JP2871458B2 - Steel pipe pile and construction method of steel pipe pile - Google Patents

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 spiral wings used as a foundation for buildings such as low-rise buildings or small-scale structures, and a construction method thereof.

[0002]

2. Description of the Related Art Conventionally, a pile having a spiral wing continuous with one or more turns on a tip of a steel pipe pile body or a pile body at a certain distance from the tip has been used as a foundation pile for an intermediate floor building. ing. This pile is disclosed in, for example, Japanese Patent Laid-Open No. 59-8502.
No. 8, as shown in FIG. 6, the steel pipe has a structure in which approximately one turn of a spiral wing having an outer diameter of about twice is provided on the outer periphery of the lower end of the steel pipe. . This pile gives a rotating torque to the pile head and is buried underground by screwing.

In this pile, the excavation blade 5 provided at the tip of the steel pipe 1 excavates and softens the ground at the tip, extrudes soil corresponding to the pile volume to the side of the pile, compresses the soil on the side of the pile, and consolidates the ground. It will be propelled and set without any earth removal. Therefore, the volume of the earth and sand compressed on the side surface of the pile acts as a frictional force by tightening the pile, and together with the spiral blade 2, a large supporting force can be developed.

[0004]

However, in the conventional pile, only one spiral wing is mounted in a continuous state, so that even if the tip of the pile is set on the pile core, the pile is rotated and the pile is rotated at the same time. There was a problem that the pile was displaced from the core, and the pile was likely to be displaced. In addition, in the case of excavating a slightly hard ground, the conventional pile has a problem that the penetrability deteriorates, the pile body is inclined, and it takes time. Further, there is another problem that the spiral wings are deformed by hitting the wrench or are rubbed by friction with the wrench, so that a predetermined vertical supporting force cannot be exhibited.

[0005] It is an object of the present invention to provide a steel pipe pile capable of improving construction accuracy and exhibiting a sufficiently large supporting force even on a slightly hard ground, and a construction method therefor.

[0006]

According to the present invention, a plurality of spiral blades are fixed at the same height position on the outer peripheral surface of the lower end portion of a steel pipe pile at equal intervals in the circumferential direction with the same spiral direction. The length per sheet is [1 ÷ (number of spiral wings + 1)]
A steel pipe pile that is not less than winding and not more than [1 ÷ (number of spiral wings) × 1.1] and is closed by attaching a bottom plate to the tip of the pile, and a plurality of spiral wings have the same height at the outer peripheral surface of the lower end of the steel pipe pile. At the same position, the helical direction is fixed at equal intervals in the circumferential direction with the same helical direction, and the length of each helical wing is [1 ÷
(Number of spiral wings + 1)] or more and [1 ［(number of spiral wings) × 1.1] or less, and by attaching a bottom plate to the tip of the pile and applying a rotational force to the closed steel pipe pile, the pile volume is increased. This is a method for constructing a steel pipe pile, which extrudes soil to the side of the pile, compresses the soil on the side of the pile, lays the pile, and improves the bearing capacity .

[0007]

According to the present invention, since a plurality of spiral blades are fixed at equal intervals in the circumferential direction at the same height position on the outer peripheral surface of the lower end portion of the steel pipe pile, the pile core is fixed at the start of excavation. Misalignment can be prevented. In addition, a stable propulsion force can be obtained, and construction efficiency can be improved. Even when excavating a slightly hard ground, the pile body does not tilt and the construction efficiency can also be increased. Furthermore, the deformation and abrasion of the spiral blade and the removal of earth and sand from the ground can be suppressed, and a frictional force is developed, so that the ultimate supporting force can be improved.

[0008]

Embodiments will be described below with reference to the drawings. FIG. 1 is a side view of the pile of the present invention. FIGS. 4 and 5 are bottom views of a pile having two spiral wound wings of the present invention. The pile body is a steel pipe 1 and usually has an outer diameter of 100 to 200 mm and a thickness of 4-1.
0 mm, length 5-20 m. A plurality of spiral blades 2 are wound around the outer peripheral surface of the tip of the steel pipe 1. The spiral blades 2 are made of steel and are attached alternately and discontinuously. Its outer diameter is desirably about 1.5 to 3 times the steel pipe, and more preferably 1.8 to 2.2 times. It can be said that the above range is preferable because the construction efficiency is further improved while the supporting force is increased. The thickness of the spiral wing 2 is 6
The thickness is preferably 6 mm or more when the N value of the ground is 30 or more, 9 mm or more when the N value is 40 or more, and 12 mm or more when the N value is 50 or more. The stroke L is preferably 50 to 200 mm in terms of workability. The spiral wing 2 is attached to the steel pipe 1 usually by welding. FIG. 1 shows an example in which two spiral wings are used in the pile circumferential direction, and the spiral wings per sheet are half-wound. Since the spiral blade tip 6 is provided symmetrically at two places, the excavation effect is twice as large as that of the conventional single spiral blade. FIG. 2 shows an example in which three spiral blades are provided at equal intervals in the pile circumferential direction, and the number of spiral blades per sheet is one-third. When the number of spiral blades is increased as described above, the excavation effect is improved, but the practically preferable length of the spiral blade is 4
It is one-half turn or more and half turn or less. The length of the spiral wings per piece is [1 ÷ (number of spiral wings + 1)] or more [1 ÷
(The number of spiral wings) × 1.1 or less, and 0.33 to 0.55 turns per one for two spiral wings and 0.25 to 0 for each three spiral wings .37 turns, 0.20 turns per sheet for four spiral wings
0.28 turns. Moreover, if the excavation pitch at the time of construction is made the same, it may be provided in multiple stages in the pile axis direction. As described above, by attaching the spiral wings discontinuously to the steel pipe, the load per spiral wing can be reduced at the time of construction, and deformation and abrasion of the spiral wings can be reduced even when excavating a somewhat hard ground. Furthermore, since the spiral wing is discontinuously attached to the steel pipe, compared to a conventional steel pipe pile in which the spiral wing is continuously wound around the steel pipe one or more times, the earth and sand corresponding to the excavated pile volume is placed on the ground. It is not carried out and the amount of soil removed is extremely small.

In the steel pipe pile of the present invention, the pile is laid down by applying a rotational force to the head of the pile. To compress the soil on the side of the pile, the tip of the steel pipe 1 is closed with a bottom plate 4 attached. According to the present invention, the soil of the pile volume is extruded to the side of the pile by excavation, and the soil on the side of the pile is compressed and the ground is propelled and set without draining while consolidating the ground. The intended purpose can be achieved. Further, an excavation blade may be provided at the lower end of the steel pipe 1 by the ground. Further, when excavating hard ground, a reinforcing plate 3 may be provided as shown in FIG. When the reinforcing plate 3 is provided, the tip 6 has a blade, but the shape may be sharp at a sharp angle as shown in FIG. 4 or may be jagged as shown in FIG.

Hereinafter, the present invention will be described in detail with reference to examples. EXAMPLE As a pile of the present invention, a spiral pipe 2 having an outer diameter of 400 mm and a thickness of 9 mm was formed on a steel pipe having an outer diameter of 200 mm, a thickness of 8 mm and a length of 10 m by setting a stroke L to 150 mm as shown in FIG. .55 helical wings of 55 turns were attached, and a reinforcing plate 3 having a thickness of 16 mm was attached thereto.
Used over the entire surface underneath. However, the reinforcing plate 3 was formed so that its tip was notched in a key shape as shown in FIG. 5 and protruded 30 mm below the steel pipe. The pile tip was closed by attaching a bottom plate 4. This pile is GL-0-1
It was constructed on soft ground with an N value of 10 or less during 1 m (distance from the ground surface), but with an N value of 30 to 40 during GL-11 to 16 m. The pile was sunk to GL-12m, and the tip of the pile was penetrated 1m into the ground. After that, a loading test was conducted according to the Japan Society of Geotechnical Engineers, "Cui's Vertical Loading Test Standard." In this test, 20 piles of the present invention were used.

As a result, the construction speed was about 1.5 minutes on average up to GL-11m, and it took about 7 minutes on average to penetrate GL-11 to 12m into the ground with a high N value. Further, at the start of excavation, the pile of the present invention did not undergo any pile displacement. At the time of the completion of the construction, no inclination of the pile had occurred. As a result of the loading test, the ultimate bearing capacity of the pile was 120 ton.

Comparative Example On the other hand, as a comparison, a conventional pile was constructed under the same conditions and a load test was performed. The conventional pile is shown in FIG. 6 and, like the present invention, a steel pipe having an outer diameter of 200 mm, a thickness of 8 mm, and a length of 10 m,
Stroke L with 400 mm outer diameter and 9 mm thick spiral wing
Was set at about 150 mm, but without a reinforcing plate. The tip was provided with a bottom plate and a cutting blade, and 20 conventional piles were used.

As a result, the construction speed was about 1.5 minutes on average until GL-11m, but it took about 12 minutes on average to penetrate the GL-11 to 12m ground with a high N value. At the start of the excavation, a pile displacement of 5 cm occurred, and at the completion of the construction, 14 of the 20 piles had an inclination of the pile body exceeding 1/100. As a result of the loading test, the pile was 95 tons
Met.

[0014]

The steel pipe pile of the present invention has a conventional spiral wing.
Compared to steel pipe piles whose tip is closed by a bottom plate , there is no displacement of the pile core at the start of excavation and no inclination of the pile body at the time of excavation even on hard ground such as rake, and the construction accuracy is high and stable propulsion force Can be up. Also has a conventional spiral wing tip
As compared with a steel pipe pile closed by a bottom plate, the same excavation effect can be exhibited with less wear and deformation of the excavation blade and less amount of earth removal and a lower rotation speed of the spiral blade. This leads to an improvement in the supporting force. Further, according to the construction method of the present invention, a bottom plate is attached to the tip and closed, and
By excavating the steel pipe pile on which the wing wings are attached by applying rotational force, the soil of the pile volume is pushed out to the side of the pile, and the soil on the side of the pile is compressed to consolidate the ground, and the soil is propelled and settled without discharging the soil. Therefore, the desired object of the steel pipe pile with a spiral wing of the present invention is achieved, and the above-described effects on construction are exhibited.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of a pile according to the present invention.

FIG. 2 is a side view showing a pile provided with three thirds of spiral wings.

FIG. 3 is a diagram showing a pile having a reinforcing plate.

FIG. 4 is a bottom view showing the pile of FIG. 1;

FIG. 5 is a bottom view showing another example of the pile of the present invention.

FIG. 6 is a side view showing a conventional pile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel pipe pile 2 Spiral wing 3 Reinforcement plate 4 Bottom plate 5 Drilling blade 6 Tip of spiral wing

Claims (2)

(57) [Claims] 1. A plurality of spiral blades are fixed at equal intervals in the circumferential direction at the same height position on the outer peripheral surface of the lower end portion of a steel pipe pile, at equal intervals in the circumferential direction, and the length of each spiral blade is one. [1
A steel pipe pile that is not less than {(number of spiral blades + 1)] winding and not more than [1 {(number of spiral blades) × 1.1] winding, and is closed by attaching a bottom plate to the tip of the pile. 2. A plurality of spiral wings are fixed at equal intervals in the circumferential direction at the same height position on the outer peripheral surface of the lower end portion of the steel pipe pile in the circumferential direction, and the length of each spiral wing is one. [1
÷ (number of spiral wings + 1)] or more and [1 ÷ (number of spiral wings) × 1.1] or less, and by attaching a bottom plate to the tip of the pile to apply rotational force to the closed steel pipe pile, A method for constructing steel pipe piles, which extrudes a volume of soil to the side of the pile, compresses the soil on the side of the pile, lays the pile, and improves the bearing capacity .