JP2900840B2 - How to build underground structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing an underground structure in which a cutting beam connected to a striking column is buried in concrete constituting a floor surface.

[0002]

2. Description of the Related Art In recent years, when constructing an underground structure, a reverse strut is installed in an underground portion, and then the ground is excavated to expose the reverse strut, and a beam is sequentially connected to the exposed reverse strut. There is a reverse striking method in which an underground frame is constructed by using a conventional method (see Japanese Patent Laid-Open No. 5-5312). Also, in this reverse driving method, for example, Japanese Patent Application Laid-Open No. 3-72119 (E02D)
29/04) to which a flat slab structure is applied has been proposed.

In the flat slab structure, a relatively thin and flat concrete floor is supported by a back strut via a thick-walled capital portion. The capital part and the flat slab are constructed for each basement floor. By applying a flat slab structure to the reverse striking method in this way, the floor height can be kept lower than that of a normal column-beam ramen frame, so the amount of excavated soil is reduced and the construction period is shortened and costs are reduced. Can be achieved.

[0004] However, in the excavation of the reverse striking method in which the flat slab is sequentially constructed from the upper floor, every time the construction of the flat slab is completed, a heavy excavator is carried under the flat slab and excavated. However, in the work in the space under the flat slab, there is a problem that the flat slab hinders the work by the heavy excavator, and the excavation cannot be performed smoothly and efficiently.

Therefore, at the stage of sequentially excavating the basement floor, instead of constructing a flat slab as the floor part of each basement floor, a beam is erected on the back strut in the form of a girder. A method of constructing a flat slab so as to bury the girder after completing excavation of an underground part has already been filed by the present applicant. By using the girder in this way, in the excavation work stage where the excavation is performed sequentially from the upper side to the lower side, the square portion of the girder incorporated girder is greatly opened, so that the excavating heavy equipment can be flexibly mounted. It can be operated and can work smoothly and efficiently compared to excavating in a space covered by a flat slab.

[0006]

However, in such a conventional method for constructing an underground structure, as described above, the underground portion is excavated while erection beams are erected, and excavation of the entire underground portion is completed. After that, the flat slab is constructed to bury the girder, so as a girder that also needs a function as a shoring to support the excavated underground part, it is necessary to ensure the predetermined strength Therefore, it is required to set the member dimensions to be reflected on the cross-section modulus and the like due to a certain amount of the cutting beam. And, when crossing up and down the cross beams that need to be made high and combining them in a girder shape and arranging them in the vertical and horizontal directions of the back strut and trying to bury them in the flat slab, the flat slab thickens inevitably As a result, there has been a problem that the floor height of the basement floor cannot be sufficiently set, and the amount of concrete cast on the floor for burying the girder increases.

In view of the above-mentioned problems, the present invention is designed so that the height of the cross-shaped cross section of the cross beam arranged vertically and horizontally with respect to the reverse strut can be reduced, and this cross beam is buried. It is an object of the present invention to provide a method of constructing an underground structure capable of achieving a thinned floor.

[0008]

In order to achieve the above object, according to the present invention, after a reverse strut having a support bracket is cast, a PCa capital plate is loosely fitted to the reverse strut at appropriate intervals. Supported by the support bracket,
Next, the cutting beams arranged vertically and horizontally with respect to the reverse strut are combined in a cross-girder shape within a plane at the same height level to form the PC.
(a) Concrete is placed on a floor form laid on a capital plate and laid so as to cover the lower side of these cut beams, and the cut beams are embedded in the concrete.

[0009]

According to the above construction, the method of constructing an underground structure according to the present invention is as follows. After the back strut is cast on the ground, the back strut is exposed while excavating the underground portion, and the support bracket of the strut is supported. The beams are combined and placed in a cross-girder shape on the PCa capital slab supported by. At this time, since the cutting beams arranged vertically and horizontally are configured to be combined in a cross-girder shape within a plane at the same height level, the cutting beams themselves can be configured with required member dimensions and can be provided in a predetermined shape. While maintaining rigidity and strength, the height of the girder-shaped intersection of the girder can be reduced to the height equivalent to the girder, and the thickness of the flat slab constructed by embedding the girder in concrete Can be made as thin as possible. Therefore, the floor height can be increased and the amount of cast concrete can be reduced. And by erection such a beam,
Of course, these cut beams can stop the earth pressure and seismic force during excavation. Then, after completing the construction of the underground skeleton downward while sequentially building the cutting beams,
The floor is constructed by laying a floor formwork under the cut beams and casting concrete, and burying the cut beams in the concrete.

[0010] Further, the cutting beam is assembled to the upright strut via a PCa capital plate, but since this PCa capital plate is loosely fitted to the upright strut at an appropriate interval, the upright strut is improperly installed due to a mounting error. Even if the position is displaced from the position, the loose fitting portion absorbs the error of setting up the back strut and allows the girder to be easily erected at the proper position without the need for machining work on site. Can be.

[0011]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 3 show an embodiment of a method of constructing an underground structure according to the present invention. FIG. 1 is a process chart showing a procedure for constructing an underground structure in order. FIG. FIG. 3 is an enlarged plan view of a main part, and FIG. 3 is a side view of FIG.

In this embodiment, basically, a support bracket 1
8, the PCa capital plate 22 is loosely fitted to the reverse strut 12 at appropriate intervals and supported by the support bracket 18, and then the reverse strut 12 is cast.
Of the PCa capital plate 22 by combining the cut beams 14 arranged in the vertical and horizontal directions in a grid pattern in a plane of the same height level.
Concrete is cast on a floor form which is placed on the top and laid so as to cover the lower side of these beams 14, and the beams 14 are embedded in the concrete.

FIG. 1 shows, in order, the process of placing the reverse strut 12 and the process of erection of the cutting beam 14. First, the reverse strut 12 is driven into the bore 16 (see FIG. 1a). In this embodiment, an underground structure serving as the second basement is shown as an example, and the reverse strut 12 is provided with support brackets in advance below the ceiling height position of the second basement (floor height position of the first basement). 18 are protruded. A steel pipe 12a is used for a general portion of the reverse strut 12 and a ribbed steel pipe 12b having a rib protruding from an inner surface is used for an upper end portion. Then, concrete 20 is cast inside the installed reverse strut 12 (see FIG. 2B).

Next, from the upper end of the reverse strut 12, PC
a While the capital plate 22 is suspended (see FIG. 3C), a ground column 24 is connected above the reverse strut 12 and
A joint member 26 of the first floor beam is erected in 4 (see FIG. 4D). The PCa capital plate 22 is formed as a square thin PCa plate, and has a circular or square insertion hole 22 that is loosely fitted to the reverse strut 12 with an appropriate gap in the center thereof.
a (see FIG. 2) is formed. Further, the joining member 26
Is formed by connecting H-section steels in a cross shape,
This joining member 26 is fixed to the lower end portion of (see FIG. 1e),
The first floor beam 28 is connected to the joining member 26 (see FIG. 5F).

Next, the first basement is excavated and the PCa
The capital plate 22 is suspended and lowered (see FIG. G).
After the excavation of the first basement floor is completed, the PCa capital plate 22 is placed on the support bracket 18 as shown in FIG. 3, and the underground first floor cutting beam 14 is assembled above the PCa capital plate 22. (See FIG. H). At this time, as shown in FIG. 2, the cut beam 14 is composed of a first cut beam 14a arranged in the x direction and a second cut beam 14 arranged in the y direction.
b, and these first and second cut beams 14a, 14b
Are assembled in a girder shape so as to surround the reverse strut 12. still,
The first and second cut beams 14a, 14b are divided at the center of the span of the back strut 12, and when they are assembled in a cross-girder shape, the first and second cut beams 14a, 14a are joined.
4b are connected to each other. Then, the mat slab 32 is constructed on the second basement floor by excavating the second basement (see FIG. 1I).

After the mat slab 32 is constructed, a reinforcing steel bar such as a column main bar 70 is arranged on the outer periphery of the back strut 12 to construct a steel reinforced concrete column 34 in order from the lower floor. At this time, at the same time as setting the reinforcement and the column formwork of the steel reinforced concrete columns 34 on the second basement level,
As shown in FIG. 2, a floor slab 36 as a floor form is laid without gaps below the cutting beam 14, and concrete 36 a is cast on the column form and the floor slab 36, thereby forming a second basement floor. A part of steel reinforced concrete column 34 and a flat slab 38 of the first basement floor are constructed. At this time, when the concrete 36a is cast on the floor slab 36, the cutting beam 14 is embedded in the concrete 36a. The support bracket 18 is buried in a steel reinforced concrete column 34 on the second basement floor. Then, after the flat slab 38 is constructed, the steel reinforced concrete columns 34 on the first basement floor are constructed. When the PCa column form is used as the column form, the PCa capital plate 22 and the joining member 26 may be loosely fitted to the reverse strut 12 prior to the carry-in. Also, the end of the floor slab 36 is the PCa
When supported by the capital plate 22, a locking member 40 is attached to the outer periphery of the PCa capital plate 22 as shown in FIGS. 2 and 3, and the end of the floor slab 36 is locked by the locking member 40. It has become.

Here, when the cutting beams 14 are assembled in a cross-girder shape, the first beams 14 are arranged in the x direction as shown in FIG.
The first beam 14a is divided at the portion where the second beam 14b is arranged in the y direction, and the end face of the first beam 14a is joined to the side surface of the second beam 14b.
The second cutting beams 14a and 14b are connected in a plane at the same height level.

The first beam 14a is connected to the second beam 14b.
When the first and second connecting beams 42a and 42b are connected to each other, a pair of connecting plates 42 and 42 are arranged over the upper and lower surfaces of the first cutting beams 14a and 14a butted on both sides of the second cutting beam 14b. The first cutting beam 14a is fixed via bolts 44 and nuts 44a. Also, triangular brackets 46, 46 welded to both ends of the first cut beam 14a are applied to both sides of the second cut beam 14b, and these brackets 46, 46 and the second cut beam 1 are attached.
4b is fixed via bolts 48 and nuts 48a. Incidentally, the connection of the first and second cut beams 14a, 14b may be fixed by only the connecting plates 42, 42 without using the brackets 46, 46 as shown in FIG. The first and second cut beams 14a and 14b are formed as steel pipe concrete formed by filling concrete inside a steel pipe having a rectangular cross section.

In the construction method of the underground structure according to the present embodiment having the above configuration, the support bracket 18 of the reverse strut 12 is used.
To support the PCa capital plate 22,
On the upper side of the Ca capital plate 22, the first and second cutting beams 14a,
14b are combined and placed in a cross-girder shape.
Is installed, the seismic beam 14 can support soil pressure and seismic force during excavation of the basement floor. At this time, the cut beams 14 combined in a cross-girder form have a lattice shape, and the squares are largely open upward. Therefore, the operability of the heavy excavator can be sufficiently secured, and the efficiency of the excavation work can be increased, and the construction period can be shortened.

Then, a floor slab 36 is arranged below the cutting beam 14 erected on the PCa capital plate 22,
By using the floor slab 36 as a floor form and placing concrete 36a, the cut beam 14 is
The flat slab 36 is constructed in a state of being buried in a. In particular, in the present embodiment, the first and second cut beams 14a and 14b to be assembled in a girder shape are connected at the same level in the horizontal direction at their intersections.
While a and 14b are formed with predetermined rigidity and strength according to the required member dimensions, the vertical arrangement space at the intersection of these cutting beams 14a and 14b is compared with a conventional case where they are overlapped and intersected. Can be significantly reduced by half. Therefore, the cutting beam 14 is
The flat slab 38 buried and embedded in the 6a can be made as thin as possible, and the floor height can be sufficiently secured, and the amount of the flat slab 38 cast into the concrete 36a is greatly reduced. The construction cost can be reduced.

In this embodiment, the beam 14 is made of PCa.
The PCa capital plate 22 is attached to the reverse strut 12 with an appropriate gap through an insertion hole 22a formed in the center portion. Therefore, even when the reverse strut 12 is displaced from the normal position due to the installation error, the insertion error of the reverse strut 12 is absorbed by the insertion hole 22, and the cutting beam 14 is erected at the normal position. It becomes possible. For this reason, there is no need to perform processing such as cutting the cutting beam 14 on site, and the work of installing the cutting beam 14 is significantly simplified.

FIG. 5 shows another embodiment, in which the same components as those in the previous embodiment are denoted by the same reference numerals, and the description thereof will be omitted. That is, in this embodiment, when the first and second cut beams 14a and 14b are connected to each other via the connection plate 42, the connection plate 42 is arranged only on the upper surfaces of the first and second cut beams 14a and 14b. The connecting plate 42 is connected to the PCa capital plate 2
Anchor bolt 7 buried in and protruded from its upper surface
1 and a nut 71a. A pressing member 50 having a U-shaped cross section is provided on the upper surfaces of the first and second cut beams 14a and 14b at the periphery of the PCa capital plate 22.
Is arranged, and the space between the pressing member 50 and the PCa capital plate 22 is tightened via the bolt 52 and the nut 52a. Further, when supporting the floor slab 36 on the PCa capital plate 22, the PCa capital plate 2
An angle member 54 protrudes from the upper surface of the outer peripheral edge of the floor 2 and the upper surface of the end of the floor slab 36 is
6, it is fixed via a nut 56a.

Further, in this embodiment, by embedding the cutting beam 14 in the flat slab 38, the amount of slab arrangement can be reduced, and the support bracket 18 of the reverse strut 12 can be used to construct the capital portion. P supported by
By using the Ca capital plate 22, it is possible to omit the use of the formwork and the shoring, and it is possible to save the temporary construction, the labor and the construction period.

In each of the embodiments described above, the structure having the second basement floor is taken as an example. However, the present invention is not limited to this and can be applied to a structure having three or more basement floors. Needless to say.

[0025]

As described above, in the method of constructing an underground structure according to the present invention, the cut beams arranged vertically and horizontally are combined in a cross-girder shape within a plane at the same height level. The girder itself can be configured with the required member dimensions, and while maintaining the required rigidity and strength, the height of the girder-shaped intersection of the girder is reduced to the height equivalent to the girder. The thickness of a flat slab constructed by embedding a cutting beam in concrete can be reduced as much as possible. Therefore, the floor height can be increased, and the amount of concrete placed on the floor can be significantly reduced, thereby reducing the construction cost.

Further, the cutting beam is assembled to the upright strut via a PCa capital plate. Since this PCa capital plate is loosely fitted to the upright strut with an appropriate gap, the upright strut may be mounted due to a mounting error. Even in the case where the position is deviated from the normal position, the loose fitting portion absorbs the error in setting up the back strut, so that the cutting beam can be easily installed at the normal position without the need for processing work on site. It has various excellent effects.

[Brief description of the drawings]

FIG. 1 is a process chart of a procedure for constructing an underground structure showing one embodiment of the present invention.

FIG. 2 is an enlarged plan view of a main part of a cross-girder combination part of a cutting beam showing one embodiment of the present invention.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is an enlarged plan view of a main part of a cross-girder combination portion of a cutting beam according to another embodiment of the present invention.

FIG. 5 is a cross-sectional side view of an essential part of an enlarged cross-girder combination portion of a cutting beam showing another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 12 reverse strut 14 cut beam 14a first cut beam 14b second cut beam 18 support bracket 22 PCa capital plate 22a insertion hole 36 floor slab 36a concrete 38 flat slab

Continued on the front page (72) Inventor Shokichi Gokan 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo Obayashi-gumi Tokyo Head Office (72) Inventor Mikio Mizuta 2-3-3 Kandaji-cho, Chiyoda-ku, Tokyo Obayashi-gumi Tokyo Co., Ltd. In-house (56) References JP-A-3-72119 (JP, A) JP-A-7-90979 (JP, A) JP-A-5-148837 (JP, A) JP-A 8-239907 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02D 29/045 E04B 1/35 E21D 13/00

Claims (1)

(57) [Claims] After a reverse strut having a support bracket is cast, a PCa capital plate is loosely fitted to the reverse strut at an appropriate interval to be supported by the support bracket,
Next, the cutting beams arranged vertically and horizontally with respect to the reverse strut are combined in a cross-girder shape within a plane at the same height level to form the PC.
a a concrete structure is placed on a capital plate, concrete is poured into a floor form laid so as to cover the lower side of these cut beams, and the cut beams are embedded in the concrete. Construction method.