JP6418683B2 - Temporary support method - Google Patents

Description

  The present invention relates to a temporary support method using a temporary support column that temporarily supports a structure when the structure is subjected to seismic isolation, for example.

Conventionally, a base-isolated retrofit construction for making an existing building base-isolated is known (see Patent Documents 1 to 3).
When an existing building with a foundation without piles is to be seismically isolated by this foundation-isolated retrofit construction, how to safely excavate the ground directly under the column where the load from the column is applied, Whether to secure is the biggest problem, for example, it is constructed in the following procedure.

  As in Patent Document 1, there are very few cases where there is no problem even when excavating the ground directly under the column with a large load suddenly. Generally, first, the ground directly under the portion other than the column, such as the foundation beam or the pressure platen, is used. After excavation, a temporary support column is installed on the bottom of the excavation space to temporarily support the foundation of the existing building. Next, the ground directly under the pillar is excavated, thereby completing the excavation space directly under the existing building. Next, a mat slab is newly constructed on the bottom of the excavation space, and a seismic isolation device such as laminated rubber is attached. Thereafter, the temporary support column is removed. Thereby, the existing building is supported from the newly established mat slab via the seismic isolation device, and the existing building is seismically isolated (see Patent Documents 1 and 2).

As described above, in order to safely excavate the ground directly below the pillar, it is necessary to temporarily support the existing building by installing a temporary support column that transmits the load applied to the pillar to the ground.
Here, which part of the foundation of the existing building can be temporarily supported depends on the structure of the foundation of the existing building. For example, if the existing building has a ramen structure, it can be temporarily supported without reinforcement for laying a temporary support post on the foundation part. Is the bottom part of the foundation that has been bulged and already reinforced (also referred to as the bottom plate part of the foundation, hereinafter referred to as the footing part). In the case of a fabric foundation, a reinforced concrete foundation with the T-shape turned upside down is installed in a band shape, and the head portion of the T-shape is a footing portion and is in contact with the ground. In the case of an independent foundation or a pile foundation, the planar shape of the footing part is often a quadrangle.

For this reason, if the existing building has a rigid frame structure and no reinforcement is required to install the temporary support struts on the foundation part, the temporary support struts are installed and temporarily supported in the footing part near the pillar in plan view. Often to do.
For example, if it does not become an obstacle to the installation work of the seismic isolation device, the provisional support posts are installed at the four corners of the footing portion to support the load. However, for that purpose, it is necessary that the footing part is wide and the excavation slope is not easily broken.
Here, the provisional support column is made of steel, for example, a bottom plate installed on the floor, a column installed upright on the steel plate, an oblique member, a reinforcing plate, and the like that connect the bottom plate and the column, Is provided.

  Patent Document 3 discloses a method in which a frozen soil wall is provided along the column row on the ground immediately below the column column, and a vertical load applied to the column of the existing building is temporarily supported by the frozen soil wall. According to this method, even in an existing building where the rigidity of the foundation beam and the pressure platen is low, the foundation can be prevented from cracking or sinking, and can be seismically isolated. Moreover, even if the ground is excavated, it is possible to prevent the excavated surface from collapsing by configuring a part of the excavated surface with a frozen soil wall. However, how much load the frozen soil wall can support depends on the strength and shape of the frozen soil and the ground strength of the ground. The strength of frozen soil is affected by factors that depend on the physical properties of the frozen soil, such as soil quality and water content, and factors that change according to external conditions such as temperature. The shape of the frozen earth wall is determined by the size of the footing part and the physical properties of the ground. For this reason, as in Patent Document 3, after providing a frozen soil wall that can support the load under the footing portion, it is possible to co-exist with a temporary support column that can support the load even after removing the frozen soil wall. There are few.

JP 2003-253911 A JP 2014-055454 A JP 2014-088714 A

Since the size of the footing portion is limited, it is advantageous for excavation work and seismic isolation device installation work to install the temporary support columns in a compact manner. If the load received by the temporary support strut is large or the ground strength is small, the base plate of the temporary support strut will become large, so the amount of excavation will increase, and the reinforcing plate that connects the base plate and the support will become large and the seismic isolation device will be installed It may be an obstacle to the construction, it may be difficult to move the temporary support columns, or a plurality of temporary support columns cannot be built in close proximity.
In addition, it is possible to provide a frozen wall that can support the load under the footing part and make the temporary support column as compact as possible, or to have a temporary support column that can support the load even after removing the frozen wall. There are cases where it is not possible.

  Even if the grounding strength is small, the footing part is not wide, and the excavation slope is likely to collapse, the existing building can be seismically isolated efficiently and without reinforcement for the provisional support struts on the foundation part. It is an object of the present invention to provide a temporary support method that can be used.

  In the temporary support method according to claim 1, when a structure (for example, an existing building 1 described later) is subjected to seismic isolation under the foundation, a footing portion (for example, a footing portion 10 described later) of the structure is used. A temporary support method for supporting from below, wherein water in at least a part of the ground below the footing portion of the structure (for example, ground 5 described later) is frozen, and the footing portion is viewed in plan view. A step (for example, steps S1 and S2 to be described later) for providing a frozen soil portion (for example, a later-described frozen soil wall 40) that covers approximately half or more, and a temporary support of the footing portion by the frozen soil portion, below the footing portion. Steps for excavating the ground (for example, step S3 to be described later) and temporary support columns (for example, temporary support columns 50A and 50B to be described later) are provided directly below the corners at the two corners of the footing portion and directly below the corners. Install A step of temporarily supporting the footing portion with a temporary support post (for example, step S4 to be described later), a step of excavating the frozen soil portion (for example, step S5 to be described later), and corners of the remaining corners of the footing portion; A temporary support post (for example, a temporary support post 50B described later) is further provided immediately below, and the footing portion is temporarily mounted by a temporary support post (for example, a temporary support post 50B described later) immediately below the four corners of the footing portion. And a supporting step (for example, steps S6 and S7 described later).

  According to this invention, the frozen ground part which covers the approximate half of a footing part by planar view was provided in the ground under the footing part. Therefore, even if the grounding strength is small, the footing part is not wide, and the excavation slope is likely to collapse, the vertical load applied to the pillars of the existing building can be It can be temporarily supported by this frozen part through the part. Therefore, even in an existing building where the rigidity of the foundation beam and the pressure platen is low, the foundation is prevented from cracking or sinking, and can be temporarily supported reliably. Moreover, even if the ground is excavated, it is possible to prevent the excavated surface from collapsing by forming a part of the excavated surface with the frozen soil portion. Moreover, since it is not necessary to enter the inside of an existing building, construction can be performed while using the existing building as it is.

In the temporary support method according to claim 1 , the temporary support columns (for example, temporary support columns 50 </ b> A and 50 </ b> B described later) are formed by excavating a ground (for example, a ground surface 5 described later) under the structure. A precast concrete frame (for example, a frame 51 to be described later) placed on the bottom surface of the excavation space (for example, a ring space 25 to be described later), and a plurality of members (for example, detachably provided on the top surface of the frame) A steel strut (for example, a strut 52 described later) that can be divided into a lower strut 521, an intermediate strut 522, and an upper strut 523, which will be described later, and a preload to the steel strut provided between the steel struts. And a jack (for example, a jack 53 described later).

According to this invention, the base of the temporary support column is made into precast concrete and is driven into the concrete as a part of the newly established mat slab. Thus, since the base of the temporary support column is a precast concrete member, the steel material used to manufacture the temporary support column can be reduced compared to the case where the frame (bottom plate) is manufactured from a steel plate as in the past. The cost is low and the mat slab can be reasonably constructed.
Since the temporary support column provided immediately below the pillar of the structure is not driven into the pressure platen, it can be used for a plurality of rotations.

Further, when the ground strength is low, if the pedestal is made of a steel plate, the reinforcing plate that connects the steel plate and the support column is enlarged, so that the reinforcing bar of the pressure-resistant plate interferes with the reinforcing plate.
However, according to the present invention, a reinforcing plate is not required, and even if the strength of the ground on which the temporary support column is installed is low by appropriately setting the size (ground contact area) of the gantry.
In addition, the bottom of the pedestal is a square, and the height of the pedestal is approximately equal to the length of the short side of the square, so the balance of the weight and shape of the gantry on the temporary support column is good, mat slab construction and seismic isolation device installation work It is possible to prevent the provisional support column from overturning without being an obstacle.

Moreover, since the support column is a steel support column that can be attached to and detached from the top surface of the frame and can be divided, it is easy to carry in and assemble. Accordingly, the temporary support column can be installed in a compact manner, and the construction of the pressure-resistant panel is facilitated, so that the structure can be efficiently and surely isolated from the base.
Moreover, member processing becomes unnecessary by using a commercially available steel mountain retaining member for the steel support.
In addition, when using a preload jack for mountain retaining that gives a preload by extending the strut up and down in the middle of the strut, this jack can be fixed by tightening the lock nut after giving the preload. Can be suppressed.

The temporary support method according to claim 2 is characterized in that the steel strut can be divided at least near the upper end level of the mat slab.

  According to the present invention, the steel strut can be divided at least near the upper end level of the pressure-resistant panel, so when removing the temporary support strut after installation of the seismic isolation device, the bolt is loosened by jacking down, The temporary support post can be easily disassembled at the top level of the panel.

According to the present invention, the frozen ground portion that covers the almost half of the footing portion in plan view is provided on the ground below the footing portion and in the vicinity of the portion immediately below the pillar. Even if the grounding strength is small, the footing part is not wide, and the excavation slope is likely to collapse, the vertical load applied to the pillars of the existing building can be passed through the footing part without reinforcing to install the temporary support pillar on the foundation part. In addition, since it can be temporarily supported by the frozen soil portion, even if the existing building has low rigidity of the foundation beam and the pressure platen, the foundation can be surely temporarily supported by preventing the foundation from cracking or sinking. Moreover, even if the ground is excavated, it is possible to prevent the excavated surface from collapsing by forming a part of the excavated surface with the frozen soil portion. Moreover, since it is not necessary to enter the inside of an existing building, construction can be performed while using the existing building as it is.
Moreover, since the support column is a steel support column that can be attached to and detached from the top surface of the frame and can be divided, it is easy to carry in and assemble. Therefore, the temporary support pillar can be installed in a compact manner, and the construction of the pressure-resistant panel becomes easy, so that the existing building can be efficiently and surely seismically isolated.

It is sectional drawing of the foundation part of the existing building where the provisional support pillar of the foundation which concerns on one Embodiment of this invention is applied. It is sectional drawing which shows the state by which the existing building which concerns on the said embodiment was seismically isolated. It is a flowchart of the procedure which seismically isolates the existing building which concerns on the said embodiment. It is FIG. (1) explaining the procedure which makes the existing building which concerns on the said embodiment seismic isolation. It is AA sectional drawing of FIG. It is FIG. (2) explaining the procedure which makes the existing building which concerns on the said embodiment seismic isolation. It is BB sectional drawing of FIG. It is a side view of the provisional support pillar which concerns on the said embodiment. It is CC sectional drawing of FIG. It is a figure explaining the method to move the provisional support pillar which concerns on the said embodiment. It is DD sectional drawing of FIG. It is a figure explaining the method of installing the temporary support pillar which concerns on the said embodiment. It is FIG. (The 3) explaining the procedure which makes the existing building which concerns on the said embodiment seismic isolation. It is EE sectional drawing of FIG. It is FIG. (4) explaining the procedure which makes the existing building based on the said embodiment seismic isolation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the existing building 1 has an underground frame 2, and the underground frame 2 includes a foundation 3 and a plurality of pillars 4 extending upward from the foundation 3.

The foundation 3 is a solid foundation without piles built on the ground 5, and the foundation 3 includes a footing portion 10 and a pressure platen 11 that connects the footing portions 10 to each other.
Each column 4 extends upward from the center of the footing portion 10.
As shown in FIG. 2, the existing building 1 is seismically isolated by supporting the foundation 3 from below with a seismic isolation device 20.

Specifically, an installation space 21 for installing the seismic isolation device 20 is formed under the foundation 3 of the existing building 1. On the bottom surface of the installation space 21, a mat slab 22 is constructed as a reinforced concrete pressure platen over the entire surface.
A reinforced concrete lower seismic isolation foundation 23 is provided directly below the pillar 4 and on the upper surface of the mat slab 22, and an reinforced concrete upper seismic isolation foundation 24 is provided immediately below the pillar 4 and on the lower face of the foundation 3. ing.

  Moreover, the surrounding space 30 which leads to the ground is formed in the circumference | surroundings of the underground frame 2 of the existing building 1 (refer FIG. 4).

The seismic isolation device 20 such as laminated rubber is provided between the lower base isolation base 23 and the upper base isolation base 24.
The seismic isolation device 20 takes a reaction force on the lower base isolation base 23 to support the upper base isolation base 24 from below, and keeps the upper base isolation base 24 movable in the horizontal direction. At this time, the surrounding space 30 functions as a seismic isolation clearance.

As shown in FIG. 3, in step S <b> 1, a surrounding space 30 is formed around the existing building 1.
That is, as shown in FIGS. 4 and 5, a mountain retaining wall (not shown) is constructed around the existing building 1, and the ground 5 between the existing building 1 and the mountain retaining wall is brought to a depth that becomes the lower end of the mat slab 22. Excavate. The space formed by this excavation becomes the surrounding space 30.

  At this time, a retaining wall is constructed inside the retaining wall, and a temporary beam (not shown) that connects the retaining wall and the underground frame 2 of the existing building 1 is constructed. This temporary beam functions as a mountain retaining work such as a cut beam that supports earth pressure and horizontally restrains it.

In step S <b> 2, a frozen soil wall 40 as a frozen soil portion is constructed on the ground 5 under the foundation 3 of the existing building 1.
That is, as shown in FIG. 4 and FIG. 5, the frozen soil wall 40 is constructed along the core of the pillar 4 so as to hang over approximately half of the footing portion 10 of the foundation 3 in plan view.

How much load the frozen soil can support depends on the strength and shape of the frozen soil and the ground strength of the ground. The strength of frozen soil is affected by factors inherent in frozen soil, such as soil quality and water content, and factors that vary depending on external conditions such as temperature. The shape of the frozen soil wall is determined by the size of the footing part and the thickness of the soil layer that tends to collapse.
The existing building 1 of this embodiment is a ramen structure having a foundation without piles, and has a footing portion 10 having a side of about 3.5 m. At the bottom of the footing portion 10 is a pumice tuff formation M1 that is likely to collapse when the restraint is lost, and the thickness is about 2.5 m. The formation M2 below it is a tuff silt formation, which is more than the formation M1. Is a stable ground. Judging from these conditions, in order to support the load without reinforcing the temporary support columns 50A and 50B on the foundation part, the stability of the frozen soil wall is also considered, and half of the footing part in plan view. It was judged that the frozen ground wall 40 covering the above was necessary.

If the frozen wall is divided into two parts so as to be applied to both ends of the footing portion 10, it is advantageous to avoid directly under the pillar 4 where the seismic isolation device 20 is installed, but considering the stability of the frozen soil wall. If it is not thin, it is uneconomical because it is necessary to provide twice the frozen soil wall.
Further, if the frozen wall is constructed at the center of the footing portion 10, that is, a position passing directly under the column 4, it is advantageous in that the column core and the core of the frozen soil wall coincide with each other to support the load. Moreover, as shown in FIG. 13, provisional support columns 50 </ b> B are installed at the four corners of the footing portion to support the load, so that the temporary support columns 50 </ b> B do not interfere with the installation work of the seismic isolation device 20, and the frozen earth wall 40 is If the temporary support struts 50B capable of supporting the load can coexist even after the removal, the replacement of the temporary support struts 50B is not necessary, which is efficient.
If the width of the frozen soil wall of the footing portion 10 is 2 m, the portion other than the frozen soil wall is 75 cm in plan view, and H-350 × 350 temporary support posts are built at the four corners of the footing portion 10. If one side is 100 cm, the gap between the bottom plate end of the temporary support column 50B and the frozen soil wall is less than 10 cm, which is not impossible. However, considering the drilling of a distance of 30 m or more on one side while drilling horizontally from the edge of the existing building 1 in the construction of the frozen earth wall, there may be a place where a construction error occurs 10 cm or more.
Therefore, in the present embodiment, the frozen ground portion that covers the approximate half of the footing portion 10 in plan view is provided on the ground below the footing portion 10 and in the vicinity immediately below the pillar 4.

  The frozen earth wall 40 is formed by a freezing method. Specifically, a plurality of freezing tubes (not shown) are arranged substantially horizontally along the core of the pillar 4 from the surrounding space 30 toward the formation M2 of the ground 5 below the right half of the footing portion 10 of the foundation 3. Type in. Then, by circulating a coolant through these freezing tubes, the surroundings of the freezing tubes are cooled to freeze the moisture in the soil. Thereby, the frozen earth wall 40 centering on these freezing pipes is formed.

Here, the ground 5 is composed of a stratum M1 directly below the foundation 3 of the existing building 1 and a stratum M2 below the stratum M1. For example, the formation M1 is a pumice tuff layer, the formation M2 is a tuff silt formation, and is a more stable ground than the formation M1.
The height of these frozen soil walls 40 is about 2.5 m from the boundary portion between the formation M1 and the formation M2 to the lower surface of the footing portion 10 of the foundation 3, and the width is about 2 m.

In step S3, a portion of the ground 5 under the foundation 3 of the existing building 1 excluding the frozen soil wall 40 is excavated.
That is, as shown in FIGS. 6 and 7, a portion of the ground 5 under the foundation 3 of the existing building 1 excluding the frozen soil wall 40 is excavated to a depth corresponding to the bottom surface of the mat slab 22. Thereby, the footing part 10 of the foundation 3 of the existing building 1 is temporarily supported by the frozen earth wall 40. Further, the excavation space 25 formed by this excavation becomes a part of the installation space 21.

In step S <b> 4, in the excavation space 25, the provisional support column 50 </ b> B is installed immediately below the corners at the two corners of the footing portion 10 in plan view, and the provisional support column 50 </ b> A is installed as directly below the column 4 as possible. Thus, the footing portion 10 is temporarily supported by the temporary support columns 50A and 50B. The provisional support columns 50A and 50B may be installed according to the excavation status, and there is no need to wait for completion of excavation. That is, the provisional support column 50B and the provisional support column 50A do not need to be installed at the same time. After the provisional support column 50B is installed and a load is applied to some extent, the temporary support column 50A is installed after further excavation. May be.
As shown in FIGS. 6 and 7, the discarded concrete 26 is placed on the bottom surface of the excavation space 25.

  The temporary support column is designed so that the load of one pillar 4 can be supported by the four temporary support columns as shown in FIG. 13 after excavation is completed, but the half immediately below the footing portion 10 covers the frozen soil wall 40. At this stage, the provisional support posts 50B cannot be installed directly below the four corners of the footing portion 10 in plan view, so the two provisional support posts 50B are installed directly below the two corners. Furthermore, two temporary support columns 50A were installed immediately below the pillar 4 as much as possible. The frozen soil wall 40 can be removed by temporarily supporting the foundation 3 from below by the total of four temporary support columns 50A and 50B. The two temporary support columns 50A added to the center are removed after the two frozen support columns 50B are installed immediately below the remaining two corners of the footing portion 10 after the frozen ground wall 40 is removed. The temporary support column 50 </ b> A is prevented from obstructing the installation work of the seismic isolation device 20. In this case, the temporary support column 50A may be moved together with the platform 51 to be removed and diverted, or the column 51 and the jack may be removed from the platform 51 and removed, and diverted to other places. Good.

  In addition, about the footing part 10A located in the outer peripheral part of the existing building 1 in plan view and facing the surrounding space 30, the temporary support column 50B located directly below the corner of the footing part 10A is in plan view. It extends in a substantially L shape along the corner of the footing portion 10A. This is because the frozen soil wall 40 is collapsed due to a rise in temperature, rain, or the like, and the area of the footing portion is smaller than the central portion because it is an end portion of the frozen soil wall 40.

FIG. 8 is a side view of the temporary support column 50B. 9 is a cross-sectional view taken along the line CC of FIG.
The temporary support column 50B includes a reinforced concrete frame 51 placed on the bottom surface of the excavation space 25, a column 52 that extends upward from the upper surface of the frame 51 and supports the lower surface of the existing building 1, and an intermediate column 52. And a jack 53 provided to preload the support column 52.

  The bottom surface of the gantry 51 is a square L × L having an area necessary for receiving the load of the column 4, and the height of the gantry 51 is approximately equal to the length L of one side of the square. . This is because the column 52 is H350 × 350 and is 3.5 m or more, so if the weight of the jack is added, it is close to 1t, and the stand 51 is at least twice as heavy as the column 52 in order to stabilize the temporary column. Is necessary, and 2.5 times or more is preferable. In addition, the shorter the length of the column 52 in consideration of buckling or the like, the more stable, but the lower the height of the gantry 51, the more stable. For this reason, considering the workability, the height of the gantry 51 is practically less than 1 m, and the length of the short side of the gantry 51 is approximately equal to the length of the short side (plus or minus 10%). Balance is preferred. Thereby, it is possible to prevent the provisional support column 50B from being overturned without obstructing the mat slab construction or the seismic isolation device installation work.

Reinforcing bars 511 arranged in a lattice shape and mechanical joints 512 joined to both ends of the reinforcing bars 511 are driven into the lower portion of the gantry 51. As the main reinforcing bar of the mat slab 22, a screw reinforcing bar 513 is prepared, and as shown by an arrow in FIG. 9, the reinforcing bar 511 driven into the gantry 51 is screwed into the mechanical joint 512 so that the reinforcing bar 511 driven into the mat 51 22 is joined to the lower main muscle.
Further, concave portions (cotters) 514 are formed in two upper and lower stages on the four side surfaces of the gantry 51, respectively.

The support column 52 is a steel support column that is detachably provided on the gantry 51 and can be divided into a plurality of members 521 to 523.
That is, the support column 52 is formed on the lower support column 521 made of H-section steel provided on the upper surface of the gantry 51, the intermediate support column 522 made of H-section steel provided on the jack 53, and the intermediate support column 522. And an upper column 523 made of an H-shaped steel provided.

The lower column 521 can be attached to and detached from the upper surface of the gantry 51, so that the column 52 can be divided at the upper end level of the mat slab 22.
In addition, a water stop plate 524 is provided in the middle of the lower column 521.
The jack 53 is provided between the lower column 521 and the intermediate column 522, and causes the lower column 521 and the intermediate column 522 to approach or separate from each other.

The provisional support column 50B drives the jack 53 to apply a reaction force to the bottom surface of the excavation space 25 and apply a force in a direction to separate the lower column 521 and the upper column 522 to introduce a preload. 3 can be temporarily supported.
Alternatively, by driving the jack 53, the preload can be released and the temporary support of the foundation 3 can be released.

  The temporary support column 50A has the same configuration as the temporary support column 50B, but is different from the temporary support column 50B in that it moves after the frozen wall 40 is removed and the support points are changed.

  Next, a method for moving the gantry 51 will be described. Of the temporary support columns 50A, the ones arranged next to each other are integrated with the gantry 51, and the weight is increased. Therefore, the gantry 51 of the integrated provisional support column 50A will be described as an example.

The vertical movement of the gantry 51 is performed by the following method.
Bolts 515 protrude from four positions on the upper surface of the gantry 51 (see FIGS. 10 and 11).
The suspension jig 70 is screwed onto the bolt 515 of the gantry 51, and the gantry 51 is lifted using the suspending jig 70 to lift the gantry 51.

On the other hand, the horizontal movement of the gantry 51 is performed by supporting the gantry 51 from below by a hand pallet or a forklift.
If horizontal movement is not possible with this method, move using the following method.
In other words, bolts 516 for attaching a bracket 60 to be described later are provided projectingly at four locations on the side surface of the gantry 51.

As shown in FIGS. 10 and 11, the bracket 60 is attached to the bolt 516 of the gantry 51, and a pair of rails 61 is installed directly below the bracket 60. The rail 61 is composed of an H-shaped steel and a pair of groove-shaped steels provided as guides at both ends of the upper surface of the upper flange of the H-shaped steel. The pair of rails 61 are extended to the installation position of the gantry 51.
Next, a roller 62 is attached to the lower surface of the bracket 60, and the roller 62 is installed on the rail 61.

  Next, for example, a wire 64 of a lever block (registered trademark) 63 is attached to a suspension jig 70 on the upper surface of the gantry 51, and a reaction force is applied to the wall surface 65 in the vicinity of the installation position of the gantry 51, thereby ) 63, the wire 64 is pulled toward the wall surface 65. Then, the roller 62 travels on the rail 61, and the gantry 51 can be moved to a predetermined position.

Next, a method for installing the gantry 51 will be described.
First, as shown in FIG. 12, a jack 66 that supports the bracket 60 from below is installed. Specifically, an iron plate 67 is laid on the discarded concrete 26 and a jack 66 is installed on the iron plate 67.
Next, the jack 66 is driven, the bracket 60 is moved up and down, and the height and levelness of the gantry 51 are adjusted.
Next, liners 68 are inserted into a plurality of positions in the gap between the gantry 51 and the discarded concrete 26 to temporarily fix the height position of the gantry 51, and then the jack 66 and the iron plate 67 are removed.
Next, the non-shrink mortar 69 is filled in the gap between the gantry 51 and the discarded concrete 26.

In step S5, the remaining ground 5 under the foundation 3 of the existing building 1 is excavated.
That is, as shown in FIG. 13 and FIG. 14, next, freezing by the freezing tube is released, and this freezing tube is removed. Then, the remaining ground 5 under the foundation 3 of the existing building 1 is excavated, the frozen earth wall 40 is removed, and the excavation space 25 is completed.

In step S <b> 6, the remaining provisional support columns 50 </ b> B are installed around the column 4.
Abandoned concrete 26 is placed on the bottom of the excavation space 25. Next, on the discarded concrete 26, the temporary support column 50 </ b> B is installed immediately below the pillar 4 in a plan view, that is, directly below the corner of the remaining corner of the footing portion 10. And the footing part 10 of the foundation 3 is temporarily supported from the bottom by these temporary support columns 50B.

In step S7, the temporary support column 50A installed immediately below the column 4 is removed.
The temporary support by the temporary support column 50A is released, and the temporary support column 50A is removed. Thereby, the foundation 3 of the existing building 1 is temporarily supported only by the provisional support column 50 </ b> B installed immediately below the corner of the footing portion 10.

In step S <b> 8, the mat slab 22 is constructed on the bottom surface of the excavation space 25.
As shown in FIG. 15, the bar is placed on the discarded concrete 26. At this time, the threaded reinforcing bar 513 is screwed into the mechanical joint 512 of the gantry 51 of the temporary support column 50B, so that the reinforcing bar 511 driven into the gantry 51 becomes the lower main bar of the mat slab 22 (FIG. 9). reference).
Next, concrete is laid and a mat slab 22 is newly provided. Then, the stand 51 of the temporary support column 50B becomes a part of the mat slab 22, and the lower portion of the column 52 of the temporary support column 50B is driven into the concrete.

In step S <b> 9, the seismic isolation device 20 is installed on the mat slab 22.
As shown in FIG. 15, a lower base isolation base 23 is constructed on the mat slab 22, and an upper base isolation base 24 is constructed on the lower surface of the foundation 3. The apparatus 20 is installed. And this seismic isolation device 20 supports the part located just under the pillar 4 of the foundation 3.

In Step S10, the temporary support column 50B installed around the column 4 is removed.
The support by the temporary support columns 50B installed immediately below the corners of the footing portion 10 is released, and then the columns 52 of the temporary support columns 50B are cut and removed. Thereby, the existing building 1 is supported by the seismic isolation device 20.

According to this embodiment, there are the following effects.
(1) The frozen ground wall 40 which covers the approximate half of the footing part 10 by planar view was provided in the ground 5 under the footing part 10. FIG. Even if the grounding strength is small, the footing part is not wide, and the excavation slope is likely to collapse, the vertical load applied to the pillar 4 of the existing building 1 without reinforcing the base support pillars 50A and 50B. Can be temporarily supported by the frozen wall 40 through the footing portion 10, so that even if the existing building 1 has a low rigidity of the foundation beam or the pressure platen 11, the foundation 3 may crack or sink. It can prevent and can be temporarily supported. Even if the ground 5 is excavated, the excavated surface can be prevented from collapsing by forming a part of the excavated surface with the frozen soil wall 40. Moreover, since it is not necessary to enter the inside of the existing building 1, it can construct while using the existing building 1 as it is.

  (2) Convert the gantry 51 of the temporary support column 50B into precast concrete and drive it into the concrete as a part of the newly installed mat slab 22. In this way, since the gantry 51 of the temporary support column 50B is a precast concrete member, the steel material used to manufacture the temporary support column 50B is compared with the conventional case where the gantry (bottom plate) is made of a steel plate. Therefore, the mat slab 22 can be rationally constructed.

Since the provisional support column 50A provided immediately below the pillar of the structure is not driven into the mat slab 22, it can be used for a plurality of rotations.
In addition, since the support column 52 of the temporary support column 50B does not penetrate the mat slab 22, the waterstop performance can be improved as compared with the case where the temporary support column penetrates the newly installed pressure-resistant panel as in the prior art.

  Moreover, even when the strength of the ground 5 on which the temporary support columns 50A and 50B are installed is low by appropriately setting the size (ground contact area) of the gantry 51.

Moreover, since the support | pillar 52 is a steel support | pillar which can be attached or detached to the upper surface of the mount frame 51 and can be divided | segmented, carrying in and an assembly are easy. Accordingly, the provisional support column 50B can be installed in a compact manner, and the construction of the mat slab 22 can be easily performed, so that the existing building 1 can be seismically isolated efficiently.
Further, by using a commercially available steel mountain retaining member for the steel support 52, no member processing is required.
In addition, when using a preload jack for mountain retaining that extends and contracts up and down in the middle of the support column 52 to give a preload, this jack can be fixed by tightening a lock nut after applying the preload. Can be suppressed.

  Further, since the steel support 52 can be divided at least near the upper end level of the mat slab 22, when the temporary support support 50B is removed after the seismic isolation device 20 is installed, the bolts are loosened by jacking down. The temporary support column 50B can be easily disassembled at the upper end level of the mat slab 22.

  (3) Since the concave portion 514 is formed on the side surface of the gantry 51 of the temporary support columns 50A and 50B, when the gantry 51 is driven into the new mat slab 22, the concrete of the mat slab 22 enters the concave 514, and the mat It is surely integrated with the slab 22.

  (4) Since the gantry 51 is L-shaped in plan view, the gantry 51 can be arranged along the shape of the edge of the footing portion 10 that is square in plan view, and the provisional support column 50B is desired at the end of the footing portion 10. It can be installed in the position.

(5) Since the bracket 60 is attached to the side surface of the gantry 51, the gantry 51 can be easily moved horizontally by attaching the roller 62 to the lower surface of the bracket 60 and running the roller 62 on the rail 61.
Moreover, the height position of the mount frame 51 can be easily adjusted by temporarily supporting the bracket 60 with the jack 66 and moving it up and down.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the present embodiment, the height of the frozen soil wall 40 is set from the boundary portion between the formation M1 and the formation M2 to the lower surface of the foundation 3. However, the present invention is not limited to this, and the height of the frozen soil wall is the lower end of the mat slab 22 It is good also from the vicinity to the lower surface of the foundation 3.

  Further, in this embodiment, excavation is started from the surrounding space 30 outside the existing building 1, but when there is not enough room on the site, an opening is provided in the pressure platen 11 of the existing building 1 and excavation is performed from this opening. You may start.

Moreover, in this embodiment, although this invention was applied to the solid foundation without a pile, it is not restricted to this, It can also apply to the pile foundation which has a pile, and the lack of pile yield strength at the time of excavation can also be compensated.
Moreover, in each above-mentioned embodiment, although this invention was applied to the existing building 1, it can apply not only to this but to structures, such as a retaining wall.

  In the present embodiment, the gantry 51 of the temporary support columns 50A and 50B is precast concrete. However, the present invention is not limited thereto, and the entire temporary support column is made of steel, for example, a bottom plate installed on a floor surface, and the steel plate It is good also as a structure which consists of the support | pillar standingly installed in this, and the diagonal material which connects this bottom board and a support | pillar, a reinforcement plate, etc. However, in that case, the center of gravity is not lower than in the case of precast concrete, so that the temporary support column is stable so that it can be excavated safely even when subjected to a large load. Desired.

  In addition, there are problems with streamlining of mat slab construction and mat slab quality as another problem with downsizing of the temporary support columns. As one of the solutions, in this embodiment, the concrete slab is not divided into a plurality of times in the mat slab of the provisional support column part and the other mat slabs, and the mat slab is kept with the provisional support column installed. As a means for construction, a gantry 51 which is a precast concrete reaction board was used, and the gantry 51 was buried and used as a part of a mat slab.

  There is also a method of burying the mat slab as it is even with the temporary support column of the steel bottom plate, but if the pitch of the lower rebar of the mat slab is about 100 mm to 150 mm, it is assumed that the column steel material of H-300 × 300 is used However, it is necessary to provide a plurality of through-holes for reinforcing bars on one surface of the steel material, and the cross-sectional defect of the steel column becomes large. There are many problems with the interference of diagonal members and reinforcing plates that connect the bottom plate and the column.

M1, M2 ... Geologic layer 1 ... Existing building (structure)
2. Basement 3 ... Foundation 4 ... Pillar 5 ... Ground 10, 10A ... Footing part 11 ... Pressure-resistant panel 20 ... Seismic isolation device (laminated rubber)
21 ... Installation space 22 ... Mat slab 23 ... Lower seismic isolation base 24 ... Upper seismic isolation base 25 ... Excavation space 26 ... Abandoned concrete 30 ... Surrounding space 40 ... Frozen earth wall (frozen earth part)
50A ... Temporary support column 50B ... Non-replacement temporary column 51 ... Base 52 ... Post 53 ... Jack 60 ... Bracket 61 ... Rail 62 ... Roller 63 ... Lever block 64 ... Wire 65 ... Wall surface 66 ... Jack 67 ... Iron plate 68 ... Liner 69 ... Non-shrink mortar 70 ... Hanging jig 511 ... Reinforcing bar 512 ... Mechanical joint 513 ... Reinforcing bar 514 ... Recessed part 515, 516 ... Bolt 521 ... Lower column 522 ... Middle column column 523 ... Upper column column 524 ... Water stop plate

Claims (2)

A temporary support method for supporting the footing portion of the structure from below when the structure is seismically isolated under the foundation,
Freezing water in at least a portion of the ground below the footing portion of the structure, and providing a frozen soil portion covering approximately half or more of the footing portion in plan view;
Excavating the ground below the footing part while temporarily supporting the footing part in the frozen soil part;
Installing temporary support struts immediately below the corners at the two corners of the footing part and directly below the corners, and temporarily supporting the footing part with the temporary support struts;
Excavating the frozen soil portion;
Installing a temporary support strut directly under the corner of the remaining corner of the footing portion, and temporarily supporting the footing portion with the temporary support strut immediately below the corner of the four corners of the footing portion ,
The temporary support column is a precast concrete frame that is placed on the bottom surface of an excavation space formed by excavating the ground below the structure;
A steel column that is detachably provided on the top surface of the gantry and can be divided into a plurality of members,
A temporary support method , comprising: a jack provided in the middle of the steel column to give a preload to the steel column . The temporary support method according to claim 1 , wherein the steel strut can be divided at least near the upper end level of the mat slab.

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