JP2000303460A - Friction pile and method for erecting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction pile excellent in construction property and a method for constructing the same capable of promoting bearing force of the whole friction pile by forming a bulbous form section in the front end of the pile to increase front end bearing capacity thereof. SOLUTION: A fin-like projection 3 is provided along the axial direction of a pile main body 2 from the circumferential surface of the pile main body 2, and the upper ends of a plurality of spread wings 4 having almost the same radius of curvature as that of the cylindrical pile main body 2 are connected to the circumference section of a pile end opening section 16 of the pile main body 2 so that the wings 4 can be spread outward. A locking body 12 for controlling the spreading of the wings 4 is interlocked with the wings 4 so as to oppose it against the pile end surface of the pile main body 2, and holding sections 7 for holding the wings 4 at a specific spread angle is formed. When the lock body 12 is moved downward, a state interlocking with the wings 4 is released, and it is so constituted that the wings 4 can be spread up to a specific spread angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved friction pile and a method for constructing a friction pile mainly used in a driving pile method.

[0002]

2. Description of the Related Art The basic concept of the bearing capacity of this kind of friction pile is that the magnitude of the bearing capacity of the entire pile is F, and that of the pile tip is F.
1. If the peripheral frictional force of the pile is F2 and the weight of the pile is W, then F =
It is assumed that the formula of F1 + F2-W holds. Therefore, by increasing at least one of the pile tip support force and the pile peripheral surface frictional force, the support force of the entire pile can be increased. Therefore, for example, Japanese Patent Application Laid-Open
As disclosed in Japanese Patent No. 20944, a friction pile has been proposed in which a fin-like projection is provided on the outer peripheral surface of a pile main body to increase the pile peripheral surface frictional force. According to this friction pile, there is also an advantage that the peripheral surface frictional force can be increased as the surface area of the fin-shaped projection is increased.

[0003]

However, there is a limit in increasing the surface area of the fin-like projections due to the connection strength between the fin-like projections and the pile main body. There is a problem that it is not suitable for foundation piles of large-scale structures. On the other hand, in order to increase the supporting force of the entire pile by increasing the supporting force at the tip, a construction method of a friction pile in which a bulb-shaped portion is formed at the tip of the pile has already been proposed. In this construction method, a friction pile is first driven into the ground, and then the hollow portion provided at the tip of the friction pile is filled with fresh concrete to form a bulb-shaped portion. However, when such a construction method is adopted, there is a problem that it takes time and effort to form the bulb-shaped portion, and the workability is reduced. The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to form a bulb-shaped portion at the tip of a pile to increase the tip supporting force of the pile, An object of the present invention is to provide a friction pile and a method for constructing a friction pile, which can improve the support force of the entire pile and have excellent workability.

[0004]

According to a first aspect of the present invention, there is provided a friction pile comprising: a cylindrical pile body having a frictional force extending along an axial direction of the pile body from an outer peripheral surface thereof; Fin-shaped projections are projected, and the upper ends of a plurality of arc-shaped expanding blades having substantially the same radius of curvature as the cylindrical pile body are expanded around the pile tip opening of the pile body. The blades are connected so as to be able to expand outward, and a lock body for restricting the expansion of the expansion blades is locked to the expansion blades so as to face the pile tip surface of the pile body. A fin-shaped projection extending in the direction of the pile tip to form a holding portion for holding the expanding blade at a predetermined expanding angle, and the expanding blade when the lock body is moved downward. Is released so that the expanding blade can be expanded to the predetermined expanding angle. Characterized in that the configuration was.

[0005] The friction pile according to claim 2 is characterized in that the edge of the fin-like projection on the pile tip side is inclined.

According to a third aspect of the present invention, there is provided a method for constructing a friction pile, wherein a fin-like projection for increasing a frictional force is protruded from an outer peripheral surface of a cylindrical pile main body along an axial direction of the pile main body. The upper ends of a plurality of arc-shaped expanding blades having substantially the same radius of curvature as the cylindrical pile main body are connected to the periphery of the pile tip opening so that the expanding blades can expand outward. At the same time, a lock body for restricting the expansion of the expanding blade is locked to the expanding blade so as to face the pile tip surface of the pile main body, and the fin-shaped projection is extended in the pile tip direction. Forming a holding portion for holding the expansion blade at a predetermined expansion angle, and when the lock body is moved downward, the locked state with the expansion blade is released, and the expansion blade is released. In the method for constructing a friction pile configured to be able to expand to the predetermined expansion angle, After driving the friction pile into the ground, a mixture of cement and aggregate is put into the tip of the friction pile in the pile main body, and then the weight is dropped into the pile main body, whereby the lock body is removed. Moving downward, and expanding the expanding blade to the predetermined expanding angle,
The mixture is spread to the tip of the friction pile, and a concrete bulb is formed at the tip of the friction pile by infiltration of groundwater into the mixture.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A friction pile 1 is a prefabricated pile manufactured at a factory. As shown in FIG. 1, four piles are opened at both ends thereof at equal intervals from an outer peripheral surface of a pile body 2 made of steel pipe. Fin-like projection 3
Are projected radially around the axis of the pile main body 2, and a bulb forming body 5 having an expanding blade 4 is attached to the tip of the pile main body 2. As shown in FIG. 1, the fin-shaped protrusions 3 are formed of a steel plate having an uneven portion 3a on the surface, for example, a checkered plate having a striped unevenness on the surface of the steel plate. It is formed in dimensions. Note that the uneven portion 3a is formed over the entire surface of the fin-shaped protrusion 3, but in the drawing, the uneven portion 3a is shown only on a part of the surface of the fin-shaped protrusion 3, and the remaining uneven portion 3a is omitted. ing.

The fin-shaped projections 3 are radially welded to the outer peripheral surface of the pile body 2. However, the fin-like projections 3
May be connected to the pile main body 2 using fasteners such as bolts and nuts.

In addition, as shown in FIG. 1, fins are provided around the pile head 6 of the pile body 2 in order to facilitate the on-site joint work between the friction piles 1 so that the driving operation can be performed smoothly. The projection 3 is not provided.

As shown in FIG. 1, a holding portion 7 for holding the expanding blade 4 at a predetermined expanding angle is formed at an end of the fin-like projection 3 on the pile tip side. The angle of inclination of the lower edge portion 7a of the holding portion 7 is such that when the outer side surface of the expanded blade 4 hits, the expansion angle of the expanded blade 4 is 30 ° to 60 °,
Preferably, the angle is set to about 45 °.

[0011] As shown in FIG. 2, the bulb forming body 5 attached to the tip of the pile main body 2 is attached to the lower end of the pile main body 2.
Arc-shaped expanding blade 4 having the same radius of curvature as hinge 1
0, the expanding blades 4 are configured to be able to expand outward, and a locking groove 11 is formed in the center of the lower edge of each expanding blade 4. Further, as shown in FIG. 2, when the above-mentioned four expanding blades 4 are suspended, the side edges of the adjacent expanding blades 4 are in close contact with each other.

As shown by a two-dot chain line in FIG. 2, the expansion of the expanding blade 4 of the bulb forming body 5 is regulated by a lock body 12. As shown in the figure, the lock body 12 is formed by assembling strip-shaped lock members 13 in a cross shape in a plan view, and a locking groove 14 is provided at an upper edge of each lock member 13. Have been.

As shown in FIGS. 1 and 3, the lock body 12 is inserted into the opening 16 of the pile tip 15 of the pile body 2 with the center of the lock body 12 aligned with the axis of the pile body 2. The locking groove 14 of the lock body 12 is opposed to the locking groove 1 of the expanding blade 4.
The lock body 12 is attached to the bulb forming body 5 by meshing with the base member 1. As a result, the expansion of the expanding blade 4 is restricted, and the expanding blade 4 is not accidentally opened during driving of the friction pile 1. On the other hand, when only the lock body 12 is moved downward,
As a result, the engagement of the locking groove 11 of the expanding blade 4 is released, and the expanding blade 4 can be expanded.

Next, a method of constructing the friction pile 1 constructed as described above will be described with reference to FIGS. First, as shown in FIG. 4, the friction pile 1 in which the lock body 12 is attached to the bulb formation body 5 is driven into the ground 17 by driving with a pile driving machine (not shown). At this time, the pile body 2 of the friction pile 1
The soil 19 of the ground 17 intrudes into the pile main body 2 from the opening 16 of the pile tip portion 15. Next, as shown in FIG. 5, the mixture 21 of the aggregate and the cement is injected from the opening 20 of the pile head 6 of the pile main body 2 of the friction pile 1, and the mixture 21 is placed on the soil 19 in the pile main body 2. Serve.

Next, as shown in FIG. 1, the mixture 22, the sediment 19 and the lock body 12 in the pile body 2 are moved downward by naturally dropping the weight 22 into the pile body 2 of the friction pile 1. Then, the locking of the lock body 12 to the expanding blade 4 is released. The weight 22 is dropped using an automatic drop device. This automatic drop device suspends the weight 22 with a rope 23 in the pile body 2 of the friction pile 1 and allows the weight 22 to fall naturally. That is, the weight 22 is lifted to a predetermined height and then dropped naturally. Then, by repeating this operation, as shown in FIG. 6, the mixture 21, the earth and sand 19 and the lock body 12 in the pile main body 2 move downward by the impact force of the weight 22.

As shown in FIG. 6, the friction pile 1 itself sinks due to the impact force of the weight 22, and the settlement of the friction pile 1 and the movement of the mixture 21 and the earth and sand 19 in the pile main body 2 cause the formation of the bulb. 5, the expanding blades 4 open outward, and the mixture 21 also spreads laterally, so that the expanding blades 4 are expanded.
Hits the holding portion 7 of the fin-shaped projection 3 to maintain a predetermined spread angle. Then, the friction pile 1 is driven to a predetermined depth, and the groundwater penetrates into the mixture 21 to form a concrete bulb-shaped portion 18 at the tip of the friction pile 1 as shown in FIG. The support force at the tip of the friction pile 1 is increased by the portion 18 and the expanded blade 4. In addition, since the lower edge 7a of the support portion 7 of the fin-shaped projection 3 is inclined, the area where the edge of the fin-shaped projection 3 on the tip side of the pile comes into contact with the ground 17 is increased, and the tip of the friction pile 1 is supported. The power is further increased. Note that a load is always applied to the friction pile 1 in the downward direction, and since the bulb-shaped portion 18 is present, the open expanding blade 4 does not close.

[0017]

As described above, according to the friction pile of the first aspect of the present invention, a plurality of circular arc-shaped portions having substantially the same radius of curvature as the cylindrical pile main body are provided around the pile tip opening of the pile main body. The upper ends of the expanding blades are connected to each other so that the expanding blades can expand outward, and a lock body for restricting the expansion of the expanding blades is positioned opposite the pile tip surface of the pile body. At the same time, the lock body is locked to the expanding blade, and the fin-like projection is extended in the direction of the pile tip to form a holding portion for holding the expanding blade at a predetermined expanding angle, so that the locking is performed in the ground. By moving the body downward and expanding the expanding blades, a bulb-shaped part can be easily formed at the tip of the pile, and the tip of the pile is supported by the bulb-shaped part and the expanded blade. The force can be increased. In addition, while the pile is being driven, the lock body can prevent the expanding blade from being carelessly opened, thereby improving workability. Further, since the spread state of the spreading blade can be maintained by using the fin-shaped projections, the structure is not complicated, and the manufacturing cost can be reduced. On the other hand, since the expanding blade has an arc shape having substantially the same radius of curvature as the pile main body, the resistance when driving the pile main body to which the open expanding blade is connected can be reduced, and when driving the pile main body into the ground, Since the ground is discharged along the outer peripheral shape of the pile main body, the area where the soil adheres to the pile main body does not decrease, and the bearing capacity of the friction pile does not decrease.

According to the friction pile according to the second aspect of the present invention, since the edge of the fin-shaped projection on the pile tip side is inclined, the area where the edge of the fin-shaped projection on the pile tip side contacts the ground increases. In addition, the tip support force of the friction pile can be further increased.

According to the method of constructing a friction pile according to the third aspect of the present invention, after the friction pile is driven into the ground, a mixture of cement and aggregate is poured into the tip of the pile body of the friction pile. By dropping the weight into the inside, the lock body is moved downward to expand the spreading blades to the predetermined spreading angle, and the mixture is spread to the tip of the friction pile, and friction is caused by the penetration of groundwater into the mixture. Since a concrete bulb-shaped part is formed at the tip of the pile, the bulb-shaped part can be formed by driving the pile except for the work of charging the mixture, and the friction pile with the conventional bulb-shaped part is constructed. This greatly improves the efficiency of construction work.

[Brief description of the drawings]

FIG. 1 is a front view showing a friction pile according to an embodiment of the present invention.

FIG. 2 is a perspective view of a bulb construct of the friction pile.

FIG. 3 is a perspective view of a pile tip portion of the friction pile.

FIG. 4 is a sectional view showing a construction step of the friction pile.

FIG. 5 is a sectional view showing a construction process of the friction pile.

FIG. 6 is a sectional view showing a construction step of the friction pile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Friction pile 2 Pile main body 3 Fin-like projection 4 Expanding blade 5 Bulb formation 7 Holding part 12 Lock body 18 Bulb-shaped part 21 Mixture

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masanori Murashima 1-88, Oyodonaka, Kita-ku, Osaka-shi, Osaka Sekisui House Co., Ltd. F-term (reference) 2D041 AA02 BA13 BA21 BA33 CA03 CB06 DB02 FA12

Claims (3)

[Claims] 1. A fin-like projection for increasing a frictional force is protruded from an outer peripheral surface of a cylindrical pile main body along an axial direction of the pile main body, and the fin-shaped projection is provided around a pile tip opening of the pile main body. The upper ends of a plurality of arc-shaped expanding blades having substantially the same radius of curvature as the cylindrical pile main body are connected so that the expanding blades can expand outward, and the expanding blades are expanded. A lock body for restricting the opening is locked to the spreading blade so as to face the pile tip surface of the pile body, and the fin-like projection is extended in the direction of the pile tip to extend the expanding blade to a predetermined width. A holding portion for holding at an open angle is formed, and when the lock body is moved downward, the locked state with the expanding blade is released, and the expanding blade expands to the predetermined expanding angle. A friction pile characterized by being configured to be openable. 2. The friction pile according to claim 1, wherein an edge of the fin-like projection on a pile tip side is inclined. 3. A fin-shaped projection for increasing a frictional force is protruded from an outer peripheral surface of a cylindrical pile main body along an axial direction of the pile main body, and the fin-shaped protrusion is provided around a pile tip opening of the pile main body. The upper ends of a plurality of arc-shaped expanding blades having substantially the same radius of curvature as the cylindrical pile main body are connected so that the expanding blades can expand outward, and the expanding blades are expanded. A lock body for restricting the opening is locked to the spreading blade so as to face the pile tip surface of the pile body, and the fin-like projection is extended in the direction of the pile tip to extend the expanding blade to a predetermined width. A holding portion for holding at an open angle is formed, and when the lock body is moved downward, the locked state with the expanding blade is released, and the expanding blade expands to the predetermined expanding angle. In the construction method of the friction pile configured to be open, after driving the friction pile into the ground, A mixture of cement and aggregate is put into the tip of the friction pile in the pile main body, and then the weight is dropped into the pile main body, thereby moving the lock body downward and expanding the lock body. The mixture is spread to the tip of the friction pile while the opening blade is expanded to the predetermined angle, and a concrete bulb is formed at the tip of the friction pile by infiltration of groundwater into the mixture. A method of constructing a friction pile.