JP7499062B2 - Prefabricated piles and their construction method - Google Patents

Description

The present invention relates to prefabricated piles used in preboring construction methods and their construction methods.

Various prefabricated piles have been developed, in which a hole of a specified depth is first drilled using an auger attached to a pile driver, and then the hole is filled with a hardening grout such as cement milk, and then the prefabricated pile is set in place. Also, various pre-boring methods have been developed, in which the prefabricated pile is set in place by erecting it in the hole.

In this pre-boring method, when erecting a prefabricated pile in a borehole, the rotational force of a rotation mechanism installed in a pile driver or similar device must be transmitted to the prefabricated pile to rotate it while pressing it in, and then it must be sunk to a specified depth and set in place. For this reason, the head of the prefabricated pile is often provided with an engaging metal fitting.

For example, at the head of the pile, a horizontally elongated, roughly rectangular steel engaging fitting (engaging claws) called a "yokan" protrudes from the outer surface and is fixed by welding in multiple places circumferentially.A rotating cap that transmits the rotational force of the rotation mechanism is engaged with this engaging fitting , and the prefabricated pile is fixed to the ground by transmitting the rotational force while being lifted.

However, when the above-mentioned engaging fittings are fixed to the end plate of the pile head by welding, the engaging fittings protrude above the pile head. Therefore, when connecting a prefabricated pile to a structure such as a pillar located above it after it has been fixed into the ground, it may be necessary to remove the engaging fittings by gas cutting or the like. The removal work of such engaging fittings takes a long time, which places a heavy burden on on-site workers and is also a factor in increasing costs.

In addition, recent advances in pile head joining technology after the installation of prefabricated piles and the development of semi-fixed pile head joining methods have created a need to keep the top surface of the pile head end plate as flat as possible, making it undesirable to fix engaging fittings to the pile head end plate.

In order to simplify the removal of such engaging fittings and to accommodate semi-fixed connection methods for the pile head, a method has been proposed in which a ring-shaped fitting 35 with a claw 34 and an outer diameter the same as the concrete pile 32 to be used is attached to an end plate 33 at the head of the concrete pile 32 by fastening it with a bolt 36, and then removed after the concrete pile 32 is installed (Patent Document 1).

Also, a prefabricated hollow foundation pile 1 and a pile rotation cap 7 have been proposed, which are provided with multiple engaging claws 4 on the underside of an end plate 2 installed on the pile head of the prefabricated hollow foundation pile 1, with the tips of the engaging claws 4 protruding into the hollow part 3 of the pile, and the engaging claws 4 can be engaged with a special pile rotation cap 7 connected to the rotating shaft of the rotation mechanism to perform the sinking work (Patent Document 2).

JP 2001-131966 A Utility Model Registration No. 3156454

However, although the task of fixing the metal fitting 35 with the bolt 36 using the screw hole provided in the end plate 33 at the head of the concrete pile 32 is extremely simple, if the concrete pile 32 is long and has a large diameter, a large load is placed on the bolt 36 and the screw hole, which creates the risk of the end plate 33 deforming near the screw hole and causing the bolt to come loose, resulting in the risk of the metal fitting 35 falling off the end plate 33. In addition, there is a problem in that the engagement claws 4 that protrude into the pile hollow portion 3 of the prefabricated hollow foundation pile 1 make it difficult to attach and detach the pile rotation cap 7 when the internal cross-sectional area of the pile hollow portion 3 of the hollow foundation pile 1 is small.

In consideration of the above problems, the present invention provides a prefabricated pile and its construction method that does not require a special pile rotation cap when lifting and setting into a borehole, regardless of the pile diameter, making it easy to install in the ground, reducing the load on the end plate and preventing deformation or damage to the end plate, and allowing it to be lifted in a safe manner.

In order to achieve the above object, the invention according to claim 1 of the present application is a prefabricated pile having a main body, a substantially annular end plate provided at an upper end thereof, and a plurality of locking members provided on the main body, wherein the main body has a base portion at a lower end and a small diameter portion at an upper end thereof, the small diameter portion having a substantially cylindrical side plate, the end plate having an upper flange portion and a lower body portion, the locking members being substantially columnar members curved toward their inner circumferential surface, and having bolt holes passing through from the outer circumferential surface to the inner circumferential surface, and a taper portion formed by connecting an upper end of the small diameter portion of the main body and a lower end of the body portion of the end plate, the bolt being inserted into the bolt hole of the locking member and screwed into a screw hole formed in the side plate to fasten the locking member to the flange portion of the end plate, and the locking member being removably attached to the side plate in a state in which the locking member is in contact with the flange portion of the end plate and protrudes from the outer circumferential surface of the base of the main body and can be engaged with the locking groove portion of a pile rotation cap .

In addition, the invention of claim 2 of the present application is characterized in that the end plate has an end plate tapered portion that narrows in diameter from the lower end of the flange portion to the upper end of the body, and in the narrowing portion formed by connecting the upper end of the small diameter portion of the main body and the lower end of the body of the end plate, a bolt is inserted into the bolt hole of the locking member and screwed into the screw hole formed in the side plate to fasten the locking member, so that the locking member contacts the end plate tapered portion and protrudes from the outer peripheral surface of the base of the main body and is removably attached to the side plate in a state in which it can engage with the locking groove portion of the pile rotation cap .

Furthermore, the invention of claim 3 of the present application is characterized in that the end plate has an end plate curved portion that narrows in diameter from the lower end of the flange portion to the upper end of the body, and in the narrowing portion formed by connecting the upper end of the small diameter portion of the main body and the lower end of the body of the end plate, a bolt is inserted into the bolt hole of the locking member and screwed into the screw hole formed in the side plate to fasten the locking member, so that the locking member contacts the end plate curved portion and protrudes from the outer peripheral surface of the base of the main body and is removably attached to the side plate in a state in which it can engage with the locking groove portion of the pile rotation cap .

The invention according to claim 4 of the present application is characterized in that a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the locking member, and a concave portion that can fit into the convex portion is formed on the other.

The invention according to claim 5 of the present application is characterized in that a reinforcing band is provided from near the upper end of the outer circumferential surface of the base portion of the main body to the lower end of the outer circumferential surface of the side plate in the small diameter portion.

The invention according to claim 6 of the present application is characterized in that an anchor portion is provided on at least one of the surfaces of the end plate, the side plate, and the reinforcing band that contact the concrete portion of the main body.

The invention of claim 7 of the present application is characterized in that, in the narrowed portion of the prefabricated pile described in claims 1 to 6, instead of the multiple engaging members, a roughly band-shaped member that is curved toward the inner surface and can fit into the narrowed portion, and a plurality of divided plates each having bolt holes that pass through from the outer surface to the inner surface are attached to the side plate by inserting bolts into the bolt holes and screwing them into screw holes formed in the side plate to fasten them, thereby covering the entire circumferential direction of the narrowed portion.

The invention according to claim 8 of the present application is characterized in that a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the divided plate, and a concave portion that can fit into the convex portion is formed on the other.

The invention according to claim 9 of the present application is a construction method for a prefabricated pile according to any one of claims 1 to 6, comprising the steps of: forming a borehole in the ground; inserting the head of the prefabricated pile into a tubular portion of a pile rotation cap and lifting it by engaging the locking member with a locking groove portion formed in the tubular portion; fixing the prefabricated pile in the borehole by rotary pressing; releasing the locking between the locking groove portion and the locking member and extracting the head of the prefabricated pile from the tubular portion; and removing the locking member from the side plate of the prefabricated pile.

In addition, the invention of claim 10 of the present application is characterized in that after the step of removing the engaging member from the side plate of the prefabricated pile , it includes a step of attaching a plurality of divided plates that can fit into the constriction portion to the side plate so as to cover the entire circumferential direction of the constriction portion of the prefabricated pile.

From the above, according to the inventions of claims 1 to 3, since the locking member protrudes from the outer peripheral surface of the base of the main body, a pile rotation cap that is generally used for fixing the pile to the ground can be used, and the work of fixing the pile to the ground is easy. Also, since the locking member is attached to the side plate in contact with the end plate, when the prefabricated pile is lifted by the pile rotation cap , the entire weight of the pile can be distributed and supported by the end plate and the screw hole in the side plate of the small diameter part of the main body into which the bolt is screwed. This reduces the load on the end plate and prevents deformation or damage to the end plate, and also reduces the load on the PC steel material connected to the end plate. Therefore, the prefabricated pile can be lifted safely.

In addition, the locking members can be easily removed from the side plates even after the prefabricated pile has been fixed into the ground. By removing the locking members, the work of connecting the head of the prefabricated pile to the footing or other structure located above it can be simplified, shortening the work time, and the removed locking members can be reused for other prefabricated piles.

In addition, according to the inventions of claims 2 and 3, by providing a tapered portion or a curved surface portion of the end plate, the strength of the flange portion of the end plate, which is subjected to a large load, can be increased, so that deformation and damage to the end plate can be more reliably prevented.

According to the invention of claim 4, a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the locking member, and a concave portion that can fit into the convex portion is formed on the other, so that alignment is easy when attaching the locking member to the side plate to form a prefabricated pile. Furthermore, when the prefabricated pile is hoisted by the pile rotating cap , the entire weight can be distributed and supported by the convex portion or the concave portion, so that the load on the end plate can be further reduced, and deformation and damage to the end plate can be prevented, and the load on the PC steel material connected to the end plate can also be further reduced.

In addition, according to the invention of claim 5, the structure is such that the area from near the upper end of the outer peripheral surface of the base of the main body to the lower end of the outer peripheral surface of the side plate at the small diameter section is covered with a reinforcing band, which improves the bending and shear resistance of the prefabricated pile and prevents the concrete part of the main body from being damaged by the locking members and the dividing plates described below when they are attached to the side plates.

In addition, according to the invention of claim 6, the structure has an anchor portion provided on the surface of the end plate, etc. that contacts the concrete portion of the main body, so the integrity of the concrete portion of the main body with the end plate, side plate, and reinforcing band is stronger. Therefore, when a prefabricated pile is lifted with the pile rotation cap, even if a load is applied to the end plate, side plate, etc., these components will not separate, and the pile can be lifted in a safer condition.

In addition, according to the invention of claim 7, the entire circumference of the squeezed portion of the precast pile is covered by multiple divided plates that can fit into the squeezed portion, which prevents a decrease in bending and shear strength due to cross-sectional loss in the squeezed portion of the precast pile.

In addition, according to the invention of claim 8, a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the split plate, and a concave portion that can fit into the convex portion is formed on the other, making it easy to align the split plate when attaching it to the side plate to form the prefabricated pile.

Furthermore, according to the invention of claim 9, the precast pile of the present invention can be safely and easily fixed into the ground.

Furthermore, according to the invention as defined in claim 10, it is possible to easily carry out work to prevent a decrease in bending and shear strength due to cross-sectional loss in the tapered portion of the precast pile according to the present invention that has been fixed into the ground.

FIG. 2 is a perspective view of a pile head of a precast concrete pile to which a locking member according to the first embodiment is attached. 1A is an exploded plan view, FIG. 1B is an assembled plan view, and FIG. 1C is an assembled front view of a precast concrete pile to which a locking member according to a first embodiment is attached. FIG. 3 is an enlarged cross-sectional view of a portion taken along line II in FIG. 1A is an exploded plan view, FIG. 1B is an assembled plan view, and FIG. 1C is an assembled front view of a precast concrete pile to which a divided plate according to a first embodiment is attached. 5 is an enlarged cross-sectional view of the part taken along line II-II of FIG. 4(b). 1 is a diagram showing a state in which the pile head of a precast concrete pile to which the locking member of the first embodiment is attached is being locked to the pile rotation cap. FIG. FIG. 2 is a diagram showing a state in which a precast concrete pile to which a locking member according to the first embodiment is attached is fixed to the ground. 8 is a view showing a state in which the locking member has been removed from the side plate from the state shown in FIG. 7 . FIG. 9 is a diagram showing a state in which the divided plates are attached to the side plates from the state shown in FIG. 8 . FIG. 11 is an assembled front view of a precast concrete pile to which a locking member according to a second embodiment is attached. FIG. 11 is an enlarged cross-sectional view taken along the line III-III in FIG. FIG. 11 is a front view of an assembled precast concrete pile to which the divided plates according to the second embodiment are attached. 13 is an enlarged cross-sectional view taken along line IV-IV of FIG. 12. FIG. 11 is an assembled front view of a precast concrete pile to which a locking member according to a third embodiment is attached. FIG. 15 is an enlarged cross-sectional view taken along the line VV in FIG. 14 . FIG. 11 is a front view of an assembled precast concrete pile to which the divided plates according to the third embodiment are attached. 17 is an enlarged cross-sectional view taken along the line VI-VI in FIG. 16 .

The present invention will be described in detail below according to the embodiment shown in Fig. 1 to Fig. 17, but the present invention is not limited thereto. The same components in each figure are given the same reference numerals, and the description thereof will be omitted. In Fig. 1 to Fig. 17, the figures of the PC steel material and the deformed steel bar embedded in the concrete part 2e of the main body 2 of the precast concrete piles 1, 1A, and 1B are omitted unless otherwise specified. First, the first embodiment according to the present invention will be described. In Fig. 1 to Fig. 9, 1 is a hollow precast concrete pile according to the present invention, and this precast concrete pile 1 has a main body 2, an end plate 3, a side plate 4, a locking member 5, a reinforcing band 6, and an anchor part 10.

1 to 3 , the main body 2 is a generally cylindrical member having a hollow portion 2a at the center and extending long in the axial direction. A base portion 2b having a long vertical length is formed at the lower end of the main body 2, and a small diameter portion 2c having an outer diameter smaller than that of the base portion 2b and a short vertical length is formed near the upper end of the main body 2. A main body tapered portion 2d is formed, the diameter of which decreases from the upper end of the base portion 2b to the lower end of the small diameter portion 2c.

As shown in Figures 2(a)-(c) and 3, a generally cylindrical side plate 4 made of steel and having a low height and thickness is embedded in the upper end of the small diameter portion 2c of the main body 2, and the side plate 4 is exposed on the outer circumferential surface of the small diameter portion 2c. This side plate 4 is formed with a screw hole 4a for fixing the locking member 5. Two screw holes 4a are formed at approximately the center position in the vertical direction of the outer circumferential surface of the side plate 4, with a small gap between them in the circumferential direction. In addition, three sets of screw holes 4a (six in total in this embodiment) are formed at equal intervals in the circumferential direction of the outer circumferential surface of the side plate 4, with the two screw holes 4a, 4a forming one set.

Also, a key hole 4b is formed in a generally rectangular parallelepiped recess at a position above the approximate center in the vertical direction on the outer peripheral surface of the side plate 4, and at approximately the center in the circumferential direction between each of the three sets of screw holes 4a, 4a of the side plate 4 (three locations in this embodiment).

A thin steel reinforcing band 6 is provided that covers the outer periphery of the concrete portion 2e of the main body 2, from near the upper end of the outer periphery of the base 2b of the main body 2, through the outer periphery of the main body tapered portion 2d, to the lower end of the outer periphery of the side plate 4 in the small diameter portion 2c. In the small diameter portion 2c, the upper end of the reinforcing band 6 is fixed so as to overlap the lower end of the side plate 4, and is formed so that the outer periphery of the upper end of the reinforcing band 6 and the outer periphery of the side plate 4 are flush with each other. In addition, in the base 2b, the outer periphery of the lower end of the reinforcing band 6 and the outer periphery of the concrete portion 2e, which is made of concrete, are formed so that they are flush with each other.

This reinforcing band 6 improves the bending and shear strength of the pile head of the precast concrete pile 1, and also prevents damage to the concrete portion 2e of the main body 2 when fixing the locking member 5 and the dividing plate 11 (described later) to the side plate 4.

As shown in Figs. 2(a)-(c) and 3, a side plate 4 located at the upper end of the small diameter portion 2c of the main body 2 is connected to an end plate 3 made of steel and having a substantially circular thickness. The end plate 3 has a hollow portion 3a with a substantially identical inner diameter to the hollow portion 2a of the main body 2, a body portion 3b with a substantially identical outer diameter to the small diameter portion 2c of the main body 2 at the bottom, and a flange portion 3c with a substantially identical outer diameter to the base portion 2b of the main body 2 at the top. In addition, an end plate tapered portion 3d is formed, the diameter of which decreases from the bottom end of the flange portion 3c to the top end of the body portion 3b. The bottom end of the body portion 3b of the end plate 3 and the top end of the small diameter portion 2c of the main body 2 are connected to each other as a single unit.

By connecting the main body 2 and the end plate 3 in this manner, a constriction portion 8, which is a depression with a roughly trapezoidal cross section, is formed near the upper end of the concrete precast pile 1 by the end plate tapered portion 3d and the body portion 3b of the end plate 3 and the small diameter portion 2c and the main body tapered portion 2d of the main body 2.

In addition, the end plate 3 that forms the tapered portion 8, the side plate 4 of the small diameter portion 2c of the main body 2, and the reinforcing band 6 that runs from the small diameter portion 2c through the main body tapered portion 2d and covers the upper end of the base 2b are all made of steel, so the outer periphery of the tapered portion 8 is entirely made of steel and has high strength.

As shown in Figures 2(a) to 2(c) and 3, three steel locking members 5, which are generally columnar members with a generally hexagonal cross section and which extend in the circumferential direction (left and right direction) of the main body 2 while curving toward the inner peripheral surface 5a, are fixed at the position of the drawn portion 8 at equal intervals in the circumferential direction. The locking members 5 have a cross section on the inner peripheral surface 5a that is generally the same in shape and size as the cross section of the drawn portion 8, and the curvatures of the upper inclined surface 5b, the inner peripheral surface 5a, and the lower inclined surface 5c of the locking members 5 are equal to those of the outer peripheral surface of the end plate tapered portion 3d of the end plate 3, the outer peripheral surface of the trunk portion 3b of the end plate 3, the outer peripheral surface of the small diameter portion 2c of the main body 2, and the outer peripheral surface of the main body tapered portion 2d of the main body 2. Therefore, the upper inclined surface 5b, the inner peripheral surface 5a, and the lower inclined surface 5c of the locking members 5 are in close contact with the drawn portion 8 and are fixed to the side plate 4 in a state of just fitting. At this time, the locking member 5 is in a state in which it largely protrudes outwardly and substantially perpendicularly to the outer circumferential surface of the base portion 2b of the main body 2 (protruding largely from the narrowed portion 8).

Two bolt holes 5e, 5e penetrating from the inner peripheral surface 5a to the outer peripheral surface 5d are formed in the locking member 5 at approximately the center in the vertical direction of the locking member 5, spaced apart in the left-right direction. When the locking member 5 is fitted into the tapered portion 8, the position where the bolt hole 5e is formed in the inner peripheral surface 5a corresponds to the position where the screw hole 4a is formed in the outer peripheral surface of the side plate 4. Therefore, the locking member 5 is fixed to the side plate 4 by screwing and fastening the bolt 9 inserted into the bolt hole 5e from the outer peripheral surface 5d side of the locking member 5 into the screw hole 4a of the side plate 4.

Furthermore, on the inner surface 5a of the locking member 5, at a position approximately in the center between two bolt holes 5e, 5e formed at a short distance apart in the left-right direction of the locking member 5, and at a position corresponding to the position where the keyhole 4b is formed on the outer surface of the side plate 4 when the locking member 5 is fitted into the narrowed portion 8 as described above and fixed by the bolt 9, there is provided a substantially rectangular prism 5f of approximately the same size as the keyhole 4b, so that the keyhole 4b and the protrusion 5f can fit together.

With the above structure, when fixing the locking member 5 to the side plate 4 during the process of manufacturing the precast concrete pile 1, the position of the key hole 4b of the side plate 4 is aligned with the position of the protrusion 5f of the locking member 5, and the inner surface 5a of the locking member 5 is fitted into the convex portion 8, thereby determining the fixed position of the locking member 5 on the side plate 4, making it easy to align the locking member 5.

In addition, as described above, the outer peripheral surface of the constriction portion 8 has a high-strength structure, which prevents damage to the constriction portion 8 when the steel locking member 5 and the dividing plate 11 described later are fitted into the constriction portion 8.

In addition, after the locking member 5 is fixed, it protrudes significantly outward, approximately perpendicular to the outer peripheral surface of the base 2b of the main body 2, and the pile rotation cap 20 (described below), which is commonly used in the fixing of precast concrete piles 1, can be used, making the fixing work easy.

As will be described later, when the precast concrete pile 1 is lifted using the pile rotation cap 20, the entire weight of the precast concrete pile 1 can be distributed and supported by the screw holes 4a, key holes 4b, and end plate tapered portion 3d of the side plate 4 of the main body 2 via the locking members 5 and bolts 9. Therefore, when the precast concrete pile 1 is lifted, the load on the end plate 3 can be reduced, preventing deformation and damage to the end plate 3, and also reducing the load on the PC steel members and the like connected to the end plate 3. This makes it possible to lift the precast concrete pile 1 in a safe state.

The locking member 5 can be easily attached to and detached from the side plate 4, and the structure allows the locking member 5 to be easily removed from the side plate 4 even after the precast concrete pile 1 has been fixed to the ground 100. Therefore, after removing the locking member 5, the work of connecting the head of the precast concrete pile 1 fixed to the ground 100 to a structure such as a footing installed above it can be simplified and the work time can be reduced.

In addition, the removed retaining member 5 can be used when manufacturing a new precast concrete pile 1, which can reduce the manufacturing costs of the precast concrete pile 1.

As shown in Figure 3, in the main body 2 and end plate 3, anchor parts 10, which are annular reinforcing bars extending in the circumferential direction of the main body 2, are fixed by welding to the respective surfaces of the end plate 3, side plate 4, and reinforcing band 6 that come into contact with the concrete part 2e of the main body 2, and all of these anchor parts 10 are embedded in the concrete part 2e of the main body 2.

The anchor parts 10 may be fixed at any position on the end plate 3, etc., as long as the position is on the surface that contacts the concrete part 2e and allows the anchor parts 10 to be embedded in the concrete part 2e.

Therefore, the anchor portion 10 strengthens the connection between the concrete portion 2e of the main body 2 and the end plate 3, side plate 4, and reinforcing band 6, and the unity between the concrete portion 2e of the main body 2 and the end plate 3, side plate 4, and reinforcing band 6 is further strengthened, ensuring unity. When the precast concrete pile 1 is lifted using the pile rotation cap 20, even if a large load is applied to the end plate 3, side plate 4, and reinforcing band 6, these components will not separate, making it possible to lift the pile in a safer condition.

In this embodiment, the locking members 5 are installed at three locations at equal intervals in the circumferential direction of the side plate 4, but it is acceptable to install multiple locking members 5 at two locations or four or more locations.

In this embodiment, the locking member 5 is a generally columnar member having a cross-section on its inner peripheral surface 5a that is generally the same size and shape as the cross-section of the narrowed portion 8, but it does not necessarily have to have a cross-section that is generally the same size and shape as the cross-section of the narrowed portion 8. It is sufficient that the locking member 5 is a generally columnar member having a cross-sectional shape that has a surface that contacts the outer peripheral surface of the end plate tapered portion 3d of the end plate 3 and the outer peripheral surface of the small diameter portion 2c of the main body 2 (side plate 4 or reinforcing band 6) when fixed to the side plate 4.

Therefore, the size of the cross section of the locking member 5 on the inner peripheral surface 5a side in the vertical direction may be smaller than the size of the cross section of the narrowed portion 8, and the locking member 5 may have a cross-sectional shape that does not contact the outer peripheral surface of the main body tapered portion 2d when fixed to the side plate 4.

In addition, the cross-sectional shape of the portion of the locking member 5 that protrudes from the outer peripheral surface of the base 2b of the main body 2 (protruding from the constriction portion 8) is approximately rectangular in this embodiment as shown in FIG. 3, but it does not necessarily have to be approximately rectangular as long as it has a size (cross-sectional area) that does not deform even when a load is applied when lifting the precast concrete pile 1 and protrudes from the outer peripheral surface of the base 2b of the main body 2 to an extent that it can be engaged with the locking groove portion 24 of the pile rotation cap 20 used when lifting. Therefore, the cross-sectional shape of the protruding portion may be a polygonal shape such as a trapezoid or a triangle.

In addition, in this embodiment, a keyhole 4b which is a recess is formed on the outer peripheral surface of the side plate 4, and a convex portion 5f which can fit into the keyhole 4b is formed on the inner peripheral surface 5a of the locking member 5, but it is also possible for the side plate 4 to be formed with a convex portion and the locking member 5 to be formed with a keyhole which is a recess.

The key hole 4b and the protrusion 5f are generally rectangular, but may be cylindrical or polygonal, such as triangular or pentagonal.

In addition, in this embodiment, the anchor portion 10 is fixed to all of the end plate 3, side plate 4, and reinforcing band 6 by welding, but the structure may be such that the anchor portion 10 is fixed to at least one of the end plate 3, side plate 4, and reinforcing band 6.

In addition, a single annular rebar is fixed to the end plate 3 as the anchor part 10, but as long as the adhesive force between the concrete part 2e of the main body 2 and the anchor part 10 (the bearing pressure acting on the anchor part 10) can be ensured, the anchor part 10 may be a rod-shaped rebar rather than an annular one, and the number of rebars may be two or more instead of one.

As shown in FIG. 1 etc., a screw hole 4c is formed on the outer peripheral surface of the side plate 4 for fixing a split plate 11 described later. A plurality of screw holes 4c (a total of six in this embodiment) are formed at approximately the center of the side plate 4 in the vertical direction, spaced apart in the circumferential direction.

Therefore, after removing the locking member 5 fixed to the side plate 4, the position of the narrowed portion 8 can be fitted with a steel divided plate 11, which is a horizontally elongated, approximately band-shaped member that has a roughly trapezoidal cross section and curves toward the inner peripheral surface 11a while extending in the circumferential direction of the main body 2, as shown in Figures 4(a) to (c) and 5.

As shown in FIG. 5, the divided plate 11 has a cross section of approximately the same shape and size as the cross section of the narrowed portion 8, and the curvatures of the upper inclined surface 11b, inner peripheral surface 11a, and lower inclined surface 11c of the divided plate 11 are equal to the curvatures of the outer peripheral surface of the end plate tapered portion 3d of the end plate 3, the outer peripheral surface of the trunk portion 3b of the end plate 3, the outer peripheral surface of the small diameter portion 2c of the main body 2, and the outer peripheral surface of the main body tapered portion 2d of the main body 2. Therefore, the divided plate 11 can be fixed to the side plate 4 in a state where its upper inclined surface 11b, inner peripheral surface 11a, and lower inclined surface 11c are in close contact with the narrowed portion 8 and fit just right.

The split plate 11 has bolt holes 11e that penetrate from the inner circumferential surface 11a to the outer circumferential surface 11d, formed near both ends in the left-right direction at approximately the center of the split plate 11 in the vertical direction, and when the split plate 11 is fitted into the tapered section 8, the position where the bolt hole 11e is formed in the inner circumferential surface 11a corresponds to the position where the screw hole 4c is formed in the side plate 4. Therefore, the split plate 11 can be fixed to the side plate 4 by inserting a bolt 12 into the bolt hole 11e from the outer circumferential surface 11d side of the split plate 11, screwing it into the screw hole 4c of the side plate 4, and tightening it with a torque wrench or the like.

In addition, on the inner peripheral surface 11a of the split plate 11, at a position approximately in the center of the split plate 11 in the left-right direction, and at a position corresponding to the position where the key hole 4b of the side plate 4 is formed when the split plate 11 is fitted into the narrowing portion 8 as described above and fixed with the bolt 12, a roughly rectangular parallelepiped convex portion 11f of roughly the same size as the key hole 4b is provided, so that the key hole 4b and the convex portion 11f can fit together.

With the above structure, after the concrete precast pile 1 is sunk to a specified depth and fixed in the ground 100, when the split plate 11 is fixed to the side plate 4, the position of the key hole 4b of the side plate 4 is aligned with the position of the convex portion 11f of the split plate 11, and the inner surface 11a of the split plate 11 is fitted into the convex portion 8, thereby determining the fixing position of the split plate 11 on the side plate 4, making it easy to align the split plate 11.

By fixing the split plate 11 to the side plate 4 while it is fitted into the constricted portion 8, the outer peripheral surface 11d of the split plate 11 becomes flush with the outer peripheral surface of the base 2b of the main body 2. In addition, as shown in Figures 4(a) to (c), three split plates 11 of approximately equal size can be fixed in the circumferential direction of the constricted portion 8, so that the entire outer peripheral surface (entire circumferential direction) of the constricted portion 8 is covered by the split plates 11. This makes it possible to prevent a decrease in bending and shear strength due to cross-sectional loss in the constricted portion 8 of the precast concrete pile 1.

In this embodiment, the structure is such that three divided plates 11 of approximately equal size are installed in the circumferential direction of the side plate 4, but any structure in which multiple divided plates 11 are installed may be used, and the number of divided plates may be two or four or more, and the structure may be such that multiple divided plates of different sizes are installed.

In addition, in this embodiment, the outer peripheral surface of the side plate 4 has a key hole 4b which is a recess, and the inner peripheral surface 11a of the divided plate 11 has a protrusion 11f which can fit into the key hole 4b, but it is also possible for the side plate 4 to have a protrusion and the divided plate 11 to have a key hole which is a recess.

In addition, the key hole 4b and the protrusion 11f are generally rectangular parallelepiped-shaped, but may be cylindrical or polygonal prism-shaped, such as a triangular prism or a pentagonal prism.

Next, the second embodiment of the present invention will be described. In Figs. 10 to 13, a precast concrete pile 1A has a main body 2, an end plate 30, a side plate 4, a locking member 50, a reinforcing band 6, and an anchor portion 10. The structure and arrangement of the main body 2, side plate 4, reinforcing band 6, and anchor portion 10 are the same as those of the main body 2, side plate 4, reinforcing band 6, and anchor portion 10 of the precast concrete pile 1 according to the first embodiment described above.

The end plate 30 is a steel member having a thickness and an approximately circular ring shape connected to the side plate 4 located at the upper end of the small diameter portion 2c of the main body 2, similar to the end plate 3 of the precast concrete pile 1 of the first embodiment, but has a different shape. Specifically, as shown in Figures 10 and 11, it has a hollow portion 30a with an inner diameter approximately equal to that of the hollow portion 2a of the main body 2, a body portion 30b with an outer diameter approximately equal to that of the small diameter portion 2c of the main body 2 at the bottom, and a flange portion 30c with an outer diameter approximately equal to that of the base portion 2b of the main body 2 at the top. The flange portion 30c is formed so as to extend from the upper end of the body portion 30b in a direction expanding in diameter approximately perpendicular to the body portion 30b. The recessed corner formed by the body portion 30b and the flange portion 30c is formed in an arc shape. In addition, the lower end of the body portion 30b of the end plate 30 and the upper end of the small diameter portion 2c of the main body 2 are connected together.

By connecting the main body 2 and the end plate 30 in this manner, a constriction portion 8A, which is a recess with a roughly trapezoidal cross section, is formed near the upper end of the concrete precast pile 1A by the flange portion 30c and the body portion 30b of the end plate 30 and the small diameter portion 2c and the main body tapered portion 2d of the main body 2.

In addition, the end plate 30 that forms the tapered portion 8A, the side plate 4 of the small diameter portion 2c of the main body 2, and the reinforcing band 6 that runs from the small diameter portion 2c through the main body tapered portion 2d and covers the upper end portion of the base 2b are all made of steel, so the outer periphery of the tapered portion 8A is entirely made of steel and has high strength.

As shown in Figures 10 and 11, three steel locking members 50, which are generally columnar members with a generally pentagonal cross section and which extend in the circumferential direction (left-right direction) of the main body 2 while curving toward the inner circumferential surface 50a, are fixed at the position of this constriction portion 8A at equal intervals in the circumferential direction. The locking members 50 differ in cross-sectional shape (the shape of the upper part on the inner circumferential surface 50a side) from the locking members 5 of the precast concrete pile 1 of the first embodiment.

Specifically, the inner peripheral surface 50a has a cross section of approximately the same shape and size as the cross section of the drawn portion 8A, and the curvatures of the inner peripheral surface 50a and the lower inclined surface 50c of the locking member 50 are equal to the curvatures of the trunk portion 30b of the end plate 30, the outer peripheral surface of the small diameter portion 2c of the main body 2, and the outer peripheral surface of the main body tapered portion 2d of the main body 2. Therefore, the locking member 50 is fixed to the side plate 4 in a state where its upper surface 50b, inner peripheral surface 50a, and lower inclined surface 50c are in close contact with the drawn portion 8A and fit just right. At this time, the locking member 50 is in a state where it protrudes significantly outwardly approximately perpendicular to the outer peripheral surface of the base portion 2b of the main body 2 (protruding significantly from the drawn portion 8A).

The locking member 50 has two bolt holes 50e, 50e that penetrate from its inner circumferential surface 50a to its outer circumferential surface 50d, and are formed in the same positions as the bolt holes 50e of the locking member 5. Therefore, the locking member 50 is fixed to the side plate 4 by screwing and fastening the bolt 9 inserted into the bolt holes 50e from the outer circumferential surface 50d side of the locking member 50 into the screw holes 4a of the side plate 4.

In addition, a roughly rectangular parallelepiped protrusion 50f is provided on the inner peripheral surface 50a of the locking member 50 and is roughly the same size as the key hole 4b on the outer peripheral surface of the side plate 4, and is located in the same position as the protrusion 5f of the locking member 5, allowing the key hole 4b and the protrusion 50f to fit together.

With the above structure, when fixing the locking member 50 to the side plate 4 during the process of manufacturing the precast concrete pile 1A, the position of the key hole 4b of the side plate 4 and the position of the protrusion 50f of the locking member 50 are aligned and fitted together, and the inner surface 50a of the locking member 50 is fitted into the convex portion 8A, thereby determining the fixed position of the locking member 50 on the side plate 4, making it easy to align the locking member 50.

In addition, as described above, the outer peripheral surface of the constricted portion 8A has a high-strength structure, which prevents damage to the constricted portion 8A when the steel locking member 50 and the dividing plate 40 described later are fitted into the constricted portion 8A.

In addition, after the locking member 50 is fixed, the locking member 50 protrudes outward perpendicular to the outer peripheral surface of the base 2b of the main body 2, and the pile rotation cap 20 can be used to fix the precast concrete pile 1A, making the fixing work easy.

As described later, when the precast concrete pile 1A is lifted using the pile rotation cap 20, the entire weight of the precast concrete pile 1A can be supported in a distributed manner by the screw holes 4a, the key holes 4b, and the flange portion 30c of the side plate 4 of the main body 2 via the locking members 50 and the bolts 9. Therefore, when the precast concrete pile 1A is lifted, the load on the end plate 30 can be reduced, preventing deformation or damage to the end plate 30, and also reducing the load on the PC steel members and the like connected to the end plate 30. This makes it possible to lift the precast concrete pile 1A in a safe state.

The locking member 50 can be easily attached to and detached from the side plate 4, and is structured so that the locking member 50 can be easily removed from the side plate 4 even after the precast concrete pile 1A has been fixed to the ground 100. Therefore, after removing the locking member 50, the work of connecting the head of the precast concrete pile 1A fixed to the ground 100 to a structure such as a footing installed above it can be simplified and the work time can be shortened.

In addition, the removed retaining member 50 can be used when manufacturing a new concrete precast pile 1A, which can reduce the manufacturing cost of the concrete precast pile 1A.

The anchor portion 10 shown in FIG. 11 is the same as that of the precast concrete pile 1 of the first embodiment, and is fixed and buried in the same position. Therefore, as with the precast concrete pile 1 of the first embodiment, the connection between the concrete portion 2e of the main body 2 and the end plate 30, side plate 4, and reinforcing band 6 is strengthened by the provision of the anchor portion 10, and the unity between the concrete portion 2e of the main body 2 and the end plate 30, side plate 4, and reinforcing band 6 is strengthened, ensuring unity. When the precast concrete pile 1A is lifted using the pile rotation cap 20, even if a large load is applied to the end plate 30, side plate 4, and reinforcing band 6, these components will not separate, making it possible to lift the pile in a safer state.

In addition, in this embodiment, as in the first embodiment, the locking members 50 are installed at three equally spaced locations in the circumferential direction of the side plate 4, but it is sufficient to install multiple locking members 50, and the number of locations may be two or four or more.

In addition, in this embodiment, the locking member 50 is a generally columnar member having a cross-section on its inner surface 50a that is generally the same size and shape as the cross-section of the narrowed portion 8A, but it does not necessarily have to have a cross-section that is generally the same shape and size as the cross-section of the narrowed portion 8A. It is sufficient that the locking member 50 has a generally columnar cross-sectional shape that contacts the outer peripheral surface of the flange portion 30 of the end plate 30 and the small diameter portion 2c of the main body 2 (side plate 4 or reinforcing band 6) when fixed to the side plate 4.

Therefore, the size of the cross section of the locking member 50 on the inner peripheral surface 50a side in the vertical direction may be smaller than the size of the cross section of the narrowed portion 8A, and the locking member 50 may have a cross-sectional shape that does not contact the outer peripheral surface of the main body tapered portion 2d when fixed to the side plate 4.

In addition, the cross-sectional shape of the portion of the locking member 50 that protrudes from the outer peripheral surface of the base 2b of the main body 2 (protruding from the narrowed portion 8A) is approximately rectangular in this embodiment as shown in FIG. 11, but it does not necessarily have to be approximately rectangular as long as it has a size (cross-sectional area) that does not deform even when a load is applied when lifting the precast concrete pile 1A and protrudes from the outer peripheral surface of the base 2b of the main body 2 to an extent that it can be engaged with the locking groove portion 24 of the pile rotation cap 20 used when lifting. Therefore, the cross-sectional shape of the protruding portion may be a polygonal shape such as a trapezoid or a triangle.

In addition, in this embodiment, the key hole 4b, which is a recess, is formed on the outer peripheral surface of the side plate 4, and the protrusion 50f, which can fit into the key hole 4b, is formed on the inner peripheral surface 50a of the locking member 50, but it is also possible for the protrusion to be formed on the side plate 4 and the key hole, which is a recess, to be formed on the locking member 50.

In addition, the key hole 4b and the protrusion 50f are generally rectangular parallelepiped-shaped, but may be cylindrical or polygonal prism-shaped, such as a triangular prism or a pentagonal prism.

In addition, in this embodiment, the anchor portion 10 is fixed to all of the end plate 30, side plate 4, and reinforcing band 6 by welding, but the structure may be such that the anchor portion 10 is fixed to at least one of the end plate 30, side plate 4, and reinforcing band 6.

As shown in FIG. 10 and other figures, the side plate 4 has a screw hole 4c for fixing the split plate 40, which will be described later. A plurality of screw holes 4c (six in total in this embodiment) are formed at approximately the center of the side plate 4 in the vertical direction, spaced apart in the circumferential direction.

Therefore, after removing the locking member 50 fixed to the side plate 4, the position of the narrowed portion 8A can be fitted with a steel split plate 40, which is a horizontally elongated, approximately band-shaped member that has a roughly trapezoidal cross section and curves toward the inner peripheral surface 40a while extending in the circumferential direction of the main body 2, as shown in Figures 12 and 13.

The divided plate 40 has a cross-sectional shape different from that of the divided plate 11 of the first embodiment. Specifically, it has a cross-section of approximately the same shape and size as the cross-section of the drawn portion 8A, and the curvatures of the inner peripheral surface 40a and the lower inclined surface 40c of the divided plate 40 are equal to the curvatures of the trunk portion 30b of the end plate 30, the outer peripheral surface of the small diameter portion 2c of the main body 2, and the outer peripheral surface of the main body tapered portion 2d of the main body 2. Therefore, the divided plate 40 can be fixed to the side plate 4 in a state where its upper surface 40b, inner peripheral surface 40a, and lower inclined surface 40c are in close contact with the drawn portion 8A and fit just right.

Two bolt holes 40e are formed in the split plate 40, penetrating from the inner circumferential surface 40a to the outer circumferential surface 40d, and are formed in the same positions as the bolt holes 11e of the split plate 11. Therefore, the split plate 40 can be fixed to the side plate 4 by inserting a bolt 12 into the bolt hole 40e from the outer circumferential surface 40d side of the split plate 40, screwing it into the screw hole 4c of the side plate 4, and tightening it with a torque wrench or the like.

In addition, a roughly rectangular parallelepiped protrusion 40f is provided on the inner peripheral surface 40a of the split plate 40 and is roughly the same size as the key hole 4b of the side plate 4, and is located in the same position as the protrusion 11f of the split plate 11, so that the key hole 4b and the protrusion 40f can fit together.

With the above structure, after the concrete precast pile 1A is sunk to a specified depth and anchored in the ground 100, when the split plate 40 is fixed to the side plate 4, the position of the key hole 4b of the side plate 4 is aligned with the position of the protrusion 40f of the split plate 40, and the inner surface 40a of the split plate 40 is fitted into the convex portion 8A, thereby determining the fixing position of the split plate 40 on the side plate 4, making it easy to align the split plate 40.

By fixing the split plate 40 to the side plate 4 while it is fitted into the drawn portion 8A, the outer peripheral surface 40d of the split plate 40 becomes flush with the outer peripheral surface of the base 2b of the main body 2. In addition, three split plates 40 of approximately equal size can be fixed in the circumferential direction of the drawn portion 8A, so that the entire outer peripheral surface (entire circumferential direction) of the drawn portion 8A is covered by the split plates 40. This makes it possible to prevent a decrease in bending and shear strength due to cross-sectional loss in the drawn portion 8A of the concrete precast pile 1A.

In this embodiment, as in the first embodiment, the structure is such that three divided plates 40 of approximately equal size are installed in the circumferential direction of the side plate 4, but any structure in which multiple divided plates 40 are installed may be used, and the number of divided plates may be two or four or more, and multiple divided plates of different sizes may be installed.

In addition, in this embodiment, the outer peripheral surface of the side plate 4 has a key hole 4b which is a recess, and the inner peripheral surface 40a of the divided plate 40 has a protrusion 40f which can fit into the key hole 4b, but the side plate 4 may have a protrusion and the divided plate 40 may have a key hole which is a recess.

In addition, the key hole 4b and the protrusion 40f are generally rectangular parallelepiped-shaped, but may be cylindrical or polygonal prism-shaped, such as a triangular prism or a pentagonal prism.

14 to 17, a precast concrete pile 1B has a main body 2, an end plate 31, a side plate 4, a locking member 51, a reinforcing band 6, and an anchor portion 10. The structures and arrangements of the main body 2, the side plate 4, the reinforcing band 6, and the anchor portion 10 are similar to those of the main body 2, the side plate 4, the reinforcing band 6, and the anchor portion 10 of the precast concrete pile 1 according to the first embodiment described above.

The end plate 31 is a steel member having a thickness and an approximately circular ring shape connected to the side plate 4 located at the upper end of the small diameter portion 2c of the main body 2, similar to the end plate 3 of the precast concrete pile 1 of the first embodiment, but has a different shape. Specifically, as shown in Figures 14 and 15, it has a hollow portion 31a having an inner diameter approximately equal to that of the hollow portion 2a of the main body 2, a body portion 31b having an outer diameter approximately equal to that of the small diameter portion 2c of the main body 2 at the bottom, and a flange portion 31c having an outer diameter approximately equal to that of the base portion 2b of the main body 2 at the top. In addition, from the lower end of the flange portion 31c to the upper end of the body portion 31b, an end plate curved surface portion 31d that curves upward and reduces in diameter is formed. The lower end of the body portion 31b of the end plate 31 and the upper end of the small diameter portion 2c of the main body 2 are connected together.

By connecting the main body 2 and the end plate 31 in this manner, a constricted portion 8B, which is a recess with a roughly trapezoidal cross section, is formed near the upper end of the concrete precast pile 1B by the end plate curved portion 31d and the body portion 31b of the end plate 31, as well as the small diameter portion 2c and the main body tapered portion 2d of the main body 2.

In addition, the end plate 31 that forms the tapered portion 8B, the side plate 4 of the small diameter portion 2c of the main body 2, and the reinforcing band 6 that runs from the small diameter portion 2c through the main body tapered portion 2d and covers the upper end of the base portion 2b are all made of steel, so the outer periphery of the tapered portion 8B is entirely made of steel, making it highly strong.

As shown in Figures 14 and 15, three steel locking members 51, which are generally columnar members with a generally pentagonal cross section and which extend in the circumferential direction (left-right direction) of the main body 2 while curving toward the inner circumferential surface 51a, are fixed at the position of this constriction portion 8B at equal intervals in the circumferential direction. The locking members 51 have a different cross-sectional shape (the shape of the upper part on the inner circumferential surface 51a side) from the locking members 5 of the precast concrete pile 1 of the first embodiment.

Specifically, the inner circumferential surface 51a has a cross section of approximately the same shape and size as the cross section of the drawn portion 8B, and the curvatures of the upper curved surface 51b, inner circumferential surface 51a, and lower inclined surface 51c of the locking member 51 are equal to the curvatures of the outer circumferential surface of the end plate curved surface portion 31d of the end plate 31, the outer circumferential surface of the trunk portion 31b of the end plate 31 and the small diameter portion 2c of the main body 2, and the outer circumferential surface of the main body tapered portion 2d of the main body 2. Therefore, the locking member 51 is fixed to the side plate 4 in a state where its upper curved surface 51b, inner circumferential surface 51a, and lower inclined surface 51c are in close contact with the drawn portion 8B and fit just right. At this time, the locking member 51 is in a state where it protrudes significantly outwardly approximately perpendicular to the outer circumferential surface of the base portion 2b of the main body 2 (protruding significantly from the drawn portion 8B).

The locking member 51 has two bolt holes 51e, 51e that penetrate from its inner circumferential surface 51a to its outer circumferential surface 51d, and these are formed in the same position as the bolt hole 51e of the locking member 5. Therefore, the locking member 51 is fixed to the side plate 4 by screwing and fastening the bolt 9 inserted into the bolt hole 51e from the outer circumferential surface 51d side of the locking member 51 into the screw hole 4a of the side plate 4.

In addition, a roughly rectangular parallelepiped protrusion 51f is provided on the inner peripheral surface 51a of the locking member 51 and is roughly the same size as the key hole 4b on the outer peripheral surface of the side plate 4, and is located in the same position as the protrusion 5f of the locking member 5, allowing the key hole 4b and the protrusion 51f to fit together.

With the above structure, when fixing the locking member 51 to the side plate 4 during the process of manufacturing the precast concrete pile 1B, the position of the key hole 4b of the side plate 4 is aligned with the position of the protrusion 51f of the locking member 51, and the inner surface 51a of the locking member 51 is fitted into the narrowed portion 8B to determine the fixed position of the locking member 51 on the side plate 4, making it easy to align the locking member 51.

In addition, as described above, the outer peripheral surface of the narrowed portion 8B has a high-strength structure, which prevents damage to the narrowed portion 8B when the steel locking member 51 and the dividing plate 41 described later are fitted into the narrowed portion 8B.

In addition, after the locking member 51 is fixed, the locking member 51 protrudes outward perpendicular to the outer peripheral surface of the base 2b of the main body 2, and the pile rotation cap 20 can be used to fix the precast concrete pile 1B, making the fixing work easy.

As described later, when the precast concrete pile 1B is lifted using the pile rotation cap 20, the entire weight of the precast concrete pile 1B can be supported in a distributed manner by the screw holes 4a, the key holes 4b, and the curved surface portion 31d of the end plate 4 of the main body 2 via the locking members 51 and the bolts 9. Therefore, when the precast concrete pile 1B is lifted, the load on the end plate 31 can be reduced, preventing deformation or damage to the end plate 31, and also reducing the load on the PC steel members and the like connected to the end plate 31. This makes it possible to lift the precast concrete pile 1B in a safe state.

The locking member 51 can be easily attached to and detached from the side plate 4, and is structured so that the locking member 51 can be easily removed from the side plate 4 even after the precast concrete pile 1B has been fixed to the ground 100. Therefore, after removing the locking member 51, the work of connecting the head of the precast concrete pile 1B fixed to the ground 100 to a structure such as a footing installed above it can be simplified and the work time can be shortened.

In addition, the removed retaining member 51 can be used when manufacturing a new concrete precast pile 1B, which can reduce the manufacturing cost of the concrete precast pile 1B.

The anchor portion 10 shown in FIG. 15 is the same as that of the precast concrete pile 1 of the first embodiment, and is fixed and buried in the same position. Therefore, as with the precast concrete pile 1 of the first embodiment, the connection between the concrete portion 2e of the main body 2 and the end plate 31, side plate 4, and reinforcing band 6 is strengthened by the provision of the anchor portion 10, and the unity between the concrete portion 2e of the main body 2 and the end plate 31, side plate 4, and reinforcing band 6 is strengthened, ensuring unity. When the precast concrete pile 1B is lifted using the pile rotation cap 20, even if a large load is applied to the end plate 31, side plate 4, and reinforcing band 6, these components will not separate, making it possible to lift the pile in a safer state.

In addition, in this embodiment, as in the first embodiment, the locking members 51 are installed at three equally spaced locations in the circumferential direction of the side plate 4, but it is sufficient to install multiple locking members 51, and the number of locations may be two or four or more.

In addition, in this embodiment, the locking member 51 has a cross-section on its inner surface 51a that is approximately the same size and shape as the cross-section of the narrowed portion 8B, but it does not necessarily have to have a cross-section that is approximately the same shape and size as the cross-section of the narrowed portion 8B. It is sufficient that the locking member 51 is an approximately columnar member with a cross-sectional shape that contacts the outer peripheral surface of the end plate curved portion 31d of the end plate 31 and the outer peripheral surface of the small diameter portion 2c of the main body 2 (side plate 4 or reinforcing band 6) when fixed to the side plate 4.

Therefore, the size of the locking member 51 in the vertical direction on the inner circumferential surface 51a side of the cross section may be smaller than the size of the cross section of the narrowed portion 8B, and the locking member 51 may have a cross-sectional shape that does not contact the outer circumferential surface of the main body tapered portion 2d when fixed to the side plate 4.

In addition, the cross-sectional shape of the portion of the locking member 51 that protrudes from the outer peripheral surface of the base 2b of the main body 2 (protruding from the narrowing portion 8B) is approximately rectangular in this embodiment as shown in FIG. 15, but it does not necessarily have to be approximately rectangular as long as it has a size (cross-sectional area) that does not deform even when a load is applied when lifting the precast concrete pile 1B and protrudes from the outer peripheral surface of the base 2b of the main body 2 to an extent that it can be engaged with the locking groove portion 24 of the pile rotation cap 20 used when lifting. Therefore, the cross-sectional shape of the protruding portion may be a polygonal shape such as a trapezoid or a triangle.

In addition, in this embodiment, the key hole 4b, which is a recess, is formed on the outer peripheral surface of the side plate 4, and the protrusion 51f, which can fit into the key hole 4b, is formed on the inner peripheral surface 51a of the locking member 51, but it is also possible for the protrusion to be formed on the side plate 4 and the key hole, which is a recess, to be formed on the locking member 51.

In addition, the key hole 4b and the protrusion 51f are generally rectangular parallelepiped-shaped, but may be cylindrical or polygonal prism-shaped, such as a triangular prism or a pentagonal prism.

In addition, in this embodiment, the anchor portion 10 is fixed to all of the end plate 31, side plate 4, and reinforcing band 6 by welding, but the structure may be such that the anchor portion 10 is fixed to at least one of the end plate 31, side plate 4, and reinforcing band 6.

As shown in FIG. 14, the side plate 4 has a screw hole 4c for fixing a split plate 41 (described later). A plurality of screw holes 4c (six in total in this embodiment) are formed at approximately the center of the side plate 4 in the vertical direction and spaced apart in the circumferential direction.

Therefore, after removing the locking member 51 fixed to the side plate 4, the position of the narrowed portion 8B can be fitted with a steel split plate 41, which is a horizontally elongated, approximately band-shaped member that has a roughly trapezoidal cross section and curves toward the inner circumferential surface 41a while extending in the circumferential direction of the main body 2, as shown in Figures 16 and 17.

The divided plate 41 has a cross-sectional shape different from that of the divided plate 11 of the first embodiment. Specifically, the divided plate 41 has a cross-section of approximately the same shape and size as the cross-section of the narrowed portion 8B, and the curvatures of the upper curved surface 41b, inner peripheral surface 41a, and lower inclined surface 41c that curve upward at the upper part of the divided plate 41, the outer peripheral surface of the end plate curved surface portion 31d of the end plate 31, the outer peripheral surface of the trunk portion 31b of the end plate 31 and the small diameter portion 2c of the main body 2, and the outer peripheral surface of the main body tapered portion 2d of the main body 2 are all formed to be equal. Therefore, the divided plate 41 can be fixed to the side plate 4 in a state where its upper curved surface 41b, inner peripheral surface 41a, and lower inclined surface 41c are in close contact with the narrowed portion 8B and fit just right.

The split plate 41 has two bolt holes 41e that penetrate from the inner circumferential surface 41a to the outer circumferential surface 41d, and are located in the same positions as the bolt holes 11e of the split plate 11. Therefore, the split plate 41 can be fixed to the side plate 4 by inserting a bolt 12 into the bolt hole 41e from the outer circumferential surface 41d side of the split plate 41, screwing it into the screw hole 4c of the side plate 4, and tightening it with a torque wrench or the like.

In addition, a roughly rectangular parallelepiped protrusion 41f is provided on the inner peripheral surface 41a of the split plate 41 and is roughly the same size as the key hole 4b of the side plate 4, and is located in the same position as the protrusion 11f of the split plate 11, so that the key hole 4b and the protrusion 41f can fit together.

With the above structure, after the concrete precast pile 1B is sunk to a specified depth and anchored in the ground 100, when the split plate 41 is fixed to the side plate 4, the position of the key hole 4b of the side plate 4 is aligned with the position of the convex portion 41f of the split plate 41, and the inner surface 41a of the split plate 41 is fitted into the convex portion 8B, thereby determining the fixing position of the split plate 41 on the side plate 4, making it easy to align the split plate 41.

By fixing the split plate 41 to the side panel 4 while it is fitted into the drawn portion 8B, the outer peripheral surface 41d of the split plate 41 becomes flush with the outer peripheral surface of the base 2b of the main body 2. In addition, three split plates 41 of approximately equal size can be fixed in the circumferential direction of the drawn portion 8B, so that the entire outer peripheral surface (entire circumferential direction) of the drawn portion 8B is covered by the split plates 41. This makes it possible to prevent a decrease in bending and shear strength due to cross-sectional loss in the drawn portion 8B of the concrete precast pile 1B.

In this embodiment, as in the first embodiment, the structure is such that three divided plates 41 of approximately equal size are installed in the circumferential direction of the side plate 4, but it is sufficient that multiple divided plates 41 are installed, and they may be installed in two or four or more locations, or multiple divided plates of different sizes may be installed.

In addition, in this embodiment, the key hole 4b, which is a recess, is formed on the outer peripheral surface of the side plate 4, and the inner peripheral surface 41a of the divided plate 41 has a protrusion 41f that can fit into the key hole 4b, but it is also possible for the protrusion to be formed on the side plate 4 and the key hole, which is a recess, to be formed on the divided plate 41.

In addition, the key hole 4b and the protrusion 41f are generally rectangular parallelepiped-shaped, but may be cylindrical or polygonal, such as triangular or pentagonal.

In addition, in this embodiment, the end plate curved surface portion 31d of the end plate 31 and the upper curved surface of the dividing plate 41 both form curved surfaces that curve upward, but they may both be curved surfaces that curve downward.

The precast concrete piles 1, 1A, 1B are fixed to the ground 100 by a commonly used pile rotation cap 20 as shown in Figure 6. This pile rotation cap 20 is composed of a tubular portion 21 having an inner diameter large enough to insert the head of the precast concrete pile 1, 1A, 1B, a top plate portion 22 that covers the upper end of the tubular portion 21, and a shaft coupling portion 23 that is provided in the center of the top surface of the top plate portion 22 and can be connected to a rotating shaft (not shown) of a rotating mechanism such as a pile driver.

The cylindrical portion 21 is formed with a generally inverted L-shaped locking groove 24 into which the locking members 5, 50, 51 of the precast concrete piles 1, 1A, 1B can be inserted, and which has a vertical groove 24a extending vertically from the lower end of the cylindrical portion 21 and a horizontal groove 24b extending circumferentially from the upper end of the vertical groove 24a. The locking grooves 24 are formed in positions (in this embodiment, three positions at equal intervals in the circumferential direction of the cylindrical portion 21) that correspond to the locking members 5, 50, 51 when the pile head of the precast concrete piles 1, 1A, 1B is inserted into the cylindrical portion 21.

The construction method for installing the precast concrete pile 1 vertically in the excavation hole 101 formed in the ground 100 using the pile rotation cap 20 as described above will be explained below. First, the excavation hole 101, whose diameter is slightly larger (approximately 100 mm to 150 mm larger) than the diameter of the precast concrete pile 1, is formed in the ground 100 at a specified position and depth using an earth auger or the like, and a root consolidation liquid and pile circumference fixing liquid are injected.

Next, the shaft coupling 23 of the pile rotation cap 20 is connected to the lower end of the rotating shaft of a rotating mechanism such as a pile driver. Then, the head of the precast concrete pile 1 is lifted and raised with a wire rope or the like by another pile driver, while the head of the pile is inserted into the tubular portion 21 of the pile rotation cap 20.

At this time, the locking member 5 of the precast concrete pile 1 is aligned with the vertical groove 24a of the locking groove 24 formed in the tubular portion 21 of the pile rotation cap 20, and the locking member 5 is inserted along the vertical groove 24a while the pile head is inserted all the way into the pile rotation cap 20.

Then, the pile rotation cap 20 is rotated to the right to move the locking member 5 from the vertical groove 24a to the horizontal groove 24b (see FIG. 6), and the locking member 5 is moved to the very back of the horizontal groove 24b, thereby locking the locking groove 24 of the pile rotation cap 20 with the locking member 5 of the precast concrete pile 1. In this state, the precast concrete pile 1 is lifted up via the pile rotation cap 20. While it is being lifted up, the pile rotation cap 20 can be rotated to the right as well by rotating the pile rotation cap 20 to the right.

Next, the concrete precast pile 1 is moved to directly above the borehole 101, and then rotated to the right and repeatedly lowered by pressing or raised by lifting, so that the concrete precast pile 1 is erected in the borehole 101, and then sunk to a specified depth to anchor the concrete precast pile 1 in the borehole 101.

After the precast concrete pile 1 is fixed, the pile rotation cap 20 is rotated counterclockwise to move the locking member 5 from the horizontal groove 24b to the vertical groove 24a, releasing the locking state with the pile rotation cap 20. The pile rotation cap 20 is then pulled straight up, so that the locking member 5 of the precast concrete pile 1 comes out of the vertical groove 24a, and the tube portion 21 of the pile rotation cap 20 is separated from the pile head (see Figure 7).

Next, as shown in Figure 8, the bolts 9 that screw into the screw holes 4a are loosened with a torque wrench or the like, and all of the locking members 5 are removed from the side plate 4. Thereafter, as shown in Figures 4(a) to (c), 5, and 9, the bolts 12 are inserted into the bolt holes 11e from the outer peripheral surface 11d side of the split plate 11, screwed into the screw holes 4c of the side plate 4, and fastened with a torque wrench or the like, thereby fixing the three split plates 11 to the side plate 4, and the installation work in the borehole 101 (ground 100) is completed.

As for the construction method of installing the precast concrete piles 1A and 1B by vertically erecting them in the excavation holes 101 formed in the ground 100 using the pile rotation cap 20, the pile heads of the precast concrete piles 1A and 1B are lifted and raised using a wire rope or the like with a pile driver or the like, and the pile heads are inserted into the tubular portion 21 of the pile rotation cap 20 connected to the lower end of the rotating shaft of the rotating mechanism of the pile driver or the like, and then lifted in a state in which the locking groove portion 24 of the pile rotation cap 20 and the locking members 50 and 51 of the precast concrete piles 1A and 1B are engaged.

Next, the precast concrete piles 1A and 1B are moved to directly above the borehole 101 formed in the ground 100, and then rotated clockwise to lower them by pressing them in or raise them by lifting them up until they are sunk to a specified depth, thereby fixing the precast concrete piles 1A and 1B in the borehole 101.

Then, rotate the pile rotation cap 20 counterclockwise and pull it upward to separate the tubular portion 21 from the pile heads of the precast concrete piles 1A, 1B, remove all of the locking members 50, 51 from the side plate 4, and fix the three split plates 40, 41 to the side plate 4 as shown in Figures 12, 13, 16, and 17, completing the installation work in the borehole 101 (ground 100).

Reference Signs List 1, 1A, 1B Precast concrete pile 20 Pile rotation cap 2 Body 21 Cylinder portion 3 End plate 22 Top plate portion 4 Side plate 23 Shaft joint 5 Locking member 24 Locking groove portion 6 Reinforcement band 30, 31 End plate 8, 8A, 8B Constriction portion 40, 41 Divided plate 9 Bolt 50, 51 Locking member 10 Anchor portion 100 Ground 11 Divided plate 101 Boring hole 12 Bolt

Claims (10)

a bolt hole is formed through the bolt hole from the outer circumferential surface to the inner circumferential surface, and a bolt is inserted into the bolt hole of the locking member at a tapered portion formed by connecting an upper end of the small diameter portion of the main body and a lower end of the trunk portion of the end plate, the bolt being inserted into the bolt hole of the locking member and screwed into a screw hole formed in the side plate to fasten the locking member to the flange portion of the end plate and to the side plate in a state in which the locking member contacts the flange portion of the end plate and protrudes from the outer circumferential surface of the base of the main body so as to be able to engage with a locking groove of a pile rotation cap . 2. The prefabricated pile according to claim 1, characterized in that the end plate has an end plate tapered portion that narrows in diameter from the lower end of the flange portion to the upper end of the body, and at the narrowing portion formed by connecting the upper end of the small diameter portion of the main body and the lower end of the body of the end plate, a bolt is inserted into the bolt hole of the locking member and screwed into the screw hole formed in the side plate to fasten the locking member so that the locking member contacts the end plate tapered portion and protrudes from the outer peripheral surface of the base of the main body so as to be able to engage with the locking groove portion of the pile rotation cap. 2. The prefabricated pile according to claim 1, characterized in that the end plate has an end plate curved portion that narrows in diameter from the lower end of the flange portion to the upper end of the body, and at a narrowing portion formed by connecting the upper end of the small diameter portion of the main body and the lower end of the body of the end plate, a bolt is inserted into the bolt hole of the locking member and screwed into the screw hole formed in the side plate to fasten the locking member so that the locking member contacts the end plate curved portion and protrudes from the outer peripheral surface of the base of the main body so as to be able to engage with the locking groove portion of the pile rotation cap. A prefabricated pile according to any one of claims 1 to 3, characterized in that a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the locking member, and a concave portion capable of engaging with the convex portion is formed on the other. A prefabricated pile as described in any one of claims 1 to 4, characterized in that a reinforcing band is provided from near the upper end of the outer peripheral surface of the base of the main body to the lower end of the outer peripheral surface of the side plate in the small diameter portion. A precast pile according to any one of claims 1 to 5, characterized in that an anchor portion is provided on at least one of the surfaces of the end plate, the side plate, and the reinforcing band that contact the concrete portion of the main body. 7. A prefabricated pile according to claim 1, wherein, in the tapered portion of the prefabricated pile , instead of the plurality of engaging members, a plurality of divided plates are provided which are approximately band-shaped members curved toward the inner surface and capable of fitting into the tapered portion, the divided plates having bolt holes passing through from the outer surface to the inner surface, the divided plates being attached to the side plates by inserting bolts into the bolt holes and screwing them into screw holes formed in the side plates to fasten them, thereby covering the entire circumferential direction of the tapered portion. The prefabricated pile according to claim 7, characterized in that a convex portion is formed on either the outer peripheral surface of the side plate or the inner peripheral surface of the dividing plate, and a concave portion that can fit into the convex portion is formed on the other. 7. A method for installing a prefabricated pile according to claim 1 in the ground, comprising the steps of: forming a borehole in the ground; inserting a head portion of the prefabricated pile into a cylindrical portion of a pile rotation cap and lifting the prefabricated pile by engaging a locking groove formed in the cylindrical portion with the locking member; fixing the prefabricated pile in the borehole by rotary pressing; releasing the locking between the locking groove and the locking member and extracting the head portion of the prefabricated pile from the cylindrical portion; and removing the locking member from the side plate of the prefabricated pile . The construction method for a precast pile according to claim 9, further comprising a step of attaching a plurality of divided plates that can be fitted into the narrowed portion to the side plate so as to cover the entire circumferential direction of the narrowed portion of the precast pile after the step of removing the engaging member from the side plate of the precast pile.

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