Anti-scour structure of deep overburden layer slope around pumped storage power station reservoir and lower reservoir

Abstract

The utility model discloses a pumped storage power station storehouse week deep overburden layer slope anti -scouring structure and lower reservoir, including spouts anchor slope protection structure and drainage hole, set up anchor plate on spouts anchor slope protection structure, set up several pile foundations along spouts anchor slope protection structure lower end edge, and the pile foundation upper end is connected to the bearing platform, and the pile foundation is close to the riverbed side and is provided with steel wire gabion and pebble backfill body, and the bearing platform middle transverse reinforcement extends to spouts anchor slope protection structure, and the drainage hole passes through the anchor plate and extends into the overburden layer, a row of anchor cables is arranged under the spouts anchor slope protection structure, and the anchor cable extends into the rock layer, and the anchor pier is arranged between the pile foundation and the slope, and the outer end of the anchor cable is connected with the anchor pier, the application is through the integration spouts anchor slope protection structure, pile foundation bearing platform system, steel wire gabion and pebble backfill body combination and directional drainage hole, and the scouring instability problem of deep overburden layer slope under high frequency water level fluctuation is effectively solved, can improve the overall stability of the slope and enhance the scouring resistance, improve the drainage performance and prolong the service life.

Description

Technical Field

[0001] This utility model belongs to the technical field of water conservancy and hydropower engineering, specifically relating to an anti-scour structure for a deep overburden slope around a pumped storage power station and a lower reservoir. Background Technology

[0002] Pumped storage power stations, as core infrastructure for peak shaving and valley filling in the power system and ensuring grid stability, have seen the prioritization of utilizing the original river channel and adopting local seepage prevention schemes in their site selection and design, which has become the mainstream choice to reduce project investment and shorten the construction period. However, the original river channel and reservoir perimeter have thick overburden layers, which are mostly composed of alluvial deposits, lacustrine deposits, or debris flow deposits. These overburden layers have complex compositions and significantly different physical and mechanical properties, often exhibiting problems such as loose particles, weak cohesion, and uneven permeability, resulting in inherently insufficient resistance to erosion.

[0003] The daily circulation operation of pumped-storage power stations results in high-frequency and drastic fluctuations in the lower reservoir water level, typically with large daily amplitudes and rapid rate of change. These frequent rises and falls not only cause repeated wetting and drying cycles and stress redistribution in the slope's soil and rock mass, but also generate strong turbulent water flows that continuously erode the slope base and drawdown zone. The erosive action of the water flow gradually erodes the underlying support structure of the slope, undermines the original stability of the overburden layer, induces seepage deformation and uneven settlement, and ultimately leads to slope instability and collapse. Such geological hazards not only affect the normal power generation and dispatch of the power station but may also reduce reservoir capacity, increase dredging and maintenance costs, and in extreme cases, even cause dam safety hazards or damage to riverside facilities.

[0004] Currently, commonly used erosion control solutions in engineering have significant limitations: traditional rigid structures such as masonry and concrete revetments are difficult to adapt to the deformation characteristics of deep overburden layers, and are prone to cracking and detachment due to foundation settlement or water flow impact. Furthermore, the materials have poor durability; under alternating wet and dry conditions and salt corrosion, the reinforcing steel corrodes rapidly, significantly shortening their service life. Retaining walls and riprap protection solutions are not only costly to construct but also poorly adaptable to complex terrain, failing to effectively address the dynamic scouring risks caused by high-frequency water level fluctuations. Existing grid anchoring technologies are mostly static designs, lacking the ability to adapt to the redistribution of soil and rock stress, and rely on heavy machinery for construction, resulting in low efficiency in complex reservoir terrain and high maintenance costs and difficulties in later maintenance. In addition, some enclosed protective structures can block soil-water exchange, disrupt the regional ecological balance, and further exacerbate surrounding erosion problems.

[0005] Therefore, for the deep overburden slopes of original river-type reservoirs, there is an urgent need to develop a protective structure that takes into account scour resistance, deformation adaptability, ease of construction, and ecological compatibility, in order to solve the problems of insufficient rigidity, short lifespan, and difficult maintenance of traditional technologies, fundamentally resist the risk of slope scouring and bank instability, ensure the long-term safe and stable operation of pumped storage power stations, and control the total life-cycle cost of the project. Utility Model Content

[0006] To address the problems existing in the prior art, this utility model provides an anti-scour structure for the deep overburden slope around the reservoir of a pumped storage power station. By integrating a shotcrete and anchor slope protection structure, a pile foundation system, a combination of steel wire gabions and pebble backfill, and directional drainage holes, it effectively solves the problem of scour instability of deep overburden slopes under high-frequency water level fluctuations. It has the advantages of improving the overall stability of the slope, enhancing its anti-scour capacity, adapting to overburden deformation, improving drainage performance, and extending its service life.

[0007] To achieve the above objectives, firstly, this utility model provides an anti-scour structure for a deep overburden slope around a pumped storage power station reservoir, including a sprayed and anchored slope protection structure and drainage holes. Anchor plates are installed on the sprayed and anchored slope protection structure, and several pile foundations are installed along the lower edge of the sprayed and anchored slope protection structure. The upper end of the pile foundation is connected to a pile cap. Steel wire gabions and gravel backfill are installed on the side of the pile foundation near the riverbed. The transverse steel bars in the pile cap extend into the sprayed and anchored slope protection structure, and the drainage holes pass through the anchor plates. A row of anchor cables is installed under the sprayed and anchored slope protection structure. The anchor cables pass through the base-overburden boundary line and extend into the rock layer. Anchor piers are installed between the pile foundations and the slope, and the outer ends of the anchor cables are connected to the anchor piers.

[0008] Furthermore, the gravel backfill body has a sloping surface on the side away from the pile foundation, with a structure that is narrow at the bottom and wide at the top.

[0009] Furthermore, the gabion is stepped, with pebble backfill above the steps. The bottoms of the gabion and the pebble backfill are on the same plane, and the top surfaces of the gabion and the pebble backfill are connected to the riverbed surface with a gentle slope of 3%.

[0010] Furthermore, the steel wire gabions are stacked in a staggered manner, and the compaction degree of the pebble backfill is 80% to 95%.

[0011] Furthermore, the shotcrete and anchor slope protection structure includes anchor rods, a shotcrete layer, and anchor plates. The anchor rods are set perpendicular to the slope surface, and the anchor plates are arranged along the slope surface, covering the outer ends of the anchor rods. Reinforcement is provided in the anchor plates, and the anchor plates are reinforced concrete structures.

[0012] Furthermore, the sprayed concrete layer is graded C20 and has a thickness of 15cm.

[0013] Furthermore, the internal reinforcement of the anchor plate is lap-welded to the reserved reinforcement of the foundation, and the lap weld is welded on both sides. The reserved reinforcement of the foundation is an extension of the transverse reinforcement of the foundation.

[0014] Furthermore, the drain hole is tilted upwards at a 5-10° angle.

[0015] Furthermore, the pile foundation adopts friction piles, with concrete grade C30 and a depth of 5-15m.

[0016] Secondly, this utility model can provide a reservoir that adopts the above-mentioned pumped storage power station reservoir perimeter deep overburden slope anti-erosion structure.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This application provides a structure for preventing erosion of deep overburden reservoir bank slopes, thus protecting the downstream slopes from erosion caused by hydropower station flood discharge. It utilizes a pier cap to connect the shotcrete and anchored slope protection structure and the pile foundation into a unified whole, ensuring the anchor plate structure is firmly anchored and preventing sagging during long-term immersion in water. Furthermore, it employs gabions for bottom protection to prevent floodwater erosion that could lead to slope instability. This invention extends the service life of the structure and ensures the normal operation of the power station. Simultaneously, the prestressed anchor cables provide shear resistance, preventing the shear force from the anchor plate sagging onto the pile foundation, thus providing a safety guarantee for slope stability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the slope excavation and pile foundation structure.

[0019] Figure 2 This is a schematic diagram of the slope anchor plate structure.

[0020] Figure 3 This is a schematic diagram of the gabion structure for riverbed protection and backfilling.

[0021] Figure 4 This is a schematic diagram showing the connection between the foundation and the anchor plate.

[0022] In the diagram: 1. Slope excavation line; 2. Soil nail anchor; 3. Shotcrete layer; 4. Pile foundation; 5. Pier cap; 6. First riverbed excavation line; 7. Drainage hole; 8. Anchor plate; 9. Second riverbed excavation line; 10. Wire mesh gabion; 11. Gravel backfill; 12. Longitudinal reinforcement of pier cap; 13. Stirrups; 14. Reserved reinforcement of pier cap; 15. Internal reinforcement of anchor plate; 16. Lap weld; 17. Anchor cable; 18. Base-cover boundary line. Detailed Implementation

[0023] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] In the design of the lower reservoir of a pumped storage power station, the slopes with thick overburden layers around the reservoir face the challenge of erosion resistance caused by high-frequency and violent fluctuations in water level. The overburden layer is mostly composed of alluvial deposits, lacustrine sediments, or debris flow deposits. Its loose particles, weak cohesion, and uneven permeability result in insufficient erosion resistance. Frequent rises and falls in water level cause repeated wet-dry cycles and stress redistribution in the slope's soil and rock mass, forming strong turbulent water flows that continuously scour the slope base and drawdown zone, gradually eroding the underlying support structure, damaging the stability of the overburden layer, inducing seepage deformation and uneven settlement, and ultimately causing slope instability and collapse. Furthermore, the significant differences in the physical and mechanical properties of the overburden layer make it difficult to effectively suppress water erosion, thus affecting the maintenance of the power station's reservoir capacity and the long-term stability of the slope.

[0025] This invention provides a structure for preventing erosion of a reservoir bank slope with a thick overburden layer, aiming to prevent the downstream slope from being eroded by the discharge of water from a hydropower station. An anchor plate 8 and pile foundation 4 are connected as a whole using a foundation 5, ensuring the anchor plate structure is firmly anchored and preventing sagging due to prolonged water immersion. Anchor cables 17 are installed under the shotcrete and anchor protection structure, extending through the base-overburden boundary line 18 into the rock layer. Anchor blocks are installed between the pile foundation 4 and the slope, with the outer ends of the anchor cables 17 connected to the anchor blocks. A gabion cage 10 is used for bottom protection to prevent the slope from becoming unstable due to flooding. This invention extends the service life of the structure and ensures the normal operation of the power station.

[0026] This application relates to an anti-scour structure for deep overburden slopes around pumped-storage power station reservoirs, aiming to solve the scour problem under high-frequency and violent water level fluctuations, and prevent scouring and hollowing of the slope bottom and slope instability and collapse. Anchor plates 8 refer to plate-shaped components installed on the shotcrete slope protection structure to enhance the overall tensile strength. Furthermore, gabions 10 refer to protective structures composed of wire mesh boxes filled with stones, which can be implemented using a single-layer flat gabion method, such as horizontally laying wire mesh boxes on the riverbed side and filling them with pebbles. The extension of transverse reinforcing bars in the foundation 5 into the shotcrete slope protection structure refers to a connection method that achieves structural integration, such as using threaded sleeves to connect the foundation reinforcing bars to the pre-reserved reinforcing bars in the slope protection. Therefore, this application, through the rational arrangement of the shotcrete and anchor slope protection structure, pile foundation 4, pile cap 5, wire mesh gabion 10, pebble backfill 11, and drainage holes 7, forms an integrated protection system capable of adapting to the deformation of deep overburden layers and effectively resisting water erosion. This overcomes the shortcomings of traditional rigid structures, such as easy cracking and detachment and short service life under alternating wet and dry conditions and water flow impact. By integrating surface reinforcement, deep support, and riverbed buffering mechanisms, this structure achieves a synergistic effect of slope stability and drainage function during water level fluctuations.

[0027] As a preferred embodiment, the drainage hole 7 can be achieved by drilling, for example, by using a drilling rig to drill into the overburden to form a drainage channel, so as to ensure effective reduction of pore water pressure.

[0028] The scour-resistant structure of the deep overburden slope around the pumped storage power station reservoir integrates surface protection, deep anchoring, and riverbed buffering mechanisms to form a synergistic scour-resistant system, addressing the challenges of scour under high-frequency and drastic water level fluctuations. The shotcrete and anchored slope protection structure, serving as the basic surface reinforcement layer, is installed on the slope surface to directly resist water flow erosion and reduce overburden particle loss. Anchor plates 8 are fixed to the surface of the shotcrete and anchored slope protection structure, enhancing the overall tensile strength of the slope and preventing localized cracking and detachment caused by alternating wet and dry deformation of the overburden, ensuring the continuity of surface protection. Several pile foundations 4, set along the lower edge of the shotcrete and anchored slope protection structure, penetrate deep into the overburden, providing deep support to suppress the overall slope sliding tendency; their precise positioning targets the high-risk scour areas at the toe of the slope. The pile cap 5 connected to the upper end of the pile foundations 4 serves as a load-integrating and transfer component, enhancing structural stability. The steel wire gabion 10 and pebble backfill 11 installed on the riverbed side of pile foundation 4 form a flexible energy-dissipating zone, effectively absorbing and dispersing the impact energy of water flow, preventing continuous erosion of the slope toe, while the permeability of pebble backfill 11 also meets drainage requirements. The transverse steel bars in the pile cap 5 extend into the interior of the shotcrete slope protection structure, achieving rigid integration of the upper and lower structures, significantly enhancing the overall deformation adaptability of the slope during water level fluctuations, and reducing structural damage caused by stress redistribution. Drainage holes 7 extend through anchor plates 8 into the overburden layer, ensuring precise and stable drainage paths, timely reducing pore water pressure in the overburden layer to prevent seepage deformation, and the fixing effect of the anchor plates 8 prevents the drainage holes 7 from shifting during overburden deformation. Furthermore, this structure effectively solves the problem of erosion resistance on the deep overburden slope around the reservoir of a pumped storage power station under high-frequency and violent water level fluctuations, preventing scouring and hollowing of the slope bottom and slope instability and collapse. The combination of the shotcrete and anchor slope protection structure with the anchor plate 8 ensures the continuity of surface protection, avoiding cracking and detachment caused by deformation in traditional rigid structures. The installation of pile foundations 4 and pile caps 5 provides reliable deep support, suppressing the overall sliding tendency of the slope. The flexible design of the wire mesh gabion 10 and the pebble backfill 11 absorbs the impact energy of the water flow, preventing continuous hollowing of the slope toe. The extension of the transverse reinforcement enhances the overall deformation adaptability, adapting to the stress redistribution caused by water level changes. The arrangement of drainage holes 7 ensures the long-term effectiveness of drainage function and prevents the risk of seepage deformation. Therefore, this structure ensures slope stability while also considering ease of construction and long-term operational reliability.

[0029] In some embodiments described above, a pebble backfill is proposed to provide scour protection for the riverbed side. However, during its implementation, the shape of the pebble backfill is not optimized for hydrodynamic characteristics. This leads to increased scouring by the water flow under high-frequency water level fluctuations in pumped-storage power stations, causing the pebbles to loosen and be lost, thereby weakening the stability of the slope support structure and increasing the risk of slope instability. To address this, this application further proposes that the pebble backfill 11 has a sloping surface on the side away from the pile foundation 4, with a structure that is narrower at the bottom and wider at the top. In practical applications, the sloping surface of the pebble backfill 11 on the side away from the pile foundation 4 refers to the inclined surface of that side, which can be achieved using a straight inclined surface or a parabolic inclined surface, with the aim of maintaining the stability of the excavated slope. The narrower-at-the-bottom, wider-at-the-top structure refers to the cross-sectional width gradually increasing from the bottom to the top, with the excavation section designed as an inverted trapezoidal cross-section. This aims to utilize the friction and cohesion between the riverbed overburden soil to prevent the overburden slope from becoming unstable under its own weight. The proposed solution involves designing the surface of the pebble backfill 11 as a 3% slope away from the pile foundation 4, combined with a structure that is narrow at the bottom and wide at the top. This allows the impact force of the water flow to be naturally dispersed along the slope, avoiding concentrated scouring of the pebbles and pile foundation. At the same time, the narrow-at-the-bottom and wide-at-the-top shape utilizes the principle of self-weight stability under repeated water flow to prevent the pebbles from loosening and being lost, thereby maintaining the overall continuity of the riverbed side fill and ensuring the long-term reliability of the slope support structure during high-frequency water level fluctuations.

[0030] As a specific implementation method, the implementation is as follows: the slope of the pebble backfill 11 can be a smooth straight inclined surface with a trapezoidal cross-section that is narrow at the bottom and wide at the top. The pebble material is filled with natural pebbles with uniform particle size. This structure forms a stable support relationship with the pile foundation 4, effectively adapting to the hydrodynamic characteristics of the riverbed.

[0031] Through the above-mentioned scheme, this application effectively enhances the erosion resistance of the gravel backfill in a dynamic water flow environment, prevents the gravel from loosening and being lost, maintains the stability of the slope support structure, and thus ensures the safe operation of the deep overburden slope around the pumped storage power station reservoir under high-frequency water level fluctuations.

[0032] This application further proposes that the wire mesh gabion 10 is stepped, with a pebble backfill 11 above the steps. The bottoms of the wire mesh gabion 10 and the pebble backfill 11 are on the same plane, and the top surfaces of the wire mesh gabion 10 and the pebble backfill 11 are at the same height near the pile foundation. The surface of the pebble backfill 11 away from the pile foundation is designed with a 3% slope, and its right side connects to the riverbed at the same height. The wire mesh gabion 10 refers to a flexible protective structure made of wire mesh filled with stones. It can be implemented by stacking multiple layers of gabion units in a stepped configuration. Its principle utilizes the synergistic effect of "flexible structure + permeability + the self-weight of the stones" to weaken the scouring force of water flow, resist water erosion with its own stability, and adapt to foundation deformation and ecological self-healing. This differs from the logic of rigid structures such as concrete "hard-resistant" water flow, leaning more towards "guidance + self-adaptation." The anti-scouring approach is as follows: the first layer of protection for pile foundation anti-scouring; the pebble backfill 11 refers to a permeable backfill structure formed by filling with pebble material, which can be achieved by filling the area behind the steps with pebbles in layers. The purpose is to utilize the natural retaining wall effect formed by the stepped gabion to keep the pebbles in a stable filling state in dynamic water flow and dissipate the remaining water flow energy, serving as the second layer of protection for pile foundation anti-scouring; the bottom of the wire mesh gabion 10 and the pebble backfill 11 are on the same plane, meaning that the foundations of both are set on the same horizontal plane. This can be achieved by excavating the foundation simultaneously and leveling it, in order to ensure that the foundation stress is evenly distributed and avoid local settlement or stress concentration caused by height differences; the top surfaces of the wire mesh gabion 10 and the pebble backfill 11 are connected to the riverbed surface with a gentle slope of 3%, which can be achieved by elevation measurement and adjustment. The purpose is to eliminate surface height differences to achieve a smooth water flow transition, suppress eddy formation, and guide the water flow away from the slope side with a thick overburden layer, thereby smoothly dissipating the impact force.

[0033] Specifically, this application utilizes the stepped configuration of the wire mesh gabion 10 to effectively weaken the scouring force of the water flow through the synergistic effect of its flexible structure, permeability, and the weight of the stones. The pebble backfill 11 set above the steps relies on the retaining wall effect formed by the stepped gabion to maintain a stable filling state in the dynamic water flow, preventing the pebble particles from being quickly eroded and lost, while also playing a permeable buffering role to dissipate the remaining water flow energy. The top surfaces of the wire mesh gabion 10 and the pebble backfill 11 are connected to the riverbed surface by a gentle 3% slope, which eliminates the surface height difference to achieve a smooth transition of water flow, effectively suppressing the formation of eddies and local scouring effects, thereby maintaining the continuity of the riverbed and guiding the water flow away from the slope side with a thick overburden layer, thus smoothly dissipating the impact force.

[0034] The specific implementation is as follows: The gabion 10 can be constructed by stacking multiple wire mesh cage units into a multi-level stepped structure, with the pebble backfill 11 filling the area behind the steps. During construction, the foundation is first excavated to the same plane, then the gabions 10 are stacked to form steps, and pebbles are backfilled on top of the steps to form the pebble backfill 11. The top elevation is adjusted to a gentle 3% slope at the junction with the riverbed surface. Through the above scheme, this application effectively disperses the dynamic water flow impact force, preventing the pebble backfill from being hollowed out and the structure from becoming locally unstable.

[0035] This application further proposes a staggered arrangement of the steel wire gabions 10, with a compaction degree of 80%–95% for the pebble backfill 11. In practical applications, the staggered arrangement of the steel wire gabions 10 means that the joints of adjacent gabions are staggered rather than aligned. This can be achieved by using a stepped staggered arrangement or an irregular random staggered arrangement, with the aim of dispersing the impact load of water flow and avoiding the formation of continuous gaps that could lead to overall structural instability. The compaction degree of 80%–95% for the pebble backfill 11 refers to controlling the density of the pebble particles within this range, which can be achieved by using vibration compaction or static compaction processes. The aim is to ensure sufficient interlocking force between the pebble particles to resist water erosion, while maintaining appropriate porosity to accommodate stress redistribution caused by foundation settlement and alternating wet and dry conditions.

[0036] By staggering the joints of the steel wire gabions 10, the impact load of the water flow is distributed to multiple discontinuous joint positions, effectively preventing local damage from expanding into chain instability. At the same time, the compaction degree of the pebble backfill 11 is controlled within the range of 80% to 95%, which ensures that the friction between particles is sufficient to resist erosion and maintains the necessary deformation adaptability, thereby maintaining the overall stability and erosion resistance of the slope bottom protection structure under high-frequency water level fluctuations.

[0037] As a specific implementation method, the steel wire gabions 10 can be stacked in a staggered manner with the assistance of manual labor and machinery to ensure that the joints of each layer of gabions are staggered from the adjacent layers; the gravel backfill 11 is compacted in layers by a vibratory roller, and the compaction degree is monitored in real time to keep it within the target range; this effectively avoids the instability caused by the continuous longitudinal joints of the steel wire gabions 10 due to continuous gaps, and at the same time optimizes the density control of the gravel backfill 11, significantly improving the erosion resistance and deformation adaptability of the bottom of the slope in a dynamic water flow environment.

[0038] This application further proposes that in the above-mentioned anti-scour structure of the deep overburden slope around the reservoir of the pumped storage power station, the internal reinforcement 15 of the anchor plate 8 is lap-welded to the reserved reinforcement 14 of the foundation, and the lap weld is welded on both sides. The reserved reinforcement 14 of the foundation is an extension of the transverse reinforcement of the foundation.

[0039] Among them, the reserved reinforcement 14 in the foundation refers to the extension of the transverse reinforcement of the foundation. It can be achieved by directly extending the reinforcement or by extending the reinforcement through mechanical connecting sleeves. Its purpose is to ensure the continuity of the reinforcement path and reduce the risk of stress concentration during stress transfer. Lap welding connection can be understood as a welding connection formed after the ends of the reinforcement are lapped. It can be achieved by electric arc welding or resistance welding. Its purpose is to provide a reliable mechanical connection to resist the shear force and tensile force generated by the deformation of the overburden. Double-sided welding specifically refers to welding reinforcement on both sides of the lap joint. It can be achieved by manual electric arc welding or automated welding equipment. Its purpose is to improve the tensile strength and fatigue resistance of the connection point and ensure the structural integrity is maintained under cyclic stress.

[0040] By using the pre-reserved steel bars 14 in the foundation as extensions of the transverse steel bars of the foundation, the introduction of additional joints is avoided, and the stress is evenly distributed along the steel bar path. On this basis, the lap weld connection between the internal reinforcement 15 of the anchor plate 8 and the pre-reserved steel bars 14 in the foundation utilizes the direct contact characteristics of the steel bar ends to form a stable mechanical transmission path. The double-sided welding at the lap weld strengthens the weld area through symmetrical welding, significantly enhancing the strength and durability of the connection point. Thus, under the dynamic load caused by the frequent rise and fall of the water level in the pumped storage power station, it effectively maintains the overall collaborative working ability of the shotcrete slope protection structure and the foundation, and prevents structural separation due to connection failure.

[0041] As a specific implementation method, when constructing the foundation 5, the transverse steel bars are extended as the foundation reserved steel bars 14; when making the anchor plate 8, lap joint positions are reserved in the internal reinforcement 15; during installation, the foundation reserved steel bars 14 are lapped with the internal reinforcement 15 of the anchor plate 8, and the connection is made by double-sided electric arc welding. Drainage holes are used to drain water from the cover layer. However, if the angle of the drainage holes is not optimized during their implementation, the drainage efficiency may be low. Under the condition of high-frequency water level fluctuation, the seepage water cannot be drained in time, forming pressurized water, which lifts the anchor plate 8, causing local saturation and softening of the cover layer, thereby aggravating the scouring effect of water flow and inducing the risk of slope instability. Further, it was proposed that drainage holes 7 be inclined downwards at 5-10°. Drainage holes 7 refer to channels installed in the sprayed concrete slope protection structure to guide the drainage of seepage from the cover layer. They are formed by drilling or pre-embedding pipes. PE drainage pipes with a diameter of φ100 are pre-embedded and penetrate 100cm into the soft soil. The inlet is wrapped with geotextile. A 30cm thick filter material is also installed at the inlet of drainage hole 7 to ensure smooth drainage of seepage and avoid water accumulation, blockage, or backflow that may occur at horizontal or upward inclination angles, thereby maintaining the dry state of the cover layer. The water in the cover layer flows directionally along the channel under the action of gravity. The selection of this angle range is based on the principle of gravity flow under water level fluctuation conditions, which ensures the reliability of water self-drainage while taking into account structural stability and construction feasibility. Thus, it can continuously play a drainage function in the operating environment of pumped storage power station with frequent rises and falls in water level and effectively prevent local saturation and softening of the cover layer.

[0042] As a specific implementation method, the drainage hole 7 can be made of a pipe with good permeability and set at an 8-degree downward angle. The hole opening is equipped with a permeable filter layer to enhance drainage reliability and prevent silt blockage. It can timely discharge seepage water in the cover layer, avoid local saturation and softening, significantly reduce the erosion effect of water flow on the slope, and effectively prevent the risk of slope instability.

[0043] The commonly used depth for pile foundation 4 is 5–15 m, and the common spacing is 3 times the pile diameter or width. Pile foundations are used to support slope structures and resist water erosion. However, during their implementation, pile foundations may fail to effectively anchor to stable soil layers due to inappropriate type, insufficient material strength, or excessively shallow burial depth. They are easily eroded by water flow or deform and fail, thereby weakening the overall slope stability and increasing the risk of overburden slippage. In this application, pile foundation 4 uses friction piles with C30 concrete.

[0044] Among them, pile foundation 4 adopts friction pile, which is a type of pile foundation that relies on the frictional resistance between the pile body and the surrounding soil to transfer the load. It can be implemented by precast concrete piles or bored cast-in-place piles. The purpose is to adapt to the geological conditions of deep overburden and lack of hard bearing layer, and to avoid settlement problems caused by insufficient bottom support of end-bearing piles. The concrete grade is C30 to ensure that the material has sufficient compressive strength and durability in alternating wet and dry and potential erosion environments. The depth of 5 to 15m specifically refers to the range of the embedment depth of pile foundation 4. The specific depth value can be selected within this range according to the actual geological conditions, or it can be determined according to the bearing capacity calculation of the pile foundation. The purpose is to enable the pile foundation to penetrate the unstable surface soil that is easily affected by water erosion and penetrate into the relatively dense stable layer. The friction pile design allows pile 4 to fully rely on the lateral frictional resistance of the loose overburden to bear the load, effectively addressing the defects of loose particles and weak cohesion in the overburden. At the same time, the selection of C30 concrete grade ensures that the material maintains structural integrity in the alternating wet and dry environment caused by frequent water level fluctuations, resisting the physical scouring and chemical erosion of dynamic water flow. Pile 4 can penetrate the surface soil that is susceptible to scouring and reach deep into the stable layer, thereby firmly supporting the pile cap 5 and the shotcrete slope protection structure under high-frequency water level fluctuations, forming a complete anti-scouring system.

[0045] Pile 4 can be constructed using in-situ drilled friction piles, with C30 grade concrete used for pouring. The pile depth is determined based on the results of on-site geological exploration and the bearing capacity of the pile, typically ranging from 5m to 15m. This ensures that the pile is anchored in a relatively dense and stable soil layer and forms a reliable connection with the pile cap 5. This effectively solves the problem that piles are easily eroded by water flow or deform and fail in deep overburden environments, significantly improving the overall stability of the slope structure under high-frequency water level fluctuations and reducing the risk of overburden slippage.

[0046] As an optional embodiment, pile foundation 4 has a square cross-section with dimensions of 0.5 × 0.5 m. The thickness of the overburden layer is to be determined, and friction piles are used. The concrete grade is C30. The depth h2 of the overburden layer and the spacing therein need to be determined based on overall stability calculations.

[0047] The slope excavation line 1 is determined based on the physical and mechanical parameters of the overburden layer. Generally, the slope of the temporary slope of the overburden layer on water can be 1:1 to 1:1.2. The diameter of the anchor bolt 2 is generally 25 to 28 mm. The spacing and length can generally be obtained through slope stability calculation. The commonly used spacing is 2.0 × 2.0 m and the length is 6.0 to 9.0 m. The purpose is to fix the anchor plate 8 on the slope.

[0048] The shotcrete layer 3 is graded C20 and has a thickness of 15cm. The pile cap 5 connects the tops of multiple piles to form an integrated load-bearing system, preventing uneven settlement or displacement of individual piles due to lateral forces, which could affect the overturning stability of the slope and anchor plate 8. Its thickness is related to the thickness of the anchor plate 8, and is usually 0.6m, with reinforcement configured according to the beam cross-section.

[0049] The first riverbed excavation line 6 serves as a platform for pile foundation construction. Its width depends on the construction machinery, but is generally 8.0m. Drainage holes 7 are generally 100mm in diameter, spaced 3.0×3.0m apart, and slope downwards at 5-10° to promptly drain water accumulated under the anchor plates, preventing them from being lifted by confined water and affecting the stability of the slope and anchor plates.

[0050] The concrete grade of anchor plate 8 is C30, with a thickness of 50cm, and a single layer of bidirectional steel mesh with a diameter of 16mm. The spacing is 20cm. The bottom of the anchor plate is integrally connected to the top of the pile cap 5, as shown in the diagram. Figure 4 .

[0051] At the contact point between the pile foundation and the slope, an excavation method is used to backfill with C30 concrete as the anchor pier for anchor cable 17. The prestressed anchor cable has a prestress of 30t and is inserted into the stable rock for approximately 10.0m, in a single row with a spacing of 8.0m. The purpose is that when the soil nail anchor rods in the anchor plate 8 loosen and can no longer maintain the stability of the anchor plate's sliding, the downward force of the anchor plate acts on the pile foundation, forming a downward shear force. The prestressed anchor cable provides shear resistance, thus providing a safety guarantee for slope stability.

[0052] The second riverbed excavation line 9 provides a platform for the construction of steel wire gabions 10. The width is determined according to the construction equipment, and 8.0m is commonly used.

[0053] The dimensions of the steel wire gabion 10 can be customized, but a standard size of 1.0×1.0×2.0m is commonly used. It is filled with crushed stone and stacked in a staggered pattern on the riverbed side of the pile foundation 5. It is used to prevent scouring at the bottom of the flood discharge slope and improve the overall stability of the protective structure.

[0054] The gravel backfill 11 is backfilled using riverbed dredging material, with a compaction degree of 80% to 95%.

[0055] The longitudinal reinforcement bars of the foundation are 12mm in diameter and spaced at 20cm intervals.

[0056] The stirrups 13 of the foundation are made of plain round steel bars with a diameter of 16mm and a spacing of 20cm.

[0057] The foundation has a reserved steel bar 14, which is intended to be welded to the internal steel bar 15 of the anchor plate.

[0058] The anchor plate 8 is reinforced with 15 bars, with a diameter of 16mm and a spacing of 20cm.

[0059] The reinforcement 15 is lap-welded to the reserved reinforcement 14 in the foundation. The lap weld is double-sided and the length is 5d, where d is 16mm.

[0060] In specific implementation, the shotcrete and anchor slope protection structure can specifically adopt a C20 shotcrete layer and HRB400 anchor rods, the anchor plate 8 can specifically be a C30 reinforced concrete slab, the pile foundation 4 can specifically be a square bored pile with a side length of 0.5m and a depth of 10m, the pile cap 5 has a width consistent with the pile diameter of 0.5m, the wire gabion 10 is woven from galvanized steel wire with a diameter of 3mm, the pebble backfill 11 is backfilled with pebbles with a particle size of 50-100mm, and the drainage hole 7 has a diameter of 100mm.

[0061] The construction method for the scour-resistant structure of the deep overburden slope around the reservoir of the pumped storage power station provided in this application can be referenced. Figure 1 Understanding includes the following steps: According to the excavation of the slope, the temporary excavation slope ratio of the cover layer above water is 1:1, and the slope excavation line is 1.

[0062] Install anchor bolts 2, and spray concrete layer 3; The first riverbed excavation line 6 is formed by excavating the bottom slab of the riverbed, and the pile foundation 4 is constructed. Then the pile cap 5 is constructed. Erect the reinforcing steel bars for the drainage pipe and anchor plate 8, and pour concrete; An anchor pier for anchor cable 17 is formed by temporarily excavating the slope between the top of pile foundation 4 and the slope. After the anchor plate 8 is poured, the prestressed anchor cable 17 is then installed. The prestress of the anchor cable is 30t, and it penetrates about 10m into stable rock to ensure anchoring force. The slope of the temporary slope can be 1:0.5 to 1:0.75.

[0063] The riverbed was excavated to form the second riverbed excavation line 9, and steel wire gabions 10 were placed. Finally, the foundation pit was backfilled with gravel backfill body 11.

[0064] This application can also provide a lower reservoir that adopts the aforementioned pumped storage power station reservoir perimeter deep overburden slope erosion resistance structure.

[0065] The anti-scour structure for the deep overburden slope around the reservoir of the pumped storage power station provided in this application effectively solves the problem of scour instability of the deep overburden slope under high-frequency water level fluctuations by integrating a shotcrete and anchor slope protection structure, a pile foundation system, a combination of steel wire gabions and gravel backfill, and directional drainage holes. It has the advantages of improving the overall stability of the slope, enhancing the anti-scour capacity, adapting to overburden deformation, improving drainage performance, and extending service life.

[0066] The above are merely illustrative examples of this utility model. All designs that are the same as or similar to this utility model fall within the protection scope of this utility model. Devices and structures not described in detail in this utility model are prior art and will not be described in detail here.

Claims

1. A scour-resistant structure for a deep overburden slope around a pumped storage power station reservoir, characterized in that, The structure includes a sprayed and anchored slope protection structure and drainage holes (7). Anchor plates (8) are installed on the sprayed and anchored slope protection structure. Several pile foundations (4) are installed along the lower edge of the sprayed and anchored slope protection structure. The upper end of the pile foundations (4) is connected to the pile cap (5). Steel wire gabions (10) and pebble backfill (11) are installed on the side of the pile foundations (4) near the riverbed. The transverse steel bars in the pile cap (5) extend into the sprayed and anchored slope protection structure. The drainage holes (7) pass through the anchor plates (8) and extend into the overburden layer. A row of anchor cables (17) is installed under the sprayed and anchored slope protection structure. The anchor cables (17) pass through the base-overburden boundary line (18) and extend into the rock layer. Anchor piers are installed between the pile foundations (4) and the slope. The outer ends of the anchor cables (17) are connected to the anchor piers.

2. The scour-resistant structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The gravel backfill (11) has a sloping side away from the pile foundation (4), and is a structure that is narrow at the bottom and wide at the top.

3. The erosion-resistant structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The wire gabion (10) is stepped, with a pebble backfill (11) above the steps. The bottoms of the wire gabion (10) and the pebble backfill (11) are on the same plane, and the top surfaces of the wire gabion (10) and the pebble backfill (11) are connected to the riverbed surface with a gentle slope of 3%.

4. The erosion-resistant structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The steel wire gabions (10) are stacked in a staggered manner, and the compaction degree of the pebble backfill (11) is 80% to 95%.

5. The anti-scour structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The shotcrete and anchor slope protection structure includes anchor rods (2), shotcrete layer (3) and anchor plate (8). The anchor rods (2) are set perpendicular to the slope surface, and the anchor plate (8) is arranged along the slope surface. The anchor plate (8) covers the outer end of the anchor rods (2). Reinforcing bars (15) are set in the anchor plate (8). The anchor plate (8) is a reinforced concrete structure.

6. The anti-scour structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The sprayed concrete layer (3) is graded C20 and has a thickness of 15cm.

7. The scour-resistant structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The internal reinforcement (15) of the anchor plate (8) is lap-welded to the reserved reinforcement (14) of the foundation, and the lap weld is welded on both sides. The reserved reinforcement (14) of the foundation is an extension of the transverse reinforcement of the foundation.

8. The scour-resistant structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The drain hole (7) is tilted upwards at a horizontal angle of 5-10°.

9. The anti-scour structure for the deep overburden slope around the reservoir of a pumped storage power station according to claim 1, characterized in that, The pile foundation (4) adopts friction piles, with concrete grade C30 and a depth of 5-15m.

10. A type of reservoir, characterized in that, The scour-resistant slope structure with a deep overburden layer around the reservoir of the pumped storage power station, as described in any one of claims 1-9, is adopted.

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