Building foundation reinforcement structure

Abstract

To provide a foundation reinforcement structure of a building which can achieve a short construction period, resource saving and low cost, when a support layer is comparatively shallow or the ground is comparatively satisfactory.SOLUTION: A foundation reinforcement structure F of a building includes a ground improvement body 1 obtained by improving a surface ground and a foundation concrete 2 placed thereon. In a case in which the position of a support layer of the surface ground is 5 m or less from the ground surface, or a case in which the surface ground is natural ground that consists of sandy soil or viscous soil, an N value is 2 or more, and the lower side thereof is not smaller than the upper side thereof in the depth distribution of the N value, the foundation reinforcement structure F is used. The ground improvement body 1 is composed of an upper improvement body 1H and a lower improvement body 1L. The foundation concrete 2 is placed in a recess formed by excavating the ground improvement body 1. The upper improvement body 1H is a whole surface improvement body A having a horizontal plate shape. The lower improvement body 1L is an independent improvement body B which is positioned below a column 3 of a building above the foundation concrete 2, and projects downward from the lower surface of the upper improvement body 1H.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foundation reinforcement structure for a building that is suitable when the supporting layer is relatively shallow or when the ground is relatively good. [Background technology]

[0002] BACKGROUND ART When a building has a relatively shallow bearing layer, rapple concrete is generally used to reinforce the foundation of the building, replacing the ground below the building foundation up to the bearing layer with concrete (see, for example, Patent Document 1).

[0003] On the other hand, there is a method of installing a ground improvement body under a mat foundation as a foundation reinforcement when constructing a building on soft ground (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 areas. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-214732 [Patent Document 2] Patent No. 3608568 Summary of the Invention [Problem to be solved by the invention]

[0005] When reinforcing foundations with ruffle concrete, it is necessary to set up a formwork for pouring the ruffle concrete, and in order to set up the formwork, it is necessary to over-excavate the excavated hole.

[0006] In addition, the local soil in the area where the rapple concrete is being poured must be disposed of. Furthermore, after the rapple concrete is poured, it is necessary to backfill the excavated area to the side of the rapple concrete with soil, and the strength of the backfill soil must be managed.

[0007] In addition, the installation and removal of the formwork requires time and effort. Furthermore, because a normal foundation is laid 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 on the sides of the foundation, and it is also necessary to manage the strength of the backfill soil.

[0008] Foundation reinforcement, in which the soil improvement body is installed under a mat foundation, is suitable for soft ground (for example, ground with a very small N-value over a depth of about 20 m).

[0009] However, if the target ground is not soft and the supporting layer is relatively shallow, or if the ground is relatively good, the volume of the outer periphery improvement body and the internal improvement body will become larger than necessary in order to form them.

[0010] Therefore, the increased volume of improved soil requires an increased amount of cement-based solidification material and construction time and effort. Furthermore, the foundation concrete is a mat foundation in which reinforced concrete is laid over the entire surface of the ground, which further increases the construction time and effort.

[0011] An object of the present invention is to provide a foundation reinforcement structure for a building 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. [Means for solving the problem]

[0012] The gist of the present invention is as follows.

[0013] [1] A foundation reinforcement structure for a building including a ground improvement body that has improved 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 where 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.

[0014] [2] The foundation concrete is an independent foundation; [1] A foundation reinforcement structure for a building. [Effects of the Invention]

[0015] The foundation reinforcement structure for a building of the present invention includes a soil improvement body and foundation concrete poured on the soil improvement body. The upper improvement body of the soil 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 soil improvement body is an independent improvement body located below the building's columns. This allows the building load transferred from the columns to the foundation concrete to be dispersed and transmitted to the existing ground, while significantly reducing the amount of soil required for improvement. 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), a short construction period, resource conservation, and low cost can be achieved.

[0016] Since the foundation concrete is poured into the recess formed by excavating the ground improvement body, the labor required for formwork construction for pouring the foundation concrete can be reduced. Also, since there is no need to provide a crushed stone layer, which is normally required under the basin concrete, the labor required for crushed stone construction can be reduced. Therefore, in the foundation reinforcement structure of a building used when the bearing layer of the surface ground is relatively shallow or when the surface ground is relatively good, it is possible to further shorten the construction period, save resources, and reduce costs.

[0017] When the foundation concrete is an independent foundation, compared to a slab foundation or a strip foundation, the structure is such that the foundation is only provided under the pillars, and therefore, in the foundation reinforcement structure of a building 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. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a plan view showing an example of a foundation reinforcement structure for a building according to an embodiment of the present invention. [Figure 2A] 2 is a cross-sectional view taken along the line X1-X1 of FIG. 1. [Figure 2B] 2 is a cross-sectional view taken along the line X2-X2 of FIG. 1. [Figure 3] FIG. 2B is an enlarged view of a main part of FIG. 2A. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] [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 line of Figure 1, Figure 2B, a cross-sectional view taken along the arrow X2-X2 line of Figure 1, and Figure 3, an enlarged view of a key portion of Figure 2A.

[0021] The foundation reinforcement structure F of a building includes a ground improvement body 1 that has improved the surface ground G and foundation concrete 2 that has been poured on the ground improvement body 1, and is used when the supporting layer of the surface ground G is relatively shallow (when the position of the supporting layer is 5 m 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 soil or clayey soil, has an N value of 2 or more, and is a ground in which the N value depth distribution is not smaller at the bottom than at the top).

[0022] [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 body 1L is a rectangular pillar-shaped independent improvement body B, nine in this embodiment, located below the steel column 3 of the building above the foundation concrete 2 and protruding downward from the underside D of the upper improvement body 1H.

[0023] In this embodiment, as shown in FIG. 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.

[0024] The height H1 of the upper improved body 1H and the height H2 of the lower improved body 1L shown in Figure 3 are, for example, 300 mm ≦ H1 ≦ 1500 mm and 300 mm ≦ H2 ≦ 1500 mm.

[0025] The upper improvement body 1H is a horizontal plate-shaped full-surface improvement body A. Therefore, the horizontal rigidity of the ground surface can be ensured, eliminating the need for underground beams. The lower improvement body 1L is an independent improvement body B, located below the steel column 3. Therefore, the building load transmitted from the steel column 3 to the foundation concrete 2 can be dispersed and transmitted to the local ground, and the amount of improved soil is significantly reduced. 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.

[0026] [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 each of the nine foundation concretes 2 is square, and an example is shown in which the foundation concrete has a three-dimensional shape similar to that of the foundation concrete in Japanese Patent No. 6868301, for example.

[0027] The depth of the recess C in the ground improvement body 1 into which the foundation concrete 2 is poured is 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.

[0028] 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. In addition, since there is no need to provide a crushed stone layer that 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 foundation reinforcement structure F for a building 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 further shorten construction time, save resources, and reduce costs.

[0029] Furthermore, since the foundation concrete 2 is an independent foundation, compared to a slab foundation or a strip foundation, the structure has the foundation only under the steel columns 3, so in the foundation reinforcement structure F of a building used when the supporting 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 savings, and lower costs.

[0030] The planar shape of the base concrete 2 does not have to be square. That is, the planar shape of the base concrete 2 may be, for example, rectangular, or may be a polygon with four or more sides. A preferred embodiment is that the planar shape of the lower improvement body 1L, which is the independent improvement body B, conforms to the planar shape of the base concrete 2, which is an independent foundation. That is, when the planar shape of the base concrete 2 is an n-sided polygon as described above, a preferred embodiment is that the planar shape of the lower improvement body 1L, which is the independent improvement body B, is also an n-sided polygon.

[0031] Also, when the size of the planar shape of the lower improvement body 1L is larger than the size of the planar shape of the base concrete, for example, in FIGS. 1 and 3, let 0 < E ≤ 1000 mm. Alternatively, there may be a case where the size of the planar shape of the lower improvement body 1L is less than or equal to the size of the planar shape of the base concrete, for example, let -500 mm < E ≤ 0.

[0032] [Construction process of building foundation reinforcement structure, etc.] The building foundation reinforcement structure F, etc. is constructed, for example, as follows.

[0033] [Ground improvement process] [Excavation process] The surface ground G below the ground surface GL shown in FIGS. 2A and 2B and FIG. 3 is excavated to the required shape of the upper improvement body 1H, for example, by hoe excavation using a backhoe.

[0034] [Primary improvement process] On the soil in the range where nine square column-shaped lower improvement bodies 1L are to be formed, a solidifying material such as a cement-based solidifying material is sprayed. The soil and the solidifying material are mixed and stirred by a backhoe equipped with a mixing fork as an attachment, and compacted by a heavy machine and a roller, etc. to form the lower improvement body 1L.

[0035] [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.

[0036] <Foundation excavation process> The upper part of the ground improvement body 1 constructed in the ground improvement process, 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.

[0037] <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.

[0038] The above steps complete the construction of the building's foundation reinforcement structure F, etc.

[0039] According to the foundation reinforcement structure for a building according to an embodiment of the present invention, the construction period is reduced to about one-third compared to, for example, when foundation reinforcement is performed using rapple concrete as in Patent Document 1. Furthermore, according to 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 reduced to about one-quarter compared to, for example, when 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 hanging down from the underside of the upper improvement body to form an outer frame, and an internal improvement body hanging down from the underside of the upper improvement body to connect the outer frames and divide the area inside the peripheral improvement body into multiple areas.

[0040] The above description of the embodiments is given by way of example only and is not intended to be limiting, and various improvements and modifications can be made without departing from the scope of the present invention. [Explanation of symbols]

[0041] 1 Ground improvement body 1H Upper improved body 1L Lower improved body 2. Foundation concrete 3 Steel columns 4 Concrete floor 5. Discarded concrete A Completely improved body B Independent improvement body C recess D Bottom surface 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. Building foundation reinforcement structure G Surface ground GL ground surface H1 Height of upper improvement body H2 Height of lower improvement body

Claims

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 for a building according to claim 1.

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