JPH10219682A - Bottom expanded steel pipe pile having collar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve soil support force of a steel pipe pile, and facilitate transport, storage and field work by welding/driving a bottom expanded screw cylinder having a large diameter collar part to/into a tip part of the steel pipe pile at a pile driving site. SOLUTION: In a bottom expanded screw cylinder 2, a disk-shaped collar part 22 having a diameter W is welded to a cylinder part 21, and its part is cut in the radial direction, and cutting parts are bent in the mutually inverse direction, and are formed as an inclined blade 23. The bottom expanded screw cylinder 2 and a hollow cylindrical main body 1 where a bottom cover 11 and a blade 12 are arranged in a tip part, are separately stored and transported, and the main body 1 is inserted into the cylinder part 21 of the bottom expanded screw cylinder 2 at a pile driving site, and is integrally welded, and is pressed in the ground while rotating it. Therefore, a compaction effect is generated over an area A expanded more than the main body 1 by the collar part 22, and an area of compacted soil is also expanded below the collar part 22 by a Monroe effect, and support force increases. Removed earth is filled around the main body 1 by the inclined blade 23, and prevents the formation of a cavity around the main body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flanged expanded bottom steel pipe pile used to reinforce a ground portion serving as a foundation of a civil engineering building.

[0002]

2. Description of the Related Art In civil engineering and construction work, it has been recognized for a long time that the bearing capacity of the ground part, which is the foundation of a building, is important. Various construction methods have been developed.

[0003] As a steel pipe pile or the like used in such a method of reinforcing the ground, for example, a steel pipe having an open straight shape as shown in Fig. 4 and which can be easily driven into the ground and is inexpensive. There is known a pile 100 or a screw steel pipe pile in which a blade 101A is provided at a tip portion as shown in FIG. 5 and a penetration is smooth due to a wood screw effect even when a press force from above is small.

[0004]

However, when the former steel pipe pile is used, the long-term bearing capacity after casting is inferior.
In sandy ground, there are problems such as initial settlement likely to occur and unsuitability for placing on hard ground.

[0005] Further, if the screw steel pipe pile 101 is used, the manufacturing cost of the pile is high, the screw portion is obstructed, and the transportation and storage is troublesome. However, there are problems that it is difficult to maintain the properties and that the periphery of the pile is likely to sink.

[0006] In view of the above circumstances, the present invention has the advantage that the initial settlement is unlikely to occur, the bearing capacity in the soil is stable, the penetration into the hard ground is easy, and the transportation and
It is an object of the present invention to provide a flanged expanded steel pipe pile that is easy to store and process on site, and not only does not damage the stratum around the tip of the steel pipe but easily maintains the uprightness, and can easily obtain a consolidation effect and accuracy.

[0007]

Means for Solving the Problems That is, the invention of claim 1 is:
In a steel pipe pile having a hollow cylindrical shape, a cylindrical portion that penetrates the main body, a disc-shaped flange portion having an outer diameter larger than that of the steel pipe pile and fixed to the outer periphery of the cylindrical portion, and one of the flange portions And a slanted blade provided with a gap for allowing soil to escape therefrom, and provided with a bottomed screw cylinder that is welded and fixed to the tip side of the steel pipe pile at a pile driving site.

According to a second aspect of the present invention, a bottom cover and a blade protruding outside from the bottom cover are provided at the tip of the main body of the first aspect.

[0009]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a flanged expanded bottom steel pipe pile according to the present invention. The flanged expanded steel pipe pile has a hollow cylindrical (straight) main body 1 having a certain strength and formed of an appropriate material (for example, a material such as structural carbon steel), and an expanded bottom fixed to the distal end side of the main body 1. And a screw cylinder 2.

The main body 1 is provided with a bottom cover 11 and a blade 12 projecting from the bottom cover 11 to the outside (front side) at the front end. The details of the bottom cover 11 and the blade 12 have already been filed by the same applicant (Japanese Patent Application No. 8-131106).
Please refer to this because it is described in the specification.

The expanded screw cylinder 2 has an outer diameter W (2.5 mm in this embodiment) which is significantly larger than the outer diameter of the main body 1.
And a cross-sectional area of about 6.25 times), and is made of, for example, a material such as structural carbon steel similar to that of the main body 1, and has a cylindrical portion 21 and a flange portion 22. When,
And inclined blades 23. The size of the outer diameter of the screw barrel is, for example, 1.
A range of about 3 to 2 times is preferable. In addition, other materials such as high-strength steel can be applied as the forming material. Further, the mounting position of the screw cylinder 2 is
The length L from the front end to the collar 22 is approximately twice as long as the outer diameter of the main body 1.

The cylindrical portion 21 of this embodiment shown in FIG. 2 has a straight cylindrical shape (outer diameter D), and is formed to have a length S substantially equal to or slightly shorter than the outer diameter D. I have.
The length S may be sufficient to ensure the straightness and strength of the screw cylinder 2 and is not particularly required to be equal. The flange portion 22 is formed in a substantially disk shape having a diameter W (approximately 2.5 to 3 times the outer diameter D), and is attached (welded) substantially at the center of the cylindrical portion 21. is there. The inclined blades 23 are formed at a part (one place in this embodiment) of the flange portion 22, and cut the flange portion 22 in the radial direction (this also forms a gap where soil escapes), and The cut portions are inclined in the opposite directions by an angle θ (although approximately 45 degrees,
(Preferably in the range of 0 to 45 degrees).
The range of the opening angle (α) of the inclined blade 23 is about 60 degrees as shown in FIG. 3, and one of the inclined blades 23 (toward the front end side) has a reinforcing plate having a substantially equal-leg trapezoidal shape. 24 are welded to the flange 2.

In the flanged expanded steel pipe pile having such a configuration, the main body 1 and the expanded screw cylinder 2 can be stored separately and compactly from storage to transportation.
At the time of the pile driving at the work site, the extended bottom screw cylinder 2 is inserted into the tip (lower end) side of the suspended main body 1 (after only the main body 1 having a constant depth is driven into the soil) and welded. Further, in this embodiment, concrete (or mortar or the like) is poured into the hollow main body 1 after being driven to the end, and the horizontal shear force stress can be increased by the strength after hardening. Therefore, it is suitable for a sheared soil layer in which the support layer is inclined and slip is likely to occur.

Therefore, according to this embodiment, the expanded screw cylinder 2 having the flange 22 whose outer diameter is significantly larger than that of the main body 1 is pressed into the ground while rotating (see this rotary press-fitting method). , Japanese Patent Application Hei 8-1
Reference is made to US Pat. No. 31,106 for a detailed description. 1), a consolidation action (a state in which the soil is hard and compressed at the time of press-fitting) occurs over a region which is larger than the main body 1 indicated by the dot A in FIG. 1 and the so-called Monroe effect occurs at the upper end thereof. Since the region of the compacted soil greatly expands and expands below the flange portion 22, the supporting force is further increased. Further, unlike the conventional screw pile, the flange portion 22 is formed in a horizontal direction, so that not only a large effective sectional area can be ensured, but also no twist displacement occurs. Moreover, in this embodiment, the blades 12 and the inclined blades 23
Is provided, so that the soil can be efficiently discharged from between the blades 23 when the rotary press-fitting is performed. Therefore, the discharged soil is filled around the main body 1 to provide vertical stability (prevention of hollowing around the pile). Further, since the main body 1 portion before the inclined blades 23 excavates the pilot hole with high accuracy by the center drill effect, the straightness can be greatly improved.

[0016] Thus, improvement work on steel pipe piles, which conventionally could only be applied up to an N value of about 10 (general stratum) for soil supporting strength (a ground material mixed with cement milk or the like, which is expensive at N values below this value) Improved method)
However, by using the flanged expanded steel pipe pile of this embodiment, a required bearing capacity can be obtained even in a soft stratum having a supporting strength of about N value 3 (the supporting strength in the vertical direction is increased to more than 6 times the conventional strength). The ground improvement work using steel pipe piles becomes possible. Moreover, since the flanged expanded bottom steel pipe pile 1 has the bottom cover 11, in other words, the bottom cover 11 is provided at the front end portion so that the front end portion has a closed structure. An efficient press-fitting operation can be realized without intrusion.

[0017]

As described above, according to the present invention, since the expanded bottom screw cylinder having the flange having an outer diameter larger than that of the main body and the inclined blade provided on a part of the flange is provided, The consolidation effect and the Monroe effect can be generated over the soil cross-sectional area greatly expanded as compared with the area of FIG.

Further, according to the present invention, since the flange having a large cross-sectional area is provided on the expanded bottom screw cylinder, great stability is provided to the underground support force without fear of causing initial settlement, and stable support force is provided. It can be exerted over a long period of time.

Further, according to the present invention, since the expanded screw cylinder is welded and fixed to the front end side of the flanged expanded steel pipe pile at the site of the pile driving, storage and transportation are easy. Various excellent effects, such as good workability and reduction in manufacturing cost, are brought about.

Further, according to the present invention, since the inclined blades are provided in a part of the flange of the bottomed screw cylinder, by press-fitting while rotating, the penetration can be performed extremely smoothly even if the pressure input is small. This has the effect that it can be reliably penetrated into hard ground.

[Brief description of the drawings]

FIG. 1 is a cutaway view showing a main part of a steel pipe pile used in the present invention.

FIG. 2 is a front view of an expanded screw cylinder of a steel pipe pile according to the present invention.

FIG. 3 is a plan view of the screw cylinder with the expanded bottom.

FIG. 4 is a schematic sectional view showing a conventional steel pipe pile.

FIG. 5 is a cutaway view showing another flanged expanded steel pipe pile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Expanded bottom screw cylinder 22 Flange 23 23 'Inclined blade

Claims (2)

[Claims] 1. A steel pipe pile having a hollow cylindrical shape, a cylindrical portion inserted into a main body of the steel pipe pile, and a flange portion having a disk shape and having an outer diameter larger than that of the steel pipe pile and fixed to the cylindrical portion. And a sloped blade provided through a gap for allowing soil to escape in a part of the flange portion, and provided with a bottomed screw cylinder that is welded and fixed to the tip side of the main body at a pile driving site. Expanded steel pipe pile with flange. 2. The apparatus according to claim 1, wherein a bottom cover and a blade protruding outside from the bottom cover are provided at a front end of the main body.
A flanged expanded bottom steel pipe pile according to item 1.