Flood discharge and sand discharge hole arrangement structure of water pumping and storage reservoir project and construction diversion method
By setting up a sand blocking dam and flood discharge cave upstream of the reservoir, the sand blocking dam water transfer cave is used for initial water storage and water replenishment during operation, the problems of high-sea head power stations' wear and high construction diversion costs are solved, and more efficient sediment protection and shortening construction period are achieved.
Patent Information
- Application Number
- CN202510916107.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-08-15
AI Technical Summary
The turbines of existing high-head power stations are susceptible to silt and sand wear, and the investment in conventional sand sinks is high and the geological risks are high. The construction diversion of pumping and storage power stations increases costs and has a long construction period. The permanent structure of the bypass diversion tunnel is worn, making it difficult to construct.
Sand blocking dams are set up upstream of the main dam of the reservoir, and flood discharge caves are used to discharge floods and silt downstream. Combined with the sand blocking dam water transfer caves to conduct initial water storage and water replenishment during operation, forming a new hub arrangement where silt does not enter the reservoir. Through the construction drainage hole, the traffic channel and diversion role can be played at different stages to avoid the impact of silt.
It reduces geological risks, improves the anti-silt effect, shortens the construction period, reduces construction costs, and avoids the wear of the permanent structure bypassing the diversion tunnel, which has good economic benefits and construction period advantages.
Smart Images
Figure CN120486326A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of water conservancy and hydropower engineering, and in particular to a flood discharge and sediment discharge tunnel arrangement structure and a construction diversion method for a pumped-storage reservoir project. Background Art
[0002] Turbine units in hydropower stations with high head, especially those with extra-high head, on mountain rivers are particularly sensitive to sediment. High sediment content in the incoming water often causes severe abrasion of turbines and other structures, leading to frequent shutdowns for overhaul or replacement. This not only severely impacts the normal operation of the power station but also increases operational costs. However, in actual projects, hydropower stations on mountain rivers often encounter unfavorable conditions such as narrow river channels, heavy sediment loads, small reservoir capacities, and high sediment particle size.
[0003] To reduce the amount of sediment flowing through high-head hydropower stations in mountainous areas, sedimentation basins are often installed ahead of the water intake to mitigate the damage caused by sediment wear on turbines. However, this often results in high project investment, increased workload, and increased construction difficulty. Furthermore, narrow river channels in mountainous areas often lack sufficient space for surface sedimentation basins. Underground sedimentation basins, on the other hand, present significant geological risks, high investment, and ineffective sedimentation. Some hydropower projects choose to reduce the number of units in operation during high-sediment seasons to reduce the size of the sedimentation basins, but this reduces power generation.
[0004] At present, the method generally adopted for diversion construction of conventional pumped-storage power station reservoirs is to design a bypass diversion tunnel next to the permanent spillway of the reservoir main dam, and to combine the bypass diversion tunnel with the permanent spillway. However, this diversion arrangement has the following shortcomings: first, the bypass diversion tunnel still needs to be built separately, which will change the structural layout of the original permanent spillway and increase the construction configuration; second, the flow through the bypass diversion tunnel inevitably carries solid impurities, which will cause certain wear and tear on the permanent structure spillway. After blocking, it needs to be fully overhauled, which increases the construction time and cost of the repair construction; third, after the diversion function of the bypass diversion tunnel is completed, it still needs to be blocked and rebuilt, which has certain construction difficulties and safety hazards. Summary of the Invention
[0005] In order to overcome the technical problems that the existing high-head power stations use underground sedimentation ponds with high geological risks and poor sedimentation effects; the construction diversion structure of the pumped storage power station requires additional buildings, high costs, long construction period and inconvenient construction, the present invention provides a flood discharge and sediment discharge hole layout structure and construction diversion method for pumped storage reservoir projects.
[0006] The technical solution adopted by the present invention to solve its technical problem is: The flood discharge and sediment discharge tunnel layout structure of the pumped-storage reservoir project where sediment does not enter the reservoir includes the main dam of the reservoir, a sand retaining dam and a flood discharge and sediment discharge tunnel. The sand retaining dam is located upstream of the main dam of the reservoir, the inlet section of the flood discharge and sediment discharge tunnel is located upstream of the sand retaining dam, the body of the flood discharge and sediment discharge tunnel passes through the mountain, and the outlet section of the flood discharge and sediment discharge tunnel is located downstream of the main dam of the reservoir; the sand retaining dam is also equipped with a sand retaining dam water diversion tunnel for transferring water to the reservoir area between the sand retaining dam and the main dam of the reservoir.
[0007] In the present invention, a sand retaining dam is set up upstream to block water, and a flood discharge and sand discharge hole is used to discharge flood water and sediment to the downstream of the main dam of the reservoir. The water diversion hole of the sand retaining dam is used to carry out initial water storage and water replenishment in the operation period of the lower reservoir, so that the lower reservoir becomes a dedicated reservoir, thereby avoiding the influence of sediment and forming a new hub layout of the pumped storage power station reservoir in which sediment does not enter the reservoir. Compared with the existing technology, such implementation has lower geological risks and better sediment prevention effects.
[0008] In some embodiments, a construction drainage hole is also included, the inlet section of the construction drainage hole is located in the reservoir area between the sand retaining dam and the main dam of the reservoir, and the outlet section of the construction drainage hole is connected to the body of the flood discharge and sand discharge hole.
[0009] In some embodiments, the angle between the construction drainage hole and the flood and sediment discharge hole is greater than or equal to 50°.
[0010] In some embodiments, a permanent plug is arranged at the connection position between the construction drainage hole and the flood discharge and sand discharge hole to prevent the interval water flow from entering the flood discharge and sand discharge hole.
[0011] In some embodiments, the construction drainage tunnel and the flood discharge and sand discharge tunnel are both in the form of pressure-free tunnels, and the cross-section of the construction drainage tunnel and the cross-section of the flood discharge and sand discharge tunnel are both in the shape of city gate tunnels.
[0012] In some embodiments, the bottom elevation of the construction drainage tunnel outlet section is higher than the flood level in the flood discharge and sand discharge tunnel corresponding to the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged from the flood discharge and sand discharge tunnel during the main flood season; it is also higher than the flood level in the flood discharge and sand discharge tunnel corresponding to the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged during the sealing period of the construction drainage tunnel.
[0013] The present invention also provides a construction diversion method for a pumped-storage reservoir project without sediment entering the reservoir, comprising the following steps: Step S1. During the construction diversion preparation phase, a drainage tunnel is constructed. The inlet section of the drainage tunnel is located between the sediment dam and the main dam of the reservoir. A flood discharge and sediment discharge tunnel is excavated at the outlet section of the drainage tunnel. Step S2. During the construction period of the main dam, the water flowing in front of the sand barrier is blocked by the sand barrier and discharged through the flood discharge tunnel. The water flowing from the main dam is connected to the flood discharge tunnel through the construction drainage tunnel. Step S3. Before water storage, the drainage hole is sealed; Step S4. During the water storage period, water is released from the water diversion tunnel of the sand dam into the interval, so that the reservoir is filled to the normal water level; Step S5. During the dam operation period, the construction drainage hole is in a blocked state to prevent water from the reservoir area from entering the flood discharge and sediment discharge hole.
[0014] In this invention, by placing a construction drainage tunnel at a suitable location within the hub area, the tunnel can serve different functions at different times. During the construction period of the flood and sediment discharge tunnel, the tunnel serves as a traffic channel for the tunnel's construction. During the construction period of the reservoir's main dam, the tunnel's designed structure diverts water. During the dam's operation period, the tunnel is sealed to prevent water from entering the flood and sediment discharge tunnel between the sand dam and the main dam, thus meeting the normal flow requirements of the flood and sediment discharge tunnel. Compared with traditional arrangements, this eliminates the need for excavating and pouring a separate bypass diversion tunnel structure, shortening the construction period and offering excellent economic benefits and time-limited advantages.
[0015] In some embodiments, step S2 comprises: Step S21. During the initial diversion phase, water flowing in front of the sand barrier is blocked by the barrier and discharged through the flood and sediment discharge tunnel. Water flowing in the section in front of the main dam of the reservoir is blocked by the cofferdam and discharged through the construction drainage tunnel to facilitate dam foundation excavation and dam body filling. Step S22. During the middle and late diversion period, the water flowing in front of the sand retaining dam is blocked by the sand retaining dam and discharged through the flood and sand discharge tunnel; the water flow in the section in front of the main dam of the reservoir is blocked by the temporary section of the dam and discharged through the construction drainage tunnel connected to the flood and sand discharge tunnel to carry out dam foundation excavation and dam body filling.
[0016] In some embodiments, step S20 is included between step S1 and step S2. Step S20: During the construction of the sand dam and the diversion period, the water flows through the water diversion tunnel of the sand dam.
[0017] This invention fully utilizes the fact that the construction period of pumped-storage power station buildings is generally longer than that of dam construction, and cleverly divides the entire construction diversion into two stages. In the first stage, the water diversion tunnel of the sand retaining dam is used to divert water, draining the water above the sand retaining dam to meet the sand retaining dam construction diversion requirements. In the second stage, the flood discharge and sand discharge tunnel is fully utilized to drain the water above the sand retaining dam, and the construction drainage tunnel diverts the water flow in front of the main dam of the reservoir. The flood discharge and sand discharge tunnel and the construction drainage tunnel jointly divert water to meet the dam construction diversion requirements, thus realizing the multi-purpose function of the construction drainage tunnel.
[0018] In some embodiments, the construction hole blocking method described in step S3 is: a temporary water retaining cofferdam is set up at the entrance of the construction drainage hole, and construction personnel and equipment enter from the entrance to the exit of the construction drainage hole to perform plugging construction. During the blocking period, the water flow is discharged into the downstream through the permanent flood discharge hole of the main dam of the reservoir.
[0019] The beneficial effects of the present invention are: By setting up a sand retaining dam upstream to block water, and using flood discharge and sediment tunnels to discharge floodwater and sediment to the downstream of the reservoir main dam, and using the sand retaining dam water diversion tunnel to carry out initial water storage and water replenishment in the lower reservoir during operation, the lower reservoir becomes a dedicated reservoir, thus avoiding the impact of sediment and forming a new hub layout for pumped storage power station reservoirs where sediment does not enter the reservoir. Compared with existing technologies, this implementation has lower geological risks and better sediment prevention effects. By arranging a construction drainage tunnel at an appropriate location in the hub area, the construction drainage tunnel can have different functions at different times. During the construction period of the flood discharge and sediment discharge tunnel, the construction drainage tunnel serves as a traffic channel for the construction of the flood discharge and sediment discharge tunnel; during the construction period of the reservoir main dam, the designed construction drainage tunnel structure plays a construction diversion role; during the dam operation period, by blocking the construction drainage tunnel, water from the reservoir area between the sand dam and the main dam of the reservoir is prevented from entering the flood discharge and sediment discharge tunnel, thus meeting the normal operation flow requirements of the flood discharge and sediment discharge tunnel. Compared with the traditional layout, it eliminates the need to excavate and cast a separate bypass diversion tunnel structure, shortens the construction period, and has good economic benefits and construction period advantages. Taking full advantage of the fact that the construction period of pumped storage power station buildings is generally longer than that of dam construction, the entire construction diversion is cleverly divided into two stages. In the first stage, the water diversion tunnel of the sand retaining dam is used to divert water, draining the water above the sand retaining dam to meet the sand retaining dam construction diversion requirements; in the second stage, the flood discharge and sand discharge tunnel is fully utilized to drain the water above the sand retaining dam, and the construction drainage tunnel is used to divert water in the area in front of the main dam of the reservoir. The flood discharge and sand discharge tunnel and the construction drainage tunnel are used together to divert water, meeting the requirements of dam construction diversion and realizing the multi-purpose function of the construction drainage tunnel. The construction drainage tunnel is located at the intersection of the flood and sediment discharge tunnel, with the exit of the construction drainage tunnel positioned higher than the larger of the design water level for the plugging period and the flood season overflow level. Firstly, this is higher than the design water level for the plugging period, meeting the requirements for pre-water storage plugging, facilitating construction, and ensuring construction safety. Secondly, it is higher than the flood season overflow level of the flood and sediment discharge tunnel. This allows the water diverted from the construction drainage tunnel to smoothly merge with the flood and sediment discharge tunnel, and when it reaches the surface, it significantly reduces wear on the permanent lining structure of the flood and sediment discharge tunnel. This overcomes the drawback of previous methods where solid matter carried by the bypass diversion tunnel could damage the permanent flood discharge tunnel. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 This is a schematic diagram of the plan layout of the construction diversion structure disclosed in the present invention; Figure 2 for Figure 1 A partial enlarged schematic diagram of the middle sand dam; Figure 3 for Figure 1 A partial enlarged schematic diagram of the main dam of the Zhongshui Reservoir.
[0021] Marked in the figure are: 1-1: inlet section of flood discharge and sand drainage tunnel, 1-2: body section of flood discharge and sand drainage tunnel, 1-3: outlet section of flood discharge and sand drainage tunnel, 2-1: inlet section of construction drainage tunnel, 2-2: body section of construction drainage tunnel, 2-3: outlet section of construction drainage tunnel, 3: sand retaining dam, 4: main dam of reservoir, 5: water diversion tunnel of sand retaining dam, 6: permanent flood discharge tunnel of main dam of reservoir. DETAILED DESCRIPTION
[0022] The present invention will be further described below with reference to the accompanying drawings.
[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.
[0024] Combine Figure 1-Figure 3 As shown, the present invention provides a flood discharge and sediment discharge hole layout structure and construction diversion method for a pumped storage reservoir project.
[0025] The flood discharge and sediment discharge tunnel layout structure of the pumped-storage reservoir project where sediment does not enter the reservoir includes the reservoir main dam 4, the sand retaining dam 3 and the flood discharge and sediment discharge tunnel. The sand retaining dam 3 is located upstream of the reservoir main dam 4, the flood discharge and sediment discharge tunnel inlet section 1-1 is located upstream of the sand retaining dam 3, the flood discharge and sediment discharge tunnel body section 1-2 passes through the mountain, and the flood discharge and sediment discharge tunnel outlet section 1-3 is located downstream of the reservoir main dam 4; the sand retaining dam 3 is also equipped with a sand retaining dam water diversion tunnel 5 for transferring water to the reservoir area between the sand retaining dam 3 and the reservoir main dam 4.
[0026] In the present invention, a sand retaining dam 3 is set up upstream to block water, and a flood discharge and sediment discharge hole is used to discharge flood water and sediment to the downstream of the main dam 4 of the reservoir. The sand retaining dam water diversion hole 5 is used to carry out initial water storage and water replenishment in the lower reservoir during operation, so that the lower reservoir becomes a dedicated reservoir, thereby avoiding the influence of sediment and forming a new hub layout mode of pumped storage power station reservoir in which sediment does not enter the reservoir. Compared with the existing technology, such implementation has lower geological risks and better sediment prevention effect.
[0027] In this embodiment, a construction drainage tunnel is included, the inlet section 2-1 of the construction drainage tunnel is located in the reservoir area between the sand retaining dam 3 and the main dam 4 of the reservoir, and the outlet section 2-3 of the construction drainage tunnel is connected to the flood discharge and sand discharge tunnel section 1-2.
[0028] In this embodiment, the angle between the construction drainage tunnel and the flood discharge and sediment discharge tunnel is equal to 50 degrees. Preferably, it should be greater than or equal to 50 degrees, so as to avoid affecting traffic and facilitate use as a construction channel for the flood discharge and sediment discharge tunnel.
[0029] In this embodiment, a permanent plug is arranged at the connection position between the construction drainage tunnel and the flood discharge and sediment discharge tunnel to prevent the interval water flow from entering the flood discharge and sediment discharge tunnel during the operation period of the main dam 4 of the reservoir.
[0030] In this embodiment, the construction drainage tunnel and the flood discharge and sand discharge tunnel are both in the form of pressure-free tunnels, and the section 2-2 of the construction drainage tunnel and the section 1-2 of the flood discharge and sand discharge tunnel are both in the shape of city gate tunnels, and the section size is designed to meet both construction needs and flood diversion needs.
[0031] In this embodiment, the bottom elevation of the construction drainage tunnel outlet section 2-3 is higher than the flood level in the flood discharge and sand discharge tunnel corresponding to the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged from the flood discharge and sand discharge tunnel during the main flood season; it is also higher than the flood level in the flood discharge and sand discharge tunnel corresponding to the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged during the sealing period of the construction drainage tunnel.
[0032] With this arrangement, the construction drainage tunnel, integrated with the flood and sediment discharge tunnel, is located at a higher level than the larger of the design water level for the plugging period and the flood season overflow level. Firstly, this is higher than the design water level for the plugging period, meeting the requirements for pre-impoundment plugging, facilitating construction, and ensuring safety. Secondly, it is higher than the flood season overflow level for the flood and sediment discharge tunnel. This allows the water diverted from the construction drainage tunnel to smoothly merge with the flood and sediment discharge tunnel, where it falls to the surface, significantly minimizing wear on the permanent lining structure of the flood and sediment discharge tunnel. This overcomes the drawback of previous methods, where solid matter carried by the bypass diversion tunnel can damage the permanent flood discharge tunnel.
[0033] The present invention also provides a construction diversion method for a pumped-storage reservoir project without sediment entering the reservoir, comprising the following steps: Step S1. During the construction diversion preparation phase, a construction drainage tunnel is first constructed. The inlet section 2-1 of the construction drainage tunnel is located between the sediment retaining dam 3 and the main dam 4 of the reservoir. A flood discharge and sediment discharge tunnel is excavated at the outlet section 2-3 of the construction drainage tunnel.
[0034] The construction drainage tunnel consists of the inlet section 2-1, the body section 2-2, and the outlet section 2-3. In practice, the locations of the sediment retaining dam 3, the reservoir main dam 4, and the flood discharge tunnels are always pre-designed based on the mountain range where they are located. Here, the construction drainage tunnel was selected based on these pre-designed locations.
[0035] After the construction of the drainage hole is completed in this stage, it will be used as a construction channel for the flood discharge and sand discharge hole. Construction personnel and construction equipment will enter through the construction drainage hole to carry out the construction of the flood discharge and sand discharge hole.
[0036] After the construction of the flood discharge and sediment discharge tunnel is completed and the flow conditions are met in step S1, the construction and diversion period begins. The construction and diversion period is divided into two phases: the construction and diversion period of the sediment retaining dam 3 and the construction and diversion period of the main dam 4 of the reservoir.
[0037] Step S20: During the construction and diversion period of the sand retaining dam 3, water flows through the water diversion tunnel 5 of the sand retaining dam 3.
[0038] After the construction of the sediment retaining dam 3 is completed, the second diversion period begins, which is also the construction and diversion period of the main dam 4 of the reservoir.
[0039] During the construction diversion period of the main dam 4 of the reservoir, the water flow in front of the sand retaining dam 3 is blocked by the sand retaining dam 3 and discharged through the flood discharge and sand discharge hole; the water flow of the main dam 4 of the reservoir is discharged through the construction drainage hole connected to the flood discharge and sand discharge hole.
[0040] Specifically, the construction diversion period of the reservoir main dam 4 includes: Step S21. During the initial diversion phase, water flowing in front of the sand barrier 3 is blocked by the sand barrier 3 and discharged downstream through the flood and sediment discharge tunnel. Water flowing in the section in front of the main dam 4 of the reservoir is blocked by the cofferdam and discharged through the construction drainage tunnel to meet the design flood flow requirements for the section. This phase focuses on dam foundation excavation and dam body filling. Step S22. In the middle and late diversion period, the reservoir main dam 4 enters the middle and late diversion period after being filled beyond the cofferdam. The water flowing in front of the sand retaining dam 3 is blocked by the sand retaining dam 3 and discharged to the downstream through the flood discharge and sediment discharge tunnel, which is required to meet the flood discharge requirements of the design flood in front of the sand retaining dam 3; the water flow in the interval in front of the main dam 4 of the reservoir is blocked by the temporary section of the dam and discharged through the construction drainage tunnel connected to the flood discharge and sediment discharge tunnel, which is required to meet the flood design flow requirements of the interval, and the dam body filling continues.
[0041] Step S3. Before water storage, the construction drainage tunnel is sealed. During the sealing period, a temporary water retaining cofferdam is built at the entrance of the construction drainage tunnel. Construction personnel and equipment enter from the entrance to the construction drainage tunnel outlet to carry out the plugging work. The designed length of the plugging body must meet the water retention requirements of the normal water storage level. During the sealing period, the water flow is pumped to the permanent spillway 6 of the reservoir main dam and then discharged downstream, thus ensuring safety during the plugging work in the construction drainage tunnel.
[0042] Step S4. During the water storage period, after the construction of the drainage hole plugging is completed, water is released into the interval from the water diversion hole 5 of the upstream sand retaining dam, so that the reservoir is filled to the normal water level to meet the needs of the pumped storage power station.
[0043] Step S5. During the dam operation period, the construction drainage hole is in a blocked state. The construction drainage hole plug blocks the reservoir flood and prevents the reservoir water from entering the flood discharge and sediment discharge hole to meet the needs of normal operation of the flood discharge and sediment discharge hole.
[0044] In this invention, by arranging a construction drainage tunnel at a suitable location in the hub area, the construction drainage tunnel has different functions at different times. During the construction period of the flood discharge and sediment discharge tunnel, the construction drainage tunnel serves as a traffic channel for the construction of the flood discharge and sediment discharge tunnel. During the construction period of the reservoir main dam 4, the designed construction drainage tunnel structure plays a construction diversion role. During the dam operation period, by blocking the construction drainage tunnel, the reservoir water between the sand retaining dam 3 and the reservoir main dam 4 is prevented from entering the flood discharge and sediment discharge tunnel, thus meeting the normal flow requirements of the flood discharge and sediment discharge tunnel. Compared with the traditional arrangement, this eliminates the need for excavating and pouring a separate bypass diversion tunnel structure, shortens the construction period, and has good economic benefits and construction time advantages.
[0045] The construction diversion method proposed in this invention fully utilizes the characteristic of pumped-storage power stations that construction is controlled during the plant construction period, not during the dam construction period. The entire construction diversion period is cleverly divided into two phases. The first phase satisfies the construction diversion requirements of the sand retaining dam 3; the second phase fully utilizes the drainage function of the flood discharge and sand discharge tunnel, allowing it to double as a diversion channel for the dam construction. This achieves the multi-purpose function of a single tunnel, eliminating the need to re-establish a new dam diversion tunnel, and achieving good economic and construction time benefits.
[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. The flood discharge and sediment discharge tunnel arrangement structure of the pumped storage reservoir project, including the reservoir main dam (4), is characterized by: It also includes a sand retaining dam (3) and a flood discharge and sand discharge tunnel. The sand retaining dam (3) is located upstream of the main dam (4) of the reservoir. The flood discharge and sand discharge tunnel inlet section (1-1) is located upstream of the sand retaining dam (3). The flood discharge and sand discharge tunnel body section (1-2) passes through the mountain. The flood discharge and sand discharge tunnel outlet section (1-3) is located downstream of the main dam (4) of the reservoir. The sand retaining dam (3) is also equipped with a sand retaining dam water delivery tunnel (5) for delivering water to the reservoir area between the sand retaining dam (3) and the main dam (4) of the reservoir.
2. The flood discharge and sediment discharge tunnel arrangement structure of the pumped storage reservoir project according to claim 1, characterized in that: It also includes a construction drainage hole. The inlet section (2-1) of the construction drainage hole is located in the reservoir area between the sand retaining dam (3) and the main dam (4) of the reservoir. The outlet section (2-3) of the construction drainage hole is connected to the main section (1-2) of the flood discharge and sand discharge hole.
3. The flood discharge and sediment discharge tunnel arrangement structure of the pumped storage reservoir project according to claim 2, characterized in that: The angle at the junction of the construction drainage tunnel and the flood and sand discharge tunnel is greater than or equal to 50°.
4. The flood discharge and sediment discharge hole arrangement structure of the pumped storage reservoir project according to claim 2, characterized in that: Permanent plugs are arranged at the connection points between the construction drainage tunnel and the flood and sand discharge tunnel to prevent water flow from entering the flood and sand discharge tunnel.
5. The flood discharge and sediment discharge hole arrangement structure of the pumped storage reservoir project according to claim 2, characterized in that: The construction drainage tunnel and the flood discharge and sand drainage tunnel are both in the form of pressure-free tunnels, and the cross-section of the construction drainage tunnel section (2-2) and the cross-section of the flood discharge and sand drainage tunnel section (1-2) are both in the shape of city gate tunnels.
6. The flood discharge and sediment discharge tunnel arrangement structure of a pumped storage reservoir project according to any one of claims 1 to 5, characterized in that: The bottom elevation of the construction drainage tunnel outlet section is higher than the flood level in the flood discharge and sand discharge tunnel at the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged during the main flood season; it is also higher than the flood level in the flood discharge and sand discharge tunnel at the connection position with the construction drainage tunnel when a flood with a return period of 20 years is discharged during the sealing period of the construction drainage tunnel.
7. The construction diversion method of the pumped storage reservoir project is characterized by: The construction diversion method using the flood discharge and sediment discharge tunnel arrangement structure of the pumped storage reservoir project according to any one of claims 2 to 6 comprises the following steps: Step S1. During the construction diversion preparation period, a drainage tunnel is constructed first. The inlet section (2-1) of the drainage tunnel is located between the sediment dam (3) and the main dam (4) of the reservoir. A flood discharge and sediment discharge tunnel is excavated at the outlet section (2-3). Step S2. During the construction diversion period of the reservoir main dam (4), the water flow in front of the sand retaining dam (3) is blocked by the sand retaining dam (3) and discharged through the flood discharge and sediment discharge tunnel; the water flow in front of the reservoir main dam (4) is discharged through the construction drainage tunnel connected to the flood discharge and sediment discharge tunnel; Step S3. Before water storage, the drainage hole is sealed; Step S4. During the water storage period, water is released from the water delivery tunnel (5) of the sand dam into the interval, so that the reservoir is filled to the normal water level; Step S5. During the dam operation period, the construction drainage hole is in a blocked state to prevent water from the reservoir area from entering the flood discharge and sediment discharge hole.
8. The construction diversion method for a pumped reservoir project as claimed in claim 7, wherein the steps S2 contains: Step S21. During the initial diversion period, the water flowing in front of the sand retaining dam (3) is blocked by the sand retaining dam (3) and discharged through the flood discharge and sediment discharge tunnel; the water flowing in the section in front of the main dam (4) of the reservoir is blocked by the cofferdam and discharged through the construction drainage tunnel connected to the flood discharge and sediment discharge tunnel, so as to carry out dam foundation excavation and dam body filling; Step S22. In the middle and late diversion period, the water flowing in front of the sand retaining dam (3) is blocked by the sand retaining dam (3) and discharged from the flood discharge and sand discharge tunnel; the water flow in the section in front of the main dam (4) of the reservoir is blocked by the temporary section of the dam and discharged from the flood discharge and sand discharge tunnel through the construction drainage tunnel, so as to carry out the dam foundation excavation and dam body filling.
9. The construction diversion method for a pumped storage reservoir project according to claim 7, wherein: Step S20 is included between step S1 and step S2. Step S20: During the construction and diversion period of the sand retaining dam (3), water flows through the sand retaining dam water diversion tunnel (5).
10. The construction diversion method for a pumped storage reservoir project according to any one of claims 7 to 9, characterized in that: The method for blocking the construction hole in step S3 is as follows: a temporary water retaining cofferdam is set up at the entrance of the construction drainage hole, and construction personnel and equipment enter from the entrance to the exit of the construction drainage hole to perform plugging construction. During the blocking period, the water flow is discharged downstream through the permanent flood discharge hole (6) of the main dam of the reservoir.