JP4589849B2 - Liquefaction prevention method for existing building foundations - Google Patents

Description

  The present invention belongs to the technical field of a liquefaction prevention method for a foundation ground of an existing building constructed on a ground that may be liquefied, such as sandy ground, and more specifically, an outer periphery of a plurality of existing buildings independently. The present invention relates to a construction method in which improved walls constructed in a cylindrical shape in the ground are connected by a connecting wall to increase rigidity and suppress out-of-plane deformation of the improved wall to increase the liquefaction prevention effect.

  Buildings built on ground that has a liquefied layer, such as sand ground saturated with groundwater, will experience a liquefaction phenomenon on the foundation ground during an earthquake and lose sufficient bearing capacity to support the structure. However, it is known to cause great damage such as tilting and collapse of buildings. In order to prevent the liquefaction phenomenon as described above, conventionally, as shown in FIG. 3, for example, an outer peripheral wall 32 having a closed shape and a lattice wall 32a is built in the ground 31 directly under the building 30. A technique for preventing liquefaction is disclosed in Patent Document 1 and is known.

In addition, the liquefaction prevention structure described in Patent Document 2 includes an outer peripheral wall 42 formed in the ground 41 of the building 40 as shown in FIG. 4, and a vertical axis perpendicular to the inner peripheral surface of the outer peripheral wall 42. A plurality of retaining walls 43 (buttresses) extending in the direction are provided upright.
Japanese Examined Patent Publication No. 4-54004 Japanese Patent Laid-Open No. 2004-92048

The liquefaction prevention method of the above-mentioned patent document 1 is constructed by constructing an outer peripheral wall 32 provided with a lattice wall 32a having rigidity higher than the ground in the ground immediately below the building to suppress shear deformation during an earthquake, The effect of preventing the liquefaction of the inner ground surrounded by is recognized. However, this liquefaction prevention method must be carried out by determining the interval between the lattice walls 32a according to the magnitude of the earthquake and the ground conditions to be assumed. Therefore, it can be carried out if it is a new building, but in the case of an existing building, it is extremely difficult to carry out in the direct foundation panel of the building, and a great cost is required. In particular, it is not practical when existing buildings are connected independently.
Therefore, in reality, an outer peripheral wall that only surrounds the outer periphery of the existing building is constructed, and the wall thickness is increased considerably to ensure the rigidity of the outer peripheral wall, and the liquefaction phenomenon is restrained by restraining its out-of-plane deformation. It is preventing. However, enormous costs are required to make the wall thickness considerably large, and when the building plane scale is increased, the range of realistic strength and wall thickness is exceeded.

  In the liquefaction prevention structure of Patent Document 2, the effect of suppressing the out-of-plane deformation of the outer peripheral wall without increasing the wall thickness of the outer peripheral wall 42 by the retaining wall 43 is recognized. However, as in the case of Patent Document 1, it is extremely difficult to carry out in a direct foundation panel of an existing building.

  In short, any of the techniques disclosed in Patent Documents 1 and 2 suggests the possibility of implementing as a construction method for preventing liquefaction of the foundation ground of an existing building, or the foundation ground of an existing building that is a plurality of independent buildings. It is not a thing.

  An object of the present invention is to provide a construction method suitable for preventing liquefaction of an existing building constructed on the ground where there is a risk of liquefaction, particularly a foundation ground of a plurality of existing buildings independently. For example, it is to provide a liquefaction prevention method that is economical and can shorten the construction period.

As a means for solving the above-described problems of the prior art, the liquefaction prevention method for a plurality of existing building foundations according to the invention described in claim 1 is:
It is a liquefaction prevention method for the foundation ground of an existing building 1 that is independently connected in series,
A cylindrical improvement wall 4 surrounding the outer periphery of the foundation ground 2a of the existing building 1 is constructed in each of the outer peripheral grounds 2 of the plurality of existing buildings 1, and adjacent improvement walls 4, 4 are 4 is connected by a connecting wall 5 arranged orthogonal to 4.

The invention according to claim 2 is a method for preventing liquefaction of a plurality of existing building foundations according to claim 1,
Among the improved walls 4 constructed in the outer peripheral ground 2 of the existing building 1 located at the end, a plurality of reinforcing retaining walls 6 are provided on the outer longitudinal wall 4 a outwardly at right angles to the improved wall 4. It is characterized by building.

The invention according to claim 3 is the liquefaction prevention method for a plurality of existing building foundations according to claim 1,
Out of the improved walls 4 constructed in the outer peripheral ground 2 of the existing building 1 located at the end, the outer longitudinal wall 4a is constructed to be large enough to exhibit rigidity that requires the wall thickness. And

  In the liquefaction prevention method according to the invention described in claim 1, the improvement walls 4 are respectively constructed in the outer peripheral ground 2 of a plurality of existing buildings 1 independently, and the adjacent improvement walls 4 are connected to each other by the walls 5. Since they are connected, it is possible to easily prevent liquefaction of the existing building constructed on the ground where liquefaction may occur, particularly the foundation ground of a plurality of independent existing buildings. The improved wall 4 can be implemented with high reliability as a general-purpose technology and conventional technology without the need for temporary construction, etc., in advance by a deep mixing treatment method, etc., which has a wealth of known construction results, and has no adverse effect on the existence of the existing building 1 Therefore, the construction period can be shortened and the cost can be reduced. Not only that, the connecting wall 5 connects the improved walls 4 and 4 built in the outer peripheral ground 2 of the plurality of existing buildings 1 to each other, so that a large improved wall structure supporting each other is formed, and the entire surface is deformed out of plane. As a result, the shear deformation suppression effect (rigidity) is dramatically improved compared to a single improved wall, and the liquefaction prevention effect is excellent.

  The liquefaction prevention method according to the invention described in claim 2 or 3 is applied to the longitudinal wall 4a located on the outermost side among the improved walls 4 constructed in the outer peripheral ground 2 of the existing building 1 located at the end. Since a plurality of reinforcing retaining walls 6 (buttresses) are constructed, or the wall thickness thereof is constructed to be large, the rigidity of the longitudinal wall 4a, which is the weak point where bending deformation and shearing force are inherently generated, can be reduced in a small space. It is possible to reliably increase and prevent liquefaction.

  A cylindrical improvement wall 4 surrounding the outer periphery of the foundation ground 2a of the existing building 1 is constructed in each of the outer peripheral grounds 2 of the plurality of existing buildings 1 that are independently connected. And the some improvement wall 4 ... which adjoins is connected by the connection wall 5 of the arrangement | positioning orthogonal to this improvement wall 4. As shown in FIG.

  Hereinafter, an embodiment of a liquefaction prevention method for a plurality of existing building foundations according to the present invention will be described with reference to the drawings.

  FIGS. 1A and 1B show the foundation ground 2a (existing building) of each existing building 1 in the outer peripheral ground 2 of a plurality of existing buildings 1 each constructed with an independent foundation structure on the ground 2 that may be liquefied. A cylindrical improvement wall 4 that individually surrounds the outer periphery of each of the direct foundation boards 1 is constructed to a depth that reaches the hardly water-permeable layer 3, and a plurality of adjacent improvement walls 4 are orthogonal to the improvement wall 4. The state where it connected with the connecting wall 5 is shown.

  The improved wall 4 and the connecting wall 5 are constructed by, for example, injecting a stabilizer such as cement milk into the ground, stirring and mixing with the excavated soil, and solidifying to form a highly rigid and hardly permeable wall. It is constructed by a known deep mixing method or soil cement wall method. According to the deep mixing method, as shown in FIGS. 1A and 1B, the cylindrical improved wall 4 surrounding the outer periphery of the foundation ground 2a of the existing building 1 can be constructed in a continuous state from the ground surface to a predetermined depth. The wall thickness is determined in consideration of the plane scale of the existing building 1 from about 50 cm to nearly 2 m depending on the selection of the outer diameter of the excavating stirring blade. In addition, the so-called appropriate lapping process can be used to construct the improved wall 4 having water stoppage continuously in the longitudinal direction.

  The improved walls 4 built in the outer peripheral ground 2 of each existing building 1 as described above are integrated with the connecting wall 5 that connects the improved walls 4 and 4 by the deep mixing method. Therefore, a large improved wall structure that supports each other is built in the ground 2 of the existing building 1, and the entire structure suppresses out-of-plane deformation. A large shear deformation inhibiting effect (rigidity) is exhibited, and a liquefaction preventing effect is obtained.

Next, a method for increasing the rigidity of the outermost longitudinal wall 4a among the improved walls 4 constructed in the outer peripheral ground 2 of the existing building 1 located at the end will be described.
Since the earth pressure from the surroundings and the dynamic water pressure due to the groundwater act directly and greatly on the longitudinal wall 4a, the longitudinal wall 4a is a weak point where bending deformation and shearing force are the largest.

  Therefore, as shown in FIG. 1B, a plurality of reinforcing retaining walls 6 (or also called buttresses) are formed on the longitudinal wall 4a so as to protrude outwardly at right angles to the longitudinal wall 4a. To ensure rigidity (invention of claim 2). The retaining wall 6 is also constructed by a deep mixing process. The height is substantially the same as that of the improved wall 4, but the protruding length, wall thickness, spacing between adjacent retaining walls 6, 6, etc. are determined depending on the degree of liquefaction of the ground 2 and the existing building 1. It is adjusted appropriately according to the building area and load.

  The construction method for ensuring the rigidity of the longitudinal wall 4a is not limited to the above. As shown in FIG. 2, it is also preferable to increase the wall thickness of the longitudinal wall 4a to such an extent that the required rigidity is exhibited (the invention according to claim 3). As a method of increasing the wall thickness, it is also a deep mixing treatment method, which is carried out by using a drilling stirring blade having a large outer diameter or by forming a plurality of columns of improved columns. In addition, it is also conceivable that the ground between the adjacent existing buildings 1 and 1 is entirely improved and implemented.

  The embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated embodiments, and design modifications and application variations that are usually made by those skilled in the art are within the scope of the technical idea of the invention. I will add a note to include the range. For example, the same method can be applied to a new building. Moreover, although the construction method which constructs | assembles an improved wall etc. with a deep-layer mixing processing machine was demonstrated, you may construct | assemble by methods, such as a mountain stop construction method.

A is a longitudinal cross-sectional view which shows the whole structure of the liquefaction prevention construction method of the existing existing building foundation which concerns on this invention. B is a plan view of A. FIG. It is the top view which showed the other Example which reinforces the longitudinal direction wall of an outer peripheral wall. It is the reference figure which showed the liquefaction prevention construction method disclosed by patent document 1. FIG. It is the reference figure which showed the liquefaction prevention structure disclosed by patent document 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Existing building 2 Ground 4 Perimeter wall 5 Connecting wall 6 Reservation wall 4a Longitudinal wall

Claims (3)

It is a liquefaction prevention method for the foundation ground of multiple existing buildings,
In the outer peripheral ground of each of the plurality of existing buildings, a cylindrical improvement wall surrounding the outer periphery of the foundation ground of the existing building is constructed, respectively, and adjacent improvement walls are connecting walls that are arranged orthogonal to the improvement wall. A liquefaction prevention method for multiple existing building foundations, characterized by connecting.   Among the improved walls constructed in the outer peripheral ground of the existing building located at the end, a plurality of reinforcing retaining walls are constructed on the outer longitudinal wall at a right angle outward with respect to the improved wall. The liquefaction prevention construction method for a plurality of existing building foundations according to claim 1. Among the improved walls constructed in the outer peripheral ground of the existing building located at the end, the outer longitudinal wall is constructed to be large enough to exhibit the rigidity that requires its wall thickness, The liquefaction prevention method for existing building foundations as described in Item 1 above.

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