JP7311456B2 - Construction method of underground structure - Google Patents

Description

The present invention relates to a method for constructing an underground structure in the form of box culverts made of reinforced concrete.

Patent Literature 1 discloses a box culvert used as a road, waterway, or the like. This box culvert is a box-shaped buried structure, comprising a bottom plate, left and right side walls and a top plate. In patent document 1, when constructing a box culvert, first, a bottom slab and left and right side walls are constructed, and then a top slab is constructed. In Patent Document 1, the top slab is composed of an embedded mold and a main body. This main body is formed by cast-in-place concrete that is poured over the embedded formwork. In Patent Document 1, after the embedded formwork is erected between the left and right side walls, various reinforcing bars are placed on the embedded formwork, and then cast-in-place concrete is placed above the embedded formwork. A top plate is constructed (see paragraphs 0020 and 0021 of Patent Document 1).

Japanese Patent No. 6395465

However, when there is an existing structure directly above the place where the box culvert is scheduled to be constructed, it is impossible to arrange reinforcing bars on the above-mentioned embedded formwork. Couldn't build a culvert.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for constructing a box culvert-shaped underground structure that can be constructed even under the above-mentioned restrictions on the altitude.

Therefore, the method for constructing an underground structure according to the present invention is a method for constructing a box culvert-shaped underground structure made of reinforced concrete. This method includes a first step of excavating the ground to form a tunnel in the ground, a second step of constructing a bottom slab and sidewalls of the underground structure in the tunnel, and a construction of the underground structure in the tunnel. and a third step of constructing the top plate. The third process includes a formwork assembling process of assembling a top slab construction formwork on the bottom slab, a reinforcing bar assembling process of assembling top slab reinforcing bars on the assembled top slab construction formwork, and a top slab reinforcing bar is placed on the top slab construction formwork, from the top of the bottom slab to a predetermined height position, and the upper surface of the top slab construction formwork located at the predetermined height position and the vertical shaft and a concrete placing step of placing concrete in the space between the top surface. In the concrete placing step, concrete is placed in the space while the top slab reinforcing bars are placed in the space.

According to the present invention, after the top slab construction form on which the top slab reinforcing bars are placed is raised to a predetermined height position from above the bottom slab, the upper surface of the top slab construction form and the ceiling of the pit Concrete is placed in this space with the reinforcing bars for the top slab placed in the space between the end faces. Therefore, it is possible to easily construct the top slab even under the above-mentioned restrictions on the sky, and eventually to construct a box culvert-shaped underground structure.

A diagram showing a schematic configuration of a tunnel in one embodiment of the present invention Flowchart of the tunnel construction method in the embodiment Flowchart of the construction method of the top slab in the embodiment The figure which shows the lateral pit formed in the lateral pit formation process in said one Embodiment. A diagram showing the bottom plate and side walls constructed in the bottom plate/side wall construction step in the embodiment. The figure which shows the construction method of the top plate in said one Embodiment. The figure which shows the construction method of the top plate in said one Embodiment. The figure which shows the construction method of the top plate in said one Embodiment. A diagram showing a method of raising the formwork for constructing the top slab by the raising means in the embodiment. The perspective view of the boxing member in said one embodiment. A diagram showing a method of fixing the top slab construction formwork at a predetermined height position in the embodiment. The figure which shows the concrete placing process in said one Embodiment. A diagram showing a post-processing method for unboxing according to the embodiment. A diagram showing a method of constructing a top slab using a plurality of top slab construction forms in the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1(a) is a diagram showing a schematic configuration of a tunnel 1 in one embodiment of the present invention. FIG. 1(a) is a cross-sectional view taken along the line AA of FIG. 1(a).

The tunnel 1 is an example of the "underground structure" of the present invention, and is in the form of a box culvert made of reinforced concrete. The tunnel 50 located above the tunnel 1 is an example of the "existing structure" of the present invention, and was constructed prior to the construction of the tunnel 1.

The tunnel 50 is, for example, a railway tunnel such as a subway tunnel or a road tunnel, and is built in the ground G (underground) under the ground GL.
The tunnel 1 is constructed in the ground so as to extend in the transverse direction directly under the existing tunnel 50, and can be used, for example, as a passage (underpass of the tunnel 50) through which pedestrians can pass.

The tunnel 1 has a rectangular cross section and is composed of a pair of left and right side walls 2L and 2R, a top plate 3 connecting the upper ends of the side walls 2L and 2R, and a bottom plate 4 connecting the lower ends of the side walls 2L and 2R. It is configured. Here, the side walls 2L, 2R, the top plate 3, and the bottom plate 4 are made of reinforced concrete.

The top surface 3 a of the top plate 3 of the tunnel 1 is in contact with the bottom surface 50 a of the tunnel 50 . Here, the lower surface 50a can be, for example, the lower surface of the lower floor slab of a subway or the lower surface of the lower floor slab of a road tunnel.

FIG. 2 is a flow chart of a tunnel 1 construction method. In this embodiment, the tunnel 1 is constructed under the existing tunnel 50 .

In the construction method of the tunnel 1, first, in step S1, as a work space forming step, work spaces 5 and 6 (see FIG. 1(a)) are formed in the ground. This work space forming step corresponds to the "fourth step" of the present invention. Here, "formation of work space" means formation of a work space for performing steps S2 to S4 (steps S11 to S16) to be described later. This "working space formation" may include constructing shafts in the ground or utilizing other construction site spaces. In this regard, FIG. 1(a) shows that the work space 5 is formed by constructing a shaft 5a in the ground, and that the space of another construction site is used as the work space 6. is shown. Here, the formation of the work spaces 5 and 6 is not limited to that shown in FIG. 1(a).
Work spaces 5 and 6 may be formed on both sides of tunnel 50 .

Next, in step S2, as a tunnel formation step, excavation of the ground G is started substantially horizontally from within the work space 5 and/or within the work space 6, and the ground directly below the tunnel 50 is excavated. A tunnel 7 is formed therein. This tunnel formation step corresponds to the "first step" of the present invention.

FIG. 4 shows a lateral pit 7 having a rectangular cross section formed in the lateral pit forming process. As shown in FIG. 4 , the tunnel formation process includes erecting steel shoring 8 along the inner peripheral surface of the tunnel 7 . The shoring 8 includes a pair of left and right side shorings 9L and 9R, an upper shoring 10 connecting the upper ends of the side shorings 9L and 9R, and a lower shoring connecting the lower ends of the side shorings 9L and 9R. It can be formed by assembling the shoring 11 into a rectangular shape. The side shorings 9L, 9R, the upper shoring 10, and the lower shoring 11 are made of H-section steel, for example.

In the pit formation step, the pit 7 communicating with the work spaces 5 and 6 is formed by repeating excavation of the ground G and installation of the support 8 at intervals of, for example, about 1 m. Here, the upper flanges of each of the plurality of upper shorings 10 installed at intervals in the extending direction of the tunnel 7 are in contact with the lower surface 50a of the tunnel 50. subsidence of the tunnel 50 during construction is suppressed. Here, the lower surface 50a of the tunnel 50 described above can function as at least part of the top end surface of the tunnel 7. As shown in FIG. Also, the upper shoring 10 is a portion of the shoring 8 that faces the top surface of the horizontal hole 7 .

In addition, prior to the tunnel formation process, the ground improvement area 12 shown in FIG. It may be formed (soil improvement process). That is, this ground improvement step can be performed prior to the above-described tunnel formation step. In addition, this ground improvement step may be performed before or after the work space formation step described above, or may be performed in parallel with the work space formation step described above.

Next, in step S3, the bottom slab 4 and the side walls 2L and 2R are constructed along the inner peripheral surface of the lateral hole 7 as a step of constructing the bottom slab and side walls. This bottom plate/side wall construction step corresponds to the "second step" of the present invention.

FIG. 5 shows the bottom plate 4 and side walls 2L and 2R constructed in the bottom plate/side wall construction step.
In the present embodiment, the entire bottom slab 4 and main body portions 2La and 2Ra of the side walls 2L and 2R are constructed in the bottom slab/side wall constructing step.

Body portions 2La and 2Ra of the side walls 2L and 2R rise from the left and right ends of the bottom slab 4. As shown in FIG. The upper surfaces 2Lb and 2Rb of the main bodies 2La and 2Ra are positioned about 50 to 80 cm lower than the lower surface 3b (see FIG. 1) of the top plate 3 constructed in the top plate construction step described later. Portions of the side shorings 9L and 9R below the upper surfaces 2Lb and 2Rb of the main bodies 2La and 2Ra are entangled with the concrete forming the main bodies 2La and 2Ra. Here, the lower shoring 11 is also caught by the concrete forming the bottom slab 4 .

At the time when the body portions 2La and 2Ra of the side walls 2L and 2R are constructed, the portions of the side supports 9L and 9R above the upper surfaces 2Lb and 2Rb of the body portions 2La and 2Ra are exposed in the tunnel 7. are doing. In addition, of the outer vertical reinforcing bars 2Lc, 2Rc and the inner vertical reinforcing bars 2Ld, 2Rd that constitute the side walls 2L, 2R, portions above the upper surfaces 2Lb, 2Rb of the main body portions 2La, 2Ra are also exposed in the tunnel 7. ing. Here, the upper ends of the outer vertical reinforcing bars 2Lc and 2Rc are positioned higher than the upper ends of the inner vertical reinforcing bars 2Ld and 2Rd. As for the side walls 2L and 2R, a plurality of outer vertical reinforcing bars 2Lc and 2Rc are arranged at intervals in the axial direction of the tunnel 1 (extending direction of the tunnel 7), and a plurality of inner vertical reinforcing bars 2Ld are arranged. , 2Rd are spaced apart in the axial direction of the tunnel 1 .

One ends of the upper reinforcing bars 3La and 3Ra are connected to the upper ends of the outer vertical reinforcing bars 2Lc and 2Rc, respectively. Each of the upper reinforcing bars 3La and 3Ra extends substantially horizontally, and the other ends thereof face each other with a space P1 therebetween. This interval P1 is shorter than the length of the upper main reinforcing bars 24 constituting the top slab reinforcing bars 20, which will be described later, by twice the length of the lap joint.

One ends of the lower reinforcing bars 3Lb and 3Rb are connected to the upper ends of the inner vertical reinforcing bars 2Ld and 2Rd, respectively. Each of the lower reinforcing bars 3Lb and 3Rb extends substantially horizontally, and the other ends thereof are opposed to each other with an interval P2 therebetween. This interval P2 is longer than the length of the upper main reinforcing bars 24 constituting the top slab reinforcing bars 20 described later, and is shorter than the length of the lower main reinforcing bars 23 by twice the length of the lap joint.

Next, in step S4, as a top slab construction step, the top slab 3 is constructed along the inner peripheral surface of the lateral hole 7. As shown in FIG. This top plate construction step corresponds to the "third step" of the present invention.
In the present embodiment, in the top plate construction step, the entire top plate 3 and the remaining portions 2Le and 2Re of the side walls 2L and 2R (portions other than the main portions 2La and 2Ra described above) are collectively constructed (see FIG. 8 to be described later). (f)).

FIG. 3 is a flow chart of the construction method of the top slab 3, which is carried out in the top slab construction process described above, and FIGS. It is a diagram.

In the method of constructing the top slab 3, first, in step S11, as a support material placement step, a support material 16 for supporting the top slab construction formwork 15 from below is placed on the bottom slab 4 (Fig. 6 (A) )reference). The height (length in the vertical direction) of the support material 16 is such that a worker can enter under the top slab construction formwork 15, and is, for example, about 1.0 to 1.5 m. . In this step, a plurality of supports 16 can be arranged on the bottom plate 4 .

Next, in step S12, as a form assembly step, the top slab construction form 15 is assembled on the support member 16 on the bottom slab 4 (see FIG. 6(a)). In this step, for example, a thick end member 17 (see FIGS. 9 and 11) made of a square pipe or the like is poured over the support member 16, and the metal foam 18 is assembled thereon. This metal form 18 constitutes the formwork 15 for constructing the top slab.

Extending portions 18a extending downward from the left and right ends of the metal foam 18 are provided. The extension 18a functions as a formwork for construction of the remaining portions 2Le and 2Re of the side walls 2L and 2R (portions other than the main portions 2La and 2Ra described above). That is, the top slab construction formwork 15 is provided with construction formwork for the remaining portions 2Le and 2Re of the side walls 2L and 2R (portions other than the main body portions 2La and 2Ra described above), and the metal form 18 and the extension portion 18a provide a core. It has a letter-shaped cross section.

Next, in step S13, as a reinforcing bar assembling step, the top slab reinforcing bars 20 are assembled on the top slab construction formwork 15 to form a reinforcing bar cage (see FIG. 6(a)). In this step, for example, first, a plurality of spacers 21 are placed on the top slab construction form 15 at intervals, and then the top slab reinforcing bars 20 are assembled on the spacers 21 to form a reinforcing bar cage. do. Here, the top slab reinforcing bars 20 may include, for example, the lower main bars 23, horse bars (not shown) (construction bars), the upper main bars 24, the shear reinforcing bars 25, and the like.

Next, in step S14, as a formwork raising process, first, the raising means 30 for raising the top slab construction formwork 15 and the formwork guide/fixing means 40 are installed in the tunnel 7 (FIG. 7). (C) see). Then, the top slab construction formwork 15 on which the top slab reinforcing bars 20 are placed via the spacers 21 is lifted from above the support material 16 on the bottom slab 4 using the lifting means 30 and the formwork guide/fixing means 40. Raise it to a predetermined height position (see FIG. 7(d)). Here, the predetermined height position is the height position at which the top slab construction formwork 15 is installed for concrete placement in the concrete placement step described later, and is set in advance. When the top slab construction formwork 15 is positioned at this predetermined height position, the height of the upper surface of the metal form 18 substantially matches the height of the lower surface 3b of the top slab 3 to be constructed. .

Here, the mold lifting process using the lifting means 30 and the mold guiding/fixing means 40 will be further described with reference to FIGS. 9 to 11 in addition to FIGS. 7(c) and (d).
FIG. 9 is a diagram showing how the top slab construction formwork 15 is lifted by the lifting means 30. As shown in FIG. 10 is a perspective view of the box extracting member 39. FIG. FIG. 11 is a diagram showing a method of fixing the top slab construction formwork 15 at a predetermined height position.

The lifting means 30 includes a plurality of linear members 31, center hole jacks 32 provided on each linear member 31, a fixing device 33 positioned above the center hole jacks 32, and positioned below the center hole jacks 32. and a reaction force receiving device 34 .

The plurality of linear members 31 are arranged parallel to each other, for example, in a matrix when viewed from above. The linear member 31 extends vertically, has an upper end fixed to the upper shoring 10 , and hangs down from the upper shoring 10 within the tunnel 7 . In the present embodiment, the linear member 31 may be, for example, a PC steel wire, a threaded reinforcing bar, a fully threaded PC steel bar such as Gevin Destave (registered trademark), or a tension rod.
In this embodiment, the upper end of the linear member 31 is fixed to the upper shoring 10, but instead of this, the upper end of the linear member 31 may be fixed to the lower surface 50a of the tunnel 50. good.

A first through-hole (not shown) is formed in the metal form 18 so as to overlap the installation position of the linear member 31 in plan view, and the linear member 31 is inserted through the first through-hole. . This first through hole is formed between the adjacent end thick members 17 , 17 .

The linear member 31 is inserted through a central through hole (not shown) of the center hole jack 32 . The center hole jack 32 includes, for example, one or more telescopic jacks 36, a lower clamp 37 attached to the lower ends of the telescopic jacks 36 and capable of gripping the linear member 31, and an upper end of the telescopic jacks 36 attached to the linear and an upper clamp 38 capable of gripping the member 31 . The telescopic jack 36 extends in the vertical direction and is configured to be telescopic in the vertical direction.

The center hole jack 32 is positioned below the first through hole of the metal foam 18 and the end thick member 17 . A fixing device 33 is arranged between the center hole jack 32 and the end thick member 17 . The fixing device 33 can be fixed to the linear member 31 . The fixing device 33 is for temporarily fixing the top slab construction formwork 15 to the linear member 31 . The fixing device 33 includes, for example, a wedge member driven into the linear member 31 . It should be noted that the fixing device 33 is not limited to one that includes a wedge member.

A reaction force receiving device 34 is arranged below the center hole jack 32 . The reaction force receiving device 34 can be fixed to the linear member 31 . The reaction force receiving device 34 functions as a reaction force receiving device when the telescopic jack 36 of the center hole jack 32 is extended (when the top slab construction formwork 15 rises with respect to the linear member 31). The reaction force receiving device 34 includes, for example, a wedge member driven into the linear member 31 . Note that the reaction force receiving device 34 is not limited to one that includes a wedge member.

A box removing member 39 is provided above the first through hole in the metal form 18 . The box-opening member 39 is, for example, a styrofoam half-cylinder shape, and the linear member 31 is inserted through the central through-hole 39a. This deboxing member 39 is for deboxing the upper surface of the metal form 18 in the concrete placing process, which will be described later.

The formwork guide/fixing means 40 includes a plurality of first linear members 41 each extending in the vertical direction, a second linear member 42 extending downward from the lower ends of the first linear members 41, and a first linear member and a fixing device 43 that can be fixed to the member 41 .

The plurality of first linear members 41 are arranged parallel to each other in a matrix form, for example, in plan view. The first linear member 41 has its upper end fixed to the upper shoring 10 and hangs down from the upper shoring 10 within the tunnel 7 . In the present embodiment, the first linear member 41 may be, for example, a PC steel wire, a threaded reinforcing bar, a fully threaded PC steel bar such as Gevin Destave (registered trademark), or a tension rod.
In this embodiment, the upper end of the first linear member 41 is fixed to the upper support 10 , but instead of this, the upper end of the first linear member 41 is fixed to the lower surface 50 a of the tunnel 50 . may be

The second linear member 42 hangs down from the lower end of the first linear member 41 within the lateral hole 7 . In the present embodiment, the second linear member 42 can be, for example, a PC steel wire, a threaded reinforcing bar, a fully threaded PC steel bar such as Gevin Destave (registered trademark), or a tension rod.

In this embodiment, an example in which the upper portion of one threaded reinforcing bar 45 functions as the first linear member 41 and the portion (remaining portion) other than the upper portion functions as the second linear member 42 will be described below. do. However, the first linear member 41 and the second linear member 42 are not limited to being integral, and may be separated and connected to each other in a separable manner.

A second through hole (not shown) is formed in the metal form 18 so as to overlap the installation position of the screw reinforcing bar 45 (the first linear member 41 and the second linear member 42) in a plan view. A screw reinforcing bar 45 can be inserted through the second through hole. This second through hole is formed between the adjacent end thick members 17 , 17 .

Similarly to the linear member 31 described above, the threaded reinforcing bar 45 is also provided with a box-cutting member 39 for box-cutting on the upper surface of the metal form 18 in the concrete placing process, which will be described later.

The fixing device 43 can be fixed to the screw reinforcing bar 45 (especially the first linear member 41). The fixing device 43 is for temporarily fixing the top slab construction formwork 15 to the screw reinforcing bars 45 (especially the first linear member 41). The fixing device 43 is composed of, for example, a nut that can be screwed onto the screw reinforcing bar 45 (especially the first linear member 41). It should be noted that the fixing device 43 is not limited to a nut.

In the formwork raising process, as shown in FIG. 7(c), a worker enters under the metal form 18 of the formwork 15 for constructing the top plate placed on the support material 16 on the bottom plate 4 and lifts the center hole jack. 32 , a fixing device 33 and a reaction force receiving device 34 are installed at the lower end of the linear member 31 . Then, by repeating the lifting cycle consisting of the steps shown in FIGS. 9A to 9D, the top slab construction formwork 15 and the top slab reinforcing bars 20 are integrally jacked up.

In the ascending cycle described above, first, in the step shown in FIG. The lower clamp 37 is in a tightened state (a state in which the lower clamp 37 grips the linear member 31), and the upper clamp 38 is in an open state (a state in which the upper clamp 38 does not grip the linear member 31), The telescopic jack 36 is shortened, and the fixing device 33 is not fixed (the fixing device 33 is not fixed to the linear member 31 and can slide up and down along the linear member 31).

Next, in the step shown in FIG. 9A, the reaction force receiving device 34 is fixed, the lower clamp 37 of the center hole jack 32 is tightened, the upper clamp 38 is opened, and the fixing device 33 is not fixed. While maintaining the state, the telescopic jack 36 of the center hole jack 32 is extended. This extension action raises the upper clamp 38 of the center hole jack 32, the fixing device 33 and the top slab building formwork 15. As shown in FIG. That is, the center hole jack 32 can take reaction force from the linear member 31 via the reaction force receiving device 34 to push up the top slab construction formwork 15 .

Next, in the step shown in FIG. 9C, while maintaining the fixed state of the reaction force receiving device 34 and the non-fixed state of the fixing device 33, the upper clamp 38 of the center hole jack 32 is tightened (upper The clamp 38 grips the linear member 31), the lower clamp 37 is opened (the lower clamp 37 does not grip the linear member 31), and the telescopic jack 36 is shortened. This shortening action pulls the lower clamp 37 upward.

Next, in the step shown in FIG. 9D, while maintaining the unfixed state of the fixing device 33, the tightened state of the upper clamp 38 of the center hole jack 32, and the shortened state of the telescopic jack 36, the lower clamp 37 is tightened, and the reaction force receiving device 34 is lifted upward and brought into contact with the lower surface of the lower clamp 37 of the center hole jack 32 to be fixed.

After repeating the lifting cycle consisting of the steps shown in FIGS. , the fixing device 33 is brought into a fixed state (a state in which the fixing device 33 is fixed to the linear member 31).

In addition, when the tightening force by the upper clamp 38 and the lower clamp 37 of the center hole jack 32 (the force with which the upper clamp 38 and the lower clamp 37 grip the linear member 31) is sufficiently large, the fixing device 33 and the reaction force receiver Device 34 may be omitted.

In the state shown in FIG. 7C, the lower end portion of the screw reinforcing bar 45 (especially the lower end portion of the second linear member 42) is inserted through the second through hole of the metal foam 18 described above. 9(a) to 9(d) are repeated to raise the top slab construction formwork 15 on which the top slab reinforcing bars 20 are placed to the above-described predetermined height position. Between them, the second linear member 42 functions as a guide device that guides the aforementioned second through-hole of the metal foam 18 to the first linear member 41 (see FIG. 7D).

FIG. 11(a) shows a state in which the top slab construction formwork 15 on which the top slab reinforcing bars 20 are placed is raised to the aforementioned predetermined height position. The lower end of the first linear member 41 inserted through the second through-hole protrudes downward from the end thick member 17 . After that, as shown in FIG. 11(a), the second linear member 42 that has served as the aforementioned guide device is separated from the first linear member 41 (in this embodiment, the threaded reinforcing bars 45 are separated from each other). The threaded reinforcing bar 45 is cut so as to leave the portion corresponding to the first linear member 41, and the portion corresponding to the second linear member 42 below it is removed). Then, as shown in FIG. 11C, the fixing device 43 is fixed to the lower end of the first linear member 41 below the second through-hole of the metal foam 18 and the end thick member 17 (FIG. 8). (e) see).

For one top slab construction formwork 15, for example, the linear members 31 are arranged at six locations, and a plurality of first linear members 41 (threaded reinforcing bars 45) for supporting the top slab construction formwork 15 are provided. If they are arranged at intervals of 1 m x 1 m, they are jacked up with six center hole jacks 32, and when they reach the aforementioned predetermined height position, the fixing device 43 is fixed to the lower end of the first linear member 41. .

Here, the upper reinforcing bars 3La and 3Ra, which are already installed reinforcing bars (precedingly installed reinforcing bars) for the top slab 3, are longer than the lower reinforcing bars 3Lb and 3Rb. As for the top slab reinforcing bars 20 assembled on the top slab construction formwork 15 , the upper main bars 24 are shorter than the lower side main bars 23 . The interval P1 between the other ends of the opposing upper reinforcing bars 3La and 3Ra is smaller than the length of the upper main reinforcing bar 24 by twice the length of the lap joint. The interval P2 between the other ends of the opposing lower reinforcing bars 3Lb and 3Rb is longer than the length of the upper main reinforcing bar 24 and shorter than the length of the lower main reinforcing bar 23 by twice the length of the lap joint. Therefore, by jacking up the top slab construction formwork 15 and the top slab reinforcing bars 20 integrally and vertically, the required lap joint length between the upper reinforcing bars 3La and 3Ra and the upper main bars 24 can be secured. While securing the required lap joint length of the lower reinforcing bars 3Lb, 3Rb and the lower main reinforcing bars 23, the top slab reinforcing bars 20 are installed to the existing reinforcing bars for the top slab 3 (the upper reinforcing bars 3La, 3Ra and the lower side It can be accurately fitted between the reinforcing bars 3Lb, 3Rb).

When the formwork raising process is completed, the process advances to step S15, and as a concrete placing process, the upper surface (the upper surface of the metal form 18) and the side surface (the extension part) of the top plate construction formwork 15 located at the predetermined height position 18a) and the top surface of the tunnel 7 (including the bottom surface 50a of the tunnel 50) and the side surface, concrete is placed in the space S (see FIGS. 8(e) and (f)). As a result, the entire top plate 3 and the remaining portions 2Le and 2Re of the side walls 2L and 2R (portions other than the main portions 2La and 2Ra described above) are assembled together. In this concrete placing step, concrete is placed in the space S with the top plate reinforcing bars 20 arranged therein.

Since the top slab construction formwork 15 may not have sufficient rigidity for the load of the concrete placed in this concrete placing process, the first linear member 41 and the fixing device 43 can be supported (see FIG. 12).
Moreover, since the spacer 21 is arranged under the reinforcing bar cage formed by assembling the reinforcing bars 20 for the top slab, it is possible to reliably secure the cover.

After the concrete placed in the concrete placing step has hardened, the process proceeds to step S16, in which the fixing device 43 is removed from the first linear member 41 as a demolding step, and the lifting cycle is reversed to the above-described lifting cycle. A cycle is performed to stepwise lower the top slab construction formwork 15 onto the aforementioned support members 16 . Then, the top slab construction formwork 15 is dismantled.

FIG. 13 is a diagram showing a post-processing method for unboxing that is performed after the demolding process.
In the above-described concrete placing step, the lower end portion of the first linear member 41 and the upper surface of the metal form 18 are deboxed using the deboxing member 39 described above. FIG. 13(a) shows a box-out portion H formed by removing the metal foam 18 and the box-out member 39. FIG. In the box-out post-processing, of the lower ends of the first linear members 41, excess exposed portions at the box-out portion H are removed (see FIG. 13(a)), and then the box-out portion is removed. H is filled with a filler 48 such as resin mortar (see FIG. 13(c)).

FIG. 14 is a diagram showing a construction method of the top slab 3 using a plurality of top slab construction forms 15 in the axial direction of the tunnel 1 .
When the length of the tunnel 1 in the axial direction is short, the top slab 3 can be constructed with one top slab construction formwork 15 . However, if the length of the tunnel 1 in the axial direction is long, it is difficult to construct the top slab 3 with one top slab construction formwork 15 . For this reason, for example, as shown in FIG. 14, the tunnel 1 is divided into a plurality of blocks in the axial direction, and the top slab construction formwork 15 is prepared for each block, and steps S11 to S13 described above are prepared for each block. (support material placement process, formwork assembly process, and reinforcing bar assembly process) are carried out. Then, step S14 (formwork raising step) is performed for each block in order from one side in the axial direction of the tunnel 1 to the other side, thereby forming a plurality of top slabs at the predetermined height positions. A formwork 15 is placed. After that, the aforementioned step S15 (concrete placing step) is performed collectively for a plurality of blocks. Then, step S16 (demolding step) is performed for each block.

In the example shown in FIG. 14, the joints of the upper main reinforcement 24' and the lower main reinforcement 23' in the axial direction of the tunnel 1 are lap joints, but these joints may not be lap joints. In that case, the length of the top slab construction formwork 15 in the axial direction of the tunnel 1, the length of the upper main reinforcement 24', and the length of the lower main reinforcement 23' are substantially the same, and the top slab construction formwork 15 The end of the upper main reinforcement 24' and the end of the lower main reinforcement 23' may be positioned immediately above the end of the .
Moreover, the construction method of the top slab 3 using a plurality of top slab construction forms 15 in the axial direction of the tunnel 1 is not limited to the above-described method.

The tunnel 1 is constructed as described above.

By the way, most of the bar arrangement work at the time of constructing the top slab 3 has hitherto been done manually upward, which is inefficient and difficult to ensure accuracy. In this regard, according to the present embodiment, after the worker performs the work of assembling the formwork 15 for constructing the top slab and the work of assembling the reinforcing bars 20 for the top slab (the work of assembling the reinforcing bar cage) downward, the center hole jack Since it is only necessary to jack up and install at 32, there is almost no upward manual work. Therefore, the work efficiency is improved and the accuracy of bar arrangement is improved.

According to this embodiment, the method for constructing an underground structure is a method for constructing a reinforced concrete box culvert-shaped underground structure (for example, the tunnel 1). This method includes a first step (horizontal tunnel formation step: S2) of forming a tunnel 7 in the ground by excavating the ground G, and a bottom plate 4 of an underground structure (for example, a tunnel 1) in the tunnel 7. and a second step of constructing the side walls 2L and 2R (bottom/sidewall construction step: S3), and a third step of constructing the top slab 3 of the underground structure (for example, the tunnel 1) in the tunnel 7 (top slab construction Step: S4). The third step (top slab construction step: S4) includes a formwork assembly step (S12) for assembling the top slab construction formwork 15 on the bottom slab 4, and A reinforcing bar assembling step (S13) for assembling the plate reinforcing bars 20, and a form raising step ( S14), and a concrete placing step (S15) of placing concrete in the space S between the upper surface of the top slab construction formwork 15 positioned at the predetermined height and the top surface of the lateral hole 7. ,including. In the concrete placing step ( S<b>15 ), concrete is placed in the space S with the top slab reinforcing bars 20 placed in the space S. Therefore, the top slab 3 can be easily constructed even under the restrictions of the sky due to the existing tunnel 50 or the like.

Further, according to the present embodiment, the method for constructing an underground structure includes the fourth step (working space forming step: S1) is further included. In the first step (horizontal tunnel formation step: S2), excavation of the ground G is started substantially horizontally from within the working spaces 5 and 6 to form a horizontal tunnel 7 . Therefore, the working spaces 5 and 6 can be used for forming the tunnel 7 .

In addition, according to the present embodiment, the third step (top slab construction step: S4) involves installing the support material 16 for supporting the top slab construction formwork 15 from below prior to the form assembly step (S12). Further includes a step of placing a support material on the bottom plate 4 (S11). As a result, a space for installing the center hole jack 32 or the like can be secured below the top slab construction formwork 15 .

Further, according to this embodiment, an underground structure (for example, tunnel 1) is constructed below an existing structure (for example, tunnel 50). Therefore, the top slab 3 can be easily constructed even under the restrictions of the sky due to existing structures.

Further, according to this embodiment, the upper surface 3a of the underground structure (for example, the tunnel 1) and the lower surface 50a of the existing structure (for example, the tunnel 50) come into contact with each other. Therefore, the underground structure (for example, the tunnel 1) can support the existing structure (for example, the tunnel 50) from below, thereby suppressing the subsidence of the tunnel 50.

Further, according to the present embodiment, the first step (horizontal tunnel formation step: S2) includes erecting the shoring 8 along the inner peripheral surface of the horizontal tunnel 7 . The lifting means 30 for lifting the top slab construction formwork 15 in the formwork raising step (S14) includes a vertically extending linear member 31 and a center hole jack 32 through which the linear member 31 is inserted through the central through hole. and including. The linear member 31 is fixed at its upper end to an existing structure (for example, the tunnel 50), or fixed to a portion (for example, the upper shoring 10) of the shoring 8 facing the top end surface of the horizontal hole 7. , hangs down in the lateral hole 7 and is inserted through the through hole (first through hole described above) of the top slab construction formwork 15 . A center hole jack 32 is positioned below the through hole (first through hole described above) of the top slab construction formwork 15 . The center hole jack 32 can take the reaction force from the linear member 31 and push up the top slab construction formwork 15 . Therefore, the raising means 30 can be configured simply.

In addition, regarding the jack-up of the top slab construction formwork 15 by a plurality of center hole jacks 32, while measuring the amount of rise (displacement) of each center hole jack 32 with an appropriate measuring means, the number of center hole jacks 32 You may make it perform expansion-contraction operation|movement control.

It may be necessary to bind with binding wires at the lap joints between the upper and lower main bars 24 and 23 of the top slab reinforcing bars 20 and the upper and lower reinforcing bars 3La and 3Ra and the lower reinforcing bars 3Lb and 3Rb. In this case, only the reinforcing bar cage formed by assembling the top slab reinforcing bars 20 is lifted to the set position, the top slab construction formwork 15 is also lifted to about 1.5 m below the reinforcing bar cage, and the top slab construction formwork 15 is lifted. After binding the reinforcing bars of the lap joint portion as the work floor, the work floor (top slab construction formwork 15) can be lifted to the above-mentioned predetermined height position and installed.

In this embodiment, the jack-up construction method using the linear member 31 and the center hole jack 32 as the lifting means 30 has been described. It is not limited to this. For example, it is also possible to install a sand on the bottom slab 4 and push up the top slab construction formwork 15 on the sand by sandwiching a jack.

The illustrated embodiments are merely illustrative of the present invention, and the present invention includes various improvements and modifications made by those skilled in the art within the scope of the claims in addition to those directly indicated by the described embodiments. It goes without saying that it is inclusive.

1 Tunnel 2L, 2R Side wall 2La, 2Ra Main body 2Lb, 2Rb Upper surface 2Lc, 2Rc Outer vertical reinforcing bar 2Ld, 2Rd Inner vertical reinforcing bar 2Le, 2Re Remainder 3 Top slab, 3a... upper surface, 3b... lower surface, 3La, 3Ra... upper reinforcing bars, 3Lb, 3Rb... lower reinforcing bars, 4... bottom slab, 5, 6... work space, 5a... vertical shaft, 7... horizontal shaft, 8... support work, 9L, 9R... Side shoring, 10... Upper shoring, 11... Lower shoring, 12... Ground improvement area, 15... Top slab construction formwork, 16... Shoring material, 17... End thick material, 18... Metal form, 18a... Extension part 20... Top plate reinforcing bar 21... Spacer 23, 23'... Lower side main bar 24, 24'... Upper side main bar 25... Shear reinforcing bar 30... Elevating means 31... Linear member, 32... Center hole jack, 33... Fixing device, 34... Reaction force receiving device, 36... Telescopic jack, 37... Lower clamp, 38... Upper clamp, 39... Box removal member, 39a... Central through-hole, 40... Form guide Fixing means 41 First linear member 42 Second linear member 43 Fixing device 45 Screw reinforcing bar 48 Filling material 50 Tunnel 50a Lower surface G Ground GL Ground , H... box-out portion, P1, P2... interval, S... space

Claims (7)

A method for constructing a reinforced concrete box culvert underground structure comprising:
A first step of forming a tunnel in the ground by excavating the ground;
a second step of constructing a bottom slab and sidewalls of the underground structure within the tunnel;
a third step of constructing a top slab of the underground structure within the tunnel;
including
The third step is
a formwork assembling step of assembling a formwork for constructing the top slab on the bottom slab;
a reinforcing bar assembling step of assembling top slab reinforcing bars on the assembled top slab construction formwork;
a formwork raising step of raising the formwork for constructing the top slab on which the reinforcing bars for the top slab are placed to a predetermined height position above the bottom slab;
a concrete placing step of placing concrete in the space between the upper surface of the top slab construction formwork positioned at the predetermined height position and the top surface of the lateral hole;
including
The method of constructing an underground structure, wherein, in the concrete placing step, concrete is placed in the space while the reinforcing bars for the top slab are placed in the space. Further comprising a fourth step of forming a work space in the ground prior to the first step,
2. The method of constructing an underground structure according to claim 1, wherein in said first step, excavation of the ground is started substantially horizontally from within said work space to form said tunnel. 3. The third step further includes a support material placement step of placing support materials on the bottom plate for supporting the top plate construction formwork from below prior to the formwork assembling step. The method for constructing an underground structure according to claim 2. The underground structure construction method according to any one of claims 1 to 3, wherein the underground structure is constructed under an existing structure. 5. The method of constructing an underground structure according to claim 4, wherein the upper surface of said underground structure and the lower surface of said existing structure are in contact with each other. 6. The method of constructing an underground structure according to claim 4, wherein said first step includes erecting shoring along the inner peripheral surface of said tunnel. The elevating means for elevating the top slab construction formwork in the formwork elevating step includes a linear member extending in the vertical direction, and a center hole jack through which the linear member is inserted through the central through hole,
The linear member is fixed at its upper end to the existing structure or fixed to a portion of the shoring that faces the top end surface of the horizontal hole, hangs down in the horizontal hole, and It is inserted into the through-hole of the formwork for slab construction,
The center hole jack is positioned below the through hole of the top slab construction formwork,
7. The method of constructing an underground structure according to claim 6, wherein said center hole jack can take reaction force from said linear member and push up said formwork for constructing top slab.