Upper reservoir of pumped storage power station with backfilling of library bottom step and layered partition type drainage and construction method

Abstract

The application discloses a pumped storage power station upper reservoir with library bottom step backfill and layered partition type drainage and a construction method, and belongs to the technical field of water conservancy and hydropower. In the backfill area, one side of the rockfill material area of the library bottom-dam body transition area is connected with the upstream side of the rockfill dam; the other side is the reservoir basin backfill area, which is sequentially composed of the library bottom soft rock backfill material area and the library bottom hard rock backfill material area from bottom to top; in the library bottom drainage layer, the first backfill area drainage layer and the second backfill area drainage layer are respectively arranged at the connection positions of the soft soil foundation, the library bottom soft rock backfill material area and the library bottom hard rock backfill material area, and the third backfill area drainage layer is arranged at the top of the library bottom hard rock backfill material area and the upstream inclined side of the rockfill dam; the inclined drainage layer is arranged at the two sides of the rockfill material area of the library bottom-dam body transition area, and the dam body drainage layer is arranged between the soft soil foundation and the rockfill dam and between the soft soil foundation and the rockfill material area of the library bottom-dam body transition area. The application can effectively alleviate the problem of insufficient stone material sources for building dams and reservoirs on deep and thick soft soil foundations, and realizes rapid drainage.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy and hydropower technology, specifically relating to the upper reservoir and construction method of a pumped storage power station with stepped backfilling at the bottom and layered and zoned drainage. Background Technology

[0002] Currently, pumped storage power stations mainly use rockfill dams as water-retaining structures for their upper and lower reservoirs. Rockfill dams can make full use of the excavated rock for filling, achieving a basic balance between excavation and filling, reducing waste and slag, and lowering project costs. At the same time, due to their large volume, high flexibility, and strong foundation adaptability, they have stronger stability, earthquake resistance, and economy compared to concrete gravity dams. For example, the rockfill dam of Zipingpu Reservoir in Sichuan Province remained stable as a whole after an earthquake, and the anti-seepage system did not completely fail.

[0003] In the plains of North and Northwest China, pumped storage power station sites often have deep loess cover, small natural elevation differences between the upper and lower reservoirs, and low water head, typically between 200m and 400m. Due to topographical constraints, these sites require large reservoir volumes, resulting in substantial excavation, but limited available stone. If a conventional rockfill dam design is adopted, with the dam body and reservoir entirely backfilled with rockfill, a dedicated quarry outside the reservoir must be established, significantly increasing project costs.

[0004] When a pumped storage reservoir basin is located on a soft soil foundation, the foundation itself has high compressibility and will experience significant settlement under water load during operation. If the drainage capacity of the backfill at the bottom of the reservoir is insufficient, reservoir water will seep into the soft soil foundation, further exacerbating foundation softening and settlement. This can easily cause uneven settlement and fracture of the upper seepage prevention structure, threatening the integrity of the upper seepage prevention structure.

[0005] Therefore, for pumped storage reservoirs with limited hard rock material sources on soft soil foundations, how to plan the excavated rock within the existing site in a zoned manner so as to reduce engineering costs and achieve rapid drainage without opening new material yards outside the reservoir is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a pumped storage power station upper reservoir and construction method with stepped backfilling at the reservoir bottom and layered and zoned drainage. The stepped backfilling method avoids the problem of limited hard rock material source on soft soil foundation, reduces engineering costs, and the zoned and layered drainage method achieves rapid drainage.

[0007] To achieve the above objectives, the present invention employs the following technical solution: A pumped storage power station upper reservoir with stepped backfilling at the bottom and layered drainage includes a rockfill dam, a backfilling zone, and a drainage layer at the bottom of the reservoir, all located on a soft soil foundation.

[0008] The backfill area includes the rockfill area in the reservoir bottom-dam transition zone and the reservoir basin backfill area; one side of the rockfill area in the reservoir bottom-dam transition zone is connected to the upstream side of the rockfill dam and is located on the downstream side of the reservoir basin backfill area.

[0009] The reservoir basin backfill area is located on the other side of the rockfill area in the transition zone between the reservoir bottom and the dam body. The reservoir basin backfill area consists of the soft rock backfill area at the bottom of the reservoir and the hard rock backfill area at the bottom of the reservoir, from bottom to top.

[0010] The reservoir bottom drainage layer includes a first backfill area drainage layer, a second backfill area drainage layer, a third backfill area drainage layer, an inclined drainage layer, and a dam body drainage layer. The first backfill area drainage layer is located between the bottom of the soft rock backfill area and the soft soil foundation. The second backfill area drainage layer is located at the junction of the soft rock backfill area and the hard rock backfill area. The third backfill area drainage layer is located at the top of the hard rock backfill area and on the upstream inclined side of the rockfill dam. The inclined drainage layer is located on both sides of the rockfill area in the reservoir bottom-dam body transition zone. The dam body drainage layer is located between the soft soil foundation and the rockfill dam, and between the soft soil foundation and the rockfill area in the reservoir bottom-dam body transition zone.

[0011] In a preferred embodiment of the present invention, the drainage layer of the first backfill area consists of a first geotextile, a reservoir bottom transition drainage material, and a second geotextile from bottom to top; the reservoir bottom transition drainage material is made of weakly weathered rock excavated material or slightly weathered rock excavated material.

[0012] In a preferred embodiment of the present invention, the drainage layer of the second backfill area consists of a third geotextile and a transitional drainage material between the bottom and top of the reservoir, from bottom to top.

[0013] The intermediate drainage material at the bottom of the reservoir is made of weakly weathered or slightly weathered excavated hard rock.

[0014] In a preferred embodiment of the present invention, the drainage layer of the third backfill area is a transitional drainage material at the top of the reservoir bottom, which is excavated material of weakly weathered rock or slightly weathered rock.

[0015] The top of the transitional drainage material at the bottom of the reservoir is successively laid with a subbase material and asphalt concrete panels for the bottom and perimeter of the reservoir from bottom to top; the subbase material is made of weakly weathered to slightly weathered rock.

[0016] In a preferred embodiment of the present invention, the inclined drainage layer includes a first inclined drainage layer, a second inclined drainage layer, and a third inclined drainage layer. The first inclined drainage layer is located between the soft rock backfill area at the bottom of the reservoir and the rockfill area in the transition zone between the bottom of the reservoir and the dam body. The second inclined drainage layer is located between the hard rock backfill area at the bottom of the reservoir and the rockfill area in the transition zone between the bottom of the reservoir and the dam body. The third inclined drainage layer is located between the rockfill area in the transition zone between the bottom of the reservoir and the rockfill dam.

[0017] The slope ratios of the first and second inclined drainage layers are both 1:1.4 to 1:1.5; the slope ratio of the third inclined drainage layer is 1:1.5 to 1:1.6.

[0018] In a preferred embodiment of the present invention, the first inclined drainage layer consists of a fourth geotextile and a first inclined transition material at the bottom of the reservoir, from the soft rock backfill area at the bottom of the reservoir to the rockfill area in the transition zone between the bottom of the reservoir and the dam body.

[0019] The second inclined drainage layer is the inclined transition material at the bottom of the second silo.

[0020] The third inclined drainage layer, from the backfill area at the bottom of the reservoir towards the rockfill dam, consists of the third inclined transition material at the bottom of the reservoir, the first drainage material, and the fourth inclined transition material at the bottom of the reservoir.

[0021] The sloping transition material at the bottom of the reservoir is made of weakly weathered or excess slightly weathered excavated material.

[0022] The drainage material is made of slightly weathered rock.

[0023] In a preferred embodiment of the present invention, the dam body drainage layer includes a first dam body drainage layer and a second dam body drainage layer. The first dam body drainage layer is located between the soft soil foundation and the rockfill area of ​​the reservoir bottom-dam body transition zone, and consists of a fifth geotextile, a first fine transition material, and a first dam body bottom transition material from bottom to top.

[0024] The second dam body drainage layer is located between the soft soil foundation and the rockfill dam, and consists of, from bottom to top, the sixth geotextile, the second fine transition material, the second dam body bottom transition material, the second drainage material, and the third dam body bottom transition material.

[0025] The fine transition material is made of slightly weathered to weakly weathered rock, mainly for reverse filtration; the transition material at the bottom of the dam body is made of slightly weathered to weakly weathered rock, with a slightly larger particle size than the fine transition material, continuous gradation with the fine transition material, and strong compactness due to its narrow gradation.

[0026] The cross section of the boundary area between the soft rock backfill area and the hard rock backfill area at the bottom of the reservoir is constructed to include a first horizontal plane, an inclined plane, and a second horizontal plane. The top of the inclined plane is connected to the end of the first horizontal plane, and the end of the second horizontal plane is connected to the bottom of the inclined plane. The slope ratio of the inclined plane is 1:2 to 1:3.

[0027] In a preferred embodiment of the present invention, the soft rock backfill area at the bottom of the reservoir is filled with strongly weathered excavated material or soft rock material.

[0028] The hard rock backfill area at the bottom of the reservoir uses weakly weathered or slightly weathered excavated material.

[0029] The rockfill area in the transition zone between the reservoir bottom and the dam body uses slightly weathered to weakly weathered hard rock.

[0030] In a preferred embodiment of the present invention, the dam body of the rockfill dam is provided with an upstream hard rockfill area and a downstream rockfill area from upstream to downstream; the rockfill area of ​​the reservoir bottom-dam body transition zone is located on the downstream side of the upstream hard rockfill area.

[0031] The downstream slope of the downstream rockfill area is provided with a downstream slope protection; the bottom of the downstream slope protection is flush with the foundation surface of the rockfill dam, and the top extends to the top of the rockfill dam.

[0032] This invention also provides a construction method for the upper reservoir of a pumped storage power station with stepped backfilling at the reservoir bottom and layered and zoned drainage, comprising the following steps: The soft soil foundation surface was excavated to form a rockfill dam area, a rockfill material area in the reservoir bottom-dam transition zone, and a reservoir basin backfill area. The foundation of each area was compacted.

[0033] A drainage layer is laid above the rockfill dam area and the rockfill material area in the reservoir bottom-dam transition zone to form a dam body drainage layer; backfilling is carried out on the dam body drainage layer above the rockfill dam area to form a rockfill dam; backfilling is carried out on the dam body drainage layer in the reservoir bottom-dam body transition zone to form a rockfill material area in the reservoir bottom-dam body transition zone.

[0034] Sloping drainage layers are laid on both sides of the rockfill area in the transition zone between the reservoir bottom and the dam body.

[0035] In the backfill area, the paving and backfilling are carried out from bottom to top to form the first backfill area drainage layer, the soft rock backfill area at the bottom of the reservoir, the second backfill area drainage layer, and the hard rock backfill area at the bottom of the reservoir.

[0036] A third backfill drainage layer is laid on the top of the hard rock backfill area at the bottom of the reservoir and on the upstream slope of the rockfill dam.

[0037] Compared with the prior art, the present invention has the following beneficial effects: (1) In areas where stone excavation is insufficient, the present invention implements zonal and stepped backfilling in the backfilling area. The bottom is backfilled with soft rock to form the soft rock backfilling area at the bottom of the reservoir, and the top is backfilled with hard rock to form the hard rock backfilling area at the bottom of the reservoir. A rockfilling area is set up in the transition zone between the rockfill dam and the backfilling area to reduce stress concentration at the transition point between the asphalt concrete panel at the bottom of the reservoir and the asphalt concrete panel at the rockfill dam. This not only allows the excavated soft rock to be backfilled at the bottom of the reservoir, making full use of the excavated material and reducing waste and dependence on external material yards, but also reasonably reduces the uneven settlement of the backfilling area and foundation at the bottom of the reservoir, which could lead to tearing of the asphalt concrete panel and leakage, thus ensuring the long-term normal operation of the reservoir.

[0038] The reservoir bottom drainage layer includes a first backfill area drainage layer, a second backfill area drainage layer, a third backfill area drainage layer, an inclined drainage layer, and a dam body drainage layer, which are set in different areas. During drainage, the water flows from the first backfill area drainage layer, the second backfill area drainage layer, and the third backfill area drainage layer into the inclined drainage layer, and finally through the dam body drainage layer. This drainage structure can achieve rapid drainage. In addition, the first backfill area drainage layer, the second backfill area drainage layer, and the third backfill area drainage layer are set from bottom to top in the reservoir bottom backfill area to carry out zoned and layered drainage, ensuring rapid drainage and improving the reliability of the drainage structure. Even if one layer is blocked and causes drainage failure, the other drainage areas can still perform drainage functions, ensuring the safe operation of the reservoir bottom structure and the dam body.

[0039] (2) In this invention, the rockfill dam can be entirely constructed using hard rock to ensure seismic safety and overall stability. Areas with significant deformation and stress at the reservoir bottom are also backfilled with hard rock, but the backfill area uses a scheme of backfilling hard rock at the top and soft rock at the bottom. Following the principles of adapting to local conditions, zoned management, key protection, and coordinated balance, the excavated material is fully utilized, meeting the design requirements of technical reliability and economic rationality. This provides an innovative solution for areas with soft soil foundations, such as Northwest China and North China, and other areas with deep overburden layers, significantly reducing the difficulty of planning site selection, regulatory compliance, and investment decisions, laying the foundation for the smooth progress of pumped storage power station projects in the early stages. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the upper reservoir structure of a pumped storage power station with stepped backfilling at the bottom and layered and zoned drainage, as provided by the present invention.

[0042] Attached reference numerals: 1. Original ground line; 2. Excavation line; 31. First geotextile; 32. Second geotextile; 33. Third geotextile; 34. Fourth geotextile; 35. Fifth geotextile; 36. Sixth geotextile; 41. First fine transition material; 42. Second fine transition material; 51. Drainage transition material at the bottom of the reservoir; 52. Middle transition drainage material at the bottom of the reservoir; 53. Top transition drainage material at the bottom of the reservoir; 541. First sloping transition material at the bottom of the reservoir; 542. Second sloping transition material at the bottom of the reservoir; 543. Third sloping transition material at the bottom of the reservoir. 544. Fourth reservoir bottom inclined transition material; 551. First dam body bottom transition material; 552. Second dam body bottom transition material; 553. Third dam body bottom transition material; 61. First drainage material; 62. Second drainage material; 7. Rockfill dam; 71. Upstream hard rockfill area; 72. Reservoir bottom-dam body transition area rockfill material area; 8. Reservoir bottom soft rock backfill area; 9. Reservoir bottom hard rock backfill area; 10. Subbase material; 11. Reservoir bottom and surrounding asphalt concrete panel; 12. Downstream rockfill area; 13. Downstream slope protection. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] In existing technologies, there is a lack of a technical solution for pumped storage projects with limited stone resources that can both fully utilize the limited excavated material and control uneven settlement in the backfill area of ​​the reservoir basin. Because soft rock has low strength and high compressibility, if it is directly backfilled into the reservoir bottom, it is prone to large compressive deformation under reservoir water load. At the same time, the mechanical properties of soft rock and hard rock riprap differ significantly, and differential settlement can easily occur at the interface due to a sudden change in modulus. This can lead to excessive flexural deformation and cracking of the reservoir bottom seepage prevention structure (such as asphalt concrete panels), causing water leakage and affecting the long-term safe operation of the reservoir.

[0045] Therefore, for pumped storage reservoirs on soft soil foundations where the source of stone is limited, this invention provides a pumped storage power station upper reservoir and construction method with stepped backfilling of the reservoir bottom and layered and zoned drainage. The reasonable stepped backfilling structure reduces engineering costs and the drainage layer enables rapid drainage, as detailed in the following embodiments.

[0046] Example 1 This embodiment provides a pumped storage power station upper reservoir with stepped backfilling at the reservoir bottom and layered, zoned drainage, such as... Figure 1As shown, a rockfill dam and backfill area are constructed on the soft soil foundation 14; the soft soil foundation 14 serves as the natural bearing layer for the dam body and the reservoir basin backfill area.

[0047] A rockfill dam 7 is provided above the soft soil foundation 14. The dam body of the rockfill dam 7 is provided with an upstream hard rockfill area 71 and a downstream rockfill area 12 from upstream to downstream.

[0048] The upstream hard rockfill zone 71 serves as the main load-bearing framework of the rockfill dam, primarily bearing the thrust and gravity of the upstream reservoir water. It evenly distributes the enormous water load to the dam foundation. The upstream hard rockfill zone 71 uses slightly weathered to weakly weathered hard rock. The gradation requirements are: a maximum particle size of 800mm to ensure the strength of the dam framework and enable it to withstand the reservoir water thrust; a particle content of no more than 20% (smaller than 5mm particles fills voids and does not interfere with the load-bearing capacity of the dam framework); and a particle content of no more than 5% (smaller than 0.075mm particles prevent internal erosion). Furthermore, the fill material in the upstream hard rockfill zone 71 is continuously graded, meaning that all particle sizes are continuously distributed without any missing intermediate particle sizes, and the permeability coefficient after compaction is no less than 1×10⁻⁶. -1 cm / s. Ensure that the upstream hard rockfill zone 71 has sufficient shear strength to withstand the upstream water thrust, while also possessing low compressibility and free drainage performance to avoid the generation of harmful pore water pressure inside the dam body.

[0049] The upstream dam slope of the upstream hard rockfill area 71 adopts a 1:m1 ratio and uses asphalt panels for seepage prevention throughout the reservoir basin. The slope selection takes into account the slope stability of the asphalt panel, the dam slope stability, and the overall seismic safety. In this invention, the value of m1 is set between 1.7 and 2.0. Within this range, the sliding force of the asphalt panel under its own weight is small, and the asphalt panel is not easy to creep or slip along the slope, which is conducive to the long-term stability of the asphalt panel slope and the overall seismic safety is good.

[0050] Downstream rockfill zone 12 and upstream hard rockfill zone 71 work together to maintain the overall stability of the dam. Downstream rockfill zone 12 primarily serves a ballast stabilizing function and can be filled with excavated material from the upper reservoir basin, consisting of weakly to strongly weathered rock. This reduces waste and external material sources, ensuring dam stability while fully utilizing the excavated material. The gradation requirements are: a maximum particle size of 800mm, with particles smaller than 5mm accounting for no more than 30%, and particles smaller than 0.075mm accounting for no more than 5%. The slope ratio at the junction of upstream hard rockfill zone 71 and downstream rockfill zone 12 is 1:m5, where m5 ranges from 0.3 to 0.5.

[0051] Downstream slope protection 13 is laid on the downstream slope of the downstream rockfill area 12. The bottom of the downstream slope protection 13 is flush with the foundation surface of the rockfill dam 7, and the top extends to the top of the rockfill dam 7. The thickness b of the downstream slope protection 13 is generally 0.5m to 1.0m. Dry-laid stone slope protection is generally used for earthquake intensity VI and below, mainly to prevent rainwater erosion of the slope surface. In high earthquake zones, grouted stone slope protection is often used, which also serves as a seismic structure, but drainage holes on the dam surface need to be installed. The downstream slope protection 13 is a multi-level stepped composite slope, consisting of a multi-level slope with a slope ratio of 1:m6 from top to bottom, and a bottom slope with a slope ratio of 1:m7. Adjacent sections are connected by inflection points. The slope ratio of each section is determined comprehensively based on the stress requirements at different elevations, panel stability, and construction conditions. Among them, the value of m6 ranges from 1.5 to 2.0, and the value of m7 ranges from 2 to 3.

[0052] The backfill area includes the reservoir bottom-dam transition zone rockfill area 72 and the reservoir basin backfill area; one side of the reservoir bottom-dam transition zone rockfill area 72 is connected to the downstream side of the upstream hard rockfill area 71 and is located downstream of the reservoir basin backfill area; the reservoir basin backfill area is located on the other side of the reservoir bottom-dam transition zone rockfill area 72, that is, far away from the upstream hard rockfill area 71.

[0053] The rockfill area 72 in the reservoir bottom-dam transition zone serves as the backfill area for the transition between the reservoir bottom and the rockfill dam 7. Based on construction experience and project statistics, the panel in this transition zone experiences stress concentration, making it prone to failure. Furthermore, the top of the rockfill area 72 is the transition point between the asphalt concrete anti-seepage panel of the dam body and the asphalt concrete panel of the reservoir bottom. Stress concentration at this point makes the asphalt panel particularly susceptible to tearing. Statistical analysis of previous projects and data further confirms this as a weak point in the asphalt panel, requiring thickening. Therefore, the rockfill area 72 in the reservoir bottom-dam transition zone is a key area for foundation protection. It is entirely filled with hard rock, with filling and compaction standards identical to those of the upstream hard rockfill area 71. The aim is to reduce uneven settlement of the backfill material and prevent excessive deflection of the top asphalt panel, leading to breakage and leakage. That is, the rockfill area 72 in the transition zone between the reservoir bottom and the dam body also uses slightly weathered to weakly weathered hard rock. The gradation requirements are: the maximum particle size of the fill material is 800mm, the content of particles smaller than 5mm is not more than 20%, and the content of particles smaller than 0.075mm is not more than 5%.

[0054] A third inclined drainage layer is installed between the upstream hard rockfill area 71 and the rockfill area 72 in the reservoir bottom-dam transition zone. From the reservoir basin towards the dam body, this layer consists of the third inclined transition material 543, the first drainage material 61, and the fourth inclined transition material 544. The purpose is to quickly drain seepage water from the upper and middle parts of the reservoir bottom and the bottom of the upstream dam face, reducing seepage pressure under the anti-seepage panel and preventing it from rupturing the asphalt panel. The slope ratio of the third inclined drainage layer is 1:m4, where m4 is between 1.5 and 1.6.

[0055] In the soft soil foundation 14, the content of clay and silt is relatively high. If it directly contacts the large-void rockfill, contact flow and piping are likely to occur under high water head. Fine particles flow into the gaps in the rockfill and are carried away by water, hollowing out the dam foundation and forming seepage channels. Based on this, the present invention sets up geotextile and fine transition material in the soft soil foundation 14 area at the bottom of the rockfill dam 7 and at the bottom of the rockfill material area 72 of the reservoir bottom-dam body transition zone, which also serves as a filter to protect the top dam body drainage layer. Furthermore, a dam body bottom transition material is set above the fine transition material. The dam body bottom transition material and the fine transition material form a double filter and transition structure at the bottom of the dam body. The fine transition material protects the fine particles in the soft soil foundation 14 and prevents piping and soil flow, while the dam body bottom transition material provides a gradual change in stiffness to prevent differential settlement. The double layer improves seepage safety and seismic redundancy.

[0056] Specifically, the thickness of the fine transition material is 0.4m to 1.0m, arranged close to the soft soil foundation (14), to intercept fine particles in the foundation and prevent their loss; the maximum particle size is 20mm, and the content of silt particles smaller than 0.075mm is ≤5%, to prevent it from becoming impermeable due to siltation. The saturated compressive strength of the rock is ≥40MPa, and the fine transition material is slightly weathered to weakly weathered limestone or sandstone with a softening coefficient greater than 0.7. The permeability coefficient after compaction is 1×10⁻⁶. -2 cm / s~1×10 -3 cm / s. This layer primarily functions as a filter, protecting fine particles in the soft soil foundation from being carried into the dam body under high-head seepage, thus preventing contact erosion and piping damage. The fine transition material includes a first fine transition material 41 and a second fine transition material 42.

[0057] The transition material at the bottom of the dam body is placed above the fine transition material, with a thickness of 0.4m to 1.0m. It protects the fine particles in the fine transition material from being carried into the main rockfill area by seepage, and also serves as a deformation transition and secondary filtration. The maximum particle size of the transition material at the bottom of the dam body is 60mm, the content of particles smaller than 0.075mm is ≤8%, the saturated compressive strength is ≥40MPa, it is hard and not easily broken, and the permeability coefficient after compaction is greater than 5×10⁻⁶. -2 cm / s, ensuring free drainage. The transition material at the bottom of the dam body includes the first dam body bottom transition material 551, the second dam body bottom transition material 552, and the third dam body bottom transition material 553.

[0058] The commonly used specification for geotextiles is 300g / m². 2 ~500g / m 2The geotextile is installed on the soft soil foundation 14 for the purpose of reverse filtration, preventing the excessive drainage material from carrying away fine particles from the soft soil or soft rock during drainage, thus avoiding piping and uneven settlement of the foundation caused by internal voids. For clarity, the geotextiles at different locations are numbered: Geotextile 31 (first geotextile), 32 (second geotextile), 33 (third geotextile), 34 (fourth geotextile), 35 (fifth geotextile), and 36 (sixth geotextile). It should be noted that in actual construction, a complete geotextile can be directly laid.

[0059] In this embodiment, drainage material is installed in different areas. The drainage material includes a first drainage material 61 and a second drainage material 62. The vertical thickness of both the first drainage material 61 and the second drainage material 62 is 3m. Its saturated unconfined compressive strength is ≥30MPa, the rock porosity is not greater than 3%, the water absorption rate is not greater than 0.8, and the softening coefficient is greater than 0.85. Slightly weathered hard rock with a permeability coefficient greater than 1×10⁻⁶ is used. -2 The aim is to smoothly and quickly discharge seepage water from the dam body and reservoir bottom outside the dam body at a speed of cm / s.

[0060] The dam body drainage layer includes a first dam body drainage layer and a second dam body drainage layer. The first dam body drainage layer is located between the soft soil foundation 14 and the rockfill area 72 of the reservoir bottom-dam body transition zone, and consists of, from bottom to top, the fifth geotextile 35, the first fine transition material 41, and the first dam body bottom transition material 551. The second dam body drainage layer is located between the soft soil foundation 14 and the rockfill dam 7, and consists of, from bottom to top, the sixth geotextile 36, the second fine transition material 42, the second dam body bottom transition material 552, the second drainage material 62, and the third dam body bottom transition material 553.

[0061] From bottom to top, the particle size gradient of the soft soil foundation 14 consists of fine soft rock, fine transition material, transition material at the bottom of the dam body, drainage material, and rockfill dam 7, forming a two-stage reverse filter from fine to coarse, with the particle size increasing progressively. If only a single-layer reverse filter is installed, if a certain part of the layer has excessively large pores due to compaction defects, this weak point may become a seepage channel, causing the reverse filter function to fail as a whole. This invention adopts a double-layer reverse filter structure, with the two layers working together to achieve double protection, greatly improving the fault tolerance and reliability of the reverse filter structure.

[0062] Based on the different backfill materials, the reservoir basin backfill area is divided into two zones from bottom to top: a soft rock backfill zone 8 and a hard rock backfill zone 9. The soft rock backfill zone 8 can be backfilled with strongly weathered excavated material, with a thickness approximately half the thickness from the designed reservoir bottom elevation to the foundation surface. The hard rock backfill zone 9 is backfilled with hard rock. The backfill depth is greater closer to the dam body, and the depth h1 of both the soft rock backfill zone 8 and the hard rock backfill zone 9 is thicker. Further away from the dam body, the reservoir bottom depth gradually decreases, and the backfill depth h2 of both zones also decreases accordingly, conforming to the principle of prioritizing dam protection. The saturated compressive strength of the soft rock backfill material is less than or equal to 30 MPa. The backfill depth h1 near the dam body is approximately half the total backfill depth of the reservoir bottom, and h2 is approximately half of h1. The downstream end of the soft rock backfill area 8 at the bottom of the reservoir extends to the bottom of the rockfill area 72 in the transition zone between the reservoir bottom and the dam body. The junction of the soft rock backfill area 8 at the bottom of the reservoir and the rockfill area 72 in the transition zone between the reservoir bottom and the dam body slopes at a gradient of 1:m8, where m8 is 2 to 3.

[0063] Specifically, a second inclined drainage layer is provided at the junction of the hard rock backfill area 9 at the bottom of the reservoir and the rockfill area 72 at the bottom of the reservoir-dam transition zone, which is the second inclined transition material 542 at the bottom of the reservoir.

[0064] At the junction of the soft rock backfill area 8 at the bottom of the reservoir and the rockfill area 72 at the bottom of the reservoir-dam transition zone, there is a first inclined drainage layer. From the soft rock backfill area 8 at the bottom of the reservoir to the rockfill area 72 at the bottom of the reservoir-dam transition zone, there are the fourth geotextile 34 and the first inclined transition material 541 at the bottom of the reservoir.

[0065] The purpose of setting up the first and second inclined drainage layers in this invention is to connect the transition drainage material 51 at the bottom of the reservoir, the intermediate transition drainage material 52 at the bottom of the reservoir, and the transition drainage material 53 at the top of the bottom of the reservoir. This arrangement achieves stepped backfilling of the reservoir bottom and zoned drainage of the first, second, and third backfilling drainage layers, ensuring rapid drainage and improving drainage reliability. If one layer becomes blocked and drainage fails, the other layers still function, ensuring the operational safety of the reservoir bottom structure and the dam body. The slope ratio of both the first and second inclined drainage layers is 1:m², with m² ranging from 1.4 to 1.5.

[0066] A first backfill drainage layer is provided between the bottom of the soft rock backfill area 8 and the soft base layer 14, consisting of a first geotextile 31, a transition drainage material 51 at the bottom of the reservoir, and a second geotextile 32, arranged from bottom to top.

[0067] At the junction of the soft rock backfill area 8 and the hard rock backfill area 9 at the bottom of the reservoir, a second backfill drainage layer is provided. The second backfill drainage layer consists of a third geotextile 33 and a middle transition drainage material 52 at the bottom of the reservoir, from bottom to top.

[0068] The purpose of installing geotextile here is to prevent fine particles from the soft rock backfill in zone 8 at the bottom of the reservoir from entering the intermediate transition drainage material 52 and the hard rock backfill in zone 9. This would prevent uneven settlement caused by the absence of particles in zone 8. Therefore, the geotextile is laid close to zone 8. If clay particles from zone 8 migrate into the intermediate transition drainage material 52, it can easily cause blockage of the voids in the intermediate transition drainage material 52, leading to drainage failure. This would prevent seepage from the top from being discharged horizontally to the dam in time, causing continued seepage and increased seepage pressure. This would increase the bottom water pressure on the asphalt slab of the reservoir basin, making it prone to heaving and fracture. The backfill modulus and stiffness of zone 8 and zone 9 at the bottom of the reservoir differ significantly; the intermediate transition drainage material 52 is used to achieve deformation coordination and particle size transition.

[0069] It should be noted that the drainage areas on the top of the hard rock backfill area 9 at the bottom of the reservoir and the upstream sloping side of the upstream hard rockfill area 71 are connected to form the drainage layer of the third backfill area. The drainage layer of the third backfill area is the transition drainage material 53 at the top of the bottom of the reservoir. The top of the drainage layer of the third backfill area is provided with a cushion material 10 and the asphalt concrete panel 11 of the bottom and perimeter of the reservoir in sequence from bottom to top.

[0070] The transitional drainage material 53 at the top of the reservoir bottom must not only meet the modulus and particle size transition requirements of the cushion material 10 and the hard rock backfill 9, but also serve as a drainage layer, promptly and horizontally guiding the seepage water from the reservoir basin asphalt panel to the drainage material below the dam for discharge into the dam body. The transitional drainage material 53 at the top of the reservoir bottom is located between the cushion material 10 and the reservoir bottom and perimeter asphalt concrete panel 11, with a thickness of 1.6m, serving as a reverse filter transition. The transitional drainage material 53 on the upstream side of the dam body has a horizontal width of 3.0m in the reservoir perimeter area, all using weakly weathered excavated material from the upper reservoir basin, with a rock type of weakly weathered rock, produced through controlled blasting and blending to create the finished material. Grading requirements: maximum particle size 300mm, content of particles smaller than 5mm 15%–25%, content of particles smaller than 0.075mm not exceeding 5%, continuous gradation, and a permeability coefficient of 5×10⁻⁶ after compaction. -3 cm / s~5×10 -2 Between cm / s.

[0071] The subbase material 10 has a vertical thickness of 0.6m in the backfill area, located below the asphalt concrete panel 11 at the bottom and around the reservoir. The drainage layer 53 at the top of the reservoir bottom requires high compressive strength, density, and good permeability to provide a uniform, stable foundation with minimal compression deformation and good drainage performance for the asphalt concrete panel 11 at the bottom and around the reservoir, allowing for timely drainage of seepage. The horizontal width of the subbase material 10 in the reservoir perimeter area is 3.0m. Therefore, the lithology of the subbase material 10 is weakly weathered and slightly weathered sandstone, which is artificially crushed and blended to produce the finished material. Grading requirements: maximum particle size 80mm, particle content less than 5mm 25%–40%, particle content less than 0.075mm not exceeding 5%, continuous gradation, and a permeability coefficient of 1×10⁻⁶ after compaction. -3 cm / s~1×10 - 2 Between cm / s.

[0072] The total thickness of the asphalt concrete panel 11 at the bottom and perimeter of the reservoir is 20.2 cm, consisting of three layers from top to bottom: a 0.2 cm thick sealing layer, a 10 cm thick impermeable layer, and a 10 cm thick leveling and bonding layer. The permeability coefficient is 1×10⁻⁶. -8 ~1×10 -10 cm / s.

[0073] It should be noted that geotextiles are installed in the areas where the soft rock backfill zone 8 at the bottom of the reservoir connects with other areas. This is because the geotextiles act as a filter to prevent clay particles from the soft soil foundation 14 at the reservoir basin from entering the transition drainage material 51 at the bottom of the reservoir, causing blockage and leading to drainage failure of the transition drainage material 51 at the bottom of the reservoir. This, in turn, increases the uplift pressure at the bottom of the asphalt, posing a risk of heaving and cracking. At the same time, if the seepage at the bottom is not drained in time, it will further infiltrate into the soft soil foundation, causing the foundation to soften and settle, exacerbating the settlement at the bottom of the reservoir, and making it more likely to cause flexural damage to the asphalt reservoir bottom panel.

[0074] In the reservoir bottom hard rock backfill area 9, excavated stone materials of weakly weathered or more severe hard rock are mainly used for backfilling. For example, weakly weathered hard rock and slightly weathered hard rock can be selected. For the safety of the dam body, the hard rock backfill near the dam body is thicker, while the hard rock backfill in areas further away from the dam body has less impact on the dam body and can be shallower. This design ensures the safety of the dam body while making full use of the excavated material.

[0075] The hard rock backfill area 9 and the soft rock backfill area 8 at the bottom of the reservoir together constitute the hard rock and soft rock stepped backfill area. The cross section of the boundary area between the soft rock backfill area 8 and the hard rock backfill area 9 at the bottom of the reservoir is constructed to include a first horizontal plane, an inclined plane and a second horizontal plane. The top of the inclined plane is connected to the end of the first horizontal plane, and the end of the second horizontal plane is connected to the bottom of the inclined plane. The inclined plane adopts a slope of 1:m3, where m3 takes the value of 2 to 3.

[0076] Example 2 This embodiment also provides a construction method, the specific steps of which are as follows: The dam foundation and reservoir basin were excavated according to the design requirements. The stones excavated from the site of the soft soil foundation 14 were classified and screened according to the construction requirements. The stones that did not meet the particle size requirements were crushed and reserved for later use.

[0077] At the original ground line 1 of the soft soil foundation 14, excavation is carried out to form excavation line 2, based on the topography, geology, vegetation cover, and foundation requirements. Specifically, this involves removing the highly compressible, low-strength, and easily permeable soft surface soil, such as plant roots and humus, within a range of 1m to 2m below the surface. This ensures uniform settlement of the dam body, anti-sliding stability, and prevents piping and leakage. The thickness of the excavation area is generally 1m to 2m. It should be noted that the original ground line 1 refers to the natural ground surface before construction, while excavation line 2 refers to the foundation surface after surface clearing and compaction.

[0078] After the excavation area is cleared, a 25t-32t heavy hammer is used to compact the dam foundation and reservoir bottom foundation surface with a drop height of 10m-14m to reduce or eliminate the collapsibility of the foundation and improve its bearing capacity.

[0079] After compaction, construction begins. It should be noted that during construction, the dam body and reservoir bottom are filled layer by layer, level with each layer. Construction proceeds from bottom to top, with strict control over the compaction parameters of each zone. Generally, an on-site compaction test is conducted before compaction to determine the roller weight, moisture content (water content), number of compaction passes, and soil thickness. For vibratory rollers, the vibration frequency and travel speed are also tested. Construction is carried out in accordance with existing technical specifications and operating procedures.

[0080] When laying the geotextile, it is fixed on the soft soil foundation 14. Above the fifth geotextile 35 in the rockfill dam 7 area, a first fine transition material 41 with a thickness of 40cm, a first dam body bottom transition material 551 with a thickness of 40cm, a second drainage material 62 with a thickness of 3m, and a third dam body bottom transition material 553 with a thickness of 40cm are laid in sequence to form the second dam body drainage layer. Hard rock is backfilled above the second dam body drainage layer to form the upstream hard rockfill area 71. Downstream rockfill area 12 is laid on the downstream side of the upstream hard rockfill area 71; downstream slope protection 13 is laid on the downstream slope of the downstream rockfill area 12; the bottom of the downstream slope protection 13 is flush with the foundation surface of the rockfill dam 7, and the top extends to the top of the rockfill dam 7 to form the rockfill dam 7. A horizontally wide reservoir bottom top transition drainage material 53 with a width of 3m is laid on the upstream sloping side of the upstream hard rockfill area 71 to form part of the drainage layer of the third backfill area.

[0081] In the reservoir bottom-dam transition zone rockfill area 72, above the sixth geotextile 36, a second fine transition material 42 with a thickness of 40cm and a second dam bottom transition material 552 with a thickness of 40cm are laid sequentially to form the first dam drainage layer. Hard rock is backfilled above the first dam drainage layer to form the reservoir bottom-dam transition zone rockfill area 72. Between the reservoir bottom-dam transition zone rockfill area 72 and the upstream hard rockfill area 71, from the reservoir bottom-dam transition zone rockfill area 72 to the upstream hard rockfill area 71, a third reservoir bottom inclined transition material 543 with a thickness of 40cm, a first drainage material 61 with a horizontal width of 4m, and a fourth reservoir bottom inclined transition material 544 with a thickness of 40cm are laid sequentially to form the third inclined drainage layer.

[0082] In the soft rock backfill area 8 at the bottom of the reservoir, a 160cm thick transition drainage material 51 and a second geotextile 32 are laid sequentially on top of the first geotextile 31 to form the drainage layer of the first backfill area. Then, soft rock backfill is used for backfilling. After backfilling to the design elevation, a third geotextile 33, a 160cm thick intermediate transition drainage material 52 at the bottom of the reservoir, hard rock backfill, and a 100cm thick top transition drainage material 53 at the bottom of the reservoir are laid sequentially to form another part of the soft rock backfill area 8 at the bottom of the reservoir, the drainage layer of the second backfill area, the hard rock backfill area 9 at the bottom of the reservoir, and the drainage layer of the third backfill area.

[0083] At the junction of the soft rock backfill area 8 at the bottom of the reservoir and the rockfill area 72 in the transition zone between the bottom of the reservoir and the dam body, a fourth geotextile 34 and a first inclined transition material 541 with a horizontal width of 100cm are laid obliquely from the soft rock backfill area 8 at the bottom of the reservoir to the rockfill area 72 in the transition zone between the bottom of the reservoir and the dam body, forming a first inclined drainage layer; at the junction of the hard rock backfill area 9 at the bottom of the reservoir and the rockfill area 72 in the transition zone between the bottom of the reservoir and the dam body, a second inclined transition material 542 with a horizontal width of 100cm is laid, forming a second inclined drainage layer.

[0084] After backfilling in each area is completed and the settlement stabilizes, a cushion layer 10 and a 20.2cm thick asphalt concrete panel 11 for the reservoir bottom and perimeter are laid sequentially from bottom to top on top of the drainage layer in the third backfill area. The cushion layer 10 in the hard rock backfill area 9 at the reservoir bottom is 60cm thick, and the horizontal width of the cushion layer 10 in the upstream sloping side area of ​​the upstream hard rockfill area 71 is 3m. It should be noted that the thicknesses mentioned in this embodiment refer to vertical thicknesses.

[0085] It should be noted that the drainage layers of the first backfill area, the second backfill area, the third backfill area, and the dam body are interconnected to form a drainage channel.

[0086] Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0087] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0088] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0089] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0090] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, and the spatial relative descriptions used herein will be interpreted accordingly.

[0091] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pumped-storage power station upper reservoir with stepped backfilling at the reservoir bottom and layered / zonal drainage, characterized in that, This includes setting up a rockfill dam (7), a backfill area, and a drainage layer at the bottom of the reservoir on a soft soil foundation (14); The backfill area includes the rockfill area of ​​the reservoir bottom-dam transition zone (72) and the reservoir basin backfill area; one side of the rockfill area of ​​the reservoir bottom-dam transition zone (72) is connected to the upstream side of the rockfill dam and is located on the downstream side of the reservoir basin backfill area; The reservoir basin backfill area is located on the other side of the rockfill area in the transition zone between the reservoir bottom and the dam body (72). The reservoir basin backfill area consists of the soft rock backfill area (8) and the hard rock backfill area (9) from bottom to top. The reservoir bottom drainage layer includes the first backfill area drainage layer, the second backfill area drainage layer, the third backfill area drainage layer, the inclined drainage layer, and the dam body drainage layer. The first backfill area drainage layer is located between the bottom of the soft rock backfill area (8) and the soft soil foundation (14). The second backfill area drainage layer is located at the junction of the soft rock backfill area (8) and the hard rock backfill area (9) at the bottom of the reservoir. The third backfill area drainage layer is located at the top of the hard rock backfill area (9) at the bottom of the reservoir and on the upstream inclined side of the rockfill dam (7). The inclined drainage layer is located on both sides of the rockfill area (72) in the reservoir bottom-dam body transition zone. The dam body drainage layer is located between the soft soil foundation (14) and the rockfill dam (7) and between the soft soil foundation (14) and the rockfill area (72) in the reservoir bottom-dam body transition zone.

2. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage according to claim 1, characterized in that, The drainage layer of the first backfill area consists of, from bottom to top, the first geotextile (31), the bottom transition drainage material (51), and the second geotextile (32).

3. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage as described in claim 1, characterized in that, The drainage layer of the second backfill area consists of, from bottom to top, the third geotextile (33) and the intermediate transition drainage material (52) at the bottom of the reservoir.

4. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage as described in claim 1, characterized in that, The third backfill area drainage layer is the transition drainage material at the top of the silo bottom (53); The top of the transition drainage material (53) at the bottom of the reservoir is also covered with a subbase material (10) and an asphalt concrete panel (11) for the bottom and perimeter of the reservoir, from bottom to top.

5. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage as described in claim 1, characterized in that, The inclined drainage layer includes a first inclined drainage layer, a second inclined drainage layer and a third inclined drainage layer. The first inclined drainage layer is located between the soft rock backfill area (8) at the bottom of the reservoir and the rockfill area (72) at the bottom of the reservoir-dam transition zone. The second inclined drainage layer is located between the hard rock backfill area (9) at the bottom of the reservoir and the rockfill area (72) at the bottom of the reservoir-dam transition zone. The third inclined drainage layer is located between the rockfill area (72) at the bottom of the reservoir-dam transition zone and the rockfill dam (7). The slope ratios of the first and second inclined drainage layers are both 1:1.4 to 1:1.5; the slope ratio of the third inclined drainage layer is 1:1.5 to 1:1.

6.

6. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage according to claim 1, characterized in that, The first inclined drainage layer consists of the fourth geotextile (34) and the first inclined transition material (541) from the soft rock backfill area at the bottom of the reservoir (8) to the rockfill area at the bottom of the reservoir-dam transition zone (72). The second inclined drainage layer is the second silo bottom inclined transition material (542). The third inclined drainage layer consists of the third inclined transition material at the bottom of the reservoir (543), the first drainage material (61), and the fourth inclined transition material at the bottom of the reservoir (544) from the rockfill area (72) to the rockfill dam (7).

7. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage according to claim 1, characterized in that, The dam body drainage layer includes the first dam body drainage layer and the second dam body drainage layer. The first dam body drainage layer is located between the soft soil foundation (14) and the rockfill area (72) of the reservoir bottom-dam body transition zone. From bottom to top, it consists of the sixth geotextile (36), the second fine transition material (42), and the second dam body bottom transition material (552). The second dam body drainage layer is located between the soft soil foundation (14) and the rockfill dam (7), and consists of the fifth geotextile (35), the first fine transition material (41), the first dam body bottom transition material (551), the second drainage material (62), and the third dam body bottom transition material (553) from bottom to top.

8. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage according to claim 1, characterized in that, The cross section of the boundary area between the soft rock backfill area (8) and the hard rock backfill area (9) at the bottom of the reservoir is constructed to include a first horizontal plane, an inclined plane and a second horizontal plane. The top of the inclined plane is connected to the end of the first horizontal plane, and the end of the second horizontal plane is connected to the bottom of the inclined plane. The slope ratio of the inclined plane is 1:2 to 1:

3. In the soft rock backfill area at the bottom of the reservoir (8), strongly weathered excavated material or soft rock excavated material is used; The hard rock backfill area at the bottom of the reservoir (9) uses weakly weathered or slightly weathered excavated material; The rockfill area in the transition zone between the reservoir bottom and the dam body (72) uses slightly weathered to weakly weathered hard rock.

9. The upper reservoir of a pumped storage power station with stepped backfilling at the bottom and layered drainage according to claim 1, characterized in that, The rockfill dam (7) has an upstream hard rockfill area (71) and a downstream rockfill area (12) set up from upstream to downstream respectively; the rockfill area (72) of the reservoir bottom-dam transition zone is located on the downstream side of the upstream hard rockfill area (71); The downstream slope of the downstream rockfill area (12) is provided with a downstream slope protection (13); the bottom of the downstream slope protection (13) is flush with the foundation surface of the rockfill dam (7), and the top extends to the top of the rockfill dam (7).

10. A construction method for the upper reservoir of a pumped-storage power station with stepped backfilling of the reservoir bottom and layered and zoned drainage as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Excavate the soft soil foundation (14) to form the rockfill dam (7) area, the reservoir bottom-dam transition zone rockfill area (72) area and the reservoir basin backfill area area, and compact the foundation of each area; A dam drainage layer is laid above the rockfill dam (7) area and the rockfill material area (72) of the reservoir bottom-dam transition zone; backfilling is carried out on the dam drainage layer above the rockfill dam (7) area to form the rockfill dam (7); backfilling is carried out on the dam drainage layer of the reservoir bottom-dam transition zone (72) area to form the rockfill material area (72) of the reservoir bottom-dam transition zone. Inclined drainage layers are laid on both sides of the rockfill area (72) in the reservoir bottom-dam transition zone; In the backfill area, the paving and backfilling are carried out from bottom to top to form the first backfill area drainage layer, the soft rock backfill area at the bottom of the reservoir (8), the second backfill area drainage layer, and the hard rock backfill area at the bottom of the reservoir (9). A third backfill drainage layer is laid on the top of the hard rock backfill area (9) at the bottom of the reservoir and on the upstream slope of the rockfill dam (7).

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