CONSTRUCTION METHOD FOR NEW UNDERGROUND STRUCTURE

TECHNICAL FIELD

The present invention relates to a construction method for a new underground structure, and in particular to a construction method for a new underground structure by which a reduction in the load imposition of the new underground structure on an existing underground structure and a reduction in construction cost can be achieved.

BACKGROUND ART

When various structures, such as a building, are rebuilt, an existing structure is required to be dismantled, but, when the existing structure is equipped with an underground structure, such as a basement floor, the existing underground structure is also required to be dismantled. However, an underground exterior wall, a post, an underground beam, a foundation, and the like which constitute the existing underground structure bear soil pressure from surrounding soil, and therefore haphazard dismantlement may cause ground collapse, ground displacement, or the like, resulting in a considerable influence on neighboring areas.

Then, a method for newly building an underground structure without dismantling an existing underground structure is suggested in a patent document 1.

According to the construction method for an underground structure suggested in the patent document 1, first, a strut is set up to a floor-height middle portion of an existing underground exterior wall of the first basement floor, and floor beams are removed while pressure is applied to the strut in the direction of the exterior wall via by a jack. This series of operations are performed on each floor, a new wall is placed within the existing underground exterior wall so as to construct a combined wall with the existing underground exterior wall, and then the floor beams are removed. This series of operations are performed on each floor so that a new underground structure is constructed.

Patent Document 1: Japanese Patent Application Laid-open Publication No. 2005-201007

SUMMARY OF THE INVENTION
Problem to Be Solved by the Invention

According to the construction method for an underground structure disclosed in the patent document 1, however, since the combined wall to be constructed is for integrating the existing underground exterior wall and a new wall with each other, the load imposition acting downstairs increases. Therefore, a larger supporting force is required to support this load, which causes the problem of increasing construction cost.

The present invention has been made in view of these circumstances, and an object thereof is to provide a construction method for a new underground structure, which can achieve reduction in the load imposition of a new underground concrete framework on an existing underground concrete framework, and reduction in construction cost for building the new underground concrete framework.

Means for Solving the Problem

In order to achieve the above object, the present invention provides a construction method for a new underground structure by which a new underground concrete framework is constructed without entirely dismantling an existing underground concrete framework, wherein: a fluidized soil wall is constructed by filling an inner circumferential face of the existing underground concrete framework with fluidized soil, and a new underground concrete framework is constructed on the inner circumferential face of the fluidized soil wall.

Further, in order to achieve the above object, the present invention provides a construction method for a new underground structure by which an existing underground concrete framework is partially utilized to construct a new underground concrete framework without entirely dismantling and removing the existing underground concrete framework, the method including: vertically providing a first formwork body on an inner circumferential face of the existing underground concrete framework at a predetermined distance from the existing underground concrete framework; filling a space between the existing underground concrete framework and the first formwork body with fluidized soil to construct a fluidized soil wall; vertically providing a second formwork body on an inner circumferential face of the fluidized soil wall at a predetermined distance from the fluidized soil wall; and casting concrete in between the fluidized soil wall and the second formwork body to construct a new underground concrete framework.

In this case, it is desired that the first formwork body and the second formwork body are kept upright by separators, and further it is desired that the first formwork body and the second formwork body are formwork panels formed by bending and cutting a plate-like steel material into a substantially rectangular front shape and a substantially angular-wave-like cross-sectional shape.

Advantageous Effects of the Invention

According to the present invention, since the new underground concrete framework formed within the existing underground concrete framework is composed of the fluidized soil wall and the new underground concrete framework when a new underground structure is constructed, the usage of concrete can be reduced as compared with the case where the new underground concrete framework is composed of only the new underground concrete framework. Further, since fluidized soil has a lower specific gravity than concrete, the load imposition of the new underground concrete framework on the existing underground concrete framework can be reduced.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a construction method for a new underground structure according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional side view showing the structure of a new underground structure constructed by the construction method according to the embodiment.

As shown in FIG. 1, the underground structure constructed by the construction method according to the embodiment is a new underground structure having a basement available as a residential space, and an underground pit which is a facility for housing piping equipment or the like, and the underground structure is constructed by holding a fluidized soil wall 300 between an existing underground concrete framework 200 and a new underground concrete framework 400.

The underground pit in this underground structure is an underground space for housing piping equipment or the like, but it is unnecessary to provide the underground pit if the basement has a space for housing piping equipment or the like. Further, though the underground structure shown in FIG. 1 is an underground structure having only a single basement floor, the number of underground floors may be plural, where the configuration and the construction method of a new underground structure according to the present invention are not changed.

When an existing underground structure is dismantled, a post and the like which were used to construct the underground structure are dismantled, and only the existing underground concrete framework 200 composed of an existing beam 201, an existing load-bearing wall 202, and an existing foundation (foundation/underground beam) 203 remains.

Within this existing underground concrete framework 200, the fluidized soil wall 300 is constructed. This fluidized soil wall 300 is constructed by filling with fluidized soil (backfill material that is slurry backfill soil which has been preliminarily blended with cement in a controlled manner in a plant and which is fluidized so that it can be cast by a pump). Specifically, the fluidized soil wall 300 is constructed by driving formwork panels 500 within the existing underground concrete framework 200 at a predetermined distance therefrom, keeping the formwork panels 500 upright by separators 501, filling a space between the formwork panels 500 and the existing underground concrete framework 200 with the fluidized soil, and solidifying the fluidized soil.

Then, a new framework, that is, the new underground concrete framework 400, is constructed within the fluidized soil wall 300. The new underground concrete framework 400 is composed of a new slab 401 which constitutes the floor of the basement and the ceiling of the underground pit, a new beam 402, and a new wall 403. This new underground concrete framework 400 is constructed by driving formwork panels 600 within the fluidized soil wall 300 at a predetermined distance therefrom, coupling these formwork panels 600 with the formwork panels 500 of fluidized soil wall 300 described above by means of separators 601 to keep the formwork panels 600 upright, and casting concrete in between the formwork panels 500 of the fluidized soil wall 300 and the new formwork panels 600.

FIGS. 2 and 3 are views showing the configuration of the formwork panels 500 and 600 used in the construction method for an underground structure according to the embodiment.

As shown in FIG. 2, the formwork panels 500 and 600 are left-in-place type formwork panels formed by bending and cutting a plate-like steel material into a substantially rectangular front shape and a substantially angular-wave-like cross-sectional shape. Since this formwork panel 500 is configured such that a plurality of ridges 11 parallel to each other are formed at predetermined distances by bending a panel steel plate into a substantially angular-wave-like cross sectional shape, resulting in reinforcement of the strength of the panel itself. Further, by forming the panel cross section into an equilateral angular-wave-like shape, the panel exerts excellent strength against pressure on the front or back face of the panel.

It should be noted that, in the embodiment, a direction in which this ridges 11 are formed is defined as a longitudinal direction of the formwork panel 500, and a direction perpendicular to the longitudinal direction is defined as a lateral direction of the formwork panel 500.

As shown in FIGS. 2 and 3, this ridge 11 is composed of a top face 31, and two side faces 32 provided so as to connect to the top face 31 in both lateral directions thereof. Further, in a recessed face between the respective ridges 11, a plurality of ribs 12 raised in their lateral cross section and grooves 16 recessed in their lateral cross section are alternately formed in parallel to the ridges 11.

Further, in both ends of the ridge 11 in the panel lateral direction, that is, on boundary lines between the ribs 12 and the grooves 16 adjacent to the ribs 12, slits 13 each having a predetermined length are provided at predetermined distances like broken lines in parallel with the ridges 11. By bending the formwork panel 500 at a predetermined angle along this row of broken-line-like slits 13, a corner portion can be formed in the formwork. Further, by bending the formwork panel 500 along this row of broken-line-like slits 13 forward and backward alternately and repeatedly, the formwork panel 500 can easily be cut into a desired size.

This slit 13 is a slit having a very narrow width and a predetermined length and penetrating the formwork panel 500. This slit 13 is formed so as to have a width (clearance) and a length which allow discharge of excess water contained in concrete or fluidized soil but do not allow leakage of liquid concrete or fluidized soil from the slit 13 after casting of concrete or filling with fluidized soil.

The top face 31 of the ridge 11 is provided with a plurality of flap-like lids 14. By opening these lids 14, separator insertion holes are formed. By inserting the above-described separators 501 and 601 into these separator insertion holes and fastening the separators together by a predetermined method, the formwork panels 500 and 600 can be kept upright.

FIG. 4 is a view showing an X-X section in FIG. 1.

As shown in FIG. 4, the new underground structure is a structure having the fluidized soil wall 300 between the existing underground concrete framework 200 and the new underground concrete framework 400.

In order to construct the fluidized soil wall 300, first, the formwork panels 500 are driven, then anchors 307 are driven into the existing underground concrete framework 200, then these driven anchors 307 are coupled with the separators 501, then the formwork panels 500 are kept upright by these separators 501, and then the space between the formwork panels 500 and the existing underground concrete framework 200 is filled with fluidized soil, resulting in construction.

Washers 301 and 302 each having its both ends bent are provided at connections between the formwork panels 500 and the separators 501. The washer 301 is provided on the back face of the formwork panel 500 (on the side of the existing underground concrete framework 200), and fastened to the formwork panel 500 by a nut 303. The washer 302 is provided on the front side of the formwork panel 500 (on the side of the new underground concrete framework 400). The washer 302 is a washer which is long in the longitudinal direction, and fastened, by a long nut 304, to a distal end of the separator 501 protruding from the formwork panel 500. Then, the fluidized soil wall 300 is constructed by filling the space between the existing underground concrete framework 200 and the formwork panels 500 with fluidized soil.

The new underground concrete framework 400, as described above, is constructed by driving the new formwork panels 600 within the fluidized soil wall 300 at a predetermined distance therefrom, coupling these formwork panels 600 with the formwork panels 500 for the fluidized soil wall 300 by means of the separators 601 so as to keep the formwork panels 600 upright, and casting concrete in between the formwork panels 500 of the fluidized soil wall 300 and the new formwork panels 600. At this time, the formwork panel 600 is kept upright by coupling one end of the separator 601 with the long nut 304 and coupling the other end thereof with the formwork panel 600, and a pipe 305 is provided on front faces of the formwork panels 600 and fixed thereto by form ties 306. In this state, by casting concrete in between the formwork panels 500 and the formwork panels 600, the new underground concrete framework 400 is constructed.

FIG. 5 is a flowchart showing a construction procedure of the underground structure, and FIGS. 6 to 11 are views showing a construction method for the underground structure according to the embodiment performed on the basis of the construction procedure.

Hereinafter, the construction method for the underground structure will be described, based on the flowchart showing the construction procedure in FIG. 5, with reference to FIGS. 6 to 11.

FIG. 6A is an illustration after the existing underground concrete framework is partially removed, FIG. 6B is an illustration where soil is carried into the underground pit after the partial removal of the existing underground concrete framework, FIG. 7A is an illustration where soil is carried into the existing underground concrete framework, FIG. 7B is an illustration where a new pile is set up in part of the foundation, FIG. 8A is an illustration where the backfill soil is removed down to a depth to which the existing load-bearing wall and the existing beam can bear soil pressure, and a strut and a wale for land retaining are set up, FIG. 8B is an illustration where a fluidized soil wall is provided in the underground pit, FIG. 9A is an illustration where a concrete framework of a new pressure plate is provided in the underground pit, FIG. 9B is an illustration where a new concrete foundation and a slab are provided in the underground pit, FIG. 10A is an illustration where a strut and wale for land retaining is dismantled and removed, FIG. 10B is an illustration where a fluidized soil wall is provided in the basement, FIG. 11A is an illustration where formwork panels for a new underground concrete framework are assembled in the basement, and FIG. 11B is an illustration where the new underground concrete framework is provided in the basement.

First, as shown in FIG. 6A, after an aboveground structure is removed, existing posts 204 constructed in the basement and the underground pit of the existing underground concrete framework 200 are dismantled and removed, an opening is created by dismantling slabs 205 and 206 in the basement and the underground pit (the removal may be performed with the existing beam 201 left so as to receive soil pressure), and an opening is created by dismantling an existing pressure plate 208 partially (step S100). By dismantling and removing the existing posts 204, spaces for constructing new underground concrete frameworks in the basement and the underground pit are secured, and by dismantling the slabs 205 and 206 with the existing beam 201 left to create an opening, a work space are secured.

Moreover, in the embodiment, the existing beam 201, the existing load-bearing wall 202, and the existing foundation 203 of the existing underground concrete framework 200 are considered as a continuous existing exterior wall, and utilized as a retaining wall for supporting underground soil pressure.

Next, the existing underground concrete framework 200 is backfilled with soil by carrying soil into the underground pit of the existing underground concrete framework 200, as shown in FIG. 6B, and carrying soil into the basement, as shown in FIG. 7A, from the opening created by dismantling the slabs 205 and 206 with the existing beam 201 left (step S101). This backfilling work can reduce the load of soil pressure on the existing underground concrete framework 200 utilized as a retaining wall. Further, this backfilling work makes it possible to secure a work space for heavy equipment (not shown) on the ground and to support the weight of the heavy equipment, and by this heavy equipment, as shown in FIG. 7B, a new pile 405a can be set up in a hole 405 preliminarily opened in the existing pressure plate 208 (step S102) . This new pile 405a is for supporting the weight of a new underground concrete framework (mainly a new wall) constructed within the existing underground concrete framework 200.

In addition, the new pile 405a is not necessarily set up, depending on load-bearing performances of the existing foundation 203 and the existing pressure plate 208 of the existing underground concrete framework 200, and a bearing power that is the bearing capacity of the ground.

Next, as shown in FIG. 8A, after the new pile 405a is set up, the backfill soil is removed from the basement and the underground pit down to a depth to which the existing load-bearing wall 202 and the existing beam 201 can bear soil pressure (step S103), and the remaining existing beam 201 is removed. Next, since the soil pressure applied on the existing underground concrete 200 from the surrounding ground increases due to the dismantlement and removal of the existing beam 201 and the removal of the backfill soil, a strut and wale for land retaining 406 is set up in a part of the existing beam 201 for a temporary aid (step S104). As the strut and wale for land retaining 406, land retaining H-section steels are used. Therefore, the soil pressure applied on the existing underground concrete framework 200 can be reduced by the strut and wale for land retaining 406. After the strut and wale for land retaining 406 is set up, the remaining backfill soil is removed (step S105).

Next, as shown in FIG. 8B, with the existing underground concrete framework 200 and the strut and wale for land retaining 406 supporting the soil pressure from the ground, the fluidized soil wall 300 is constructed in the underground pit. In order to construct this fluidized soil wall 300, first, a plurality of anchors 307 are driven into the existing foundation 203 which functions as a wall of the underground pit, and separators 501 are coupled with the respective anchors 307 (step S106). Next, the above-described formwork panels 500 are assembled so as to fit on the internal shape of the existing underground concrete framework 200, and these formwork panels 500 are kept upright by the separators 501 (step S107). Further, the formwork panels 500 and the separators 501, as described above, are fastened to each other with washers 301 and 302 and nuts 303 to be fixed to each other.

Next, the fluidized soil wall 300 is constructed in the underground pit by filling a space between the existing foundation 203 and the formwork panels 500 with fluidized soil and solidifying the fluidized soil (step S108). The fluidized soil used here is slurry backfill soil which is preliminarily blended with cement in a controlled manner in a plant and which can be transported by a fresh concrete mixer vehicle and can be cast by a pump. And, by using the formwork panels 500 when constructing the fluidized soil wall 300, excess water can be discharged through the slits 13 created in these formwork panels 500, and therefore the time required to harden the fluidized soil can be shortened.

Next, as shown in FIG. 9A, reinforcing bars (not shown) for constructing a new pressure plate 407 are assembled on the existing pressure plate 208 in the underground pit (step S109), and concrete for constructing the new pressure plate 407 is cast (step S110). Next, as shown in FIG. 9B, in order to construct a new slab 401 and a new foundation (foundation/underground beam) 404, formwork panels 600 are set up within the fluidized soil wall 300 (step S111). First, reinforcing bars are assembled within the fluidized soil wall 300 (step S112), separators 601 are coupled with the separators 501 protruding from the formwork panels 500, and the assembled formwork panels 601 are kept upright by these separators 601. Further, in order to construct the new slab 401 for the underground pit, formwork panels 600 are provided so as to form a shape of a slab while being supported by a supporting post. At this time, since the formwork panel 600 can easily be bent along the slits 13 created in the formwork panel 600, the formwork panels 600 can be assembled into the shape of a slab. Further, the formwork panels 600 kept upright and the formwork panels 600 assembled into the shape of a slab are set up so as to connect to each other.

In the formwork panels 600 thus set up, in order to support lateral pressure applied to the formwork panels 600 when concrete is cast, the pipe 305 extending in the longitudinal direction of the formwork panels 600 is fixed on the side of surfaces of the formwork panels 600 by the form ties 306, as described above. Next, the new slab 401 and the new foundation 404 are constructed by casting concrete (step S113). In this manner, the new underground concrete framework 400 can be constructed in the underground pit.

Further, when the new underground concrete framework 400 is constructed, the slits 13 created in the formwork panels 600 can prevent leakage of concrete and can discharge excess water in the concrete when the concrete is cast.

Next, as shown in FIG. 10A, the strut and wale for land retaining 406 set up to the existing beam 201 is dismantled and removed (step S114), and, as shown in FIG. 10B, a fluidized soil wall 300 is constructed in the basement.

First, a plurality of anchors 307 are driven into the existing beam 201 and the existing load-bearing wall 202 of the existing underground concrete framework 200, and the respective anchors 307 are coupled with separators 501 (step S115). Next, formwork panels 500 are assembled so as to connect to the formwork panels 500 set up in the underground pit, and kept upright by the separators 501 (step S116). At this time, the formwork panels 500 and the separators 501 are fastened and fixed to each other by washers 301 and 302 and nuts 303.

Then, a fluidized soil wall 300 is constructed by filling a space between the existing underground concrete framework 200 and the formwork panels 500 with fluidized soil (step S117). Thus, the fluidized soil wall 300 constructed in the underground pit and the fluidized soil wall 300 constructed in the basement are constructed as a continuous single wall. And, the load of this fluidized soil wall 300 is supported by the existing beam 201, the existing load-bearing wall 202, and a part of the existing foundation 203 that constitute the existing underground concrete framework 200.

Next, as shown in FIG. 11A, on the new underground concrete framework 400 constructed in the underground pit, reinforcing bars are assembled to construct a post, a beam, a wall, and a floor that constitute the new underground concrete framework 400 (step S118). Next, separators 601 are coupled with the separators 501 protruding from the formwork panels 500 of the fluidized soil wall 300 constructed for the basement (steps S119), and formwork panels 600 are kept upright by these separators 601. Then, formwork panels 600 for constructing the new slab 401 and the new beam 402 for the basement are assembled (step S120). These formwork panels 600 are supported by supporting posts.

It should be noted that the formwork panels 600 kept upright and the formwork panels 600 assembled into shapes of a slab and a beam are joined and assembled so as to obtain a continuous formwork panel 600.

Next, reinforcing bars for the new slab 401 are assembled (step S121), and concrete is cast into a space between the fluidized soil wall 300 and the formwork panels 600 (step S122). In this manner, the new underground concrete framework 400 for the basement can be constructed. Further, the new underground concrete framework 400 constructed in the underground pit and the new underground concrete framework 400 constructed in the basement form a continuous new concrete framework, the weight of which is supported by the new pile 405a.

As described above, in the construction method for an underground structure according to the embodiment, a new underground structure can be constructed, without dismantling the existing underground concrete framework, by utilizing this existing underground concrete framework as a retaining wall, and constructing the fluidized soil wall and the new underground concrete framework within the existing underground concrete framework.

And, since the fluidized soil wall and the new underground concrete framework which are constructed within the existing underground concrete framework are independent of each other via the formwork panel, the load of the fluidized soil wall can be supported by a portion contacting with the existing underground concrete framework, and the load of the new underground concrete framework can be supported by the new pile provided preliminarily and the foundation of the existing underground concrete framework.

Thus, since the loads of the fluidized soil wall and the new underground concrete framework can be distributed and supported by the existing underground concrete framework, the load supported by the existing underground concrete framework can be reduced.

Further, by providing the fluidized soil wall between the existing underground concrete framework and the new underground concrete framework, the fluidized soil wall makes it possible to reduce the thickness of the new underground concrete framework, as compared with the construction method in which the new underground concrete framework is directly provided in the existing underground concrete framework, and therefore the amount of concrete can be reduced.

Further, since the formwork panel according to the embodiment is formed by bending a panel steel plate into a substantially angular-wave-like cross sectional shape so as to have a plurality of ridges arranged in parallel at predetermined distances, the strength of the panel itself can be reinforced. This makes it possible for the formwork panel to sufficiently bear lateral pressure applied to the formwork panel even after filling with the fluidized soil or casting concrete. And, the slits with a predetermined length provided in this formwork panel make it easy to bend the formwork panel itself, and can promote discharge of excess water while preventing leakage of the fluidized soil or concrete. Thus, it becomes easy to bend the formwork panel at a corner, while constructing of the fluidized soil wall and the new underground concrete framework can be expedited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the configuration of a new underground structure according to an embodiment of the present invention;

FIG. 2 is a schematic configuration view of a formwork panel used in the embodiment;

FIG. 3 is a view showing an A-A cross section of the formwork panel shown in FIG. 2;

FIG. 4 is a cross-sectional view showing an X-X cross section of the underground structure shown in FIG. 1;

FIG. 5 is a flowchart showing the procedure of a construction method of the new underground structure according to the embodiment;

FIG. 6 is a schematic illustration of the construction method of the new underground structure according to the embodiment;

FIG. 7 is a schematic illustration of the construction method of the new underground structure according to the embodiment;

FIG. 8 is a schematic illustration of the construction method of the new underground structure according to the embodiment;

FIG. 9 is a schematic illustration of the construction method of the new underground structure according to the embodiment;

FIG. 10 is a schematic illustration of the construction method of the new underground structure according to the embodiment; and

FIG. 11 is a schematic illustration of the construction method of the new underground structure according to the embodiment.

EXPLANATION OF REFERENCE NUMERALS

11: Ridge

12: Rib

13: Slit

14: Lid

16: Groove

31: Top face

32: Side face

200: Existing underground concrete framework

201: Existing beam

202: Existing load-bearing wall

203: Existing foundation (foundation or underground beam)

204: Existing post

205, 206: Slab

208: Existing pressure plate

300: Fluidized soil wall

301, 302: Washer

303: Nut

304: Long nut

305: Pipe

306: Form tie

307: Anchor

400: New underground concrete framework

401: New slab

402: New beam

403: New wall

404: New foundation (foundation or underground beam)

405: New hole

405
a: New pile

406: Strut and wale for land retaining

407: New pressure plate

500, 600: Formwork panel

501, 601: Separator

CONSTRUCTION METHOD FOR NEW UNDERGROUND STRUCTURE

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