How to erect a rebar cage

Abstract

To provide a reinforcement cage building method capable of being suitably applied even when an overhead clearance is limited, and suppressing cutting of sediment of a hole wall.SOLUTION: A reinforcement cage 1 is a telescopic type having a cage body 2 connecting hoops and strands with flexibility such that an intersection angle therebetween is variable, wherein on the cage body 2, reinforcement rings 4a along a circumferential direction of the cage body 2 are provided in three or more stages with an interval in an axial direction of the cage body 2. When building the reinforcement cage 1 in an excavated hole 100, the following steps are repeated: a steps in which the reinforcement rings 4a adjacent in the axial direction of the cage body 2 are connected by connection members 5 and the reinforcement cage 1 in a state where the cage body 2 is contracted is arranged above the excavated hole 100, then the connection member 5 positioned the lowest is removed, the reinforcement cage 1 is lifted up from the reinforcement ring 4a in the uppermost stage, and the cage body 2 in a section between the reinforcement rings 4a connected by the connection members 5 is extended upward; and a step in which the reinforcement cage 1 is suspended down, and the cage body 2 in the extended section is inserted into the excavated hole 100.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a method for erecting an expandable reinforcing cage. [Background technology]

[0002] One construction method for constructing cast-in-place concrete piles under low-head construction conditions is to use a telescopic reinforcing cage. Patent documents 1 to 3 describe examples of telescopic reinforcing cages, in which flexible prestressing steel strands (hereinafter referred to as strands) are used as the axial steel material that makes up the cage body instead of ordinary deformed reinforcing bars, and the strands and hoops are connected by connecting members so that the crossing angle between them is variable, allowing the cage body to expand and contract by twisting it.

[0003] The cage body is provided with multiple reinforcing rings at intervals in the axial direction of the cage body, including at both ends of the cage body, to maintain its shape. The reinforcing rings are made of flat steel (flat bar) or steel sections (angle bars or channel steel) processed into a ring shape and are arranged around the cage body.

[0004] When constructing a cast-in-place concrete pile using an extendable rebar cage, the cage is first assembled horizontally in a factory with the cage body fully extended, then transported to the unloading point by land transport such as a truck while the cage body is contracted and secured. The rebar cage is then erected and placed in the borehole with the cage body extended. Concrete is then poured into the borehole to construct the cast-in-place concrete pile. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-048519 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-132190 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-214990 Summary of the Invention [Problem to be solved by the invention]

[0006] The simplest method of erecting a reinforcing cage is to leave it erected near the borehole, then lift the top reinforcing ring with a crane to fully extend the cage body, and then lower it into the borehole.

[0007] If there are no headroom restrictions near the borehole, the above method can be used to erect the cage. However, if there are headroom restrictions, this method may be difficult to use. In such cases, the upper end of the reinforcing cage is temporarily fixed to the hole mouth, and the wire attached to the lowest reinforcing ring is wound down, allowing the cage to extend downward within the borehole. However, with this method, the cage may rotate as it extends within the borehole, potentially coming into contact with the hole wall and scraping away soil and sand.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a method for erecting a reinforcing cage that can be suitably applied even when there is a headroom restriction and that can also suppress the scraping off of soil from the hole wall. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present invention provides a method for erecting an expandable reinforcing cage into a borehole, the cage having a cage body in which ties and flexible strands are joined so that the crossing angle is variable, the cage body being provided with reinforcing rings along the circumferential direction of the cage body in three or more stages spaced apart in the axial direction of the cage body, and the reinforcing rings adjacent to each other in the axial direction of the cage body being connected by a connecting member, the connecting members are attached to the reinforcing rings so as to transition from a state in which they are disposed obliquely with respect to the axial direction of the cage body to a state in which they are disposed along the axial direction of the cage body in response to extension of the cage body in the section between the reinforcing rings connected by the connecting members,This method for erecting a reinforcing bar cage comprises the steps of: (a) suspending the reinforcing bar cage, with the cage body in a contracted state, from the top reinforcing ring so that the axial direction of the cage body is vertical, and placing it above the borehole; (b) removing the lowest connecting member, suspending the reinforcing bar cage from the top reinforcing ring, and extending upward the section of the cage body between the reinforcing rings that was connected by the connecting member; and (c) lowering the reinforcing bar cage and inserting the extended section of the cage body into the borehole, and is characterized in that the reinforcing bar cage is erected in the borehole by repeating steps (b) and (c).

[0010] According to the present invention, by connecting the upper and lower reinforcing rings with a connecting member while the cage body is contracted, relative rotation between the reinforcing rings, i.e., extension of the cage body, is suppressed, and only the section of the cage body where the connecting member is removed can be partially extended. Therefore, by repeating the partial extension of the cage body and inserting the extended section of the cage body into the borehole using the above-mentioned installation method, a lower headroom is required compared to the case where the cage body is fully extended upward and then inserted into the borehole, as described above, and this can be applied even in construction conditions with low headroom restrictions. Furthermore, with this invention, the extended section of the cage body is inserted into the borehole by simply lowering the reinforcing cage, without rotating the cage body or scraping away soil from the borehole wall. This also has the advantage of eliminating the need for complex shapes for the spacers attached to the reinforcing cage to prevent soil scraping away, allowing for a simple configuration.

[0011] After inserting the cage body of the section extended in step (c) into the borehole, it is desirable to carry out step (b) while fixing the reinforcing ring above that section so that it does not rotate in a plane, thereby extending the cage body of the section above that section upward. This makes it possible to suppress rotation of the cage body inserted into the borehole when the cage body of the extended section is inserted into the borehole and then the cage body of the section above is extended upward, thereby preventing scraping away of soil and sand from the borehole wall.

[0012] When the connecting member is removed in the step (b), it is desirable to hang and support the reinforcing ring below which the connecting member is attached. The reinforcing ring is provided, for example, on the outside of the cage body. By suspending the lower reinforcing ring to which the connecting material is attached, the load borne by the connecting material can be temporarily supported, and the connecting material can be easily removed. Also, by connecting the reinforcing rings on the outside of the cage body with connecting material, the connecting material can be easily removed from the outside of the reinforcing cage. [Effects of the Invention]

[0013] The present invention can provide a method for erecting a reinforcing cage that can be suitably applied even when there is a headroom restriction and that can also prevent soil from being scraped off the hole wall. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. [Figure 2] 10 is a diagram showing the arrangement of reinforcing rings 4 (4a, 4b). FIG. [Figure 3] 1 is a diagram illustrating the production of a reinforcing bar cage 1. FIG. [Figure 4] 4A and 4B are diagrams illustrating the connection of reinforcing rings 4a by connecting materials 5. FIG. [Figure 5] 10A and 10B are diagrams illustrating the transportation of the reinforcing bar cage 1. [Figure 6] FIG. 10 is a diagram illustrating the erection of the reinforcing bar cage 1. [Figure 7] FIG. 10 is a diagram illustrating the erection of the reinforcing bar cage 1. [Figure 8] A diagram showing frame 8. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0016] (1. Rebar cage 1) Fig. 1(a) is a diagram showing an expandable reinforcing bar cage 1 according to an embodiment of the present invention. As shown in Fig. 1(a), the reinforcing bar cage 1 has a cage body 2 made of strands 21, which are flexible axial steel materials, and ties 22, to which reinforcing rings 4 are attached.

[0017] In the cage body 2, the strands 21 and the ties 22 are connected by connecting members at their intersections so that the crossing angle between the strands 21 and the ties 22 in the vertical plane is variable, and by twisting the cage body 2 as shown by arrow A, the cage body 2 contracts as shown in Figures 1(b) and 1(c). On the other hand, by rotating the cage body 2 in the direction opposite to arrow A as shown by arrow B in Figure 1(c), the cage body 2 expands. The above connecting members are described in Patent Documents 1 to 3, and a description thereof will be omitted here.

[0018] Fig. 2(a) is a diagram showing the arrangement of the reinforcing rings 4 (4a, 4b), and shows the inside of the cage body 2. As shown in Fig. 2(a), the reinforcing rings 4 (4a, 4b) are provided in three or more rows spaced apart in the axial direction of the cage body 2 at both axial ends and in the intermediate section between the ends. When the upper end of the cage body 2 is rotated as shown by arrows A and B in Fig. 1, adjacent reinforcing rings 4a rotate relative to each other as the cage body 2 expands and contracts.

[0019] 2(b) is a diagram showing a reinforcing ring 4a on the outside of the cage body 2. The reinforcing ring 4a is a ring-shaped steel material having an L-shaped cross section formed by a vertical portion 41 and a horizontal portion 42. The reinforcing ring 4a can be formed, for example, by processing an angle iron into a ring shape.

[0020] The reinforcing ring 4a on the outside of the cage body 2 is arranged along the circumferential direction of the cage body 2 with the vertical portion 41 on the inside (the cage body 2 side), and holes 411 are formed in the vertical portion 41. The holes 411 are used to attach a rotary connecting member (not shown) that connects the reinforcing ring 4a and the strands 21 so that they can rotate in a vertical plane. The vertical portion 41 has holes 411 formed at equal intervals in the circumferential direction, the number of holes corresponding to the number of strands 21.

[0021] An example of a rotary coupling member is described in Patent Document 3, but to put it simply, it is a member having an axial member such as a stud bolt attached to the outer surface of the sleeve through which the strand 21 is inserted. The rotary coupling member can be attached to the reinforcing ring 4a by passing the axial member through the hole 411 and tightening a nut onto the tip of the axial member.

[0022] On the other hand, holes 421 are formed at equal intervals in the circumferential direction in the horizontal portion 42 of the reinforcing ring 4a. These holes 421 are used to attach connecting members, which will be described later.

[0023] A plurality of holes 421 are provided at intervals in the circumferential direction in the horizontal portion 42 of the reinforcing ring 4a. A plurality of holes 421 (12 in this embodiment) are provided at equal intervals in the horizontal portion 42. It is preferable that the circumferential position of each hole 421 be different from the circumferential position of the holes 411 in the vertical portion 41, so that cross-sectional defects due to the holes 411, 421 are not concentrated.

[0024] The reinforcing ring 4b on the inside of the cage body 2 has a configuration in which the vertical portion 41 and horizontal portion 42 of the reinforcing ring 4a on the outside of the cage body 2 are reversed, with the vertical portion being positioned on the outside (cage body 2 side). No holes are formed in the horizontal portion. The rest of the configuration is the same as the outer reinforcing ring 4a.

[0025] (2. How to erect the rebar cage 1) In this embodiment, the reinforcing bar cage 1 manufactured in a factory or the like is transported by land transport means such as a truck to the construction site or a nearby unloading point, and then the reinforcing bar cage 1 is transported, while suspended by a crane, to the excavation hole where the cast-in-place concrete pile will be constructed, and is erected into the excavation hole.

[0026] In a factory or the like, the reinforcing bar cage 1 is manufactured with the cage body 2 stretched (and laid horizontally), as shown in Figure 3(a) showing the outer surface of the reinforcing bar cage 1, and then the cage body 2 is twisted and contracted as shown in Figure 3(b). Then, as shown in Figure 3(c), adjacent reinforcing rings 4a in the axial direction of the cage body 2 are connected with connecting members 5, and the contracted cage body 2 is secured with a securing member (not shown) such as a band. The connecting members 5 can be threaded rebar, threaded rods, PC steel rods, etc., but threaded rebar, which can be cut to any length, is preferred in terms of workability.

[0027] 4(a) is a diagram showing the attachment portion of the connecting member 5 to the reinforcing ring 4a. The end of the connecting member 5 is passed through a hole 421 in the horizontal portion 42 of the reinforcing ring 4a, and a nut 51 is tightened onto the end of the connecting member 5 protruding from the hole 421. The diameter of the hole 421 is larger than the diameter of the end of the connecting member 5, but the outer diameter of the nut 51 is larger than the diameter of the hole 421, so that the end of the connecting member 5 is locked onto the horizontal portion 42 of the reinforcing ring 4a by the nut 51. By attaching both ends of the connecting member 5 to adjacent reinforcing rings 4a as described above, the adjacent reinforcing rings 4a are connected by the connecting member 5.

[0028] Fig. 4(b) is a diagram showing the state in which the reinforcing rings 4a are connected by the connecting material 5. As shown in Fig. 4(b), when the cage body 2 is contracted, the circumferential positions of the holes 421 in the horizontal portions 42 of the reinforcing rings 4a differ between adjacent reinforcing rings 4a, and the connecting material 5 is disposed obliquely with respect to the axial direction of the cage body 2.

[0029] Ideally, the circumferential positions of the holes 421 should be the same between adjacent reinforcing rings 4a, but as described above, the cage body 2 of the reinforcing cage 1 is manufactured in an extended state and then contracted, which causes the reinforcing rings 4a to rotate as the cage body 2 twists. Since it is difficult to accurately predict the amount of rotation, in this embodiment, multiple holes 421 are provided at intervals around the circumferential direction of the reinforcing ring 4a, and the connecting members 5 are attached by selecting appropriate holes 421 that are close to each other in the circumferential direction for each of the adjacent reinforcing rings 4a, allowing the connecting members 5 to be oblique to the axial direction of the cage body 2 while transitioning to a state in which the connecting members 5 are arranged along the axial direction of the cage body 2 when the cage body 2 is extended, as described below.

[0030] For example, three to six connecting members 5 are provided in the cross section of the cage body 2 (cross section perpendicular to the axial direction of the cage body 2), and in this embodiment, four are provided. However, the number of connecting members 5 can be determined appropriately taking into consideration the steel material used for the connecting members 5, the weight of the reinforcing bar cage 1, cross-sectional loss due to perforation of the reinforcing rings 4a, etc. The number of holes 421 in the reinforcing rings 4a is set to be greater than the number of connecting members 5 in the cross section of the cage body 2.

[0031] At the unloading point, the reinforcing bar cage 1 is erected so that the axial direction of the cage body 2 is vertical, and then, as shown in Figure 5, a hanging member L1 such as a wire hanging from a crane is sling-hooked onto the top reinforcing ring 4a and the reinforcing bar cage 1 is transported while hanging from the top reinforcing ring 4a. At this time, the cage body 2, which is in a contracted state, is slightly stretched although it is fastened, and as the cage body 2 and reinforcing ring 4a rotate in a direction that eliminates the twist, the connecting member 5 transitions to a state in which it is arranged along the axial direction of the cage body 2.

[0032] In this embodiment, the upper and lower reinforcing rings 4a are connected to each other by connecting materials 5, so that the weight of the reinforcing cage 1 in the section H1 from the top reinforcing ring 4a to the second reinforcing ring 4a (referring to the number of stages counted from the top; the same applies below) is supported by the connecting materials 5 in that section H1 and the second reinforcing ring 4a.

[0033] Similarly, the weight of the cage reinforcing bar 1 in section H2 from the second reinforcing ring 4a to the third reinforcing ring 4a is supported by the connecting members 5 in section H2 and the third reinforcing ring 4a, and the weight of the cage reinforcing bar 1 in section H3 from the third reinforcing ring 4a to the bottom reinforcing ring 4a is supported by the connecting members 5 in section H3 and the bottom reinforcing ring 4a. As a result, in this embodiment, the entire weight of the cage reinforcing bar 1 does not act on the lower end of the cage body 2, and the connecting members between the strands 21 and the ties 22 at the lower end of the cage body 2 are not damaged.

[0034] The reinforcing bar cage 1 transported by the crane is placed above the drilling hole 100 with the axial direction of the cage body 2 aligned vertically, as shown in Figure 6(a), and furthermore, a hanging material L2 such as a wire hanging down from a hoisting balance 7 suspended and supported by the crane is sling-hooked onto the lowest reinforcing ring 4a.

[0035] When this hanging member L2 is wound up until it becomes taut, the lowest reinforcing ring 4a is suspended and supported by the hanging member L2, and the load carried by the connecting member 5 of section H3 (the connecting member 5 located lowest) is temporarily supported by the hanging member L2. In this state, the connecting member 5 of section H3 is removed as shown in Figure 6(b).

[0036] In this way, by supporting the lower reinforcing ring 4a (the lowest reinforcing ring 4a) to which the connecting material 5 of section H3 is attached by the hanging material L2, the connecting material 5 of section H3 can be easily removed.

[0037] Next, as shown in Figure 6(c), the sling L1 attached to the top reinforcing ring 4a is hoisted up, and the reinforcing cage 1 is lifted from the top reinforcing ring 4a, thereby extending upward the cage body 2 in section H3 from which the connecting material 5 has been removed. At this time, the bottom reinforcing ring 4a and the third reinforcing ring 4a, which were connected by the connecting material 5, rotate relative to each other as the cage body 2 extends.

[0038] On the other hand, in sections H1 and H2 above section H3, the relative rotation between the upper and lower reinforcing rings 4a, that is, the extension of the cage body 2, is prevented by the connecting members 5 between the upper and lower reinforcing rings 4a.

[0039] Therefore, if the lowest reinforcing ring 4a is fixed so that it does not rotate in a plane, the cage body 2 in sections H1 and H2 will rise while rotating together in a contracted state as the third reinforcing ring 4a rotates. The lowest reinforcing ring 4a can be fixed, for example, by temporarily joining the reinforcing ring 4a with a bolt or the like to a pin (not shown) hung across the mouth of the borehole 100, but the fixing means for the reinforcing ring 4a is not limited to this. The fixing means, such as the pin, is removed after the cage body 2 in section H3 has been fully extended.

[0040] When the cage body 2 in section H3 is fully extended, the entire weight of the reinforcing bar cage 1 is suspended and supported from the top reinforcing ring 4a via the connecting members 5, and the suspension members L2 are loosened. After that, the loosened suspension members L2 are removed from the bottom reinforcing ring 4a, and as shown in Figure 7(a), the suspension members L1 suspending the top reinforcing ring 4a are wound down, the reinforcing bar cage 1 is lowered, and the extended cage body 2 in section H3 is inserted into the borehole 100. In this embodiment, the cage body 2 in section H3 is inserted into the borehole 100 simply by lowering the reinforcing bar cage 1, so the cage body 2 does not rotate and scrape away the hole wall.

[0041] Then, as shown in Figure 7(b), a sling L2 is attached to the third-stage reinforcing ring 4a, and the hanging material L2 is wound up until it is taut.With the third-stage reinforcing ring 4a suspended and supported by the hanging material L2, the connecting material 5 in the section H2 between the third-stage reinforcing ring 4a and the second-stage reinforcing ring 4a (the connecting material 5 located lowest at this point) is removed.

[0042] Thereafter, as shown in Figure 7(c), the hanging member L1 is wound up to lift the reinforcing bar cage 1 from the top reinforcing ring 4a, and the cage body 2 in section H2 from which the connecting member 5 has been removed is extended. As in Figure 6(c), the third-stage reinforcing ring 4a and the second-stage reinforcing ring 4a, which were connected by the connecting member 5, rotate relative to each other as the cage body 2 extends, but in section H1 above section H2, the relative rotation between the upper and lower reinforcing rings 4a, i.e., the extension of the cage body 2, is prevented by the connecting member 5 between the upper and lower reinforcing rings 4a.

[0043] Therefore, if the third-stage reinforcing ring 4a (the reinforcing ring 4a above section H3) is fixed so as not to rotate in a plane with a fixing means such as a pin, as described above, the cage body 2 in section H1 will rise while rotating in a contracted state as the second-stage reinforcing ring 4a rotates. On the other hand, the cage body 2 in section H3 located inside the borehole 100 will not rotate and will not scrape off the hole wall.

[0044] When the cage body 2 of section H2 is fully extended in this way, the entire weight of the reinforcing bar cage 1 is suspended and supported from the top reinforcing ring 4a via the connecting members 5, and the hanging members L2 are loosened. The loosened hanging members L2 are removed from the third reinforcing ring 4a, and as shown in Figure 7(d), the hanging members L1 suspending the top reinforcing ring 4a are lowered, the reinforcing bar cage 1 is lowered, and the extended cage body 2 of section H2 is inserted into the borehole 100.

[0045] 7(a) to 7(d) are repeated to successively erect the extended sections of the cage body 2 into the borehole 100, until the entire cage body 2 in the extended state is erected into the borehole 100. Thereafter, concrete can be poured into the borehole 100 to construct a cast-in-place concrete pile.

[0046] As described above, according to this embodiment, by connecting the upper and lower reinforcing rings 4a with the connecting members 5 while the cage body 2 is contracted, relative rotation between the reinforcing rings 4a, i.e., extension of the cage body 2, is suppressed, and only the section of the cage body 2 from which the connecting members 5 are removed can be partially extended. Therefore, by using the erection method of this embodiment, by repeatedly partially extending the cage body 2 and inserting the extended section of the cage body 2 into the borehole 100, a lower headroom is required compared to the case where the cage body 2 is fully extended upward and then inserted into the borehole 100 as described above, and this method can be applied even in construction conditions with low headroom restrictions. Furthermore, in this embodiment, the extended section of the cage body 2 is inserted into the borehole 100 by simply lowering the reinforcing cage 1, without the cage body 2 rotating or scraping away soil from the hole wall. The reinforcing bar cage 1 is also provided with a spacer (not shown) to ensure a distance from the hole wall, but in this embodiment, the shape of the spacer does not need to be complex to prevent the scraping off of soil and sand (see, for example, Figure 4 of JP 2006-274726 A), which has the advantage of allowing for a simple configuration.

[0047] In addition, in this embodiment, after the cage body 2 of the extended section H3 is inserted into the borehole 100 as shown in Figure 7(a), the reinforcing ring 4a (third-stage reinforcing ring 4a) above the section H3 is fixed so as not to rotate.Therefore, when the cage body 2 of the section H2 above the section H3 is extended upward in the process shown in Figure 7(c), the rotation of the cage body 2 inserted into the borehole 100 can be suppressed, and the scraping away of soil and sand from the hole wall can be prevented.

[0048] 6(b) and 7(b), the lower reinforcing ring 4a to which the connecting material 5 is attached is suspended by a hanging member L2, thereby temporarily supporting the load borne by the connecting material 5, and the connecting material 5 can be easily removed. Furthermore, by connecting the reinforcing rings 4a on the outside of the cage body 2 with the connecting material 5, the connecting material 5 can be easily removed from the outside of the reinforcing cage 1.

[0049] However, the present invention is not limited to the above embodiment. For example, in this embodiment, the lowest reinforcing ring 4a and the like are suspended from the hoist 7 by the suspension member L2, which is longest at the beginning and shortens as the erection work of the reinforcing cage 1 progresses. Furthermore, the amount of suspension member L2 wound up at one time is sufficient to tension the suspension member L2 when removing the connecting member 5 in the process shown in Figure 6(b) or Figure 7(b).

[0050] Therefore, instead of using a crane, it is also possible to assemble a simple frame 8 around the borehole 100 as shown in Figure 8, and suspend the lowest reinforcing ring 4a etc. using a hanging member L2 such as a lever hoist hanging from the top of the frame 8.In this case, too, the cage body 2 can be extended and erected using the same procedure as described above.

[0051] Alternatively, the lifting balance 7 can be suspended from the top of the frame 8 by a lever hoist or the like, and the lowest reinforcing ring 4a and the like can be suspended by a suspension member L2 hanging down from the lifting balance 7. Additionally, the top reinforcing ring 4a can be suspended by a suspension member L1 from a hoist (not shown) provided at the top of the frame 8, and the cage body 2 can be extended by hoisting up the suspension member L1.

[0052] In this embodiment, the reinforcing rings 4a on the outside of the cage body 2 are connected by the connecting material 5, but it is also possible to connect the reinforcing rings 4b on the inside of cage bodies 2 that are adjacent in the axial direction of the cage body 2 by the connecting material 5 in a manner similar to this embodiment. However, removing the connecting material 5 on the inside of the cage body 2 is more time-consuming than removing the connecting material 5 on the outside of the cage body 2.

[0053] In this embodiment, the reinforcing bar cage 1 is transported to the borehole 100 while being suspended by a crane, but depending on the construction site, it may also be possible to transport it to the vicinity of the borehole 100 using a helicopter or a mobile transport frame.

[0054] In addition, in this embodiment, the reinforcing bar cage 1 is used to construct cast-in-place concrete piles, but this is not limited to this and can be applied to general construction work such as erecting the reinforcing bar cage 1 into the excavation hole 100, and can also be used for constructing deep foundations, for example.

[0055] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that those skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas disclosed herein, and it is understood that these modifications also fall within the technical scope of the present invention. [Explanation of symbols]

[0056] 1: Reinforced concrete cage 2:Cage body 4, 4a, 4b: Reinforcement ring 5: Connecting material 21: Strand 22: Stirrup 100: Borehole

Claims

1. A method for erecting an expandable reinforcing cage into a borehole, the cage having a cage body in which ties and flexible strands are connected so that the crossing angle is variable, The cage body is provided with reinforcing rings along the circumferential direction of the cage body in three or more stages spaced apart in the axial direction of the cage body, the reinforcing rings adjacent to each other in the axial direction of the cage body are connected by a connecting member, and the connecting member is attached to the reinforcing ring so as to transition from a state in which the reinforcing rings are disposed obliquely with respect to the axial direction of the cage body to a state in which the reinforcing rings are disposed along the axial direction of the cage body in accordance with extension of the cage body in the section between the reinforcing rings connected by the connecting member, A step (a) of suspending the reinforcing bar cage in a contracted state from the uppermost reinforcing ring so that the axial direction of the cage body is vertical and placing it above the borehole; (b) removing the lowest connecting member, lifting the reinforcing cage from the uppermost reinforcing ring, and extending upward the cage body in the section between the reinforcing rings that was connected by the connecting member; (c) a step of lowering the reinforcing bar cage and inserting the cage body of the extended section into the excavation hole; and A method for erecting a reinforcing bar cage, characterized in that the reinforcing bar cage is erected into the excavated hole by repeating steps (b) and (c).

2. A method for erecting a reinforcing bar cage according to claim 1, characterized in that after inserting the cage body of the section extended in step (c) into the borehole, step (b) is carried out while fixing the reinforcing ring above the section so that it does not rotate in a plane, thereby extending the cage body of the section above the section upward.

3. 2. The method for erecting a reinforcing cage according to claim 1, wherein when removing the connecting material in step (b), the lower reinforcing ring to which the connecting material is attached is suspended and supported.

4. 2. The method for erecting a reinforcing cage according to claim 1, wherein the reinforcing ring is provided on the outside of the cage body.

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