A method for constructing cofferdams for artificial islands at sea

Abstract

This invention relates to a method for marine transportation of steel cylinders and a method for constructing cofferdams for artificial islands at sea, belonging to the field of water conservancy engineering technology. The method for marine transportation of steel cylinders includes the following steps: loading a fixing device onto a transport vessel. The fixing device includes a platform fixed to the transport vessel and fixing components for fixing the steel cylinders. The platform includes multiple support platforms arranged sequentially from bottom to top, with multiple fixing components on each support platform. Steel cylinders of different diameters are hoisted onto the corresponding support platforms of the fixing device, one steel cylinder hoisted onto each support platform. During hoisting, the lower-level steel cylinder is fitted over the adjacent upper-level support platform and steel cylinder. After each steel cylinder is hoisted, it is fixed with the fixing components. After all hoisted steel cylinders are fixed, the steel cylinders are transported to the construction area by the transport vessel. This method allows for the transport of multiple steel cylinders at once, significantly improving the efficiency of steel cylinder transportation.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering technology, and particularly relates to the field of marine artificial island construction technology, specifically to a method for marine transportation of steel cylinders and a method for constructing marine artificial island cofferdams. Background Technology

[0002] Steel cylinder cofferdam construction is a method for rapidly building artificial islands at sea, with large-diameter steel cylinders being one of the main components. Currently, during the construction of artificial island cofferdams, steel cylinders are typically fabricated in a prefabrication plant and then transported to the construction site by transport ships. To facilitate the transportation of steel cylinders, some offshore transport and securing devices have been developed (see patents CN206766286U, CN215922480U, etc.). However, existing offshore transport and securing devices can only secure one steel cylinder at a time, meaning that transport ships can only transport one cylinder at a time, resulting in extremely low transportation efficiency and severely impacting the construction cycle of the artificial island cofferdam. Therefore, improving the transportation efficiency of steel cylinders and shortening the construction cycle of the artificial island cofferdam is a pressing technical problem that needs to be solved. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for transporting steel cylinders at sea and a method for constructing cofferdams for artificial islands at sea. This method allows for the transport of multiple steel cylinders at once, significantly improving the efficiency of steel cylinder transportation.

[0004] This invention provides a method for marine transportation of steel cylinders, comprising the following steps:

[0005] A fixing device is installed on the transport ship. The fixing device includes a pedestal fixed to the transport ship and fixing components for fixing the steel cylinder. The pedestal includes multiple support platforms arranged sequentially from bottom to top. The size of the support platforms decreases from bottom to top so that the outer edges of the multiple support platforms form a stepped shape. Multiple fixing components are provided on each support platform. The fixing components on each support platform are located on the stepped surface. Multiple fixing components on the same support platform are used to fix a steel cylinder together.

[0006] Steel cylinders of different diameters are hoisted sequentially onto the support platforms of the fixing device from top to bottom or bottom to top, in order of increasing or decreasing diameter. One steel cylinder is hoisted onto each support platform. When hoisting the steel cylinders, they are hoisted to the stepped surface, and the steel cylinders on the lower level are placed over the support platform and steel cylinders on the adjacent upper level. After each steel cylinder is hoisted, it is fixed in place using multiple fixing components on the corresponding support platform.

[0007] After all the steel cylinders have been hoisted and secured, they will be transported to the construction area by a transport ship.

[0008] In some embodiments, when hoisting the steel cylinder, the steel cylinder is placed on the support platform with its axis vertical.

[0009] In some embodiments, the fixing assembly includes a pair of fixing clamps; when hoisting the steel cylinder, the lower end wall of the steel cylinder is placed between the pair of fixing clamps so as to use the fixing clamps to hold and fix the lower end wall of the steel cylinder.

[0010] In some embodiments, the fixing clamp includes a connecting part arranged parallel to the support platform surface and a clamping part arranged perpendicular to the support platform surface. The connecting part is fixedly connected to the support platform surface, and the clamping part is used to fit and connect the steel cylinder wall.

[0011] In some embodiments, the support platform is cylindrical, with the diameter of the cylindrical support platform decreasing layer by layer from bottom to top, and the multiple support platforms are arranged coaxially; multiple fixing components located on the same layer of support platform are evenly distributed on the stepped surface along the circumference of the support platform.

[0012] In some embodiments, a steel cylinder lifting device is used to lift the steel cylinder; the steel cylinder lifting device includes a lifting frame, and the lifting frame is connected to a plurality of clamps for clamping the upper end wall of the steel cylinder, the plurality of clamps being distributed in a ring; the clamps are slidably connected to the lifting frame to move relative to the lifting frame in a radial direction along the ring; before lifting the steel cylinder, the clamps are moved to adjust the position of the clamps so that the position of the clamps matches the diameter of the steel cylinder to be lifted.

[0013] In addition, the present invention also provides a method for constructing a cofferdam for an artificial island at sea, comprising the following steps:

[0014] Based on the shape of the cofferdam for the artificial island to be built, the required steel cylinders are divided into various specifications of steel cylinders with different diameters.

[0015] The above-mentioned method of transporting steel cylinders by sea was used to transport steel cylinders of different specifications to the construction area.

[0016] Steel cylinders of different specifications transported by transport ships are hoisted to their designated positions and sunk to form an artificial island cofferdam.

[0017] In some embodiments, steel cylinders of different sizes are arranged alternately to form a cofferdam for the artificial island.

[0018] In some embodiments, when the cofferdam of the artificial island to be built has multiple closed areas, the required number of steel cylinders is determined according to the number of closed areas; steel cylinders of the same specification are used to enclose a closed area, and steel cylinders of different specifications are used to enclose different closed areas.

[0019] In some embodiments, when the cofferdam of the artificial island to be built has a symmetrical structure, the symmetrical parts are arranged with steel cylinders of the same specifications.

[0020] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0021] 1. The method for transporting steel cylinders at sea provided by the present invention uses a fixing device installed on the transport ship to fix steel cylinders of different diameters sequentially from the outside to the inside of the transport ship, thereby realizing the fixing and transportation of multiple steel cylinders, significantly improving the transportation efficiency of steel cylinders and shortening the construction cycle.

[0022] 2. The steel cylinder marine transportation method provided by the present invention uses a simple fixing device structure, which will not cause a significant increase in construction costs. On the contrary, due to the improvement of transportation efficiency, the construction costs can be significantly reduced.

[0023] 3. The method for constructing a marine artificial island cofferdam provided by the present invention divides the steel cylinders required for constructing the artificial island cofferdam into various specifications with different diameters. Then, the steel cylinders of different specifications are transported to the construction water area by the same transport ship in a manner of being nested from the outside to the inside. The steel cylinders of different specifications are then hoisted to the predetermined positions corresponding to the steel cylinders of different specifications and sunk. Thus, the construction cycle of the artificial island cofferdam is significantly shortened without affecting the construction quality of the artificial island cofferdam. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0025] Figure 1 A flowchart illustrating the method for marine transportation of steel cylinders provided in an embodiment of the present invention;

[0026] Figure 2 A front view of the fixing device used in the marine transportation method of the steel cylinder provided in an embodiment of the present invention;

[0027] Figure 3 A top view of the fixing device used in the marine transportation method of the steel cylinder provided in the embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the mounting and fixing device on the transport ship in the method for transporting steel cylinders by sea according to an embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram showing the steel cylinder being fixed to the transport ship in the marine transportation method for steel cylinders provided in an embodiment of the present invention.

[0030] Figure 6This is a front view of the steel cylinder after it has been fixed to the fixing device in the steel cylinder marine transportation method provided in this embodiment of the invention;

[0031] Figure 7 This is a top view of the steel cylinder after it has been fixed to the fixing device in the steel cylinder marine transportation method provided in this embodiment of the invention;

[0032] Figure 8 For along Figure 7 Sectional view of line AA in the middle;

[0033] Figure 9 for Figure 7 A magnified view of a portion of point B in the middle;

[0034] Figure 10 This is a front view of the steel cylinder lifting device used in the steel cylinder marine transportation method provided in this embodiment of the invention;

[0035] Figure 11 A bottom view of the steel cylinder lifting device used in the steel cylinder marine transportation method provided in the embodiments of the present invention;

[0036] Figure 12 This is a schematic diagram of the steel cylinder hoisting process in the steel cylinder marine transportation method provided in an embodiment of the present invention;

[0037] Figure 13 A flowchart illustrating the method for constructing a cofferdam for an artificial island at sea, as provided in an embodiment of the present invention.

[0038] Figure 14 A schematic diagram of an artificial island cofferdam using the first steel cylinder arrangement method in the construction method of an artificial island cofferdam provided in the embodiments of the present invention;

[0039] Figure 15 This is a schematic diagram of an artificial island cofferdam using the second steel cylinder arrangement method in the marine artificial island cofferdam construction method provided in the embodiments of the present invention;

[0040] Figure 16 This is a schematic diagram of an artificial island cofferdam using a third type of steel cylinder arrangement in the construction method of an artificial island cofferdam provided in an embodiment of the present invention.

[0041] In the picture:

[0042] 1. Fixing device; 2. Steel cylinder; 3. Transport ship; 4. Steel cylinder lifting device;

[0043] 11. Base; 111. Support platform; 12. Fixing component; 121. Fixing clamp; 1211. Connecting part; 1212. Clamping part; 1213. Stiffening rib;

[0044] 21. First steel cylinder; 22. Second steel cylinder; 23. Third steel cylinder;

[0045] 41. Hanger; 42. Clamp; 43. Slide rail. Detailed Implementation

[0046] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this 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. Therefore, they should not be construed as limitations on this invention.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] As attached Figures 1-12 As shown, in an illustrative embodiment of the method for transporting steel cylinders by sea according to the present invention, the method includes the following steps:

[0050] S101. Mount a fixing device 1 on the transport ship 3. The fixing device 1 includes a base 11 fixed to the transport ship 3 and fixing components 12 for fixing the steel cylinder 2. The base 11 includes multiple support platforms 111 arranged sequentially from bottom to top. The size of the support platforms 111 decreases from bottom to top, so that the outer edges of the multiple support platforms 111 form a stepped shape. Multiple fixing components 12 are provided on each support platform 111. The fixing components 12 on each support platform 111 are located at the stepped surface. Multiple fixing components 12 on the same support platform 111 are used to fix a steel cylinder 2 together.

[0051] S102. Steel cylinders 2 of different diameters are hoisted onto the support platforms 111 of the fixing device 1 in order of increasing or decreasing diameter. One steel cylinder 2 is hoisted onto each support platform 111. When hoisting the steel cylinder 2, the steel cylinder 2 is hoisted to the stepped surface, and the steel cylinder 2 located on the lower layer is fitted over the support platform 111 of the adjacent upper layer and the steel cylinder 2. After each steel cylinder 2 is hoisted, the steel cylinder 2 is fixed by multiple fixing components 12 on the corresponding support platform 111.

[0052] S103. After all the steel cylinders 2 to be hoisted are fixed, the steel cylinders 2 are transported to the construction water area by the transport ship 3.

[0053] The aforementioned method for transporting steel cylinders at sea utilizes a fixing device 1 installed on the transport vessel 3 to sequentially mount and fix steel cylinders 2 of different diameters onto the vessel 3 from the outside in. This achieves the fixing and transportation of multiple steel cylinders 2, significantly improving the transportation efficiency and shortening the construction cycle. Furthermore, the fixing device 1 used in this method has a simple structure and does not significantly increase construction costs; on the contrary, the improved transportation efficiency leads to a substantial reduction in construction costs. In addition, when fixing multiple steel cylinders 2 using the fixing device 1, one steel cylinder 2 is fixed on each support platform 111. Since the support platforms 111 rise in a stepped manner, and the height of the steel cylinders 2 used in a construction project is consistent, the upper end of the steel cylinder 2 also rises in a stepped manner from the outside in, facilitating the hoisting of the steel cylinders 2.

[0054] In step S102, it should be noted that, as Figure 11 As shown, when hoisting the steel cylinder 2, the steel cylinder 2 is placed on the support platform 111 with its axis in a vertical position to facilitate the hoisting of the steel cylinder 2 layer by layer.

[0055] Regarding the fixing device 1 used in the above-mentioned method of transporting steel cylinders by sea, it should be noted that, as Figure 3 As shown, the support platform 111 is cylindrical, and the diameter of the cylindrical support platform 111 decreases layer by layer from bottom to top. Multiple support platforms 111 are arranged coaxially. Using a cylindrical support platform 111 allows for better matching with the steel cylinder 2, enabling the transportation of steel cylinders 2 with small diameter differences. Preferably, as... Figure 2 As shown, the number of layers of support platform 111 is 2-4. In order to avoid affecting the construction quality of the artificial island cofferdam, the diameter difference of the steel cylinder 2 should not be too large. Therefore, in the same construction project, the specifications of steel cylinder 2 should not be too many. The number of layers of support platform 111 can be determined according to the specifications of steel cylinder 2.

[0056] Furthermore, such as Figure 3As shown, multiple fixing components 12 located on the same support platform 111 are evenly distributed on the stepped surface along the circumference of the support platform 111. This arrangement of the fixing components 12 ensures that the steel cylinder 2 is firmly fixed, and at the same time, makes the force between the steel cylinder 2 and each fixing component 12 uniform, effectively preventing the fixing components 12 from being damaged due to uneven force during transportation.

[0057] To facilitate fixing the steel cylinder 2, such as Figure 8 and Figure 9 As shown, in this embodiment, the fixing component 12 includes a pair of fixing clips 121; as Figure 11 As shown, when hoisting the steel cylinder 2, the lower end wall of the steel cylinder 2 is placed between the paired fixing clamps 121, so that the fixing clamps 121 can be used to clamp and fix the lower end wall of the steel cylinder 2. Specifically, as shown... Figure 9 As shown, in this embodiment, the fixing clamp 121 includes a connecting portion 1211 parallel to the surface of the support platform 111 and a clamping portion 1212 perpendicular to the surface of the support platform 111. The connecting portion 1211 is fixedly connected to the surface of the support platform 111, and the clamping portion 1212 is used to adhere to and connect the wall of the steel cylinder 2. When fixing the steel cylinder 2, the lower end of the steel cylinder 2 is inserted between the clamping portions 1212 of the two fixing clamps 121, so that the clamping portions 1212 adhere to the wall of the steel cylinder 2. The clamping portions 1212 and the wall of the steel cylinder 2 can be fixed by appropriate welding. The fixing assembly 12 with the above structure is simple in structure and has low manufacturing cost. It is understood that stiffening ribs 1213 can be provided between the connecting portion 1211 and the clamping portion 1212 to improve the structural rigidity and strength of the fixing clamp 121.

[0058] To facilitate the hoisting of steel cylinder 2, such as Figures 10-12 As shown, in this embodiment, a steel cylinder lifting device 4 is used to lift the steel cylinder 2. The steel cylinder lifting device 4 includes a lifting frame 41, and the lifting frame 41 is connected to a plurality of clamps 42 for clamping the upper wall of the steel cylinder 2. The plurality of clamps 42 are arranged in a ring. The clamps 42 are slidably connected to the lifting frame 41 to move relative to the lifting frame 41 in a radial direction along the ring. Before lifting the steel cylinder 2, the clamps 42 are moved to adjust their positions so that the positions of the clamps 42 match the diameter of the steel cylinder 2 to be lifted. It should be noted that, as Figure 11 As shown, in this embodiment, the hanger 41 is provided with multiple slide rails 43 extending radially along the ring, and the clamps 42 are slidably connected to the slide rails 43 in a corresponding manner; by sliding the clamps 42 along the slide rails 43, the clamps 42 can move relative to the hanger 41, thereby matching steel cylinders 2 of different diameters.

[0059] like Figure 13 As shown in the figure, this embodiment of the invention also provides a method for constructing a cofferdam for an artificial island at sea, comprising the following steps:

[0060] S201. Based on the shape of the cofferdam of the artificial island to be built, the required steel cylinder 2 is divided into steel cylinders 2 of various specifications with different diameters.

[0061] S202. The steel cylinders 2 of different specifications are transported to the construction water area using the above-mentioned marine transportation method.

[0062] S203. The steel cylinders 2 of different specifications transported by the transport ship 3 are hoisted to the predetermined positions corresponding to the steel cylinders 2 of different specifications and then sunk to form an artificial island cofferdam through the steel cylinders 2.

[0063] In the above-mentioned method for constructing cofferdams for artificial islands at sea, it should be noted that the diameter difference between two adjacent steel cylinders 2 is 0.3m to 0.5m. Since the diameter of the steel cylinders 2 used in constructing artificial island cofferdams is usually over 20 meters, dividing the steel cylinders 2 into different specifications according to a diameter difference of 0.3m to 0.5m has little impact on the construction quality of the cofferdam. Furthermore, a diameter difference of 0.3m to 0.5m is sufficient to facilitate the nesting and transportation of the steel cylinders 2, thereby improving the transportation efficiency. It should also be noted that the preferred number of specifications for the steel cylinders 2 is 2 to 4. Too many specifications will result in an excessively large diameter difference between the largest and smallest steel cylinders 2, affecting the construction quality of the artificial island cofferdam.

[0064] The above-mentioned method for constructing cofferdams for artificial islands divides the steel cylinders 2 required for the construction of the cofferdams into various specifications with different diameters. Then, the steel cylinders 2 of different specifications are transported to the construction water area by the same transport ship 3 in a manner that is nested from the outside to the inside. The steel cylinders 2 of different specifications are then hoisted to the predetermined positions corresponding to the steel cylinders 2 of different specifications and sunk. Thus, the construction period of the cofferdams for artificial islands is significantly shortened without affecting the construction quality of the cofferdams.

[0065] Figure 14 The diagram illustrates one arrangement of steel cylinders 2 in the cofferdam of an artificial island. It should be noted that, to clearly show the different specifications of the steel cylinders 2, Figure 14 The diameter difference of steel cylinders 2 of different specifications (namely, first steel cylinder 21, second steel cylinder 22, and third steel cylinder 23, in descending order of size) is magnified. However, in actual construction, the ratio of the diameter difference of steel cylinders 2 of different specifications to the diameter of steel cylinder 2 is even smaller. For example... Figure 14 As shown, steel cylinders 2 of different specifications are arranged alternately to form a cofferdam for the artificial island. Specifically, the first steel cylinder 21, the second steel cylinder 22, and the third steel cylinder 23 (i.e., steel cylinders 2 of decreasing size) are arranged in a cyclical alternation to form the cofferdam for the artificial island. This arrangement of steel cylinders 2 helps to ensure the construction quality of the cofferdam for the artificial island.

[0066] Figure 15Another arrangement of steel cylinders 2 in the cofferdam of the artificial island is shown. It should be noted that, in order to clearly show the different specifications of steel cylinders 2, Figure 15 The diameter difference of steel cylinders 2 of different specifications is enlarged (the specifications are from largest to smallest: first steel cylinder 21 and second steel cylinder 22). In actual construction, the ratio of the diameter difference of steel cylinders 2 of different specifications to the diameter of steel cylinder 2 is even smaller. For example... Figure 15 As shown, when the cofferdam of the artificial island to be constructed has multiple closed areas, the required number and specifications of steel cylinders 2 are determined according to the number of closed areas. Steel cylinders 2 of the same specification are used to enclose one closed area, while different specifications of steel cylinders 2 are used to enclose different closed areas. Specifically, the upper closed area is enclosed by the second steel cylinder 22, and the lower closed area is enclosed by the first steel cylinder 21. This arrangement of steel cylinders 2 helps to ensure the construction quality of the artificial island cofferdam.

[0067] Figure 16 This illustrates another arrangement of steel cylinders 2 in the cofferdam of the artificial island. It should be noted that, in order to clearly show the different specifications of steel cylinders 2, Figure 16 The diameter difference of steel cylinders 2 of different specifications is enlarged (the specifications are from largest to smallest: first steel cylinder 21 and second steel cylinder 22). In actual construction, the ratio of the diameter difference of steel cylinders 2 of different specifications to the diameter of steel cylinder 2 is even smaller. For example... Figure 16 As shown, when the cofferdam of the artificial island to be constructed has a symmetrical structure, the symmetrical parts are arranged with steel cylinders 2 of the same specifications. Specifically, the upper left part and its symmetrical upper right part both use second steel cylinders 22, and the lower left part and its symmetrical lower right part both use first steel cylinders 21. This arrangement of steel cylinders 2 helps to ensure the construction quality of the artificial island cofferdam.

[0068] Through the description of several embodiments of the steel cylinder marine transportation method and the marine artificial island cofferdam construction method of the present invention, it can be seen that the embodiments of the steel cylinder marine transportation method and the marine artificial island cofferdam construction method of the present invention have at least one or more of the following advantages:

[0069] 1. The method for transporting steel cylinders by sea provided in this embodiment of the invention uses a fixing device 1 installed on the transport ship 3 to fix steel cylinders 2 of different diameters sequentially from the outside to the inside on the transport ship 3, thereby realizing the fixing and transportation of multiple steel cylinders 2, significantly improving the transportation efficiency of steel cylinders 2 and shortening the construction cycle.

[0070] 2. In the method for transporting steel cylinders at sea provided in this embodiment of the invention, the fixing device 1 has a simple structure and will not cause a significant increase in construction costs. On the contrary, due to the improvement in transportation efficiency, the construction costs can be significantly reduced.

[0071] 3. The method for constructing a marine artificial island cofferdam provided in this embodiment of the invention divides the steel cylinders 2 required for constructing the artificial island cofferdam into various specifications with different diameters. Then, the steel cylinders 2 of different specifications are transported to the construction water area by the same transport ship 3 in a manner of being nested from the outside to the inside. The steel cylinders 2 of different specifications are then hoisted to the predetermined positions corresponding to the steel cylinders 2 of different specifications and sunk. Thus, the construction cycle of the artificial island cofferdam is significantly shortened without affecting the construction quality of the artificial island cofferdam.

[0072] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0073] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for constructing cofferdams for artificial islands at sea, characterized in that, Includes the following steps: Based on the shape of the cofferdam for the artificial island to be built, the required steel cylinders are divided into various specifications of steel cylinders with different diameters. The steel cylinders of different specifications were transported to the construction area by sea using the steel cylinder marine transport method; The steel cylinders of different specifications transported by the transport ship are hoisted to the predetermined positions corresponding to the steel cylinders of different specifications and then sunk to form an artificial island cofferdam; wherein, the steel cylinders of different specifications are arranged alternately to form the artificial island cofferdam. The method for transporting the steel cylinder by sea includes the following steps: A fixing device is installed on the transport ship. The fixing device includes a pedestal fixed to the transport ship and fixing components for fixing a steel cylinder. The pedestal includes multiple support platforms arranged sequentially from bottom to top. The size of the support platforms decreases from bottom to top, so that the outer edges of the multiple support platforms form a stepped shape. Each support platform is provided with multiple fixing components. The fixing components on each support platform are located at the stepped surface. Multiple fixing components on the same support platform are used to jointly fix one steel cylinder. Steel cylinders of different diameters are hoisted sequentially onto the support platforms of the fixing device from top to bottom or bottom to top, in order of increasing or decreasing diameter. One steel cylinder is hoisted onto each support platform. When hoisting the steel cylinder, it is hoisted to the stepped surface, and the lower steel cylinder is fitted over the support platform and the steel cylinder of the adjacent upper layer. After each steel cylinder is hoisted, it is fixed by multiple fixing components on the corresponding support platform. After all the steel cylinders have been hoisted and secured, they will be transported to the construction area by the transport vessel.

2. The method for constructing a cofferdam for an artificial island at sea according to claim 1, characterized in that, When hoisting the steel cylinder, the steel cylinder is placed on the support platform with its axis vertical.

3. The method for constructing a cofferdam for an artificial island at sea according to claim 2, characterized in that, The fixing assembly includes a pair of fixing clamps; when hoisting the steel cylinder, the lower end wall of the steel cylinder is placed between the pair of fixing clamps so as to use the fixing clamps to hold and fix the lower end wall of the steel cylinder.

4. The method for constructing a cofferdam for an artificial island at sea according to claim 3, characterized in that, The fixing clamp includes a connecting part arranged parallel to the support platform surface and a clamping part arranged perpendicular to the support platform surface. The connecting part is fixedly connected to the support platform surface, and the clamping part is used to fit and connect to the cylinder wall of the steel cylinder.

5. The method for constructing a cofferdam for an artificial island at sea according to claim 3 or 4, characterized in that, The support platform is cylindrical, and the diameter of the cylindrical support platform decreases layer by layer from bottom to top. The multiple support platforms are arranged coaxially. The multiple fixing components located on the same layer of the support platform are evenly distributed on the stepped surface along the circumference of the support platform.

6. The method for constructing a cofferdam for an artificial island at sea according to claim 1, characterized in that, The steel cylinder is lifted using a steel cylinder lifting device. The steel cylinder lifting device includes a lifting frame, which is connected to a plurality of clamps for holding the upper wall of the steel cylinder. The plurality of clamps are arranged in a ring. The clamps are slidably connected to the lifting frame to move relative to the lifting frame in a radial direction along the ring. Before lifting the steel cylinder, the clamps are moved to adjust their positions so that the positions of the clamps match the diameter of the steel cylinder to be lifted.

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