JP2003293367A - Foundation pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foundation pile being easily buried into a ground (having burying speed faster than a closed type foundation pile) and ensuring sufficient bearing capacity after burying. <P>SOLUTION: The open type foundation pile in which a plurality of excavating edges 13 are fixed onto a pile body 11 having an opening end face 12 at a front end (a lower end) and being made of a steel pipe by a welding or the like is constituted by fixing a front-end spiral blade 14 in one winding and an upper spiral blade 15 on the outer peripheral surface of the pile body 11 by the welding or the like. The front end of the pile body 11 is projected from the front-end spiral blade 14 by the approximately diameter section of the pile body, and a space 17 in which soil and sand are consolidated and held is partitioned between the outer peripheral surface at the front end section of the pile body 11 and the base of the front-end spiral blade 14. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a foundation pile that can be buried in soft ground without vibration and can maintain a sufficient bearing capacity after being buried.

[0002]

2. Description of the Related Art Foundation piles with spiral blades that are buried in soft ground with no soil, noise, and vibration, for example, a closed type in which the tip of the pile body is made of steel pipe are closed, and a pile body It is known as an open type with the tip of the open.

The closed-type foundation pile whose tip is closed is excellent in that, after being buried in the ground, the tip of the pile body as well as the spiral blade can receive the ground reaction force to secure a sufficient supporting force. . However, when buried in the ground, there is a problem that a large pressing force is required to push the pile body into the ground in order to push out the soil corresponding to the volume of the pile body to the side surface side of the pile body. In addition, although the sand and sand pushed out to the side surface of the pile body generate a rotational propulsion reaction force of the spiral blade and the pile body propels into the ground, the rotation of the tip spiral blade attached to the tip side surface of the pile body causes the pile to rotate. There is a problem that the center of the body is misaligned. That is, there is a problem that the tip of the pile main body is closed, there is resistance to bite into the ground, and the tip of the pile main body is likely to move in the rotational direction of the tip spiral blade due to the rotation of the tip spiral blade.

On the other hand, in an open foundation pile with an open tip, when it is buried in the ground, the amount of earth and sand of the pile body is taken in from the opening at the tip of the pile body. It is expected that the problems of closed foundation piles can be solved, but in reality there are the following problems. When the pile main body is rotated when it is buried in the ground, the spiral blade bites into the ground by half rotation of the pile main body and propels the pile main body into the ground, but the remaining half rotation presses the soil and sand, It works to push earth and sand into the inside of the pile main body from the opening at the tip of the pile, and as a result, the earth and sand above the volume of the pile main body is pushed into the inside of the pile main body, and the inside of the pile main body is immediately closed by the sediment. . Therefore, in order to further propel the pile main body into the ground, a large pressing force is required to push the pile main body into the ground like the closed foundation pile. In addition, in the case of a silt layer with a soil N value of around 0 to 3 and a high water content, there is almost no resistance due to sediment, no rotational propulsion force is generated by the spiral blades, and it is long for burying foundation piles. It takes time. That is, even if the pile main body is rotated, the spiral blade only scratches around the soil having a high water content around it, and the rotation propulsion is not performed as in the case of rotating the spiral blade in water, and idling is repeated. Therefore, it is necessary to leave it for a day and night and wait until the resistance due to the sand and sand is restored to continue the work of burying the foundation piles, and it takes a long time to bury the foundation piles.
Furthermore, after the tip of the pile body reaches the support layer, a load test to confirm the safety of the pile can support the design load, but considering the safety factor,
When a double load is applied, sinking of the pile progresses, and when a triple load is applied, only 75% to 80% of this triple load can be supported, which is greater than the closed foundation pile. It has been proved that the bearing capacity cannot be secured. The cause is
It is speculated that the sediment acting on the ground from the lower part of the spiral wing slips and breaks, and this sediment enters the inside of the pile body through the tip opening.

Open type foundation piles were expected to solve the problems of closed type foundation piles, but there are various problems as described above.

As shown in FIGS. 5 to 7, the tip end of a steel pipe 50 having an open tip is cut out along the spiral blade, and the outer diameter of the cutout end 51 is larger than the outer diameter of the steel pipe. Large, donut-shaped steel plate with an inner diameter smaller than the inner diameter of the steel pipe 5
2 are fixed by welding, and the steel pipe 50 is provided at a height position from the tip of the steel pipe 50 to approximately 0.5 to 2.0 times the steel pipe inner diameter 50a.
There has been proposed a steel pipe pile provided with an annular protrusion 53 for promoting the clogging of the earth and sand that has entered the interior (see, for example, Patent Document 1).

[0007]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-146741 (page 8, FIG. 4, FIG. 10)

[0008]

However, the proposed steel pipe pile has a problem that the tip of the pile tip is efficiently inserted into the support layer where the ground is relatively hard. The burial (construction) speed until reaching the support layer was not a problem, and the burial speed was no different from that of the closed foundation pile, and was not satisfactory.

The foundation piles are required to be easily buried in the ground (the embedding speed is higher than that of the closed foundation piles),
Although it is possible to secure a sufficient bearing capacity after burial, none of the foundation piles proposed so far satisfy this requirement sufficiently.

The present invention has been made in view of the above circumstances, and it is easy to bury it in the ground (the burying speed is higher than that of the closed foundation stake), and a sufficient supporting force can be secured after burying. The purpose is to provide.

[0011]

[Means for Solving the Problems] When the problems of the above-mentioned open foundation pile were examined, in order to promote the burying of the pile body into the ground, the tip of the pile body was opened and the pile body was opened. It is necessary to prevent the volume of earth and sand from entering the pile body as the pile body is buried and not exceeding the volume (it is necessary to prevent internal blockage). It was found that in order to maintain the bearing capacity, it is necessary to prevent the sliding and breaking of the sediment beneath the tip spiral wing so that the sediment does not enter (inflow) from the tip of the pile body. The present inventor has conducted diligent research so as to satisfy these requirements, and it is possible to satisfy these requirements by securely holding the soil between the tip side surface of the pile body and the bottom surface of the tip spiral blade. The present invention has been completed and the present invention has been completed.

That is, in the foundation pile of the present invention which achieves the above-mentioned object, the tip of the pile main body is such that the bottom surface of the tip spiral blade which is the spiral blade located closest to the tip of the pile main body and the outer peripheral surface on the tip side of the pile main body. It is characterized in that it is made to protrude from the tip spiral blade by a predetermined length so as to hold the soil between and. More specifically, by projecting the tip of the pile body by a predetermined length from the tip spiral blade, which is the spiral blade located closest to the tip of the pile body, the tip spiral blade is rotated by the rotation of the tip spiral blade when the foundation pile is buried. It is characterized in that the earth and sand pressed by the bottom surface of the blade is held between the bottom surface of the tip spiral blade and the outer peripheral surface on the tip side of the pile body so as not to flow into the pile body from the opening.

Construction of the pile is carried out by transmitting the load and the rotational force of the excavator to the pile body from the upper part. When the load and the rotational force of the excavator are transmitted to the pile body, the protrusion of the pile tip rotates,
Since the pile tip cross-sectional area is small, the pile body propels it while intruding sand and sand inside, and the spiral blade at the tip rotates so as to cut into the ground, and the ground strength due to the composition of the soil is used as the reaction force of the rotation propulsion. Is buried in the ground to pull in the
While generating the rotational propulsion force of the pile body, the earth and sand pressed by the bottom surface of the tip spiral wing is held by the tip side surface of the pile body so that it does not enter (inflow) into the pile body from the opening at the tip of the pile body. To prevent internal blockage, which promotes rotational propulsion of the pile body. Also, after the pile body is buried, it is possible to consolidate the earth and sand between the bottom surface of the tip spiral wing and the tip side surface of the pile body, prevent slipping and breaking of the earth and sand, and ensure sufficient bearing capacity. .

The length of the tip of the pile body protruding from the tip spiral blade is preferably set to, for example, about 1 to 2 times the diameter of the pile body. If the projecting length is less than 1 times the diameter of the pile body, due to the flow of sediment at the bottom of the tip spiral blade, the sediment volume above the volume of the pile body will flow into the pile body and the inside of the pile body will be internal. It will be in a closed state and the construction efficiency will decrease, and the effect of preventing pile misalignment due to the protrusion will decrease, and after reaching the support layer, it will hold the earth and sand between the bottom surface of the tip spiral blade and the tip side surface of the pile body. It is difficult to consolidate, and if the protruding length exceeds more than twice the diameter of the pile body, it is possible to retain soil and consolidate it, but the tip spiral blade is far away from the tip of the pile body, This is because the supporting force of the pile exerts the supporting force depending on the sum of the bottom area of the spiral blade and the supporting layer, and therefore the pile supporting force does not need to be more than twice the diameter of the pile main body.

The outer diameter of the tip spiral blade is preferably set to, for example, 2 to 3 times the diameter of the pile body. If the outer diameter of the tip spiral wing is less than twice the diameter of the pile body, the rotation propulsive force of the tip spiral wing is small and the area of the tip spiral wing that receives the ground reaction force is small, so that sufficient supporting force can be obtained. If the outer diameter of the tip spiral blade exceeds three times the diameter of the pile body, a large rotational force and pressing force are required when the tip spiral blade is cut into a hard support layer, which may damage the pile body. It may happen.

Further, for example, two spiral blades are arranged on the outer peripheral surface of the pile main body, one is a tip spiral blade, and the other is an outer diameter of the tip spiral blade upward from the tip spiral blade. Of 1.5
It is preferable that the upper spiral blades have an outer diameter larger than the outer diameter of the tip spiral blades and are arranged at a distance of twice or twice. In this way, even if the tip spiral blade enters the soft silt layer with a high water content and the rotary thrust generated by the tip spiral blade biting into the ground is not obtained,
Since the upper spiral blade that does not reach the silt layer penetrates into the ground and obtains rotational propulsion force, the pile body can be embedded and propelled in the ground, and the tip spiral blade passes through the silt layer, and the upper spiral blade becomes silt. Even if it moves to the layer, the tip spiral blade can bite into the ground and obtain the rotational propulsion force. That is, it is possible to prevent a situation in which one of the spiral blades bites into the ground and the spiral blade idles in the ground, and the rotational propulsive force cannot be obtained. further,
When the rotary burial is completed at the predetermined position of the support layer and the building load is applied to the pile tip, the load is transmitted to the ground by the tip spiral wing and the bottom surface of the upper spiral wing, and the two spiral blades make a big difference. It is possible to exert supportive power.

Further, for example, a reinforcing plate can be provided along the outer peripheral surface of the tip portion protruding from the tip spiral blade of the pile body, and the excavating blade can be fixed to the reinforcing plate. This way,
Even if the tip of the pile body enters the hard ground that serves as a support layer, there is no possibility of being deformed or crushed by the pressure from the ground.

Further, for example, a friction cut plate is provided along the inner peripheral surface of the tip portion projecting from the tip spiral blade of the pile body, and the end portion of the friction cut plate is projected from the tip of the pile body,
A cutting edge can be formed on this protruding end. In this way, the friction cut plate narrows the opening area of the opening at the tip of the pile body (the opening is narrowed), and the earth and sand excavated and softened by the cutting blade enters the inside of the pile body through the opening. At this time, although it temporarily controls the ingress of sediment,
When the earth and sand pass through the friction cut plate, the earth and sand enter into a space wider than the opening, and thereafter the earth and sand move smoothly in the pile body. In the present specification, the friction cut plate does not eliminate friction between itself and the earth and sand, but once the inflow of earth and sand is squeezed and then released, the inflow of earth and sand into the pile body is prevented. It means that it contributes to making it run smoothly.

Further, the spiral blade arranged on the outer peripheral surface of the pile body is composed of the tip spiral blade, the upper spiral blade and a plurality of auxiliary spiral blades, and the plurality of auxiliary spiral blades are The auxiliary spiral blades, which are arranged at regular intervals in the axial direction of the pile and are closest to the upper spiral blade, are 1.5 times to 2 times the outer diameter of the tip spiral blade upward from the upper spiral blade.
It is also possible that the outer diameters of the upper spiral blades are larger than the outer diameter of the upper spiral blades.

The outer diameter of the auxiliary spiral blade closest to the upper spiral blade is the smallest, and the outer diameter of the auxiliary spiral blade arranged at the top is the largest, The diameter can be increased at a constant rate.

Further, at least one inner spiral blade may be provided on the inner peripheral surface of the pile body at a position about 1 to 2 times the diameter of the pile body from the opening.
For example, it is preferable to provide one inner spiral blade at the same position as the position where the tip spiral blade is provided.

Further, a connecting pile having an outer diameter larger than the outer diameter of the pile body of the foundation pile can be connected to the base end of the foundation pile.

[0023]

1 is a perspective view showing an embodiment of the foundation pile of the present invention, FIG. 2 is a partially omitted perspective view showing a modification of the foundation pile of FIG. 1, and FIG. 3 is a perspective view of the present invention. FIG. 4 is a perspective view showing another embodiment of the foundation pile, and FIG. 4 is a partial sectional view of the foundation pile shown in FIG.

An embodiment of the foundation pile of the present invention will be described with reference to FIG. The foundation pile 10 is an open-type foundation pile in which a plurality of excavating blades 13 are fixed to the opening end surface 12 of the tip (lower end) of the steel pipe pile body 11 by welding or the like, and one winding is made around the outer peripheral surface of the pile body 11. The tip spiral blade 14 and the upper spiral blade 15 are fixed by welding or the like.

Specifically, from the tip of the pile body 11 to the pile body 1
One having an outer diameter of approximately twice the pile diameter, which extends upward in a spiral shape along the outer peripheral surface of the pile main body 11 with a position separated upward by a length substantially equal to the diameter of 1 (pile diameter) as a starting point 16. A spiral tip spiral wing 14 is fixed by welding or the like. In addition, a position higher than the tip spiral wing 14, that is, the tip spiral wing 14
Has a diameter larger than the blade diameter, which spirally extends upward along the outer peripheral surface of the pile body 11 starting from the outer peripheral surface position of the pile body 10 that is 1.5 to 2 times the diameter (blade diameter). One turn of the upper spiral wing 15 is fixed by welding or the like.

A space 17 for holding soil and sand in a compacted state is defined between the bottom surface of the tip spiral wing 14 and the outer peripheral surface on the tip side of the pile body 11. In other words, the space 17 that holds the soil in a compacted state is defined around the tip protruding portion 11a that protrudes from the tip spiral blade 14 of the pile body 11. This space 17
When the pile body 11 is buried in the ground, the tip spiral wing 14 rotates to consolidate the earth and sand pressed by the bottom surface of the tip spiral wing 14, and this acts as a resistance of the tip spiral wing 14 and Rotating propulsion force is generated while the tip spiral blade 14
The earth and sand pressed by the bottom surface of the pile do not enter (flow) into the inside from the opening end surface 12 to prevent the pile main body 11 from being internally blocked. Further, the space 17 can consolidate the earth and sand even after the pile body 11 is buried, prevent slipping and breaking of the earth and sand, and ensure a sufficient supporting force.

According to the foundation pile of the above-mentioned embodiment, when the load and the rotational force of the excavator are transmitted from the upper portion to the pile body 11, the tip projecting portion 11a of the pile body 11 rotates and the opening end face of the tip of the pile body 11 is rotated. Since the cross-sectional area of 12 is small, the pile main body 11 is propelled while the earth and sand are advancing inside, and the tip spiral wing 14 is rotated to cut into the ground, and the strength of the ground due to the composition of the soil is used as the reaction force of the rotational propulsion. The pile main body 11 is pulled in to be buried underground by rotation. During this rotation propulsion, earth and sand enter the inside of the pile main body 11 from the open end surface 12 of the pile main body 11, but since the soil and sand are held compactly in the space 17 (because the space 17 exerts ground retention force), It is possible to prevent the earth and sand pressed by the bottom surface of the spiral wing 14 from entering from the opening end surface 12 (to prevent the earth and sand from entering more than necessary), and to avoid the internal blockage due to the earth and sand, and in the ground of the pile body 11. Can accelerate the entry into. Until the tip of the pile body 11 reaches a stratum having a predetermined N value,
Rotate and propel into the ground while adding steel pipes. During the rotational propulsion into the ground, the tip spiral wing 14 enters the soft silt layer having a high water content, and even if the rotary propulsion force generated by the tip spiral wing 14 biting into the ground is not obtained, the tip When the upper spiral wing 15 located at an upper position 1.5 to 2 times the diameter of the spiral wing 14 is located in another hard ground and does not reach the silt layer, the upper spiral wing 15 bites into the ground and rotates. Since the propulsive force is obtained, the pile main body 11 can be embedded and propelled in the ground without any trouble. And
The tip spiral blade 14 passes through the silt layer, and the upper spiral blade 15
Even if is moved to the silt layer, the tip spiral blade 14 can bite into the ground and obtain the rotational propulsion force.

After the foundation pile 10 is buried, the building load on the foundation pile 10 is increased by the pile body 11, the tip spiral blade 14, and the upper spiral blade 15.
While acting on the ground through the etc., from the ground to the pile body 11,
Ground reaction force acts on the tip spiral wing 14, the upper spiral wing 15, etc. to firmly support the building on the ground. At this time, although a pressing force acts on the earth and sand by the bottom surface of the tip spiral wing 14, the earth and sand is compacted and held in the space 17 (the space 17 exerts a ground holding force), and slip failure occurs to cause pile failure from the opening end face 12. The support force can be maintained without invading the inside of the main body 11.

FIG. 2 shows a modified example of the foundation pile 10 shown in FIG. 1 described above.
An outer pipe 18 made of a steel pipe as a reinforcing plate is fixed to the outer peripheral surface of the tip of the pile main body 11 for partitioning the pile by welding or the like.
And the outer tube 18 are concentric. In addition, foundation pile 1
In 0a, three digging blades 13 are fixed to the open end surface of the outer pipe 18 instead of the open end surface 12 of the pile body 11 by welding or the like with a predetermined interval in the circumferential direction. If the excavating blade 13 is attached to the open end surface of the outer pipe 18 having a short length instead of the open end surface 12 of the pile body 11, the excavating blade 13 can be easily attached.

In the case of the modified foundation pile 10a, the pile body 11
Even if the tip of the pile is in the hard ground, the outer pipe 18 protects the outer peripheral surface of the tip of the pile body 11, and there is no risk of being crushed by the pressure of the ground.

Next, another embodiment of the foundation pile of the present invention will be described with reference to FIGS. 3 and 4. In the figure, the same parts as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In the foundation pile 10b of this embodiment, the pile body 11 is
A tubular friction cut plate 19 having a short length is fixed to the opening 12a at the tip of the pipe along its inner peripheral surface by welding or the like, and the pile body 11 and the friction cut plate 19 are concentric. .
The friction cut plate 19 is thicker than the wall thickness of the steel pipe that constitutes the pile main body 11, and the end thereof is formed on the cutting blade 20 so as to project from the tip of the pile main body 11.

When burying the foundation pile 10b in the ground,
The cutting blade 20 excavates and softens the earth and sand, and the earth and sand enters the inside of the pile body 11 through the opening 12a whose opening area (earth and sand inlet) is reduced by the friction cut plate 19. When the sand and sand enter the inside of the pile main body 11, the friction cut plate 19 temporarily suppresses the sand and sand from entering (squeezes the flow of the sand and sand), but when the sand and sand passes through the friction cut plate 19, the sand and sand are wider than the opening 12a. Since it will enter the space, the earth and sand will move smoothly in the pile body 11 thereafter. In other words, once the aperture 12a is squeezed, excess sediment (earth and sand that causes internal clogging)
Is prevented, the friction between the earth and sand and the inner wall of the pile main body 11 is reduced, and the flow of earth and sand inside the pile main body 11 is made smooth.

That is, according to the foundation pile 10b, combined with the effect of the space 17 defined between the bottom surface of the tip spiral wing 14 and the outer peripheral surface of the pile body 11 on the tip side, the pile body 11 is
The flow of earth and sand inside becomes smooth, and it becomes possible to improve the efficiency of burying work in the ground.

The friction cut plate 19 is the outer tube 1 of FIG.
Similarly to 8, the tip of the pile body 11 is reinforced.

In the embodiments shown in FIGS. 1 to 4, the case where one upper spiral blade 15 is provided in addition to the tip spiral blade 14 is shown, but the upper spiral blade 15 may not be provided, and the upper spiral blade 15 may be omitted. Two or more spiral blades 15 may be provided.

Next, another embodiment of the foundation pile according to the present invention will be described with reference to FIGS. 12 and 13. Figure 1
2 shows a perspective view of the tip spiral wing 14, and FIG.
The bottom view of the tip spiral blade 14 is shown. As shown in FIGS. 12 and 13, the front end 14 a of the tip spiral blade 14 has:
The excavating blade 14b is provided by welding or the like. By providing the excavating blade 14b in this way, the rotational propulsion force of the pile main body can be improved and smooth construction can be performed. Further, as shown in FIG. 12, the front end 14a of the tip spiral blade 14 is
By chamfering to form the inclined surface 14c, it is possible to further improve the rotational propulsion force of the pile body and perform a smoother construction.

Next, still another embodiment of the foundation pile according to the present invention will be described with reference to FIG. As shown in FIG. 8, in the foundation pile 10c of this modified example, the spiral blades arranged on the outer peripheral surface of the pile body 11 have the tip spiral blade 14 and the upper spiral blade 1
5 and two auxiliary spiral blades 30a and 30b. The two auxiliary spiral wings 30a and 30b are the foundation pile 10c.
The auxiliary spiral blades 30a, which are arranged at regular intervals in the axial direction of the pile main body 11 and are closest to the upper spiral blade 15, have 1.5 times the outer diameter of the tip spiral blade 14 upward from the upper spiral blade 15. The outer diameter of the upper spiral blade is larger than the outer diameter of the upper spiral blade. Also, the outer diameters of the auxiliary spiral blades 30a and 30b are set so that the outer diameter of the auxiliary spiral blade 30a closest to the upper spiral blade 15 is the smallest and the outer diameter of the auxiliary spiral blade 30b arranged at the top is large. It is increasing at a constant rate. In the illustrated example, the plurality of auxiliary spiral blades is composed of two, but the invention is not limited to this and may be composed of three or more. For example, when a plurality of auxiliary spiral blades are configured by three, the outer diameter of the auxiliary spiral blade closest to the upper spiral blade 15 is the smallest, the outer diameter of the auxiliary spiral blade arranged at the top is large, and The outer diameter of the auxiliary spiral blade located at is larger than the outer diameter of the auxiliary spiral blade closest to the upper spiral blade 15 and smaller than the outer diameter of the auxiliary spiral blade arranged at the top. Therefore, the outer diameters of the three auxiliary spiral blades increase at a constant rate.

As described above, the spiral blade arranged on the outer peripheral surface of the pile main body 11 is constituted by adding not only the tip spiral blade 14 and the upper spiral blade 15 but also a plurality of auxiliary spiral blades, whereby the rotational propulsion force is increased. And the bearing capacity of the pile can be increased. In particular, when the support layer is soft, it is effective to increase the support force by such a structure.

Next, still another embodiment of the foundation pile according to the present invention will be described with reference to FIGS. 9 and 10. FIG. 9 shows a partial cross-sectional view of the foundation pile, and FIG. 10 shows a front view of the tip of the foundation pile. As shown in FIGS. 9 and 10, at least one or more inner spiral blades 31 are welded to the inner peripheral surface of the pile body 11 at a position approximately 1 to 2 times the diameter of the pile body 11 from the opening. It is provided in. In the illustrated example, one inner spiral blade 31 is provided at a position about 1 to 2 times the diameter of the pile main body 11 from the opening and at the same position as the position where the tip spiral blade 14 is provided. . More specifically, the inner spiral blade 31 is provided along the inner surface of the tip spiral blade 14.

By providing the inner spiral blades 31 on the inner peripheral surface of the pile body 11 as described above, the bending stress of the pile main body 11 received by the spiral blades provided on the outer peripheral surface of the pile body 11 is reduced, and the pile main body 11 is supported. The power can be increased.

Next, another embodiment of the foundation pile according to the present invention will be described with reference to FIG. As shown in FIG. 11, the base pile 10d is welded or jointed at its base end (upper side in FIG. 11) with a connecting pile 32 having an outer diameter larger than the outer diameter of the pile body 11 of the base pile 10d. The length of the pile is long because it is connected. Connection pile 3 shown in FIG.
2 is connected to the foundation pile 10d by a flange joint 33.

With this structure, a sufficient supporting force can be obtained against the horizontal force applied to the upper part of the pile.

[0044]

As described above, according to the foundation pile of the present invention, the tip of the pile body is projected by a predetermined length from the tip spiral blade which is the spiral blade located closest to the tip of the pile body. , The earth and sand pressed by the bottom surface of the tip spiral wing by the rotation of the tip spiral wing when burying the foundation pile is held between the bottom surface of the tip spiral wing and the outer peripheral surface on the tip side of the pile main body from the opening. Since it is prevented from flowing into the pile body, earth and sand are retained between the tip spiral blade and the tip outer peripheral surface of the pile body during or after the pile body is embedded in the ground, so that the rotation and promotion to the ground can be facilitated. It can be promoted to shorten the construction time, and the bearing capacity can be maintained for a long time. That is, in the foundation pile according to the present invention, the spiral blade bites into the earth and sand due to the rotation of the pile body, and the propelling force of the ground is used as a reaction force to rotate and propel. At this time, the soil below the tip spiral blade is
Since the tip of the pile main body protrudes from the tip spiral blade by a predetermined length, it does not penetrate into the pile main body through the opening, and it is possible to prevent internal clogging in the pile main body. Further, unlike the conventional closed pile, the side surface of the pile body is not compacted with the volume of the pile body, so that the side surface of the pile body does not generate frictional resistance against excess sand, which facilitates rotary propulsion. It can be performed and the efficiency of construction can be improved. Further, when the tip of the pile reaches the support layer, it is possible to widely disperse the load on the ground by holding the earth and sand in a wide area between the bottom surface of the tip spiral wing and the tip outer peripheral surface of the pile body. , It is possible to maintain the pile for a long period of time with a bearing capacity larger than that of the conventional closed pile.

If the length of the tip of the pile main body protruding from the tip spiral wing is set to be about 1 to 2 times the diameter of the pile main body, rotation propulsion to the ground is facilitated and the ground holding force is ensured. Can be demonstrated.

When the outer diameter of the tip spiral wing is set to be 2 to 3 times the diameter of the pile main body, a sufficient reaction force can be obtained by receiving the ground reaction force, while it is large in order to dig into the ground. No turning force is required.

Further, two spiral blades are arranged on the outer peripheral surface of the pile body, one is a tip spiral blade, and the other is an outer diameter of the tip spiral blade upward from the tip spiral blade. 1.5 times to 2
In the case of an upper spiral blade with an outer diameter that is larger than the outer diameter of the tip spiral blade, which is arranged with a double interval, a soft silt layer with a high water content is formed before reaching the relatively hard ground. Even if it exists, the pile body can be embedded and promoted in the ground without any trouble. After embedding, the tip spiral blade and the upper spiral blade can exert their supporting forces respectively.

If a reinforcing plate is provided at the tip of the pile body protruding from the tip spiral blade and the drilling blade is fixed to the reinforcing plate,
Even if the tip of the pile body enters the hard ground that serves as a support layer, there is no possibility of being deformed or crushed by the pressure from the ground.

Further, a friction cut plate is provided along the inner peripheral surface of the tip portion projecting from the tip spiral blade of the pile body, and the end portion of the friction cut plate is projected from the tip of the pile body, and the projecting end is provided. If the cutting edge is formed in the portion, it becomes possible to improve the work efficiency of burying the foundation pile.

Further, the spiral blade arranged on the outer peripheral surface of the pile main body is composed of a tip spiral blade, an upper spiral blade and a plurality of auxiliary spiral blades, and the plurality of auxiliary spiral blades are fixed in the axial direction of the foundation pile. Arranged at intervals, the auxiliary spiral blade closest to the upper spiral blade,
The outer diameter of the tip spiral blade is 1.5 upward from the upper spiral blade.
By arranging them at a distance of 2 to 2 times and having an outer diameter larger than the outer diameter of the upper spiral blade, it is possible to increase the rotational propulsion force and the supporting force of the pile. it can. Furthermore, it can also be used as a multi-blade bearing pile (friction pile) supported by the intermediate layer of the ground where the support layer is deep.

Further, by providing at least one or more inner spiral blades on the inner peripheral surface of the pile main body at a position about 1 to 2 times the diameter of the pile main body from the opening, the outer peripheral surface of the pile main body 11 is It is possible to reduce the bending stress of the pile body 11 that is received by the provided spiral blades and increase the supporting force.

Further, by connecting a connecting pile having an outer diameter larger than the outer diameter of the pile main body of the foundation pile to the base end of the foundation pile, a sufficient supporting force can be resisted against the horizontal force applied to the upper portion of the pile. Can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a foundation pile of the present invention.

FIG. 2 is a partially omitted perspective view showing a modified example of the foundation pile of FIG.

FIG. 3 is a perspective view showing another embodiment of the foundation pile of the present invention.

FIG. 4 is a partial cross-sectional view of the foundation pile of FIG. 3 in which a tip spiral blade is omitted.

FIG. 5 is a partially omitted perspective view showing a steel pipe pile of the related art.

6 is a vertical cross-sectional view of the steel pipe pile of FIG. 5 with a part thereof omitted.

FIG. 7 is a cross-sectional view taken along the line AA of FIG.

FIG. 8 is a partial perspective view showing another embodiment of the foundation pile of the present invention.

FIG. 9 is a partial cross-sectional view showing still another embodiment of the foundation pile of the present invention.

FIG. 10 is a front side view of the foundation pile shown in FIG.

FIG. 11 is a partial perspective view showing still another embodiment of the foundation pile of the present invention.

FIG. 12 is a partial perspective view showing still another embodiment of the foundation pile of the present invention.

13 is a front side view of the foundation pile shown in FIG.

[Explanation of symbols]

10, 10a, 10b, 10c, 10d Foundation pile 11 Pile body 11a Tip protrusion 12 Opening end 12a Opening 13 Excavation 14 Tip spiral blade 14a Front end 14b Excavation blade 14c Inclined surface 15 Upper spiral blade 17 Space 18 Reinforcement plate (outer tube ) 19 Friction cut plate 20 Cutting blades 30a, 30b Auxiliary spiral blade 31 Inner spiral blade 32 Connection pile 33 Flange joint

Claims (11)

[Claims] 1. A foundation pile comprising one or more spiral blades arranged on the outer peripheral surface of a pile main body having an opening at the tip, wherein the spiral blade is located closest to the tip of the pile main body. By projecting the tip of the pile main body from the tip spiral blade by a predetermined length, the earth and sand pressed by the bottom surface of the tip spiral blade by the rotation of the tip spiral blade when the foundation pile is buried is A foundation pile, characterized in that it is held between the bottom surface of the spiral wing and the outer peripheral surface on the tip side of the pile body so as not to flow into the pile body from the opening. 2. The foundation pile according to claim 1, wherein the predetermined length is about 1 to 2 times the diameter of the pile main body. 3. The foundation pile according to claim 2, wherein the tip spiral wing has an outer diameter that is 2 to 3 times the diameter of the pile body. 4. The foundation pile according to claim 1, wherein the spiral blade arranged on the outer peripheral surface of the pile body is two,
One of the tip spiral blades, and the other one is arranged above the tip spiral blade at a distance of 1.5 to 2 times the outer diameter of the tip spiral blade. Is an upper spiral blade having an outer diameter larger than the outer diameter of
Foundation pile. 5. The foundation pile according to claim 4, wherein the spiral blade arranged on the outer peripheral surface of the pile main body includes the tip spiral blade, the upper spiral blade, and a plurality of auxiliary spiral blades. , The plurality of auxiliary spiral blades are arranged at a constant interval in the axial direction of the foundation pile, and the auxiliary spiral blades closest to the upper spiral blade are upward of the upper spiral blade of the tip spiral blade. A foundation pile, characterized in that it is arranged with an interval of 1.5 to 2 times the outer diameter and has an outer diameter larger than the outer diameter of the upper spiral blade. 6. The foundation pile according to claim 5, wherein the auxiliary spiral blade closest to the upper spiral blade has the smallest outer diameter, and the auxiliary spiral blade arranged at the top has the largest outer diameter. As described above, the foundation pile is characterized in that the outer diameter of each of the auxiliary spiral blades is increased at a constant rate. 7. The foundation pile according to any one of claims 1 to 6, wherein at least one inner spiral blade is provided on the inner peripheral surface of the pile body from the opening to the pile body. A foundation pile, which is provided at a position of about 1 to 2 times the diameter. 8. The foundation pile according to claim 7, wherein one inner spiral blade is provided at the same position as the position where the tip spiral blade is provided. 9. The foundation pile according to any one of claims 1 to 8, wherein a reinforcing plate is provided along an outer peripheral surface of a tip portion protruding from the tip spiral blade of the pile body, and the reinforcing plate is provided. Foundation pile, characterized in that the excavating blade is fixed to the foundation pile. 10. The foundation pile according to claim 1, wherein a friction cut plate is provided along an inner peripheral surface of a tip portion of the pile body protruding from the tip spiral blade of the pile body, A foundation pile, characterized in that an end of the friction cut plate is projected from the tip of the pile main body, and a cutting blade is formed at the projected end. 11. The foundation pile according to claim 1, wherein the base pile of the foundation pile has an outer diameter larger than an outer diameter of a pile body of the foundation pile. Foundation piles characterized by being connected to each other.