JP5298859B2 - Screwed pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an economical screwed type pile constituted by attaching a blade to a distal end or its vicinity of a steel pipe and can penetrate into the ground by giving rotating force to the steel pipe to bury it in the ground and achieve excellent durability and construction property. <P>SOLUTION: In this screwed type pile, a reinforcing rigid member 40 for reinforcing the steel pipe 2 is attached to a first step part 4a to which a start end and a terminal of the spiral blade 10 are attached. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a screwed pile that is buried in the ground by a wood screw action of a wing by attaching a wing to the tip of the steel pipe or in the vicinity thereof and applying a rotational force to the steel pipe.

  Many screw-in type piles that have been buried in the ground by the wood screw action of the wing by attaching a wing to the tip of the steel pipe or in the vicinity thereof and applying rotational force to the steel pipe have been proposed so far (for example, Patent Documents). 1-3).

  First, the rotary press-fit type steel pipe pile described in Patent Document 1 (screw-in type pile) is provided with a blade having an inclined front surface for pushing extending in the vertical direction at the lower part of a steel cylindrical body, and from the lower end of the inclined front surface. An inclined drill head that rises obliquely toward the rear in the direction of rotation of the cylindrical body is fixed to form an annular drill head, and the lower end portion of the steel pipe pile is attached to the upper end portion of the drill head.

  In this structure, a narrow arc-shaped inclined blade provided at the bottom of the steel cylinder is cut into the ground, and a small amount of soil corresponding to the cross-sectional area of the cylinder is laterally moved by the inclined inclined front surface for pushing. It only needs to be pushed in, and the press-in speed can be increased with the same press input as compared with the conventional rotary press-fit pile, and a small press input is sufficient at the same press-in speed. Moreover, since a pile body is an open end state, soil can be taken in in a pipe | tube and the improvement of workability can be expected.

  Next, the winged screw-type steel pipe pile described in Patent Document 2 has an outer diameter substantially equal to the outer diameter of the steel pipe, a mounting member having a wall thickness or strength larger than that of the steel pipe, and one or a diameter larger than the diameter of the steel pipe. It has a plurality of spiral plates or steel plates, has a structure in which a spiral plate or steel plate is joined to the mounting portion to form a substantially spiral wing, and welded to the tip of the steel pipe is there.

  Usually, a bending moment is generated from a spiral plate or a steel plate, but in such a configuration, a large bending stress is not generated by an attachment member having a large thickness or strength. Further, since the vicinity of the end of the steel pipe is reinforced by the mounting member, it is economical because it is not necessary to increase the total thickness of the steel pipe only by increasing the thickness in this range.

  Next, the rotary press-fit steel pipe pile described in Patent Document 3 (screw-in type pile) has a spiral blade at the tip, an outer diameter of 1.5 to 3 times the outer diameter of the steel pipe, and 0.4 of the inner diameter of the steel pipe pile. Cut one or more donut-shaped steel sheets with an inner diameter of ~ 0.9 times, concentrically weld and fix them to the ends of the steel pipe piles that have been cut in a spiral shape, and project the spiral blades inside and outside the tip of the steel pipe piles It is comprised in the shape which becomes.

  In this structure, since the spiral blades are overhanging inside and outside the steel pipe pile tip, smooth construction and sufficient pile support function that could not be solved by any of the conventional closed-end pile or open-end pile The problem of ease of production has been solved. Further, the step portion at the beginning and end of the steel pipe pile end portion cut in a spiral shape is formed in an arc shape, thereby reducing stress concentration and preventing the pile from being broken.

JP 61-098818 A Japanese Patent Laid-Open No. 10-159087 JP 2001-193063 A

  However, in the above-mentioned Patent Document 1, as seen in FIG. 1, since the protruding amount of the inclined blade from the pile body is small, the propulsive force for penetrating the pile body into the ground is insufficient, and the hard support There is a problem that the layer becomes difficult to penetrate, and the vertical bearing force after the pile penetration becomes small. In addition, the drill head to which the inclined blade is attached is thicker than the pile main body and needs to be manufactured separately, so that there is a problem that the cost increases.

  Also in Patent Document 2, the tip portion is separately manufactured and attached to the steel pipe main body in the same manner as Patent Document 1, and welding with the steel pipe main body becomes troublesome and not economical.

  Moreover, in patent document 3, since a big force concentrates on the level | step-difference part of the steel pipe pile edge part cut | disconnected helically at the time of rotation press injection, if this part is cut | disconnected at an acute angle, from a corner | angular part Since cracks may occur in the steel pipe of the pile main body, this step portion is formed in an arc shape to alleviate stress concentration and prevent pile destruction. However, there is no problem when the rotational torque is small, but when a pile with a large diameter is constructed with a torque close to the allowable torque of the pile, a large stress may be generated in the stepped portion and the steel pipe may be broken. Measures such as increasing the wall thickness are required as in Patent Document 1 and Patent Document 2, which is uneconomical.

  The present invention has been made in view of the circumstances as described above, and is a screw-in type pile that is embedded and embedded in the ground by applying a rotational force to the steel pipe with a wing attached to or near the tip of the steel pipe. The purpose of the present invention is to provide an economical screw-in pile with excellent durability and workability.

  In order to solve the above problems, the present invention has the following features.

[1] In a screwed pile in which a wing is attached at or near the tip of a steel pipe and embedded in the ground by applying a rotational force to the steel pipe,
A screw-type pile characterized in that a stiffening material for reinforcing a steel pipe is attached to a step portion to which the start and end of a wing are attached.

  [2] The screwed pile according to [1], wherein the stiffener is attached to an inner surface of a steel pipe.

  [3] The screwed pile according to [1], wherein the stiffener is attached to an outer surface of a steel pipe.

  [4] The screwed pile according to [1], wherein the stiffener is attached to an inner surface and an outer surface of a steel pipe.

  [5] The screwed pile according to any one of [1] to [4], wherein the stiffener is a plate material.

  In the screwed pile according to the present invention, the stiffener for reinforcing the steel pipe is attached to the stepped portion where the start and end of the wing are attached. Therefore, the thickness of the tip of the steel pipe is increased. In addition, it has a structure that can withstand a large rotational torque at low cost with less processing. In addition, by installing this stiffener, the steel pipe can withstand the bending moment from the blade tip of the blade that receives the ground reaction force from the new ground first against vertical load, so the bending moment is also in service. It is possible to reduce the increase in stress of the steel pipe due to.

  Therefore, the screwed pile according to the present invention is excellent in durability and workability and is an economical screwed pile.

1 is a perspective view showing a first embodiment of the present invention. It is a side view which shows the 1st Embodiment of this invention. It is a side view which shows the 1st Embodiment of this invention. It is a figure for demonstrating the function of the stiffener in the 1st Embodiment of this invention. It is a figure for demonstrating the function of the stiffener in the 1st Embodiment of this invention. It is a figure which shows the front-end | tip part of the steel pipe in the 1st Embodiment of this invention. It is a side view which shows the 2nd Embodiment of this invention. It is a side view which shows the 3rd Embodiment of this invention. It is a side view which shows the 4th Embodiment of this invention. It is a side view which shows the other example of the 1st Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The screwed pile which concerns on the 1st Embodiment of this invention is shown in FIGS. 1-3. 1 is a perspective view of a screwed pile according to the first embodiment, FIG. 2 is a side view seen in the direction of arrow X in FIG. 1, and FIG. 3 is a side view seen in the direction of arrow Y in FIG.

  As shown in FIGS. 1 to 3, the screw-type pile 1A according to the first embodiment includes two fan-shaped flat plates (steel plates) 11a having a total inner angle of 360 ° at the tip of the steel pipe 2. A substantially spiral wing 10 formed by 11b is attached, and is a screw-in type pile embedded in the ground by applying a rotational force to the steel pipe 2. Here, the fan-shaped flat plate 11a that first penetrates into the ground is referred to as the lower wing 11a, and the other fan-shaped flat plate 11b is referred to as the upper wing 11b. And the 1st level | step-difference part 4a to which the front-end | tip (inclined lower end part of the lower side wing | blade 11a) and termination | terminus (inclined upper end part of the upper side wing | blade 11b) of the spiral wing | blade 10 are attached to the front-end | tip part of the steel pipe 2; A second step portion 4b to which an intermediate portion of the spiral wing 10 (a connection portion between the inclined upper end portion of the lower wing 11a and the inclined lower end portion of the upper wing 11b) is attached is provided. An opening 30 is provided near the center of the spiral wing 10.

  In addition, in the screwed pile 1A according to this embodiment, the stiffener 40 for reinforcing the steel pipe 2 is provided on the first step portion 4a to which the start end and the end end of the spiral wing 10 are attached. It is attached.

  Normally, when constructing a screw-type pile, as shown in FIG. 4, in the first stepped portion 4a, the vicinity of the portion where the lower wing 11a is attached and the portion where the upper wing 11b is attached by the rotational torque. Stress concentration occurs in the vicinity, and sometimes a crack 52 starts from the stress concentration portion 51. Therefore, by reinforcing the vicinity of the stress concentration portion 51 with the stiffener 40, it is possible to cope with the torque during construction.

  After the construction, as shown in FIG. 5, the starting end of the wing 10 is first installed on a new ground 60 where the wing 10 has not passed, and the wing 10 has already passed through other parts of the wing 10. It is installed on a weak ground (disturbed ground) 61 than the new ground 60. At the time of service, since the new ground 60 is hard, the starting end portion of the wing 10 receives the largest ground reaction force, and the bending moment due to this is first transmitted to the steel pipe 2. Therefore, by reinforcing the steel pipe 2 with the stiffener 40, it is possible to cope with a bending moment caused by the ground reaction force.

  The stiffener 40 is desirably attached to the steel pipe 2 by bending a steel plate and welding, and may be attached to the steel pipe 2 by bolts or the like as other means. Further, the steel plate may be divided and attached as it is without bending, or may be attached so that the stiffener 40 and the steel pipe 2 are almost integrated.

  The attachment point of the stiffener 40 may be inside or outside the steel pipe 2, or may be both inside and outside the steel pipe 2. However, if it is attached to the outside of the steel pipe 2, it also serves as a friction cutter for reducing the frictional force on the peripheral surface, so that the workability is improved, but the degree of the peripheral frictional force may be reduced. Is more preferable.

  The plate thickness of the stiffener 40 may be determined according to an external force such as a rotating torque to be applied, and is preferably determined by FEM analysis or the like, but is in a range of about 0.5 to 3 times the plate thickness of the steel pipe 2. Become. For example, when the outer diameter of the steel pipe 2 is φ1200 mm, if the plate thickness of the stiffener 40 is about 20 mm with respect to the plate thickness of 18 mm, the torque up to about 3500 kN · m can be withstood. Incidentally, when there is no stiffener 40, the steel pipe 2 yields locally with a torque of about 2500 kN · m.

  As shown in FIG. 3, the attachment range of the stiffener 40 is about 5 ° to 45 ° in the circumferential angle of the steel pipe 2 from the end of the lower wing 11a with respect to the distance a1 from the end of the upper wing 11b. The distance a2 is about 5 ° to 45 ° in the circumferential angle of the steel pipe 2, and the distance b from the lower wing 11a is about 0.1 to 1.0 times the outer diameter D of the steel pipe 2; The distance c from 11b is preferably about 0 to 0.5 times the outer diameter D of the steel pipe 2 (c may be 0).

  The attachment range of the stiffener 40 may not only be attached as shown in FIG. 3 but also attached so that only the stress concentration portion 51 shown in FIG. 4 is stiffened. Further, when it can be confirmed by FEM analysis or the like that the range of the stress concentration portion 51 changes depending on the magnitude of the external force, the stiffener 40 may be attached so as to correspond to the range.

  In addition, as shown in FIG. 6, the steel pipe 2 is divided into two in the circumferential direction via the first step portion 4a and the second step portion 4b as shown in FIG. The 1st attaching part 3a (the front-end | tip part side of the steel pipe 2) which consists of an inclined surface which faces is provided, and the 2nd attaching part 3b is provided. The first attachment portion 3a and the second attachment portion 3b are discontinuous but substantially spiral. Note that the second stepped portion 4b is not provided (that is, h2 = 0), and the first mounting portion 3a and the second mounting portion 3b are continuous, and the mounting portion is formed of a substantially spiral inclined surface. Good. And although the height h1 of the 1st level | step-difference part 4a changes with conditions of the ground which penetrates the pile 1A, the outer diameter of the steel pipe 2, etc., generally h1 = 0.1-0.5D (D is the outside of the steel pipe 2) The height h2 of the second stepped portion 4b is in a range from 0 to a height that is slightly higher than the thickness of the fan-shaped flat plates 11a and 11b constituting the wing 10. Is desirable. When the height h1 of the first stepped portion 4a is less than 0.1D, the penetration amount of the pile 1A per revolution is remarkably reduced, and when it exceeds 0.5D, the penetration of the pile 1A per revolution Since the amount becomes too large, the torque for rotating the pile 1A becomes excessive.

  The blade 10 is formed by using fan-shaped flat plates 11a and 11b obtained by dividing a circular steel plate or an elliptical steel plate having an outer diameter larger than the outer diameter D of the steel pipe 2 from the center. The size of the wing 10 varies depending on the condition of the ground penetrating the screwed pile 1A, the outer diameter of the steel pipe 2, etc., but considering the balance between the screwing workability and the size of the support force, About 1.2 to 3 times the diameter D is desirable.

  And in this embodiment, as above-mentioned, the opening part 30 is provided in the center of the wing | blade 10, and thereby it is made to take in earth and sand in the steel pipe 2, but even if it obstruct | occludes depending on the case. Good.

  In the case where the opening 30 is provided, the opening 30 is preferably opened in a substantially circular shape at the center of the blade 10. The diameter of the opening 30 is about 0.25 to 0.9 times the outer diameter D of the steel pipe 2, but if the opening is opened more than 0.4 times the outer diameter D of the steel pipe 2, the effect of taking up soil by the opening is large. Become. However, if the opening 30 is enlarged, the workability is improved, but the supporting force is lowered, so it is preferable to determine the shape by balancing both. Further, if the diameter of the blade 10 is increased and the overhang from the steel pipe 2 is increased, the balance of the bending moment caused by the ground reaction force at the time of service is also deteriorated. Therefore, it is desirable to reduce the opening 30 when the overhang is large. .

  On the other hand, in the case of closing, since a closing plate that closes the gap between the lower wing 11a and the upper wing 11b is attached, the lower wing 11a and the upper wing 11b are integrated into a structure that is strong against torque, etc. When carrying out the construction, it is better to attach the stiffener 40 in order to improve the workability.

  Thus, in the screwed pile 1A according to this embodiment, the stiffener 40 for reinforcing the steel pipe 2 is attached to the stepped portion 4a to which the start and end of the wing 10 are attached. The structure is such that, without increasing the thickness of the tip portion of the steel pipe 2, the processing is reduced, the cost is low, and it can withstand a large rotational torque. Further, by attaching the stiffener 40, the steel pipe 2 can withstand the bending moment from the blade tip of the blade that first receives the ground reaction force from the new ground 60 with respect to the vertical load. The stress increase of the steel pipe 2 due to the bending moment can be reduced.

  Therefore, the screwed pile 1A according to this embodiment is an economical screwed pile while having excellent durability and workability.

  In this embodiment, the shape of the blade 10 is a spiral blade formed by two steel plates 11a and 11b. However, the shape of the blade is not limited to this, and the two steel plates intersect each other. The blade can be applied to any shape, such as a wing attached by bending a steel plate in a spiral manner, a wing attached by three or more steel plates or a bent steel material. Further, when there are a plurality of step portions to be reinforced depending on the shape of the wing, a stiffener may be attached to each of them.

  An example in the case of the wing | blade which attached the two steel plates 13a and 13b in crossing is shown in FIG. In this embodiment, as shown in a side view in FIG. 10, a stiffener 40 for reinforcing the steel pipe 2 is attached to each of the two stepped portions.

(Second Embodiment)
The basic structure of the screwed pile according to the second embodiment of the present invention is the same as that of the screwed pile 1A according to the first embodiment, but as shown in a side view in FIG. The screwed pile 1B according to the second embodiment is a case where the distance between the end of the lower wing 11a and the end of the upper wing 11b in the first stepped portion 4a is separated, and the stiffener 40 is It is attached to a wide range accordingly.

  The range of attachment of the stiffener 40 is about 5 ° to 45 ° in the circumferential angle of the steel pipe 2 for the distance a1 from the end of the upper wing 11b, and about the distance a2 from the end of the lower wing 11a. The circumferential angle of 2 is about 5 ° to 45 °, the range a3 of the first stepped portion 4a is about 0 ° to 60 ° in the circumferential angle of the steel pipe 2, and the distance b from the lower wing 11a is about The outer diameter D of the steel pipe 2 is preferably about 0.1 to 1.0 times, and the distance c from the upper blade 11b is preferably about 0 to 0.5 times the outer diameter D of the steel pipe 2.

(Third embodiment)
The basic configuration of the screwed pile according to the third embodiment of the present invention is the same as that of the screwed pile 1A according to the first embodiment or the screwed pile 1B according to the second embodiment. However, as shown in the side view of FIG. 8, the screw-type pile 1C according to the third embodiment has the stiffeners 40a and 40b attached only to positions where stiffening is necessary, such as a position 51 where stress concentration occurs. This is a case where the size of the stiffener is reduced.

  The attachment range of the stiffeners 40a and 40b depends on the degree and magnitude of stress concentration, but the height b2 is about 0.1 times the outer diameter D of the steel pipe 2, and the width a4 is 15 ° in the circumferential angle. Degree is desirable.

(Fourth embodiment)
The basic structure of the screwed pile according to the fourth embodiment of the present invention is the same as that of the screwed pile 1A according to the first embodiment or the screwed pile 1B according to the second embodiment. However, as shown in a side view in FIG. 9, the screwed pile 1 </ b> D according to the fourth embodiment has a second wing 12 attached to the peripheral surface portion of the steel pipe 2 in addition to the wing 10 at the tip of the steel pipe 2. The step portion between the start end and the end of the second blade 12 is reinforced by another stiffener 41. In this case, since it takes time to attach the stiffener 41 to the inside of the steel pipe 2, it is realistic to attach the stiffener 41 to the outside of the steel pipe 2.

  The standard of the attachment range of the stiffener 41 is that the width a5 is about 15 ° to 90 ° in the circumferential angle of the steel pipe 2, and the height b3 is about 0.1 to 1.0 times the outer diameter D of the steel pipe 2. desirable. Moreover, you may make it attach a stiffener only to the required position of the position where stress concentration generate | occur | produces like 3rd Embodiment.

DESCRIPTION OF SYMBOLS 1A Screw-in type pile 1B Screw-in type pile 1C Screw-in type pile 1D Screw-in type pile 2 Steel pipe 3a First attachment part 3b Second attachment part 4a First step part 4b Second step part 10 Wing 11a Lower wing 11b Upper wing 12 Second Wing 30 Opening 40 Stiffening Material 40a Stiffening Material 40b Stiffening Material 41 Stiffening Material 51 Stress Concentration Portion 52 Crack 60 New Ground 61 Disturbed Ground

Claims (4)

In the screwed pile that is attached to the tip of the steel pipe or the vicinity thereof, and is embedded in the ground by giving a rotational force to the steel pipe,
A screw-type pile, wherein a stiffening material for reinforcing the steel pipe is attached to a stepped part to which at least one of the inner surface and the outer surface of the steel pipe is attached to the wing start and end. The starting edge of the wing is the inclined lower end of the wing on the side that first penetrates into the ground,
The stiffener extends from the step portion to both sides in the circumferential direction of the steel pipe,

A portion extending to one side from the stepped portion is a minimum in the circumferential direction of the steel pipe from the starting end to a circumferential angle of the steel pipe of 5 °, a maximum from the starting end to a circumferential angle of the steel pipe of 45 °, and
  In the lengthwise direction of the steel pipe, the steel pipe extends from the wing on the side that first penetrates into the ground to 0.1 times the outer diameter of the steel pipe, and from the wing on the side that penetrates first into the ground at the maximum. The screwed pile according to claim 1, wherein the pile is attached in a range of 1.0 times the outer diameter of the pile. The stiffener has a portion extending from the stepped portion to the other in the circumferential direction of the steel pipe, at a minimum, from the end to a circumferential angle of the steel pipe of 5 °, and at a maximum, a circumferential angle 45 from the end to the steel pipe. The screwed pile according to claim 2, wherein the pile is attached in a range of up to °. The screwed pile according to any one of claims 1 to 3, wherein the stiffener is a plate material.

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