Sacrificial pile for offshore pile foundation protection and offshore protection system

Abstract

The invention discloses a sacrifice pile for offshore pile foundation protection and an offshore protection system. The sacrifice pile comprises a pile body and at least two layers of annular guide plates, and the annular guide plates are arranged at intervals in the axial direction of the pile body and fixedly connected with the pile body; the annular guide plate on the lowermost layer is arranged close to the bottom end of the pile body; the two layers of annular guide plates are parallel or form an included angle, so that an energy dissipation chamber is formed between the two adjacent layers of annular guide plates; through holes are formed in each layer of annular flow guide plate; at least two layers of annular flow guide plates with holes are fixedly connected with the bottom of the sacrifice pile to form an energy dissipation cavity which is through up and down, so that the flow guide plate on the lowest layer is arranged in front to interfere with a scouring core area of a pile-soil interface, and water flow passes through the through holes and is dissipated in the cavity; source weakening and energy dissipation of down flow and horseshoe-shaped vortex in front of the pile are achieved. According to the structure, the anti-scouring stability and durability of the sacrifice pile are improved, the overall reliability of an offshore pile foundation front protection system formed by the sacrifice pile is remarkably improved, and the engineering service life of the offshore pile foundation front protection system is remarkably prolonged.

Description

Technical Field

[0001] This invention relates to scour protection structures for offshore structures such as offshore wind power foundations and offshore platform pile foundations, and particularly to a sacrificial pile for offshore pile foundation protection and an offshore protection system. Background Technology

[0002] In marine engineering, sacrificial pile groups are often installed on the upstream side of the main pile foundation (such as offshore wind turbine monopiles) as a front-end protective component to protect it from direct scouring and impact. However, sacrificial piles themselves also face severe scouring problems during service. When water flows impact the sacrificial pile, it generates strong downflow and horseshoe-shaped vortices at the pile-soil interface, continuously eroding the surrounding soil and forming scour pits, resulting in a reduction in effective embedment depth and stability. Currently, scouring prevention measures for sacrificial piles mostly follow traditional approaches: passive covering (such as rock dumping) is prone to instability under high-speed currents and the accuracy of underwater construction is difficult to guarantee; while active intervention devices (such as single-layer guide plates) are often installed in the middle of the pile, with limited intervention effect on the pile bottom area where scouring originates, and they are usually independently installed additional components, with risks to the reliability of the connection with the pile and the structural integrity under complex marine loads. Therefore, existing technologies cannot achieve a sacrificial pile structure that is both firmly integrated and can accurately act on the source of scour, while efficiently dissipating the energy of the water flow. As a result, sacrificial piles often fail prematurely due to their own scour, and cannot achieve long-term reliable protection for the main pile foundation. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a sacrificial pile for marine pile foundation protection that is integrated with the bottom of the sacrificial pile, can actively intervene in the flow field at the pile-soil interface, and has a high energy dissipation capacity; on the other hand, it provides a marine protection system.

[0004] Technical solution: The sacrificial pile for marine pile foundation protection according to the present invention includes a pile body and at least two layers of annular guide plates, wherein the annular guide plates are arranged at intervals along the axial direction of the pile body and are all fixedly connected to the pile body; wherein the lowest layer of annular guide plates is located near the bottom end of the pile body; the two layers of annular guide plates are arranged parallel to each other or at an angle to each other, thereby forming an open energy dissipation chamber that surrounds the pile body and runs vertically through the adjacent two layers of annular guide plates; each layer of annular guide plates is provided with through holes.

[0005] Preferably, the through-hole shape of the annular guide plate is circular, oblong, or venturi-shaped, wherein the long axis of the oblong through-hole is arranged radially along the guide plate, which can guide the water flow into the energy dissipation chamber more smoothly and reduce the local resistance generated by the water flow impact.

[0006] Preferably, the through holes are arranged in a staggered pattern on the guide plate to avoid forming concentrated water flow channels, making the water flow more evenly distributed on the surface of the guide plate, and further weakening the power of vortex formation.

[0007] Preferably, the diameter of the through hole is 30mm to 150mm.

[0008] Preferably, the thickness of the annular guide plate is 15mm to 60mm.

[0009] Preferably, the height of the energy dissipation chamber is 50mm to 200mm. This spacing range ensures that the water flow has enough space to dissipate energy, while also preventing the chamber from being too large, which would lead to a decrease in structural stability.

[0010] Preferably, the energy dissipation chamber is filled with a porous energy-absorbing material.

[0011] Preferably, the porous energy-absorbing material is polyurethane foam.

[0012] Preferably, the energy dissipation chamber is an unfilled cavity.

[0013] Preferably, along the axial direction of the pile, the opening ratio of the annular guide plate located in the upper layer is greater than that of the annular guide plate located in the lower layer.

[0014] Preferably, it further includes a connection reinforcement structure; the connection reinforcement structure includes a connection flange fixed to the circumference of the pile body, and a plurality of stiffening ribs evenly distributed along the circumference of the pile body, the stiffening ribs being connected between the connection flange and at least one layer of the annular guide plate.

[0015] Preferably, the upper end of the stiffening rib is welded to the pile wall and the connecting flange, and the lower end is welded to the upper surface of the annular guide plate.

[0016] Preferably, the sacrificial pile and the annular guide plate are assembled as a whole by welding in a land prefabrication yard to form an integral structure that cannot be disassembled.

[0017] Preferably, the annular guide plate is a horizontal annular plate or an inclined annular plate that forms an acute angle with the horizontal plane.

[0018] Preferably, the ratio of the projected area of ​​the total outer contour of the annular guide plate on the horizontal plane to the cross-sectional area of ​​the pile body is 3:1 to 8:1, which maintains the protective effect while optimizing the structural economy and construction feasibility.

[0019] Preferably, the pile body is a hollow pile structure with radial grouting holes at the bottom.

[0020] Preferably, high-pressure permeation grouting is performed on the soil below the pile bottom and the guide plate through the grouting system and radial grouting holes inside the pile.

[0021] Preferably, the grouting material is a highly permeable, early-strength cement-based grout to form a cement-soil reinforced plug.

[0022] Preferably, the lower surface of the bottom annular guide plate is provided with a silt-promoting layer, and the upper surface of the top annular guide plate is provided with a protective coating.

[0023] Preferably, the siltation-promoting layer is a biodegradable fiber pad or bio-attachment substrate laid on the lower surface of the lowest guide plate.

[0024] Preferably, the protective coating is a corrosion-resistant elastic coating applied to the uppermost guide plate surface, or a bonded layer of graded crushed stone.

[0025] Preferably, the sacrificial pile or guide plate also integrates a monitoring unit, which includes a micro flow meter and an inclination sensor. The data is transmitted to the host computer via a cable or wireless module laid along the pile body.

[0026] Preferably, the material of the annular guide plate is seawater corrosion resistant steel, duplex stainless steel, fiberglass composite material, or carbon fiber reinforced polymer.

[0027] A marine pile foundation protection system includes a main pile foundation and a protective structure located on its upstream side, the protective structure including at least one of the aforementioned sacrificial piles for marine pile foundation protection.

[0028] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: By fixing at least two layers of perforated annular guide plates to the bottom of the sacrificial pile to form an open energy dissipation chamber that runs vertically through it, the lowest layer of guide plates intervenes in the core scour area of ​​the pile-soil interface. Combined with the flow of water through the through-holes and dissipation within the chamber, this weakens and dissipates the source of the downward flow and horseshoe-shaped vortex in front of the pile. This structure significantly improves the scour resistance and durability of the sacrificial pile itself, and solves the problem of premature degradation of the sacrificial pile's protective effectiveness caused by weak connections between the protective structure and the pile body and inaccurate positioning in existing technologies. Therefore, it significantly enhances the overall reliability and engineering life of the marine pile foundation pre-protection system constructed from this structure. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 This is a schematic cross-sectional view of the overall structure of the present invention;

[0031] Figure 3 This is a top view of the overall structure of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0033] like Figure 1-3As shown in this embodiment, a sacrificial pile and marine protection system for marine pile foundation protection are provided. The core of this system lies in the innovative structure of the sacrificial pile, which actively intervenes in the flow field through an integrated design, solving the scouring problem of the sacrificial pile itself at its source. The sacrificial pile includes a pile body 1 as the core supporting component, and at least two layers of annular guide plates 2 fixedly connected to it. These annular guide plates 2 are arranged at intervals along the axial direction of the pile body 1, with the lowest annular guide plate 2 intentionally positioned near the bottom of the pile body 1, allowing it to directly cover and act on the pile-soil interface where the scouring force is strongest, thereby proactively intercepting the downward flow in front of the pile that causes scouring. The annular guide plates 2 can be designed as horizontal rings or slightly inclined rings at an angle of 0-15 degrees to the horizontal plane. Their inclination angle helps guide the water flow to diffuse outwards, further reducing the direct impact on the soil around the pile. To withstand harsh marine corrosion environments and ensure long service life, the annular guide plate 2 can be made of seawater corrosion-resistant steel (such as Q355NH), duplex stainless steel, fiberglass composite material, or carbon fiber reinforced polymer. Its thickness is designed between 15mm and 60mm based on hydrodynamic loads, ensuring sufficient structural strength. Adjacent annular guide plates 2, arranged parallel or at an angle, form an open energy dissipation chamber 3 that surrounds the pile body 1 and extends vertically. Each annular guide plate 2 features a carefully designed array of through-holes arranged in a staggered pattern. The through-hole shapes include circular, oblong, or venturi-shaped, with diameters ranging from 30mm to 150mm, and an overall open area ratio controlled between 20% and 50%. The combination of this open chamber and through-hole array physically constitutes a highly efficient "flow guidance-energy dissipation" unit: it can both divide and guide the water flow in front of the pile, while allowing some water flow to pass smoothly through, avoiding the negative pressure under the plate and local scouring transfer that may be caused by completely blocking the water flow, thus achieving a dynamic balance between "guidance" and "permeability". To ensure the overall reliability of this composite structure during construction and operation, the sacrificial pile also includes a connecting reinforcement structure 4, which consists of an annular connecting flange 6 welded to the bottom of the pile body 1 and multiple circumferentially distributed stiffening ribs 5, which firmly transfer the load of the pile body 11 to the guide plate, forming a high-strength rigid whole. To further improve the energy dissipation effect, the energy dissipation chamber 3 can be filled with porous energy-absorbing materials such as polyurethane foam, and the opening ratio of the upper annular guide plate 2 is usually set to be greater than that of the lower layer, so as to guide the water flow to undergo more sufficient turbulence and energy dissipation in the chamber. The ratio of the total projected area of ​​the annular guide plate 2 to the cross-sectional area of ​​the pile body 1 is 3:1 to 8:1, which ensures the effectiveness of the protection range. Furthermore, the pile body 1 itself can be designed as a hollow structure with radial grouting holes at the bottom, creating conditions for subsequent foundation reinforcement. A biodegradable fiber mat or other silt-promoting layer can be added to the lower surface of the bottom annular guide plate 2 to accelerate sediment deposition and stabilize the seabed; a protective covering layer can be applied to the surface of the top annular guide plate 2 to resist impact. The entire structure is prefabricated in one integrated manner on land, achieving convenient "one-time sinking" construction at sea.

[0034] The sacrificial pile works by actively intervening in the flow field at the pile-soil interface to suppress scour at its source. When the ocean current impacts the pile 1, the lowest annular guide plate 2, closest to the pile bottom, directly obstructs the formation of the downward flow in front of the pile, dividing the water flow. Part of the water flow enters the energy dissipation chamber 3 through the through-holes of the upper annular guide plate 2. In this chamber, due to changes in the flow cross-section and interaction with the chamber wall or the porous energy-absorbing material, violent turbulence and friction are generated, thereby dissipating a large amount of its kinetic energy. Subsequently, the weakened water flow flows out through the through-holes of the lower annular guide plate 2. This process achieves a balance between "guidance-energy dissipation-permeability," effectively weakening the intensity and scale of the horseshoe-shaped vortex that causes scour, avoiding the formation of scour pits, and thus ensuring the burial depth stability and bearing capacity of the sacrificial pile itself.

[0035] Its installation and use follow an integrated construction concept to ensure the integrity of the structure. First, the assembly of all core structures is completed in a land-based prefabrication yard: pile body 1 is prepared, and connecting flange 6 is welded to its circumference; the prefabricated annular guide plate 2, stiffening ribs 5, and connecting flange 6 are assembled into a component, forming a non-removable integrated structure; all welds undergo non-destructive testing, and the entire structure is coated with heavy-duty anti-corrosion paint or sacrificial anodes are installed. Subsequently, the integrated structure is transported to the target sea area and erected using a crane vessel. For driven pile construction, a hydraulic hammer is used to drive the sacrificial pile to the designed seabed elevation, during which the levelness or design inclination of the guide plate needs to be monitored and adjusted; for drilled pile construction, a hole is drilled first, then the structure is hoisted and implanted, and finally underwater concrete is poured around the pile. After pile driving is completed, an optional step is to use the grouting system within pile body 1 to perform high-pressure permeation grouting into the soil below the pile bottom and guide plate, injecting early-strength cement-based grout to form a "cement-soil reinforcement plug." In addition, silt-promoting layers, protective cladding layers, or flow velocity and tilt angle monitoring sensors integrated into the structure can be installed using underwater robots (ROVs). Ultimately, the entire offshore pile foundation protection system consists of one or more such sacrificial piles located on the upstream side of the main pile foundation, forming a stable forward protective barrier.

Claims

1. A sacrificial pile for marine pile foundation protection, comprising a pile body (1), characterized in that, Also includes: At least two layers of annular guide plates (2) are arranged at intervals along the axial direction of the pile body (1) and are fixedly connected to the pile body (1); the lowest layer of annular guide plates (2) is set near the bottom end of the pile body (1); the two layers of annular guide plates (2) are arranged parallel to each other or at an angle, thereby forming an open energy dissipation chamber (3) that surrounds the pile body (1) and runs vertically between the two adjacent layers of annular guide plates (2); each layer of annular guide plates (2) is provided with through holes.

2. The sacrificial pile according to claim 1, characterized in that, The energy dissipation chamber (3) is filled with porous energy-absorbing material.

3. The sacrificial pile according to claim 1, characterized in that, Along the axial direction of the pile, the opening ratio of the annular guide plate (2) located in the upper layer is greater than that of the annular guide plate (2) located in the lower layer.

4. The sacrificial pile according to claim 1, characterized in that, It also includes a connecting reinforcement structure (4); the connecting reinforcement structure (4) includes a connecting flange (6) fixed to the circumference of the pile body (1), and a plurality of stiffening ribs (5) evenly distributed along the circumference of the pile body (1), the stiffening ribs (5) being connected between the connecting flange (6) and at least one layer of the annular guide plate (2).

5. The sacrificial pile according to claim 1, characterized in that, The annular guide plate (2) is a horizontal annular plate or an inclined annular plate that forms an acute angle with the horizontal plane.

6. The sacrificial pile according to claim 1, characterized in that, The ratio of the projected area of ​​the total outer contour of the annular guide plate (2) on the horizontal plane to the cross-sectional area of ​​the pile body (1) is 3:1 to 8:

1.

7. The sacrificial pile according to claim 1, characterized in that, The pile body (1) is a hollow pile structure with radial grouting holes at the bottom.

8. The sacrificial pile according to claim 1, characterized in that, The lower surface of the bottom annular guide plate (2) is provided with a siltation-promoting layer, and the upper surface of the top annular guide plate (2) is provided with a protective coating.

9. The sacrificial pile according to claim 1, characterized in that, The material of the annular guide plate (2) is seawater corrosion resistant steel, duplex stainless steel, fiberglass composite material or carbon fiber reinforced polymer.

10. A marine pile foundation protection system, comprising a main pile foundation and a protective structure located on its current-facing side, characterized in that, The protective structure includes at least one sacrificial pile for marine pile foundation protection as described in any one of claims 1 to 9.

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