JP5258984B2 - Pile head structure - Google Patents

Description

  The present invention relates to the structure of a pile head of a foundation pile, and more particularly to the structure of a pile head when the foundation pile is also used as an underground heat exchanger.

  When the underground temperature exceeds a certain depth, it changes at a temperature of about the average annual temperature, which is lower than the outside temperature in summer and higher than the outside temperature in winter. There is a geothermal heat utilization system that uses the temperature difference between the underground and the outside air temperature to obtain the heat required for building air conditioning and road surface snow melting with a small amount of energy. This system has already spread widely in Europe and the United States, and has gradually started to spread in Japan.

In the underground heat utilization system, generally, a narrow tube (in the present specification, referred to as “heat medium flow pipe” or “heat medium pipe”) is provided in a vertical hole dug by a boring machine. Although exchange with geothermal heat is performed, this method has a drawback of high boring costs. Then, the method which uses a foundation pile as an underground heat exchanger attracts attention (refer patent document 1).
As shown in Patent Document 1, the heat transfer pipe arranged in the foundation pile usually passes from the pile head to the foundation concrete (footing foundation, cloth foundation, solid foundation, underground beam, etc.) above it. It goes directly to the outside and then leads to air conditioning equipment such as a heat pump.

  However, this piping method requires maintenance such as inspection, repair or replacement of the heat medium pipe when the heat medium pipe is damaged or clogged in the pile body, but it is taken out because it is embedded in the foundation concrete. Cannot be maintained.

As a method to solve these problems, there is a proposal that a heat medium pipe is taken out from the side of the underground pipe by providing a notch or a hole for passing the heat medium pipe near the upper end of the underground pipe. (See Patent Document 2).
Furthermore, in the case of using foundation piles as underground heat exchangers, it is possible to easily maintain the heat transfer pipe and to obtain a pile head structure that excels in workability and safety on site during construction. Has been proposed (see Patent Document 3).

Patent Document 3 proposes the following as one aspect.
A structure of a pile head of a hollow ready-made pile that uses the hollow ready-made pile as an underground heat exchanger by disposing a pipe for heat medium flow in a hollow ready-made pile that is a foundation pile of a structure, A pile head with a hole is installed on the pile head, and a bent pipe for passing a heat medium flow pipe is inserted into the hole of the pile head or brought into contact with the periphery of the pile head, and the other end is foundation concrete. A structure of a pile head characterized by being arranged so as to protrude from the side surface or the upper surface of the pile.

JP-A-1-123951 JP 2005-69538 A JP 2006-343004 A

In the method of Patent Document 2, when the underground pipe is also used as a foundation pile, a part near the pile head on which a large external force acts is cut and removed, so that the part tends to be a structural weakness. There are drawbacks and structural safety issues.
In addition, the outlet of the heat transfer pipe is the upper end of the pile, but this position is directly below the foundation concrete, and it is necessary to excavate the ground surface for maintenance. Since the position is sandwiched between the bottom surfaces of the concrete, there is a problem that workability during maintenance is extremely poor.

In this regard, by adopting the structure of the pile head according to Patent Document 3, there is no problem in structural safety, there is no need to excavate the ground surface for maintenance, and the workability during maintenance is excellent. .
However, the following problems remain in Patent Document 3 as well.
Some of the pipes used for heat medium flow have a U-shaped bent end, and the bent part is manufactured separately from the other parts. In such a case, a step is formed at the joint between the U-shaped bent portion and the other portion, and this step is the opening edge of the pile skull when the heat medium flow pipe is inserted and pulled out during maintenance. It may get caught in the department. For this reason, the heat medium flow piping cannot be smoothly inserted or pulled out, which may hinder maintenance.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a structure of a pile head that can smoothly insert and pull out a heat medium pipe into a hollow ready-made pile. .

  The position of the end of the guide tube for guiding the heat medium pipe, that is, the position of the insertion port for inserting the heat medium pipe, may be various in view of the relationship with the basic concrete and its upper structure. Therefore, regarding the shape of the guide tube, there are various modes, for example, when a straight tube is used, when a bent tube is used, and when a bent tube is further used, there are more various types depending on what bending form is used. The following embodiments are possible.

In such a situation, in order to always achieve smooth insertion and withdrawal of the heat medium flow pipe, the guide pipe is inserted into the pile via the guide pipe in relation to the shape of the guide pipe, the position where the guide pipe is attached, etc. It is necessary to know how the inserted heat transfer medium pipe behaves and know its behavior, and then devise to realize smooth insertion and withdrawal.
Therefore, the inventor conducted experiments using guide tubes of various shapes, found the behavior of the heat medium flow tube with respect to various guide tube embodiments, and completed the present invention based on this knowledge. Specifically, it has the following configuration.

(1) The structure of the pile head according to the present invention uses the hollow ready-made pile as an underground heat exchanger by disposing a heat medium flow pipe in a hollow ready-made pile that is a foundation pile of the structure. The structure of the pile head of a hollow ready-made pile that
A pile skull having an opening, and a guide pipe that is joined to the opening of the pile skull and through which the heat medium flow pipe is inserted,
The guide pipe is a straight pipe joined to the upper surface of the pile skull at an inclination angle of 45 degrees or more and less than 90 degrees, and the opening of the pile skull is provided close to the inclined side of the guide pipe. In the state where the pile head is installed on the pile head, the portion closest to the outer edge of the lid in the peripheral wall portion of the opening is configured not to protrude to the inner side of the opening than the inner wall of the pile.

The angle formed by the guide tube and the pile skull upper surface can be in the range of 0 to 180 degrees. In this specification, the angle formed by the guide tube and the pile skull upper surface is specified with an acute angle side.
The side on which the guide tube is inclined refers to the side on which the guide tube is projected when the guide tube connected to the pile skull is viewed in plan.

(2) Further, by placing a heat medium flow pipe in a hollow ready-made pile that is a foundation pile of a structure, a pile head of a hollow ready-made pile that uses the hollow ready-made pile as an underground heat exchanger Structure,
A pile skull having an opening, and a guide pipe that is joined to the opening of the pile skull and through which the heat medium flow pipe is inserted,
The guide pipe is a straight pipe joined with the upper surface of the pile skull at an inclination angle of 45 degrees or more and less than 90 degrees, and the guide pipe in the path from the inner face of the pile skull to the inner face of the guide pipe is inclined. It is characterized by chamfering so that the side path is smooth.

  “Chamfered so that the path is smooth” means, for example, that an acute angle portion existing in the path is cut to make it obtuse or smooth.

(3) Further, by placing a heat medium flow pipe in a hollow ready-made pile that is a foundation pile of a structure, a pile head of a hollow ready-made pile that uses the hollow ready-made pile as an underground heat exchanger Structure,
A pile skull having an opening, and a guide pipe that is joined to the opening of the pile skull and through which the heat medium flow pipe is inserted,
The guide tube is formed of a bent tube having a bent portion, and the opening of the pile skull is provided close to the bending direction of the first bent portion on the pile skull side of the guide tube. In the state installed in the head, the portion closest to the outer edge of the lid in the peripheral wall portion of the opening is configured not to protrude to the inner side of the opening than the inner wall of the pile.

  The “bending direction” refers to the center side when the bending radius of the bent portion is viewed in plan. Further, “the side opposite to the bending direction” refers to the circumferential side when the bending radius of the bent portion is viewed in plan.

(4) Further, by placing a heat medium flow pipe in a hollow ready-made pile that is a foundation pile of a structure, a pile head of a hollow ready-made pile that uses the hollow ready-made pile as an underground heat exchanger Structure,
A pile cradle having an opening, and a guide pipe that is joined to the pile cranium so as to communicate with the opening and through which the heat medium flow pipe is inserted,
The guide pipe is formed of a bent pipe having a bent portion, and among the paths from the pile skull inner surface to the guide pipe, the path on the opposite side to the bending direction of the first bent portion on the pile skull side of the guide pipe is smooth. It is characterized by chamfering so as to become.

  In the present invention, it comprises a pile skull having an opening, and a guide tube joined to the pile skull so as to communicate with the opening, and the heat medium flow pipe is inserted, the guide tube being bent Chamfering so that the path on the opposite side to the bending direction of the first bent part on the pile skull side of the guide pipe is smooth among the paths from the inner surface of the pile skull to the inside of the guide pipe. As a result, the heat medium pipe installed through the guide pipe can be smoothly inserted and taken out during maintenance, and the workability is extremely excellent.

It is explanatory drawing of the structure of the pile head which concerns on Embodiment 1 of this invention. It is an arrow AA figure in FIG. It is explanatory drawing of the state in the middle of construction in the structure of the pile head which concerns on Embodiment 1 of this invention. It is explanatory drawing of the construction completion state in the structure of the pile head which concerns on Embodiment 1 of this invention. It is explanatory drawing of the insertion operation | movement of the heat-medium piping in the structure of the pile head which concerns on Embodiment 1 of this invention. It is explanatory drawing of the other aspect of the arrangement | positioning relationship between the opening part in the pile skull which concerns on Embodiment 1 of this invention, and a hollow control pile. It is explanatory drawing of the other aspect of the arrangement | positioning relationship between the opening part in the pile skull which concerns on Embodiment 1 of this invention, and a hollow control pile. It is explanatory drawing of the structure of the pile head which concerns on Embodiment 2 of this invention. It is explanatory drawing of the insertion operation | movement of the heat medium piping in the structure of the pile head which concerns on Embodiment 2 of this invention. It is explanatory drawing of the other aspect of the structure of the pile head which concerns on Embodiment 2 of this invention. It is explanatory drawing of the structure of the pile head which concerns on Embodiment 3 of this invention. It is an enlarged view of the A section enclosed with the circle of FIG. It is explanatory drawing of the structure of the pile head which concerns on Embodiment 4 of this invention. It is an enlarged view which expands and shows a part of FIG.

[Embodiment 1]
FIG. 1 is an explanatory view of a structure of a pile head according to an embodiment of the present invention, and is a cross-sectional view around the pile head. In general, pile head reinforcing bars and foundation concrete reinforcing bars are arranged around the pile head, but these reinforcing bars are shown in Fig. 1 because there are several types of reinforcing bar arrangement methods and to make it easier to see the figure. Is omitted, and an example is shown in FIGS. 3 and 4 to be described later.

In the present embodiment, a hollow ready-made pile 3 is supported by supporting a structure 5 with a hollow ready-made pile 3 that is a foundation pile through a foundation concrete 1 and arranging a heat medium flow pipe in the hollow ready-made pile. It is a structure of a pile head of a hollow ready-made pile 3 used as an underground heat exchanger, and a straight pipe is used as a guide pipe 7 for inserting a heat medium flow pipe into the hollow ready-made pile 3. Inclined arrangement.
Hereinafter, details of each component will be described more specifically.

1. Hollow ready-made pile The kind of hollow ready-made pile 3 is not specifically limited, For example, a steel pipe pile and a concrete pile are mentioned.

2. Pile skull The pile skull 9 is provided with an opening 11 communicating with the guide tube 7. FIG. 2 is a view taken along the line AA in FIG. 1, and as shown in FIG. The reason why the opening 11 is elliptical is as follows. In this embodiment, the lower end portion of the guide tube 7 having a circular cross section perpendicular to the axial direction is obliquely cut and used, and the obliquely cut surface is elliptical. Since the guide tube 7 is inclined by bringing the elliptical surface into contact with the pile skull 9, the opening 11 in the pile skull 9 has an elliptical shape.

The opening 11 formed in the pile head 9 has a portion 11a closest to the outer edge of the elliptical long axis in the opening 11 (hereinafter referred to as "opening outermost edge 11a") substantially flush with the pile inner wall 3a. It is supposed to be. Therefore, as shown in FIG. 1, the pile inner wall 3a, the opening outermost edge portion 11a, and the guide tube inner wall are smoothly continuous.
As will be described later, when the straight pipe is inclined and installed on the pile skull 9, when the heat medium pipe is inserted and pulled out, the tip of the heat medium pipe passes through the outermost edge 11a of the opening. By doing in this way, the level | step difference formed in the heat-medium piping front-end | tip is no longer caught on the edge of the opening part 11, and insertion and extraction of a heat-medium piping become easy.

In addition, although the example using the plate-shaped pile skull 9 was shown in FIG. 1, the shape of the pile skull 9 is not limited to a circular flat plate shape, for example, a sphere recessed toward the lower side of the hollow ready-made pile 3 It may be a coronal one.
The diameter of the pile skull 9 may be either the inner diameter or the outer diameter of the pile, and may be larger than the outer diameter of the pile or may be a rectangle.
Further, the pile head 9 may be solidified to the pile head by welding or the like, and may or may not be solidified.
In addition, since a vertical force acts on the pile head 9, it is generally preferable to use a steel plate for the pile head 9.

3. Guide tube The guide tube 7 of the present embodiment is a straight tube having a circular cross section perpendicular to the tube axis, the lower end surface thereof is cut obliquely, and the cut surface is welded to the pile head cover 9. As described above, the lower end surface of the guide tube 7 cut obliquely has an elliptical shape, and this surface is installed so as to correspond to the elliptical opening 11 of the pile skull 9.
In this example, the guide tube 7 is installed with an inclination of about 70 degrees with respect to the pile skull 9. However, when a hard synthetic resin material is used for the heat transfer medium pipe, the guide tube 7 can be inserted and removed if the inclination angle with respect to the pile head 9 is in the range of 45 degrees to less than 90 degrees. Since it was confirmed that there is a certain angle, any angle may be used.

The basic function of the guide tube 7 is to secure a passage for the heat medium pipe, and the material thereof is not limited. However, since the guide tube 7 is disposed in the foundation concrete 1, a cavity is provided in the foundation concrete 1, so that if this may become a structural weakness, a material such as steel that can secure the necessary strength is used. Good.
The guide tube 7 may be cut at the site and joined to the pile head 9, but may be cut into a necessary angle in advance and joined to the pile head 9 by welding or the like.

4). Basic Concrete The basic concrete 1 is constructed below the ground 13, and a structure 5 (specifically, a column or a wall) is installed on the upper part. The foundation concrete 1 includes various types such as a footing foundation, a cloth foundation, a solid foundation, and an underground beam.

Next, the method for constructing the structure of the pile head shown in FIG. 1 is shown in FIG. 1 and FIG. 3 showing the state during the insertion of the heat medium pipe, and the state when the insertion of the heat medium pipe is completed. 4 will be described.
(1) After the hollow ready-made pile 3 made of an 8-inch steel pipe is installed on the ground, the pile skull 9 is installed on the pile head. Here, a steel guide pipe 7 made of a 6-inch straight pipe was previously attached to the pile skull 9 at an angle of 70 degrees.
The guide tube 7 was cut at one end according to the installation angle. The outer diameter of the pile skull 9 was substantially equal to the outer diameter of the pile, and was joined to the pile by welding. The shape of the opening 11 provided in the pile skull 9 is elliptical as described above, and the outermost inner wall of the ellipse, that is, the outermost edge 11a of the opening and the pile inner wall 3a are flush with each other.

(2) Next, pile head reinforcing bars 17 and foundation concrete reinforcing bars 19 are arranged (see FIG. 3). In addition, although the system which fixes the pile head reinforcement bar 17 to a pile head outer peripheral surface by welding is shown in FIG. 3, the arrangement | positioning method of the pile head reinforcement bar 17 is not limited to this. Further, the arrangement of the foundation concrete reinforcing bars 19 is not limited to that shown in FIG.
(3) Next, a concrete form is placed for placing concrete.
(4) Further, the heat medium pipe 15 is inserted into the hollow portion of the hollow ready-made pile 3 through the guide pipe 7 (see FIGS. 3 and 4).
Note that a hard material having a certain degree of flexibility, such as a polyethylene pipe, is used for the piping material of the heat medium pipe 15.

FIG. 5 is an explanatory view illustrating the relationship between the insertion path and the heat medium pipe 15 when the heat medium pipe 15 is inserted into the hollow ready-made pile 3 via the guide pipe 7. In FIG. 5, in order to make the behavior of the heat medium pipe 15 remarkable, the inclination angle of the guide pipe 7 is smaller than those of FIGS.
As shown in FIG. 5, in the first stage of insertion, as shown in a in the figure, the heat medium pipe 15 is inserted into the hollow preformed pile 3 along the bottom of the guide pipe 7, and the heat medium pipe 15 The tip of the abutment comes into contact with the inner wall 3 a of the hollow preformed pile 3.
In the second stage, in order to further insert the heat medium pipe 15, the heat medium pipe 15 is lifted on the ground as shown by b in the figure. Thereby, the front-end | tip of the heat-medium piping 15 falls along the pile inner wall 3a.
In the third stage, the heat medium pipe 15 is further inserted. At this time, the opening outermost edge part 11a is strongly pressed as a fulcrum.

  As described above, when the heat medium pipe 15 is inserted, the front end portion of the heat medium pipe 15 passes through the outermost edge portion 11a of the opening. In this embodiment, this portion is flush with the pile inner wall 3a. The heat medium pipe 15 can be inserted smoothly.

(5) Both ends of the heat medium pipe 15 are connected to a heat pump installed on the ground, and heat exchange is performed with water filled in the hollow part of the hollow ready-made pile 3.
(6) When the heat medium pipe 15 needs to be taken out for maintenance, the heat medium pipe 15 is pulled out. In this case, the behavior of the heat medium pipe 15 is the reverse of that described with reference to FIG. Therefore, the tip of the heat medium pipe 15 passes through the opening outermost edge portion 11 a of the pile skull 9 in the latter half of the drawing.
However, as described above, in this embodiment, this portion is flush with the pile inner wall 3a, so that even if there is a step at the tip of the heat transfer pipe 15, it can pass smoothly without being caught. It has become.
When the heat medium pipe 15 is pulled out, if the circulating water in the heat medium pipe is pulled out and then pulled out, buoyancy can be used, so the work load is reduced.

  As described above, according to the present embodiment, when the heat medium pipe 15 is inserted and pulled out, the distal end portion of the heat medium pipe 15 is not caught by the opening 11 provided in the pile skull 9 and can be inserted smoothly. And can be pulled out.

  In the above embodiment, the example in which the portion of the opening 11 of the pile head 9 that is closest to the outer edge of the elliptical long axis is substantially flush with the inner wall 3a of the pile is shown. Is not limited to this, for example, as shown in FIGS. 6 and 7, even when the outermost edge 11a of the opening of the pile head 9 is located outside the inner wall 3a of the hollow preformed pile 3. Good.

[Embodiment 2]
FIG. 8 is an explanatory diagram of a structure of a pile head according to another embodiment of the present invention, and the same or corresponding parts as those in FIGS. 1 to 4 showing the first embodiment are denoted by the same reference numerals. It is.
In the present embodiment, a bent tube 21 in which two elbows having a bending angle of 90 degrees and a straight tube are combined is used as a guide tube. That is, as shown in FIG. 8, the bent pipe 21 of the present embodiment rises vertically from the pile head 9, bends in the horizontal direction, and further bends upward in the vertical direction.

  In the present embodiment, the opening 11 of the pile cranium 9 is formed such that the joint to be joined is close to the bending direction side of the first bending portion on the lid side of the tube 21, and the outermost edge of the opening 11a is made to be substantially flush with the pile inner wall 3a. Therefore, as shown in FIG. 8, the pile inner wall 3a, the opening outermost edge portion 11a, and the bent pipe inner wall are smoothly continuous.

FIG. 9 is an explanatory diagram for explaining the relationship between the insertion path and the heat medium pipe when the heat medium pipe is inserted in the present embodiment. As shown in FIG. 9, at the first stage of insertion, the tip of the heat medium pipe 15 comes into contact with the first bent portion of the bent pipe 21 as shown by a in the figure. By inclining the heat medium pipe 15 (b) and further pushing in, the tip of the heat medium pipe 15 comes into contact with the inner wall on the back side of the second bent portion (c). When further pushed in, the heat medium pipe 15 is bent with the second bent portion as a fulcrum, and the tip thereof is pressed against the pile inner wall 3a and inserted along the pile inner wall 3a.
At this time, the front end portion of the heat medium pipe 15 passes through the outermost edge portion 11a of the opening in the pile skull 9, but since there is no step in this portion, smooth insertion can be performed.

  Further, when the heat medium pipe 15 is pulled out, the operation is reverse to the above-described a to d, and the tip of the heat medium pipe 15 passes through the outermost edge portion 11 a of the opening in the pile skull 9. However, since this portion is flush, even if there is a step at the tip of the heat medium pipe 15, it can be pulled out smoothly without being caught.

  When a bent tube is used as the guide tube, the radius of the bent portion of the bent portion of the bent tube is set to 500 mm or more and the bent angle is 90 degrees in consideration of smooth operation of the heat medium pipe insertion and extraction. The following is preferable.

Further, in addition to the case where the straight pipe and the elbow are combined, as shown in FIG. 10, in the case of the bent pipe 23 having a bent portion in the middle of the pipe, the opening of the pile skull is set in the same manner as described above. The first outer bent portion 11a is provided close to the bending direction of the first bent portion so that the outermost edge portion 11a of the opening does not protrude to the inner side of the opening than the inner wall 3a of the pile in a state where the pile head 9 is installed on the pile head. Therefore, smooth insertion and withdrawal of the heat medium pipe can be realized.
In addition, although the example shown in FIG. 10 has shown what made the central angle of the bending part about 30 degree | times, if it is 90 degrees or less, it will not be limited to this, The arrangement | positioning of the reinforcing bar of the foundation concrete 1 The shape may be determined in consideration of the shape of the foundation concrete 1 and the workability during construction and maintenance.

[Embodiment 3]
FIG. 11 is an explanatory diagram of the third embodiment, and the same components as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals. FIG. 12 is an enlarged view of a circled portion A in FIG.
In the present embodiment, when a straight pipe is inclined as the guide pipe 7, the chamfering process is performed so that the path on the side where the guide pipe 7 is inclined in the path from the inner surface of the pile skull to the inner surface of the guide pipe is smooth. It is.

In this example, as shown in FIG. 12, a part 11b on the left side of the peripheral wall of the opening 11 in the figure is chamfered to have a smooth arc shape.
When the guide tube 7 is inserted into the opening 11 and attached, both the guide tube 7, the end, and a part of the peripheral wall of the opening 11 may be chamfered.

  According to the present embodiment, when the heat medium pipe inserted into the hollow preformed pile 3 is pulled out during maintenance, the tip of the heat medium pipe passes through the part 11b of the peripheral wall of the opening 11, but this part Is smoothly processed, so that even if a step is formed at the end of the heat medium pipe, smooth drawing can be performed without being caught.

[Embodiment 4]
FIG. 13 is an explanatory diagram of the fourth embodiment, and the same components as those in FIG. 10 shown as the modified example of the second embodiment are denoted by the same reference numerals. FIG. 14 is a partially enlarged view of FIG.
In the present embodiment, when a bent pipe is used as the guide pipe 23, the path from the inner surface of the pile skull to the inside of the guide pipe 23 is opposite to the bending direction of the first bent portion on the pile skull side of the guide pipe 23. Chamfered so that the side path is smooth.

  In the present embodiment, the guide tube 23 is bent at one place, and the “bending direction”, that is, the center side when the bending radius of the bent portion is viewed in plan is the right side in the figure. Therefore, the “opposite side to the bending direction” is the left side in the figure, and the path on the opposite side to the bending direction of the bent part is in the part circled in FIGS. 13 and 14. In the present embodiment, as in the third embodiment, a part 11b on the left side in the drawing on the peripheral wall of the opening 11 is chamfered into a smooth arc shape so that this path is smooth. .

In the present embodiment, the behavior when the heat medium pipe 15 is inserted is as indicated by a, b, and c in FIG. 13, and when the heat medium pipe 15 is pulled out, the behavior is reversed.
Therefore, when the heat medium pipe inserted into the hollow preformed pile 3 is pulled out during maintenance, the tip of the heat medium pipe passes through a part 11b of the peripheral wall of the opening 11, but this part is smooth. Since it is processed, even if a step is formed at the tip of the heat medium pipe, it can be pulled out smoothly without being caught.

DESCRIPTION OF SYMBOLS 1 Foundation concrete 3 Hollow preformed pile 3a Pile inner wall 5 Structure 7 Guide pipe 9 Pile head 11 Opening part 11a Opening outermost edge part 15 Heat transfer medium pipe 21 Curved pipe 23 Bending pipe

Claims (1)

A structure of a pile head of a hollow ready-made pile that uses the hollow ready-made pile as an underground heat exchanger by arranging a heat medium flow pipe in a hollow ready-made pile that is a foundation pile of a structure,
A pile cradle having an opening, and a guide pipe that is joined to the pile cranium so as to communicate with the opening and through which the heat medium flow pipe is inserted,
The guide pipe is formed of a bent pipe having a bent portion, and among the paths from the pile skull inner surface to the guide pipe, the path on the opposite side to the bending direction of the first bent portion on the pile skull side of the guide pipe is smooth. Pile head structure characterized by chamfering so as to become.

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