JP4734151B2 - Pile head joint structure and construction method - Google Patents

Description

  The present invention relates to a pile head joint structure and a construction method thereof.

Conventionally, as a joint structure of a pile head when connecting a concrete-filled steel pipe pile or a steel pipe pile and a foundation, for example, an inner anchor method for inserting and fixing one end of an anchor bar inside the pile head, There are a beard bar method in which one end of an anchor bar is welded to the outer peripheral surface of the pile head, and a coupler method in which a screw rebar is fixed to a coupler mounted on the outer peripheral surface of the pile head (for example, see Patent Document 1).
In the inner collar method and the beard reinforcement method, when a large bending moment is generated at the pile head, there is a drawback that the anchor reinforcement becomes an overcrowded arrangement and the workability is inferior. Furthermore, there is a problem that the pile head stress at the time of fixing the pile head cannot be processed because the necessary number of anchor bars cannot be arranged.
In the coupler method, on-site welding of anchor bars is not required, and since installation is easy, both workability and quality are improved. However, since the coupler is expensive, the construction cost is likely to increase. In addition, when the pile head bending stress is increased, the necessary number of anchor bars cannot be arranged, and the pile head stress when the pile head is fixed may not be processed.
For example, Patent Document 2 and Patent Document 3 describe structures that improve such a problem in the pile head joint structure.
In Patent Document 2 and Patent Document 3, an outer pipe having an outer circumference slightly larger than the pile head is attached in a state of being surrounded by the outside of the pile head, and concrete is filled between the pile head and the outer pipe. This is a double steel pipe type pile head joint where one end of the anchor bar is embedded. In this joint structure, since the distance from the center of the pile head to the anchor muscle can be increased, the axial load of the anchor muscle can be reduced compared to the inner collar method, the beard muscle method, or the coupler method. .
Japanese Patent Publication No. 3-54736 Japanese Patent Laid-Open No. 11-13139 JP 2000-297472 A

However, in the joint structure of the pile head by the double steel pipe method shown in Patent Document 2 and Patent Document 3, since the anchor bars are fixed to the concrete between the pile head and the outer pipe, this fixing length is ensured. For this reason, there has been a drawback that the length of the outer tube becomes longer. For example, the length of the outer pipe is required to be 1.5 times the pile diameter. For this reason, when the pile diameter is large, the excavation depth for installing the outer pipe increases and the amount of the outer pipe members and the concrete to be filled increases. There was a problem that increased.
Moreover, in the construction method for constructing the pile head joint structure, an outer pipe is arranged around the pile head, anchor bars are arranged in the gap between the outer pipe and the pile head, and a filler is provided in the gap. Was filling. In this way, there is a problem that the work cost is increased because the number of work steps at the site is large and the construction time increases.

  This invention is made | formed in view of the problem mentioned above, and aims at providing the joining structure of the pile head which improves workability | operativity, and reduces construction cost, and its construction method.

In order to achieve the above object, the pile head joint structure according to the present invention is a pile head joint structure for joining a pile to a foundation of a structure, and an outer tube surrounding the pile head from the surroundings. A diameter increasing member composed of a diaphragm fixed to the lower end of the outer pipe and having a hole through which the pile head is inserted, and a first anchor bar provided in the outer pipe, A filler is filled between the pile heads, a first projecting member protruding from the outer periphery of the pile heads is provided, and the piles are inserted in a non-fixed state with respect to the diaphragm . .
In the present invention, the enlarged member can be disposed at a predetermined position of the pile head, and the enlarged member and the pile head can be integrated with the filler to form a rigid joint structure. For this reason, since joining means, such as welding, become unnecessary in joining with a diameter-expanding member and a pile head, construction in the field is simplified and work man-hours can be reduced. Therefore, the construction cost can be reduced because the construction time can be shortened.
By attaching the first anchor bar to the outer pipe, the first anchor bar is not fixed by the filler as in the conventional double steel pipe system. For this reason, since it is not necessary to ensure the fixing length of the first anchor bar and the filler, the length of the outer tube can be shortened. For this reason, since the construction work of a diameter-expanding member and the filling work of a filler can be simplified and construction time can be shortened, construction costs can be reduced.
In addition, since the first projecting member is fixed to the concrete filled between the enlarged member and the pile head, the adhesion strength between the pile head and the concrete is increased, thereby preventing the displacement. It can resist the tensile force and bending moment acting in the axial direction.

Moreover, it is preferable that the 2nd anchor muscle is provided in the upper part of the pile head as for the joining structure of the pile head which concerns on this invention.
In the present invention, by providing the second anchor bar in addition to the first anchor bar attached to the outer pipe, the pile head bending strength at which the anchor bar is laid increases and the load applied to the outer pipe is increased. The effect that can be reduced. Thereby, the proof stress of a pile head junction part increases and it can respond also when a pile head bending stress is large.

In the pile head joint structure according to the present invention, it is preferable that a second projecting member that protrudes from the inner periphery of the pile head is provided.
In the present invention, the second projecting member can be fixed to concrete or the like placed inside the pile 1 to resist displacement, that is, resist the pulling force of the pile (the tensile force in the axial direction of the pile). .

Moreover, in the pile head joint structure according to the present invention, the second projecting member is an end plate fixed to the upper end portion of the pile head, and the inner peripheral side of the end plate is closer to the inner periphery of the pile head. It is preferable to make it protrude.
In the present invention, the inner periphery of the end plate can be protruded to the inside of the pile head, and the protruding portion can be fixed to concrete or the like placed on the inside of the pile and can serve to prevent displacement.

Further, the pile head construction method according to the present invention includes an outer pipe that surrounds the pile head from the periphery, and a diameter-expanded structure that includes a diaphragm that is fixed to the lower end of the outer pipe and has a hole that passes through the pile head. A first projecting member provided with a member and a first anchor bar provided on the outer pipe, and provided with a first projecting member projecting from the outer periphery of the pile head, and a pile inserted in a non-fixed state with respect to the diaphragm A method of constructing a pile head to be joined to the foundation of the first method, the first step of arranging the enlarged member around the pile head so that the pile head is inserted into the hole of the diaphragm, and the enlarged member The second step of filling the gap between the outer pipe and the pile head with a filler and integrating them, and before the second step, the anchor bars were attached to the outer pipe. It is a feature.
In the present invention, a diameter expanding member is manufactured in advance at a factory or the like, and the diameter expanding member is inserted into the pile head at the construction site, and a filler is provided in the gap between the diameter expanding member and the pile head. Pile head joints can be constructed. In this way, the diameter-expanding member only needs to be placed at a predetermined position on the pile head, and since no fixing means such as welding is required, the construction at the site is simplified, the construction process is shortened, and Cost can be reduced.

According to the pile head joint structure and the construction method thereof according to the present invention, the enlarged member is arranged at a predetermined position of the pile head, and the enlarged member and the pile head are integrated by the filler so that the rigid joint is joined. The structure can be configured. For this reason, since joining means, such as welding, become unnecessary in joining with a diameter-expanding member and a pile head, construction in the field is simplified and work man-hours can be reduced. Therefore, the construction cost can be reduced because the construction time can be shortened.
By attaching the first anchor bar to the outer pipe, the first anchor bar is not fixed by the filler as in the conventional double steel pipe system. For this reason, since the construction work of a diameter-expanding member and the filling work of a filler can be simplified and construction time can be shortened, construction costs can be reduced.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pile head joint structure and a construction method thereof according to the present invention will be described with reference to FIGS. 1 to 4.
FIG. 1 is an elevational sectional view showing a pile head joint structure according to the embodiment, FIG. 2 is a cross-sectional view taken along line AA of the pile head joint structure shown in FIG. 1, and FIGS. The figure which shows the joining process of a pile head structure, FIG. 4 (a)-(d) is the figure which shows the construction procedure of a pile head joint, FIG. 5 (a), (b) is explanatory drawing which shows the construction method of a pile head 6 (a) and 6 (b) are plan views showing the arrangement state of the suspension bar.

In the pile head joint structure according to the embodiment, all pile types such as steel pipe pile, SC pile (prefabricated concrete pile covered with steel pipe), concrete filled steel pipe pile, PC pile without steel pipe covering (including PHC pile), etc. The pile 1 is targeted.
As shown in FIGS. 1 and 2, the pile head joint structure is provided with a diameter expanding member 3 around the pile head 2, and a filler 4 is provided between the diameter expanding member 3 and the pile head 2. The structure is filled and integrated.
As shown in FIG. 1, the diameter-expanding member 3 includes a diaphragm 6 having an outer pipe 5 that is surrounded by a cylindrical steel pipe and a hole 6 a that is fixed to the lower end 5 a of the outer pipe 5 and passes through the pile head 2. It consists of and.
The outer pipe 5 is made of a steel pipe whose inner diameter is larger than the outer diameter D of the steel pipe constituting the pile 1, and its member length is about 0.25 to 1.5 times the outer diameter D of the steel pipe. ing.
As shown in FIGS. 1 and 2, the hole 6 a of the diaphragm 6 is formed to have a diameter slightly larger than the outer diameter D of the pile 1. The outer peripheral portion 6b of the diaphragm 6 is fixed to the lower end 5a of the outer tube 5 by fixing means such as welding. On the other hand, the pile head 2 is inserted in a non-adhered state into the hole 6a forming the inner periphery thereof.

  As shown in FIGS. 1 and 2, a plurality of anchor bars 8 embedded in the foundation 7 are fixed to the upper outer peripheral surface 5 b of the outer tube 5 at predetermined intervals by fixing means such as welding. The anchor bars 8 are embedded in the foundation 7 whose other end is constructed above the pile 1, and such a structure forms a joint structure with the foundation 7.

As shown in FIG. 1, an excavation area 9 is formed around the diameter expansion member 3 in order to secure a work area for attaching the diameter expansion member 3. In the present embodiment, the diaphragm 6 is placed on the bottom plate 9a of the excavation area, so that the diameter-expanding member 3 is positioned and arranged with respect to the pile head 2 in the height direction.
Further, as shown in FIG. 1, the gap between the outer tube 5 and the pile head 2 is filled with a filler 4 made of concrete, soil mortar, mortar, or the like. The diameter-expanding member 3 and the pile head 2 are joined by being filled with the filler 4.

Next, a pile head construction method according to an embodiment of the present invention will be described with reference to the drawings.
First, as shown in FIG. 3, as a preparatory process for joining construction, for example, a diaphragm 6 is welded to one end face of the outer tube 5 in advance at a factory or the like to produce the diameter-expanded member 3, and the upper portion of the outer tube 5 A plurality of anchor bars 8 are fixed to and integrated with the outer peripheral surface 5b by welding or the like.
And as shown to Fig.4 (a), in order to expose the pile head 2 of the existing pile 1 laid underground, as shown in FIG.4 (b), the excavation area | region around the pile head 2 is shown. 9 is excavated. And the bottom board 9a of the excavation area | region 9 is formed so that the diaphragm 6 can be mounted in a predetermined position.

In the first step of joining construction, as shown in FIG. 4 (c), the diameter expanding member 3 is arranged around the pile head 2 so that the pile head 2 is inserted through the hole 6a of the diaphragm 6 ( (Refer FIG.3 (b)). Then, the excavation region 9 around the diameter expanding member 3 is backfilled with a backfilling material 10 such as sand.
Then, in a 2nd process, as shown in FIG.4 (d), after cleaning the inside of the diameter expansion member 3 well, the diameter expansion member 3 from the opening part 11 between the outer tube 5 and the pile head part 2 is shown. The filler 4 is filled inside.
And the reinforcement structure is arranged on the upper part of the diameter-expanding member 3 and the foundation 7 is constructed by placing concrete, and the joining structure of the pile head 2 is provided. The procedure of filling the filler 4 in the diameter-expanding member 3 may be performed simultaneously with the construction of the foundation 7.

In the pile head joint structure and its construction method according to the embodiment, the enlarged diameter member 3 is arranged at a predetermined position while the pile head 2 is inserted into the hole 6a of the diaphragm 6, and the pile head 2 and the outer pipe Since it is only necessary to fill the gap 4 with the filler 4 and there is no need to fix the pile head 2 and the diaphragm 6 by, for example, welding, the construction at the site is simplified and the workability is improved. Can reduce the number of work steps. Therefore, the construction cost can be reduced because the construction time can be shortened.
In the pile head joint structure and its construction method according to the embodiment, as shown in FIG. 1, the anchor bar 8 is attached to the outer pipe 5, so that the filler 4 as in the conventional double steel pipe system. Therefore, the anchor muscle 8 is not fixed. In this embodiment, the overlap length L of the outer pipe 5 can be made about 0.25 to 1.5 times the pile diameter D by having the diaphragm 6 as described above, and the length is less than half that of the conventional method. can do.
Thus, by shortening the length of the outer tube 5, it is possible to simplify the construction work of the diameter-expanding member 3 and the filling work of the filler 4. Further, the depth of excavation and the excavation area 9 can be reduced when the diameter expanding member 3 is built in the pile head 2. Therefore, construction time can be shortened and construction cost can be reduced.

Next, the construction method installed in the pile head 2 by suspending the diameter expanding member 3 will be described based on the drawings.
As shown in FIG. 5A and FIG. 6A, in the state where the horizontal diaphragm 6 and the outer tube 5 are integrally assembled in the diameter expanding member 3, the two suspension rods 31 and 32 are connected to the outer tube 5. Are arranged so as to intersect with each other in the shape of a cross in plan view, and the suspension bar members 31 and 32 and the outer tube 5 are fixed by welding or the like. Then, a part of the suspension rods 31 and 32 is locked by the wire 33 or the like, lifted by using a lifting machine such as a crane (not shown), and is inserted and attached so as to cover a predetermined position of the pile head 2 ( (Refer FIG.5 (b)). Thereby, when attaching the enlarged member 3 provided with the outer tube 5 to the pile head 2 as in the prior art, there is no need to provide a support base for supporting the enlarged member 3 from below, and in a short time. Construction can be performed.
Note that the arrangement of the suspension rods 31 and 32 is not limited to the crossing arrangement as shown in FIG. 6 (a), and two other hanging bars as shown in FIG. 6 (b). The bars 31 and 32 may be arranged so as to be substantially parallel in plan view. The point is that the suspension bar members 31 and 32 and the outer tube 5 are fixed and can be lifted so as not to fall.

  In the joint structure of pile heads according to the embodiment and the construction method thereof, since the anchor bars 8 are provided on the outer pipe 5 as described above, the pile head is compared with, for example, a conventional double steel pipe system. The distance from the center of 2 to the anchor muscle 8 increases. For this reason, overcrowded bar arrangement can be eliminated and the bar arrangement density can be freely adjusted by changing the outer diameter of the outer tube 5 in which the anchor bar 8 is arranged. In addition, the bending strength and pulling-out strength of the pile head 2 can be easily increased as compared with the structure of the conventional beard muscle method or the inner collar method, and the strength of the joint structure of the pile head 2 can be increased. It is possible to prevent the preceding destruction of the pile head joint.

Next, modifications of the embodiment will be described with reference to FIGS. 7 to 12. However, the same or similar members and parts as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted. A configuration different from the embodiment will be described.
FIG. 7 is a perspective view of a pile head showing a first modification according to the present embodiment, and FIG. 8 is a perspective view of a pile head showing a second modification according to the present embodiment.
In the first and second modifications, in addition to the anchor bars 8 (see FIG. 1) joined to the outer tube 5, the second anchor bars 12 and 13 (see FIGS. 7 and 8A) are connected to the pile head. This is a joint structure provided in the portion 2. Moreover, the 2nd modification shown in FIG.8 (b) is the joining structure which provided the 2nd anchor reinforcement 14 as a core reinforcement in the filling concrete of the pile head part 2. FIG.
The first modification is applied to a pile 1 whose outer periphery is covered with a steel pipe. As shown in FIG. 7, the second anchor bars 12 are joined to the outer periphery 2 b of the pile head 2 by a fixing means such as welding. The fixed position of the second anchor muscle 12 may be on the inner peripheral side of the pile head 2.
The second modification is applied to a pile 1 such as a concrete PC pile or a PHC pile. As shown in FIG. 8A, the second anchor bar 13 is formed by welding a pile stud or the like to the steel plate at the upper end of the pile 1 instead of the second anchor bar 12 of the first modification. It is what. Moreover, what is necessary is just to attach a steel plate and weld a pile stud etc. on it, when the steel plate is not provided.
In the first and second modified examples described above, by providing the second anchor muscle 12, 13, or 14 in addition to the anchor muscle 8 of the embodiment, in addition to the effect obtained in the embodiment, Since the anchor muscles increase, the effect of reducing the load on the outer tube 5 is achieved. Thereby, the proof stress of a pile head junction part increases and it becomes possible to respond also when a pile head bending stress is large.

Next, the 3rd modification by this invention is demonstrated based on FIG.
FIG. 9 is a perspective view of a diameter-expanding member showing a third modification according to the present embodiment.
As shown in FIG. 9, the diameter-expanding member 15 according to the third modification includes an outer tube 5 that surrounds the pile head 2 from the periphery, and a hole 6 a that is fixed to the lower end of the outer tube 5 and passes through the pile head 2. The diaphragm 6 includes a concrete cylinder 16 that is integrated with an inner peripheral portion of the outer tube 5 on the diaphragm 6 and has a through hole 16 a so as to extend the hole 6 a of the diaphragm 6. The anchor muscle 8 is provided on the upper outer peripheral surface 5b of the outer tube 5 as in the embodiment. The pile head joining structure has a structure in which a consolidation material 17 such as mortar is injected into the gap between the concrete cylinder 16 of the diameter expanding member 15 and the pile head 2 and integrated.

Moreover, the construction method of the pile head 2 which has the joining structure by the 3rd modification is demonstrated based on FIG.
First, the diameter expanding member 15 is manufactured by integrating the outer tube 5, the diaphragm 6, and the concrete cylinder 16 at a factory, for example. Then, in the first step, the diameter expanding member 15 is arranged so that the pile head 2 is inserted through the hole 6 a of the diaphragm 6 and the through hole 16 a of the concrete cylinder 16. Next, in the second step, the consolidation material 17 is injected and integrated into the gap between the concrete cylinder 16 of the diameter expanding member 15 and the pile head 2. The anchor muscle 8 may be attached to the outer tube 5 before the second step. For example, either the anchor bar 8 is attached and fixed in advance when the diameter-expanding member 3 is manufactured in a factory or the like, or the anchor bar 8 is fixed after the diameter-expansion member 15 is arranged on the site. Good.
Compared to the filling operation of the filler 4 (see FIG. 1) in the embodiment, in the third modification, since the injection amount of the consolidated material 17 is small, the time of the injection operation can be shortened, and the workability is improved. Can be improved. That is, in this third modification, there is no need to weld the pile head 2 and the diaphragm 6 of the diameter-expanding member 3 on site, so the concrete cylinder 16 is formed in the diameter-expanding member 15 in advance, The work at the site is limited to the injection of a small amount of the caking material 17, and the workability at the site is further improved.

Next, FIG. 10 is an elevational sectional view showing a pile head joint structure according to a fourth modification of the present embodiment.
As shown in FIG. 10, in the 4th modification, the protrusion member 20 (1st protrusion member) is provided in the outer peripheral upper part 2c of the pile head 2 continuously or partially in the circumferential direction. The protruding member 20 is formed by fixing a steel material such as a flat steel or a reinforcing bar in advance by a fixing means such as welding, or by forming a weld bead without using a steel material. It is provided so as to protrude outward. Thereby, since the projection member 20 adheres to the filler 4 such as concrete filled between the diameter expanding member 3 and the pile head 2, the adhesion strength between the pile head 2 and the filler 4 increases. Thus, it can act to prevent slippage and resist axial tensile force and bending moment acting on the pile head 2.

FIG. 11 is an elevational sectional view showing a pile head joint structure according to a fifth modification of the present embodiment.
As shown in FIG. 11, in the fifth modified example, an end plate 21 (first projecting member) having a substantially donut shape in plan view is provided on a pile head upper end portion 2d of a pile 1 such as an SC pile, An inner peripheral protrusion 21 a protrudes inside the pile head 2. The axial force acting on the pile 1 is transmitted directly from the end plate 21 to the pile body. And the protrusion part 21a of the end plate 21 adheres to the concrete C cast | injected inside the pile 1, and it has a slippage prevention effect | action, ie, the effect | action which resists the pulling-out force (the axial force of the pile 1) of the pile 1. Can be fulfilled. In addition, what is necessary is just to arrange | position the 2nd anchor reinforcement 18 in the pile 1 as needed as shown in FIG.

FIG. 12 is an elevational sectional view showing a pile head joint structure according to a sixth modification of the present embodiment.
As shown in FIG. 12, in the sixth modified example, a protruding member 22 (first protruding member) formed on the inner peripheral upper portion 2e of the pile head 2 from a steel material or a weld bead as in the fourth modified example. ) Are provided at two locations in the vertical direction of the pile 1. Thereby, while being able to transmit the axial force which acts on the foundation 7 to the pile 1, there exists an effect made to resist drawing force similarly to the 5th modification. In addition, when a tensile force acts on the pile 1 similarly to the 5th modification, it arrange | positions the 2nd anchor reinforcement 18 in the pile 1 as needed.

As mentioned above, although embodiment of the joining structure of the pile head by this invention and its construction method was described, this invention is not limited to said embodiment, In the range which does not deviate from the meaning, it can change suitably. It is.
For example, in the present embodiment, the anchor muscle 8 is attached to the diameter-expanding member 3 in advance at a factory, for example. However, the present invention is not necessarily limited to this and is changed in consideration of workability at the site. be able to. For example, the anchor member 8 may be disposed on the pile head 2 by fixing means such as welding after the diameter-enlarged member 3 to which the anchor muscle 8 is not attached is built in the pile head 2. Moreover, although the anchor reinforcement 8 was attached to the outer surface of the outer tube | pipe 5, you may attach to an inner surface so that the anchor reinforcement 8 may not rust.
Further, in the present embodiment, the positioning when attaching the diameter expanding member 3 to the predetermined position of the pile head 2 is a method of placing on the bottom plate 9a of the excavation area 9, but this is not limited to this positioning method. Absent. For example, a positioning method may be used in which a ring-shaped flat plate is welded in advance to a predetermined position on the periphery of the pile head 2 and the diameter-expanding member 3 is placed on the flat plate.
Furthermore, in the present embodiment, the shape of the outer tube 5 is a cylinder. Instead, for example, the outer tube 5 is a polygonal shape such as a quadrangle or an octagon in cross section, and has a columnar shape or a truncated pyramid shape. Also good.
The outer tube 5 and the diaphragm 6 may be made of a material that is strong against tension, such as carbon fiber and carbon fiber reinforced plastic, in addition to the steel material.

It is an elevation sectional view showing the joining structure of a pile head by an embodiment of the invention. It is an AA line sectional view of the joining structure of a pile head shown in FIG. (A), (b) is a figure which shows the joining process of a pile head structure. (A)-(d) is a figure which shows the construction procedure of pile head joining. (A), (b) is explanatory drawing which shows the construction method of a pile head. (A), (b) is a top view which shows the arrangement | positioning state of a suspension bar. It is a perspective view of the pile head which shows the 1st modification by this Embodiment. (A), (b) is a perspective view of the pile head which shows the 2nd modification by this Embodiment. It is a perspective view of the diameter-expansion member which shows the 3rd modification by this Embodiment. It is an elevation sectional view showing the joining structure of the pile head by the 4th modification of this embodiment. It is an elevation sectional view showing the joining structure of the pile head by the 5th modification of this embodiment. It is a sectional elevation showing the pile head joint structure by the 6th modification of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pile 2 Pile head 3, 15 Diameter expansion member 4 Filler 5 Outer pipe 6 Diaphragm 6a Hole 7 Foundation 8 Anchor reinforcement 9 Excavation area 12, 13, 14, 18 Second anchor reinforcement 16 Concrete cylinder 17 Solidified material 20 22 Projection member (first projection member)
21 End plate (second protruding member)
31, 32 Hanging bar D Outer diameter L Overlap length

Claims (5)

A pile head joint structure for joining a pile to the foundation of a structure,
A diameter-enlarging member composed of an outer pipe that surrounds the pile head from the periphery, and a diaphragm that is fixed to a lower end of the outer pipe and has a hole that passes through the pile head;
A first anchor muscle provided in the outer tube;
With
A filler is filled between the outer pipe of the diameter-expanding member and the pile head ,
A first protruding member is provided that protrudes from the outer periphery of the pile head;
The pile head joining structure, wherein the pile is inserted in a non-fixed state with respect to the diaphragm . 2. The pile head joint structure according to claim 1, wherein a second anchor bar is provided on an upper portion of the pile head. Junction structure of pile head according to claim 1 or 2, wherein the second projection member formed to protrude from the inner periphery of the pile head is al provided. The second projecting member is an end plate fixed to an upper end portion of the pile head, and an inner peripheral side of the end plate protrudes from an inner periphery of the pile head. Item 4. The pile head joint structure according to Item 3 . A diameter expanding member composed of an outer tube surrounding the pile head from the periphery, a diaphragm fixed to the lower end of the outer tube and having a hole through which the pile head is inserted, and a first provided in the outer tube A first projection member provided with an anchor bar and projecting from an outer periphery of the pile head, and a pile head that joins a pile inserted in a non-fixed state with respect to the diaphragm to a foundation of a structure. A construction method,
Around the pile head, a first step of arranging the diameter-expanding member so that the pile head is inserted through a hole of the diaphragm;
A second step of filling and integrating a filler in a gap between the outer pipe of the diameter-expanding member and the pile head; and
Have
The construction method of a pile head characterized by attaching the anchor reinforcement to the outer pipe before the second step.

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