JPS6340896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a submarine cable installation method and apparatus used to carry out the method. Methods for laying submarine cables include a method in which high-pressure water is injected into the seabed ground to excavate a cable burial trench, and the cables are successively laid into the excavated trench, or a method is used in combination with a vibrating excavator and high-pressure water jetting means. Both of these methods are suitable for relatively flexible submarine ground, but are completely impractical for hard ground at high depths with an N value of 30 to 50. This is because in the former case, excavation becomes impossible due to the weakening of the jet collision force due to the influence of water depth, and in the latter case, not only the jet collision force weakens, but also the towing resistance becomes extremely large. and due to extremely poor excavation progress. It is an object of the present invention to provide a method and apparatus that can reliably and efficiently perform seabed excavation and lay submarine cables even in hard ground that could not be constructed using conventional means.

First, the method of the present invention will be explained in detail.The method includes a composite jet impingement means in which low water pressure is injected around high-pressure water, which is supplied with pressurized air at a pressure equivalent to water depth to the jet part, and a jet part which is supplied with pressurized air at a pressure equivalent to the water depth. An excavated trench is formed on the seabed by using either or both of the low-pressure water jet injection means supplied with pressurized air at a pressure of This submarine cable installation method is characterized by:

Although the above method can be applied to conventional submarine cable laying equipment, it will become clearer with the equipment of the present invention and its operation described below.

The apparatus of the present invention is a laying apparatus for sequentially laying cables 2 on the seabed, which are supplied by sinking from a laying ship 1 floating on the sea surface, and will be explained as follows using an illustrated example.

3 is a sled frame body with ballast packed in a C-shaped box in plan, a submersible motor pump 4 mounted on the deck, and a grounding system equipped with a grounding meter on the swinging pivot on the left and right sides. Confirmation arms 5, 5' are attached. Further, at the bottom of the sled frame 3 and directly below the cable guide 6, which will be described later, there is an obstacle removing spade 7.
is installed.

Reference numeral 6 denotes a cable guide, the free end of which is located within the C-shape of the sled frame 3, and the base end of which is pivoted to a support leg 8 with a buried depth gauge fixed to the deck portion of the sled frame 3; The free end of the swing arm 9 extending in the direction perpendicular to the pivot axis of the base end is pivotally connected to one end of a hydraulic cylinder 10 pivotably mounted on the deck.

As shown in FIGS. 3 and 6, this cable guide 6 has a tunnel-shaped cable passage 13 with left and right side plates, a top plate 11, and a partition plate 12, with one end opening at a proximal end and the other end opening at a free end. is formed, and between the partition plate 12 and the channel opening surface, along the free end to the proximal end, there is a sludge removal section A consisting of a sludge ejector, a composite jet nozzle set 14, a sludge removal section B, and a low pressure Water jet nozzle sets 15 are sequentially installed.

As shown in FIG. 4, the composite jet nozzle set 14 includes a protective tube 18 in which the injection port 17 of the high-pressure water injection nozzle 16 is oriented in the axial direction and extends into the tube, and an outer cylindrical tube 19 whose one end is connected to a low-pressure water source. A low-pressure water injection nozzle 21 is interposed in a ring shape in the low-pressure water passage 20 between the outer cylindrical pipe 19 and the protection tube 18 to form a double pipe. The protective tube 18 has a pressurized air inlet 22.
A large number of single composite jet nozzles 23 having a plurality of jet nozzles 23 are fixed to a support plate 24 at various angles with the injection direction directed toward the channel opening surface. It is supported by a cylinder 25 so as to be swingable.

The sludge removal parts A and B, which are composed of sludge ejectors, are
A jet nozzle 28 is installed at an intermediate position between the sludge suction port 26 and the sludge discharge port 27, with the jet nozzle 28 facing the direction of the sludge discharge port 27, and the sludge suction port 26 It is fixedly installed on the left and right side plates or partition plate of the cable guide 6 in a state facing in the direction of suctioning earth and sand.

The low pressure water jet nozzle set 15 is the fifth
As shown in the figure, the injection port 30 of the low pressure water injection nozzle 29
A large number of individual low-pressure water jet nozzles 33 that exit into the protection pipe 32 in which the pressurized air inlet 31 is opened are connected to branch pipes branching from the low-pressure water supply pipe, forming a composite jet nozzle assembly. High pressure water supply to the 14 high pressure water jet nozzles 16, and pressurized air inlet ports 22, 31 of the low pressure water jet nozzle set 15 and the composite jet nozzle set 14, respectively.
are connected to the supply sources on the laying ship on the sea surface by pipes passing through the base end of the cable guide 6, and the low pressure water jet nozzles and sludge removal section of the low pressure water jet nozzle set 15 and the composite jet nozzle set 14 are connected to the supply sources on the laying ship on the sea surface. The injection jet nozzles A and B are connected to a submersible motor pump 4 installed on the deck. Further, mud discharge ports 27 of each of the mud discharge parts A and B
is a cable guide 6 along the cable passage 13.
The cable guide 6 is connected to two mud removal pipes 34 that open on the side plates of the base end of the cable guide 6, and these mud removal pipes 34 are further connected to a mud removal return pipe 35 that opens onto the top plate of the cable guide 6.

Further, on the deck, which is an extension line in plan view of the cable passage 13 that opens at the base end of the cable guide 6, the starting end becomes a cable introduction part 36 that spreads out from side to side, and the terminal end becomes the cable passage 13. 1
A guide table 39 equipped with a cable stopper 38 that approaches the opening 37 of 3 and bridges the passage is installed, and the guide table 39 is equipped with a cable stopper 38 that approaches the opening 37 of
The terminal end of a guide ring 41 connected and supported by a guide ring suspension rope 40 from the laying ship 1 is facing.

In addition, in the above explanation, the buried depth meter and the ground meter are designed to measure the rotation angle of the arm part electrically or mechanically, and the buried depth and grounding can be determined based on the known arm length and the measurement value. This is to check the depth. Furthermore, in the above embodiment, the device was explained as a device for laying one cable, but when laying multiple cables, cable guides corresponding to the number of cables can be installed inside the C-shape of the sled frame. Needless to say, it must be established.

The cable installation device configured above is towed to the seabed (at a depth of about 50 m) by a laying ship on the sea surface.
A cable burial groove is excavated, the cables are passed through the guide ring, and then passed from the guide table to the cable passage of the cable guide, and the cables are successively laid from the free end opening of the cable passage into the excavated groove.
By passing the cable through a swingable cable guide to its free end, it is possible to reliably lay the cable at the bottom of an excavated trench. A composite jet nozzle set with low pressure water (approximately 10 atm) surrounding the center and supplying pressurized air (more than water depth pressure) to prevent cavitation due to injection, and a jet nozzle set near the low pressure water injection port. Since the submarine ground is excavated using a low-pressure water jet nozzle set that supplies pressurized air to Dried hard ground with a high N value can be excavated easily and efficiently, and the construction period for submarine cable installation can be shortened. That is, when high-pressure water is injected into water, a vortex is generated near the injection port, resulting in a significant loss of injection energy. The loss is particularly significant when spraying into water where the flow velocity is slow compared to the jet flow velocity, or when the water is stationary, or when jetting into water at a great depth. When it is released, it plunges into the water without creating a whirlpool caused by the high-pressure water at the center. Therefore, when the ground to be excavated lies within the excavation distance range surrounded by low-pressure water, the jet power of high-pressure water can be used extremely effectively for excavation, and the low-pressure water surrounding the high-pressure water It not only protects the high-pressure water jet, but also works to collapse the surrounding ground, which has become weakened by the impact of the high-pressure water jet. These effects can be made even more effective by making the protective tube from which the injection port of the high-pressure water injection nozzle emerges a double tube covered with an outer cylindrical tube, and by introducing pressurized air into the protective tube. This is because the negative pressure eddy current phenomenon that occurs around the injection port of the high-pressure water injection nozzle and the negative pressure eddy current phenomenon that occurs inside the low-pressure water injection nozzle formed between the protection tube and the cladding tube cause the flow of pressurized air to be supplied. This is because the problem is eliminated by the introduction of water, and an air film is formed at the boundary between high-pressure water and low-pressure water, which becomes a kind of lubricating film.

Such effects are the same for low-pressure water injection nozzles, in which the vortex phenomenon around the low-pressure water jet is eliminated, and a lubricating film is formed by pressurized air around the low-pressure water, thereby significantly reducing friction loss. That's what happens.

Furthermore, by passing the cable through a cable passage provided within the cable guide, the cable can be protected from excavated earth, sand, stones, etc., and can be laid to the bottom of an excavated trench without causing damage.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the submarine cable installation state, FIG. 2 is a plan view of an embodiment of the submarine cable installation device of the present invention,
Figure 3 is a front view of the same, Figure 4 is a sectional view of the composite jet nozzle alone, Figure 5 is a sectional view of the low pressure water jet nozzle alone, Figure 6 is a partially detailed view of the inside of the cable guide with piping omitted, and Figure 7. shows an example of piping. 3... Sled frame body, 6... Cable guide, 10... Hydraulic cylinder A, 13... Cable passage, A, B...
Sludge removal section, 14...Composite jet nozzle set, 15...Low pressure water jet nozzle set.

Claims (1)

[Scope of Claims] 1. A composite jet injection collision means in which low-pressure water is injected around high-pressure water centered around high-pressure water to which pressurized air with a pressure equal to or higher than the water depth is supplied to the jet portion, and a jet portion having a water depth-equivalent pressure Using either or both of the above low-pressure water jet jet impingement means to which pressurized air is supplied, the jet jet collides with the ground to be excavated to excavate and form a cable laying trench, and while the excavation is being carried out, A submarine cable laying method characterized by laying a cable. 2. In a cable laying device in which a cable guide equipped with a pressurized water injection nozzle is installed on a submarine sled frame, one end of the cable guide, which is a channel that opens downward, is swingable via a telescoping device. The cable guide is pivotally supported on the submarine sled frame body, and a cable passage opening at the base end and the free end is formed inside the cable guide, and between the cable passage and the channel opening surface, high-pressure water is provided. A composite jet nozzle set consisting of a large number of single composite jet nozzles surrounded by low-pressure water and equipped with a pressurized air inlet near the high-pressure water jet, and a pressurized air inlet near the low-pressure water jet. A submarine cable laying device characterized in that a low-pressure water jet nozzle set consisting of a large number of individual low-pressure water jet nozzles with openings is installed, each of which is provided with fluid supply piping.