JP4073339B2 - Steel pipe pile - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a steel pipe pile that is press-fitted into the ground by rotation and a bottom expansion metal fitting for the steel pipe pile.
[0002]
[Prior art]
Japanese Laid-Open Patent Publication No. 2002-221947 (Patent Document 1) discloses a bottomed steel pipe pile according to the present applicant. In this steel pipe pile, a conical bottom support wing is fixed to the outer periphery of the pile near the tip, and the disturbance to the surrounding ground at the tip of the pile is reduced by the press-fitting or non-rotating press-fitting by the rotation, and the support force of the pile tip is increased. Therefore, it can be effectively used as a steel pipe pile that is press-fitted into the ground as the foundation of a small building such as a house. In particular, compared to conventional steel pipe piles, where the ground is not very strong and the initial settlement occurs when the support area is small such that the bottom area is the cross-sectional area of the tip of the pile, with spiral blades. It has gained a great support to the tip of the steel pipe pile. Japanese Laid-Open Patent Publication No. 9-291528 (Patent Document 2) discloses a steel pipe pile in which a bottom cover of a certain depth is provided inside the vicinity of the tip of the steel pipe pile and a blade having a fixed length protrudes from the bottom cover to the tip side. Has been. In this steel pipe pile, since the soil is not discharged upward from the hollow steel pipe pile by the bottom lid during press-fitting, the soil on the pile tip side is compressed and the blade also acts and the soil at the pile tip part becomes consolidated, and the pile tip The support force will increase. In Utility Model Registration No. 3008369 (Patent Document 3), a metal fitting provided with excavation blades formed by alternately bending a plate-like triangular plate up and down at the tip of a steel pipe pile is attached to bite into the ground. An improved steel pipe pile is disclosed. In JP-A-11-293670 (Patent Document 4), a flat plate body in which a blade-shaped earth removing plate is suspended from a flat plate support is fixed to the tip of a steel pipe pile, and the soil below the tip of the steel pipe pile is centered. The steel pipe pile which makes it easy to press-fit the steel pipe pile is disclosed by discharging to the outside and breaking the hard ground to make it soft.
[0003]
[Patent Document 1]
JP 2002-221947 A [Patent Document 2]
Japanese Patent Laid-Open No. 9-291528 [Patent Document 3]
Utility Model Registration No. 3008369 [Patent Document 4]
Japanese Patent Laid-Open No. 11-293670
[Problems to be solved by the invention]
The steel pipe pile described in Patent Document 1 is preferable because a large supporting force is obtained at the tip of the pile when pressed into a ground that is not strong. However, it is necessary to fix a conical bottom expanding support wing near the tip of the steel pipe pile by welding or the like, and the steel pipe pile becomes expensive in terms of manufacturing cost and the like. In the steel pipe pile described in Patent Document 2, since the soil is not discharged from the hollow steel pipe pile by the bottom cover during press-fitting, the soil on the pile tip side is compressed and the supporting force of the pile tip is increased, but it is soft. In order to obtain a large bearing capacity on the ground, it is necessary to increase the outer diameter of the steel pipe pile, but in order to enable press-fitting, there is a limit to increasing the outer diameter of the steel pipe pile. The large bearing capacity to the steel pipe pile tip in the ground cannot be expected. The steel pipe pile of patent document 3 aims at increasing the biting into the ground, and the reinforcement of the supporting force at the steel pipe pile tip cannot be expected. The steel pipe pile of Patent Document 4 is a steel pipe pile that facilitates the press-fitting by breaking the hard ground and softening it for the purpose of press-fitting the steel pipe pile into the hard ground. It does not gain power.
[0005]
Accordingly, an object of the present invention is to provide a low-cost steel pipe pile, which is a steel pipe pile that obtains a large supporting force at the tip of the pile when driven into a weak ground such as a soft ground or a ground with many gaps. In particular, an object of the present invention is to provide an expanded metal fitting used for the steel pipe pile.
[0006]
[Means for Solving the Problems]
In order to achieve such an object, according to the present invention, a steel pipe pile that is press-fitted into the ground by rotation has a plate-shaped bottom-up metal fitting having an area larger than the cross-sectional area of the steel pipe pile fixed to the tip of the steel pipe pile, The metal fitting is fixed so that the excavating blade for excavating the ground below the tip of the steel pipe pile hangs down, and the excavating blade is connected to the steel pipe on the outer side of the bottom expansion metal fitting by the rotation of the steel pipe pile. The bottom metal fitting is formed from a square flat plate member, and the excavating blade is formed by bending the triangular portion of the four corners downward from the flat plate portion at a right angle. cage, the flat portion of the拡底fitting is octagonal, Ru der approximately 50 degrees the angle formed by the fold line between adjacent sides as viewed in the rotational direction digging edge tip side of the steel pipe pile of the digging edge portion It is characterized by that.
Moreover, in another steel pipe pile which press-fits to the ground by rotation according to the present invention, the bottom metal fitting is formed from a regular triangular flat plate member, and the excavating blade has a triangular portion at three corners from the flat plate portion. It is formed by bending downward at a right angle, and the flat plate portion of the bottom-up metal fitting is hexagonal, and the angle formed between the fold line of each excavating blade portion and the adjacent side is excavated as seen in the rotation direction of the steel pipe pile It is characterized by approximately 65 degrees on the blade tip side.
[0007]
According to the steel pipe pile according to the present invention, a flat bottom expansion metal fitting having an area larger than the cross-sectional area of the steel pipe pile is fixed, and only the support area of the pile tip is increased by increasing the support area of the pile tip. However, the excavation blade of the bottom expansion bracket collects the soil on the outer peripheral side of the bottom expansion bracket under the tip of the steel pipe pile on the center side by the rotation of the steel pipe pile, so the soil on the pile tip side is compressed to the center side of the pile and consolidated Even if the ground is not so strong, or the soil density is low and faint, a solid ground is formed on the pile tip side, thereby increasing the support force of the pile tip. In particular, when the bottom expansion metal fitting is formed from a square flat plate member and the excavation blade is formed by bending the triangular portion of the four corners downward from the flat plate portion at a right angle, each excavation blade in the flat plate portion of the octagonal bottom expansion metal fitting The angle formed by the fold line of the part and the adjacent side is about 50 degrees on the excavating blade tip side when viewed in the direction of rotation of the steel pipe pile, and it is formed so that it opens about 45 degrees from 45 degrees. In addition to scooping, the rear end portion of the excavating blade in the rotational direction is radially inward by an angle of 50 degrees, that is, an angle of 5 degrees more than 45 degrees. Collect more soil from the side under the steel pipe pile tip on the center side, and compact the soil on the pile tip side to the center side of the pile.
Further, in the case where the bottom metal fitting is formed from a regular triangular flat plate member and the excavating blade is formed by bending the triangular portion of the three corners downward at right angles from the flat plate portion, each excavating blade in each hexagonal flat plate portion The angle formed between the fold line of the part and the adjacent side is formed to be approximately 65 degrees on the tip side of the excavating blade as viewed in the rotation direction of the steel pipe pile, and is formed so as to be opened by about 5 degrees from 60 degrees. While scooping up a lot of soil, gather more scooped soil under the steel pipe pile tip on the center side, and compact the soil on the pile tip side to the center side of the pile.
Therefore, when the steel pipe pile of the present invention is driven into a ground that is not strong, such as a soft ground or a ground with many gaps, a large support force can be obtained at the tip of the pile. Since it is a simple structure which fixed the excavation blade to the flat plate member, the steel pipe pile which fixed this bottom expansion metal fitting can also be obtained at low cost.
[0009]
It is preferable to press-mold a long and narrow concave portion or convex portion for reinforcement extending in the radial direction from the center in the flat plate portion of the flat bottom expansion metal fitting of the steel pipe pile. As a result, the thickness of the bottom-expanded metal fitting can be made, for example, from 12 mm to 9 mm, further reducing the cost and reducing the weight of the steel pipe pile tip. Moreover, it is preferable to fix so that the guide pin aligned with the center axis line of a steel pipe pile may hang down to the center of the flat plate part of a bottom expansion metal fitting, and center positioning before driving of a steel pipe pile can be performed easily. Furthermore, in the flat plate part of the bottom expansion bracket, a cut extending radially from the outer periphery of the steel pipe pile toward the outer periphery of the bottom expansion bracket is formed so that the soil excavated by the excavation blade is discharged upward in the portion without the excavation blade. It is preferable to do this.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the steel pipe pile with a bottom expansion metal fitting concerning the present invention is explained. FIG. 1 shows a portion in the vicinity of the tip of a steel pipe pile 2 to which the bottom expansion metal fitting 1 is fixed to the tip according to the first embodiment. In FIG. 1, a steel pipe pile 2 is formed in a hollow cylindrical body and extends upward as a steel pipe pile pressed into the ground as a foundation of a small-scale building such as a house. Only the tip is shown. FIG. 2 shows a bottom view of the bottom expanding metal fitting 1 as seen from the lower side of FIG. 1 before the steel pipe pile of FIG. 1 is fixed. FIG. 3 shows a cross-sectional view taken along the line AA of the bottom expanding metal fitting 1 of FIG. In FIG. 1, the bottom expansion metal fitting 1 is fixed to the tip of the steel pipe pile 2 by welding, for example. The expanded metal fitting 1 fixed to the tip of the steel pipe pile 2 is formed of a metal plate (for example, steel plate) material having a constant strength. The steel pipe pile 2 is press-fitted into the ground, for example, by pressing in the axial direction while rotating in the direction of the arrow 3 in FIG. 1 (including the arrow 3A in FIG. 2).
[0012]
The expanded bottom metal fitting 1 is formed of a plate-shaped member having an area larger than the cross-sectional area of the steel pipe pile 2. In the first embodiment, the bottom metal fitting 1 is formed from a square flat plate member. An excavating blade 5 for excavating the ground below the tip of the steel pipe pile 2 is fixed to the bottom expansion metal fitting 1 so as to hang down. In the first embodiment, four excavation blades 5 are formed by bending downward at right angles from the triangular partial flat plate portions at the four corners of a square flat plate member. Since the four excavating blades 5 are formed, the flat plate portion 6 of the bottom expansion metal fitting 1 is substantially a regular octagon. Empirically, it is preferable that the size of the bottom-expanded metal fitting 1 is such that the flat plate portion 6 is roughly circular and the diameter is preferably 2.5 times (2.5D) the diameter (D) of the steel pipe pile 2. I know it.
[0013]
The excavation blade 5 is formed to collect the soil on the outer peripheral side of the bottom-expanded metal fitting 1 at the center side, that is, below the tip of the steel pipe pile 2 by the rotation of the steel pipe pile 2. In the first embodiment, in the flat plate portion 6 of the octagonal bottom expansion metal fitting 1, the angle formed by the fold line 7 (7A, 7B, 7C) of each excavating blade portion and the adjacent side 9 (9A, 9B, 9C). α is formed at approximately 50 degrees on the tip side of the excavating blade as viewed in the direction of rotation of the steel pipe pile, and is formed so as to open approximately 45 degrees from 45 degrees. When the steel pipe pile 2 rotates in the direction of the arrow 3 (FIG. 1), the bottom expansion metal fitting 1 rotates in the direction of the arrow 3A (FIG. 2), and the tip side of each excavation blade is located on the outer peripheral side from the inscribed circle 10, Scoop a lot of soil on the outer periphery of the metal fitting 1. In addition, the rear end side portion of the digging blade 5 in the rotational direction is inwardly seen from the tip side portion in the radial direction of the inscribed circle 10 by an angle of 50 degrees, that is, an angle of 5 degrees more than 45 degrees. Therefore, a lot of soil scooped from the outer peripheral side of the bottom expansion metal fitting 1 by the rotation of the steel pipe pile by each excavating blade 5 is gathered under the center side of the bottom expansion metal fitting 1, that is, below the tip of the steel pipe pile 2, and the soil at the tip end of the pile is piled up. Compressed to the center side. Therefore, the soil at the pile tip side is compressed to the center side of the pile to become consolidated, and when the steel pipe pile 2 is driven into a less strong ground such as a soft ground or a ground with many gaps, a large support force is obtained at the pile tip. be able to. Note that the angle α is determined by the balance between the resistance of the soil when the steel pipe pile 2 rotates and the amount of scraping of the soil.
[0014]
The flat plate portion 6 of the bottom-expanded metal fitting 1 is formed by press molding so that a reinforcing elongated concave portion 11 (or convex portion) extending in the radial direction from the center is spaced so that a portion supporting the drilling blade 5 is reinforced. It is formed in accordance with the number of 5 (4 in the illustrated example). FIG. 2 and FIG. 3 show the elongate concave portion 11 (or convex portion) for reinforcement. The reinforcing elongated concave portion 11 (or convex portion) can increase the strength of the flat plate portion 6 of the bottom-expanded metal fitting 1, particularly the support portion of the excavating blade 5. The bottom-expanded metal fitting 1A in FIG. 4 does not have an elongated concave portion for reinforcement. When a steel pipe pile was press-fitted into the ground with such a bottom expansion metal fitting 1A, the thickness of the bottom expansion metal fitting required a thickness of 12 mm. On the other hand, in the case of the steel pipe pile to which the bottom expanded metal fitting 1 in which the elongate concave part 11 (or convex part) for reinforcement was formed was fixed, the bottom expanded metal fitting 1 could be 9 mm thick. As a result, the cost can be reduced and the weight of the tip of the steel pipe pile can be reduced. Note that this reinforcing elongated recess (or protrusion) is not essential, and the bottom-expanded metal fitting 1A of FIG. 4 without the reinforcing elongated recess (or protrusion) may be fixed to the tip of the steel pipe pile 2.
[0015]
In addition, a guide pin 13 aligned with the central axis of the steel pipe pile 2 is fixed to the center of the flat plate portion 6 of the bottom expansion metal fitting 1 so as to hang down. The guide pin 13 is not essential, but there is an advantage that the guide pin 13 can easily place the center of the tip of the steel pipe pile 2 at a predetermined position on the target ground. Moreover, when press-fitting into the ground, it acts as a center guide to ensure that the direction of press-fitting of the steel pipe pile 2 is properly maintained.
[0016]
Further, a cut 14 extending in the radial direction from the position corresponding to the outer periphery of the steel pipe pile 2 to the outer peripheral edge of the flat plate portion 6 of the bottom expansion metal fitting 1 is formed in the portion of the flat plate portion 6 of the bottom expansion metal fitting without the excavating blade 5. . This cut 14 acts to discharge the soil excavated by the excavating blade 5 upward. The incision 14 forms a dividing line in the flat plate portion 6 that extends in a radial direction from a position corresponding to the outer periphery of the steel pipe pile 2 to the outer peripheral edge of the flat plate portion 6, and in the rotational direction (direction of arrow 3A) of the portions on both sides thereof. It can be formed by inclining the front side portion 15 upward and inclining the rear side portion 17 downward. The reason why the radially inner portion of the cut 14 ends at a position corresponding to the outer periphery of the steel pipe pile 2 is that the soil just below the steel pipe pile is compressed and should not be discharged to the outside.
[0017]
FIG. 5 shows the state of the ground press-fitted while rotating the steel pipe pile 2 having the bottom expansion metal fitting 1 fixed to the tip thereof. Each excavation blade 5 collects the soil scooped from the outer peripheral side of the bottom expansion bracket 1 by the rotation of the steel pipe pile, and collects the soil at the center side of the bottom expansion bracket 1, that is, directly below the front end of the steel pipe pile 2, so Compress to compact. Therefore, even if the steel pipe pile 2 is driven into the ground which is not strong, such as the soft ground or the ground with many gaps, the soil portion 18 on the pile tip side is compressed and consolidated to the center side of the pile. A large supporting force can be obtained through the bottom-expanded metal fitting 1. In addition, as mentioned above, since the bottom expansion metal fitting 1 can be formed from a flat plate member by sheet metal processing such as bending or press molding, it can be manufactured at an extremely low cost.
[0018]
6 and 7 show a bottom-expansion metal fitting 21 according to the second embodiment. As shown in FIG. 7, the expanded metal fitting 21 is formed from a regular triangular flat plate member. The excavation blade 22 is formed by bending a triangular portion at three corners downward from a flat plate portion at a right angle. The flat plate portion 23 after being formed by bending the excavating blade 22 is formed in a substantially hexagonal shape. In each of the excavating blades 22, the angle β formed by the folding line 25 of the excavating blade portion and the adjacent side 26 is set to approximately 65 degrees on the excavating blade tip side in the rotation direction of the steel pipe pile 2 (direction of the arrow 3 </ b> A). Is done. In this way, it is formed at approximately 65 degrees on the tip side of the excavating blade as viewed in the direction of rotation of the steel pipe pile, and is formed so as to open about 5 degrees from 60 degrees. Collect more under the steel pipe pile tip and compress the soil on the pile tip side to the center side of the pile. When the excavation blade 22 is bent downward at right angles from the triangular flat plate at three corners, the excavation blade 22 becomes longer downward and the resistance at the time of rotary press-fitting increases, so that the cutting line 27 in FIGS. It may be cut with. The other parts are the same as those of the bottom-expansion metal fitting 1 according to the first embodiment, and therefore the same reference numerals are given and the description is omitted. Note that three elongated recesses 11 (or protrusions) for reinforcement are formed in accordance with the number of excavation blades 22. Moreover, the point which this elongate recessed part 11 for a reinforcement is not essential, and the point which the guide pin 13 is not essential are the same as that of the bottom expansion metal fitting 1 of 1st Example.
[0019]
【The invention's effect】
According to the steel pipe pile according to the present invention, not only the support area of the pile tip is increased to increase the support force of the pile tip, but also the soil at the pile tip side is compressed and consolidated to the center side of the pile, and the ground Is not so strong, or even if the soil density is low and faint, a solid ground is formed on the pile tip side, and the support force of the pile tip is increased. Therefore, when the steel pipe pile of the present invention is driven into a ground that is not strong, such as a soft ground or a ground with many gaps, a large support force can be obtained at the tip of the pile. Since it is a simple structure which fixed the excavation blade to the flat plate member, the steel pipe pile which fixed this bottom expansion metal fitting can also be obtained at low cost.
[Brief description of the drawings]
FIG. 1 is a front view showing a tip portion of a steel pipe pile with an expanded bottom fitting according to a first embodiment of the present invention.
2 is a bottom view of the bottom expansion metal fitting of FIG. 1 as viewed from the lower surface side of FIG. 1;
3 is a cross-sectional view taken along line AA of the bottom expansion metal fitting of FIG. 2;
4 is a bottom view similar to FIG. 2 of a bottom expansion metal fitting that does not form a reinforcing concave portion (or projection) in the bottom expansion metal fitting of FIG. 2;
FIG. 5 is a diagram showing a consolidated state of the ground when a steel pipe pile with an expanded metal fitting according to the first embodiment of the present invention is pressed while being rotated.
FIG. 6 is a front view showing a tip portion of a steel pipe pile with an expanded bottom fitting according to a second embodiment of the present invention.
7 is a bottom view of the bottom expansion metal fitting of FIG. 6 as viewed from the lower surface side of FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Expanded bottom metal fitting 2 Steel pipe pile 5 Excavation blade 6 Flat plate part 7 Folding line 9 Adjacent side 10 Inscribed circle 11 Elongated recessed part 13 Guide pin 14 Cutting 15 Front side part 17 Rear side part 18 Consolidated soil part 21 In 2nd Example Expanded bottom metal fitting 22 Excavating blade 23 Flat plate portion 25 Folding line 26 Adjacent side 27 Cutting line

Claims (5)

A steel pipe pile that is pressed into the ground by rotation,
A plate-shaped bottom expansion bracket having an area larger than the cross-sectional area of the steel pipe pile is fixed to the tip of the steel pipe pile, and a drilling blade for excavating the ground below the tip of the steel pipe pile is suspended on the bottom expansion bracket. The excavating blade is formed so as to collect the soil on the outer peripheral side of the bottom-expansion fitting under the tip of the steel pipe pile on the center side by rotation of the steel pipe pile ,
The bottom metal fitting is formed from a square flat plate member, and the excavating blade is formed by bending a triangular portion of four corners downward from the flat plate portion at a right angle,
The flat portion of the拡底fitting is octagonal, Ru der approximately 50 degrees angle as viewed in the direction of rotation digging edge tip side of the steel pipe pile that form in the side adjacent the fold line of each digging edge portion,
A steel pipe pile characterized by that. A steel pipe pile that is pressed into the ground by rotation ,
A plate-shaped bottom expansion bracket having an area larger than the cross-sectional area of the steel pipe pile is fixed to the tip of the steel pipe pile, and a drilling blade for excavating the ground below the tip of the steel pipe pile is suspended on the bottom expansion bracket. The excavating blade is formed so as to collect the soil on the outer peripheral side of the bottom-expanded metal fitting under the tip of the steel pipe pile on the center side by rotation of the steel pipe pile,
The bottom metal fitting is formed from a regular triangular flat plate member, and the excavating blade is formed by bending a triangular portion of three corners downward at right angles from the flat plate portion ,
The flat plate portion of the bottom expansion metal fitting is hexagonal, and the angle formed between the fold line of each excavation blade portion and the adjacent side is approximately 65 degrees on the excavation blade tip side in the rotation direction of the steel pipe pile,
A steel pipe pile characterized by that. 3. The steel pipe pile according to claim 1, wherein the flat plate portion of the bottom expansion metal fitting is press-molded with a reinforcing elongated concave or convex portion extending radially from the center. 3. . A steel pipe pile according to any one of claims 1 to 3 that the center of the flat plate portion of said拡底fitting that is secured to the guide pins to align the central axis of the steel pipe pile droops A characteristic steel pipe pile. A steel pipe pile according to any one of claims 1 to 4, the flat plate portion of the拡底bracket radially toward the outer periphery of the拡底fitting from the outer periphery of the steel pipe pile in part without the digging edge A steel pipe pile characterized in that the extending cut is formed so as to discharge the soil excavated by the excavating blade upward.

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