JP2012136841A - Method for excavating ground under spread foundation of existing building, and base-isolating method for existing building - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excavate ground under a spread foundation even without construction of a temporary bearing pile.SOLUTION: Ground below a footing 24A is excavated in a cylindrical shape while leaving in-envelope ground 47 enclosed with a failure envelope 46, and a foundation section 34 is continuously supported by the cylindrical ground 38A. A cylindrical section 60 is shaped on the outside of the failure envelope 46 of the upper section of the cylindrical ground 38A, and restrained by a ring 50 surrounding the cylindrical section 60. The ring 50 is split in two; a split part is provided with a flange; and the flange is provided with a through-hole for inserting a stopper. After the ring 50 is integrated by the stopper 52, cement 56 is injected into a gap between the ring 50 and the cylindrical section 60 from an injection port 54. The same procedures are repeated; a section from below the footing 24A to an excavated bottom surface 48 is restrained by the plurality of rings 50; and a temporary support section 58 for supporting the foundation section 34 is constructed in a cylindrical shape by an outside diameter of an upper end of the failure envelope 46. Subsequently, the periphery of the temporary support section 58 is supported by a jack, and the temporary support section 58 is removed.

Description

  The present invention relates to a method for excavating a direct foundation foundation of an existing building and a method for seismic isolation of an existing building.

  For seismic isolation of existing foundations, expansion of underground spaces, construction of underground passages, etc., it is necessary to excavate the ground beneath the foundations of existing buildings. For example, in seismic isolation repair, it is common to install a seismic isolation device in the seismic isolation pit after excavating directly beneath the foundation to construct the seismic isolation pit. At this time, excavation directly under the foundation is performed by newly constructing a temporary receiving pile (Patent Document 1).

  Specifically, the newly constructed temporary support pile is used to support the direct foundation of the existing building, and the direct foundation supported by the temporary support pile is excavated. In other words, the construction of seismic isolation pits will be promoted while constructing temporary support piles. After installing the seismic isolation device in the seismic isolation pit, the temporary support pile is removed from the seismic isolation pit.

  However, the seismic isolation pit is required to have a low height in order to reduce excavation costs. For this reason, in the method of patent document 1, the method of connecting a short pile as a temporary receiving pile will be employ | adopted, and it was a cost increase. Also, after installing the seismic isolation device, it takes time to remove the temporary support pile.

JP 2009-155794 A

  An object of this invention is to provide the excavation method of the direct foundation | foundation base board of the existing building which can excavate the ground under a foundation directly, without constructing a temporary receiving pile in view of the said fact.

  A method for excavating a direct foundation foundation of an existing building according to the invention described in claim 1 includes a shaft construction process for constructing a vertical shaft, the direct foundation foundation of an existing building from the vertical shaft to the bottom of the excavation, Excavation process to excavate the ground directly below the ground receiving part of the foundation, leaving the ground in the envelope surrounded by the fracture envelope, which is the boundary where the ground collapses due to its own weight, and the ground in the envelope And a temporary support step in which the outer peripheral portion is constrained by a ring to be a temporary support portion, and the existing building is continuously supported by the temporary support portion.

  According to the first aspect of the present invention, the ground under the foundation is directly excavated, leaving the ground in the envelope surrounded by the fracture envelope of the ground below the ground receiving portion. The fracture envelope is distributed in a cone shape under the ground receiving part, and the ground under the ground receiving part extends from the surroundings into a shape that includes this cone shaped fracture envelope inside, for example, a columnar shape or a truncated cone shape. Excavated. Thereby, the existing building can be continuously supported by the ground within the envelope without collapsing the ground within the envelope.

Thereafter, the ground in the envelope is shaped into a cylindrical shape and the outer periphery is restrained by a ring. Because the restraining force of the ring prevents the outer circumference of the envelope inner ground from collapsing, even if the envelope inner ground is shaped into a cylinder, the existing building is continued on the envelope inner ground of the temporary support section. Can be supported.
Thereby, even if it does not support the direct foundation of an existing building with a temporary receiving pile, the existing building can be continuously supported by the ground in the envelope which originally existed. As a result, the construction of the temporary support pile and the trouble of removing the temporary support pile do not occur.

  According to a second aspect of the present invention, in the method for excavating a direct foundation foundation of an existing building according to the first aspect, the temporary support step injects a filler into a gap between the ring and the ground in the envelope. It is characterized by having a filler injection step.

  According to invention of Claim 2, a filler is inject | poured into the clearance gap between a ring and the ground in an envelope. As the filler, for example, mortar or concrete can be used. Thereby, the support strength of the ground in an envelope of the temporary support part restrained with the ring can be raised.

  According to a third aspect of the present invention, in the method for excavating a direct foundation foundation of an existing building according to the second aspect, the temporary support step is constrained between the direct foundation and the bottom surface of the excavation by a plurality of the rings. It is characterized in that the filler injection step is performed every time.

  According to the third aspect of the present invention, the space from the direct foundation to the bottom of the excavation is constrained sequentially from the top by the plurality of rings. At this time, whenever it restrains with a ring, a filler is inject | poured into the clearance gap between a ring and an envelope inner ground, and the bearing yield strength of an envelope inner ground is raised. As a result, the start position of the fracture envelope is sequentially moved downward by the height of the ring. That is, the temporary support portion can be shaped into a cylindrical shape with the smallest diameter at the top of the fracture envelope distributed in a cone shape as the outer diameter of the ground in the envelope.

The invention according to claim 4 is the excavation method for a direct foundation foundation of an existing building according to any one of claims 1 to 3, wherein the ground receiving part is a column lower part or a foundation beam lower part of the existing building. It is characterized by being.
According to invention of Claim 4, the ground receiving part is made into the column lower part or foundation beam lower part of the existing building. Thereby, the vertical load of the existing building can be efficiently supported by a small number of temporary support portions.

  According to a fifth aspect of the present invention, in the excavation method for a direct foundation foundation of an existing building according to any one of the first to fourth aspects, a jack is provided around the temporary support portion after the temporary support step. It has a temporary support part removal process which installs and makes the said jack support the said existing building, and removes the said temporary support part.

  According to the invention described in claim 5, after the existing building is supported by the temporary support portion, the existing building is supported by the jack installed around the temporary support portion. Thereafter, the temporary support portion is removed with the jack supporting the existing building. As a result, the existing building can be transferred from the temporary support portion to the jack.

According to a sixth aspect of the present invention, there is provided a seismic isolation method for an existing building, wherein a seismic isolation device is installed between the existing building and the ground of the excavation bottom after the temporary support portion removing step according to the fifth aspect. The existing building is seismically isolated.
According to invention of Claim 6, a seismic isolation apparatus is installed in the direct foundation | foundation baseboard after a temporary support part is removed. Thereby, even if it does not construct a temporary receiving pile, it can excavate the foundation foundation directly of an existing building, and can make an existing building seismic isolation.

  Since this invention is set as the said structure, even if it does not construct a temporary receiving pile, it can excavate a foundation foundation board directly.

It is a figure which shows the procedure of the excavation method of the direct foundation ground board of the existing building which concerns on the 1st Embodiment of this invention. It is a figure explaining the retaining wall construction process of the excavation method of the direct foundation ground board concerning the 1st embodiment of the present invention. It is a figure explaining the retaining wall construction process of the excavation method of the direct foundation ground board concerning the 1st embodiment of the present invention. It is a figure explaining the retaining wall construction process of the excavation method of the direct foundation ground board concerning the 1st embodiment of the present invention. It is a figure explaining the vertical shaft construction process of the excavation method of the direct foundation ground board which concerns on the 1st Embodiment of this invention. It is a figure explaining the excavation process of the excavation method of the direct foundation ground board which concerns on the 1st Embodiment of this invention. It is a figure explaining the temporary support process of the excavation method of the direct foundation ground board which concerns on the 1st Embodiment of this invention. It is a figure explaining the temporary support process of the excavation method of the direct foundation ground board which concerns on the 1st Embodiment of this invention. It is a figure explaining the temporary support process of the excavation method of the direct foundation ground board which concerns on the 1st Embodiment of this invention. It is a figure explaining the jack replacement | exchange process and temporary support part removal process of the excavation method of the direct foundation | foundation board which concern on the 1st Embodiment of this invention. It is a figure explaining the attachment procedure of the seismic isolation apparatus of the direct foundation | foundation base board which concerns on the 2nd Embodiment of this invention. It is a figure explaining the attachment procedure of the seismic isolation apparatus of the direct foundation | foundation base board which concerns on the 2nd Embodiment of this invention.

(First embodiment)
The direct foundation ground excavation method for an existing building according to the first embodiment is executed according to the procedure shown in the construction flow of FIG.

First, the retaining wall construction step 10 is executed.
Specifically, as shown in FIG. 2, a mountain retaining wall 36 is constructed surrounding the outer peripheral wall 27 of the existing building 8. FIG. 2A is a side view of the existing building 8 and the ground 29, and FIG. 2B is a plan view. 2A is a cross-sectional view taken along line X2-X2 in FIG. 2B, and FIG. 2B is a cross-sectional view taken along line X1-X1 in FIG.

  The foundation part 34 of the existing building 8 is directly used as a foundation, and a concrete bottom slab 26 is constructed on the bottom surface of the foundation part 34 to partition the ground 29 and the existing building 8. In addition, footings 23 and 24 are provided under the pillars 28 of the existing building 8 to transmit the vertical load of the existing building 8 to the ground 29. The footings 23 and 24 are connected by a foundation beam 25, respectively.

The ground 29 will be described by taking as an example a case where the surface soil 30 and the gravel soil 32 are formed in this order from the top. The configuration of the ground 29 may be another configuration.
In the mountain retaining wall 36, H-section steel is vertically built except for the excavation part P in which the entrance for excavation work is formed. Corresponding to the progress of excavation, a cross sheet pile is bridged between the H-section steels to prevent the ground 29 from collapsing.

  Next, as shown in FIG. 3, the primary outer periphery excavation is performed. That is, the surface soil 30 is excavated and removed across the entire circumference of the existing building 8 between the outer peripheral wall 27 and the mountain retaining wall 36. Thereafter, a concrete retaining wall 40 is constructed on the inner peripheral side of the excavated mountain retaining wall 36.

  Further, a first-stage concrete horizontal constraining slab 42 surrounding the outer peripheral wall 27 is constructed horizontally at the height of the ground surface. The horizontal restraint slab 42 is provided so as to surround the outer peripheral wall 27 except for the excavation part P serving as a pier, and connects the outer peripheral wall 27 and the retaining wall 40. Thereby, even if an earthquake occurs during the period of excavation work, vibration of the existing building 8 can be suppressed.

  Subsequently, as shown in FIG. 4, secondary outer periphery excavation is executed. That is, the space between the outer peripheral wall 27 and the mountain retaining wall 36 is excavated to the bottom surface of the foundation portion 34. The retaining wall 40 is extended to the excavated mountain retaining wall 36 for construction. Further, the second stage horizontal restraint slab 44 is constructed below the first stage horizontal restraint slab 42 so as to surround the outer peripheral wall 27. Thereby, the vibration of the foundation part 34 of the existing building 8 is also suppressed.

Next, the vertical shaft construction process 12 is executed.
Specifically, as shown in FIG. 5, the ground 29 in the entrance portion (between the footing 23 </ b> A and the footing 24 </ b> A) is excavated to the excavation bottom surface 48. That is, the shaft is excavated between the retaining wall 40 and the retaining wall 40 in the excavation part P and around the footing 23A and the footing 24A. At this time, the ground 29 below the footings 23 </ b> A and 24 </ b> A is excavated from the surroundings while leaving the ground 47 within the envelope surrounded by the fracture envelope 46. For example, a cylindrical cylindrical ground 37A is left below the footing 23A, and a cylindrical cylindrical ground 38A is left below the footing 24A.

Accordingly, the footings 23A and 24A are supported by the cylindrical grounds 37A and 38A, respectively, and are continuously supported even if the surrounding ground 29 is deleted.
Here, the fracture envelope 46 is a line indicating a range in which the ground 29 can maintain its shape without being naturally collapsed by the load of the ground 29 itself even when excavated from the surroundings. It is formed. The cone shape varies depending on the type of soil and the water content constituting the ground 29.

Further, the excavation bottom surface 48 refers to the bottom surface of the excavation part excavated from the bottom surface of the foundation part 34 while ensuring a required excavation height. In the plan view of FIG. 5B, the ground 29 in the unexcavated part and the part being excavated is indicated by dots, and the ground 29 whose excavation depth has reached the excavation bottom surface 48 is indicated in white.

Next, the excavation process 14 is performed.
Specifically, as shown in FIG. 6, excavation under the base 34 is advanced in the same manner as the lower portions of the above-described footings 23A and 24A.
The excavation of the ground 29 is not limited, but in general, it is desirable to proceed from the entrance to the opposing outer peripheral wall 27. That is, it is advanced in the direction of the footings 24A, 24B, 24C.

As a result, the columnar grounds 37B and 38B that support the footings 23B and 24B are left under the footings 23B and 24B, and the columnar grounds 37C and 38C that support the footings 23C and 24C are left under the footings 23C and 24C. Is left uncut.
In the same manner, excavation under all the foundations 34 is advanced, and the cylindrical ground is left under the footing. In addition, in the construction procedure, in a place where the cylindrical ground has already been left uncut, a temporary support process described later may be started, and the excavation process 14 and the temporary support process may proceed in parallel.

Next, the temporary support process 16 is performed.
Specifically, as shown in FIG. 7 (A), the uppermost part of the cylindrical ground 38A left uncut at the bottom of the footing 24A is excavated from the periphery and shaped into a cylindrical part 60 having a height H1 and an inner diameter D1. . The fracture envelope 46 is formed downward from the end portion of the bottom surface of the footing 24A, and the lower portion is expanded in a cone shape. The inner diameter D1 is larger than the fracture envelope 46, and the enveloped ground 47 is left in the cylindrical portion 60 after shaping. Thereby, the footing 24A can be supported without collapsing. That is, the existing building 8 is supported.

  Next, as shown in FIG. 7B, the cylindrical portion 60 is enclosed by a ring 50 from the outside and restrained. The ring 50 is a metal ring having a height H2 (H2 <H1) and an inner diameter D1, and is divided into two. The division part is provided with a flange 50F for joining, and the flange 50F is provided with a through hole into which a fixing stopper is inserted.

  Next, as shown in FIG. 8, the ring 50 is integrated with a stopper (for example, a bolt and a nut) 52 using the through hole of the flange 50 </ b> F. Thereby, even if a disturbance is added, collapse of the outer peripheral part of the cylindrical part 60 is prevented.

  Thereafter, cement 56 is injected from an injection port 54 provided in the ring 50. As shown in FIG. 8B, the cement 56 is filled in a gap between the periphery of the envelope inner ground 47 and the inner peripheral surface of the ring 50, and improves the bearing strength of the envelope inner ground 47. As a result, the starting position of the fracture envelope 46 moves downward by the height H2 of the ring 50, and the fracture envelope 46 is formed downward from the bottom surface of the ring 50. FIG. 8B is a cross-sectional view taken along line X1-X1 in FIG.

  Next, as shown in FIG. 9A, the lower side of the ring 50 is shaped into a height H1 and an outer shape D1 to form a cylindrical portion 60. At this time, the upper end of the fracture envelope 46 has moved below the ring 50, and even if excavated with the outer shape D <b> 1, the envelope inner ground 47 remains, and the cylindrical portion 60 does not collapse.

  Next, as shown in FIG. 9B, the shaped cylindrical portion 60 is restrained by another ring 50. Thereafter, cement 56 is injected from the inlet 54 of the ring 50. Thereafter, the lower side of the ring 50 is further shaped into a height H1 and an outer shape D1 to form a cylindrical portion 60.

  The above procedure is repeated, and as shown in FIG. 9 (C), a plurality of rings 50 are sequentially restrained from the bottom of the footing 24A to the excavation bottom surface 48. Thereby, one temporary support part 58 is constructed under the footing 24A.

  The temporary support part 58 is constructed in a cylindrical shape with a diameter D3 smaller than the diameter D2 of the cylindrical ground 38A. However, by restraining the outer periphery with the ring 50, the envelope ground ground 47 is prevented from collapsing, and the ring 50 is filled with the cement 56, whereby the support strength of the envelope ground ground 47 is improved. As a result, the direct foundation can be continuously supported.

Next, in step 18, it is determined whether or not the temporary support process 16 is necessary.
Furthermore, when it is necessary to perform the temporary support process 16, the above-mentioned temporary support process 16 is repeatedly performed. And the temporary support process 16 is repeated until the lower part of all the footings is temporarily supported. When the lower portions of all the footings are temporarily supported, the temporary support process 16 is finished. In addition, the temporary support process 16 may be started in parallel with both the outer peripheral walls 27 facing each other, and may be ended in the existing building 8. Further, for the temporary support portion 58 that has finished the temporary support step 16, a jack replacement step 20 described later may be executed in parallel with the temporary support step 16.

Next, the jack replacement process 20 is executed.
Specifically, as shown in FIG. 10A, a jack 62 is provided around the temporary support portion 58, and the footing 24 </ b> A is supported by the jack 62. The jacks 62 only have to have the strength necessary to support the footing 24A, and a plurality of jacks 62 are provided between the excavation bottom surface 48 and the footing 24A in the vertical direction. In the same manner, all the temporary support portions 58 are replaced with the jacks 62.

Next, the temporary support part removal process 22 is performed.
Specifically, as shown in FIG. 10B, the temporary support portion 58 is removed while the footing 24 </ b> A is supported by the jack 62. That is, the ring 50 is removed, and the ground in the envelope 47 is removed. This process is repeated until all the temporary support portions 58 are removed. As a result, the base portion 34 is replaced by the jack 62.

Thereby, even if it does not construct a temporary receiving pile, the existing building 8 can be supported and a foundation foundation board can be directly excavated. In the present embodiment, the bottom surface of the footing is the ground receiving portion. However, the present invention is not limited to this, and may be the bottom surface of the foundation beam, for example. Moreover, when the vertical load from the existing building 8 is small, the arbitrary bottom face of a direct foundation may be sufficient.
In the present embodiment, the case of the footing foundation has been described as an example. However, the present invention is not limited to this, and may be a direct foundation. For example, the foundation can be applied to a solid foundation.

(Second Embodiment)
In the seismic isolation method for an existing building according to the second embodiment, the seismic isolation device is installed on the ground excavated by the excavation method for the direct foundation foundation of the existing building described in the first embodiment. This is a method for seismic isolation of existing buildings. Since the direct excavation method of the foundation base plate has been described, it will be omitted, and the installation method of the seismic isolation device will be described with reference to FIGS.

First, an example of expansion of an existing building to seismic isolation repair will be described with reference to FIGS.
As shown in FIG. 11, after excavation of the lower portion of the foundation portion 34 is completed and all the temporary support portions 58 are removed, a concrete pressure plate 64 is constructed on the excavation bottom surface 48.
At this time, although illustration is omitted, anchor bolts are embedded in a position below the footing 24A and where the seismic isolation lower foundation 66 is constructed. The lower part of the retaining wall 40 is integrated with the pressure plate 64. Further, the footing 24 </ b> A and the foundation beam 25 around the footing are reinforced with the reinforcing material 70.

  Thereafter, a seismic isolation base 66 made of concrete is constructed on the pressure plate 64. The seismic isolation lower foundation 66 is constructed at an inner central portion surrounded by the jack 62. After the seismic isolation lower foundation 66 is cured, the new isolation device main body 68 is installed. The lower part of the new isolation device main body 68 is fixed to the seismic isolation lower base 66. Also, anchor bolts 74 are embedded in the position of the seismic isolation upper base for fixing the upper part of the new isolation device main body 68.

Finally, as shown in FIG. 12, after the curing device main body 68 is cured 69, the seismic isolation upper foundation 72 is constructed on concrete on the breaking device main body 68.
Then, although illustration is abbreviate | omitted, the jack 62 is removed, the horizontal restraint slabs 42 and 44 are removed, the base part 34 is received by the new apparatus main body 68, and seismic isolation repair is complete | finished.

  In addition, as an example of development of the embodiment, the present invention can be applied to, for example, extension of an underground space, construction of an underground passage, and the like. That is, although not shown in the drawings, a underground space may be extended by building a column at the position of the temporary support portion 58 while being supported by the jack 62 on the foundation base plate excavated by this excavation method. Further, a wall body may be constructed on the foundation foundation board excavated by the present excavation method, and an underground passage may be formed between the wall bodies.

8 Existing building 23 Footing (ground receiving part)
24 Footing (ground receiving part)
29 Ground 34 Foundation (Direct foundation)
46 Fracture envelope 47 Ground in envelope 48 Bottom of excavation 50 Ring 56 Cement (filler)
58 Temporary support 62 Jack

Claims (6)

Vertical shaft construction process for constructing vertical shafts,
From the vertical shaft, from the direct foundation foundation of the existing building to the bottom of excavation, the ground below the ground receiving portion of the direct foundation is surrounded by a fracture envelope that is a boundary line where the ground collapses due to its own weight An excavation process for excavating the inner ground,
Temporary support step of shaping the envelope inner ground into a columnar shape, constraining the outer peripheral portion with a ring as a temporary support portion, and continuously supporting the existing building with the temporary support portion;
Excavation method for direct foundation foundation of existing building with   2. The method for excavating a direct foundation foundation of an existing building according to claim 1, wherein the temporary support step includes a filler injection step of injecting a filler into a gap between the ring and the ground in the envelope.   3. The excavation of the direct foundation foundation of the existing building according to claim 2, wherein the temporary support step implements the filler injection step every time the space between the direct foundation and the bottom of the excavation is constrained by the plurality of rings. Method.   The method for excavating a direct foundation foundation of an existing building according to any one of claims 1 to 3, wherein the ground receiving part is a column lower part or a foundation beam lower part of the existing building. After the temporary support step,
The existing installation of any one of Claims 1-4 which has a temporary support part removal process which installs a jack around the temporary support part, makes the jack support the existing building, and removes the temporary support part. Excavation method for direct foundation foundation of building.   A seismic isolation method for an existing building, wherein a seismic isolation device is installed between the existing building and the ground on the bottom of the excavation after the temporary support portion removing step according to claim 5.

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