JP2002115250A - Steel pipe pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel pipe pile with a helical bottom plate, allowing rotation and propulsion into the ground to be easily conducted even when a pile body has a large diameter and enabling a reduction in material cost by making the pile body as thin as possible. SOLUTION: The end section of the tubular pile body 10 is helically notched along and approximately all around the perimeter of the end thereof, and the helical bottom plate 11 also serving as an excavating blade is welded to the helically notched end surface of the pile body 10. The bottom plate 11 is constituted by undergoing such notching that a radial notch reaching a center is made along the end surface of the pile body 10 in an annular disc having an approximately twice larger diameter than the pile body 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel pipe pile with a helical bottom plate which is used as a foundation pile for a structure constructed in an urban area and which is rotatably driven without earth removal and vibration.

[0002]

2. Description of the Related Art In recent years, a construction method has been adopted in which a pile is buried in the ground with no earth removal, no noise, and no vibration using a steel pipe pile provided with a spiral blade on the outer peripheral surface of the tip. In this steel pipe pile, a drilling blade is protruded from the bottom plate at the tip of the pile body, and a spiral wing having a radius more than twice the radius of the pile body is protruded from the outer peripheral surface near the tip over substantially one turn. The foundation pile,
By rotating as if screwing into the soft ground, excavating and softening the soil at the tip of the pile body by the excavation blade, while making the spiral wings bite into the undigged soil on the side of the pile body,
It is rotated and propelled underground using the strength of the soil as a reaction force.

[0003]

However, according to the conventional steel pipe pile, when the pile main body has a large diameter, the amount of sediment softened by the excavation blade and extruded to the side surface of the pile main body increases. As the diameter of the pile body increases, the thickness of the spiral wing also increases, making it difficult for the side of the pile body to dig into the undigged earth and sand, resulting in compression of the earth and sand at the tip of the pile body. In some cases, it became difficult to rotate the pile body.

[0004] After the steel pipe pile is buried, while the load supporting the building acts on the pile main body, the load also acts on the spiral wing equally with the pile main body. Has a bending moment. However, since the spiral wing is joined to the outer peripheral surface near the tip of the pile main body, this bending moment also acts near the weld, which is the joint between the spiral wing and the pile main body, and becomes the maximum at this part Therefore, the thickness of the pile body must be set thick to withstand this. This thickness is nearly twice as large as the thickness that can withstand the vertical load (compression load) acting on the pile body, and there is a problem that the material cost increases in the case of a long steel pipe pile.

SUMMARY OF THE INVENTION The present invention aims to reduce the material cost by making the pile main body as thin as possible, in addition to the fact that the pile main body can be easily propelled into the ground even if it has a large diameter. It is an object of the present invention to provide a steel pipe pile with a spiral bottom plate that can be used.

[0006]

In order to achieve the above-mentioned object, according to the steel pipe pile of the present invention, the tip of the tubular pile body is cut off spirally along the outer periphery of the tip, and this spiral is formed. It is characterized in that a spiral bottom plate having a diameter about twice as large as the pile main body and also serving as an excavating blade is fixed along the cutout tip end surface of the pile main body.

Here, a cutting blade having a stepped blade is provided on the spiral bottom plate so as to extend in the diametrical direction from the center of the spiral bottom plate and to be inclined by 40 ° to 45 ° with respect to the bottom surface of the spiral bottom plate. It may be fixed.

[0008] Further, a sediment entrance for guiding excavated and softened earth and sand into the pile body may be provided at the center of the spiral bottom plate.

Further, a spout hole such as a grout spout hole or an air spout hole may be provided at the tip of the pile body.

[0010]

Embodiment 1 Hereinafter, a steel pipe pile according to Embodiment 1 of the present invention will be described in detail with reference to the drawings. 1 and 2 show a first embodiment of the present invention. FIG. 1 is a perspective view showing the steel pipe pile of the present invention with a part omitted, and FIG. 2 is a perspective view of the spiral bottom plate of the steel pipe pile shown in FIG.

As shown in FIGS. 1 and 2, a steel pipe pile according to the present embodiment is provided at the tip of a tubular pile body 10.
Spiral bottom plate 1 having a diameter about twice as large as the excavating blade
1 is fixed over substantially one turn.

That is, the tip portion of the tubular pile body 10 is spirally cut along the outer periphery of the tip over substantially one round. On the other hand, the spiral bottom plate 11 also serving as a digging blade is shown in FIG.
As shown in FIG. 2, a circular disk having a diameter about twice as large as the pile main body 10 is cut in a radial direction reaching the center of the circular disk, and the circular disk is cut into a spirally cut end surface of the pile main body 10. It is formed by bending along the line. Then, a steel pipe pile shown in FIG. 1 is formed by welding a spiral bottom plate 11 also serving as an excavating blade to the tip end surface of the spirally cut pile main body 10.

The thickness of the spiral bottom plate 11 is determined by the diameter of the pile body 10 and the hardness of the ground in which the steel pipe pile is embedded. The spiral bottom plate 11 is provided with a closing plate 12 which closes a gap between the start end and the end, and a pile body 10 is provided at the center thereof.
An earth and sand entry hole 13 is provided to allow earth and sand to enter the inside.

According to the steel pipe pile of the above embodiment, the pile main body 10 is erected on the ground on which the pile is to be buried, and a rotary push-in drive device (not shown) is mounted on the upper end thereof, and the pile main body 10 is driven by the driving. When pressed and rotated inward, the spiral bottom plate 11 at the tip of the pile body 10 pushes out the side of the pile body 10 while excavating and softening the soil at the tip of the pile body 10 as an excavation blade, and the steel pipe pile rotates underground. Propelled and embedded.

In this embedding work, the spiral bottom plate 11 functions as a spiral blade and a digging blade, so that it can easily penetrate into the ground, and even if the diameter of the pile body 10 is increased as in the conventional case, the lower end of the pile body 10 There is no risk of compressing the earth and sand, and the rotation of the steel pipe pile is smoothly promoted. Therefore, construction can be performed even on hard ground, which has been difficult in the past, and a large supporting force can be obtained.

After the burial of the steel pipe pile is completed, the load supported by the building acts on the pile body 10 and the spiral bottom plate 11 respectively, while the vertical reaction force of the ground against this load causes the pile body 10 and the spiral bottom plate to fall. 11 respectively. A compressive force acts on the pile body 10 due to the supporting load and the vertical reaction force in the opposite direction. A bending moment acts on the spiral bottom plate 11 by a vertical reaction force. However, unlike the conventional spiral blade, the bending moment of the spiral bottom plate 11 does not act on the pile main body 10 because the spiral bottom plate 11 is fixed to the tip end surface of the pile main body 10.
In other words, although a bending moment acts on the spiral bottom plate 11 by a vertical reaction force, only a compressive force acts on the pile body 10. For this reason, the pile main body 10 only needs to have a wall thickness that can withstand the compressive force, and it is not necessary to set the wall thickness of the pile main body 10 nearly twice as thick as in the related art in order to withstand the bending moment. Therefore, the wall thickness can be reduced by approximately 50% as compared with the conventional steel pipe pile.

[Second Embodiment] FIGS. 3 and 4 are explanatory views of a steel pipe pile according to a second embodiment of the present invention. FIG. 3 is a front view partially omitted, and FIG. 2 is a side view of the steel pipe pile. In the drawings, the same portions as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the spiral bottom plate 11 is provided with excavating blades 14 and 14 having stepped blades.
Is fixed so as to extend diametrically from the center of the spiral bottom plate and to be inclined by 40 ° to 45 ° with respect to the bottom surface of the spiral bottom plate 11.
Here, the inclination angle with respect to the bottom surface of the spiral bottom plate 11 is set in this manner for the following reason. That is, the inclination angle of the excavating blade 14 with respect to the bottom surface of the spiral bottom plate 11 is 40 °.
If it is smaller, sufficient excavation capacity cannot be obtained, and 45
If it is larger than 0 °, the excavating ability is high, but the resistance to excavation becomes too large, which is not preferable.
This is because the resistance to excavation does not increase in the range of 45 ° to 45 °, and a desired excavation ability can be obtained.

According to the present embodiment, the spiral bottom plate 11 and the excavating blades 14, 14 are connected to the pile main body 1 during the embedding work of the steel pipe pile.
Since the earth and sand at the leading end is excavated and softened, a large amount of earth and sand can be excavated and softened in a short time, and the construction time can be reduced. In addition, the excavating blades 14 and 14 are the spiral bottom plate 1.
1 serves as a rib for reinforcing the spiral bottom plate 1 and the thickness of the spiral bottom plate 11 can be set thin.

In both of the above embodiments, a grout ejection hole may be provided at the tip of the pile body 10 so that cement milk is ejected from the grout ejection hole during excavation. Further, an air ejection hole may be provided.

[0021]

As described above, according to the steel pipe pile of the present invention, the excavation having a diameter of about twice the diameter of the pile main body along the spiral cut end of the pile main body. Since the spiral bottom plate that is also used as a blade is fixed, the excavation and softening of the soil at the tip of the pile body can be promoted, and even if the pile body has a large diameter, it can be easily rotated and driven into the ground. Since no bending moment acts on the joint with the spiral bottom plate,
The material cost can be reduced by making the thickness of the pile body as thin as possible.

[Brief description of the drawings]

FIG. 1 is a perspective view in which a part of a steel pipe pile according to Embodiment 1 of the present invention is omitted.

FIG. 2 is a perspective view of a spiral bottom plate of the steel pipe pile shown in FIG.

FIG. 3 is a front view in which a part of a steel pipe pile according to Embodiment 2 of the present invention is omitted.

FIG. 4 is a side view of the steel pipe pile of FIG. 3;

[Explanation of symbols]

 10 Pile body 11 Spiral bottom plate 14 Drilling blade

Claims (4)

[Claims] 1. A tip portion of a tubular pile body is spirally notched along the outer periphery of the tip, and is approximately twice as large as the pile body along the tip surface of the spirally cut pile body. A steel pipe pile comprising a spiral bottom plate having a diameter and also serving as an excavating blade, fixed thereto. 2. The steel pipe pile according to claim 1, wherein a cutting blade having a step-shaped blade is diametrically extended from the center of the spiral bottom plate to the spiral bottom plate, and the cutting blade has a cutting edge with respect to the bottom surface of the spiral bottom plate. A steel pipe pile fixed at an angle of 40 ° to 45 °. 3. A steel pipe pile according to claim 1 or 2, characterized in that a sediment entrance for introducing excavated and softened earth and sand into the pile body is provided at the center of the spiral bottom plate. . 4. The steel pipe pile according to claim 1, wherein a spout hole is provided at a tip of the pile main body.