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

Technical Field

[0001] The present disclosure relates to a method for laying a submarine cable and components for laying a submarine cable. This application claims priority based on Japanese Patent Application No. 2023-207667 filed on December 8, 2023, and incorporates all the descriptions set forth in the Japanese application.

Background Art

[0002] Patent Document 1 discloses a method for monitoring the landing state of a long object such as an optical fiber cable paid out from a laying vessel while guiding it to the seabed by guiding means. The guiding means includes a guide wire suspended in water from the laying vessel and a plurality of guide rings provided at predetermined intervals on the guide wire. Each guide ring is connected to the guide wire so as to be disposed behind the laying vessel in the traveling direction of the guide wire. The long object is disposed on the seabed through the inside of each guide ring. A monitoring means for monitoring the landing point is provided at 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.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] A method for laying a submarine cable according to the present disclosure comprises the steps of laying a submarine cable mounted on a ship on the seabed. The steps of laying the submarine cable include monitoring the bottoming point of the submarine cable using images from a camera and positional information from a first transponder of an acoustic positioning device, and, while monitoring the bottoming point, guiding the submarine cable unloaded from the ship through the inside of a guide pipe suspended in the water from the ship to the bottoming point. The guide pipe is not connected to an excavator that excavates the seabed, but is connected to a wire extended in the water from the ship 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 pipe or the wire located near the bottoming point. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a schematic diagram illustrating the method for laying an underwater cable in Embodiment 1. [Figure 2] Figure 2 is a schematic perspective view showing a cylindrical cage-like member that constitutes a guide pipe used in the underwater cable laying method of Embodiment 1. [Figure 3] Figure 3 is a schematic front view of the cylindrical cage-like member shown in Figure 2. [Figure 4] Figure 4 is a schematic top view showing the cylindrical cage-like members of Figure 2 arranged in series. [Figure 5] Figure 5 is a schematic diagram illustrating the method for laying the underwater cable in Embodiment 2. [Figure 6] Figure 6 is a schematic diagram illustrating the method for laying the underwater cable in Embodiment 3. [Modes for carrying out the invention]

[0006] [Issues this disclosure aims to address] The following may occur when the guide ring is connected to the guide wire in such a way that it is positioned aft of the ship in the direction of travel: As the elongated object passes through the inside of the guide ring, the guide ring and the elongated object come into contact, causing the guide ring to rotate so that it is positioned aft of the ship in the direction of travel on the guide wire. The rotating guide ring and the elongated object rub against each other, causing damage to the elongated object. In addition, the umbilical cable may become entangled.

[0007] One of the purposes of this disclosure is to provide a method for laying submarine cables that makes it less likely for the submarine cables to be damaged during the cable laying process.

[0008] [Effects of this disclosure] The method for laying submarine cables described herein makes it less likely for the submarine cables to be damaged during the laying process.

[0009] Description of Embodiments in this Disclosure First, the embodiments of this disclosure will be listed and described.

[0010] (1) A method for laying a submarine cable according to one embodiment of the present disclosure comprises the steps of laying a submarine cable mounted on a ship on the seabed. The steps of laying the submarine cable include monitoring the bottoming point of the submarine cable using images from a camera and positional information from a first transponder of an acoustic positioning device, and, while monitoring the bottoming point, moving the submarine cable unloaded from the ship through a guide pipe suspended in the water from the ship to the bottoming point. The guide pipe is not connected to an excavator that excavates the seabed, but is connected to a wire extended in the water from the ship 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 pipe or the wire located near the bottoming point.

[0011] In the submarine cable laying method described in (1) above, the guide pipe is connected to the wire so that it is positioned ahead of the direction of the ship's movement on the wire. Therefore, even if the guide pipe and the submarine cable come into contact as the submarine cable passes through the inside of the guide pipe, the guide pipe is prevented from rotating around the wire as its pivot point. Thus, friction between the rotating guide pipe and the submarine cable is prevented, making the submarine cable less susceptible to damage.

[0012] The method of laying the submarine cable described in (1) above allows for the determination of the distance from the camera to the seabed using images of the seabed taken by the camera. Furthermore, the first transponder allows for the acquisition of 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, the vertical distance from the stern to the bottom can be determined, 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 seabed.

[0013] The submarine cable laying method described in (1) above allows for continuous monitoring of the bottom contact point using a camera and a first transponder. By monitoring the bottom contact point, the submarine cable can be laid in the designed location. Furthermore, it is possible to confirm whether the laid submarine cable is properly buried in the seabed. By determining the vertical distance from the stern to the bottom contact point, the submarine cable can be laid with residual tension within the design range. Furthermore, the submarine cable can be laid with the bending radius of the submarine cable at the bottom contact point within the allowable range. In addition, abnormalities in the appearance of the submarine cable can be observed using the camera's image. Moreover, the distance between the lower end of the guide pipe or wire located near the bottom contact point and the seabed can be determined. By determining this distance, the three-dimensional coordinates of the lower end of the guide pipe can be adjusted.

[0014] The submarine cable laying method described in (1) above does not require the use of an ROV (Remotely Operated Vehicle) because the landing point can be monitored by a camera and a first transponder. ROVs have limitations on the hydrological conditions under which they can be used. In cases where ROVs cannot be used, for example, when the water flow velocity is high, the laying work must be put on hold. However, the submarine cable laying method described in (1) above does not use an ROV, so it has fewer or no limitations on hydrological conditions compared to when an ROV is used. In other words, the submarine cable laying method described in (1) above can shorten or eliminate waiting time due to hydrological conditions. Moreover, the submarine cable laying method described in (1) above is easier to reduce costs by not using an ROV.

[0015] (2) In the method for laying the submarine cable described in (1) above, the step of laying the submarine cable may further include 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 step of arranging the submarine cable is to arrange the submarine cable at the bottom while monitoring the alignment.

[0016] The method of laying submarine cables described in (2) above allows monitoring of the alignment of the submarine cable within the conduit by monitoring the alignment of the conduit. Therefore, the method of laying submarine cables described in (2) above allows determining whether the submarine cable within the conduit is being subjected to unnecessary loads such as bending.

[0017] (3) In the method for laying a submarine cable according to (1) or (2) above, the step of laying the submarine cable may further include the step of excavating the seabed with the excavator suspended in the water from the ship. The step of arranging the submarine cable is to arrange the submarine cable in 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 at the bottom of the water and discharge the sucked-up sediment. Therefore, the method for laying the underwater cable in (4) above can continuously perform the formation of a groove by excavating the underwater bottom, the placement of the underwater cable at the touchdown point of the underwater cable in the groove, and the embedding of the placed underwater cable. That is, the method for laying the underwater cable in (4) above can place the underwater cable at the touchdown point of the underwater cable in the formed groove while excavating the underwater bottom to form a groove, and can embed the underwater cable while placing the underwater cable at the touchdown point of the groove.

[0019] (4) The underwater cable laying component according to one aspect of the present disclosure includes a guide pipe having a plurality of cylindrical cage-like members through which the underwater cable passes, and a wire connecting the plurality of cylindrical cage-like members so that the plurality of cylindrical cage-like members are arranged in series. Each of the plurality of cylindrical cage-like members has a through hole through which the wire passes. The central axis of the through hole is parallel to the central axis of each of the plurality of cylindrical cage-like members. The wire has a stopper portion for positioning by abutting or fixing the plurality of cylindrical cage-like members with a gap therebetween.

[0020] The underwater cable laying component in (4) above can be suitably used in the method for laying the underwater cable in (1) above. The wire has a plurality of stopper portions. Therefore, each individual stopper portion only needs to support the weight of the cylindrical cage-like member arranged between the stopper portions, and the load acting on each stopper portion can be reduced. If the number of stopper portions is one and the stopper portion is provided at the lower end of the wire, it is necessary to support the weight of all the cylindrical cage-like members with one stopper portion.

[0021] (5) In the underwater cable laying component in (4) above, each of the plurality of cylindrical cage-like members may have a main body portion configured in a cylindrical cage shape so that the underwater cable passes through, and a protruding portion extending from the main body portion along a direction away from the central axis of the main body portion. The through hole is provided in the protruding portion.

[0022] The underwater cable laying component described in (5) above has a through-hole through which the wire passes, which is located on a protruding part separate 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 in (5) above, the main body may have a base portion and a door portion that is connected to the base portion so as to be openable and closable, thereby opening and closing the inside and outside of the main body.

[0024] The underwater cable laying component described in (6) above has a door section, which allows the cylindrical cage-like member to be fitted onto the underwater cable from the side. Therefore, the cylindrical cage-like member can be fitted onto the underwater cable from the side on the ship and then lowered into the water to be placed underwater. Thus, the underwater cable laying component described in (6) above can improve the workability of the underwater cable laying method.

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

[0026] The underwater cable laying component described in (7) above allows the cylindrical cage-like member to be fitted onto the wire from the side as the door is opened and closed.

[0027] Details of the embodiments of this disclosure The embodiments of the submarine cable laying method and components for submarine cable laying described herein will be explained below with reference to the drawings. The shapes, sizes, and positional relationships shown in each figure are for illustrative purposes only and do not necessarily represent the actual shapes, sizes, and positional relationships. The same reference numerals in the figures indicate the same parts. The present invention is not limited to the configurations shown in the embodiments, but is intended to be expressed in the claims and to include all modifications within the meaning and scope of the claims.

[0028] In the embodiments, the term "water" in phrases such as "bottom of the water," "in water," and "water surface" refers to "sea," "lake," or "river." That is, the bottom of the water is the seabed, lakebed, or riverbed; in water is the sea, lake, or river; and the water surface is the sea surface, lake surface, or river surface.

[0029] Embodiment 1 [Methods for laying underwater cables] The method for laying a submarine cable in Embodiment 1 will be described with reference to Figures 1 to 4. The method for laying a submarine cable in Embodiment 1 is a method for laying a submarine cable 2 along the seabed 90 to electrically connect land-based equipment and surface equipment, land-based equipment and underwater equipment, surface equipment to each other, underwater equipment to each other, or surface equipment to each other. The method for laying a submarine cable in Embodiment 1 can construct a submarine cable line equipped with a submarine cable 2 connecting these facilities. Land-based equipment is, for example, a substation. Surface equipment is, for example, an offshore plant or offshore power plant. Offshore power plants include, for example, offshore wind turbines or wave turbines. Offshore wind turbines are either fixed-bottom type with a foundation fixed to the seabed, or floating type wind turbines with a foundation moored on the sea. Underwater equipment is, for example, an underwater power plant. Underwater power plants include, for example, tidal power plants or ocean current power plants. For the submarine cable 2, known submarine cables, such as known dynamic cables, can be used. The method for laying a submarine cable in Embodiment 1 includes step A, which involves laying a submarine cable 2, which is mounted on a ship 1, on the seabed 90. One of the features of the method for laying a submarine cable in Embodiment 1 is that step A includes step A1, which involves monitoring the bottom contact point of the submarine cable 2, and step A2, which involves positioning the unfurled submarine cable 2 at the bottom contact point.

[0030] As shown in Figure 1, the vessel 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 for controlling the operation of the vessel 1, controlling the braking device 13, monitoring the bottoming point (described later), and monitoring the alignment of the guide pipe 5. The control room 11 is 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 unwinding speed of the underwater cable 2 wound in the cable tank 12, i.e., the travel speed of the underwater cable 2. The guide 14 guides the unwinding underwater cable 2 to the water surface 92. The first winch 15 winds up the first wire 31 that suspends the guide pipe 5 (described later). The first pulley 16 guides the first wire 31 unwinding from the first winch 15 toward the water surface 92. Although not shown in the diagram, ship 1 has a transceiver for the acoustic positioning device 61. The transceiver is extended from ship 1 into the water 93. The transceiver transmits signals to the first transponder 611 and the second transponder 612, which will be described later, and receives signals from the first transponder 611 and the second transponder 612. The acoustic positioning device 61 can acquire the three-dimensional coordinates of the first transponder 611 and the second transponder 612 by transmitting and receiving signals.

[0031] [Process A] Process A is the process of laying the submarine cable 2 on the seabed 90. Process A includes process A1 of monitoring the bottom landing point of the submarine cable 2 and process A2 of positioning the unfurled submarine cable 2 at the bottom landing point. Process A may further include process A3 of monitoring the alignment of the guide pipe 5.

[0032] (Process A1) In step A1, the bottoming point of the submarine cable 2 is monitored using the video from camera 60 and the position information of the first transponder 611 of the acoustic positioning device 61. The bottoming point is the point of contact between the submarine cable 2 and the seabed 90. By having step A1, in step A2 the submarine cable 2 can be positioned at the bottoming point while monitoring the bottoming point of the submarine cable 2. The camera 60 and the first transponder 611 are attached to the lower end of the guide pipe 5 or the first wire 31, which will be described later, located near the bottoming point. The camera 60 and the first transponder 611 may be directly attached to the lower end of the guide pipe 5 or the first wire 31, or the camera 60 and the first transponder 611 may be attached to a mounting jig (not shown), and the mounting jig may be attached to the lower end of the guide pipe 5 or the first wire 31. In this example, the camera 60 and the first transponder 611 are attached to a cylindrical cage-like member 5a, which will be described later, and is positioned closest to the landing point.

[0033] The distance from camera 60 to the seabed 90 can be determined from the image of the seabed 90 captured by camera 60. The first transponder 611 can acquire three-dimensional positional information of the location where it is attached. Therefore, the vertical distance and horizontal distance from the stern to the first transponder 611 can be determined. The first transponder 611 is attached to the guide pipe 5 at the same height as camera 60. By attaching the first transponder 611 at the same height as camera 60, the vertical distance from the stern to the first transponder 611 and the distance from the first transponder 611 and camera 60 to the seabed 90 can be determined, which is the sum of these two distances.

[0034] The camera 60 and the first transponder 611 allow for continuous monitoring of the bottom contact point. By monitoring the bottom contact point, the submarine cable 2 can be laid in the designed position. By determining the vertical distance from the stern to the bottom contact point, the submarine cable 2 can be laid with its residual tension within the design range. Furthermore, the submarine cable 2 can be laid with its bending radius at the bottom contact point within the allowable range. In addition, the camera 60 allows for observation of any abnormalities in the appearance of the submarine cable 2. Since the camera 60 is attached to the cylindrical cage-like member 5a located closest to the bottom contact point, the distance H between the seabed 90 and the cylindrical cage-like member 5a located closest to the bottom contact point can be determined. By determining the distance H, the three-dimensional coordinates of the lower end of the guide pipe 5 can be adjusted.

[0035] In this example of submarine cable laying, the landing point can be monitored by camera 60 and first transponder 611, thus eliminating the need for an ROV. ROVs have limitations on the hydrological conditions under which they can be used. In cases where ROVs cannot be used, for example, when the water flow velocity is high, the laying work must be put on hold. However, since this example of submarine cable laying does not use an ROV, it has fewer or no limitations on hydrological conditions compared to cases where an ROV is used. In other words, this example of submarine cable laying can shorten or eliminate waiting time due to hydrological conditions. Furthermore, by not using an ROV, this example of submarine cable laying is easier to reduce costs.

[0036] In step A1, the positional information of the altimeter 62 may be further used to determine the vertical distance from the stern to the bottoming point. The altimeter 62 is attached, for example, to the lower end of the guide pipe 5 located near the bottoming point.

[0037] (Process A2) In process A2, as shown in Figure 1, the submarine cable 2, which has been unfurled from the ship 1, is guided through a guide pipe 5 located in the water 93 to reach its bottom. The guide pipe 5 is suspended in the water 93 by being connected to a first wire 31 that extends from the ship 1 into the water 93. The guide pipe 5 is connected to the first wire 31 so as to be positioned in front of the direction of travel of the ship 1 on the first wire 31, i.e., to the right of the page in Figure 1. The guide pipe 5 is not connected to an excavator that excavates the seabed 90. By having the submarine cable 2 pass through the guide pipe 5, it is less likely that the submarine cable 2 will bend to the point of being damaged during its movement to the seabed 90. In addition, twisting of the submarine cable 2, so-called kinking of the submarine cable 2, is less likely to occur during its movement to the seabed 90.

[0038] Unlike this example, if the guide pipe 5 is connected to the first wire 31 so that it is positioned behind the direction of travel of the ship 1 on the first wire 31, i.e., to the left of the page in Figure 1, the following may occur: As the submarine cable 2 passes through the inside of the guide pipe 5, the submarine cable 2 and the guide pipe 5 come into contact, causing the guide pipe 5 to rotate around the first wire 31 as its pivot point, so that it is positioned from behind to the front of the direction of travel of the ship 1 on the first wire 31. The submarine cable 2 is damaged as it rubs against the rotated guide pipe 5.

[0039] In contrast, in this example, the guide pipe 5 is connected to the first wire 31 so as to be positioned in front of the direction of travel of the ship 1 on the first wire 31. Therefore, even if the guide pipe 5 and the submarine cable 2 come into contact as the submarine cable 2 passes through the inside of the guide pipe 5, the guide pipe 5 is prevented from rotating around the first wire 31 as the pivot point. As a result, friction between the rotating guide pipe 5 and the submarine cable 2 is prevented, making the submarine cable 2 less likely to be damaged. Furthermore, by preventing the rotation of the guide pipe 5, it is easier to prevent the umbilical cable 4, which will be described later, from becoming entangled.

[0040] 〈Decoration conduit〉 The conduit 5 has a plurality of cylindrical cage-like members 5a. The material of each cylindrical cage-like member 5a is, for example, a metal such as steel. Each cylindrical cage-like member 5a may have a base portion made of a metal such as steel and a rust-preventive layer covering the surface of the base portion. The presence of the rust-preventive layer prevents the base portion from rusting. The plurality of cylindrical cage-like members 5a are arranged in series by a first wire 31. As shown in Figure 2, each of the plurality of cylindrical cage-like members 5a has a through hole 55a through which the first wire 31 shown in Figure 1 passes. The central axis of the through hole 55a is parallel to the central axis of each of the plurality of cylindrical cage-like members 5a. As shown in Figure 1, the first wire 31 has stopper portions 311 that position the plurality of cylindrical cage-like members 5a by pressing or fixing them at intervals. There are multiple stopper portions 311. The number of stopper portions 311 can be appropriately selected according to the number of cylindrical cage-like members 5a. If there is only one stopper portion 311 and it is located at the lower end of the first wire 31, then the weight of all the cylindrical cage-like members 5a must 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-like members 5a positioned between the stopper portions 311s, thus reducing the load acting on each individual stopper portion 311. The number of stopper portions 311 can be set to, for example, a number that allows for positioning every five cylindrical cage-like members 5a. In addition to the first wire 31, the umbilical cable 4 shown in Figure 1 may also be passed through the through-hole 55a. The umbilical cable 4 is a bundle of cables that are connected to the camera 60, the first transponder 611 and second transponder 612 of the acoustic positioning device 61, and the altimeter 62, respectively, to supply power and transmit and receive signals.

[0041] As shown in Figure 2, each of the multiple cylindrical cage-like members 5a has a main body 50 through which the underwater cable 2 passes, and at least one projection 55 extending from the main body 50 in a direction away from the central axis of the main body 50.

[0042] The main body 50 in this example has a base 501 and a door 502. The base 501 in this example is the part to which the engaging projection 591 and engaging recess 592, described later, are connected, and the door 502 is the part to which the engaging projection 591 and engaging recess 592 are not connected. The base 501 has an arc-shaped first base 511, an arc-shaped second base 521, and a plurality of rod-shaped parts 54 connecting the first base 511 and the second base 521. The door 502 is connected to the base 501 so that it can be opened and closed to the inside and outside of the main body 50. The door 502 in this example has an arc-shaped first opening / closing part 512, an arc-shaped second opening / closing part 522, and a plurality of rod-shaped parts 54 connecting the first opening / closing part 512 and the second opening / closing part 522. The presence of the door portion 502 allows the cylindrical cage-like member 5a to be fitted onto the underwater cable 2 from the side. Therefore, the cylindrical cage-like member 5a can be fitted onto the underwater cable 2 from the side on the ship 1 and then dropped into the water 93 to be positioned in 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 made of a plate-shaped member. Through holes 55a are 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 projection 581 connected to the base portion 501 of the main body portion 50, and a second projection 582 connected to the door portion 502. Because the first projection 581 is connected to the base portion 501 and the second projection 582 is connected to the door portion 502, the second projection 582 can be opened and closed relative to the first projection 581 when the door portion 502 is opened and closed. The first projection 581 and the second projection 582 have notches 581a and 582a facing each other when the door portion 502 is closed, as shown by the solid lines in Figure 3. A through hole 55a is formed between the notches 581a and 582a. The dashed line in Figure 3 shows the door section 502 in the open position. As the door section 502 is opened and closed, the cylindrical cage-like member 5a can be fitted into the side of the first wire 31. In this example, the connecting section 55b is connected to both first projections 581.

[0044] The main body 50 in this example has a first annular section 51, a second annular section 52, and a plurality of rod-shaped sections 54, which will be described later. The first annular section 51 and the second annular section 52 are spaced apart from each other along the central axis of the main body 50. The central axis of the first annular section 51 and the central axis of the second annular section 52 are coaxial. The shapes of the first annular section 51 and the second annular section 52 in this example are circular. Unlike this example, the shapes of the first annular section 51 and the second annular section 52 may be rectangular annular.

[0045] The first annular portion 51 has a first base portion 511 and a first opening / closing portion 512. In this example, the shape of the first base portion 511 is arc-shaped. The first opening / closing portion 512 is connected to the first base portion 511 so that it can be opened and closed both inside and outside the first annular portion 51. In this example, the first opening / closing portion 512 is connected to the first base portion 511 by a hinge 53. In this example, the shape of the first opening / closing portion 512 is arc-shaped. The second annular portion 52 has a second base portion 521 and a second opening / closing portion 522. In this example, the shape of the second base portion 521 is arc-shaped. The second opening / closing portion 522 is connected to the second base portion 521 so that it can be opened and closed both inside and outside the second annular portion 52. In this example, the second opening / closing portion 522 is connected to the second base portion 521 by a hinge 53. In this example, the shape of the second opening / closing portion 522 is arc-shaped. The position of the first annular portion 51 around the central axis in the first opening / closing section 512 and the position of the second annular portion 52 around the central axis in the second opening / closing section 522 are the same. The hinge 53 connecting the second base section 521 and the second opening / closing section 522 has thin-walled portions at the ends of the second base section 521 and the second opening / closing section 522. A shaft hole is provided in each thin-walled portion. The hinge 53 is constructed by overlapping the thin-walled portions of the second base section 521 and the second opening / closing section 522, and passing the shaft through the shaft holes of the overlapped thin-walled portions. The hinge 53 connecting the first base section 511 and the first opening / closing section 512 is constructed similarly.

[0046] Multiple rod-shaped sections 54 connect the first annular section 51 and the second annular section 52. The number of rod-shaped sections 54 is not particularly limited and can be selected as appropriate. In this example, there are six rod-shaped sections 54. One or more of the multiple rod-shaped sections 54 connect the first base section 511 and the second base section 521. Also, one or more of the multiple rod-shaped sections 54 connect the first opening / closing section 512 and the second opening / closing section 522. In this example, the first base section 511 and the second base section 521 are connected by three rod-shaped sections 54. Also, in this example, the first opening / closing section 512 and the second opening / closing section 522 are connected by three rod-shaped sections 54.

[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 axes 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 projection 581 and a second projection 582. The first projection 581 and the second projection 582 have a through hole 583 that communicates with each other when the door portion 502 is closed. The closed state of the door portion 502 is maintained by inserting a pin (not shown) through this through hole 583. In this example, the first projection 581 and the second projection 582 have notches 581a and 582a at diagonal positions on a roughly rectangular plate. As shown in Figure 3, the first projection 581 has a notch 581a at the upper right corner of the roughly rectangular plate, and the second projection 582 has a notch 582a at the lower left corner of the roughly rectangular plate. When the base portion 501 and the door portion 502 are closed, the notches 581a and 582a face each other to form a through hole 55a.

[0048] Each of the multiple cylindrical cage-like members 5a may further include an engaging projection 591 and an engaging recess 592. The engaging projection 591 is connected to a first projection 56. The engaging projection 591 extends along the central axis of the through hole 55a from the first projection 56 toward the opposite side of the second projection 57. The engaging recess 592 is connected to a second projection 57. The engaging recess 592 extends along the central axis of the through hole 55a from the second projection 57 toward the opposite side of the first projection 56. The engaging recess 592 corresponds to the engaging projection 591. Of the three cylindrical cage-like members 5a arranged in series as shown in Figure 4, the central cylindrical cage-like member 5a is designated as the first cylindrical cage-like member 5a, the rightmost cylindrical cage-like member 5a as the second cylindrical cage-like member 5a, and the leftmost cylindrical cage-like member 5a as the third cylindrical cage-like member 5a. The statement that the engaging recess 592 corresponds to the engaging projection 591 means that the engaging projection 591 of the first cylindrical cage-like member 5a engages with the engaging recess 592 of the second cylindrical cage-like member 5a, and the engaging recess 592 of the first cylindrical cage-like member 5a engages with the engaging projection 591 of the third cylindrical cage-like member 5a.

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

[0050] (Process A3) In step A3, the alignment of the guide pipe 5 is monitored using the position information of the first transponder 611 of the acoustic positioning device 61 and the position information of the second transponder 612 of the acoustic positioning device 61. If step A3 is included, step A2 positions the submarine cable 2 at the bottom while monitoring the alignment of the guide pipe 5. The second transponder 612 is attached to the upper end of the guide pipe 5 or the first wire 31 located in the water 93 near the water surface 92. The upper end of the first wire 31 is the point on the first wire 31 that is at the same height as the upper end of the guide pipe 5. The second transponder 612 may be directly attached to the upper end of the guide pipe 5 or the first wire 31, or the second transponder 612 may be attached to a mounting jig (not shown), and the mounting jig may be attached to the upper end of the guide pipe 5 or the first wire 31. In this example, the second transponder 612 is attached to the upper end of the cylindrical cage-like member 5a, which is positioned closest to the water surface 92. By monitoring the alignment of the conduit 5, the alignment of the underwater cable 2 inside the conduit 5 can be monitored. Therefore, it is possible to determine whether any unnecessary loads, such as bending, are acting on the underwater cable 2 inside the conduit 5.

[0051] Embodiment 2 [Methods for laying underwater cables] Referring to Figure 5, the method for laying a submarine cable in Embodiment 2 will be described. The method for laying a submarine cable in Embodiment 2 differs from the method for laying a submarine cable in Embodiment 1 in that the step A for laying the submarine cable 2 further includes a step A4 in which the seabed 90 is excavated by an excavator 7 suspended in the water 93 from a ship 1.

[0052] The excavator 7 is suspended by a second wire 32. The second wire 32 is a separate component from the first wire 31. Although not shown in the illustration, the second wire 32 is wound onto a second winch and guided toward the water surface 92 by a second pulley. The second wire 32 extends into the water 93 at approximately a right angle to the water surface 92. That is, the entry angle of the second wire 32 toward the water surface 92 is substantially 90°. In this example, the second wire 32 is spaced apart from the guide pipe 5 so as not to be connected to the guide pipe 5. The second wire 32 is positioned ahead of the guide pipe 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 seabed 90 and discharge the sucked-up sediment. Therefore, the method for laying the submarine cable in this example allows for the formation of a trench 91 by excavating the seabed 90, the placement of the submarine cable 2 at its bottoming point in the trench 91, and the burial of the placed submarine cable 2 to be carried out in a continuous manner. In other words, the method for laying the submarine cable in this example allows for the placement of the submarine cable 2 at its bottoming point in the formed trench 91 while excavating the seabed 90, and allows for the burial of the submarine cable 2 while it is placed at its bottoming point in the trench 91. The bottoming point of the submarine cable 2 in this example is the point of contact between the submarine cable 2 and the bottom of the trench 91.

[0053] Embodiment 3 [Methods for laying underwater cables] Referring to Figure 6, the method for laying the submarine cable in Embodiment 3 will be described. The method for laying the submarine cable in Embodiment 3 differs from the method for laying the submarine cable in Embodiment 2 in that a portion of the guide pipe 5 is connected to the second wire 32 that suspends the excavator 7.

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

[0055] 1 ship, 11 control room, 12 cable tank, 13 braking system 14 Guide, 15 First winch, 16 First pulley 2 Underwater Cables 31 First wire, 311 Stopper part, 32 Second wire 4 Umbilical Cables 5 Conduit, 5a Cylinder cage-like member, 50 Main body 501 Base section, 502 Door section 51 First ring section, 511 First base section, 512 First opening / closing section 52 Second ring section, 521 Second base section, 522 Second opening / closing section 53 Hinge, 54 Rod-shaped part, 55 Protruding part 55a through hole, 55b connecting portion, 56 first protrusion, 57 second protrusion 581 First projection, 581a Notch, 582 Second projection, 582a Notch 583 Through hole, 591 Engagement protrusion, 591a Through hole 592 Engaging recess, 592a Through hole 60 cameras, 61 acoustic positioning devices 611 Transponder 1, 612 Transponder 2, 62 Altimeter 7 Excavator 90 Bottom, 91 Groove, 92 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.

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