JP6675173B2 - Foundation building method - Google Patents

Description

  The present invention relates to a foundation construction method.

  Patent Literature 1 below discloses a method for newly constructing a support pile in the ground below the existing building and newly constructing a pillar on the support pile to reinforce the foundation of the existing building in order to expand the existing building. Have been.

JP 2008-13926 A

  However, according to the construction method of Patent Document 1, the position of the newly installed pillar is limited to just above the support pile. Also, when the vertical load increases, the pile diameter must be increased as the cross-sectional area of the column increases. Therefore, there is a limit to the degree of freedom in designing an extension building.

  An object of the present invention is to increase the degree of freedom in designing a structure when renovating an existing structure or constructing a new structure above the existing structure in consideration of the above facts.

The method for constructing a foundation according to claim 1, wherein a steel pipe is laterally press-fitted into a lower ground of an existing structure, and the steel pipe is formed by digging a lower ground of the steel pipe from a horizontal direction. A step of installing a cylinder in the lower ground of the, building a pile on the lower ground from inside of the cylinder, a step of using the cylinder as a foundation beam , pillars of a new building on the upper surface of the cylinder Fixing , wherein the steel pipe is left on the lower ground of the existing structure.

  For example, in the case of an existing structure such as a road or a track, it is difficult to stop traffic and operation and cut the lower ground of the existing structure to install a cylinder, but according to the method for constructing a foundation according to claim 1, By excavating the lower ground of the existing structure from the lateral direction, a cylinder can be installed in the lower ground without stopping traffic and operation. Similarly, in existing structures, such as buildings, a cylinder can be installed in the lower ground without stripping the floor or foundation slab.

  Then, by constructing the pile from the inside of the cylindrical body to the lower ground, it is possible to obtain a foundation beam having a supporting strength with which the cylindrical body can support a column or the like.

  When the foundation beams and piles are provided in the lower ground of the existing structure and used as the foundation for the existing structure or the new structure to be built on the upper part of the existing structure, the piles are struck without the foundation beams. Compared with a structure in which one pillar and one pillar are provided, the pile diameter can be reduced and the scale of the structure can be increased. In addition, since the position where the new pillar is provided does not necessarily need to be directly above the pile, the degree of freedom of the pillar division is increased. Therefore, the degree of freedom in designing the structure is high.

  In the foundation construction method according to claim 2, in the foundation construction method according to claim 1, the cylindrical body is composed of a plurality of box culverts, and a reinforcing bar is arranged inside the box culvert and concrete is poured. .

  According to the foundation construction method of claim 2, by arranging reinforcing steel inside the box culvert and placing concrete, the box culvert can be integrated into a foundation beam, and the strength of the foundation beam can be increased. it can.

  In addition, for example, the pile head can bear a bending moment by rigidly contacting the box head and the box culvert. Alternatively, the semi-rigid contact between the pile head and the box culvert can reduce the transmission of bending moment and suppress the loss of the pile head.

  According to a third aspect of the present invention, in the foundation construction method according to the first or second aspect, a space is provided below the cylindrical body.

According to the foundation construction method of claim 3, while using the existing structure, construction work for providing a new space in the lower ground of the existing structure can be performed. For this reason, for example, it is possible to newly establish an overpass without stopping traffic on the road, or to newly construct an underground mall without stopping the operation of the train.
In one embodiment, a pillar is mounted on the upper part of the cylindrical body.
According to a fourth aspect of the present invention, the tubular body is installed along a direction in which the existing piles are arranged in the existing structure, and a footing for connecting the cylindrical body and the existing piles is formed.

  As described above, according to the basic construction method of the present invention, when renovating an existing structure or constructing a new structure above an existing structure, the degree of freedom in designing the structure can be increased. .

(A) is a front sectional view showing a state where the pipe roof is pressed into the lower ground in the foundation building method according to the first embodiment of the present invention, and (B) is a side sectional view. (A) is a front sectional view showing a state where a lower ground is dug from the lateral direction and a box culvert is arranged in the foundation construction method according to the first embodiment of the present invention, (B) is a side sectional view, (C) is an enlarged view of the joint part of the box culvert shown by the encircling line in (B). (A) is a front sectional view showing a state where a pile is constructed below the box culvert in the foundation construction method according to the first embodiment of the present invention, and (B) is a side sectional view showing a state where the pile is constructed. FIG. (A) is a front sectional view showing a state in which reinforcing bars are arranged inside the box culvert and columns are installed above the box culvert in the foundation building method according to the first embodiment of the present invention. () Is a side sectional view, and (C) is an enlarged view of the anchor bolt shown by a surrounding line in (B). (A) is front sectional drawing which shows the state which poured concrete in the foundation construction method which concerns on 1st Embodiment of this invention, (B) is a side sectional drawing, (C) is enclosed in (B). It is an enlarged view of the anchor bolt and the column base shown by the line. (A) is a front sectional view showing a state in which reinforcing bars are arranged inside the box culvert and side holes in the foundation building method according to the second embodiment of the present invention, and (B) is a plan view. FIG. 2 is a front sectional view showing a state in which a building has been built on the upper part of the track in the foundation building method according to the first embodiment of the present invention.

[First Embodiment]
Hereinafter, the basic construction method according to the first embodiment of the present invention will be described with reference to the drawings.

  First, an outline of the basic construction method according to the first embodiment will be described. As shown in FIG. 7, the foundation construction method according to the first embodiment is a method for constructing a foundation structure 14 of a building 12 to be constructed above a track 10. The foundation structure 14 includes a foundation beam 20 and a stake 40. Note that the track 10 is an example of an existing structure in the present invention, and includes a roadbed on which rails or the like on which a railcar travels are mounted, a platform of a station building, and the like. In addition, existing structures include roads, rivers, waterways, etc., in addition to structures such as buildings.

(Tube installation process)
Next, the basic construction method according to the first embodiment will be described for each process. First, a process of installing the cylindrical body 26 on the lower ground 16B of the track 10 will be described. As shown in FIG. 1B, first, a shaft 16A is formed on the ground 16. The opening of the shaft 16A is desirably provided on the ground surface near the track 10. However, when the ground surface 16C near the track 10 is used for a building or a passage, the opening is located away from the track 10. It may be provided.

  Then, the pipe roof 22 is press-fitted in the lateral direction (horizontal direction) from the shaft 16A toward the lower ground 16B (a part of the ground 16) of the track 10. The pipe roof 22 is a steel pipe body for suppressing the subsidence of the ground 16 and reducing the friction between the ground 16 and the box culvert 24 to improve workability when a box culvert 24 described later is propelled and constructed. It is constructed at a depth of about 2 to 3 m from the ground surface 16C. In addition, the said depth can be adjusted in the range of about 1-10 m according to conditions, such as the hardness of the ground 16 and the presence or absence of an existing underground structure.

  In addition, in this embodiment, the pipe roof 22 has a gate-type arrangement installed above the box culvert 24 as shown in FIG. 1A. May be arranged in a single character so as to cover a wider area than the box culvert 24, or may be arranged in a rectangular shape along the upper plate, the side plate, and the bottom plate of the box culvert 24. The pipe roof arranged along the upper plate of the box culvert 24 is effective in suppressing settlement of the ground 16. Further, the pipe roof arranged along the side plate of the box culvert 24 is effective for suppressing the side earth pressure received from the ground 16 and for suppressing the settlement of the ground 16. Furthermore, the pipe roof arranged along the bottom plate of the box culvert 24 is effective in suppressing the boiling and swelling of the ground 16 due to groundwater. In the present invention, these pipe roofs are appropriately selected. Can be used. When the lower ground is strong, the pipe roof 22 can be omitted.

  As shown in FIGS. 2A and 2B, after the pipe roof 22 is press-fitted, the ground 16 below the pipe roof 22 is excavated little by little, and the box culvert 24 is brought into sliding contact with the pipe roof 22 so as to slide. Propulsion is performed in the direction (the direction of the material axis of the pipe roof 22). The box culvert 24 is a tubular precast concrete member having a rectangular cross section, and a plurality of box culverts 24 are connected to each other so that the tube axis direction coincides with the material axis direction of the pipe roof 22 to form a long tubular body 26.

  As shown in the enlarged view of FIG. 2 (C), the box culverts 24 adjacent to each other in the cylinder axis direction are attached to a sleeve 24A embedded on the end face of one box culvert 24 and the other box culvert 24 to the other. The streak 24B protruding from the end face is inserted, grout is injected into the gap between the sleeve 24A and the streak 24B and connected. The difference bar 24B is embedded along the cylinder axis direction of the box culvert 24, and the other end is inserted into a sleeve 24A embedded on the opposite end surface. As a result, the difference bar 24B functions as a main bar of the box culvert 24, and the connected box culvert 24 is rigidly connected to function as the foundation beam 20.

  In the present embodiment, the box culvert 24 is used as a member constituting the cylindrical body 26, but the embodiment of the present invention is not limited to this. For example, an arch culvert having an arched cross section or a reinforced concrete pipe having a circular cross section may be used.

(Pile construction process)
Next, the pile 40 is constructed from the inside of the cylindrical body 26 to the lower ground 16B.
As shown in FIGS. 3A and 3B, in constructing the pile 40, first, a through hole 24 </ b> D is formed in the bottom plate of the box culvert 24, and the lower ground 16 </ b> B is excavated vertically downward to support the support layer. An excavation hole 42 is formed which reaches up to. The formation of the through hole 24D and the excavation hole 42 is performed using a drilling machine that can be installed and operated inside the box culvert 24. Next, a root consolidation liquid and a pile circumference fixing liquid are appropriately injected into the excavation hole 42, and the pile material 44 is inserted. The pile member 44 is an existing pile formed in advance of precast concrete. The pile member 44 is inserted into the excavation hole 42 while being connected vertically by a mechanical joint, and the pile 40 is constructed. A pile head reinforcement 48 protrudes from a pile member 44 installed on the pile head, and is fixed to concrete C described later. Thereby, the pile head of the pile 40 is rigidly connected to the foundation beam 20. Note that the axial length of the pile member 44 is shorter than the height of the space inside the box culvert 24.

  In the present embodiment, the excavation hole 42 is formed using a drilling machine, but it is not always necessary to use a machine, and the lower ground 16B may be excavated by hand excavation. Excavation by hand digging is applied to, for example, a deep foundation method of retaining earth using a corrugated steel plate and a ring frame. Further, the pile 40 is constructed by joining existing pile members 44 together, but as a cast-in-place pile in which a reinforcing steel cage is joined while being welded on site and inserted into the excavation hole 42, and concrete is poured into the excavation hole 42. Is also good.

(Upper excavation process)
Next, in order to install the column 12A of the building 12 on the upper surface of the foundation beam 20, the ground 16 above the cylindrical body 26 (box culvert 24) is excavated. The building 12 is a new structure to be constructed on the upper part of the track 10. In this step, as shown in the enlarged view of FIG. 4C, the ground 16 is dug vertically downward from the ground surface 16C at the installation location of the column 12A, penetrates through the exposed pipe roof 22, and the box culvert 24 To the top of the

(Bar arrangement process)
Next, as shown in FIGS. 4A and 4B, a reinforcing bar 28 as a main bar and a stirrup of the foundation beam 20 is arranged inside the cylindrical body 26.

(Pillar installation process)
Next, the column 12A in which the base plate 12C and the linear (not hook-shaped) anchor bolts 12B are integrated is placed on the upper part of the box culvert 24. At this time, the anchor bolt 12B is passed through the through hole 24E of the box culvert 24. Then, a nut is screwed into the anchor bolt 12B from inside the box culvert 24, and the column 12A is fixed to the box culvert 24. Further, a fixing hardware is fixed to the tip of the anchor bolt 12B, or the tip of the anchor bolt is bent like a hook as shown in FIG. 5C.

  In addition, the through hole of the pipe roof 22 and the through hole 24E of the box culvert 24 may be made larger than the outer periphery of the column 12A so as to penetrate the column 12A. In this case, by fixing the column 12A to the bottom plate of the box culvert 24, the column base of the column can be an embedded type having a high degree of fixing.

(Concrete casting process)
After the installation of the column 12A, concrete C is poured into the entire inside of the cylindrical body 26. Concrete C is placed and cast with an unillustrated formwork at the end of the cylindrical body 26 on the shaft 16A side, and after the concrete C is hardened, the shaft 16A is backfilled.

  By placing the concrete C in this manner, the column base of the pile 40 is rigidly connected to the foundation beam 20. A base plate 12C for fixing the column 12A is rigidly connected to the foundation beam 20 via an anchor bolt 12B.

  In the foundation construction method of the present embodiment, the foundation structure 14 including the foundation beams 20 and the piles 40 is constructed on the lower ground 16B of the track 10 by the above steps.

(Action and effect)
According to the foundation building method according to the present embodiment, the box culvert 24 is propelled by slidingly contacting the pipe roof 22 while excavating the lower ground 16B of the pipe roof 22 laterally from the shaft 16A. Until the lower ground 16 </ b> B is excavated and the box culvert 24 is propelled to the excavated portion, the load of the train running on the ground 16 and the track 10 at the upper portion of the excavated portion is supported by the pipe roof 22. Therefore, settlement of the lower ground 16B of the track 10 is suppressed. Therefore, the foundation beam 20 can be constructed without stopping the operation of the train on the track 10.

  In addition, the construction accuracy of the box culvert 24 for propulsion construction using the pipe roof 22 as a guide can be improved by constructing the pipe roof 22 with a small bend while confirming the construction accuracy using a transit or the like.

  Further, according to the foundation construction method according to the present embodiment, the foundation structure 14 including the foundation beams 20 and the stakes 40 becomes the foundation of the building 12 newly installed on the upper part of the track 10. The pile head of the pile 40 is rigidly connected to the foundation beam 20.

  On the other hand, when a new building is constructed without providing the foundation beam 20, a pillar-by-pile foundation structure is adopted in which only the piles support the axial force of the columns of the new building.

  For example, when compared with a case where a building of the same scale is newly constructed, the pile 40 in the present embodiment has a proof strength compared with a pillar-and-pile type foundation structure because the pile head is connected and fixed by the foundation beam 20. Larger, smaller pile diameter. Alternatively, in comparison with the case where the pile diameter of the pile 40 in the present embodiment is equal to the pile diameter in the one-pillar-one-pile foundation structure, in the present embodiment, the scale of a newly-installed building can be increased.

  In addition, for example, as shown in FIG. 7, when a long-span frame is newly constructed, the pile 40 in the present embodiment is constructed from inside the box culvert 24. (300 mm to ∞ mm). In other words, the cross-sectional dimension of the box culvert 24 can be increased according to the pile diameter, or a plurality of the box culverts 24 can be connected in a direction orthogonal to the cylinder axis direction, so that the digging area of the digging hole can be appropriately secured. Thereby, it is possible to provide a foundation structure having sufficient strength to support a long span frame.

  On the other hand, in the case of a one-pillar-one-pile foundation structure, the pile is excavated from the ground surface 16C as shown by the broken line G in FIG. Cannot be used during construction.

  In the foundation construction method according to the present embodiment, the foundation beam 20 is constructed between the pile 40 and the column 12A. Therefore, the position where the column 12A is provided does not necessarily need to be directly above the pile 40. Therefore, the degree of freedom of the pillar splitting is increased as compared with the one-column-one-pile type foundation structure in which the column position is limited to immediately above the pile.

[Second embodiment]
Next, a foundation construction method according to the second embodiment will be described. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  First, an outline of the foundation building method according to the second embodiment will be described. The foundation construction method according to the second embodiment is a method of constructing a foundation structure 54 for reinforcing the foundation (existing pile 52B) of the existing building 52. As shown in FIG. 6 (A), the existing building 52 is provided with a foundation structure of a one-post-one-pile type in which an existing pillar 52A is supported by an existing pile 52B. The foundation structure 54 for reinforcing the foundation structure (the existing pile 52B) includes a foundation beam 60, a pile 80, and a footing 90 connecting the existing pile 52B and the foundation beam 60.

(Tube installation process)
Next, a foundation building method according to the second embodiment will be described for each step. Similarly to the foundation construction method of the first embodiment, first, a not-shown shaft is formed on the ground 56 near the existing building 52, and from the shaft, the lower ground 56B (a part of the ground 56) of the existing building 52 is formed. The pipe roof 62 is press-fitted in the lateral direction (horizontal direction) along the arrangement direction L of the existing pile 52B.
Then, after press-fitting the pipe roof 62, the box culvert 64 is propelled while excavating the ground 56 below the pipe roof 62, and the box culvert 64 is connected to form a cylinder 66. At this time, the box culvert 64 is constructed along the disposition direction L of the existing pile 52B similarly to the pipe roof 62 (see FIG. 6B).

(Pile construction process)
Next, a through hole 64D is formed in the bottom plate of the box culvert 64, and the lower ground 56B is excavated to form an excavation hole 82. A piling material and a pile fixing liquid are appropriately injected into the excavation hole 82, a pile material 84 formed in advance by precast concrete is inserted, and the pile materials 84 are joined to form the pile 80. Although not shown, a pile head reinforcing bar protrudes from a pile member 84 installed on the pile head, and is fixed to concrete C described later. Thereby, the pile head of the pile 80 is rigidly connected to the foundation beam 60.

(Side hole forming process)
Next, a step of forming an opening 64E in the side wall of the cylindrical body 66 and forming a side hole 92 afterward in order to form the footing 90 for connecting the existing pile 52B and the foundation beam 60 will be described.

  First, a perforation (not shown) is formed in the side wall of the box culvert 64, and a ground improvement material is injected into the lower ground 56B from the perforation to improve the ground around the existing pile 52B. As shown in FIGS. 6 (A) and 6 (B), the area for soil improvement is the area M which encloses a side hole 92 which will be described later. Infiltrate the ground improvement material to the back side of 52B.

  After the ground improvement, the side wall of the box culvert 64 is stripped to form an opening 64E, and the lower ground 56B is dug laterally (horizontally) from the opening 64E toward the existing pile 52B to envelop the existing pile 52B. The area of soil is removed to form side holes 92.

(Concrete casting process)
Next, a process of casting concrete into the cylindrical body 66 and the side holes 92 to construct the foundation beam 60 will be described. As shown in FIGS. 6A and 6B, after constructing the pile 80 or forming the side hole 92, the reinforcing bar 68 as the main bar and the stirrup of the foundation beam 60 is arranged inside the cylindrical body 66. I do. Furthermore, a reinforcing bar 98 as a main bar of the footing 90 is arranged inside the side hole 92. After the reinforcing bars 68 and 98 are arranged, concrete C is poured into the entire inside of the cylindrical body 66 and the side holes 92. Thereby, the foundation beam 60 and the footing 90 are formed.

  In this way, the foundation structure 54 that includes the foundation beam 60, the pile 80, and the footing 90 in the lower ground 56B of the existing building 52 and reinforces the foundation of the existing building 52 (the existing pile 52B) is constructed.

(Action and effect)
According to the foundation construction method according to the present embodiment, a pipe roof 62 and a box culvert 64 are constructed from a shaft formed on the ground 56 near the existing building 52 to construct the foundation beam 60. For this reason, it is not necessary to remove the floor of the existing building 52 and the foundation slab, install a drilling machine in the foundation slab, and cut the lower ground 56B from the upper part. Therefore, for example, at the time of renovation for expanding the existing building 52 or changing the usage, the reinforcing work of the foundation structure can be performed while using the existing building 52.

[Modification]
Next, a modification of the above embodiment will be described. In the first embodiment, only the pile 40 reaching the support layer is constructed below the box culvert 24. However, the embodiment of the present invention is not limited to this. The underground space may be formed below the box culvert 24 by laying on the ground 16B.

  At this time, instead of the pile 40, a pile having a pile head located at the lowermost part of the underground space to be formed is constructed, and a trussed pillar is erected in the pile and solidified. In addition, a capital is provided at the capital of the vertical shaft so that the vertical shaft can support the load of the box culvert 24, and is integrated with the box culvert 24.

  Thereafter, a sill is constructed at the lower part of the box culverts 24 and 64 to perform earth retaining, and the shaft formed for constructing the box culvert 24 is dug further downward, and the lower ground 16B of the box culvert 24 is removed from the shaft. Excavate. At this time, an underground space is formed while appropriately constructing beams and slabs on the columns.

  In this way, the construction for providing a new space in the lower ground 16B, 56B can be performed while using the track 10 and the existing building 52.

  In the first and second embodiments, the pile head reinforcements 48 and 88 are provided on the piles 40 and 80, respectively, and are rigidly connected to the foundation beams 20 and 60. However, the embodiment of the present invention is not limited to this. I can't. For example, the pile head and the foundation beams 20 and 60 may be semi-rigidly connected without providing the pile head reinforcing bars 48 or reducing the number thereof. By making the pile head and the foundation beams 20 and 60 semi-rigidly contact, transmission of bending moment from the foundation beams 20 and 60 to the piles 40 and 80 can be reduced, and loss of the pile head can be suppressed. Thus, the method of fixing the pile head can be appropriately selected.

Further, in the first and second embodiments, the concrete C is cast on the entire inside of the cylindrical bodies 26 and 66, but the embodiment of the present invention is not limited to this. For example, if the strength as a foundation beam can be secured, it is sufficient to drive only the lower portions of the cylindrical bodies 26 and 66. Alternatively, a formwork may be arranged so as to surround the periphery of the pile head reinforcing bars 48, 88 of the piles 40, 80 shown in FIG. 3, and the concrete C may be poured only around the pile head. . Further, when it is not necessary to increase the degree of fixation of the piles 40 and 80 to the foundation beams 20 and 60 as described above, a pile cap is provided at the pile head to apply a vertical load from the foundation beams 20 and 60 to the pile head. The concrete C need not be cast. That is, the amount of concrete C to be poured in the first and second embodiments can be reduced as appropriate.
By reducing the amount of concrete C to be cast, a cavity is formed inside the cylinders 26 and 66, and the cavity can be used as, for example, an underground passage or a common groove for piping.

  As described above, the present invention may be appropriately combined with the above-described embodiment and various modifications, and may be embodied in various modes without departing from the gist of the present invention.

10 orbit (existing structure)
16B, 56B Lower ground 20, 60 Foundation beam 24, 64 Box culvert 26, 66 Cylindrical body 28, 68 Reinforcing bar 40, 80 Pile 52 Existing building (existing structure)
C Concrete V Underground space (space)

Claims (4)

A process of laterally pressing a steel pipe into the lower ground of an existing structure;
Digging the lower ground of the steel pipe body from the lateral direction and installing a tubular body in the lower ground of the steel pipe body,
Constructing a pile on the lower ground from the inside of the cylindrical body, and using the cylindrical body as a foundation beam;
Fixing a pillar of the new building on the upper surface of the cylindrical body,
Has, the steel pipe is left in the lower ground of the existing structure,
How to build a foundation. The cylinder is composed of a plurality of box culverts,
The foundation construction method according to claim 1, wherein a reinforcing bar is arranged inside the box culvert and concrete is cast.   The foundation construction method according to claim 1 or 2, wherein a space is provided below the cylindrical body. A process of laterally pressing a steel pipe into the lower ground of an existing structure;
Digging the lower ground of the steel pipe body from the lateral direction and installing a tubular body in the lower ground of the steel pipe body,
Constructing a pile in the lower ground from the inside of the cylindrical body, and using the cylindrical body as a foundation beam,
Installing the cylindrical body along the direction of arrangement of the existing piles in the existing structure,
A foundation construction method for forming a footing connecting the cylindrical body and the existing pile.

Images