Steel pipe piles, construction methods for steel pipe piles

Abstract

The present invention provides a steel pipe pile and a method for constructing steel pipe piles that can prevent contaminated soil from moving to the lower layers of the impermeable layer and can be constructed without the need to treat the contaminated soil. [Solution] The steel pipe pile 1 according to the present invention is equipped with a rotating blade 5 on the tip surface of the steel pipe 3, A downwardly convex tip surface portion 7 is provided on the lower surface of the rotor blade 5 where the tip surface of the steel pipe 3 is projected. The tip surface portion 7 has its center located at the lowest point and is an inclined surface that slopes diagonally upward from the center.

Description

Technical Field

[0001] The present invention relates to a steel pipe pile suitable for construction in contaminated ground and a construction method thereof.

Background Art

[0002] When driving a pile into soil where a part of the stratum is contaminated, there are cases where it is necessary to punch through an impervious layer existing below the contaminated stratum and drive down to the supporting layer below. In this case, if the ground is excavated to the supporting layer with an auger or the like in the same manner as normal pile driving, there is a risk that the contaminated soil and water will move down to the lower layer of the impervious layer, causing the contamination range to spread.

[0003] Therefore, for example, as disclosed in the pile driving method of Patent Document 1, it is common to press a steel pipe called a casing into the ground while rotating it, excavate the inside of the pipe, discharge the soil to the ground, and then construct a place - driven pile.

[0004] Also, as described in Non - Patent Document 1, there is a method of inserting a casing up to the impervious layer, filling it with a water - blocking material, and then driving a pile.

[0005] The above relates to place - driven piles. However, for example, in the case of a screwed steel pipe pile provided with propulsion wings on the outer periphery of the tip disclosed in Patent Document 2, pile driving without soil discharge is possible.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non - Patent Documents

[0007]

Non - Patent Document 1

[0008] The method disclosed in Patent Document 1 requires the contaminated soil to be discharged onto the surface, which incurs significant costs for its disposal. Furthermore, when the casing is removed, a water channel may form around the pile in the impermeable layer, potentially allowing contamination to spread to the lower layers of the impermeable layer. While it is possible to leave the casing in place to avoid this, it is extremely expensive and not practical.

[0009] In this regard, while the method described in Non-Patent Document 1 allows for the removal of the casing, it still incurs significant costs for the treatment of the contaminated soil, similar to the method described in Patent Document 1.

[0010] In contrast, the screw-type steel pipe pile disclosed in Patent Document 2 does not require soil removal, thus eliminating the need to treat contaminated soil. Furthermore, in cases where the tip of the steel pipe is closed, as in the screw-type steel pipe pile described in Patent Document 2, the soil equivalent to the volume of the pile is pressed against the outside of the steel pipe, resulting in an increased density.

[0011] However, if conventional screw-type steel pipe piles are installed in contaminated ground, there is a risk of the contamination spreading. This point will be explained using diagrams.

[0012] Conventional threaded steel pipe piles 15, as shown in Figure 9, have a rotating blade 5 consisting of two semicircular flat plates attached to the tip of a steel pipe 3, and the tip is closed. When such a threaded steel pipe pile 15 is rotated and driven into the ground, as shown in Figure 10, the soil below the tip of the pile is pushed to the outside of the steel pipe 3, and as the pile penetrates downward, it moves upward relative to the pile.

[0013] However, as shown in Figure 10, the soil 17 that remains below the pile tip surface may move downward along with the pile. Therefore, when such screw-type steel pipe piles 15 are constructed in contaminated ground, as shown in Figure 11, the contaminated soil 19 that has passed through the contaminated layer may be left behind in the permeable layer or move along with the pile to the supporting layer, thereby potentially spreading the contamination.

[0014] This invention was made to solve the aforementioned problems and aims to provide a steel pipe pile and a method for constructing steel pipe piles that can prevent contaminated soil from moving to the lower layer of the impermeable layer and can be constructed without the need to treat the contaminated soil. [Means for solving the problem]

[0015] (1) The steel pipe pile according to the present invention is equipped with a rotating blade on the tip surface of the steel pipe, A downwardly convex tip surface is provided on the lower surface of the rotor blade where the tip surface of the steel pipe is projected. This tip surface has its lowest point in the center and slopes upward from the center.

[0016] (2) In addition, in the case described in (1) above, the lowest end of the tip surface portion does not protrude below the lowest end of the rotor blade.

[0017] (3) Furthermore, the steel pipe pile according to the present invention is equipped with a rotating blade on the circumferential surface of the tip of the steel pipe, The tip surface of the steel pipe is provided with a downwardly convex tip surface portion, the tip surface portion having its central part located at the lowest point and sloping diagonally upward from the central part.

[0018] (4) In addition, in the case described in (3) above, the height of the tip surface is 1 / 3 or less of the diameter of the steel pipe.

[0019] (5) In addition, in any of the above (1) to (4), the inclined surface portion is a smooth curved surface that protrudes outward.

[0020] (6) Further, the construction method of the steel pipe pile according to the present invention is a construction method of a steel pipe pile using the steel pipe pile described in any one of (1) to (4) above, Targeting the ground with a contaminated layer on the upper part, an impervious layer below it, and a supporting layer further below it, the steel pipe pile is rotationally penetrated, and when passing through the impervious layer, the sediment adhering to the pile tip when passing through the contaminated layer is moved upward at the tip surface portion so as not to accompany below the impervious layer.

Advantages of the Invention

[0021] The steel pipe pile of the present invention can prevent contaminated soil from moving to the lower layer of the impervious layer when constructed in contaminated ground, and since it is constructed with completely non-disposal of soil, there is no need to treat contaminated soil. In addition, the soil on the peripheral surface of the steel pipe pile adheres closely to the steel pipe pile due to the influence of being spread, and the water permeability is extremely low, so contamination does not spread from the upper contaminated soil through the peripheral surface of the pile.

Brief Description of the Drawings

[0022] [Figure 1] It is an explanatory view of the steel pipe pile according to Embodiment 1. [Figure 2] It is a view for explaining the tip surface portion by enlarging a part of the steel pipe pile in FIG. 1. [Figure 3] It is a view for explaining the action of the steel pipe pile in FIG. 1. [Figure 4] It is a view for explaining the effect of the steel pipe pile in FIG. 1. [Figure 5] It is an explanatory view of another aspect of the steel pipe pile.​​​​​​​​​​​​​​This diagram illustrates the movement of soil when conventional screw-type steel pipe piles are installed. [Figure 11] This is a diagram illustrating the problems with conventional screw-type steel pipe piles. [Modes for carrying out the invention]

[0023] [Embodiment 1] As shown in Figure 1, the steel pipe pile 1 according to this embodiment is equipped with a rotating blade 5 made of two semicircular flat plates on the tip surface of the steel pipe 3, and a tip surface portion 7 is provided on the lower surface of the rotating blade 5 where the tip surface of the steel pipe 3 is projected. In Figure 1, the same parts as in Figure 9 are denoted by the same reference numerals.

[0024] <Rotorwing> In this example, the rotor blade 5 is constructed by attaching two flat plates to the tip surface of the steel pipe 3 at an angle. The inclination angle θ of the flat plates is preferably between 7° and 15°.

[0025] <Tip section> The tip surface 7 has a convex shape that curves downwards. Furthermore, the tip surface 7 has its lowest point at the center and slopes upwards from the center, forming an inclined surface. The inclined surface is preferably a smooth, curved surface that protrudes outward, as shown in Figure 1, but is not limited to this. For example, the inclined surface may consist of multiple planes, such as the surface shape of a polygonal pyramid.

[0026] Furthermore, the central portion located at the lowest point of the tip surface 7 is not limited to a minimum area such as a curved surface or the vertex of a polygonal pyramid, but may also be a plane with a certain degree of spread. For example, it may be a plane with an area of ​​about 25% of the area of ​​the steel pipe pile 1. Even if there is a flat area in the center of the tip surface 7, if the area of ​​the flat surface is small, the soil will not remain on the flat surface.

[0027] The tip surface portion 7 may be made by cutting a block of steel, or it may be made by processing a plate member by welding, pressing, etc., as long as it has sufficient strength and rigidity to withstand the load-bearing force.

[0028] Since the tip surface portion 7 is provided on the lower surface of the rotor blade 5 where the tip surface of the steel pipe 3 is projected, the portion where the tip surface of the steel pipe 3 is projected will be described. As shown in Figure 1, when a flat plate wing is attached to the tip of the steel pipe 3, the tip surface portion 7 is located on the underside of the flat plate wing. Therefore, the portion onto which the tip surface of the steel pipe 3 is projected in this case is the underside of the flat plate wing, which has the same area as the tip surface of the steel pipe.

[0029] In this embodiment, when the tip surface portion 7 is provided on the lower surface of the rotor blade 5, it is preferable that the lowest end of the tip surface portion 7 does not protrude below the lowest end of the rotor blade 5, as shown in Figure 2. This is because, if the tip surface 7 protrudes significantly downward, the hardness of the ground where the rotor blade 5 is located and the ground where the tip surface 7 is located may differ, which could negatively affect the bearing capacity. In other words, because the lowest end of the tip surface portion 7 does not protrude below the lowest end of the rotor blade 5, it is possible to secure the same level of support as a pile without a tip surface portion 7, even while providing the tip surface portion 7.

[0030] Next, the operation and effects of the steel pipe pile 1 configured as described above will be explained based on Figures 3 and 4. As shown in Figure 3, as the steel pipe pile 1 rotates and penetrates the ground, the soil moves onto the rotor blades 5 and is pushed laterally by the steel pipe 3. At this time, if there is a recess at the tip as shown in Figure 10 above, the soil in that area will not move onto the rotor blade 5, but will be carried downwards as the steel pipe pile 1 penetrates the ground.

[0031] In contrast, the steel pipe pile 1 of this embodiment has a tip surface portion 7, which eliminates the recess at the tip of the pile, so all the soil moves above the rotor blade 5. As a result, contaminated soil is not brought beneath the impermeable layer, and as shown in Figure 4, there is no diffusion of contamination.

[0032] The tip surface portion 7 will take on the bearing force after reaching the support layer, but in this embodiment, the projected shape from the lower surface of the rotor blade 5 is the same as that of a conventional rotor without a tip surface portion 7, and there is no particular change in the bearing force.

[0033] [Embodiment 2] In the second embodiment, as shown in Figure 5, the steel pipe pile 9 has a rotating blade 11 made of two flat plates, each being a donut-shaped flat plate cut in half, which is provided on the circumferential surface of the tip of the steel pipe 3. In this case, the tip surface portion 7 is provided on the tip surface of the steel pipe 3. In this configuration, as shown in Figure 5, the tip surface portion 7 is located below the lowest end of the rotor blade 11. However, as mentioned above, if the amount of protrusion of the tip surface portion 7 is large, it may adversely affect the bearing capacity of the pile. Therefore, in this embodiment, it is desirable that the amount δ of the tip surface portion 7 protruding from the tip of the steel pipe is 1 / 3 or less of the steel pipe diameter D.

[0034] In this second embodiment as well, the same functions and effects as in the first embodiment can be obtained by providing the tip surface portion 7.

[0035] Furthermore, the configuration in which the rotor blade 11 is provided on the circumferential surface of the tip of the steel pipe 3 is not limited to the case where the rotor blade 11 is a flat plate, but may also be a helical blade 13 as shown in Figure 6. Furthermore, in the case of the helical blade 13, it is desirable that the pitch be small, such as 0.2 to 0.5 times the diameter of the steel pipe, as this makes it less likely to carry in contamination. [Examples]

[0036] A scaled-down model of the steel pipe pile 1 described in Embodiment 1 was created, and a penetration test was conducted in a contaminated ground layer artificially created as shown in Figure 4. Photographs of the created model are shown in Figures 7 and 8. The penetration test confirmed that the contaminated soil was not drawn into the permeable layer or the supporting ground, as shown in Figure 4. [Explanation of Symbols]

[0037] 1. Steel pipe pile (Embodiment 1) 3 Steel pipe 5 rotor blades 7 Tip surface section 9. Steel pipe pile (Embodiment 2) 11 Rotary blades 13 spiral wing 15. Screw-in type steel pipe piles Saturday, the 17th 19 Contaminated soil

Claims

1. A steel pipe pile having a rotating blade on the tip surface of the steel pipe, A steel pipe pile is provided with a downwardly convex tip surface portion on the lower surface of the rotor blade where the tip surface of the steel pipe is projected, and the tip surface portion has its lowest point in the center and is an inclined surface that slopes diagonally upward from the center.

2. The steel pipe pile according to claim 1, wherein the lowest end of the tip surface portion does not protrude below the lowest end of the rotor blade.

3. A steel pipe pile having rotating blades on the circumferential surface of the tip of the steel pipe, A steel pipe pile having a downwardly convex tip surface on the tip surface of the steel pipe, wherein the tip surface has its lowest point in the center and slopes diagonally upward from the center.

4. The steel pipe pile according to claim 3, wherein the height of the tip surface is 1 / 3 or less of the diameter of the steel pipe.

5. The steel pipe pile according to any one of claims 1 to 4, wherein the inclined surface portion is a smooth curved surface that protrudes outward.

6. A method for constructing steel pipe piles according to any one of claims 1 to 4, A method for constructing steel pipe piles, targeting ground with a contaminated layer at the top, an impermeable layer below that, and a supporting layer further below that, wherein the steel pipe pile is driven in by rotation, and when it passes through the contaminated layer, the soil attached to the tip of the pile is moved upward at the tip surface when it passes through the impermeable layer, so that it does not adhere below the impermeable layer.

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