Multi-layer energy dissipation device for pile foundation scour prevention, energy dissipation method and construction method

Abstract

The invention relates to a multi-layer energy dissipation device for pile foundation scour prevention, an energy dissipation method and a construction method.The multi-layer energy dissipation device comprises a flow guide energy dissipation shield and three steel wire layers, the flow guide energy dissipation shield comprises an energy dissipation shield body, the energy dissipation shield body is arranged on a pile foundation in a sleeving mode, a flange plate is arranged on the portion, at the top of the energy dissipation shield body, of the pile foundation in a sleeving mode, and the energy dissipation shield body is fixed to the pile foundation through the flange plate; a hoisting disc is installed on a pile foundation at the bottom of the energy dissipation shield body in a sleeving mode, a plurality of hoisting steel wires are vertically connected between the flange plate and the hoisting disc, and the hoisting steel wires surround the periphery of the energy dissipation shield body to form three layers; a steel wire mesh is wound on each hoisting steel wire, three steel wire layers are also formed outside the energy dissipation shield body, the three layers are defined as the first steel wire mesh layer, the second steel wire mesh layer and the third steel wire mesh layer from inside to outside, and the density of the first steel wire mesh layer is gt; the density of the second-layer steel wire mesh is gt; the density of the third layer of steel wire mesh and the porosity of the third layer of steel wire mesh are gt; 70%. Dynamic characteristics of water flow are fully considered, energy of the water flow can be effectively dispersed, and scouring force to the pile foundation is reduced.

Description

Technical Field

[0001] This invention relates to a multi-layer energy dissipation device, energy dissipation method, and construction method for pile foundation scour prevention. It is mainly applied in the fields of marine engineering and infrastructure protection, and is particularly suitable for pile foundation protection of offshore wind power, bridges, wharves, and offshore platforms. Background Technology

[0002] With the rapid development of marine engineering, pile foundations are increasingly used in marine structures. Consequently, the problem of water erosion around these pile foundations has become increasingly prominent, seriously affecting their stability and service life. Traditional erosion prevention measures often require complex construction processes, specialized equipment, and technology, increasing the overall cost and time of the project. Furthermore, existing systems are susceptible to the marine environment during use, easily damaged or corroded, leading to frequent maintenance and replacement, increasing the difficulty and cost of subsequent management.

[0003] For example, invention application number 202310419701.8 discloses an anti-scouring energy dissipation and ecological protection structure for offshore wind turbine monopile foundations, comprising: a wave energy dissipation ring filled with absorbent sponge and air; an energy dissipation device installed at the bottom of the wave energy dissipation ring; a multi-layer energy dissipation protective net, the upper end of which is fixedly connected to the wave energy dissipation ring, and the multi-layer energy dissipation protective net is arranged in a ring along the outer perimeter of the bottom surface of the wave energy dissipation ring at a distance proportional to the circumference; and an anti-scouring base, the top surface of which is fixedly connected to the lower end of the multi-layer energy dissipation protective net, and the bottom surface of which is fixed to the bottom of the seabed. It can maximally resist the long-term wave loads and the scouring and impact of seabed currents on the offshore wind turbine monopile.

[0004] However, the aforementioned existing technologies do not fully consider the dynamic characteristics of water flow, resulting in unsatisfactory protection effects under strong current or special tidal conditions, and failing to effectively reduce scouring forces. Therefore, there is an urgent need to develop a new type of anti-scouring device that can overcome the above-mentioned shortcomings and provide a more efficient, economical, and reliable solution to protect pile foundations from the effects of scouring. Summary of the Invention

[0005] This invention provides a multi-layer energy dissipation device, energy dissipation method, and construction method for pile foundation scour prevention. It fully considers the dynamic characteristics of water flow, effectively disperses the energy of water flow, and reduces the scour force on the pile foundation.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A multi-layer energy dissipation device for pile foundation scour prevention includes a flow-guiding energy dissipation shield and three layers of steel wire. The flow-guiding energy dissipation shield includes an energy dissipation shield body, which is sleeved on the pile foundation. An installation flange is sleeved on the pile foundation at the top of the energy dissipation shield body, and the energy dissipation shield body is fixed on the pile foundation by the flange.

[0008] A lifting plate is installed on the pile foundation at the bottom of the energy dissipation shield body. Several lifting steel wires are vertically connected between the flange and the lifting plate. The several lifting steel wires are wrapped around the energy dissipation shield body to form three layers.

[0009] Each suspension steel wire is wrapped with wire mesh, and three layers of wire mesh are formed on the outside of the energy dissipation shield. The three layers from the inside out are defined as the first layer of wire mesh, the second layer of wire mesh, and the third layer of wire mesh. The density of the first layer of wire mesh is greater than that of the second layer of wire mesh, which is greater than that of the third layer of wire mesh. The porosity of the third layer of wire mesh is greater than 70%.

[0010] Furthermore, with the central axis of the pile foundation as the center line, the first layer of wire mesh is located at 1.5 times the diameter of the pile foundation, the second layer of wire mesh is located at 1.6 times the diameter of the pile foundation, and the third layer of wire mesh is located at 1.8 times the diameter of the pile foundation.

[0011] Furthermore, the energy dissipation shield body has a hollow part that can be fitted onto the pile foundation, and the remaining part forms a ring structure. Several hexagonal guide holes are evenly opened on the ring structure, and the hexagonal guide holes are arranged in a honeycomb pattern.

[0012] Among them, the hexagonal guide holes arranged in a honeycomb pattern include rounded hexagonal guide holes and small hexagonal guide holes. The hexagonal guide holes are arranged in rows parallel to the central axis of the pile foundation, with one row consisting of rounded hexagonal guide holes and the other row consisting of small hexagonal guide holes that are staggered.

[0013] The radius of the rounded corners of the hexagonal guide hole is R ≥ 1.5t, where t is the wall thickness of the rounded corner hexagonal guide hole;

[0014] Furthermore, the suspension steel wires include nine wires, that is, three suspension steel wires are set for each layer, and the three suspension steel wires are arranged in an equilateral triangle shape with the central axis of the pile foundation as the center line;

[0015] Furthermore, the diameter of the lifting steel wire is 20mm;

[0016] Furthermore, four sand-leaking holes are opened at the connection between the energy dissipation shield body and the hoisting plate, and the four sand-leaking holes are evenly distributed around the central axis of the pile foundation.

[0017] The energy dissipation method of the multi-layer energy dissipation device for pile foundation scour prevention, as described above, includes the following specific steps:

[0018] In step S1, the water flows through the third layer of wire mesh for coarse filtration, and the water flow is transformed into eddies and turbulent flows.

[0019] After the third layer of coarse filtration with wire mesh, the formula for calculating head loss is:

[0020]

[0021] In the formula, φ is the porosity, and d p ρ is the equivalent diameter of the steel wire, v0 is the incoming flow velocity, L3 is the water penetration coefficient, μ is the dynamic viscosity coefficient of the water (valued at 0.00105), ρ is the density of seawater, and g is the acceleration due to gravity.

[0022] The energy dissipation efficiency at this time is:

[0023]

[0024] In step S2, the water flows through the second layer of wire mesh, increasing the friction loss between the water and the wire mesh layer, forming a turbulent boundary layer on the surface of the wire mesh layer, and entering the turbulent friction stage;

[0025] After friction from the second layer of wire mesh, the formula for calculating head loss is:

[0026]

[0027] In the formula, μ is the dynamic viscosity coefficient of water, with a value of 0.00105, ρ is the density of seawater, g is the acceleration due to gravity, K is the permeability of the wire mesh, and v3 is the flow velocity through the outlet of the third layer of wire mesh. L2 is the water penetration coefficient, C F This is the inertial drag coefficient;

[0028] The energy dissipation efficiency at this time is:

[0029]

[0030] In step S3, the water continues to pass through the first layer of wire mesh and enters the dense barrier stage, forming a strong scouring zone that blocks the remaining scouring force of the water flow.

[0031] After the first layer of wire mesh obstruction, the formula for calculating head loss is:

[0032]

[0033] In the formula, v2 is the flow velocity through the outlet of the second layer of wire mesh. ξ is the drag coefficient;

[0034] The energy dissipation efficiency at this time is:

[0035]

[0036] In step S4, the water flow slows down after passing through the third, second, and first layers of wire mesh and continues to pass through several hexagonal guide holes arranged in a honeycomb pattern. This guides the water flow to change its path, forming several small vortex regions, and entering the vortex dissipation stage to complete energy dissipation.

[0037] The formula for calculating head loss after passing through the hexagonal guide hole is:

[0038]

[0039] In the formula, C v Let v be the eddy current constant, and v1 be the outlet velocity through the first layer of wire mesh.

[0040] The energy dissipation efficiency at this time is:

[0041]

[0042] Furthermore, the total energy dissipation is synthesized as follows:

[0043]

[0044] After filtration through steps S1-S4, an energy dissipation efficiency of ≥60% can be achieved.

[0045] The construction method for the multi-layer energy dissipation device used for pile foundation scour prevention is as follows:

[0046] The first step is to assess the water flow and scouring conditions around the pile foundation to determine the installation location and dimensions of the diversion and energy dissipation shield.

[0047] The second step is to first install the flange on the pile foundation. The flange is then fixed to the pile foundation with bolts to ensure the stability of the connection.

[0048] The third step is to fasten the top of the energy dissipation shield body to the flange with bolts, and to cast the lifting plate and the bottom of the energy dissipation shield body as a whole to ensure stability under the action of water flow.

[0049] The fourth step is to fix three equilateral triangle-shaped lifting wires at a position 1.5 times the diameter of the pile foundation between the flange and the lifting plate, with the central axis of the pile foundation as the center line. Then, fix three more equilateral triangle-shaped lifting wires at a position 1.6 times the diameter of the pile foundation, and finally fix three more equilateral triangle-shaped lifting wires at a position 1.8 times the diameter of the pile foundation.

[0050] The fifth step involves wrapping the first layer of wire mesh around the sling wire at a position 1.5 times the diameter of the pile foundation, the second layer of wire mesh around the sling wire at a position 1.6 times the diameter of the pile foundation, and the third layer of wire mesh around the sling wire at a position 1.8 times the diameter of the pile foundation, with the density of the first, second, and third layers of wire mesh gradually decreasing.

[0051] Step 6: After installation, inspect the multi-layer energy dissipation device to ensure that the connections are secure and free from obvious damage.

[0052] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art:

[0053] 1. The multi-layer energy dissipation device for pile foundation scour prevention provided by the present invention effectively disperses the energy of water flow through an innovative design that utilizes a combination of multi-layer steel wire mesh and flow-guiding energy dissipation shield;

[0054] 2. The multi-layer energy dissipation device for pile foundation scour prevention provided by the present invention has three layers of steel wire wound sequentially from the inside to the outside on each suspension steel wire, which imitates the wave energy dissipation mechanism in nature and improves the protection effect.

[0055] 3. The multi-layer energy dissipation device for pile foundation scour prevention provided by the present invention has a design that changes the path of water flow and forms a small eddy region, further reducing the kinetic energy and impact force of the water flow, thereby reducing the disturbance to the mud and sand around the pile foundation.

[0056] 4. The energy dissipation method of the multi-layer energy dissipation device for pile foundation scour prevention provided by the present invention sequentially passes through the coarse filtration stage, the turbulent friction stage, the dense barrier stage and the eddy current dissipation stage, gradually reducing the water flow velocity until the kinetic energy is weakest, thereby achieving all-round protection of the pile foundation and extending the service life of the pile foundation.

[0057] 5. The construction method of the multi-layer energy dissipation device for pile foundation scour prevention provided by the present invention makes the device stable and ensures long-term use. Attached Figure Description

[0058] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0059] Figure 1 This is a schematic diagram of the overall structure of a preferred embodiment provided by the present invention;

[0060] Figure 2 This is a cross-sectional view of the overall structure of a preferred embodiment provided by the present invention;

[0061] Figure 3 This is a schematic diagram of the structure of the three-layer steel wire layer according to a preferred embodiment of the present invention;

[0062] Figure 4 This is a schematic diagram of the structure of the rounded hexagonal guide hole according to a preferred embodiment of the present invention.

[0063] In the diagram: 0 is the pile foundation, 1 is the flange, 2 is the sand leakage hole, 3 is the three-layer steel wire layer, 4 is the suspension steel wire, 5 is the energy dissipation shield body, 6 is the suspension plate, 7 is the high-strength bolt, and 8 is the rigid base. Detailed Implementation

[0064] The present invention will now be described in further detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side," "right side," "upper part," "lower part," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. "First," "second," etc., do not indicate the importance of the components, and therefore should not be construed as a limitation of the present invention. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the scope of protection of the present invention.

[0065] As described in the background section, water flow exhibits significant dynamic characteristics in real, complex, and variable natural water bodies. Existing devices lack effective designs for dispersing and guiding the impact force of water flow, thus failing to adequately mitigate its force. Therefore, this application provides a multi-layer energy dissipation device for scour prevention of pile foundations. Figures 1-2 The structure provided in this application consists of a multi-layered steel wire mesh, which, through a mesh design of different densities, gradually absorbs and disperses the impact of dynamic water flow, effectively disperses local energy, and prevents the formation of strong eddies in the bottom area of ​​the pile foundation, thereby ensuring the safety of the pile foundation.

[0066] The multi-layer energy dissipation device in this application includes a flow-guiding energy dissipation shield and three layers of steel wire 3. The flow-guiding energy dissipation shield includes an energy dissipation shield body 5, which is sleeved on the pile foundation 0. A flange 1 is installed on the pile foundation at the top of the energy dissipation shield body, and the energy dissipation shield body is fixed to the pile foundation by the flange. A lifting plate 6 is installed on the pile foundation at the bottom of the energy dissipation shield body. The flange, the energy dissipation shield body, and the lifting plate are arranged coaxially. Several lifting steel wires 4 are vertically connected between the flange and the lifting plate. The lifting steel wires surround the energy dissipation shield body and form three layers. Each lifting steel wire is wrapped with a steel wire mesh, which also forms three layers of steel wire outside the energy dissipation shield body. The three layers from the inside out are defined as the first layer of steel wire mesh, the second layer of steel wire mesh, and the third layer of steel wire mesh.

[0067] The most significant innovation of this application lies in the gradually increasing density of the wire mesh from the outside in. The outermost layer, the third layer, is relatively sparse, primarily used to disperse most of the water flow energy, effectively mitigating the direct impact of the water flow on subsequent structures. The middle layer, the second layer, has a moderate density, further weakening the impact force of the water flow. The innermost layer, the first layer, is relatively dense, forming a robust barrier to ultimately block the remaining scouring force, ensuring effective protection for the energy dissipation shield and the pile foundation. This multi-layered design not only significantly reduces the concentrated scouring force of the water flow but also effectively disperses local energy, preventing the formation of strong eddies at the bottom of the pile foundation, thus ensuring the safety of the pile foundation. While ensuring that each layer of wire mesh functions effectively, the use of only three layers achieves a combination of advantages such as economic efficiency, ease of installation, energy dissipation, and convenient maintenance. This application also provides a further preferred embodiment, wherein the density of the first layer of wire mesh is greater than the density of the second layer of wire mesh, which is greater than the density of the third layer of wire mesh, and the porosity of the third layer of wire mesh is greater than 70%.

[0068] The three-layer steel wire structure is the core component of the energy dissipation device. High-strength steel wires are interwoven together using a mechanical weaving process to form three layers of mesh structure with different densities. The placement of each steel wire layer is also ingeniously designed. Figure 3 As shown, the innermost wire mesh (first layer) is located at 1.5 times the diameter of the pile foundation, the middle wire mesh (second layer) is located at 1.6 times the diameter of the pile foundation, and the outermost wire mesh (third layer) is located at 1.8 times the diameter of the pile foundation. The suspension wires are arranged in groups of three, forming an equilateral triangle, which provides high stability and can withstand the impact of waves from different directions.

[0069] Another innovative highlight of this application is the structure of the energy dissipation shield. Since water flow is dynamic, it is necessary to enhance adaptability to changes in water flow while simultaneously achieving energy dissipation. Therefore, the energy dissipation shield provided in this application has a cylindrical structure with a hollow portion that can be fitted onto the pile foundation. The remaining portion forms a ring structure. The energy dissipation shield is made of high-strength composite material, and several hexagonal guide holes are evenly distributed on the ring structure, arranged in a honeycomb pattern. Among these honeycomb-patterned hexagonal guide holes are rounded hexagonal guide holes and small hexagonal guide holes. The hexagonal guide holes are arranged in rows parallel to the central axis of the pile foundation, with one row consisting of rounded hexagonal guide holes and another row of small hexagonal guide holes staggered.

[0070] The design of the rounded hexagonal guide hole is based on the fact that in traditional working conditions, sharp corners are stress concentration sources, which can easily lead to fatigue cracks. According to elasticity mechanics, the stress concentration factor K... t The relationship with the fillet radius R is as follows:

[0071]

[0072] Where, when R≥1.5t, K t It can be reduced to below 2.0, significantly lower than the sharp angle (K). t >5). Referring to the Peterson stress concentration factor handbook, the rounded corner design will significantly improve the high-cycle fatigue life of the deflector shield. Figure 4 As shown, the preferred radius of the rounded hexagonal guide hole is R ≥ 1.5t, where t is the wall thickness of the rounded hexagonal guide hole. The dimensions of each rounded hexagonal guide hole are optimized according to the kinetic energy of the water flow. The rounded edges of the holes reduce local stress concentration caused by water flow impact and extend the service life of the guide energy dissipation shield.

[0073] These rounded hexagonal guide holes not only effectively alter the water flow path, creating multiple small vortex regions, but also significantly reduce water velocity and impact force, thereby minimizing the disturbance of local turbulence to the surrounding sediment. The small hexagonal guide holes further help disperse the water flow; this design not only improves the energy dissipation efficiency of the device but also enhances its adaptability to changes in water flow.

[0074] Since the steel wire layer is wound around the suspension steel wire, the selection of the suspension steel wire must also fully consider its mechanical properties and structural stability. From a mechanical perspective, the wire diameter must first meet the tensile strength requirements of the suspension steel wire under the impact load of ocean currents. A diameter that is too small is prone to breakage, while a diameter that is too large increases weight and cost. In the marine environment, water currents are dynamic cyclic loads, so fatigue life must be considered; the diameter needs to be verified using material mechanics formulas.

[0075]

[0076] Where σ is the working stress, F is the maximum water flow impact force, and A = πd 2 / 4 represents the cross-sectional area of ​​the steel wire, and [σ] represents the ultimate bearing capacity of the material. Since a safety factor needs to be considered, it is generally taken as 0.6-0.8 times the yield strength of the material. A steel wire with a diameter of 20mm (2 units) can balance the requirements of strength and lightweight.

[0077] From a structural stability perspective, since the suspension wire is a slender component, to prevent instability, the diameter-to-length ratio must meet the following requirements:

[0078]

[0079] Where i = d / 4 is the radius of gyration of the cross section, λ 临界 This is the critical slenderness ratio (generally 120-150 for steel components). Therefore, a diameter of 20mm satisfies the slenderness ratio requirement.

[0080] The above verifications show that setting the diameter of each sling wire to 20mm provides good tensile strength and corrosion resistance, making it suitable for use in highly corrosive marine environments. Furthermore, the sling wire is coated for protection, effectively preventing corrosion caused by prolonged exposure to salt spray, further enhancing its service life.

[0081] Preferably, this application provides nine suspension steel wires evenly distributed around the energy dissipation shield body. The two ends of these nine suspension steel wires are fixed to the flange and the suspension plate, respectively. Three suspension steel wires are set for each layer, and the three suspension steel wires are arranged in an equilateral triangle shape with the central axis of the pile foundation as the center line.

[0082] Four sand-draining holes 2 are evenly arranged around the connection between the energy dissipation shield and the lifting plate to prevent fine particles of silt from accumulating inside the wire mesh and on the outer wall of the energy dissipation shield. This design not only improves the energy dissipation efficiency of the device but also enhances its adaptability to changes in water flow.

[0083] Finally, the flange and lifting plate are fixed using a modular installation method. The flange is secured with 10 high-strength bolts, each with a diameter of 3 units. These high-strength bolts pass through the flange and fit tightly with the nuts. The nut holes are precisely machined to ensure a seamless fit with the bolts. To further enhance the sealing and corrosion resistance of the connection, a sealing gasket is used between the nut and the flange. The gasket is made of a rubber-metal composite material, effectively preventing external water flow from corroding the connection. Furthermore, during installation, a precise preload is applied to the nuts using a specialized torque tool to ensure the tightness and stability of the flange connection. The lifting plate is integrally cast with the energy dissipation shield body, effectively guaranteeing the stability of the entire device.

[0084] Meanwhile, to connect the device to the pile foundation, bolts also pass through pre-drilled holes on the energy dissipation shield body, and are tightened to the flange via threads to ensure its stability during operation. The lifting steel wire is fixed to the flange or lifting plate via a rigid base bracket. The rigid base bracket is equipped with a steel wire fixing groove, which can firmly fix the steel wire and maintain its tension, ensuring that the position of the wire mesh around the flow guide shield body remains fixed. This carefully designed connection method not only effectively disperses the water flow load, can cope with inflows from all directions and avoids excessive radial bending moment on the energy dissipation shield body, but also ensures that the three layers of steel wire are not prone to loosening or falling off during long-term use, ensuring the stability and reliability of the entire external tension ring structure, thereby extending the service life of the entire device.

[0085] Regarding the overall structure, a separate point needs to be addressed: can the internal and external installation relationship between the three-layer steel wire mesh and the energy dissipation shield be altered? The outer layer of the three-layer steel wire mesh intercepts large particles of sediment, preventing them from entering the guide shield and causing blockages. Simultaneously, the three-layer steel wire mesh is connected to the flange and lifting plate via suspension wires, forming an external tension ring structure that evenly distributes the water flow load, preventing the energy dissipation shield from bearing radial bending moments. If the three-layer steel wire mesh and the energy dissipation shield are arranged in opposite directions, the energy dissipation shield will directly bear the impact of high-speed water flow, potentially leading to stress concentration at the edges of the guide holes (due to the impact of unfiltered high-speed water flow) and reduced structural fatigue life. Furthermore, as a vulnerable component, the steel wire mesh is installed modularly for easy disassembly and replacement. If placed internally, the energy dissipation shield must be removed first, increasing maintenance costs. Therefore, the sequence of the three-layer steel wire mesh and the energy dissipation shield cannot be changed.

[0086] In actual working conditions, the multi-layer energy dissipation device for pile foundation scour prevention provided in this application achieves energy dissipation through the collaborative action of multiple layers of steel wire mesh and flow-guiding energy dissipation shields. The structural design effectively reduces the impact force and kinetic energy of the water flow. The specific energy dissipation method includes four stages:

[0087] Step S1: When the water flows into the device, it penetrates the third layer of wire mesh (the outermost sparse wire mesh) to perform the coarse filtration stage.

[0088] At this stage, the head loss is calculated based on the resistance formula (corrected from the Ergun equation):

[0089]

[0090] Where φ is porosity (porosity > 70% → φ ≈ 0.7), d p ρ is the equivalent diameter of the steel wire, and the typical value of 0.005m is used in this calculation. v0 is the incoming flow velocity (typical flow velocity in the coastal waters of China). L3 is the water penetration coefficient (not geometric thickness), with a value of 0.10. μ is the dynamic viscosity coefficient of the water (Pa·s), with a value of 0.00105. ρ is the density of seawater (kg / m3), with a value of 1025.

[0091] Energy dissipation efficiency:

[0092]

[0093] In the formula, ρ is the density of seawater (kg / m³). 3 v3 is the flow velocity through the outlet of the third layer of wire mesh. g is the acceleration due to gravity.

[0094] Because the porosity of the third layer of wire mesh is greater than 70%, the cross-section of the water flow suddenly expands. According to Bernoulli's equation, the decrease in flow velocity is accompanied by an increase in pressure, and the energy of the water flow is gradually transformed into eddies and turbulence, reducing the direct impact on the pile foundation.

[0095] Step S2: Entering the turbulent friction stage, specifically, the water flows through the second layer of wire mesh, further reducing the flow velocity and increasing the flow resistance to prevent the water from directly impacting the guide shield and causing structural overload. The head loss is based on the Darcy loss in porous media (modified Forchheimer equation):

[0096]

[0097] In the formula, g is the acceleration due to gravity, and K is the permeability (which can be measured by CT scan in actual engineering; the typical value of 1.2e-5m is used in this theory). 2 ), C F L1 is the inertial drag coefficient (typically 0.08), and L2 is the water penetration coefficient, with a value of 0.72.

[0098] Energy dissipation efficiency:

[0099]

[0100] Where K is the penetration rate, C F The turbulence drag coefficient is 0.08 (for wire mesh). This formula shows that by increasing the frictional loss between the water flow and the wire mesh layer, a turbulent boundary layer is formed on the wire mesh surface, effectively weakening the impact force of the water flow and preventing the formation of a strong scouring zone. The outlet velocity after passing through the second layer of wire mesh is...

[0101] In step S3, the water continues to flow through the first layer of wire mesh. The innermost and densest wire mesh acts as a barrier, blocking the remaining scouring force of the water flow. The head loss is characterized by the local resistance loss method (Idelchik formula, typical value of resistance coefficient ξ is 1.8):

[0102]

[0103] Energy dissipation efficiency:

[0104]

[0105] In step S4, the water flow is slowed down after passing through the third, second, and first layers of wire mesh and continues through the rounded hexagonal guide holes. This guides the water flow to change its path, forming several small vortex regions. The head loss is calculated using the vortex dissipation theory.

[0106]

[0107] In the formula, C v ν is the eddy current constant, which can be taken as 1.8 for the hexagonal guide hole (calculated using the Miller correction formula), and v1 is the flow velocity through the outlet of the first layer of wire mesh.

[0108] Energy dissipation efficiency:

[0109]

[0110] This design, based on the principles of flow separation and reattachment, reduces water flow velocity and kinetic energy, minimizing direct impact on the pile foundation. Energy is completely dissipated through vortex collisions and viscosity. This energy dissipation mechanism not only effectively reduces the intensity of local turbulence but also prevents partial disturbance to surrounding sediment, thus achieving comprehensive protection of the pile foundation, extending its service life, and ultimately completing energy dissipation.

[0111] Total energy dissipation synthesis:

[0112]

[0113] This application further provides specific verification cases, with layered calculation data verification (incoming flow velocity v0 set to 2.5 m / s):

[0114]

[0115] The dissipation rates mentioned are theoretical values ​​under ideal working conditions. In actual engineering, an adjustable energy dissipation rate of 60%+ can be achieved by adjusting the spacing between steel wire mesh layers (1.5D-1.8D) and the pore gradient.

[0116] Finally, this application also provides a construction method for the multi-layer energy dissipation device for pile foundation scour prevention, characterized in that: the specific steps are as follows:

[0117] The first step is to assess the water flow and scouring conditions around the pile foundation to determine the installation location and dimensions of the diversion and energy dissipation shield.

[0118] The second step is to first install the flange on the pile foundation. The flange is then fixed to the pile foundation with bolts to ensure the stability of the connection.

[0119] The third step is to fasten the top of the energy dissipation shield body to the flange with bolts, and to cast the lifting plate and the bottom of the energy dissipation shield body as a whole to ensure stability under the action of water flow.

[0120] The fourth step is to fix three equilateral triangle-shaped lifting wires at a position 1.5 times the diameter of the pile foundation between the flange and the lifting plate, with the central axis of the pile foundation as the center line. Then, fix three more equilateral triangle-shaped lifting wires at a position 1.6 times the diameter of the pile foundation, and finally fix three more equilateral triangle-shaped lifting wires at a position 1.8 times the diameter of the pile foundation.

[0121] The fifth step involves wrapping the first layer of wire mesh around the sling wire at a position 1.5 times the diameter of the pile foundation, the second layer of wire mesh around the sling wire at a position 1.6 times the diameter of the pile foundation, and the third layer of wire mesh around the sling wire at a position 1.8 times the diameter of the pile foundation, with the density of the first, second, and third layers of wire mesh gradually decreasing.

[0122] Step 6: After installation, inspect the multi-layer energy dissipation device to ensure that the connections are secure and free from obvious damage.

[0123] Of course, regular maintenance is essential to ensure the long-term effectiveness of the system. This includes regularly inspecting and cleaning the surfaces and components of the energy dissipation device to remove any dirt and deposits, maintaining good water flow guidance. Simultaneously, the coating protection of the wire mesh should be regularly assessed to ensure its corrosion resistance is maintained, especially in highly corrosive marine environments. If any component damage is found, the damaged wire mesh, flow-guiding energy dissipation shield, or bolted flange connection system should be replaced immediately to ensure proper functioning of the system. In extreme weather conditions or under conditions of increased scouring intensity, it is recommended to evaluate the system's performance to make necessary adjustments and optimizations based on the specific circumstances.

[0124] Through the meticulously designed construction and maintenance process described above, this multi-layered energy dissipation device can play an optimal role in preventing pile foundation scour, significantly extending the service life of the pile foundation, reducing maintenance frequency and costs, while also possessing excellent adaptability and durability. This innovative design not only provides effective protection for pile foundations but also offers a completely new solution for water flow scour protection in the field of marine engineering.

[0125] Of course, the multi-layer energy dissipation device provided in this application can be used in combination according to actual working conditions.

[0126] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0127] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0128] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0129] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A multi-layer energy dissipation device for scour prevention of pile foundations, characterized in that: It includes a flow-diverting energy dissipation shield and a three-layer steel wire layer. The flow-diverting energy dissipation shield includes an energy dissipation shield body, which is sleeved on the pile foundation. An installation flange is sleeved on the pile foundation at the top of the energy dissipation shield body, and the energy dissipation shield body is fixed on the pile foundation by the flange. A lifting plate is installed on the pile foundation at the bottom of the energy dissipation shield body. Several lifting steel wires are vertically connected between the flange and the lifting plate. The several lifting steel wires are wrapped around the energy dissipation shield body to form three layers. Each suspension steel wire is wrapped with wire mesh, and three layers of wire mesh are formed on the outside of the energy dissipation shield. The three layers are defined from the inside out as the first layer of wire mesh, the second layer of wire mesh, and the third layer of wire mesh. The density of the first layer of wire mesh is greater than that of the second layer of wire mesh, which is greater than that of the third layer of wire mesh. The porosity of the third layer of wire mesh is greater than 70%.

2. The multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: With the central axis of the pile foundation as the center line, the first layer of wire mesh is located at 1.5 times the diameter of the pile foundation, the second layer of wire mesh is located at 1.6 times the diameter of the pile foundation, and the third layer of wire mesh is located at 1.8 times the diameter of the pile foundation.

3. The multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: The energy dissipation shield body has a hollow part inside that can be fitted onto the pile foundation, and the remaining part forms a ring structure. Several hexagonal guide holes are evenly opened on the ring structure, and the hexagonal guide holes are arranged in a honeycomb pattern. Among them, the hexagonal guide holes arranged in a honeycomb pattern include rounded hexagonal guide holes and small hexagonal guide holes. The hexagonal guide holes are arranged in rows parallel to the central axis of the pile foundation, with one row consisting of rounded hexagonal guide holes and the other row consisting of small hexagonal guide holes that are staggered. The radius of the rounded corners of the hexagonal guide hole is R≥1.5t, where t is the wall thickness of the rounded hexagonal guide hole.

4. The multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: The suspension steel wires include nine wires, with three wires installed on each layer. The three suspension steel wires are arranged in an equilateral triangle shape with the central axis of the pile foundation as the center line.

5. The multi-layer energy dissipation device for pile foundation scour prevention according to claim 4, characterized in that: The diameter of the lifting steel wire is 20mm.

6. The multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: Four sand-leaking holes are opened at the connection between the energy dissipation shield and the hoisting plate. The four sand-leaking holes are evenly distributed around the central axis of the pile foundation.

7. The energy dissipation method of the multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: The specific steps are as follows: In step S1, the water flows through the third layer of wire mesh for coarse filtration, and the water flow is transformed into eddies and turbulent flows. After the third layer of coarse filtration with wire mesh, the formula for calculating head loss is: In the formula, φ is the porosity, and d p ρ is the equivalent diameter of the steel wire, v0 is the incoming flow velocity, L3 is the water penetration coefficient, μ is the dynamic viscosity coefficient of the water (valued at 0.00105), ρ is the density of seawater, and g is the acceleration due to gravity. The energy dissipation efficiency at this time is: In step S2, the water flows through the second layer of wire mesh, increasing the friction loss between the water and the wire mesh layer, forming a turbulent boundary layer on the surface of the wire mesh layer, and entering the turbulent friction stage; After friction from the second layer of wire mesh, the formula for calculating head loss is: In the formula, μ is the dynamic viscosity coefficient of water, with a value of 0.00105, ρ is the density of seawater, g is the acceleration due to gravity, K is the permeability, and v3 is the flow velocity through the outlet of the third layer of wire mesh. L2 is the water penetration coefficient, C F This is the coefficient of inertial drag. The energy dissipation efficiency at this time is: In step S3, the water continues to pass through the first layer of wire mesh and enters the dense barrier stage, forming a strong scouring zone that blocks the remaining scouring force of the water flow. After the first layer of wire mesh obstruction, the formula for calculating head loss is: In the formula, v2 is the flow velocity through the outlet of the second layer of wire mesh. ξ is the drag coefficient; The energy dissipation efficiency at this time is: In step S4, the water flow slows down after passing through the third, second, and first layers of wire mesh and continues to pass through several hexagonal guide holes arranged in a honeycomb pattern. This guides the water flow to change its path, forming several small vortex regions, and entering the vortex dissipation stage to complete energy dissipation. The formula for calculating head loss after passing through the hexagonal guide hole is: In the formula, C v Let v be the eddy current constant, and v1 be the outlet velocity through the first layer of wire mesh. The energy dissipation efficiency at this time is:

8. The energy dissipation method of the multi-layer energy dissipation device for pile foundation scour prevention according to claim 7, characterized in that: Total energy dissipation synthesis is as follows: After filtration through steps S1-S4, an energy dissipation efficiency of ≥60% can be achieved.

9. The construction method of the multi-layer energy dissipation device for pile foundation scour prevention according to claim 1, characterized in that: The specific steps are as follows: The first step is to assess the water flow and scouring conditions around the pile foundation to determine the installation location and dimensions of the diversion and energy dissipation shield. The second step is to first install the flange on the pile foundation. The flange is then fixed to the pile foundation with bolts to ensure the stability of the connection. The third step is to fasten the top of the energy dissipation shield body to the flange with bolts, and to cast the lifting plate and the bottom of the energy dissipation shield body as a whole to ensure stability under the action of water flow. The fourth step is to fix three equilateral triangle-shaped lifting wires at a position 1.5 times the diameter of the pile foundation between the flange and the lifting plate, with the central axis of the pile foundation as the center line. Then, fix three more equilateral triangle-shaped lifting wires at a position 1.6 times the diameter of the pile foundation, and finally fix three more equilateral triangle-shaped lifting wires at a position 1.8 times the diameter of the pile foundation. The fifth step involves wrapping the first layer of wire mesh around the sling wire at a position 1.5 times the diameter of the pile foundation, the second layer of wire mesh around the sling wire at a position 1.6 times the diameter of the pile foundation, and the third layer of wire mesh around the sling wire at a position 1.8 times the diameter of the pile foundation, with the density of the first, second, and third layers of wire mesh gradually decreasing. Step 6: After installation, inspect the multi-layer energy dissipation device to ensure that the connections are secure and free from obvious damage.

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