JP2023094160A - Method for constructing small-diameter cast-in-place pile - Google Patents

Abstract

To provide a method for constructing a small-diameter cast-in-place pile capable of improving workability while reducing a weight of a core material.SOLUTION: A reinforcing core material 30 in which a plurality of depressions 32 are formed along a pipe axial direction and a pipe circumferential direction on an outer peripheral surface of a pipe main body 31 is used. After the reinforcing core material 30 is inserted into a pile hole 20, a consolidating material 25 is injected into the pile hole 20 and inside the reinforcing core material 30 through the reinforcing core material 30 to construct a small-diameter cast-in-place pile 10.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for constructing a small-diameter cast-in-place pile using a reinforcing core material.

Ground reinforcement soil construction methods (for example, root pile construction method, EP root pile construction method) using multiple small-diameter cast-in-place piles as tensile reinforcement or compression reinforcement for natural ground or slopes are known from Patent Documents 1 and 2. be.
A core material 40 used for a small-diameter cast-in-place pile will be described with reference to FIG.
A conventional core member 40 includes a rod member 41 to be inserted into a pile hole, and a flange member 42 screwed to the rod member 41 with an appropriate space therebetween.
A commercially available threaded deformed steel bar is used as the bar 41, and the attachment position of the flange 42 screwed to the deformed steel bar can be adjusted.

The installation method of the core material 40 is as follows.
(1) Drilling process A pile hole with a predetermined depth (4 to 20 m) is drilled using a boring machine.
(2) Step of injecting consolidation material A consolidation material 25 made of mortar is injected into the pile hole by setting the injection hose so as to reach the bottom of the hole.
(3) Step of Inserting Core Material The core material 40 is inserted into the pile hole 20 .
(4) Casing withdrawal process The inside of the pile hole is pressurized while removing the casing that was left behind during drilling.
(5) Pile head treatment process Adjust and protect the pile heads exposed on the ground surface.

Japanese Utility Model Laid-Open No. 61-6531 JP-A-58-17931

Conventional small-diameter cast-in-place pile construction technology has the following problems to be solved.
<1> In consideration of axial compression resistance and bending resistance, deformed reinforcing bars of D29 to D51 (name) are used for the bar 41 for the core material.
For example, if the bar 41 is D29, the weight is about 5 kg/m, and if it is D51, the weight is 16 kg/m. Difficult to handle manually.
<2> The price of deformed reinforcing bars with a large diameter (D29 to 51) is relatively high, which causes the cost of the core material 40 to increase.
<3> In the mortar injection process, it is difficult to install the tip of the injection hose at the bottom of the hole, making it difficult to inject the consolidating material from the bottom of the hole.
<4> In order to increase the bonding strength between the bars 41 made of deformed reinforcing bars and the consolidation material, a plurality of flanges 42 are screwed to the bars 41, and only the installation of the flanges 42 requires time and effort. Instead, the collar material 42 contributes to an increase in the cost of the core material.

An object of the present invention is to provide a method for constructing a small-diameter cast-in-place pile that can improve workability while reducing the weight of the core material.

The present invention is a method for constructing a small-diameter cast-in-place pile, comprising a step of drilling a pile hole, and having a plurality of depressions along the pipe axial direction and the pipe circumferential direction on the outer peripheral surface of a pipe body having a hollow structure. The method includes at least the steps of inserting a reinforcing core into the pile hole, and injecting a consolidation material into the pile hole and inside the reinforcing core through the reinforcing core.
In another aspect of the present invention, in the step of drilling the pile hole, a drilling tool having an inner rod and a casing is used, and after drilling the pile hole, only the inner rod is extracted and the casing is inserted into the pile hole. remain.
In another aspect of the present invention, after the step of injecting the consolidating material, the step of extracting the casing for pressurizing the inside of the pile hole while extracting the casing is further provided.
In another aspect of the present invention, after the consolidation material has hardened, concrete is cast in place until the head of the reinforcing core protruding to the ground surface is hidden, and the concrete structure is constructed integrally with the head of the reinforcing core. A pile head processing step is further provided.

The present invention can obtain at least one of the following effects by the means for solving the above problems.
<1> By using a cylindrical reinforcing core instead of the threaded joint deformed steel bar, it is possible to significantly reduce the weight of the core material while exhibiting cross-sectional performance several times or more that of the threaded joint deformed steel bar.
<2> Since the weight of the core material can be reduced, it becomes easier to manually construct the core material.
<3> A reinforcing core material can be used as a substitute for a conventional injection hose.
Therefore, it is possible to reduce the injection hose insertion process and the injection hose removal process that were performed in the conventional construction method, and shorten the construction period.
<4> Since the outer peripheral surface and the inner peripheral surface of the reinforcing core material are uneven, a high adhesive force can be obtained between the reinforcing core material and the consolidating material.
<5> By performing the pile head treatment step of embedding the pile head of the reinforcing core material in the concrete structure on the ground surface, it is possible to adjust the pile interval, suppress deformation of the pile head, and prevent rust.

BRIEF DESCRIPTION OF THE DRAWINGS Longitudinal cross-sectional view of a small-diameter cast-in-place pile according to Example 1 of the present invention Explanatory drawing of the reinforcing core material, (A) is an explanatory view of a form in which a plurality of depressions are formed on the same circumference of the pipe body, and (B) is a row of plural depressions adjacent to each other in the circumferential direction. is formed with a phase difference in the direction of the tube axis Cross-sectional view of the reinforcing core material, (A) is a cross-sectional view of III-III in FIG. 1, (B) is a cross-sectional view of the reinforcing core material in which three recesses are formed in the circumferential direction of the pipe body. Perspective view of a partially broken recess Explanatory drawing of the method of constructing a small-diameter cast-in-place pile, (A) is an explanatory drawing of the drilling process, (B) is an explanatory drawing of the extraction of the inner rod, and (C) is the insertion process and consolidation of the reinforcing core material. Explanatory diagram of the material injection process, (D) is an explanatory diagram of the casing withdrawal process Explanatory drawing of Example 2 which attached the tip cap to the tip part of a pipe main body, (A) is explanatory drawing of the tip part of a reinforcing core material, (B) is the whole perspective view of a tip cap. Explanatory drawing of Example 3 which attached the head cap to the head of the pipe main body, (A) is explanatory drawing of the head of a reinforcing core material, (B) is the whole perspective view of a head cap. Illustration of conventional root pile construction method

The present invention will be described below with reference to the drawings.

[Example 1]
<1> Small diameter cast-in-place pile Referring to FIG. and at least a reinforcing core material 30.

<2> Reinforcing Core Material In the present invention, a tubular reinforcing core material 30 is used as the core material of the small-diameter cast-in-place pile 10 without using a deformed steel bar.
The reinforcing core member 30 is a hollow tubular body with both ends open, and for example, a steel pipe can be used.
The diameter d and the body thickness t of the reinforcing core material 30 can be appropriately selected.
Practically, a steel pipe having a diameter d of 40A (diameter 48.6 mm) and a frame thickness t of 6 mm is suitable for the reinforcing core member 30 so that manual construction is possible.

The overall length of the single reinforcing core material 30 is set to an appropriate short size that is easy to handle manually, and by connecting multiple reinforcing core materials 30 via a screw joint such as a coupler, an arbitrary length can be obtained. adjust to

<2.1> Recessed Portion The outer peripheral surface of the pipe body 31 of the reinforcing core member 30 is not flat, but has an uneven shape to enhance adhesion with the consolidating material 25 .
The reinforcing core member 30 of this example has a plurality of recessed portions 32 along the pipe axial direction and the circumferential direction of the pipe main body 31 .

When connecting a plurality of reinforcing core members 30, conventional welded joints are not suitable because the cross-sectional shape of the reinforcing core members 30 is not a perfect circle due to the presence of the recessed portion 32. FIG. Therefore, as described above, it is desirable to connect them by mechanical joints such as screw joints.

<2.2> Arrangement Example of Recess FIG. 2 shows an arrangement example of the recess. 4A shows a configuration in which a plurality of recessed portions 32 are formed in rows along the axial direction of the tube body 31 at regular intervals, and are formed at regular intervals on the same circumference of the tube body 31. , and FIG. 4B shows a form in which rows of a plurality of recessed portions 32 adjacent in the circumferential direction are formed with phase differences in the tube axial direction.

<2.3> Number of recesses formed in the circumferential direction A plurality of recesses 32 are formed at equal intervals in the circumferential direction of the pipe body 31 .
3A shows a form in which four depressions 32 are formed along the circumferential direction of the pipe body 31, and FIG. A configuration in which three recessed portions 32 are formed along the circumferential direction is shown.

<2.4> Structural Example of Recessed Portion To explain the recessed portion 32 illustrated in FIG. A columnar groove 32b deeper than the flat portion 32a is formed in the center of the flat portion 32a.
The size of the flat portion 32a and the depth of the columnar groove 32b can be appropriately selected.

In this example, the recessed portion 32 has both the flat portion 32a and the columnar groove 32b.

When the recessed portion 32 is provided with the columnar grooves 32b, the entry of the solidifying material 25 into the columnar grooves 32b causes frictional force or shear at the interface between the solidifying material 25 entering the columnar grooves 32b and the surrounding solidifying material 25. Since the force is exerted and the columnar groove 32b functions as a slip stopper, the adhesive force in addition to the adhesive force in the recessed portion 32 can be further improved.

<2.5> Method for Forming Recessed Portions These recessed portions 32 can be formed, for example, by hot roll forming using steel pipe forming rolls having protrusions on their surfaces.
Although the reinforcing core member 30 has a plurality of depressions 32 formed on its peripheral surface, it has substantially the same compression performance and bending performance as a straight pipe.

<3> Performance Comparison between Reinforcing Core Material and Screw-nodular Steel Bar Performance comparison between the reinforcing core material 30 having substantially the same outer diameter and the conventional core material made of threaded-nodular deformed steel bar is as follows.

なお、従来のネジ節異形棒鋼製芯材にＪＩＳＧ３１１２に記載のＳＤ３４５を用いた場合の降伏点強度は３４５ＭＰａ以上となり、補強芯材３０にＪＩＳＧ３４４４に記載のＳＴＫ４００に相当する品を用いた場合の降伏点強度は２３５ＭＰａ以上となる。

In addition, the yield point strength when SD345 described in JISG3112 is used for the conventional threaded joint deformed bar steel core material is 345 MPa or more, and the yield strength when using a product corresponding to STK400 described in JISG3444 for the reinforcing core material 30 Point strength is 235 MPa or more.

The reinforcing core material 30 has a section modulus (Z) of 3.3 times and a geometrical moment of inertia of 5.7 times that of the conventional core material made of threaded joint deformed bar steel.
The reinforcing core material 30 used in the present invention has cross-sectional performance three times or more that of a core material made of conventional threaded joint deformed bar steel, so it can be applied as a core material for small-diameter cast-in-place piles. .

[Construction method of small-diameter cast-in-place piles]
Next, a method for constructing the small-diameter cast-in-place pile 10 will be described.

<1> Drilling process Using a boring machine, a drilling tool having a double inner rod 21 and casing 22 is rotated and struck to drill a pile hole 20 of a predetermined depth (Fig. 5 (A )).
After drilling the hole, the inner rod 21 is pulled out and the casing 22 is left in the hole (Fig. 5(B)).

<2> Step of Inserting Reinforcing Core Material In the present invention, the reinforcing core material 30 is inserted into the pile hole 20 immediately after drilling (FIG. 5(C)).

<3> Step of Injecting Consolidating Material The consolidating material 25 is injected into the pile hole 20 through the reinforcing core material 30 (FIG. 5(C)).
The consolidating material 25 is mortar, cement milk, or the like. An expansive material may be mixed into the consolidating material 25 as necessary.
A consolidating material 25 is discharged from the hole bottom of the pile hole 20 to fill the pile hole 25 .

In the present invention, since the reinforcing core material 30 can be substituted for the injection hose, not only can the conventional injection hose insertion work be omitted, but the injection error of the consolidation material 25 can be prevented by injecting the consolidation material 25 without inserting the injection hose. can be reliably eradicated.

<4> Casing Extraction Step The casing 22 left behind during drilling is extracted.
At this time, while extracting the casing 22, air is supplied into the pile hole to pressurize it, and the construction of the small-diameter cast-in-place pile 10 is completed (Fig. 5(D)).

<5> Pile head treatment process Adjust and protect the reinforcing core material 30 exposed on the ground surface.
Specifically, after the consolidation material 25 has hardened, concrete is cast in place until the head of the reinforcing core material 30 protruding to the ground surface is hidden, thereby constructing a concrete structure such as a retaining wall. Integrate the head and the concrete structure.
That is, measures are taken to adjust the distance between the pile heads of the adjacent reinforcing core members 30 exposed to the ground surface, and to prevent the reinforcing core members 30 from being deformed or rusted.

<6> Work process that can be omitted compared with the conventional construction method In the present invention, the reinforcing core material 30 can be substituted for the injection hose, so the conventional injection hose is not used.
Therefore, in the construction of the small-diameter cast-in-place pile 10, the steps of inserting the injection hose and removing the injection hose, which have been conventionally performed, can be reduced.
The injection hose insertion process and the injection hose removal process account for about 10% of all the processes in the conventional construction method, and the construction period can be shortened by about 10%.
In an actual site, several tens to hundreds of small-diameter cast-in-place piles 10 are constructed at one site, so the shortening period of construction period is increased in proportion to the number of small-diameter cast-in-place piles 10 to be constructed.

<7> Adhesion between Reinforcement Core Material and Consolidation Material The reinforcement core material 30 adheres to the consolidation material 25 on the outer peripheral surface of the pipe body 31 formed in an uneven shape.
In particular, since the recessed portion 32 formed on the outer peripheral surface of the pipe body 31 and the recessed portion 32 formed on the inner peripheral surface of the pipe body 31 are in close contact with the consolidating material 25, the adhesion between the pipe main body 31 and the consolidating material is high. Adhesive force (frictional resistance) can be obtained.

Further, the consolidating material 25 also adheres to the inner peripheral surface of the pipe body 31 .
Since the inner peripheral surface of the pipe main body 31 has an uneven shape obtained by inverting the outer peripheral surface, the inner peripheral surface of the pipe main body 31 and the consolidating material 25 are in close contact with each other. It is possible to obtain a high adhesive strength with the binding material 25 .

[Example 2]
Other embodiments will be described below. In the description, the same parts as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

<1> tip cap (Fig. 6)
In the above-described first embodiment, the tip end cap 33 may be attached to the tip end portion of the tube body 31 that constitutes the reinforcing core member 30 .
The tip cap 33 is attached to the tip of the pipe main body 31, has a function of suppressing the intrusion of mud and a function of discharging the consolidating material 25, and is entirely made of a metal material.
The tip cap 33 has a bottomed cylindrical portion 34 and one or more outlets 35 opened on the side surface of the cylindrical portion 34 .

The cylindrical portion 34 has a size that allows it to be attached to the tip opening of the pipe body 31, and can be fixed to the pipe body 31 by adhesion means, fusing means, screw joining means, riveting means, or the like.

<2> Function of tip cap Mud 23 remains in the hole when drilling the pile hole 20, but the bottom surface 34a of the cylindrical part 34 of the tip cap 33 functions as a cover material for the opening of the reinforcing core material 30. Therefore, when inserting the reinforcing core material 30 into the pile hole 20 , it becomes difficult for the mud 23 to enter the pipe main body 31 through the tip cap 33 .

Further, in the step of injecting the consolidating material 25, the consolidating material 25 supplied into the tube main body 31 of the reinforcing core material 30 is directed in the diameter expanding direction through the discharge port 35 opened on the side surface of the cylindrical portion 34 of the tip cap 33. can be ejected.

<3> Effect of this example In this example, in addition to the effect of Example 1 described above, the reinforcing core material 30 can be In the process of inserting into the pile hole 20, the backflow of the mud 23 into the pipe body 31 can be effectively suppressed, and in the process of injecting the consolidation material 25, the consolidation material 25 is injected through the discharge port 35 of the tip cap 33. It can be discharged in the diameter expanding direction.

[Example 3]
<1> Head cap (Fig. 7)
In the first and second embodiments described above, a head cap 36 may be attached to the head of the pipe body 31 that constitutes the reinforcing core member 30 .

The head cap 36 is attached to the proximal end of the pipe body 31 and has a function of protecting the head of the pipe body 31 and a function of fixing the head of the reinforcing core 30 to the concrete structure 26 forming the ground surface. , entirely made of metal.

The head cap 36 has a bottomless or bottomed cylindrical portion 37 and an annular fixing plate 38 protruding from the outer surface of the cylindrical portion 37 in the radially expanding direction. The fixing plate 38 is integrally formed.
The outer diameter of the fixing plate 38 larger than the diameter of the tubular portion 37 is appropriately selected.
In this example, a form in which a reinforcing rib 39 is provided between the cylindrical portion 37 and the fixing plate 38 is shown, but the reinforcing rib 39 is not essential.

The cylindrical portion 37 has a dimension that allows it to be attached to the head of the tube body 31, and can be fixed to the head of the tube body 31 by means of adhesion means, fusion means, screw joining means, riveting means, or the like.

<2> Function of head cap The head cap 36 exhibits a protective function so that the head of the pipe body 31 is not damaged when the reinforcing core 30 is handled.
Furthermore, the head cap 36 is constructed such that the fixing plate 38 of the head cap 36 increases the connection strength between the head of the reinforcing core member 30 and the concrete structure 50 in the pile head treatment process for constructing the concrete structure 26 on the ground surface. Works to enhance.

<3> Effect of this example In this example, in addition to the effects described in Example 1 or 2, by fixing a cap-type head cap 36 to the head of the pipe main body 31, , the pipe main body 31 can be physically protected, and the fixing plate 38 of the head cap 36 increases the connection strength with the reinforcing core material 30, so that the concrete structure formed between the head of the small-diameter cast-in-place pile 10 and the ground surface. 26 can be increased.

10 Small-diameter cast-in-place pile 20 Pile hole 21 Inner rod 22 Casing 23 Mud 25 Consolidation material 30 Reinforcing core material 31 Tube main body 32 Recessed portion 32a Flat portion 32b of recessed portion Columnar groove 33 of recessed portion Tip cap 34 Tip cap tube portion 35 Tip cap discharge port 36 Head cap 37 Head cap tube portion 38・・Fastening plate of the head cap

Claims (4)

A method for constructing a small-diameter cast-in-place pile, comprising:
drilling a pile hole;
a step of inserting into the pile hole a reinforcing core material having a plurality of recessed portions along the pipe axial direction and the pipe circumferential direction on the outer peripheral surface of the pipe body having a hollow structure;
At least a step of injecting a consolidation material into the pile hole and inside the reinforcing core through the reinforcing core,
Construction method of small diameter cast-in-place piles. In the step of drilling the pile hole, a drilling tool equipped with an inner rod and a casing is used, and after drilling the pile hole, only the inner rod is extracted and the casing is left in the pile hole. The method for constructing a small-diameter cast-in-place pile according to claim 1. The method for constructing a small-diameter cast-in-place pile according to claim 2, further comprising, after the step of injecting the consolidating material, a step of extracting the casing for pressurizing the inside of the pile hole while extracting the casing. After the consolidation material hardens, it further comprises a pile head processing step of placing concrete in place until the head of the reinforcing core protruding to the ground surface is hidden, and constructing a concrete structure integrally with the head of the reinforcing core. The method for constructing a small-diameter cast-in-place pile according to claim 1 or 3, characterized by:

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