JPS6314909A - Scour-proof construction for underwater structure - Google Patents

Abstract

PURPOSE:To improve the efficiency of laying work, by paying out wires for suspending a scour-proof mat, to lay it for settling on the water bottom on the periphery of an underwater structure. CONSTITUTION:A caisson 1 is constructed in a dock, and a working scaffold is set up, and after that, a scour-proof mat 2 is suspended below the scaffold 5 via a suspension wires 6 and is taken in two to the spot of the settled caisson 1. Besides, a second and a third scour-proof mats 3, 4 are suspended and moved down on a base vessel 8 under water, and in its state, the mats are taken in two respectively to the spots. Then, the caissons 1 are settled and set on the spots, and the base vessels 8 are respectively connected to the outer peripheries of the scaffolds 5 and after that, through winches 9, wires are turned back, and the respective mats 2, 3, 4 are laid on the surface E of the sea bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a scour prevention construction method suitable for underwater structures submerged in a deep seabed under forced drift.

(Prior Art) The scouring phenomenon of underwater structures such as caissons is widespread and significant, especially under forced flow.

As a construction method to prevent this scale from scouring, either a method of reducing the scouring force by improving the ground based on the principle, or a method of increasing the scouring resistance of the ground is adopted.

However, in deep water and under forced flow, it is extremely difficult to increase the scour resistance.Therefore, a method of reducing the scour force has been adopted, but this method has the following problems.

(Problem 31 to be solved by the invention) In other words, anti-scouring pine that reduces scour force has traditionally been a method of laying protective material on the bottom surface of the underwater structure with a surface larger than the horizontal cross section of the underwater structure. Since this work was carried out exclusively by underwater work such as a dipper, there was a problem of low work efficiency and a long construction period of 111J.

This invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to enable the construction of anti-scouring works to be carried out in a short period of time and without any underwater work. In order to achieve the above object, the present invention includes a scaffold placed around an underwater structure, and a scour prevention mat suspended from a plurality of hanging wires at the bottom of the scaffold, It is characterized in that the anti-scouring mat is deposited and laid on the bottom surface of the water surrounding the underwater structure while the wire is being fed out.

(Function) As the anti-scouring mat is lowered into the water while the wire is being fed out, it will surely sink to the desired bottom surface even without underwater work! I can set it up. Additionally, by adjusting the feeding of each wire, it is possible to cope with uneven surfaces such as slopes.

(Example) Hereinafter, an example of this invention construction method will be described in detail using the drawings.

Figures 1 to 3 show the first embodiment of this invention construction method; Figure 1 is a plan view showing the connection relationship between a caisson and a scour prevention mat to which the same construction method is applied; Figures 2 and 3; These are process explanatory diagrams showing the procedure for laying the bathing prevention mat in the same construction method.

In each figure, 1 is a cylindrical steel caisson, and 2 is a scour prevention mat for bottom covering that is laid on the seabed in a plurality of pieces on the outer periphery of caisson 1 (hereinafter referred to as mat 1). , 3.4 is a scour prevention mat (1:
1. (referred to as 2.3 anti-scouring mat).

The first anti-scouring mat 2 is suspended from a fixed work scaffold 5 assembled on the peripheral edge of the top surface of the caisson 1 via a plurality of hanging wires 6. Further, the second and third anti-scouring mats 3゜4 are floating bodies, that is, barges 8.
It is similarly held in a suspended state via a plurality of hanging wires 1'-6 on the lower surface of.

Anti-scouring mat 2.3.4 is a chain mat.

It consists of a concrete mat, a gravel (rubble) mat, an asphal mat, a concrete mat, a concrete block pine 1-, etc., and each is held at the lower part of a hanging frame 7 connected to the lower end of the wire 6.

Then, after the construction of the caisson 1 in the construction dock is completed, and after the work scaffolding 5 is assembled in the ship rigging process, the first anti-scouring mat 2 is suspended from its lower part via a hanging wire 6. In this state, it will be towed by a tugboat to the site where Caisson 1 was sunk.

Also, the second. The third anti-scouring mats 3 and 4 are assembled at a place different from the laying site, and are suspended underwater from a 11-barge 8, which is then towed by a tugboat and brought to the sinking site. Each of them is arranged on the outer periphery of the first anti-scouring pine t-2. A plurality of winches 9, the number of which corresponds to the number of winter wires 6, are provided on the work scaffold 5 and the barge 8.

Therefore, as shown in FIG. 2 at the sinking site, after the caisson 1 is sunk, the barges 8 are connected to the outer periphery of the work scaffold, and after each barge 8 is fixed with a mooring cable or the like, the winch 9 is wound. When it is returned, each scour prevention mat 2 descends as shown by the Mi face line, and the first scour prevention mat 2 is laid on the seabed surface E at the outer periphery of the caisson 1, as shown in FIG.

Furthermore, if the 2.3 anti-scouring mats 3 and 4 land on an uneven surface, such as a slope E, instead of on a flat surface, each wire 6 may become tensed along the shape. Since the tassels may become loose, by checking the tension while winding the tassels with the winch 9, it is possible to lay the tassels in a state that corresponds to the uneven shape.

What about this work? Since the work is carried out under the A current, the winch 9 is operated according to the tension state of each wire 6, so that the wire can be laid at the desired installation position with high accuracy.

In addition, during installation work, each anti-scouring mat 2.3.
By connecting four mats or adjacent mats with wire or the like, the gap between each mat is small and a large scouring prevention effect can be achieved (q).

Incidentally, each of the anti-scouring mats 2.3.4 and the hanging frame 7 can be separated by an appropriate remote control.

Next, FIG. 4 shows a second embodiment of this invention construction method.

In the figure, the first anti-scouring mat 2 is located at the lower part of the work scaffold 5 as before, and is fixed to the lower part of the hanging frame 7 in a suspended state, and this hanging frame 7 is connected to the guide wire. It is held at the bottom of the scaffold 5 by 6'.

The first anti-scouring mat 2 is connected to a crane 20 via a hanging wire 6 in place of the winch 9, and by the lowering operation of the crane 20, the first anti-scouring mat 2 sinks and is laid on the seabed surface E in the same manner as described above. Ru.

Further, the anti-scouring mat 10 on the outer peripheral side is supported under the hanging frame 7 in an integrated state, unlike the first embodiment.

This is then transported to the sinking site in a suspended state via a plurality of hanging wires 6 to a crane 31 installed on a crane ship 30, and is attached to the outer periphery of the first anti-scouring mat 2 by the crane. It will be submerged by the operation of 31.

According to this embodiment, unlike the first embodiment, it is not possible to sink and install the anti-scouring mats all at once, but by sequentially operating the crane 20 and the crane ship 30, It will be installed sequentially on the surface,
Since the work is carried out using one crane 20 and crane ship 30, the construction period becomes longer, but the equipment cost is lower than in the first embodiment.

(Effects of the Invention) As explained in detail in each of the embodiments above, according to the scour prevention effect of the present invention, the scour prevention mat can be laid by work from the sea surface, so the laying work can be carried out with high efficiency. This can shorten the construction period.

In addition, it can be laid with sufficient followability on any uneven surface, such as slopes, and is extremely useful in preventing scouring of underwater structures at deep seabeds under strong tidal currents.

[Brief Description of the Drawings] Figures 1 to 3 show a first embodiment of the present invention, and Figure 1 is a plan view showing the arrangement relationship between the caisson and the washing prevention mat, Figure 12, and Figure 3. 4 is an explanatory cross-sectional view showing the scouring procedure of the scouring prevention mat in the same construction, and FIG. 4 is an explanatory view showing a second embodiment of the construction method of the present invention.

Claims (5)

[Claims] (1) A scaffold placed around an underwater structure, and a scour prevention mat suspended by a plurality of hanging wires at the bottom of the scaffold, and the scour prevention mat is submerged while the wires are being let out. A pioneer scour prevention construction method for underwater structures, characterized in that the construction is carried out by settling on the bottom surface of the water surrounding the structure. (2) The scour prevention method for an underwater structure according to claim 1, wherein the scaffold is a fixed scaffold provided in an overhanging state around the underwater structure. (3) The scaffolding consists of a fixed scaffolding provided in an overhanging state around the underwater structure, and a floating body that is located on the outer periphery of the fixed scaffolding and holds the scour prevention mat in a suspended state in the water. A scour prevention method for underwater structures according to claim 1, characterized in that: (4) Preventing scouring of an underwater structure according to any one of claims 1 to 3, characterized in that a winch for feeding out the hanging wire is used as the means for settling. Construction method. (5) The scour prevention method for an underwater structure according to any one of claims 1 to 3, characterized in that a crane is used as the means for settling.