Pile pulling-out method

Abstract

To backfill a pile hole after extraction at low cost when an existing pile is a rotary pile.SOLUTION: A pile pulling-out method includes the steps of: pouring a fluid solidification material F into an inside of a rotary pile 10 having a steel pipe embedded in the ground; and dropping the fluid solidification material F poured into the inside of the rotary pile 10 into a pile hole H through an opening 13 formed at a tip of the rotary pile while pulling-out the rotary pile 10.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for pulling out piles.

Background Art

[0002] For example, in the process of pulling out existing piles carried out when demolishing a structure, after drilling around the existing pile with a casing to cut off the ground from the existing pile and pulling out the existing pile, cement milk, solidifying material slurry, etc. are injected into the pile hole formed by the pulling out, and the hole is filled back while stirring with the surrounding soil. Examples of such techniques are described in, for example, Patent Document 1, Patent Document 2, and Patent Document 3.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] When filling back the pile hole after pulling out by injecting a solidifying material or the like as in the techniques described in the above documents, especially when the pile hole is deep, stirring by a dedicated heavy machine is required for reliable filling of the solidifying material, resulting in an increase in construction cost.

[0005] Therefore, an object of the present invention is to provide a method for pulling out a pile that can fill back the pile hole after pulling out at low cost when the existing pile is a rotary pile.

Means for Solving the Problems

[0006] [1] A step of injecting a fluidized solidifying material into the inside of a rotary pile having a steel pipe buried in the ground, and a step of dropping the fluidized solidifying material injected into the inside of the rotary pile into a pile hole from an opening formed at the tip of the rotary pile while pulling out the rotary pile. A method for pulling out a pile having the above steps. [2] The method for pulling out a pile according to [1], comprising a step of cutting the rotary pile during the pulling out of the rotary pile, and a step of injecting the fluidized solidifying material into the rotary pile after cutting. [3] The method for pulling out a pile according to [1] or [2], further comprising a step of removing the soil inside the pipe of the rotary pile before injecting the fluidized solidifying material. [4] The method for pulling out a pile according to [3], wherein the soil inside the pipe is removed using an auger screw or a hammer club. [5] The method for pulling out a pile according to [1] or [2], wherein when pulling out the rotary pile, the ground is stirred by making the spiral pitch of the blades of the rotary pile different from the amount of movement per rotation of the rotary pile. [Advantages of the Invention]

[0007] According to the present invention, since the fluidized solidifying material is dropped into the pile hole while pulling out the rotary pile, for example, if the soil inside the pipe of the rotary pile is removed in advance, the fluidized solidifying material can be surely supplied to the bottom of the pile hole. Therefore, for example, a step of stirring the fluidized solidifying material injected from the upper end of the pile hole with a dedicated heavy machine becomes unnecessary, and the pile hole after pulling out can be filled back at low cost. [Brief Description of the Drawings]

[0008]

Figure 1

Figure 2

[0009] First, the structure of the rotary pile 10 to be pulled out in the pile pulling method of the present invention will be described. FIG. 1 is a perspective view of the tip portion of the rotary pile 10. The rotary pile 10 is an open-ended pile, and an opening 13 is formed at the tip portion. The rotary pile 10 has a cylindrical portion 11 formed of a steel pipe and blades 12 joined to the end face on the tip side of the cylindrical portion 11, and is rotationally penetrated into the ground by being press-fitted while being rotated forward using a construction machine. The blades 12 have a spiral shape coaxial with the cylindrical portion 11. By adjusting the amount of movement per rotation during rotational penetration to match the spiral pitch of the blades 12, the rotary pile 10 can be penetrated into the ground without disturbing the ground. Since it is possible to take in earth and sand into the pile from the opening 13, the resistance at the tip portion during rotational penetration can be reduced.

[0010] FIG. 2 is a diagram schematically showing a pile pulling method using the rotary pile 10 as shown in FIG. 1. The rotary pile 10 in FIG. 2 is buried in the ground G1, and the cylindrical portion 11 has a length of, for example, 5 m to 70 m. The rotary pile 10 has a pile diameter of, for example, 300 mm to 1600 mm.

[0011] The operator makes a work plan for pulling out the pile based on the length of the rotary pile 10 buried in the ground G1. For example, when the rotary pile 10 is a spliced pile or when the rotary pile 10 is long (for example, 10 m or more), a plan is made to cut the rotary pile 10 during the pulling process without pulling out the rotary pile 10 all at once. In the present embodiment, the rotary pile 10 is cut at the stage where it is pulled out halfway. The number of cuts may be two or more (dividing the rotary pile 10 into three parts), or it may be pulled out without cutting. The cutting length of the rotary pile 10 can be set based on the length that the construction crane can lift, but considering the transportation after pulling out, it is preferably about 10 m.

[0012] Hereinafter, a method for pulling out the rotary pile 10 and filling back the formed pile hole H will be described. As shown in Fig. 2(a), when the head of the rotary pile 10 is underground, heavy machinery such as an excavator is used to excavate the ground around the pile to expose the head of the rotary pile 10.

[0013] Next, after setting the auger screw 20 for removing the soil S inside the pipe of the rotary pile 10 above the rotary pile 10 using a crane or the like, as shown in Fig. 2(b), the auger screw 20 is rotationally inserted into the rotary pile 10. After the tip of the auger screw 20 reaches the tip of the rotary pile 10, as shown in Fig. 2(c), the auger screw 20 is pulled up to remove the soil S inside the pipe of the rotary pile 10. In addition, when the pile diameter of the rotary pile 10 is, for example, 800 mm to 1600 mm, since it is a construction method of gripping the steel pipe using a construction crane which is a full-slewing crane, the soil S inside the pipe of the rotary pile 10 may be removed using a hammer club.

[0014] Next, as shown in Fig. 2(d), the fluidizable solidifying material F (backfilling material) is poured into the rotary pile 10 using the hopper 21. The hopper 21 has a storage part 21A for temporarily storing the fluidizable solidifying material F and a charging part 21B for charging the fluidizable solidifying material F inside the storage part into the rotary pile 10. The fluidizable solidifying material F is a liquid mixture having fluidity and solidifying after a predetermined time has elapsed. Examples of the fluidizable solidifying material F include fluidized treated soil (stabilized soil with a high fluidity obtained by adding a solidifying material to muddy water and kneading), high-fluidity mortar, high-fluidity grout, and the like. The charging amount of the fluidizable solidifying material F is determined based on the work plan. In this embodiment, since the rotary pile 10 is cut at the stage where about half of the total length of the rotary pile is pulled up, the fluidizable solidifying material F is charged so that about half of the total length of the rotary pile 10 is filled.

[0015] Next, as shown in Fig. 2(e), after removing the hopper 21, as shown in Fig. 2(f), the rotary pile 10 is pulled out by rotating the rotary pile 10 in the reverse direction. As the rotary pile 10 moves upward, a space forming the pile hole H is formed below the rotary pile 10, and the fluidizable solidifying material F falls into the pile hole H through the opening 13 of the rotary pile 10. Thereby, the pile hole H is filled with the fluidizable solidifying material F. After a predetermined time has elapsed, as the fluidizable solidifying material F solidifies, the inside of the pile hole H becomes the backfill ground G2. When filling the pile hole H with the fluidizable solidifying material F, it is not always necessary to let the fluidizable solidifying material F fall freely. Instead, the fluidizable solidifying material F may be sucked out from the opening 13 by taking advantage of the fact that the space forming the pile hole H becomes a negative pressure, or the upper part of the rotary pile 10 may be blocked to make the inside a positive pressure, and pressure may be applied to the fluidizable solidifying material F to extrude it from the opening 13 into the pile hole H.

[0016] When pulling out the rotary pile 10, it is more preferable to stir the ground G1 with the blades 12 by making the spiral pitch of the rotary pile 10 and the amount of movement per one rotation of the rotary pile 10 different, and to mix the fluidizable solidifying material F and the ground G1. In the example of Fig. 2, a backfill ground G3 in which the surrounding ground G1 and the fluidizable solidifying material F are mixed by the blades 12 is shown. As methods for making the spiral pitch of the rotary pile 10 and the amount of movement per one rotation of the rotary pile 10 different, there are (1) a method of making the amount of movement smaller than the spiral pitch, (2) a method of making the amount of movement larger than the spiral pitch, (3) a method of only rotating (including normal rotation) without pulling out, and (4) a method of penetrating the rotary pile 10 in the direction opposite to pulling out. These methods may be combined or repeated.

[0017] The pulling out of the rotary pile 10 is performed until the cutting position determined by the work plan is exposed and all of the fluidizable solidifying material F inside the rotary pile 10 flows into the pile hole H. When the cutting position is exposed, as shown in Fig. 2(g), the rotary pile 10 is cut at the cutting position. Note that it is not necessary for all of the fluidizable solidifying material F to flow into the pile hole H, and the fluidizable solidifying material F may remain inside the rotary pile 10. Also, the fluidizable solidifying material F inside the rotary pile 10 may disappear before the cutting position is exposed.

[0018] Next, as shown in Fig. 2(h), after the fluidized solidifying material F is again introduced into the inside of the rotary pile 10 using the hopper 21, the hopper 21 is removed as shown in Fig. 2(i). Next, the rotary pile 10 is pulled out to fill the pile hole H. When pulling out the rotary pile 10, it may be pulled out while stirring the ground G1 by the method described above. After a predetermined time has elapsed, the fluidized solidifying material F solidifies, and as shown in Fig. 2(j), the pile hole H is filled by the backfill ground G2, G3, and the pulling out of the pile is completed.

[0019] According to the above embodiment, since the fluidized solidifying material F is dropped into the pile hole H while pulling out the rotary pile 10, for example, if the soil S in the pipe of the rotary pile 10 is removed in advance, the fluidized solidifying material F can be surely supplied to the bottom of the pile hole H. Therefore, for example, a process of stirring the fluidized solidifying material F introduced from the upper end of the pile hole H with a dedicated heavy machine becomes unnecessary, and the pile hole H after pulling out can be filled at low cost.

[0020] Also, by pulling out the rotary pile 10 while stirring the ground G1, the agitated soil and the fluidized solidifying material F are more likely to be integrated, and the ground strength of the backfill ground G2 after solidification can be ensured.

[0021] In the above embodiment, the pulling out of the rotary pile 10 is started after the completion of the introduction of the fluidized solidifying material F, but the present invention is not limited to this, and the introduction and pulling out of the fluidized solidifying material F may be performed in parallel to shorten the working time.

Explanation of Reference Numerals

[0022] 10... rotary pile, 11... cylindrical part, 12... blade, 13... opening, 20... auger screw, 21... hopper, F... fluidized solidifying material, G1... ground, G2, G3... backfill ground, H... pile hole, S... soil in the pipe.

Claims

1. A step of injecting a fluidized solidifying material into the inside of a rotary pile having a steel pipe buried in the ground; A method for pulling out a pile, comprising a step of dropping the fluidized solidifying material injected into the inside of the rotary pile into a pile hole from an opening formed at the tip of the rotary pile while pulling out the rotary pile.

2. A step of cutting the rotary pile during the pulling out of the rotary pile; The method for pulling out a pile according to claim 1, further comprising a step of injecting the fluidized solidifying material into the rotary pile after cutting.

3. The method for pulling out a pile according to claim 1 or 2, further comprising a step of removing the soil inside the pipe of the rotary pile before injecting the fluidized solidifying material.

4. The method for pulling out a pile according to claim 3, wherein the soil inside the pipe is removed using an auger screw or a hammer club.

5. The method for pulling out a pile according to claim 1 or 2, wherein the ground is agitated by making the spiral pitch of the blades of the rotary pile different from the amount of movement per rotation of the rotary pile when pulling out the rotary pile.

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