A combined foundation for a box-type substation and a construction method thereof

Abstract

This invention discloses a prefabricated substation combined foundation and its construction method, belonging to the technical field of prefabricated substation combined foundation construction. The combined foundation includes multiple precast pipe piles and a precast platform. The lower ends of the precast pipe piles are embedded in the foundation, while the upper ends protrude above the ground. The bottom surface of the precast platform is fixedly connected to the tops of all the precast pipe piles. The precast platform includes a load-bearing frame and a panel laid on the frame. During construction, the pile position deviation is first measured and controlled by setting out lines. Then, the piles are driven, and the verticality of the pile body is orthogonally checked using a double theodolite. Next, the precast platform is hoisted and aligned. Finally, it is welded and fixed, and multi-layer composite anti-corrosion treatment is applied. This invention adopts a fully prefabricated dry construction method, eliminating the need for cast-in-place concrete and curing. The construction cycle for a single foundation is shortened from the traditional 35 days to 2 days. Through designs such as a weld height ≥8mm and an epoxy coal tar pitch and fiberglass cloth composite anti-corrosion layer, the connection strength and durability are guaranteed.

Description

Technical Field

[0001] This invention belongs to the technical field of prefabricated substation combined foundation construction, and particularly relates to a prefabricated substation combined foundation and construction method. Background Technology

[0002] Photovoltaic power generation has achieved explosive growth as the main force of clean energy. Centralized photovoltaic power plants are developing rapidly towards large-scale and clustered development. As the core hub for the collection, voltage boosting and transmission of photovoltaic power plants, the quality and efficiency of the basic construction of box-type substations directly determine the grid connection progress, investment benefits and long-term operational safety of photovoltaic power plants.

[0003] Traditional transformer substation foundations generally use cast-in-place reinforced concrete structures. Although the technology is mature, it has inherent drawbacks: the construction process is complicated, requiring earthwork excavation, rebar tying, formwork, concrete pouring, and 28 days of moisture curing, with a single foundation construction cycle of more than 35 days; there is a large amount of wet work on site, with each transformer substation foundation requiring 1.5-1.7 tons of steel bars, 2m³ of C20 concrete, 17m³ of C30 concrete, and 0.5 tons of embedded iron, as well as a large amount of consumable materials such as binding wire and formwork, relying on a large number of skilled workers, resulting in high labor costs and complex management; there are many quality control points, and the positioning accuracy of embedded parts and the compaction of concrete are easily affected by human factors, especially the embedded foundation channel steel, which is prone to hollowing and other hidden dangers; construction is highly constrained by the environment, and work must be stopped in windy, rainy, or low-temperature weather. The maintenance is even more difficult in water-scarce desert areas, and there is a risk of slope collapse when the foundation pit is deep. Summary of the Invention

[0004] The purpose of this invention is to provide a prefabricated substation combined foundation and construction method to solve the problems of long construction cycle, large amount of wet work, high difficulty in quality control, and strong environmental constraints of existing cast-in-place concrete foundations.

[0005] To achieve the above objectives, the present invention provides the following solution: A prefabricated substation foundation includes multiple precast pipe piles and a precast platform. The lower ends of the precast pipe piles are embedded in the foundation soil, while the upper ends protrude above the ground at a predetermined height to bear vertical loads. The bottom surface of the precast platform is fixedly connected to the top ends of all the precast pipe piles, and the upper surface of the precast platform forms an installation base for mounting the prefabricated substation equipment. The precast platform includes a load-bearing frame and panels laid on the frame.

[0006] In the above technical solution, the precast pipe piles are PHC pipe piles with a strength grade of not less than C80. The frame of the precast platform includes a frame and load-bearing beams made of steel profiles, with panels laid on the load-bearing beams. The panels are made of checkered steel plates or galvanized mesh plates. The precast platform is fixed to the top of each precast pipe pile by welding to the frame at its bottom, forming a rigid connection node with a weld height of not less than 8mm. In addition, the precast substation combined foundation also includes a precast fiberglass emergency oil tank, which is buried underground and connected to the precast substation equipment through an emergency oil leakage pipe.

[0007] The present invention also provides a construction method based on the above-mentioned prefabricated substation combined foundation, comprising the following steps: (a) surveying and setting out: determining the pile positions of each prefabricated pipe pile according to the design drawings; (b) pile driving construction: using a pile driver, driving or pressing the prefabricated pipe piles vertically into the foundation soil at the designed depth; (c) hoisting and alignment: hoisting the prefabricated platform to the top of each prefabricated pipe pile that has been constructed, and aligning it so that the frame at the bottom of the prefabricated platform is aligned with the top of each prefabricated pipe pile; (d) fixing and connecting: welding and fixing the prefabricated platform to the top of each prefabricated pipe pile to form a combined foundation.

[0008] In the above construction method, step (a) specifically includes: using a total station to lay out and determine the predetermined pile positions of each of the precast pipe piles, and setting positioning piles at each predetermined pile position to control the pile position deviation within ±50mm based on the positioning piles; and setting theodolites at 90° intervals on both sides of the pile driver guide frame to measure the verticality of the guide frame and adjust the verticality of the guide frame according to the measurement results to provide a vertical reference for pile driving construction. In step (b), theodolites are set at 90° intervals on both sides of the precast pipe piles to monitor the verticality of the precast pipe pile body in real time and adjust the verticality of the precast pipe piles to ensure that the verticality deviation of the pile body is not greater than 1% of the pile length. The fixed connection method in step (d) is on-site welding. After welding, the weld is treated with anti-corrosion. The anti-corrosion treatment includes: applying epoxy coal tar primer to the top of the precast pipe pile and the connection node; wrapping fiberglass cloth around the primer before it dries; and then applying epoxy coal tar topcoat to the fiberglass cloth to form a multi-layer composite anti-corrosion layer. The construction method is dry construction. During the entire construction process from step (a) to step (d), no cast-in-place concrete or its curing is carried out. When applied to mountainous geology, the pile driving construction in step (b) can be replaced by: first drilling a pilot hole, then constructing a cast-in-place pile; after the cast-in-place pile reaches the design strength, then proceeding to steps (c) and (d) to form a combined foundation of the pilot hole cast-in-place pile and the precast platform.

[0009] Compared with the prior art, the present invention has the following advantages and technical effects: This invention adopts a fully prefabricated structure of "precast pipe piles + precast platform". On-site work only requires pile driving, hoisting and welding, eliminating the need for cast-in-place concrete and 28 days of curing. The on-site construction cycle for a single foundation is shortened from the traditional 35 days to 2 days, increasing efficiency by more than 17 times.

[0010] This invention reduces on-site wet work by more than 90%, eliminating dependence on water for concrete curing. In water-scarce areas such as deserts, there is no need to transport large amounts of curing water, and construction is not limited by water sources; in low temperatures or rainy / snowy weather, there is no need to stop work due to concrete curing conditions, truly achieving year-round, all-weather construction.

[0011] Both precast pipe piles and precast platforms are manufactured in a standardized factory: the precast pipe piles use C80 high-strength concrete, prestressed tensioning technology, and autoclaving, ensuring high dimensional accuracy and reliable strength; the precast platforms employ a structure of welded steel channel frame and panels, with all welding and corrosion protection completed in the factory, ensuring controlled welding quality. On-site assembly and connection are all required, fundamentally avoiding hidden quality hazards such as hollow embedded parts, insufficient concrete compaction, and formwork displacement found in cast-in-place foundations. Engineering verification has shown that the transformer substation foundation constructed using this invention exhibits minimal long-term settlement and excellent structural stability.

[0012] This invention employs a welding fixing method with a weld height of no less than 8mm. This weld height is the optimal value calculated and verified through engineering: compared to a weld height of 5-6mm, the shear and tensile bearing capacity is increased by approximately 40% to 70%, meeting the requirements of vertical pressure, horizontal shear force, and dynamic loads such as wind vibration and equipment operation vibration at the pile top, preventing local crushing or weld tearing. Simultaneously, the sufficiently high weld height allows for a smooth transition between the weld and the base material, significantly reducing the stress concentration factor, ensuring sufficient penetration and eliminating defects such as incomplete welds or incomplete penetration. Under long-term dynamic loads, it exhibits excellent fatigue resistance, avoiding cracking caused by stress concentration. The use of full welding combined with an 8mm weld height forms a rigid ring, completely connecting the pile top to the frame or load-bearing beam of the superstructure, effectively resisting torque, lateral displacement, and uneven settlement, preventing joint loosening and deformation. Long-term dynamic load monitoring has shown no cracking or fatigue damage in the weld.

[0013] This invention employs a multi-layered composite anti-corrosion layer consisting of "epoxy coal tar primer + fiberglass cloth wrapping + epoxy coal tar topcoat" at the top of the pipe pile and connection nodes. The epoxy coal tar coating exhibits extremely strong adhesion, water resistance, acid and alkali resistance, and impermeability; the fiberglass cloth, as a reinforcing material, effectively constrains the internal stress generated by the coating's drying shrinkage, preventing cracking. This composite anti-corrosion layer achieves a service life of 10-15 years in harsh outdoor environments such as desert sandstorms and extreme temperature variations, far exceeding the 3-5 years of ordinary coating processes.

[0014] This invention utilizes a prefabricated fiberglass emergency oil tank, which is directly buried underground and connected to the prefabricated substation equipment via an emergency oil leakage pipe, completing the process simultaneously with the foundation construction. Compared to traditional cast-in-place reinforced concrete oil tanks, which require on-site formwork, reinforcement binding, pouring, and curing, this invention completely eliminates these wet operations, requiring only excavation of the foundation pit, placement of the oil tank, and backfilling, significantly improving efficiency. Simultaneously, it avoids the coordination issues of phased construction of the emergency oil tank and the prefabricated substation foundation in traditional methods, shortening the overall construction period.

[0015] This invention is applicable to PHC pipe pile driving construction (static pressure or hammer driving) in plains and desert areas, and can also be extended to mountain photovoltaic projects through a combination of "drilled cast-in-place piles + prefabricated platforms". Compared with traditional cast-in-place foundations, even when using cast-in-place piles in mountainous areas, the assembly advantages of prefabricated platforms can still be retained, shortening the construction cycle by about 70% and reducing labor input by more than 40%.

[0016] Although the costs of precast pipe piles and pile driving are slightly higher, the expenses for concrete curing water, formwork, binding wire, and earthwork transportation are eliminated, making the direct material cost per foundation roughly the same as that of traditional cast-in-place methods. Furthermore, the shorter construction period saves on construction machinery rental fees, site management fees, and financial costs, and the early grid connection brings significant power generation revenue. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the structure of the prefabricated substation combined foundation of the present invention; Figure 2 This is an application state diagram of the prefabricated substation combined foundation of the present invention; Figure 3 This is a flowchart illustrating the construction method of the prefabricated substation combined foundation of the present invention.

[0018] Among them, 1. precast pipe pile; 2. precast platform; 201. skeleton; 202. panel. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1: Prefabricated Substation Combined Foundation like Figure 1 and Figure 2 As shown, this embodiment provides a prefabricated substation combined foundation, including multiple prefabricated pipe piles 1 and a prefabricated platform 2.

[0022] Precast pipe pile 1 is a PHC pipe pile with a metal end plate at its top for welding to the precast platform 2. The strength grade of precast pipe pile 1 is not lower than C80, and the specific model can be PHC-300B-4.5m, with a wall thickness ≥95mm and a prestressed steel reinforcement strength grade ≥1470MPa. The lower end of precast pipe pile 1 is vertically embedded in the foundation soil, with the embedment depth determined according to geological conditions. For example, in arid desert geology, the embedment depth is 3.5 meters, and its upper end protrudes above the ground at a predetermined height. Multiple precast pipe piles 1 share the vertical load, and their number is calculated based on the weight of the box-type substation equipment being supported, the characteristic value of the vertical bearing capacity of a single pile, and the safety factor. For example, for a 3200KVA box-type substation, 9 precast pipe piles 1 can be used; for small box-type substations with a capacity less than 3200KVA, 6 precast pipe piles 1 can be used. This on-demand configuration avoids the material waste caused by the over-design of traditional cast-in-place foundations.

[0023] The bearing mechanism of precast pipe pile 1 consists of two parts: first, the pile side friction, which is the frictional force between the pile body and the surrounding soil; and second, the pile end bearing capacity, which is the reaction force of the pile bottom supported on a hard soil or rock layer. These two components work together to form a "pile-soil" synergistic force-bearing system. The greater the weight of the transformer substation equipment, the more pipe piles are required. Multiple pipe piles share the load, ensuring that the foundation does not settle, tilt, or collapse under conditions such as equipment weight, wind load, and seismic action. This synergistic force-bearing system is the mechanical basis for the high bearing capacity and high stability achieved in this invention.

[0024] The bottom surface of the prefabricated platform 2 is fixedly connected to the top of all the prefabricated pipe piles 1, and its upper surface forms the installation base surface for installing the box-type substation equipment. The prefabricated platform 2 includes a load-bearing frame 201 and panels 202 laid on the frame 201. The frame 201 is a planar frame structure formed by welding steel sections, preferably using channel steel (such as 16# or 18# channel steel) to make the frame and load-bearing beams. Channel steel has the advantages of reasonable cross-section, high bending stiffness, and easy welding. The spacing of the load-bearing beams is designed according to the position of the prefabricated pipe piles 1 and the size of the box-type substation equipment base to ensure that each prefabricated pipe pile 1 has a corresponding load-bearing beam to transfer the load. The panels 202 are laid on the load-bearing beams. The panels 202 can be 3mm thick checkered steel plates or galvanized grating plates. Checkered steel plates have good anti-slip properties, suitable for personnel walking and equipment installation; galvanized grating plates have the advantages of water and snow permeability and no water accumulation, which can effectively avoid the slip hazard and additional load caused by water and snow accumulation on the checkered steel plates in rainy and snowy weather. The appropriate method can be chosen flexibly depending on the climate conditions of the project location.

[0025] The precast platform 2 is welded to the top of each precast pipe pile 1 via a frame 201 located at its bottom, forming a rigid connection node. To ensure connection strength and durability, the weld height is no less than 8mm. This weld height is the optimal value determined after load-bearing capacity calculation, fatigue analysis, and construction feasibility verification. Its technical effects are reflected in the following: First, the load-bearing capacity (shear and tensile strength) of the fillet weld is directly proportional to the weld height (i.e., weld leg size). Compared with the conventional 5-6mm weld height, the 8mm weld height increases the load-bearing capacity by about 40%-70%, and can reliably withstand the vertical pressure, horizontal shear force, and dynamic loads such as wind vibration and equipment operation vibration at the pile top, preventing local crushing or weld tearing. Second, the sufficiently high weld height allows for a smooth transition between the weld and the base material, significantly reducing the stress concentration factor; the 8mm weld height ensures sufficient penetration depth, without defects such as incomplete welding or incomplete penetration, and has good fatigue resistance under long-term dynamic loads, avoiding cracking caused by stress concentration. Third, the use of full welding with an 8mm weld height creates a rigid ring that completely connects the pile top to the frame or load-bearing beam of the superstructure, effectively resisting torque, lateral displacement, and uneven settlement, and preventing loosening and deformation of the joint. Fourth, the full weld is free of porosity, slag inclusions, and gaps, reducing the entry channels for corrosive media; at the same time, the sufficient weld height facilitates the subsequent application of anti-corrosion coatings and the wrapping of fiberglass cloth, ensuring continuous coverage of the anti-corrosion layer and extending the service life of the joint.

[0026] The load transfer path of the entire foundation is as follows: the self-weight of the transformer substation and the vibration load generated during operation are first transferred to the panel 202 of the precast platform, then transferred to the top of each precast pipe pile 1 through the load-bearing beams and frame of the frame 201, and finally transferred to the foundation soil through the pile side friction and pile end bearing capacity. This force transfer path is clear, direct, and uninterrupted. Moreover, due to the use of rigid welded connections, there is no loosening at the nodes, the overall structural integrity is good, and the coordinated work of the "pile-soil-platform" is realized.

[0027] In addition, the prefabricated fiberglass emergency oil tank (not shown in the figure) is also included in the prefabricated fiberglass emergency oil tank of this embodiment. This prefabricated fiberglass emergency oil tank is made of finished fiberglass material, which has advantages such as light weight, corrosion resistance, and easy installation. The oil tank is buried underground and connected to the oil drain port of the prefabricated substation equipment through an emergency oil leakage pipe. It is used to collect transformer oil leaked in the event of an accident, preventing oil from seeping into the soil and causing environmental pollution. This integrated design avoids the cumbersome process of secondary excavation and secondary pouring of the emergency oil tank after the foundation is completed in traditional foundations, realizing the integrated and simultaneous construction of "foundation + environmental protection facilities".

[0028] Example 2: Construction Method of Combined Foundation for Prefabricated Substation like Figure 3 As shown, this embodiment provides a construction method based on the above-mentioned prefabricated substation combined foundation, including the following steps.

[0029] Step (a): Measurement and Layout. Based on the design drawings, a total station is used to accurately determine the location of each precast pipe pile 1. Specifically, a total station is used to lay out the predetermined location of each precast pipe pile 1, and positioning piles are set at each predetermined location. The positioning piles are used as a reference to control the pile position deviation within ±50mm. Positioning piles are typically made of small steel bars or wooden piles and are only used for marking positions; they do not bear any load. Simultaneously, theodolites are set up at 90° angles on both sides of the pile driver guide frame to measure the verticality of the guide frame. Based on the measurement results, the verticality of the guide frame is manually adjusted to provide a vertical reference for pile driving. The total station layout accuracy can reach millimeter level. Combined with positioning piles and crosshairs, the planar deviation of the pile position can be strictly controlled within ±50mm, providing an accurate position for subsequent platform hoisting and alignment. The theodolites are used to correct the verticality of the guide frame, ensuring that the pile driver is in an absolutely vertical state before pile driving.

[0030] Step (b): Pile driving construction. A pile driver (selecting either static pressure or hammer-driven type depending on geological conditions) is used to vertically drive or press the precast pipe pile 1 into the foundation soil to the designed depth. During pile driving, theodolites are set up at 90° intervals on both sides of the precast pipe pile 1 to monitor the verticality of the pile body in real time. The verticality of the precast pipe pile 1 is adjusted by adjusting the pile driver guide frame or clamps to ensure that the verticality deviation of the pile body is no more than 1% of the pile length. Traditional single-direction observation can only detect the verticality of one plane, and the deviation of the other plane cannot be detected in time. This invention uses a dual theodolite orthogonal calibration technology at 90° intervals, which can simultaneously monitor the verticality of two orthogonal planes, forming a three-dimensional spatial positioning. Once the precast pipe pile 1 tilts in any direction, the corresponding theodolite will read and alarm, and the operator can promptly adjust the pile driver's clamping device or hammer-driven guide frame to correct the deviation. This technology can strictly control the verticality deviation of the pile to within 1% of the pile length (e.g., no more than 10cm for a 10m pile), far superior to the 2%-3% deviation level of conventional construction. Precise verticality control ensures that the tops of all pipe piles are located at the same horizontal projection position, creating the prerequisite for seamless connection of the steel platform. During pile driving, force should be applied evenly, avoiding sudden stops and starts to prevent pile breakage or tilting. After pile driving is completed, the pile top protrudes above the ground at a predetermined height. The excess portion of the pile top is cut off and laitance is removed, exposing the metal end plate at the top of the precast pipe pile 1, providing a clean surface for welding.

[0031] Step (c): Lifting and Alignment. A 15T crane is used to lift the prefabricated platform 2 from the factory onto each completed prefabricated pipe pile 1, and align it so that the frame 201 at the bottom of the prefabricated platform 2 is aligned with the top of each prefabricated pipe pile 1. Lifting should be done slowly to avoid damaging the components through hard impacts. After alignment, the levelness of the prefabricated platform 2 is checked to ensure the deviation is no greater than 2mm / m.

[0032] Step (d): Fixed Connection. The precast platform 2 is welded and fixed to the top of each precast pipe pile 1 to form a combined foundation. Full welding is used, with a weld height of not less than 8mm. After welding, promptly remove the weld slag and conduct a visual inspection of the weld to ensure there are no incomplete or missing welds.

[0033] After welding, the weld is subjected to anti-corrosion treatment. The anti-corrosion treatment includes: applying epoxy coal tar primer to the top of the precast pipe pile 1 and the connection nodes, wrapping fiberglass cloth around it while the primer is still wet, and then applying epoxy coal tar topcoat to the fiberglass cloth to form a multi-layer composite anti-corrosion layer.

[0034] The multi-layer composite anti-corrosion layer exhibits significant technical benefits. Epoxy coal tar coating, with epoxy resin and coal tar as the main film-forming substances, possesses extremely strong adhesion (bonding strength to steel can reach over 10 MPa), excellent water resistance, acid and alkali corrosion resistance, and impermeability. Fiberglass cloth, as a reinforcing material, is wound around the undried primer, and after curing together with the coating, forms a "coating-cloth-coating" composite structure. This composite structure offers multiple technical benefits: First, the fiberglass cloth effectively constrains the internal stress generated by the drying shrinkage of the coating, preventing cracking and ensuring the integrity of the anti-corrosion layer; second, the fiber network of the fiberglass cloth divides the coating into multiple tiny regions, forcing corrosive media to bypass the fiberglass cloth fibers multiple times during penetration, significantly extending the penetration path and thus greatly improving the impermeability of the anti-corrosion layer; third, the fiberglass cloth itself possesses high strength, corrosion resistance, and water resistance, working synergistically with the epoxy coal tar coating to form a composite anti-corrosion layer that combines good adhesion with excellent physical barrier properties.

[0035] Compared to simply applying epoxy coal tar pitch (with an anti-corrosion life of about 3-5 years), this invention uses a multi-layer composite anti-corrosion layer of "coating + fiberglass cloth". In harsh outdoor environments such as desert strong winds and sandstorms and high and low temperature differences, the anti-corrosion life can reach 10-15 years, and the impact resistance and wear resistance are greatly improved.

[0036] The above construction method is a dry construction method. No cast-in-place concrete or its curing is performed during the entire construction process from step (a) to step (d). The on-site construction period for a single foundation is only 2 days, saving more than 33 days compared to the traditional cast-in-place process.

[0037] Example 3: Extended Applications under Special Geological Conditions When applied to hard geological conditions such as mountainous areas, direct pile driving is difficult. This invention provides an alternative solution: replacing step (b) with the following: first, a pilot hole is drilled (using a pilot hole drilling machine to the designed depth), then a cast-in-place pile is constructed within the pilot hole (reinforcing cage binding and concrete pouring). After the cast-in-place pile reaches its designed strength, steps (c) and (d) are performed, i.e., the precast platform 2 is hoisted and welded to the top of the cast-in-place pile, forming a combined foundation of "pilot hole cast-in-place pile + precast platform". Although this alternative solution still requires a concrete curing period, compared to traditional fully cast-in-place foundations, it significantly reduces the amount of on-site pouring work (only the pile body needs to be poured, not the platform), avoids the problem of hollow areas in the platform's embedded parts, shortens the construction cycle by approximately 70%, and reduces labor input by more than 40%. This extended application fully demonstrates the portability and wide adaptability of the core module of the "precast platform" of this invention.

[0038] Example 4: Engineering Application Verification The technical solution of this invention has been applied and verified in multiple actual photovoltaic power station projects, achieving significant technical results.

[0039] Verification Example 1: A large-scale desert photovoltaic power station project with a total installed capacity of 50MW requires the construction of 50 transformer substation foundations. The site geology consists of aeolian sand with low bearing capacity and scarce water resources. The technical solution of this invention was adopted for construction: PHC pipe piles of model PHC-300B-4.5m were selected, with a pile length of 3.5 meters. A 3200KVA transformer foundation requires 9 piles, and a small transformer foundation requires 6 piles. The prefabricated platform 2 uses 16# channel steel frames and load-bearing beams, and is laid with 3mm patterned steel plates, with production outsourced to a professional company. The average construction period for a single foundation is 2 days, while the traditional cast-in-place process requires 35 days (including 28 days of curing) per foundation. By organizing construction in parallel flow, and investing sufficient resources to construct all foundations simultaneously, the total construction period for the traditional process is approximately 35 days, while the total construction period for this invention is approximately 2 days, shortening the overall project duration by approximately 33 days compared to the traditional process. On-site labor input is reduced from 8 people per foundation in the traditional process to 3 people per foundation, significantly reducing labor costs. The project was connected to the grid ahead of schedule, resulting in significant revenue from the increased power generation. After two years of operation and monitoring, the foundation settlement was ≤3mm, the structure was stable, there were no cracks in the welds, no peeling of the anti-corrosion layer, and no potential quality issues.

[0040] Verification Example 2: A photovoltaic power station project in a plain area, with a total installed capacity of 150MW, including 75 transformer foundations. The site geology is cohesive soil with a high groundwater level. The project adopted the technical solution of this invention: static pressure pile driving technology was used to avoid mud pollution; prefabricated platforms were mass-produced and installed on-site using a 15T crane. The construction cycle for a single foundation was 2 days, compared to 35 days using traditional methods. Parallel assembly line operations shortened the overall project duration by approximately 33 days compared to traditional methods. The verticality deviation of all pipe piles was controlled within 0.8%, exceeding the standard requirements. Galvanized grating plates were used instead of checkered steel plates for the prefabricated platforms, effectively solving the problems of water and snow accumulation. The anti-corrosion coating withstood 3 years of outdoor testing without peeling or rust. The project saved approximately 600,000 yuan in overall costs, achieved grid connection and power generation ahead of schedule, and demonstrated significant economic benefits. Furthermore, this construction method was extended to the construction of the substation perimeter wall, using precast concrete slabs with interlocking joints for installation. All perimeter wall installations were completed in 2 days, with both quality and efficiency superior to traditional masonry methods.

[0041] The above application verification shows that the technical solution of the present invention can stably achieve the expected goals of rapid construction, controllable quality, and reasonable overall cost under different geological conditions such as deserts and plains, and has good repeatability and promotion value.

[0042] The core inventive concept of this invention is the industrialized construction model of "factory prefabrication and on-site assembly," which is not only applicable to the foundations of prefabricated substations but can also be extended to other construction scenarios of photovoltaic power stations. For example, cable wells for collector lines can use prefabricated concrete components (upper and lower parts). An excavator digs the pits on-site, hoisting the components into place, and filling the joints with foam sealant or cement grout. One excavator, working with two construction workers, can complete 4-6 cable wells per day, achieving a construction efficiency several times higher than traditional formwork and pouring processes. Another example is the substation perimeter wall, which can use prefabricated concrete slabs with interlocking joints, inserted between the buttress columns, allowing for completion of the entire perimeter wall in just two days. Furthermore, 35kV prefabricated cabin foundations, neutral grounding equipment foundations, and substation transformer foundations can all utilize a design where prefabricated platforms are directly placed on top of the piles, avoiding the problem of hollow pre-embedded channel steel and simplifying the leveling and alignment process. These extended applications all embody the "building block" assembly technical approach of this invention, further amplifying its technical value and scope of application.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A prefabricated substation combined foundation, characterized in that: include Multiple precast pipe piles (1) are embedded in the foundation at their lower ends and exposed above the ground at a predetermined height at their upper ends to bear vertical loads; a precast platform (2) is provided, the bottom surface of which is fixedly connected to the top of all the precast pipe piles (1), and the upper surface of which forms an installation base for installing box-type substation equipment; the precast platform (2) includes a load-bearing frame (201) and a panel (202) laid on the frame (201).

2. The prefabricated substation foundation according to claim 1, characterized in that: It also includes a prefabricated fiberglass emergency oil tank, which is buried underground and connected to the box-type substation equipment through an emergency oil leakage pipe.

3. The prefabricated substation combined foundation according to claim 1, characterized in that: The precast pipe pile (1) is a PHC pipe pile with a strength grade of not less than C80; the frame (201) includes a frame and a load-bearing beam made of steel profiles, and the panel (202) is laid on the load-bearing beam. The panel (202) is a patterned steel plate or a galvanized grid plate.

4. The prefabricated substation combined foundation according to claim 3, characterized in that: The prefabricated platform (2) is welded to the top of each prefabricated pipe pile (1) by the frame (201) located at its bottom, forming a rigid connection node with a weld height of not less than 8mm.

5. A construction method for a prefabricated substation combined foundation based on any one of claims 1 to 4, characterized in that: Includes the following steps: (a) Surveying and setting out: Determine the pile positions of each precast pipe pile (1) according to the design drawings; (b) Pile driving construction: Using a pile driver, precast pipe piles (1) are driven or pressed vertically into the foundation soil to the designed depth; (c) Lifting and positioning: Lift the precast platform (2) above all the precast pipe piles (1) that have been constructed and position it so that the frame (201) at the bottom of the precast platform (2) is aligned with the top of each precast pipe pile (1); (d) Fixed connection: The precast platform (2) is welded and fixed to the top of each precast pipe pile (1) to form a combined foundation.

6. The construction method according to claim 5, characterized in that: Step (a) includes: The predetermined pile positions of each of the precast pipe piles (1) are determined by setting out with a total station, and positioning piles are set at each predetermined pile position. The pile position deviation is controlled within ±50mm based on the positioning piles. Theodolites are set at 90° angles on both sides of the pile driver guide frame to measure the verticality of the guide frame and adjust the verticality of the guide frame according to the measurement results, so as to provide a vertical reference for pile driving construction.

7. The construction method according to claim 6, characterized in that: In step (b), theodolites are set on both sides of the precast pipe pile (1) at 90° angles to monitor the verticality of the precast pipe pile (1) in real time and adjust the verticality of the precast pipe pile (1) to ensure that the verticality deviation of the pile body is not greater than 1% of the pile length.

8. The construction method according to claim 7, characterized in that: The fixed connection method in step (d) is on-site welding. After the welding is completed, the weld is treated with anti-corrosion. The anti-corrosion treatment includes: applying epoxy coal tar primer to the top of the precast pipe pile (1) and the connection node, wrapping glass cloth around it before the primer dries, and then applying epoxy coal tar topcoat to the glass cloth to form a multi-layer composite anti-corrosion layer.

9. The construction method according to claim 5, characterized in that: The construction method is dry construction, and no cast-in-place concrete or its curing work is carried out during the entire construction process from step (a) to step (d).

10. The construction method according to claim 5, characterized in that: The pile driving construction in step (b) is replaced by: first drilling a pilot hole, then constructing a cast-in-place pile, and after the cast-in-place pile reaches the design strength, proceeding to steps (c) and (d) to form a combined foundation of the pilot hole cast-in-place pile and the precast platform.

Images