JP2010281205A - Rotary penetration steel pipe pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary penetration steel pipe pile easily machinable, supporting a large load, and having excellent penetration efficiency. <P>SOLUTION: In this rotary penetration steel pipe pile, a steel blade 3 formed by bending a flat plate is secured to the front end face of a steel pipe at right angle to the axial direction of the steel pipe 5. In the steel blade 3, a slit 7 is formed within a predetermined area so as to extend along the front end outer periphery of the steel pipe 5, a cutoff part 9 is formed by cutting off a predetermined area including the slit 7 in a fan shape, an upward tilted surface part 13 is formed by upwardly bending one side of the portion of the steel blade at which the slit 7 is formed through, as a bending line 11, the extension of the segment connecting each terminal 7a of the slit 7 and the center of the pile, and a downward tilted surface part 15 is formed by downwardly bending the other side of the portion at which the slit 7 is formed. The cross sections of the tilted parts and the non-tilted parts of the upward tilted surface part 13 and the downward tilted surface part 15 at the slit portion are joined to each other by welding. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rotary penetrating steel pipe pile formed by fixing a steel blade to a steel pipe tip.

A rotary penetrating steel pipe pile formed by fixing a steel blade to a steel pipe tip part can be buried without soil removal, and has a characteristic that a large supporting force can be secured because the blade area is large.
As such a rotating penetrating steel pipe pile, for example, a type in which a spiral blade is attached to the outer peripheral surface of the steel pipe has been proposed (see Patent Document 1).
However, since the thing of patent document 1 attaches a spiral wing | blade to a steel pipe outer peripheral surface, the welding part of a spiral wing | blade and a steel pipe requires a groove welding or fillet weld from both up and down directions, and becomes high cost. . Further, since the bending moment from the wing portion is transmitted to the steel pipe body, it is necessary to increase the thickness of the steel pipe of the steel pipe body, which also increases the cost.

Moreover, as another example of the rotational penetrating steel pipe pile, there is one in which a steel pipe tip is cut in a spiral shape and a donut-like spiral blade is fixed to the spiral steel pipe tip (see Patent Document 2).
Certainly, since the thing of patent document 2 has attached the helical blade | wing at the steel pipe front-end | tip, the transmission of the bending moment from a wing | blade part to a steel pipe main body which became a problem in patent document 1, and the difficulty of welding of a wing | blade part The problem is reduced.
However, the thing of patent document 2 has to cut the tip of a steel pipe spirally, and the cost of this cutting is high. Moreover, since the opening is provided in the front-end | tip of a pile, there is anxiety about the supporting force of a pile. Furthermore, since there is an opening at the tip of the pile, there is a risk of boiling during sand construction in the sand ground.

As described above, Patent Document 2 has the above-mentioned problems because the tip of the steel pipe is cut into a spiral shape, but the following two are proposed as excavation blades attached to the tip of the steel pipe while being straight cut. Has been.
At the tip of the steel pipe, a flat triangular plate protrudes from the center of the steel pipe, and a horizontal excavation blade is provided on the tip surface of the steel pipe, and the tip of the excavation blade is alternately bent vertically. A steel pipe pile (see Patent Document 3).

A steel pipe pile (1) having a drilling blade (4) at the tip and drilling and penetrating by rotating the shaft, and forming a flange-shaped bottom expansion plate (3) on the outer periphery of the lower end of the steel pipe pile (1), With the outer peripheral point of the steel pipe pile (1) where two radial lines having a predetermined included angle θ intersect at one or more places on the bottom plate (3), the two radial lines are respectively A relief opening (30) is formed by cutting out a line segment formed by rotating the steel pipe pile (1) in the reverse rotation direction by a predetermined angle (α, β), and the relief opening (30) is rotated forward. An upper blade (31) extending upward in the reverse rotation side at a predetermined inclination angle is attached to the edge on the direction side, and an edge on the reverse rotation direction side of the relief opening (30) is attached to the edge at the predetermined inclination angle. A rotary penetration steel pipe pile characterized by attaching a lower blade (32) extending downward on the positive rotation side (see Patent Document 4).
JP 2001-31147 A JP 2001-193063 A Utility Model Registration No. 3008369 JP 2003-27475 A

The steel pipe piles described in Patent Documents 3 and 4 both have a drilling blade attached horizontally to the steel pipe pile tip, so the steel pipe tip mentioned in Patent Document 2 must be cut into a spiral shape, It is considered that the point that there is anxiety of lowering the supporting force due to the opening at the tip can be solved.
However, Patent Documents 3 and 4 have the following problems.

1. Problems of Patent Document 3 FIG. 9 is an explanatory diagram of the excavation blade of the steel pipe pile of Patent Document 3, and shows a state of the excavation blade before the tip portion is bent. As shown in FIG. 9, the excavating blade of Patent Document 3 is provided with cutting lines in the diagonal direction at the four corners of a rectangular flat plate, and the portions on both sides of the cutting line are bent in opposite directions up and down. The part is formed.
In the device described in Patent Document 3, the fold line forming the tip of the excavating blade does not pass through the center of rotation (the center of the plate). For this reason, there is a problem that the earth and sand hitting the inclined portion does not move along the inclination, the propulsive force is weak, and the construction efficiency is poor.

2. Problems of Patent Document 4 In Patent Document 4, the folding line is intentionally shifted by α and β from the radial direction. (It is shifted in the direction opposite to the rotation direction.) According to the description of the specification, the earth and sand are discharged to the side periphery with a blade to be compacted to ensure efficient penetration even on hard ground (reducing penetration resistance) .). From this explanation, it is surmised that the inventor intended to reduce the peripheral resistance at the time of penetration by reducing the density in the vicinity of the steel pipe by consolidating the earth and sand at a position away from the steel pipe.
Certainly, considering the direction of the blade, it is considered that the earth and sand move away from the steel pipe. However, in actuality, especially on hard ground, when it passes through the upper surface of the blade, it moves to the side for a moment, but when it passes through the blade, it returns immediately. In other words, earth and sand, especially hard earth, has strong elastic properties, does not compact in a short time, and the inventor's intention cannot be exhibited.

The intrusion principle of the rotating penetrating steel pipe pile is that when the pile body is rotated, the earth and sand on the upper surface of the wing receives a compressive force. It is to work.
However, when the folding line is shifted from the radial direction as in Patent Document 4, the earth and sand climbs obliquely without climbing the straight inclined surface, and as a result, no large propulsive force is generated. As a result, an effect opposite to the intention of the inventor is produced.

  In addition, since the inclined portion (blade) of Patent Document 4 is attached separately rather than by bending the wing (bottom plate), there is a problem that the manufacturing cost is high. The reason for the separate attachment is presumably because the blade is shifted by α and β from the radial direction, so that bending is difficult.

Further, in Patent Document 4, it is recommended that the downward blade and the upward blade overlap each other for the purpose of increasing the support force when the bottom expansion plate is viewed from above.
However, in reality, when a vertical force is applied to the pile, the earth and sand under the expanded plate integrally resist the compressive force, so even if there is a slight gap, the supporting force is hardly adversely affected. If the downward blade and the upward blade overlap each other, the clearance between the upper blade and the lower blade is reduced, so that large gravel is difficult to pass through, the earth and sand are easily clogged, and the penetration efficiency is reduced.

  The present invention has been made to solve such a problem, and an object of the present invention is to obtain a rotating penetrating pile that is easy to process, has a large supporting force, and is excellent in penetration efficiency.

(1) A rotary penetrating steel pipe pile according to the present invention is formed by fixing a steel wing formed by bending a flat plate to a steel pipe front end surface at a right angle to the pipe axis direction of the steel pipe, The steel wing is provided with a cut in a predetermined range along the outer periphery of the tip of the pile body, and a predetermined range including the cut is cut into a fan shape to form a cut portion, and each end of the cut is connected to the pile center. One of the portions provided with the incision is bent upward with the extension line of the line segment as a fold line to form an upward inclined surface portion, and the other portion of the portion provided with the cut is bent downward and the downward inclined surface portion. The crossing part of the inclined part and the non-inclined part in the cut part of the upward inclined surface part and the downward inclined surface part is joined by welding.

(2) Further, in the above-described (1), the steel blade is provided with the upward inclined surface portion and the downward inclined surface portion at one place in the circumferential direction, and a substantially triangular shape is formed below the steel blade. A drilling blade is provided.

The rotary penetrating steel pipe pile in the present invention is formed by fixing a steel wing formed by bending a flat plate to a steel pipe tip surface at a right angle to the pipe axis direction of the steel pipe, An incision is provided in a predetermined range along the outer periphery of the tip of the pile body, a predetermined range including the incision is cut into a fan shape to form a cut portion, and an extension of a line segment connecting each end of the incision and the pile center Using the line as a fold line, one of the portions provided with the cut is bent upward to form an upward inclined surface portion, and the other portion of the cut is provided to be bent downward to form a downward inclined surface portion. Therefore, the following various effects are produced.
・ Because a steel wing formed by bending a flat plate is fixed to the steel pipe tip surface at a right angle to the pipe axis direction of the steel pipe, it is necessary to machine the tip of the steel pipe to which the wing is attached in a spiral or oblique manner. There is no cost.
-Since the steel pipe and blade can be joined by one side fillet welding, the blade installation cost is low.
・ Since the pile tip is completely closed, the bearing capacity is large and its reliability is high. In addition, no boiling occurs during construction.
・ By making the bending line coincide with the radial direction of the steel pipe, the inclination direction coincides with the rotation direction of the pile, so that a large driving force can be obtained.
-By providing the cut portion between the upward inclined portion and the downward inclined portion, the clearance can be increased, and the construction efficiency is improved because the earth and sand can easily pass therethrough.
・ Because the intersection of the inclined part and the non-inclined part in the cut part of the upward inclined surface part and the downward inclined surface part is joined by welding, the pile (the inclined part is When the reaction force acts from the earth and sand, the stress concentration on the notch can be reduced.

It is explanatory drawing of the rotation penetration steel pipe pile which concerns on Embodiment 1 of this invention. It is a partial expanded sectional view of the rotation penetration steel pipe pile shown in FIG. It is a top view which shows the state before the process of the steel blade 3 shown in FIG. It is an end elevation of the side surface of the steel blade of the rotary penetration steel pipe pile shown in FIG. It is an enlarged view of the base end part of the downward inclination part 15 of the steel blade 3 shown in FIG. It is explanatory drawing of the steel wing | blade which concerns on Embodiment 2 of this invention. It is a side end elevation of the rotation penetration steel pipe pile concerning Embodiment 3 of the present invention. It is a bottom view of the rotation penetration steel pipe pile concerning Embodiment 3 of the present invention. It is explanatory drawing of the prior art example described in patent document 3. It is explanatory drawing of the prior art example described in patent document 4.

[Embodiment 1]
Drawing 1 is an explanatory view of the rotation penetration steel pipe pile concerning one embodiment of the present invention. As shown in FIG. 1, the rotary penetrating steel pipe pile 1 of the present embodiment has a steel blade 3 formed by bending a disk-shaped flat plate at a steel pipe tip surface at a right angle to the pipe axis direction of the steel pipe 5. The steel wing 3 is provided with a cut 7 in a predetermined range along the outer periphery of the tip of the steel pipe 5, and the predetermined range including the cut 7 is cut out in a fan shape. Part 9 is formed, one of the portions where the cuts 7 are provided is bent upward with the extension line of the line connecting each end 7a of the cuts 7 and the center of the pile as the folding line 11, and the upward inclined surface part 13 is formed. The other part of the part where the cut 7 is provided is bent downward to form a downward inclined surface part 15. This will be described in more detail below.

1. FIG. 2 is an enlarged view of a fixed portion between the steel pipe 5 and the steel wing 3. As shown in FIG. 2, the steel pipe 5 and the steel wing 3 constituting the pile main body are arranged at right angles to each other and fixed by fillet welding on the outside of the steel pipe.
Thus, since the steel blade 3 is fixed by fillet welding without processing the tip of the steel pipe 5 into a slanted shape or a spiral shape, it is easy to attach the steel blade 3 and cost. Can also be reduced.

2. Steel Blade FIG. 3 is a plan view showing a state before the steel blade 3 is bent. In FIG. 3, the cut line is indicated by a bold line. Hereinafter, the processing method of the steel blade 3 will be described with reference to FIG. As shown in FIG. 3, the steel blade 3 is provided with a cut 7 in a predetermined range along the outer periphery of the tip of the steel pipe 5, and a predetermined range including the cut 7 (a central portion of the cut line 7) is cut into a fan shape. Thus, the excision 9 is formed. Then, an extension line segment connecting each end 7a of the cut 7 and the pile center O is used as a folding line 11, and one of the portions where the cut 7 is provided is bent upward to form the upward inclined surface portion 13, and the cut 7 The other side of the part provided with is bent downward to form the downward inclined surface portion 15.

  When the steel blade 3 is formed with the upward inclined surface portion 13 and the downward inclined surface portion 15, the steel blade 3 is bent along the bending line 11, which is an extension of the line segment connecting each end 7 a of the cut 7 and the pile center O. Therefore, the inclination directions of the upward inclined surface portion 13 and the downward inclined surface portion 15 coincide with the rotation direction of the pile, and thus a large propulsive force can be obtained at the time of rotation penetration.

  FIG. 4 is an end view of the side surface of the steel wing 3 bent as described above. In the steel blade 3, since the cut portion 9 is formed, a large clearance 17 is formed between the upward inclined surface portion 13 and the downward inclined portion 15. By forming such a large clearance 17, earth and sand can easily pass during construction of the pile, and the construction efficiency is improved.

FIG. 5 is an enlarged view of the base end portion of the downwardly inclined portion 15 of the steel blade 3, and FIG. 5B is an enlarged view of the A portion surrounded by a circle in FIG.
As shown in FIG. 5, the steel blade 3 according to this embodiment has an inner side portion of the downward inclined portion 15 and the steel blade when bent along the folding line 11 when forming the downward inclined portion 15. The crossing portion 19 intersects with the horizontal portion 3 in FIG. 3. This crossing portion 19 is fixed by welding.

When a reaction force acts on the wing from the earth and sand (including the inclined part) during the rotation penetration of the pile and when the vertical force is applied after service, stress concentration occurs around the edge 7a of the cut 7 and the material strength is sufficiently strong. Otherwise, it may be damaged. Therefore, in order to reduce this stress concentration, as described above, the intersecting portion 19 is joined by welding.
The same applies to the upward inclined portion 13.

In the rotary-penetrating steel pile of the present embodiment configured as described above, when the steel pipe 5 is rotated and penetrated into the ground, the downward inclined portion 15 excavates the ground that has not been disturbed yet, and the pile It functions to obtain a driving force that drags the body downward. Further, the upward inclined portion 13 functions so as to obtain a driving force. By these functions of the downward inclined portion 15 and the upward inclined portion 13, the rotary penetrating steel pipe pile 1 penetrates into the ground. And since the inclined surface of the upward inclined surface part 13 and the downward inclined surface part 15 corresponds with the rotation direction of a pile, a big driving force is obtained.
Further, since the tip of the steel pipe 5 is perpendicular to the axial direction, the manufacturing cost can be reduced as compared with the conventional example in which the tip of the steel pipe is processed in a spiral shape or obliquely.
Furthermore, since the pile tip is completely closed, the bearing force is large and its reliability is high, and no boiling occurs during construction.

[Embodiment 2]
FIG. 6 is an end view of the side surface of the steel blade 3 of the rotary penetrating steel pipe pile according to Embodiment 2 of the present invention. In the present embodiment, the inclination angle θ1 of the upward inclined surface portion 13 is made larger than the inclination angle θ2 of the downward inclined surface portion 15. The reason for this is as follows.

The functions of the downward inclined portion 15 are two functions of excavating the ground that has not yet been disturbed and obtaining a propulsive force that drags the pile body downward. On the other hand, the function of the upward inclined portion 13 is only to obtain a driving force.
The propulsive force increases as the inclination increases, but the rotational resistance also increases, so the torque required for construction also increases. In particular, since the downward inclined portion 15 excavates the ground that has not been disturbed yet, the torque increases as the angle increases. On the other hand, since the earth and sand on the upper surface of the upward inclined portion is already disturbed and softened by the downward inclined portion 15, a large propulsive force cannot be obtained if the angle is small. For this reason, the inclination angle of the upward inclined portion 13 is set larger than the inclination angle of the downward inclined portion 15.

In order to confirm the effect of making the inclination angle of this upward slope 13 greater than that of the downward slope 15, the actual ground (depth 2mm, N value about 40) is excavated with 267.4mm steel pipe pile. The following tests were conducted for the following three cases A, B, and C.
Case A: Inclined angle of downward inclined part 30 degrees Inclined angle of upward inclined part 30 degrees Case B: Inclined angle of downward inclined part 20 degrees Inclined angle of upward inclined part 30 degrees Case C: Inclined angle of downward inclined part 30 degrees Upward Inclination angle of inclined part 20 degrees

As a result of the test, the penetration speed was in the order of B, A, C. From this, it was demonstrated that the penetration efficiency is improved by making the inclination angle θ1 of the upward inclined surface portion 13 larger than the inclination angle θ2 of the downward inclined surface portion 15.
Practically, it is preferable to set the inclination angle of the upward inclined portion in the range of 25 to 40 degrees and the inclination angle of the downward inclined portion in the range of 15 to 30 degrees.
If the inclination angle of the upward inclined part exceeds 40 degrees, the ground disturbance around the steel pipe becomes too large and the peripheral friction decreases. Further, when the inclination angle of the downward inclined portion becomes smaller than 15 degrees, the rotational torque becomes small, but the penetration amount per one rotation is reduced and the construction efficiency is lowered.

[Embodiment 3]
7 and 8 are explanatory views of Embodiment 3 of the present invention, in which FIG. 7 is a side end view and FIG. 8 is a bottom view. 7 and 8, the same parts as those of the first embodiment are denoted by the same reference numerals.
The rotary penetrating steel pipe pile of the present embodiment is provided with a substantially triangular excavating blade 21 on the lower side of the steel blade 3.
Since the central part of the steel blade 3 is horizontal, there is no excavation function in the central part. Therefore, a substantially triangular excavation blade 21 is provided at the center of the steel blade 3, and the excavation blade 21 supplements the ground excavation function.
Moreover, since the steel blade 3 according to the present embodiment is provided with an inclined portion at one place in the circumferential direction, the steel blade 3 itself is asymmetric with respect to the point of intrusion from the ground at the time of penetration. As a result, misalignment is likely to occur. In this regard, by providing the substantially triangular excavating blade 21 of the present embodiment, eccentricity at the time of penetration can be prevented.
However, the triangular plate is not a necessity, and may be attached according to the construction depth and the hardness of the ground.

  Further, the steel blade 3 according to the third embodiment is provided with a notch 15 a at the tip of the downward inclined portion 15. Thus, by providing the notch 15a, the resistance at the time of penetration can be reduced and the rotational torque can be reduced.

  In addition, in said Embodiment 1-3, although the example which provided the inclination part in one place of the steel blade 3 was shown, this invention is not restricted to this, The several places of the steel blade 3 You may make it provide an inclination part in this. In this case, if an inclined portion is provided at a portion that is symmetrical with respect to the center of the pile, eccentricity at the time of penetration can be prevented.

  DESCRIPTION OF SYMBOLS 1 Rotation penetration steel pipe pile, 3 steel blades, 5 pile main body, 7 cut, 9 cut part, 11 fold line, 13 upward slope part, 15 downward slope part.

Claims (2)

A rotary penetrating steel pipe pile in which a steel wing formed by bending a flat plate is fixed to a steel pipe tip surface at a right angle to the pipe axis direction of the steel pipe,
The steel wing is provided with a cut in a predetermined range along the outer periphery of the tip of the pile body, a predetermined range including the cut is cut into a fan shape to form a cut portion, and each end of the cut and the pile center are formed. Using the extended line of the connecting line as a fold line, one of the portions provided with the cut is bent upward to form an upward inclined surface portion, and the other portion provided with the cut is bent downward and inclined downward. A rotary penetrating steel pipe pile formed by forming a surface portion and joining an intersection of an inclined portion and a non-inclined portion in a cut portion of the upward inclined surface portion and the downward inclined surface portion.   2. The steel blade according to claim 1, wherein the steel blade is provided with the upward inclined surface portion and the downward inclined surface portion at one place in a circumferential direction, and a substantially triangular excavation blade is provided below the steel blade. Rotating penetrating steel pipe pile.

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