JP6334970B2 - Temporary support method for foundation - Google Patents

Description

  The present invention relates to a temporary provisional support method. Specifically, it relates to a temporary support method for the foundation of the existing building when the existing building is seismically isolated under the foundation.

Conventionally, there has been known a base-isolated retrofit construction for making an existing building base-isolated under the foundation (see Patent Document 1).
This base-isolation retrofit work involves excavating the existing building directly under the base of the existing building and laying a support work on the excavated part to apply a reaction force to the bottom of the excavated part. Support the foundation temporarily. Then, attach a seismic isolation device such as laminated rubber directly under the foundation, and then remove the jack. As a result, the base is supported by the seismic isolation device and the existing building is seismically isolated.

  In addition, piles may be added or the foundations may be reinforced in addition to the reinforcement work for the upper part of the existing building, even in the event that seismic isolation is not required. There is.

  For example, when an existing building with a foundation without piles is to be seismically isolated, the vertical load of the upper layer of the building is transmitted to the lower layer mainly through the pillar, so the part of the foundation of the existing building located directly under the pillar ( Hereinafter, the portion immediately below the column is subjected to a larger vertical load than the remaining portion (hereinafter referred to as the non-column directly below). Therefore, when temporarily supporting the foundation of an existing building, supporting a position away from the lower part of the column will cause a large moment and shearing force in the part from the lower part of the foundation to the support point, thus reinforcing the foundation. Since the necessity arises, the construction cost becomes high. Therefore, it is necessary to support a portion as close as possible to the lower part of the column as much as possible.

  Therefore, as shown in Patent Document 1, it has been proposed that a simple vertical retaining wall is provided so as to surround the ground directly below the pillar, and the vicinity of the retaining wall is temporarily supported by a supporting work. .

JP 2002-242450 A

  However, even if the ground supporting the lower part of the pillar is surrounded by a retaining wall, a large load is applied to the lower part of the pillar, so depending on the strength and properties of this ground, the stability of the ground should be ensured. It was difficult.

  The present invention provides stability of the ground when there is no pile in the existing building, or even if there is a pile in the existing building, it is a light existing pile or a pile that does not have sufficient bearing capacity after excavation due to damage. It is an object to provide a temporary support method for a foundation that can safely or easily reinforce or reinforce an existing building at low cost.

  The temporary support method for a foundation according to claim 1 is a temporary support method for a foundation (for example, a foundation 3 to be described later) of an existing building (for example, an existing building 1 to be described later), and a pillar (for example, A step of excavating the ground (for example, a non-column direct lower portion 15 of the below-described ground 6) located below between columns 5 described later to form an excavation space that becomes narrower downward (for example, steps described later) S1), a reaction board (for example, a laid iron plate 25 described later) is provided at the bottom of the excavation space, and a platform (for example, a platform 31 described later) composed of a plurality of steel members is provided on the reaction board. A step (for example, steps S2 and S3 to be described later) of providing a support (for example, a support 30 to be described later) having a jack (for example, a hydraulic jack 32 to be described later) and temporarily supporting the foundation by the support. And) To.

According to this invention, the ground located below between the columns is excavated to form an excavation space that becomes narrower as it goes downward. Therefore, the ground located below the pillar has a shape that expands downward. Thereby, it is possible to prevent the ground supporting the pillar from slipping and to ensure the stability of the ground.
In addition, since a reaction force plate is laid on the bottom of the excavation space and a support made up of a base made of a plurality of steel members and a jack provided on this stand is used, the reaction force of the support work through the reaction force plate Can be reliably transmitted to the ground, and the foundation can be simply temporarily supported using off-the-shelf components immediately after excavation, so the unstable period can be shortened, and the possibility of the ground breaking and sliding can be reduced. Can be seismically isolated at low cost.

The temporary support method for a foundation according to claim 1 is characterized in that the gantry includes at least two lower members (for example, a lower member 40 described later) provided substantially in parallel, and substantially in a direction orthogonal to the lower member. At least two middle members (for example, a later-described middle member 41) provided in parallel, and an upper member (for example, a later-described upper member 42) provided in a direction orthogonal to the middle member are viewed from below. The reaction force board is a laying iron plate (for example, a laying iron plate 25 described later).

The temporary support method for a foundation according to claim 1 is characterized in that the steel member is a mountain steel material.

According to the present invention, the laying iron plate is laid on the flat bottom portion of the excavation space, and the frame is constructed by assembling the ready-made yamadome steel materials to the end, so that the load can be stably transmitted to the ground.
In addition, since the platform is constructed by combining Yamatome steel materials, workability is good even in a narrow space such as an excavation space.
In addition, if the bolts are tightened by using the holes in the steel retaining material, the support work is further stabilized.

  According to the present invention, an existing building can be seismically isolated or reinforced at a low cost while ensuring the stability of the ground.

It is sectional drawing of the foundation part of the existing building with which the temporary support method of the foundation which concerns on one Embodiment of this invention is applied. It is a cross section which shows the state where the existing building which concerns on the said embodiment was seismically isolated. It is a flowchart of the procedure which seismically isolates the existing building which concerns on the said embodiment. It is FIG. (1) for demonstrating the procedure which makes the existing building which concerns on the said embodiment seismic isolation. It is FIG. (2) for demonstrating the procedure which makes the existing building which concerns on the said embodiment a seismic isolation. It is a top view of the part in which the support work of excavation space is installed in the procedure of isolating the existing building which concerns on the said embodiment. It is a side view of the support work which concerns on the said embodiment. It is FIG. (3) for demonstrating the procedure which makes the existing building which concerns on the said embodiment a seismic isolation. It is FIG. (4) for demonstrating the procedure which makes the existing building which concerns on the said embodiment seismic isolation. It is a side view of the provisional support pillar used when making the existing building which concerns on the said embodiment seismic isolation. It is FIG. (5) for demonstrating the procedure to make the existing building based on the said embodiment a seismic isolation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a foundation portion of an existing building 1 to which a foundation temporary support method according to an embodiment of the present invention is applied.
The existing building 1 has an underground frame 2, and the underground frame 2 includes a foundation 3, a floor 4 provided on the foundation 3, a plurality of pillars 5 extending upward from the foundation 3, and It has.

The foundation 3 is a foundation by existing piles 13 constructed on a relatively good ground 6, and this foundation 3 includes a footing 10, a foundation beam 11 that connects these footings 10, and a foundation beam 11. A pressure-resistant plate 12 provided therebetween and an existing pile 13 provided immediately below the footing 10 are provided.
The aforementioned pillar 5 extends upward from the center of the footing 10.

For each footing 10, five existing piles 13 are arranged (see FIG. 6). One of these existing piles 13 is located at the center of the footing 10, and the rest is located at the peripheral edge of the footing 10.
Further, hereinafter, the central portion of the footing 10 in the foundation 3 is referred to as a column direct lower portion 14 positioned immediately below the columns 5, and the remaining portion such as between the columns 5 is referred to as a non-column direct lower portion 15.

In the present invention, as shown in FIG. 2, an installation space 21 is formed under the foundation 3 of the existing building 1, and the seismic isolation device 20 is installed in the installation space 21. By supporting the foundation 3, the foundation 3 of the existing building 1 is seismically isolated.
Moreover, it is not restricted to this, and it may be only reinforcement of foundations, such as expansion of a pile, without making it a seismic isolation.

When seismic isolation is used, the structure is as follows.
That is, an installation space 21 for installing the seismic isolation device 20 is formed under the foundation 3 of the existing building 1.
A steel pipe pile 24 is driven into the bottom surface of the installation space 21, and a reinforced concrete mat slab 22 is constructed over the entire surface. In the mat slab 22, a base isolation base 23 made of reinforced concrete is provided immediately below the center of the footing 10 (under the column 14), and the base isolation device 20 is provided on the base isolation base 23. ing.

  The seismic isolation device 20 supports the center portion of the footing 10 of the foundation 3 from below by applying a reaction force to the mat slab 22 while keeping the foundation 3 movable in the horizontal direction.

FIG. 3 is a flowchart showing a procedure for isolating the foundation 3 of the existing building 1.
In step S1, an excavation port is provided outside the existing building 1 and the excavation port digs under the foundation 3 of the existing building 1, and as shown in FIG. The excavation space 21a which becomes narrow as it goes down is formed.

The excavation space 21a extends in a tunnel shape in a direction intersecting in the horizontal plane, and becomes a part of the installation space 21 described above.
In addition, the ground 6 below the pillar lower part 14 has a shape that expands downward from the pillar direct lower part 14, and the surface 6 a of the ground 6 becomes a slope. In this embodiment, since the existing pile 13 exists under the foundation 3, excavation is performed until the surface 6 a contacts the existing pile 13. Thereby, when the steel pipe pile 24 mentioned later is laid, damage, inclination, etc. of the steel pipe pile 24 can be confirmed directly, and it can construct more safely.

  The excavation space 21a is a space that is excavated from the ground 6 located below the pillars and becomes narrower as it goes downward, and in particular, by hitting a pile head with a hydraulic hammer when placing an existing pile. It is easy to check the soundness of pile heads that are often damaged.

In step S2, as shown in FIG. 5, the bottom iron plate 25 as a reaction force board is laid on a flat bottom of the excavation space 21a. Although different depending on the ground supporting force and load, in this embodiment, two laying iron plates having a thickness of 1.5 m × 1.5 m and a thickness of 22 mm are laid at one place. Thereby, when the ground supporting force is 20 t / m ² , a supporting force of about 90 t can be secured.

  In step S3, as shown in FIG. The support 30 is disposed at a predetermined position in the excavation space 21a, for example, directly below the foundation beam 11.

FIG. 6 is a plan view of a portion where the support 30 in the excavation space 21a is installed. FIG. 7 is a side view of the support work 30.
The supporting work 30 includes a gantry 31 provided on the laying iron plate 25 and a hydraulic jack 32 provided on the gantry 31.

The gantry 31 is constructed by assembling a plurality of steel frame members, specifically, steel piles made of H-shaped steel in a cross-beam shape, and has a shape that expands downward.
Specifically, the pedestal 31 is constructed between a pair of lower stage members 40 made of a mountain steel material provided in parallel on the laid iron plate 25 and between the lower stage members 40 so as to be substantially parallel to each other. A pair of middle stage members 41 made of mountain steel members provided side by side, one upper stage member 42 made of mountain steel members laid between these middle stage members 41, and extending substantially vertically from the upper stage member 42. And a vertical member 43 made of Yamadome steel.

That is, the gantry 31 includes a pair of lower stage members 40 provided substantially parallel to each other, a pair of middle stage members 41 provided substantially parallel to the lower stage member 40 in a direction orthogonal to the lower stage members 40, and a direction orthogonal to the middle stage member 41. One upper member 42 provided is stacked in order from the bottom.
The hydraulic jack 32 is a jack used for mountain retaining work, and is provided between the top of the vertical member 43 of the gantry 31 and the foundation beam 11 of the foundation 3.

  Then, by pressing the lower surface of the foundation beam 11 with the hydraulic jack 32 of the support work 30, the support work 30 temporarily supports the foundation 3 from below by applying a reaction force to the bottom iron plate 25 on the ground 6. As a result, the support work 30 temporarily supports the position of the non-column direct lower portion 15 near the column direct lower portion 14.

  In step S4, as shown in FIG. 8, the ground 6 below the column lower part 14 is excavated, the seismic isolation device 20 is installed, and the installation space 21 for press-fitting the steel pipe pile 24 is completed.

  In step S5, as shown in FIG. 8, a steel pipe pile 24 is press-fitted using the foundation 3 as a reaction force in the immediate lower part 14 of the existing building 1 or in the vicinity thereof (see FIG. 6). This steel pipe pile 24 is not removed either in the case of seismic isolation or in the case of non-seismic isolation, and becomes a main support pile.

In step S <b> 6, as shown in FIG. 9, a temporary support column 50 is installed immediately above the steel pipe pile 24.
FIG. 10 is a side view of the temporary support column 50.
The temporary support column 50 includes a first vertical member 51 extending in the vertical direction from the stigma of the steel pipe pile 24, a hydraulic jack 52 provided on the first vertical member 51, and a vertical direction from above the hydraulic jack 52. A second vertical member 53 extending to the lower surface of the foundation 3.

  Then, by pressing the lower surface of the foundation beam 11 with the hydraulic jack 52 of the provisional support column 50, the provisional support column 50 temporarily supports the foundation 3 from below by applying a reaction force to the steel pipe pile 24. As a result, the provisional support column 50 temporarily supports the portion directly below the column 14 of the foundation 3 or the vicinity thereof.

  The support capacity of the steel pipe pile 24 is expected to be twice that of the support work 30, and if sufficient support power can be expected, the support work 30 can be dismantled, and if seismic isolation is used, it interferes with the seismic isolation device. You can also remove existing piles.

  In step S7, as shown in FIG. 11, the temporary support by the support work 30 is cancelled | released, and the support work 30 and the laying iron plate 25 are removed. Moreover, the part exposed to the installation space 21 among the existing piles 13 is removed.

In step S8, the mat slab 22 is placed.
In step S <b> 9, the seismic isolation device 20 is installed on the mat slab 22 and the foundation 3 is supported by the seismic isolation device 20.
Specifically, the base isolation base 23 is constructed on the mat slab 22, the base isolation device 20 is installed on the base isolation base 23, and the column lower part 14 is supported by the base isolation device 20.

  In step S10, the temporary support by the temporary support column 50 is released, and the temporary support column 50 is removed.

According to this embodiment, there are the following effects.
(1) The ground 6 located below the non-columnar lower part 15 was excavated to form an excavation space 21a that becomes narrower as it goes downward. Therefore, the ground 6 below the pillar lower portion 14 has a shape that expands downward. Thereby, it is possible to prevent the ground 6 supporting the pillar lower part 14 from slipping and to ensure the stability of the ground 6.
In addition, since the laying iron plate 25 serving as a reaction board is laid on the bottom of the excavation space 21a, and the support work 30 including the pedestal 31 made of a plurality of pile steel materials and the hydraulic jack 32 provided on the pedestal 31 is used. In addition, the reaction force of the support work 30 can be reliably transmitted to the ground 6 via the laying iron plate 25, and the foundation 3 can be temporarily supported using the temporary support column 50 made of a ready-made member immediately after excavation. By shortening the period, the possibility of the ground breaking and slipping can be reduced, and the existing building 1 can be seismically isolated at low cost.

(2) The laying iron plate 25 is laid on the flat bottom of the excavation space 21a, and the frame 31 is constructed by assembling members 40, 41, 42, and 43 made of ready-made yamatome steel material so that the load is stable on the ground 6 Can be transmitted.
Moreover, since the mount frame 31 is constructed by combining the members 40 to 43 made of Yamadome steel material, the workability is good even in a narrow space such as the excavation space 21a.
Moreover, if it bolts using the hole of a mountain steel material, the support 30 will be stabilized further.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Existing building 2 ... Underground frame 3 ... Foundation 4 ... Floor 5 ... Pillar 6 ... Ground 6a ... Ground surface 10 ... Footing 11 ... Foundation beam 12 ... Pressure-resistant plate 13 ... Existing pile 14 ... Directly under the pillar 15 ... Directly under the pillar Part 20 ... Seismic isolation device 21 ... Installation space 21a ... Excavation space 22 ... Mat slab 23 ... Seismic isolation foundation 24 ... Pipe pile 25 ... Laying iron plate (reaction board)
DESCRIPTION OF SYMBOLS 30 ... Supporting work 31 ... Stand 32 ... Hydraulic jack 40 ... Lower stage member 41 ... Middle stage member 42 ... Upper stage member 43 ... Vertical member 50 ... Temporary support column 51 ... 1st vertical member 52 ... Hydraulic jack 53 ... 2nd vertical member

Claims (1)

A temporary support method for the foundation of an existing building,
Excavating the ground located below the foundation beam of the existing building to form an excavation space that narrows as it goes downward;
A base iron plate is provided directly below the foundation beam and at the bottom of the excavation space, and has a base made of a plurality of pile steel members in a shape that expands downward on the base iron plate and a jack provided on the base Providing a support work, and temporarily supporting the foundation beam by the support work ,
The gantry includes a pair of lower members extending substantially orthogonal to the foundation beam, a pair of middle members extending substantially parallel to the foundation beam, and one upper member extending substantially orthogonal to the foundation beam. A temporary support method for a foundation characterized by being stacked in order from the bottom .

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