JPH0815364B2 - How to lay or lift submarine cables - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for laying or hoisting a submarine cable branching device, and more specifically, for laying or hoisting submarine cable branching devices without twisting each other. It is about the method.

[Prior Art] FIG. 8 shows the concept of a general submarine cable branch transmission line. Here, reference numeral 1 is a third submarine cable, 2 is a first submarine cable, and 3 is a second submarine cable. These cables 1 to 3 connect three points A, B, and C. There is. Reference numeral 5 denotes a branching device, which has a function of connecting the cables 1 to 3 to each other and branching the transmission paths of the cables 1 to 3 spatially, temporally, or in frequency.

A general method for laying a transmission line thus branched in three directions on the seabed will be described below.

FIG. 9 is an explanatory view of a general method of laying a submarine cable branch. First, as shown in FIGS. 9 (a) and 9 (b), the first submarine cable 2 is laid from the point B to the branch point D by the laying ship 10, and the buoy 11 is attached to the tip of the first submarine cable 2. Attach and leave. Next, as shown in FIG. 9C, the second submarine cable 3 is laid by the laying ship 10 from the point C to the point D. Then, as shown in FIG. 9 (d), the first submarine cable 2 which has already been laid is wound up on the ship, and the branching device 5 is provided at each end of the first submarine cable 2 and the second submarine cable 3. And the third submarine cable 1 loaded in the tank of the ship is connected to the other end of the branching device 5.

In this way, the three cables 1, 2, and 3 are connected to the branch device 5.
Connected via Finally, as shown in FIG. 9 (e), by feeding the third submarine cable 1 from the inside of the ship to the seabed, the branching device to which the three cables are connected is settled to the seabed, and The submarine cable 1 is laid up to point A, and the construction of all transmission lines is completed.

The structure of the submarine cable used for such laying is various, but in any case, it has a tensile strength member and is designed to withstand a huge tension applied to the cable during laying or lifting.

FIG. 10 shows an example of the structure of such a submarine cable. In this example, an optical fiber is used as the transmission medium. Here, 21 is a unit including a plurality of optical fiber transmission bodies, 22 is a metal pipe for protecting the unit 21, and 23 is a metal pipe.
Is a strength member, 24 is a metal pipe for pressing the strength member 23, and 25 is a plastic jacket.

FIG. 11 is a sectional view showing a part of the submarine cable shown in FIG. 10 in a cutaway manner. The tensile strength member 23 is usually an assembly formed by winding an iron wire or the like in a specific direction, as shown in FIG. Such winding is called S twist, and is wound clockwise toward the front.

Therefore, when the tension F is applied to the tension member 23, a rotational torque T acting in the circumferential direction is generated as shown in FIG. This rotation torque T is given by the following equation (1).

F: Tension D: Twisted wire winding layer core diameter p: Twisted pitch As can be seen from the above description, a cable with a stranded wire as a tensile strength member generally rotates when tension F is applied. The torque T is generated and the cable itself is twisted. The direction of the twist is a direction in which the twist is unwound when the tension increases, and a direction in which the twist is tightened when the tension decreases.

FIG. 13 shows an example of measurement of the amount of rotation of the cable end when tension is applied, which is measured using the submarine optical fiber cable shown in FIG. Here, the horizontal axis represents the tension and the vertical axis represents the rotation amount.

Considering the above points, it is assumed that all the cables connected to the branching device 5 have the same tension-rotation characteristics as shown in FIG. 13, and FIG. The twisting phenomenon of the cable in the shown installation will be described with reference to FIG. .

The two cables 2 and 3 below the branching device 5
Since the length of the suspended cable gradually decreases as the connected cable sinks, the tension applied to the cable by its own weight also gradually decreases. Therefore, a rotational torque acts on the first submarine cable 2 and the second submarine cable 3 in a direction in which the stranded wire is about to be tightened. Now, assuming that all the tensile strengths of the cables 1, 2 and 3 are in the S direction (they are wound clockwise toward the front), the first submarine cable 2 and the second submarine cable When the cable is viewed from above, the twisting directions of 3 are clockwise as shown in FIG.

On the other hand, the third submarine cable 1 that suspends these cables, which was initially not tensioned when it was in the ship, when it is thrown into the seabed, the first submarine cable 2 and the second submarine cable 2 Due to the weight of the submarine cable 3 and the branching device 5, the tension is applied, and the stranded wire tends to be twisted in the direction in which the stranded wire is about to be unwound. On the branching device 5 side, this direction is also clockwise when viewed from above, as shown in FIG.

When the three cables including the branching device 5 are settled on the seabed in this way, they all try to cause a clockwise twist when viewed from above with the branching device 5 in the center. As a result, the branching device 5 rotates, and the first submarine cable 2 and the second submarine cable 3 are entangled with each other and laid in a state as shown in FIG. Such twisting causes bending with an extremely small bending radius for the cable, which leads to deterioration of transmission characteristics and mechanical characteristics, and damage to the plastic used for the cable jacket. Problems such as receiving will occur.

On the other hand, if the transmission line including such a branching device 5 has some trouble, it is necessary to lift it up on the laying ship 10 and collect it in order to replace the branching device 5 or the cable. So, for example, search for the third submarine cable 1,
The twisting phenomenon of the cable when the branching device 5, the first submarine cable 2 and the second submarine cable 3 are pulled up from this cable will be described with reference to FIG. 16 as well as FIG.

In the seabed, the two first submarine cables 2 and the second submarine cables 3 below the branching device 5 have no tension, and as they are pulled up, the first submarine cable 2 and the second submarine cable 2
The tension of the submarine cable 3 increases due to its own weight, and the rotatable length also increases. For this reason, the rotational torque which tries to unwind the stranded wire acts on the first submarine cable 2 and the second submarine cable 3. In the case of the S-strand cable, this direction is a counterclockwise direction as seen from the ship side, as shown in FIG. On the other hand, in the third submarine cable 1 connected to the branching device 5, the tension action section becomes short, and the untwisted stranded wire tries to return to its original state. Therefore, the first submarine cable 2 and the second submarine cable 1 Submarine cable 3
On the contrary, the rotational torque that tries to tighten acts. This direction is also the counterclockwise direction as seen from the laying ship side, as shown in FIG. Therefore, the branching device 5 rotates counterclockwise as a whole, the first submarine cable 2 and the second submarine cable 3 are entangled with each other, and are pulled up on the ship in a twisted state, which is just opposite to that in FIG. It will be.

Such twisting of the cables with each other not only impairs transmission characteristics and mechanical characteristics as described above, but also
Even when the first submarine cable 2 has an obstacle when it is pulled up on the ship, and it is desired to replace it, it is not easy to remove it from the second submarine cable 3, which makes the work extremely difficult. There was a problem.

As a method of preventing the twist due to the rotation of such a cable, there is a method of using a so-called torque balance cable having a special tensile strength structure so that torque is not generated in the cable itself when tension is applied to the cable.

FIG. 17 shows an example of the structure of such a torque balance cable. The cable has at least two layers of tensile strength strands 31, 32, which are twisted in opposite directions. Only when the wire diameters and the twist pitches of the tensile strength members 31, 32 satisfy specific conditions, it is possible to cancel the mutual torques so that no torque is generated in the cable itself.

[Problems to be Solved by the Invention] However, in general, the longer the cable, the sharper the rigidity against twisting, so the torque generated in the first submarine cable 2 and the second submarine cable 3 causes the second submarine cable 3 and the branching device 5 are easily rotated, and the cables are twisted with each other as in the case of FIG. 15, so that the above problems cannot be solved.

FIG. 18 shows a method of laying or lifting when the torque balance cable 33 having the above-mentioned features is connected to the upper side of the branching device 5 instead of the third submarine cable 1. In this case, no torque is generated by applying tension to the cable 33, but the normal first submarine cable 2 and second submarine cable 3 connected to the lower side of the branching device 5 are the same as those in FIG. The right rotation torque (during installation) or the left rotation torque similar to that in Fig. 16 (during lifting) will be applied.

As described above, as long as the conventional submarine cable laying / lifting method is used, twisting occurs at the submarine cable branching part, which leads to deterioration of transmission characteristics and mechanical characteristics due to cable bending, There is also a problem that it is difficult to handle cables and the like on a laying ship.

Therefore, an object of the present invention is to solve the above-mentioned problems and to propose a method of laying or lifting a stable submarine cable that is free from twisting at the submarine cable branching portion.

[Means for Solving the Problems] In order to achieve the above object, a method of laying a submarine cable according to the present invention is a method of laying first, second, and third submarine cables through a branching device. In the above, the step of predetermining the first and second submarine cables so as to generate rotational torques in mutually opposite directions when tension is applied, and one end of the first submarine cable and the second submarine cable. A step of connecting one end of the submarine cable to the branching device; a step of connecting the one end of the first submarine cable and one end of the second submarine cable to the branching device; A step of connecting one end, and a step of supporting the other end of the third submarine cable with a ship while throwing the branching device connected to one end of the third submarine cable into the seabed. It is characterized by the following.

Preferably, the third submarine cable is a torque balance cable that does not generate rotational torque when tension is applied.

The submarine cable lifting method according to the present invention includes a step of predetermining the first and second submarine cables so that when the tensions are applied, rotational torques in opposite directions are generated in advance. Connecting one end of the first submarine cable and one end of the second submarine cable to the branching device; and the branching in which one end of the first submarine cable and one end of the second submarine cable are connected. A step of connecting one end of a third submarine cable to the device; and a branching device connected to one end of the third submarine cable while supporting the other end of the third submarine cable by a ship. And a step of searching for the third submarine cable when the first, second, and third submarine cables laid by the submarine cable laying method, including the step of placing the submarine cable in the seabed. Holding the searched third submarine cable with a ship, and lifting the first and second submarine cables and the branching device via the third submarine cable held with the ship. And at least performing steps.

Further, preferably, the third submarine cable is a torque balance cable that does not generate a rotational torque when tension is applied.

[Operation] In the present invention, at least on the lower side of the branching device,
By connecting two cables that cancel each other's torque generated by tension and laying the branching device on the seabed or pulling it up from the seabed, there is no twisting of the cable centering on the branching device and it is stable. Can perform laying / lifting work. Furthermore, handling of the cable and the branching device on the ship is facilitated, and the work efficiency is improved.

EXAMPLES The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram for explaining the first embodiment of the present invention.
In FIG. 1, the first submarine cable (hereinafter, simply referred to as the first
41) and the second submarine cable (hereinafter,
(Also referred to as the second cable) 42, the rotational torques generated when tension is applied are in opposite directions, and cancel the torque of the other party. These first and second cables 41, 42 are connected to the lower side of the branching device 5. Further, one end of a third submarine cable (hereinafter, also simply referred to as a third cable) 43 which is a means for laying the first and second cables 41 and 42 on the seabed is connected to the branching device 5. The other end is supported by the laying ship. Therefore, the third cable 43 is used to sink the branching device 5 and the first and second cables 41 and 42 from the laying ship 10 to the seabed, or to lift the diverting device 5 to the laying ship 10 from the seabed. The structure of the third cable 43 can be, for example, as shown in FIG. First cable 41 and second
The structure of the cable 42 is also not particularly limited and may be exactly the same as in FIG. In order to cancel the torque between these cables, there is no need to change the cross-sectional structures of both cables, and the twist directions of the tensile members 23 of both cables may be simply reversed. That is, for example, when the strength member of the first cable 41 is twisted in the S direction (clockwise toward the front) as shown in FIG. 2A, the strength member of the second cable 42 is
As shown in Fig. 13 (b), it may be twisted in the Z direction (counterclockwise toward the front).

In this way, by making the twisting directions of the respective cables opposite to each other, it is possible to generate the first cable 41 and the second cable 42 as shown in FIG. The torques applied are clockwise and counterclockwise as viewed from the laying ship 10. The tensile strength structure of each cable is exactly the same except that the twisting directions are opposite,
Since the magnitudes of the torques are also the same, the torque around the cable, which is the resultant force of these torques, is completely canceled, so that the branching device 5 and the third cable 43 do not rotate. Further, at the time of lifting, as shown in FIG. 3 (b), the generated torques are reversed, but as in the case of laying, the torques can be canceled out by each other and rotation can be suppressed.

On the other hand, if the third cable 43 has, for example, the same tensile strength structure as the first cable 41, clockwise rotation torque is generated with the installation. Comparing this with the case of the installation shown in FIG. 18, it can be seen that the torque application state is completely opposite with the branching device 5 as the boundary. That is, 18th
In the illustrated example, the cable 33 on the branching device 5 does not generate torque, and the cables 2 and 3 under the branching device 5 try to rotate, whereas in FIG. 3, the first cable 41 under the branching device 5 is rotated. The torque is not generated in the second cable 42, and the branching device 5
Torque is generated in the upper third cable 43. Although the generated torque is almost the same in FIGS. 18 and 3, the twisting phenomenon of the branching device 5 is completely different, and the twisting hardly occurs in the configuration of FIG.

This difference is easily explained by the experimental results shown in FIG.

FIG. 4 shows the relationship between the amount of rotation of the terminal and the torque when a constant tension and torque are simultaneously applied to the terminal for the various cable components as shown. Here, (a) is a structure composed of one S twist and one Z twist,
(B) is a structure with one torque balance cable,
(C) is a structure with two S twists, and (d) is a structure with one S twist. The difference in the correlation between the cable components (a) to (d) is caused by the correlation between the self-twisting property that the cable itself tends to twist due to the applied tension and the torsional rigidity that resists the torque as the external force. There is a difference.

For example, in the case of (d), since the cable is S-twisted, it has the property of rotating itself counterclockwise only by applying tension, and even when the torque is 0, it rotates constantly. . Therefore, if further counterclockwise torque is applied,
Since this tendency is further increased, the rotation amount is rapidly increased. Also in the case of (c), since it has the property of counterclockwise rotation originally and rotation is generated, since the shape is held at three points, the torsional rigidity against torsion as an external force is larger than that of (d). Therefore, the increase in the amount of rotation is gradual.

On the other hand, in the case of (b) corresponding to FIG. 18, since the generated torque is balanced, the cable itself does not tend to twist, and when the external force torque is 0, no rotation is shown. However, since the torsional rigidity against external force is almost the same as that of (d) and is small, the rotation cannot be suppressed against the increase of external force torque.

In contrast to these cases, the case of (a), that is, the third
In the case corresponding to the figure, in addition to the self-twisting property of the cable itself, in addition to the high torsional rigidity due to the same shape effect (holding three points) as in (c), the amount of rotation is in the other three examples. Compared to this, it is extremely small and almost no problem.

As described above, if the generated torque of the cable connected to the lower part of the branching device 5 is set to 0 and the self-twisting property is eliminated, the twisting of the branching part during laying and lifting does not occur, and the prior art described above. As described above, stable laying and lifting work can be performed without deteriorating the transmission characteristics and mechanical characteristics and making the onboard work difficult.

Moreover, according to the method of the present embodiment, it is not necessary to use a cable with a special torque balance,
Since it is only necessary to change the twisting direction of the tensile strength wire of the conventional normal cable, it is possible to economically configure the transmission line.

FIG. 5 shows a second embodiment of the present invention, which is a branching device 5
A first cable 44 and a second cable 45 connected to
The torque balance cable shown in Fig. 17 is used. Also in this case, torque is not generated in the cable below the branching device 5, which is similar to the first embodiment.

FIG. 6 shows a third embodiment of the present invention, which is a branching device 5
The cable structure of the lower part of the first cable is the same as that of the first embodiment, and the cable having the opposite generated torque is connected.
This is an example in which the torques generated in 41 and the second cable 42 are mutually canceled out, and a torque balance cable is used for the third cable 46 above the branching device 5. In this case, as compared with the first embodiment, the torque generated from the cable on the branching device 5 can be canceled, so that the upper and lower torques of the branching device 5 can be canceled completely, and a more stable installation is possible. / It has the advantage that it can be lifted.

FIG. 7 shows first, second and third upper and lower parts of the branching device 5.
It is a fourth embodiment of the present invention in which all the cables 44, 45 and 46 of FIG. 8 are torque balance cables, and is a combined form of the embodiments shown in FIGS. 5 and 6.

Even in this laying method, there is no torque generated from the upper and lower cables of the branching device 5, and the rotation of the first cable 44, the second cable 45, and the branching device 5 can be completely suppressed, so that stable laying / lifting can be performed. It goes without saying that it is possible. Moreover, in the fourth embodiment, the branching device 5
Since all three cables are arranged symmetrically through the cable, there is also an advantage that the cable used for laying and the cable used for lifting do not necessarily have to match. This is
Considering repairs that occur due to various factors, only the necessary cables can be pulled up, which has the advantage of being able to greatly contribute to simplification of construction work and shortening of the construction period.

[Effects of the Invention] As described above, according to the present invention, at least the lower side of the branching device is connected to two cables that cancel the torque generated by the tension, and the branching device is laid on the seabed. Alternatively, since the cable is lifted from the seabed, there is no twisting of the cable centering on the branching device, and there is an effect that stable laying / lifting work can be performed.
Furthermore, there is also an effect that the handling of the cable and the branching device on the ship is facilitated and the work efficiency is improved.

Although the case where the submarine cable is an optical fiber cable has been described above, it goes without saying that the present invention can be applied to all submarine cables including a conventional metal cable. However, as is clear from the above description, it is particularly suitable when the optical fiber cable is likely to be adversely affected by twisting.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing an example of a tensile strength member of a cable, FIG. 3 is an explanatory diagram of torque in the first embodiment of the present invention, FIG. 4 is a correlation diagram between applied torque and terminal rotation amount, FIGS. 5 to 7 are configuration diagrams showing second to fourth embodiments of the present invention, and FIG. 8 is a general submarine cable branching state. Conceptual explanatory diagram, FIG. 9 is an explanatory diagram of a general laying method of a branched submarine cable, FIG. 10 is a diagram showing an example of the structure of the submarine cable, and FIG. 11 is a sectional view showing a partially broken submarine cable. , Fig. 12 and Fig. 13 are explanatory views of rotation occurring in the submarine cable, Fig. 14 and Fig. 15 are explanatory diagrams of conventional submarine cable laying, and Fig. 16 is an explanatory diagram of conventional submarine cable lifting, Fig. 17 is a diagram showing an example of the structure of the torque balance cable, and Fig. 18 uses the torque balance cable. It is a figure which shows an example of the installed method. 1,2,3,41,42,43 …… Submarine cable, 5 …… Branching device, 10 …… Installed ship, 11 …… Float, 21 …… Unit, 22,24 …… Metal pipe, 23 …… Tensile strength Body, 25 ... Jacket, 31 ... Inner layer strength member, 32 ... Outer layer strength member, 33,44,45,46 ...... Torque balance cable.

Claims (4)

[Claims] 1. A method of laying first, second, and third submarine cables through a branching device, wherein the first and second submarine cables are in mutually opposite directions when tension is applied. A step of presetting to generate a rotation torque; a step of connecting one end of the first submarine cable and one end of the second submarine cable to the branching device; and one end of the first submarine cable. Connecting the one end of the third submarine cable to the branching device to which one end of the second submarine cable is connected, and supporting the other end of the third submarine cable with a ship, A step of charging the branching device connected to one end of the third submarine cable to the seabed, and a method for laying the submarine cable. 2. The method of laying a submarine cable according to claim 1, wherein the third submarine cable is a torque balance cable that does not generate a rotational torque when tension is applied. 3. A submarine cable hoisting method, wherein the first and second submarine cables are preliminarily determined to generate rotational torques in opposite directions when tension is applied, respectively. Connecting one end of the submarine cable and one end of the second submarine cable to the branching device, one end of the first submarine cable, and the second submarine cable.
To the branching device connected to one end of the submarine cable of
Further, connecting one end of the third submarine cable, and supporting the other end of the third submarine cable with a ship,
Inserting the branching device connected to one end of the third submarine cable into the seabed, and the first, second, and third submarine cables laid by a submarine cable laying method.
When retrieving the submarine cable, the step of searching for the third submarine cable, the step of holding the searched third submarine cable in a ship, and the third seabed held in the ship A method of lifting a submarine cable, wherein at least a step of lifting the first and second submarine cables and the branching device via a cable is performed. 4. The method for lifting a submarine cable according to claim 3, wherein the third submarine cable is a torque balance cable that does not generate a rotational torque when tension is applied.