Design method for carrying out secondary stability intervention on submarine cable by adopting pressing block type structure

Abstract

The invention belongs to the technical field of submarine cable engineering, and discloses a design method for carrying out secondary stability intervention on a submarine cable by adopting a pressing block type structure. The method comprises the following steps: 1) based on water velocity, wave height and tide period data of a target sea area, calculating a seabed flow characteristic velocity in an extreme environment through an empirical formula; 2) calculating hydrodynamic characteristics and in-place stability of the cable by combining the diameter, the dead weight and the flow parameters of the cable, and determining required additional lateral resistance; 3) analyzing the hydrodynamic coefficient and the self stability of the pressing block type structure through numerical simulation or physical experiments, and quantifying the lateral resistance provided by the pressing block for the cable; 4) according to the cable stability requirement, designing the distribution spacing and total number of the pressing blocks to form a preliminary layout scheme; and 5) improving the anti-skid performance by optimizing the structural size and shape of the pressing block, and carrying out iterative optimization on the layout scheme in combination with construction quantity evaluation so as to reduce the engineering cost.

Description

Technical Field

[0001] The invention belongs to the technical field of submarine cable engineering, and relates to a design method for performing secondary stabilization intervention on a submarine cable by using a compression block structure, aiming to improve the stability and safety of the submarine cable in a complex marine environment. Background Art

[0002] Submarine cables are important infrastructure for marine energy transmission, communication and data transmission, and are widely used in offshore wind power, cross-sea communication, marine observation and other fields. However, submarine cables face complex marine environmental challenges during operation, including water currents, waves, tides, changes in seabed topography, etc. These factors may cause cable displacement, wear, fatigue and even breakage, seriously affecting their safety and service life.

[0003] Traditional submarine cable stabilization methods mainly rely on the weight of the cable itself and the burial depth. For example, by burying the cable at a certain depth below the seabed, the covering effect of the soil is used to reduce the direct impact of water flow and waves. However, this method has many limitations in practical applications: Limited burial depth: In some sea areas, the geological conditions of the seabed are complex (such as rock layers or hard soil), making it difficult to achieve deep burial. Poor environmental adaptability: Under extreme environmental conditions (such as storms, typhoons, and strong currents), buried cables may still be subject to significant hydrodynamic loads, causing displacement or damage. Difficult construction: Deeply buried cables require complex construction equipment and techniques, which are costly and take a long time. Difficult maintenance: Once a cable fails, it is difficult to repair and maintain deeply buried cables, which may result in long-term service interruptions.

[0004] In order to overcome the shortcomings of traditional methods, some secondary stabilization intervention technologies have emerged in recent years, such as the use of counterweights, anchoring devices or flexible protective structures. However, these technologies still have the following problems in practical applications. Lack of systematic design: Existing technologies are often designed only for a single environmental condition and lack comprehensive consideration of the complex marine environment. Insufficient stability: Some secondary stabilization structures are difficult to provide sufficient anti-slip and anti-overturning capabilities under extreme environmental conditions. Poor economy: Some technologies require a large amount of materials and high-cost construction, making them difficult to promote and apply on a large scale. Environmental impact: Some stabilization structures may have adverse effects on the marine ecological environment, such as destroying seabed habitats or hindering the activities of marine organisms.

[0005] Therefore, there is an urgent need for a systematic, economical, efficient and environmentally friendly method for secondary stabilization intervention of submarine cables to cope with the challenges of complex marine environments and ensure the long-term stability and safety of submarine cables. In response to the above problems, the present invention proposes a design method for secondary stabilization intervention of submarine cables using a briquetting structure. Through scientific calculation of the forces on the submarine cable and the briquetting structure and optimization of the briquetting structure form and layout, the ability of the submarine cable to resist environmental interference is significantly improved, while reducing construction costs and environmental impacts. Summary of the invention

[0006] The purpose of the present invention is to provide a design method for secondary stability intervention of submarine cables using a briquette-type structure, by scientifically calculating the stress and instability modes of the submarine cable and the submarine briquette structure, and optimizing the parameters and layout of the briquette structure, to ensure the long-term stability of the submarine cable in a complex marine environment.

[0007] The technical solution of the present invention:

[0008] A design method for secondary stability intervention of submarine cables using a briquette structure comprises the following steps:

[0009] (1) Calculation of seabed flow conditions

[0010] Collect marine environmental data of the target sea area, including water velocity, wave height, and tidal period; use numerical simulation tools or empirical formulas to calculate seabed flow conditions, including unidirectional flow velocity and wave water particle velocity;

[0011] (2) Hydrodynamics and in-situ stability assessment of submarine cables

[0012] Forces on exposed submarine cables, including horizontal hydrodynamic component F x-c , vertical hydrodynamic component F y-c , the friction force F between the cable and the seabed f-c and the buoyancy weight W of the cable s-c The hydrodynamic force on the submarine cable is calculated as follows:

[0013]

[0014] Among them, C x-c , C y-c are the horizontal and vertical hydrodynamic coefficients of the submarine cable, respectively, and the values ​​are taken according to DNV-RP-F109, u w-c is the velocity amplitude at the center elevation of the submarine cable caused by waves, u c-c is the flow velocity at the center elevation of the submarine cable caused by the unidirectional flow, ρ w is the density of seawater;

[0015] The safety factor of the horizontal stability of the submarine cable is defined as:

[0016]

[0017] Among them, μ c is the friction coefficient between the submarine cable and the seabed;

[0018] Assume that the minimum allowable safety factor for cables is SF c-min , then the average additional horizontal resistance per meter required to ensure the stability of the submarine cable is:

[0019] F r-c =SF c-min F x-c -μ c (W s-c -F y-c ) (4)

[0020] (3) Hydrodynamics and stability assessment of the briquetting structure

[0021] According to the shape and size of the briquette structure, its corresponding hydrodynamic coefficient is obtained through numerical simulation or physical experimental method, and its stability and anti-slip ability under the action of hydrodynamic force are calculated;

[0022] Under the action of unidirectional flow, the block is subjected to a horizontal drag force F d-b and the vertical lift F l-b ; Cross-sectional area of ​​the pressure block facing the flow surface A c , the maximum downward projection area of ​​the pressure block is A s , then the horizontal drag force F on the block is d-b and the vertical lift F l-b for:

[0023]

[0024] Among them, u c-b is the flow velocity at the top of the briquette, C d-b and C y-b are the drag coefficient and lift coefficient of the compact;

[0025] Under the combined action of waves and unidirectional flow, the block is subjected to a horizontal drag force F. d-b and inertial force F i-b , vertical lift F y-b , the calculation formula is as follows:

[0026]

[0027] Among them, u w-b is the velocity amplitude caused by the wave at the top of the briquette, C i-b is the inertia coefficient, V r is the volume of the briquette;

[0028] The pressure block maintains stability through the friction between it and the seabed. The friction between the pressure block and the seabed is F f-b for:

[0029] F f-b =μ b (W s-b -F l-b ) (10)

[0030] Among them, μ b is the friction coefficient between the briquette and the seabed, W s-b is the buoyant weight of the briquette;

[0031] Safety factor SF of the briquette's own stability b Defined as:

[0032]

[0033] Assume that the minimum allowable safety factor for the briquetting is defined as SF b-min , then the additional lateral resistance provided by a single pressure block to the submarine cable is:

[0034] F r-b =μ b (W s-b -F l-b )-SF b-min (F d-b +F i-b ) (12)

[0035] (4) Block layout design

[0036] Determine the spacing and quantity of the block-type structures according to the cable length and stability requirements. The layout design is as shown in the attached Figure 4 Assume that the total length of the submarine cable is L c , then the block spacing ΔL b And the total number of briquettes N b They are:

[0037] ΔL b = F r-b / F r-c (13)

[0038] N b = L c / ΔL (14)

[0039] (5) Optimization of block structure and layout

[0040] Optimize the size and weight of the briquette to reduce material costs and construction difficulty while meeting stability requirements. 1) The briquette structure is made of concrete or composite materials, which has good corrosion resistance and durability. 2) The shape of the briquette structure is designed to be streamlined to reduce the impact of hydrodynamic loads on the stability of the briquette itself. 3) The layout spacing of the briquette structure is dynamically adjusted according to the cable length and seabed flow conditions to ensure uniform distribution of stability.

[0041] Beneficial effects of the present invention:

[0042] 1) Through scientific calculation and optimized design, the stability of submarine cables in complex marine environments has been significantly improved.

[0043] 2) The design and layout of the briquetting structure are flexible and can adapt to the environmental conditions of different sea areas.

[0044] 3) It reduces the risk of displacement, wear and breakage of submarine cables due to environmental factors and extends the service life of the cables.

[0045] 4) The construction is simple, the cost is controllable, and it has high engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A flow chart of the design method of the present invention.

[0047] Figure 2 Schematic diagram of the forces acting on submarine cables.

[0048] Figure 3 This is a schematic diagram of the force on the briquette structure.

[0049] Figure 4 Schematic diagram of the layout of the briquette structure. DETAILED DESCRIPTION

[0050] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0051] 1) Calculation of submarine flow conditions: Collect the water flow velocity, wave height and tidal cycle data of the target sea area through marine environmental monitoring equipment, and calculate the corresponding characteristic velocity under extreme environmental conditions according to the empirical formula. 2) Evaluation of hydrodynamics and in-situ stability of submarine cables: Calculate the hydrodynamics and lateral resistance of the submarine cable under design conditions according to conditions such as cable diameter, deadweight and flow parameters, evaluate the in-situ stability of the cable, and determine the additional lateral resistance required for the submarine cable. 3) Evaluation of the hydrodynamics and stability of the block structure itself: Use numerical simulation or physical experiments to obtain the hydrodynamic coefficients of a specific form of block structure under typical flow conditions, evaluate the stability of the block itself and calculate the additional lateral resistance that the block can provide for the submarine cable. 4) Block layout design: Calculate the block distribution spacing and the total number of blocks according to the stability requirements of the submarine cable. 5) Block structure and layout optimization: Evaluate the above block layout scheme according to the construction volume. By optimizing the block structure and size, changing its hydrodynamic characteristics, improving its lateral anti-slip performance, and redesigning the layout, the engineering volume can be further reduced.

Claims

1. A design method for secondary stability intervention of submarine cables using a briquette structure, characterized in that: The following steps are involved: (1) Calculation of seabed flow conditions Collect marine environmental data of the target sea area, including water velocity, wave height, and tidal period; use numerical simulation tools or empirical formulas to calculate seabed flow conditions, including unidirectional flow velocity and wave water particle velocity; (2) Hydrodynamics and in-situ stability assessment of submarine cables Forces on exposed submarine cables, including horizontal hydrodynamic component F x-c , vertical hydrodynamic component F y-c , the friction force F between the cable and the seabed f-c and the buoyancy weight W of the cable s-c The hydrodynamic force on the submarine cable is calculated as follows: Among them, C x-c , C y-c are the horizontal and vertical hydrodynamic coefficients of the submarine cable, respectively, and the values ​​are taken according to DNV-RP-F109, u w-c is the velocity amplitude at the center elevation of the submarine cable caused by waves, u c-c is the flow velocity at the center elevation of the submarine cable caused by the unidirectional flow, ρ w is the density of seawater; The safety factor of the horizontal stability of the submarine cable is defined as: Among them, μ c is the friction coefficient between the submarine cable and the seabed; Assume that the minimum allowable safety factor for cables is SF c-min , then the average additional horizontal resistance per meter required to ensure the stability of the submarine cable is: F r-c =SF c-min F x-c -μ c (W s-c -F y-c )(4) (3) Hydrodynamics and stability assessment of the briquetting structure According to the shape and size of the briquette structure, its corresponding hydrodynamic coefficient is obtained through numerical simulation or physical experimental method, and its stability and anti-slip ability under the action of hydrodynamic force are calculated; Under the action of unidirectional flow, the block is subjected to a horizontal drag force F d-b and the vertical lift F l-b ; Cross-sectional area of ​​the pressure block facing the flow surface A c , the maximum downward projection area of ​​the pressure block A s , then the horizontal drag force F on the block is d-b and the vertical lift F l-b for: Among them, u c-b is the flow velocity at the top of the briquette, C d-b and C y-b are the drag coefficient and lift coefficient of the compact; Under the combined action of waves and unidirectional flow, the block is subjected to a horizontal drag force F. d-b and inertial force F i-b , vertical lift F y-b , the calculation formula is as follows: Among them, u w-b is the velocity amplitude caused by the wave at the top of the briquette, C i-b is the inertia coefficient, V r is the volume of the briquette; The pressure block maintains stability through the friction between it and the seabed. The friction between the pressure block and the seabed is F f-b for: F f-b =μ b (W s-b -F l-b )(10) Among them, μ b is the friction coefficient between the briquette and the seabed, W s-b is the buoyant weight of the briquette; Safety factor SF of the briquette's own stability b Defined as: Assume that the minimum allowable safety factor for the briquetting is defined as SF b-min , then the additional lateral resistance provided by a single pressure block to the submarine cable is: F r-b =μ b (W s-b -F l-b )-SF b-min (F d-b +F i-b )(12) (4) Block layout design Determine the spacing and number of clamps based on cable length and stability requirements. Assume the total length of the submarine cable is L. c , then the block spacing ΔL b And the total number of briquettes N b They are: ΔL b =F r-b / F r-c (13) N b =L c / ΔL(14) (5) Optimization of block structure and layout Optimize the size and weight of the briquette to reduce material costs and construction difficulty while meeting stability requirements.

2. The design method for secondary stability intervention of submarine cables using a briquetting structure according to claim 1 is characterized in that: Briquettes are made of concrete or composite materials.

3. The design method for secondary stability intervention of submarine cables using a briquetting structure according to claim 1 is characterized in that: The shape of the pressing block is designed to be streamlined.

4. The design method for secondary stability intervention of submarine cables using a briquetting structure according to claim 1 is characterized in that: The spacing of the pressure blocks is dynamically adjusted according to the cable length and seabed flow conditions to ensure uniform distribution of stability.

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