JP7724000B2 - Building foundation reinforcement structure - Google Patents

Description

The present invention relates to a foundation reinforcement structure for buildings that is suitable when the supporting layer is relatively shallow or the ground is relatively good.

When reinforcing the foundations of buildings where the supporting layer is relatively shallow, rapple concrete is commonly used, which replaces the ground below the building's foundation up to the supporting layer with concrete (see, for example, Patent Document 1).

On the other hand, one method of reinforcing the foundation when constructing a building on soft ground involves installing a ground improvement body under a mat foundation (see, for example, Patent Document 2). This ground improvement body improves the surface layer of soft ground and is made up of a horizontal plate-shaped upper improvement body, a peripheral improvement body that hangs down from the underside of the upper improvement body to form an outer frame, and at least one internal improvement body that hangs down from the underside of the upper improvement body, connects the outer frames, and divides the area inside the peripheral improvement body into multiple regions.

Japanese Patent Application Publication No. 5-214732 Patent No. 3608568

When reinforcing foundations with ruffle concrete, it is necessary to install formwork for pouring the ruffle concrete, and in order to install this formwork, it is necessary to over-excavate the excavated hole significantly.

In addition, the local soil in the area where the rapple concrete is being poured will need to be disposed of. Furthermore, after the rapple concrete is poured, it will be necessary to backfill the excavated area to the side of the rapple concrete with soil, and the strength of the backfill soil will need to be managed.

In addition, installing and removing the formwork requires time and effort. Furthermore, because a standard foundation is placed on top of the wrap concrete, it is necessary to install the formwork for the foundation, arrange the reinforcement, remove the formwork, and backfill the soil to the side of the foundation, as well as manage the strength of the backfill soil.

Foundation reinforcement, which involves installing the ground improvement body under a mat foundation, is suitable for soft ground (e.g., ground with a very low N-value over a depth of approximately 20 m).

However, if the target ground is not soft, the bearing layer is relatively shallow, or the ground is relatively good, the volume of the outer periphery improvement body and the inner improvement body will be larger than necessary in order to form them.

As a result, an increase in the volume of improved soil requires an increase in the amount of cement-based solidification materials used, and construction takes longer and takes more work. Furthermore, the foundation concrete is a mat foundation in which reinforced concrete is laid across the entire surface of the ground, which further increases construction time and effort.

The purpose of the present invention is to provide a foundation reinforcement structure for buildings that can be constructed in a short period of time, with reduced resource consumption, and at low cost when the supporting layer is relatively shallow or the ground is relatively good.

The gist of the present invention is as follows:

[1]
A foundation reinforcement structure for a building including a ground improvement body that improves the surface ground and foundation concrete poured on the ground improvement body,
This method is used when the position of the supporting layer of the surface ground is 5 m or less from the ground surface, or when the surface ground is natural ground, is sandy soil or clayey soil, has an N value of 2 or more, and is ground in which the N value depth distribution is not smaller at the bottom than at the top,
The ground improvement body consists of an upper improvement body and a lower improvement body,
The foundation concrete is poured into a recess formed by excavating the ground improvement body,
The upper improved body is a horizontal plate-shaped full improved body,
The lower improvement body is an independent improvement body located below the column of the building above the foundation concrete and protruding downward from the underside of the upper improvement body.
Foundation reinforcement structure of a building.

[2]
The foundation concrete is an independent foundation;
The foundation reinforcement structure of the building described in [1].

The foundation reinforcement structure for a building of the present invention includes a ground improvement body and foundation concrete poured on the ground improvement body. The upper improvement body of the ground improvement body is a horizontal plate-shaped, full-surface improvement body, ensuring the planar rigidity of the ground surface and eliminating the need for underground beams. The lower improvement body of the ground improvement body is an independent improvement body located below the building's columns. Therefore, the building load transmitted from the columns to the foundation concrete can be dispersed and transmitted to the existing ground, and the amount of soil to be improved is significantly reduced. Therefore, when the bearing layer of the surface ground is relatively shallow (when the bearing layer is located 5 m or less from the ground surface) or when the surface ground is relatively good (when the surface ground is natural ground, is sandy or clayey, has an N value of 2 or more, and the N value depth distribution is not smaller at the bottom than at the top), short construction periods, resource conservation, and low costs can be achieved.

Since the foundation concrete is poured into a recess formed by excavating the ground improvement body, the labor required for constructing formwork to pour the foundation concrete can be reduced. Furthermore, since there is no need to provide a crushed stone layer, which is normally required under the base concrete, the labor required for crushed stone construction can be reduced. Therefore, in foundation reinforcement structures for buildings used when the bearing layer of the surface ground is relatively shallow or when the surface ground is relatively good, shorter construction periods, resource conservation, and low costs can be achieved.

When the foundation concrete is an independent foundation, compared to a mat foundation or a strip foundation, the foundation is only installed under the columns, which means that in foundation reinforcement structures for buildings used when the bearing layer of the surface ground is relatively shallow or when the surface ground is relatively good, it is possible to achieve even shorter construction periods, resource conservation, and low costs.

1 is a plan view showing an example of a foundation reinforcement structure for a building according to an embodiment of the present invention. 2 is a cross-sectional view taken along the line X1-X1 of FIG. 1. 2 is a cross-sectional view taken along the line X2-X2 of FIG. 1. FIG. 2B is an enlarged view of a main part of FIG. 2A.

Embodiments of the present invention will be described below with reference to the drawings.

[Building foundation reinforcement structure]
An example of a foundation reinforcement structure F for a building according to an embodiment of the present invention is shown in the plan view of Figure 1, Figure 2A, a cross-sectional view taken along the arrow X1-X1 in Figure 1, Figure 2B, a cross-sectional view taken along the arrow X2-X2 in Figure 1, and Figure 3, an enlarged view of a key portion of Figure 2A.

The foundation reinforcement structure F for a building includes a ground improvement body 1 that has been improved from the surface ground G, and foundation concrete 2 poured on top of the ground improvement body 1. It is used when the bearing layer of the surface ground G is relatively shallow (when the position of the bearing layer is 5m or less from the ground surface GL), or when the surface ground G is relatively good (when the surface ground G is natural ground, is sandy or clayey soil, has an N value of 2 or more, and is a ground where the N value depth distribution is not smaller at the bottom than at the top).

[Ground improvement body]
The ground improvement body 1 consists of an upper improvement body 1H and a lower improvement body 1L. The upper improvement body 1H is a horizontal plate-shaped full-surface improvement body A. The lower improvement bodies 1L are rectangular pillar-shaped independent improvement bodies B, nine in number in this embodiment, located below the steel columns 3 of the building above the foundation concrete 2 and protruding downward from the underside D of the upper improvement body 1H.

In this embodiment, as shown in Figure 1, the planar shape of one upper improvement body 1H is square, and the planar shapes of the nine lower improvement bodies 1L are also square.

The height H1 of the upper improvement body 1H and the height H2 of the lower improvement body 1L shown in Figure 3 are, for example, 300 mm ≦ H1 ≦ 1500 mm and 300 mm ≦ H2 ≦ 1500 mm.

The upper improvement body 1H is a horizontal plate-shaped full-surface improvement body A. This ensures the planar rigidity of the ground surface, eliminating the need for underground beams. The lower improvement body 1L is an independent improvement body B, located below the steel column 3. This allows the building load transmitted from the steel column 3 to the foundation concrete 2 to be dispersed and transmitted to the on-site ground, while significantly reducing the amount of improved soil. Therefore, when the bearing layer of the surface ground G is relatively shallow or when the surface ground G is relatively good, short construction periods, resource conservation, and low costs can be achieved.

[Foundation concrete]
As shown in Figures 2A and 3, the foundation concrete 2 is poured into a recess C formed by excavating the ground improvement body 1, and in this embodiment, it is an independent foundation. As shown in Figure 1, in this embodiment, the planar shape of the nine foundation concrete 2 is each square, and an example of a three-dimensional shape similar to the foundation concrete in Japanese Patent No. 6868301 is shown.

The depth of the recess C in the ground improvement body 1 into which the foundation concrete 2 is poured can be either within the upper improvement body 1H as shown in Figure 3, flush with the underside D of the upper improvement body 1H, or extending into the lower improvement body 1L.

By pouring the foundation concrete 2 into the recess C formed by excavating the ground improvement body 1, it is possible to reduce the labor required for constructing formwork to pour the foundation concrete 2. Furthermore, since there is no need to provide a crushed stone layer, which is normally required under the basin concrete (see basin concrete 5 in Figure 3), the labor required for crushed stone construction can be reduced. Therefore, in a building foundation reinforcement structure F used when the bearing layer of the surface ground G is relatively shallow or when the surface ground G is relatively good, it is possible to achieve even shorter construction periods, resource conservation, and low costs.

Furthermore, because the foundation concrete 2 is an independent foundation, compared to a mat foundation or a strip foundation, the structure has a foundation established only below the steel columns 3. This allows for even shorter construction periods, resource conservation, and lower costs in the foundation reinforcement structure F of a building used when the bearing layer of the surface ground G is relatively shallow or when the surface ground G is relatively good.

The planar shape of the foundation concrete 2 does not have to be square. That is, the planar shape of the foundation concrete 2 may be, for example, rectangular, or any polygon with four or more sides. It is a preferred embodiment that the planar shape of the lower improvement body 1L, which is the independent improvement body B, matches the planar shape of the foundation concrete 2, which is the independent foundation. In other words, if the planar shape of the foundation concrete 2 is an n-gon, which is a polygon, it is a preferred embodiment that the planar shape of the lower improvement body 1L, which is the independent improvement body B, is also an n-gon.

Furthermore, if the planar size of the lower improvement body 1L is made larger than the planar size of the foundation concrete, for example, in Figures 1 and 3, it is set to 0 < E ≦ 1000 mm. Alternatively, the planar size of the lower improvement body 1L may be made smaller than the planar size of the foundation concrete, for example, -500 mm < E ≦ 0.

[Construction process for building foundation reinforcement structures, etc.]
The foundation reinforcement structure F of a building is constructed, for example, as follows.

<Soil improvement process>
(Drilling process)
The surface ground G below the ground surface GL shown in Figures 2A and 2B and Figure 3 is excavated to the required shape of the upper improved body 1H, for example, by plowing with a backhoe.

(Primary improvement process)
A solidification material such as a cement-based solidification material is spread on the soil in the area where nine rectangular pillar-shaped lower improvement bodies 1L will be formed. The soil and the solidification material are mixed and stirred using a backhoe or similar device equipped with a mixing fork, and then compacted with heavy machinery and rollers to form the lower improvement bodies 1L.

(Secondary improvement process)
The soil excavated in the excavation process is backfilled and spread evenly in the horizontal plate-shaped upper improvement body 1H using a backhoe or similar tool. A solidification material such as a cement-based solidification material is spread on top of the backfilled and spread evenly. The soil and the solidification material are mixed and stirred using a backhoe or similar tool equipped with a mixing fork, and then compacted using heavy machinery and rollers to form the upper improvement body 1H.

<Foundation excavation process>
For the ground improvement body 1 constructed in the ground improvement process, the upper part of the ground improvement body 1 located below the above-ground part of the steel column 3 is excavated to a predetermined depth using a backhoe or the like to form a three-dimensional shape of the foundation concrete 2, thereby forming a recess C.

<Foundation pouring process>
The basal concrete 5 shown in Figure 3 is poured. The column base anchor bolts for fixing the steel column 3 are fixed to the basal concrete 5, the foundation reinforcement is arranged, and the foundation concrete 2 is poured. The steel column 3 is installed, and the concrete floor 4 is poured.

The above steps complete the construction of the building's foundation reinforcement structure F, etc.

With the foundation reinforcement structure for a building according to an embodiment of the present invention, the construction period is approximately one-third of that required when, for example, foundation reinforcement is performed using rapple concrete as in Patent Document 1. Furthermore, with the foundation reinforcement structure for a building according to an embodiment of the present invention, the amount of improved soil in the primary improvement process is approximately one-quarter of that required when, for example, a ground improvement body is installed under a mat foundation as in Patent Document 2, and the ground improvement body is formed by a horizontal plate-shaped upper improvement body, a peripheral improvement body that hangs down from the underside of the upper improvement body to form an outer frame, and an internal improvement body that hangs down from the underside of the upper improvement body, connects the outer frames, and divides the area inside the peripheral improvement body into multiple areas.

The above description of the embodiments is by way of example only and is not intended to be limiting. Various improvements and modifications may be made without departing from the scope of the present invention.

1 Ground improvement body 1H Upper improvement body 1L Lower improvement body 2 Foundation concrete 3 Steel column 4 Floor concrete 5 Disposal concrete A Full surface improvement body B Independent improvement body C Recess D Underside E Difference between the size of the planar shape of the lower improvement body and the size of the planar shape of the foundation concrete F Foundation reinforcement structure of the building G Surface ground GL Ground surface H1 Height of upper improvement body H2 Height of lower improvement body

Claims (2)

A foundation reinforcement structure for a building including a ground improvement body that improves the surface ground and foundation concrete poured on the ground improvement body,
This method is used when the position of the supporting layer of the surface ground is 5 m or less from the ground surface, or when the surface ground is natural ground, is sandy soil or clayey soil, has an N value of 2 or more, and is ground in which the N value depth distribution is not smaller at the bottom than at the top,
The ground improvement body consists of an upper improvement body and a lower improvement body,
The foundation concrete is poured into a recess formed by excavating the ground improvement body,
The upper improved body is a horizontal plate-shaped full improved body,
The lower improvement body is an independent improvement body located below the column of the building above the foundation concrete and protruding downward from the underside of the upper improvement body.
Foundation reinforcement structure of a building. The foundation concrete is an independent foundation;
The foundation reinforcement structure for a building according to claim 1.