JP7640860B2 - Steel pipe pile structure and stop plate for steel pipe pile structure - Google Patents

Description

The present invention relates to a steel pipe pile structure and a retaining plate for a steel pipe pile structure.

Conventionally, steel pipe piles are subjected to vertical loads (axial force) and horizontal loads due to earthquakes, wind, etc., and these horizontal loads generate bending moments. Therefore, when designing steel pipe piles, it is necessary to take into account the vertical and horizontal bearing capacity. In particular, for horizontal loads, it is common to adopt methods such as increasing the pile diameter or thickening the plate thickness to deal with the large bending moment that occurs at the top of the pile.

In response to this, a technique for efficiently reinforcing the pile head is known, for example, the CFT structure (concrete filled steel tube structure) shown in Patent Documents 1 and 2, in which the pile head is filled with concrete to increase rigidity.
The steel pipe pile of the CFT structure shown in Patent Document 1 describes providing a retaining plate for holding back concrete at the lowest end of the section to be filled with concrete.

Patent document 2 describes another retaining plate structure in which the base plate member is suspended via a steel bar that is fixed to and suspended from the pile head.

JP 2007-297865 A Japanese Patent Application Publication No. 10-311045

In steel pipe piles with a CFT structure as shown in Patent Document 1 above, in order to install the retaining plate at a specified height, a manufacturing process is required in which retaining claws or steel rings for supporting the retaining plate from below are welded inside the steel pipe. In this case, there is a problem that the manufacturing process and costs increase because the inside of the steel pipe is processed, and there is room for improvement in this regard.

In addition, in the case of the above-mentioned Patent Document 2, there were problems such as the need to combine multiple steel materials as components and the laborious task of installing the fixing brackets.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a steel pipe pile structure and a retaining plate for a steel pipe pile structure that allows a retaining plate for concrete filling to be easily installed inside a steel pipe pile, improves construction efficiency, and reduces construction costs.

To achieve the above-mentioned objective, the steel pipe pile structure of the present invention is characterized by comprising a steel pipe pile having a tapered section that narrows in diameter from the upper end to the lower end, a disk-shaped retaining plate installed inside the tapered section and having an outer diameter smaller than the upper end diameter of the tapered section and larger than the lower end diameter, and concrete filled above the retaining plate inside the steel pipe pile.

According to the present invention, by providing a tapered portion at a position that matches the pouring height of the concrete, a disk-shaped retaining plate with an outer diameter smaller than the upper end diameter of the tapered portion and larger than the lower end diameter can be easily installed on the tapered portion. This makes it possible to provide a retaining plate that functions as a bottom cover for the concrete filled in the steel pipe pile, and eliminates the need for welding members such as steel pipe rings to fix the retaining plate at a predetermined height inside the steel pipe pile, as in the conventional method, thereby reducing the manufacturing process and costs.
Furthermore, in the present invention, even if the pile driving depth deviates from the initial plan, the installation level of the retaining plate can be adjusted on-site by changing the diameter of the retaining plate.

In the steel pipe pile structure of the present invention, it is preferable that the upper end of the tapered portion is located at a distance of 6D or less from the head of the steel pipe pile relative to the head diameter D of the steel pipe pile.

In this case, the tapered portion is located at a distance of 6D or less from the head of the steel pipe pile, where D is the diameter of the head of the steel pipe pile. Therefore, the tapered portion, where the cross section of the steel pipe pile becomes smaller, can be placed at a position where the bending moment acting on the steel pipe pile converges.

In the steel pipe pile structure according to the present invention, a tapered surface that narrows from the upper end to the lower end is formed on the outer periphery of the retaining plate, and it is preferable that the steel pipe pile side taper angle α of the tapered portion of the steel pipe pile and the retaining plate side taper angle β of the tapered surface of the retaining plate satisfy formula (1).

In this case, the stop plate can be placed with the top surface of the outer edge of the stop plate in contact with the inner surface of the pipe in the tapered section, allowing the stop plate to be placed in a stable position and improving the filling of the concrete.

The steel pipe pile structure according to the present invention may also be characterized in that the retaining plate is provided with a guide member that protrudes downward and is supported in a state where it is inserted into the steel pipe below the tapered portion of the steel pipe pile.

With this configuration, the guide member fits into the steel pipe below the tapered portion, stabilizing the position of the stop plate. This allows the stop plate to be placed in a stable position when it is installed, and prevents the stop plate from shifting and causing concrete to leak out downwards when concrete is filled into the steel pipe. This improves construction efficiency and reduces construction costs.

In addition, in the steel pipe pile structure according to the present invention, the guide member, in the portion inserted into the lower steel pipe, may be characterized in that the distance L from the lower end of the tapered portion of the steel pipe pile to the lower end of the guide member when the retaining plate is installed satisfies formula (2), and when the lower end diameter of the tapered portion of the steel pipe pile is D', at least a part of the guide member is present in the region between the imaginary circles of 0.8D' and 0.9D' in the horizontal cross section of the lower steel pipe, and the outer end of the guide member is not located outside the imaginary circle of 0.9D'.

This configuration allows the guide member to be stably fitted into the steel pipe below the tapered portion, stabilizing the position of the stop plate, improving positional stability when the stop plate is installed, and preventing the stop plate from rotating when concrete is poured.

The steel pipe pile structure according to the present invention may also be characterized in that the guide member is located within the range of the distance L that satisfies formula (3).

In this case, the position of the stop plate can be more stabilized, the positional stability of the stop plate when it is installed can be improved, and the rotation of the stop plate when concrete is poured can be suppressed to, for example, less than approximately 6°.

The retaining plate for a steel pipe pile structure according to the present invention is characterized in that it is used in the above-mentioned steel pipe pile structure.

The steel pipe pile structure and the retaining plate for the steel pipe pile structure of the present invention allow the retaining plate for concrete filling to be easily installed inside the steel pipe pile, improving construction efficiency and reducing construction costs.

FIG. 1 is a vertical cross-sectional view showing a steel pipe pile structure according to a first embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view of a main part of the steel pipe pile structure shown in FIG. 1 . FIG. FIG. FIG. 11 is a side view showing an example of a retaining plate having another shape. FIG. 13 illustrates bending moments at depth. FIG. 13 is a diagram showing the relationship between depth and bending moment for each N value. 1A to 1C are diagrams showing a construction method for a steel pipe pile structure. FIG. 11 is a vertical cross-sectional view showing a steel pipe pile structure according to a second embodiment. FIG. 11 is an enlarged longitudinal sectional view of a main part of the steel pipe pile structure according to the second embodiment. FIG. 10 is a side view showing the configuration of a retaining plate according to the second embodiment. FIG. 10 is a horizontal cross-sectional view showing the configuration of a retaining plate according to a second embodiment. 13A and 13B are diagrams for explaining the rotation angle of the retaining plate. FIG. 11 is a side view showing another embodiment of the guide member. FIG. 11 is a side view showing another embodiment of the guide member. FIG. 11 is a side view showing another embodiment of the guide member. FIG. 11 is a side view showing another embodiment of the guide member. FIG. 11 is an enlarged longitudinal sectional view of a main part of the steel pipe pile structure according to the third embodiment. FIG. 13 is a perspective view showing a retaining plate structure according to a first modified example. FIG. 11 is a horizontal cross-sectional view showing a retaining plate structure according to a first modified example. FIG. 11 is a perspective view showing a retaining plate structure according to a second modified example. FIG. 13 is a perspective view showing a retaining plate structure according to a third modified example. FIG. 13 is a horizontal cross-sectional view showing a retaining plate structure according to a third modified example. 13A is a horizontal cross-sectional view of a retaining plate structure according to a fourth modified example, as viewed from below, and FIG. 13B is a retaining plate structure for comparison. 13A and 13B are horizontal cross-sectional views of a retaining plate structure according to a fifth modified example, as viewed from below. 13A and 13B are horizontal cross-sectional views of a retaining plate structure according to a sixth modified example, as viewed from below. 13A and 13B are horizontal cross-sectional views of a retaining plate structure according to a seventh modified example, as viewed from below.

Below, a steel pipe pile structure and a retaining plate for a steel pipe pile structure according to an embodiment of the present invention will be described with reference to the drawings.

First Embodiment
In the steel pipe pile structure 1 according to this embodiment shown in Figures 1 and 2, a steel pipe pile 2 is installed with its pipe axis O facing up and down and filled with concrete 4, and a cover member (a retaining plate 3 described later) is provided in the vertical middle part of the pipe body of the steel pipe pile 2 to hold back the concrete 4.

The steel pipe pile structure 1 includes a steel pipe pile 2 having a tapered section 20 that narrows from the upper end to the lower end, a disk-shaped retaining plate 3 that is installed on the inner pipe surface 20c of the tapered section 20 and has an outer diameter smaller than the upper end diameter D1 and larger than the lower end diameter D2 of the tapered section 20, and concrete 4 that is filled above the retaining plate 3 within the steel pipe pile 2. Note that, if a tapered surface is formed on the outer periphery of the retaining plate 3 as described below, the diameter of the upper surface 3a of the retaining plate 3 is taken as the outer diameter of the retaining plate 3.

The steel pipe pile 2 has, in order from the top, a large diameter section 21, a tapered section 20, and a small diameter section 22. The tapered section 20 is tapered from the lower end of the large diameter section 21 (upper end 20a of the tapered section 20) to the upper end of the small diameter section 22 (lower end 20b of the tapered section 20). The large diameter section 21 is a steel pipe above the tapered section 20. The inner diameter of the large diameter section 21 is the same as the inner diameter of the upper end 20a of the tapered section 20 (upper end diameter D1). The small diameter section 22 is a steel pipe below the tapered section 20. The inner diameter of the small diameter section 22 is the same as the inner diameter of the lower end 20b of the tapered section 20 (lower end diameter D2). The plate thickness of the steel pipe pile 2 is constant over the entire length. That is, the plate thicknesses of the large diameter section 21, the tapered section 20, and the small diameter section 22 are constant.

The height position of the upper end 20a of the tapered portion 20 of the steel pipe pile 2 (the distance from the pile head 2A (upper end of the pile) of the steel pipe pile 2) is set to be 6D or less with respect to the pile head diameter D of the steel pipe pile 2.

As shown in Figures 1 and 2, the retaining plate 3 is placed in the vertical middle of the tapered section 20. The retaining plate 3 has a holding force that holds down the concrete 4 filled in the pipe from below when it is in contact with the pipe inner surface 20c of the tapered section 20. The retaining plate 3 is formed in a plate shape made of a steel plate or a plastic plate. Note that the material of the retaining plate 3 and its shape, such as whether it is hollow or solid, or whether it is flat or curved/uneven, are not important as long as it can ensure stability when installed and the holding force that holds down the concrete from below.

As shown in Figures 3 and 4, the outer periphery of the retaining plate 3 is formed with an inclined surface (tapered surface 3c) that gradually narrows from the upper surface 3a to the lower surface 3b. The steel pipe pile side taper angle α (see Figure 2) of the tapered portion 20 of the steel pipe pile 2 and the retaining plate side taper angle β (see Figures 3 and 4) of the tapered surface 3c of the retaining plate 3 are set to satisfy formula (1).

The stop plate 3A shown in FIG. 5 may have an outer peripheral edge 3d that does not have a tapered surface formed on the outer peripheral edge. In this case, the outer diameters of the upper surface 3a and the lower surface 3b of the stop plate 3A are constant. The outer diameter of the stop plate 3A is set to be smaller than the inner diameter of the large diameter portion 21 (upper end diameter D1 of the tapered portion 20) shown in FIG. 2 and larger than the inner diameter of the small diameter portion 22 (lower end diameter D2 of the tapered portion 20).

In this way, in the construction of the steel pipe pile structure 1, as shown in Figure 2, the steel pipe pile 2 has a tapered section 20 that gradually narrows downward from a large diameter section 21 near the pile head, and a disk-shaped stop plate 3 that is smaller than the inner diameter of the large diameter section 21 (upper end diameter D1 of the tapered section 20) and larger than the inner diameter of the small diameter section 22 (lower end diameter D2 of the tapered section 20) is installed on the pipe inner surface 20c of the tapered section 20, thereby providing a lid member that receives the concrete 4 to be filled.

Here, the position in the height direction where the tapered portion 20 is provided and the tapered shape of the tapered portion 20 will be specifically described.
1, it is known that the bending moment when a horizontal force acts on the pile head 2A is small and converges at a depth of 6D or more from the pile head 2A relative to the pile head diameter D. Therefore, by locating the position of the upper end 20a of the tapered portion 20 within a range of 6D from the pile head 2A, it is possible to fill the concrete 4 at low cost.

The two-dot chain line M shown in FIG. 1 indicates the bending moment acting on the steel pipe pile 2 .
As shown in Fig. 1, the specific position (height) of the tapered portion 20 is preferably such that the portion Ma of the pile head 2A where the bending moment M changes suddenly is located above the upper end of the tapered portion 20. In other words, the tapered portion 20 is set so as to be located at a position where the bending moment M has converged to a certain extent.

Figure 6 shows a comparison of bending moment distribution in a straight pile (solid line M1) and a tapered pile with a tapered section (dotted line M2) in ground G with an N value of 5. The straight pile has a diameter of 300 mm and a steel pipe thickness of 6 mm. The tapered pile has a pile head diameter of 300 mm, a lower pile diameter of 200 mm, a steel pipe thickness of 6 mm, and a tapered shape 1 m to 1.5 m from the pile head. The magnitude of the bending moment M (kN·m) in the pile head area (depth of approximately 0 m to 1 m) is similar for the straight pile (M1) and tapered pile (M2). The bending moment M2 of the tapered pile is smaller than the bending moment M1 of the straight pile because the lower pile diameter (inner diameter of the small diameter section) below the tapered section is smaller.

Figure 7 also shows a comparison of the distribution of bending moments in three types of ground with different N values (N values = 2.5, 5, 10) for tapered piles. The symbols M3, M4, and M5 indicate the bending moments at N values of 2.5, 5, and 10, respectively. The vertical axis shows the bending moment, its absolute value as a ratio to the pile head moment, and the horizontal axis shows the depth (distance y) and the pile head diameter D, expressed as y/D. It can be seen that the bending moment M monotonically decreases and then increases slightly at depths of 4D to 7D relative to the pile head diameter D, but converges to a certain value or less at depths of 3D to 5D.

In addition, the rate of reduction in the section modulus due to diameter reduction is about 0.24 times even when the inner diameter of the small diameter part becomes half of the pile head diameter D, but it can be confirmed that the bending moment M at a depth of 3D to 5D in each area is kept to less than 0.2 times the moment generated at the pile head 2A.
For these reasons, in practice, it is preferable to position the upper end position of the tapered portion 20 of the steel pipe pile 2 3D to 5D from the pile head 2A.

Next, a construction procedure for the steel pipe pile structure 1 using the retaining plate 3 described above will be specifically described with reference to the drawings such as FIG.
As shown in Fig. 8(a) , first, the steel pipe pile 2 is driven into the ground G by pressing (rotary pressing in the case of a blade pile). As a method for driving the steel pipe pile 2, for example, a center trenching method, a pre-boring method, a striking method, a rotary pressing method, etc. can be applied.

Next, as shown in FIG. 8(b), the retaining plate 3 is lowered into the steel pipe pile 2 using a wire 5 such as a wire cable, and the retaining plate 3 is installed on the inner pipe surface 20c of the tapered portion 20 of the steel pipe pile 2 (see FIG. 8(c)).
At this time, the retaining plate 3 is dropped in a suspended state from above the steel pipe pile 2 onto the pipe inner surface 20c of the tapered portion 20. The position at which the retaining plate 3 is dropped is determined so that the lower end surface 4a of the concrete 4 filled in the steel pipe pile 2 becomes the upper surface 3a of the retaining plate 3, as shown in Figures 2 and 8(c).
If bentonite liquid has accumulated inside the driven steel pipe pile 2 before the installation of the retaining plate 3, a weight may be attached to the retaining plate 3 to sink it into the bentonite liquid. Also, the retaining plate 3 may be installed after the bentonite liquid accumulated inside the steel pipe pile 2 is drained before the installation of the retaining plate 3.

Next, as shown in FIG. 8(c), the tapered surface 3c of the stop plate 3 is brought into contact with the pipe inner surface 20c of the tapered portion 20. This allows the frictional force and binding force between the pipe inner surface 20c and the tapered surface 3c of the stop plate 3 to be fully exerted, and the stop plate 3 can form a bottom cover that blocks the concrete 4 to be poured later from below. After that, the bentonite liquid in the steel pipe pile 2 (not shown) is sucked up and discharged using a vacuum, the concrete pipe is inserted into the steel pipe pile 2, and the concrete is poured.

After that, as shown in FIG. 8(c), concrete 4 is poured into the pile head 2A of the steel pipe pile 2 to fill it. Pouring the concrete 4 completes the construction of the tubular structure in which the steel pipe pile 2 is filled with concrete 4. This allows the steel pipe pile 2 filled with concrete 4 to have improved strength as a tubular structure.

Next, the function of the above-mentioned steel pipe pile structure 1 and the retaining plate 3 for the steel pipe pile structure will be described in detail with reference to the drawings.
As shown in Fig. 2, according to this embodiment, by providing the tapered portion 20 of the steel pipe pile 2 at a position corresponding to the pouring height of the concrete 4, it is possible to easily install a disk-shaped retaining plate 3 having an outer diameter smaller than the upper end diameter D1 and larger than the lower end diameter D2 of the tapered portion 20 in the tapered portion 20. Therefore, it is possible to provide the retaining plate 3 that functions as a bottom cover for the concrete 4 filled in the steel pipe pile 2, and since it is not necessary to weld a member such as a steel pipe ring for fixing the retaining plate at a predetermined height inside the steel pipe pile as in the conventional method, it is possible to reduce the manufacturing process and costs.
In addition, in this embodiment, even if the pile driving depth deviates from the initial plan, the installation level of the retaining plate 3 can be adjusted on site by changing the diameter of the retaining plate 3.

In addition, in this embodiment, the tapered portion 20 is positioned at a distance of 6D or less from the pile head 2A of the steel pipe pile 2 relative to the pile head diameter D of the steel pipe pile 2. Therefore, the tapered portion 20, where the cross section of the steel pipe pile 2 becomes smaller, can be positioned at a position where the bending moment acting on the steel pipe pile 2 converges.

In addition, in this embodiment, the steel pipe pile side taper angle α of the tapered portion 20 of the steel pipe pile 2 and the retaining plate side taper angle β of the tapered surface 3c of the retaining plate 3 satisfy the above formula (1), so the retaining plate 3 can be placed with the upper surface side of the outer periphery of the retaining plate 3 in contact with the inner pipe surface of the tapered portion 20. Therefore, the retaining plate 3 can be placed in a stable position, and the filling of the concrete 4 can be improved.

In the steel pipe pile structure 1 and the retaining plate 3 for the steel pipe pile structure according to the present embodiment described above, the tapered portion 20 is provided on the steel pipe pile 2, so that the retaining plate 3 for filling with concrete 4 can be easily installed, improving construction efficiency and reducing construction costs.

Second Embodiment
As shown in Figures 9 and 10, in the steel pipe pile structure 1A of the second embodiment, a cylindrical guide member 31 is provided on the retaining plate 3, which protrudes downward from the lower surface 3b of the retaining plate 3 and is supported in a state inserted inside the steel pipe pile 2 (see Figure 11).

The retaining plate 3 is installed by suspending it using a wire 5 (see Figure 8 (b)) after the steel pipe pile 2 has been driven. At that time, a guide member 31 that acts as a guide is attached to the underside 3b of the retaining plate 3 to prevent the retaining plate 3 from rotating and to ensure stability. As with the retaining plate 3, the guide member 31 may be of any material or have any shape, such as hollow or solid, as long as it can ensure stability when the retaining plate 3 is installed.

In the portion where the guide member 31 is inserted into the small diameter portion 22 (the lower steel pipe), the distance L from the lower end 20b of the tapered portion 20 of the steel pipe pile 2 to the lower end 31a of the guide member 31 when the retaining plate 3 is installed satisfies equation (2).
When the lower end diameter of the tapered portion 20 of the steel pipe pile 2 is D2 (hereinafter, "D'" is used), as shown in Fig. 12, in the horizontal cross section of the small diameter portion 22, at least a part of the guide member 31 is present in an area H between the inner virtual circle K1 of 0.8D' and the outer virtual circle K2 of 0.9D', and the outer end portion 31b of the guide member 31 is set not to be located outside the outer virtual circle K2 of 0.9D'. Furthermore, it is more preferable to set the guide member 31 so as to be located within the range of distance L that satisfies formula (3).
Here, the outer end portion 31b of the guide member 31 is defined as the portion of the guide member 31 located farthest from the central axis of the retaining plate 3 in a plan view seen from the tube axis O direction.

Thus, in this embodiment, the outer end of the guide member has at least one, preferably two or more, and more preferably three or more in the region H between the inner virtual circle K1 of 0.8D' and the outer virtual circle K2 of 0.9D'.

12, a part (outer peripheral portion) of the cylindrical guide member 31 is present in the region H. In this embodiment, the guide member 31 is cylindrical with the central axis C1 of the retaining plate 3 as its cylindrical axis, and the central axis of the guide member 31 coincides with the tube axis O. Therefore, the guide member 31 is evenly disposed in the region H without being misaligned from the center over the entire circumference.
In this way, when the central axis of the guide member 31 coincides with the central axis C1 of the retaining plate 3, the relationship between the distance d from the central axis C1 of the guide member 31 to the outer end portion 31b of the guide member 31 and the inner diameter D' of the small diameter portion 22 can be expressed by equation (4).

In other words, when a cylindrical guide member 31 is used as in the second embodiment, it is possible to suppress the rotation angle θ of the stop plate 3 (see Figures 13(a) and (b)) to approximately 6°.

Here, the reason why the rotation angle θ of the retaining plate 3 is less than 6° will be described.
Fig. 13(a) shows a cross-sectional view of the stop plate 3 when the plate surface is installed in a position perpendicular to the pipe axis O of the steel pipe pile 2. The rotation angle θ at this time is 0°. The distance indicated by the symbol L' in Fig. 13(a) indicates the distance extending in the direction of the central axis C1 of the guide member 31, but as described below, in calculating the maximum value of the rotation angle θ, this is the same as the distance L from the lower end 20b of the tapered portion 20 to the lower end 31a of the guide member 31 (L' = L).

As shown in FIG. 13( b ), a cross-sectional view of the retaining plate 3 rotated about a horizontal axis passing through the pipe axis O of the steel pipe pile 2 is shown.
In this case, rotation stops when the guide member 31 comes into contact with the inner surface 22a of the small diameter portion 22, so the distance x between the guide member 31 and the inner surface 22a rotates by (D'-2d)/2. From the triangle surrounded by the three vertices A, B, and C shown in Figure 13(b), the rotation angle θ can be calculated by tan θ = side BC / side AB. Here, since AB = L', BC ≦ (D'-2d)/2, tan θ is given by the following formula (5).
In this case, if L≧D' and 2d≧0.8D', the rotation angle θ is maximum when 2d=0.8D', the upper end of the guide member 31 is positioned at the position (depth) of the lower end 20b of the tapered portion 20 of the steel pipe pile (L'=L), and the distance from the lower end 20b of the tapered portion 20 to the lower end of the guide member 31 is D'(L=D'), therefore, from equation (6), the rotation angle θ≦5.8°.

Next, the configuration of guide member 31 satisfying the above-mentioned formulas (2) and (4) is shown in Figs. 14 and 15, and the configuration of guide member 31 satisfying the formulas (3) and (4) is shown in Figs. 16 and 17.
The guide member 31A shown in Fig. 14 has a form in which the distance L is greater than 0. This guide member 31A has a small diameter cylindrical portion 310 at an upper portion and a large diameter cylindrical portion 311 at a lower portion. The small diameter cylindrical portion 310 is disposed in the tapered portion 20 of the steel pipe pile 2. The diameter 2d of the small diameter cylindrical portion 310 may be less than 0.8D'. The diameter 2d of the large diameter cylindrical portion 311 is set so that there is a portion that satisfies the above formula (4) at a position deeper than the lower end 20b of the tapered portion 20.

The guide member 31B shown in FIG. 15 has a form in which the distance L is greater than 0. The upper and lower parts of this guide member 31B are large diameter cylindrical parts 312, 313 of the same diameter, and the middle part is a small diameter cylindrical part 314. Furthermore, a part of the upper large diameter cylindrical part 312 and the lower large diameter cylindrical part 313 are located deeper than the lower end 20b of the tapered part 20, and a part of the lower large diameter cylindrical part 313 is in a range of 1D' or more in depth from the lower end 20b of the tapered part 20 of the steel pipe pile. The small diameter cylindrical part 314 is located in a range of less than 1D' in the depth direction from the lower end 20b of the tapered part 20. The diameter 2d of the small diameter cylindrical part 314 may be less than 0.8D'. The diameter 2d of the upper large diameter cylindrical part 312 and the lower large diameter cylindrical part 313 is set so that there is a part that satisfies the above formula (4) at a position deeper than the lower end 20b of the tapered part 20.

The guide member 31C shown in FIG. 16 has a shape in which the distance L is in a range that satisfies the formula (3). The upper and lower parts of this guide member 31C are large diameter cylindrical sections 315, 316 of the same diameter, the middle part is a small diameter cylindrical section 317, and a part of the lower large diameter cylindrical section 316 is disposed in a range of 1D' or more in the depth direction from the bottom end of the tapered section. A part of the small diameter cylindrical section 317 is disposed in the tapered section 20, and the other part is disposed in a range of less than 1D' in the depth direction from the bottom end of the tapered section. The diameter 2d of the small diameter cylindrical section 317 may be less than 0.8D'. The diameter 2d of the lower large diameter cylindrical section 316 is set so that there is a part that satisfies the formula (4) above at a depth of 1D' or more from the bottom end of the tapered section.

The guide member 31D shown in FIG. 17 has a shape in which the distance L is in a range that satisfies formula (3). The upper part of this guide member 31D is a large-diameter cylindrical portion 318, and the lower part is a reduced-diameter portion 319 that is reduced in diameter downward. Furthermore, a part of the reduced-diameter portion 319 at the lower part is disposed in a range of 1D' or more in the depth direction from the lower end of the tapered portion. A part of the large-diameter cylindrical portion 318 is disposed in the tapered portion 20, and another part is disposed in a range of less than 1D' in the depth direction from the lower end of the tapered portion. The diameter 2d of the reduced-diameter portion 319 may be less than 0.8D' in the other parts as long as there is a part that satisfies formula (4) at a depth of 1D' or more from the lower end of the tapered portion. The diameter 2d of the large-diameter cylindrical portion 318 is set to satisfy formula (4) at a depth of 1D' or more from the lower end of the tapered portion.

In addition, in this embodiment, the relationship between the distance L from the bottom end of the tapered portion 20 of the steel pipe pile 2 to the bottom end of the guide member 31 satisfies equations (3) and (4), so the guide member 31 is stably fitted into the small diameter portion 22 from the tapered portion 20, which stabilizes the position of the retaining plate 3 and improves the filling property of the concrete 4.

Furthermore, in this embodiment, the guide member 31 is fitted into the steel pipe below the tapered portion 20, so the position of the stop plate 3 can be stabilized. When the stop plate 3 is installed, the stop plate 3 can be placed in a stable position. In addition, when the concrete 4 is filled into the steel pipe, the stop plate 3 can be prevented from shifting and causing the concrete 4 to leak downward. This makes it possible to further improve construction efficiency and reduce construction costs.

Third Embodiment
Next, there are no limitations on the material or thickness of the retaining plate 3 of the second embodiment shown in Fig. 2 described above, as long as it has the strength to withstand the weight of the concrete 4 and ensures the filling property of the concrete 4. The retaining plate 3B of the third embodiment shown in Fig. 18 is thicker than the retaining plate 3 of the first embodiment described above.

In the third embodiment, by increasing the thickness of the retaining plate 3B, the contact area with the inner pipe surface 20c of the tapered portion 20 of the steel pipe pile 2 can be increased, and adhesion can be improved. This makes it possible to more reliably prevent the concrete 4 filled from above from flowing below the retaining plate 3B.

(First Modification)
Next, a first retaining plate structure 30A according to a first modified example shown in Figure 19 has a configuration in which a rectangular prism-shaped guide member 32 having a rectangular cross-section when viewed from the top and bottom direction is provided below the non-tapered retaining plate 3A of the second embodiment described above.
In the first retaining plate structure 30A, the guide member 32 is inserted into the small diameter portion 22 (see Figure 2) of the steel pipe pile 2, and the four corner portions 32a (outer ends) of the guide member 32 are positioned in close proximity to the inner surface of the small diameter portion 22.

In the case of the first modified example, as shown in FIG. 20, in order for the guide member 32 to exhibit its stability, there are at least three positions (four positions in the first modified example) through which the corner portion 32a of the guide member 32 passes within a range of 0.8 to 0.9 times the inner diameter of the small diameter portion 22 in a horizontal cross section (region H between the inner virtual circle K1 and the outer virtual circle K2).

(Second Modification)
Next, a second retaining plate structure 30B according to a second modified example shown in Fig. 21 is configured to include a guide member 33 having a plurality of long members 33A such as steel bars, long bolts, reinforcing bars, etc., extending downward from the lower surface 3b of the non-tapered retaining plate 3A of the above-mentioned second embodiment. In the second retaining plate structure 30B, the long members 33A of the guide member 33 are inserted into the small diameter portion 22 (see Fig. 2) of the steel pipe pile 2, and the four long members 33A are arranged in close proximity to the inner surface of the small diameter portion 22.

In the case of the second modified example, in order for the guide member 33 to exhibit its stability, there are at least three or more positions (four in the second modified example) through which the multiple long members 33A of the guide member 33 pass within a range of 0.8 to 0.9 times the inner diameter of the small diameter portion (see FIG. 2) (the region indicated by the symbol H surrounded by the dotted line in FIG. 24(a) and (b) described later).

(Third Modification)
Next, a third retaining plate structure 30C according to a third modified example shown in Fig. 22 has a configuration in which a guide member 34 made of an H-shaped steel is provided on the lower surface 3b of the retaining plate 3A without a taper of the second embodiment described above. The material axis direction of the guide member 34 is perpendicular to the lower surface 3b of the retaining plate 3A. In the third retaining plate structure 30C, the guide member 34 is inserted into the small diameter portion 22 (see Fig. 2) of the steel pipe pile 2, and four corners 34a (outer ends) of the guide member 34 are arranged in close proximity to the inner surface of the small diameter portion 22.

In the case of the third modified example, as shown in FIG. 23, in order for the guide member 34 to exhibit its stability, there are at least three positions (four positions in the third modified example) through which the corner portion 34a of the guide member 34 passes within a range of 0.8 to 0.9 times the inner diameter of the small diameter portion (see FIG. 2) (region H between the inner virtual circle K1 and the outer virtual circle K2).

(Fourth Modification)
Next, a fourth retaining plate structure 30D according to a fourth modified example shown in Fig. 24(a) has a configuration in which a guide member 35 in the shape of a triangular prism having a triangular cross section in a plan view from the top and bottom direction is provided below the retaining plate 3A without a taper of the second embodiment described above. In the fourth retaining plate structure 30D, the guide member 35 is inserted into the small diameter portion 22 (see Fig. 2) of the steel pipe pile 2, and three corners 35a (outer ends) of the guide member 35 are arranged in close proximity to the inner surface of the small diameter portion 22.

In the case of the fourth modified example, in order for the guide member 35 to exhibit its stability, there are at least three positions (three positions in the fourth modified example) through which the corner portion 35a of the guide member 35 passes within the region H that is 0.8 to 0.9 times the inner diameter of the small diameter portion 22 (see Figure 2).
In the case of a plate-like guide member 36 having an I-shaped cross section in a plan view viewed from the top and bottom below a non-tapered retaining plate 3A as shown in FIG. 24(b), the end portion 36a of the guide member 36 passes through two positions in the region H that is 0.8 to 0.9 times the inner diameter of the small diameter portion 22 (see FIG. 2), making it difficult to obtain stability as a guide.

Next, a fifth modified example shown in FIGS. 25(a) and 25(b) has a configuration in which the ends of the guide members 41, 42 are not disposed at equal distances from the central axis (the tube axis O) of the retaining plate.
25(a) has an isosceles triangular cross section, and each of the three apexes 41a, 41b, and 41c is present in an area H between an inner imaginary circle K1 of 0.8D' and an outer imaginary circle K2 of 0.9D'. In this case, only the single apex 41a is the outer end portion farthest from the tube axis O when viewed from the tube axis direction.

The guide member 42 in FIG. 25(b) has an equilateral triangular cross section, and each of the three vertices 42a, 42b, and 42c is present in the region H between the inner imaginary circle K1 of 0.8D' and the outer imaginary circle K2 of 0.9D'. In this case, the two vertices 42b and 42c are the outer ends that are farthest from the tube axis O when viewed from the tube axis direction.

Next, a sixth modified example shown in FIGS. 26(a) and 26(b) shows a state in which the central axis C1 (center of gravity) of the guide members 43, 44 and the tube axis O are misaligned.
26(a) has an equilateral triangular cross section, and each of the three apexes 43a, 43b, and 43c exists in an area H between an inner imaginary circle K1 of 0.8D' and an outer imaginary circle K2 of 0.9D'. In this case, the apex 43a among the three apexes 43a, 43b, and 43c is the outer end portion farthest from the tube axis O when viewed from the tube axis direction.

The guide member 44 in FIG. 26(b) has a square cross section, and each of the four vertices 44a, 44b, 44c, and 44d exists in the region H between the inner imaginary circle K1 of 0.8D' and the outer imaginary circle K2 of 0.9D'. In this case, of the four vertices 44a, 44b, 44c, and 44d, the two vertices 44a and 44b are the outer ends that are farthest from the tube axis O when viewed from the tube axis direction.

Next, a seventh modified example shown in FIGS. 27(a) and 27(b) has a configuration in which only a portion of the top of the guide members 45, 46 exists in the region H described above.
27(a) has an equilateral triangular cross section, and only one apex 45a of three apexes 45a, 45b, and 45c exists in an area H between an inner virtual circle K1 of 0.8D' and an outer virtual circle K2 of 0.9D', and the other two apexes 45b and 45c exist inside the inner virtual circle K1. In this case, one apex 45a of the three apexes 45a, 45b, and 45c becomes the outer end portion farthest from the tube axis O when viewed from the tube axis direction.
Even if there is only one outer end in this manner, the presence of that one outer end (apex 45a) in region H has the effect of preventing rotation in a specific direction.

The guide member 46 in FIG. 27(b) has a rectangular cross section, and of the four vertices 46a, 46b, 46c, and 46d, two vertices 46a and 46b are present in the region H between the inner imaginary circle K1 of 0.8D' and the outer imaginary circle K2 of 0.9D', and the other two vertices 46c and 46d are present inside the inner imaginary circle K1. In this case, the two vertices 46a and 46b are the outer ends that are farthest from the tube axis O when viewed from the tube axis direction.

The above describes the embodiments of the steel pipe pile structure and the retaining plate for the steel pipe pile structure according to the present invention, but the present invention is not limited to the above-mentioned embodiments and can be modified as appropriate without departing from the spirit of the invention.

For example, in this embodiment, the upper end 20a of the tapered portion 20 of the steel pipe pile 2 is configured to be located at a distance of 6D or less from the pile head 2A of the steel pipe pile 2 relative to the pile head diameter D of the steel pipe pile 2, but is not limited to this.

In addition, in this embodiment, a tapered surface 3c that narrows from the upper end to the lower end is formed on the outer peripheral edge of the retaining plate 3, and the steel pipe pile side taper angle α of the tapered portion 20 of the steel pipe pile 2 and the retaining plate side taper angle β of the tapered surface 3c of the retaining plate 3 satisfy the above formula (1), but are not limited to this.

The retaining plate 3 is provided with a guide member 31 that protrudes downward and is supported in a state where it is inserted inside the steel pipe pile 2, but it is possible to omit such a guide member 31. In other words, the structure may consist of only the disk-shaped retaining plate 3.

In this embodiment, the guide member 31 is set to satisfy the above formula (2) (formula (3)) and formula (4) in terms of the relationship between the distance d from the center of the stop plate 3 to the outer end 31b of the guide member 31, the inner diameter D' of the lower end of the tapered portion 20 of the steel pipe pile 2, and the distance L from the lower end of the tapered portion of the steel pipe pile 2 to the lower end 31a of the guide member 31 when the stop plate is installed, but this is not limited to this. Furthermore, in this embodiment, the guide member is set to satisfy the above formula (2) and to be in the region H between the inner virtual circle K1 of 0.8D' and the outer virtual circle K2 of 0.9D' in the horizontal cross section of the small diameter portion 22, and the outer end of the guide member is not located outside the outer virtual circle K2 of 0.9D', but this is not limited to this.

The length, number, and shape of the stop plates 3 can be set arbitrarily.

In addition, the thickness of the steel pipe pile 2 does not need to be constant over the entire length in the direction of the pipe axis O, but can be set arbitrarily.

In addition, the components in the above-described embodiments may be replaced with well-known components as appropriate without departing from the spirit of the present invention.

REFERENCE SIGNS LIST 1 Steel pipe pile structure 2 Steel pipe pile 3, 3A, 3B Retaining plate 4 Concrete 20 Tapered portion 20c Pipe inner surface 21 Large diameter portion 22 Small diameter portion 30A to 30E Retaining plate structure 31 Guide member

Claims (7)

A steel pipe pile having a tapered portion whose diameter decreases from the upper end side to the lower end side;
a disk-shaped stopper plate disposed inside the tapered portion and having an outer diameter smaller than an upper end diameter of the tapered portion and larger than a lower end diameter of the tapered portion;
Concrete filled above the retaining plate in the steel pipe pile;
A steel pipe pile structure comprising: The steel pipe pile structure described in claim 1, characterized in that the upper end of the tapered portion is located at a distance of 6D or less from the head of the steel pipe pile relative to the head diameter D of the steel pipe pile. The stop plate has an outer circumferential edge formed with a tapered surface that decreases in diameter from the upper end side to the lower end side,
The steel pipe pile structure according to claim 1 or 2, characterized in that the steel pipe pile side taper angle α of the tapered portion of the steel pipe pile and the retaining plate side taper angle β of the tapered surface of the retaining plate satisfy formula (1).

The steel pipe pile structure according to any one of claims 1 to 3, characterized in that the retaining plate is provided with a guide member that protrudes downward and is supported in a state where it is inserted into the steel pipe below the tapered portion of the steel pipe pile. The guide member satisfies formula (2) at the distance L from the lower end of the tapered portion of the steel pipe pile to the lower end of the guide member at the time of installation of the retaining plate, in the portion inserted into the lower steel pipe,
The steel pipe pile structure described in claim 4, characterized in that when the lower end diameter of the tapered portion of the steel pipe pile is D', in a horizontal cross section of the lower steel pipe, at least a part of the guide member is located in the area between the imaginary circles of 0.8D' and 0.9D', and the outer end of the guide member is not located outside the imaginary circle of 0.9D'.

The steel pipe pile structure according to claim 5, characterized in that the guide member is located within the range of the distance L that satisfies formula (3).

A retaining plate for a steel pipe pile structure, characterized in that it is used in the steel pipe pile structure according to any one of claims 1 to 6.

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