Winged pile

Abstract

To provide a winged pile with high performance with less stress concentration.SOLUTION: In a disclosed winged pile 1, a flat plate blade 5 or a pseudo-helical blade with a diameter larger than the diameter of a tube 3 is attached to the tip of the tube 3 in an axially inclined state that is inclined with respect to the central axis of the tube 3 on the tip of the tube 3. Both the inner and outer sides of the tube 3 at the distal end surface of the tube 3 that are in contact with the upper surface of the flat plate blade 5 or the pseudo-helical blade are in contact with the upper surface of the flat plate blade 5 or the pseudo-helical blade over the entire circumference.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a winged pile having flat plate or pseudo-spiral wings attached to the tip surface of a cylindrical pipe at an angle to the central axis of the pipe. In this specification, a pseudo-helical blade refers to a blade formed by cutting a radial line at one point on a circular or doughnut-shaped plate and deforming the circular or doughnut-shaped plate so that the cut point separates in the vertical direction to form a pseudo-helical shape. [Background technology]

[0002] A commonly used construction method for steel pipe piles is to attach tip wings larger than the diameter of the steel pipe to the tip face or near the tip face of the steel pipe, and rotate the pile into the ground. As low-cost tip wings for such winged steel pipe piles, there are pseudo-helical wings (hereinafter referred to as "pseudo-helical wings") made by simply bending a flat plate (see Patent Document 1), and flat plate wings made by combining multiple flat plates and attaching them at a certain inclination to the steel pipe axis (see Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-220738 A [Patent Document 2] Japanese Patent Application Publication No. 9-324419 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a helical impeller, whose blade shape is strictly helical, when viewed in the radial direction from the center of the steel pipe, the helical impeller is perpendicular to the pipe axis over its entire circumference. However, in the case of pseudo-spiral blades and flat blades, the blades are inclined when viewed in the radial direction from the center of the steel pipe. More specifically, when viewed from the center of the steel pipe, the angle between the blade and the outer surface of the steel pipe is an obtuse angle when viewed from the top of the steel pipe in a direction in which the outer periphery of the blade is closer to the pile tip than the steel pipe attachment part, and the angle is an acute angle when viewed from the top of the steel pipe in a direction in which the outer periphery of the blade is closer to the pile head than the steel pipe attachment part.

[0005] This point will be explained with reference to FIG. 6, taking as an example a winged steel pipe pile 11 in which two semicircular flat plate wings 5 ​​are attached to the end of a steel pipe 3. FIG. 6(a) is a side view of the tip of the winged steel pipe pile 11, FIG. 6(b) is a view taken along the line AA of FIG. 6(a), and FIG. 6(c) is a view taken along the line BB of FIG. 6(b).

[0006] As shown in Figure 6(c), when viewed from the center of the steel pipe 3, the angle α between the outer surface of the steel pipe and the flat plate wing 5 in the direction where the outer periphery of the flat plate wing 5 is located toward the pile tip side from the steel pipe attachment part is an obtuse angle, and the angle β between the outer surface of the steel pipe and the flat plate wing 5 in the direction where the outer periphery of the flat plate wing 5 is located toward the pile head side from the steel pipe attachment side is an acute angle.

[0007] The steel pipe 3 is usually cut by first marking the outer periphery of the steel pipe with the inclination of the flat blade 5, and then cutting perpendicular to the steel pipe surface using gas or the like. Therefore, the cut surface becomes a flat surface 13 perpendicular to the outer surface of the steel pipe 3, and when the flat blade 5 is aligned with such a flat surface 13, in most positions only either the outer surface or the inner surface of the steel pipe comes into contact with the flat blade 5, and a gap S is created on the non-contact side (see the enlarged view in Figure 6(c)). Therefore, for example, when joining flat plate blades 5 by welding, if the outer surfaces are in contact, normal fillet welding is possible, but if there is a gap S on the outer surface side, there is a possibility that the weld bead will partially melt into the gap S, making welding defects more likely to occur. In addition, when a compressive load is applied to a pile, the load is transmitted only at the welded parts and the parts in contact, which may result in extremely high local stress (stress concentration). Such problems occur not only when the flat plate wing 5 is joined by welding, but also when it is joined with a structural adhesive.

[0008] The present invention has been made to solve such problems, and has an object to provide a winged pile that is less susceptible to stress concentration and has high performance. [Means for solving the problem]

[0009] (1) The winged pile according to the present invention is a pile having a cylindrical pipe, and a flat plate wing or a pseudo-spiral wing having a diameter larger than the diameter of the pipe is attached to the tip of the pipe in a state inclined in the axial direction relative to the central axis of the pipe, At the tip surface of the tube that abuts against the upper surface of the flat plate blade or the pseudo-spiral blade, both the inner surface side and the outer surface side of the tube are in contact with the upper surface of the flat plate blade or the pseudo-spiral blade over the entire circumference.

[0010] (2) In the configuration described in (1) above, the tip surface is an inclined end surface that is inclined in the axial direction and also in the radial direction. Effect of the Invention

[0011] According to the winged pile of the present invention, both the inner and outer sides of the pipe at the tip surface of the pipe that abuts against the upper surface of the flat wing or pseudo-spiral wing are in contact with the upper surface of the flat wing or pseudo-spiral wing all around, so that stress concentration is less likely to occur at the joint and a high-performance pile can be manufactured. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is an explanatory diagram of a winged pile according to the present embodiment. [Diagram 2] FIG. 2 is an explanatory diagram illustrating steps of a method for manufacturing the winged pile shown in FIG. [Diagram 3] FIG. 1 is an explanatory diagram illustrating a gap that occurs when the tip of a steel pipe is cut perpendicular to the surface of the steel pipe and a flat plate blade is attached. [Figure 4] 1 is a graph showing the relationship between the height of the outer surface and inner surface of the steel pipe that are in contact with the flat plate blades at the tip surface of the steel pipe and the circumferential angle. [Diagram 5]1 is a graph showing the relationship between the gap and the circumferential angle when a flat blade is attached to the tip face of a steel pipe cut perpendicular to the steel pipe surface. [Figure 6] FIG. 1 is an explanatory diagram illustrating the problems that arise when a flat blade is attached to a tip surface of a steel pipe cut perpendicular to the steel pipe surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The winged pile 1 according to this embodiment will be described with reference to Figs. 1 to 5, taking as an example a case where a flat wing 5 is attached to the tip of a steel pipe. In each figure, the same parts as those in Fig. 6 and corresponding parts are given the same reference numerals, and their description will be omitted. Here, in Fig. 1(b), C is marked at a position rotated 90° counterclockwise from B on the right side, and C' is marked at a position rotated 90° counterclockwise from B on the left side. Therefore, the dashed line indicating the vertical center line of the pipe coincides with the line connecting C and C'.

[0014] As shown in FIG. 1, the winged pile 1 of this embodiment comprises a cylindrical steel pipe 3 at the tip of which a flat plate wing 5 having a diameter larger than that of the steel pipe 3 is attached at an axial inclination relative to the central axis of the pipe. Both the inner and outer sides of the tip end surface of the steel pipe 3 that abuts against the upper surface of the flat plate wing 5 are in contact with the upper surface of the flat plate wing 5 over the entire circumference. In addition, in this embodiment, the tip surface is inclined in the axial direction as well as in the radial direction to form an inclined end surface 7, so that when the flat plate wing 5 is joined, both the inner and outer sides of the steel pipe 3 at the tip surface (inclined end surface 7) of the steel pipe 3 contact the upper surface of the flat plate wing 5 around the entire circumference.

[0015] The winged pile 1 of this embodiment as described above can be manufactured by, as an example shown in Figure 2, including an inclined end face forming step (see Figure 2(a)) of forming an inclined end face 7 that is inclined in the axial direction as well as in the radial direction on the tip face of the steel pipe 3 that abuts against the upper face of the flat plate wing 5, and a wing joining step (see Figures 2(b) and (c)) of abutting and joining the upper face of the flat plate wing 5 to the inclined end face 7. Below, the features of the winged pile 1 will be explained by explaining each step in detail.

[0016] <Inclined end face formation step> As described above, the inclined end surface forming step is a step of forming the inclined end surface 7 that is inclined in both the axial direction and the radial direction on the tip surface of the steel pipe 3 that abuts against the upper surface of the flat plate blade 5. The inclined end face forming step forms the inclined end face 7 so that the radial inclination angle changes depending on the circumferential position, so that the upper surface of the flat plate wing 5 abuts against the entire thickness-wise surface of the tip face of the steel pipe 3.

[0017] Here, a method for forming the inclined end surface 7 so that the inclined end surface 7 abuts against the upper surface of the flat plate blade 5 and the entire surface in the plate thickness direction of the tip end surface of the steel pipe 3 will be described. The pitch of the winged pile 1 shown in Figure 1 determines how far the pile penetrates with one rotation, and if the ground is soft, the winged pile 1 penetrates at a rate close to the pitch. Normally, the pitch is 25% to 50% of the pile diameter. Also, the thickness of the steel pipe 3 to which the flat plate wings 5 ​​are attached is generally about 1.5% to 2.0% of the pile diameter.

[0018] As mentioned above, when the tip of the steel pipe 3 to which the flat plate wing 5 is to be attached is cut perpendicular to the surface of the steel pipe and the flat plate wing 5 is aligned with the cut surface (flat surface 13), a gap S will be created between the cut surface and the flat plate wing 5 in most positions (for example, in the case of Figure 1(b) , all positions except for the dotted line connecting C and C'). Figure 3 shows the relationship between pile diameter, pitch, steel pipe thickness, and gap S when two flat plate wings 5 ​​as shown in Figure 1 are attached. Figure 3 shows the gap S (maximum gap) at the part where the flat plate wings 5 ​​abut on the inside in the thickness direction of the tip face of the steel pipe. The gap amounts calculated based on FIG. 3 are shown in Table 1.

[0019] [Table 1]

[0020] As shown in Table 1, the larger the pile diameter, the larger the gap S, and when the pile diameter is 400 mm or more, the gap S is 1 mm or more. As described above, when such a gap S occurs between the flat plate 5 and the tip face of the steel pipe, problems such as the occurrence of welding defects, waste of welding material, and stress concentration occur.

[0021] The reason why such a gap S occurs is that the height of the steel pipe tip surface that contacts the flat plate blade 5 differs between the outer surface and the inner surface of the steel pipe, and this height changes depending on the circumferential angle. FIG. 4 shows an example of a flat plate 5, with an outer diameter D of 400 mm, a plate thickness t of 8 mm, and an inclination angle θ of the flat plate 5 of 7.125016° (when two flat plates form a pseudo-spiral, the pitch / pile diameter is equivalent to 25%). 1 shows how the height of the outer surface and inner surface of the steel pipe in contact with the flat plate 5 changes depending on the angle in the case of In Fig. 4, the horizontal axis indicates the circumferential angle φ (°), which is a linear expansion of the circumferential position of the steel pipe 3. The lowest position of the flat plate blade 5 inclined in the axial direction is taken as 0 (°). The vertical axis indicates the height of the steel pipe tip face, and the position where the height of the steel pipe outer surface and the steel pipe inner surface are the same (the 90° position on the horizontal axis, i.e., the position on the dashed line connecting C and C' in Fig. 1(b)) is taken as 0 (mm).

[0022] As shown in FIG. 4, the height of the outer surface of the steel pipe (solid line) and the height of the inner surface of the steel pipe (dashed line) are not the same, but each changes depending on the circumferential angle. Therefore, when the tip of the steel pipe 3 is cut at a right angle to the surface of the steel pipe, the tip surface of the steel pipe will be at the same height on the outer surface and the inner surface of the steel pipe, resulting in a gap S corresponding to the difference in height between the outer surface and the inner surface of the steel pipe as shown in Figure 4. This gap S changes in the circumferential direction of the steel pipe 3, as shown in Figure 5.

[0023] In order to prevent such a gap S from occurring, the end face of the steel pipe should be made into an inclined end face 7 that connects the solid and broken lines in Fig. 4 in the radial direction, rather than being perpendicular to the outer surface of the steel pipe. By making such an inclined end face 7 at the location where a gap S occurs, the flat plate wing 5 abuts against the end face of the steel pipe over the entire surface from the outer surface side to the inner surface side of the steel pipe at any point in the circumferential direction, and as a result, both the inner and outer surfaces of the steel pipe 3 at the end face of the steel pipe 3 abutting against the upper surface of the flat plate wing 5 contact the upper surface of the flat plate wing 5 over the entire circumference.

[0024] In order to mechanically form the inclined end surface 7 on the tip end surface of the steel pipe, a cutting machine with a blade larger than the diameter of the steel pipe 3 may be used, and the steel pipe 3 may be cut by inclining the blade so as to satisfy the height relationship in Fig. 4. A laser cutting machine may also be used instead of a blade.

[0025] In order to perform gas cutting, it is possible to mechanically adjust the torch angle, but if it is done manually, it is sufficient to draw a line corresponding to the solid line in Figure 4 on the outer surface of the tip of the steel pipe 3, draw a line corresponding to the dashed line in Figure 4 on the inner surface of the tip of the steel pipe, and connect these lines in the thickness direction of the steel pipe 3 before cutting. Alternatively, the two lines shown in Figure 4 may be scored on the inner and outer surfaces of the steel pipe 3, the longer side of the steel pipe 3 may be cut vertically as usual, and the remaining part may then be cut off. By the above-described method, the inclined end surface 7 is formed as shown in FIG. 2(a).

[0026] <Wing joining step> The blade joining step is a step in which the upper surface of the flat plate blade 5 is brought into contact with the inclined end surface 7 (see FIG. 2(b)), and joined by, for example, welding (see FIG. 2(c)). Since the tip end surface 7 of the steel pipe 3 is provided with an inclined end surface 7, the inclined end surface 7 and the flat plate blade 5 can be joined together without any gaps, as shown in Fig. 2(c). In other words, the contact surface between the tip end surface of the steel pipe and the flat plate blade 5 can be welded in close contact from the inner peripheral surface of the steel pipe to the outer peripheral surface of the steel pipe, so there is little possibility of welding defects, and the load is transmitted over the entire contact surface and the welded part, so no stress concentration occurs.

[0027] As described above, in this embodiment, when the flat plate wing 5 is joined to the pipe end, the inclined end face 7 and the flat plate wing 5 can be brought into contact without any gaps, and as a result, both the inner and outer sides of the steel pipe 3 at the tip face of the steel pipe 3 that abuts against the upper surface of the flat plate wing 5 are in contact with the upper surface of the flat plate wing 5 over the entire circumference, resulting in a high-performance steel pipe pile that is less likely to have poor joints or stress concentration and has smooth stress transmission.

[0028] From the viewpoint of manufacturing, when forming the inclined end surface 7 at the tip of the steel pipe 3, lines corresponding to the solid lines and dashed lines in FIG. 4 are drawn on the inner and outer surfaces of the tip of the steel pipe, and these lines are cut so as to connect in the thickness direction of the steel pipe 3, so that the inclined end surface 7 can be formed accurately and simply.

[0029] In the above embodiment, the flat plate wing 5 is used as an example of the wing, but the winged pile 1 of the present invention is not limited to this, and the wing may be a pseudo-helical wing that is not a strictly helical wing. Also, in the above embodiment, the flat plate wing 5, which is almost semicircular and has wings extending around the central axis, is used as an example of the wing, but a flat plate wing that is open around the central axis can also be manufactured in the same manner. Further, in the above description, the blade and the tip end face of the steel pipe are welded together, but they may be bonded together with a structural adhesive. Furthermore, in the above example, the steel pipe 3 is given as an example of the pipe that constitutes the pile, but the material of the pipe is not limited to steel, and it may be other metals or non-metallic materials, such as concrete. [Explanation of symbols]

[0030] 1. Winged pile (embodiment) 3 Steel pipe 5 flat wing 7 Slanted end face 11 Winged steel pipe pile (conventional example) 13 Flat surface S Gap

Claims

[Claim 1] A winged pile in which a flat plate wing having a diameter larger than the diameter of a cylindrical pipe is attached to the tip of the pipe in a state inclined in the axial direction relative to the central axis of the pipe, The tip surface of the pipe that abuts against the upper surface of the flat wing is an inclined end surface that is inclined in the axial direction as well as in the radial direction, and the radial inclination angle changes depending on the circumferential position, resulting in a winged pile that abuts against the upper surface of the flat wing over the entire surface in the plate thickness direction.

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