CN108316335B - A tensioned mooring submersible floating foundation and its construction method - Google Patents

Abstract

The invention belongs to the technical field of offshore wind power foundations, and discloses a tensioned mooring submersible floating foundation and a construction method thereof, which consist of a floating platform and a mooring system. The system includes mooring lines and anchoring foundations; during construction, the floating platform with the upper wind turbine tower and the mooring system will be towed separately, and the anchoring foundations will sink and be embedded in the seabed; The reserved channel and the first reserved channel of the connecting section, the mooring line is anchored to the connecting section after the floating platform sinks in place. The invention can provide sufficient buoyancy stability during towage, and is less affected by wave loads in the in-position state; realizes the tension system on the water, and reduces the difficulty of installing the mooring line underwater; the anchor foundation uses the ballast load and frictional resistance to provide pull-out resistance force, and penetrate into the seabed through surcharge and internal and external pressure difference, and the construction is convenient.

Description

A tensioned mooring submersible floating foundation and its construction method

technical field

The invention belongs to the technical field of offshore wind power foundations, and in particular relates to a tensioned mooring submersible floating foundation and a construction method thereof, which have good stability, convenient construction and installation, and low engineering and installation costs.

Background technique

The concept of floating foundation comes from the deep-sea oil and gas development platform, which means that the foundation is not in direct contact with the seabed, but is connected to the seabed through anchor cables or cables, so that the wind turbine can move freely in a relatively fixed area. The foundation is currently mainly in the research and development and demonstration stage, but it has strong adaptability to the marine environment. Compared with the implanted foundation, the construction is less difficult and the operation and maintenance costs are lower. Therefore, it has a good application prospect in the development of deep-sea wind power.

Compared with offshore waters, the deep sea environment is harsher, and there are various hydrological phenomena such as ocean currents, waves, tides, and internal waves, as well as long-term physical and chemical effects such as corrosion, erosion, and emptying. More stringent requirements were put forward. Considering the factors of technical difficulty and construction cost, fixed foundations are no longer applicable, and deep-sea wind farms mainly use floating foundations.

The main types of existing offshore wind power floating foundations are: Spar type, TLP type and semi-submersible type foundation. The Spar type foundation has a small water surface and is less affected by wave loads. It is suitable for deep sea areas and is inconvenient to install and move; the TLP type foundation has better motion performance, and the mooring uses tension tendons, which are costly and limited by water depth; The semi-submersible foundation can be floated and towed, but the large water plane makes it greatly affected by wave loads and has poor stability. The above foundation forms have their own disadvantages in terms of stability and economy, and the mooring lines of the three foundation types all need to be installed underwater, making construction difficult.

Contents of the invention

The present invention aims to solve the technical problems that the offshore wind power floating foundation has a large motion response under wind and wave loads, and the underwater construction process is complicated and costly. It provides a tensioned mooring submersible floating foundation and its construction. According to the method, the water surface of the foundation form is small, the stability is good, the construction and installation are convenient, and the installation cost is low, so that the offshore wind power floating foundation can be better applied to actual projects.

In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

A construction method for a tensioned mooring submersible floating foundation, wherein the tensioned mooring submersible floating foundation is composed of a floating platform and a mooring system;

The floating platform includes a connection section and a buoyancy tank both of which are hollow structures, the upper end of the connection section is connected to the fan tower through a flange ring, and the lower end of the connection section is fixedly connected with the buoyancy tank; the connection section is formed by the upper The arc-shaped connecting section is composed of an arc-shaped connecting section and a lower column-shaped connecting section. The arc-shaped connecting section is set from top to bottom with a variable cross-section and its side wall is in a concave arc shape; a first reserved hole; the inside of the buoyant tank is provided with a first circumferential division plate, a second circumferential division plate and multiple radial division plates, the first circumferential division plate, the The second circumferential subdivision plate and the multiple radial subdivision plates divide the inside of the buoy into multiple compartments, and each subcompartment is provided with a valve system that can replace water and air; the first ring A plurality of second reserved holes are evenly arranged in the circumferential direction between the dividing plate and the second circumferential dividing plate, and the bottom of the second reserved holes is fixedly connected with the bottom plate of the buoy; the first The number of the two reserved channels is the same as that of the first reserved channel, and the second reserved channel is connected and communicated with the first reserved channel one by one;

The mooring system includes mooring lines and anchor foundations, the number of the mooring lines is the same as that of the second reserved tunnel and the first reserved tunnel, and the mooring lines are arranged in a staggered and uniform ring direction. The straight mooring line is composed of a straight mooring line and an oblique mooring line, the straight mooring line is vertically set between the buoyancy tank and the anchor foundation, and the oblique mooring line is between the buoyancy tank and the anchor foundation It is arranged radially from top to bottom from the center to the outside; the lower ends of the mooring lines are all anchored to the anchor foundation, and the upper ends pass through the second reserved tunnel and the first reserved tunnel in turn, and are anchored to the The top of the connecting section; the anchoring foundation includes a hollow anchoring plate, the inner and outer edges of the upper part of the anchoring plate are provided with tube walls, and the inner and outer edges of the lower part are provided with aprons;

The construction method is carried out according to the following steps:

(1) First prefabricate the floating platform and the mooring system on land respectively, install the wind turbine tower on the floating platform stably, and tow the floating platform with the wind tower installed Transport to the operating sea area, and at the same time tow the mooring system to the operating sea area, and the upper ends of the mooring lines are equipped with buoy balls;

(2) apply ballast to sink the anchor foundation, and embed the anchor foundation into the seabed for fixing by surcharge and internal and external pressure difference;

(3) Pass the upper end of the mooring line through the second reserved tunnel and the first reserved tunnel sequentially according to the position indicated by the buoy ball, and pre-tension the mooring line by 10% to 50%. in tension to balance the buoyancy of said floating platform;

(4) Inject water into the sub-chamber through the valve system of water-air replacement, so that the floating platform installed with the fan tower loses part of its buoyancy and sinks. When it sinks to the design draft position, the mooring line is completed. The remaining 50% to 90% of the pre-tensioning is used to balance the buoyancy of the floating platform, and the upper end of the mooring line is anchored to the top of the connecting section;

(5) the water body in the sub-chamber is discharged through the valve system of water vapor replacement;

(6) The water body brought into the second reserved channel and the first reserved channel by the mooring line is discharged through high-pressure pumping, and the bottom of the buoyant tank is sealed;

(7) Adjusting the position of the center of gravity of the tensioned mooring submersible floating foundation through the sub-chambers.

Preferably, the arc-shaped connecting section and the column-shaped connecting section of the connecting section are formed by integral casting of concrete.

Preferably, the second reserved channel is smoothly connected with the first reserved channel in an arc.

The number of the mooring lines is 8-32, wherein the number of the straight mooring lines and the oblique mooring lines each account for half.

Preferably, the angle between the inclined mooring line and the vertical direction is 3°-60°.

Preferably, the upper end of the mooring line is provided with a buoy ball before anchoring, and each anchor point after anchoring is provided with a maintenance device.

Preferably, the exposed parts of the mooring lines are all wrapped with rubber sleeves.

The beneficial effects of the present invention are:

(1) Tensioned mooring submersible floating foundation of the present invention and construction method thereof, its floating platform combines the design of the connecting section of variable cross-section and the buoyancy tank of large water plane surface, guarantees that the foundation is towed by large The buoyant tank on the waterline surface provides sufficient buoyancy stability. At the same time, the buoyant tank is submerged underwater when the fan is in position. The upper waterplane surface of the connecting section with variable cross-section is smaller and less affected by wave loads, ensuring the stability of the foundation.

(2) The tensioned mooring submersible floating foundation of the present invention and its construction method, its mooring system combines the design of the straight mooring line and the inclined mooring line, and the straight mooring line provides better heave and rotation performance, the inclined mooring line provides a large horizontal restraint force, so that the movement response of the foundation in all directions is small and the stability is good; the circular arrangement of the mooring line can resist the wave force from all directions; the straight mooring line and The upper end of the inclined mooring line is anchored on the top of the arc-shaped connecting section to realize the tension system on the water, which reduces the difficulty of installing the mooring line underwater and facilitates construction; both the straight mooring line and the inclined mooring line are made of steel strands, which is economical .

(3) The tensioned mooring submerged floating foundation of the present invention and its construction method, the anchorage foundation of its mooring system utilizes the frictional resistance provided by the ballast weight and the skirt plate to provide pull-out resistance, which is the direct mooring line and the inclined mooring line. Mooring line positioning, the anchor foundation is a structure that can be filled with sand and ballasted on the upper part, and has a skirt plate on the lower part. The large water plane enables it to be towed to the operating water area, and can penetrate into the seabed through surcharge and internal and external pressure differences. Construction convenient.

Description of drawings

Fig. 1 is the schematic diagram of the three-dimensional structure of the tension type mooring submersible floating foundation provided by the present invention;

Fig. 2 is a schematic diagram of mooring line distribution of the tensioned mooring submersible floating foundation provided by the present invention;

Fig. 3 is the front view of the tension type mooring submersible floating foundation provided by the present invention;

Fig. 4 is a top view of the tensioned mooring submersible floating foundation provided by the present invention.

In the figure: 1. Flange ring, 2. Arc connection section, 3. Column connection section, 4. Floating tank, 5. Mooring line, 6. Anchorage foundation, 7. The first reserved channel, 8. The second Reserved channels, 9, the first circumferential division plate, 10, the second circumferential division plate, 11, the radial division plate.

Detailed ways

In order to further understand the invention content, characteristics and effects of the present invention, the following examples are given, and detailed descriptions are as follows in conjunction with the accompanying drawings:

As shown in Figures 1 to 4, this embodiment discloses a tensioned mooring submersible floating foundation, which consists of a floating platform and a mooring system.

The floating platform includes a connection section and a buoyancy tank 4. The connection section is composed of an arc-shaped connection section 2 and a column-shaped connection section 3. Box 4 is connected. Considering that the cabin and blades of offshore wind turbines are heavy and are 80-100m above the water surface, in order for the wind turbines to generate electricity normally, it is necessary to ensure the stability of the foundation under the combined action of wind and waves and the ability to resist wind and wave loads. The arc-shaped connecting section 2 and the column-shaped connecting section 3 are integrally poured with concrete, which can carry large wind and electric loads. The design of the combination of the variable cross-section connecting section and the large waterline surface buoyancy tank 4, the large waterline surface buoyancy tank 4 provides sufficient buoyancy to realize the overall floating and towing of the floating platform-tower-wind turbine, which is convenient for installation and transportation; And when in position state, buoyant tank 4 submerges below the water surface, and the connecting section top of variable section is positioned at water surface, and water plane surface is less, reduces the influence of wave load.

The diameter of the upper flange ring 1 is 6.6m, the height is 4m, and the wall thickness is 50mm. The arc-shaped connecting section 2 is a cavity cylindrical structure with a certain wall thickness and a concave arc-shaped wall surface. It is set with a variable cross-section from top to bottom, with an upper diameter of 6.6m, a lower diameter of 20m, a height of 16.8m, and a wall thickness of 800mm. The columnar connecting section 3 is a cylindrical structure with a cavity, its diameter is 20m, its height is 1.2m, and its wall thickness is 800mm. The arc-shaped connecting section 2 and the column-shaped connecting section 3 are integrally cast with concrete to form the connecting section, and twenty-four first reserved channels 7 are evenly arranged in the circumferential direction inside the side wall of the connecting section.

The floating tank 4 is a flat cylindrical structure with a cavity, its diameter is 32m, its height is 10m, and its wall thickness is 15mm. The buoy box 4 has a larger cross-sectional area, which can increase the additional mass and potential flow damping of the heaving motion, and provide good motion performance. The inside of the buoyancy tank 4 is provided with a first circumferential subdivision plate 9 with a diameter of 20m and a second circumferential subdivision plate 10 with a diameter of 18m, and the first circumferential subdivision plate 9 and the second circumferential subdivision plate 10 will The inside of the buoyancy tank 4 is divided into an inner ring, an outer ring and a middle section. Twenty-four second reserved channels 8 are arranged in the annulus between the first circumferential subdivision plate 9 and the second circumferential subdivision plate 10, and the bottom of the second reserved channels 8 is fixedly connected to the bottom plate of the buoyancy tank 4 . The twenty-four second reserved tunnels 8 correspond to and communicate with the twenty-four first reserved tunnels 7 one by one, for the mooring line 5 to pass through. The second reserved channel 8 and the first reserved channel 7 are smoothly connected with a certain arc, so as to avoid damage caused by stress concentration when the mooring line 5 is stretched and stressed, and affects the normal operation of the system. The second reserved channel 8 and the first reserved channel 7 can prevent the mooring line 5 from contacting with water, so as to ensure that the mooring anchor point is not damaged. The inside of the buoyancy tank 4 is also provided with four radially uniformly distributed radial subdivision plates 11, and the radial subdivision plate 11 divides the inner ring and the outer ring of the buoyant tank 4 into four sub-chambers, each sub-chamber A valve system capable of water-air replacement is provided, and the position of the center of gravity of the buoyancy tank 4 can be adjusted by adding water ballast in each sub-chamber to ensure basic towing stability.

The mooring system includes twenty-four mooring lines 5 and anchor foundations 6 .

Twenty-four mooring lines 5 include twelve straight mooring lines and twelve oblique mooring lines, and the straight mooring lines and oblique mooring lines are staggered and uniformly arranged in a circular direction. The straight mooring line is set vertically between the buoyancy tank 4 and the anchor foundation 6, and the oblique mooring line is set between the buoyancy tank 4 and the anchor foundation 6 from top to bottom radially from the center to the outside. The included angle in the vertical direction is in the range of 3° to 60°. The lower ends of the twenty-four mooring lines 5 are all anchored to the anchor foundation 6, and the upper ends of the twenty-four mooring lines 5 pass through the second reserved channel 8 of the buoyancy tank 4 and the first reserved channel 7 of the connecting section in turn, and are anchored in The top of the arc-shaped connecting section 2 forms an above-water tension system, which reduces the difficulty of installing the mooring line underwater. Straight mooring lines provide good heave and rotation performance, oblique mooring lines provide greater horizontal restraint, and the circular arrangement of mooring lines 5 can resist wave current forces from all directions. The diameters of the mooring lines 5 are all 167mm, and steel strands, polyester fiber lines, etc. can be used; the outside is wrapped with rubber sleeves to avoid corrosion and damage in seawater. The upper end of the mooring line 5 is provided with a buoy ball before anchoring, so that it can pass through the second reserved channel 8 and the first reserved channel 7; after anchoring, the anchor point is provided with a maintenance device.

The anchoring foundation 6 comprises a hollow square anchoring plate with an outer side length of 32m and an inner side length of 14m; the inner and outer edges of the upper part of the anchoring plate are provided with a square tube wall with a height of 2m, and the inner and outer edges of the lower part are provided with a height of 2m. 5m square apron. The anchor plate body is used to provide the anchor point at the lower end of the mooring line 5. The superstructure formed by the anchor plate body and the cylinder wall can be filled with sand and ballasted, and the skirt plate penetrates into the seabed through the ballast weight and the internal and external pressure difference. After the anchor foundation 6 penetrates into the seabed through the heap load and the internal and external pressure difference, the mooring line 5 is positioned by using the friction resistance provided by the ballast weight and the skirt plate to provide pull-out resistance.

In this way, the mooring system can effectively control the movement of the floating platform in the six degrees of freedom of heaving, surge, sway, yaw, roll, and pitch, ensuring that the tensioned mooring submersible floating foundation It has a small motion response, thus showing good dynamic performance, thus greatly reducing the design requirements for wind turbines.

The construction method of the above-mentioned tension type mooring submersible floating foundation is carried out according to the following steps:

(1) The floating platform and mooring system are prefabricated on land respectively, the wind turbine tower is installed stably on the floating platform, the wind turbine tower and the floating platform are towed and transported to the operating sea area, and the large water plane is used The buoyant tank 4 provides buoyancy to realize the overall floating and towing of the floating platform-tower-wind turbine; at the same time, the mooring system is towed and transported to the operating sea area, and a buoy ball is arranged at the upper end of the mooring line 5;

(2) After the floating platform and the mooring system installed with the wind tower are towed and transported to the operation sea area respectively, ballast is applied to sink the anchor foundation 6 in the mooring system, The anchor foundation 6 is embedded in the seabed to fix the load and the internal and external pressure difference;

(3) Pass the upper ends of the twenty-four mooring lines 5 through the second reserved tunnel 8 and the first reserved tunnel 7 in turn according to the position indicated by the buoy ball, and mooring the mooring lines 5 in a certain proportion (10% to 50%) Pre-tensioning makes it in a tensioned state to balance the buoyancy of the floating platform;

(4) Inject water into the inner sub-chamber of the buoyancy tank 4 through the valve system of water-gas replacement, so that the floating platform installed with the fan tower loses part of its buoyancy and sinks, and in the sub-compartment of the outer ring of the buoyancy tank 4 during the sinking process The air provides a certain buoyancy to the foundation to ensure the stability of the offshore wind power floating foundation; when the floating platform sinks to the design draft position, the mooring line 5 reaches the preset length, and the mooring line 5 completes the remaining ratio (50 %～90%) pre-tensioning to balance the buoyancy of the floating platform; anchor the upper end of the mooring line 5 to the top of the arc connecting section 2;

(5) The water body in the sub-chambers of the inner ring of the buoyancy tank 4 is discharged through the valve system of water-air replacement, so as to ensure that the tensioned mooring submersible floating foundation has a certain buoyancy;

(6) The water body that brings the mooring line 5 into the second reserved channel 8 and the first reserved channel 7 is discharged through high-pressure pumping, and the bottom of the buoyancy tank 4 is sealed to ensure that the second reserved channel 8 and the first reserved channel 7 in a dry state;

(7) After being in place, adjust the center of gravity position of the tensioned mooring submersible floating foundation by injecting water into the outer ring compartment of the buoyancy tank 4 to ensure safe and stable operation of the tensioned mooring submersible floating foundation.

Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are only illustrative and not restrictive. Those of ordinary skill in the art Under the enlightenment of the present invention, without departing from the purpose of the present invention and the scope of protection of the claims, personnel can also make specific changes in many forms, and these all belong to the protection scope of the present invention.

Claims (7)

1. The construction method of the tension mooring submerged floating foundation is characterized in that the tension mooring submerged floating foundation consists of a floating platform and a mooring system;

the floating platform comprises a connecting section and a buoyancy tank which are both hollow structures, the upper end of the connecting section is connected with a fan tower through a flange ring, and the lower end of the connecting section is fixedly connected with the buoyancy tank; the connecting section consists of an arc-shaped connecting section at the upper part and a columnar connecting section at the lower part, wherein the arc-shaped connecting section is arranged from top to bottom in a variable cross section manner, and the wall surface of the side wall of the arc-shaped connecting section is of a concave arc shape; a plurality of first reserved holes are uniformly distributed in the circumferential direction inside the side wall of the connecting section; the floating box is internally provided with a first annular cabin dividing plate, a second annular cabin dividing plate and a plurality of radial cabin dividing plates, the first annular cabin dividing plate, the second annular cabin dividing plate and the plurality of radial cabin dividing plates divide the floating box into a plurality of cabin dividing chambers, and each cabin dividing chamber is provided with a valve system capable of replacing water and air; a plurality of second reserved pore passages are uniformly distributed between the first annular dividing plate and the second annular dividing plate in the circumferential direction, and the bottoms of the second reserved pore passages are fixedly connected with the bottom plate of the buoyancy tank; the number of the second reserved pore canals is the same as that of the first reserved pore canals, and the second reserved pore canals are correspondingly connected and communicated with the first reserved pore canals one by one;

the mooring system comprises mooring lines and an anchoring foundation, the number of the mooring lines is the same as that of the second reserved pore canals and the first reserved pore canals, the mooring lines consist of straight mooring lines and inclined mooring lines which are uniformly and annularly arranged in a staggered manner, the straight mooring lines are vertically arranged between the floating box and the anchoring foundation, and the inclined mooring lines are radially and obliquely arranged from the center to the outside from top to bottom between the floating box and the anchoring foundation; the lower ends of the mooring lines are anchored to the anchoring foundation, and the upper ends of the mooring lines sequentially pass through the second reserved pore canal and the first reserved pore canal and are anchored to the top of the connecting section; the anchoring foundation comprises a hollow anchoring plate body, wherein the inner and outer edges of the upper part of the anchoring plate body are provided with cylinder walls, and the inner and outer edges of the lower part of the anchoring plate body are provided with skirtboards;

the construction method comprises the following steps:

(1) Firstly prefabricating the floating platform and the mooring system on land, installing a fan tower on the floating platform stably, towing and transporting the floating platform with the fan tower installed to an operation sea area, towing and transporting the mooring system to the operation sea area, wherein buoy balls are arranged at the upper ends of mooring lines;

(2) Applying ballast to sink the anchoring foundation and embedding the anchoring foundation into the sea floor for fixation by stacking and internal and external pressure differences;

(3) Sequentially passing the upper end of the mooring line through the second reserved pore canal and the first reserved pore canal according to the buoy ball indication position, and pre-tensioning the mooring line by 10% -50% to enable the mooring line to be in a tensioning state so as to balance the buoyancy of the floating platform;

(4) Injecting water into the sub-cabins through a water-gas replacement valve system, so that the floating platform provided with the fan tower loses part of buoyancy and sinks, when sinking to a designed draft position, the mooring line is pre-tensioned by 50% -90% to balance the buoyancy of the floating platform, and the upper end of the mooring line is anchored at the top of the connecting section;

(5) Discharging the water body in the sub-cabins through a valve system for replacing water and air;

(6) The mooring line is brought into the water body in the second reserved pore canal and the first reserved pore canal to be discharged through high-pressure inflation, and the bottom of the buoyancy tank is sealed;

(7) And adjusting the gravity center position of the tension mooring submerged floating foundation through the sub-cabins.

2. The construction method of a tension mooring submerged floating foundation according to claim 1, wherein the arc-shaped connecting section and the columnar connecting section of the connecting section are integrally cast with concrete.

3. The method of claim 1, wherein the second pre-tunnel is smoothly joined to the first pre-tunnel in an arc.

4. The method of constructing a tension moored submerged foundation according to claim 1, wherein the number of mooring lines is 8-32, wherein the number of straight mooring lines and the number of inclined mooring lines each account for half.

5. The method of constructing a tension mooring submerged floating foundation of claim 1, wherein the inclined mooring line is at an angle of 3 ° to 60 ° to the vertical.

6. The method of constructing a tension mooring submerged foundation according to claim 1, wherein the mooring line upper ends are provided with buoy balls before anchoring, and each anchoring point after anchoring is provided with a maintenance device.

7. The method of constructing a tension mooring submerged foundation of claim 1, wherein the exposed portions of the mooring lines are each encased in rubber bushings.

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