JP2009114695A - Underground structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an underground structure being like a wall when viewed in a plane and capable of obtaining sufficient yield strength without using a reinforced concrete cage. <P>SOLUTION: This underground continuous wall 100 is constituted by burying a plurality of main reinforcements 20 in the vertical direction in steel fiber concrete 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an underground structure such as an underground continuous wall in which main bars are embedded in steel fiber concrete.

  Conventionally, underground continuous walls made of reinforced concrete have been used as temporary structures such as earth retaining walls or foundation structures. Such a reinforced concrete underground continuous wall excavates the part corresponding to the underground continuous wall of the ground, and inserts a reinforcing steel cage in which the main reinforcement, shear reinforcement, and horizontal reinforcement are assembled into a cage shape in the excavation hole, It was constructed by placing concrete.

  Here, the assembly and erection work of the reinforcing bar cage is very complicated. For example, in Patent Document 1, the underground continuous wall is formed into a planar polygonal shape or a circular shape, and the concrete constituting the underground continuous wall is made of fiber concrete. It is described that the reinforcing bars are omitted.

In the method described in Patent Document 1, since tensile strength is improved by using concrete as fiber concrete, shear reinforcement bars and transverse bars can be omitted. In addition, since the underground continuous wall is a ring shape such as a polygon or a circle in plan view, the earth and water pressure acting from the surroundings acts as a compressive force, and the concrete resists this compressive force, so the reinforcing bars are omitted. It becomes possible.
JP 2006-125148 A

  However, even if it is going to apply the composition of patent documents 1 to a wall-like underground continuous wall, since earth pressure acting from the ground acts as a bending load and tensile load acts on concrete on the ground side, compression of concrete There is a problem in structural performance because it cannot be resisted by force alone.

  The present invention has been made in view of the above problems, and its purpose is to reduce the amount of reinforcing bars and provide sufficient structural strength when constructing a wall-like underground structure in plan view. is there.

  The underground structure of the present invention is a wall-shaped reinforced concrete underground structure, and is characterized in that a plurality of main bars or steel materials are embedded in fiber concrete so as to extend in the vertical direction.

  In the above underground structure, the fiber concrete may be steel fiber concrete. The underground structure may be an underground continuous wall.

  Further, in the above underground structure, the amount of the plurality of main bars or steel materials may be smaller than the underground structure when designed without using fiber concrete, and the wall thickness of the underground structure. May be smaller than the underground structure when designed without using fiber concrete.

  According to the present invention, by using steel fiber concrete, the tensile strength can be borne by the concrete. For this reason, since it becomes possible to reduce or abbreviate a horizontal bar, a shear reinforcement bar, and a main bar, a reinforcing bar cage becomes unnecessary.

Hereinafter, an embodiment of the underground structure of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an underground continuous wall 100 which is an embodiment of an underground structure of the present invention, (A) is a front view partially showing an internal main reinforcing bar, and (B) is (A It is BB 'sectional drawing in). As shown in the figure, the underground continuous wall 100 of the present embodiment is a wall-like underground structure 100 that extends linearly in plan view, and is used as a temporary structure such as a retaining wall or a part of a foundation. It is done. The underground continuous wall 100 is constructed by being divided into a plurality of sections in the longitudinal direction (left-right direction in the figure), and each section is a steel fiber placed in a drilling hole formed by excavating the ground. Concrete 10 and a plurality of main reinforcing bars 20 embedded in the vicinity of the front and back surfaces of steel fiber concrete 10 so as to extend in the vertical direction are provided.

  The steel fiber concrete 10 is a concrete in which steel fibers 11 are mixed. The steel fibers 11 bear a part of the tensile load, and even if cracks are generated, the steel fibers 11 cause the progress of the cracks. to bound. For this reason, the steel fiber concrete 10 has a larger tensile strength than ordinary concrete (that is, concrete in which fibers are not mixed).

  For this reason, according to the underground continuous wall 100 of this embodiment, the horizontal force which the horizontal reinforcement and the shear reinforcement had borne in the underground continuous wall using normal concrete can be borne by the steel fiber concrete 10. For this reason, it is possible to reduce or omit the transverse bars and the shear reinforcement bars.

  In addition, it resists the bending load that has been applied by the soil pressure applied from the surrounding ground by the tensile strength of the main reinforcing bar on the side where the tensile stress acts and the compressive strength of the concrete on the side where the compressive stress acts However, according to the underground continuous wall 100 of this embodiment, in addition to these proof stresses, a bending load can be resisted by the tensile proof strength of the steel fiber concrete 10 on the side where tensile stress acts. For this reason, since the tensile load which the main reinforcement 20 should bear can be reduced, the amount of reinforcement can be reduced compared with the past. In addition, when a bending load is applied to the underground continuous wall 100, the tensile stress of the steel fiber concrete 10 can be expected, and the effect of increasing the amount of reinforcing bars is substantially obtained. It becomes possible to reduce wall thickness compared with the conventional underground wall.

The underground continuous wall 100 as described above can be constructed as follows, for example.
First, as shown in FIG. 2, a portion corresponding to a section to be constructed of the underground continuous wall 100 of the ground is excavated to form an excavation hole 30. Then, a rebar panel 25A is lifted through a jig 80 by a lifting device (not shown) such as a crane, and is built into the excavation hole 30 along the inner wall on one side in the wall thickness direction. The upper end of the reinforcing bar panel 25 </ b> A is held by the reinforcing bar temporary support 31 </ b> A provided so as to protrude above the excavation hole 30.

  In addition, 31 A of reinforcing rod temporary support stands are members provided with the mechanism fixed to the edge of the excavation hole 30, and hold | maintaining a reinforcing bar at the front-end | tip. The reinforcing bar panel 25 </ b> A is a panel-like member formed by restraining a plurality of reinforcing bars 21 constituting the main reinforcing bar 20 by a restraining member 22 at a predetermined interval. These reinforcing bar panels 25 </ b> A are carried into the site in advance and placed in a state of being stacked on the stand 23.

  Next, as shown in FIG. 3, the reinforcing bar panel 25B is installed along the inner wall of the excavating hole 30 on the other side of the excavating hole 30 (the side opposite to the side where the reinforcing bar panel 25A is installed in the above process). In the same manner as in the case of the reinforcing bar panel 25A, the reinforcing bar panel 25B is held by the reinforcing bar temporary support 31B.

  Next, as shown in FIG. 4, the reinforcing bar panels 25A and 25B on both sides in the wall thickness direction built in the excavation hole 30 in the above process are lifted by the lifting device via the jig 80 and pulled up to the ground.

  Then, as shown in FIG. 5, while lowering the reinforcing bar panels 25A and 25B by the lifting device, the reinforcing bar panels 25A and 25B lifted by the lifting device are connected to each other at a height above the ground. The holding member 40 is held at a plurality of levels in the vertical direction, and the restraining member 22 is held at a predetermined interval in the wall width direction. Moreover, the spacer 41 for ensuring cover thickness is attached to the wall thickness direction outer side of the reinforcing bar panels 25A and 25B on both sides. In addition, in the figure, although the case where the space | interval holding | maintenance material 40 is provided between the restraining members 22 of the reinforcing bar panels 25A and 25B is shown, the space between the reinforcing bars 21 constituting the reinforcing bar panels 25A and 25B is not limited thereto. A holding member 40 may be provided.

  Next, as shown in FIG. 6, the reinforcing bar panels 25C and 25D are built along the wall surface inside the built-in reinforcing bar panels 25A and 25B. These reinforcing bar panels 25C and 25D are held by reinforcing bar temporary support bases 31C and 31D provided at the edges.

  Next, as shown in FIG. 7, the reinforcing bars 25 </ b> C and 25 </ b> D built later in the above-described process are lifted by the lifting device, and the lower ends of the reinforcing bars 25 </ b> A are held by the temporary reinforcing steel stand 31 </ b> A and 31 </ b> B. , 25B.

  Next, as shown in FIG. 8, the lower ends of the reinforcing bars 21 of the reinforcing bar panels 25 </ b> C and 25 </ b> D lifted by the lifting device and the reinforcing bars held in the excavation hole 30 by the reinforcing steel temporary support bases 31 </ b> A and 31 </ b> B. The upper ends of the reinforcing bars 21 of the panels 25A and 25B are connected. As a connection method, a method of connecting by welding, a method of connecting using a mechanical joint, a method of connecting the reinforcing bars 21 by a lap joint, or the like can be used. Then, the reinforcing bars 31C and 31D that hold the reinforcing bar panels 25C and 25D built later are removed, and the connected reinforcing reinforcing bar panel 25 is lowered into the excavation hole 30, and the upper reinforcing bar is lowered. Between the reinforcing bars 21 of the panels 25C and 25D, a plurality of stages of the spacing member 40, the restraining member 22 and the spacer 41 are attached.

  Next, as shown in FIG. 9, the rebar panel 25 in a connected state is lowered to a predetermined depth in the excavation hole 30 by a lifting device, and the upper part of the rebar panel 25 is held by the rebar temporary support bases 31A and 31B. To do.

  Next, as shown in FIG. 10 (A), the weight (weight) 50 to which the wire 51 for pulling up into the excavation hole 30 is lowered, and is placed on the upper part of the spacing member 40 attached at the lowest position. A weight 50 is arranged. In this state, as shown in FIG. 10 (B), the steel fiber concrete 10 is placed until the lower end of the reinforcing bar panel 25 is buried below the excavation hole 30 by the tremy tube 60. At this time, due to the weight of the weight 50, it is possible to prevent the rebar 21 from being lifted or displaced when the steel fiber concrete 10 is placed. After placing the steel fiber concrete 10 to a height at which the lower end of the reinforcing bar panel 25 is buried, the weight 50 is pulled up to the outside of the excavation hole 30 by the wire 51.

Next, as shown in FIG. 10C, the steel fiber concrete 10 is placed in the excavation hole 30. In addition, since the space | interval holding | maintenance material 40 is attached between the rebar panels 25 which oppose as mentioned above, and also the lower end of the rebar panel 25 is embed | buried in the steel fiber concrete 10, placement of the steel fiber concrete 10 is carried out. It is possible to prevent displacement and lifting of the reinforcing bar panel 25 due to pressure.
The underground continuous wall 100 can be constructed by repeating the above steps.

  According to the underground continuous wall 100 of the present embodiment, by using the steel fiber concrete 10, the steel fiber concrete 10 bears the tensile stress that the horizontal and shear reinforcing bars bear on the conventional underground continuous wall. Therefore, it is possible to omit or reduce the transverse bars, the shear reinforcement bars, and the main reinforcing bars while providing sufficient structural strength. Moreover, since the steel fiber concrete 10 can bear the tensile stress conventionally borne by the main reinforcing bars, the amount of reinforcing bars can be reduced or the wall thickness can be reduced compared with the conventional underground continuous wall. It becomes possible and the cost can be reduced.

  In addition, when constructing underground structures such as subways that extend over a long distance, the underground structure should be extended along both sides of the underground structure in order to support the surrounding ground when excavating the ground. A continuous wall is constructed, and an underground structure is constructed by excavating the ground in the space between the underground continuous walls. FIG. 11 is necessary when constructing such an underground structure 200 when the conventional underground continuous wall 110 is used as the retaining wall and when the underground continuous wall 100 of the present embodiment is used. It is a figure for comparing the width of a site. As shown in the figure, by using the underground continuous wall 100 of the present embodiment, the wall thickness of the underground continuous wall 100 can be made thinner than when the conventional underground continuous wall 110 is used. The necessary land width can be reduced.

  In the present embodiment, the case where the steel fiber concrete 10 is used has been described. However, the present invention is not limited thereto, and may be fiber concrete mixed with a fiber material capable of bearing a tensile stress such as carbon fiber or glass fiber. Can be used.

  Moreover, in this embodiment, although the underground continuous wall 100 in which the main reinforcement 20 was embed | buried as a stress bearing material was demonstrated, not only this but PC steel wire etc. can also be used. Even with this configuration, the same effect as the above-described embodiment can be obtained.

  Moreover, although this embodiment demonstrated the case where this invention was applied to the underground continuous wall 100 by which the reinforcing bar was embed | buried in the wall thickness direction both sides, steel materials, such as H-shaped steel, are not restricted to this, but the steel fiber concrete 10. The present invention can also be applied to a buried underground continuous wall. Even with such underground continuous walls, the amount of steel frames can be reduced, and the wall thickness can be reduced.

The underground continuous wall of this embodiment is shown, (A) is a front view which partially shows an internal main reinforcement, (B) is BB 'sectional drawing in (A). It is a figure which shows a mode that a reinforcing bar panel is built in one side in a digging hole, (A) is wall thickness direction sectional drawing, (B) is a top view, (C) is wall width direction sectional drawing FIG. It is a figure which shows a mode that a reinforcing bar panel is built in the other side in a digging hole, (A) is wall thickness direction sectional drawing, (B) is a top view. It is a figure which shows a mode that the reinforcing bar panel of both sides is lifted. It is a figure which shows a mode that a space | interval maintenance material is attached between a reinforcing bar panel, (A) is wall thickness direction sectional drawing, (B) is a top view. It is a figure which shows the state which built the reinforcing bar panel which comprises the upper part of a main reinforcement, (A) is wall thickness direction sectional drawing, (B) is a top view. It is a figure which shows a mode that a reinforcing bar is connected. It is a figure which shows a mode that a space | interval holding | maintenance material is attached between upper rebar panels. It is a figure which shows a mode that the connected reinforcing bar panel was built, (A) is wall thickness direction sectional drawing, (B) is a top view. It is a figure which shows a mode that steel fiber concrete is laid. When constructing underground structures extending over long distances such as subways, the width of the site required when using the conventional underground continuous wall and the underground continuous wall of this embodiment is set. It is a figure to compare.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Steel fiber concrete 11 Steel fiber 20 Main reinforcement 21 Reinforcement 22 Restraint member 23 Stand 25, 25A, 25B, 25C, 25D Reinforcement panel 30 Excavation hole 31A, 31B, 31C, 31D Reinforcing bar temporary support base 40 Spacing holding material 41 Spacer 50 Weight 51 Wire 60 Tremy tube 80 Jig 100 Underground continuous wall

Claims (5)

A wall-shaped reinforced concrete underground structure,
An underground structure characterized in that a plurality of main bars or steel materials are embedded in fiber concrete so as to extend in the vertical direction.   The underground structure according to claim 1, wherein the fiber concrete is steel fiber concrete.   The underground structure according to claim 1 or 2, wherein the underground structure is an underground continuous wall. The underground structure according to any one of claims 1 to 3,
An underground structure characterized in that the amount of the plurality of main bars or steel materials is smaller than that of an underground structure when designed without using fiber concrete. The underground structure according to any one of claims 1 to 4,
An underground structure characterized in that the wall thickness of the underground structure is smaller than that of an underground structure designed without using fiber concrete.

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