JP2021067115A - Ground improvement method and ground improvement structure - Google Patents

Abstract

To provide a ground improvement method and a ground improvement structure which can be constructed using versatile materials, which can be easily constructed and can shorten a construction period, and which can obtain excellent liquefaction prevention effect.SOLUTION: A ground improvement method comprises: a step of drilling a vertical hole P in a ground G using an earth auger drill 10; a step of forming a recessed groove T communicating with an opening portion P1 of the vertical hole P in the ground G; a step of feeding a ground improvement material 5 into the vertical hole P and the recessed groove T; and a step of compacting by applying pressure to the ground improvement material 5 fed into the vertical hole P and the recessed groove T. The ground improvement material 5 is formed by mixing and kneading at least one of crushed stone 1 and decomposed granite soil, a cement-based solidification material 2, an aggregating agent 3 and water 4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a construction method for improving ground that is likely to be liquefied in the event of an earthquake or the like to ground that is difficult to liquefy, and a ground improvement structure formed by this ground improvement construction method.

If the ground liquefies when an earthquake occurs, the buildings and structures built on it may sink or collapse, causing enormous damage. Various liquefaction prevention techniques have been proposed and implemented in order to deal with such a situation. As a conventional technique related to the present invention, for example, "Liquefaction prevention structure of residential ground" described in Patent Document 1 is provided. , And "Liquefaction Countermeasure Foundation Pile and Liquefaction Countermeasure Foundation Structure" described in Patent Document 2.

The "liquefaction prevention structure of residential ground" described in Patent Document 1 is composed of a ground restraint wall and a surface layer ground improvement body, and the gap between the ground restraint wall and the surface layer ground improvement body is treated into a watertight structure to form a watertight structure. The restraint wall is constructed as a floating structure with a depth that does not reach the non-liquefaction layer from the ground surface, and is a support column or support that reaches the non-liquefaction layer at the key position of the ground restraint wall. It is configured to include a supporting wall-like body or steel pipe pile in which a plurality of columnar bodies are connected.

The "basic structure for liquefaction countermeasures" described in Patent Document 2 is a liquefaction prevention structure composed of a tubular body obtained by molding a three-dimensional network structure made of polypropylene into a tubular shape and a water-permeable member covering the side surface of the tubular body. It is composed of a liquefaction countermeasure foundation pile equipped with means on the side surface of the pile and a drainage ditch of a three-dimensional network structure made of polypropylene covered with a water-permeable member. A ditch is laid under the foundation crushed stone approximately horizontally with the ground surface, connected to the liquefaction countermeasure foundation pile, and excess pore water in the ground rising in the tubular body of the liquefaction countermeasure foundation pile is drained to the drainage ditch. Excessive pore water is drained through a drainage ditch in a direction approximately horizontal to the ground surface.

Japanese Unexamined Patent Publication No. 2015-161565 Japanese Unexamined Patent Publication No. 2015-206174

It can be predicted that the predetermined liquefaction prevention effect can be obtained by constructing the "liquefaction prevention structure of residential ground" described in Patent Document 1 and the "liquefaction countermeasure foundation structure" described in Patent Document 2. However, all of them require special materials, the construction process is complicated, and there is a problem that it takes a lot of labor and time to complete the construction.

Therefore, the problem to be solved by the present invention is ground improvement, which can be constructed with a general-purpose material, can be easily constructed, the construction period can be shortened, and an excellent liquefaction prevention effect can be obtained. The purpose is to provide a construction method and a ground improvement structure.

The ground improvement method according to the present invention is
The process of excavating a vertical hole in the ground and
The process of putting the ground improvement material into the vertical hole and
A step of applying pressure to the ground improving material put into the vertical hole to compact it to form a water-permeable pile-shaped body in the ground is provided.
The ground improving material is characterized by containing one or more of crushed stone, decomposed granite soil, and soil material, a cement-based solidifying material, an agglomerating agent, and water.

In the ground improvement method,
The process of excavating multiple vertical holes in the ground and
A step of forming a concave groove in the ground that communicates the upper end openings of the adjacent vertical holes with each other.
The process of putting the ground improvement material into the concave groove and
It is possible to provide a step of applying pressure to compact the ground improving material put into the concave groove to form a lattice-like or net-like water permeable structure integrated with the head of the pile-like body.

In the ground improvement method,
It is also possible to provide a step of providing a drainage means communicating with the head of the pile-shaped body or the water permeable structure.

In the ground improvement method,
The drainage means
A step of forming a drainage groove communicating with the head of the pile-shaped body or the permeable structure in the ground.
The process of putting the ground improvement material into the drainage ditch and
It can be formed through a step of applying pressure to the ground improving material put into the drainage ditch to compact it and integrating it with the head of the pile-shaped body or the water permeable structure.

In the ground improvement method, it is desirable that the agglomerating agent contains a polymer compound composed of a composite of a magnesium salt of an acrylic acid / dimethylaminoethyl methacrylate copolymer and polyethyleneimine.

Next, the ground improvement structure according to the present invention is
Multiple permeable piles erected in the ground,
A water-permeable structure that communicates the heads of adjacent pile-shaped bodies with each other,
A drainage means that communicates with the pile-shaped body or the water-permeable structure is provided.
The pile-shaped body and the water-permeable structure are characterized in that one or more of crushed stone, decomposed granite soil, and earthen material, a cement-based solidifying material, an agglomerating agent, and a ground improving material containing water are solidified. And.

In the ground improvement structure, it is desirable that the agglomerating agent contains a polymer compound composed of a composite of a magnesium salt of an acrylic acid / dimethylaminoethyl methacrylate copolymer and polyethyleneimine.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a ground improvement method and a ground improvement structure which can be constructed with a general-purpose material, can be easily constructed, can shorten the construction period, and can obtain an excellent liquefaction prevention effect. be able to.

It is explanatory drawing which shows the construction process of the ground improvement construction method which is an embodiment of this invention. It is a partially omitted plan view which shows the ground under construction of the ground improvement method shown in FIG. It is a partially omitted plan view which shows the ground improvement structure formed by the ground improvement method shown in FIG. It is a partially omitted vertical cross-sectional view which shows the ground improvement structure formed by the ground improvement method shown in FIG.

Hereinafter, the ground improvement method according to the embodiment of the present invention and the ground improvement structure constructed by this ground improvement method will be described with reference to FIGS. 1 to 4.

First, the ground improvement method will be described with reference to FIGS. 1 to 3. As shown in FIG. 1 (a), a vertical hole P extending in the vertical direction is drilled from the surface Ga of the ground G, which is the construction target of the ground improvement method, toward the inside of the ground G with an earth auger drill 10 or the like. Form. Further, before (or after) excavation of the vertical hole P, a concave groove T communicating with the upper end opening P1 of the vertical hole P is formed on the surface Ga portion of the ground G. The inner diameter and depth of the vertical hole P can be arbitrarily set based on the properties of the ground G and the construction conditions. However, if the vertical hole P having a depth reaching the bedrock R is excavated, FIG. 1 (d) described later. ), It is possible to form a pile-shaped body 6 in which the lower end portion 6b reaches the bedrock R.

When a plurality of vertical holes P are excavated in the ground G and a concave groove T communicating with the upper end openings P1 of all the adjacent vertical holes P is formed on the surface Ga of the ground G, they are adjacent to each other as shown in FIG. A plurality of recessed grooves T communicating with the upper end opening P1 of the matching vertical holes P are arranged in a grid pattern. Further, in the present embodiment, a drainage groove T1 is provided which communicates a plurality of water collecting basins 7 provided on the outer peripheral portion of the ground G and an upper end opening P1 of a vertical hole P located immediately in the vicinity of the water collecting basin 7. Has been done.

When the vertical hole P reaches a predetermined depth by the excavation work shown in FIG. 1 (a), the ground improvement material 5 is thrown into the vertical hole P from the ground as shown in FIG. 1 (b). The ground improving material 5 is formed by mixing and kneading crushed stone 1, cement-based solidifying material 2, agglomerating agent 3, and water 4. Since the blending amount (blending ratio) of each component such as the crushed stone 1 and the cement-based solidifying material 2 constituting the ground improvement material 5 is not limited, it can be arbitrarily set according to the construction conditions and the like. In the form, it was blended as follows.

For 1 cubic meter of crushed stone 1 (particle size 0.075 mm to 40 mm)
Cement-based solidifying material 2:10 kg to 120 kg
Aggregating agent 3: 0.5L-2.0L
Water 4: Appropriate amount (for example, 60L to 100L) according to the mixed state
Was added, and the mixture was thoroughly mixed and kneaded.

The aggregating agent 3 is not limited, but is preferably a drug containing a polymer compound composed of a composite of a magnesium salt of an acrylic acid / dimethylaminoethyl methacrylate copolymer and polyethyleneimine. The product name "SS-M1" of "Global Research Institute Co., Ltd." diluted 10 to 50 times with water was used.

After a predetermined amount of the ground improving material 5 is put into the vertical hole P, as shown in FIG. 1C, the ground improving material 5 is compacted while applying pressure using an improving machine auger (not shown). In this way, the work of putting the ground improvement material 5 into the vertical hole P and the work of pressurizing the ground improvement material 5 by the improving machine auger (not shown) are repeated so as to approach the opening P1 at the upper end of the vertical hole P. The ground improvement material 5 is filled.

Here, in the steps shown in FIGS. 1 (b) and 1 (c), in the ground improving material 5 charged into the vertical hole P, the crushed stone 1 and the cement-based solidifying material are formed by the action of the ions contained in the agglomerating agent 3. An aggregate structure in which 2 and 2 are three-dimensionally bonded is formed, and as a result, continuous voids are formed in the ground improvement material 5.

In the aggregate structure formed in the ground improvement material 5 in the steps shown in FIGS. 1 (b) and 1 (c), the crushed stone 1 becomes the main material for keeping the pile-shaped body 6 in a constant shape, and is an aggregate agent. 3 exerts an action of changing the crushed stone 1 and the cement-based solidifying material 2 into a three-dimensional aggregate structure, and the cement-based solidifying material 2 plays a role of solidifying the aggregate structure formed by the agglomerating agent 3.

Next, as shown in FIG. 1 (d), the ground improvement material 5 is put in until the upper surface of the ground improvement material 5 reaches the upper end opening P1 of the vertical hole P, and the inside of the concave groove T and the inside of the drainage groove T1 (FIG. 2) is also filled with the ground improvement material 5 and compacted by pressurization. After that, when a predetermined time elapses, the ground improving material 5 is solidified by the solidifying action of the cement-based solidifying material 2 contained in the ground improving material 5, and the vertical hole P has a substantially cylindrical shape along its internal shape. The pile-shaped body 6 is formed, and as shown in FIG. 3, a water permeable structure 8 is formed in each of the concave groove T and the drainage groove T1. Since compaction is also applied in the horizontal direction by the compaction work (pressurization work) in the formation process of the pile-shaped body 6 and the water-permeable structure 8, a sturdy pile-shaped body 6 having high frictional resistance even if the ground G is soft. And the water permeable structure 8 can be formed.

In this way, according to the steps shown in FIGS. 1 (b) to 1 (c), the ground improvement material 5 is put into the vertical hole P, the concave groove T, and the drainage groove T1 (see FIG. 2) of the ground G to pressurize. When solidified, a substantially cylindrical pile-shaped body 6 is formed along the internal shape of the vertical hole P, and a water-permeable structure 8 is formed in the concave groove T and the drainage groove T1 (see FIG. 2). As shown in FIG. 3, a plurality of water-permeable structures 8 communicating with each other of the heads 6c of the adjacent pile-shaped bodies 6 are arranged in a grid pattern.

Since the pile-shaped body 6 and the water-permeable structure 8 have an aggregate structure having continuous voids, they exhibit excellent water permeability and water retention. Further, since the pile-shaped body 7 and the water-permeable structure 8 are solidified by the cement-based solidifying material 2, the external force from the surrounding ground G caused by the shaking at the time of an earthquake or the vibration of a vehicle passing in the vicinity is present. Demonstrates strength that is not destroyed. It should be noted that decomposed granite soil or soil material (not shown) can be used instead of the crushed stone 1 or in combination with the crushed stone 1.

Next, the ground improvement structure 9 constructed by constructing the ground improvement method shown in FIG. 1 will be described with reference to FIGS. 3 and 4.

When the ground improvement method shown in FIG. 1 is applied, as shown in FIGS. 1 (d) and 3, a plurality of pile-shaped bodies 6 are erected in the ground G, and the surface Ga of the ground G is covered with a plurality of pile-shaped bodies 6. A plurality of water-permeable structures 8 communicating with each other of the heads 6c of the adjacent pile-shaped bodies 6 are arranged in a grid pattern.

After that, if a reinforced concrete foundation structure B is formed so as to cover the surface Ga of the ground G, the upper end portions 6a of the plurality of pile-shaped bodies 6, and the lattice-shaped water-permeable structure 8, the foundation structure B can be placed on the foundation structure B. Any building H can be constructed.

The work of putting the ground improvement material 5 into the vertical hole P formed by excavating the ground G and pressurizing it to form the pile-shaped body 6 can be performed with general-purpose materials such as crushed stone 1 and cement-based solidifying material 2. Yes, the construction machine to be used is only about 10 earth auger drills, so the construction is easy, and since there is no need for bar arrangement work, it is possible to shorten the construction period.

In general, the liquefaction phenomenon occurs when water and earth and sand are originally mixed uniformly, but they are separated by shaking (vibration) at the time of an earthquake and the water pressure rises locally. As shown, since the pile-shaped body 6 having an aggregated structure having water permeability and water retention is present in the ground G, the pile-shaped body 6 can absorb the locally increased water pressure at the time of an earthquake.

Further, the water absorbed in the pile-shaped body 6 rises inside the pile-shaped body 6, but the water that has risen to the head 6c of the pile-shaped body 6 is a water-permeable structure that communicates with the head 6c. It permeates into the water permeable structure 8, moves horizontally in the water permeable structure 8, passes through the water permeable structure 8 in the drainage groove T1, and flows into the water collecting basin 7 which is a drainage means. Since the concave groove T and the drainage groove T1 (see FIG. 2) filled with the permeable structure 8 form a downward slope toward the collecting basin 7, the water permeated into the permeable structure 8 collects smoothly. It is discharged to the water basin 7.

In this way, when an earthquake occurs, the water in the ground G permeates into the pile-shaped body 6, rises in the pile-shaped body 6, moves horizontally in the water-permeable structure 8, and then is drained to the catchment basin 7. Therefore, it is possible to prevent the ground G itself from becoming unstable and the ground G from liquefying.

The ground improvement method and the ground improvement structure 9 described with reference to FIGS. 1 to 4 show an example of the ground improvement method and the ground improvement structure according to the present invention. It is not limited to the ground improvement method and the ground improvement structure described above.

The ground improvement method and the ground improvement structure of the present invention can be widely used in industrial fields such as the civil engineering construction industry as a means for preventing liquefaction of the ground in residential areas and other lands.

1 Crushed stone 2 Cement-based solidifying material 3 Aggregating agent 4 Water 5 Ground improving material 6 Pile-shaped body 6a Upper end 6b Lower end 6c Head 7 Water collecting basin 8 Water permeable structure 9 Ground improving structure 10 Earth auger drill B Foundation G Ground H Building P Vertical hole P1
R bedrock T concave groove T1 drainage ditch

Claims (7)

The process of excavating a vertical hole in the ground and
The process of putting the ground improvement material into the vertical hole and
A step of applying pressure to the ground improving material put into the vertical hole to compact it to form a water-permeable pile-shaped body in the ground is provided.
A ground improvement method in which the ground improvement material contains one or more of crushed stone, decomposed granite soil, and soil material, a cement-based solidifying material, an agglomerating agent, and water. The process of excavating multiple vertical holes in the ground and
A step of forming a concave groove in the ground that communicates the upper end openings of the adjacent vertical holes with each other.
The process of putting the ground improvement material into the concave groove and
Claim 1 comprising a step of applying pressure to compact the ground improving material put into the concave groove to form a grid-like or net-like water-permeable structure integrated with the head of the pile-shaped body. The described ground improvement method. The ground improvement method according to claim 1 or 2, further comprising a step of providing a drainage means communicating with the head of the pile-shaped body or the water-permeable structure. The drainage means
A step of forming a drainage groove communicating with the head of the pile-shaped body or the permeable structure in the ground.
The process of putting the ground improvement material into the drainage ditch and
The ground improvement method according to claim 3, wherein the ground improvement material put into the drainage ditch is compacted by applying pressure to be integrated with the head of the pile-shaped body or the water permeable structure. .. The ground according to any one of claims 1 to 4, wherein the aggregating agent contains a polymer compound composed of a composite of a magnesium salt of an acrylic acid / dimethylaminoethyl methacrylate copolymer and polyethyleneimine. Improved construction method. Multiple permeable piles erected in the ground,
A water-permeable structure that communicates the heads of adjacent pile-shaped bodies with each other,
A drainage means that communicates with the pile-shaped body or the water-permeable structure is provided.
The pile-shaped body and the water-permeable structure are solidified ground improvement materials containing one or more of crushed stone, decomposed granite soil, and earth materials, a cement-based solidifying material, an agglomerating agent, and water. .. The ground improvement structure according to claim 6, wherein the aggregating agent contains a polymer compound composed of a composite of a magnesium salt of an acrylic acid / dimethylaminoethyl methacrylate copolymer and polyethyleneimine.

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