HK1164953B - Steel pipe pile and method of installing steel pipe pile - Google Patents

Description

Steel pipe pile and construction method thereof

Technical Field

The present invention relates to a steel pipe pile and a method of constructing a steel pipe pile, and more particularly, to a steel pipe pile in which helical blades are provided around a steel pipe and a method of constructing a steel pipe pile.

Background

Steel pipe piles are used for supporting upper structures of civil engineering structures such as buildings, roads, railroad viaducts, piers, and iron towers, and are constructed on foundations. At this time, the steel pipe pile is pressed into the ground while being rotated by using a steel pipe pile rotary press-fitting device such as a full-rotation full-casing excavator or a self-propelled small-sized heavy machine. As such a steel pipe pile for rotary driving, there is a steel pipe pile in which a helical blade is provided at the tip of the pile, for example.

Patent document 1 discloses a method of driving a steel pipe pile into the ground, in which a helical blade is provided at the tip of the steel pipe pile, and the steel pipe pile is driven to rotate and buried in the ground in a vertical direction from the ground surface. Further, patent documents 2 to 4 disclose a pile in which a spiral plate (spiral wing) is provided around the pile.

Documents of the prior art

Patent document

Japanese patent application laid-open No. 2001-146741 of patent document 1

Patent document 2 Japanese laid-open patent publication No. 8-35228

Patent document 3 Japanese patent application laid-open No. 8-284160

Patent document 4 Japanese patent application laid-open No. 10-183617

Disclosure of Invention

Problems to be solved by the invention

When a steel pipe pile having helical fins provided around a steel pipe is inserted into a foundation, the pitch of the helical fins is constant and the pile is not constructed by the insertion amount of the pitch, and the pile is lifted and lowered underground by the position of the helical fins of the foundation, which causes a problem that the foundation around the pile is loosened during construction and the supporting force of the pile is lowered. In other words, in order to increase the supporting force of the pile, it is preferable to make the ground around the pile as loose as possible and to make the sand filled between the spiral fins dense.

However, as in patent document 3, in some cases, a plurality of helical fins are provided around a steel pipe and one helical fin is attached to the steel pipe pile with a predetermined distance therebetween. However, when one spiral wing passes through the foundation around the steel pipe and the other spiral wing passes through the foundation around the steel pipe, the other spiral wing may pass through a different position even if the pitch is set, and thus the foundation may be loosened.

In addition, the same problem as described above occurs not only in the case of a steel pipe pile in which a plurality of helical fins are provided around one steel pipe, but also in the case of a steel pipe pile in which one continuous helical fin is provided around one steel pipe, and in the case of a steel pipe pile in which a steel pipe pile is connected to another steel pipe pile and a pile is inserted into a ground. For example, when the helical fin of one steel pipe pile passes through the foundation around the steel pipe and then the helical fin of the other steel pipe pile passes through the foundation around the steel pipe, the other helical fin may pass through a different position even if the pitch is set, and thus the foundation may be loosened.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a novel and improved steel pipe pile and a construction method of the steel pipe pile, which can secure a pile supporting force without loosening a surrounding foundation at the time of pile construction.

Means for solving the problems

In order to solve the above problem, according to an aspect of the present invention, there is provided a steel pipe pile including: a first steel-pipe pile having: a hollow first steel pipe; and at least one turn of first helical blades spirally formed on the outer periphery of the first steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the first steel pipe; and a second steel-pipe pile having: a hollow second steel pipe; and a second helical fin formed in a spiral shape at least one turn at a constant and equal pitch on an outer periphery of the second steel pipe in a direction from one end side to the other end side of the second steel pipe, wherein the second steel pipe pile is connected to the other end of the first steel pipe pile at an end portion, the pitch of the first helical fin is equal to the pitch of the second helical fin, and the first helical fin and the second helical fin are continuous on an imaginary spiral at a connection portion of the first steel pipe pile and the second steel pipe pile. According to this configuration, the first helical fin provided in the first steel-pipe pile and the second helical fin provided in the second steel-pipe pile have the same fin pitch, and the first helical fin and the second helical fin are continuous on the virtual helix at the connection portion between the first steel-pipe pile and the second steel-pipe pile, so that the surrounding ground is not loosened during pile construction in which the steel-pipe pile is driven into the ground. As a result, the supporting force of the steel pipe pile can be increased.

The interval between the first helical blade and the second helical blade is an integral multiple of the pitch of the first helical blade or the pitch of the second helical blade.

Further provided with: a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and a second notch portion formed by connecting a start end portion and a terminal end portion of the first notch portion at one end side of the first steel pipe and cutting out a peripheral portion of the other portion of the entire periphery of the first steel pipe except the partial peripheral portion.

And a third helical blade which protrudes from the same base as the first helical blade in a direction opposite to the protruding direction of the first helical blade and propagates spirally on the inner circumference of the steel pipe, wherein the first cut portion is formed by cutting along the first helical blade and the third helical blade.

The first cut portion is cut away from the first helical blade by a predetermined distance.

The first cut portion is formed by cutting out an outer surface of the first helical blade.

At one end of the steel pipe, the thickness of either or both of the first helical blade and the steel pipe at least at the tip of the first helical blade is greater than the thickness of the first helical blade or the other portion of the steel pipe. Further, at one end side of the steel pipe, a blade diameter of at least a tip portion of the first helical blade is larger than a blade diameter of another portion of the first helical blade. Further, the first helical blade and the steel pipe at least at the tip of the first helical blade are manufactured by casting on one end side of the steel pipe.

The second helical blade protrudes from the base to the tip by a length different from that of the first helical blade.

In order to solve the above problem, according to another aspect of the present invention, there is provided a steel pipe pile comprising: a hollow first steel pipe; a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and a fourth helical fin spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe at a position spaced apart from the first helical fin, the pitch of the first helical fin being equal to the pitch of the fourth helical fin, the first helical fin and the fourth helical fin being continuous on an imaginary spiral.

According to this configuration, the first helical fin and the fourth helical fin formed on the outer periphery of the first steel pipe have the same fin pitch, and the first helical fin and the fourth helical fin are continuous on the virtual helix, so that the surrounding ground is not loosened during pile construction in which the steel pipe pile is driven into the ground. As a result, the supporting force of the steel pipe pile can be increased.

The pitch between the first helical blade and the fourth helical blade is an integral multiple of the pitch between the first helical blade and the fourth helical blade.

The fourth helical blade protrudes from the base to the tip by a length different from that of the first helical blade.

Further provided with: a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and a second notch portion formed by connecting a start end portion and a terminal end portion of the first notch portion at one end side of the first steel pipe and cutting out a peripheral portion of the other portion of the entire periphery of the first steel pipe except the partial peripheral portion.

Any one or all of the first to fourth helical blades are made of a reinforcing bar.

Provided is a method for constructing a steel pipe pile, characterized by comprising: and a step of rotationally driving a first steel-pipe pile into the buried site, the first steel-pipe pile including: a hollow first steel pipe; and a first helical blade formed at least one turn spirally at a constant and equal pitch on the outer periphery of the first steel pipe in a direction from one end side to the other end side of the first steel pipe; adjusting a press-in speed so that the first helical blades of the first steel-pipe pile pass through substantially the same path in the foundation when the steel-pipe pile is press-fitted into the foundation by rotation; a step of connecting a second steel-pipe pile to the first steel-pipe pile such that a pitch of the first helical blade is equal to a pitch of a second helical blade included in the second steel-pipe pile, the first helical blade and the second helical blade being continuous in an imaginary helix at a connection portion of the first steel-pipe pile and the second steel-pipe pile, the second steel-pipe pile including: a hollow second steel pipe; and at least one turn of the second helical fin is formed spirally at least on the outer periphery of the second steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the second steel pipe, and the second steel-pipe pile is connected at an end portion to the other end of the first steel-pipe pile; a step of rotationally driving the steel-pipe pile formed by connecting the first steel-pipe pile and the second steel-pipe pile into a buried site; and adjusting the press-fitting speed so that the first helical blade and the second helical blade of the steel pipe pile pass through substantially the same path in the ground when the steel pipe pile is press-fitted into the ground by rotation.

Provided is a method for constructing a steel pipe pile, characterized by comprising: a step of rotationally driving a steel pipe pile into a buried site, the steel pipe pile comprising: a hollow first steel pipe; a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and a fourth helical fin formed spirally at a constant and equal pitch on the outer periphery of the first steel pipe at a position spaced apart from the first helical fin, the pitch of the first helical fin being equal to the pitch of the fourth helical fin, the first helical fin and the fourth helical fin being continuous on an imaginary spiral; and adjusting a press-fitting speed so that the first helical blade and the fourth helical blade of the steel pipe pile pass through substantially the same path in a ground when the steel pipe pile is rotationally press-fitted into the ground.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the supporting force of the pile can be ensured without loosening the surrounding foundation during pile construction.

Drawings

Fig. 1 is a side view showing a steel pipe pile 100 according to a first embodiment of the present invention.

Fig. 2 is a side view showing a lower pile 102 of the steel pipe pile 100 according to the same embodiment.

Fig. 3 is a side view showing a lower pile 102 of the steel pipe pile 100 according to the same embodiment.

Fig. 4 is a side view showing a lower pile 102 of the steel pipe pile 100 according to the same embodiment.

Fig. 5 is a developed view showing a lower pile 102 of the steel-pipe pile 100 according to the same embodiment.

Fig. 6 is a bottom view showing a lower pile 102 of the steel pipe pile 100 according to the same embodiment.

Fig. 7 is a cross-sectional view showing a lower pile 102 of the steel pipe pile 100 according to the same embodiment.

Fig. 8 is a side view showing an upper pile 104 of the steel pipe pile 100 according to the same embodiment.

Fig. 9 is a development view showing a modification of the lower pile 102 of the steel-pipe pile 100 according to the same embodiment.

Fig. 10 is a side view showing a lower pile 102 and an upper pile 104 of a steel pipe pile 100 according to the same embodiment.

Fig. 11 is a side view showing an upper pile 204 of a steel pipe pile 200 according to a second embodiment of the present invention.

Fig. 12 is a side view showing a steel pipe pile 300 according to a third embodiment of the present invention.

Fig. 13 is a side view showing a lower pile 402 according to a first modification of the first to third embodiments of the present invention.

Fig. 14 is a side view showing a lower pile 402 according to a first modification of the same embodiment.

Fig. 15 is a bottom view showing a lower pile 402 according to a first modification of the same embodiment.

Fig. 16 is a sectional view showing a lower pile 402 according to a first modification of the same embodiment.

Fig. 17 is a side view showing a lower pile 502 according to a second modification of the same embodiment.

Fig. 18 is a side view showing a lower pile 502 according to a second modification of the same embodiment.

Fig. 19 is a bottom view showing a lower pile 502 according to a second modification of the same embodiment.

Fig. 20 is a sectional view showing a lower pile 502 according to a second modification of the same embodiment.

Fig. 21 is a sectional view showing a pile tip 602 and an upper pile 104 according to a third modification of the same embodiment.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, the same reference numerals are given to the components having substantially the same functional configuration, and redundant description thereof is omitted.

(first embodiment)

First, a structure of a steel-pipe pile 100 according to a first embodiment of the present invention will be described with reference to fig. 1. Fig. 1 is a side view showing a steel pipe pile 100 according to the present embodiment. Fig. 1 shows a state in which a steel pipe pile 100 is buried under the ground.

The steel pipe pile 100 is used for supporting an upper structure of a civil structure such as a building, a road, a railroad overpass, a pier, and a tower, and is constructed on a foundation. At this time, the steel-pipe pile 100 is pressed into the ground while being rotated by using a steel-pipe pile rotary press-fitting device such as a full-rotation full-casing excavator or a self-propelled small-sized heavy machine. The steel-pipe pile 100 may be press-fitted in the vertical direction with respect to the horizontal plane, or may be press-fitted obliquely at a predetermined angle other than the vertical direction with respect to the horizontal plane.

As shown in fig. 1, the steel pipe pile 100 is composed of, for example, one lower pile 102 and a plurality of upper piles 104. The lower pile 102 is buried with its cut-out-shaped tip side positioned below, and is connected to one end of the upper pile 104 at its upper end side opposite to the tip side. The upper pile 104 is connected to one end of another upper pile 104 on the upper end side opposite to the lower end side to which the lower pile 102 is connected. The lower pile 102 and the upper pile 104 or the two upper piles 104 are connected by welding or mechanical joint, for example, at the site of press-fitting construction of the steel pipe pile 100.

The lengths of the lower pile 102 and the upper pile 104 may be arbitrarily determined according to the length of the steel pipe pile 100 pressed into the ground. In fig. 1, the length of the lower pile is 5800mm and the length of the upper pile is 6000mm, but is not limited to the example shown in fig. 1. The steel pipe pile 100 may be formed of only the lower pile 102, or the number of upper piles 104 connected to the upper portion of the lower pile 102 may be one or three or more.

Next, a lower pile 102 of the steel-pipe pile 100 according to the present embodiment will be described with reference to fig. 2 to 7, and an upper pile 104 of the steel-pipe pile 100 according to the present embodiment will be described with reference to fig. 8.

Fig. 2 to 4 are side views showing a lower pile 102 of the steel pipe pile 100 according to the present embodiment. Fig. 2 to 4 show the side surfaces of the same lower pile 102, respectively, as viewed from different directions. Fig. 5 is a developed view showing a lower pile 102 of the steel-pipe pile 100 according to the present embodiment. Fig. 5 is a view after the lower pile 102 is cut and spread by a line a parallel to the axial direction of the lower pile 102. Fig. 6 is a bottom view showing a lower pile 102 of the steel pipe pile 100 according to the present embodiment. Fig. 7 is a cross-sectional view showing a lower pile 102 of the steel pipe pile 100 according to the present embodiment. Fig. 7 is a view showing the lower pile 102 cut in the axial direction. Fig. 8 is a side view showing an upper pile 104 of the steel pipe pile 100 according to the present embodiment.

The lower pile 102 includes a steel pipe 112, a helical blade 114, a stopper (コマ)116, a first cut portion 122, a second cut portion 124, and the like. The upper pile 104 includes a steel pipe 112, a helical blade 114, a stopper 116, and the like.

The steel pipe 112 is, for example, a hollow circular steel pipe. In the example shown in fig. 1, the pile diameter Dp as the diameter of the steel pipe is 400 mm. The pile diameter Dp is not limited to the example shown in fig. 1, and is, for example, 40mm to 1200mm, and is determined according to the strength design of the structure.

The helical blade 114 is a plate-like member, and is continuously provided from one end side to the other end side of the steel pipe 112, and is provided in a helical shape of at least one turn at a constant pitch on the outer periphery of the steel pipe 112. By providing the helical blades 114, a higher propulsive force can be applied to the lower pile 102 or the upper pile 104 than in the case where the helical blades are provided only at the tip of the steel pipe pile 100. Further, as described later, the blade diameter Dw can be regarded as the outer diameter of the pile required for calculating and determining the support force by the frictional force, and the pile outer diameter can be thickened by the helical blades 114, so that it is not necessary to increase the steel pipe diameter to increase the support force. As a result, the amount of steel material required for manufacturing the steel-pipe pile 100 can be reduced.

Since the blade diameter Dw can be considered as the outer diameter of the pile required to calculate and determine the bearing force created by the friction forces, the ratio Pch/Dw of the blade pitch Pch to the protrusion length Dw of the blade needs to satisfy Pch/Dw ≦ 24. If Pch/dw exceeds 24, the frictional force cannot be evaluated on the cylindrical surface having the blade outer shape as the diameter, and the blade is greatly affected by the soil from the outside of the cylindrical surface, resulting in problems such as an excessively large blade thickness and an increase in the variation in the supporting force.

The helical blades 114 are connected to the steel pipe 112 at short sides of the plate portions thereof. The connection of the steel pipe 112 and the helical blade 114 is performed by, for example, welding. The helical blade 114 may be formed by, for example, coil welding a reinforcing bar. The helical blade 114 protrudes from a base 114b, which is a connecting portion with the steel pipe 112, to a tip 114c, and the protruding length Dw of the helical blade 114 and the pile diameter Dp are combined, and the outer diameter is expressed as a blade diameter Dw. In the example shown in FIG. 1, the case where the blade diameter Dw is 600mm is shown. The blade diameter Dw is not limited to the example shown in fig. 1, and may be, for example, 1.2Dp to 1.5Dp, or may be, in some cases, up to 2.0 Dp. By increasing the blade diameter Dw to 1.5Dp, the propulsive force can be increased when the lower pile 102 and the upper pile 104 are driven into the ground.

When the distance between the adjacent helical blades 114 when the helical blades 114 are wound around the outer periphery of the steel pipe 112 for one revolution is the blade pitch Pch, the blade pitch Pch is 600mm in the example shown in fig. 1. As will be described later, the blade pitch Pch is preferably the same at either of the lower pile 102 and the upper pile 104. The blade pitch Pch is not limited to the example shown in fig. 1, and may be, for example, 0.6Dw to 2.0Dw, but is preferably 0.6Dw to 1.2 Dw. However, if the blade pitch Pch is too large, insertion work of about the size of the blade pitch may become difficult. Further, it is also considered that the load applied to the blade per one rotation when the vertical force acts is excessive. Therefore, it is sometimes preferable to match the size of the blade diameter Dw (pile diameter Dp) without excessively increasing the blade pitch Pch. Further, when the blade pitch Pch is too small, the amount of steel material increases, and therefore the blade pitch Pch can be determined by the balance between the obtained thrust force and the amount of steel material.

Although the stopper 116 is not described in detail here, the stopper 116 is a member that is attached to the outer periphery of the steel pipe 112 so as to protrude therefrom, and has a shape that corresponds to the use of a hanging component, a steel pipe rotating component, or the like. The stopper 116 as a suspension member functions when the lower pile 102 or the upper pile 104 is suspended by a crane or the like to install the lower pile 102 or the upper pile 104 in the steel pipe pile rotary press-fitting device. The stopper 116 as a steel pipe rotating member is used to transmit the rotational force of the steel pipe rotating and pushing device to the lower pile 102 or the upper pile 104 when the lower pile 102 or the upper pile 104 is pushed into the ground by the steel pipe pile rotating and pushing device. The stopper is not limited to the outer stopper and may be attached to the outer periphery of the steel pipe 112. The stopper may be attached as an inner stopper so as to protrude inward on the inner circumferential surface of the steel pipe 112. By providing the stopper on the inner circumferential surface of the steel pipe 112, the length from the upper end or the lower end of the lower pile 102 or the upper pile 104 to the region where the helical blade 114 is not provided at the attachment tip of the helical blade 114 can be shortened.

The first notch 122 is formed by cutting a part of the entire circumferential length of the steel pipe 112 along the helical blade 114 at one end side of the steel pipe 112. In this case, a portion of the first cut portion 122 located at the end of the lower pile 102 is referred to as a starting end portion 122a, and an end portion opposite to the starting end portion 122a of the first cut portion 122 is referred to as an ending end portion 122 b. As shown in fig. 2 to 5 and 7, the first cut-out portion 122 of the present embodiment is cut away from the first helical blade 114 to the lower end portion of the lower pile 102 by a predetermined distance.

The second notch 124 is formed by connecting and cutting off the starting end portion 122a and the ending end portion 122b of the first notch 122 at a portion other than the portion where the first notch 122 is formed in the entire circumferential length of the steel pipe 112 on the one end side of the steel pipe 112.

In the example shown in fig. 1 to 7, the first cut portion 122 occupies a portion of 3/4Dp × pi in the circumferential length (Dp × pi) of the entire circumferential length (Dp × pi) of the steel pipe 112, and the second cut portion 124 occupies a portion of 1/4Dp × pi in the circumferential length (Dp × pi) of the entire circumferential length (Dp × pi) of the steel pipe 112.

The angle formed by the first cut portion 122 and the second cut portion 124 when the lower pile 102 is deployed as shown in fig. 5 is an angle B as shown in the drawing. Since the angle B has its apex located near the spiral blade 114, the angle B varies depending on the position of the apex (i.e., the circumferential length occupied by the first and second cut-out portions 122 and 124). In the case where the angle B is an obtuse angle, durability can be improved when the steel-pipe pile 100 is pressed into the ground, as compared with the case where the angle B is an acute angle.

Although fig. 5 shows an example in which the intersection position (122b) of the first cut portion 122 and the second cut portion 124 has an apex, the present invention is not limited to this example. For example, as shown in fig. 9, the second notch 124 is formed of a straight line portion 124A and a curved line portion 124B, so that the vicinity of the intersection position (122B) of the first notch 122 and the second notch 124 can be smoothly continuous. Fig. 9 is a development view showing a modification of the lower pile 102 of the steel-pipe pile 100 according to the first embodiment of the present invention. Thus, the force acting on the intersection portion of the first cut portion 122 and the second cut portion 124 can be dispersed, and the strength of the leading end portion of the lower pile 102 can be improved.

When the steel pipe pile 100 is pressed into the ground, the second cut portion 124 and the tip 114a of the helical blade 114 first enter the ground. Then, the steel pipe pile 100 is driven into the ground by the driving force of the steel pipe pile rotation driving device and the propulsive force generated by the helical blades 114. At this time, as shown in fig. 7, the foundation also enters the hollow lower pile 102 and the upper pile 104. In this case, the blade diameter of at least one turn of the helical blade is made larger than the blade diameter of the other portion at the end of the steel pipe, so that a larger thrust force can be obtained and the steel pipe pile can be easily pushed in.

As described above, the distal end portion of the lower pile 102 has a shape obtained by cutting the steel pipe 112, and the steel pipe 112 is hollow, so that the insertion property of the steel-pipe pile 100 is improved as compared with the case where the pile distal end has a closed shape. Further, since the insertion property is good, the tip portion can be formed in a simple shape, and the strength required for the steel pipe pile can be ensured. Further, since the tip portion has a simple shape, the notch shape can be easily processed, and the processing cost can be reduced.

Next, the connection between the lower pile 102 and the upper pile 104 or the connection between the upper piles 104 will be described with reference to fig. 10. Fig. 10 is a side view showing a lower pile 102 and an upper pile 104 of the steel pipe pile 100 according to the present embodiment.

For the lower pile 102 and the upper pile 104, the upper end of the lower pile 102 and the lower end of the upper pile 104 are connected by, for example, welding or mechanical joints. Further, for the two upper piles 104, the upper end of one upper pile 104 and the lower end of the other upper pile 104 are connected by, for example, welding or mechanical joint.

At this time, as shown in fig. 10, the helical blade 114 may not be provided so as to reach the end portion at the upper end of the lower pile 102 and the upper end and/or the lower end of the upper pile 104. In this case, connection may be made such that the helical blade 114 of the lower pile 102 (upper pile 104) and the helical blade 114 of the upper pile 104 are continuous on an imaginary helix. That is, the connection is made such that the interval between the end of the helical blade 114 of the lower pile 102 (upper pile 104) and the end of the helical blade 114 of the upper pile 104 is equal to or an integral multiple of the blade pitch Pch of the lower pile 102 or the upper pile 104. As a result, the pitch Pch of the blades of the lower pile 102 and the upper pile 104 becomes equal, and the helical blade 114 of the lower pile 102 (upper pile 104) and the helical blade 114 of the upper pile 104 are continuous. Further, the driving speed is adjusted when the lower pile 102 or the upper pile 104 is driven in rotation so that the helical blades 114 can be buried by the blade pitch Pch (the allowable blade pitch is about ± 10%), that is, the helical blades 114 pass through substantially the same path in the ground.

As a result, when the steel pipe pile 100 is driven into the ground, the helical blades 114 always pass through the same position in the ground. Therefore, the ground S2 between the spiral blades 114 is not loosened, and the ground S2 is densely filled between the spiral blades 114. The steel pipe pile 100 can support a load from above according to the shear strength of the soil of the foundation S2 that is dense between the foundation S1 and the helical blades 114 around the steel pipe pile 100. At this time, the blade diameter Dw may be regarded as the outer diameter of the steel pipe pile 100 to calculate the bearing force.

(second embodiment)

Next, a steel pipe pile 200 according to a second embodiment of the present invention will be described.

The steel pipe pile 200 is composed of, for example, an upper pile 204 and a lower pile (not shown). In the first embodiment described above, the lower pile 102 and the upper pile 104 are formed on the outer peripheral surface of the steel pipe 112 while one helical blade 114 is continuously formed from the vicinity of one end portion to the vicinity of the other end portion as shown in fig. 1 and 8, but the present embodiment differs in the formation of the helical blades 214A, 214B, and 214C. Next, an upper pile 204 of the steel-pipe pile 200 according to the present embodiment will be described with reference to fig. 11. Fig. 11 is a side view showing an upper pile 204 of a steel pipe pile 200 according to a second embodiment of the present invention.

The upper pile 204 includes the steel pipe 112, helical blades 214A, 214B, 214C, a stopper 116, and the like. The steel pipe 112 and the stopper 116 are the same as those of the first embodiment, and therefore, detailed description thereof is omitted.

In the upper pile 204, a plurality of helical blades, in the example shown in fig. 11, three helical blades 214A, 214B, 214C are provided. The helical blades 214A, 214B, and 214C are formed on the outer peripheral surface of the steel pipe 112 so as to be spaced apart from each other. The helical blades 214A, 214B, and/or 214C may be formed by, for example, coil welding steel bars. At this time, the helical blades 214A, 214B, and 214C of the upper pile 204 may be arranged so that the respective pitches are equally continuous on the imaginary helix. That is, the helical blades 214A, 214B, and 214C are arranged such that the interval between the respective ends of the helical blades 214A, 214B, and 214C of the upper pile 204 is equal to or an integral multiple of the blade pitch Pch of the helical blades 214A, 214B, and 214C.

As a result, when the blade pitches Pch of the helical blades 214A, 214B, and 214C are equal, the helical blades 214A, 214B, and 214C of the upper pile 204 are continuous on the imaginary helix. When the upper pile 204 is rotated and pressed in, the pressing speed is adjusted so that the helical blades 214A, 214B, and 214C can be embedded at a blade pitch Pch (allowable blade pitch ± about 10%), that is, the helical blades 214A, 214B, and 214C pass through substantially the same path in the ground.

As a result, when the steel pipe pile 200 is driven into the ground, the helical blades 214A, 214B, and 214C always pass through the same position in the ground. As a result, the ground S2 between the spiral blades 214A, 214B, and 214C is not loosened, and the ground S2 is densely filled between the spiral blades 214A, 214B, and 214C. Although fig. 11 illustrates an example of the upper pile 204, this modification is similarly applicable to the lower pile.

The lower pile, not shown, is provided with a plurality of helical blades, as with the helical blades 214A, 214B, 214C of the upper pile 204. The upper pile 204 and the lower pile are connected by welding. Although the steel pipe pile 200 described above is composed of the upper pile 204, the lower pile, and the plurality of helical blades, the present invention is not limited to this example. For example, the steel pipe pile may be configured by a combination of the lower pile 102 of the first embodiment and the upper pile 204 of the present embodiment, a combination of the lower pile of the present embodiment and the upper pile 104 of the first embodiment, or the like.

(third embodiment)

Next, a steel-pipe pile 300 according to a third embodiment of the present invention will be described with reference to fig. 12. The steel-pipe pile 300 has a different configuration of the helical blades 114 than the steel-pipe pile 100 according to the first embodiment. Fig. 12 is a side view showing a steel pipe pile 300 according to the present embodiment. Fig. 12 shows a state in which a steel pipe pile 300 is buried under the ground.

As shown in fig. 12, the steel pipe pile 300 is composed of, for example, a lower pile 302 and upper piles 304 and 305. The lower pile 302 and the upper pile 304 are the same as the lower pile 102 and the upper pile 104, and the lower pile 302 includes a steel pipe 112, a helical blade 313, a stopper 116, a first cut portion 122, a second cut portion 124, and the like. Further, the upper pile 304 includes the steel pipe 112, the spiral blade 314, the stopper 116, and the like, and the upper pile 305 includes the steel pipe 112, the spiral blade 315, the stopper 116, and the like. The helical blades 313, 314, 315 may be formed by, for example, coil welding reinforcing steel bars.

The helical blade 313 of the lower pile 302 has a blade diameter Dw1, the helical blade 314 of the upper pile 304 has a blade diameter Dw2, and the helical blade 315 of the upper pile 305 has a blade diameter Dw 3. The blade diameter Dw2 is greater than the blade diameter Dw1, and the blade diameter Dw3 is greater than the blade diameter Dw 2. The peg diameter Dp and the blade pitch are all the same at the lower peg 302 and the upper pegs 304, 305. The helical blade 313 of the lower pile 302 and the helical blades 314 and 315 of the upper piles 304 and 305 are connected to each other continuously on an imaginary helix.

The example shown in fig. 12 is a case where the blade diameter is changed according to the foundation strength (N value) in the depth direction of the foundation. As a result of the construction of the steel pipe pile 300, the helical blades 313 having small blade diameters are located at a depth where the foundation strength is high, and the helical blades 314 and 315 having large blade diameters are located at a depth where the foundation strength is low. In this way, the size of the spiral blades 313, 314, 315 can ensure a supporting force corresponding to the foundation by changing the blade diameter in accordance with the foundation strength in the depth direction of the foundation, for example. Further, by reducing the blade diameter at a portion where the foundation strength is high, the force acting on the helical blade 313 from above can be reduced, and the plate thickness of the helical blade 313 can be made thinner than when the blade diameter is large. Further, by reducing the blade diameter, the frictional force in the foundation during construction can be reduced, and therefore, the workability can be improved.

According to the present embodiment, the blade diameters Dw1, Dw2, and Dw3 can be regarded as the outer diameter of the steel-pipe pile 300, and the outer circumferential surface area of the steel-pipe pile 300 required for calculating and determining the supporting force of the steel-pipe pile 300 can be calculated from the blade diameters Dw1, Dw2, and Dw 3. Further, the outer peripheral surface area of the steel-pipe pile 300 can be increased and the supporting force can be increased by simply increasing the blade diameter without actually increasing the pile diameter Dp. Therefore, the steel-pipe pile 300 of the present embodiment can reduce the amount of steel plates required to secure the structure of the steel-pipe pile and secure high bearing force with a smaller amount of material, as compared to the case where the outer diameter is enlarged by increasing the pile diameter in a steel-pipe pile without helical blades.

Although the lower pile 302 and the upper piles 304 and 305 have a constant blade diameter and have different blade diameters according to the piles, the present invention is not limited to this example. For example, the lower pile or the upper pile may have a configuration in which the diameter of the blade changes at the middle portion of the lower pile or the upper pile. Further, although an example in which the blade diameter increases from the lower portion to the upper portion of the steel pipe pile 300 is described, the present invention is not limited to this example. The upper pile located at the upper portion of the steel pipe pile 300 may be made smaller in diameter than the upper pile or the lower pile located at the lower portion.

(modification of the first to third embodiments)

Next, a lower pile 402 according to a first modification of the first to third embodiments of the present invention will be described with reference to fig. 13 to 16.

Fig. 13 and 14 are side views showing the lower pile 402 according to the first modification of the present embodiment, as viewed from different directions. Fig. 15 is a bottom view showing a lower pile 402 according to a first modification of the present embodiment. Fig. 16 is a sectional view showing a lower pile 402 according to a first modification of the present embodiment.

The lower pile 402 of the present modification includes the steel pipe 112, the helical blade 114, the helical blade 414, the stopper 116, the first cut portion 122, the second cut portion 124, and the like. Unlike the lower pile 102 of the first embodiment, the lower pile 402 is further provided with a helical blade 414 on the inner surface of the lower pile 402. The steel pipe 112, the helical blade 114, the stopper 116, the first notch 122, and the second notch 124 are the same as those of the first embodiment, and therefore, detailed description thereof is omitted.

The helical blade 414 provided on the inner periphery of the lower pile 402 protrudes from the same base as the base 114b of the helical blade 114 in the direction opposite to the protruding direction of the helical blade 114. The pitch of the helical blades 414 is the same as the pitch of the helical blades 114. The helical blade 414 protrudes from the base 414b to the leading end 414c on the inner side, so that the blade inner diameter Dwi can be made smaller than the pile diameter Dp as shown in fig. 16. When the protrusion length of the helical fin 114 is increased in one direction from the steel pipe 112 to the outside to increase the fin area, the moment acting on the connection portion between the steel pipe 112 and the helical fin 114 increases. On the other hand, by projecting the helical blade 414 not only in the outward direction but also in the inward direction as in the present embodiment, it is possible to increase the blade area of the pile tip while maintaining the pile diameter Dp while reducing the moment acting on the connection portion between the steel pipe 112 and the helical blade 114. As a result, even if the lower pile 402 is configured to have a tip with a steel pipe thickness smaller than that of the tip of the lower pile 102 of the steel-pipe pile 100 according to the first embodiment, a tip supporting force equal to or greater than that of the lower pile 102 of the steel-pipe pile 100 can be obtained.

In fig. 16, the helical blades 414 provided on the inner periphery of the lower pile 402 are provided continuously about two times from the tip 414a located at the lower portion of the lower pile 402, but the present invention is not limited to this example. For example, the helical blade 414 may be provided in any length such as only one turn from the tip 414a, or from the tip 414a to the middle of the lower pile 402.

Next, a lower pile 502 according to a second modification of the present embodiment will be described with reference to fig. 17 to 20. The lower pile 502 is different in the cut portion from the lower pile 402 described with reference to fig. 13 to 16.

Fig. 17 and 18 are side views showing a lower pile 502 according to a second modification of the present embodiment. Fig. 19 is a bottom view showing a lower pile 502 according to a second modification of the present embodiment. Fig. 20 is a sectional view showing a lower pile 502 according to a second modification of the present embodiment.

The lower pile 502 of the present modification includes the steel pipe 112, the helical blade 114, the helical blade 514, the stopper 116, a first cut portion 522, a second cut portion 524, and the like. The lower pile 502 is provided with a helical blade 514 on the inner surface of the lower pile 502, as in the lower pile 402 of the second embodiment. The steel pipe 112 and the helical blade 114 are not described in detail.

The first notch 522 is formed by cutting a part of the entire circumferential length of the steel pipe 112 along the helical blade 114 at one end side of the steel pipe 112. In the first cut portion 522 at this time, a portion located at an end of the lower pile 102 is referred to as a starting end portion 522a, and an end portion opposite to the starting end portion 522a of the first cut portion 522 is referred to as a terminal end portion 522 b.

The second notch portion 524 is formed by connecting and cutting a start end portion 522a and a terminal end portion 522b of the first notch portion 522 at one end side of the steel pipe 112, at a portion other than the portion where the first notch portion 522 is formed in the entire circumferential length of the steel pipe 112.

In the present embodiment, unlike the lower piles 102 and 402, the first cut-out portions 522 are formed by cutting out the outer surfaces of the helical blades 114 and 514 as shown in fig. 17 to 19. Thus, at the lowermost end of the lower pile 502, a plane P is formed by the helical blade 114 and the helical blade 514.

Next, a pile tip 602 according to a third modification of the present embodiment will be described with reference to fig. 21. Fig. 21 is a sectional view showing a pile tip 602 and an upper pile 104 according to a third modification of the present embodiment.

As shown in fig. 21, the pile tip 602 is connected to the upper pile 104. Pile tip 602 includes steel pipe 612, helical blade 614, first cut portion 622, second cut portion (not shown), and the like. The first cut portion 622 and the second cut portion have the same configuration as the first cut portion 122 and the second cut portion 124 of the steel pipe pile 100 according to the first embodiment.

In the first embodiment, the thickness of the steel pipe 112 and the thickness of the helical blade 114 are the same in both the lower pile 102 and the upper pile 104, but in the present embodiment, the thickness of the steel pipe 612 at the pile tip 602 is larger than the thickness of the steel pipe 112 at the upper pile 104. Further, the plate thickness tw2 of the helical blade 614 at the pile tip 602 is thicker than the plate thickness tw1 of the helical blade 114 of the upper pile 104. In the example shown in fig. 21, a helical fin 614 is provided around the outer circumference of the steel pipe 612. The spiral vane 614 may be provided in the size of one circumference of the outer periphery. Although the steel pipe 612 and the helical fin 614 are both thicker than the steel pipe 112 and the helical fin 114 of the upper pile 104, either the steel pipe 612 or the helical fin 614 may be thicker and the other may have the same thickness.

By thickening the tip end portion of the steel-pipe pile 600 as described above, the tip end supporting force of the steel-pipe pile 600 can be increased. The helical blade at the tip of the steel pipe pile generates a larger vertical reaction force than the helical blades at other portions. As in the present embodiment, by increasing the thickness of the helical blades 614 and the thickness of the steel pipe 612 at the pile tip 602 of the steel-pipe pile 600, not only a large tip supporting force can be secured, but also deformation of the tip can be prevented.

Examples of the method of producing the pile tip 602 according to the present embodiment include (1) a method of producing the pile tip from a raw material in which the thickness of either or both of the helical fin 614 and the steel pipe 612 is larger than the thickness of the other helical fin 114 or the steel pipe 112, and (2) a method of producing the entire pile tip 602 by casting.

As described above, according to the first embodiment of the present invention and the modification thereof, the distal end portions of the lower piles 102, 302, 402, 502, and 602 have the shape in which the steel pipe 112 is cut, and the steel pipe 112 is hollow, so that the insertability of the steel pipe pile 100 is improved as compared with the case where the pile distal end has a closed shape. Further, since the insertion property is good, the tip portion can be formed in a compact shape, and necessary strength can be secured. Further, since the tip portion has a simple shape, the notch shape can be easily processed, and the processing cost can be reduced.

In the conventional steel pipe pile in which the spiral blade is provided only at the tip portion, the spiral blade and the steel pipe at the tip portion have a larger plate thickness than in the present embodiment because most of the pile support force acts on the pile tip. In addition, in the conventional steel pipe pile in which the helical blades are provided only at the tip portion, it is not considered to provide the helical blades over the entire length of the pile as in the present embodiment, and the blade at the tip supports a large load.

On the other hand, in the present embodiment, the helical blades 114 are continuously formed around the steel pipe 112, and the blade pitch Pch is larger than that of the conventional design, with a view to increasing the friction of the circumferential surface of the pile. In the present embodiment, the support force of the steel-pipe pile 100 can be calculated by considering the blade diameter Dw of the helical blades 114 as the outer diameter of the steel-pipe pile 100, and therefore, a pile in which not only friction between the pile tip and the pile circumferential surface but also a large support force can be expected is obtained. In the steel-pipe pile 100 of the present embodiment, the force acting on the middle part of the pile for one turn of the blade is often smaller than the force acting on the front end of the pile for one turn, and therefore the thickness of the helical blade 114 can be smaller than the thickness of the conventional pile front end blade. However, when a particularly large supporting force is expected at the pile tip, the thicknesses of the blade and the steel pipe at the pile tip may be increased.

Further, when a conventional steel pipe pile provided with helical blades only at the tip portion is used to form helical blades around the middle portion of a steel pipe while maintaining a small blade pitch as in the conventional helical blades, the blades are closely arranged around the steel pipe, and therefore the amount of steel material increases. Further, since the blade pitch is small, the construction efficiency is also lowered. Therefore, it is considered that a steel pipe pile in which helical blades are continuously formed cannot be realized based on a conventional steel pipe pile in which helical blades are provided only at the tip portion.

Further, according to the first to third embodiments of the present invention, different helical blades provided separately are arranged so as to be continuous on a virtual helix. That is, the interval between the end of one helical blade and the end of the other helical blade is arranged to be equal to or an integral multiple of the blade pitch Pch. As a result, the blade pitches Pch are equal, and the plurality of helical blades are continuous on the virtual helix, so that the helical blades always pass through the same position in the ground when the steel pipe pile 100 is pressed into the ground. As a result, the ground between the spiral blades is not loosened, and the ground is densely filled between the spiral blades. Further, the steel pipe pile 100 can support a load from above according to the shear strength of the soil of the foundation between the foundation around the steel pipe pile 100 and the dense helical blades 114.

On the other hand, conventionally, the pitch of the blades and the distance between the adjacent spiral wings have not been considered, and therefore, when one spiral wing passes through the foundation around the steel pipe and the other spiral wing passes through the foundation around the steel pipe, the other spiral wing may pass through a different position, and the foundation may be loosened. In contrast, according to the present embodiment, the foundation can be prevented from loosening, and the supporting force can be increased as compared with the conventional one.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to these examples. Various modifications and alterations that can be made by those skilled in the art within the scope of the technical idea described in the claims are possible as long as they have a general knowledge in the technical field to which the present invention pertains, and it is obvious that these modifications and alterations belong to the technical scope of the present invention.

Industrial applicability

The present invention is applicable to a steel pipe pile and a method of constructing a steel pipe pile, and particularly, to a steel pipe pile and a method of constructing a steel pipe pile in which helical blades are provided around a steel pipe.

Description of the reference numerals:

100: steel pipe piles; 102: pile setting; 104: pile installing; 112: a steel pipe; 114: a helical blade; 114 a: a front end portion; 116: a stopper; 122: a first incision portion; 124: a second cut-out portion; 200: steel pipe piles; 214A: a helical blade; 214B: a helical blade; 214C: a helical blade; 300: steel pipe piles; 302: pile setting; 304: pile installing; 305: pile installing; 313: a helical blade; 314: a helical blade; 315: a helical blade; 400: steel pipe piles; 402: pile setting; 414: a helical blade; 414 a: a front end portion; 500: steel pipe piles; 502: pile front end; 514: helical blade: 514 a: a front end portion; 522: a first incision portion; 524: a second cut-out portion; 600: steel pipe piles; 602: pile front end; 612: a steel pipe; 614: a helical blade; 622: first incision part

Claims (21)

1. A steel pipe pile is characterized in that,

the disclosed device is provided with:

a first steel-pipe pile having: a hollow first steel pipe; and at least one turn of first helical blades spirally formed on the outer periphery of the first steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the first steel pipe; and

a second steel-pipe pile having: a hollow second steel pipe; and at least one turn of second helical blades spirally formed at regular and equal intervals on the outer periphery of the second steel pipe in a direction from one end side to the other end side of the second steel pipe, the second steel-pipe pile being connected at an end portion thereof to the other end of the first steel-pipe pile,

the pitch of the first helical fin is equal to the pitch of the second helical fin, and the first helical fin and the second helical fin are continuous on an imaginary helix at a joint portion of the first steel-pipe pile and the second steel-pipe pile,

the steel pipe pile further includes:

a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and

a second notch formed by connecting a start end portion and a terminal end portion of the first notch at one end side of the first steel pipe and cutting a peripheral portion of the first steel pipe other than the partial peripheral portion,

the first cut portion is cut away from the first helical blade by a predetermined distance.

2. A steel pipe pile is characterized in that,

the disclosed device is provided with:

a first steel-pipe pile having: a hollow first steel pipe; and at least one turn of first helical blades spirally formed on the outer periphery of the first steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the first steel pipe; and

a second steel-pipe pile having: a hollow second steel pipe; and at least one turn of second helical blades spirally formed at regular and equal intervals on the outer periphery of the second steel pipe in a direction from one end side to the other end side of the second steel pipe, the second steel-pipe pile being connected at an end portion thereof to the other end of the first steel-pipe pile,

the pitch of the first helical fin is equal to the pitch of the second helical fin, and the first helical fin and the second helical fin are continuous on an imaginary helix at a joint portion of the first steel-pipe pile and the second steel-pipe pile,

the steel pipe pile further includes:

a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and

a second notch formed by connecting a start end portion and a terminal end portion of the first notch at one end side of the first steel pipe and cutting a peripheral portion of the first steel pipe other than the partial peripheral portion,

at one end of the steel pipe, the thickness of either or both of the first helical fin and the steel pipe at least at the tip of the steel pipe pile is greater than the thickness of the first helical fin or the other portion of the steel pipe.

3. The steel pipe pile according to claim 1 or 2,

the interval between the first helical blade and the second helical blade is an integral multiple of the pitch of the first helical blade or the pitch of the second helical blade.

4. The steel pipe pile according to claim 1 or 2,

and a third helical blade spirally formed on the inner circumference of the steel pipe so as to protrude from the same base as the base of the first helical blade in a direction opposite to the protruding direction of the first helical blade,

the first cut portion is cut along the first helical blade and the third helical blade.

5. The steel pipe pile according to claim 2,

the first cut portion is cut away from the first helical blade by a predetermined distance.

6. The steel pipe pile according to claim 2,

the first cut portion is formed by cutting out an outer surface of the first helical blade.

7. The steel pipe pile according to claim 1 or 2,

at one end of the steel pipe, the diameter of the first helical fin at least at the tip end thereof is larger than the diameter of the first helical fin at the other portion thereof.

8. The steel pipe pile according to claim 1 or 2,

the first helical blade and the steel pipe at least at the tip of the first helical blade are manufactured by casting on one end side of the steel pipe.

9. The steel pipe pile according to claim 1 or 2,

the second helical blade protrudes from the base to the tip by a length different from that of the first helical blade.

10. The steel pipe pile according to claim 1 or 2,

any one or all of the first helical blade and the second helical blade is made of a steel bar.

11. The steel pipe pile according to claim 1 or 2,

a ratio Pch/dw of a pitch Pch of the first helical blade and a projection length dw of the second helical blade satisfies: pch/dw is less than or equal to 24.

12. A steel pipe pile is characterized in that,

comprising:

a hollow first steel pipe;

a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and

a fourth helical fin formed helically at a position spaced apart from the first helical fin on the outer periphery of the first steel pipe at a constant and equal pitch,

the pitch of the first helical blade is equal to the pitch of the fourth helical blade, the first helical blade and the fourth helical blade are continuous on an imaginary helix,

the steel pipe pile further includes: a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and

a second notch formed by connecting a start end portion and a terminal end portion of the first notch at one end side of the first steel pipe and cutting a peripheral portion of the first steel pipe other than the partial peripheral portion,

the first cut portion is cut away from the first helical blade by a predetermined distance.

13. A steel pipe pile is characterized in that,

comprising:

a hollow first steel pipe;

a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and

a fourth helical fin formed helically at a position spaced apart from the first helical fin on the outer periphery of the first steel pipe at a constant and equal pitch,

the pitch of the first helical blade is equal to the pitch of the fourth helical blade, the first helical blade and the fourth helical blade are continuous on an imaginary helix,

the steel pipe pile further includes: a first cut-out portion formed by cutting out a part of the entire circumference of the first steel pipe along the first helical blade at one end side of the first steel pipe; and

a second notch formed by connecting a start end portion and a terminal end portion of the first notch at one end side of the first steel pipe and cutting a peripheral portion of the first steel pipe other than the partial peripheral portion,

at one end of the steel pipe, the thickness of either or both of the first helical fin and the steel pipe at least at the tip of the steel pipe pile is greater than the thickness of the first helical fin or the other portion of the steel pipe.

14. The steel pipe pile according to claim 12 or 13,

the pitch between the first helical blade and the fourth helical blade is an integral multiple of the pitch between the first helical blade and the fourth helical blade.

15. The steel pipe pile according to claim 12 or 13,

the fourth helical blade protrudes from the base to the tip by a length different from that of the first helical blade.

16. The steel pipe pile according to claim 12 or 13,

any one or all of the first helical blade and the fourth helical blade is made of a steel bar.

17. The steel pipe pile according to claim 12 or 13,

a ratio Pch/dw of a pitch Pch of the first helical blade and a projection length dw of the fourth helical blade satisfies: pch/dw is less than or equal to 24.

18. A method for constructing a steel pipe pile, comprising:

and a step of rotationally driving a first steel-pipe pile into the buried site, the first steel-pipe pile including: a hollow first steel pipe; and at least one turn of first helical blades spirally formed on the outer periphery of the first steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the first steel pipe;

adjusting a press-fitting speed so that the first helical blades of the first steel-pipe pile pass through substantially the same path in a ground when the first steel-pipe pile is rotationally press-fitted into the ground;

a step of connecting a second steel-pipe pile to the first steel-pipe pile such that a pitch of the first helical blade is equal to a pitch of a second helical blade included in the second steel-pipe pile, the first helical blade and the second helical blade being continuous in an imaginary helix at a connection portion of the first steel-pipe pile and the second steel-pipe pile, the second steel-pipe pile including: a hollow second steel pipe; and at least one turn of the second helical fin is formed spirally at a constant and equal pitch on the outer periphery of the second steel pipe in a direction from one end side to the other end side of the second steel pipe, and the second steel pipe pile is connected at an end portion to the other end of the first steel pipe pile;

a step of rotationally pressing the steel-pipe pile formed by connecting the first steel-pipe pile and the second steel-pipe pile into a buried site; and

adjusting the press-fitting speed so that the first helical blade and the second helical blade of the steel pipe pile pass through substantially the same path in the ground when the steel pipe pile is rotationally press-fitted into the ground,

a first cut portion formed by cutting a part of the circumferential portion of the entire circumference of the first steel pipe along the first helical blade, and a second cut portion formed by connecting a start end portion and an end portion of the first cut portion and cutting the circumferential portion of the other portion than the part of the circumferential portion of the entire circumference of the first steel pipe are provided on one end side of the first steel pipe,

the first cut portion is cut away from the first helical blade by a predetermined distance.

19. A method for constructing a steel pipe pile, comprising:

and a step of rotationally driving a first steel-pipe pile into the buried site, the first steel-pipe pile including: a hollow first steel pipe; and at least one turn of first helical blades spirally formed on the outer periphery of the first steel pipe at a constant and equal pitch in a direction from one end side to the other end side of the first steel pipe;

adjusting a press-fitting speed so that the first helical blades of the first steel-pipe pile pass through substantially the same path in a ground when the first steel-pipe pile is rotationally press-fitted into the ground;

a step of connecting a second steel-pipe pile to the first steel-pipe pile such that a pitch of the first helical blade is equal to a pitch of a second helical blade included in the second steel-pipe pile, the first helical blade and the second helical blade being continuous in an imaginary helix at a connection portion of the first steel-pipe pile and the second steel-pipe pile, the second steel-pipe pile including: a hollow second steel pipe; and at least one turn of the second helical fin is formed spirally at a constant and equal pitch on the outer periphery of the second steel pipe in a direction from one end side to the other end side of the second steel pipe, and the second steel pipe pile is connected at an end portion to the other end of the first steel pipe pile;

a step of rotationally pressing the steel-pipe pile formed by connecting the first steel-pipe pile and the second steel-pipe pile into a buried site; and

adjusting the press-fitting speed so that the first helical blade and the second helical blade of the steel pipe pile pass through substantially the same path in the ground when the steel pipe pile is rotationally press-fitted into the ground,

a first cut portion formed by cutting a part of the circumferential portion of the entire circumference of the first steel pipe along the first helical blade, and a second cut portion formed by connecting a start end portion and an end portion of the first cut portion and cutting the circumferential portion of the other portion than the part of the circumferential portion of the entire circumference of the first steel pipe are provided on one end side of the first steel pipe,

at one end of the steel pipe, the thickness of either or both of the first helical fin and the steel pipe at least at the tip of the steel pipe pile is greater than the thickness of the first helical fin or the other portion of the steel pipe.

20. A method for constructing a steel pipe pile, comprising:

a step of rotationally driving a steel pipe pile into a buried site, the steel pipe pile comprising: a hollow first steel pipe; a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and a fourth helical fin formed spirally at a constant and equal pitch on the outer periphery of the first steel pipe at a position spaced apart from the first helical fin, the pitch of the first helical fin being equal to the pitch of the fourth helical fin, the first helical fin and the fourth helical fin being continuous on an imaginary spiral; and

adjusting a press-fitting speed so that the first helical blade and the fourth helical blade of the steel-pipe pile pass through substantially the same path in a ground when the steel-pipe pile is rotationally press-fitted into the ground,

a first cut portion formed by cutting a part of the circumferential portion of the entire circumference of the first steel pipe along the first helical blade, and a second cut portion formed by connecting a start end portion and an end portion of the first cut portion and cutting the circumferential portion of the other portion than the part of the circumferential portion of the entire circumference of the first steel pipe are provided on one end side of the first steel pipe,

the first cut portion is cut away from the first helical blade by a predetermined distance.

21. A method for constructing a steel pipe pile, comprising:

a step of rotationally driving a steel pipe pile into a buried site, the steel pipe pile comprising: a hollow first steel pipe; a first helical blade spirally formed at a constant and equal pitch on the outer periphery of the first steel pipe; and a fourth helical fin formed spirally at a constant and equal pitch on the outer periphery of the first steel pipe at a position spaced apart from the first helical fin, the pitch of the first helical fin being equal to the pitch of the fourth helical fin, the first helical fin and the fourth helical fin being continuous on an imaginary spiral; and

adjusting a press-fitting speed so that the first helical blade and the fourth helical blade of the steel-pipe pile pass through substantially the same path in a ground when the steel-pipe pile is rotationally press-fitted into the ground,

a first cut portion formed by cutting a part of the circumferential portion of the entire circumference of the first steel pipe along the first helical blade, and a second cut portion formed by connecting a start end portion and an end portion of the first cut portion and cutting the circumferential portion of the other portion than the part of the circumferential portion of the entire circumference of the first steel pipe are provided on one end side of the first steel pipe,

at one end of the steel pipe, the thickness of either or both of the first helical fin and the steel pipe at least at the tip of the steel pipe pile is greater than the thickness of the first helical fin or the other portion of the steel pipe.