Offshore large-scale assembly type UHPC special-shaped pile foundation system and construction method thereof

Abstract

This invention relates to the field of marine civil engineering technology, and in particular to a large-scale prefabricated UHPC irregular pile foundation system for marine applications. The system includes a steel outer shell A and a steel outer shell B. Slide grooves are formed on all four sides of the outer walls of both steel outer shells A and B. Steel connecting columns and connecting expansion heads are provided on the inner walls of both sets of slide grooves. A UHPC cantilever connecting plate is fixedly connected to one outer end of each set of steel connecting columns and connecting expansion heads. UHPC load-bearing plates A and B are respectively fixedly connected to one outer end of each set of UHPC cantilever connecting plates. Steel grooves are formed on both the upper and lower sides of one outer end of each UHPC load-bearing plate A and UHPC load-bearing plate B. A connecting thread is formed on one inner end of each steel groove. A connecting reinforcing steel plate is provided on the inner wall of each set of steel grooves. This invention creates a highly efficient spatial force-bearing system through the combination of steel outer shell A, steel outer shell B, UHPC load-bearing plate A, and UHPC load-bearing plate B, achieving high rigidity while saving materials.

Description

Technical Field

[0001] This invention relates to the field of marine civil engineering technology, and in particular to a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method. Background Technology

[0002] With the deepening development and utilization of marine resources globally, the construction of large-scale offshore structures such as offshore wind power, cross-sea bridges, and offshore platforms is increasing. These structures operate in complex and harsh marine environments, facing not only enormous horizontal loads from wind, waves, and currents, but also placing extremely high demands on the vertical bearing capacity, bending stiffness, and durability of their foundation structures. As a key structural element supporting these structures, the performance of pile foundations directly affects the safety and lifespan of the entire project.

[0003] Currently, the large pile foundations widely used in offshore engineering are mainly traditional large-diameter steel pipe piles. Although this type of pile foundation has accumulated rich experience in engineering practice, its inherent technical limitations are becoming increasingly prominent: First, to meet the huge load-bearing requirements, it is often necessary to continuously increase the pile diameter or pile length, leading to a sharp increase in steel consumption, reduced economic efficiency, and the huge piles pose severe challenges to transportation, hoisting, and pile driving construction; Second, traditional uniform cross-section circular piles mainly rely on the bending capacity of the pile itself and the passive earth pressure of the surrounding soil when resisting horizontal loads. Their pile-soil interaction efficiency is low, and it is often necessary to meet design requirements through "deep burial and long driving," which not only significantly increases construction difficulty and energy consumption but also prolongs the offshore operation window, significantly increasing project costs and risks.

[0004] To overcome the aforementioned shortcomings, the industry has attempted to develop irregularly shaped piles (such as expanded-diameter piles and helical piles) to improve bearing efficiency by enlarging the pile tip or local cross-section of the pile body. However, most existing irregularly shaped piles are designed as precast monoliths or cast-in-place, and their massive irregular structures cause significant inconvenience for onshore prefabrication, offshore transportation, and driving construction. Furthermore, during the driving process, the enlarged head of large irregularly shaped piles encounters enormous soil resistance, leading to driving difficulties and even pile damage. Regarding connection technology, for ultra-long piles requiring segmented driving, existing segmented connection methods often suffer from insufficient connection stiffness, difficulty in ensuring centering accuracy, and complex construction procedures, becoming weak points in the overall structural performance.

[0005] In addition, although some existing technologies use water injection or grouting to assist pile driving or enhance pile side friction, these measures are usually single-function and fail to be systematically and integrated with the structural design, modular assembly and final overall performance improvement of the pile foundation.

[0006] Therefore, there is an urgent need in this field for a new type of marine pile foundation system and its supporting construction methods that integrate high load-bearing efficiency, excellent resistance to horizontal loads, convenient modular construction, and controllable sinking resistance, in order to solve the economic, construction, and structural problems existing in the current technology. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: a large-scale prefabricated UHPC irregular pile foundation system for marine applications, comprising a steel outer shell A and a steel outer shell B. Slide grooves are provided on all four sides of the outer walls of both steel outer shells A and B. Steel connecting columns and connecting enlarged heads are provided on the inner walls of both sets of slide grooves. A UHPC cantilever connecting plate is fixedly connected to one outer end of each set of steel connecting columns and connecting enlarged heads. A UHPC load-bearing plate A and a UHPC load-bearing plate B are respectively fixedly connected to one outer end of each set of UHPC cantilever connecting plates. Steel grooves are provided on both the upper and lower sides of one outer end of each UHPC load-bearing plate A and UHPC load-bearing plate B. A connecting threaded opening is provided on one inner end of each steel groove. A connecting reinforcing steel plate is provided on the inner wall of each set of steel grooves. Symmetrically distributed connecting threaded holes are provided on each connecting reinforcing steel plate. The UHPC load-bearing plate A and UHPC load-bearing plate B are rigidly fixed by high-strength bolts and connecting reinforcing steel plates.

[0009] Preferably, both the steel outer shell B and the steel outer shell A are filled with concrete. A shaped connection port A, a steel water injection pipe B, a connecting thread B, a shaped connection port B, a steel water injection pipe A, and a connecting thread A are pre-embedded inside each of the two filled concrete sections. The shaped connection port A, the steel water injection pipe B, and the connecting thread B are fixed by welding. The shaped connection port B, the steel water injection pipe A, and the connecting thread A are also fixed by welding.

[0010] Preferably, the inner wall of the connecting thread B is provided with a hollow connecting bolt B, and a conical steel base plate is fixedly connected to the bottom end of the hollow connecting bolt B. A jet outlet is provided in the middle of the bottom end of the conical steel base plate.

[0011] Preferably, a hollow connecting bolt A is threaded on the inner wall of the connecting thread A, and a special-shaped connecting bolt is fixedly connected to the bottom end of the hollow connecting bolt A. The special-shaped connecting bolt is disposed on the inner wall of the special-shaped connecting port A.

[0012] Preferably, water injection pipes are symmetrically embedded on both UHPC load-bearing plate A and UHPC load-bearing plate B. Irregularly shaped enlarged connection ports are embedded at the upper and lower ends of UHPC load-bearing plate A and UHPC load-bearing plate B on the outer side of the water injection pipes. Irregularly shaped reinforcing blocks are provided between each group of irregularly shaped enlarged connection ports. Irregularly shaped reinforcing steel rods are fixedly inserted through each irregularly shaped reinforcing block. The irregularly shaped reinforcing steel rods are placed between UHPC load-bearing plate A and UHPC load-bearing plate B to transmit shear force.

[0013] Preferably, the top of the steel outer shell A is provided with an irregularly shaped connecting platform, the top of the irregularly shaped connecting platform is fixedly connected to a pile leg connecting pipe, the bottom of the irregularly shaped connecting platform has square notches on all four sides, the square notches are provided on the UHPC cantilever connecting plate, and bolt connection holes A are provided on all four sides of the outer wall of the irregularly shaped connecting platform.

[0014] Preferably, the top of each of the UHPC cantilever connecting plates on the upper side is provided with a rib plate for connecting irregular piles and the foundation. One outer end of each rib plate is provided with a bolt connection hole C, and one inner end of each rib plate is provided with a bolt connection hole B. The rib plate and the foundation are fixedly connected by fixing bolts B, and the rib plate and the UHPC load-bearing plate A are fixedly connected by fixing bolts A.

[0015] A construction method for large-scale prefabricated UHPC irregular pile foundations at sea includes the following steps: Step 1: Prefabricate steel shell A, steel shell B, UHPC load-bearing plate A and UHPC load-bearing plate B in the factory. UHPC load-bearing plate A and UHPC load-bearing plate B are prefabricated using ultra-high performance concrete and have pre-embedded connecting reinforcing steel plates and steel grooves. Step 2: After hoisting the steel outer shell B to the designed pile position on the seabed, the driving operation will be carried out. During the driving process, pressure water will be injected to reduce the driving resistance. Step 3: Hoist the UHPC load-bearing plate B to the top of the already driven steel shell B, so that the steel connecting column is embedded in the groove. Auxiliary water injection is carried out during the installation process, followed by the cyclic assembly and driving of subsequent pile segments.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By combining steel shell A, steel shell B, UHPC load-bearing plate A and UHPC load-bearing plate B, a highly efficient spatial load-bearing system is created, which saves materials and has high rigidity. Modular design allows large pile foundations to be prefabricated to high standards in the factory, requiring only on-site assembly, ensuring quality control and rapid construction. The unique construction process of "first injecting water to reduce resistance, then injecting grout to enhance strength" has resolved the contradiction between the penetration of irregular piles and high-performance bearing capacity. Multi-level and multi-type rigid connection schemes ensure the integrity and reliability of prefabricated pile foundations. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method, as described in this invention. Figure 2 This is a separate view of the steel outer shell A and steel outer shell B of the large-scale prefabricated UHPC irregular pile foundation system and its construction method for marine applications according to the present invention. Figure 3 This invention relates to a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method. Figure 2 Enlarged view of the structure at point A in the middle; Figure 4 This is a bottom view of the steel outer shell A and steel outer shell B separated from the steel outer shell of the present invention, which describes a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method. Figure 5 This is a structural diagram of the steel outer shell B and the UHPC load-bearing plate B of a large-scale prefabricated UHPC irregular pile foundation system and its construction method at sea according to the present invention. Figure 6 This is a structural diagram of the UHPC load-bearing plate B of a large-scale prefabricated UHPC irregular pile foundation system and its construction method for marine applications according to the present invention. Figure 7 This is a structural diagram of the steel outer shell B of the large-scale prefabricated UHPC irregular pile foundation system and its construction method for marine applications according to the present invention. Figure 8 This is a separate diagram of the connecting thread B and the hollow connecting bolt B of the large-scale prefabricated UHPC irregular pile foundation system and its construction method at sea according to the present invention. Figure 9 This is a structural diagram of the steel shell A and the UHPC load-bearing plate A of a large-scale prefabricated UHPC irregular pile foundation system and its construction method at sea according to the present invention. Figure 10 This is a structural diagram of the connecting thread A and the hollow connecting bolt A of a large-scale prefabricated UHPC irregular pile foundation system and its construction method at sea according to the present invention. Figure 11 This is a structural diagram of the rib plate connecting the irregular pile and the pile cap in the present invention, which describes a large-scale prefabricated UHPC irregular pile foundation system for marine applications and its construction method. Figure 12 This is a structural diagram of the irregularly shaped connection pile cap of a large-scale prefabricated UHPC irregular pile foundation system and its construction method for marine applications, as described in this invention.

[0018] In the diagram: 1. Steel outer shell A; 2. Steel outer shell B; 3. UHPC load-bearing plate A; 4. UHPC load-bearing plate B; 5. Irregularly shaped connecting pile cap; 6. Pile leg connecting pipe; 7. Irregularly shaped pile and pile cap connecting rib plate; 8. Irregularly shaped connection port A; 9. UHPC cantilever connecting plate; 10. Water injection pipe; 11. Irregularly shaped enlarged connection port; 12. Connecting enlarged head; 13. Connecting reinforcing steel plate; 14. Steel groove; 15. Connecting threaded port; 16. Connecting threaded hole; 17. Irregularly shaped reinforcing steel bar; 18. High-strength bolt; 19. Irregularly shaped 20. Reinforcing block; 21. Irregularly shaped connecting bolt; 22. Conical steel base plate; 23. Slide groove; 24. Filled concrete; 25. Steel water injection pipe A; 26. Steel connecting column; 27. Steel water injection pipe B; 28. Connecting thread A; 29. ​​Hollow connecting bolt A; 30. Bolt connecting hole A; 31. Fixing bolt A; 32. Bolt connecting hole C; 33. Bolt connecting hole B; 34. Fixing bolt B; 35. Square notch; 36. Irregularly shaped connecting port B; 37. Connecting thread B; 38. Hollow connecting bolt B; 39. Jet port. Detailed Implementation

[0019] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0020] like Figures 1-12 The illustrated large-scale prefabricated UHPC irregular pile foundation system includes a steel outer shell A1 and a steel outer shell B2. The outer walls of both steel outer shells A1 and B2 are provided with grooves 22 on all four sides. The inner walls of both sets of grooves 22 are equipped with steel connecting columns 25 and connecting expansion heads 12. A UHPC cantilever connecting plate 9 is fixedly connected to one end of each set of steel connecting columns 25 and connecting expansion heads 12. A UHPC load-bearing plate A3 is fixedly connected to one end of each set of UHPC cantilever connecting plates 9. UHPC load-bearing plate B4, UHPC load-bearing plate A3 and UHPC load-bearing plate B4 all have steel grooves 14 on the upper and lower sides of one side of the outer side. Each steel groove 14 has a connecting threaded port 15 on one side of the inner side. Each set of steel grooves 14 has a connecting reinforcing steel plate 13 on its inner wall. Each connecting reinforcing steel plate 13 has symmetrically distributed connecting threaded holes 16. UHPC load-bearing plate A3 and UHPC load-bearing plate B4 are rigidly fixed by high-strength bolts 18 and connecting reinforcing steel plates 13.

[0021] Both steel outer shells B2 and A1 are filled with concrete 23. The two concrete filling 23 are respectively embedded with irregular connection port A8, steel water injection pipe B26, connecting thread B36, irregular connection port B35, steel water injection pipe A24 and connecting thread A27. Irregular connection port A8, steel water injection pipe B26 and connecting thread B36 are fixed by welding, and irregular connection port B35, steel water injection pipe A24 and connecting thread A27 are fixed by welding.

[0022] The inner wall of the connecting thread B36 is provided with a hollow connecting bolt B37. The bottom end of the hollow connecting bolt B37 is fixedly connected to a conical steel base plate 21. A jet port 38 is provided in the middle of the bottom end of the conical steel base plate 21.

[0023] A hollow connecting bolt A28 is provided on the inner wall of the connecting thread A27. A special-shaped connecting plug 20 is fixedly connected to the bottom end of the hollow connecting bolt A28. The special-shaped connecting plug 20 is located on the inner wall of the special-shaped connecting port A8.

[0024] Water injection pipes 10 are symmetrically embedded on both UHPC load-bearing plates A3 and B4. Irregularly shaped enlarged connection ports 11 are embedded at the upper and lower ends of UHPC load-bearing plates A3 and B4, corresponding to the outer sides of the water injection pipes 10. Irregularly shaped reinforcing blocks 19 are provided between each set of irregularly shaped enlarged connection ports 11. Irregularly shaped reinforcing steel rods 17 are fixedly inserted through each irregularly shaped reinforcing block 19. Irregularly shaped reinforcing steel rods 17 are placed between UHPC load-bearing plates A3 and B4 to transmit shear force.

[0025] The top of the steel outer shell A1 is provided with an irregularly shaped connecting platform 5. The top of the irregularly shaped connecting platform 5 is fixedly connected to the pile leg connecting pipe 6. The bottom of the irregularly shaped connecting platform 5 has square notches 34 on all four sides. The square notches 34 are set on the UHPC cantilever connecting plate 9. The outer wall of the irregularly shaped connecting platform 5 has bolt connection holes A29 on all four sides.

[0026] The top of the upper UHPC cantilever connecting plate 9 is provided with irregular pile and pile cap connecting rib plate 7. The outer end of the irregular pile and pile cap connecting rib plate 7 is provided with bolt connection hole C31, and the inner end of the irregular pile and pile cap connecting rib plate 7 is provided with bolt connection hole B32. The irregular pile and pile cap connecting rib plate 7 and the irregular connecting pile cap 5 are fixedly connected by fixing bolt B33. The irregular pile and pile cap connecting rib plate 7 and UHPC load-bearing plate A3 are fixedly connected by fixing bolt A30.

[0027] A construction method for large-scale prefabricated UHPC irregular pile foundations at sea includes the following steps: Step 1: Prefabricate steel shell A1, steel shell B2, UHPC load-bearing plate A3 and UHPC load-bearing plate B4 in the factory. Pour concrete 23 into steel shell A1 and steel shell B2 and pre-embed steel water injection pipe A24, irregular connection port B35, connecting thread A27, irregular connection port A8, steel water injection pipe B26 and connecting thread B36. UHPC load-bearing plate A3 and UHPC load-bearing plate B4 are prefabricated using ultra-high performance concrete and pre-embed water injection pipe 10, connecting reinforcing steel plate 13 and steel groove 14. Step 2: Connect the conical steel base plate 21 to the bottom of the steel outer shell B2, hoist it to the designed pile position on the seabed and carry out the sinking operation. During the sinking process, pressurized water is injected through the steel water injection pipe A24, steel water injection pipe B26 and jet port 38 to reduce the sinking resistance. Step 3: Hoist the UHPC load-bearing plate B4 to the top of the already driven steel shell B2, so that the steel connecting column 25 is embedded in the sliding groove 22, and the connecting enlarged head 12 is coupled with the irregular connecting port A8. During the installation process, auxiliary water is injected through the water injection pipe 10, and then the subsequent pile segments are cyclically assembled and driven. Example 1

[0028] This embodiment demonstrates a standardized construction application under conditions of moderate water depth (e.g., 30 to 50 meters) and conventional sandy or clayey seabed.

[0029] First, standardized prefabrication of all components is completed in the land-based prefabrication plant. The steel shells A1 and B2 are made of Q355 steel and filled with C60 micro-expansion concrete to form filling concrete 23. DN50 steel water injection pipes A24 and B26 are pre-embedded. UHPC load-bearing plates A3 and B4 are prefabricated with ultra-high performance concrete with a compressive strength of not less than 120 MPa. Water injection pipes 10 with diameters matching steel water injection pipes A24 and B26, steel connecting columns 25 of Q345B material, and steel grooves 14 with internal threads are pre-embedded inside. At the same time, connecting reinforcing steel plates 13, high-strength bolts 18, and special-shaped connecting bolts 20 are prepared.

[0030] In the construction area, the conical steel base plate 21 and the steel outer shell B2 are connected on the deck using a crane vessel. After the hoisting system vertically lowers the assembly to the designed pile position on the seabed, the hydraulic pile hammer is used for driving. When driving into the central dense sand layer and the number of hammer blows increases significantly, the water injection system is immediately activated. Water is injected at a pressure of 0.8 to 1.2 MPa through the steel water injection pipes A24 and B26 and the jet nozzles 38 on the conical steel base plate 21 to effectively disturb and lubricate the soil at the pile tip, allowing the driving to proceed smoothly until the pile top elevation reaches about five meters above the seabed surface.

[0031] Subsequently, four UHPC load-bearing plates B4 were hoisted in sequence. When each UHPC load-bearing plate B4 was in place, the operator guided its steel connecting column 25 to slide accurately into the groove 22 of the steel outer shell B2 until its connecting enlarged head 12 was tightly coupled with the irregular connecting port A8. To facilitate installation, a small amount of water was injected through the water injection pipe 10 during the placement process to reduce the friction between the UHPC plate and the soil.

[0032] Subsequent pile segments are extended using a cyclical operation method. Specifically: First, the irregularly shaped connecting bolt 20 is screwed into the connecting thread A27; the steel outer shell A1 is hoisted and connected to the steel outer shell B2; then, the irregularly shaped reinforcing block 19 and the irregularly shaped enlarged connecting port 11 of the UHPC load-bearing plate B4 are inserted, and the UHPC load-bearing plate A3 is installed. After aligning the steel grooves 14 of the UHPC load-bearing plate A3 and UHPC load-bearing plate B4, the connecting reinforcing steel plate 13 is embedded and locked with high-strength bolts 18. This assembly process forms an efficient connection node where the irregularly shaped reinforcing steel bar 17 transmits shear force and the connecting reinforcing steel plate 13 transmits bending moment. Afterwards, the segment is driven through, and water is injected to reduce drag as needed. This cycle is repeated until the pile penetrates all designed soil layers and reaches the predetermined bearing layer elevation.

[0033] After pile completion, the system immediately switches to grouting mode via a network of water injection pipes throughout the pile. A grouting pump with a pressure of 2 to 2.5 MPa is used to inject high-strength cement mortar with a water-cement ratio of 0.4 into the pile tip and surrounding area. The grout not only fills the cavities and joints within the pile but also, through penetration and fracturing, forms a cement-soil reinforcement of a certain thickness around the pile.

[0034] Finally, as Figure 8 , Figure 9 and Figure 10 As shown, a rib plate 7 for connecting the irregularly shaped pile and the pile cap is installed on the pile top and securely connected to the pile body using fixing bolts A30. The pile leg connecting pipe 6 of the prefabricated irregularly shaped connecting pile cap 5 is then fitted onto the rib plate 7 for connecting the irregularly shaped pile and the pile cap, completing the connection with the upper wind turbine jacket foundation. This forms the final integrated external structure of the pile foundation. Example 2

[0035] This embodiment addresses high-requirement scenarios with water depths exceeding seventy meters and complex geological conditions such as thick layers of soft clay or isolated boulders, and features targeted enhancements based on standardization.

[0036] First, reinforcement measures are taken during the prefabrication stage of the components. Steel shells A1 and B2 are made of higher strength Q420 steel, and the internal concrete grade is increased to C80. Steel fibers are incorporated into the UHPC material of UHPC load-bearing plates A3 and B4, and their structural thickness is increased to cope with greater soil pressure and possible local impacts.

[0037] During the immersed tunnel construction, a more proactive water injection strategy was adopted to address the potential "soil plugging effect" and sidewall adsorption resistance caused by thick layers of soft clay. Not only was the high-pressure water injection at the pile tip increased to 1.5 to 2 MPa, but water injection pipes 10 on the UHPC bearing plates A3 and B4 were used to simultaneously lubricate the sidewalls of specific soil layers above and below, effectively overcoming the "stagnation" problem in deep penetration. When encountering localized hard interlayers or small boulders, controlled penetration was achieved by adjusting the combination of water injection pressure and hammering energy.

[0038] At the connection nodes, the thickness of all connecting reinforcing steel plates 13 is increased, the preload of high-strength bolts 18 is correspondingly increased, and epoxy structural adhesive is applied to all connection interfaces to enhance the fatigue performance and long-term durability of the nodes and adapt to complex dynamic loads in deep water areas.

[0039] The post-grouting process is a key enhancement in this embodiment. A segmented, quantitative, and pressure-controlled grouting technique is employed. First, initial grouting is performed at the pile tip to form an enlarged head. After initial setting, water injection pipes 10 on UHPC load-bearing plates A3 and B4 are used to perform secondary or even tertiary fracturing grouting at different depths of the pile body. This primarily forms a series of "skewer-like" reinforced structures in the soft soil layer around the pile, significantly improving the pile's side friction and overall stability. The grouting pressure reaches a maximum of three MPa, and the grout uses a special grouting material incorporating expanding agents and early-strength agents.

[0040] The connection with the pile cap is also strengthened accordingly. The size and thickness of the connecting rib 7 between the irregular pile and the pile cap are increased, and the number and specifications of bolts are improved to ensure absolute reliability of the connection node in extreme marine environments such as typhoons and giant waves. Its connection method with the irregularly shaped pile cap 5 is as follows: Figure 11 and Figure 12 As shown. The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0041] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A large-scale prefabricated UHPC irregular pile foundation system for marine applications, comprising a steel outer shell A (1) and a steel outer shell B (2), characterized in that: The steel outer shell A (1) and steel outer shell B (2) are provided with sliding grooves (22) on all four sides of their outer walls. The inner walls of the two sets of sliding grooves (22) are provided with steel connecting columns (25) and connecting expansion heads (12). A UHPC cantilever connecting plate (9) is fixedly connected to one end of the outer side of each set of steel connecting columns (25) and connecting expansion heads (12). A UHPC load-bearing plate A (3) and a UHPC load-bearing plate B (4) are fixedly connected to one end of the outer side of the two sets of UHPC cantilever connecting plates (9). The UHPC load-bearing plate A (3) Steel grooves (14) are provided on the upper and lower sides of one side of the outer side of the UHPC load-bearing plate B (4). A connecting threaded port (15) is provided on one side of the inner side of each steel groove (14). A connecting reinforcing steel plate (13) is provided on the inner wall of each group of steel grooves (14). A symmetrically distributed connecting threaded hole (16) is provided on each connecting reinforcing steel plate (13). The UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4) are rigidly fixed by high-strength bolts (18) and connecting reinforcing steel plates (13).

2. The marine large-scale prefabricated UHPC irregular pile foundation system according to claim 1, characterized in that: Both the steel outer shell B (2) and the steel outer shell A (1) are filled with concrete (23). The two filled concrete (23) are respectively embedded with a special-shaped connection port A (8), a steel water injection pipe B (26), a connecting thread B (36), a special-shaped connection port B (35), a steel water injection pipe A (24), and a connecting thread A (27). The special-shaped connection port A (8), the steel water injection pipe B (26), and the connecting thread B (36) are fixed by welding. The special-shaped connection port B (35), the steel water injection pipe A (24), and the connecting thread A (27) are fixed by welding.

3. The marine large-scale prefabricated UHPC irregular pile foundation system according to claim 2, characterized in that: The inner wall of the connecting thread B (36) is provided with a hollow connecting bolt B (37), and a conical steel base plate (21) is fixedly connected to the bottom end of the hollow connecting bolt B (37). A jet port (38) is provided in the middle of the bottom end of the conical steel base plate (21).

4. The marine large-scale prefabricated UHPC irregular pile foundation system according to claim 3, characterized in that: The inner wall of the connecting thread A (27) is provided with a hollow connecting bolt A (28), and the bottom end of the hollow connecting bolt A (28) is fixedly connected with a special-shaped connecting bolt (20), which is located on the inner wall of the special-shaped connecting port A (8).

5. A marine large-scale prefabricated UHPC irregular pile foundation system according to claim 3, characterized in that: Water injection pipes (10) are symmetrically embedded on both UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4). Irregularly shaped enlarged connection ports (11) are embedded on the outer sides of the water injection pipes (10) at both ends of UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4). Irregularly shaped reinforcing blocks (19) are provided between each set of irregularly shaped enlarged connection ports (11). Irregularly shaped reinforcing steel rods (17) are fixedly inserted through each irregularly shaped reinforcing block (19). Irregularly shaped reinforcing steel rods (17) are provided between UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4) to transmit shear force.

6. The marine large-scale prefabricated UHPC irregular pile foundation system according to claim 1, characterized in that: The top of the steel outer shell A (1) is provided with an irregular connecting platform (5), and the top of the irregular connecting platform (5) is fixedly connected with a pile leg connecting pipe (6). The bottom of the irregular connecting platform (5) is provided with square notches (34) on all four sides. The square notches (34) are provided on the UHPC cantilever connecting plate (9). The outer wall of the irregular connecting platform (5) is provided with bolt connection holes A (29) on all four sides.

7. A marine large-scale prefabricated UHPC irregular pile foundation system according to claim 6, characterized in that: The top of the UHPC cantilever connecting plate (9) on the upper side is provided with a rib plate (7) for connecting irregular piles and the foundation. The outer end of the rib plate (7) for connecting irregular piles and the foundation is provided with a bolt connection hole C (31). The inner end of the rib plate (7) for connecting irregular piles and the foundation is provided with a bolt connection hole B (32). The rib plate (7) for connecting irregular piles and the foundation and the irregular connecting foundation (5) are fixedly connected by fixing bolts B (33). The rib plate (7) for connecting irregular piles and the foundation and the UHPC load-bearing plate A (3) are fixedly connected by fixing bolts A (30).

8. A construction method for large-scale prefabricated UHPC irregular pile foundations at sea, characterized in that: The large-scale prefabricated UHPC irregular pile foundation system for marine applications according to any one of claims 1-7 includes the following steps: Step 1: Prefabricate steel shell A (1), steel shell B (2), UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4) in the factory. UHPC load-bearing plate A (3) and UHPC load-bearing plate B (4) are prefabricated with ultra-high performance concrete and pre-embedded with connecting reinforcing steel plates (13) and steel grooves (14). Step 2: After hoisting the steel outer shell B (2) to the designed pile position on the seabed, carry out the sinking operation. During the sinking process, pressurized water is injected to reduce the sinking resistance. Step 3: Hoist the UHPC load-bearing plate B (4) to the top of the already driven steel shell B (2), so that the steel connecting column (25) is embedded in the sliding groove (22). Auxiliary water injection is carried out during the installation process, and then the subsequent pile segments are cyclically assembled and driven.

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