JP7570792B2 - Hybrid Rotary Pile Construction Method and Pile Construction Jig - Google Patents

Description

The present invention relates to a construction method for hybrid rotary piles and a pile construction tool used in said construction method, which prevents the joint between the lower pile and the upper pile from being adversely affected by excessive rotational force when a hybrid rotary pile, which has a lower pile body made of a steel pipe with wings on the outer periphery and an upper pile joined to the upper end of the lower pile, is rotated and pressed into the ground, and also makes it possible to easily correct any inclination of the pile that occurs during construction.

In the fields of architecture and civil engineering, temporary platforms are constructed prior to the start of the main construction work in order to secure work space for construction machinery and space for the temporary storage of construction materials (see Figures 11(a) and (b)). In these cases, H-shaped steel piles are generally used as the platform piles for the temporary platforms.

Also known as prefabricated steel piles are rotary piles (Patent Documents 1 and 2) that have one or more blades on the outer periphery of the tip support part of the pile body made of steel pipe, and rotary piles (Patent Document 3) that have a lower pile (rotary pile) with blades on the outer periphery of the tip support part and a steel pile such as an H-shaped steel pile joined to the upper end of the lower pile (rotary pile).

This type of rotary pile has blades that not only function as tunneling blades, but also act as resistance blades against the surrounding ground after construction. This means that even in intermediate layers that are shallower than the original supporting layer, a certain level of support can be ensured by the blades of the lower pile, allowing the pile length to be shortened. It also has the advantage of reducing the amount of waste soil that accompanies drilling, and demand is expected to grow in the future.

This type of rotary pile is set on the ground surface along the leader of a pile driver and then installed in the ground by rotating it with a reducer and pushing it into the ground. However, the latter type of rotary pile in particular has an issue in that the joint between the lower pile and the upper pile is easily adversely affected by excessive rotational force.

As a method for solving such problems, for example, Patent Document 3 discloses an invention for a steel pile installation device that includes a steel pile with an auger screw at the tip and an external steel pipe that fits around the steel pile and rotary-drills it into the ground.

Simply put, the steel pile is constructed such that the shaft of the auger screw and the web of the steel are integrated, and a tip support plate/rotation stabilizing plate that is inscribed in the outer steel pipe is fixed to the tip of the steel pipe, and a torque receiver is provided to engage with the outer steel pipe. Meanwhile, the outer steel pipe can be rotated at its upper part by a motor suspended from the crane of a work vehicle, and its lower part engages with the torque receiver to transmit the torque of the outer steel pipe to the auger screw for rotary excavation, and the rotation diameter of the auger screw is configured to be larger than the rotation diameter of the outer steel pipe.

Patent document 4 also discloses an invention for a connection structure between an excavation member that is used at the tip of a foundation pile and functions as the foundation of a building, and a pipe section that is connected to the upper end of the excavation member.

Simply put, the excavation member has a cylindrical base body with a closed lower end, a rotor blade on the outer circumferential surface of the base body that rotates around an axis together with the base body to excavate the soil, and a cylindrical protrusion on the outer circumferential surface of the base body that protrudes radially outward.

The tube section comprises a cylindrical tube body and an abutment section that protrudes downward from the lower end of the tube body, the abutment section being composed of a first extension section and a second extension section that intersect with each other to form an L-shape, and an abutment surface having a surface normal that faces diagonally upward is formed at the interior angle formed by the intersection of the two extension sections.

By abutting the protrusion against the contact surface and applying a contact force, the excavation member is pressed against the tubular body, eliminating any gaps at the joint between the excavation member and the tubular body, and preventing the inflow of soil and sand through these gaps.

JP 2016-079619 A JP 2015-129386 A Japanese Patent Application Laid-Open No. 6-272249 JP 2015-200092 A

However, in the invention of Patent Document 3, the torque of the motor is transmitted to the screw auger by a clutch mechanism, which can result in a structurally complex and expensive pile installation device.

In addition, the invention of Patent Document 4 has an L-shaped abutment portion that protrudes from the lower end of the pipe body, which is formed on only one side of the protrusion that protrudes from the outer circumferential surface of the base of the excavation member. This means that only the rotational force of the pipe body in one direction can be transmitted to the excavation member, and therefore there is a problem that the excavation member cannot be rotated freely in both forward and reverse directions.

The present invention has been made to solve these problems, and in particular aims to provide a construction method for a hybrid rotary pile that allows the hybrid rotary pile to be freely rotated in either the clockwise or counterclockwise direction and can also be pulled out, thereby enabling the hybrid rotary pile to be installed effortlessly and extremely efficiently at a specified depth, and a pile construction jig for use in said construction method.

The present invention is a construction method for a hybrid rotary pile, which comprises a lower pile having wings on the outer periphery of a lower pile body made of a steel pipe, and an upper pile formed from structural steel and joined to the upper end of the lower pile, and which involves pressing the hybrid rotary pile into the ground while rotating it.The present invention is characterized by using a pile construction jig which comprises a jig body formed in a cylindrical shape through which the upper pile can be inserted, and an engaging portion provided at the lower end of the jig body and which engages with an engaged portion provided on the outer periphery of the upper end of the lower pile, the engaging portions being vertically installed on both sides of the engaged portion along the outer periphery of the lower pile body, and which includes the following steps.
(1) A process of erecting the lower pile on the ground surface along the leader of a pile driver and connecting a reducer that moves up and down along the leader to the upper end of the lower pile.
(2) activating the reducer and rotating the lower pile by the reducer while pressing it into the ground along the leader.
(3) A process of temporarily stopping the reducer while leaving a portion of the upper end of the lower pile above ground, and disconnecting the reducer from the upper end of the lower pile.
(4) A process of attaching the pile construction jig, with the upper pile already installed, to the upper end of the lower pile along the leader of the pile driver, and joining the upper pile and the lower end of the pile construction jig to the upper end of the lower pile.
(5) A process of operating the reducer and rotating the lower pile via the pile construction jig while pressing the lower pile together with the upper pile into the ground.
(6) A process in which, after the lower pile and the upper pile are pressed into the supporting layer, only the pile construction jig is pulled out from the ground.

In particular, by vertically installing the engaging parts of the pile construction jig on both sides of the engaged part along the outer periphery of the lower pile body, the lower pile can be freely rotated in both clockwise and counterclockwise directions. In addition, by providing a hook (horizontal part) at the lower end of the engaging part that protrudes in an L-shape in the circumferential direction of the lower pile body along the outer periphery of the lower pile body, the lower pile can be pulled out via the pile construction jig, making it easy to excavate hard ground and easily correcting any inclination of the lower pile body that occurs during excavation. Furthermore, by rotating the lower pile, excessive rotational force can be avoided from acting on the joint between the lower pile and the upper pile.

In addition, by forming the jig body of the pile construction jig with an inner diameter that can circumscribe the upper end of the lower pile body and the engaged portion (capable of containing the upper end of the lower pile body and the engaged portion), and by providing the engaging portion on the inside of the jig body, the engaging portion can be easily engaged with the engaged portion of the upper end of the lower pile body.

In other words, when the lower end of the jig body is circumscribed around the upper end of the lower pile body and the engaged part, the pile construction jig is rotated around its axis, and the engaged part is automatically inserted between the engaging parts at a position where the engaged part and the gap w coincide.

When the engaged portion is inserted between the engaging portions, the lower end of the jig body is placed on the topmost wing attached to the upper end of the lower pile body, so that the pile construction jig can be held at the upper end of the lower pile body and will not fall below the lower pile body. Also, a stopper that receives the lower end of the jig body may be separately attached to the outer periphery of the upper end of the lower pile body.

In addition, since the engagement portion is stored within the jig body and does not protrude from the periphery or bottom end of the jig body, it does not become a resistance to the hole wall when the hybrid rotary pile is pressed into the ground, allowing the hybrid rotary pile to be pressed into the ground very efficiently. It also prevents damage to the engagement portion when the pile construction jig is installed, transported, or otherwise handled.

According to the present invention, when constructing a hybrid rotary pile consisting of a lower pile made of a steel pipe and an upper pile made of shaped steel such as an H-shaped steel joined to the upper end of the lower pile, the lower pile can be rotated and pressed into the ground without applying excessive rotational force to the joint between the lower pile and the upper pile.

In addition, the engaging parts at the bottom end of the pile construction jig are vertically installed along the outer periphery of the lower pile body on both sides of the engaged parts at the top end of the lower pile, allowing the lower pile to be freely rotated in both clockwise and counterclockwise directions. Also, a hook is provided at the bottom end of the engaging parts that protrudes in an L-shape along the outer periphery of the lower pile body from the underside of the engaged parts in the circumferential direction of the lower pile body, allowing the lower pile to be pulled out. This makes it easy to excavate hard ground and also makes it easy to correct any inclination of the pile that occurs during excavation.

FIG. 1 is a front view of a pile construction jig according to one embodiment of the present invention, which is used when installing a hybrid rotary pile made of a steel pipe and a shaped steel by rotary pressing into the ground. Figure (a) is an enlarged view of a portion of the hybrid rotary pile and the pile construction jig, and Figure (b) is a cross-sectional view along line I-I in Figure (a). FIG. 2 is a front view showing the state in which the lower end of the pile construction jig is engaged with the upper end of the lower pile of the hybrid rotary pile. 1 shows an example of a hybrid rotary pile, where FIG. 1(a) is a front view and FIG. 1(b) is an enlarged cross-sectional view of line R-R in FIG. 13 is another embodiment of the pile construction jig, in which FIG. 13(a) is a partially enlarged view of the hybrid rotary pile and the pile construction jig, and FIG. 13(b) is a cross-sectional view taken along line H-H in FIG. 13(a). FIG. 2 is a front view showing the state in which the lower end of the pile construction jig is engaged with the upper end of the lower pile of the hybrid rotary pile. 13 is another embodiment of the pile construction jig, in which FIG. 13(a) is a partially enlarged view of the hybrid rotary pile and the pile construction jig, and FIG. 13(b) is a cross-sectional view taken along line N-N in FIG. 13(a). FIG. 2 is a front view showing the state in which the lower end of the pile construction jig is engaged with the upper end of the lower pile of the hybrid rotary pile. FIG. 11 is another embodiment of the pile construction jig, in which FIG. 11(a) is a partially enlarged view of the hybrid rotary pile and the pile construction jig, and FIG. 11(b) is a cross-sectional view taken along line HO-HO in FIG. Figures (a) to (d) are explanatory diagrams showing the construction procedure of a hybrid rotary pile using a pile construction jig. This is a temporary platform that uses hybrid rotating piles as the platform piles, where Fig. 1(a) is a partial perspective view and Fig. 1(b) is a partial plan view.

Figure 1-9 shows one embodiment of the present invention, illustrating a hybrid rotary pile and a pile construction jig that transmits the rotational force of a reducer installed in a pile driver to the hybrid rotary pile when the hybrid rotary pile is rotated and pressed into the ground.

In the figure, the hybrid rotary pile 1 is formed from a lower pile 2 and an upper pile 3 joined to the upper end of the lower pile 2. The lower pile 2 has a lower pile body 4 made of a steel pipe and one or more blades 5 attached to the outer periphery of the lower pile body 4. An engaged portion 8 is formed on the outer periphery of the upper end of the lower pile body 4, which engages with an engaging portion 7 formed on the lower end of a pile construction jig 6 (described later).

The engaged portion 8 is formed from a vertically elongated rectangular steel piece, which is attached to the outer periphery of the upper end of the lower pile body 4 along the pipe axis direction of the lower pile body 4 by welding or by mounting bolts, and is also attached at equal intervals (for example, 45° or 90° intervals) around the circumference of the lower pile body 4.

The steel pieces serving as the engaged parts 8 are attached so that their upper end portions (e.g., the upper halves) protrude a certain length above the upper end surface of the lower pile body 4, and are attached facing each other in the diametric direction of the lower pile body 4.

The bolted steel pieces are removable, and steel pieces with optimal cross-sectional diameter and length are attached depending on the magnitude of the rotational force transmitted to the lower pile 2.

The blades 5 are attached at equal intervals, one at the tip of the lower pile body 4, and one or more above the tip. The blades 5 are attached in a disk shape that continues for one revolution around the circumference of the lower pile body 4, or in a spiral shape that continues for several revolutions around the circumference of the lower pile body 4.

Furthermore, the blades 5 are attached to the outer periphery of the lower pile body 4 by welding or by mounting bolts, and in particular the bolted blades 5 are removable, and by changing the outer diameter, number and/or spacing according to the bearing capacity of the stratum at the tip of the pile, a specified bearing capacity can be obtained even in an intermediate layer that is shallower than the original bearing layer.

The upper pile 3 is made of steel such as H-beam, I-beam or channel steel, or a cross-shaped steel, and is joined to the upper end of the lower pile body 4 by welding or by mounting bolts.

The upper piles 3 can be extended in length as needed by adding additional sections depending on the depth of the supporting layer. As the upper piles 3 are made of steel sections such as H-beams or cross-shaped steel, they can be easily joined to the lower piles 2 and to each other by welding or bolts using the flanges and/or webs of the upper piles 3. Furthermore, the upper piles 3 can be erected on the ground as temporary columns, and beams, braces, and other components can be easily joined using the flanges and/or webs as joints.

The pile construction jig 6 has a jig body 9 and multiple engagement parts 7 formed at the lower end of the jig body 9, and the jig body 9 is formed from a steel pipe with an outer diameter approximately the same as that of the lower pile body 4 of the lower pile 2 and an inner diameter through which the upper pile 3 can be inserted.

The engagement portion 7 is formed from a steel piece having a rectangular cross section and a vertically long L-shape, and the steel piece is attached to the outer peripheral surface of the lower end of the jig body 9 by welding or by mounting bolts, and is attached at a predetermined interval around the circumference of the jig body 9.

The lower end of each engaging portion 7 (e.g., the lower half) is attached so that it protrudes a certain length downward from the lower end surface of the jig body 9, and two engaging portions 7, 7 adjacent to each other in the circumferential direction of the jig body 9 form a pair, with one steel piece attached to each pair in an inverted L-shape.

Furthermore, the hooks (horizontal portions) 7a, 7a at the lower end are opposed to each other, and are attached so that there is a gap w between the opposed hooks 7a, 7a that is slightly wider than the width of the engaged portion 8.

Then, when the pile construction jig 6 is erected on the upper end of the lower pile 2, the engaged portions 8, 8 of the lower pile 2 are inserted between each pair of engaging portions 7, 7 through the gaps w between the hooks 7a, 7a.

In addition, with the engaged portion 8 inserted between each pair of engaging portions 7, 7, the pile construction jig 6 rotates around its axis, and at the same time, one of the engaging portions 7, 7 engages (abuts) with the engaged portion 8 in the circumferential direction of the pile construction jig 6, causing the lower pile 2 to rotate clockwise or counterclockwise together with the pile construction jig 6.

Furthermore, the engaged portion 8 is located on one side of the engaging portions 7,7, and the lower end portion 8a of the engaged portion 8 engages (abuts) with one of the hooks 7a of the engaging portions 7,7, so that the lower pile 2 is pulled up together with the pile construction jig 8.

With this configuration, with the engaged portion 8 inserted between the engaging portions 7, 7, the pile construction jig 6 can be rotated alternately clockwise and counterclockwise and raised and lowered, allowing the lower pile 2 to be rotated clockwise and counterclockwise and raised and lowered together with the pile construction jig 6. This allows the lower pile 2 to be rotated and pressed together with the upper pile 3 to a specified depth very efficiently without applying excessive rotational force to the joint between the lower pile 2 and the upper pile 3.

Figures 5 and 6 show another embodiment of the pile construction jig, in which each pair of engagement parts 7, 7 does not have a hook (horizontal part) 7a, 7a at the lower end, is formed with a rectangular cross section, and is formed into a simple columnar shape that continues along the axial direction of the lower pile 2, making it easy to manufacture.

In addition, if tapered surfaces 7b, 7b that diverge downward in an eight-shape are formed on the opposing surfaces of the lower ends of each pair of engaging parts 7, 7, the engaged part 8 of the lower pile 2 can be smoothly inserted between the engaging parts 7, 7 even if the gap w between the engaging parts 7, 7 is narrow.

Figures 7 and 8 also show another embodiment of the present invention, in which the jig body 9 of the pile construction jig 6 has an inner diameter that can circumscribe the upper end and engaged portion 8 of the lower pile body 4 of the lower pile 2, and the engaging portions 7, 7 are formed on the inner peripheral surface of the lower end of the jig body 9.

In addition, guide ribs 10 are attached between each of the circumferentially adjacent engagement parts 7, 7 of the jig body 9, except for the gap W. The guide ribs 10 are formed from steel pieces that form an arc along the inner circumferential surface of the jig body 9, and the steel pieces are attached at the same level as the hooks 7a, 7a of each engagement part 7, 7, and are attached horizontally along the inner circumferential surface of the jig body 9.

Figure 9 also illustrates another embodiment of the present invention, in which the jig body 9 of the pile construction jig 6 has an inner diameter that can circumscribe the lower pile body 4 and engaged portion 8 of the lower pile 2, and the engaging portions 7, 7 are formed on the inner peripheral surface of the lower end of the jig body 9. In addition, the engaging portion 7 does not have a hook 7a, and the engaging portion 7 is formed in a columnar shape in the axial direction of the lower pile body 4.

In addition, guide ribs 10 are attached between each of the circumferentially adjacent engagement parts 7, 7 of the jig body 9, except for the gaps W. The guide ribs 10 are attached at the same level as the lower ends of the engagement parts 7, 7, and are attached horizontally along the inner circumferential surface of the jig body 9.

In all of the embodiments shown in Figures 7 to 9, the engagement portions 7, 7 are attached inside the jig body 9 and do not protrude beyond the lower end of the jig body 9, so that the lower end of the pile construction jig 6 can be easily engaged with the upper end of the lower pile 2.

That is, by bringing the lower end of the jig body 9 into contact with the upper end of the lower pile body 4 and the engaged portion 8, and rotating the jig body 9 around its axis, the engaged portion 8 is inserted between the engaging portions 7, 7 at a position where the engaged portion 8 and the gap portion w are aligned.

When the lower end of the jig body 9 is in contact with the upper end of the lower pile body 4 and the engaged part 8, the hook (horizontal part) 7a of the engaging part 7 and the guide rib 10 come into contact with the upper end of the engaged part 8 from above and below, preventing the jig body 9 from falling. Therefore, the pile construction jig 6 can be freely rotated around its axis at the upper end of the lower pile body 4.

In addition, when the engaged portion 8 is inserted between the engaging portions 7, 7, the lower end of the jig body 9 is placed on the blade 5 attached to the upper end of the lower pile body 4, so that the pile construction jig 6 does not fall any further. A stopper (not shown) that receives the lower end of the jig body 9 may be separately attached to the outer periphery of the upper end of the lower pile body 4.

In addition, the engagement parts 7,7 are stored within the jig body 9 and do not protrude from the lower end of the jig body 9, so damage to the engagement parts 7,7 can be prevented when handling the pile construction jig 6.

The pile construction jig 6 thus formed is connected to the reducer 12 of the pile driver 11, and is rotated by the reducer 12 while ascending and descending along the leader 13 together with the reducer 12 (see Figure 10).

Next, a method for constructing a hybrid rotary pile using the pile driving jig 6 of the present invention will be described (see Figs. 10(a) to (d)).
(1) First, the lower pile 2 is set vertically on the ground surface along the leader 13 of the pile driver 11, and the reducer 12 is connected to the upper end of the lower pile 2.
(2) Next, the reducer 12 is operated, and the lower pile 2 is rotated by the reducer 12 while being pressed into the ground along the leader 13. Then, the reducer 12 is stopped temporarily with the upper end of the lower pile 2 remaining partially above ground, and the reducer 12 is temporarily disconnected from the upper end of the lower pile 2.
(3) Next, the pile construction jig 6, into which the upper pile 3 has been inserted beforehand, is vertically attached to the upper end of the lower pile 2 along the leader 13. Then, the lower end of the upper pile 3 is joined to the upper end of the lower pile 2, and the lower end of the pile construction jig 6 is engaged with the upper end of the lower pile 2.
In this case, the pile construction jig 6 is erected on the upper end of the lower pile 2, and at the same time, the engaged portion 8 of the lower pile 2 is inserted between the engaging portions 7, 7 of the pile construction jig 6 through the gap w between the hooks 7a, 7a, so that the lower end of the pile construction jig 6 is engaged with the upper end of the lower pile 2. The lower end of the upper pile 3 may be joined to the upper end of the lower pile body 4 of the lower pile 2 by welding or by a joining plate and a joining bolt.
In addition, the upper pile 3 may be first set up on the upper end of the lower pile 2 , and then the pile construction jig 6 may be placed over the upper pile 3 and its lower end engaged with the upper end of the lower pile 2 .

(4) Next, the reducer 12 is operated again, and the lower pile 2 is rotated together with the pile construction jig 6 while being pressed into the ground together with the upper pile 3. During the construction of the lower pile 2, if the lower pile 2 hits a hard stratum and cannot be pressed in smoothly, or if the lower pile 2 is tilted at an angle, the pile construction jig 6 can be rotated together with the lower pile 2 several times clockwise and counterclockwise, or raised and lowered while rotating forward and backward, thereby enabling the lower pile 2 to be pressed in smoothly and the tilt of the lower pile 2 to be easily corrected.
(5) Then, once the lower pile 2 and the upper pile 3 have been installed in the specified stratum, only the pile construction jig 6 is detached from the upper end of the lower pile 2 and pulled out from the ground, completing the construction of the hybrid rotary pile 1.

The present invention allows a hybrid rotary pile consisting of a lower pile with wings on the outer periphery of the lower pile body made of steel pipe, and an upper pile formed from structural steel and joined to the upper end of the lower pile, to be rotary-driven into the ground extremely efficiently without applying excessive rotational force to the joint between the lower pile and the upper pile, and also allows easy correction of any inclination of the hybrid rotary pile that occurs during construction.

Reference Signs List 1 Hybrid rotary pile 2 Lower pile 3 Upper pile 4 Lower pile body 5 Wing 6 Pile construction jig 7 Engagement part
7a Hook (horizontal part)
7b Taper 8 Engaged part
8a Lower end 9 Jig body
10 Guide rib
11 Pile driver
12 Gearbox
13 Leader gap

Claims (4)

A construction method for a hybrid rotary pile, which comprises a lower pile having wings on the outer periphery of a lower pile body made of a steel pipe, and an upper pile formed of a shaped steel and joined to the upper end of the lower pile, and which presses the hybrid rotary pile into the ground while rotating it, the construction method for a hybrid rotary pile comprising: a jig body formed in a cylindrical shape through which the upper pile can be inserted; and an engagement portion provided at the lower end of the jig body , the engagement portion having an engagement portion provided in a columnar shape along the axial direction of the lower pile body on the upper outer periphery of the lower end of the lower pile body, the engagement portion being vertically arranged in a columnar shape along the axial direction of the lower pile body, the lower end of the engagement portion being provided with an L-shaped hook that protrudes in a circumferential direction of the lower pile body along the outer periphery of the lower pile body, and the engagement portion is arranged so as to be engageable between the engagement portions through a gap provided between the tip ends of the hooks.
(1) A process of erecting the lower pile on the ground surface along the leader of a pile driver and connecting a reducer that moves up and down along the leader to the upper end of the lower pile.
(2) activating the reducer and rotating the lower pile by the reducer while pressing the lower pile into the ground along the leader.
(3) A process of temporarily stopping the reducer while leaving a portion of the upper end of the lower pile above ground, and then disconnecting the reducer from the upper end of the lower pile.
(4) A process of attaching the pile construction jig, into which the upper pile has already been installed, to the upper end of the lower pile along the leader .
(5) A step of joining the lower end of the upper pile to the upper end of the lower pile.
(6) A process of engaging the engaging portions of the pile construction jig with both sides of the engaged portion of the upper end portion of the lower pile.
(7) A process of operating the reducer to rotate the lower pile via the pile construction jig while pressing the lower pile together with the upper pile into the ground.
(8) A process of pulling out only the pile construction jig from the ground after the lower pile and the upper pile are pressed into the supporting layer. 2. The method for constructing a hybrid rotary pile according to claim 1, further comprising a step of raising and lowering the pile construction jig together with the lower pile and the upper pile while rotating them forward and backward during construction. A pile construction jig used to press a hybrid rotary pile, which consists of a lower pile having wings on the outer periphery of a lower pile body made of a steel pipe, and an upper pile formed of a structural steel and joined to the upper end of the lower pile, into the ground while rotating it, characterized in that the pile construction jig has a jig body formed in a cylindrical shape into which the upper pile can be inserted, and an engaging portion provided at the lower end of the jig body and engaging both sides of an engaged portion provided in a columnar shape along the axial direction of the lower pile body on the upper outer periphery of the lower end of the lower pile body, the engaging portion being vertically provided in a columnar shape along the axial direction of the lower pile body, and the lower end side of the engaged portion is provided along the outer periphery of the lower pile body in an opposing circumferential direction of the lower pile body, and the engaged portion is provided so as to be engageable between the engaging portions through a gap provided between the tip ends of the hooks . 4. The pile construction jig according to claim 3, wherein the jig body has an inner diameter capable of circumscribing the upper end portion of the lower pile body and the engaged portion, and the engaging portion and the L-shaped hook are provided on the inner side of the jig body.

Images