Optimization method of anti-scour device for offshore jacket pile leg, anti-scour device and method

Abstract

The invention belongs to the technical field of ocean engineering, and provides an offshore jacket pile leg anti-scouring device optimization method and an anti-scouring device and method.The anti-scouring device comprises a plurality of anti-scouring assemblies connected end to end; each anti-scouring assembly comprises an arc-shaped surrounding plate, a fan-shaped horizontal plate vertically arranged on the arc-shaped surrounding plate, a first wing plate, a second wing plate and supporting legs, wherein the first wing plate and the second wing plate are arranged at the two ends of the fan-shaped horizontal plate, and the supporting legs are arranged on the fan-shaped horizontal plate. The height of the arc-shaped surrounding plate is determined according to the maximum scouring influence depth; the width of the fan-shaped horizontal plate is determined based on the diameter of the pile leg by considering the impact force of water flow on the pile leg; the height of the supporting legs is determined based on prediction of the maximum scouring depth of the target sea area and the effective built-in depth of the supporting legs under the seabed, the height of the arc-shaped surrounding plate, the width of the fan-shaped horizontal plate, the height of the supporting legs and other main sizes are determined by considering the actual environment, and the adaptability of the anti-scouring device to the actual environment requirement is improved.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology, and in particular relates to an optimization method for an anti-scour device for offshore jacket leg piles, an anti-scour device and method. Background Technology

[0002] Offshore jacket platforms are critical infrastructure for offshore oil and gas resource development. Their legs, as the core load-bearing components supporting the entire platform, are subjected to repeated dynamic loads such as waves and ocean currents over long periods. This scouring process leads to the continuous loss of seabed soil around the piles, forming localized scour pits. This severely weakens the vertical and lateral bearing capacity of the pile foundation, significantly affecting the overall stability of the jacket platform and posing a significant risk of catastrophic accidents such as structural overturning.

[0003] Currently, in addition to measures such as riprap, concrete pads, or flexible protection systems, the addition of wing plates to pile legs has been widely used in scour prevention technologies. However, current wing plate-type scour prevention devices directly utilize the scour prevention effect of the wing plates, and the design does not take into account the main dimensional requirements of the wing plates and other key components, resulting in poor adaptability of current scour prevention devices to actual environmental requirements. Furthermore, current wing plate-type scour prevention devices require bolts and other fasteners for installation, which is a complex process, and the bolts and other fasteners are prone to unstable connections and damage over time. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an optimization method, device, and method for an anti-scour device for offshore jacket foundation legs. The height of the arc-shaped circumferential plate is determined based on the maximum scour impact depth. Considering the impact force of water flow on the legs, the width of the fan-shaped horizontal plate is determined based on the leg diameter. The height of the legs is determined based on the predicted maximum scour depth of the target sea area and the effective embedment depth of the legs under the seabed. Taking into account the actual environment, the main dimensions such as the height of the arc-shaped circumferential plate, the width of the fan-shaped horizontal plate, and the height of the legs are determined, thereby improving the adaptability of the anti-scour device to the requirements of the actual environment.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an optimization method for an anti-scour device for offshore jacket foundation legs, employing the following technical solution: An optimization method for an anti-scour device for offshore jacket foundation legs, the anti-scour device comprising multiple anti-scour components connected end-to-end; each anti-scour component comprising an arc-shaped circumferential plate, a fan-shaped horizontal plate vertically disposed on the arc-shaped circumferential plate, a first wing plate and a second wing plate disposed at both ends of the fan-shaped horizontal plate, and a support leg disposed on the fan-shaped horizontal plate; the method comprising: The height of the arc-shaped circumferential plate is determined based on the maximum scour impact depth; considering the impact force of water flow on the pile leg, the width of the fan-shaped horizontal plate is determined based on the pile leg diameter; the height of the support leg is determined based on the prediction of the maximum scour depth of the target sea area and the effective embedment depth of the support leg under the seabed.

[0006] Furthermore, the height of the arc-shaped circumferential plate is the sum of the maximum scour impact depth and the safety margin.

[0007] Furthermore, for common flow velocity ranges, the ratio of the width of the fan-shaped horizontal plate to the diameter of the pile leg is a prefabricated value.

[0008] Furthermore, the height of the outriggers is predicted based on the maximum possible scour depth of the target sea area, and ensures that the effective embedment depth of the outriggers under the seabed is still greater than the preset depth after scour occurs.

[0009] Furthermore, the effective embedment depth of the outrigger Must meet: and ; in, To estimate the upward pulling force; It is the horizontal bending moment; The diameter of the outrigger; This refers to the side friction resistance of the soil. This represents the ultimate resistance of the soil.

[0010] Furthermore, the first wing plate is provided with a protrusion; the second wing plate is provided with a slot for inserting into the protrusion; the protrusion is provided with protrusions on both sides, and the inner wall of the slot is provided with a groove that matches the protrusion.

[0011] To achieve the above objectives, in a second aspect, the present invention also provides an anti-scouring device for the legs of a offshore jacket foundation, employing the following technical solution: A scour protection device for offshore jacket foundation legs includes multiple scour protection components connected end to end; each scour protection component includes an arc-shaped circumferential plate, a fan-shaped horizontal plate vertically arranged on the arc-shaped circumferential plate, a first wing plate and a second wing plate arranged at both ends of the fan-shaped horizontal plate, and a support leg arranged on the fan-shaped horizontal plate. The height of the arc-shaped circumferential plate is determined based on the maximum scour impact depth; considering the impact force of water flow on the pile leg, the width of the fan-shaped horizontal plate is determined based on the pile leg diameter; the height of the support leg is determined based on the prediction of the maximum scour depth of the target sea area and the effective embedment depth of the support leg under the seabed.

[0012] Furthermore, the first wing plate is provided with a protrusion; the second wing plate is provided with a slot for inserting into the protrusion.

[0013] Furthermore, the protrusions are provided on both sides of the protrusion, and the grooves on the inner wall of the slot are adapted to the protrusions.

[0014] To achieve the above objectives, in a third aspect, the present invention also provides a method for preventing scour of the legs of a offshore jacket foundation, employing the following technical solution: A method for preventing scour of offshore jacket foundation legs, using the offshore jacket foundation leg scour prevention device described in the second aspect, includes: using the arc-shaped circumferential plate to suppress the formation of scour pits, using the fan-shaped horizontal plate to achieve disturbance and energy dissipation of the water flow around the leg, using the first wing plate and the second wing plate to transfer wave loads to the entire scour prevention device; and using the support legs to ensure the overall stability of the scour prevention device.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention comprises multiple anti-scour components connected end-to-end; each anti-scour component includes an arc-shaped circumferential plate, a fan-shaped horizontal plate vertically disposed on the arc-shaped circumferential plate, a first wing plate and a second wing plate disposed at both ends of the fan-shaped horizontal plate, and a support leg disposed on the fan-shaped horizontal plate; wherein, the height of the arc-shaped circumferential plate is determined based on the maximum scour influence depth; considering the impact force of water flow on the support leg, the width of the fan-shaped horizontal plate is determined based on the diameter of the support leg; the height of the support leg is determined based on the prediction of the maximum scour depth of the target sea area and the effective embedment depth of the support leg under the seabed. The main dimensions such as the height of the arc-shaped circumferential plate, the width of the fan-shaped horizontal plate, and the height of the support leg are determined considering the actual environment, thereby improving the adaptability of the anti-scour device to the requirements of the actual environment.

[0016] 2. The present invention provides a protrusion on the first wing plate and a slot for inserting the protrusion on the second wing plate. The protrusion has protrusions on both sides and grooves on the inner wall of the slot that are adapted to the protrusions. The installation on the pile leg is achieved by inserting adjacent anti-scour components, without the need for bolts or other fasteners. Attached Figure Description

[0017] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0018] Figure 1 This is a schematic diagram of the device structure according to Embodiment 1 of the present invention; Figure 2 This is a top view of the device according to Embodiment 1 of the present invention; Among them, 1. Anti-erosion component; 101. Arc-shaped circumferential plate; 102. Fan-shaped horizontal plate; 103. First wing plate; 104. Second wing plate; 105. Protrusion; 106. Slot; 107. Raised; 2. Support leg. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] Existing protective technologies typically employ measures such as rock dumping, concrete mattresses, or flexible protective systems. However, these methods generally suffer from problems such as cumbersome construction, high costs, insufficient durability, and limited protective effectiveness. In complex and harsh marine environments, there is a particular lack of comprehensive solutions that can simultaneously meet the requirements of efficient flow diversion, modular and rapid installation, and self-resistance to erosion.

[0022] Traditional methods focus on temporary protection during construction, lacking long-term durability and thus unsuitable as a permanent solution. Existing technologies have limitations in terms of durability, economy, ease of construction, and long-term reliability. Material-based methods have high maintenance costs, structural installation methods are complex to construct and have limited adaptability, temporary protection methods lack durability, and numerical simulation methods cannot directly provide engineering protection.

[0023] As described in the background section, the method of adding wing plates to the pile legs has been well applied. Current wing plate-type scour protection devices directly utilize the scour protection effect of the wing plates. However, the design does not take into account the main dimensional requirements of the wing plates and other major components, resulting in poor adaptability of the current scour protection devices to actual environmental requirements. In addition, current wing plate-type scour protection devices require the use of bolts and other fasteners for installation, which is complicated. Furthermore, bolts and other fasteners have problems such as unstable connections and easy damage over time.

[0024] To solve the above problems, such as Figure 1 As shown, one embodiment of the present invention provides an optimized method for an anti-scour device for offshore jacket foundation legs, which can fundamentally alleviate scour around the pile, is easy to construct and maintain, and has good environmental adaptability. The anti-scour device includes multiple anti-scour components 1 connected end-to-end, and legs 2 mounted on each anti-scour component 1; each anti-scour component 1 includes an arc-shaped circumferential plate 101, a fan-shaped horizontal plate 102, a first wing plate 103, a second wing plate 104, a protrusion 105, a groove 106, and a protrusion 107, etc.

[0025] Optionally, the anti-scour device is arranged around the periphery of the guide frame pile leg. The anti-scour device includes four identical anti-scour components 1, which are connected end to end to form a closed ring structure. Each anti-scour component 1 includes a vertically arranged arc-shaped circumferential plate 101, a horizontally arranged fan-shaped horizontal plate 102 (1 / 4 circular ring plate), and a vertically arranged first wing plate 103 and second wing plate 104. The inner wall curvature radius of the arc-shaped circumferential plate 101 matches the pile leg radius, and after closing, it fits tightly against the outer wall of the pile leg to form a ring with a diameter of 3000mm. The fan-shaped horizontal plate 102 is arranged between the bottom of the first wing plate 103 and the second wing plate 104. The first wing plate 103 and the second wing plate 104 are vertically arranged at both ends of the fan-shaped horizontal plate 102, and the extension line of the center normal of the fan-shaped horizontal plate 102 passes through the central axis of the pile leg.

[0026] like Figure 1 and Figure 2 As shown, at least one protrusion 105 is provided on the first wing plate 103; at least one slot 106 is provided on the second wing plate 104 that can be inserted into the protrusion 105. Adjacent anti-erosion components 1 are mated and locked together by the protrusions 105 and slots 106 radially provided on the first wing plate 103 and the second wing plate 104. Optionally, two protrusions 105 and two slots 106 are arranged at each mating point. Protrusions 107 can be provided on both sides of the protrusion 105. When the protrusion 105 is inserted into the slot 106, the protrusion 107 presses against the slot 106 to improve connection stability. To further improve the insertion stability, a groove adapted to the protrusion 107 can be provided on the inner wall of the slot 106. The protrusion 107 is inserted into the groove to prevent the protrusion 105 from coming out of the slot 106. This connection method facilitates load transfer between plates, ensures the integrity of the structure, and is easy to install and prevents displacement.

[0027] Optional optimization methods for the anti-scour device of offshore jacket foundation legs include: The arc-shaped circumferential plate 101 has a thickness of 100mm and a vertical height of 2000mm. This height has been optimized to cover the depth range where waves and water flow cause the main scouring of the seabed around the pile, thereby effectively suppressing the formation of scouring pits.

[0028] The radial width of the fan-shaped horizontal plate 102 is 7000mm, ranging from an inner diameter of 3000mm to an outer diameter of 10000mm, and its thickness is 100mm. This radial width balances protective effect and construction cost, achieving both flow disturbance and energy dissipation around the pile legs while reasonably controlling the amount of steel used. Simultaneously, the fan-shaped horizontal plate 102 serves as an integral base, and its outward extension allows the anchoring points of the bottom support legs 2 to be located away from the pile center, thereby significantly enhancing the device's anti-overturning capability.

[0029] The first wing plate 103 and the second wing plate 104 are 100 mm thick and have the same height as the arc-shaped circumferential plate 101, which is 2000 mm. The main function of the first wing plate 103 and the second wing plate 104 is to ensure the connection stiffness between adjacent anti-scour components 1 and to effectively transfer wave loads to the entire annular structure. Their thickness design ensures sufficient section modulus to resist shear forces, while their height, consistent with the arc-shaped circumferential plate 101, ensures the continuity of force flow transmission and avoids local stress concentration caused by abrupt changes in stiffness. This is crucial for maintaining the structural integrity of the device under long-term fluctuating loads.

[0030] The support leg 2 is a cylindrical structure with a radius of 500mm and a height of 1500mm. It is vertically fixed to the lower surface of the fan-shaped horizontal plate 102, and its lower end is equipped with a sharp cutting edge to facilitate insertion into the seabed. The height of the support leg 2 is set with reference to the expected scour depth to ensure that the support leg can maintain an effective embedding depth after local scour of the seabed, ensuring the overall stability of the device. The design of the support leg 2 facilitates installation; it is initially embedded into the seabed by its own weight to achieve temporary fixation, providing convenience for the subsequent installation of other units.

[0031] The arc-shaped circumferential plate 101, the fan-shaped horizontal plate 102, the first wing plate 103, the second wing plate 104, and the support leg 2 are integrally welded structures. The anti-erosion device is made of high-strength materials resistant to seawater corrosion, such as stainless steel, galvanized steel, or marine-grade aluminum alloy.

[0032] The dimensions of the key components of the anti-scouring device are determined based on a system optimization design that considers marine environmental loads and protection objectives, rather than conventional selection. The determination process is as follows: S1. Determination of the height H of the arc-shaped circumferential plate 101: The primary consideration is the depth of impact of major waves and currents on the seabed. The maximum scouring depth is determined by analyzing the wave spectrum and current velocity profile of the target sea area. The height H of the arc-shaped circumferential plate 101 must meet the following requirements: ; in, To provide a safety margin and to accommodate extreme sea conditions and installation errors, the 2000mm height is based on typical operating conditions in a preset sea area (e.g., significant wave height). (Period T = 8-10 s), determined through numerical simulation and water tank experiments. Approximately 1.5m, and take =0.5m was optimized to ensure that the pile-around flow and vortex development can be effectively suppressed under the design sea conditions, thereby controlling the formation and expansion of scour pits.

[0033] S2. Determination of the radial width L of the sector-shaped horizontal plate 102: The design objective of the fan-shaped horizontal plate 102 is to provide sufficient turbulence dissipation area and anti-overturning moment while controlling material usage. The width L of the fan-shaped horizontal plate 102 is related to the impact force of the water flow on the pile leg. The required overturning stability of the device is directly related to this. Based on the momentum theorem and empirical formulas for flow resistance, the required turbulence range is initially estimated. The width L = 7000mm (outer diameter 10000mm) is based on a leg diameter D = 3000mm, and is derived through simulation or optimization calculations for a common flow velocity range v = 1-3m / s. or At the same time, without significantly increasing the amount of steel used, the protection range is sufficient to change the flow field at the stagnation point in front of the pile leg and guide the high-speed water flow to the periphery, effectively dissipating energy, while ensuring that the bottom support leg anchorage point obtains sufficient anti-overturning lever arm. Through parameter sensitivity analysis, this ratio achieves the optimal balance between cost and protection effectiveness.

[0034] S3, Bottom support leg height h Determination: Bottom leg height h When determining the target depth, the key is to ensure that the maximum expected scour depth is reached. Under these conditions, the device remains stable. The outriggers must provide sufficient embedment depth to resist the uplift and horizontal forces caused by waves and currents. Based on marine soil mechanics and pile foundation design principles, the effective embedment depth of the outriggers... Must meet and Conditions, among which, To estimate the upward force, d is the horizontal bending moment, and d is the diameter of the support leg. For soil side friction, This represents the ultimate resistance of the soil. The 1500mm height is based on the maximum possible scour depth in the target sea area. (Approximately 0.8-1.0m) Predict and ensure the effective embedment depth of the outriggers under the seabed after scour occurs. The diameter remains greater than 1.0m to meet safety requirements for overturning and slippage resistance. The cutting edge design is based on the principle of static pressing, reducing penetration resistance and facilitating installation.

[0035] S4. Determination of plate thickness t: The main consideration is the strength and stiffness requirements of the structure under wave load. Through finite element analysis, the dynamic water pressure generated by the design wave height on the arc-shaped circumferential plate and the circular ring plate is simulated, and the stress is checked by considering the combination of loads such as the structure's self-weight and earth pressure.

[0036] An embodiment of the present invention also provides a method for preventing scour of offshore jacket foundation legs, which uses the aforementioned offshore jacket foundation leg scour prevention device, including: using the arc-shaped circumferential plate to suppress the formation of scour pits, using the fan-shaped horizontal plate to achieve disturbance and energy dissipation of the water flow around the leg, using the first wing plate and the second wing plate to transfer wave loads to the entire scour prevention device; and using the support legs to ensure the overall stability of the scour prevention device.

[0037] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. An optimization method for the anti-scour device of the legs of a offshore jacket foundation, characterized in that, The anti-erosion device includes multiple anti-erosion components connected end-to-end; each anti-erosion component includes an arc-shaped circumferential plate, a fan-shaped horizontal plate vertically disposed on the arc-shaped circumferential plate, a first wing plate and a second wing plate disposed at both ends of the fan-shaped horizontal plate, and a support leg disposed on the fan-shaped horizontal plate; the method includes: The height of the arc-shaped circumferential plate is determined based on the maximum scour impact depth; considering the impact force of water flow on the pile leg, the width of the fan-shaped horizontal plate is determined based on the pile leg diameter; the height of the support leg is determined based on the prediction of the maximum scour depth of the target sea area and the effective embedment depth of the support leg under the seabed.

2. The optimization method for the anti-scouring device of the offshore jacket foundation leg as described in claim 1, characterized in that, The height of the arc-shaped circumferential plate is the sum of the maximum scour impact depth and the safety margin.

3. The optimization method for the anti-scouring device of the offshore jacket foundation leg as described in claim 1, characterized in that, For common flow velocity ranges, the ratio of the width of the sector-shaped horizontal plate to the diameter of the pile leg is a prefabricated value.

4. The optimization method for the anti-scouring device of the offshore jacket foundation leg as described in claim 1, characterized in that, The height of the outriggers is based on the prediction of the maximum possible scour depth in the target sea area, and ensures that the effective embedment depth of the outriggers under the seabed is still greater than the preset depth after scour occurs.

5. The optimization method for the anti-scour device of the offshore jacket foundation leg as described in claim 4, characterized in that, The effective embedment depth of the outrigger Must meet: and ; in, To estimate the upward force; It is the horizontal bending moment; The diameter of the outrigger; This refers to the side friction resistance of the soil. This represents the ultimate resistance of the soil.

6. The optimization method for the anti-scouring device of the offshore jacket foundation leg as described in claim 1, characterized in that, The first wing plate is provided with a protrusion; the second wing plate is provided with a slot for inserting into the protrusion; the protrusion is provided with protrusions on both sides, and the inner wall of the slot is provided with a groove that matches the protrusion.

7. A scour prevention device for the legs of a offshore jacket foundation, characterized in that, It includes multiple anti-scour components connected end to end; each anti-scour component includes an arc-shaped circumferential plate, a fan-shaped horizontal plate vertically arranged on the arc-shaped circumferential plate, a first wing plate and a second wing plate arranged at both ends of the fan-shaped horizontal plate, and a support leg arranged on the fan-shaped horizontal plate. The height of the arc-shaped circumferential plate is determined based on the maximum scour impact depth; considering the impact force of water flow on the pile leg, the width of the fan-shaped horizontal plate is determined based on the pile leg diameter; the height of the support leg is determined based on the prediction of the maximum scour depth of the target sea area and the effective embedment depth of the support leg under the seabed.

8. The anti-scouring device for offshore jacket foundation legs as described in claim 7, characterized in that, The first wing plate is provided with a protrusion; the second wing plate is provided with a slot for insertion into the protrusion.

9. The anti-scouring device for offshore jacket foundation legs as described in claim 8, characterized in that, The protrusion has protrusions on both sides, and the inner wall of the slot has grooves that fit the protrusions.

10. A method for preventing scour of the legs of a offshore jacket foundation, characterized in that, The scour protection device for offshore jacket legs as described in any one of claims 7-9 is used, comprising: using the arc-shaped circumferential plate to suppress the formation of scour pits; using the fan-shaped horizontal plate to achieve disturbance and energy dissipation of the water flow around the legs; using the first wing plate and the second wing plate to transfer wave loads to the entire scour protection device; and using the legs to ensure the overall stability of the scour protection device.

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