JPS62129418A - Constructing method for underwater structure - Google Patents

Abstract

PURPOSE:To improve the safety of temporary coffering and construct an underwater structure efficiently, by using a caisson as a coffering unit. CONSTITUTION:A caisson 1 with upper and lower opening ends is used as a coffering unit, and by means of the caisson 1 for the coffering unit insulated from the peripheral water area, a structure 10 is constructed. After that, the caisson 1 is removed, and is used for the component of another structure. In this manner, the caisson 1 is used not only for temporary coffering, but for the component of a structure,and so the term of construction can be economically shortened, and in case that the caisson is used for temporary coffering, the water-stopping property is improved because of no joints, and accordingly, an under-water structure can be constructed in a safe circumstance.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a construction method for constructing underwater structures such as bridge pier foundations while performing temporary cofferdams.

<Conventional Technology> For example, when constructing bridge piers as the substructure of a bridge, a temporary coffering method has traditionally been employed.

In this construction method, sheet piles, etc. are driven around the planned location of the pier foundation to isolate it from the surrounding water area, and water within the sheet piles is drained to secure a work space.

Then, after assembling is performed in the space surrounded by sheet piles, concrete is poured to construct a concrete structure.

Finally, the sheet pile is removed to complete the work.

Problems to be Solved by the Present Invention> The conventional underwater structure construction techniques described above have the following problems.

(b) In sites where the current is fast, such as in a strait, it is not only extremely difficult to construct a site because the sheet piles are washed away, but also difficult to assemble shoring to reinforce the sheet piles.

Therefore, there are limitations to the construction site environment.

(b) Because the bedrock line is shallow near the shore, it is not possible to ensure sufficient penetration depth of the sheet pile.

(c) It is very difficult to ensure watertightness at the joints of sheet piles, which is a problem because surrounding water often leaks into the air space surrounded by the sheet piles.

(d) Because temporary cofferdams are composed of single connecting bodies such as sheet piles, there are concerns about safety against abnormal loads such as those caused by waves.

<Objective of the present invention> The present invention has been made to solve the above-mentioned problems, and provides a construction method for underwater structures that improves the safety of temporary cofferdams and enables efficient construction of underwater structures. The purpose is to provide.

Furthermore, it is an object of the present invention to provide a construction method for underwater structures that can be used economically as part of other structures, instead of being removed or dismantled after the temporary cofferdam is completed, as is the case with sheet piles. .

Structure of the Present Invention> Hereinafter, the construction technology of the present invention will be described with reference to the drawings, but first, the caisson frame that will be a part of the components of the temporary cofferdam and the underwater structure will be described.

Kui〉Caisson frame structure The caisson frame 1 is shown in Figure 1.2.

The caisson frame 1 is a box with open top and bottom ends.

The caisson frame 1 used in the present invention is used not only as a temporary cofferdam but also as a component of the caisson's original structure.

In this embodiment, a case where the caisson frame 1 is made of steel will be described, but it goes without saying that it can also be made of concrete.

The caisson frame 1 is, for example, a cylindrical box, and has a sharp cutting edge 2 formed at its lower end.

The body 3 of the caisson frame 1 is formed by arranging double cylinders made of steel, and a ballast chamber 4 is formed between the steel plates.

Further, within the ballast chamber 4, a plurality of supports 5 such as H-shaped steel are arranged in the axial direction.

[Structure of the blade mouth part] A bracket 3 is installed at the lower part of the inner circumference of the body part 3 of the caisson frame 1.
A plurality of 1 are installed protrudingly.

This bracket 31 is used as a jack 3 when removing the adhesive between the concrete layer 8 and the inner periphery of the cutting edge 2 as described later.
Used as a supporting member for the second part.

Further, a release agent may be applied to the inner periphery of the blade mouth 2 in some cases.

The above items are manufactured in advance at a factory on land.

Construction method <When using a caisson frame for temporary cofferdam> (1) Preparation for temporary cofferdam When the slope of the water bottom ground is steep or when there is a thick layer of soft ground such as sludge on the foundation ground G1 Underwater excavation should be carried out in advance to the extent that the foundation ground is exposed.

(2) Creasing and installation of the caisson frame (Figs. 1 to 3) [Creating] The caisson frame 1 having the above structure is transported to the site using a work boat or the like.

[Installation] Next, the caisson frame 1 is suspended by a crane or the like, and the caisson frame 1 is placed on the ground.

When the water depth is greater than or equal to the height of the caisson frame 1, extension caissons having only a body 3 without a cutting edge 2 are successively connected.

During this installation, the ballast chamber 4 of the caisson frame 1
Filling the inside with water improves the stability of the caisson frame 1 after landing on the bottom.

Furthermore, if the influence of waves is a concern, it is also possible to backfill the outer periphery of the caisson frame 1 with earth and sand G2 to counteract waves with earth pressure.

[Fall prevention work 1 Before removing the water inside the caisson frame 1,
It is necessary to take measures to prevent falls.

Specifically, for example, a raised support 6 is placed on top of the caisson frame 1. (Fig. 1.2) Next, tension members 7 made of PCC steel rings are stretched between the shoring 6 and the foundation ground G1.

To fix one end of the tension material 7 to the foundation ground G1, for example, the tip of the tension material 7 is inserted into a poling hole drilled in the foundation ground G1, and then the anchor hole is filled with grout and fixed.

Thereafter, a tension force is introduced into the tendon material 7 from the shoring 6 side to tension it.

Moreover, as shown in FIG. 6, it is also possible to use a combination of struts 5, supports 6, and tendons 7 to prevent falls.

In other words, the caisson frame 1 at the concrete top of the cutting edge 2
The caisson frame 1 is tensioned inside to prevent floating of the caisson frame 1 and water leakage, and to deal with lateral shaking due to waves etc., tensioning material 7 such as PCM wire is stretched diagonally. be.

[In order to prevent the caisson frame 1 from floating due to the installation buoyancy of underwater concrete columns and to prevent water from springing from the foundation ground G1, the caisson frame 1
An underwater concrete layer 8 of a constant thickness is formed on the foundation ground Gl within.

(3) Dry up The water in the caisson frame 1 is drained by a known method.

In the present invention, there are no seams in the temporary cofferdam.

Further, spring water from the foundation ground 7 is blocked by the underwater concrete layer 8.

Therefore, it is impossible for outside water to enter into the caisson frame 1, and high water-stopping performance can be ensured.

(4) Construction of foundation structure Within the dry-up caisson frame 1, formwork is constructed in the same manner as in conventional construction methods, and concrete is poured to construct an underwater structure 10 such as a concrete foundation or a bridge pier.

(5) Removal of the caisson frame (Fig. 5) When the use of the caisson frame 1 as a temporary cofferdam is finished, the water in the ballast chamber 4 is drained to reduce the weight, and the shoring 6 and tension members 7 are removed. Remove.

A jack 32 is installed between the underwater concrete layer 8 and the bracket 31.

Next, while suspending the upper part of the caisson frame 1 with a crane, each jack 32 is extended to separate the inner periphery of the cutting edge 2 of the caisson frame 1 from the underwater concrete layer 8.

Since the inner circumferential surface of the cutting edge 2 is coated with a release agent in advance, it can be easily removed.

After separating the cutting edge 2 and the underwater concrete layer 8, the caisson frame 1 is lifted and removed.

As explained above, the caisson frame 1 can be used as a temporary cofferdam material.

Furthermore, as will be described below, the caisson frame 1 that has been used as a temporary cofferdam can also be made into a part of the structure.

(1) Removal of caisson frame The caisson frame 1 used as a temporary cofferdam is removed in the same manner as described above.

(2) Reinstallation of the caisson frame The caisson frame 1, which was once used for temporary cofferdaming and then removed, is used as a constituent material for bridge piers, etc., which is the original purpose of the caisson.

Effects> Since the present invention is as explained above, the following effects can be obtained.

(a) It can be used not only as a temporary cofferdam but also as a structural material.

Therefore, the construction period can be shortened and the construction can be carried out economically.

(b) When used as a temporary cofferdam, there are no joints and the underwater concrete is placed on the exposed ground inside the caisson frame, so the water quality is significantly improved compared to when it is surrounded by conventional sheet piles. .

Therefore, construction work of underwater structures can be carried out in a safe environment.

(c) By injecting water into the caisson frame to give it weight or applying anchorage, etc., it can sufficiently resist water pressure and waves, and its stability as a cofferdam material is increased.

(d) When constructing a bridge over a strait with shallow coasts such as coral reefs, direct foundations are the main method.

In this case, it is simply used as a cofferdam (this allows for economical construction.

[Brief explanation of drawings]

Fig. 1 Longitudinal explanatory diagram of two caisson frames Figure 2: Explanatory diagram of the upper part of the caisson frame Figures 3 to 5: Explanatory diagram of construction method

Claims (1)

[Scope of Claims] When constructing an underwater structure, a box with open top and bottom ends is used as a cofferdam, and the structure is constructed using the box as a cofferdam while being isolated from the surrounding water body. After constructing the box, the box is removed, and the box is then used as a constituent material of another structure to build a structure.