JPH0711637A - Steel pipe pile - Google Patents

Abstract

PURPOSE:To increase the bearing force of a pile in a hard ground, by winding up a spiral blade with a specified size by a plurality of rounds and fixing it at the lower end of a steel pipe and attaching an excavating and thrusting blade on it to form a pile member. CONSTITUTION:The bottom of a steel pipe 1 is closed with a bottom plate 4 and a spiral blade having a diameter as large as about twice of the outer diameter of the steel pipe 1 and a thickness as thick as about 6-2mm is attached by a plurality rounds. And an excavating and thrusting blade 3 is welded by about 1/4 rounds at the under face of spiral blade 2. In this way, even in the case of a hard sand and gravel ground, the excavating blade 3 is penetrated into the ground without idle rotation and hence, a high bearing force can be secured.

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 spiral wing used as a foundation for a building such as a middle-story house or a small-scale structure.

[0002]

2. Description of the Related Art Conventionally, as a foundation pile for a low-rise building, a pile having a spiral wing is used at the tip of a steel pipe pile body or at the pile body spaced apart from the tip by a certain distance. This pile is disclosed, for example, in Japanese Patent Laid-Open No. 59-85028, and has a structure as shown in FIG. This pile gives a rotating torque to the pile head and is buried in the ground by twisting.

In this pile, the tip ground is excavated and softened by the excavation blade 5 provided at the tip of the steel pipe 1, the soil corresponding to the volume of the pile is pushed out to the side surface of the pile, and the soil on the side surface of the pile is compressed to consolidate the soil. It is propelled and settled without soil. Therefore, the volume of soil compressed on the side surface of the pile tightens the pile and acts as a frictional force, and a large supporting force can be expressed together with the spiral blade 2.

[0004]

When the pile can be propelled and settled by the stroke L of the spiral blade 2 each time the pile is rotated once, the pile does not disturb the ground and the above-mentioned effects can be exhibited. Therefore, this pile is particularly effective for soft ground. However, if this pile becomes slightly harder with an N value of 30 or more, for example, it will be difficult for the excavating blade to penetrate into the ground. The stakes will have to be sunk in and out little by little. For this reason, there is a problem that the ground is agitated and disturbed by the spiral blade or the excavating blade provided at the tip, and a predetermined frictional force cannot be expressed.

Further, in the ground containing a large amount of gravel, there is a problem that the spiral wing may be deformed by hitting the gravel, or may be worn away due to friction with the gravel, so that a predetermined vertical supporting force cannot be exhibited. An object of the present invention is to provide a pile capable of exhibiting a sufficiently large bearing force even on a slightly hard ground as described above.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a pile in which at least one spiral blade is fixedly mounted on the outer peripheral surface of a lower end of a steel pipe pile, and the steel pipe pile is used for excavation without providing an excavating blade at the lower end. It is a steel pipe pile in which a propulsion blade is attached so as to overlap with the spiral blade. Hereinafter, description will be given with reference to the drawings.

FIG. 1 is a side view of the pile of the present invention. Also,
FIG. 2 is a bottom view of the pile of the present invention. The pile body is a steel pipe 1, and usually has an outer diameter of 100 to 300 mm, a thickness of 4 to 10 mm,
The length is 5 to 10 m. The spiral blade 2 is attached to the outer peripheral surface of the tip portion of the steel pipe 1 one or more times. If the number of turns is one or less, a sufficient supporting force cannot be obtained. The spiral blade 2 is made of steel, and its outer diameter is preferably about 1.5 times to 3 times that of steel winding, and more preferably about 2 times. It can be said that when the content is within the above range, the supporting efficiency becomes high, but the construction efficiency does not decrease, which is preferable. The thickness of the spiral wing 2 is preferably 6 to 20 mm. When the ground N value is 30 or more, the thickness is 6 mm or more, when the N value is 40 or more, it is 9 mm or more, and when the N value is 50 or more, the thickness is 12 mm. The above is appropriate. The stroke L is preferably about 50 to 200 mm in terms of workability. The spiral blade 2 is usually attached to the steel pipe 1 by welding.

A bottom plate 4 may be attached to the tip of the steel pipe 1 to close it, or it may be left open. Further, it is preferable not to provide an excavating blade at the lower end of the steel pipe 1 so as not to disturb the ground during excavation. From the lower end of this spiral blade 2, excavating and propelling blade 3
Are mounted so as to be superposed on the spiral wing. The excavating and propelling blade 3 is made of steel, and is preferably made of a material having high strength such as stainless steel or heat-treated one. The excavation and propulsion blade 3 is attached to the upper or lower side of the spiral blade 2 by welding or the like. At this time, it is preferable that the excavating and propelling blade is welded to the steel pipe pile body in terms of strength. The length of the excavating and propelling blade may be about 1/4 round from the lower surface of the spiral blade, but it is more preferable to lengthen it because the spiral blade is reinforced. The excavation and propulsion blade 3 has a blade at the tip 6, but its shape may be sharp as shown in FIG. 2 or may be serrated like a key as shown in FIG. Furthermore, it is preferable that the tip 6 of the excavating and propelling blade is projected before the tip of the spiral blade 2. Most preferably, the excavation and propulsion blade 3 is attached to the lower side of the spiral blade 2 and the tip 6 of the excavation and propulsion blade is projected below the steel pipe 1 because the pile easily penetrates into the ground. .

The thickness of the excavating and propelling blade 3 varies depending on the size of gravel, the mixing ratio, and the N value of the ground. However, considering workability and bearing capacity, a thickness of about 6 mm to 30 mm is suitable.

[0010]

With the above-mentioned structure, the excavation and propulsion blades along the spiral wing can penetrate into the ground without idling even on hard ground, and stable propulsion force can be obtained. Since it is possible to prevent the ground from being disturbed due to idle rotation, it also improves the bearing capacity. Furthermore, since the excavating and propelling blade also has the effect of reinforcing the spiral blade, it is possible to prevent deformation and abrasion of the spiral blade.

[0011]

The present invention will be described in detail below with reference to examples. The pile of the present invention has an outer diameter of 200 mm, a thickness of 8 mm,
A spiral blade 2 having an outer diameter of 400 mm and a thickness of 9 mm is attached to a steel pipe having a length of 10 m with a stroke of 150 mm as shown in FIG. 1, and a 16 mm-thick excavation and propulsion blade 3 is attached to the lower side of the spiral blade 2. The one attached over 1/4 round was used. However, the tip of the excavating and propelling blade 3 was knurled like a key as shown in FIG. 3, and was projected 30 mm below the steel pipe. A bottom plate 4 was attached to the tip of the pile to close it.

This pile is GL-8 ~ 8m (distance from the ground surface), although it is a soft ground with an N value of 10 or less.
It was applied to the gravel ground having an N value of 30 to 40 during 12 m.
The pile was sunk to GL-9m, and the tip of the pile penetrated into the gravel ground for 1m. Then, the loading test was implemented. On the other hand, as a comparison, a conventional pile was constructed under the same conditions and a load test was conducted. The conventional pile is shown in FIG. 4, and similarly to the pile of the present invention, a steel blade having an outer diameter of 200 mm, a thickness of 8 mm, and a length of 10 m is attached to a spiral blade having an outer diameter of 400 mm and a thickness of 9 mm with a stroke of 15.
Although it was attached at 0 mm, it does not have a reinforcing plate,
The tip used a bottom plate and a drilling blade attached.

As a result, the construction speed of the pile of the present invention and the conventional pile was the same as about 1 minute up to GL-8m.
The stake of the present invention took about 6 minutes between -8 and 9 m, while the conventional stake required about 12 minutes. As a result of the loading test, the ultimate supporting force of the pile of the present invention was 110 tons, whereas that of the conventional pile was 75 tons. After the loading test, both were pulled out and the shape was observed. As a result, in the pile of the present invention, the spiral blade was not deformed at all, whereas in the conventional pile, the tip portion of the spiral blade was deformed in a wave shape due to the gravel, and further, from the tip of the spiral blade by loading. It was observed that the range of 1/4 lap greatly turned up. Moreover, in the pile of the present invention, the reinforcing plate was worn down by 3 mm at the maximum, whereas in the conventional pile, the helical blade was worn by up to 6 mm.

[0014]

The pile of the present invention can obtain a stable propulsive force because the excavating blade does not idle even on hard ground such as gravel. In addition, since the spiral blade can be constructed without being deformed or worn down, and the spiral blade does not turn up due to loading,
A large tip supporting force can be expressed. Further, as compared with the conventional pile, the number of rotations of the spiral wing is small when penetrating into the hard ground, so that the ground is less disturbed and peripheral friction can be expected to occur. Further, since the excavating blade at the tip of the pile is unnecessary, the supporting force is not reduced.

[Brief description of drawings]

FIG. 1 is a side view of a pile of the present invention.

FIG. 2 is a bottom view of the pile of the present invention shown in FIG.

FIG. 3 is a bottom view of another example of the pile of the present invention.

FIG. 4 is a side view of a conventional pile.

[Explanation of symbols]

 1 Steel Pipe 2 Spiral Blade 3 Reinforcement Plate 4 Bottom Plate 5 Drilling Blade 6 Tip of Reinforcement Plate

Claims (1)

[Claims] 1. A pile having one or more spiral blades fixedly mounted on the outer peripheral surface of a lower end portion of a steel pipe pile, wherein the lower end of the steel pipe pile does not have an excavating blade, and the excavating and propelling blade is attached to the spiral blade. A steel pipe pile characterized by being stacked and mounted.