How to erect a rebar cage

Abstract

To provide a method for erecting a reinforcing bar cage that can be suitably applied even if there are restrictions such as overhead clearance.SOLUTION: Reinforcing bar cages 1a and 1b are telescopic ones each having a cage body 2 in which tie hoops and flexible strands are connected such that the intersection angle is variable. When erecting these reinforcing bar cages 1a and 1b into an excavation hole 100, above the reinforcing bar cage 1a inserted into the excavation hole 100 with the axial direction of the cage body 2 being the vertical direction, the reinforcing bar cage 1b in which at least a portion including an upper end portion of the cage body 2 is contracted is arranged with the axial direction of the cage body 2 being the vertical direction. After that, the lower end of the strand of the upper reinforcing bar cage 1b and the upper end of the strand of the lower reinforcing bar cage 1a are connected. Two reinforcing bar cages 1a and 1b whose strands are connected to each other are suspended into the excavation hole 100. At this time, at least the cage body 2 of the upper reinforcing bar cage 1b is expanded.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] One construction method for constructing cast-in-place concrete piles or circular caulking foundations under low head conditions uses a telescopic reinforcing cage. Patent Documents 1 to 3 describe examples of such telescopic reinforcing cages.

[0003] Figure 17 is a diagram illustrating the telescopic reinforcing bar cage 1. As shown in Figure 17(a), the telescopic reinforcing bar cage 1 uses flexible PC steel strands (hereinafter referred to as strands) 21 as the axial steel material that makes up the cage body 2, instead of ordinary deformed reinforcing bars.

[0004] 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 upper end of the cage body 2 as shown by arrow A, the cage body 2 contracts as shown in Figures 17(b) and (c). On the other hand, by rotating the upper end of the cage body 2 in the direction opposite to arrow A as shown by arrow B in Figure 17(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. [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] When constructing long cast-in-place concrete piles or the like underground using telescopic reinforcing cages, it is necessary to erect the cages into the borehole while joining them together. One possible method for doing this is to lift the top end of the cage body with a crane on the ground near the hole mouth, extend the entire length of the cage body, and then insert the cages into the borehole and join them together.

[0007] However, the above-mentioned method of extending the cage body on the ground requires that there is enough headroom or the crane's ground lifting height to fully extend the cage body on the ground, but if there are limitations on these, it may be difficult to erect the cage using the above-mentioned method.

[0008] The present invention has been made in view of the above problems, and aims to provide a method for erecting a reinforcing cage that can be suitably applied even when there are restrictions such as headroom. [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 bar 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 method comprising the steps of: The reinforcing bar cage with the cage body shrunk Insert the cage into the borehole with the axial direction of the cage vertical. Step (a') of carrying out the above This method for erecting reinforcing bar cages comprises the steps of: (a) placing a reinforcing bar cage, with at least a portion of the cage body in a contracted state including the upper end of the cage body, above the reinforcing bar cage, with the axial direction of the cage body in the vertical direction; (b) connecting the lower ends of the strands of the upper reinforcing bar cage to the upper ends of the strands of the lower reinforcing bar cage; and (c) suspending the two reinforcing bar cages with their strands connected together into an excavated hole, wherein in step (c), at least the cage body of the upper reinforcing bar cage is extended. The cage body of the lower reinforcing bar cage is provided with multiple stages of reinforcing rings spaced apart vertically along the circumferential direction of the cage body, and in step (a'), the reinforcing bar cage is inserted into the excavated hole while being suspended and supported by a suspension member attached to the lowest reinforcing ring, and the planar position of the suspension member is desirably fixed to the planar center of the reinforcing bar cage by a centering mechanism provided on the highest reinforcing ring.

[0010] In this embodiment, when joining the upper and lower reinforcing bar cages and erecting them, the upper reinforcing bar cage is transported and placed in a contracted state using a crane or the like, and joined to the lower reinforcing bar cage located within the borehole directly above the borehole, etc. Therefore, even in construction conditions with low overhead or when there is a limit to the crane's ground lift, the reinforcing bar cages can be joined to make them longer, making it possible to build structures such as cast-in-place concrete piles deep underground.

[0011] Before connecting the strands together in step (b), it is desirable that at least a portion of the cage body of the lower reinforcing bar cage, including the lower end thereof, is put into a contracted state, and in step (c), the lower end thereof is lowered into the borehole to extend the cage bodies of the upper and lower reinforcing bar cages. In this case, the reinforcing bar cage can be extended in one go, and the work can be completed in a short time.

[0012] Before connecting the strands together in step (b), it is also desirable that the entire length of the cage body of the lower reinforcing bar cage and the lower end of the cage body of the upper reinforcing bar cage are in an extended state, and that the lower end of the strand of the upper reinforcing bar cage and the upper end of the strand of the lower reinforcing bar cage are arranged vertically. This makes it possible to easily connect the strands.

[0013] The cage body of the upper reinforcing cage is provided with reinforcing rings along the circumferential direction of the cage body, in three or more rows spaced apart from one another, and adjacent reinforcing rings are connected to each other by connecting members.It is also desirable to remove the lowest connecting member and extend the cage body in the section between the reinforcing rings that were connected by the connecting member before connecting the strands to each other in step (b). This allows the lower end of the cage body of the upper reinforcing bar cage to be partially extended, making it easy to connect the reinforcing bar cages even under low-head construction conditions.

[0014] In step (c), it is also desirable to remove the lowest connecting member of the upper reinforcing cage, extend the cage body in the section between the reinforcing rings that was connected by the connecting member, and repeat the process of lowering the two reinforcing cages with their strands connected to each other. By following the above procedure, the cage body of the upper reinforcing bar cage is partially extended and the cage is repeatedly inserted into the excavated hole, so that the reinforcing bar cage can be erected even under low-head construction conditions.

[0015] In step (c), when removing the lowest connecting member of the upper reinforcing cage and extending the cage body in the section between the reinforcing rings located on the ground that was connected by the connecting member, it is desirable to restrain the rotation of the reinforcing cage in the borehole located below that section, and after extending the cage body in that section, to lower the two reinforcing cages with strands connected to each other vertically without rotating them. This has the advantage that the reinforcing bar cage will not rotate within the borehole and scrape away the hole wall, and the spacer for the upper reinforcing bar cage can be simplified. [Effects of the Invention]

[0016] The present invention can provide a method for erecting a reinforcing cage that can be suitably applied even when there are restrictions such as headroom. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 shows reinforcing cages 1a and 1b. [Figure 2] FIG. 4 is a diagram showing a reinforcing ring 4b and a centering mechanism 43. [Figure 3] A diagram showing how to erect the reinforcing bar cages 1a and 1b. [Figure 4] A diagram showing how to erect the reinforcing bar cages 1a and 1b. [Figure 5] 10A and 10B are diagrams for explaining the connection between strands 21. FIG. [Figure 6] A diagram showing how to erect the reinforcing bar cages 1a and 1b. [Figure 7] A diagram showing reinforcing bar cages 1c and 1d. [Figure 8] A diagram showing how to erect the reinforcing bar cages 1c and 1d. [Figure 9] A diagram showing how to erect the reinforcing bar cages 1c and 1d. [Figure 10] A diagram showing how to erect the reinforcing bar cages 1c and 1d. [Figure 11] A diagram showing how to erect the reinforcing bar cages 1c and 1d. [Figure 12] A diagram showing the reinforcing bar cage 1e. [Figure 13] A diagram showing how to erect the reinforcing bar cages 1d and 1e. [Figure 14] A diagram showing how to erect the reinforcing bar cages 1d and 1e. [Figure 15] A diagram showing how to erect the reinforcing bar cages 1d and 1e. [Figure 16] A diagram showing how to erect the reinforcing bar cages 1d and 1e. [Figure 17] 10A and 10B are diagrams illustrating the expansion and contraction of the reinforcing bar cage 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0019] [First embodiment] (1. Reinforced concrete cages 1a, 1b) 1(a) and 1(b) are diagrams showing the reinforcing bar cages 1a and 1b used in this embodiment, respectively showing the inside and outside of the cage body 2 in a contracted state. Similar to the reinforcing bar cage 1 described above, the reinforcing bar cages 1a and 1b have a cage body 2 in which strands 21, which are flexible axial steel materials, and ties 22 are joined so that the crossing angle is variable, and reinforcing rings 4 (4a, 4b) are provided on the inside and outside of the cage body 2, respectively.

[0020] The reinforcing rings 4 (4a, 4b) are provided in multiple rows at intervals in the axial direction of the cage body 2 at both axial ends and in the intermediate section between the ends of the cage body 2. When the cage bodies 2 of the reinforcing cages 1a, 1b are twisted as shown by arrows A, B in Figures 17(a) and (c), the vertically adjacent reinforcing rings 4 (4a, 4b) rotate relative to each other in accordance with the expansion and contraction of the cage body 2.

[0021] 2(a) is a diagram showing a reinforcing ring 4b arranged inside the cage body 2. The reinforcing ring 4b 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 4b can be formed, for example, by processing an angle iron into a ring shape.

[0022] The reinforcing ring 4b on the inside of the cage body 2 is arranged along the circumferential direction of the cage body 2 with the vertical portion 41 on the outer side (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 4b 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.

[0023] 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 4b by passing the axial member through the hole 411 and tightening a nut onto the tip of the axial member.

[0024] The reinforcing ring 4a on the outside of the cage body 2 has a configuration in which the vertical portion 41 and horizontal portion 42 of the reinforcing ring 4b on the inside of the cage body 2 are reversed, with the vertical portion being positioned on the inside (cage body 2 side). The other configurations are substantially the same as those of the reinforcing ring 4b.

[0025] The reinforcing bar cage 1a in Figure 1(a) is a reinforcing bar cage joined below the reinforcing bar cage 1b, and the second row (referring to the row counted from the top, same below) reinforcing rings 4a and 4b are placed at the same height near the upper end of the cage body 2. The upper ends of the strands 21 of the cage body 2 are protruded upward by a certain length from the hoops 22 of the uppermost row.

[0026] Additionally, a hanging member L1 having a length that extends beyond the cage body 2 is attached to the lowest reinforcing ring 4b. For example, a wire or chain is used for the hanging member L1, and it is attached to the reinforcing ring 4b via a hanging jig h such as a Column Lock (registered trademark).

[0027] The uppermost reinforcing ring 4b is provided with a centering mechanism 43 for the hanging member L1, which fixes the planar position of the hanging member L1 at the center of the planar surface of the reinforcing cage 1a.

[0028] 2(b) is a diagram showing an example of the centering mechanism 43. The centering mechanism 43 supports a cylindrical body 432 placed in the planar center of the reinforcing bar cage 1a, for example, by an arm 431 extending inward from the reinforcing ring 4b. By passing the hanging member L1 through this cylindrical body 432, the planar position of the hanging member L1 can be fixed in the planar center of the reinforcing bar cage 1a.

[0029] The reinforcing bar cage 1b in Fig. 1(b) is a reinforcing bar cage joined above the reinforcing bar cage 1a, and the second-row reinforcing ring 4a and the third-row reinforcing ring 4b are arranged at the same height near the lower end of the cage body 2. The lower ends of the strands 21 of the cage body 2 are protruded downward by a certain length from the lowest-row hoop 22.

[0030] Furthermore, a hanging member L2 such as a wire having a length long enough to extend from the top and bottom of the cage body 2 is placed inside the cage body 2. The uppermost reinforcing ring 4b is provided with a centering mechanism 43 similar to that described above, which fixes the planar position of the hanging member L2 to the center of the planar surface of the reinforcing bar cage 1b.

[0031] (2. How to erect the reinforcing bar cages 1a and 1b) The reinforcing bar cages 1a, 1b are fabricated in advance in a factory or the like with the cage body 2 in a contracted state. In this embodiment, the reinforcing bar cages 1a, 1b fabricated in a factory or the like are transported by land transport means such as a truck to the construction site or a nearby unloading point, and then the reinforcing bar cages 1a, 1b are transported, suspended by a crane or the like, to the borehole where the cast-in-place concrete pile will be constructed.

[0032] In this embodiment, first, the reinforcing bar cage 1a is erected in the borehole 100 as shown in Fig. 3(a). The upper end of the hanging member L1 of the reinforcing bar cage 1a is attached to a crane, and the cage body 2 is suspended and supported by the crane in a contracted state, and the second-stage reinforcing rings 4a and 4b are inserted into the borehole 100 until they reach the hole mouth level.

[0033] The reinforcing bar cage 1a is transported and erected by crane with the axial direction of the cage body 2 aligned vertically and the second and bottom reinforcing rings 4a secured with securing members La such as lever hoists. The horizontal position of the hanging member L1 is fixed to the center of the plane of the reinforcing bar cage 1a by a centering mechanism 43, which prevents the cage body 2 from tipping over.

[0034] Next, as shown in Figure 3(b), the top reinforcing rings 4a, 4b are manually pulled up, and the steel material to be used as the hairpin 200 is inserted over the second reinforcing rings 4a, 4b and spanned across the hole opening, and the second reinforcing rings 4a, 4b and the hairpin 200 are joined with joining means such as bolts (not shown).

[0035] Here, since the second and bottom reinforcing rings 4a are secured by the securing material La, by lifting the top reinforcing rings 4a and 4b, only the cage body 2 (the upper end of the cage body 2) in the section between the top and second reinforcing rings 4a extends slightly upward, while the cage body 2 (a part including the lower end of the cage body 2) in the section between the second and bottom reinforcing rings 4a remains in a contracted state.

[0036] Thereafter, as shown in FIG. 3(c), the upper end of the hanging member L1 is detached from the crane, the centering mechanism 43 is removed, and the entire weight of the reinforcing bar cage 1a is supported by the bar 200.

[0037] Then, as shown in Figure 4(a), the reinforcing bar cage 1b is transported by being suspended from the main hoist of the crane by a hanging member L3 attached to the top reinforcing ring 4a, and is placed above the reinforcing bar cage 1a, with the lower end of hanging member L2 attached to the upper end of hanging member L1.

[0038] The reinforcing bar cage 1b is transported with the axial direction of the cage body 2 aligned vertically, with the top and second reinforcing rings 4a secured by securing materials La such as lever hoists, and the cage body 2 in the section between the two reinforcing rings 4a (a part of the cage body 2, including its upper end) is in a contracted state. On the other hand, the bottom reinforcing ring 4a is not secured by securing materials La, so the cage body 2 in the section below the second reinforcing ring 4a (the lower end of the cage body 2) is slightly extended downward due to its own weight.

[0039] Next, the reinforcing bar cage 1b is lowered, and the reinforcing bar cages 1a, 1b are joined together. In this embodiment, as shown in FIG. 5(a), apartments (external threads) 221 are formed at the ends of the strands 21 of the reinforcing bar cages 1a, 1b, and the apartments 211 of both strands 21 are connected to each other, thereby joining the reinforcing bar cages 1a, 1b together. A coupler 212 with an internal thread is used to connect the strands 21 (apartments 211). The coupler 212 is attached in advance by screwing it into the apartment 211 at the lower end of the strand 21 of the reinforcing bar cage 1b.

[0040] The apartments 211 at the ends of the strands 21 of both reinforcing bar cages 1a and 1b are butted together, and a dedicated apartment holding jig (not shown) is used to pull the apartments 211 together to align their axes, correcting any twisting of the apartments 211. By rotating and advancing the coupler 212, the apartment 211 at the top end of the strand 21 of reinforcing bar cage 1a is screwed into the coupler 212, as shown in Figure 5(b). After the apartment 211 has been screwed into the coupler 212 to the appropriate length, both apartments 211 are fixed to the coupler 212 using fixing means such as a setscrew (not shown). This joins the reinforcing bar cages 1a and 1b together, as shown in Figure 4(b).

[0041] After this, the upper end of hanging member L2 is attached to the auxiliary hoist of the crane, and as shown in Figure 4(c), hanging member L2 is wound up and the hairpin 200 is removed, the reinforcing bar cage 1a is lifted from its lower end, and the fastening member La of the reinforcing bar cage 1a is removed to release the fastening of the cage body 2. The planar position of hanging member L2 is fixed to the center of the planar surface of the reinforcing bar cage 1b by the centering mechanism 43 of the reinforcing bar cage 1b, which prevents the cage body 2 of the reinforcing bar cages 1a and 1b from tipping over.

[0042] Next, the fastening material La of the reinforcing bar cage 1b is removed to release the fastening of the cage body 2, and the hanging materials L2 and L3 are simultaneously wound down, and the reinforcing bar cages 1a and 1b are suspended and lowered into the borehole 100 as shown in Figure 6(a). In this embodiment, once the reinforcing bar cages 1a and 1b have been suspended and lowered to a predetermined depth in the borehole 100, a pin 200 is hung across the hole opening, and the top reinforcing ring 4b of the reinforcing bar cage 1b and the pin 200 are connected by a hanging reinforcing bar 201.

[0043] Then, the hanging member L3 is removed from the top reinforcing ring 4a of the cage reinforcing bar 1b, and the hanging member L2 is wound down to lower the bottom end of the cage reinforcing bar 1a, and the cage bodies 2 of the cage reinforcing bar 1a, 1b begin to extend. These cage bodies 2 begin to extend from top to bottom in order, and rotate as they descend. As shown in Figure 6(b), when the bottom end of the cage reinforcing bar 1a is lowered until the entire length of the cage bodies 2 of the cage reinforcing bar 1a, 1b is extended, the cage reinforcing bar 1a, 1b are supported by the hairpin 200.

[0044] As shown in Figure 6(c), when the hanging members L1 and L2 are retrieved, the erection of the reinforcing bar cages 1a and 1b is completed. After this, the centering mechanism 43 of the reinforcing bar cage 1b is removed, and concrete is poured into the borehole 100 to construct a cast-in-place concrete pile. Note that the structure constructed using the reinforcing bar cages 1a and 1b is not limited to this, and may be, for example, a circular deep foundation. The centering mechanism 43 is removed to allow for smooth pouring of concrete, and the removed centering mechanism 43 can be reused.

[0045] Furthermore, if necessary, it is also possible to attach a hanging member L3 to the top reinforcing ring 4a of the reinforcing bar cage 1b, and after the hanging member L3 is hoisted up from a crane and tensioned, remove the hanging reinforcing bar 201 from the bar holder 200 and lower the hanging member L3, thereby lowering the reinforcing bar cages 1a, 1b again and adjusting the erection height. After adjusting the height, the hanging reinforcing bar 201 is again connected to the bar holder 200, and the hanging member L3 is removed.

[0046] Thus, in this embodiment, when the upper and lower extendable reinforcing bar cages 1a, 1b are joined and erected, the upper reinforcing bar cage 1b is transported and positioned in a contracted state using a crane, and is joined to the lower reinforcing bar cage 1a located within the borehole 100 directly above the borehole 100. Therefore, even in cases where construction conditions require low overhead or there is a limit to the crane's ground lift, the reinforcing bar cages 1a, 1b can be joined to increase their length, making it possible to build structures such as cast-in-place concrete piles deep underground.

[0047] In addition, in this embodiment, the lower reinforcing bar cage 1a is also transported and placed in a contracted state, which is effective when there are restrictions such as headroom, and the extension work of the cage body 2 of the reinforcing bar cages 1a and 1b (see Figure 6(b)) can be done in one go by winding down the hanging material L2 once, which takes an extremely short time.

[0048] The reinforcing bar cages 1a and 1b are provided with spacers (not shown) to maintain a distance from the wall of the borehole 100, but the reinforcing bar cages 1a and 1b rotate within the borehole 100 during the above-mentioned extension. Therefore, the spacers need to have skids in the rotation direction so that the spacers of the reinforcing bar cages 1a and 1b do not scrape away soil from the hole wall.

[0049] The skid is the inclined shape of the spacer, and in order to prevent the spacer from scraping away soil and sand from the hole wall during rotation, it is necessary to form the skid in the direction of rotation (horizontal direction) by making it rounded not only in the vertical direction but also in the horizontal direction, or by bending the plate material, as shown in Figure 4 of JP 2006-274726 A.

[0050] Furthermore, when assembling the cage reinforcing bars 1a and 1b in the factory, the ties 22 near the top of the cage body 2 of the cage reinforcing bar 1a are shifted downward by a predetermined length (e.g., several tens of centimeters) from the top of the strand 21 to ensure the protruding length of the tip of the strand 21. The ties 22 near the bottom of the cage body 2 of the cage reinforcing bar 1b are also shifted upward by a predetermined length from the bottom of the strand 21. These ties 22 are returned to their appropriate positions after the strands 21 are connected. Alternatively, these ties 22 may be half ties 22 that are attached after the strands 21 are connected. Furthermore, the top reinforcing rings 4a and 4b of the cage reinforcing bar 1a and the bottom reinforcing rings 4a and 4b of the cage reinforcing bar 1b may be disassembled and removed to adjust the orientation of the tip of the strand 21 when connecting the strands 21. The same applies to the examples described below.

[0051] Other examples of the present invention will be described below as the second and third embodiments. Each embodiment will be described mainly focusing on differences from the first embodiment, and similar features will be denoted by the same reference numerals in the drawings and will not be described again. The configurations described in each embodiment, including the first embodiment, can be combined as necessary.

[0052] [Second embodiment] (1. Reinforced concrete cage 1c, 1d) 7(a) and 7(b) are diagrams showing reinforcing cages 1c and 1d used in the second embodiment, respectively showing the inside and outside of the cage body 2 in a contracted state.

[0053] The reinforcing bar cage 1c of FIG. 7(a) differs from the reinforcing bar cage 1a used in the first embodiment mainly in that outer reinforcing rings 4a are provided in two tiers, one above the other, at both ends of the cage body 2.

[0054] On the other hand, the reinforcing bar cage 1d in Figure 7(b) has reinforcing rings 4a, 4b arranged in three or more rows (four rows in the example shown) at both axial ends of the cage body 2 and at the intermediate portion between the two ends, with spacing in the axial direction of the cage body 2, and adjacent reinforcing rings 4a in the vertical direction are connected by connecting material 5.

[0055] (2. How to erect rebar cages 1c and 1d) The reinforcing bar cages 1c and 1d are also prefabricated in a factory or the like with the cage body 2 in a contracted state, transported to the unloading point, and after unloading, are transported suspended by a crane or the like to the excavation hole where the cast-in-place concrete pile will be constructed.

[0056] In this embodiment, first, the reinforcing bar cage 1c is erected in the borehole 100 as shown in Fig. 8(a). The upper end of the hanging member L1 of the reinforcing bar cage 1c is attached to a crane, and the cage body 2 is suspended from the crane in a contracted state, and the reinforcing bar cage 1c is inserted into the borehole 100 until the top reinforcing ring 4 reaches the hole mouth level.

[0057] The reinforcing bar cage 1c has the axial direction of the cage body 2 aligned vertically, and the top and bottom reinforcing rings 4a secured with securing members La such as lever hoists, which are removed after the reinforcing bar cage 1c is lowered. As in the first embodiment, the planar position of the hanging members L1 is fixed to the center of the planar surface of the reinforcing bar cage 1c by a centering mechanism 43, preventing the reinforcing bar cage 1c from tipping over.

[0058] Next, as shown in Fig. 8(b), the top reinforcing rings 4a and 4b are manually pulled up, and a steel material to be used as the hairpin 200 is inserted under the top reinforcing rings 4a and 4b and hung over the hole opening. Then, the reinforcing rings 4a and 4b and the hairpin 200 are joined with joining means (not shown) such as bolts.

[0059] Then, as shown in Figure 8(c), the hanging member L1 is wound down, and the cage body 2 of the reinforcing bar cage 1c is extended downward within the borehole 100. The cage body 2 extends while rotating, and when the entire length of the cage body 2 is extended, the upper end of the strand 21 is positioned vertically, and the reinforcing bar cage 1c is supported by the hairpin 200. The hanging member L1 is then retrieved. At this point, the centering mechanism 43 may be removed.

[0060] In this embodiment, a cage 1d is joined onto the cage 1c. At this time, as shown in Figure 9(a), a gate-shaped frame 8 is assembled in advance at the opening of the excavation hole 100, and the cage 1d is suspended by a crane with the axial direction of the cage body 2 aligned vertically and with its entire length contracted, and then placed above the cage 1c. A suspending member L3, such as a lever hoist, hanging from the top beam of the frame 8 is attached to the top reinforcing ring 4a of the cage 1d, thereby suspending and supporting the cage 1d.

[0061] Then, the connecting member 5 (the lowest connecting member) connecting the third and lowest reinforcing rings 4a of the reinforcing cage 1d is removed, and the cage body 2 in the section between these reinforcing rings 4a is extended as shown in Figure 9(b). At this time, the lower ends of the strands 21 of the reinforcing cage 1d are positioned vertically.

[0062] As a method for extending the cage body 2, for example, a lid (not shown) may be placed over the opening of the borehole 100, the hanging members L3 may be lowered, and the reinforcing bar cage 1d may be temporarily placed on the lid, so that the connecting members 5 are not carrying any load. After removing the connecting members 5, the reinforcing bar cage 1d may be lifted up by the hanging members L3. Alternatively, the reinforcing bar cage 1d may be transported with the top reinforcing ring 4a secured to the bottom reinforcing ring 4a with a securing member (not shown) such as a lever hoist, and after placing it as shown in Figure 9(a), the securing member may be lifted up, so that the connecting members 5 are not carrying any load. Therefore, the cage body 2 in the section between the third and bottom reinforcing rings 4a may be extended downward by removing the connecting members 5 and loosening the securing member.

[0063] After this, as shown in Figure 9(c), the reinforcing bar cage 1d is lowered, and as in the example of Figure 5, the apartment 211 at the lower end of the strand 21 of the reinforcing bar cage 1d is connected to the apartment 211 at the upper end of the strand 21 of the reinforcing bar cage 1c using a coupler 212. This joins the reinforcing bar cages 1c and 1d together. In this embodiment, the tips of these strands 21 are vertical, so the work of connecting the apartments 211 together is easier than in the first embodiment, and no special tools are required.

[0064] After joining the reinforcing bar cages 1c and 1d together, the hanging member L3 is slightly wound up and the hairpin 200 is removed. Then, as shown in Figure 10(a), the hanging member L3 is wound down and the cage body 2 of the section of the reinforcing bar cage 1d that was extended in Figure 9(b) is inserted into the borehole 100.

[0065] Additionally, a hanging member L4 such as a lever hoist hanging from the top beam of the frame 8 is attached to the third-stage reinforcing ring 4a of the reinforcing cage 1d, which is located above the above-mentioned section, and the third-stage reinforcing ring 4a is suspended and supported by the hanging member L4. In this state, when the connecting member 5 between the second-stage and third-stage reinforcing rings 4a, which are located on the ground (the connecting member 5 located lowest at this point), is removed and the hanging member L3 is wound up as shown in Figure 10(b), the cage body 2 in the section between the second-stage and third-stage reinforcing rings 4a from which the connecting member 5 has been removed rotates and extends upward.

[0066] If the third reinforcing ring 4a of the reinforcing bar cage 1d is fixed so that it does not rotate in a plane, the rotation of the reinforcing bar cages 1c and 1d located below the above section of the reinforcing bar cage 1d inside the borehole 100 is restricted, and the hole wall is not scraped away. The third 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 of the above section of the reinforcing bar cage 1d is fully extended in Figure 10(b).

[0067] Once the extension of the cage body 2 of the reinforcing bar cage 1d in the above section is complete, the hanging member L4 is removed from the third reinforcing ring 4a, and the hanging member L3 is lowered as shown in Figure 10(c), and the reinforcing bar cages 1c and 1d are lowered vertically without rotating, and the cage body 2 of the above extended section is inserted into the borehole 100. By repeating the operations of Figures 10(a) to (c), the entire length of the cage body 2 of the reinforcing bar cage 1d is extended. When the hanging member L3 is further lowered, the reinforcing bar cages 1c and 1d, with the entire length of the cage body 2 extended, are lowered into the borehole 100 as shown in Figure 11.

[0068] In this embodiment, a hanging reinforcing bar 201 is attached to the top reinforcing ring 4b of the reinforcing bar cage 1d while the reinforcing bar cages 1c and 1d are being lowered, and once the reinforcing bar cages 1c and 1d have been lowered to a predetermined depth in the borehole 100, a pin 200 is placed at the opening of the hole and the pin 200 is connected to the hanging reinforcing bar 201. After this, the hanging member L3 is detached from the top reinforcing ring 4a of the reinforcing bar cage 1d and removed, completing the installation. The installation height can also be adjusted in the same manner as in the first embodiment.

[0069] In this way, in this embodiment, the entire length of the cage body 2 of the cage reinforcing bar 1c is first extended inside the borehole 100, and then the cage reinforcing bar 1c and cage reinforcing bar 1d are joined together, and the cage reinforcing bar 1d in a contracted state is erected while being extended section by section directly above the borehole 100. This also provides the same effect as the first embodiment.

[0070] Furthermore, since not only the upper reinforcing bar cage 1d but also the lower reinforcing bar cage 1c are transported and placed in a contracted state, this is effective when there are restrictions such as headroom, and since the tips of the strands 21 of the reinforcing bar cages 1c, 1d are in a vertically standing state before they are connected to each other, it becomes easy to connect the strands 21. Therefore, it is easy to accommodate a structure in which the connected parts of the strands 21 are not aligned at the same height but are arranged in a staggered pattern.

[0071] Furthermore, with regard to the upper reinforcing bar cage 1d, the cage body 2 can be partially extended before the strand 21 is connected (see FIG. 9(b), etc.), making it possible to easily connect the reinforcing bar cages 1c and 1d even under low-head construction conditions. However, a slightly higher headroom is required compared to the first embodiment, and the headroom that can be used for construction is determined by the length of the reinforcing bar cage 1d. Therefore, it is also desirable to make the reinforcing bar cage 1d shorter than the reinforcing bar cage 1c.

[0072] Furthermore, when erecting the reinforcing bar cages 1c, 1d, by repeatedly partially extending the cage body 2 of the upper reinforcing bar cage 1d and inserting the extended section of the cage body 2 into the borehole 100, the erection of the reinforcing bar cages 1c, 1d can be carried out even under low-head construction conditions. In this embodiment, the frame 8 at the mouth of the borehole 100 is used to hoist and lower the reinforcing bar cages 1c, 1d, making the erection work easy. Furthermore, by using the frame 8 as an auxiliary, the lifting capacity of the crane can be relatively low.

[0073] In this embodiment, the reinforcing bar cage 1d does not rotate within the borehole 100. Therefore, the spacers for the reinforcing bar cage 1d do not require the aforementioned rotational skid, and simple and inexpensive ones can be used. It is also possible to attach the spacers on the ground while extending the cage body 2 section by section. Note that the reinforcing bar cage 1c extends while rotating within the borehole 100 in the process shown in Figure 8(c), so the spacers require a rotational skid.

[0074] In the first and second embodiments, an example in which two reinforcing cages are joined together at the top and bottom has been described, but the same method can be implemented when three or more reinforcing cages are joined together at the top and bottom.

[0075] For example, in the first embodiment, after joining the cage reinforcing bars 1a and 1b as shown in Fig. 4(b), the entire weight of the upper and lower cage reinforcing bars 1a and 1b is suspended and supported by the hanging members L1 and L2, the second reinforcing ring 4a of cage reinforcing bar 1b and the bottom reinforcing ring 4a of cage reinforcing bar 1a are re-fastened with the fastening member La, and then the second reinforcing rings 4a and 4b of cage reinforcing bar 1b are supported at hole opening level by the pins 200, and a new cage reinforcing bar 1b is joined on top of that. Meanwhile, in the second embodiment, in the process shown in Fig. 11, the top reinforcing rings 4a and 4b of cage reinforcing bar 1d are supported at hole opening level by the pins 200, and a new cage reinforcing bar 1d is joined on top of them.

[0076] In this embodiment, the frame 8 is assembled during construction and a hanging member L3 such as a lever hoist is hung down, but the frame 8 may be assembled from the beginning, a hanging member such as a lever hoist is hung down from the frame 8, and connected to the hanging member L1, and the reinforcing bar cage 1c may be suspended and supported in the steps shown in Figures 8(a) to 8(c). Also, although the connecting member 5 connects the outer reinforcing rings 4a of the cage body 2, it may also connect the inner reinforcing rings 4b of the cage body 2. In this case, however, removing the connecting member 5 requires some effort.

[0077] [Third embodiment] (1. Reinforced concrete cage 1e) 12 is a diagram showing a reinforcing bar cage 1e used in the third embodiment, showing the inside of the cage body 2 in a contracted state. In this embodiment, this reinforcing bar cage 1e and the above-mentioned reinforcing bar cage 1d (see FIG. 7(b)) are joined together and erected in the borehole 100.

[0078] The reinforcing bar cage 1e differs from the reinforcing bar cage 1a used in the first embodiment in that the hanging reinforcing bars 44 protruding upward from the cage body 2 are attached to the topmost reinforcing ring 4b, and a steel ring for temporary support (hereinafter referred to as the temporary support ring) 6 is attached to the upper end of the hanging reinforcing bars 44.

[0079] (2. How to erect rebar cages 1e and 1d) The reinforcing bar cages 1e and 1d are prefabricated in a factory or the like with the cage body 2 in a contracted state, transported to the unloading point, and after unloading, are transported suspended by a crane or the like to the excavation hole where the cast-in-place concrete pile will be constructed.

[0080] In this embodiment, first, the reinforcing bar cage 1e is erected in the borehole 100 as shown in Fig. 13(a). The upper end of the hanging member L1 of the reinforcing bar cage 1e is attached to a crane, and the axial direction of the cage body 2 is vertical, and the cage body 2 is suspended and supported by the crane in a contracted state, and the reinforcing bar cage 1e is inserted into the borehole 100 until the temporary support ring 6 is positioned slightly above the hole mouth.

[0081] Then, the pin 200 is inserted under the temporary support ring 6 and hung over the opening of the borehole 100, and the pin 200 and the temporary support ring 6 are joined with a joining means (not shown) such as a bolt. As in the second embodiment, the reinforcing bar cage 1e has the uppermost and lowermost reinforcing rings 4a fastened with fastening materials La such as lever hoists, and the fastening materials La are removed after the reinforcing bar cage 1e has been lowered.

[0082] 13(b), the hanging member L1 is wound down, and the cage body 2 of the reinforcing bar cage 1e is extended downward within the borehole 100. The cage body 2 extends while rotating, and when the entire length of the cage body 2 is extended, the upper end of the strand 21 is positioned vertically, as in the second embodiment. The distance between the temporary support ring 6 and the uppermost reinforcing rings 4a, 4b of the reinforcing bar cage 1e is set to a distance such that the apartment 211 at the upper end of the strand 21 does not interfere with the temporary support ring 6 or the hairpin 200.

[0083] Thereafter, the hanging member L1 is replaced with the temporary support ring 6, the hairpin 200 is removed, and the reinforcing bar cage 1e is lifted up by the hanging member L1 as shown in Figure 13(c), and the hairpin 200 is reinserted under the uppermost reinforcing rings 4a and 4b. Thereafter, the hanging member L1 is retrieved, and the temporary support ring 6, centering mechanism 43, hanging reinforcing bar 44, etc. are also removed.

[0084] In this embodiment, a cage 1d is joined onto the cage 1e. As shown in Figure 14(a), a gate-shaped frame 8 is assembled in advance at the opening of the excavation hole 100, and the cage 1d is lifted and transported with a crane, with the axial direction of the cage body 2 aligned vertically and with the cage body 2 contracted to its full length, and placed above the cage 1e. A suspending member L3, such as a lever hoist, hanging from the top beam of the frame 8 is then attached to the top reinforcing ring 4a of the cage 1d, thereby suspending and supporting the cage 1d.

[0085] 14(b), in the same manner as in the second embodiment, the connecting member 5 between the third and lowest reinforcing rings 4a (the lowest connecting member 5) is removed, and the cage body 2 in the section between these reinforcing rings 4a is extended. As a result, the lower ends of the strands 21 of the reinforcing cage 1d are positioned vertically.

[0086] After this, reinforcing bar cage 1d is lowered, and reinforcing bar cages 1d and 1e are joined together as in the second embodiment, and then hanging member L3 is hoisted up as shown in Figure 14(c). When the upper end of reinforcing bar cage 1d approaches the top beam of frame 8, said beam and the topmost reinforcing ring 4a of reinforcing bar cage 1d are connected with hanging reinforcing bar 44. In this embodiment, reinforcing bar cages 1d and 1e are joined together by connecting the apartment 211 at the bottom end of strand 21 of reinforcing bar cage 1d to the apartment 211 at the top end of strand 21 of reinforcing bar cage 1e with coupler 212. Since apartments 211 are connected vertically, the work is easy and does not require special tools.

[0087] 15(a), the hanging member L3 is then attached to the top reinforcing ring 4b of the reinforcing cage 1e. Also, a hanging member L4 such as a lever hoist hanging from the top beam of the frame 8 is attached to the third reinforcing ring 4a of the reinforcing cage 1d.

[0088] Next, as shown in Figure 15(b), the reinforcing bar cage 1e is suspended and supported by the suspension member L3, and the hairpin 200 is removed. With the third reinforcing ring 4 of the reinforcing bar cage 1d suspended and supported by the suspension member L4, the connecting member 5 between the second and third reinforcing rings 4a of the reinforcing bar cage 1d (the connecting member 5 located lowest at this point) is removed.

[0089] 15(c), when hanging member L4 is loosened and hanging member L3 is simultaneously wound down, the cage body 2 in the section between the second and third reinforcing rings 4a from which the connecting member 5 of the reinforcing bar cage 1d has been removed rotates and extends downward, and the reinforcing bar cages 1d and 1e are suspended and lowered into the borehole 100. At this time, the portion of the reinforcing bar cage 1d below the third reinforcing ring 4a to which hanging member L4 is attached rotates and is suspended and lowered into the borehole 100. After the reinforcing bar cages 1d and 1e have been suspended and lowered, hanging member L4 is removed from the third reinforcing ring 4a of the reinforcing bar cage 1d.

[0090] 16(a), a hanging member L4 is attached to the second-stage reinforcing ring 4a of the reinforcing cage 1d, which is located above the extended section, and with the reinforcing ring 4a suspended and supported by the hanging member L4, the connecting member 5 between the top and second-stage reinforcing rings 4a is removed. Also, the hanging member L3 is attached to the third-stage reinforcing ring 4b of the reinforcing cage 1d.

[0091] Then, as shown in Figure 16(b), when hanging member L4 is loosened and hanging member L3 is simultaneously wound down, similar to Figure 15(c), the cage body 2 in the section between the topmost reinforcing ring 4a of reinforcing bar cage 1d, from which the connecting member 5 has been removed, and the second reinforcing ring 4a, rotates and extends, and reinforcing bar cages 1d and 1e are suspended and lowered into the borehole 100. At this time, the portion of reinforcing bar cage 1d below the second reinforcing ring 4a, to which hanging member L4 is attached, rotates and is suspended and lowered into the borehole 100. After the reinforcing bar cages 1d and 1e have been suspended and lowered, hanging member L4 is removed from the second reinforcing ring 4a of reinforcing bar cage 1d.

[0092] In this embodiment, the above steps extend the entire length of the cage body 2 of the cage reinforcing bar 1d. If the cage reinforcing bar 1d has a large number of reinforcing rings 4a, the steps of Figures 16(a) and 16(b) can be repeated according to the number of reinforcing rings 4a. After extending the entire length of the cage body 2 of the cage reinforcing bar 1d in this way, the hanging member L3 is replaced with the topmost reinforcing ring 4a of the cage reinforcing bar 1d, and the hanging reinforcing bar 44 is removed while the cage reinforcing bar 1d and 1e are suspended and supported by the hanging member L3.

[0093] Thereafter, the hanging member L3 is wound down, and the reinforcing bar cages 1d and 1e are suspended and lowered into the borehole 100 as shown in Figure 16(c). In this embodiment, while the reinforcing bar cages 1d and 1e are being suspended and lowered, a hanging reinforcing bar 44 is attached to the uppermost reinforcing ring 4b of the reinforcing bar cage 1d, and once the reinforcing bar cages 1d and 1e have been suspended and lowered to a predetermined depth in the borehole 100, a pin 200 is placed at the opening of the hole, and the pin 200 is connected to the hanging reinforcing bar 44. After this, the hanging member L3 is detached and removed, completing the installation.

[0094] In this way, in this embodiment as well, the entire length of the cage body 2 of the reinforcing bar cage 1e is first extended inside the borehole 100, and then the reinforcing bar cages 1e and 1d are joined, and the cage body 2 of the reinforcing bar cage 1d in a contracted state is extended section by section directly above the borehole 100, and the reinforcing bar cages 1d and 1e are erected. This provides the same effects as the second embodiment.

[0095] In this embodiment, the cage body 2 of the reinforcing bar cage 1d is extended and inserted into the borehole 100 simultaneously in the process shown in Figure 16(b) etc., so the construction time can be shortened compared to the second embodiment in which these steps are performed separately. However, since the cage body 2 of the reinforcing bar cage 1d is inserted into the borehole 100 while rotating, the above-mentioned skid is required for the spacer.

[0096] In this embodiment, the cage 1e is temporarily lifted in Fig. 13(c), but this is because the work described in the first embodiment, in which the uppermost tie bars 22 of the cage 1e and the lowermost tie bars 22 of the cage 1d are returned to their appropriate positions after the strands 21 are connected, can be performed on the ground. It is also possible to join the cages 1e and 1d with the upper end of the cage body 2 positioned inside the borehole 100 as shown in Fig. 13(b), but performing the above work inside the borehole 100 is somewhat time-consuming.

[0097] In the second and third embodiments, the reinforcing cage is suspended from the frame 8. However, it is also possible to suspend the reinforcing cage using a different hoisting device, such as a crane, instead of the frame 8. At least two hoisting members L4, such as lever hoists, are required, but three or more are preferable to maintain the horizontality of the suspended reinforcing ring 4a. Furthermore, in the third embodiment, when the hoisting members L4 are loosened and the hoisting members L3 are lowered at the same time, the cage body 2 rotates, which may result in contact between the hoisting members L4 and the cage body 2 depending on the specifications. In such cases, it is preferable to use four or more hoisting members L4 and rearrange the circumferential attachment positions of two hoisting members on the same reinforcing ring 4a to avoid contact. At least two hoisting reinforcing bars 44 are required, but three or more are preferable to maintain the horizontality of the suspended reinforcing ring 4a. Screw-type reinforcing bars are suitable.

[0098] 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]

[0099] 1, 1a, 1b, 1c, 1d, 1e: Reinforced concrete cage 2:Cage body 4, 4a, 4b: Reinforcement ring 5: Connecting material 8: Frame 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, A step (a') of inserting the reinforcing bar cage with the cage body contracted into the borehole with the axial direction of the cage body being vertical; A step (a) of arranging a reinforcing bar cage in a state in which at least a portion including the upper end of the cage body is contracted above the reinforcing bar cage, with the axial direction of the cage body being the vertical direction; (b) connecting the lower ends of the strands of the upper reinforcing bar cage with the upper ends of the strands of the lower reinforcing bar cage; (c) a step of lowering the two reinforcing bar cages with the strands connected to each other into the borehole; and wherein in the step (c), at least the cage body of the upper reinforcing bar cage is extended.

2. The cage body of the lower reinforcing cage is provided with multiple reinforcing rings spaced apart vertically along the circumferential direction of the cage body, In the step (a'), the reinforcing bar cage is inserted into the borehole while being suspended and supported by a suspension member attached to the lowest reinforcing ring, 2. A method for erecting a reinforcing cage according to claim 1, wherein the planar position of the hanging member is fixed to the center of the planar portion of the reinforcing cage by a centering mechanism provided on the uppermost reinforcing ring.

3. Before connecting the strands together in step (b), at least a portion of the lower cage body of the reinforcing bar cage, including the lower end portion thereof, is in a contracted state; 2. The method for erecting reinforcing bar cages according to claim 1, wherein in step (c), the lower end of the cage body of the lower reinforcing bar cage is lowered into the excavated hole to extend the cage bodies of the upper and lower reinforcing bar cages.

4. A method for erecting reinforcing bar cages according to claim 1, characterized in that before connecting the strands together in step (b), the entire length of the cage body of the lower reinforcing bar cage and the lower end of the cage body of the upper reinforcing bar cage are extended, and the lower end of the strand of the upper reinforcing bar cage and the upper end of the strand of the lower reinforcing bar cage are arranged vertically.

5. The cage body of the upper reinforcing cage is provided with reinforcing rings along the circumferential direction of the cage body at intervals in three or more rows, and adjacent reinforcing rings in the vertical direction are connected by connecting materials.

5. A method for erecting a reinforcing bar cage according to claim 4, characterized in that, before connecting the strands together in step (b), the lowest connecting material is removed and the cage body in the section between the reinforcing rings connected by said connecting material is extended.

6. A method for erecting reinforcing bar cages according to claim 5, characterized in that in step (c), the connecting material located at the bottom of the upper reinforcing bar cage is removed, the cage body in the section between the reinforcing rings connected by said connecting material is extended, and the two reinforcing bar cages with their strands connected to each other are lifted down, and this operation is repeated.

7. In step (c), When removing the lowest connecting member of the upper reinforcing cage and extending the cage body in the section between the reinforcing rings located on the ground that was connected by the connecting member, the rotation of the reinforcing cage in the borehole located below the section is restrained; 7. A method for erecting a reinforcing cage according to claim 6, wherein after the cage body in the section in question has been extended, the two reinforcing cages with their strands connected to each other are lowered vertically without being rotated.

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