Anchor cable system construction method of offshore split type floating structure

Abstract

The invention discloses an anchor cable system construction method for an offshore split type floating structure. The anchor cable system construction method comprises the steps that 1, a plurality of holding power anchors are placed on a seabed on the periphery of a design point of a first structure in a radial shape through a workboat; an anchor rod of the holding power anchor faces the first structure; the holding power anchor is connected with a buoy; 2, floating the first structure to a design point, and respectively connecting a plurality of holding power anchors with a cable adjusting device on the first structure by adopting a main cable; in the connection sequence, a group of main cables which are oppositely arranged in the tidal flow direction are preferentially connected; 3, after positioning sinking construction of the first structure is completed, the holding power anchor and the main cable are disconnected, and then the holding power anchor is transferred to the anchor position corresponding to the second structure; and floating the second structure to the design point, and connecting the main cable of the second structure according to the mode in the step 2. According to the method, the holding power anchor is adopted to replace a traditional positioning structure, the method is suitable for limited construction water areas, turnover use is convenient, and the construction requirement of the split type floating structure is met.

Description

Technical Field

[0001] The present invention relates to the technical field of marine engineering construction, and particularly relates to a construction method for an anchor cable system of a marine split floating structure. Background Art

[0002] With the continuous progress and improvement of the bridge construction system, people are increasingly pursuing the novelty and innovation of bridge structures, and strive to explore more innovative and advanced technologies in design and construction to improve project efficiency and quality. The anchor block of the Liuwudian Channel Bridge in the Xiamen Third East Passage Project adopts a split caisson foundation, which is the first case in China. Based on this, a positioning anchor cable system and its construction method suitable for marine split floating structures are designed.

[0003] To ensure the installation accuracy of large floating structures such as steel caissons, an anchor cable system is usually used to fix the steel caisson to resist the influence of external forces such as wind, water flow, and waves on the position and attitude of the caisson. Traditional anchor cable systems usually adopt positioning structures such as positioning boats, anchor piers, anchor piles, and gravity anchors. In the above projects, these positioning structures have the following deficiencies:

[0004] (1) The construction water area of the east anchor block of the Liuwudian Channel Bridge is between the Liuwudian Channel and the Jintong Channel, and the operation space is limited. If the positioning method of a positioning boat is adopted, the anchor cables of the positioning boat will invade the channel, posing a certain safety risk. (2) Two sets of positioning anchor cable systems need to be arranged in the adjacent position for the split steel caisson. The anchor piers and anchor piles are immovable structures, so they cannot be recycled. The gravity anchor has a large self-weight, and its casting and displacement both require large lifting equipment and storage sites, resulting in high construction costs. (3) Typhoons occur frequently in coastal areas, and the operation window period is precious. Usually, after the first caisson is lowered, the positioning of the second caisson needs to be carried out immediately. The production cycle of structures such as anchor piers, anchor piles, and gravity anchors is long, and they cannot quickly meet the on-site construction requirements. Summary of the Invention

[0005] The main technical problem to be solved by the present invention is to provide a construction method for an anchor cable system of a marine split floating structure, which is not only applicable to limited construction water areas, but also convenient for recycling to meet the construction needs of split structures.

[0006] To solve the above technical problems, the present invention provides a construction method for an anchor cable system of a marine split floating structure, which is characterized in that: the split floating structure at least includes a first structure and a second structure;

[0007] The anchor cable system includes a plurality of drag anchors, a main cable, and a cable adjusting device; the drag anchors are embedded in the seabed; a set of the cable adjusting devices are respectively arranged on the first structure and the second structure; the main cable is used to connect the drag anchors and the cable adjusting devices;

[0008] The construction method includes the following steps:

[0009] Step 1: Lowering the drag anchors; using a construction vessel to radially lower the several drag anchors onto the seabed outside the design points of the first structure; the shanks of the drag anchors face the first structure; the drag anchors are connected with buoys;

[0010] Step 2: Connecting the main cables; floating the first structure to the design point, and using the main cables to respectively connect the several drag anchors with the cable adjusting devices on the first structure; in terms of the connection sequence, preferentially connect a group of main cables arranged oppositely along the tidal flow direction;

[0011] Step 3: Transfer of the anchor-cable system; after the positioning and sinking construction of the first structure is completed, disconnect the drag anchors from the main cables and transfer them to the corresponding anchor positions of the second structure; float the second structure to the design point and connect the main cables of the second structure in the manner of Step 2.

[0012] In a preferred embodiment, Step 1 includes:

[0013] Step 11: Determining the lowering sequence of the drag anchors; driving the construction vessel to the anchor position and keeping it parallel to the layout orientation of the drag anchors;

[0014] Step 12: Connect a section of anchor chain to the end of the drag anchor far from the anchor claw; use steel wire ropes to respectively connect the free end of the anchor chain and the end of the drag anchor close to the anchor claw to hang the drag anchor; horizontally lower the drag anchor to the seabed;

[0015] Step 13: Hang the buoy at the free end of the steel wire rope.

[0016] In a preferred embodiment, in Step 2, when the first structure is floated to the design point, it is at the ebb tide stage, and the connection sequence of the main cables is: connect the main cable of the first structure along the downstream direction of the ebb tide before the low slack tide, then connect the main cable of the first structure along the downstream direction of the flood tide after the low slack tide, and finally connect the main cable in the non-tidal flow direction during the subsequent high slack tide or low slack tide stage.

[0017] In a preferred embodiment, in Step 2, when the first structure is floated to the design point, it is at the flood tide stage, and the connection sequence of the main cables is: connect the main cable of the first structure along the downstream direction of the flood tide before the high slack tide, then connect the main cable of the first structure along the downstream direction of the ebb tide after the high slack tide, and finally connect the main cable in the non-tidal flow direction during the subsequent low slack tide or high slack tide stage.

[0018] In a preferred embodiment, Step 2 includes:

[0019] Step 21: Float the first structure to a distance downstream from the design point and stabilize it;

[0020] Step 22: one end of the main cable is connected to the grab anchor in the downstream direction of the first structure, and the other end is towed to the first structure by a construction vessel and connected to the cable adjustment device on the first structure; during this process, the construction vessel operates upstream;

[0021] Step 23: After the tidal current turns, the first structure is floated to the designed point and stabilized; the construction vessel is equipped with a main cable, and the gripping anchor in the downstream direction of the first structure is connected to the cable adjustment device in the manner described in step 22; during this process, the construction vessel operates upstream;

[0022] Step 24: In the subsequent slack tide stage, stabilize the first structure and use the construction vessel to connect the main cable in the non-tidal flow direction.

[0023] In a preferred embodiment, step 3 includes:

[0024] Step 31: After the positioning and sinking construction of the first structure is completed, the plurality of main cables are disconnected from the gripping anchors and then recovered;

[0025] Step 32: After lifting the plurality of gripping anchors and the buoys from the seabed, they are transferred to the anchor position corresponding to the second structure according to the principle of proximity, and then the gripping anchors are lowered in the manner of step 1; the plurality of gripping anchors are also arranged radially with the second structure as the center;

[0026] Step 33: Float the second structure to the design point; connect the transferred grab anchors to the cable adjustment devices on the second structure using the main cables in the manner of step 2; in terms of connection sequence, a group of main cables that are relatively arranged along the tidal current direction are preferentially connected.

[0027] In a preferred embodiment, the buoy comprises a first buoy; an end of the gripping anchor away from the fluke is connected to a section of anchor chain; and the first buoy is connected to the free end of the anchor chain via a section of rope.

[0028] In a preferred embodiment, the buoy further comprises a second buoy; the second buoy is connected to an end of the gripping anchor close to the fluke via a rope at one end.

[0029] In a preferred embodiment, the first structure and the second structure are rectangular caissons, and each side is connected to at least two of the main cables.

[0030] In a preferred embodiment, the construction vessel includes a floating crane, an anchor boat and a tugboat; the floating crane is used to lower or lift the drag anchor; the anchor boat is used to tow the main cable and provide an operating surface for connecting or disconnecting the main cable from the drag anchor; the tugboat is used to float and stabilize the first structure and the second structure.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0032] The construction method provided by the present invention innovatively uses a drag anchor to replace the traditional positioning structure. The drag anchor has a compact structure, a small occupied space, and a small self-weight. It does not need to rely on large-scale lifting equipment and storage sites, thus avoiding the risk of cable intrusion into the waterway by large equipment and sites, significantly improving the safety of offshore operations, and meeting the positioning construction needs within a limited construction water area. The drag anchor has excellent ground-gripping performance and strong stability, getting rid of the dependence on immovable structures such as anchor piers and anchor piles. The advantage of being easy to lay and shift enables it to overcome the technical problem of the long transfer period of gravity anchors, thus greatly shortening the transfer construction period of the anchor cable system. It is not only flexibly applicable to the construction needs of split-type floating structures, but also can make full use of the short operation window in coastal areas with frequent typhoons, thereby improving the construction efficiency. In addition, the construction method rationally utilizes the flow direction of the tidal current to connect the main cable, achieving twice the result with half the effort in construction organization, reducing the difficulty and risk of water operation, and improving the construction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is an elevation schematic diagram of the anchor cable system in Embodiment 1 of the present invention;

[0034] Figure 2 It is a hoisting schematic diagram of the drag anchor in Embodiment 1 of the present invention;

[0035] Figure 3 It is a schematic diagram of the drag anchor being lowered to the seabed in Embodiment 1 of the present invention;

[0036] Figure 4 It is a construction organization diagram of the main cable connection under Working Condition 1 in Embodiment 1 of the present invention;

[0037] Figure 5 It is a construction organization diagram of the main cable connection under Working Condition 2 in Embodiment 1 of the present invention;

[0038] Figures 6 to 10 It is a construction schematic diagram of the main cable connection in Embodiment 1 of the present invention;

[0039] Figure 11 It is a schematic diagram of the transfer of the anchor cable system in Embodiment 1 of the present invention (the dashed line in the figure represents the main cable on the side span side);

[0040] Figure 12 This is the length statistical table of the main cable described in Embodiment 1 of the present invention.

[0041] In the figure, the markings are: 1 - steel caisson, 11 - main span side caisson, 12 - side span side caisson, 2 - grab anchor, 3 - anchor chain, 4 - main cable, 5 - cable adjusting device, 61 - first steel wire rope, 62 - second steel wire rope, 63 - third steel wire rope, 71 - first buoy, 72 - second buoy, 8 - floating crane, 81 - first main hook, 82 - second main hook, 9 - anchor boat, 10 - tugboat. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "provided with", "sheathed / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a wall-mounted connection, a detachable connection, or an integral connection, it can be a mechanical connection or an electrical connection, it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0045] As Figures 1 to 12 shown, the embodiment of the present invention provides an anchor cable system for an offshore split floating structure, including a positioning anchor, an anchor chain 3, a main cable 4, and a cable adjusting device. In this embodiment, the floating structure is a steel caisson 1. As Figure 1As shown, the positioning anchor is fixed in the seabed. Shackles that can be unlocked and locked are provided at both ends of the anchor chain 3. One end of the anchor chain 3 is connected to the positioning anchor through the shackle, and the other end is connected to the main cable 4. The end of the main cable 4 away from the anchor chain 3 is connected to the cable adjusting device on the steel caisson 1. The cable adjusting device adjusts the tension length of the main cable 4 under the drive of a jack or a winch, and adjusts the relative position between the steel caisson 1 and the positioning anchor, thereby realizing the positioning of the steel caisson 1.

[0046] Now, the selection of the anchor cable system will be described. The influence of wind, waves, and water flow is considered during the positioning process of the steel caisson 1. In this embodiment, when selecting the anchor cable system, the parameter values of the above influence factors are as follows: wind force of level 6, wind speed of 13.8 m / s; wave height of 0.8 m, wave period of 4 s; water flow velocity of 1.0 m / s. According to the above boundary conditions and the structural parameters of the steel caisson 1, it is calculated that the maximum cable force of the anchor cable system under this working condition is 315.8 tons. Based on this, the following is carried out:

[0047] (1) Selection of the main cable 4. According to "Design and Analysis of Floating Structure Positioning System" (SY-T10040-2016), in the case of adjacent structures, according to the quasi-static analysis method, it is recommended that the safety factor of the steel wire rope is not less than 2.2. Therefore, in this embodiment, the minimum breaking force of the main cable 4 needs to be not less than 694.8 tons. The main cable 4 is selected as a standard steel core with models 8XK46WS and IWRC-104 respectively, and a right regular lay of one steel wire rope. Closed cable sockets are configured at both ends of a single main cable 4, and the cutting length of the main cable 4 is the center distance between the two closed cable sockets. In this embodiment, restricted by the existing trestle platform and construction red line on site, the lengths of the main cables 4 in the anchor cable system are different, divided into two types: 220 m and 170 m. The split steel caisson 1 includes two parts, namely the main span side caisson 11 and the side span side caisson 12. In this embodiment, both the main span side caisson 11 and the side span side caisson 12 are rectangular, and two main cables 4 are correspondingly connected to each side. Therefore, there are a total of 8 positioning anchors. The numbering of the anchor cable system is as shown in the figure, and the length statistics of the corresponding main cables 4 are as Figure 12 shown. It is not difficult to understand that the first structure described in the claims is the main span side caisson 11, and the second structure is the side span side caisson 12.

[0048] (2) Selection of the anchor chain 3. The anchor chain 3 adopts a three-stage anchor chain 3 with a diameter of 87 mm and a breaking force of 550 tons.

[0049] (3) Selection of positioning anchors. To adapt to the limited construction water area and enable the rapid transfer of the anchor cable system between the two parts of the split steel caisson 1, the positioning anchor adopts a drag anchor with a compact structure and light self-weight. Different from the traditional anchor cable system of the offshore steel caisson, the drag anchor replaces the anchor pile, gravity anchor, etc., and provides a fixed positioning point for the steel caisson 1 by being embedded in the seabed. The self-weight of the drag anchor is 35 tons, and the minimum anchor holding force it can provide is 10 times its self-weight, that is, 350 tons, which is greater than the maximum cable force of 315.8 tons described above, so it meets the anchoring requirements. The drag anchor includes an anchor claw and an anchor rod. For the convenience of description, the end of the drag anchor close to the anchor claw is defined as the anchor tail, and the end far from the anchor claw is positioned as the anchor head. When the drag anchor works, the anchor tail is embedded in the seabed, and the anchor head is connected to the anchor chain 3.

[0050] This embodiment also provides a construction method for the above-mentioned anchor cable system, which includes the lowering of the drag anchor on the main span side, the connection of the main cable 4 on the main span side, the transfer of the drag anchor system, and the connection of the main cable 4 on the side span side. Now, with reference to the drawings, the construction method will be described in detail. The construction method includes the following steps:

[0051] Step 1: Lowering the drag anchor on the main span side. This step includes:

[0052] Step 11: Construction preparation, including determining the lowering sequence and the construction ship taking its position and waiting. As Figures 6 to 11 shown, the drag anchors are radially arranged on the seabed outside the design points of the main span side caisson 11 by the construction ship. To minimize the time spent on the transfer of the construction ship, the drag anchors are lowered in a counterclockwise or clockwise order. The specific lowering sequence adopted in this embodiment is North 3 → South 3 → South 1 → South 2 → South 4 → North 4 → North 2 → North 1. The construction ships involved in this step include the floating crane 8, the flat barge, and the anchor boat 9. After the floating crane 8 sails to the set anchor position of the drag anchor, it drops the anchor and takes its position, and fine-tunes its own position and attitude to face the main span side caisson 11. The floating crane 8 is equipped with a first main hook 81 and a second main hook 82 for lifting and lowering the drag anchor. The flat barge loads the drag anchor and berths beside the floating crane 8. The anchor rod of the drag anchor faces the main span side caisson 11. The anchor boat 9 sails to the nearby waters and waits.

[0053] Step 12: Hoisting and lowering the drag anchor. As Figure 2As shown in the figure, the tail of the holding power anchor is connected to a first steel wire rope 61 with a diameter of 60 mm through a shackle with a maximum tensile force of 55 tons. Connect the first main hook 81 of the floating crane 8 to the first steel wire rope 61 to hoist the tail of the anchor; connect the second main hook 82 of the floating crane 8 to the free end of the anchor chain 3 to hoist the head of the anchor. In this embodiment, at the free end of the first steel wire rope 61 and the free end of the anchor chain 3, a second steel wire rope 62 with a diameter of 36 mm is continued to facilitate the hooking operation of the construction workers. Then the floating crane 8 hoists the holding power anchor to the lowering point. After being checked and verified by the surveyors, the holding power anchor is horizontally lowered to the seabed.

[0054] Step 13: Hang the buoy. As Figure 3 shown, after the holding power anchor is lowered in place, the anchor boat 9 approaches the hanging end of the anchor chain 3. Lower the second main hook 82 to near the deck surface of the anchor boat 9 to disengage the anchor chain 3 from the second main hook 82, and then hang the first buoy 71 at the free end of the anchor chain 3. To enable the anchor chain 3 to completely fall on the seabed after being released from the anchor boat 9, a third steel wire rope 63 with a diameter of 36 mm is connected between the anchor chain 3 and the first buoy 71. Both ends of the third steel wire rope 63 are connected to the anchor chain 3 and the first buoy 71 through a 17-ton shackle respectively. Similarly, the anchor boat 9 approaches the first steel wire rope 61 at the tail of the anchor, lower the first main hook 81 to near the deck surface of the anchor boat 9 to disengage the first steel wire rope 61 from the first main hook 81. Then hang the second buoy 72 at the free end of the first steel wire rope 61 through a 17-ton shackle. It is not difficult to understand that in steps 12 and 13, the lengths of the first steel wire rope 61 and the second steel wire rope 62 should be long enough so that after the holding power anchor is lowered to the seabed, the first buoy 71 and the second buoy 72 are not completely submerged in the sea.

[0055] Step 2: Connect the main cables 4 on the main span side.

[0056] The construction vessels involved in this step include: a floating crane 8 for loading the main cable 4; a flat barge for storing spare materials and equipment; an anchor boat 9 including a main anchor boat 9 for connecting the main cable 4 and an auxiliary anchor boat 9 for dealing with emergencies; a tugboat 10 for stabilizing the position and attitude of the steel caisson 1.

[0057] Since each side of the caisson 11 on the main span side is connected to two main cables 4, 2 main anchor boats 9 are used to connect the main cables 4 simultaneously. In this embodiment, the water flow of the ebb and flow tides in the construction water area is close to the north-south direction, so the overall connection sequence of the main cables 4 is to connect South 1, South 2 or North 1, North 2 first, and then connect South 3, South 4, North 3, North 4. There are two working conditions for the tide level when the caisson 11 on the main span side is floated to the construction water area, corresponding to different connection sequences of the main cables 4:

[0058] Condition 1: The caisson 11 on the main span side is towed to the construction water area 3 hours before the low tide. At this time, the ebb tide is approaching from north to south. Then, before the low tide, connect the main cables 4 South 1 and South 2 along the downstream direction of the ebb tide on the caisson 11 on the main span side. Then, after the low tide, connect the main cables 4 North 1 and North 2 along the downstream direction of the flood tide. Finally, during the subsequent high tide and low tide stages, connect the main cables 4 North 3, North 4 and South 3, South 4 in the non-tidal flow direction. The specific construction organization is as Figure 4 shown.

[0059] Condition 2: The caisson 11 on the main span side is towed to the construction site 1 hour before the high tide. At this time, the flood tide is approaching from south to north. Then, before the high tide, connect the main cables 4 North 1 and North 2 along the downstream direction of the flood tide on the caisson 11 on the main span side. Then, after the high tide, connect the main cables 4 South 1 and South 2 along the downstream direction of the ebb tide. Finally, during the subsequent low tide and high tide stages, connect the main cables 4 South 3, South 4 and North 3, North 4 in the non-tidal flow direction. The specific construction organization is as Figure 5 shown.

[0060] In this embodiment, taking Condition 1 as an example, the connection process of the main cable 4 is introduced in detail. It includes the following steps:

[0061] Step 21: As Figure 6 shown, use the tugboat 10 to tow the caisson 11 on the main span side to a position 30m to 40m east-south of the design point, and control the position of the caisson at this position, waiting for the cable connection. At the same time, two main anchor boats 9 sail to the anchor positions of South 1 and South 2 to make preparations for receiving the cables. Moving the caisson 11 on the main span side to a position closer to the anchor positions of South 1 and South 2 is to make the main cable 4 in a slack state, which is convenient for connection. Therefore, as can be seen in the figure, only 2 hours are left for connecting the main cables 4 of South 1 and South 2.

[0062] Step 22: As Figure 7 shown, use several tugboats 10 to hold and stabilize the position and attitude of the caisson 11 on the main span side, and the two main anchor boats 9 connect the main cables 4 of South 1 and South 2. Specifically, fish up the anchor chain 3 at the South 1 anchor position, then connect one end of the South 1 main cable 4 to the anchor chain 3 through a shackle. Then, the main anchor boat 9 pulls the other end of the South 1 main cable 4 and sails towards the south side of the caisson 11 on the main span side, and connects the South 1 main cable 4 to the cable adjusting device on the caisson. The connection method of the South 2 main cable 4 is the same as that of the South 1 main cable 4. During this process, the main anchor boat 9 operates against the water flow, which is more conducive to operation. Therefore, it is selected to connect the main cables 4 of South 1 and South 2 first during the ebb tide.

[0063] Step 23: As Figure 8As shown, the main cables 4 of North 1 and North 2 are connected by referring to the methods of step 21 and step 23. Specifically, after the tide rises in the construction waters, the main span side caisson 11 is floated to the design point, and the caisson is stabilized by a tugboat 10. Then, the two main anchor boats 9 install the main cables 4 at the floating crane 8, and then connect the gripping anchors of North 1 and North 2 to the cable adjustment device on the caisson.

[0064] Step 24: Figure 9 As shown, when approaching high tide, the posture and position of the main span side caisson 11 are stabilized by the tugboat 10, and the two main anchor boats 9 are connected to the main cables 4 of South 3 and South 4 in the above manner.

[0065] Step 25: Figure 10 As shown, when approaching low tide, the posture and position of the main span side caisson 11 are stabilized by the tugboat 10, and the two main anchor boats 9 are connected to the main cables 4 of the north 3 and north 4 in the above manner. At this point, the main cables 4 of the main span side caisson 11 are all connected. It should be understood that because the cable connection is selected during the low tide period when the north-south water flow is relatively slow, in steps 24 and 25, the connection order of the south 3, south 4 and north 3, north 4 main cables 4 can be exchanged.

[0066] For working condition 2, due to the difference in tidal flow direction, the connection sequence of the main cable 4 is a mirror image of working condition 1, and the cable connection operation is the same, which will not be described in detail in this article. The construction process of caisson positioning and sinking is a mature existing technology and is not the core technical feature of the present invention, so it will not be described in detail in this article.

[0067] Step 3: Transfer of the grip anchor system. Figure 11 As shown, this step includes the following steps:

[0068] Step 31: After the positioning and sinking construction of the main span side caisson 11 is completed, the eight main cables 4 are recovered one by one to the floating crane 8 through the main anchor boat 9.

[0069] Step 32: Adopting the principle of proximity, transfer the above 8 holding anchors to the anchor positions corresponding to the side span caisson 12, that is, transfer the South 1 holding anchor to the South 1' anchor position, and the same applies to other anchor positions. Specifically, in this embodiment, a 35-ton holding anchor requires a maximum lifting force of 60 tons to be lifted vertically from the seabed, so a 350-ton floating crane 8 is selected for anchoring. Then, lift the holding anchor together with the first buoy 71 and the second buoy 72, and move them to the corresponding 8 anchor positions of the side span caisson 12. Lower the holding anchor and the buoy in the manner described in step 1 to complete the transfer of the holding anchor system. Figure 11It can be seen that after the grab anchor is transferred, it is also radially arranged with the second structure as the center. In this embodiment, since the maximum transfer distance of the grab anchor is relatively small, only 77 meters at most, which is less than the anchoring upper limit of 300 meters of the floating crane 8, after the floating crane 8 transfers the grab anchor, there is no need to re-anchor to stabilize the ship position, which saves construction time.

[0070] Step 4: After the side-span caisson 12 is floated and positioned in place, connect the corresponding 8 main cables 4 in the manner described in Step 2.

[0071] After the side-span caisson 12 is positioned and sunk, sequentially recover the main cable 4, and salvage the grab anchor and the anchor chain 3, thus completing the construction of the anchor cable system.

[0072] In summary, the construction method provided in this embodiment innovatively uses a grab anchor to replace the traditional positioning structure. The grab anchor has a compact structure, a small occupied space, and a small self-weight. It does not rely on large-scale lifting equipment and storage sites, thus avoiding the risk of the anchor cables of large equipment and sites invading the waterway, significantly improving the safety of offshore operations, and meeting the positioning construction needs within a limited construction water area. The grab anchor has excellent ground-gripping performance and strong stability, getting rid of the dependence on immovable structures such as anchor piers and anchor piles. The advantage of being easy to lay and shift enables it to overcome the technical problem of the long transfer period of the gravity anchor, thus greatly shortening the transfer construction period of the anchor cable system. It is not only flexibly applicable to the construction needs of split steel caissons, but also can make full use of the short operation window in the coastal areas where typhoons occur frequently, thereby improving the construction efficiency. In addition, the construction method reasonably utilizes the flow direction of the tidal current to connect the main cable 4, achieving twice the result with half the effort in construction organization, reducing the difficulty and risk of water operation, and improving the construction efficiency.

[0073] The above is only the preferred specific implementation manner of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent transformation made using the content of the specification of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for constructing an anchor cable system of an offshore split floating structure, characterized in that: The split floating structure at least includes a first structure and a second structure; The anchor cable system includes a plurality of gripping anchors, a main cable and a cable adjusting device; the gripping anchors are embedded in the seabed; a group of the cable adjusting devices are respectively arranged on the first structure and the second structure; the main cable is used to connect the gripping anchors and the cable adjusting device; The construction method comprises the following steps: Step 1: lowering the gripping anchors; using a construction vessel to lower the plurality of gripping anchors radially onto the seabed outside the design point of the first structure; the anchor rods of the gripping anchors face the first structure; the gripping anchors are connected to buoys; Step 2: Main cable connection: float the first structure to the design point, and use the main cable to connect the plurality of gripping anchors to the cable adjustment devices on the first structure respectively; in terms of connection sequence, a group of main cables arranged opposite to each other along the tidal flow direction are preferentially connected; Step 3: Transfer of the anchor cable system; after the positioning and sinking construction of the first structure is completed, the grab anchor is disconnected from the main cable and transferred to the anchor position corresponding to the second structure; the second structure is floated to the designed point and the main cable of the second structure is connected in the manner of step 2.

2. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: The step 1 comprises: Step 11: Determine the order of lowering the gripping anchors; drive the construction vessel to the anchor position and keep it parallel to the arrangement direction of the gripping anchors; Step 12: Connect a section of anchor chain to the end of the gripping anchor away from the anchor claw; use a steel wire rope to connect the free end of the anchor chain and the end of the gripping anchor close to the anchor claw to hang the gripping anchor; and lower the gripping anchor horizontally to the seabed; Step 13: Hang the buoy at the free end of the steel wire rope.

3. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: In step 2, when the first structure is floated to the design point, it is the ebb tide stage, and the connection order of the main cables is: connecting the main cables of the first structure in the downstream direction of the ebb tide before the low tide, then connecting the main cables of the first structure in the downstream direction of the rising tide after the low tide, and finally connecting the main cables in the non-tidal flow direction in the subsequent high tide or low tide stage.

4. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: In step 2, when the first structure is floated to the design point, it is the high tide stage, and the connection order of the main cables is: connecting the main cables of the first structure in the downstream direction of the high tide before the high tide, then connecting the main cables of the first structure in the downstream direction of the low tide after the high tide, and finally connecting the main cables in the non-tidal flow direction in the subsequent low tide or high tide stage.

5. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: The step 2 comprises: Step 21: Float the first structure to a distance downstream from the design point and stabilize it; Step 22: one end of the main cable is connected to the grab anchor in the downstream direction of the first structure, and the other end is towed to the first structure by a construction vessel and connected to the cable adjustment device on the first structure; during this process, the construction vessel operates upstream; Step 23: After the tidal current turns, the first structure is floated to the designed point and stabilized; the construction vessel is equipped with a main cable, and the gripping anchor in the downstream direction of the first structure is connected to the cable adjustment device in the manner described in step 22; during this process, the construction vessel operates upstream; Step 24: In the subsequent slack tide stage, stabilize the first structure and use the construction vessel to connect the main cable in the non-tidal flow direction.

6. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: The step 3 comprises: Step 31: After the positioning and sinking construction of the first structure is completed, the plurality of main cables are disconnected from the gripping anchors and then recovered; Step 32: After lifting the plurality of gripping anchors and the buoys from the seabed, they are transferred to the anchor position corresponding to the second structure according to the principle of proximity, and then the gripping anchors are lowered in the manner of step 1; the plurality of gripping anchors are also arranged radially with the second structure as the center; Step 33: Float the second structure to the design point; connect the transferred grab anchors to the cable adjustment devices on the second structure using the main cables in the manner of step 2; in terms of connection sequence, a group of main cables that are relatively arranged along the tidal current direction are preferentially connected.

7. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: The buoy comprises a first buoy; one end of the gripping anchor away from the fluke is connected with a section of anchor chain; the first buoy is connected to the free end of the anchor chain through a section of rope.

8. The method for constructing an anchor cable system of an offshore split floating structure according to claim 7, characterized in that: The buoy also includes a second buoy; the second buoy is connected to one end of the gripping anchor close to the fluke through one end of a rope.

9. The method for constructing an anchor cable system of an offshore split floating structure according to claim 1, characterized in that: The first structure and the second structure are rectangular caissons, and each side is connected to at least two of the main cables.

10. A method for constructing an anchor cable system of an offshore split floating structure according to any one of claims 1 to 9, characterized in that: The construction vessel includes a floating crane, an anchor boat and a tugboat; the floating crane is used to lower or lift the grab anchor; the anchor boat is used to tow the main cable and provide an operating surface for the main cable to connect to or disconnect from the grab anchor; the tugboat is used to float and stabilize the first structure and the second structure.

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