Reinforcing bar cage for reinforcing head of foundation pile and method for reinforcing head of foundation pile

Abstract

To provide a reinforcing bar cage for reinforcing a head of a foundation pile, which can be fitted into the head of the foundation pile even if a protrusion exists on an outer peripheral surface of the head of the foundation pile, and which is easy to manufacture.SOLUTION: This reinforcing steel cage 1 is placed in a surrounding space S of a pile head 21 of a foundation pile 2 buried in the ground, and a hardened body cast into the surrounding space S forms a reinforcing steel hardened body portion of the pile head 21. In the reinforcing steel cage 1, a grid shape is formed by a plurality of annular reinforcing bar sections 11 that are spaced apart from each other in the height direction of the pile head 21 and have a ring shape that is spaced apart from the outer periphery of the pile head 21, a plurality of connecting reinforcing bars 12 that interconnect the plurality of annular reinforcing bar sections 11, four straight reinforcing bars 13 that are located inside the annular reinforcing bar sections 11 and have both ends fixed to the annular reinforcing bar sections 11. The pile head 21 passes through the four sides of the center of the grid shape, and the outer circumferential surface of the pile head 21 is close to the center of each side of the four sides.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reinforcing bar cage for reinforcing the head of a foundation pile used for ground improvement and a method for reinforcing the head of a foundation pile. [Background technology]

[0002] Conventionally, a construction method has been put into practical use in which the ground surrounding prefabricated foundation piles is excavated and the pile heads are reinforced with brittle materials such as concrete. In this type of construction method, when the horizontal displacement of the foundation piles increases during a large earthquake, large stress is generated inside the reinforcement around the foundation piles, which is thought to result in cracks and damage.

[0003] Patent Document 1 discloses a reinforcing bar cage for reinforcing the head of a foundation pile. This reinforcing bar cage is formed into a cylindrical cage shape, for example, from a plurality of rod-shaped main reinforcements extending in the axial direction and ring-shaped hoop reinforcements arranged in a horizontal plane. A guide metal fitting is arranged in this reinforcing bar cage to align the axes of the foundation pile and the reinforcing bar cage. This guide metal fitting is composed of an annular member having an inner diameter slightly larger than the outer diameter of the foundation pile, and a positioning member to hold this annular member in the center position of the reinforcing bar cage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-115453 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the reinforcing bar cage shown in Patent Document 1 has an annular member with an inner diameter slightly larger than the outer diameter of the foundation pile, so if there are protrusions on the outer periphery of the foundation pile, the reinforcing bar cage cannot be fitted into the foundation pile. Also, it is desired to use straight reinforcing bars as much as possible to make the reinforcing bar cage easier to manufacture.

[0006] Furthermore, in the method of reinforcing the head of a foundation pile as disclosed in Patent Document 1, there is a risk that the concrete cover may not be adequately secured in the lower portion of the reinforced concrete constructed around the head of the foundation pile.

[0007] In view of the above circumstances, the present invention provides a reinforcing cage for reinforcing the head of a foundation pile, which can be fitted into the head of the foundation pile even if a protrusion is present on the outer peripheral surface of the head of the foundation pile and is easy to manufacture. Another object of the present invention is to provide a method for reinforcing the head of a foundation pile, which can ensure an appropriate covering of concrete or the like on the lower part of the reinforced concrete or the like that is made around the head of the foundation pile. [Means for solving the problem]

[0008] In order to solve the above problems, the reinforcing bar cage for the pile head of the foundation pile according to the present invention is a reinforcing bar cage that is placed in a surrounding space formed around the pile head of the foundation pile buried in the ground, and forms a reinforcing bar hardened body part of the pile head by a hardened body that is cast in the surrounding space and hardens over time, A plurality of annular reinforcement portions having a ring shape spaced apart from the outer peripheral surface of the pile head of the foundation pile and spaced apart from each other in the height direction of the pile head; A plurality of connecting muscles that connect the plurality of circular muscle portions to each other; At least four straight reinforcing bars are positioned inside the circular reinforcement section and have both ends fixed to the circular reinforcement section, forming a I shape when viewed in a plane, with the pile head passing through the four sides of the center of the I shape and the outer circumferential surface of the pile head being close to the center of each side of the four sides.

[0009] With the above configuration, the straight reinforcing bars form a square shape in plan view, and the pile head passes through the four sides of the square shape, so even if there is a protrusion on the outer periphery of the pile head of the foundation pile, the protrusion can pass through the diagonal of the four sides. Also, since the square shape is formed by the straight reinforcing bars, it is easy to manufacture and the strength of the reinforced concrete hardened body can be improved.

[0010] Furthermore, the method of reinforcing the head of a foundation pile according to the present invention is a method of reinforcing the head of a foundation pile using the reinforcing bar cage, characterized in that the reinforcing bar cage is positioned within the surrounding space, within the four sides of the L-shaped reinforcing bar cage, through the pile head, and the hardened body is poured while the reinforcing bar cage is floating above the bottom surface of the surrounding space.

[0011] With the above-mentioned reinforcement method, the hardened body is cast while the reinforcing steel cage is floating above the bottom surface of the surrounding space, thereby ensuring an appropriate cover of the hardened body on the lower part of the hardened steel body section created around the head of the foundation pile.

[0012] In the above-mentioned method for reinforcing the head of a foundation pile, On the outer peripheral surface of the pile head, two to four cage support protrusions are provided in the same horizontal plane to support the center of each side of the four sides of the straight reinforcing bar of the uppermost ring reinforcing bar, The cage support protrusion portion may be positioned on the diagonal of the four sides of the I shape of the straight reinforcing bars of each annular reinforcement section below the topmost annular reinforcement section, and each of the lower annular reinforcement sections may be positioned below the cage support protrusion portion.The reinforcing reinforcement cage may then be rotated in a horizontal plane to support the central sides of each of the four sides of the I shape of the straight reinforcing bars of the topmost annular reinforcement section with the cage support protrusion portion, thereby floating the reinforcing reinforcement cage above the bottom surface of the surrounding space.

[0013] In the method for reinforcing the head of the foundation pile, the four cage support protrusions may be provided so that their positions can be adjusted in the height direction of the head of the pile. With this, even if the foundation pile buried in the ground remains high due to the hardness of the ground, the height positions of the four cage support protrusions can be lowered to raise the lower end of the reinforcing steel cage by a certain distance from the bottom surface of the surrounding space.

[0014] In the above-mentioned method for reinforcing the pile head of a foundation pile, the foundation pile may be a steel pipe pile, and the four cage support protrusions may be magnetically attached to the steel pipe pile.

[0015] In the method of reinforcing the pile head of the above-mentioned foundation pile, the reinforcing bar cage is suspended from the upper end of the pile head by a hanging device hooked to the upper end of the pile head, thereby floating the reinforcing bar cage above the bottom of the surrounding space, and after the cast hardened body has hardened to a predetermined extent, at least the hook portion of the hanging device hooked to the upper end of the pile head can be retrieved.

[0016] The hook portion of the hoisting tool hooked onto the upper end of the pile head may be retrieved by cutting the connecting portion connecting the hook portion to the portion hooked onto the reinforcing bar cage. Effect of the Invention

[0017] The reinforcing bar cage for the pile head of a foundation pile of the present invention can be fitted into the foundation pile even if a protrusion is present on the outer peripheral surface of the foundation pile, and is easy to manufacture. Furthermore, the reinforcing method for the pile head of a foundation pile of the present invention has the effect of ensuring an appropriate cover for the hardened body part on the lower part of the reinforcing bar hardened body part fabricated around the pile head of the foundation pile. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is an explanatory diagram showing a reinforcing bar cage for the pile head of the foundation pile according to the embodiment. [Diagram 2] FIG. 1 is an explanatory diagram showing the construction procedure for driving foundation piles and forming a surrounding space around them, where FIG. 1(A) is a plan view and FIG. 1(B) is a front view. [Diagram 3] This is a diagram showing the continuation of the construction procedure shown in Figure 2, and is an explanatory diagram showing the procedure for installing the reinforcing steel bar cages shown in Figure 1, where Figure (A) is a plan view and Figure (B) is a front view. [Figure 4] 10 is an explanatory diagram showing an operation of rotating the reinforcing steel bar cage 45 degrees to support the reinforcing steel bar cage on the cage support protrusion portion. FIG. [Diagram 5] 13 is a perspective view showing a state in which a reinforcing steel bar cage is supported by a cage support protrusion. FIG. [Figure 6]This is a diagram showing the continuation of the construction procedure shown in Figure 3, and is an explanatory diagram showing the process of pouring a hardened body into the surrounding space, where (A) is a plan view and (B) is a front view. [Figure 7] FIG. 11 is an explanatory diagram showing the operation of suspending a reinforcing steel cage from the upper edge of the pile head using a hoisting device, where FIG. 11(A) is a plan view and FIG. 11(B) is a front view. [Figure 8] 1 is a perspective view showing a state in which a reinforcing steel cage is suspended from the upper edge of a pile head by a hoisting device. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. As shown in Fig. 1, a reinforcing steel cage 1 is arranged in a surrounding space S of a pile head 21 of a foundation pile 2 made of a prefabricated pile such as a circular steel pipe buried in the ground, and a hardened body such as concrete or mortar (not shown) is poured into the surrounding space S to form a reinforcing steel hardened body part of the pile head 21.

[0020] The reinforcing steel bar cage 1 of the embodiment includes, for example, three annular reinforcement sections 11 positioned at a distance from each other in the height direction of the pile head 21, for example, six connecting bars 12 connecting these three annular reinforcement sections 11 to each other, and for example, four straight reinforcement bars 13 fixed to each annular reinforcement section 11, and is fabricated in a factory in advance and transported to the construction site.

[0021] The three annular reinforcement portions 11 are each made of reinforcing bar processed into a circular (ring) shape, made with a diameter spaced apart from the peripheral surface of the pile head 21 of the foundation pile 2, and each located in a different horizontal plane.

[0022] The six connecting bars 12 are each a straight reinforcing bar arranged in the vertical direction, and are fixed to the inside of the annular reinforcing bar portion 11 by welding at intervals of, for example, 60 degrees.

[0023] The four straight reinforcing bars 13 are positioned inside each annular reinforcement portion 11, with both ends welded to the annular reinforcement portion 11. Two sets of two parallel straight reinforcing bars 13 are positioned at 90 degrees from each other to form a square shape in plan view. The four sides of the center of the square shape are positioned at the center of the annular reinforcement portion 11, the pile head 21 passes through these four sides, and the outer periphery of the pile head 21 is close to each side of the four sides. In addition to the four straight reinforcing bars 13 that form the square shape, other reinforcing bars can be provided in an arrangement that does not cross the four sides.

[0024] In the above-mentioned reinforcing bar cage 1, the four straight reinforcing bars 13 form a well shape in plan view, and the pile head 21 passes through the four sides of the well shape, so that even if there is a protrusion on the outer periphery of the pile head 21 of the foundation pile 2, the protrusion can be passed through on the diagonal of the four sides. Furthermore, since the well shape is formed by the four straight reinforcing bars 13, it is easy to manufacture, and the strength of the reinforcing bar hardened body portion formed around the pile head 21 can be improved.

[0025] Next, a method for reinforcing the pile head 21 of the foundation pile 2 using the reinforcing steel cage 1 will be described with reference to Figs.

[0026] As shown in Fig. 2(A) and Fig. 2(B), a foundation pile 2 is buried in the ground. This burying work can be performed by driving the foundation pile 2 using heavy machinery or by rotary pressing. Next, a cylindrical surrounding space S is formed around the pile head 21 of the foundation pile 2. The surrounding space S is formed by rotating an excavation rotary tool 5 equipped with an excavation screw around a pipe body fitted on the pile head 21 while supporting it with heavy machinery, and excavating the soil around the pile head 21. Note that the surrounding space S may be excavated first, and then the foundation pile 2 may be buried from the bottom of the surrounding space S.

[0027] On the outer peripheral surface of the pile head 21, for example, four cage support protrusions 21a that engage the four sides of the cross-shaped portion of the straight reinforcing bars 13 of the uppermost annular reinforcing bar portion 11 are welded and fixed at 90 degree intervals in the same horizontal plane (180 degrees in the case of two cage support protrusions). Note that in the foundation pile 2 used in this embodiment, for example, two driving tips 21b are welded at 180 degree intervals in the same horizontal plane to the outer peripheral surface above the cage support protrusions 21a, and the two cage support protrusions 21a are positioned so as to overlap the two tips 21b in a plan view.

[0028] Next, as shown in Figures 3(A) and 3(B), the lifted reinforcing bar cage 1 is gradually lowered to pass the pile head 21 through the four sides of the shape of the cross of the reinforcing bar cage 1. At this time, the two tips 21b and the four cage support protrusions 21a are positioned on the diagonal lines of the four sides of the cross of the straight bars 13 of each annular bar portion 11 below the topmost annular bar portion 11, and each of the lower annular bar portions 11 is positioned below the four cage support protrusions 21a.

[0029] Then, as shown in Fig. 4, the worker manually rotates the reinforcing bar cage 1 by 45 degrees in a horizontal plane, and the center sides of the four sides of the above-mentioned cross shape of the uppermost ring-shaped reinforcement portion 11 are supported by the four cage support protrusions 21a, as shown in Fig. 5. In terms of design, the distance between the cage support protrusions 21a of the buried foundation pile 2 and the bottom surface of the surrounding space S is set to be a certain distance higher than the height of the reinforcing bar cage 1, so that when the uppermost ring-shaped reinforcement portion 11 is supported by the four cage support protrusions 21a, the reinforcing bar cage 1 floats above the bottom surface of the surrounding space S.

[0030] Next, as shown in Fig. 6(A) and Fig. 6(B), the hardened body C is cast in a state in which the reinforcing steel cage 1 is floating above the bottom surface of the surrounding space S. As a result, a reinforcing steel hardened body part RC is created around the pile head 21.

[0031] Since the pile head 21 and the reinforcing steel hardened body RC are integrated, the bending moment and shear force acting on the foundation pile 2 can be borne by the reinforcing steel hardened body RC (the stress and bending moment generated in the foundation pile 2 can be reduced). In addition, even when the horizontal displacement of the pile head 21 is very large, the occurrence of cracks and damage to the reinforcing steel hardened body RC due to the reinforcing effect of the reinforcing steel cage 1 can be suppressed.

[0032] Furthermore, with the above-mentioned reinforcement method, the hardened body C is cast while the reinforcing bar cage 1 is floating above the bottom surface of the surrounding space S of the pile head 21, so that an appropriate cover of the hardened body can be ensured on the lower part of the reinforcing bar hardened body part RC created around the pile head 21.

[0033] In the above-mentioned reinforcing method, the four cage support protrusions 21a are fixed by welding to the outer circumferential surface of the pile head 21, but the present invention is not limited to this. The four cage support protrusions 21a may be provided so that their positions can be adjusted in the height direction of the foundation pile 2. In this way, even if the foundation pile 2 buried in the ground remains high due to the hardness of the ground, the lower end of the reinforcing steel cage 1 can be raised a certain distance above the bottom surface of the surrounding space S by lowering the height position of the four cage support protrusions 21a.

[0034] Such position-adjustable cage support protrusions 21a may be provided with a powerful magnet that is magnetically attached to the foundation pile 2, which is a steel pipe pile. In order to prevent the four cage support protrusions 21a made of magnets from losing their 90-degree intervals when adjusting their positions, the four cage support protrusions 21a may be connected to each other in a circular ring shape so that their positions can be adjusted as a unit. Also, a vertical groove may be formed on the outer circumferential surface of the pile head 21, while a vertical convex portion that is guided by the vertical groove may be formed on the back surface of the cage support protrusions 21a, so that the cage support protrusions 21a are guided in the height direction of the pile head 21.

[0035] The above-mentioned four cage support protrusions 21a may not be welded to the foundation pile 2 in advance, but may be fixed to the outer peripheral surface of the foundation pile 2 by on-site welding after checking the condition of the foundation pile 2 buried in the ground.

[0036] 7(A) and 7(B), the reinforcing steel cage 1 may be suspended from the upper end of the pile head 21 by four hoists 6 hooked onto the upper end of the pile head 21, thereby floating the reinforcing steel cage 1 above the bottom of the surrounding space S. The hoists 6 are manually hooked onto the upper end of the pile head 21 by a worker. Then, in this state in which the reinforcing steel cage 1 is suspended above the bottom of the surrounding space S, the hardened body C is cast, and after the cast hardened body C has hardened to a predetermined degree, all or part of the hoists 6 are withdrawn.

[0037] As shown in FIG. 8, each hoist 6 includes a wire 61 (connecting portion) and a hook 62 (hooking portion) connected to one end of the wire 61. The hook 62 is hooked to the upper edge of the pile head 21. A loop portion 61a is formed on the other end of the wire 61. The wire 61 is half-wound so as to hook the uppermost annular reinforcing bar portion 11 of the reinforcing steel cage 1, so that the loop portion 61a comes to the upper side and can be positioned near the hook 62. A nut portion 62a is provided on the base side of the hook 62, and the tip of the screw portion of the bolt 63 passed through the loop portion 61a can be screwed into the nut portion 62a. This allows the reinforcing steel cage 1 to be hung at a certain height from the upper end of the pile head 21.

[0038] The sling 6 can be retrieved by removing the bolt 63 from the nut portion 62a and the ring portion 61a and pulling the hook 62 upward.

[0039] The hoisting device for suspending the reinforcing bar cage 1 from the upper end of the pile head 21 is not limited to the above structure, and may be, for example, a structure in which hooking parts (hooks, clips, etc.) are provided on both the upper and lower ends of a wire, the lower hooking part is hooked onto the reinforcing bar cage 1, and the upper hooking part is hooked onto the upper edge of the pile head 21. In such a hoisting device, after the cast hardened body C has hardened to a predetermined extent, for example, the wire above the hardened body C may be cut, the wire and the lower hooking part inside the hardened body may be left in place, and only the upper hooking part and part of the wire may be retrieved.

[0040] When the top end of the pile head 21 is cut off due to the foundation pile 2 buried in the ground being stuck high due to the hardness of the ground, the length of the wire (connecting part) in the hoisting tool described above does not need to be adjustable. On the other hand, if the top end of the pile head 21 is not to be cut off when the pile is stuck high, it is preferable to use a hoisting tool with an adjustable length of the wire (connecting part). This length adjustment can be performed using, for example, a commercially available wire stopper that fixes the wire by the screwing pressure of a bolt, or a wire lock.

[0041] Although the embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to the illustrated embodiment. Various modifications and variations can be made to the illustrated embodiment within the same scope as the present invention or within an equivalent scope. [Explanation of symbols]

[0042] 1: Reinforcing steel cage 2: Foundation piles 5: Excavation rotary tool 6: Hanging device 11: Circular muscle 12: Connecting muscles 13: Straight rebar 21:Pile head 21a:Cage support protrusion 21b: Chip 61: Wire 61a :limbum 62: Hook 62a: Nut part 63: Bolt C: Cured body RC: Reinforced concrete reinforcement S: Surrounding space

Claims

1. A reinforcing bar cage is disposed in a surrounding space formed around the head of a foundation pile buried in the ground, and a reinforcing bar hardened body part of the head of the pile is formed by a hardening body that is cast in the surrounding space and hardens over time, A plurality of annular reinforcement portions having a ring shape spaced apart from the outer peripheral surface of the pile head of the foundation pile and spaced apart from each other in the height direction of the pile head; A plurality of connecting muscles that connect the plurality of circular muscle portions to each other; A reinforcing bar cage for the head of a foundation pile, characterized in that at least four straight reinforcing bars located inside the annular reinforcement portion and both ends fixed to the annular reinforcement portion form a well shape when viewed in a plane, with the pile head passing through the four sides near the center of the well shape and the outer periphery of the pile head being close to the center of each side of the four sides.

2. 2. A method for reinforcing the head of a foundation pile using the reinforcing bar cage described in claim 1, characterized in that the reinforcing bar cage is positioned within the surrounding space, passing the pile head through the four sides of the reinforcing bar cage in the shape of the well, and the hardened body is poured into the pile while the reinforcing bar cage is floating above the bottom of the surrounding space.

3. The method for reinforcing the head of a foundation pile according to claim 2, On the outer peripheral surface of the pile head, two to four cage support protrusions are provided in the same horizontal plane to support the center of each side of the four sides of the straight reinforcing bars of the uppermost ring reinforcing bar, A method for reinforcing the head of a foundation pile, comprising: positioning the cage support protrusion portion on the diagonal of the four sides of the I-shape of the straight reinforcing bars of each annular reinforcement section below the topmost annular reinforcement section, positioning each of the lower annular reinforcement sections below the cage support protrusion portion, and then rotating the reinforcing bar cage in a horizontal plane to support the center sides of each of the four sides of the I-shape of the straight reinforcing bars of the topmost annular reinforcement section with the cage support protrusion portion, thereby floating the reinforcing bar cage above the bottom surface of the surrounding space.

4. 4. The method for reinforcing the head of a foundation pile as described in claim 3, wherein the four cage support protrusions are arranged so that their positions can be adjusted in the height direction of the head of the foundation pile.

5. 5. The method for reinforcing the head of a foundation pile as described in claim 4, wherein the foundation pile is a steel pipe pile, and the four cage support projections are magnetically attached to the steel pipe pile.

6. 3. A method for reinforcing the head of a foundation pile as described in claim 2, characterized in that the reinforcing steel cage is suspended from the upper end of the pile head by a hanging device hooked to the upper end of the pile head, thereby floating the reinforcing steel cage above the bottom of the surrounding space, and after the cast hardened body has hardened to a predetermined extent, at least the hook portion of the hanging device hooked to the upper end of the pile head is retrieved.

7. 7. The method for reinforcing the head of a foundation pile as described in claim 6, characterized in that the hooked portion of the hanging device hooked to the upper end of the pile head is retrieved by cutting the connecting portion connecting the hooked portion to the portion hooked to the reinforcing bar cage.

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