JP6710999B2 - Temporary receiving method for existing structures - Google Patents

Description

The present invention relates to a method for temporarily receiving an existing structure supported by a footing foundation.

BACKGROUND ART Conventionally, a seismic isolation retrofit has been known in which a seismic isolation device is incorporated into a foundation or an intermediate layer of an existing structure to make the existing structure a seismic isolated structure without being significantly modified. Above all, when installing a seismic isolation device under the foundation of an existing structure, the vertical load of the existing structure is transferred from the existing foundation to a temporary receiving member, and then the seismic isolation device is installed under the foundation. It becomes necessary to provide a space for interposing.

For example, in Patent Document 1, first, the bottom of a foundation beam that connects footing foundations is first excavated to reinforce the foundation beam, then the bottom of the reinforced foundation beam is secondarily excavated, and then the bottom of the foundation beam and the excavated bottom surface are A temporary receiving member is installed between them. Next, the footing foundation is excavated with the temporary receiving member temporarily receiving the total vertical load of the existing building, and a pressure plate is constructed below the footing foundation. Then, a temporary receiving member is installed between the pressure plate and the footing foundation, and the total vertical load of the existing building is changed from the temporary receiving member under the foundation beam to the temporary receiving member under the footing foundation.

After this, after removing the temporary receiving member under the foundation beam and constructing a pressure resistant plate below the foundation beam, a temporary receiving member is installed between the pressure resistant plate and the foundation beam to foot the entire vertical load of the existing building. Replace the temporary receiving member under the foundation with the temporary receiving member under the foundation beam, and remove the temporary receiving member under the footing foundation. A seismic isolation device is installed in the space between the pressure plate and the footing foundation thus formed.

JP, 2011-7008, A

In the above method, in the case of secondary excavation under the reinforced foundation beam, if the floor slab can be removed, the excavation work under the foundation beam and the temporary receiving member of the area surrounded by the foundation beam and open above Installation can be performed efficiently.

However, under the condition that the floor slab cannot be removed, a work pit that can pass under the foundation beam of the existing structure is constructed by excavating between adjacent footing foundations to a depth where temporary support members can be installed under the foundation beam. After reinforcing the foundation beam, after the secondary excavation from the work pit toward the footing foundation under the foundation beam to the bottom depth of the work pit, the temporary receiving member is installed. In this case, for example, when the excavated slope becomes steeper than the internal friction angle, the slope is likely to collapse and the safety of the operator cannot be ensured. Further, as the footing foundation is approached, the area affected by the stress is excavated, and if the ground does not have sufficient bearing capacity, the ground may loosen under the footing foundation and uneven settlement may occur.

On the other hand, as a general conventional method under the condition that the floor slab cannot be removed, a work pit is constructed between adjacent footing foundations, and after performing primary excavation to the bottom level of the footing foundations, the footing foundations and foundations are A method is known in which the beam is reinforced and then a secondary pile is excavated under the foundation beam while placing a temporary receiving pile in the work pit.

In both cases of the method described in Patent Document 1 and the general conventional construction method, when secondary excavation under the foundation beam is performed, not only is earth retaining provided, but also a space under the foundation beam is provided each time the excavation proceeds. Temporary receiving members or temporary receiving piles must be installed one by one and the vertical load of the existing building supported by the footing foundation must be changed stepwise, which is complicated and the construction is likely to take a long time.

The present invention has been made in view of such problems, and its main purpose is to efficiently temporarily receive a vertical load of an existing structure directly supported by a footing foundation even in an environment in which a floor slab cannot be removed. It is to provide a temporary receiving method for existing structures that can be done.

To achieve the above object, temporary supporting method of the existing structure of the present invention is a temporary supporting method of existing structures for receiving temporary vertical load directly supported existing structures in footing foundation, primary As excavation, the intermediate position of the adjacent footing foundations is excavated to a depth below the bottom surface of the footing foundation to construct a groove-like working pit, and the periphery of the foundation beam is excavated to the depth of the bottom surface of the footing foundation to provide a reinforcement space. a first step of constructing a, by using the reinforcing space, a second step of reinforcing the foundation beam and footing foundation, and a third step of ground improvement the footing foundation and under its periphery two As the next excavation, a fourth step of excavating the ground under the foundation beam leaving the ground under the footing foundation to a depth from the work pit toward the footing foundation to the bottom of the work pit , A fifth step of placing a temporary support pile under at least one of the foundation beam and the footing foundation.

According to the method for temporarily receiving the existing structure of the present invention described above, the ground slab can be removed because the excavation slope is less likely to collapse by performing the secondary excavation under the foundation beam after performing the ground improvement. Instead, it is possible to safely perform the secondary excavation even when a working pit is constructed under the floor slab and the secondary digging is advanced from the working pit toward the footing foundation. Further, after the secondary excavation, it is possible to drive a temporary support pile near the footing foundation under the foundation beam, so that the reinforcement for improving the bending resistance of the foundation beam can be reduced.

In addition, since the ground strength under the footing foundation is improved by improving the ground under the footing foundation, depending on the load of the existing structure, secondary excavation may be performed without placing temporary support piles under the foundation beam. It can be carried out. In this case, when performing secondary excavation under the foundation beam, it is possible to install a large number of temporary receiving members under the foundation beam and omit the work of stepwise reassembling the vertical load of the existing structure on the temporary receiving member. It is possible to significantly improve the workability of secondary excavation.

Further, in the temporary receiving method for the existing structure of the present invention, in the fourth step, secondary excavation under the foundation beam is performed, and the ground remaining under the footing foundation is constrained by a constraining member. Characterize.

According to the above-described method for temporarily receiving an existing structure according to the present invention, the ground strength under the footing foundation is significantly improved by both the ground improvement and the restraining member. Therefore, it is possible to support even when the vertical load applied to the footing foundation is large.

According to the present invention, by performing the secondary excavation under the foundation beam after improving the ground under the footing foundation and its surroundings, even in an environment where the floor slab cannot be removed, the work pit constructed under the floor slab is used. Therefore, it becomes possible to efficiently and safely carry out the work related to the temporary receiving work of the existing structure.

It is a figure which shows the procedure of 1st Embodiment of the temporary receiving method of the existing structure in this invention (the 1). It is a figure which shows the procedure of 1st Embodiment of the temporary receiving method of the existing structure in this invention (the 2). It is a figure which shows the procedure of 1st Embodiment of the temporary receiving construction method of the existing structure in this invention (the 3). It is a figure which shows the procedure of 1st Embodiment of the temporary receiving construction method of the existing structure in this invention (the 4). It is a figure which shows the procedure of 1st Embodiment of the temporary receiving construction method of the existing structure in this invention (the 5). It is a figure which shows the procedure of 1st Embodiment of the temporary receiving construction method of the existing structure in this invention (the 6). It is a figure which shows the procedure of 2nd Embodiment of the temporary receiving construction method of the existing structure in this invention (the 1). It is a figure which shows the procedure of 2nd Embodiment of the temporary receiving construction method of the existing structure in this invention (the 2). It is a figure which shows the procedure of 2nd Embodiment of the temporary receiving construction method of the existing structure in this invention (the 3). It is a figure which shows the procedure of 3rd Embodiment of the temporary receiving construction method of the existing structure in this invention (the 1). It is a figure which shows the procedure of 3rd Embodiment of the temporary receiving construction method of the existing structure in this invention (the 2). It is a figure which shows the procedure of 4th Embodiment of the temporary receiving construction method of the existing structure in this invention (the 1). It is a figure which shows the procedure of 4th Embodiment of the temporary receiving construction method of the existing structure in this invention (the 2). It is a figure which shows the procedure of 4th Embodiment of the temporary receiving construction method of the existing structure in this invention (the 3).

INDUSTRIAL APPLICABILITY The present invention is adopted, for example, when performing a seismic isolation retrofit in which a space is provided under a footing foundation to interpose a seismic isolation device, and a part of the vertical load of an existing structure is temporarily used as a temporary support pile. It is an invention relating to a method of temporarily receiving. Hereinafter, the method for temporarily receiving the existing structure will be described in detail with reference to FIGS. 1 to 14.

As shown in FIG. 1A, the existing structure 1 is a structure supported by a footing foundation 21, and the footing foundations 21 are connected to each other via foundation beams 22. Then, the floor slab 3 is installed above the foundation beam 22, but in the present embodiment, a temporary receiving pile is installed under the footing foundation 21 or the foundation beam 22 without removing the floor slab 3, and the existing slab is installed. A method of temporarily receiving the vertical load of the structure 1 will be described step by step.

<First embodiment>
First, in the first step, as shown in FIG. 1( b ), a work pit 4 is constructed, primary excavation is performed below the floor slab 3 of the existing structure 1, and the footing foundation 21 and foundation beam 22 are reinforced. The reinforcement space 5 for constructing is constructed. As shown in the plan view of FIG. 6A, the work shaft 4 is a groove constructed so as to be orthogonal to the foundation beam 22, and is an intermediate portion of the footing foundations 21 adjacent to each other so as to pass below the foundation beam 22. It is arranged at each position and excavated to a depth below the bottom surface of the footing foundation 21. In addition, the reinforcing space 5 may be provided with an appropriate space depending on the shapes of the footing foundation 21 and the foundation beam 22 after reinforcement, and in the present embodiment, the plane direction of the footing foundation 21 and the foundation beam 22. The reinforcing space 5 is provided in the beam width direction and the beam formation direction.

Next, in the second step, as shown in FIG. 2A, the footing foundation 21 and the foundation beam 22 are reinforced by utilizing the reinforcing space 5. These reinforcing methods may be performed by pasting a carbon fiber sheet, installing a steel plate, or the like, but in the present embodiment, the cross-section of the foundation beam 22 is increased by placing additional concrete, and the reinforcement foundation beam is The footing foundation 21 is reinforced according to the cross section of 62.

When the reinforcement of the foundation 2 is completed, in the third step, as shown in FIG. 2B, the first temporary receiving pile 7 is driven in the work pit 4 located below the reinforcing foundation beam 62. Any method may be used to drive the first temporary receiving pile 7, but in the present embodiment, the underpinning method is used.

The underpinning method is a method that is generally widely used when correcting the subsidence of an unevenly set direct foundation, and specifically, the reaction force of a jack (not shown) is applied to the lower surface of the reinforcing foundation beam 62. While taking it, the first temporary receiving pile 7 is pressed into the ground and placed. After driving the first temporary receiving pile 7, the jack is removed, and the piece member 71 is installed between the pile head of the first temporary receiving pile 7 and the reinforcing foundation beam 62. Thereby, a part of the vertical load of the existing structure 1 transmitted from the reinforcing foundation beam 62 can be efficiently transmitted to the first temporary receiving pile 7 via the piece member 71.

As shown in the plan views of FIGS. 3(a) and 6(b) in conjunction with this work, the ground G below and around the reinforcing footing foundation 61 is improved to include the surrounding ground including the lower portion of the reinforcing footing foundation 61. Improve the G bearing capacity. Although any ground improvement method may be adopted, the chemical solution injection method is adopted in the present embodiment. Specifically, an injection hole is constructed from the side from the work pit 4 toward the lower region of the reinforcing footing foundation 61 by a boring drill (not shown). Then, the chemical liquid 10 is press-fitted into the ground G by the chemical liquid injector M through the injection hole, and the ground G below and around the reinforcing footing foundation 61 is solidified by penetration.

In the fourth step, as shown in FIG. 3( b ), the ground G below the reinforcing footing foundation 61 is left and the lower part of the reinforcing foundation beam 62 is moved toward the reinforcing footing foundation 61 from the work pit 4. Secondly excavate to the depth of the excavation bottom of the work pit 4. At this time, since the ground G below and around the reinforcing footing foundation 61 has been improved, the slope of the excavation slope does not collapse even if the excavation slope is steep. Therefore, even when secondary excavation is carried out from the work pit 4 constructed below the bottom surface of the reinforcing footing foundation 61, if the vertical load of the existing structure 1 is relatively light, earth retaining is not performed and the efficiency is safe. It is possible to carry out excavation work well.

After that, in the fifth step, as shown in the plan views of FIGS. 4A and 6C, the first position is located below the reinforcing foundation beam 62 and at a position close to the joint with the reinforcing footing foundation 61. 2 temporary support pile 8 is installed. As a result, the vertical load of the existing structure 1 is shared by the three members of the first and second temporary receiving piles 7 and 8 and the reinforcing footing foundation 61, which are installed on the reinforcing foundation beam 62, to temporarily receive the temporary load. Will be supported.

The ground G below and around the reinforcing footing foundation 61 can easily excavate the ground G around the reinforcing footing foundation 61, and after excavating the surrounding ground G, the vertical load of the existing structure 1 It is advisable to improve a part of the reinforcing footing foundation 61 so that the reinforcing footing foundation 61 can exhibit sufficient strength.

As a result, the secondary excavation can be performed while part of the vertical load of the existing structure 1 is being borne by the reinforcing footing foundation 61, so that it is possible to safely perform the secondary excavation and the reinforcing footing foundation 61 and Since the second temporary receiving pile 8 can be driven at a position close to the joint portion, the reinforcement for improving the bending resistance of the foundation beam 22 can be reduced.

As described above, after the vertical load of the existing structure 1 is temporarily supported by the three members, that is, the first temporary receiving pile 7 and the second temporary receiving pile 8 and the reinforcing footing foundation 61, the vertical load of FIG. As shown in (b), while the remaining ground G under the reinforcing footing foundation 61 is removed, the third temporary support pile 9 is driven at a position close to the peripheral edge under the footing foundation, and the reinforcement footing foundation 61 The working space 12 is formed below and below the foundation beam 22.

As shown in FIG. 5A, tertiary excavation is performed to secure the space 13 for constructing the seismic isolation pit 14. Then, as shown in FIG. 5(b), after placing the bottom concrete 141 on the excavation bottom of the tertiary drilling, the seismic isolation foundation 151 and the seismic isolation device 152 are provided between the bottom concrete 141 and the reinforced footing foundation 61. Install. Finally, the parts of the first temporary pile 7, the second temporary pile 8 and the third temporary pile 9 that project upward from the bottom concrete 141 are cut and removed to reinforce all vertical loads of the existing structure 1. The work is finished by exchanging it with the foundation 61.

It should be noted that both the second temporary pile 8 and the third temporary pile 9 may be driven by the underpinning method like the first temporary pile 7, and although not shown, the first temporary pile 7, A watertight cap may be installed on the pile heads of the second temporary pile 8 and the third temporary pile 9 after cutting.

<Second Embodiment>
By the way, when the vertical load borne by the footing foundation 21 is large, or when the ground strength required for the ground G cannot be obtained only by the ground improvement, the reinforcement footing foundation 61 is used to carry out the temporary receiving method for the existing structure. It is advisable to restrain and reinforce the ground G, which is left below, with the restraining member 11. Therefore, in the second embodiment, a method of temporarily receiving the existing structure 1 using the restraint member 11 will be described.

From the first step of performing the primary excavation down to the footing foundation 21 and the foundation beam 22 of the existing structure 1, the footing foundation 21 and the foundation beam 22 are reinforced, and the first temporary receiving pile 7 is driven and reinforced. Up to the third step of ground improvement of the ground G below and around the footing foundation 61, it is the same as in the first embodiment. Thereafter, in the fourth step, as shown in FIG. 8B, the secondary excavation is divided into a plurality of stages from the upper side to the lower side, and the secondary excavation is left below the reinforcing footing foundation 61 for each stage of excavation. The restrained member 11 restrains the ground G thus made.

Specifically, as shown in FIG. 7A, the surrounding ground G excluding the portion immediately below the reinforcing footing foundation 61 is scraped off from just below the reinforcing foundation beam 62 to a certain depth, and the reinforcement remaining after this is removed. The ground G under the footing foundation 61 is constrained by the constraining member 11 as shown in the plan view of FIG. The restraint member 11 may be any metal band, carbon fiber sheet, or the like that is commonly used when reinforcing a concrete member, but in the present embodiment, a frame member having a rectangular shape in plan view which is a combination of steel materials is adopted. ing.

Here, if a frame member is adopted as the restraint member 11, a gap is created between the restraint member 11 and the ground G left below the reinforcing footing foundation 61, and the restraint effect by the restraint member 11 cannot be sufficiently obtained. Occurs. Therefore, as shown in the plan view of FIG. 8A, a grout injection port 111 is provided in a frame material forming the restraint member 11, and a hardening material C such as grout is injected into a gap between the ground G and the restraint member 11. Good to fill.

As shown in FIG. 8(b), the above work is repeated step by step from the upper side to the lower side, so that FIG. 9(a) is provided below the reinforcing footing foundation 61 after the completion of the secondary excavation. The ground G and a plurality of constraining members 11 for constraining the ground G are arranged as shown in FIG. Then, in a fifth step, a second temporary receiving pile 8 as shown in FIG. 9B is installed below the reinforcing foundation beam 62 and in the vicinity of the joint with the reinforcing footing foundation 61. As a result, the vertical load of the existing structure 1 is shared by the three members of the first and second temporary receiving piles 7 and 8 and the reinforcing footing foundation 61, which are installed on the reinforcing foundation beam 62, to temporarily receive the temporary load. Will be supported.

Thereafter, the restraining member 11 is removed to expose the ground G left below the reinforcing footing foundation 61 as shown in FIG. 4A, and while removing the ground G, as shown in FIG. It suffices to drive the third temporary receiving piles 9 below 61 and form the working space 12 below the reinforcing footing foundation 61 and below the foundation beam 22 as in the first embodiment.

As described above, in the fourth step, the vertical load of the existing structure 1 is shared by the ground G that is left below the reinforcing footing foundation 61 and is restrained by the restraining member 11 and the first temporary receiving pile 7. Is in a state. Therefore, even if the vertical load borne by the footing foundation 21 is large or if the ground strength required for the ground G cannot be obtained only by ground improvement, until the second temporary bearing pile is driven in the fifth step. During this time, it is possible to proceed with work safely.

In addition, in this Embodiment, although the 3rd temporary receiving pile 9 was drive|operated below the reinforcement footing foundation 61, it is not necessarily limited to this. For example, when the load of the existing structure 1 is small enough to support the vertical load of the existing structure 1 by the first temporary pile 7 and the second temporary pile 8 installed on the lower surface of the reinforcing foundation beam 62, or When the proof footing foundation 61 and the reinforced foundation beam 62 have sufficient proof stress against the load of the existing structure 1, even if the step of installing the third temporary receiving pile 9 on the reinforced footing foundation 61 is omitted. Good.

<Third Embodiment>
In the third embodiment, as shown in FIG. 4( a ), after the second temporary receiving pile is placed below the foundation beam 62, as shown in FIG. 4( b ), the reinforcing footing foundation 61 is provided. An example of a placing procedure when placing the third temporary receiving pile below the is shown.

First, a part of the ground G left below the reinforcing footing foundation 61 is divided so that each of the sections A, B, C, and D includes one corner, as shown in the plan view of FIG. 11. Next, the ground G in the area corresponding to the section A of the reinforcing footing foundation 61 is cut, and the third temporary receiving pile 9 as shown in FIG. Such work is sequentially performed on all the sections A, B, C, and D.

Then, as shown in the plan view of FIG. 11, the third temporary receiving piles 9 are driven at each of the four corners of the reinforcing footing foundation 61. Thus, the vertical load of the existing structure 1 is, as shown in FIG. 10B, the first temporary receiving pile 7 and the second temporary receiving pile 8 installed on the reinforcing foundation beam 62, and the reinforcing footing foundation 61. The third temporary receiving pile 9 that is placed below the first temporary receiving pile 9 shares and temporarily supports the third temporary receiving pile 9. As a result, there is no situation in which the vertical load applied to the reinforcing footing foundation 61 is supported only by the foundation beams 22, and the ground under the reinforcing footing foundation 61 or the first to third temporary receiving piles 7, 8, and 9 are always shared. Therefore, the reinforcement of the foundation beam 21 can be reduced.

<Fourth Embodiment>
On the other hand, in carrying out the fourth step and the fifth step, when the load of the existing structure 1 is small or the ground is improved by the ground improvement so that the first temporary pile 7 and the second temporary pile 8 are unnecessary. When it is possible to secure the required earth bearing strength for G, the step of placing the first temporary pile 7 and the second temporary pile 8 can be omitted. Therefore, in the fourth embodiment, a method of temporarily receiving the existing structure 1 only by the third temporary receiving pile 9 will be described.

From the first step of performing the primary excavation down to the footing foundation 21 and the foundation beam 22 of the existing structure 1 to the second step of reinforcing the footing foundation 21 and the foundation beam 22, the same as in the first embodiment. Is. Thereafter, in the third step, as shown in FIG. 12A, the work pit 4 located below the reinforcing foundation beam 62 is utilized to improve the ground G below the reinforcing footing foundation 61 and the surrounding area thereof, The bearing capacity of the surrounding ground G including the lower portion of the reinforcing footing foundation 61 is improved.

Next, in the fourth step, as shown in FIG. 12B, the ground G below the reinforcing footing foundation 61 is left, and the reinforcing foundation beam 62 is moved from the work pit 4 toward the reinforcing footing foundation 61. Secondary drilling is performed below to a depth reaching the drilling bottom of the work pit 4. After that, in the fifth step, as shown in FIG. 13(b), the third temporary receiving pile 9 is driven under the reinforcing footing foundation 61 by the method shown in the third embodiment. To do.

That is, a part of the ground G left below the reinforcing footing foundation 61 is divided so that each of the sections A, B, C, and D includes one corner, as shown in the plan view of FIG. Next, the ground G in the area corresponding to the section A of the reinforcing footing foundation 61 is cut, and the third temporary receiving pile 9 as shown in FIG. Such work is sequentially performed on all the sections A, B, C, and D.

According to the above-mentioned method for temporarily receiving the existing structure, since the ground proof strength under the reinforcing footing foundation 61 is improved by performing the ground improvement, the first temporary receiving pile 7 and the second temporary receiving pile 7 are provided under the reinforcing foundation beam 62. Since the secondary excavation can be performed without placing the temporary receiving piles 8, the workability can be significantly improved.

Needless to say, the method for temporarily receiving the existing structure of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, the shapes of the ground G and the restraint member 11 left under the reinforcing footing foundation 61 are not necessarily limited to the rectangular shape in plan view. For example, when the restraint member 11 is formed in a circular shape in plan view, stress is distributed and the shape in plan view can be reduced.

Further, in the work pit 4, an operator can excavate the ground G and place the first to third temporary receiving piles 7, 8 and 9 and can carry in/out and install the chemical liquid injector M. For example, the cross-sectional shape may be any, but it is preferable to secure a width of about 2000 to 2500 mm and a height of about 1200 to 1500 mm. Also, as for the reinforcing space 5, it is only necessary to secure a necessary space according to the reinforcing method. For example, when reinforcement is performed by placing additional concrete, the additional space (for example, about 300 mm) is added to the working space. It is advisable to secure a degree to which necessary dimensions (for example, about 200 to 300 mm for installing a mold, etc.) are added.

1 Existing structure 21 Footing foundation 22 Foundation beam 3 Floor slab 4 Work mine 5 Reinforcement space 61 Reinforcement footing foundation 62 Reinforcement foundation beam 7 First temporary receiving pile 71 Piece member 8 Second temporary receiving pile 9 Third temporary receiving Pile 10 Chemical solution 11 Restraint member 111 Chemical solution inlet 12 Working space 13 Space for seismic isolation pit 14 Seismic isolation pit 141 Bottom concrete 151 Seismic isolation foundation 152 Seismic isolation device G Ground M Chemical fluid injection machine

Claims (2)

A method of temporarily receiving an existing structure for temporarily receiving the vertical load of an existing structure directly supported by a footing foundation,
As a primary excavation, the intermediate position of the adjacent footing foundations is excavated to a depth below the bottom surface of the footing foundation to construct a groove-like working pit, and the periphery of the foundation beam is excavated to the depth of the bottom surface of the footing foundation for reinforcement. The first step of building a space,
A second step of reinforcing the foundation beam and footing foundation using the reinforcement space;
A third step of improving the ground under and around the footing foundation,
As a secondary excavation, a fourth step of excavating the ground under the foundation beam leaving the ground under the footing foundation to a depth reaching the excavation bottom of the work well from the work well toward the footing foundation, and
A fifth step of placing a temporary support pile on at least one of the bottom of the foundation beam and the bottom of the footing foundation;
A method for temporarily receiving an existing structure, which comprises: In the method for temporarily receiving the existing structure according to claim 1,
In the fourth step, a method for temporarily receiving an existing structure is characterized in that secondary excavation is performed under the foundation beam and the ground remaining under the footing foundation is constrained by a constraining member.