JPS5833763B2 - How to bury submarine cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for burying a submarine cable.

When laying a submarine cable, it is required to bury it on the seabed in order to prevent damage to the cable, but especially when laying it in a port or shipping route, it is necessary to bury the cable in the seabed to prevent damage from anchoring. Of course, from now on, burying will be required as an essential requirement by port administrators.

There are two known methods for burying cables on the seabed: dynamic burying and water jet burying, which can be broadly divided from excavation methods.

For example, as shown in Figures 1 and 2, a general burying method that employs water jet burying is to install an anchor 2 on the seabed approximately 800 meters in front of the construction vessel 1, and
A wire rope 3 for a tow 9 is laid from the cable holder 1 to the cable laying boat 1, and this rope 3 is wound around a winch 4 installed on the cable laying boat 1, and then attached to the rear of the cable laying boat 1 via a cable guide 5 and a towing wire 6. By attaching the burying machine 7 and winding up the wire rope 3 with the winch 4, the laying ship 1 is moved forward while towing the burying machine 7.

Burying machine 7 excavates the seabed with a water jet and sends it to the laying vessel 1.
The submarine cable 8 fed out from above is laid in the trench as it moves forward along the planned laying route 9.

When the laying ship 1 moves 400 to 500 doors, the wire rope 3 becomes angled to spread to both sides of the front of the laying ship 1, as shown by the dashed line in FIG. 1, and no longer plays a role in advancing the laying ship.

For this reason, it is necessary to repeatedly install the next anchor approximately 800 meters in front of the construction vessel 1, change the wire rope, and move forward again. It usually takes 30 minutes to reposition the anchor as described above. It takes ~1 hour.

Furthermore, when the laying ship 1 winds up the wire rope 3 and moves forward, the traction tension of the burying machine 7 ranges from several tons to about 201, depending on the bottom sediment and burial depth. As shown in Figure 2, due to the tension, the anchor 2 and the laying ship 1 form a substantially straight line and float off the seabed, and near the laying ship 1, the wire rope 3 becomes a hindrance, making it impossible for other ships to navigate. becomes.

In this case, since the entire length of the wire rope 3 floats, the range of obstruction to navigation is extremely large.

To avoid this, port authorities sometimes require that the anchor be installed within a range of, for example, 160 m or less from the laying ship, to minimize interference with the navigation of other ships.

As mentioned above, if the anchor is installed closer to the laying ship, the range of obstruction to navigation will be reduced, but on the other hand, the amount of advance the laying ship will make at one time will be drastically reduced to 20 to 30 m. Compared to moving forward 400 to 500 meters with one anchor installation, the anchor must be repositioned more frequently, and a lot of time and effort is spent on this positioning, so it is completely impossible to do so from an efficiency standpoint. This may result in no work being done, and it may become virtually impossible to do the work.

This invention was made in view of the above points, and a sinker is attached in the middle of a towing wire rope to reduce the floating range of the wire rope when a laying ship moves forward, thereby preventing navigation of other ships. The range of interference is very narrow,
To provide a burying method that allows work to be carried out even if the work range is restricted by a port administrator without having to frequently change the position of an anchor.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 7.

As shown in FIGS. 3 and 4, the front 800 of the laying ship 11
A wire rope 13 for towing is laid between the anchor 12 installed at position m and the laying ship, and by winding this wire rope 13 with the winch 14 on the laying ship 11, the laying ship 11 is moved. Advance.

A burying machine 15 is connected to the rear of the laying ship 11 via a towing wire 14, and when the laying ship 11 is moved forward, the cable 16 loaded on the laying ship is transferred to a tension meter 17.
The cables 16 are fed out to a burying machine via a cable guide 18, and the cables 16 are sequentially buried in the seabed.

In the middle of the wire rope 13, this wire rope 1
A sinker 19 is suspended at the above point so that the rising point from the seabed of No. 3 toward the laying ship 11 is, for example, 70 m in front of the laying ship 11.

This sinker 19 has a weight commensurate with the pulling tension of the wire rope 13 generated when the laying ship 11 moves forward, and
0 to the wire rope 13 so as to be movable.

The sinker 19 is placed in the middle of the wire rope 13 by the laying ship 1.
1, the rising edge of the wire rope 13 approaches the laying ship 11, and most of the rest from the rising edge to the anchor 12 is laid along the seabed, as shown in Figure 4. , the range of interference with the navigation of other ships will be extremely small.

A water depth gauge 21 is attached to the sinker 19 as shown in FIGS. 5 and 6, and a water depth gauge 21 is installed on the laying ship 11 to check whether the position of the sinker 19, that is, the rising position of the wire rope 13 is at a predetermined depth. The water depth indicator 22 can be used for constant monitoring.

This sinker 19 is connected to the pulley 2 with respect to the wire rope 13.
Since it is movable at 0, even if the wire rope 13 is wound up with the winch 14 in order for the laying ship 11 to move forward,
The wire rope 13 does not wind up toward the laying ship 11, but rather, since the position of the anchor 12 is lower than the position of the sinker 19, it slides toward the anchor 12 and lands on the seabed, causing the rise of the wire rope 13 to reach the laying ship 11. Since the purpose of getting closer may not be achieved, the position adjustment rope 23 and winch 2
4, the sinker 19 can be moved up and down according to the water depth.

The weight of the sinker 19 is determined by the following formula with reference to FIG.

For example, if the rising point of the wire rope 13 from the seabed is limited to 70 m in front of the installation ship 11, the depth H of the rising point of the wire rope and the traction tension F1 are H = 10 m 15 m 20 mF = 20 t
The weight W of the sinker 19 is calculated as shown in the following table, assuming that the weight is 10t and 5t.

That is, when the traction tension of the wire rope 13 is 20 tons in a sea area with a depth of 20 m, a sinker with a weight of 5.51 is used, and the position of the sinker 19 from the sea is adjusted so that it is 70 m in front of the laying ship 11. The wire rope 13 can float up from the seabed within the limit of 70 m, and the anchor 12 can be set at a depth of 700 to 800 m.
Since it can be installed in the front, there is no need to frequently change the position of the anchor, making it possible to bury the anchor.

Also, the traction tension of 20t is reduced, for example, 101
When this happens, the tension of the wire rope 13 becomes loose and the sinker 19 lands on the seabed.

On the other hand, when the traction tension becomes larger than 201, the tension of the wire rope 13 increases, the rising point of the wire rope 13 becomes faster from 70 m in front of the laying ship 11, and the depth indicator shows that the depth of the sinker 19 becomes shallower. is shown.

In this case, the forward speed of the laying ship 11 is slowed down and the burying is carried out while maintaining the traction tension below 20.

In addition, when a large ship approaches the wire rope 13, it is enough to loosen the wire rope 13 slightly, and the sinker will land on the seabed, and the wire rope between the sinker 19 and the anchor 12 will descend to the seabed surface and fully navigate. It becomes possible.

As described above, according to the present invention, a sinker is installed in the middle of the towing wire rope that carries the laying ship in both directions, and the floating range of the wire rope is reduced. The range for interfering with navigation becomes extremely narrow.

At the same time, set the anchor to 80'rrL as usual.
Since it can be installed approximately forward, there is no need to frequently change the position of the anchor, making it possible to bury submarine cables even if the work area is restricted by port authorities.

Also, the sinker is aligned along the wire rope.

By moving the sinker according to the water depth and wire rope tension, it has the excellent effect of always keeping the floating range within the restricted range, contributing to improving the efficiency of burial work. It is extremely dog-like.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a conventional burying method, and FIG. 2 is a front view of the same. 3 is a plan view showing the burying method of the present invention, FIG. 4 is a front view of the same, FIG. 5 is an enlarged plan view showing the sinker attachment part in the same, FIG. 6 is a front view of the same, and The figure is an explanatory diagram showing the relationship between the weight of the sinker and the balance of force. 11... Laying ship, 12... Anchor, 13... Wire loaf, 16... Cable, 19... Sinker, 20... Pulley, 21... Water depth gauge, 22... Water depth indicator Total, 23...rope for position adjustment.

Claims (1)

[Scope of Claims] 1. A sinker is suspended in the middle of a towing wire rope that connects a cable laying ship and an anchor installed in front of the cable laying ship and moves the cable laying ship forward by winding it up on the laying ship, 1. A method for burying a submarine cable, characterized in that the floating range of the towing wire rope caused by tension due to the towing tension is reduced by the sinker when the laying ship moves forward. 2. The seabed according to claim 1, wherein the sinker is movable along the towing wire rope, and the hanging position is adjusted according to changes in water depth or changes in the tension of the towing wire rope. How to bury the cable.