JPS6250520A - Construction of underwater concrete structure - Google Patents

Abstract

PURPOSE:To permit a concrete structure under water to be protected by a formwork without leaving residual water in the formwork by a method in which the upper end face of a formwork is inclined at almost the same angle as the repose angle of concrete, and concrete is supplied from the top of the inclined face. CONSTITUTION:Formworks 2 and 10 are set on the bottom 1 under water, a tremie tube 3 is thrust through the hole 10c of the formwork 2, and concrete C is placed. The inclined face 10a of the top formwork 10 is almost equalized with the flow slope of concrete C, and water in the formwork 2 is discharged to the outside through the gap between the tube 3 and the hole portion 10c. The top face of the concrete C so placed is closely contacted with the downside of the top formwork 10 to protect the structure sufficiently with the formworks 2 and 10. The separation of the concrete materials can thus be lessened while preventing the generation of residual water.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for constructing an underwater structure.

(Prior art and problems) As is well known, foundations such as bridge piers and abutments are often installed underwater, and this type of underwater structure is usually constructed of reinforced concrete. It was done in the manner shown.

The method shown in Figure (A) is widely used, and involves installing a formwork 2 with an open top on the water bottom 1, placing reinforcement inside, and then pouring concrete using tremie pipes 3. .

However, with this method, sludge etc. that are thrown up during the installation of the formwork 2 may flow in from the top of the formwork 2, or the top of the poured concrete may be washed away by water, causing material separation of the concrete. Cheap.

Also, when concrete is compacted using a vibrator, material separation and water pollution occur.

The method shown in FIG. 5(B) improves the problems of material separation and water contamination, and involves closing the upper opening of the formwork 2 with a substantially horizontal ceiling formwork 4. There is.

Concrete is poured by inserting the tremie pipe 3 into a hole previously provided in the ceiling formwork 4, but this method also has the following problems.

In other words, the concrete placed in the formwork 2 is
As shown by the broken line in Figure (B), the residual water 5 forms a mountain around the tremie tube 3, and in the example shown in the figure, residual water 5 is generated on both sides and the center of the formwork 2.

This is because when the concrete is discharged from the tremie pipe 3 and flows, it flows so as to form a constant angle of repose θ determined by its composition ratio, but if any residual water 5 remains, it will rot. However, there was a problem in that the top of the poured concrete did not come into close contact with the ceiling formwork 4, and the ceiling formwork 4 did not protect the concrete.

This invention was made in view of these problems, and its purpose is to prevent residual water from remaining in the formwork and to allow the formwork to fully exert its protective function for underwater concrete structures. The purpose of the present invention is to provide a method for constructing an underwater concrete structure that is possible.

(Means for Solving the Problems) In order to achieve the above object, the construction method of the present invention is a method of constructing a structure by pouring concrete into a formwork installed underwater. It is characterized in that the end face is an inclined surface having approximately the same angle of repose as the angle of repose of the concrete, and the concrete is supplied from the top of the inclined surface.

(Function) In the construction method of the present invention having the above-mentioned configuration, the upper end surface of the form is an inclined surface having approximately the same angle as the flow gradient (angle of repose) of the poured concrete filled inside. No residual water remains between the top of the poured concrete and the top of the formwork.
These can be attached closely, and the formwork can effectively protect the concrete structure.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 to 4 show an embodiment of the method for constructing an underwater concrete structure according to the present invention.

The construction method shown in the figure is to construct an underwater concrete structure by pouring concrete C using a tremie pipe 3 into a formwork 2 installed on the underwater bottom 1, and the basic structure is as described above. This is the same as the conventional construction method.

The construction method shown in the figure has the following features.

That is, a ceiling formwork 10 fixed to the upper end of the formwork 2
is at the point where the slope 10a has an angle θ that is approximately the same as the flow gradient (angle of repose θ) of the concrete C to be placed. As shown in Fig. 3, the angle of repose (θ) of concrete C is the angle with respect to the horizontal plane determined by the composition ratio of concrete C when it is released by free falling inside the tremie pipe 3, and is generally 1/20~1/100
That's about it.

In this embodiment, as shown in FIG. 2, the sloped surface 10a is formed at the center point of dividing the nearly square formwork 2 into four parts so as to rise from all sides, and the top of the sloped surface 10a There are four holes m10b into which the tremie tube 3 is inserted.

As shown in FIG. 4, the diameter of each hole 10b is slightly larger than the diameter of the tremie tube 3, so that the water inside the formwork 2 can flow out of the formwork 2 through these gaps. However, an overflow water outlet 10C may be provided at the periphery of the ceiling formwork 10.

Now, when the formwork 2.10 configured as described above is installed on the water bottom surface 1, the tremie tube 3 is inserted into the hole 10c.
The concrete C is poured by inserting it through the hole. Then, when the concrete C is gradually filled into the formwork 2 and its top surface reaches the inclined surface 10a of the ceiling formwork 10,
The pouring of concrete C is completed.

Here, the inclined surface 10a of the ceiling formwork 10 has almost the same angle as the flow gradient of the poured concrete C, and since the concrete C is supplied from the top thereof through the tremie pipe 3, the formwork 2 The water inside flows through the tremie tube 3 and the hole 10c.
It is prevented from flowing out to the outside through the gap and remaining in the formwork 2.

Therefore, the top surface of the poured concrete C is the ceiling formwork 10.
The formwork 2.10 can sufficiently protect the structure.

Furthermore, even if a vibrator is inserted through the hole 10c to compact the concrete C after the concrete C has been placed, the material separation of the concrete C will be small and the problem of water pollution will not occur too much. No.

(Effect of the invention) As explained above in the examples, according to the construction method of the present invention,
A relatively simple configuration in which the ceiling formwork is sloped to correspond to the angle of repose of the poured concrete, and concrete is supplied from the top of the slope, prevents the generation of residual water and allows material separation of the poured concrete. Excellent effects can be obtained, such as reducing the amount of

[Brief explanation of drawings]

Figures 1 to 4 show an embodiment of the construction method of the present invention, with Figure 1 being an overall explanatory diagram, Figure 2 being a plan view of the formwork,
FIG. 3 is an explanatory diagram of the concrete flow gradient, and FIG. 4 is an explanatory diagram at the end of concrete placement. FIG. 5 is a schematic explanatory diagram of the conventional construction method. 1... Water bottom surface 2... Form frame 3... Tremy tube 4... Ceiling formwork 10a... Inclined surface 10b... Hole portion 10
c... Overflow water outlet Figure 5 (A) (B)

Claims (1)

[Claims] In a method of constructing a structure by pouring concrete into a formwork installed in water, the top end of the formwork is an inclined surface with approximately the same angle as the angle of repose of the concrete, and from the top of the inclined surface A method for constructing an underwater concrete structure, comprising supplying the concrete.