JP7485231B2 - Screw-in type steel pipe pile, design method for screw-in type steel pipe pile, manufacturing method for screw-in type steel pipe pile, and construction method for screw-in type steel pipe pile - Google Patents

Description

The present invention relates to a screw-in type steel pipe pile in which two or more arc-shaped rotors, each formed by radially dividing a disk or doughnut-shaped disk larger than the outer diameter of the steel pipe, are provided consecutively at the tip of the steel pipe in the circumferential direction; a design method for a screw-in type steel pipe pile; a manufacturing method for a screw-in type steel pipe pile; and a construction method for a screw-in type steel pipe pile.

As shown in Fig. 3, a conventional screw-in type steel pipe pile 21 has rotors 23 attached to the tip and periphery of the steel pipe 2, which are larger than the pile diameter. This steel pipe pile 21 is designed to push the soil scraped from the ground 25 below the rotors 23 up to the top of the rotors 23 by rotating the pile body, and penetrate into the ground using the ground reaction force as a driving force. Then, construction is completed when the part from the tip of the steel pipe to 1 times the steel pipe outer diameter D penetrates into the supporting ground 27 (see Fig. 3). The rotors 23 of the screw-in type steel pipe pile 21 shown in Fig. 3 are composed of two wings, a lower wing 23a and an upper wing 23b, and the installation angle α1 of the lower wing 23a is equal to the installation angle α2 of the upper wing 23b.

The rotor 23 (lower wing 23a, upper wing 23b) has an inclined surface that is inclined as a whole, and the inclination angle of this inclined surface is the mounting angle. The mounting angle is an angle that indicates the degree to which the rotor as a whole is mounted to the steel pipe 2. For example, as shown in FIG. 4, when the rotor 23 is mounted along the outer peripheral surface of the steel pipe tip, the inclination angle of the surface including the curve that the inner peripheral surface of the rotor 23 touches on the outer peripheral surface of the steel pipe 2 with respect to the orthogonal plane P that is perpendicular to the steel pipe axis is the mounting angle α (α1 or α2 in FIG. 4). In addition, when the steel pipe tip surface is cut at an angle and the rotor 23 is attached by abutting against the steel pipe tip surface, the inclination angle of the steel pipe tip surface is the mounting angle.

The main rotational resistance of screw-in steel pipe piles comes from the resistance near the blade tips when scraping away soil, so a large rotational torque is required to penetrate hard ground. In addition, once construction is complete, the rotating blades can provide a large bearing capacity.

Such screw-in steel pipe piles include those whose tips are closed to prevent soil and sand from being drawn into the pile, such as that disclosed in Patent Document 1, and those whose tips have an opening to allow soil and sand to be drawn into the pile, such as that disclosed in Patent Document 2.

Pile tips that are closed off can exert bearing capacity over the entire underside of the wing, including the pile diameter, but for soil inside the pile diameter, it is necessary not only to push it upwards but also to push it outward, which requires a very large rotational torque. Therefore, when the diameter is large, there is a risk of problems with construction.

On the other hand, piles with openings at the tip can take in soil and sand into the pile body, so they can be constructed with less rotational torque than piles with closed tips, but since the bearing capacity cannot be expected at the opening, there is a risk of the bearing capacity of the pile as a whole being reduced. Of course, soil can sometimes get stuck inside the pile body during construction, blocking the opening, in which case the situation will be the same as that of piles with closed tips mentioned above.

In order to increase the propulsive force, it is effective to increase the diameter of the impeller and the amount of soil pushed up to the top of the impeller with one rotation, but this also increases the rotational resistance. Therefore, in relation to the torsional strength of the pile body and the strength of the impeller, the impeller blade diameter is usually limited to about three times the pile diameter.

Patent No. 2861937 JP 2009-209674 A

Screw-in steel pipe piles have the problem that their construction workability can deteriorate depending on the ground conditions. For example, in soft ground, the driving force caused by the ground reaction force generated when the soil scraped off from below the rotor during construction is pushed up to the top of the rotor may decrease, preventing the pile from penetrating. On the other hand, in hard ground, the resistance near the blade tips when scraping off soil during construction and the frictional resistance during rotation may become too large, and the applied rotational torque may exceed the torsional strength of the pile body, causing it to twist and break.

The present invention has been made to solve such problems, and aims to provide a screw-in type steel pipe pile that does not adversely affect bearing capacity and can be constructed in a manner suitable for various ground conditions, such as soft ground or hard ground, a design method for a screw-in type steel pipe pile, a manufacturing method for a screw-in type steel pipe pile, and a construction method for a screw-in type steel pipe pile.

(1) The screw-in type steel pipe pile according to the present invention is a screw-in type steel pipe pile having two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, arranged in succession in the circumferential direction at the tip of the steel pipe, and the mounting angle of the lowermost rotor, which is the rotor located furthest below the steel pipe, is smaller than the mounting angle of the uppermost rotor, which is the rotor located furthest above.

(2) Furthermore, in the above (1), the mounting angle of the lowest wing is greater than or equal to 3 degrees and less than or equal to 7 degrees.

(3) Also, a screw-in steel pipe pile has two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, arranged in succession in the circumferential direction at the tip of the steel pipe, and the mounting angle of the lowermost rotor, which is the rotor located furthest below the steel pipe, is greater than the mounting angle of the uppermost rotor, which is the rotor located furthest above.

(4) Furthermore, in the item (3) above, the mounting angle of the uppermost wing is greater than or equal to 3 degrees and less than or equal to 7 degrees.

(5) Furthermore, the design method for a screw-in type steel pipe pile according to the present invention is a design method for a screw-in type steel pipe pile in which two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, are provided consecutively in the circumferential direction at the tip of the steel pipe, and the mounting angle of the rotors is set so as to satisfy the following conditions (A) to (C):
(A) When the hardness of the ground on which construction is to be carried out exceeds a predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made smaller than the mounting angle of the uppermost wing, which is the rotor attached highest, and when the hardness of the ground on which construction is to be carried out is equal to or less than the predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made larger than the mounting angle of the uppermost wing, which is the rotor attached highest.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors.

(6) A method for constructing a screw-in type steel pipe pile according to any one of (1) to (4) above, comprising investigating the hardness of the ground to be constructed, selecting any one of (1) to (4) above based on the investigation results, and gripping an upper end of the steel pipe of the selected screw-in type steel pipe pile to rotate and penetrate the pile into the ground.

(7) Furthermore, the manufacturing method for a screw-in type steel pipe pile according to the present invention is a manufacturing method for a screw-in type steel pipe pile in which two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, are provided consecutively in the circumferential direction at the tip of the steel pipe, and the mounting angle of the rotors is formed so as to satisfy the following conditions (A) to (C).
(A) When the hardness of the ground on which construction is to be carried out exceeds a predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made smaller than the mounting angle of the uppermost wing, which is the rotor attached highest, and when the hardness of the ground on which construction is to be carried out is equal to or less than the predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made larger than the mounting angle of the uppermost wing, which is the rotor attached highest.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors.

In the present invention, the mounting angle of the lowermost blade, which is the blade positioned furthest below the steel pipe, is smaller than the mounting angle of the uppermost blade, which is the blade positioned furthest above. This prevents the resistance near the blade tips and the frictional resistance during rotation from becoming too large when working on hard ground, and ensures propulsive force.

FIG. 1 is an explanatory diagram of a screw-in type steel pipe pile according to the first embodiment. FIG. 2 is an explanatory diagram of a screw-in type steel pipe pile according to the second embodiment. FIG. 3 is an explanatory diagram of a conventional screw-in type steel pipe pile in a completed installation state. FIG. 4 is an explanatory diagram of the tip portion of the screw-in type steel pipe pile shown in FIG.

[First embodiment]
The screw-in type steel pipe pile 1 according to the first embodiment is suitable for the case where the rotation resistance during rotational penetration is large in hard ground. As shown in FIG. 1, the screw-in type steel pipe pile 1 has two arc-shaped rotors 3, each of which is formed by dividing a doughnut-shaped disk larger than the outer diameter of the steel pipe 2 in the radial direction, provided consecutively at the tip of the steel pipe 2 in the circumferential direction. Furthermore, in the screw-in type steel pipe pile 1, the installation angle α1 of the lowermost rotor 3a, which is the rotor 3 arranged and attached most downward of the steel pipe 2, is smaller than the installation angle α2 of the uppermost rotor 3b, which is the rotor 3 arranged and attached most upward. Each configuration will be described in detail below.

<Steel pipes>
The steel pipe 2 is a main component of the pile, and the tip of the steel pipe 2 may be closed or open. In addition, the steel pipe 2 does not have to be a single pile, and may be connected during construction by welding or a mechanical joint.

<Rotor>
The rotor 3 is used to obtain propulsive force by rotation, and is made of an arc-shaped flat plate obtained by dividing a disk or a doughnut-shaped disk larger than the outer diameter of the steel pipe 2 in the radial direction. The arc-shaped plate is attached to the tip of the steel pipe 2 in a pseudo-spiral shape from the plate on the deeper side (lowest wing 3a) to the plate on the shallower side (uppermost wing 3b) during construction.

The reason for α1 < α2 will be explained below. The screw-in steel pipe pile 1 rotates the steel pipe 2 to push soil scraped from the ground below the rotor 3 up to the top surface of the rotor 3, and the resulting ground reaction force is used as a propulsion force to penetrate into the ground.

Therefore, the mounting angle of the rotor 3 has a large effect on the rotational torque and thrust. Regarding the rotational torque, the resistance near the blade tip when scraping off soil from the ground is the main rotational resistance, so the mounting angle of the lowest blade 3a has a large effect on the rotational torque. For example, if the mounting angle of the lowest blade 3a is large, the inclination of the lowest blade 3a becomes steeper and the height difference H between the lower end and the upper end of the lowest blade 3a becomes larger, so the amount of soil scraped off per rotation of the rotor 3 increases, the rotational resistance increases, and the rotational torque increases. Conversely, if the mounting angle of the lowest blade 3a is small, the inclination of the lowest blade 3a becomes gentler and the height difference H between the lower end and the upper end of the lowest blade 3a becomes smaller, so the amount of soil scraped off per rotation of the rotor 3 decreases, the rotational resistance decreases, and the rotational torque decreases.

In terms of propulsive force, the larger the mounting angle, the greater the amount of soil on the top surface of the rotor 3, and the greater the propulsive force obtained as a ground reaction force. Conversely, the smaller the mounting angle, the less soil there is on the rotor 3, and the smaller the propulsive force obtained as a ground reaction force.

In this regard, the screw-in steel pipe pile 1 according to the first embodiment has a small mounting angle α1 of the lowest wing 3a and a large mounting angle α2 of the highest wing 3b. That is, the mounting angle α1 of the lowest wing 3a is smaller than the mounting angle α2 of the highest wing 3b. As a result, in cases where the ground is hard and there is concern that the pile body may be damaged due to an increase in rotational torque, the amount of soil scraped off from the hard ground on the deeper side by the lowest wing 3a is reduced, thereby reducing the resistance near the blade tip and lowering the rotational resistance. On the other hand, in terms of propulsion force, the uppermost wing 3b, which has a large mounting angle α2, collects a lot of soil on the shallower side that has already been disturbed and softened, and pushes it up to the top of the rotating wing 3, thereby obtaining a large ground reaction force and obtaining a large propulsion force.

In this way, in the screw-in steel pipe pile 1 of this embodiment, the relationship between the mounting angle α1 of the lowest wing 3a and the mounting angle α2 of the uppermost wing 3b is set to α1 < α2, making it possible to ensure propulsion force while suppressing rotational torque against hard ground.

In addition, by reducing the mounting angle α1 of the lowermost blade 3a and increasing the mounting angle α2 of the uppermost blade 3b, it is possible to prevent clogging with sediment and prevent an increase in rotational torque due to clogging with sediment. This point will be explained below. If only the reduction of rotational torque is considered, it may be thought that both the mounting angle α1 of the lowermost blade 3a and the mounting angle α2 of the uppermost blade 3b should be reduced. However, if both the mounting angles α1 and α2 are reduced, the gap k (see FIG. 1) between the uppermost blade 3b and the lowermost blade 3a becomes small, causing clogging with sediment and increasing the rotational torque.
In this embodiment, the mounting angle α1 of the lowermost blade 3a is reduced to reduce the rotational torque, and the mounting angle α2 of the uppermost blade 3b is increased to ensure a sufficient gap k between the uppermost blade 3b and the lowermost blade 3a, thereby preventing an increase in the rotational torque due to clogging with sand.

In other words, the rotor 3 in this embodiment has a shape that is rational in terms of the behavior of soil and sand during construction of the screw-in steel pipe pile 1 by asymmetrically arranging the lowest wing 3a and the uppermost wing 3b so that α1 < α2.

Furthermore, a more desirable embodiment satisfies the following conditions.
(a) The setting angle α1 of the lowermost wing 3a is 3 degrees or more and 7 degrees or less. On the other hand, the setting angle α2 of the uppermost wing 3b is desirably larger from the viewpoint of propulsive force, and is desirably 11 degrees or less from the viewpoint of ensuring supporting force.
(b) The height h (see FIG. 1) from the tip of the steel pipe 2 to the upper surface of the uppermost wing 3b is within 1 time the outer diameter D of the steel pipe.
(c) The distance k between the end of the lowermost wing 3a and the end of the uppermost wing 3b is greater than 75 mm.
The reasons for the above conditions (a) to (c) will be explained below.

Regarding (a), in order to fully exert the effect of reducing the rotational torque, it is desirable that the setting angle α1 of the lowermost blade 3a is small, and from this viewpoint, it is desirable that the setting angle α1 is 7 degrees or less.
On the other hand, if the mounting angle α1 is too small, the effect of scraping away soil from the ground cannot be ensured, and from this viewpoint, the mounting angle α1 is preferably 3 degrees or more.

Regarding (b), the screw-in type steel pipe pile 1 is usually constructed so that the height from the tip of the steel pipe to one time the steel pipe outer diameter D penetrates into the supporting ground. Therefore, if the installation angle α2 of the lowest wing 3a is too large, the height from the lower end of the lowest wing 3a to the upper end of the uppermost wing 3b becomes large, and the upper end of the uppermost wing 3b cannot be contained within the supporting ground. In order to fully exert the supporting force, it is desirable for the rotor 3 to be within the supporting ground, and from this viewpoint, it is desirable for the height h from the tip of the steel pipe 2 to the upper surface of the uppermost wing 3b to be within one time the steel pipe outer diameter D.

Regarding (c), the maximum particle size of the ground on which the screw-in type steel pipe pile 1 is usually constructed is 75 mm, which is the maximum diameter of gravel. As described above, the screw-in type steel pipe pile 1 is designed to push up the soil scraped from the ground below the rotor 3 to the top of the rotor 3 by rotating the steel pipe 2, and to penetrate into the ground using the ground reaction force as a driving force. If the interval k between the end of the lowest wing 3a and the end of the highest wing 3b is small, soil clogging occurs and the rotation torque increases. Therefore, in order to suppress the increase in rotation torque due to clogging during construction, it is desirable to make the interval k between the end of the lowest wing 3a and the end of the highest wing 3b larger than the maximum diameter of gravel, 75 mm. It is not impossible to construct the pile on ground with a particle size exceeding 75 mm, and construction can be performed by using a separate auxiliary construction method in combination.

[Embodiment 2]
The screw-in type steel pipe pile 11 according to the second embodiment is suitable for cases where there is concern about poor penetration of the pile body due to insufficient driving force in soft ground, and as shown in Fig. 2, two arc-shaped rotors 3, each formed by dividing a doughnut-shaped disk larger than the outer diameter of the steel pipe 2 in the radial direction, are provided consecutively in the circumferential direction at the tip of the steel pipe 2, and the mounting angle α1 of the lowermost blade 3a, which is the rotor 3 disposed and attached most downward of the steel pipe 2, is larger than the mounting angle α2 of the uppermost blade 3b, which is the rotor 3 disposed and attached most upward. The reason why the mounting angle α1 of the lowermost blade 3a is made larger than the mounting angle α2 of the uppermost blade 3b will be explained below.

By increasing α1, the amount of soil scraped off by the lowest wing 3a is increased, and the propulsive force is increased. From the viewpoint of propulsive force, it is desirable that α2 is also large. However, if α2 is also large, the height from the bottom end of the lowest wing 3a to the top end of the highest wing 3b becomes large, and it will not fit within the supporting ground, and there is a concern that the supporting force will decrease. Therefore, the mounting angle α1 of the lowest wing 3a, which contributes greatly to the propulsive force, is increased so that the entire rotor 3 fits within the supporting ground, thereby ensuring the supporting force. In other words, in this embodiment, by making α1 > α2, it is possible to obtain both propulsive force and supporting force on soft ground.

It is desirable that the mounting angle α2 of the uppermost wing 3b be 3 degrees or more so that soil particles can move smoothly over the wing. It is also desirable that the mounting angle α2 of the uppermost wing 3b be 7 degrees or less from the viewpoint of ensuring the supporting force. On the other hand, it is desirable that the mounting angle α1 of the lowermost wing 3a be large from the viewpoint of the propulsive force, and it is desirable that the mounting angle α1 be 11 degrees or less from the viewpoint of ensuring the supporting force.

In addition, from the standpoint of ensuring supporting force, even in this embodiment, it is desirable that the height h from the tip of the steel pipe 2 to the upper surface of the uppermost wing 3b be within 1 time the outer diameter D of the steel pipe.

As in embodiment 1, it is desirable for the distance k between the end of the lowest wing 3a and the end of the highest wing 3b to be greater than 75 mm.

In the above-mentioned first and second embodiments, the rotor 3 of one stage is composed of two blades, but the present invention is not limited to this, and the rotor 3 of one stage may be composed of three or more blades. In this case, the blade mounting angle between the lowest blade 3a and the highest blade 3b may be an angle between α1 and α2. That is, in the case of the first embodiment, the blade mounting angle between the lowest blade 3a and the highest blade 3b may be α1 or more and α2 or less, and in the case of the second embodiment, it may be α2 or more and α1 or less.

In addition, for a specific rotor blade between the bottom blade 3a and the top blade 3b (especially when there are multiple rotor blades between the bottom blade 3a and the top blade 3b), the mounting angle may be between the mounting angle of the rotor blade that is located higher among the adjacent rotor blades and the mounting angle of the rotor blade that is located lower among the adjacent rotor blades. This point will be specifically explained below using the example of a four-blade rotor.

Assume that between the bottom wing 3a and the top wing 3b, from bottom to top, there is a rotor 3c with an installation angle α3 and a rotor 3d with an installation angle α4. In this case, the installation angle α3 of the rotor 3c is an angle between the installation angles α1 and α2 and between the installation angles α1 and α4. Similarly, the installation angle α4 of the rotor 3d is an angle between the installation angles α1 and α2 and between the installation angles α3 and α2. That is, in the case of embodiment 1, the installation angle α3 of the rotor 3c may be α1 or more and α2 or less and α1 or more and α4 or less, and the installation angle α4 of the rotor 3d may be α1 or more and α2 or less and α3 or more and α2 or less. Similarly, in the case of embodiment 2, the installation angle α3 of the rotor 3c may be α2 or more and α1 or less and α4 or more and α1 or less, and the installation angle α4 of the rotor 3d may be α2 or more and α1 or less and α2 or more and α3 or less.

In addition, taking into consideration the impact on nearby structures, it is appropriate for the outer diameter Dw of the rotor 3 to be approximately three times larger, similar to the conventional screw-in type steel pipe pile 21. In addition, in the above-mentioned first and second embodiments, the rotor 3 is exemplified as a single stage, but the rotor 3 may be multi-staged in order to improve the bearing capacity, and if multi-staged, it is desirable for the rotor 3 to have the same shape as the tip blade from the viewpoint of stability of behavior.

The shape of the rotor 3 in the above-mentioned embodiments 1 and 2 consists of a flat plate attached along the mounting surface defined by the mounting angle, but even if the rotor 3 is curved in an out-of-plane direction relative to the mounting surface, it is included in the present invention as long as it satisfies the conditions of the mounting angle of the rotor 3 defined by the present invention.

As can be seen from the above explanation, it is preferable to design the screw-in type steel pipe pile according to the present invention taking into consideration the hardness of the ground, and for this purpose, a reference ground hardness is set in advance, and the mounting angles of each rotor are set in relation to this reference ground hardness. Specifically, the design method is as follows.

A design method for a screw-in type steel pipe pile in which two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, are provided in succession in the circumferential direction at the tip of the steel pipe, and the mounting angle of the rotors is set so as to satisfy the following conditions (A) to (C).
(A) If the hardness of the ground exceeds a predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made smaller than the mounting angle of the uppermost wing, which is the rotor attached highest, and if the hardness of the ground to be worked on is equal to or less than the predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made larger than the mounting angle of the uppermost wing, which is the rotor attached highest.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors.
Here, the "angle between the mounting angle of the lowermost blade and the mounting angle of the uppermost blade" in (B) above includes the same angle as the mounting angle of either the lowermost blade or the uppermost blade. Similarly, the "angle between the mounting angle of the blade disposed higher among the adjacent blades and the mounting angle of the blade disposed lower among the adjacent blades" in (C) includes the same angle as the mounting angle of either the adjacent blades.

By designing as described above, it is possible to design a screw-in steel pipe pile that is most suitable for the ground in which the pile will be constructed.

In addition, it is preferable to manufacture the screw-in type steel pipe pile according to the present invention while taking into consideration the hardness of the ground. To this end, a reference ground hardness is set in advance, and the mounting angles of each rotor are set in relation to this reference ground hardness. Specifically, the manufacturing method is as follows.

A method for manufacturing a screw-in type steel pipe pile in which two or more arc-shaped rotors, each formed by radially dividing a disk or donut-shaped disk larger than the outer diameter of the steel pipe, are provided in succession in the circumferential direction at the tip of the steel pipe, and the mounting angle of the rotors is formed so as to satisfy the following conditions (A) to (C).
(A) If the hardness of the ground exceeds a predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made smaller than the mounting angle of the uppermost wing, which is the rotor attached highest, and if the hardness of the ground to be worked on is equal to or less than the predetermined hardness, the mounting angle of the lowermost wing, which is the rotor attached lowest, is made larger than the mounting angle of the uppermost wing, which is the rotor attached highest.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors.
Here, the "angle between the mounting angle of the lowermost blade and the mounting angle of the uppermost blade" in (B) above includes the same angle as the mounting angle of either the lowermost blade or the uppermost blade. Similarly, the "angle between the mounting angle of the blade disposed higher among the adjacent blades and the mounting angle of the blade disposed lower among the adjacent blades" in (C) includes the same angle as the mounting angle of either the adjacent blades.

By manufacturing in the manner described above, it is possible to produce screw-in steel pipe piles that are most suitable for the ground in which they are to be constructed.

It is also preferable to take the hardness of the ground into consideration when constructing a screw-in type steel pipe pile, and the hardness of the ground to be constructed is investigated, and based on the results of this investigation, a screw-in type steel pipe pile of either embodiment 1 or 2 is selected. Specifically, in the method for constructing a screw-in type steel pipe pile described in either embodiment 1 or 2, the hardness of the ground to be constructed is investigated, and based on the results of this investigation, a screw-in type steel pipe pile of either embodiment 1 or 2 is selected, and the upper end of the steel pipe of the selected screw-in type steel pipe pile is gripped and rotated to penetrate the ground.

By carrying out the construction as described above, it is possible to install screw-in steel pipe piles that are most suitable for the ground to be constructed.

The present invention is suitable for use in a screw-in type steel pipe pile in which two or more arc-shaped rotors, each consisting of a disk or donut-shaped disk larger than the outer diameter of the steel pipe and divided radially, are provided consecutively at the tip of the steel pipe in the circumferential direction.

1. Screw-in steel pipe pile (embodiment 1)
2 Steel pipe 3 Rotor 3a Lowermost wing 3b Uppermost wing 11 Screw-in steel pipe pile (Embodiment 2)
21 Screw-in steel pipe pile (conventional example)
23 Rotor 23a Lower wing 23b Upper wing 25 Ground 27 Support ground α, α1, α2 Mounting angle P Perpendicular plane

Claims (8)

A screw-in type steel pipe pile having two or more arc-shaped rotors formed by radially dividing a disk or a doughnut-shaped disk larger than the outer diameter of the steel pipe at the tip of the steel pipe, the rotors being provided continuously in the circumferential direction,
The mounting angle of a lowermost blade, which is the blade arranged at the lowest position of the steel pipe, is smaller than the mounting angle of an uppermost blade, which is the blade arranged at the highest position of the steel pipe,
The installation angle of the lowest wing is 3 degrees or more and 7 degrees or less,
The uppermost wing has a mounting angle of 11 degrees or less,
The installation angle of the rotor between the lowest wing and the highest wing is the angle between the installation angle of the lowest wing and the installation angle of the highest wing, and the installation angle of a particular rotor is the angle between the installation angle of a rotor that is located higher among adjacent rotors and the installation angle of a rotor that is located lower among adjacent rotors. A screw- in steel pipe pile. The screw-in type steel pipe pile according to claim 1 , wherein a height from a tip of the steel pipe to an upper surface of the uppermost wing is equal to or less than an outer diameter of the steel pipe. A screw-in type steel pipe pile having two or more arc-shaped rotors formed by radially dividing a disk or a doughnut-shaped disk larger than the outer diameter of the steel pipe at the tip of the steel pipe, the rotors being provided continuously in the circumferential direction,
The installation angle of a lowermost blade, which is the blade arranged at the lowest position of the steel pipe, is larger than the installation angle of an uppermost blade, which is the blade arranged at the highest position of the steel pipe,
The uppermost wing has a mounting angle of 3 degrees or more and 7 degrees or less,
The installation angle of the lowest wing is 11 degrees or less,
The installation angle of the rotor between the lowest wing and the highest wing is the angle between the installation angle of the lowest wing and the installation angle of the highest wing, and the installation angle of a particular rotor is the angle between the installation angle of a rotor that is located higher among adjacent rotors and the installation angle of a rotor that is located lower among adjacent rotors. A screw- in steel pipe pile. The screw-in type steel pipe pile according to claim 3 , wherein a height from a tip of the steel pipe to an upper surface of the uppermost wing is equal to or less than an outer diameter of the steel pipe. A threaded steel pipe joint as described in claim 1 or 3, wherein the distance between the end of the lowest wing and the end of the highest wing is greater than 75 mm. A method for designing a screw-in type steel pipe pile in which two or more arc-shaped rotors formed by radially dividing a disk or doughnut-shaped disk larger than the outer diameter of the steel pipe are provided continuously in the circumferential direction at the tip of the steel pipe,
A method for designing a screw-in type steel pipe pile, comprising: setting the mounting angle of the rotor so as to satisfy the following conditions (A) to (C):
(A) When the hardness of the ground on which construction is to be carried out exceeds a predetermined hardness, the mounting angle of the lowermost blade, which is the rotor attached lowest, is set to 3 degrees or more and 7 degrees or less, which is smaller than the mounting angle of the uppermost blade, which is the rotor attached highest, and the mounting angle of the lowermost blade is set to 11 degrees or less; when the hardness of the ground on which construction is to be carried out is equal to or less than a predetermined hardness, the mounting angle of the lowermost blade, which is the rotor attached lowest, is set to 11 degrees or less, which is larger than the mounting angle of the uppermost blade, which is the rotor attached highest, and the mounting angle of the uppermost blade is set to 3 degrees or more and 7 degrees or less.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors. A method for constructing a screw-in type steel pipe pile according to any one of claims 1 to 5,
A method for constructing a screw-in type steel pipe pile, comprising: investigating the hardness of the ground to be constructed; selecting a screw-in type steel pipe pile according to any one of claims 1 to 5 based on the investigation result; and gripping the upper end of the steel pipe of the selected screw-in type steel pipe pile and rotating it into the ground. A method for manufacturing a screw-in type steel pipe pile in which two or more arc-shaped rotors formed by radially dividing a disk or a doughnut-shaped disk larger than the outer diameter of the steel pipe are provided continuously in the circumferential direction at the tip of the steel pipe,
The mounting angle of the rotor is formed so as to satisfy the following conditions (A) to (C).
(A) When the hardness of the ground on which construction is to be carried out exceeds a predetermined hardness, the mounting angle of the lowermost blade, which is the rotor attached lowest, is set to 3 degrees or more and 7 degrees or less, which is smaller than the mounting angle of the uppermost blade, which is the rotor attached highest, and the mounting angle of the lowermost blade is set to 11 degrees or less; when the hardness of the ground on which construction is to be carried out is equal to or less than a predetermined hardness, the mounting angle of the lowermost blade, which is the rotor attached lowest, is set to 11 degrees or less, which is larger than the mounting angle of the uppermost blade, which is the rotor attached highest, and the mounting angle of the uppermost blade is set to 3 degrees or more and 7 degrees or less.
(B) The mounting angle of the rotor between the lowest wing and the highest wing is an angle between the mounting angle of the lowest wing and the mounting angle of the highest wing.
(C) For a particular rotor, the mounting angle is the angle between the mounting angle of the rotor that is located higher among adjacent rotors and the mounting angle of the rotor that is located lower among adjacent rotors.

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