Methods for laying underwater cables

Abstract

This method for laying a subaqueous cable includes a process for laying, on the water bottom, a subaqueous cable mounted on a ship. The process for laying the subaqueous cable includes: a step for monitoring a landing point of the subaqueous cable by using a video from a camera and positional information on a first transponder of an acoustic positioning device; and a step for disposing on the landing point, while monitoring the landing point, the subaqueous cable drawn from the ship by causing the subaqueous cable to pass through the inside of a steering pipe suspended in the water from the ship. The steering pipe is connected to a wire, which extends in the water from the ship, so as to be disposed at the front in the ship traveling direction with respect to the wire without being connected to an excavator for excavating the water bottom. The camera and the first transponder are attached to a lower end of either one of the steering pipe or the wire which is located in the vicinity of the landing point.

Description

Method for laying underwater cables and components for laying underwater cables

[0001] This disclosure relates to a method for laying an underwater cable and components for laying an underwater cable. This application claims priority to Japanese Patent Application No. 2023-207667 filed on December 8, 2023, and incorporates the entire contents of said Japanese application by reference.

[0002] Patent Document 1 discloses a method for monitoring the bottom-settlement state of a long object to be laid on the seabed, such as an optical fiber cable, that is paid out from a laying vessel and guided to the seabed by a guide means. The guide means includes a guide wire suspended underwater from the laying vessel and a plurality of guide rings attached to the guide wire at predetermined intervals. Each guide ring is connected to the guide wire so as to be positioned rearward of the laying vessel in the direction of travel of the guide wire. The long object is placed on the seabed through the inside of each guide ring. A monitoring means for monitoring the bottom-set point is attached to the lower end of the guide wire. An umbilical cable extending from the laying vessel is connected to the monitoring means. The umbilical cable is fixed to the guide wire at predetermined intervals.

[0003] Japanese Patent Application Publication No. 04-321887

[0004] The disclosed method for laying a submarine cable comprises the steps of laying a submarine cable on the water bottom mounted on a vessel. The step of laying the submarine cable comprises the steps of monitoring the bottom landing point of the submarine cable using images from a camera and position information from a first transponder of an acoustic positioning device, and, while monitoring the bottom landing point, passing the submarine cable, which has been let out from the vessel, through a conduit suspended underwater from the vessel and placing it at the bottom landing point. The conduit is not connected to an excavator that excavates the water bottom, but is connected to a wire extended from the vessel into the water so as to be positioned forward in the direction of travel of the vessel. The camera and the first transponder are attached to the lower end of the conduit or the wire, which is located near the bottom landing point.

[0005] Fig. 1 is a schematic diagram illustrating a method for laying a submarine cable according to a first embodiment. Fig. 2 is a schematic perspective view showing a cylindrical cage member constituting a conduit used in the method for laying a submarine cable according to the first embodiment. Fig. 3 is a schematic front view of the cylindrical cage member shown in Fig. 2. Fig. 4 is a schematic top view of the cylindrical cage members shown in Fig. 2 arranged in series. Fig. 5 is a schematic diagram illustrating a method for laying a submarine cable according to a second embodiment. Fig. 6 is a schematic diagram illustrating a method for laying a submarine cable according to a third embodiment.

[0006] [Problems to be Solved by the Present Disclosure] Connecting the guide ring to the guide wire so that it is positioned at the rear of the guide wire in the direction of travel of the vessel may result in the following: As the elongated body passes through the inside of the guide ring, the guide ring comes into contact with the elongated body, causing the guide ring to rotate around the guide wire as the center of rotation so that it is positioned at the front of the guide wire in the direction of travel of the vessel. The rotated guide ring rubs against the elongated body, damaging the elongated body. Furthermore, the umbilical cable may become tangled.

[0007] An object of the present disclosure is to provide a method for laying an underwater cable that is less likely to damage the underwater cable during the laying process.

[0008] [Advantages of the Present Disclosure] The method for laying an underwater cable according to the present disclosure makes it difficult for the underwater cable to be damaged during the laying process.

[0009] <Description of Embodiments of the Present Disclosure> First, embodiments of the present disclosure will be listed and described.

[0010] (1) A method for laying a submarine cable according to one aspect of the present disclosure comprises the steps of laying a submarine cable on the water bottom mounted on a vessel. The laying step comprises the steps of monitoring the bottom landing point of the submarine cable using video from a camera and position information from a first transponder of an acoustic positioning device, and, while monitoring the bottom landing point, passing the submarine cable, which has been let out from the vessel, through a conduit suspended underwater from the vessel and placing it at the bottom landing point. The conduit is not connected to an excavator that excavates the water bottom, but is connected to a wire extended from the vessel into the water so as to be positioned forward in the direction of travel of the vessel. The camera and the first transponder are attached to the lower end of the conduit or the wire, which is located near the bottom landing point.

[0011] In the above-mentioned (1) method of laying an underwater cable, the conduit is connected to the wire so that it is positioned forward of the wire in the direction of travel of the ship. Therefore, even if the conduit and the underwater cable come into contact as the underwater cable passes through the conduit, the conduit is prevented from rotating around the wire as its center of rotation. This prevents the conduit from rubbing against the underwater cable as it rotates, making it less likely that the underwater cable will be damaged.

[0012] The method for laying a submarine cable described above (1) makes it possible to determine the distance from the camera to the bottom of the water using an image of the water bottom taken by the camera. Furthermore, the first transponder can provide three-dimensional positional information of the location where the first transponder is attached. That is, the vertical distance from the stern to the first transponder can be determined. Therefore, it is possible to determine the vertical distance from the stern to the bottom landing point, which is the sum of the vertical distance from the stern to the first transponder and the distance from the first transponder and camera to the water bottom.

[0013] The submarine cable laying method (1) above allows for continuous monitoring of the bottom landing point using a camera and a first transponder. Monitoring the bottom landing point allows the submarine cable to be laid in the designed position. Furthermore, it is possible to confirm whether the laid submarine cable is properly buried in the water bottom. Determining the vertical distance from the stern to the bottom landing point allows the submarine cable to be laid with its residual tension within the design range. Furthermore, the submarine cable can be laid with its bending radius at the bottom landing point within the allowable range. Furthermore, the camera images allow for observation of any abnormalities in the appearance of the submarine cable. Furthermore, the distance between the bottom of the conduit or wire, located near the bottom landing point, and the water bottom can be determined. Determining this distance allows for the adjustment of the three-dimensional coordinates of the bottom end of the conduit.

[0014] The submarine cable laying method (1) above does not require the use of a remotely operated vehicle (ROV) because the landing point can be monitored using a camera and a first transponder. ROVs are subject to limitations on the hydrological conditions under which they can be used. Under hydrological conditions that preclude the use of an ROV, such as when the water current is fast, laying work must wait. However, because the submarine cable laying method (1) above does not use an ROV, it is subject to fewer or no hydrological conditions compared to when an ROV is used. In other words, the submarine cable laying method (1) above can shorten or eliminate the wait time due to hydrological conditions. Furthermore, the submarine cable laying method (1) above is more cost-effective because it does not use an ROV.

[0015] (2) In the method for laying a submarine cable described above in (1), the step of laying the submarine cable may further include a step of monitoring the alignment of the conduit using the position information of the first transponder and the position information of the second transponder of the acoustic positioning device attached to the upper end of the conduit or the wire located underwater near the water surface. The step of placing the submarine cable places the submarine cable at the bottom landing point while monitoring the alignment.

[0016] The underwater cable laying method (2) above can monitor the alignment of the underwater cable inside the conduit by monitoring the alignment of the conduit, and therefore, it can determine whether or not the underwater cable inside the conduit is being subjected to loads such as excessive bending.

[0017] (3) In the method for laying a submarine cable according to (1) or (2), the step of laying the submarine cable may further include a step of excavating the water bottom using the excavator suspended underwater from the ship. The step of placing the submarine cable places the submarine cable at the location excavated by the excavator. The excavator is equipped with a sand pump.

[0018] An excavator equipped with a sand pump can suck up sediment from the water bottom and discharge the sediment. Therefore, the submarine cable laying method described in (4) above can continuously perform the steps of forming a trench by excavating the water bottom, laying the submarine cable at its landing point in the trench, and burying the laid submarine cable. That is, the submarine cable laying method described in (4) above can excavate the water bottom to form a trench, lay the submarine cable at its landing point in the trench, and then bury the submarine cable while laying it at its landing point in the trench.

[0019] (4) An underwater cable laying component according to one aspect of the present disclosure comprises a conduit having a plurality of tubular cage members through which an underwater cable is passed, and a wire connecting the plurality of tubular cage members so that the plurality of tubular cage members are arranged in series. Each of the plurality of tubular cage members has a through-hole through which the wire is passed. The central axis of the through-hole is parallel to the central axis of each of the plurality of tubular cage members. The wire has stoppers that abut or secure the plurality of tubular cage members at intervals to position them.

[0020] The underwater cable laying components (4) above can be suitably used in the underwater cable laying method (1) above. The wire has multiple stoppers. Therefore, each stopper only needs to support the weight of the tubular cage members located between them, reducing the load acting on each stopper. If there is only one stopper and it is located at the bottom end of the wire, the weight of all the tubular cage members must be supported by that one stopper.

[0021] (5) In the submarine cable laying component of (4), each of the plurality of tubular cage-shaped members may have a main body configured in a tubular cage shape to allow the submarine cable to pass through, and a protrusion extending from the main body in a direction away from the central axis of the main body. The through-hole is provided in the protrusion.

[0022] The underwater cable laying component (5) has a through hole through which the wire passes provided in a protruding part that is different from the main body through which the underwater cable passes, thereby making it less likely for the wire and the underwater cable to interfere with each other.

[0023] (6) In the underwater cable laying component described above in (5), the main body may have a base and a door that is connected to the base in an openable and closable manner to open and close the inside and outside of the main body.

[0024] The underwater cable laying component (6) has a door, which allows the tubular cage member to be fitted onto the underwater cable from the side. Therefore, the tubular cage member can be fitted onto the underwater cable from the side on a ship and then dropped into the water to be placed underwater. Therefore, the underwater cable laying component (6) improves the workability of the underwater cable laying method.

[0025] (7) In the submarine cable laying component of (6) above, the protrusion may have a first protrusion connected to the base and a second protrusion connected to the door, and the second protrusion forms the through hole between the first protrusion and the second protrusion when the door is closed.

[0026] In the underwater cable laying component (7) above, the cylindrical cage member can be fitted onto the wire from the side as the door is opened or closed.

[0027] Details of the embodiments of the present disclosure Below, embodiments of the submarine cable laying method and submarine cable laying components disclosed herein are described with reference to the drawings. The shapes, sizes, and positional relationships shown in each figure are depicted for the purpose of clarity and do not necessarily represent the actual shapes, sizes, and positional relationships. The same symbols in the figures indicate the same items. Note that the present invention is not limited to the configurations shown in the embodiments, but is defined by the claims, and all modifications within the meaning and scope of the claims are intended to be included.

[0028] In the embodiments, the term "water" in the phrases "bottom of the water," "underwater," and "water surface" refers to the "sea," "lake," or "river." That is, the bottom of the water refers to the bottom of an ocean, lake, or river, "underwater" refers to the inside of an ocean, lake, or river, and the surface of the water refers to the surface of an ocean, lake, or river.

[0029] <<Embodiment 1>> [Method for laying a submarine cable] A method for laying a submarine cable according to embodiment 1 will be described with reference to Figures 1 to 4. The method for laying a submarine cable according to embodiment 1 involves laying a submarine cable 2 along the water bottom 90, electrically connecting land and surface facilities, land and underwater facilities, surface facilities to each other, underwater facilities to each other, or surface and underwater facilities. The method for laying a submarine cable according to embodiment 1 can be used to construct a submarine cable line equipped with a submarine cable 2 connecting these facilities. The land facility is, for example, a substation. The surface facility is, for example, an offshore plant or offshore power plant. The offshore power plant is, for example, equipped with an offshore wind turbine or a wave power generator. The offshore wind turbine is, for example, a bottom-mounted type whose foundation is fixed to the seabed, or a floating type whose foundation is moored above the sea. The underwater facility is, for example, an undersea power plant. The undersea power plant is, for example, equipped with a tidal power generator or an ocean current power generator. The submarine cable 2 can be a known submarine cable, for example, a known dynamic cable. The method for laying a submarine cable in accordance with the first embodiment comprises step A of laying a submarine cable 2 mounted on a ship 1 on the water bottom 90. One of the features of the method for laying a submarine cable in accordance with the first embodiment is that step A comprises step A1 of monitoring the bottom landing point of the submarine cable 2, and step A2 of placing the reeled-out submarine cable 2 at the bottom landing point.

[0030] As shown in Figure 1, the ship 1 is equipped with a control room 11, a cable tank 12, a braking device 13, a guide 14, a first winch 15, and a first pulley 16. The control room 11 is a room where operation control of the ship 1, control of the braking device 13, monitoring of the bottom landing point (described later), and monitoring of the alignment of the conduit 5 are carried out. The control room 11 is also equipped with the equipment necessary for these controls. The cable tank 12 stores the underwater cable 2 in a wound state. The braking device 13 adjusts the payout speed of the underwater cable 2 wound around the cable tank 12, i.e., the running speed of the underwater cable 2. The guide 14 guides the paid-out underwater cable 2 to the water surface 92. The first winch 15 winds up the first wire 31 that suspends the conduit 5 (described later). The first pulley 16 guides the first wire 31 paid out from the first winch 15 toward the water surface 92. Although not shown in the figure, the ship 1 has a transceiver for the acoustic positioning device 61. The transceiver is pulled out from the ship 1 into the water 93. The transceiver transmits signals to a first transponder 611 and a second transponder 612 (described below), and receives signals from the first transponder 611 and the second transponder 612. The acoustic positioning device 61 can obtain the three-dimensional coordinates of the first transponder 611 and the second transponder 612 by transmitting and receiving signals.

[0031] [Step A] Step A is a step of laying the submarine cable 2 on the water bottom 90. Step A includes step A1 of monitoring the bottom landing point of the submarine cable 2, and step A2 of placing the reeled-out submarine cable 2 at the bottom landing point. Step A may further include step A3 of monitoring the alignment of the conduit 5.

[0032] (Step A1) In step A1, the bottom landing point of the submarine cable 2 is monitored using the image from the camera 60 and the position information of the first transponder 611 of the acoustic positioning device 61. The bottom landing point is the point of contact between the submarine cable 2 and the water bottom 90. By including step A1, the bottom landing point of the submarine cable 2 can be monitored in step A2 while the submarine cable 2 is positioned at the bottom landing point. The camera 60 and the first transponder 611 are attached to the lower end of the conduit 5 or the first wire 31, which will be described later, located near the bottom landing point. The camera 60 and the first transponder 611 may be attached directly to the lower end of the conduit 5 or the first wire 31, or the camera 60 and the first transponder 611 may be attached to an attachment jig (not shown), and the attachment jig may be attached to the lower end of the conduit 5 or the first wire 31. In this example, the camera 60 and the first transponder 611 are attached to a cylindrical cage member 5a (described later) that is located at a position closest to the bottom landing point.

[0033] The distance from the camera 60 to the bottom 90 can be calculated from the image of the bottom 90 captured by the camera 60. The first transponder 611 can acquire three-dimensional positional information of the location where the first transponder 611 is attached. Therefore, the vertical distance and horizontal distance from the stern to the first transponder 611 can be calculated. The first transponder 611 is attached to the conduit 5 at the same height as the camera 60. By attaching the first transponder 611 at the same height as the camera 60, the vertical distance from the stern to the bottom landing point can be calculated, which is the sum of the vertical distance from the stern to the first transponder 611 and the distance from the first transponder 611 and the camera 60 to the bottom 90.

[0034] The camera 60 and the first transponder 611 enable continuous monitoring of the bottom landing point. Monitoring the bottom landing point allows the submarine cable 2 to be laid at the designed position. Calculating the vertical distance from the stern to the bottom landing point allows the submarine cable 2 to be laid while ensuring that its residual tension is within the design range. Furthermore, the submarine cable 2 can be laid while ensuring that the bending radius of the submarine cable 2 at the bottom landing point is within the allowable range. Images captured by the camera 60 also allow for observation of any abnormalities in the appearance of the submarine cable 2. The camera 60 is attached to the tubular cage member 5a located closest to the bottom landing point, allowing for the distance H between the water bottom 90 and the tubular cage member 5a located closest to the bottom landing point to be calculated. Calculating the distance H allows for the three-dimensional coordinates of the lower end of the conduit 5 to be adjusted.

[0035] The submarine cable laying method of this example does not require the use of an ROV, since the landing point can be monitored using the camera 60 and the first transponder 611. ROVs are subject to limitations on the hydrological conditions under which they can be used. Under hydrological conditions that preclude the use of an ROV, such as when the water current is fast, laying operations must be put on hold. However, because the submarine cable laying method of this example does not use an ROV, there are fewer or no hydrological conditions limitations compared to when an ROV is used. In other words, the submarine cable laying method of this example can shorten or eliminate waiting times due to hydrological conditions. Furthermore, by not using an ROV, the submarine cable laying method of this example can more easily achieve low costs.

[0036] In step A1, the position information of the altimeter 62 may be further used to calculate the vertical distance from the stern to the bottom landing point. The altimeter 62 is attached to, for example, the lower end of the conduit 5 located near the bottom landing point.

[0037] (Step A2) In step A2, as shown in Figure 1, the submarine cable 2 is paid out from the vessel 1 and placed at the bottom landing point by passing it inside a conduit 5 placed underwater 93. The conduit 5 is suspended underwater 93 by being connected to a first wire 31 that is extended from the vessel 1 into the water 93. The conduit 5 is connected to the first wire 31 so that it is located forward of the vessel 1's traveling direction on the first wire 31, i.e., to the right of the page in Figure 1. The conduit 5 is not connected to the excavator that excavates the water bottom 90. By passing the submarine cable 2 inside the conduit 5, the submarine cable 2 is less likely to bend to a degree that would cause damage during its movement to the water bottom 90. Furthermore, the submarine cable 2 is less likely to twist, or kink, during its movement to the water bottom 90.

[0038] Unlike this example, if the conduit 5 is connected to the first wire 31 so as to be positioned rearward of the first wire 31 in the direction of travel of the ship 1, i.e., to the left of the paper surface in Figure 1, the following may occur: As the submarine cable 2 passes through the conduit 5, the submarine cable 2 comes into contact with the conduit 5, causing the conduit 5 to rotate around the first wire 31 as the center of rotation so that it is positioned forward of the first wire 31 in the direction of travel of the ship 1. The rotated conduit 5 rubs against the submarine cable 2, damaging the submarine cable 2.

[0039] In contrast, in this example, the conduit 5 is connected to the first wire 31 so as to be positioned forward of the first wire 31 in the direction of travel of the ship 1, so even if the conduit 5 comes into contact with the underwater cable 2 as it passes through the inside of the conduit 5, the conduit 5 is prevented from rotating around the first wire 31. This prevents the rotated conduit 5 from rubbing against the underwater cable 2, making it less likely that the underwater cable 2 will be damaged. Furthermore, preventing the conduit 5 from rotating helps to prevent the umbilical cable 4, which will be described later, from becoming tangled.

[0040] <Conduit> The conduit 5 includes a plurality of cylindrical cage-shaped members 5a. Each cylindrical cage-shaped member 5a is made of a metal such as steel. Each cylindrical cage-shaped member 5a may have a base made of a metal such as steel and a rust-preventive layer covering the surface of the base. The rust-preventive layer prevents the base from rusting. The plurality of cylindrical cage-shaped members 5a are arranged in series by a first wire 31. As shown in FIG. 2, each of the plurality of cylindrical cage-shaped members 5a has a through-hole 55a through which the first wire 31 shown in FIG. 1 is passed. The central axis of the through-hole 55a is parallel to the central axis of each of the plurality of cylindrical cage-shaped members 5a. As shown in FIG. 1, the first wire 31 has stopper portions 311 that abut or fix the plurality of cylindrical cage-shaped members 5a at intervals to position them. There are a plurality of stopper portions 311. The number of stopper portions 311 can be appropriately selected depending on the number of cylindrical cage-shaped members 5a. If there is only one stopper portion 311 and it is provided at the lower end of the first wire 31, the weight of all of the cylindrical cage-shaped members 5a needs to be supported by that single stopper portion 311. In contrast, if there are multiple stopper portions 311, each stopper portion 311 only needs to support the weight of the cylindrical cage-shaped members 5a disposed between the stopper portions 311, thereby reducing the load acting on each stopper portion 311. The number of stopper portions 311 can be set to a number that allows positioning of, for example, five cylindrical cage-shaped members 5a. In addition to the first wire 31, the umbilical cable 4 shown in FIG. 1 may be passed through the through hole 55a. The umbilical cable 4 is a bundle of cables that are connected to each of the camera 60, the first transponder 611, the second transponder 612 of the acoustic positioning device 61, and the altimeter 62 described below, and that supply power and send and receive signals.

[0041] As shown in Figure 2, each of the multiple cylindrical cage-shaped members 5a has a main body portion 50 configured to allow the underwater cable 2 to be passed through, and at least one protrusion portion 55 extending from the main body portion 50 in a direction away from the central axis of the main body portion 50.

[0042] The main body 50 of this example has a base 501 and a door 502. The base 501 of this example is a portion where an engaging protrusion 591 and an engaging recess 592 (described later) are connected, and the door 502 is a portion where the engaging protrusion 591 and the engaging recess 592 are not connected. The base 501 has an arc-shaped first base 511 (described later), an arc-shaped second base 521 (described later), and a plurality of rod-shaped portions 54 connecting the first base 511 and the second base 521. The door 502 is connected to the base 501 so as to be able to open and close the main body 50. The door 502 of this example has an arc-shaped first opening / closing portion 512 (described later), an arc-shaped second opening / closing portion 522 (described later), and a plurality of rod-shaped portions 54 connecting the first opening / closing portion 512 and the second opening / closing portion 522. The door portion 502 allows the tubular cage member 5a to be fitted from the side of the underwater cable 2. Therefore, the tubular cage member 5a can be placed in the water 93 by fitting it from the side of the underwater cable 2 on the ship 1 and dropping it into the water 93.

[0043] The number of protrusions 55 may be one or more. In this example, there are two protrusions 55. In this example, each protrusion 55 is formed of a plate-shaped member. A through hole 55a is provided in each protrusion 55. In this example, both protrusions 55 are connected by a rod-shaped connecting portion 55b. Each protrusion 55 has a first protrusion 581 connected to the base portion 501 of the main body 50 and a second protrusion 582 connected to the door portion 502. Since the first protrusion 581 is connected to the base portion 501 and the second protrusion 582 is connected to the door portion 502, when the door portion 502 is opened or closed, the second protrusion 582 can be opened or closed relative to the first protrusion 581. As shown by the solid lines in FIG. 3 , the first protrusion 581 and the second protrusion 582 have notches 581a and 582a that face each other when the door portion 502 is closed. A through-hole 55a is formed between the notches 581a and 582a. The two-dot chain line in Figure 3 indicates the state in which the door portion 502 is open. As the door portion 502 is opened or closed, the cylindrical cage-shaped member 5a can be fitted onto the first wire 31 from the side. In this example, the connecting portion 55b is connected to both first protrusions 581.

[0044] The main body 50 of this example has a first annular portion 51, a second annular portion 52, and a plurality of rod-shaped portions 54, which will be described later. The first annular portion 51 and the second annular portion 52 are arranged at intervals along the central axis of the main body 50. The central axis of the first annular portion 51 and the central axis of the second annular portion 52 are coaxial. The first annular portion 51 and the second annular portion 52 of this example have a circular ring shape. Unlike this example, the first annular portion 51 and the second annular portion 52 may have a rectangular ring shape.

[0045] The first annular portion 51 has a first base portion 511 and a first open-close portion 512. In this example, the first base portion 511 has an arc-shaped configuration. The first open-close portion 512 is connected to the first base portion 511 so as to freely open and close the inside and outside of the first annular portion 51. In this example, the first open-close portion 512 is connected to the first base portion 511 by a hinge 53. In this example, the first open-close portion 512 has an arc-shaped configuration. The second annular portion 52 has a second base portion 521 and a second open-close portion 522. In this example, the second base portion 521 has an arc-shaped configuration. The second open-close portion 522 is connected to the second base portion 521 so as to freely open and close the inside and outside of the second annular portion 52. In this example, the second open-close portion 522 is connected to the second base portion 521 by a hinge 53. In this example, the second open-close portion 522 has an arc-shaped configuration. The position of the first annular portion 51 around the central axis of the first open-close portion 512 and the position of the second annular portion 52 around the central axis of the second open-close portion 522 are the same. The hinge 53 connecting the second base portion 521 and the second open-close portion 522 has thin-walled portions at the ends of the second base portion 521 and the second open-close portion 522. A shaft hole is provided in each thin-walled portion. The hinge 53 is configured by overlapping the thin-walled portion of the second base portion 521 and the thin-walled portion of the second open-close portion 522 with each other, and passing the shaft portion through the shaft holes of the overlapped thin-walled portions. The same is true for the hinge 53 connecting the first base portion 511 and the first open-close portion 512.

[0046] The plurality of rod-shaped portions 54 connect the first annular portion 51 and the second annular portion 52. The number of rod-shaped portions 54 is not particularly limited and can be selected as appropriate. In this example, the number of rod-shaped portions 54 is six. One or more of the plurality of rod-shaped portions 54 connect the first base portion 511 and the second base portion 521. Furthermore, one or more of the plurality of rod-shaped portions 54 connect the first opening / closing portion 512 and the second opening / closing portion 522. In this example, three rod-shaped portions 54 connect the first base portion 511 and the second base portion 521. Furthermore, in this example, three rod-shaped portions 54 connect the first opening / closing portion 512 and the second opening / closing portion 522.

[0047] The two protrusions 55 are a first protrusion 56 extending from the first annular portion 51 in a direction away from the central axis of the first annular portion 51, and a second protrusion 57 extending from the second annular portion 52 in a direction away from the central axis of the second annular portion 52. The first protrusion 56 and the second protrusion 57 face each other. The first protrusion 56 and the second protrusion 57 have through holes 55a. The central axis of the through hole 55a of the first protrusion 56 is parallel to the central axis of the first annular portion 51. The central axis of the through hole 55a of the second protrusion 57 is parallel to the central axis of the second annular portion 52. The central axis of the through hole 55a of the first protrusion 56 and the central axis of the through hole 55a of the second protrusion 57 are coaxial. The first protrusion 56 and the second protrusion 57 have a first protrusion 581 and a second protrusion 582. The first protrusion 581 and the second protrusion 582 have a through hole 583 that communicates with each other when the door portion 502 is closed. A pin (not shown) is inserted into this through hole 583 to maintain the door portion 502 in a closed state. In this example, the first protrusion 581 and the second protrusion 582 have notches 581a and 582a at diagonal positions of the generally rectangular plate. As shown in FIG. 3 , the first protrusion 581 has the notch 581a at the upper right corner of the generally rectangular plate, and the second protrusion 582 has the notch 582a at the lower left corner of the generally rectangular plate. When the base portion 501 and the door portion 502 are closed, the notch 581a and the notch 582a face each other to form the through hole 55a.

[0048] Each of the multiple cylindrical cage members 5a may further include an engaging protrusion 591 and an engaging recess 592. The engaging protrusion 591 is connected to the first protrusion 56. The engaging protrusion 591 extends from the first protrusion 56 toward the opposite side of the second protrusion 57 along the central axis of the through hole 55a. The engaging recess 592 is connected to the second protrusion 57. The engaging recess 592 extends from the second protrusion 57 toward the opposite side of the first protrusion 56 along the central axis of the through hole 55a. The engaging recess 592 corresponds to the engaging protrusion 591. Of the three cylindrical cage members 5a arranged in series as shown in FIG. 4 , the central cylindrical cage member 5a is referred to as the first cylindrical cage member 5a, the right cylindrical cage member 5a is referred to as the second cylindrical cage member 5a, and the left cylindrical cage member 5a is referred to as the third cylindrical cage member 5a. The engagement recess 592 corresponds to the engagement protrusion 591, which means that the engagement protrusion 591 of the first cylindrical cage-shaped member 5a engages with the engagement recess 592 of the second cylindrical cage-shaped member 5a, and the engagement recess 592 of the first cylindrical cage-shaped member 5a engages with the engagement protrusion 591 of the third cylindrical cage-shaped member 5a.

[0049] As shown in FIG. 2 , the engaging protrusion 591 in this example is formed by a single protrusion connected to the tip of the rod-shaped portion connected to the first protrusion 581, and the engaging recess 592 in this example is formed by a bifurcated piece connected to the tip of the rod-shaped portion connected to the second protrusion 582. The rod-shaped portion connected to the first protrusion 581 and the rod-shaped portion connected to the second protrusion 582 may be formed by members independent of the connecting portion 55b, or may be formed by part of the connecting portion 55b. In the latter case, the rod-shaped portion connected to the first protrusion 581 and the rod-shaped portion connected to the second protrusion 582 may be formed by the connecting portion 55b that penetrates the first protrusion 581 and the second protrusion 582. In this case, the through holes of the first protrusion 581 and the second protrusion 582 and the connecting portion 55b may be fixed by welding or the like. As shown in Fig. 4, the first cylindrical cage member 5a and the second cylindrical cage member 5a are connected, and the first cylindrical cage member 5a and the third cylindrical cage member 5a are connected, by inserting the engaging protrusion 591, which is a protruding piece, into the engaging recess 592, which is a bifurcated piece. As shown in Fig. 2, the engaging protrusion 591 in this example further has a through hole 591a, and the engaging recess 592 has a through hole 592a. The through holes 591a and 592a are arranged to communicate with each other when the engaging protrusion 591 is inserted into the engaging recess 592. The engagement state between the engaging protrusion 591 and the engaging recess 592 is maintained by inserting a pin (not shown) through the through holes 591a and 592a.

[0050] (Step A3) In step A3, the alignment of the conduit 5 is monitored using position information from the first transponder 611 of the acoustic positioning device 61 and position information from the second transponder 612 of the acoustic positioning device 61. When step A3 is included, step A2 involves placing the submarine cable 2 at the bottom landing point while monitoring the alignment of the conduit 5. The second transponder 612 is attached to the upper end of the conduit 5 or the first wire 31 located underwater 93 near the water surface 92. The upper end of the first wire 31 is a point on the first wire 31 that is at the same height as the upper end of the conduit 5. The second transponder 612 may be attached directly to the upper end of the conduit 5 or the first wire 31, or the second transponder 612 may be attached to an attachment jig (not shown), and the attachment jig may be attached to the upper end of the conduit 5 or the first wire 31. In this example, the second transponder 612 is attached to the upper end of the cylindrical cage member 5a located closest to the water surface 92. By monitoring the alignment of the conduit 5, it is possible to monitor the alignment of the underwater cable 2 inside the conduit 5. Therefore, it is possible to determine whether or not a load due to excessive bending is acting on the underwater cable 2 inside the conduit 5.

[0051] Second Embodiment [Method for laying a submarine cable] A method for laying a submarine cable according to the second embodiment will be described with reference to Figure 5. The second embodiment differs from the first embodiment in that step A for laying the submarine cable 2 further includes step A4 of excavating the water bottom 90 using an excavator 7 suspended underwater 93 from the ship 1.

[0052] The excavator 7 is suspended by a second wire 32. The second wire 32 is an independent member from the first wire 31. Although not shown, the second wire 32 is wound around a second winch and guided toward the water surface 92 by a second pulley. The second wire 32 extends into the water 93 at a substantially right angle to the water surface 92. In other words, the water entry angle of the second wire 32 with respect to the water surface 92 is substantially 90°. In this example, the second wire 32 is spaced apart from the conduit 5 so as not to be connected to the conduit 5. The second wire 32 is positioned forward of the conduit 5 in the direction of travel of the ship 1. The excavator 7 is equipped with a sand pump. The excavator 7 equipped with a sand pump can suck up sediment from the water bottom 90 and discharge the sucked up sediment. Therefore, in this example, the method for laying a submarine cable can be performed in succession by excavating the water bottom 90 to form a trench 91, placing the submarine cable 2 at its landing point in the trench 91, and burying the placed submarine cable 2. In other words, in this example, the method for laying a submarine cable can be performed by excavating the water bottom 90 to form a trench 91, placing the submarine cable 2 at its landing point in the formed trench 91, and burying the submarine cable 2 while placing it at its landing point in the trench 91. In this example, the landing point of the submarine cable 2 is the point of contact between the submarine cable 2 and the bottom of the trench 91.

[0053] Third Embodiment [Method of laying a submarine cable] A method of laying a submarine cable in a third embodiment will be described with reference to Figure 6. The method of laying a submarine cable in the third embodiment differs from the method of laying a submarine cable in the second embodiment in that a part of the conduit 5 is connected to the second wire 32 that suspends the excavator 7.

[0054] In this example, the conduit 5 is connected to the second wire 32 with a gap between the upper end of the conduit 5 and the middle of the upper and lower ends. The conduit 5 and the second wire 32 are connected, for example, by a clip (not shown). Alternatively, the conduit 5 may have an openable / closable protrusion having a through-hole through which the second wire 32 is passed, although this is not shown. The openable / closable protrusion is connected to the base 501 so as not to interfere with the opening and closing of the door 502 shown in Figures 2 and 3. The conduit 5 is not connected to the second wire 32 from the middle to the lower end.

[0055] DESCRIPTION OF SYMBOLS 1 Ship, 11 Control room, 12 Cable tank, 13 Brake device 14 Guide, 15 First winch, 16 First pulley 2 Underwater cable 31 First wire, 311 Stopper portion, 32 Second wire 4 Umbilical cable 5 Conduit, 5a Cylindrical cage-shaped member, 50 Main body portion 501 Base portion, 502 Door portion 51 First annular portion, 511 First base portion, 512 First opening / closing portion 52 Second annular portion, 521 Second base portion, 522 Second opening / closing portion 53 Hinge, 54 Rod-shaped portion, 55 Protruding portion 55a Through hole, 55b Connecting portion, 56 First protruding portion, 57 Second protruding portion 581 First protruding piece, 581a Notch, 582 Second protruding piece, 582a Notch 583 Through-hole, 591 Engagement protrusion, 591a Through-hole 592 Engagement recess, 592a Through-hole 60 Camera, 61 Acoustic positioning device 611 First transponder, 612 Second transponder, 62 Altimeter 7 Excavator 90 Bottom of water, 91 Groove, 92 Water surface, 93 Underwater H Distance

Claims

1. A method for laying a submarine cable, comprising the step of laying a submarine cable mounted on a ship on the seabed, The process of laying the aforementioned underwater cable is as follows: A step of monitoring the bottom contact point of the submarine cable using the image from the camera and the position information of the first transponder of the acoustic positioning device, The process includes monitoring the landing point and guiding the submarine cable, which has been extended from the ship, through a guide pipe suspended underwater from the ship to the landing point, The guide pipe is not connected to the drilling machine that drills the seabed, but is connected to the wire that extends from the ship into the water, so as to be positioned ahead of the ship in the direction of travel of the ship. The camera and the first transponder are attached to the lower end of the guide tube or the wire located near the landing point. Methods for laying underwater cables.

2. The process of laying the underwater cable further includes the step of monitoring the alignment of the guide pipe using the position information of the first transponder and the position information of the second transponder of the acoustic positioning device attached to the upper end of the guide pipe or the wire located in the water near the water surface, The method for laying a submarine cable according to claim 1, wherein the step of laying the submarine cable is to lay the submarine cable at the landing point while monitoring the alignment.

3. The process of laying the seabed cable further comprises the process of excavating the seabed with the excavator suspended in the water from the ship, The process of laying the submarine cable involves laying the submarine cable in the area excavated by the excavator, The method for laying a submarine cable according to claim 1 or claim 2, wherein the excavator is equipped with a sand pump.