JP2005264718A - Ground foundation reinforcing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foundation reinforcing structure useful to reinforce a building to be constructed on a soft ground, in particular, and superior in construction property. <P>SOLUTION: In the ground foundation reinforcing structure for various kinds of buildings, a geogrid is placed on a ground foundation to be reinforced and a light aggregate or a granular material having water hard powder mixed and deposited on the light aggregate is placed thereon to form a reinforcing layer. A geogrid is further applied thereon so that the reinforcing layer is embraced with the geogrid, and the surface layer thereof is further embraced with a geotextile, as desired. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ground foundation reinforcing structure for various structures. In particular, the present invention relates to a foundation reinforcing structure excellent in workability, which is useful for reinforcing a structure constructed on soft ground.

  When constructing a built-up structure on a foundation ground or surface foundation where the bearing capacity is insufficient, the soil of the surface layer is discharged, and instead of the discharged soil, soil with high-quality soil or cement-based solidified material mixed in mountain sand A method of strengthening the ground by replacing it is known. When the lower part of the improved ground obtained by this construction method is soft, there is a disadvantage that ground subsidence easily occurs due to an increase in weight due to the ground improvement. For this reason, a construction method for reducing the weight by replacing a soft portion of the ground with lightweight soil is also known. However, this method has a limit in ground strength, and there is a risk that the built structure will be damaged by the buoyancy generated based on the fluctuation of the water level in the ground.

  Accordingly, the object of the present invention is to provide a foundation reinforcing structure that is suitable for forming a reinforcing foundation for overlaid structures such as embankments, concrete retaining walls, and box culverts, especially a reinforcing foundation provided on soft ground, and that has excellent workability. There is to do.

  That is, according to the present invention, the ground foundation to be reinforced is a lightweight structure or a reinforcing structure formed by wrapping a reinforcing layer made of a granular material obtained by mixing and adhering hydraulic powder to a lightweight aggregate with a geogrid. A ground foundation reinforcing structure is provided, which is characterized in that the ground foundation reinforcing structure is provided. Such a ground foundation reinforcement structure is preferably constructed by laying a geogrid on the ground foundation to be reinforced, and a lightweight aggregate or a granular material mixed with and adhering hydraulic powder to the lightweight aggregate. It can be formed by forming a reinforcing layer, covering it with a geogrid, and wrapping the reinforcing layer with the geogrid. Such a ground foundation reinforcement structure is a granular material in which a geogrid is left over the ground foundation to be reinforced, and a lightweight aggregate or a hydraulic powder is mixed and adhered to the reinforcement part on the ground base. It is preferable to form the reinforcing layer by laying and covering the reinforcing layer by turning over the surplus geogrid and wrapping the reinforcing layer with the geogrid. Furthermore, in such a ground foundation reinforcing structure, it is preferable that the surface layer of the geogrid is further wrapped with a geotextile. As the geogrid, it is preferable to use a stretched plastic net, and as the geotextile, it is preferable to use a non-woven fabric.

The lightweight aggregate used for forming the reinforcing layer is preferably a lightweight fine aggregate and / or a lightweight coarse aggregate. Furthermore, as a lightweight aggregate or the hardened | cured material of the said granular material, a thing with a density of 0.3-1.5 t / m < ³ > is preferable. In the case of using the granulate as a reinforcing layer is preferably lightweight aggregate 1 m 3 relative to ^(bulk volume) is obtained by a hydraulic powder were mixed at a ratio of less than 150kg deposition.

  ADVANTAGE OF THE INVENTION According to this invention, the ground foundation reinforcement structure excellent in workability, drainage property, and durability can be provided which is lightweight and resistant to fluctuations in groundwater level. In particular, if the interstitial material is heavy, such as earth and sand or crushed stone, it is necessary to allow for the necessary ground strength and subsidence due to its own weight, but the ground foundation reinforcement structure of the present invention is lightweight, so Since a sufficient effect can be exhibited even in the reinforcement of soft ground with low yield strength, it can be used as a basis for various structures such as embankments and other structures.

  As the geogrid used for the ground foundation reinforcement structure of the present invention, any support can be used as long as it has a large supporting force, has a reinforcing layer retention capability, and is water permeable. It is preferable to use a stretchable plastic mesh, especially considering rigidity, strength, water resistance, durability, light weight, workability, etc., such as polyethylene or polypropylene containing a filler such as carbon black. It is preferable to use a reticulate produced by preparing a perforated sheet from polyolefin and stretching it uniaxially or biaxially. Among these, it is preferable to use a biaxially stretched type with little difference in strength between the vertical direction and the horizontal direction. The size of the mesh and the thickness of the mesh in the geogrid are arbitrary, but, for example, a mesh size having a side of about 1 to 10 cm can be suitably used. FIG. 1 shows a partial perspective view of such a biaxially stretched polyolefin geogrid 1. For example, a product of TENSER (registered trademark) sold by Mitsui Chemicals, Inc. Available on the market.

  The ground foundation reinforcing structure of the present invention wraps a reinforcing layer made of a granular material obtained by mixing and adhering light-weight aggregate or light-weight aggregate to a ground foundation to be reinforced at a construction site with a geogrid. The reinforcing structure formed by is disposed. Such a reinforcing structure can be constructed by previously forming the reinforcing structure in another place, bringing it into a construction site and placing it on the ground foundation. However, it can also be formed directly on the ground foundation. In other words, the above-mentioned geogrid is laid on the ground foundation to be reinforced at the construction site, and then the lightweight aggregate or the granular material mixed with and adhering hydraulic powder to the lightweight aggregate is laid to the desired thickness for reinforcement. A layer can be formed and further covered with a geogrid, and the reinforcing layer can be wrapped with a geogrid. Therefore, a geogrid having a length slightly more than twice the length of the reinforcement layer is laid, the above reinforcement layer is laid on the geogrid part of the predetermined reinforcement section, and the remaining geogrid is turned over to reinforce the reinforcement layer. It is preferable to employ a covering method because the construction is easy and the integrity of the resulting reinforcing structure is increased.

For the formation of the reinforcing layer, lightweight aggregates or lightweight aggregates mixed with hydraulic powder and adhered can be used, and these have various densities depending on the type of the ground or the built structure. Things can be used. Moreover, as a lightweight aggregate, a lightweight fine aggregate, a lightweight coarse aggregate, or mixtures thereof can be used. When a lightweight aggregate is used for the reinforcing layer in a simple manner, in consideration of the reinforcing effect and lightness, a material having a density of 0.3 t / m ³ or more, for example, about 0.3 to 1.5 t / m ³ is used. It is preferable to use, particularly when the buoyancy when the groundwater level increases becomes a problem, it is preferable to use one having a density of about 1 to 1.5 t / m ³ , for example.

In particular, when it is necessary to form a reinforcing layer having a high compressive strength, it is preferable to use a granular material in which hydraulic powder is mixed and adhered to a lightweight aggregate. In this case, it is preferable to use a lightweight aggregate in a wet state because the hydraulic powder is easily attached and hardening after the formation of the reinforcing layer is promoted. As the lightweight aggregate of the case, similarly 0.3 t / ^{m 3} or more, for example using 0.3~1.5t / ^{m 3} approximately lightweight fine aggregate or lightweight coarse aggregate, or mixtures thereof, density after deposition and curing of hydraulic powder 0.3 t / ^{m 3} or more, for example, preferred to use what the 0.3~1.5t / ^{m 3} density of about. It is effective to improve the compressive strength when such a granular material is mixed and adhered to 150 kg or less, for example, about 5 to 150 kg per 1 m ³ (bulk volume) of the lightweight aggregate. In this case, particularly considering the density, compressive strength, drainage performance, etc., it is preferable to use a lightweight fine aggregate and a lightweight coarse aggregate in combination as the lightweight aggregate. For example, as a lightweight aggregate, it is advantageous to use a mixed aggregate of a lightweight fine aggregate and a lightweight coarse aggregate, preferably in a ratio of 10 to 50% by weight, more preferably 15 to 45% by weight. Is. In addition, a lightweight fine aggregate having a wet density of 1.1 t / m ³ or more and a lightweight coarse aggregate having a wet density of 0.8 t / m ³ or more are used. It is preferable to blend so as to be m ³ or more, preferably 1.1 to 1.5 t / m ³ . As described above, preferably only the lightweight aggregate is used as the aggregate, and the lightweight fine aggregate and the lightweight coarse aggregate are mixed and used at an appropriate ratio, so that the hydraulic powder is adhered and cured. density of the reinforcing layer, 1t / ^{m 3} or more, preferably obtainable ones 1.1~1.5t / ^{m 3,} has sufficient supporting force for the lightweight, yet overburden construction thereof, and drainage performance An excellent reinforcing layer can be formed. Such lightweight aggregates usually hold about 3 to 15% by weight of water in a wet state.

  The hydraulic powder that can be used by mixing and adhering to the lightweight aggregate in the present invention is an inorganic binder exhibiting curability when kneaded with water, specifically, ordinary Portland cement, early strength Portland cement, Low exothermic Portland cement, high iron oxide Portland cement, white Portland cement, titanium cement, manganese cement, chromium cement, silica cement, alumina cement, blast furnace cement, hozolan cement, blast furnace slag, fly ash, silica etc. Examples thereof include mixed cement, cement-based solidifying agent, lime-based solidifying agent and the like. These may be used alone or in combination of two or more. By using such a lightweight aggregate with wet hydraulic powder as a reinforcing layer material, the hydraulic powder hardens and the lightweight aggregate is bonded to each other at the contact point. And a reinforcing layer having sufficient compressive strength can be formed.

In particular, when it is desired to obtain a reinforcing layer having a high compressive strength, the mixing ratio of the hydraulic powder is preferably 10 to 150 kg, particularly 30 to 70 kg with respect to 1 m ³ (bulk volume) of the lightweight aggregate. . That is, if the mixing ratio of the hydraulic powder is too small, adhesion between the lightweight aggregates becomes insufficient, and the compressive strength tends to decrease. On the other hand, if the mixing ratio of the hydraulic powder is excessive, the density of the cured product becomes too large, the lightness is impaired, and the drainage tends to be insufficient.

  In the ground foundation reinforcing structure of the present invention, in order to prevent clogging of the reinforcing layer and to enhance the retention of the reinforcing layer in the geogrid, the surface layer of the geogrid is further wrapped with geotextile. preferable. When using the above granular material for the reinforcing layer, although it depends on the type of hydraulic powder used, it may take several days to harden, so by using a structure that uses geotextile, Further, there is an advantage that the surface drying of the resin can be prevented and the curing can be completed in a short time, and therefore, a reinforcing layer having a desired strength can be formed in a short time. Such a reinforcing structure can be formed by performing the above-described construction method in a similar manner except that the geogrid and the geotextile are laid so that the geotextile is on the lower surface.

As the geotextile, those having excellent water permeability and durability are preferable, and considering strength, water resistance, light weight, workability, etc., it is preferable to use a nonwoven fabric made of polyolefin such as polyethylene or polypropylene. In consideration of water permeability and strength, it is preferable to use a fiber having a fiber diameter of about 10 to 500 μm and a basis weight of about 50 to 500 g / m ² .

FIG. 2 shows an embodiment in which the reinforcing structure of the present invention is applied to a ground foundation for embankment. The ground 4 of the embankment construction site in front of the ground 3 is dug shallowly, and the non-woven fabric 2 and the geogrid 1 are left over and laid on the ground. When using the above granular material for the reinforcing layer, a predetermined amount of wet lightweight aggregate, preferably wet lightweight aggregate and lightweight coarse aggregate, is put into a mixer at the construction site and mixed. After that, the hydraulic powder is further charged and mixing is continued, or the lightweight lightweight aggregate in a wet state and the lightweight coarse aggregate and the hydraulic powder are collectively charged into the mixer and mixed. Adhere hydraulic powder to the surface of The lightweight aggregate or the granular material obtained as described above is filled in the reinforcing portion at the upper part of the geogrid 1, and the reinforcing layer 5 is formed by leveling and rolling as necessary. Although the density and the compressive strength of the reinforcing layer 5 are increased by the rolling, the water permeability and the like are lowered on the other hand. Therefore, the strength of the rolling may be adjusted according to the purpose. As described above, the density of the reinforcing layer is 0.3 t / m ³ or more, for example, 0.3 to 1.5 t / m ³ , especially 1 t / m ³ or more, preferably 1.1 when it is desired to increase the compressive strength. It is better to adjust the type and amount of lightweight aggregate, the amount of hydraulic powder, the degree of rolling, etc. so that the uniaxial compressive strength is 1.0 N / mm ² or more at ˜1.5 t / m ³ . . After the reinforcement layer 5 is formed, the remaining geogrid 1 and the nonwoven fabric 2 are turned over to enclose the reinforcement layer 5 to form the illustrated reinforcement structure.

  Soil is spread on the obtained structure to level the ground, an L-shaped grid form 6 having an inclined front surface portion and a bottom surface portion is placed, a geogrid 7 as a reinforcing material is laid, In between, the embankment layer 8 is formed. In the figure, this operation is repeated three times. As this embankment material, a lightweight and high-strength embankment layer can be formed by using a lightweight aggregate as described above, or a granular material obtained by mixing and adhering hydraulic powder to a lightweight aggregate. Resistance to settlement can be further increased.

  FIG. 3 shows an example in which the reinforcing structure of the present invention is applied to the foundation of the concrete retaining wall 9, and a reinforcing layer 15 formed in the same manner as in the above embodiment is applied to the geogrid 11 on the foundation portion where the ground 10 is dug shallowly. And the structure wrapped with the nonwoven fabric 12 is provided. FIG. 4 is an example in which the reinforcing structure of the present invention is applied to the foundation of the box culvert 23, and a reinforcing layer 25 formed in the same manner as in the above embodiment is applied to the geogrid 21 on the foundation portion where the ground 20 is dug shallowly. And the structure wrapped with the nonwoven fabric 22 is provided.

It is drawing which shows an example of a geogrid. It is the Example which applied the reinforcement structure of this invention to the foundation of the embankment. It is the Example which applied the reinforcement structure of this invention to the foundation of the concrete retaining wall. It is the Example which applied the reinforcement structure of this invention to the foundation of a box culvert.

Explanation of symbols

1 Geogrid 2 Nonwoven fabric 4 Ground 5 Reinforcement layer 8 Embankment layer 9 Concrete retaining wall 10 Ground
11 Geogrid 12 Nonwoven fabric 15 Reinforcement layer 20 Ground
21 Geogrid 22 Nonwoven fabric 23 Box culvert 25 Reinforcement layer

Claims (9)

A reinforced structure formed by wrapping a lightweight aggregate or a reinforcing layer made of granular material mixed with and adhering hydraulic powder to a lightweight aggregate with geogrid is arranged on the ground foundation to be reinforced Ground foundation reinforcement structure. The ground foundation reinforcement structure lays a geogrid on the ground foundation to be reinforced, and then forms a reinforcing layer by laying a lightweight aggregate or granular material mixed with and adhering hydraulic powder to a lightweight aggregate. The ground foundation reinforcing structure according to claim 1, wherein the ground base is further covered with a geogrid and the reinforcing layer is wrapped with the geogrid. The ground foundation reinforcement structure is laid with extra geogrid on the ground foundation to be reinforced, and a lightweight aggregate or a granular material mixed with and adhering hydraulic powder to the lightweight aggregate is laid on the reinforcement part above it. The ground foundation reinforcing structure according to claim 2, wherein a reinforcing layer is formed, the remaining geogrid is turned over to cover the reinforcing layer, and the reinforcing layer is wrapped with the geogrid. The ground foundation reinforcement structure according to claim 1, wherein the geogrid surface layer is further wrapped with geotextile. The ground foundation reinforcing structure according to claim 1, wherein the lightweight aggregate is a lightweight fine aggregate and / or a lightweight coarse aggregate. The ground foundation reinforcing structure according to claim 1, wherein the lightweight aggregate or the cured product of the granular material has a density of 0.3 to 1.5 t / m ³ . The ground foundation reinforcing structure according to any one of claims 1 to 6, wherein the granular material is obtained by mixing and adhering hydraulic powder at a ratio of 150 kg or less to 1 m ³ (bulk volume) of lightweight aggregate. The ground foundation reinforcing structure according to claim 1, wherein the geogrid is a plastic net-like body subjected to a stretching process. The ground foundation reinforcing structure according to claim 4, wherein the geotextile is a nonwoven fabric.

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