JP3785147B2 - Tip blade for rotary press-fit pile and rotary press-fit pile with the tip blade - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a rotary press-fit pile used for foundation support of a building or a civil engineering structure, and a rotary press-fit pile provided with the tip blade.
[0002]
[Prior art and its problems]
The rotary press-in pile is rotated while applying a load in the vertical direction to a pile standing on the ground, and press-fitted into the ground, and press-fitted to a depth at which a sufficient supporting force can be obtained by sequentially connecting a plurality of piles.
[0003]
In conventional rotary press-fit piles, for example, as shown in FIGS. 8 and 9, there are those provided with blades 32 and 32 for excavating the ground at the tip of a pile main body 31 made of a steel pipe. Even if there is an obstacle, the obstacle can be crushed with a blade or pushed outward.
[0004]
With rotary press-in piles, if the rotational resistance at the time of press-fitting is small, it is possible to perform rotary press-fitting smoothly into a harder and deeper ground, which can shorten the construction period and reduce the construction cost by shortening the construction period. In addition, a greater support force can be obtained, and the power source for rotating the pile can be miniaturized.
[0005]
However, in the conventional rotary press-fit pile, the earth and sand at the lower end of the pile is difficult to be discharged to the outer periphery of the pile, causing rotational resistance and hindering smooth rotary press-fit work.
[0006]
In addition, the obstacles in the ground and the rotation resistance of the pile cause the eccentricity of the pile, and if the pile is eccentric, there is a possibility that sufficient support force may not be obtained, and the building provided on the pile The foundation of an equal structure cannot be constructed accurately, which may cause a decrease in the strength of the structure.
[0007]
【the purpose】
The object of the present invention is that the sediment at the lower end of the pile is smoothly discharged to the outer periphery of the pile, the rotational resistance at the time of rotary press-fitting of the pile is small, and the construction is easy, and the centering of the pile is accurately performed. An object of the present invention is to provide a tip blade for a rotary press-fit pile and a rotary press-fit pile provided with the tip blade.
[0008]
[Structure of the invention]
In order to achieve the above object, a tip blade for rotary press-fitting piles according to the present invention includes a prismatic guide blade extending downward at the center of the bottom formed following the lower end of the cylindrical portion, A structure in which a plurality of outer blades formed in a plate shape are suspended around the guide blade so as to radiate around the guide blade, and the lower end of the guide blade protrudes below the lower edge of the outer blade. In addition, the bottom portion is formed in the shape of a narrow cone, and the outer blade is configured to have a shape that decreases in thickness toward the outside.
Moreover, the rotary press-fit pile according to the present invention has a configuration in which the tip blade having the above-described configuration is connected to the lower end of a pile body made of a steel pipe.
[0009]
【Example】
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a tip blade according to the present invention will be described below in detail based on specific examples shown in the accompanying drawings.
The tip blade 1 has a pointed head 3 that forms a conical cone that is the bottom of the tip blade, following the lower end of the cylindrical portion 2 for connection to the steel pipe pile, and a corner is formed at the center of the pointed head. A columnar, for example, square columnar guide blade 4 is provided.
[0010]
In some cases, the guide blade may be cylindrical or cone-shaped, but it has been confirmed by experiments that a square column such as a square column is better cut into the ground.
[0011]
A plurality (two in FIG. 2) of outer blades 5 and 5 formed in a plate shape are provided radially around the shaft around the guide blade 4 of the pointed head 3.
[0012]
As shown in FIG. 2, the outer blades 5 and 5 are formed so that the thickness decreases from the center side toward the outer peripheral side, and a part of the outer peripheral side is outside the pointed head. Overhangs. When the thickness of the outer blade is small toward the outside in this way, the earth and sand pressed around the guide blade by the outer blade is easily pushed outward along the surface of the outer blade, so that smooth earth and sand can be discharged. It is possible, and because part of the outer blade protrudes outside the pointed head, sufficient pressure is applied to the earth and sand around the pile, and the frictional support force between the pile and earth and sand is further increased. be able to.
[0013]
The number of outer blades is appropriately determined according to the number of obstacles in the ground, the N value of the ground, or the diameter of the pile, but if the number is too large, it may hinder the discharge of earth and sand. The degree is preferred.
[0014]
As shown in FIG. 3, the tip blade 1 having the above-described configuration is welded to the lower end of a pile body 6 made of a steel pipe to constitute a rotary press-fit pile, and is formed at the upper end of the cylindrical portion 2 of the tip blade. The tip 2a is butted against the lower open end of the pile body 6 and welded. In addition, the code | symbol 7 shows the welding part in FIG.
[0015]
Moreover, the joint 8 for connection with another pile is provided in the upper end part of the pile main body 6, This joint 8 is the internal thread body provided in the upper end of the lower pile main body 6 as FIG. 4 shows. 9 and a male threaded body 11 provided at the lower end of the pile 10 connected to the upper side thereof, and the piles can be sequentially connected by screwing the female threaded body and the male threaded body together.
[0016]
The screw formed in the female screw body and the male screw body is preferably a square screw having high load resistance, and the winding direction of the screw is set to be a direction to be tightened in the rotation direction when the pile is press-fitted. In addition, when the press-fitting resistance is large at the time of rotary press-fitting of the pile, reverse rotation may be performed. Therefore, it is desirable to provide a locking stopper such as a key penetrating the female screw body and the male screw body.
[0017]
The connecting joint 8 described above is also welded and attached to the pile when the tip blade 1 is welded to the pile body 6 at the factory. This eliminates the need for welding work between piles at the site, enables high-precision welding regardless of the weather at the site, and eliminates the need for the welding worker to visit the site. There is an advantage that the construction cost can be reduced while shortening.
[0018]
If the pile body 6 is long enough to obtain the necessary supporting force and no pile connection is required, the connection joint may not be provided. In some cases, welding is performed on site.
[0019]
In the above-described embodiment, the cylindrical portion 2, the pointed head 3, the guide blade 4 and the outer blade 5 of the tip blade 1 are integrally formed of the same material, for example, by casting. May be manufactured as a separate part and assembled by welding.
[0020]
Next, another embodiment of the tip blade according to the present invention will be described with reference to FIGS.
The tip blade 12 of this embodiment is suitable for a rotary press-in pile used in a site where the hardness (N value) of the ground is small, that is, the ground is soft and the supporting ground is deep, and the cylindrical portion 13 is used as the first embodiment. It is formed longer in the axial direction than the cylindrical portion 2, and a pair of left and right settling prevention blades 14, 14 are provided on the outer periphery of the cylindrical portion 13 in a stepwise manner.
[0021]
Each blade has an elliptical hole concentric with the outer periphery in the center of the ellipse, and is semi-circular in the major axis direction, and is inclined downward in the rotational direction when the pile is rotationally press-fitted. Yes.
[0022]
Note that the above-described blades 14 and 14 for preventing settlement may not be inclined, or a plurality of pairs of left and right blades may be provided, and circular blades may be provided on the entire circumference of the cylindrical portion 13. Sometimes it is provided. Such variations in the number and shape of the blades and the diameter of the blades are appropriately determined according to the N value at the site.
[0023]
As with the first embodiment, the tip blade 12 of the above-described embodiment is welded to the lower end of the pile body 6 made of a steel pipe to constitute a rotary press-fit pile, and is attached to the upper end of the cylindrical portion 13 of the tip blade. The formed groove 13a is butted against the lower end of the opening of the pile body 6 and welded.
Moreover, the internal thread body 9 which comprises the joint 8 for a connection with another pile is provided in the upper end part of the pile main body 6. FIG.
[0024]
Furthermore, also in the second embodiment described above, the cylindrical portion 13, the tip 3, the guide blade 4, the outer blade 5, and the blades 14 and 14 of the tip blade 12 are integrally formed of the same material, for example, by casting. However, some or all of these may be manufactured as separate parts and assembled by welding.
[0025]
It should be noted that the rotary press-in pile of each of the above-described embodiments is assumed to be rotary press-fitted with the periphery of the upper end held by a pile holding mechanism such as a hydraulic chuck of the rotary press-fitting device. Although an engagement portion with the device is not provided, an engagement member such as a protruding piece for engagement with the pile holding mechanism may be provided depending on the pile holding mechanism of the rotary press-fitting device.
[0026]
[Operation and effect of the invention]
According to the tip blade and the rotary press-fitting pile according to the present invention, the guide blade accurately captures the center of the pile placement position to prevent the eccentricity of the pile, and the earth and sand below the tip blade is scraped by the outer blade. The inclined surface of the cusp composed of the outer blade and the cone is smoothly discharged to the outside of the pile, and the rotational resistance during the press-fitting of the pile is reduced.
[0027]
In addition, since the thickness of the outer blade becomes smaller toward the outside, the earth and sand are discharged more smoothly to the outer periphery of the pile, and this also reduces the rotational resistance when the pile is press-fitted. Can be reduced.
[0028]
Moreover, the earth and sand discharged | emitted from the downward | lower direction of the pile to the outer side are pressed and compacted in the outer periphery of a pile, and the frictional support force of a pile is increased.
[0029]
Therefore, the rotary press-fitting of the pile can be performed more quickly without being eccentric, and thus the construction period of the pile can be shortened and the construction cost can be reduced.
[0030]
The tip blade can be easily used by simply welding a steel pipe pile that is widely used as a pile body to the tip of the pile body.
[Brief description of the drawings]
FIG. 1 is a partially cutaway front view showing a first embodiment of a tip blade according to the present invention.
FIG. 2 is a bottom view of the tip blade according to the first embodiment of the present invention.
FIG. 3 is a partially broken front view of a rotary press-fitting pile including a tip blade according to the first embodiment.
FIG. 4 is a partially broken front view showing a connection portion of a pile body.
FIG. 5 is a partially broken front view showing a second embodiment of the tip blade according to the present invention.
FIG. 6 is a bottom view of a tip blade according to a second embodiment of the present invention.
FIG. 7 is a partially broken front view of a rotary press-fitting pile including a tip blade according to a second embodiment.
FIG. 8 is a front view showing an example of a conventional rotary press-fit pile.
FIG. 9 is a bottom view of a conventional rotary press-fit pile.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tip blade 2 Cylindrical part 3 Pointed head 4 Guide blade 5 Outer blade 6 Pile main body 7 Welded part 8 Joint 9 Female thread body 10 Pile 11 Male thread body 12 Tip blade 13 Cylindrical part 14 Blade

Claims (8)

A prismatic guide blade extending downward is provided at the center of the bottom portion formed following the lower end of the cylindrical portion, and a plurality of outer blades formed in a plate shape around the guide blade in the bottom portion with the guide blade as a center. A tip blade for a rotary press-fit pile that is hung down to form a radial shape and has the lower end of the guide blade protrude below the lower edge of the outer blade. The tip blade for rotary press-fit piles according to claim 1, wherein the bottom portion is formed in a shape of a narrow cone. The tip blade for rotary press-fit piles according to claim 1, wherein the outer blade is formed of a shape whose thickness decreases toward the outside. The tip blade for rotary press-fit piles according to claim 1, wherein the cylindrical portion, the bottom portion, the guide blade and the outer blade are integrally formed of the same material . A prismatic guide blade extending downward is provided at the center of the bottom portion formed following the lower end of the cylindrical portion, and a plurality of outer blades formed in a plate shape around the guide blade in the bottom portion with the guide blade as a center. Rotating press-fitting formed by connecting the upper edge of the cylindrical portion of the tip blade with the lower end of the guide blade projecting downward from the lower edge of the outer blade to the lower end of the pile body made of steel pipe. Pile. The rotary press-fit pile according to claim 5, wherein a bottom portion of the tip blade is formed in a shape of a narrow cone. The rotary press-fit pile according to claim 5, wherein the outer blade of the tip blade is configured with a shape whose thickness decreases toward the outside. The rotary press-fit pile according to claim 5, wherein the cylindrical portion, the bottom portion, the guide blade and the outer blade of the tip blade are integrally formed of the same material .

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