JP3722201B2 - Method of placing underwater concrete using lightweight aggregate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a concrete placing method for constructing underwater structures such as bridge footings and caissons with underwater concrete using lightweight aggregates.
[0002]
[Prior art]
When building bridge footings and caissons, so-called underwater concrete is often used, but if the ground at the construction site is soft, footing or caisson can be used to minimize ground improvement work. It is desirable to make the foundation structure as light as possible.
[0003]
On the other hand, when reducing the weight of concrete, it is common to use a lightweight aggregate.
[0004]
[Problems to be solved by the invention]
However, when underwater concrete is cast using lightweight aggregates, the lightweight aggregate with a small specific gravity rises in the fresh concrete during concrete placement, and if it is lighter than water, it jumps out of the fresh concrete into the water. Or fresh concrete may splash into the water and pollute the surrounding water area.
[0005]
For this reason, it is necessary to use underwater concrete that normally uses aggregates. As a result, there has been a problem that it is almost impossible to reduce the weight of the foundation structure.
[0006]
Even if the light-weight aggregate can be prevented from jumping out, it is not possible to prevent the light-weight aggregate from being unevenly distributed in the fresh concrete and becoming uneven, and there is room for improvement in terms of quality.
[0007]
The present invention has been made in consideration of the above-described circumstances, and is an underwater using a lightweight aggregate capable of preventing the splashing of a lightweight aggregate and, consequently, the scattering of fresh concrete in the water and improving the quality of the concrete. The object is to provide a method for placing concrete.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the method for placing underwater concrete using the lightweight aggregate according to the present invention, as described in claim 1, stores the lightweight aggregate in a mesh bag and puts it in a bag state. The light weight aggregate in the bagged state is placed at a predetermined position in the underwater placement area, and then cement milk is pressurized and injected into the gap between the light weight aggregates to construct a lightweight concrete.
[0009]
In the method for placing underwater concrete using the lightweight aggregate according to the present invention, first, the lightweight aggregate is housed in a mesh bag to form a bag.
[0010]
The mesh bag size and material of the mesh so that the stored lightweight aggregate will not rise out due to the buoyancy received from water or cement milk and will not pop out, and the pressurized injection of cement milk will be performed smoothly. The strength is appropriately selected. In addition, the amount of the lightweight aggregate to be accommodated is appropriately determined in consideration of the scale and shape of the underwater placement area or the convenience of handling.
[0011]
Next, the light weight aggregate in a bag state is placed at a predetermined position in the underwater placement area.
[0012]
When placing the light-weight aggregate in the bag at a predetermined position in the underwater placement area, the light-weight aggregate in the bag is fixed by a predetermined method so that the light-weight aggregate in the bag is not lifted by buoyancy from water or cement milk.
[0013]
Here, the method of fixing the light weight aggregate in the bag state is arbitrary. For example, after stacking all the light weight aggregates in the bag state, placing the grating on the upper surface and fixing the grating to the formwork In addition, a method of pressing together by placing a weight on the grating or a method of fixing the light-weight aggregate in a bag state to the inner surface of the mold can be considered.
[0014]
Next, cement milk is injected under pressure into the gap between the lightweight aggregates to construct lightweight concrete.
[0015]
In this case, the lightweight aggregates were floated from the surrounding water before cement milk injection and buoyant from the cement milk after cement milk injection, but were packed in a mesh bag. Since it is fixed at a predetermined position in the underwater placement area in the state, even if such buoyancy is applied, it does not rise and stays at the place where it was initially placed. And since cement milk is pressurized and injected into the gaps between such lightweight aggregates, the constructed lightweight concrete is composed of high-quality concrete that is evenly dispersed without uneven distribution of lightweight aggregates. Become.
[0016]
Further, in the present invention, even in a situation where the lightweight aggregate floats in the fresh concrete and jumps into the water because of its light weight, in the present invention, as described above, the buoyancy from the surrounding cement milk However, the lightweight aggregate is not likely to lift from the original installation position because it is fixed in place in the underwater placement area in a state of being packed in a mesh-like bag body. There is no concern of rising to the top and jumping out of the top.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a method for placing underwater concrete using a lightweight aggregate according to the present invention will be described with reference to the accompanying drawings. Note that components that are substantially the same as those of the prior art are assigned the same reference numerals, and descriptions thereof are omitted.
[0018]
FIG. 1 is a construction procedure diagram showing a case where an underwater concrete placement method using a lightweight aggregate according to the present embodiment is applied to underwater concrete placement in a caisson, and FIG. 2 is a mesh bag used for the underwater concrete placement method. It is the perspective view which showed the lightweight aggregate accommodated in it.
[0019]
First, prior to placing underwater concrete using lightweight aggregates, caisson 1 is installed as shown in FIG. When the caisson 1 is installed, the caisson 1 is towed to the site, the caisson installation location is excavated flat in advance, and then the caisson is poured into the caisson 1 to sink the caisson to the seabed 2. .
[0020]
On the other hand, the lightweight aggregate 11 used for the underwater concrete is stored in a mesh bag 12 as shown in FIG.
[0021]
The mesh bag 12 has a mesh size so that the stored lightweight aggregate 11 is lifted by buoyancy received from water or cement milk and does not jump out and the pressurized injection of cement milk is performed smoothly. The sheath material strength may be selected as appropriate, and for example, it may be configured by a net made of steel or FRP. The mesh bag 12 is preferably set to have an opening of about 5 to 10 mm, for example, according to the size of the lightweight aggregate 11.
[0022]
Next, as shown in FIG. 1 (b), the lightweight aggregate 11 packed in the mesh bag 12 is placed at a predetermined position in the underwater placement area inside the caisson 1.
[0023]
When placing the lightweight aggregate 11 in the bag at a predetermined position in the underwater placement area, for example, the lightweight bone 11 in the bag is prevented from being lifted by the buoyancy received from water or cement milk. After all the materials 11 are stacked from the bottom surface of the caisson 1, the top surface thereof is pressed with a grating or the like, or the lowermost one is fixed to the bottom surface of the caisson 1, and then sequentially stacked from the lowermost step while being interconnected vertically. It is better to do so.
[0024]
Next, as shown in FIG. 3, cement milk 21 is pressurized and injected into the gaps between the lightweight aggregates 11 while draining the caisson 1 appropriately to construct lightweight concrete. The injection tube 22 for injecting the cement milk 21 under pressure is simultaneously provided when the lightweight aggregate 11 packed in the mesh bag 12 is placed at a predetermined position in the underwater placement area inside the caisson 1. It is good to pipe and to draw out gradually according to the progress of the cement milk 21 injection process.
[0025]
In this way, the lightweight aggregate 11 is buoyant from the surrounding water before the cement milk 21 is poured, and buoyant from the cement milk after the cement milk 21 is poured. 12 is fixed at a predetermined position in the underwater placement area in a state of being packed in the bag 12, so that even if such buoyancy is applied, it does not rise and stays at the place where it was initially placed. The cement milk 21 is injected under pressure into the gap between the lightweight aggregates 11 and hardened.
[0026]
As described above, according to the method for placing underwater concrete using the lightweight aggregate according to the present embodiment, the predetermined position of the underwater placement area in a state where the lightweight aggregate 11 is packed in the mesh bag 12. Since the cement milk 21 is injected under pressure in such a state, the lightweight aggregate 11 is prevented from rising, and the cement milk 21 remains in the gap between the lightweight aggregate 11 remaining at the original installation position. Will be injected.
[0027]
For this reason, it is possible to place lightweight concrete in a uniformly dispersed state in which the lightweight aggregate 11 is not unevenly distributed, and the quality of the lightweight concrete can be greatly improved.
[0028]
Further, according to this embodiment, according to the present embodiment, as described above, the surrounding cement is used even in a situation where the lightweight aggregate 11 floats in the fresh concrete and jumps out into the water due to its light weight. Even when receiving buoyancy from the milk 21, the lightweight aggregate 11 is not likely to be lifted from the initial installation position because it is fixed at a predetermined position in the underwater placement area while being packed in the mesh bag body 12. .
[0029]
Therefore, it is possible to prevent the lightweight aggregate 11 from jumping out from the cement milk 21 and the accompanying scattering of the cement milk 21 in water, and thus contamination of the surrounding water area. As a result, the lightweight aggregate is used. It is also possible to reduce the weight of the foundation structure with underwater concrete.
[0030]
【The invention's effect】
As described above, according to the method for placing underwater concrete using the lightweight aggregate of the present invention, it is possible to place the lightweight concrete in a uniformly dispersed state in which the lightweight aggregate is not unevenly distributed. The quality of concrete can be greatly improved.
[0031]
[Brief description of the drawings]
FIG. 1 is a construction procedure diagram showing a state in which underwater concrete is placed on a caisson according to a method for placing underwater concrete using a lightweight aggregate according to the present embodiment.
FIG. 2 is a perspective view of a mesh bag used in the placing method according to the present embodiment and a lightweight aggregate 11 accommodated therein.
FIG. 3 is a construction procedure diagram showing a state in which underwater concrete is placed on a caisson according to a method for placing underwater concrete using the lightweight aggregate according to the present embodiment.
[Explanation of symbols]
11 Lightweight aggregate 12 Reticulated bag 21 Cement milk

Claims (1)

The lightweight aggregate is stored in a mesh bag and put into a bag, and the lightweight aggregate in the bag is placed at a predetermined position in the underwater placement area, and then cement milk is placed in the gap between the lightweight aggregates. A method for placing underwater concrete using a lightweight aggregate, characterized in that a lightweight concrete is constructed by pressure injection.

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