Rotary penetrating pile

Abstract

To provide a rotary penetration pile capable of surely securing bearing capacity and reducing penetration resistance.SOLUTION: A rotary penetration pile 1 according to the present invention includes a pile main body 3 made of a steel pipe, and a steel blade 5 horizontally attached to a lower end of the pile main body 3, wherein the steel blade 5 is formed by attaching one disc-shaped steel plate so as to cover an opening of the pile main body 3, and includes an upper blade 9 having an inclined surface bent obliquely upward and a lower blade 11 having an inclined surface bent obliquely downward and facing the upper blade 9 in a part of a peripheral edge portion. The lower blade 11 is extended from the outer edge of the steel blade 5 to the inside of the pile body 3, and an opening 13 for taking sediment into the pile body 3 is formed by extending the lower blade 11 to the inside of the pile body 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a rotary penetration pile having steel pipe wings attached horizontally to the lower end of a steel pipe pile body. [Background technology]

[0002] Rotary piles have the advantage of being able to provide large vertical bearing capacity by providing wings at the tip of the pile that are larger in area than the pile itself. In addition, because they do not require soil removal and are easy to install, this method of screwing the pile into the ground by rotating it has become widely used.

[0003] Two examples of prior art rotary penetration piles are given below. Patent Document 1 discloses a rotary penetration steel pipe pile in which steel wings, each with an upwardly inclined surface and a downwardly inclined surface formed by cutting and bending part of a flat plate, are attached to the bottom end of the steel pipe. The pile disclosed in Patent Document 1 has the advantage that the tip of the steel pipe is completely closed, making it easy to obtain a large vertical bearing capacity.

[0004] The steel pipe pile disclosed in Patent Document 2 is similar to that disclosed in Patent Document 1, but has a circular earth removal port formed in the center of the large-diameter end plate, allowing earth and sand to be taken into the pipe. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-281205 [Patent Document 2] Japanese Patent Application Publication No. 2022-167394 Summary of the Invention [Problem to be solved by the invention]

[0006] The rotary penetration steel pipe pile of Patent Document 1 has a completely closed tip, so during rotary penetration, a volume of soil equivalent to the volume of the pile must be moved to the side of the pile. This requires a large rotational torque, which results in the problem of a large pile driver being required.

[0007] The steel pipe pile of Patent Document 2 is provided with an earth removal port, so that it is possible to reduce the rotational torque compared to Patent Document 1. However, when an opening is simply provided in the end plate, as in the case of the soil discharge port in Patent Document 1, the opening area functions as an area for taking in soil into the pile body, but the opening area also becomes an area for loss of tip bearing capacity. In this case, increasing the opening area will facilitate the taking in of soil into the pile, but on the other hand, it will result in a decrease in tip bearing capacity. Conversely, reducing the opening area will prevent the decrease in tip bearing capacity, but the opening will be blocked by soil during construction, making it impossible to take in soil. As such, simply creating an opening in the steel blade makes it difficult to simultaneously facilitate the incorporation of soil into the pile, reducing penetration resistance, and ensuring tip bearing capacity.

[0008] The present invention has been made in light of the above background, and aims to provide a rotary penetration pile that can reliably ensure tip bearing capacity and reduce penetration resistance. [Means for solving the problem]

[0009] (1) The rotary penetration pile according to the present invention has a steel pipe pile body and a steel wing attached horizontally to the lower end of the pile body, The steel wing is a disk-shaped steel plate attached to cover the opening of the pile body, and has an upper blade consisting of an inclined surface bent diagonally upward on a part of the peripheral edge, and a lower blade consisting of an inclined surface bent diagonally downward opposite the upper blade, the upper blade being provided in a range from the outer edge of the steel wing to just near the outer edge of the lower end of the pile body, and the lower blade being provided extending from the outer edge of the steel wing further inward than the pile body, The lower blade extends inward from the pile body to form an opening for taking soil and sand into the pile body.

[0010] (2) In addition, in the above-mentioned (1), a plate-shaped protrusion is provided that passes through the vicinity of the center of the lower surface of the steel wing and extends radially, and the radial length of the protrusion is equal to or greater than the diameter of the pile body, and is fixed to the lower blade by contacting the inner edge of the lower blade perpendicularly; It is characterized by a protrusion that can perform three functions: disturbing soil and sand, stiffening the steel blades, and reinforcing the lower blade.

[0011] (3) Furthermore, in the above-mentioned (1) or (2), a reinforcing member is attached to connect the lower surface of the lower blade to the lower surface of the horizontal surface of the steel blade, and the reinforcing member is used to prevent deformation of the lower blade.

[0012] (4) Furthermore, in any of the above (1) to (3), the lower part of the pile body to which the steel wing is connected is a thickened part made of a steel pipe that is thicker than the pile body above it, and the length of the thickened part is less than the outer diameter of the steel wing. [Effects of the Invention]

[0013] According to the present invention, a steel wing having an upper blade and a lower blade is provided at the lower end of the pile body, and the lower blade is extended inward from the pile body to take in soil and sand into the pile body, forming an opening. This makes it possible to obtain a rotary penetration pile that reduces penetration resistance, has excellent penetration efficiency, and can ensure tip bearing capacity. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view of a rotary penetration pile according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a bottom view of the rotary driving pile of FIG. 1. [Figure 3] FIG. 2 is an explanatory diagram of the shapes of an upper blade and a lower blade. [Figure 4]10A and 10B are explanatory diagrams illustrating the effect of arranging the upper blade and the lower blade opposite each other. [Figure 5] FIG. 10 is an explanatory diagram of another embodiment of the upper blade and the lower blade. [Figure 6] This is a diagram explaining the relationship between the gap B when viewing the steel blades from the vertical direction and the opening width C from the perspective of taking in sediment. [Figure 7] FIG. 4 is an explanatory diagram of the shape of a protrusion. [Figure 8] 10 is an explanatory diagram of the relationship between the inclination angle of the lower blade and the force received from soil and sand. FIG. [Figure 9] This is an explanatory diagram of a method for reinforcing the lower blade (part 1). [Figure 10] This is an explanatory diagram of a method for reinforcing the lower blade (part 2). [Figure 11] FIG. 10 is an explanatory diagram of a thickened portion provided on the pile body. DETAILED DESCRIPTION OF THE INVENTION

[0015] As shown in Figures 1 and 2, the rotary penetration pile 1 according to this embodiment comprises a steel pipe pile body 3, steel wings 5 ​​attached horizontally to the lower end of the pile body 3, and plate-like protrusions 7 that pass near the center of the underside of the steel wings 5 ​​and extend radially. Each component and function will be described in detail below.

[0016] <Steel wing> The steel wing 5 is a single circular steel plate attached to cover the lower end opening of the pile body 3, and has an upper blade 9 on part of the periphery, which consists of an inclined surface bent diagonally upward, and a lower blade 11, which consists of an inclined surface bent diagonally downward opposite the upper blade 9. The upper blade 9 is provided in the range from the outer edge of the steel wing 5 to just near the outer edge of the lower end of the pile body 3, and the lower blade 11 is provided extending from the outer edge of the steel wing 5 inward beyond the pile body 3. The lower blade 11 extends inward beyond the pile body 3 to form an opening 13 for taking soil and sand into the body 3.

[0017] About the lower blade The lower blade 11 has the function of excavating and disturbing unexcavated soil below the steel blade 5 when the rotary penetration pile 1 is rotated and penetrated. Furthermore, when the rotary penetration pile 1 is rotated in the forward direction (the direction in which the rotary penetration pile 1 penetrates downward), the soil and sand hit the inclined portion of the lower blade 11 facing diagonally downward, generating a component force that pushes the lower blade 11 downward, and thus generating a force that propels the rotary penetration pile 1 downward.

[0018] However, according to the inventors' experience, the downward propulsive force acting on the lower blade 11 alone is not enough to rotate and penetrate the pile body, so the pile body spins freely and does not penetrate downward. To compensate for this lack of propulsive force, the upper blade 9 is provided.

[0019] About the upper blade The soil excavated by the lower blade 11 moves to the upper surface of the steel blade 5 and strikes the upper surface of the inclined upper blade 9 as the pile body rotates. At this time, the struck soil generates a force that propels the pile body downward, just as in the case of the lower blade 11 described above.

[0020] <About the shape of the upper and lower blades> Examples of the shapes of the upper blade 9 and the lower blade 11 are shown in Fig. 3. In Fig. 3(a), both the upper blade 9 and the lower blade 11 are parallel blades in which the bent portions and edges are parallel. 3(b) shows an example in which both the upper blade 9 and the lower blade 11 are fan-shaped blades. Specifically, the bent portions of the upper blade 9 and the lower blade 11 are oblique to the edges. However, the shapes of the upper blade 9 and the lower blade 11 are not limited to this. For example, the upper blade 9 may be a fan-shaped blade and the lower blade 11 a parallel blade, or the upper blade 9 may be a parallel blade and the lower blade 11 a fan-shaped blade.

[0021] <About the arrangement of the upper and lower blades> In this embodiment, the upper blade 9 and the lower blade 11 are provided opposite each other, and the soil excavated by the lower blade 11 rises along the slope of the lower blade 11 and moves to the upper surface side of the steel blade 5. In this case, for example, if the upper blade 9 is not positioned opposite the lower blade 11 (the upper blade 9 is positioned differently from the lower blade 11), as shown in Figure 4(a), the gap between the end face of the steel blade 5 and the lower blade 11 becomes narrower, making it difficult for the soil to move, and the penetration resistance increases.

[0022] In contrast to this, when the upper blade 9 is disposed opposite the lower blade 11, the gap becomes larger as shown in FIG. 4(b), which increases the excavation efficiency and reduces the penetration resistance. In addition, if there is a risk that large-grained soil and sand will clog the opening 13, such as in ground mixed with boulders, a notch can be formed in the steel blade 5 beforehand, and then the lower blade 11 and upper blade 9 can be formed, as shown in Figure 5.

[0023] About the opening If the tip of the pile is completely blocked, all the soil and sand below the pile body 3 must be pushed out to the side of the pile body 3 when the pile is penetrated, resulting in a large penetration resistance. In this regard, in the present invention, the opening 13 is formed by extending the lower blade 11 to the inside of the pile body 3. As a result, some of the earth and sand excavated by the lower blade 11 moves along the slope of the lower blade 11 and is taken into the pile body 3 through the opening 13. As a result, the penetration resistance during construction is reduced.

[0024] By providing the openings 13 in the steel blades 5 in this way, it is possible to reduce the penetration resistance. On the other hand, the presence of the openings 13 may reduce the tip support force. When the underside of the steel wing 5 is viewed from below in the direction of the pile axis, i.e., when the underside of the steel wing 5 is viewed vertically upward when the pile is upright, the larger the area of ​​the defect, the stronger the tendency for the tip bearing capacity to decrease. For example, when an opening is simply provided in the steel blade 5, as in the earth discharge port of Patent Document 1, the area of ​​the opening functions as the area for taking in soil and sand into the pile body, but the area of ​​the opening also becomes the area where the tip bearing capacity is lost. Therefore, as stated in the "Problem to be solved by the invention," with the method of simply providing an opening in the steel blade 5, it is difficult to achieve both smooth taking in of soil and sand into the pile and ensuring tip bearing capacity.

[0025] In this regard, in this embodiment, the steel blade 5 is cut out radially and bent diagonally downward to form the lower blade 11, thereby forming an opening 13, which achieves both smooth intake of soil and sand into the pile and ensuring tip bearing capacity. This point will be explained with reference to FIG. If the length of the lower blade 11 is L, the inclination angle of the lower blade 11 is θ, and the gap when the steel blade 5 is viewed vertically is B, then B = L(1-cosθ). In other words, the opening width C from the perspective of sediment intake is relatively large as shown in Figure 6, but the gap B from the perspective of tip bearing capacity is small.

[0026] <Plate-shaped protrusion> The plate-shaped protrusion 7 is provided so as to pass near the center of the underside of the blade and extend radially. Since the lower blade 11 alone may not be able to sufficiently excavate and disturb the soil near the center of the steel blade 5, by providing the protrusion 7 near the center of the underside of the steel blade 5, the soil near the center of the steel blade 5 can be excavated and disturbed. However, if the excavation and disturbance functions of the lower blade 11 are sufficient, the projections 7 are not essential.

[0027] Furthermore, since the lower blade 11 and the upper blade 9 are provided on a part of the steel blade 5, the rigidity and strength of the steel blade 5 are reduced compared to a simple disk. For this reason, it is desirable that the projections 7 be sized and positioned so as to also reinforce the steel wings 5. Therefore, the radial length of the projections 7 is made equal to or greater than the diameter of the pile body 3, thereby increasing the rigidity and strength of the steel wings 5. In this embodiment, the protrusions 7 are fixed to the lower blade 11 in contact with the inner edge of the lower blade 11 at right angles, thereby preventing the lower blade 11 from falling over. In this way, the projections 7 of this embodiment can perform three functions: disturbing soil and sand, stiffening the steel blades 5, and reinforcing the lower blades 11. The shape and material of the protrusions 7 are not particularly limited, but for example, as shown in FIG. 7, it is preferable to use a steel plate having a trapezoidal or triangular shape.

[0028] <Regarding bedknife reinforcement> In order to improve the excavation efficiency of the lower blade 11, it is effective not only to increase the area of ​​the lower blade 11 but also to increase the inclination angle. FIG. 8 shows a schematic diagram of the force that the lower blade 11 receives from the earth and sand depending on the inclination angle of the lower blade 11. In tests conducted by the inventors, the penetration efficiency increased when the inclination angle (angle from horizontal) was set to 30° to 45°. On the other hand, if the inclination angle was set to this large, a large bending moment would be generated at the base of the lower blade 11 when penetrating hard ground, causing it to bend at the bent part and preventing it from functioning as a lower blade 11. To prevent this, the bending strength (thickness and material) of the lower blade 11 could be increased, but this would increase costs. Therefore, in this embodiment, as shown in Figures 9 and 10, a reinforcing member 15 for preventing deformation is attached to the underside of the lower blade 11. Figure 9 shows an example in which a rectangular steel plate is attached so as to straddle the bent portion of the lower blade 11. Figure 10 shows an example in which a triangular steel plate, with an apex angle equal to the bending angle of the lower blade 11, is attached so as to straddle the bent portion of the lower blade 11 and to follow the horizontal plane of the lower blade 11 and steel blade 5.

[0029] <Thickened section> When a vertical load such as a building is applied to the pile, an upward reaction force from the ground acts on the steel wing 5, resulting in a bending moment on the wing. This bending moment is transmitted to the pile body 3, and bending stress as well as axial compressive stress are generated in the pile body 3 near the base. This bending stress can be countered by providing a thickened section 17 at the bottom of the pile body 3, as shown in Figure 11. Because the bending stress gradually decreases upward, the thickened section 17 only needs to be as long as the diameter of the steel wing 5. [Explanation of symbols]

[0030] 1 Rotary penetration pile 3 Pile body 5 steel wings 7 protrusions 9 Upper blade 11 Lower blade 13 Opening 15 Reinforcement member 17 Thickened section

Claims

1. A rotary penetration pile having a steel pipe pile body and a steel wing attached horizontally to the lower end of the pile body, The steel wing is a disk-shaped steel plate attached to cover the opening of the pile body, and has an upper blade consisting of an inclined surface bent diagonally upward on a part of the peripheral edge, and a lower blade consisting of an inclined surface bent diagonally downward opposite the upper blade, the upper blade being provided in a range from the outer edge of the steel wing to just near the outer edge of the lower end of the pile body, and the lower blade being provided extending from the outer edge of the steel wing further inward than the pile body, A rotary penetration pile characterized in that the lower blade extends inward beyond the pile body, thereby forming an opening for taking soil and sand into the pile body.

2. A plate-shaped protrusion extends radially through the center of the lower surface of the steel wing, and the radial length of the protrusion is equal to or greater than the diameter of the pile body. The protrusion is fixed to the lower blade by contacting the inner edge of the lower blade perpendicularly.

2. The rotary driving pile according to claim 1, characterized in that the protrusions have three functions: disturbing soil and sand, stiffening the steel blades, and reinforcing the lower blade.

3. A rotary penetration pile as described in claim 1 or 2, characterized in that it has a reinforcing member attached to connect the lower surface of the lower blade and the lower surface of the horizontal surface of the steel wing, and the reinforcing member prevents deformation of the lower blade.

4. A rotary penetration pile according to claim 1 or 2, characterized in that the lower part of the pile body to which the steel wing is connected is a thickened section made of a steel pipe that is thicker than the pile body above it, and the length of the thickened section is less than the outer diameter of the steel wing.

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