JPH062331A - Construction method of cast-in-place reinforced concrete under-reamed pile and reinforced cage used therefor - Google Patents

Abstract

PURPOSE:To construct a cast-in-place reinforced concrete under-reamed having simple construction with high work efficiency at a low cost. CONSTITUTION:For constructing a cast-in-place reinforced concrete under-reamed pile, hollow lead pipes 3 are fixed to a cylindrical reinforced cage B positioned in a pile widening section in parallel crosses, and under-reamed pile reinforced widening cages freely inserting slide reinforcing bars 5 fixed to widening section reinforcing bars 4 in a slidable manner are used for the lead pipes 3. The under- reamed pile reinforced widening cages are suspended and lowered in pile holes A, and the widening section reinforcing bars 4 are widened at pile hole widening section Al by means of widening devices C in the pile holes. After that, the widening devices C are withdrawn, and concrete is placed into the pile holes A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing cast-in-place concrete reinforced concrete bottom piles by an earth drill method, a reverse method, a benot method, etc., and a reinforced cage used for the method.

[0002]

2. Description of the Related Art Conventionally, cast-in-place concrete reinforced concrete bottom piles, as shown in FIGS. 8 and 9, do not have reinforcing bars in the widened portion of the pile, so that the shearing force generated by the ground reaction force applied to the widened portion of the pile is Since it will be supported by the concrete of the pile widening part, the inclination angle θ of the pile bottom part
Must be designed to be 12 degrees or less, and if the soil bearing capacity of the pile is to be increased, that is, if the bottom area of the pile widened portion is to be increased, the height h of the pile widened portion must be increased. The cost has risen due to the increase in In addition, the cast-in-place concrete reinforced concrete bottom pile is constructed by suspending the rebar cage B formed by connecting the required number of main reinforcements 1 by the hoop reinforcements 2 in the pile hole A, and then placing concrete. The inclination angle θ of the pile widened portion is 12 degrees or less as described above, the rising portion h1 is 30 cm or more, the pile bottom rebar amount is 0.4% or more of the pile cross-sectional area, and the number of rebars used is 6 or more. ing. Further, the height h of the pile widened portion is determined by the required bottom area of the pile widened portion.

[0003]

In order to deal with this,
Attempts have also been made to provide reinforcing bars to the widened portions of the piles (Japanese Patent Publication No. 49-41848 and Japanese Patent Laid-Open No. 58-29917), but all of them have complicated structures such as the use of hinges as the widening mechanism of the widened portion reinforcing bars. There was a problem in workability, and it was costly. It is an object of the present invention to provide a method for constructing cast-in-place reinforced concrete bottom piles, which solves the above-mentioned problems of the prior art, and a rebar cage used for the method.

[0004]

The present invention has been made to achieve the above object. (1) In a method of constructing cast-in-place reinforced concrete bottom piles, a hollow cylindrical reinforcing bar cage located in the pile widening portion is used. The lead pipe is fixed in the shape of a cross girder, and the rebar cage for expanded piles, which is slidably inserted into the lead pipe, is slidably inserted into the widening bar reinforcement, and is suspended in the pile hole. After expanding the widening part reinforcing bar to the pile hole widening part using a widening device, placing concrete in the pile hole (first invention) (2) In the first invention, widening in the pile hole After expanding the partial rebar to the pile widening part, recover the expanding device (2nd invention) (3) Place cast-in-place reinforced concrete bottom pile reinforcing bar cage is hollow in the cylindrical rebar basket located in the pile widening part The lead tube of the The slides reinforcing bar loosely inserted slidably, it has to be expanded to the wider section rebar Kuiana widened portion in the pile hole (3
(Invention) (4) The gist of the third invention is that a stopper for regulating the sliding length of the slide rebar is provided (fourth invention).

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in FIGS. 3 and 4 show a vertical cross-sectional view of a cylindrical rebar cage B and a transverse cross-section of the pile widening part used in the rebar cage for expanded bottom piles of the present invention, in which two small steel pipes having an appropriate diameter are arranged in parallel. Two sets of lead tubes 3, 3 which are welded to and integrated with each other are arranged at intervals on the hoop muscle 2 at the bottom of the cylindrical rebar cage B formed by connecting the main bar 1 and the hoop bar 2. The lead pipes 3, 3 are fixed on the hoop muscle 2 by fixing the two sets of similar lead pipes 3, 3 in the directions perpendicular to both ends of the two sets of lead pipes 3, 3 in a cross pattern. Fix it. In the present embodiment, the lead pipe 3 is formed by welding two steel pipes in parallel. However, if the bottom area of the pile widened portion is not so large, one steel pipe is used as the lead pipe. It is also possible to configure. Further, in order to increase the strength of the reinforcing bar cage for the expanded pile, two cross-shaped hoop reinforcements 2 are provided, but the number of the hoop reinforcements 2 may be one, or three or more.

FIGS. 5 and 6 are perspective views of the widened portion reinforcing bar 4 and a cross-sectional view of the pile widened portion of the widened portion reinforcing bar 4 and the cylindrical reinforcing bar cage B for the bottom expanded pile reinforcing bar cage. The widening rebars 4 and 4 are the insertion part 4a into the cylindrical rebar cage B and the inclined part 4b.
And the rising portion 4c, and the reinforcing bars 4, 4 for widening
Are fixed by the spacing member 7 so as to maintain a predetermined spacing. Further, slide reinforcing bars 5 and 5 which are slidably inserted into the lead tubes 3 and 3 are fixedly installed on the widening reinforcing bars 4 and 4. The lengths of the slide rebars 5 and 5 are almost the same as those of the lead pipes 3 and 3 when the lead pipe 3 in which two steel pipes are welded in parallel is used as in this embodiment. If one steel pipe is used, the lead pipe 3
Half of the length. Furthermore, the widening rebars 4 and 4 are
A radiation streak 6 which is slid on the lead tubes 3 and 3 so as to radiate from the axial center of the cylindrical rebar cage B when the widening rebars 4 and 4 are expanded is fixed, and the spacing member 7 is provided. A sliding reinforcing bar 17 to which a tip 16 of a frame 14 of the expansion device C described later is connected is fixedly provided via the.

When constructing a cast-in-place concrete reinforced concrete bottom pile, slide rebars 5 and 5 fixed to the widened part rebars 4 and 4 are loosely inserted into the lead pipes 3 and 3 fixed to the cylindrical rebar cage B. Inside the pile hole A with the expanded bottom pile reinforcing bar cage in a state where the rising portions 4c of the expanding bars 4 are closely attached to the outer periphery of the cylindrical reinforcing bar cage B, that is, with the outer diameter of the expanded bottom reinforcing bar cage minimized. After hanging down to the pile hole A and expanding the widening part reinforcing bar 4 in the pile hole A to the pile hole widening part A1 using the expanding device C,
Concrete is placed in the pile hole A.

Expanding device C used for expanding the widening bar 4
As shown in FIGS. 1 and 2, the upper fixed ring 9 and the lower fixed ring 10 are provided at the upper end of the shaft tube 8 and the lower fixed ring 10 slides on the shaft tube 8 between the upper fixed ring 9 and the lower fixed ring 10. By sliding the sliding ring 11 that is moved by the hydraulic cylinder 12, the distal end 16 of the frame 14 that is connected to the upper fixed ring 9 is expanded and contracted in the axial direction of the shaft tube 8 by the link motion of the link 15 that is connected to the sliding ring 11. It is constructed to be vulnerable. Then, on the ground, the fixed leg 13 connected to the lower fixed ring 10 of the expansion device C is fixed to the lead tube 3, and the frame 14 is fixed.
16 is slidably connected to the sliding reinforcing bar 17 fixed to the widening part reinforcing bar 4 via the spacing member 7 and then the expanded bottom reinforcing bar cage is hung in the pile hole A as described above. , The hydraulic cylinder 12 of the expansion device C is operated, and the frame 1
After expanding the widening part reinforcing bar 4 to the pile hole widening part A1 through the tip 16 of 4, the sliding reinforcing bar 17 and the spacing member 7, concrete is placed in the pile hole A. In this case, before the concrete is placed in the pile hole A after expanding the widening part reinforcing bar 4 to the pile hole widening part A1, the hydraulic cylinder 12 is operated to move the tip 16 of the frame 14 and the sliding reinforcing bar. 17
It is desirable that the connection of the above and the fixing of the fixed leg 13 and the lead tube 3 be released, and the wire 18 be operated from the ground so that the expansion device C is recovered.

A stopper for restricting the sliding length of the slide reinforcing bar 5 in the lead tube 3 so that the widening part reinforcing bar 4 surely expands to the pile hole widening part A1 and maintains the expanded state. D can be provided. FIG. 7 shows an example of the stopper D, which is provided with a through hole 19 in the lead tube 3 and a projecting portion 20 in the slide rebar so that when the slide rebar 5 slides in the lead tube 3 for a predetermined length, the lead By preventing the slide rebar 5 from sliding in the pipe 3, the widened part rebar 4
In this configuration, the axis of the cylindrical rebar cage B is made symmetrical so that the cylindrical rebar cage B can be reliably expanded in the pile hole widened portion A1 and the expanded state can be maintained.

The state in which the widened portion reinforcing bar 4 is widened to the pile hole widened portion A1 can be confirmed by installing an underwater camera or various sensors. Further, like the expansion device C, it is desirable that these underwater cameras and various sensors be installed so that they can be collected after confirmation of the expansion of the widened part reinforcing bar 4.

Although the present invention relates to a cast-in-place concrete reinforced concrete bottom pile, by installing a large number of widening mechanisms consisting of the lead tube 3 and the slide reinforcing bars 5 of the present invention in the longitudinal direction of the rectangular reinforced cage, It is also possible to construct a reinforced concrete bottomed underground wall.

[0012]

According to the present invention, in constructing cast-in-place concrete reinforced concrete bottom piles, since reinforcing bars are also provided in the pile widening portions, the shearing force generated by the ground reaction force applied to the pile widening portions causes the concrete in the pile widening portions to be concrete. Also, since it is supported by reinforcing bars, the inclination angle θ of the pile bottom part can be designed to be large, so the height h of the pile widening part can be made smaller than that without reinforcing bars, and the amount of concrete used can be reduced. Therefore, the cost can be reduced. Furthermore, to widen the widening part rebar of the rebar cage for the bottom pile, a widening mechanism with a simple structure consisting of a lead tube and slide rebar was used.
Compared with a widening mechanism having a complicated structure that conventionally uses a hinge, it has advantages such as better workability and lower cost. Furthermore, according to the second aspect of the present invention, after expanding the widening part reinforcing bar to the widening part of the pile in the pile hole, the expanding device is collected and reused, so that there is an advantage that the cost can be further reduced. Further, according to the fourth aspect of the present invention, since the stopper for restricting the sliding length of the slide reinforcing bar is provided, there is an advantage that the widening part reinforcing bar can be reliably expanded to the pile hole widening part and the expanded state can be maintained. is there.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a method for expanding a reinforcing bar of a widened portion according to the present invention.

FIG. 2 is a cross-sectional view showing a method for expanding the reinforcing bar of the widened portion of the present invention.

FIG. 3 is a vertical cross-sectional view of a cylindrical rebar cage used in a rebar cage for a bottom pile according to the present invention.

FIG. 4 is a cross-sectional view of a pile widening portion of a cylindrical reinforcing bar cage used in the reinforcing bar cage for the bottom expanding pile of the present invention.

FIG. 5 is a perspective view showing a reinforcing bar of the widened portion of the present invention.

FIG. 6 is a transverse cross-sectional view of the pile widening portion of the reinforcing bar cage for the bottom expanding pile to which the widening portion reinforcing bar of the present invention is attached.

FIG. 7 is a sectional view of the stopper of the present invention.

FIG. 8 is a vertical cross-sectional view of a conventional bottomed pile

FIG. 9 is a transverse cross-sectional view of a pile widening portion of a conventional bottom spreading pile.

[Explanation of symbols]

 A Pile hole A1 Pile hole widening part B Cylindrical rebar cage C Expanding device D Stopper 3 Reed tube 4 Widening part rebar 5 Slide rebar

Claims (4)

[Claims] 1. A method for constructing cast-in-place reinforced concrete bottom piles, wherein hollow lead pipes (3) are fixed to the cylindrical reinforcing cage (B) located in the pile widening part in a cross beam shape, and the lead pipes (3) ), The slide bar (5) fixedly mounted on the widened part reinforcing bar (4) is slidably inserted, and the rebar cage for expanded bottom piles is hung in the pile hole (A), and the widened part reinforcing bar is inside the pile hole. (4) is expanded to the pile hole widening part (A1) using the expansion device (C), and then concrete is placed in the pile hole (A) to construct a cast-in-place concrete reinforced concrete bottom pile how to. 2. The cast-in-place concrete reinforced concrete bottom pile according to claim 1, characterized in that the expansion device (C) is recovered after expanding the widening part reinforcing bar (4) into the pile widening part in the pile hole. How to build. 3. A rebar basket for cast-in-place reinforced concrete bottom piles, wherein hollow lead pipes (3) are fixed to the cylindrical rebar basket (B) located in the pile widening portion in a cross beam shape, and the lead pipe (3) is provided. The slide reinforcing bar (5) fixed to the widened part reinforcing bar (4) is slidably inserted into the pile hole (A) and the widened part reinforcing bar (4) is expanded to the pile hole widening part (A1). Reinforcing bar cage for cast-in-place reinforced concrete bottom piles. 4. The rebar cage for cast-in-place concrete reinforced concrete bottom piles according to claim 3, further comprising a stopper (D) for restricting a sliding length of the slide rebar (5).