JP5298574B2 - Screwed pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screwed type pile, including a blade suitable for the chip of a steel pipe or its vicinity, and penetrated in the ground by applying turning force to the steel pipe to be buried, which includes excellent work efficiency and durability and is economical. <P>SOLUTION: A reinforcing steel plate 20 is welded and joined to the inner peripheral surface or the outer peripheral surface of the vicinity of the chip of the steel pipe fitted with the blade 10 along the peripheral surface to cover the substantially whole periphery. <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, 2).

  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.

  In addition, the screwed steel pipe pile with wings described in Patent Document 2 has an outer diameter substantially equal to the outer diameter of the steel pipe, a mounting member having a thickness or strength greater than that of the steel pipe, and one or a plurality of diameters larger than the diameter of the steel pipe. It has a structure in which a spiral plate or a steel plate is provided, a spiral plate or a steel plate is joined to the mounting portion to form a substantially spiral wing, and the tip of the steel pipe is welded. .

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

  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.

  Moreover, also in patent document 2, similarly to patent document 1, the front-end | tip part is separately manufactured and attached to the steel pipe main body, and welding with a steel pipe main body becomes troublesome, and it is not economical.

  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 present invention aims to provide an economical screw-in pile with excellent workability and durability.

  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 screwed pile, wherein a reinforcing steel plate is welded and joined to an inner peripheral surface or an outer peripheral surface of a steel pipe in the vicinity of which a wing is attached so as to cover almost the entire circumference along the peripheral surface.

  In the screwed pile according to the present invention, the reinforcing steel plate is welded and joined to the inner peripheral surface of the steel pipe or the outer peripheral surface of the steel pipe in the vicinity where the wing is attached so as to cover the entire circumference along the peripheral surface. Therefore, the structure is such that the thickness of the tip of the steel pipe is not increased, the processing is reduced, the cost is low, and it can withstand a large rotational torque. Also, by welding this reinforcing steel plate, the steel pipe can withstand the bending moment transmitted from the blade against vertical loads, so the increase in steel pipe stress due to the bending moment can be reduced even during service. .

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

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

  A screw-type pile according to an embodiment of the present invention is shown in FIGS. FIG. 1 is a perspective view of a screw-in type pile according to this embodiment, and FIG. 2 is a side view seen in the direction of arrow X in FIG.

  As shown in FIGS. 1 and 2, the screw-in type pile 1 according to this embodiment is formed by two fan-shaped flat plates (steel plates) 11 a and 11 b having a total inner angle of 360 ° at the tip of the steel pipe 2. This is a screwed pile which is attached to the substantially spiral wing 10 and penetrates into the ground by giving 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 1 according to this embodiment, the reinforcing steel plate 20 is attached to the outer peripheral surface of the steel pipe near the tip of the steel pipe to which the blade 10 is attached so as to cover almost the entire circumference of the peripheral surface. It has been.

  Although the reinforcing steel plate 20 is attached to the outer peripheral surface of the steel pipe here, the reinforcing steel plate 20 may be attached to the inner peripheral surface of the steel pipe as shown in FIG.

  The reinforcing steel plate 20 is attached by bending the steel plate in advance according to the circumferential curved surface (outer circumferential surface or inner circumferential surface) of the steel pipe 2 and performing fillet welding along the circumferential direction of the steel pipe 2. Shall. In addition, the axial direction of the steel pipe 2 does not necessarily need to be welded.

  Incidentally, covering almost the entire circumference of the outer peripheral surface or inner peripheral surface of the steel pipe is desirable to completely cover the entire circumference of 360 °, but it is allowed to have a slight gap between the start end and the end of the reinforcing steel plate 20 It means to do. It is preferable to cover 350 ° or more of the peripheral surface.

  Further, in order to facilitate transport and processing, the reinforcing steel plate 20 may be divided into a plurality of pieces in the circumferential direction of the steel pipe 2 and attached, and if the steel pipe 2 and the reinforcing steel plate 20 are attached so as to be almost integrated. Good.

  Here, the plate thickness of the reinforcing steel plate 20 is determined according to the external force such as the rotating torque to be applied. For example, in the case of a steel pipe pile of φ1200 mm, the steel plate 2 has a plate thickness of about 9 mm with respect to the plate thickness of 18 mm. If the steel plate 20 is attached, it can endure a torque of up to about 3500 kN · m. Incidentally, when there is no reinforcing steel plate 20, the steel pipe 2 yields locally with a torque of about 2500 kN · m. The appropriate plate thickness of the reinforcing steel plate 20 is desirably determined by FEM analysis or the like, but normally, the sum of the plate thicknesses of the steel pipe 2 and the steel plate 20 is about 2% to 3% of the diameter of the steel pipe 2.

  At the time of construction, as shown in FIG. 4, a stress concentration portion 51 is generated in the vicinity of the step portion 4a and in the vicinity of the step portion 4b (particularly, in the vicinity of the step portion 4a), and sometimes a crack 52 is generated from the stress concentration portion 51. Therefore, it is desirable that the steel plate 20 is not cut in this vicinity.

  When in service, as shown in FIG. 5, since the bending moment is transmitted from the blade 10 (the lower blade 11 a and the upper blade 11 b) to the steel pipe 2 by the ground reaction force 61, the tip of the steel pipe 2 has an axial force. The bending moment must be borne by the reinforcing steel plate 20, but this can be dealt with when the reinforcing steel plate 20 bears a part thereof. Normally, the range of influence of the bending moment is from the tip of the steel pipe 2 up to about 1.5D (D is the diameter of the steel pipe 2), and as shown in FIG. About 0.5D-1.5D from the front-end | tip of the steel pipe 2 is desirable.

  In addition, as shown in FIG. 7, it forms in the front-end | tip part of the steel pipe 2 by dividing into 2 via the 1st step part 4a and the 2nd step part 4b in the circumferential direction, and it is the same direction at the substantially same angle. 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. Note that the first mounting portion 3a and the second mounting portion 3b are discontinuous but have a substantially spiral shape. And although the height h1 of the 1st level | step-difference part 4a changes with conditions of the ground which penetrates the pile 1, the outer diameter of the steel pipe 2, etc., generally h1 = 0.1-0.5D (D is the diameter of the steel pipe 2). The height h2 of the second stepped portion 4b is slightly higher than the thickness of the fan-shaped flat plates 11a and 11b constituting the wing 10. When the height h1 of the first step portion 4a is less than 0.1D, the penetration amount of the pile 1 per revolution is remarkably reduced, and when it exceeds 0.5D, the penetration amount per revolution is increased. Therefore, the torque for rotating the pile 1 becomes excessive.

  The blade 10 is configured 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 through which the screwed pile 1 penetrates, the outer diameter of the steel pipe 2, etc., but considering the balance between the screwing workability and the magnitude of the supporting 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, although improved workability by increasing the open mouth 30, since the supporting force decreases, it is to decide the shape in both the balance. 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 screw-in type pile 1 according to this embodiment, the inner peripheral surface or the outer peripheral surface in the vicinity of the tip of the steel pipe to which the blade 10 is attached is covered so as to cover almost the entire periphery along the peripheral surface. Since the reinforcing steel plate 20 is welded and joined, the structure is such that the thickness of the tip portion of the steel pipe 2 is not increased, the processing is reduced, the cost is low, and it can withstand a large rotational torque. ing. Further, by welding the reinforcing steel plate 20, the steel pipe 2 can withstand the bending moment transmitted from the blade 10 against a vertical load. Therefore, the stress of the steel pipe 2 increases due to the bending moment even in service. Can be reduced.

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

  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.

It is a perspective view which shows one Embodiment of this invention. It is a side view which shows one Embodiment of this invention. It is a side view which shows one Embodiment of this invention. It is explanatory drawing of the stress state at the time of construction. It is explanatory drawing of the ground reaction force at the time of service. It is a figure for demonstrating the height of the steel plate for reinforcement in one Embodiment of this invention. It is a figure which shows the front-end | tip part of the steel pipe in one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screwed-type pile 2 Steel pipe 3a 1st attachment part 3b 2nd attachment part 4a 1st level | step difference part 4b 2nd level | step difference part 10 wing | blade 11a lower side wing | blade 11b upper wing | blade 12 2nd wing | blade 20 reinforcement steel plate 30 opening part 51 Stress concentration part 52 Crack 61 Ground reaction force

Claims (1)

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 steel plate for reinforcement is welded and joined to the inner peripheral surface of the steel pipe or the outer peripheral surface of the steel pipe in the vicinity where the blades are attached so as to cover almost the entire circumference along the peripheral surface .
The reinforcing steel plate has a length not more than 1.5 times the diameter of the steel pipe from the tip of the steel pipe,
A screw-type pile characterized in that a cut portion of the reinforcing steel plate is not disposed near a step portion to which a starting end and a terminal end of a spiral wing are attached and in the vicinity of the step portion .

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