Tool for closing tip of rotational pile and construction method of rotational pile

Abstract

To provide a tool for closing a tip of a rotational pile allowing processes to be simplified by using no casing pipes when constructing a pile in the ground including a polluted layer.SOLUTION: A tool for closing a tip of a rotational pile detachably attached on a rotational pile having a cylindrical part and a spiral-shaped blade part connected on one end surface of the cylindrical part is provided with: a shaft part arranged coaxially with the rotational pile, with a diameter corresponding to a diameter of a hollow part of the blade part; a spiral guide part fixed on an outer peripheral surface of a shaft part at one end part of the shaft and formed in a spiral shape with a pitch corresponding to a spiral pitch of the blade part; and a blade end abutment part projecting from an end part of the spiral guide part to one end part side of the shaft part.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a rotary pile tip closing jig and a rotary pile installation method. [Background technology]

[0002] When constructing steel pipe piles or the like in ground contaminated with specific hazardous substances, a special construction method using a casing pipe is used to prevent the contaminants present in the aquifer near the ground surface from diffusing to the lower layers. For example, Patent Document 1 describes a pile construction method in which a casing pipe with a blocking cap attached to the tip is rotated and pressed into the impermeable layer below the contaminated layer, the blocking cap is removed and a fluidized solidified material is poured into the casing pipe, a prefabricated pile is constructed into the casing pipe with the fluidized solidified material poured in, the pile is driven into the supporting layer, and the casing pipe is then pulled out. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-66634 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using a casing pipe, the casing pipe must be installed separately from the pile and the process of removing the casing pipe is required, which increases the burden on construction. Also, the method described in Patent Document 1 requires a process and equipment for introducing the fluidized solidified material.

[0005] Therefore, an object of the present invention is to provide a rotary pile tip blocking jig and a rotary pile construction method that make it possible to simplify the process by not using a casing pipe when constructing a pile in ground containing a contaminated layer. [Means for solving the problem]

[0006] [1] A rotary pile tip closing jig that can be detachably attached to a rotary pile having a cylindrical portion and a spiral-shaped blade portion joined to one end face of the cylindrical portion, the rotary pile tip closing jig comprising: a shaft portion that is arranged coaxially with the rotary pile and has a diameter corresponding to the diameter of the hollow portion of the blade portion; a spiral guide portion that is fixed to the outer peripheral surface of the shaft portion at one end and is formed in a spiral shape with a pitch corresponding to the spiral pitch of the blade portion; and a blade end abutment portion that protrudes from the end of the spiral guide portion toward the one end side of the shaft portion. [2] A rotary pile tip blocking jig as described in [1], further comprising a return plate portion protruding from the end portion opposite the spiral guide portion of the blade end abutment portion. [3] A rotary pile tip blocking jig as described in [2], wherein the rotation angle of the spiral shape of the blade portion is less than 360°, and the return plate portion has a length less than the distance between the start and end points of the spiral shape of the blade portion. [4] A rotary pile tip blocking jig as described in [1], wherein the outer diameter of the spiral guide portion corresponds to the inner diameter of the cylindrical portion. [5] The rotary pile tip blocking jig described in [1], further comprising a conical reduced diameter portion formed at one end of the shaft portion. [6] A construction method for penetrating a rotary pile into ground in which a contaminated aquifer, an impermeable layer, and a supporting layer are layered in that order from the ground surface, comprising the steps of: attaching a rotary pile tip blocking jig described in any one of [1] to [5] to the rotary pile by arranging a part of the screw guide section along the blade section, arranging an end of the shaft section and an end of the screw guide section outside the tip open section of the rotary pile, and abutting the blade end abutment section against the end of the blade section; rotating the rotary pile to which the rotary pile tip blocking jig is attached into the ground to reach the impermeable layer; releasing the abutment between the blade section of the rotary pile that has reached the impermeable layer and the blade end abutment section of the rotary pile tip blocking jig, and pulling the rotary pile tip blocking jig upward inside the cylindrical section; and further rotating the rotary pile into the ground to remove soil from the impermeable layer through the tip open section. A method for constructing a rotary pile, comprising the steps of: taking the rotary pile into the interior of the cylindrical portion; and reaching the rotary pile to the supporting layer. Effect of the Invention

[0007] According to the above configuration, by using a jig having a shaft portion corresponding to the blade portion of the rotary pile and a spiral guide portion that fits along the blade portion of the rotary pile, it is possible to block the open tip portion of the rotary pile in a simpler manner and to attach and detach the rotary pile. Furthermore, when constructing rotary piles in ground containing a contaminated aquifer, the diffusion of contaminants can be prevented without using a casing pipe, and the pile construction process can be simplified. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a perspective view of a rotary pile to which a rotary pile tip closing jig according to an embodiment of the present invention is attached. [Diagram 2] FIG. 2 is a view seen from the direction II in FIG. [Diagram 3] FIG. 2 is a side view of a rotary pile tip closing jig according to an embodiment of the present invention. [Figure 4] 1 is a diagram illustrating a method of attaching a rotary pile tip blocking jig to a rotary pile according to an embodiment of the present invention. FIG. [Diagram 5] 1 is a diagram illustrating a method of attaching a rotary pile tip blocking jig to a rotary pile according to an embodiment of the present invention. FIG. [Figure 6] FIG. 2 is a perspective view showing a state in which a rotary pile tip closing jig according to an embodiment of the present invention is attached to a rotary pile. [Figure 7] FIG. 2 is a diagram illustrating a method for constructing a rotary pile using a rotary pile tip blocking jig according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment of the present invention will be described in detail below with reference to the attached drawings. The rotary pile tip closing jig of the present invention is a jig that is detachably attached to a rotary pile to be driven into the ground, and closes the tip open part of the rotary pile by being attached. In this specification, closing does not necessarily mean closing without any gaps, and there may be a gap between the rotary pile and the jig.

[0010] First, the configuration of the rotary pile to which the rotary pile tip closing jig of the present invention is attached will be described. Fig. 1 is a perspective view of the rotary pile to which the rotary pile tip closing jig of the embodiment of the present invention is attached. Fig. 2 is a view from the direction II in Fig. 1. The rotary pile 100 has a cylindrical portion 101 formed of a steel pipe and a blade portion 102 joined to the end surface at the tip side of the cylindrical portion 101, and is rotated and driven into the ground using a construction machine. The blade portion 102 has a helical shape coaxial with the rotary pile 100. By matching the amount of penetration per rotation during rotational penetration to the helical pitch of the blade portion 102, the rotary pile 100 can be driven into the ground without disturbing the ground.

[0011] The rotary pile 100 is an open-ended pile, and an open tip portion E is formed at the tip portion. Since it is possible to take in soil and sand from the open tip portion E into the inside of the pile, the resistance at the tip portion during rotary penetration can be reduced. As shown in FIG. 2, a hollow portion 102A is provided at the center of the blade portion 102, and the tip portion of the rotary pile 100 is not blocked. The hollow portion diameter D of the blade portion 102 is smaller than the inner diameter of the cylindrical portion 101, and therefore the inner end portion of the blade portion 102 protrudes inward beyond the inner circumferential surface of the cylindrical portion 101.

[0012] In the illustrated example, the rotation angle A of the spiral shape of the blade portion 102 of this embodiment is less than 360°. Preferably, the rotation angle A of the spiral shape of the blade portion 102 is 340° or less, and between the starting end 102S and the terminal end 102E in the circumferential direction of the blade portion 102, a start-end distance G corresponding to a rotation angle of 20° or more of the blade portion 102 is generated, as shown in Fig. 2. Note that in order to obtain sufficient propulsive force and supporting force by the blade portion 102, the rotation angle A of the spiral shape is preferably 315° or more.

[0013] Next, there will be described the rotary pile tip closing jig 10 which is detachably attached to the above-mentioned rotary pile 100. Fig. 3 is a side view of the rotary pile tip closing jig 10 according to the embodiment of the present invention. As shown in Fig. 3, the jig 10 has a cylindrical shaft portion 11, a screw guide portion 12 fixed to the outer circumferential surface of the shaft portion 11 at one end of the shaft portion 11, and a joint portion 13 provided at the other end of the shaft portion 11. When the jig 10 is attached to the rotary pile 100, the shaft portion 11 is arranged coaxially with the rotary pile 100, and the screw guide portion 12 is arranged inside the cylindrical portion 101 such that the outer diameter of the screw guide portion 12 corresponds to the inner diameter of the cylindrical portion 101. Since the outer diameter of the screw guide portion 12 corresponds to the inner diameter of the cylindrical portion 101, it is possible to suppress rattling of the jig 10 when the jig 10 is attached to the rotary pile 100.

[0014] The shaft 11 is cylindrical, and the diameter of the shaft 11 corresponds to the hollow diameter D (see FIG. 2) of the blade 102 of the rotary pile 100. Here, the "corresponding diameter" means a diameter slightly smaller than the hollow diameter D, taking into consideration the clearance required when the shaft 11 passes through the blade 102.

[0015] A reduced diameter section 14 is formed at one end of the shaft section 11. The reduced diameter section 14 has a conical shape that gradually reduces in diameter. By providing the reduced diameter section 14 at the shaft section 11 of the jig 10, soil can be smoothly diverted away when the rotary pile 100 is penetrated, thereby further reducing the resistance from the ground. In the jig 10 of the present embodiment, the reduced diameter portion 14 is formed at one end of the shaft portion 11, but this is not limited to this. In other examples, the end of the shaft portion 11 may be formed in a hemispherical shape or a flat shape.

[0016] The spiral guide portion 12 is formed in a spiral shape with a pitch corresponding to the spiral pitch of the blade portion 102. The spiral guide portion 12 of this embodiment is formed with a length that wraps around the outer circumference of the shaft portion 11 approximately twice. The length of the spiral guide portion 12 is not particularly limited, but in order to stably close the tip of the rotary pile 100, it is preferable that the spiral guide portion 12 has a length that wraps around the outer circumference of the shaft portion 11 once or more. When the spiral guide portion 12 is formed with a length that wraps around the outer circumference of the shaft portion 11 approximately twice as in the illustrated example, even if soil flows in through the gaps in the spiral guide portion 12, the space between the spirals of the spiral guide portion 12 is blocked with soil, so that further inflow of soil can be prevented. The spiral guide part 12 has a rectangular cross-sectional shape perpendicular to the extending direction of the spiral guide part 12, and its inner surface is joined to the outer circumferential surface of the shaft part 11. The outer surface 12A of the spiral guide part 12 opposite to the inner surface joined to the shaft part 11 is shaped to conform to the inner circumferential surface of the rotary pile 100, and the outer diameter of the spiral guide part 12 corresponds to the inner diameter of the cylindrical part 101. The "corresponding outer diameter" here means an outer diameter that is slightly smaller than the inner diameter of the cylindrical part 101, taking into consideration the clearance when the spiral guide part 12 passes through the cylindrical part 101. The cross-sectional shape of the screw guide portion 12 is not limited to a rectangle as long as the inner surface can be fixed to the outer circumferential surface of the shaft portion 11. In another example, the cross-sectional shape of the screw guide portion 12 may be a circle.

[0017] The end of the spiral guide portion 12 is provided with a blade end abutment portion 15 and a return plate portion 16, and the spiral guide portion 12, the blade end abutment portion 15, and the return plate portion 16 form a recess 18 into which the end 102B of the blade portion 102 (see Figure 1) is inserted when the jig 10 is attached to the rotary pile 100.

[0018] The blade end abutment portion 15 is provided at the end of the screw guide portion 12. The blade end abutment portion 15 is a portion that abuts against the end 102B (see FIG. 1 ) of the blade portion 102 when the jig 10 is attached to the rotary pile 100. The blade end abutment portion 15 protrudes from the end of the screw guide portion 12 toward one end of the shaft portion 11.

[0019] The return plate portion 16 is provided at the end of the blade end abutment portion 15 opposite to the spiral guide portion 12 so as to protrude from the end in the circumferential direction of the shaft portion 11. The length of the return plate portion 16 in the circumferential direction of the shaft portion 11 is less than the distance G (see FIG. 2) between the start and end points of the spiral shape of the blade portion 102 at any radial position of the shaft portion 11 in a state in which the jig 10 is attached to the rotary pile 100. In other words, the return plate portion 16 is formed to a length that allows it to pass between the start and end points of the spiral shape of the blade portion 102 without rotating the jig 10 while lifting it up when removing the jig 10 as described below.

[0020] The joint part 13 is cylindrical, and is a part that is connected to a lifting rod (described later) when the jig 10 is pulled up in the construction of the rotary pile 100. A pair of protrusions 17 that protrude outward from the joint part 13 is provided on the outer circumferential surface of the joint part 13. The protrusions 17 are a part that engages with the tip of the lifting rod when the lifting rod and the joint part 13 are connected.

[0021] Next, a method for attaching the jig 10 to the rotary pile 100 will be described. FIG. 4 is a diagram for explaining a method of attaching the jig 10 to the rotary pile 100, and shows a state in which the jig 10 is inserted into the rotary pile 100 while being rotated. As shown in FIG. 4, when the jig 10 is attached to the rotary pile 100, the end 12B of the screw guide part 12 opposite to the blade end abutment part 15 is inserted into the tip open part E of the rotary pile 100, and then the screw guide part 12 is inserted along the blade part 102 while rotating the jig 10 around the axis. Then, as shown in FIG. 5 and FIG. 6, the jig 10 is inserted until the blade end abutment part 15 abuts against the end 102B of the blade part 102. As a result, a part of the screw guide part 12 is aligned along the blade part 102, one end of the shaft part 11 and the end of the screw guide part 12 on the blade end abutment part 15 side are positioned outside the tip open part E, and the other end 102B of the blade part 102 is inserted into the recess 18 formed by the screw guide part 12, the blade end abutment part 15, and the return plate part 16.

[0022] If the jig 10 is moved from this state to one side in the axial direction (downward in Figure 5), the spiral guide portion 12 comes into contact with the blade portion 102, and if the jig 10 is moved to the other side in the axial direction, the return plate portion 16 comes into contact with the blade portion 102, thereby restricting the movement of the jig 10. As a result of the above, the jig 10 is attached to the rotary pile 100, and the open end E of the rotary pile 100 is closed.

[0023] When removing the jig 10 from the rotary pile 100, the jig 10 is rotated in a direction in which the blade end abutment portion 15 moves away from the end portion 102B of the blade portion 102, thereby releasing the abutment between the blade portion 102 and the blade end abutment portion 15. The jig 10 is rotated to a position where the return plate portion 16 and the blade portion 102 do not overlap when viewed from the axial direction. After rotating the jig 10, the jig 10 is moved inside the cylindrical portion 101 to the other axial side, thereby removing the jig 10 from the rotary pile 100.

[0024] Next, a method for constructing the rotary pile 100, including the steps of attaching and detaching the jig 10 as described above, will be described. 7 is a diagram illustrating a method for constructing a rotary pile using the jig 10. Here, the rotary pile 100 is driven into ground in which a contaminated aquifer G1, an impermeable layer G2, an uncontaminated aquifer G3, and a supporting layer G4 are layered in this order from the ground surface side. The construction method of the rotary pile is a so-called joint pile construction method in which the rotary pile 100 is divided into a plurality of pieces and the piles are joined by welding, etc. In the method described below, the rotary pile 100 is divided into a lower pile 100A, a middle pile 100B, and an upper pile 100C. In the above embodiment, a joint pile is used as a construction method for the rotary pile, but the jig 10 of the present invention is also applicable to a construction method that does not use a joint pile.

[0025] The specific construction procedure for the rotary pile is explained below. First, as shown in FIG. 7(a), the lower pile 100A to which the jig 10 is attached by the above-mentioned jig attachment method is lifted up using a construction machine (not shown). Since the attachment is performed on the ground, the orientation of the rotary pile 100 during attachment does not matter. For example, the jig 10 may be attached in a state in which the lower pile 100A is laid horizontally on the ground, and then the lower pile 100A may be lifted up. By attaching the jig 10, the tip open portion E of the lower pile 100A is blocked by the jig 10. Next, as shown in FIG. 7(b), the lower pile 100A is rotated and penetrated from the ground surface into the ground. In the illustrated example, the lower pile 100A is rotated and penetrated until only the vicinity of the upper end thereof is exposed above the ground surface. When the lower pile 100A is rotated and penetrated, (the resistance force acting from the ground on the jig 10 in the rotational direction is resisted by the blade end abutment portion 15), the resistance force in the vertical direction from the ground is resisted by the contact between the return plate portion 16 and the blade portion 102, and the jig 10 can be maintained in a state where it is attached to the lower pile 100A. Note that there may be cases where the frictional force generated by the blade end abutment portion 15 being pressed against the starting end portion 102S in the rotational direction can resist the resistance force in the vertical direction, in which case the return plate portion 16 does not necessarily have to be formed.

[0026] Next, as shown in Fig. 7(c), the lower end of the middle pile 100B is joined to the upper end of the lower pile 100A, and as shown in Fig. 7(d), the rotary pile 100 is further rotated and penetrated to reach the impermeable layer G2. Since the tip open part E of the rotary pile 100 is blocked by the jig 10 until the rotary pile 100 reaches the impermeable layer G2, even if soil from the contaminated aquifer G1 gets into the gap between the jig 10 and the blade parts 102, the tip open part E of the rotary pile 100 is not entirely blocked by the soil of the contaminated aquifer G1.

[0027] 7(e), a lifting rod R, which is a lifting means, is connected to the joint 13 of the jig 10. Then, the lifting rod R is operated to rotate the jig 10 about its axis, and after the blade portion 102 and the blade end abutment portion 15 are released from contact with each other, the jig 10 is lifted up. This causes the entire tip open portion E of the rotary pile 100 to open.

[0028] Next, as shown in FIG. 7(g), the lower end of the upper pile 100C is joined to the upper end of the middle pile 100B, and then, as shown in FIG. 7(h), the rotary pile 100 is rotated and penetrated until it reaches the supporting layer G4. At this time, the soil of the impermeable layer G2 is taken in from the tip open part E of the rotary pile 100. Since the jig 10 is removed from the rotary pile 100 after the rotary pile 100 reaches the impermeable layer G2, the soil of the impermeable layer G2 is smoothly taken in the inside of the rotary pile 100. The soil of the impermeable layer G2 separates the soil of the contaminated aquifer G1 that has entered through the gap between the jig 10 and the blade part 102 from the uncontaminated aquifer G3, and even if the tip of the rotary pile 100 reaches the uncontaminated aquifer G3, it is possible to prevent contaminants contained in the soil of the contaminated aquifer G1 from being mixed into the uncontaminated aquifer G3. Also, at this time, since the jig 10 has already been removed, it is possible to confirm whether the soil of the impermeable layer G2 has been taken into the rotary pile 100 by monitoring the inside of the pipe of the rotary pile 100 visually from the pile head or with a camera inserted into the pile head.

[0029] According to the embodiment described above, by using the jig 10 having the shaft portion 11 corresponding to the blade portion 102 of the rotary pile 100 and the spiral guide portion 12 along the blade portion 102 of the rotary pile 100, it is possible to block the tip open portion E of the rotary pile 100 in a simpler manner and to attach and detach the rotary pile 100. Furthermore, when constructing the rotary pile 100 in the ground containing the contaminated aquifer G1, the diffusion of contaminants can be prevented without using a casing pipe, and the construction process of the pile can be simplified.

[0030] In the above embodiment, the rotation angle A of the spiral shape of the blade portion 102 is less than 360°, but this is not limited to this. For example, if the blade end abutment portion 15 and the return plate portion 16 are made smaller so that the jig 10 can be rotated and then removed after the abutment between the blade portion 102 and the blade end abutment portion 15 is released, then the rotation angle A of the blade portion 102 can be made 360° or more.

[0031] In the above embodiment, the length of the spiral guide portion 12 is set to a length that wraps around the outer periphery of the shaft portion 11 twice, but this is not limited as long as it can suppress rattling of the jig 10 and prevent soil from flowing in. In other examples, the length of the spiral guide portion 12 may be set to a length that wraps around the outer periphery of the shaft portion 11 once, or may be set to a length that wraps around the outer periphery of the shaft portion 11 three times. The length of the spiral guide portion 12 can be changed depending on the properties of the soil, etc. [Explanation of symbols]

[0032] 10...tool for blocking tip of rotary pile, 11...shaft portion, 12...spiral guide portion, 12A...outer surface, 13...joint portion, 14...reduced diameter portion, 15...blade end abutment portion, 16...return plate portion, 17...protrusion, 18...recess, 100...rotary pile, 101...cylindrical portion, 102...blade portion, 102A...hollow portion, 102S...starting end portion, 102E...terminal end portion, A...rotation angle, D...hollow portion diameter, E...tip open portion, G...distance between start and end points, G1...contaminated aquifer, G2...impermeable layer, G3...non-contaminated aquifer, G4...supporting layer.

Claims

1. A rotary pile tip closing jig that is detachably attached to a rotary pile having a cylindrical portion and a spiral-shaped blade portion joined to one end surface of the cylindrical portion, A shaft portion arranged coaxially with the rotary pile and having a diameter corresponding to the hollow diameter of the blade portion; a spiral guide portion fixed to an outer circumferential surface of the shaft portion at one end thereof and formed in a spiral shape with a pitch corresponding to the spiral pitch of the blade portion; a blade end abutment portion protruding from an end of the spiral guide portion toward one end of the shaft portion; A rotary pile tip blocking jig equipped with:

2. The rotary pile tip closing jig according to claim 1 , further comprising a return plate portion protruding from an end portion of the blade end abutment portion opposite the spiral guide portion.

3. The rotation angle of the spiral shape of the blade portion is less than 360°, The rotary pile tip closing jig according to claim 2 , wherein the return plate portion has a length less than a distance between the start and end points of the spiral shape of the blade portion.

4. 2. The rotary pile tip closing jig according to claim 1, wherein an outer diameter of the spiral guide portion corresponds to an inner diameter of the cylindrical portion.

5. The rotary pile tip closing jig according to claim 1 , further comprising a cone-shaped reduced diameter portion formed on one end of the shaft portion.

6. A construction method in which a rotary pile is inserted into ground in which a contaminated aquifer, an impermeable layer, and a supporting layer are layered in this order from the ground surface side, A step of attaching the rotary pile tip closing jig according to any one of claims 1 to 5 to the rotary pile by arranging a part of the screw guide section along the blade section, arranging the end of the shaft section and the end of the screw guide section outside the tip open section of the rotary pile, and abutting the blade end abutment section against the end of the blade section; A step of rotating and penetrating the rotary pile to which the rotary pile tip blocking jig is attached into the ground to reach the impermeable layer; A step of releasing the contact between the blade portion of the rotary pile that has reached the impermeable layer and the blade end abutment portion of the rotary pile tip closing jig, and pulling the rotary pile tip closing jig upward inside the cylindrical portion; Further, the rotary pile is rotated and inserted into the ground, and the soil of the impermeable layer is taken into the cylindrical portion through the tip opening. reaching the rotary pile to the supporting layer; A method for installing a rotary pile, including:

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