JP2592079B2 - Small diameter steel pipe pile - Google Patents

Description

[Detailed Description of the Invention] [Industrial application field] This invention is used as a foundation for soft ground such as alluvial ground in the construction of buildings such as middle-to-low-rise buildings or small-scale buildings. The present invention relates to a small-diameter steel pipe pile with a spiral wing that can be constructed without vibration.

[Conventional technology]

In recent years, as construction sites for middle- and low-rise houses, etc., there is an increase in the number of places where construction capacity requires small countermeasures, where there is some In many cases, no noise and no vibration are requested due to complaints and the like. In addition, it has become important to reduce the amount of construction waste as much as possible, but there has been no conventional method that satisfies these requirements.

As a noise-free and vibration-free construction method, a digging method for digging a hole and inserting a pile is performed, but this method is also becoming difficult due to the removal of earth and sand. Also, concrete piles are heavy in terms of pile material, making them unsuitable for small-scale construction. Ground improvement piles using cement slurry etc. are also increasing,
It is not an essential method of pile construction, but the cost of foundation work, including foundation concrete, is high, and as a result, many complaints such as sinking or tilting of houses are heard.

On the other hand, various methods using a pile with a spiral wing have been developed as other noiseless and vibrationless construction methods.

For example, JP-B-49-18922, JP-A-51-94615, and JP-A-59-85028 disclose steel pipe piles provided with a spiral wing at the lower end and capable of being rotationally press-fitted. In the official gazette of Kaisho 62-25612, a pile with a sharp tip is used.
A screw pitch at the rear end is narrowed. In addition, Japanese Patent Laid-Open Publication No. Sho 57-66225 discloses a spiral pile.

In addition, Japanese Patent Publication No. 58-58491 discloses an underground pile used as a foundation for transmission line towers, etc., in which a plurality of concentric cylindrical shafts having different diameters are fitted and connected. In order to achieve this, a screw having a diameter gradually increasing is provided, and a screw that can be rotationally press-fitted is disclosed.
In Japanese Patent Laid-Open Publication No. Sho 61-155430, a pile provided with a plurality of spiral wings is also disclosed.

[Problems to be solved by the invention]

In the case of a small-scale building, the allowable strength per pile is about 5 to 15 tons due to the design, but it is easy to use, but such a thing is not found in the steel pipe pile in the conventional construction method, There is no suitable base for soft ground. This is because the conventional technology is derived from the basic technology of large structures, and there is no one aimed at small buildings.

That is, if steel pipe piles are used for small-scale buildings,
From the viewpoint of cost and handling, an outer diameter of about 100 to 200 mm will be used.
The pile is about 2 to 6.0 mm, which is quite thin. A spiral wing is provided on such a small-diameter, thin-walled steel pipe pile, and in order to rotationally press-fit it into the ground, a structure that can be press-fitted with as small a rotating torque as possible, that is, a structure with a penetration resistance as small as possible. Need to be devised.

Also, when a small-diameter pile is rotationally press-fitted, if there are obstacles such as looseness and stones in the ground, the rotary press-fitting becomes difficult, or the press-fit direction is easily bent by these obstacles, Verticality may not be maintained.

On the other hand, the pile itself with the spiral wing has its own advantages and disadvantages, especially when the spiral wing is continuously provided on the periphery of the pile, the weight increases, the friction with the surrounding earth and sand increases, and earth discharging occurs. There is also a problem.

The present invention aims to solve the above-described problems, and is particularly suitable for construction of buildings such as low-rise buildings or small-scale buildings, and secures required strength even for soft ground such as alluvial ground. Small diameter with small material strength
It is an object of the present invention to provide a small-diameter steel pipe pile that can be constructed with no rotational torque as small as possible, without deforming a thin-walled steel pipe pile, with no noise, no vibration, and no earth removal.

[Means for solving the problem]

The small-diameter steel pipe pile A of the present invention is a commercially available steel pipe having an outer diameter of 100 to 200 mm and a pipe thickness of 3.2 to 6.0 mm. A plurality of spiral wings 2 of one or two turns having an outer diameter of 1.5 to 2.5 times the outer diameter of the steel pipe 1 are discontinuously welded.

At the center of the tip of the steel pipe 1, a trapezoidal plate-shaped support fitting 4 which is tapered downward is provided so as to protrude, and at the outer periphery of the tip, a plate-shaped excavation aid 3 having a bit function is provided.
Are installed diagonally according to the direction of rotary excavation.

[Action]

First, the interval between the small-diameter steel pipe pile having an outer diameter of 100 to 200 mm and a pipe thickness of 3.2 to 6.0 mm and the spiral wing 2 is described. FIG. 7 shows the spiral wing 2 attached to the outer periphery of the small-diameter steel pipe pile A. It shows the relationship between the interval and the ultimate load (the maximum load that can be supported by the pile, multiplied by a safety factor, for example, 1/3 to 1/4, and becomes the design load). Until the interval is about 3m, there is not much difference in the ultimate load, and when it is 3m or more, the ultimate load becomes small.

The limit load becomes smaller at 3 m or more because the spiral wings 2 have too large an interval and the effective area of the spiral wings 2 that gives the pile supporting force is lost (the area of the spiral wings 2 restricts the spiral wings due to the interval). (It becomes smaller at the center between the wings 2.)
The frictional resistance due to the lateral pressure of the earth and sand acting on the main pipe increases, the thrust decreases, and the rotation torque increases.
The problem of poor penetration occurs.

On the other hand, from the state where the spiral wings 2 are continuously densely provided, the earth and sand are clogged between the upper and lower spiral wings 2 until the interval between the spiral wings 2 is about 1 m.
It becomes dango-shaped, and cannot lift earth and sand up, the propulsive force drops, and the penetrability deteriorates. Therefore, a large rotation torque is required at the time of construction due to friction between the spiral wing 2 and the earth and sand, and there is a disadvantage that the amount of steel material used and the labor for manufacturing are increased.

As described above, the rotational torque is large even if it is 1 m or less or 3 m or more, so that it cannot be buried by rotation alone, and a force for pushing from above is required. A small-diameter, thin-walled steel pipe having a small material strength is easily deformed by a large rotating torque or a force pressed from above.

For this reason, in the present invention, the interval between the spiral wings 2 is limited to 1 to 3 m. Also, in this area, the soil around the pile is squeezed during the burial and bulges toward the surrounding soft soil, so it is difficult for the soil to be discharged to the ground, and the surrounding ground is compacted. An improvement effect can also be expected.

In addition, since the spiral wings 2 are not continuous and are provided at an interval of 1 to 3 m, the earth and sand are not discharged to the ground, and the friction between the spiral wings 2 and the surrounding earth and sand in the ground is small. By applying the torque, the construction can be easily performed without discharging the soil.

Next, the relationship between the outer diameter of the steel pipe 1 and the outer diameter of the spiral wing 2 will be described. The pile strength of the small-diameter steel pipe pile A of the present invention depends on the bearing pressure of the soil due to the wing area of the spiral wing 2 and the strength of the steel pipe 1 body and the surrounding soil. It is considered to be determined by the sum of the shearing forces due to adhesion.

For this reason, if the outer diameter of the spiral wing 2 is large, the supporting force of the pile is also large, but the penetration resistance becomes too large to be buried. Also, if the outer diameter is large, the rotational torque is large, and the resistance to obstacles such as rattles and stones is weak, and it is easy to deform. Therefore, it is necessary to increase the thickness of the spiral wing 2.

Conversely, if the outer diameter is too small, the force for cutting the soil will be weak.
The spiral wing 2 has a dango-like shape around the spiral wing 2 and has poor penetration, and the rotational torque increases.

Furthermore, if the spiral wing 2 is too large or too small, the rotational torque increases, and it is necessary to increase the tube material thickness.

The outer diameter targeted by the present invention is 100 to 200 mm, and the tube thickness is 3.
Since the material strength of the steel pipe 1 of 2 to 6.0 mm is small, the rotating torque to be applied must be reduced so that the pipe is not deformed.

For this reason, in the present invention, the outer diameter of the spiral wing 2 is limited to 1.5 to 2.5 times the outer diameter of the steel pipe 1.

In addition, the trapezoidal plate-shaped support metal 4 at the center of the tip and the excavation auxiliary metal 3 at the outer periphery of the tip are provided with the support 4 so as to eliminate obstacles in the ground during excavation while maintaining the verticality. The auxiliary metal fitting 3 reduces the ground penetration resistance at the time of rotational press-fitting by the spiral wing 2 and reduces the rotational torque required for rotary press-fitting, thereby enabling the construction of a small-diameter, thin-walled steel pipe pile with a small material strength.
In addition, since pile construction can be performed only by rotating torque, there is no noise and vibration pollution.

With the above configuration, the performance as a pile is almost the same as that of a pile material having the same diameter as the outer diameter of the spiral wing 2, and a higher strength can be expected. Since the pile A body is small in diameter and thin, it is lightweight. Become.

In addition, if the length of one pile A is usually less than 6 m, the weight can be further reduced, and the construction machine can be used in a small size corresponding to this, so it can be constructed in narrow places Becomes

In the conventional pile, the tip is usually supported by a hard ground having an N value of 30 or more. However, in the case of the pile A of the present invention, the N value is targeted to be about 20 or less. It becomes possible to align head levels. It is sufficient for a medium- to low-rise house or a small-scale building to have an allowable strength of about 5 to 15 t per one, and the applicable range of the pile A is wide.

〔Example〕

 Next, the illustrated embodiment will be described.

FIG. 1 shows an embodiment of a small-diameter steel pipe pile A according to the present invention, and FIG. 2 shows a structure of a tip portion thereof.

In the small diameter steel pipe pile A in this embodiment, the pile body is
3 of 165.2mm, 5.0mm long, 5.0m long steel pipe for steel structure
This was a permanent joint, and the pile length was 15.0 m. The spiral wing 2 has an outer diameter of 350 mm, a thickness of 6.0 mm, and a spiral pitch of 10 mm.
Using a tube having a diameter of 0 mm, the steel tube 1 was welded to the outer surface of the steel pipe 1 by one turn at an interval of 2 m.

Further, a digging auxiliary metal fitting 3 and a supporting metal fitting 4 as shown in FIG. Drilling aid 3
A plurality of wings are attached diagonally to the outer periphery of the tip of the pile A to assist the excavation of the spiral wing 2 by the rotation of the pile A. In addition, the trapezoidal support bracket 4 is a pile A
Projecting downward from the center of the tip, penetrating into the ground surface prior to the burial of the pile A, increasing the stability of supporting the pile A vertically, and removing obstacles such as looseness and stones in the excavated ground. The vertical removal of the pile is facilitated by removing it by flipping.

FIG. 3 shows a pile A with a spiral wing 2 according to the present invention.
This shows an outline of a pile driver for constructing a pile.

In this pile driver, a hydraulic motor 7 and the like move up and down along a leader 6 rising from the pile driver main body 5, and the head of the pile A can be gripped by the cap 8 connected to the hydraulic motor 7. By operating the hydraulic motor 7,
By rotating the pile A, the pile A can be buried underground by the action of the spiral wing 2 and the excavation auxiliary fitting 3 at the tip.

FIGS. 4 (a) to 4 (e) show a construction procedure of the small-diameter steel pipe pile A, and the work is performed in the following procedure.

Piling the pile (Fig. 4 (a)) The pile A is suspended, and the pile A is set in accordance with the core of the pile.

Fixing the pile (FIG. 4 (b)) When the tip of the pile A is completely set on the core of the pile, the pile is fixed by using the support bracket 4 at the tip.

Rotational embedding (FIG. 4 (c)) After confirming the verticality of the pile A, a forward rotation (right rotation) is given to the pile A, and the pile A is penetrated by the drilling force of the spiral wing 2.

Joint Welding (FIG. 4 (d)) After the first wire is buried, the second wire and the third wire are sequentially added by welding or threaded joints, and then rotatively buried.

Completion of embedding (Fig. 4 (e)) When the auger reaches the specified depth, reverse the auger (turn left)
Then, the cap 8 is removed to complete the construction.

In addition, as shown in FIG. 4 (e), the cap 8 has a notch 10, which is engaged with a projection 11 on the head of the pile A to transmit the rotational force.

FIG. 5 shows the relationship between the load and the settlement amount of a small-diameter steel pipe pile to which the spiral wing 2 of the present invention is attached and a pile to which no spiral wing is attached as a comparative example. It has been examined. As is clear from the graph, the pile (A) to which the spiral wing 2 is attached has a maximum proof stress of twice or more as compared with the pile (B) without the spiral wing 2, indicating the excellent performance of the pile A of the present invention. . The constructed ground is soft alluvial ground, and the conventional technology required high construction cost to obtain the required strength, but the small diameter steel pipe pile of the present invention makes it possible to construct a pile foundation on such ground. It becomes simple, and the construction cost can be reduced and the construction period can be shortened by the dry construction method.

FIG. 6 shows an example of a joint portion when a plurality of piles A are added. That is, in this example, the lower pile 1a
A male screw 12 is formed at the upper end, and a female screw 13 is formed at the lower end of the upper pile 1b. Since the pile A is buried by the rotation torque as described above, the connection of the upper and lower piles can be performed by the rotation of the pile A by using a threaded joint, and the construction time can be reduced. This threaded joint can be formed by rolling plastic working of the end of the main body of the steel pipe 1 or pressing an iron plate. In the present invention, the connection of the pile A is not necessarily required to be a screw type joint, but may be a welded type joint.

[Effects of the Invention] A commercially available small-diameter, thin-walled steel pipe can be expected to have sufficient supporting force as a pile, can be reduced in weight, and can be handled with a small construction mechanism, so it is possible to carry equipment even in a narrow place. it can.

Spiral wing spacing is 1 to 3m and outer diameter is 1.5 to 2.5 times the outer diameter of steel pipe, which reduces penetration resistance and reduces rotational torque required for rotational press-fitting. It enables the construction of small-diameter, thin-walled steel pipe piles, and provides pile support utilizing the area of the spiral wing.

The trapezoidal plate-shaped support metal fitting at the center of the tip and the drilling auxiliary metal fitting at the outer periphery of the tip reduce the ground penetration resistance during rotary press-fitting with the spiral wing while maintaining verticality, and reduce the rotational torque required for rotary press-fitting. This enables the construction of small-diameter, thin-walled steel pipe piles with low material strength. In addition, since pile construction can be performed only by rotating torque, there is no noise and vibration pollution.

Since the spiral wing is not continuous, there is no discharge of earth and sand on the ground, and the surrounding ground is compacted by the pile volume, which can be expected to improve the ground.

As for the pile strength, the required strength can be expected even on soft ground due to the spiral wing, so the pile design becomes easy even on soft alluvial ground.

The same strength as when the spiral wing is continuously provided on the entire steel pipe can be expected, and the discontinuous spiral wing saves weight and material, and facilitates assembly by welding or the like.

Since the pile head diameter is only the small diameter steel pipe pile main body, the width of the underground beam and the cloth foundation is small, the amount of excavated earth and the amount of concrete is small, and economical construction is possible.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a small-diameter steel pipe pile according to the present invention, FIG. 2 is a front view showing details of a tip, FIG. 3 is a side view showing the structure of a pile driver, FIG. (A) to (e) are front views showing the construction procedure, FIG. 5 is a graph showing the effect of the spiral wing from the relationship between the load and the amount of settlement, and FIG. 6 is a front view showing an example of the structure of the pile joint. Figure (left half is a sectional view),
FIG. 7 is a graph showing the relationship between the interval between spiral wings and the ultimate load. A: pile, 1 ... steel pipe, 2 ... spiral wing, 3
...... Drilling auxiliary bracket, 4 ... Support bracket, 5 ... Pile driver body, 6 ... Leader, 7 ... Hydraulic motor, 8 ... Cap, 9 ... Pile sway, 10 ... Notch, 11 …… projections,
12 ... male thread, 13 ... female thread

Claims (1)

(57) [Claims] An outer diameter of a steel pipe having an outer diameter of 100 to 200 mm and a pipe thickness of 3.2 to 6.0 mm is provided at an interval of 1 to 3 m on an outer surface of the steel pipe.
A plurality of spiral wings of one or two turns having an outer diameter of up to 2.5 times are welded in a discontinuous manner, and a trapezoidal plate-shaped support fitting that protrudes downward at the center of the tip of the steel pipe is projected. A small-diameter steel pipe pile comprising a plurality of plate-shaped drilling auxiliary fittings having a bit function attached to an outer peripheral portion thereof obliquely in accordance with a rotating drilling direction.