JP6826864B2 - Restoration method of existing foundation and restoration structure of existing foundation - Google Patents

Description

The present invention relates to a method for restoring an existing foundation and a structure for restoring an existing foundation.

Patent Document 1 discloses a method of forming an improved portion by high-pressure jet stirring under the outer peripheral portion of the improved portion improved by injecting a chemical solution.

Patent Document 2 discloses a method of constructing a first ground improvement body by a deep mixing treatment method and then constructing an additional ground improvement body under the first ground improvement body by a vertical jet grout method.

Here, a technique is known in which mortar is injected between an existing foundation such as a foundation beam that has subsided due to liquefaction and an existing ground improvement body underneath to push up the existing foundation and restore the subsided existing foundation. ing.

However, in this construction method, if the existing ground improvement body under the existing foundation sinks due to the injection pressure of mortar, it becomes difficult to restore the existing foundation.

JP-A-2009-144421 Japanese Unexamined Patent Publication No. 2012-177278

In view of the above facts, it is an object of the present invention to suppress the subsidence of the existing ground improvement body and to push up and restore the subsided existing foundation on the existing ground improvement body.

The first aspect is a step of constructing a new ground improvement body directly under the existing ground improvement body constructed under the subsided existing foundation, and injecting an injection material between the existing foundation and the existing ground improvement body. It is a method of restoring an existing foundation, which comprises a step of pushing up and restoring the existing foundation.

In the restoration method of the first aspect , a new ground improvement body is constructed directly under the existing ground improvement body constructed under the existing foundation, and the ground is reinforced. Therefore, the subsidence of the existing ground improvement body due to the injection pressure when the injection material is injected between the existing foundation and the existing ground improvement body is suppressed. Therefore, it is possible to suppress the subsidence of the existing ground improvement body due to the injection pressure and push up the existing subsidence foundation on it to restore it.

The second aspect is the method for restoring the existing foundation according to the first aspect , wherein the newly constructed ground improvement body is constructed by improving the ground by a high-pressure injection stirring method.

In the restoration method of the second aspect, by using the high-pressure injection stirring method, it is possible to easily improve the ground directly under the existing ground improvement body to construct a new ground improvement body.

The third aspect is the existing foundation, the existing ground improvement body constructed under the existing foundation, the new ground improvement body constructed directly under the existing foundation, and the existing foundation and the existing ground improvement body. It is a restored structure of an existing foundation with an injection material injected in between.

In the restoration structure of the third aspect , a new ground improvement body is constructed directly under the existing ground improvement body constructed under the existing foundation, and the ground is reinforced. Therefore, the subsidence of the existing ground improvement body due to the injection pressure when the injection material is injected between the existing foundation and the existing ground improvement body is suppressed. Therefore, the existing subsided foundation is pushed up and restored by the injection pressure.

According to the present invention, it is possible to suppress the subsidence of the existing ground improvement body and push up the subsided existing foundation on the existing ground improvement body to restore it.

It is a vertical cross-sectional view which shows the foundation beam in the state which the restoration structure of one Embodiment of this invention is applied and restored. It is a top view along the line 2-2 of FIG. It is a perspective view which shows typically the state of constructing the fan-shaped improvement body which constitutes the new ground improvement body by the high pressure injection stirring method. FIG. 2 is a plan view showing a fan-shaped improved body constituting the newly constructed ground improved body. (A) is a vertical cross-sectional view showing a state in which the foundation beam constructed on the ground and the existing ground improvement body are unevenly subsided, and (B) is a construction of a new ground improvement body directly under the existing ground improvement body of (A). It is a vertical cross-sectional view which shows the state which was done. (A) is a vertical cross-sectional view of the state where mortar is injected between the foundation beam and the existing ground improvement body after FIG. 5 (B) and restored to the design GL, and (B) is the foundation beam after (A). It is a vertical cross-sectional view explaining the repair of the joint part with a pillar. (A) is a vertical cross-sectional view showing a state in which an expansion material is filled between the slab on the first floor and the ground after FIG. 6 (B) and repaired, and (B) is a repair to the beam after (A). It is a vertical cross-sectional view which shows the state which joined the beam and repaired and reinforced the beam.

<Embodiment>
The restoration structure of the existing foundation and the restoration method of the existing foundation according to the embodiment of the present invention will be described.

[Restoration structure]
First, a state (restoration structure) in which an existing foundation that has subsided due to liquefaction of the ground has been restored will be described.

As shown in FIG. 1, an existing ground improvement body 40 (hereinafter referred to as “existing ground improvement body 40”) is constructed under the foundation 30 as an example of the existing foundation constructed on the ground 10. A slab 12 and a pillar 16 on the first floor are joined and supported on the foundation 30. Further, a beam 20 for supporting the slab 18 on the second floor is joined to the pillar 16. In the present embodiment, the foundation 30 is made of reinforced concrete, and the columns 16 and beams 20 are made of steel, but the present invention is not limited thereto.

The lower part of the existing ground improvement body 40 in the ground 10 is liquefied due to a large earthquake or the like larger than expected, and the foundation 30 and the existing ground improvement body 40 are subsided. A new ground improvement body 50 (hereinafter referred to as "new ground improvement body 50") is constructed directly under the existing ground improvement body 40 in the subsided state.

Then, a mortar 60 as an example of the injection material is injected between the foundation 30 and the existing ground improvement body 40, and the foundation 30 is pushed up by the injection pressure and restored to the design GL.

As shown in FIGS. 1 and 2, the foundation 30 is provided with an injection hole 32 for injecting the mortar 60. Further, the existing ground improvement body 40 is composed of a plurality of columnar improvement bodies 42 that are wrapped or in contact with each other. Note that FIG. 2 omits the illustration of diagonal lines (hatching) representing the cross section.

Further, as shown in FIG. 4, the newly constructed ground improvement body 50 is composed of a plurality of fan-shaped improvement bodies 52 (see also FIG. 3) that are wrapped around each other.

[Restoration method]
Next, an example of a restoration method for restoring the foundation 30 that has subsided due to liquefaction of the ground 10 or the like will be described.

As shown in FIG. 5A, the foundation 30 and the existing ground improvement body 40 are constructed on the ground 10. A slab 12 and a pillar 16 on the first floor are joined and supported on the foundation 30. Further, a beam 20 for supporting the slab 18 on the second floor is joined to the pillar 16.

Then, the lower part of the existing ground improvement body 40 in the ground 10 is liquefied due to a larger earthquake or the like than expected, and the foundation 30 and the existing ground improvement body 40 are subsided unevenly. Therefore, the slab 12 on the first floor is located below 1FL (design GL), and the slab 18 on the second floor is located below 2FL.

As shown in FIG. 5 (B), the new ground improvement body 50 is constructed directly under the existing ground improvement body 40 in the subsided state. In the present embodiment, the newly constructed ground improvement body 50 is constructed by improving the ground by a high-pressure injection stirring method. The high-pressure injection stirring method will be described later.

As shown in FIG. 6A, the foundation 30 is restored by the JOG (jacking off grout) method.

Specifically, an injection hole 32 for injecting the mortar 60 is formed in the foundation 30 (see also FIG. 2). An injection pipe (not shown) is inserted through the injection hole 32 to inject the mortar 60 between the foundation 30 and the existing ground improvement body 40. Then, the foundation 30 is pushed up by the injection pressure of the mortar 60, the slab 12 on the first floor is restored to 1FL (design GL), and the slab 18 on the second floor is restored to 2FL.

At this time, since the new ground improvement body 50 is constructed directly under the existing ground improvement body 40 to reinforce the ground 10, the subsidence of the existing ground improvement body 40 due to the injection pressure is suppressed.

In the present embodiment, a gap 11 is formed between the subsided ground 10 and the slab 12 on the first floor. Further, FIG. 1 illustrates the state of FIG. 6 (A).

As shown in FIG. 6B, the injection hole 32 is filled. In addition, the joint portion 17 between the foundation 30 and the pillar 16 is repaired. The repair content is to scrape off the parts that are heavily damaged, such as press-fitting the repair material into cracks caused by uneven settlement of the foundation 30 and the pillar 16 and the joints, and exposing the reinforcing bars of the foundation 30, and newly forming the formwork. Repair of the provided cross section, etc.

As shown in FIG. 7A, the slab 12 on the first floor is repaired. As an example, the repair method is to fill the gap 11 between the slab 12 and the ground 10 on the first floor with an expansion material 70 such as hard urethane resin, and after filling, the expansion material 70 expands to form the slab 12 and the ground 10. Fill the gap and push up the slab 12 to flatten it.

As shown in FIG. 7B, the repair beam 22 is joined to the beam 20 to repair and reinforce the beam 20.

The steps after FIG. 6B may be unnecessary depending on the situation such as breakage. In addition, depending on the situation such as damage, steps other than these may be required.

(High pressure injection stirring method)
Next, the construction of the new ground improvement body 50 directly under the existing ground improvement body 40 by the high-pressure injection stirring method will be described.

As shown in FIGS. 5B and 4, the ejection tube 100 inserted into the ground 10 outside the existing ground improvement body 40 swings left and right (arrow R in FIG. 3) as shown in FIG. While moving upward (arrow T in FIG. 3), the solidifying material is injected at high pressure (arrow F in FIG. 3). As a result, the ground 10 is mixed and agitated while being cut to improve the ground, and the fan-shaped improved body 52 is constructed.

Then, as shown in FIG. 4, the new ground improvement body 50 is constructed by constructing the four fan-shaped improvement bodies 52 so as to wrap them.

<Action and effect>
Next, the operation and effect of this embodiment will be described.

A new ground improvement body 50 is constructed directly under the existing ground improvement body 40 under the foundation 30 to reinforce the ground 10. Therefore, the subsidence of the existing ground improvement body 40 due to the injection pressure when the mortar 60 is injected between the foundation 30 and the existing ground improvement body 40 is suppressed, so that the subsidence foundation 30 is easily pushed up to the design GL level. Can be restored to.

From another point of view, it is prevented that the existing ground improvement body 40 under the foundation 30 is subsided by the injection pressure of the mortar 60, which makes it difficult or impossible to restore the foundation 30.

Further, in the present embodiment, since the high-pressure injection stirring method is used, it is possible to easily improve the ground directly under the existing ground improvement body 40 to construct the new ground improvement body 50.

<Others>
The present invention is not limited to the above embodiment.

For example, in the above embodiment, the mortar 60 is injected between the foundation 30 and the existing ground improvement body 40, but the present invention is not limited to this. An injection material other than the mortar 60, for example, fluidized concrete, high fluidized concrete, or the like may be injected.

Further, for example, in the above embodiment, the new ground improvement body 50 is constructed by the high pressure injection stirring method, but the present invention is not limited to this. The new ground improvement body 50 may be constructed by a method other than the high-pressure injection stirring method.

Further, for example, in the above embodiment, the existing foundation is the foundation 30, but the foundation is not limited to this. For example, it may be a solid foundation, a continuous (cloth) foundation, a composite foundation, or the like.

Furthermore, it goes without saying that it can be carried out in various embodiments without departing from the gist of the present invention.

30 foundations (an example of existing foundations)
40 Existing ground improvement body 50 New ground improvement body 60 Mortar (an example of injection material)

Claims (5)

The process of constructing a new ground improvement body directly under the existing ground improvement body built under the subsided existing foundation,
A step of injecting an injection material between the existing foundation and the existing ground improvement body and pushing up the existing foundation to restore it.
How to restore an existing foundation with. The newly constructed ground improvement body is constructed by improving the ground by a high-pressure injection stirring method.
The method for restoring an existing foundation according to claim 1. A step of filling a gap between a slab joined to and supported by the existing foundation and the ground with an expanding material, filling the gap between the slab and the ground by expanding the expanding material, and pushing up the slab is provided.
The method for restoring an existing foundation according to claim 1 or 2. With the existing foundation
The existing ground improvement body constructed under the existing foundation and
A new ground improvement body constructed directly under the existing foundation,
The injection material injected between the existing foundation and the existing ground improvement body,
Restoration structure of the existing foundation with. It has an expansive material that fills the gap between the ground and the slab that is joined and supported by the existing foundation.
The restoration structure of the existing foundation according to claim 4.