Pumped storage system based on seabed parallel pilot tunnel reconstruction and construction method

Abstract

The invention belongs to the technical field related to ocean energy storage, and provides a pumped storage system based on seabed parallel pilot tunnel reconstruction and a construction method in order to solve the problem that an existing ocean energy storage system is large in construction risk. Expanding excavation is conducted in the parallel pilot tunnels to form a plant, a hydraulic turbine set is installed in the plant, a water diversion channel connected with an upstream reservoir and a downstream reservoir is excavated, and a complete water diversion and energy storage structure system is formed; when the power grid is in a power utilization trough period and surplus electric energy exists, the surplus electric energy of the power grid drives the hydraulic turbine set to operate to generate water pumping power, and seawater is pumped from the upstream reservoir to the downstream reservoir through the water diversion channel; the downstream reservoir completes seawater energy storage; when the power grid is in a power utilization peak period and a power gap exists, potential energy and kinetic energy of seawater in a downstream reservoir are converted into electric energy; and the predictability and the safety of the project are improved.

Description

Technical Field

[0001] This invention belongs to the field of marine energy storage technology, and in particular relates to a pumped storage system and construction method based on the modification of a seabed parallel tunnel. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Pumped hydro storage is currently the most technologically mature and widely used large-scale energy storage technology. It achieves peak shaving and valley filling of the power grid load through the mutual conversion of electrical energy and potential energy, playing an irreplaceable role in ensuring the safe and stable operation of the power grid and improving the capacity for new energy consumption.

[0004] However, the construction and promotion of traditional land-based pumped storage power stations are severely constrained by geographical conditions. The operation of these stations relies on upstream and downstream reservoirs with suitable water level differences, and the selection of these reservoirs must match specific mountainous terrain, making site selection difficult and time-consuming. Furthermore, the construction of land-based pumped storage power stations often involves large-scale resettlement of displaced residents and can easily disrupt the regional ecological environment. In coastal areas and other regions with highly concentrated electricity loads, finding suitable sites is particularly challenging, severely limiting their application value in absorbing renewable energy near load centers.

[0005] To overcome the site selection limitations of onshore pumped storage power stations, offshore pumped storage technology has emerged. However, its development also faces significant bottlenecks. Constructing new reservoirs or excavating tunnels in deep-sea environments requires overcoming multiple technical challenges, including seawater corrosion, complex geological conditions, and deep-water construction. This not only leads to high construction costs and significantly increased construction risks but also prolongs the project construction period, hindering the large-scale application of offshore pumped storage technology. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a pumped-storage system and construction method based on the modification of a parallel pilot tunnel on the seabed. By utilizing the existing parallel pilot tunnel in the submarine tunnel project to construct a marine pumped-storage system, the predictability and safety of the project are improved, and large-scale energy storage facilities can be built in harsh deep-sea environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a pumped storage system based on the modification of a submarine parallel tunnel, comprising: a parallel tunnel already constructed during the construction of the submarine tunnel as a downstream reservoir, seawater as an upstream reservoir, a powerhouse formed by excavation within the parallel tunnel, a turbine unit installed in the powerhouse, and a water diversion channel connecting the upstream and downstream reservoirs. When the power grid is in a period of low electricity demand and there is surplus power, the surplus power drives the turbine unit to operate and generate pumping power. Seawater is drawn from the downstream reservoir to the upstream reservoir through the water diversion channel, and the water level of the downstream reservoir drops, reserving water space for the next energy storage. When the power grid is in peak demand and there is a power shortage, the water diversion channel is opened so that the high-pressure seawater stored in the upstream reservoir flows towards the powerhouse at high speed under the combined effect of potential energy difference and pressure difference, impacting the turbine blades. The turbine unit performs work and generates electricity under the driving force of the seawater, converting the potential energy and kinetic energy of the seawater into electrical energy. The seawater after power generation is stored in the downstream reservoir.

[0008] Secondly, the present invention provides a construction method for a pumped storage system based on the modification of a submarine parallel tunnel, comprising: The existing parallel pilot tunnel of the undersea tunnel will be used as the downstream reservoir chamber, and the seawater will be used as the upstream reservoir. In the rock mass of the area to be excavated in the parallel pilot tunnel, a support frame is first constructed by drilling and grouting, and then excavation is carried out to form a powerhouse, where water turbine units are installed. The casing is lowered and the bottom is sealed to create a waterless environment inside the casing. The surrounding rock between the bottom of the casing and the parallel guide tunnel is reinforced by grouting. The main water intake pipe is then lowered into the waterless environment inside the casing and fixed. The connection points of the water intake pipes are welded and sealed, and water-stop valves are installed to complete the construction of the water intake channel connecting the upstream and downstream reservoirs.

[0009] The above one or more technical solutions have the following beneficial effects: In this invention, an existing parallel pilot tunnel in the submarine tunnel project is utilized as the downstream reservoir, and seawater is used as the upstream reservoir. A powerhouse is formed within the parallel pilot tunnel, and turbine units are installed within the powerhouse. A water diversion channel connecting the upstream and downstream reservoirs is excavated, forming a complete water diversion and energy storage structure system. The parallel pilot tunnel was constructed during the main tunnel construction, and its geological conditions and hydrological characteristics have been fully revealed and verified. Based on this parallel pilot tunnel, modifications are made to greatly avoid the huge construction risks such as water inrush and collapse faced by new large-scale excavation in a complex, high-pressure seabed environment. This improves the predictability and safety of the project, making it possible to build large-scale energy storage facilities in harsh deep-sea environments. It avoids new, large-scale seabed excavation for the construction of energy storage reservoirs, fundamentally reduces the amount of work, shortens the construction period, and significantly reduces project costs and operation and maintenance costs.

[0010] In this invention, the construction of the plant adopts an active control mode of prefabricated support system → stress guidance → excavation. Before full-scale excavation, a three-dimensional, prestressed, invisible support skeleton is constructed in the rock mass of the area to be excavated by drilling and high-pressure grouting. This skeleton actively improves the stress state of the rock mass before excavation, so that subsequent excavation is only to remove the rock blocks that have been wrapped and solidified by this skeleton, thereby avoiding the construction risks of complex seabed environments from the root and ensuring the long-term stability of the structure.

[0011] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0012] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0013] Figure 1 This is a cross-sectional view of the parallel guide tunnel and the connecting channel in an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of the parallel guide tunnel and the connecting channel in an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view of the pumped storage system in an embodiment of the present invention; Among them, 1. Parallel pilot tunnel, 2. Glass flake / epoxy resin composite coating, 3. C20 cast-in-place reinforced concrete, 4. Grouting pipe, 5. Connecting passage, 6. Main tunnel, 7. Water diversion passage, 8. Plant expansion section, 9. Plant, 10. Water pump turbine unit, 11. Maintenance shaft. Detailed Implementation

[0014] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0015] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0016] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0017] Example 1 This embodiment proposes a submarine pumped storage system based on a parallel pilot tunnel, including: a parallel pilot tunnel already built during the construction of the submarine tunnel as a downstream reservoir, seawater as an upstream reservoir, a powerhouse formed by excavation within the parallel pilot tunnel, a turbine unit installed in the powerhouse, and a water diversion channel connecting the upstream and downstream reservoirs. When the power grid is in a period of low electricity demand and there is surplus power, the surplus power drives the turbine unit to operate and generate pumping power. Seawater is drawn from the downstream reservoir to the upstream reservoir through the water diversion channel, and the water level of the downstream reservoir drops, reserving water space for the next energy storage. When the power grid is in peak demand and there is a power shortage, the water diversion channel is opened, allowing the high-pressure seawater stored in the upstream reservoir to flow towards the powerhouse at high speed and impact the turbine blades under the combined effect of potential energy difference and pressure difference. The turbine unit generates electricity under the driving force of the seawater, converting the potential energy and kinetic energy of the seawater into electrical energy. The seawater after power generation is stored in the downstream reservoir chamber. When the power grid's electricity demand is at its lowest point, the seawater in the downstream reservoir chamber is pumped out and discharged into the upstream reservoir using low-priced electricity. The water level in the downstream reservoir drops, reserving water space for the next energy storage operation. like Figure 1 As shown, the subsea pumped storage system proposed in this embodiment is mainly based on a parallel pilot tunnel 1 pre-constructed beside the main tunnel 6. It mainly includes a downstream reservoir chamber converted from the parallel pilot tunnel 1, a water diversion channel 7 connecting the upper reservoir chamber (i.e., the ocean) and the parallel pilot tunnel 1, and a pump-turbine unit 10.

[0018] like Figure 2 As shown, the plant expansion section 8, the end of the water diversion channel 7, and the water pump turbine unit 10 together form the plant 9. The plant 9 is expanded next to the connecting channel 5, and the water turbine unit 10 and the water diversion pipeline 7 are installed. The connecting channel 5 is backfilled with concrete and coated with an anti-corrosion coating to ensure sealing and durability against seawater erosion.

[0019] In this embodiment, the parallel guide tunnel 1 is reinforced with C20 cast-in-place reinforced concrete 3. At the same time, 3Ф42 grouting pipes 4 are reserved during construction. The grouting pipes 4 are opened at intervals of 0.3m to actively and controllably inject grout to compensate for and strengthen the defects of the backfill body, ensuring its long-term stability and sealing.

[0020] Within the existing parallel pilot tunnel, the location of the water diversion pipeline was coordinated with the selection of sections with relatively good surrounding rock and lining integrity as the expansion site for the pumped storage powerhouse. Specifically, through advanced geological forecasting and borehole exploration, it was confirmed that the target expansion area consisted of intact, slightly weathered andesite with undeveloped joints, good rock mass quality, and no large fault zones. The parallel pilot tunnel site was selected based on the local tide table, at a distance greater than the lowest sea level to ensure water supply from the upstream reservoir.

[0021] like Figure 1As shown, a coating is applied to the inner wall of the water diversion channel and the downstream reservoir chamber. The coating mainly uses glass flake / epoxy resin composite coating 2, which is mainly composed of synthetic functionalized glass flakes and composite epoxy resin.

[0022] First, amino functional groups (–NH2) need to be introduced onto the surface of the glass flakes to enhance their compatibility and interfacial bonding with epoxy resin. The steps are as follows: Disperse the glass flakes in a 1.5M NH4OH solution, stir in an ice bath (5°C) for 30 minutes, slowly add triethoxysilane and continue stirring in an ice bath for another 30 minutes, then continue stirring at room temperature for 6 hours. Collect the functionalized glass flakes by vacuum filtration, wash with ethanol and water until neutral pH, and obtain the functionalized glass flakes through surface modification with (3-aminopropyl)triethoxysilane (3AS). Finally, obtain the glass flake / epoxy resin composite coating through in-situ polymerization and thermosetting. The complex shielding layer formed by the glass flakes, combined with the low permeability of the epoxy resin, greatly extends the penetration path of corrosive media, exhibits excellent corrosion and wear resistance, and can withstand a certain amount of cyclic load in water flow buffer areas.

[0023] Example 2 This embodiment proposes a construction method for a pumped storage system based on the modification of a submarine parallel tunnel, including: The existing parallel pilot tunnel of the undersea tunnel will be used as the downstream reservoir chamber, and the seawater will be used as the upstream reservoir. In the rock mass of the area to be excavated in the parallel pilot tunnel, a support frame is first constructed by drilling and grouting, and then excavation is carried out to form a powerhouse, where water turbine units are installed. The casing is lowered and the bottom is sealed to create a waterless environment inside the casing. The surrounding rock between the bottom of the casing and the parallel guide tunnel is reinforced by grouting. The main water intake pipe is then lowered into the waterless environment inside the casing and fixed. The connection points of the water intake pipes are welded and sealed, and water-stop valves are installed to complete the construction of the water intake channel connecting the upstream and downstream reservoirs.

[0024] This embodiment of the plant construction abandons the traditional passive response mode of "excavation → stress release → support" and transforms it into an active control mode of "prefabricated support system → stress guidance → excavation". Its core lies in constructing a three-dimensional, prestressed "invisible support framework" in the rock mass of the area to be excavated through drilling and high-pressure grouting before full-scale excavation. This framework actively improves the stress state of the rock mass before excavation, so that subsequent excavation is merely the removal of rock blocks that have been "wrapped" and "solidified" by this framework.

[0025] The specific implementation steps for factory construction are as follows: Step 1: Laser measurement, building a working model and platform.

[0026] Specifically, using precision instruments such as total stations and laser scanners, ultra-high precision 3D laser scanning was conducted on the factory area within parallel pilot tunnel 1 to generate a real-scene digital model that perfectly matches the design model. This real-scene digital geological model integrates rock rheology and damage constitutive relationships, simulating stress migration and time-dependent deformation of the rock mass during excavation. Simultaneously, the planned excavation area of ​​the factory and the surrounding rock mass within a certain range are defined as the design domain. The design domain includes the bottom boundary of factory 9, the arching line of the arch, and the location of the central pilot tunnel.

[0027] Based on rock mechanics calculations within the digital geological model, the optimal anchor cylinder grid spatial arrangement is planned, outputting a non-uniform, three-dimensional material density distribution cloud map. High-density areas represent the core support zones requiring high-strength anchor cylinders; low-density areas can accommodate ordinary anchor bolts or require no reinforcement. This network morphology may be fractal, dendritic, or anisotropic, and is far from a simple uniform grid or ring arrangement. The aim of this step is to create a predictable and simulable digital geological model that evolves synchronously with real-world operations, providing a decision-making basis for all subsequent intelligent construction.

[0028] Using an intelligent rock drilling rig equipped with a high-degree-of-freedom robotic arm, and positioned according to a digital geological model, the rig drills a series of deep holes vertically upwards and slightly outwards, reaching depths above the designed roof arch of the factory building. The holes are arranged in a ring within the factory building's outline, forming a group of main stress columns supporting the building's structure. Each stress column is not a single anchor bolt, but rather a group of closely spaced holes.

[0029] Step 2: Construction of intelligent support network.

[0030] A combination of fiber optic smart anchors and a dynamic synergistic grouting system is employed, with a distributed fiber optic sensing system pre-embedded inside and on the surface of the hollow anchor. This anchor serves as both a grouting pipe and a sensory nerve, capable of real-time monitoring of strain, temperature, and vibration along its entire length, as well as sensing the flow and solidification state of the grout. The aim is to grow a dynamically adjustable intelligent load-bearing framework within the rock mass before excavation.

[0031] In the digital twin platform, a design domain extending 5 meters outward from the factory building's design outline is used. Finite element simulation software is employed to create a model incorporating the design chamber dimensions, rock mass parameters, and geostress field. This model simulates the entire excavation process, performing elastoplastic calculations. The maximum principal stress distribution cloud map and plastic zone distribution cloud map are directly extracted and visualized from the calculation results. High stress concentration areas where the maximum principal stress exceeds 70% of the rock mass's uniaxial compressive strength are identified, as well as areas where shear or tensile yielding (plastic strain > 0) occurs after excavation. Finally, based on the cloud maps generated by the finite element simulation, the "principal stress column" region and "secondary stress beam" are determined, and a three-dimensional borehole layout diagram is generated.

[0032] Based on the generated 3D hole layout map, the construction team used a fully automated rock drilling rig to perform precise drilling inside the pilot tunnel; the drilling depth needs to penetrate 2-3 meters above the future factory building's roof arch.

[0033] A fiber optic smart anchor rod is inserted into the drilled hole. The fiber optic smart anchor rod is a hollow steel pipe with a distributed fiber optic sensor network pre-installed on its surface and inner wall. The rod body has multiple controllable opening and closing grouting valves. The anchor rod is connected to the central grouting control system and the fiber optic demodulator.

[0034] Initiating the four-stage grouting process: Phase A (Exploration Phase): Low-viscosity, low-pressure clean water or thin slurry is injected. Temperature field changes and acoustic emission events are monitored using fiber optics to locate the source of the seepage. A network map of the original fractures around the borehole is drawn. If a large seepage channel is found, a quick-setting paste-like slurry is injected to seal it first. Only when the exploration grouting has fully revealed the fracture system around the borehole and completed the initial sealing of the main seepage channels, and the rock mass has reached a stable state of "controllable fracturing," can the active fracturing phase begin. Phase B (Fracturing Phase): Inject medium-viscosity cement-based grout and analyze the spatial sequence (fracture development order) and energy of acoustic emission events in real time. If the fractures extend orderly along the designed principal stress direction, maintain the current pressure; if disordered, scattered events occur, reduce the pressure to prevent excessive disturbance. The goal is to form well-connected main grout veins with minimal energy. When the dominant grout veins in the principal stress direction have extended and connected sufficiently, forming an effective skeletal support, and the energy efficiency of further fracturing decreases sharply, transition to the filling phase, which focuses on penetration and healing.

[0035] Phase C (Filling Phase): Switch to ultrafine cement or chemical grout, employing low-pressure, slow-speed, intermittent grouting. By monitoring the correlation of fiber optic strain responses between different grouting holes, determine if the grout has formed a connection between the holes. When the strain of adjacent anchor bolts changes synchronously, it indicates that the network has been bridged, and grouting in that area is stopped.

[0036] Phase D (Control Phase): After the initial setting and before the final setting of the grout, the key grout veins are subjected to post-tensioning prestress using small hydraulic bladders through intelligent anchor bolts, so that they are under pressure and can more effectively support the surrounding rock. The stress relaxation is monitored through optical fiber.

[0037] After the first round of grouting was completed, the digital twin platform recalibrated the geological digital model based on the strain field of the solidified grout and the acoustic emission events of the rock mass fed back by all smart anchors. First, a multi-source sensor array deployed in the smart grouting anchors and surrounding rock was used to collect heterogeneous data streams in real time, including grouting process parameters and rock mass multi-physics field responses. Then, the data streams were input into an inversion algorithm engine with built-in simplified physical rules for grout flow-rock fracture coupling, which simplified the complex rock fracture network into an equivalent, parameterized three-dimensional porous media pipeline network.

[0038] Its governing equations are as follows:

[0039] Among them, w ij For pipelines ij The equivalent hydraulic aperture is one of the core variables in the inversion, representing the "thickness" of the slurry vein, in meters; Pi , Pj For nodes ij The pressure of the slurry at the point, in Pascals; μ The viscosity of the slurry is a known input related to the stage, in Pascals per second. L ij The length of the pipe is determined by the geometric location of the nodes, and the unit is meters. τ y The yield stress of the slurry is used to describe the rheological properties of paste-like slurries. The unit is Pascal. α This is an empirical correction factor.

[0040] This engine uses reverse computation to dynamically interpret and reconstruct the spatial distribution of the 3D grout flow network that best matches the measured data. Finally, the system implants and integrates the reconstructed "digital grout" component into the initial geomechanical model, while simultaneously updating the rock mass parameters of the modified areas in the geomechanical model accordingly. This allows the digital model to evolve synchronously with the physical entity in terms of geometry and mechanical properties. Running the second-generation topology optimization may involve adding reinforcing short anchors in certain areas based on the first-round network, or adding "connecting beam" boreholes along the stress transfer path; repeating the implantation of fiber optic smart anchors and the initial grouting steps for reinforcement grouting.

[0041] This process typically involves 1-2 iterations until the safety margin of the support system predicted by the geological digital model reaches a set threshold.

[0042] Step 3: Cellular unit excavation under the protection of an intelligent framework.

[0043] At this point, the rock mass to be excavated has been divided into relatively independent cell units by the anchor cylinder grid. Non-blasting excavation is then carried out using a large cantilever tunneling machine or a high-pressure water jet breaker.

[0044] The excavation sequence was strictly followed: "core first, then perimeter, staggered excavation." This means excavating one unit in the central area of ​​the plant first, then excavating units diagonally opposite it, always ensuring that each excavated unit is surrounded by supported or unexcavated rock mass. Under the protection of the established intelligent framework, the rock mass was removed safely and efficiently, with each excavation cycle controlled at 1.0-1.5 meters, and the exposed framework was immediately covered with a sensing and adjustable "skin."

[0045] Each time a cell unit is excavated, the rock surface is immediately cleaned, and a layer of flexible, early-strength concrete infused with synthetic fibers is immediately sprayed. This concrete layer does not primarily bear weight, but rather acts as a "skin": a) preventing rock weathering; b) further connecting the individual "anchor cylinders" into a unified whole; c) its flexibility allows it to adapt to minor deformations without cracking. The first layer is a "sealing layer," quickly sealing the rock surface; the second layer is a "structural layer," tightly bonding to the exposed smart anchor veins and the original rock mass. The spray thickness is fine-tuned based on real-time feedback from the digital twin platform.

[0046] Real-time monitoring and dynamic adjustment. Fiber optic sensors are installed on the anchor bolts of each "principal stress column" to monitor stress and strain changes in real time. The data is transmitted to a digital twin platform in real time. Through algorithm analysis, the platform can predictively identify which cell units in a given area can be safely excavated next, or whether additional grouting is needed, achieving intelligent and adaptive construction throughout the entire process.

[0047] Step 4: Transform the excavated hole into a safe, durable, and fully functional permanent factory building.

[0048] Specifically, once all the rock mass has been excavated, the entire plant space has been stabilized by a built-in "anchor grid-sprayed skin" composite system.

[0049] Building upon this, a smart spraying machine is used to precisely spray steel fiber reinforced concrete of the designed thickness onto the initial spray layer, forming a smooth, high-strength permanent lining. Due to its perfect integration with the "anchor grid," this lining thickness can be thinner than traditional methods, achieving material savings.

[0050] Integrated construction: During the design and construction of the "anchor grid," pipes and cable trays for ventilation, water, and electricity were pre-installed. During the internal lining construction, these functional pipelines were directly embedded, achieving integrated structure and function. Finally, all functional facilities inside the plant, including ventilation, water, electricity, and equipment foundations, were commissioned, completing the final transformation from a "cave" to a "plant."

[0051] In this embodiment, the specific construction steps of the water diversion channel are as follows: Step 1: Lowering the casing.

[0052] Precise positioning was achieved using a total station, marking the center position and sinking trajectory of the casing. A guide frame was installed to ensure the casing's verticality deviation was less than 0.5%. The sinking method employed segmented sinking. First, a crane was used to slowly lower a 1.5m diameter casing by 2m. Sand and gravel were symmetrically backfilled around the casing to initially fix its position. A combination of vibratory hammer and internal soil sampling was used for segmented sinking. Verticality was checked every 1.5m, and parameters such as sinking speed and resistance changes were recorded to assess the geological conditions. When 1m from the design elevation, the sinking speed was reduced, and the position was precisely controlled. A level was used for real-time monitoring to ensure the elevation error was within ±20mm. After sinking to the designated position, clay balls were immediately placed around the casing as temporary water-stopping rings, and the bottom was sealed to create a water-free environment inside the casing.

[0053] Step 2: Bottom sealing and waterless environment creation.

[0054] First, the casing must be sealed with a base plate, and the sealing performance must be tested using a vacuum leak test. A pressure drop of less than 5% is considered acceptable. Any leaks found should be sealed with quick-drying cement. Simultaneously, a submersible pump should be installed to remove internal water and ensure a safe working environment.

[0055] Step 3: Grouting and reinforcement of the bottom to connect the parallel guide tunnel.

[0056] A cement-water glass dual-liquid grouting system was adopted, with the grouting pressure controlled at 0.5-0.8MPa. Grouting was used to reinforce the surrounding rock between the bottom of the casing and the parallel guide tunnel 1. A total station was used to accurately locate the center line of the casing pipe, and a special bracket was used to fix the pipe to ensure that the slope met the design requirements. A 1m diameter water diversion pipe was inserted to connect the tail pipe to the parallel guide tunnel 1, and a sealing treatment was performed and a water stop valve was installed to ensure construction quality and safety.

[0057] Step 4: Submerge into the main water supply pipe.

[0058] In a waterless environment within a 1.5m diameter conduit, the pipe is horizontally lifted using a "double-point support" method with slings or specialized pipe hooks. This "double-point support" method employs two independent lifting slings, positioned symmetrically around the pipe's bottom centerline, passing under the pipe from both sides. The two slings jointly support the lower semi-circular wall of the pipe. The contact area between the slings and the pipe's outer wall is below the pipe's horizontal centerline, primarily providing upward support and preventing the inward "clamping" force exerted on the pipe's sidewalls when the lifting point is at the top. This effectively protects the pipe's coating or structure, preventing damage to the sidewalls. Guide cables are attached to both ends of the pipe for manual control.

[0059] Slowly hoist the main water intake pipe to a position directly above the center of the casing, then lower it at a uniform and deliberate pace. During the lowering process, use guide cables and manual intervention to ensure that the main water intake pipe does not violently collide or rub against the inner wall of the casing. When the lower end of the main water intake pipe is about to contact the bottom of the casing, reduce the speed to the minimum and precisely align the lower end of the main water intake pipe with the previously laid-out tail pipe interface position.

[0060] After the main water intake pipeline is in place, use hydraulic jacks, manual hoists, and steel supports for fine-tuning to ensure that the centerline of the main water intake pipeline is completely aligned with the design centerline and that the slope of the main water intake pipeline is consistent with the design slope. Once adjusted, immediately use steel supports to firmly and temporarily support and fix the main water intake pipeline to the base at the bottom of the casing to prevent displacement or overturning during subsequent operations.

[0061] Step 5: Backfilling, sealing, and joint sealing.

[0062] After the water supply pipeline is connected, a 1.5m sleeve is backfilled in time to fix the water supply pipeline and ensure its waterless environment. Welding is performed to seal the connection point of the water supply pipeline, and a water stop valve is installed. The sealing performance is checked by vacuum measurement method, and leaks are repaired in time to ensure effective water blocking.

[0063] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A pumped-storage system based on the modification of a parallel seabed tunnel, characterized in that, include: The parallel pilot tunnel already built during the construction of the undersea tunnel serves as the downstream reservoir, the seawater serves as the upstream reservoir, the powerhouse is formed by widening and excavating inside the parallel pilot tunnel, the turbine units installed in the powerhouse, and the water diversion channel connecting the upstream and downstream reservoirs. When the power grid is in a period of low electricity demand and there is surplus power, the surplus power drives the turbine unit to operate and generate pumping power. Seawater is drawn from the downstream reservoir to the upstream reservoir through the water diversion channel, and the water level of the downstream reservoir drops, reserving water space for the next energy storage. When the power grid is in peak demand and there is a power shortage, the water diversion channel is opened so that the high-pressure seawater stored in the upstream reservoir flows towards the powerhouse at high speed under the combined effect of potential energy difference and pressure difference, impacting the turbine blades. The turbine unit performs work and generates electricity under the driving force of the seawater, converting the potential energy and kinetic energy of the seawater into electrical energy. The seawater after power generation is stored in the downstream reservoir.

2. The pumped-storage system based on the modification of a submarine parallel tunnel as described in claim 1, characterized in that, The parallel pilot tunnels already constructed during the construction of the undersea tunnel were reinforced with reinforced concrete, and grouting pipes were pre-embedded in the lining.

3. A pumped-storage system based on the modification of a submarine parallel tunnel as described in claim 1, characterized in that, It also includes a pumped storage maintenance channel, which will be used as a maintenance channel for the parallel pilot tunnel.

4. A pumped-storage system based on the modification of a submarine parallel tunnel as described in claim 1, characterized in that, The connecting passage of the parallel pilot tunnel is backfilled with concrete and coated with an anti-corrosion coating; the parallel pilot tunnel is located in an area above the lowest sea level.

5. A construction method for a pumped storage system based on the modification of a submarine parallel pilot tunnel, characterized in that, include: The existing parallel pilot tunnel of the undersea tunnel will be used as the downstream reservoir chamber, and the seawater will be used as the upstream reservoir. In the rock mass of the area to be excavated in the parallel pilot tunnel, a support frame is first constructed by drilling and grouting, and then excavation is carried out to form a powerhouse, where water turbine units are installed. The casing is lowered and the bottom is sealed to create a waterless environment inside the casing. The surrounding rock between the bottom of the casing and the parallel guide tunnel is reinforced by grouting. The main water intake pipe is then lowered into the waterless environment inside the casing and fixed. The main water intake pipe is then connected to the water intake pipe. The connection point of the water intake pipe is welded and sealed, and a water stop valve is installed to complete the construction of the water intake channel connecting the upstream and downstream reservoirs.

6. The construction method for a pumped storage system based on the modification of a submarine parallel tunnel as described in claim 5, characterized in that, In the rock mass of the area to be excavated in the parallel pilot tunnel, a support framework is first constructed through drilling and grouting, and then excavation is carried out to form the plant, specifically: A three-dimensional laser scan is performed on the target area inside the parallel pilot tunnel to generate a real-scene digital model integrating rock rheology and damage constitutive relations. Based on rock mechanics calculations, the spatial layout of the anchor tube grid is planned. According to the three-dimensional hole layout diagram calculated by simulation, deep holes are drilled inside the parallel pilot tunnel. Fiber optic anchors with built-in distributed fiber optic sensing networks are inserted into deep holes. An intelligent support network is constructed through grouting. The grouting is adjusted according to simulation until the safety margin of the support system reaches the set threshold. The rock mass was excavated using a non-blasting method, following the sequence of core excavation, periphery excavation, and staggered excavation. Flexible early-strength concrete was sprayed immediately after excavation to form a protective layer, and stress and strain were monitored in real time. Steel fiber reinforced concrete is sprayed onto the protective layer to form a permanent lining, and pre-embedded ventilation, water and electricity pipes and cable trays are integrated to complete the factory construction.

7. The construction method for a pumped storage system based on the modification of a submarine parallel tunnel as described in claim 6, characterized in that, A smart support network is constructed using grouting technology, specifically as follows: Inject low-viscosity, low-pressure clean water or thin slurry, draw a network diagram of the original fractures around the holes, and inject quick-setting paste slurry to seal large leakage channels; Inject medium-viscosity cement-based grout, and adjust the grouting pressure according to acoustic emission event analysis to form a main grout vein with good connectivity; Switch to ultrafine cement or chemical grout, and use low-pressure, slow-speed, intermittent grouting. By analyzing the correlation of strain response between different grouting holes, determine whether a grout connection has been formed between the holes. After the initial setting of the grout and before the final setting, post-tensioning prestress is applied to the key grout veins to put them under pressure, and the stress relaxation is monitored.

8. The construction method for a pumped storage system based on the modification of a submarine parallel tunnel as described in claim 5, characterized in that, The expansion area of ​​the factory was selected from sections with good surrounding rock and lining integrity, and the rock mass quality was confirmed through advanced geological forecasting and borehole exploration.

9. A construction method for a pumped-storage system based on the modification of a submarine parallel tunnel as described in claim 6, characterized in that, The rock mass was excavated using a non-blasting method, following the sequence of core excavation, periphery excavation, and staggered excavation. Specifically, one unit in the central area of ​​the plant was excavated first, followed by units in the diagonal direction, ensuring that each excavated unit was always surrounded by supported or unexcavated rock mass.

10. The construction method for a pumped storage system based on the modification of a submarine parallel tunnel as described in claim 5, characterized in that, The main water intake pipe is submerged and fixed in a water-free environment inside the casing. The main water intake pipe is then connected to the water intake pipe. The connection point is welded and sealed, and a stop valve is installed. Specifically: Hoist the main water intake pipe to the center of the casing and then to the bottom, aligning the lower end of the main water intake pipe with the previously laid-out tail pipe interface position. After the main water intake pipeline is in place, fine adjustments are made to ensure that the centerline of the main water intake pipeline is completely aligned with the design centerline and that the slope of the main water intake pipeline is consistent with the design slope. After the main water intake pipeline is adjusted into place, it is fixed on the base at the bottom of the casing. After the water intake pipeline is connected, the connection point is welded and sealed, and a water stop valve is installed.

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