JPH0534555B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method of laying submarine cables, pipelines, etc. (hereinafter referred to as "pipelines").

<Conventional technology> Submarine cables, pipelines, and other linear bodies (hereinafter referred to as "pipelines") are installed 3m to 4m below the seabed surface to avoid damage due to dropping or dragging anchors.
It is necessary to bury it to a certain extent.

The following two methods are known as methods for burying pipelines under the sea.

One method is to excavate the seabed using a grab ship or pump ship before pulling out the pipeline, and then drop the pipeline into the excavated trench and bury it.

The other method is to use an underwater excavator equipped with a high-pressure water injection device and a sand pump to lay the pipeline, first by temporarily placing the pipeline on the seabed throughout the entire area.

Thereafter, an underwater excavator straddles the pipeline, excavates the ground below the pipeline while sliding the pipeline, lowers the pipeline into the trench, and finally backfills the trench.

<Problems to be Solved by the Present Invention> The conventional pipeline laying technology described above has the following problems.

(b) The former method of installation requires high construction costs and a long construction period.

(b) In the latter method, the temporary laying of the pipeline and the excavation work are carried out independently, resulting in a long construction period.

(c) Regarding the latter method of laying the pipeline, it is conceivable to use an underwater excavator to excavate without a guide member and lay the pipeline before temporarily placing the pipeline in order to shorten the construction period. Without these parts, the direction of excavation by the underwater excavator cannot be determined, making it impractical.

(d) Other pipeline laying methods are disclosed in US Pat. No. 3,333,432.

This laying method involves placing an excavator over the pipeline to be laid, and excavating the trench and laying the pipeline at the same time.

However, in this method, since the pipeline cannot be expected to have the function of guiding the excavation direction of the excavation device, there is a disadvantage that the groove tends to meander and it is not possible to excavate an accurate groove along the planned installation line.

Furthermore, since this method of laying trenches excavates by jetting high-pressure water, there is a limit to the jetting pressure, and there is a limit to the depth of the trench that can be excavated.

In addition, in this laying method, the trench excavation position and the pipeline drop-in position are approximately the same, so the pipelines that can be laid are limited to those with excellent flexibility.

<Objective of the present invention> The present invention has been made in view of the above points, and its purpose is to be able to excavate a trench accurately along the pipeline installation line, and to improve the depth of burial of the pipeline. The goal is to provide a method for laying pipelines that can be freely changed.

<Configuration of the Present Invention> An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. First, an underwater excavator used in the present invention will be described.

(a) Underwater excavator An example of an underwater excavator 1 is shown in FIGS. 1 and 2.

This underwater excavator 1 includes a plurality of nozzles 3 that inject high-pressure water toward the lower part of a main body 2, a plurality of sand pumps 4, and a shielding means for shielding an earth removal section.

The details of the structure of the underwater excavator 1 will be described later, but one of the features of the present invention is that the underwater excavator 1 is used by being integrally assembled with the short pipe 5.

The short pipe 5 is a guide member for stabilizing the direction of excavation of the underwater excavator 1, and can be made by cutting a pipeline P to be laid into a predetermined length, for example.

(B) Main body The top of the main body 2 has a hanging hook 11, and on both sides there are stays 1 extending horizontally.
2, the free end side of each stay 12 is bent downward, and a plate-shaped ski 13 for sliding on the seabed is provided at each end.

The main body 2 is placed over the short pipe 5, and both are fixed by welding, bolting, or the like.

(C) Nozzle The nozzle 3 is an excavating tool that excavates a groove 81 in the seabed ground 8 by injecting high-pressure water. Multiple nozzles are provided on both sides of the main body 2, and the nozzle 3 is a drilling tool that sprays high-pressure water to excavate a groove 81 in the seabed ground 8. It is designed to spray water.

(d) Sand pump The sand pump 4 is a well-known pump having a function of suctioning slurry-like earth and sand, and a plurality of sand pumps are fixed to the lower part of the main body 2.

The earth discharge pipe 41 connected to each sand pump 4 is
It protrudes right sideways on both sides of the main body 2, and its ends are bent downward for piping.

(e) Shielding measures Since the excavated soil will be discharged into the sea, there is a concern that the sea water will become cloudy.

Therefore, shielding members 7 are attached above and on the sides of each soil discharge pipe 41 so as to shield the periphery of the discharge portion of each soil discharge pipe 41 group that protrudes from both sides of the main body 2.

The barrier material 7 is made of a material that can prevent the permeation of earth and sand, such as a steel plate, a resin sheet, or a cloth body. If the barrier material 7 is flexible, such as a sheet, reinforcement is provided above each earth discharge pipe 41. The shape of the blocking material 7 is maintained by attaching the member 14.

Furthermore, if a screen 71 is provided at the edge of the shielding material 7, the shielding effect will be further improved.

In addition, in this example, a case will be described in which construction is performed using an underwater excavator 1 equipped with a shielding material 7, but
It is also possible to use various types of excavators, such as a known underwater excavator without the barrier 7 or an excavator that excavates mechanically.

<Function> Next, the method of laying the pipeline will be explained.

(a) Excavation work The short pipe 5 with the underwater excavator 1 attached is brought to the bottom on the seabed ground 8.

The operation of the underwater excavator 1 is started, and at the same time, the towing rope 61 connected to the tip of the short pipe 5 is towed by the work boat 6.

As a result, high-pressure water is injected from each nozzle 3 of the underwater excavator 1 toward the seabed ground below the short pipe 5, and a groove 81 is excavated in the seabed ground 8 where the short pipe 5 touches the bottom.

The underwater excavator 1 excavates a groove 81 while sliding on the seabed ground 8 via skis 13.

During the excavation work of the groove 81, the short pipe 5 performs a guiding function, so that meandering of the underwater excavator 1 is reliably prevented.

(b) Earth and sand excavated by the underwater excavator 1 is sucked by the sand pump 4 and discharged to the seabed ground 8 on both sides of the trench 81 via the earth and earth discharge pipe 41.

Since the excavated earth and sand are discharged into the sea area shielded by the seabed ground 8 on both sides of the trench 81, the shielding material 7, and the screen 71, turbidity of seawater and the spread of earth and sand are restricted.

Finally, the excavated soil is left on the seabed ground 8 on both sides of the trench 81 with a shielding width.

(c) Pipeline installation work A separate work boat 62 is used to sequentially drop the pipeline P into the groove 81 that has been opened where the short pipe 5 has passed.

According to the conventional laying method using an underwater excavator, excavation was carried out after waiting for the completion of the temporary laying work of the pipeline P.

On the other hand, in the present invention, the underwater excavator 1 can be attached to the short pipe 5 to carry out preliminary excavation, so the excavation work by the underwater excavator 1 and the laying work of the pipeline P can be performed in parallel.

(d) Backfilling After filling a small amount of the pipeline P into the trench 81, the trench 81 is sequentially backfilled with the pipeline P.

Earth and sand left on both sides of the trench 81 can be used as backfilling material.

If the excavated soil is too soft to be used as backfill material, it is still necessary to use good quality backfill material.

<Other Embodiments> (Fig. 3) In the above embodiment, the case where excavated earth and sand are discharged onto the seabed has been described, but the excavated earth and sand are transferred to a loading ship 63 on the sea using the short pipe 5 as a part of the transfer pipe. It is also possible to collect it.

That is, a separate transfer pipe 9 is connected to the tip of the short pipe 5, and one end of the transfer pipe 9 is guided to the loading ship 63.

By connecting each earth discharge pipe 41 to the short pipe 5 and blocking the opening on the tail end side of the short pipe 5, the earth and sand excavated by the underwater excavator 1 can be prevented from being discharged into the sea, and a loading ship at sea can It can be collected at 63.

In addition, sand pump 4 is used to transfer the excavated soil.
If the discharge force is insufficient, an auxiliary pump (not shown) is installed on the loading vessel 63 to recover the liquid.

<Effects of the Present Invention> Since the present invention is as described above, the following effects can be expected.

(b) Since the excavator is integrally attached to the short pipe,
It is possible to prevent the excavator from meandering and excavate a trench at an accurate position along the planned laying line.

(b) The pipeline can be dropped into the trench at a distance from the location where the trench is excavated by the excavator.

Therefore, even pipelines that are difficult to bend can be laid.

(C) (C) The excavation depth of the trench can be freely set because the soil is stirred by high-pressure water injection and collected by negative pressure suction.

Therefore, deep trenches can be excavated without increasing the injection pressure of high-pressure water, which is advantageous when the pipeline is laid at a large depth.

[Brief explanation of the drawing]

FIG. 1: An explanatory diagram of one embodiment of the pipeline laying method according to the present invention, FIG. 2: A cross-sectional view taken at - in FIG. 1, and FIG. 3: An explanatory diagram of another embodiment.

Claims (1)

[Claims] 1. An independent short pipe is used for guiding the excavation direction, and the short pipe has the function of spraying high-pressure water toward the water level and stirring it, and the function of suctioning and collecting the stirred earth and sand. , a first step in which an excavator is attached to the short pipe, and the short pipe is guided in the excavation direction and the short pipe is towed to excavate a trench along the line where the pipeline is planned to be laid; A pipeline laying method comprising a second step of dropping the pipeline into the trench in parallel with the work, and a third step of backfilling the trench where the pipeline has been dropped and burying the pipeline.