JP2001348867A - Screwed type steel pipe and its work execution method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screwed type steel pipe pile and its work execution method that can (1) enlarge the applied range of the screwed type steel pipe pile of low vibration, executable without discharging soil and obtaining large tip support force, to a large diameter steel pipe pile, (2) apply a head enlarged steel pipe pile economically designed with respect to a foundation pile placed under the action of large horizontal force and bending moment from an upper construction, to the screwed type steel pipe pile at a low cost without strain in design work execution and (3) reduce the cost of the diameter enlarged part while forming structure free from stress concentration on a pile body near the diameter enlarged part. SOLUTION: This screwed type steel pipe comprises a lower steel pipe 2 having a blade 10 at the tip part or in its vicinity, and an upper steel pipe 3 larger in diameter than the lower steel pipe 2 and jointed to the upper end part of the lower steel pipe 2. The outer diameter of the upper steel pipe 3 is formed to be not larger than the outer diameter of the blade 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw-in type steel pipe pile and a method of constructing the same, and more particularly, to a method for applying a rotational force to a steel pipe pile having wings attached at least at or near the tip end of the steel pipe. The present invention relates to a screw-in type steel pipe pile in which a pile is buried underground, and a method of constructing the pile.

[0002]

2. Description of the Related Art Numerous methods have been proposed for embedding steel pipe piles in the ground by applying a rotational force to a steel pipe pile having winged plates attached to the tip and side surfaces of the steel pipe by a machine installed on the ground, and by screw action. Some of them are intended for small diameter piles, but they have been put to practical use. Here, the invention considered to be representative will be described below.

A method of burying a steel pipe pile described in Japanese Patent Publication No. 2-62848 is to fix a bottom plate at a lower end of a steel pipe pile body, provide a drilling blade on the bottom plate, and provide an outer peripheral surface of a lower end of the pile body. The steel pipe pile, which has a wing with a wing width almost twice as large as the outer diameter of the pile body and is screwed into a soft ground, is screwed into a soft ground. While excavating and softening the soil at the tip of the pile body with the drilling blade at the lower end, causing the spiral wings to bite into the undigged earth and sand on the side of the pile, and rotating and propeling the pile as a reaction force against the strength of the soil. In addition, excavated and softened earth and sand is extruded to the side of the pile and compressed, and the pile is screwed into the ground without discharging the soil (prior art 1).

[0004] In the screw-in type steel pipe pile described in Japanese Patent Application Laid-Open No. 9-324419, the tip is divided into a plurality of pieces in the circumferential direction, and each of the divided parts is shaped like a letter in the same direction. A steel pipe having an annular mounting portion, a steel plate (wing) having a substantially semicircular or fan-shaped flat plate obtained by dividing a circular steel plate or an elliptical steel plate having an outer diameter larger than the outer diameter of the steel pipe into a plurality of pieces. The steel plate is attached to the R-shaped attachment portion provided at the distal end of the steel pipe so as to cover the opening of the distal end of the steel pipe. Is formed in a flat plate shape, and the blades are attached to the tip of the steel pipe instead of the outer peripheral surface (prior art 2).

Next, a description will be given of a conventional technique relating to a pile having an enlarged pile diameter near the pile head (hereinafter referred to as a head enlarged pile). Japanese Patent Application Laid-Open No. 52-7109 discloses a method for driving a head enlarged foundation pile, in which a lower pile and a head are joined in a steel pipe pile formed by joining a lower pile and a head enlarged pile having a diameter larger than that of the lower pile. By striking the tapping surface provided at the joint part with the part enlarged pile and penetrating the pile, by hitting the joint part in the pipe without hitting the upper end of the pile like the conventional striking method It is intended to reduce the stress acting on the head enlarged pile and to reduce its wall thickness (prior art 3).

Further, a head reinforcing pile forming apparatus described in Japanese Patent Publication No. 58-27366 discloses a method for forming a cast-in-place concrete pile or an existing pile of a head enlarged type, in which a casing having an upper portion having a larger diameter than a lower portion is provided. It is constructed by inserting an auger for agitation excavation whose upper part is larger in diameter than the lower part and rotating it in the opposite directions, thereby inserting it into a soil cement column for embedding a head enlarged pile. In addition, a digging blade is provided at the joint between the upper and lower casings in order to reduce the penetration resistance due to the enlargement of the head, and sediment is taken into the casing (prior art 4).

[0007] As described above, the screw-in type steel pipe pile is such that the steel pipe pile is buried in the ground by the screw action of the wing attached to the tip portion or in the vicinity thereof by applying a rotating force to the steel pipe pile. , Low vibration, no earth removal,
It has the characteristic that a large tip support force can be obtained by utilizing the area of a wide wing. The screw-in type steel pipe piles currently in practical use are only the above-mentioned prior arts 1 and 2, but the former is applied to a steel pipe having an outer diameter of less than 300 mm, and the latter is applied in a range of 300 to 600 mm. Both are designed as steel pipe piles that secure a large tip supporting force of about 1.5 to 2.0 times that of ordinary steel pipe piles.

Considering that about half of the steel pipe piles currently used in Japan are occupied by large-diameter steel pipe piles of 700 mm or more, it can be understood that the applicable range of the screw-in type steel pipe piles is narrow. The reason why the screw-in type steel pipe pile is not applied to the large diameter steel pipe pile is that the driving torque for rotating the steel pipe pile becomes extremely large.

According to the tests by the inventors, 75 to 85% of the rotational resistance generated during the penetration of the steel pipe pile into the support layer occurs near the wing, and the resistance is almost proportional to the area of the wing. I understood. That is, it is approximately proportional to the square of the outer diameter of the wing. For this reason, when the outer diameter of the steel pipe pile is increased (therefore, the diameter of the wing is also increased), the construction machine that can be generally used at present has insufficient capacity, and often exceeds the allowable torsional moment of the steel pipe pile. For this reason, screw-on steel pipe piles cannot be applied to large-diameter steel pipe piles of 700 mm or more unless a large hole is drilled at the tip of the steel pipe pile to greatly reduce the torque, but a large hole is drilled at the tip. And the tip support force is reduced.

[0010] As described above, the screw-in type steel pipe pile has an increased projection area due to the wings, so that the tip support force increases. For this reason, when used as a foundation pile of a superstructure, the number of installations can be reduced or the outer diameter of a steel pipe can be reduced as compared with a normal steel pipe pile without wings. However, the resistance against the horizontal force is insufficient due to the reduction in the number of steel pipe piles, and if the horizontal force is to be guaranteed, the number of installations cannot be reduced, so that the above effects cannot be expected.

On the other hand, when the outer diameter of the steel pipe is reduced, the proof stress of the horizontal force is reduced accordingly. Therefore, even if the wall thickness of the steel pipe pile is increased to cope with this, the bending of the steel material is not increased but the weight is increased. The effect of increasing the yield strength is small. Therefore, when a large horizontal force or bending moment is received from the superstructure, the wall thickness of the steel pipe pile must be increased, and the effect of reducing the outer diameter of the steel pipe is reduced.

The small-diameter steel pipe pile has a small rigidity and a small section modulus for its sectional area. For example, an outer diameter of 600 mm and a thickness of 9
The cross-sectional area of a steel pipe pile of mm is 800 mm in outer diameter and 9 mm in wall thickness.
Is 74% of the cross-sectional area of the steel pipe pile, while the second moment of area is 42% and the section modulus is only 56%. For this reason, if a large horizontal force or bending moment is received from the superstructure during an earthquake, the horizontal displacement and bending stress near the pile head will be too large for a small-diameter steel pipe pile. There was a problem with scaling down.

By the way, in order to economically respond to a large horizontal force or bending moment from a superstructure, the idea of expanding the pile diameter near the pile head (head enlarged pile) was several decades ago. Has already been widely used in cast-in-place concrete piles. However, in the field of pre-built piles, pile head enlarged piles have not been put into practical use. In the field of steel pipe piles, in particular, they have been adopted several times in the past, but have not been used recently.

[0014]

The reason why the head enlarged pile has not been put to practical use as described above mainly involves a problem in its construction method. Generally used methods for constructing steel pipe piles are roughly classified into three types: a driving method, a digging method, and a pre-boring method. The case where the head enlarged pile is applied to these methods is as follows.

FIG. 13 shows a structure of a connection portion between a lower steel pipe and an upper steel pipe of a head enlarged pile adopted when a steel pipe pile was constructed by a driving method about 20 years ago. This head enlarged pile 1
A plurality of joining members 9 between the lower steel pipe 2 and the upper steel pipe 3
Are vertically arranged and joined. This joining structure is intended to allow earth and sand to pass through the gap between the joining members 9 at the time of driving, but actually the earth and sand clog in the gap and the penetration resistance becomes extremely large, so that the striking was difficult.

In the method of driving a head-enlarged foundation pile according to prior art 3, the joint between the lower pile and the head-expanded pile is hit in a pipe. Even if the stress degree is reduced compared to the normal driving method, the penetration resistance generated at the joint does not decrease. Therefore, the difficulty in driving is the same as in the above-described technique.

In the prior art 4, since the diameter of the auger inserted into the pipe is smaller than the diameter of the lower steel pipe, the penetration resistance generated at the connecting portion is the same as the former two techniques. On the other hand, the press-in force of the digging method is a fraction of the impact force due to driving.
And small. For this reason, it is almost impossible to apply the inside digging method to the head enlarged pile. It is mechanically possible to protrude the auger from the tip of the lower steel pipe and then increase the auger diameter to about the same as the diameter of the upper steel pipe.However, in order to excavate and mix earth and sand in an area larger than the area of the lower steel pipe, The supporting force is reduced.

It is technically easy to apply the pre-boring method to the head enlarged pile, and it has been partially used in the field of precast concrete piles. However, there is a problem that the construction cost increases. Prior art 3 described above
Is an example of this, but it is a two-stage construction method in which a casing with different diameters in the upper and lower parts and a drilling auger are combined in advance to create a soil-selent columnar body for an enlarged head pile and then insert the pile body. Therefore, the construction cost is higher than that of the driving method or the digging method.

As described above, applying the generally used pile driving method to the head enlarged pile has problems in construction and cost. Further, in the joint structure of the lower steel pipe and the upper steel pipe shown in FIG. 13 and the joint structure of the prior art 3, the transmission of stress from the upper steel pipe to the lower steel pipe is not smooth, and a local stress is generated in the pile body. There is a problem that it is easy.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to obtain the following screw-in type steel pipe pile having the features of a screw-in type steel pipe pile and an enlarged head pile, and a method for constructing the same. It is intended. (1) To expand the applicable range of screw-in type steel pipe piles that can perform low vibration and no earth removal and provide a large supporting force to large diameter steel pipe piles. (2) Head piled steel pipe piles, which can be economically designed, can be applied to screw-in steel pipe piles at a low cost without difficulty in design and construction for foundation piles where large horizontal force and bending moment are applied from the superstructure. To do. (3) A structure in which stress concentration does not occur in the pile body near the enlarged diameter portion, and the cost of the enlarged diameter portion can be reduced.

[0021]

A threaded steel pipe pile according to the present invention has a lower steel pipe having a wing at least at or near a tip end thereof, and has a diameter larger than that of the lower steel pipe and is joined to an upper end of the lower steel pipe. The upper steel pipe is formed such that the outer diameter of the upper steel pipe is equal to or less than the outer diameter of the blade.

The outer diameter of the upper steel pipe of the screw-in type steel pipe pile is set to a range of 1.15 to 1.6 times the outer diameter of the lower steel pipe, and the outer diameter of the upper steel pipe is set to the outer diameter of the blade. 60-90
%, Or a lower steel pipe and an upper steel pipe are connected by a tapered steel pipe.

[0023] Further, in the method for constructing a screw-in type steel pipe pile according to the present invention, the lower steel pipe provided with a wing at least at a front end or in the vicinity thereof, and the tapered steel pipe connected to the lower steel pipe at the lower end are joined. A steel pipe pile consisting of an upper steel pipe having a diameter larger than the lower steel pipe and having the same diameter as or smaller than the outer diameter of the wing, and a tapered steel pipe joined to the upper steel pipe is welded to the lower steel pipe at a construction site. The steel pipe pile is buried in the ground by applying a rotational force to the steel pipe pile.

[0024]

[First Embodiment] FIG. 1 is an explanatory view of a first embodiment of the present invention. In the figure, reference numeral 1 denotes a screwed steel pipe pile with an enlarged head (hereinafter simply referred to as a steel pipe pile).
The lower steel pipe 2 includes a lower steel pipe 2 and an upper steel pipe 3 having a diameter larger than that of the lower steel pipe 2.

The lower steel pipe 2 is made of a steel pipe for a normal steel pipe pile (for example, having an outer diameter of 600 mm or less).
As shown in FIG. 2 (in FIG. 2, the lower steel pipe 2 is turned upside down for ease of explanation), and the circumferential direction is
a, 4b, the slope is continuous from the lower end of one step 4a to the upper end of the other step 4b, and is continuous from the upper end of step 4a to the lower end of step 4b. As the inclined surfaces, mounting portions 5a and 5b of the V-shaped wing 10 which are oriented in the same direction by these inclined surfaces are provided.

The height h of the steps 4a, 4b varies depending on the condition of the ground in which the steel pipe pile 1 is buried, the outer diameter of the steel pipe pile 1, the state of the wing 10, and the like. .4D
₁₎ / 2 (D ₁ is preferably a outer diameter) about the lower steel tube 2. When the height h is less than (0.1D ₁ ) / 2, the amount of penetration of the steel pipe pile 1 per rotation decreases, and
If (0.4D ₁ ) / 2 is exceeded, the amount of penetration per rotation becomes too large, so that the torque for rotating the steel pipe pile 1 becomes excessive, and the depth of the earth and sand that is excavated and softened by the wing 10 is reduced. Due to the increase, the supporting force may decrease.

The blade 10 is, as shown in FIG.
Flat steel blade 11a to a circular steel plate or elliptical steel having an outer diameter D ₁ greater than the outer diameter D ₃ was divided into two parts from the center of, 11b
It is constituted by. The steel wings 11a, 1
The size (outer diameter D ₃ ) of the wing 10 made of 1b is generally
1.4 to 2.1 times the outer diameter D ₁ of the lower steel pipe 2 is desirable.

The steel wings 11a, 11b as described above are attached to the mounting portions 5a, 5
The blade 10 is mounted on the wing b and is attached by being inclined in the opposite direction by welding or the like to form the wing 10. In addition, both steel plates 11
The opening caused by the discrepancy between a and 11b may be closed by a closing plate, for example.

As shown in FIG. 4, the steel blades 11a and 11b are provided with one step 4 at the tip of the lower steel pipe 2, and make one round from the lower end of the step 4 to the upper end. It is also possible to provide a mounting portion 5 having a V-shape (spiral shape) that reaches, and attach the steel wings 11a and 11b to the mounting portion 5 by inclining in opposite directions. In this case, the height h ₁ of the step portion 4 is
It is desirable to be about 0.1 to 0.4 D ₁ (D ₁ is the outer diameter of the lower steel pipe 2).

The outer diameter D ₂ of the upper steel pipe 3 is preferably 1.15 to 1.6 times the outer diameter D ₁ of the lower steel pipe 2 in terms of design and construction. If it is smaller than 1.15 times, the processing cost for diameter enlargement is greater than the advantage of diameter enlargement, and even if it is 1.6 times or more, no further design advantage can be obtained. The outer diameter D ₂ of the upper steel pipe 3 is
It is desirable to set the outer diameter of the wing 10 to about 60 to 90%.
When it is 60% or less, the processing cost is greater than the design advantage, and when it is 90% or more, the upper steel pipe 3 is required at the time of construction.
Since the penetration resistance of the blade 10 may increase, it is preferable to set it within 90%.

Further, the length L of the upper steel pipe 3₁Is 1 / β
The range of 範 囲 2 / β is desirable. Where β is the upper steel pipe pile 3
And the characteristic value determined from the hardness of the ground. Length of upper steel pipe 3
L ₁Is less than 1 / β, the large bending moment is lower
It is transmitted to the steel pipe 2, and if it is longer than 2 / β,
Will be done. Generally, the length of the upper steel pipe 3 is about 4 to 10 m
It is.

The lower steel pipe 2 and the upper steel pipe 3 as described above are
For example, as shown in FIG. 5, a donut-shaped connecting member 6 having an outer diameter equal to the outer diameter of the upper steel pipe 3 and having a hole 6a in the center substantially equal to the outer diameter of the lower steel pipe 2 is used.
By connecting the connecting member 6 to the lower end of the lower steel pipe 2 by welding, and fitting the upper end of the lower steel pipe 2 into the hole 6a of the connecting member 6 and welding, the two are integrally connected.

The steel pipe pile 1 constructed as described above is connected to an electric motor 22 mounted on a base machine 21 and rotated by the electric motor 22, as shown in FIG. It is screwed into the ground by the screw action of the wings 11a and 11b and is buried. At this time, the steel wing 11
When there is an opening at the staggered portion between a and 11b, a small amount of earth and sand enters the steel pipe pile 1, and when the opening is closed, the earth and sand do not enter the steel pipe pile 1. When the outer diameter of the steel pipe pile 1 is large, a rotating force may be directly applied to the body of the steel pipe pile 1 near the ground, and the lower steel pipe 2 may be a connection pile connecting a plurality of steel pipes. Good.

As described above, the screw-in type steel pipe pile penetrates into the ground without discharging the soil by the screw action of the wing, and the earth and sand located below the wing is excavated and softened by the wing, and the gap between the wings is reduced. After passing through, it moves to the outer periphery of the steel pipe pile 1 and is compressed (Fig. 1
20). At this time, when part or all of the tip of the steel pipe pile 1 is open, a part of the earth and sand is taken into the steel pipe pile 1.

The earth and sand that has moved to the outer periphery of the steel pipe pile 1 is not easily disturbed during the construction, and is compressed to increase the pore water pressure. Since no frictional resistance occurs, the steel pipe pile 1 can penetrate smoothly. However, as time passes, the shearing resistance of the earth and sand recovers due to the recovery of the soil particle binding force and the decrease in the pore water pressure, and a large peripheral friction force is exerted when the pile is put into service.

As described above, the screw-in type steel pipe pile is softened during construction by disturbing the soil around the steel pipe pile in an area corresponding to the outer diameter thereof by the wings. If the outer diameter D ₂ of the 3 following the outer diameter D ₃ of the blade 10, as in the case of head enlarged steel pipe pile of small resistance of the ground by the expanded during construction, driving piles method and medium digger pressed pile method ,
It can be smoothly screwed into the ground without extremely lowering construction efficiency or falling into construction difficulties. In this case, the outer diameter D ₂ of the upper steel tube 3 is more than 90% of the outer diameter D ₃ of the blade 10, since the upper steel tube 2, which will penetrate the equivalent compress soil Nevertheless was once disruptor, since penetration resistance is increased, the outer diameter D ₂ of the upper steel tube 3 is the outer diameter D ₂ of the blade 10
Is preferably 90% or less.

The steel according to this embodiment configured as described above
When the pipe pile 1 is used as a foundation pile, the wing 10
Because it functions as a pressure receiving body that receives end ground reaction force,
Tip support can be obtained. In this case, the upper steel pipe 3
Outer diameter D of_TwoIs the outer diameter D of the lower steel pipe 2.₁1.15 to 1.6
And the outer diameter D of the wing 10_ThreeIs the outer diameter D of the lower steel pipe 2. ₁
If it is about 1.4 to 2.1 times of
Can be improved. Also, the lower steel pipe 2 is
The influence of horizontal force and bending moment transmitted from
Sufficiently large resistance to large vertical loads
It can exert its capacity.

In this embodiment, the outer diameter D ₂ of the upper steel pipe 3 is set to be equal to or less than the outer diameter D ₃ of the blade 10, so that the driving torque for screwing and penetrating the steel pipe pile 1 can be reduced. The penetration of the screw-in type steel pipe pile with the enlarged part can be constructed smoothly.

The outer diameter D ₂ of the upper steel pipe 3 is
Of about 1.15 to 1.6 times the outer diameter D ₁ of the steel pipe pile 1, it is possible to cope with a large bending moment generated near the pile head of the steel pipe pile 1, and the bending stress and the horizontal displacement during the earthquake The amount can be suppressed. Further, by configuring as described above, an economical head enlarged screw-in type steel pipe pile can be put to practical use.

Further, according to the present invention, an ideal foundation pile could be obtained by combining an enlarged head pile and a screw-in type steel pipe pile under certain conditions. In other words, by adopting the screw-in pile method while taking advantage of the design advantage of the head-enlarged pile, the problems in the construction of the head-expanded steel pipe pile are eliminated, and the large tip support is achieved with low vibration and no earth removal. By taking advantage of the strength of the screw-in type steel pipe pile in which the force can be obtained, it was possible to overcome the difficulty in the construction of the large-diameter steel pipe pile over the entire length, which was conventionally difficult.

[Second Embodiment] FIG. 7 is an explanatory diagram of a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, the lower steel pipe 2 and the upper steel pipe 3 are joined by a short tapered steel pipe 7 having an inverted truncated cone shape.
Equal to the outer diameter of the lower end and the outer diameter D ₁ of the lower steel tube 2, also the outer diameter of the upper portion equally formed to the outer diameter D ₂ of the upper steel tube 3 is these that are joined by welding. The length L ₂ of the tapered steel pipe 7 is equal to the outer diameter D ₁ of the lower steel pipe 2.
About 5 to 1.5 times, and the taper angle θ
Is desirably 20 ° or less.

A method for constructing the steel pipe pile 1 according to the present embodiment,
The operation and effect are almost the same as those in the first embodiment, but since the space between the lower steel pipe 2 and the upper steel pipe 3 is continuously changed by the tapered steel pipe 7, the excavated and softened soil is excavated in the construction. , The penetration resistance is small, and the steel pipe pile 1 can penetrate more smoothly. In addition, the vertical load is smoothly transmitted from the upper steel pipe 3 to the lower steel pipe 2 as compared with the conventional technique described with reference to FIG.

Third Embodiment FIG. 8 is an explanatory diagram of a third embodiment of the present invention. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted. In the present embodiment, in Embodiment 2, the upper steel pipe 3 and the tapered steel pipe 7 are joined at a factory, and the lower steel pipe 2 and the tapered steel pipe 7 are joined at a construction site.

That is, in joining the upper steel pipe 3 and the tapered steel pipe 7, for example, as shown in FIG. 9, the outer periphery of the lower end of the upper steel pipe 3 is obliquely cut off, and the outer periphery of the lower end is obliquely cut off. A groove is formed with the upper end of 7 and the two are joined by welding at the factory. And
The upper steel pipe 3 in which the lower steel pipe 2 and the tapered steel pipe 7 are joined is transported to the construction site.

At the construction site, first, the lower steel pipe 2 having the wings 10 attached to the tip is connected to the electric motor 22 of the base machine 21 and is given a rotational force to penetrate the ground, leaving the upper part on the ground. In this state, the electric motor 22 is removed. Next, the upper steel pipe 3 to which the tapered steel pipe 7 is joined is suspended by a crane or the like, and the tapered steel pipe 7 is placed on the lower steel pipe 2 and both are joined by welding. Then, the upper steel pipe 3 is connected to the electric motor 22 of the base machine 21 to apply a rotational force, and the steel pipe pile 1 to which the upper steel pipe 3 is connected is screwed and buried in the ground. In this case, when the steel pipe pile 1 has a large diameter, a rotating force may be directly applied to the trunk of the steel pipe pile 1 on the ground.

When joining the lower steel pipe 2 and the tapered steel pipe 7 joined to the upper steel pipe 3, as shown in FIG.
A backing metal 8 is attached inside the upper end of the lower steel pipe 2 and the lower end of the tapered steel pipe 7, and a groove formed on the outer peripheral surface is welded to join the two. When the lower steel pipe 2 is a joint steel pipe, the upper and lower steel pipes 2a and 2b are joined by welding at a construction site.

In the present embodiment configured as described above, the number of welding points can be reduced by one as compared with the case where all of the lower steel pipe 2, the tapered steel pipe 6, and the upper steel pipe 3 are welded and joined at the factory. . Further, when welding steel pipes having different outer diameters at the factory via the tapered steel pipe 7, it is necessary to perform the work by installing the steel pipes on turning rollers having different heights. There are few factories, and the cost is high. In the present embodiment, since the lower steel pipe 2 is embedded in the ground and the tapered steel pipe 6 is directly welded and joined on site, the welding operation is simple and the cost can be reduced.

When transporting a steel pipe pile on a truck or the like, it is difficult to load steel pipes having different outer diameters on a carrier, so that loading and transportation costs are high. In the present embodiment, the lower end of the upper steel pipe 3 is used. Is joined to a short tapered steel pipe 7 having a smaller diameter than the upper steel pipe 3, so that it can be loaded similarly to the case of a steel pipe pile having a constant diameter. In addition, by setting the taper angle θ of the tapered steel pipe 7 to 20 ° or less, on-site welding can be performed under almost the same working conditions as in the case of on-site welding of the same diameter steel pipe, and equivalent welding quality can be obtained.

[Comparative Example] Outer diameter 500 mm, wall thickness 9 mm,
8 m long pile, outer diameter 500 mm, wall thickness 9 mm, length 1
It consists of a 3m middle pile and a lower pile.
An ordinary screw-in type steel pipe pile having a total length of 34 m (hereinafter referred to as steel pipe pile A) having a wing in which steel wings obtained by dividing a circular steel plate having a thickness of 00 mm and a thickness of 40 mm into two parts and crossing each other, and an outer diameter of 7 mm
Upper steel pipe of 00 mm, wall thickness of 9 mm and length of 7.5 m, taper steel pipe of length 0.5 m welded to the lower end of the upper steel pipe at the factory, and outer diameter of 500 mm, wall thickness of 9 mm and length of 13 m A threaded steel pipe pile according to the present invention (hereinafter referred to as a steel pipe pile B) comprising a lower steel pipe composed of a pile and a lower pile, and having the same wing as the steel pipe pile A attached to the tip of the lower pile, was prepared.

The upper part is a sandy ground having an N value of 5 to 10, the middle part is an alternate layer of silt and sand having an N value of 5 to 15, and the lower part is an N
The pile heads of steel pipe piles A and B were connected to electric motors mounted on a base machine, respectively, on the ground consisting of gravel ground having a value of 50 or more, and were rotated. Thereby, both were screwed into the ground and penetrated smoothly to the support layer. The time required for the construction was 3.7 hours for the normal steel pipe pile A and 3.9 hours for the steel pipe pile B according to the present invention, and there was almost no difference between the two. The workability of welding the tapered steel pipe joined to the lower end of the upper steel pipe and the middle pile constituting the lower steel pipe was the same as the welding work of steel pipes of the same diameter.

[Embodiment 4] This embodiment shows another example of the blade 10 provided at the lower end of the lower steel pipe 2 or in the vicinity thereof. In the first to third embodiments, the flat steel wings 11a and 11b are attached to the tip of the lower
Is shown, but in this example, FIG.
As shown in FIG. 1A, a blade 10 is formed by attaching a spiral steel blade 12 instead of the flat steel blades 11a and 11b. At the tip of the lower steel pipe 2, the spiral mounting portion 5 described with reference to FIG. 4 is formed.

That is, as shown in FIG.
Diameter D_Three(D_ThreeIs the outer diameter D of the lower steel pipe 2 ₁1.4 to 2.1
Holes 13 are provided in the center of a circular steel plate
And cut one place from this hole 13 to the outer periphery
Bent into a shape corresponding to the mounting part 5 provided at the tip of the steel pipe 2
To form one spiral steel wing 12,
The wing 12 is welded to the mounting portion 5 of the lower steel pipe 2 to weld the wing 10
It is what constituted.

In the example of FIG. 11, as shown in FIG. 11B, a hole 15 having a diameter D ₄ substantially equal to the outer diameter D ₁ of the lower steel pipe 2 is formed at the center of a circular steel plate having an outer diameter D _3. And this is 2
The steel plates 14a and 14b are formed by dividing into flat steel wings 14a and 14b. As shown in FIG.
Blade 1 attached by welding to the outer periphery of the lower steel pipe 2 in continuous helical pitch P (corresponding to the height h ₁ of the step portion 4 of FIG. 4)
0. Incidentally, reference numeral 16 denotes a closing plate for closing the opening at the tip of the lower steel pipe 2, but this may be omitted or a donut plate with a hole may be attached.

In the example of FIG. 12, as shown in FIG. 12 (b), one portion from the hole 15 of the circular steel plate shown in FIG. parts corresponding to the height h ₁ of 4) spirally bending processed to one steel blade 17
The steel wing 17 is attached to the outer periphery of the lower steel pipe 2 by welding, as shown in FIG.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and although not shown, for example, the following embodiment is available. (1) In the above description, the case where two semicircular steel wings 11a and 11b are attached to the tip of the lower steel pipe 2 or the outer periphery near the tip to form the wing 10 has been described. 2, three or more L-shaped mounting portions may be provided at the tip of the fan, and a fan-shaped steel wing obtained by dividing a circular steel plate into three or more portions may be mounted on the mounting portion or the outer periphery. Alternatively, the spiral steel wing may be divided into a plurality of parts and attached to the tip or outer periphery of the lower steel pipe 2.

(2) Although the case where the blade 10 is provided at or near the tip of the lower steel pipe 2 has been described, a blade may be provided further above the lower steel pipe 2 to constitute a plurality of stages. (3) Further, in the first to fourth embodiments, the case where the sum of the internal angles of the plurality of steel blades constituting the blade 10 is 360 ° has been described, but the sum of these internal angles is in the range of 320 ° to 400 °. You may comprise so that it may become.

[0057]

The screw-in type steel pipe pile according to the present invention comprises a lower steel pipe having wings at least at or near the tip, and an upper steel pipe having a diameter larger than the lower steel pipe and joined to an upper end of the lower steel pipe. Since the outer diameter of the upper steel pipe is less than the outer diameter of the wing, the driving torque for screwing and penetrating the ground can be reduced, and the penetration of the screw-in type steel pipe pile with an enlarged head can be performed smoothly. it can.

Further, since the outer diameter of the upper steel pipe is set to a range of 1.15 to 1.6 times the outer diameter of the lower steel pipe, it is possible to cope with a large bending moment generated near the pile head. In addition, it is possible to suppress the degree of bending stress and the amount of horizontal displacement during an earthquake. Further, by forming the upper steel pipe into the above-described size, an economical screw-in type steel pipe pile with an enlarged head can be obtained.

Further, the outer diameter of the upper steel pipe is set to 60 times the outer diameter of the blade.
With the range of ~ 90%, the upper steel pipe can smoothly penetrate into the excavated and softened soil due to the rotation of the blades, and the screw-in type steel pipe pile can be easily built in the ground.

Furthermore, since the lower steel pipe and the upper steel pipe are connected by a continuously changing tapered steel pipe, the excavated and softened earth and sand smoothly moves during construction, so that the penetration resistance is small and the penetration can be smoothly performed. Also,
Vertical load is smoothly transmitted from the upper steel pipe to the lower steel pipe.

Further, the method for constructing a screw-in type steel pipe pile according to the present invention is characterized in that a lower steel pipe having wings provided at least at or near the tip and a tapered steel pipe joined to the lower steel pipe at the lower end are joined. A steel pipe pile consisting of an upper steel pipe having a diameter larger than that of the steel pipe and having the same diameter as or smaller than the outer diameter of the wing, and a tapered steel pipe joined to the upper steel pipe is welded and joined to a lower steel pipe at a construction site. The steel pipe pile is buried in the ground by applying a rotational force to the steel pipe, so that the above-described effects can be obtained and the welding and joining work between the steel pipe and the lower steel pipe is easy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory view of a mounting portion of a blade provided at a lower end portion of a lower steel pipe of FIG. 1;

FIG. 3 is an explanatory view showing the manufacture of a wing.

FIG. 4 is an explanatory view showing another example of a mounting portion of a wing.

FIG. 5 is an explanatory diagram showing a connection example of a lower steel pipe and an upper steel pipe.

FIG. 6 is a construction explanatory diagram of the steel pipe pile according to the first embodiment.

FIG. 7 is an explanatory diagram of Embodiment 2 of the present invention.

FIG. 8 is an explanatory diagram of Embodiment 3 of the present invention.

FIG. 9 is an explanatory diagram showing a connection example of a lower steel pipe and an upper steel pipe according to the third embodiment.

FIG. 10 is an explanatory diagram of Embodiment 4 of the present invention.

FIG. 11 is an explanatory diagram of another example of the fourth embodiment.

FIG. 12 is an explanatory diagram of another example of the fourth embodiment.

FIG. 13 is an explanatory view of a main part of a conventional head-enlarged steel pipe pile.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw-in type steel pipe pile (steel pipe pile) 2 Lower steel pipe 3 Upper steel pipe 5, 5a, 5b Attachment part of wing 6 Connection member 7 Tapered steel pipe 10 Wing 11a, 11b, 14a, 14b Steel wing 12, 17 Spiral wing 21 Base machine 22 Electric motor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Gen Mori 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Hisashito Shimaoka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Masahiro Hayashi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Takashi Okamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon F Tube (in reference) 2D041 AA02 CA03 CA05 DB02 DB11 FA14

Claims (5)

[Claims] 1. A lower steel pipe having a wing at least at a tip end or in the vicinity thereof, and an upper steel pipe having a diameter larger than that of the lower steel pipe and joined to an upper end of the lower steel pipe. Screw-in type steel pipe pile formed below the outer diameter of the wing. 2. The screw-in type steel pipe pile according to claim 1, wherein the outer diameter of the upper steel pipe is set in a range of 1.15 to 1.6 times the outer diameter of the lower steel pipe. 3. The outer diameter of the upper steel pipe is 60 to 9 times the outer diameter of the blade.
The screw-in type steel pipe pile according to claim 1 or 2, wherein the range is 0%. 4. The screwed steel pipe pile according to claim 1, wherein the lower steel pipe and the upper steel pipe are connected by a tapered steel pipe. 5. A lower steel pipe having a wing provided at least at or near a tip end thereof, and a tapered steel pipe joined to the lower steel pipe at a lower end thereof and having a larger diameter than the lower steel pipe and an outer diameter of the wing. By having a steel pipe pile consisting of an upper steel pipe of the same diameter or smaller than that, welding the tapered steel pipe joined to the upper steel pipe to the lower steel pipe at a construction site, and applying a rotational force to the steel pipe pile. A method for constructing a screw-in type steel pipe pile, wherein the steel pipe pile is buried in the ground.