped storage power station flood discharge system, the smooth section 122 of the steep slope base 12 is an area where no energy dissipation building is set. Since the energy dissipation building is arranged at the exit of the flood discharge tunnel 1, the length of the smooth section 122 on the steep slope base 12 is much greater than the length of the energy dissipation section 121. This allows the water flow to maintain a high speed on the smooth section 122, which helps to improve the flood discharge efficiency and facilitates the rapid diversion of sediment in the water flow to the downstream to reduce the siltation of sediment-rich floods in the flood discharge structure. In addition, the embodiment of the present invention arranges the energy dissipation building only within a range of 100m from the exit of the flood discharge tunnel 1. The principle of the difference from the existing conventional step overflow dam and step spillway full-length arrangement is: first, the flood discharge tunnel 1 is usually nearly a kilometer long, and is arranged in steps along the way. The engineering volume is quite large and the cycle is long. The embodiment of the present invention is arranged within 100m from the outlet of flood discharge tunnel 1, which effectively saves engineering work and is also convenient for later maintenance; secondly, it is verified by model tests that the water flow within 100m from the outlet of flood discharge tunnel 1 can form an aerated uniform flow, and the aerated uniform flow means that the flow rate tends to be stable and can no longer be reduced. Therefore, the energy dissipation building is only arranged within 100m from the outlet of flood discharge tunnel 1, and the flow rate at the outlet of flood discharge tunnel 1 is the same as that of the full arrangement stage.

[0027] Preferably, an energy dissipation section 121 is arranged on the steep slope base 12, and the position where the energy dissipation section 121 connects with the smooth section 122 is 100m away from the outlet of the flood discharge tunnel 1, so that the arrangement of the multi-level energy dissipation steps 2 ensures that the water flow forms an aerated uniform flow and effectively saves the engineering workload.

[0028] Preferably, an energy dissipation section 121 is arranged on the steep slope base 12. The position where the energy dissipation section 121 connects with the smooth section 122 is 70m away from the outlet of the flood discharge tunnel 1. The arrangement of the multi-level energy dissipation steps 2 ensures that the water flow forms an aerated uniform flow and greatly saves the engineering workload.

[0029] Preferably, an energy dissipation section 121 is arranged on the steep slope base 12, and the position where the energy dissipation section 121 connects with the smooth section 122 is 80m away from the exit of the flood discharge tunnel 1, so that the arrangement of the multi-level energy dissipation steps 2 ensures sufficient energy dissipation and saves engineering workload.

[0030] Furthermore, combined with Figure 5 As shown, the step plane 21 is an inclined plane formed by rotating a horizontal plane clockwise at a preset angle along the water flow direction, and the step facade 22 is an inclined plane formed by rotating a vertical plane counterclockwise at a preset angle along the water flow direction, and the step facade 22 of the energy dissipation step 2 and the step plane 21 of the next energy dissipation step 2 are located at the connection to form a scouring concave angle greater than 90°.

[0031] Through the implementation of the above-mentioned pumped storage power station flood discharge system, the step plane 21 of the energy dissipation step 2 provides the water flow with opportunities for collision, shearing, aeration and friction, so that the energy in the water flow can be dissipated, and then the design of the multi-stage energy dissipation step 2 provides multiple energy dissipation stages, so that the water flow can gradually slow down when passing through the flood discharge tunnel 1, reduce the transfer of energy, effectively reduce the speed and impact force of the water flow, and achieve the purpose of energy dissipation. On this basis, the inclined setting of the step plane 21 can form a slope for silt diversion, so that the silt can pass smoothly, so as to reduce the stagnation and accumulation of silt on the step plane 21. In addition, by using the step facade 22 with the same inclined setting, when the water flow encounters the step facade 22, the direction of the water flow will change along the step facade 22, and the change in the direction of the water flow will increase the turbulence of the water flow, and the 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 effect of energy dissipation. And due to the large slope of the step facade 22, the silt in the water flow can be quickly diverted to the downstream. In addition, by using the step facade 22 of the energy dissipation step 2 and the step plane 21 of the next energy dissipation step 2 to form a scouring angle greater than 90° at the connection point, it is possible to prevent the formation of a silt accumulation angle between two adjacent energy dissipation steps 2, so that the silt carried in the water flow can pass smoothly, reducing the stagnation and accumulation of silt, so as to avoid the collision and wear of the energy dissipation step 2 by the silt accumulation, improve the sand discharge effect, increase the service life of the energy dissipation building, reduce maintenance costs, and prevent the influence of long-term siltation on the tunnel performance. Preferably, in order to achieve the best effect of sand discharge and prevention of silt accumulation, the step plane 21 is rotated clockwise at an angle of 3-5° with the horizontal plane of the conventional step, and the step facade 22 is rotated counterclockwise at an angle of 15-30° with the vertical plane of the conventional step.

[0032] Further, look back Figure 2 The corresponding widths, step lengths and step heights between any two energy dissipation steps 2 in the widening area 1212 are consistent, and the step length and step height of the uppermost energy dissipation step 2 in the widening area 1212 are greater than the step length and step height of the lowermost energy dissipation step 2 in the diffusion area 1211.

[0033] Through the implementation of the above-mentioned pumped storage power station flood discharge system, the sizes of the energy dissipation steps 2 at each level are not exactly the same. The corresponding widths, step lengths and step heights between the multiple energy dissipation steps 2 in the diffusion area 1211 are all increased in sequence along the water flow direction, while the corresponding widths, step lengths and step heights between the multiple energy dissipation steps 2 in the widening area 1212 are all consistent. The multiple energy dissipation steps 2 in the diffusion area 1211 gradually reduce the water flow speed during the flood discharge process, thereby improving 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 multiple energy dissipation steps 2 in the widening area 1212 ensure that the water flow is uniformly dissipated, reducing the change in local water flow speed, which helps to prevent water flow impact and erosion.

[0034] Furthermore, the flood discharge system of the pumped storage power station further includes oppositely arranged side walls 6, and the flood discharge tunnel 1 is arranged between the two side walls 6. The connecting line of the outer sides of the multi-stage energy dissipation step 2 is collinear with the side wall 6 on the corresponding side, and the connecting line of the central axis of the multi-stage energy dissipation step 2 along the water flow direction is a straight line.

[0035] Through the implementation of the above-mentioned pumped storage power station flood discharge system, by placing the outer side of the multi-stage energy dissipation step 2 in line with the side wall 6 on the corresponding side, it is possible to ensure that the water flow maintains a stable flow direction when passing through the multi-stage energy dissipation step 2, and avoid the water flow from scouring the inner wall of the flood discharge tunnel 1. At the same time, by using the central axis line of the multi-stage energy dissipation step 2 along the water flow direction as a straight line, when the water flow passes through any energy dissipation step 2, it can be evenly diffused to both sides at the middle position of the step plane 21 of the energy dissipation step 2 to form a horizontal axis vortex, and shear friction with the water body normally discharged from above to achieve the energy dissipation effect, so that the multi-stage energy dissipation step 2 forms a complete energy dissipation system, so as to improve the energy dissipation efficiency through different energy dissipation mechanisms, such as resistance, turbulence, collision, etc.

[0036] Furthermore, combined with Figure 4 and Figure 6 As shown, the energy dissipation pool 3 includes a pool body and an energy dissipation assembly arranged on the bottom plate of the pool body, and the bottom plate of the pool body is flush with the outlet of the flood discharge tunnel 1. The energy dissipation assembly includes multiple rows of energy dissipation piers 31 arranged along the vertical water flow direction, and the energy dissipation piers 31 between two adjacent rows are staggered. The energy dissipation piers 31 are trapezoidal structures parallel to the water flow direction, and the side surfaces of the energy dissipation piers 31 facing the upstream water flow are arranged obliquely.

[0037] Through the implementation of the above-mentioned pumped storage power station flood discharge system, by making the bottom plate of the stilling pool 3 flush with the outlet of the flood discharge tunnel 1, it is helpful for the water flow to carry away the silt when passing through the stilling pool 3, so that there is no need to set a tail sill in the stilling pool 3, and there is no need to dig deep downwards, so as to prevent the silt from accumulating in the stilling pool 3. At the same time, the stilling pier 31 with a trapezoidal structure has better structural stability than the stilling pier 31 of other shapes, and can better withstand the thrust and pull of the water flow, so that the water level in the stilling pool 3 can be raised to form a water jump, so that the water flow rolls in the stilling pool 3, and the water flow flowing out of the flood discharge tunnel 1 is secondary dissipated. When the water flow is large, the oblique side surface of the stilling pier 31 facing the upstream water flow is used to collide with the water flow and dissipate energy, and the silt flowing through can be diverted to avoid silt accumulation at the stilling pier 31. The multiple rows of energy dissipation piers 31 increase the chances of contact and collision between the water flow and the energy dissipation piers 31, thereby improving the energy dissipation effect. In addition, the energy dissipation piers 31 in two adjacent rows are arranged in a staggered manner, so that the water flow at different positions in the energy dissipation pool 3 can be affected by the energy dissipation piers 31, avoiding the concentration of water flow in certain areas, thereby reducing local scouring and stress concentration, and increasing the uniformity and comprehensiveness of energy dissipation.

[0038] Furthermore, the protective facility 4 includes a concrete apron layer 41, a reinforced gabion layer 42 and a crushed stone layer 43 which are arranged in sequence at the outlet of the energy dissipation pool 3, so that the water flow at the outlet of the energy dissipation pool 3 can be transitionally buffered through the concrete apron layer 41, the reinforced gabion layer 42 and the crushed stone layer 43 in sequence.

[0039] Through the implementation of the above-mentioned pumped storage power station flood discharge system, three sections of protective layers with different structures are sequentially arranged between the energy dissipation pool 3 and the original riverbed cover layer 5, so that the surface of the concrete apron layer 41, the steel gabion layer 42, the crushed stone layer 43 and the original riverbed cover layer 5 are all flush with the bottom plate of the energy dissipation pool 3. After the water flow out of the flood discharge tunnel 1 passes through the energy dissipation pool 3 for the second time, it flows along the surface of the concrete apron layer 41, the steel gabion layer 42 and the crushed stone layer 43 in sequence, and part of the water flow seeps from the surface of the concrete apron layer 41, the steel gabion layer 42 and the crushed stone layer 43 respectively. That is, the concrete apron layer 41 first directly bears the impact of the high-speed water flow, and its thick structure reduces the direct impact force of the water flow on the downstream, so as to protect the original riverbed cover layer 5 downstream. It can also evenly disperse the water flow, reduce the vortex and pulsation in the water flow, and improve the stability of the water flow. The reinforced gabion layer provides additional structural strength, which can withstand greater water flow pressure and impact to resist a certain degree of erosion and impact, thus reducing the need for long-term maintenance. The crushed stone layer 43 further absorbs and disperses the energy of the water flow, reducing the continuous impact of the water flow on the original riverbed cover 5. The porosity of the crushed stone layer 43 enables it to adapt to different water flow speeds and flow rates, providing flexible buffering and protection. Therefore, the gradual transition protection form of the concrete apron layer 41, the reinforced gabion layer 42 and the crushed stone layer 43 is adopted, so that the energy of the water flow coming out of the energy dissipation pool 3 is further lost in different areas in turn, avoiding the direct connection between the concrete apron layer 41 or the reinforced gabion layer 42 and the original riverbed cover 5, resulting in easy formation of pits at the junction, thereby threatening the stability of the protective structure.

[0040] Furthermore, combined with Figure 7 As shown, the reinforced gabion layer 42 includes a plurality of interconnected hexahedral reinforced cages 421, and the hexahedral reinforced cages 421 include 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 formed by weaving low-carbon steel wires, and 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 fillers are also arranged in the cage body, and the crushed stone fillers are filled in the stone gaps between two adjacent filling stones in the cage body.

[0041] Through the implementation of the above-mentioned pumped storage power station flood discharge system, a plurality of interconnected hexahedral steel cages 421 are used to form a steel cage layer 42, and its 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 steel mesh structure formed by weaving low-carbon steel wire, and the filling of filling stones in the cage body, the entire hexahedral steel cage 421 forms a solid protective layer, which can withstand the large impact and erosion of the water flow, and help protect the downstream structure. Among them, setting the mesh of the cage body to be smaller than the particle size of the filling stone can prevent the filling stone from being lost during the filling or flood control process, so as to improve the stability of the steel cage layer 42. In addition, by coating the steel wire of the cage body with a resin protective film, the corrosion resistance of the cage body steel wire structure can be increased, and the service life of the steel cage layer 42 can be extended. And setting the crushed stone filler to fill the stone seam between two adjacent filling stones can further strengthen the structure, reduce the gap between the filling stones, and improve the compactness and stability of the inside of the hexahedral steel cage 421. Preferably, low-carbon steel wire is woven into a hexagonal double-twisted steel wire mesh by a special machine to assemble into a cage of 2m×1m×1m (length×width×height). The particle size of the stone filling in the cage is between 150mm and 300mm, and the stone gaps 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 shall not exceed 15%, and its porosity shall not exceed 20%, and different hexahedral steel cages 421 are connected to each other by steel wires to improve the overall stability (reference Figure 8 ).

[0042] The flood discharge system of the pumped storage power station of the present invention arranges the energy dissipation building only within the range of 100m from the outlet of the flood discharge tunnel 1. Compared with the full tunnel arrangement scheme, it saves engineering work and is more convenient for the later step maintenance. And by using the horizontal width gradient setting of the energy dissipation section 121 in the diffusion area 1211, it only widens the marked range of the outlet of the flood discharge tunnel 1, thereby effectively reducing the single-width flow rate under the condition of increasing less excavation volume, and significantly improving the energy dissipation effect of the energy dissipation building. Then, through the scheme of gradually transitioning from small size to large size of the multi-level energy dissipation step 2, the phenomenon of water splashing on the energy dissipation step 2 is avoided, the water flow connection is more stable, and the flow state of the water flow is improved. The energy dissipation pool 3 is neither provided with a traditional tail sill nor dug deep downward. The bottom plate of the energy dissipation pool 3 is flush with the outlet of the flood discharge tunnel 1. By arranging the energy dissipation pier 31 of the trapezoidal structure to form a high water depth to form a water jump energy dissipation, the sediment can be discharged to the river channel through the gap of the energy dissipation pier 31, and the sediment can be prevented from silting up in the energy dissipation pool 3. Finally, a concrete protective layer 41, a reinforced gabion layer 42 and a crushed stone layer 43 are sequentially arranged between the energy dissipation pool 3 and the original riverbed covering layer 5, thereby avoiding the situation where the energy dissipation pool 3 and the original riverbed covering layer 5 are connected, resulting in a pit at the junction, thereby threatening the stability of the protective structure.

[0043] The present invention also discloses a flood discharge method, which adopts the above-mentioned pumped storage power station flood discharge system, comprising: A flood discharge tunnel 1, an energy dissipation building, an energy dissipation pool 3 and protective facilities 4 are arranged in the target basin. When a flood occurs in the target basin, the flood in the target basin carries sediment and is introduced into the flood discharge tunnel 1, and flows in sequence along the gentle slope base 11 and the steep slope base 12; When the water flows along the steep slope base 12 to the energy dissipation section 121, the water first passes through the multi-stage energy dissipation steps 2 in the diffusion area 1211 to dissipate energy, and gradually reduces the single-width flow until it transitions to the multi-stage energy dissipation steps 2 in the widening area 1212, and continues to dissipate energy while keeping the single-width flow unchanged. The sediment in the water flow is diverted to the downstream along the multi-stage energy dissipation steps 2; After the water flows through the multi-stage energy dissipation steps 2 for primary energy dissipation, it carries the sediment and is introduced into the energy dissipation pool 3 along the outlet of the flood discharge tunnel 1, and swirls in the energy dissipation pool 3 for secondary energy dissipation, and the sediment is discharged from the energy dissipation pool 3 along with the water flow; The water flowing out of the energy dissipation pool 3 flows through the protective facilities 4 and gradually loses energy until it flows into the original riverbed cover 5 to complete flood discharge.

[0044] Through the implementation of the above-mentioned flood discharge method, when rainfall occurs in the basin, the flood carries sediment particles into the flood discharge tunnel 1, and first passes through the gentle slope base 11, and the smooth section 122 of the steep slope base 12. The smooth section 122 is most conducive to drainage and sediment removal while reducing wear. Before leaving the tunnel, the water flows through the multi-level energy dissipation steps of the energy dissipation 121 to consume the kinetic energy of the water. Among them, the water flows through the diffusion area 1211 to the widening area 1212, the water width becomes larger, the single-width flow rate is reduced, and the step aeration energy dissipation effect is significantly improved. At the same time, when the water flows from the smooth section 122 through the diffusion area 1211 of the energy dissipation section 121, it first transitions through the multi-level energy dissipation steps 2 of increasing sizes, which effectively avoids the splashing of water and sediment particles caused by the water flowing directly into the large-size energy dissipation steps 2 through the smooth section 122. The step facade 22 and the step plane 21 are rotated by a certain angle on the basis of the traditional conventional steps, which increases the flow velocity at the scouring concave corner where two adjacent energy dissipation steps 2 are connected, and completely avoids the sediment accumulation at the scouring concave corner.

[0045] Based on the hydraulic model test, it is found that after the water flow passes through the multi-stage energy dissipation steps 2, a specific working condition can reduce the original flow velocity of 23m / s to 12m / s, and then the potential energy effect of increasing the flow velocity and the aeration and friction effects of reducing the flow velocity reach a balance, 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 only arranges the multi-stage energy dissipation steps 2 within the calibrated range from the outlet of the flood discharge tunnel 1, which greatly saves the engineering workload. The water flows into the energy dissipation pool 3 through the outlet of the flood discharge tunnel 1, and the water flow is affected by the energy dissipation piers 31 and swirls in the energy dissipation pool 3 for secondary energy dissipation, so that the flow velocity is reduced from 12m / s to about 5m / s. And the sediment can be gradually discharged from the energy dissipation pool 3 from the gaps between the two adjacent rows of energy dissipation piers 31.

[0046] The water flowing out of the energy dissipation pool 3 passes through the concrete apron layer 41, the reinforced gabion layer 42, and the crushed stone layer 43 in turn, and the energy is gradually lost. When it reaches the original riverbed cover layer 5, the flow velocity is less than 3m / s. This gradually transitional protection facility does not produce any scour pits, and effectively protects the stability of the structural foundation of the energy dissipation pool 3 and the riverbed slope.

[0047] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to 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 the steep slope base is provided with an energy dissipation section within a calibrated range of an outlet of the flood discharge tunnel, and the energy dissipation section comprises a diffusion area whose horizontal width increases in sequence along a water flow direction, and a widening area whose horizontal width remains unchanged from the end of the diffusion area; The energy dissipation structure comprises a plurality of energy dissipation steps which are sequentially connected and arranged 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 comprise a step plane for dissipating the energy of the upstream water flow, and a step facade for diverting the 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 sequentially increased along the water flow direction, and are used for gradually transitioning the upstream water flow to the plurality of energy dissipation steps in the widening area through a gradual change in flow velocity. 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 steep slope base also includes a smooth section connected between the gentle slope base and the energy dissipation section. The steep slope base is located on the layer surface of the smooth section to form a smooth diversion surface for diverting sediment in the water flow to the downstream. 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 range of the calibrated distance n is 70m≤n≤100m.

4. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The step plane is an inclined plane formed by rotating a horizontal plane clockwise at a preset angle along the water flow direction, and the step facade is an inclined plane formed by rotating a vertical plane counterclockwise at a preset angle along the water flow direction, and the step facade of the energy dissipation step and the step plane of the next level of the energy dissipation step are located at the connection point to form a scouring angle greater than 90°.

5. The flood discharge system of a pumped storage power station according to claim 1, characterized in that: The corresponding widths, step lengths and step heights 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.

6. 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 relatively arranged side walls, the flood discharge tunnel is arranged between the two side walls, the connecting line of the outer sides of the multiple levels of energy dissipation steps and the side walls on the corresponding sides are collinear, and the connecting line of the central axes of the multiple levels of energy dissipation steps along the water flow direction is a straight line.

7. 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.

8. 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.

9. The flood discharge system of a pumped storage power station according to claim 8, 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.

10. A flood discharge method, using the pumped storage power station flood discharge system according to any one of claims 1 to 9, 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 multiple energy dissipation steps in the diffusion area to dissipate energy, and gradually reduces the single-width flow until it transitions to the multiple 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 multiple 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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