Existing pile removal method

Abstract

To provide a removal method of an existing pile capable of preventing processes from increasing.SOLUTION: A removal method of an existing pile comprises: an edge cutting step of inserting a cylindrical casing 1 having an inner diameter larger than an outer diameter of an existing pile P into a ground G where the existing pile P is buried while supplying self-hardening stable liquid L around the existing pile P to surround the existing pile P with the casing 1; a pulling-out step of pulling out the existing pile P from the ground G by moving a movable claw 4 provided on a lower end part of the casing 1 to position the movable claw 4 below the lower end part of the existing pile P or to align with the lower end part and then moving the casing 1 upward; and an agitation step of placing the casing 1, from which the existing pile P has been removed, again in a hole H left after the existing pile P has been pulled out, supplying additional self-hardening stable liquid L and moving the casing 1 up and down several times to agitate sediment S in the left hole H and the self-hardening stable liquid.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for removing existing piles, which involves removing existing piles buried in the ground by pulling them out and then backfilling the holes formed in the ground by the pulling out. [Background technology]

[0002] One example of a method for removing existing piles is described in Patent Document 1 by the same applicant. This method involves digging a hole surrounding the existing pile while injecting a self-hardening stabilizer (such as a cement-bentonite liquid) from near the tip of a cylindrical casing used to separate the existing pile from the ground. The self-hardening stabilizer fills the hole left behind after the existing pile is extracted. When the tip of the casing reaches at least the bottom of the existing pile, the casing and the existing pile are extracted. The injected self-hardening stabilizer is then injected into the hole, filling it with new self-hardening stabilizer. The existing pile is extracted by hooking it with a wire. Patent Document 2 also describes a method (chucking method) for extracting the existing pile using a casing by hooking the existing pile onto a chuck claw protruding from the inside of the bottom end of the casing.

[0003] Patent Document 1 describes using an auger screw to mix the self-hardening stabilizer mixed with soil and sand that has accumulated below the remaining hole with the newly injected self-hardening stabilizer that has accumulated above it. By mixing in this way, the soil and self-hardening stabilizer inside the remaining hole can be mixed uniformly.

[0004] However, in the configuration described in Patent Document 1, which describes mixing, the casing used to pull out the existing piles must be removed from the construction equipment (such as construction machinery) on which it was installed and the auger screw must be reattached, resulting in an increase in the number of steps. In particular, if the existing piles are long, the casing used for removal will also be long, making it difficult to replace it with an auger screw. As a result, mixing using conventional methods requires a lot of time and money. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-23788 [Patent Document 2] Patent No. 3052135 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a method for removing existing piles that can suppress an increase in the number of processes. [Means for solving the problem]

[0007] The present invention is a method for removing an existing pile, comprising: an edge-cutting step of inserting a cylindrical casing, the inner diameter of which is larger than the outer diameter of the existing pile, into the ground in which the existing pile is buried while supplying self-hardening liquid around the existing pile, and surrounding the existing pile with the casing; an extraction step of moving movable claws provided at the lower end of the casing so that the movable claws are positioned below the lower end of the existing pile or are aligned with the lower end, and then moving the casing upward to extract the existing pile from the ground; and a stirring step of relocating the casing, from which the existing pile has been removed, into the hole remaining after the existing pile has been extracted, supplying additional self-hardening liquid, and moving the casing up and down multiple times to stir the soil and the self-hardening liquid in the remaining hole.

[0008] With this configuration, the casing used in the edge-cutting and extraction processes can be used as is to mix the soil and self-hardening stabilizer in the remaining hole in the mixing process. Therefore, unlike the conventional auger screw, there is no need to change the jig for mixing in the construction equipment.

[0009] The casing may also include a cylindrical main body and stirring blades that protrude radially from the main body and stir the soil and sand with the self-hardening stabilizing liquid as the casing moves up and down during the stirring step.

[0010] According to this configuration, the casing is provided with the stirring blades, so that the soil and sand and the self-hardening stabilizer can be efficiently stirred in the stirring step.

[0011] Furthermore, the movable claws that are in the same state as when they are moved in the pulling-out step can be used as the stirring blades.

[0012] According to this configuration, the movable claws provided on the casing are used as stirring blades, so there is no need to provide a special structure for stirring. [Effects of the Invention]

[0013] The present invention does not require changing jigs for stirring in the construction equipment, which prevents an increase in the number of processes. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing the state before the casing is inserted into the ground (before the edge separation process is performed) in a construction method according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the state in which the casing is inserted into the ground and placed around the existing pile during the edge separation process in the construction method. [Figure 3] (a) is a schematic diagram showing the state in which, prior to the extraction process in the construction method, the movable claws provided at the lower end of the casing are protruding inward and closed, and the movable claws are hooked onto the lower end of the existing pile, and (b) is a schematic diagram showing an enlargement of the circled area in (a). [Figure 4] FIG. 10 is a schematic diagram showing the state in the middle of the extraction process in the construction method, in which the casing is pulled out of the ground and the existing pile is pulled out. [Figure 5]This is a schematic diagram showing the state in which the casing has been pulled out of the ground and the existing pile has been completely pulled out in the pulling-out process of the construction method. [Figure 6] FIG. 1 is a schematic diagram showing a state in which a casing from which an existing pile has been removed is inserted into a remaining hole and the soil and self-hardening stabilizer inside the remaining hole are stirred during the stirring step of the construction method. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below with reference to the drawings, focusing on a method for removing an existing pile P according to one embodiment. The directions in the following description are the directions when the method is carried out.

[0016] The construction method of this embodiment mainly includes a cutting process, a pulling process, and agitation process, which are carried out in the order described. The construction method of this embodiment can be carried out using known construction equipment. The construction equipment is, for example, a pile driver, a crane, or other heavy construction equipment. A cylindrical (specifically, cylindrical) casing 1 is attached to the construction equipment.

[0017] The casing 1 of the construction equipment is capable of vertical movement and axial rotation by receiving driving force from a driving source (engine, motor, hydraulic pump, etc., not shown). The casing 1 has an inner diameter larger than the outer diameter of the existing pile P to be removed. A drilling blade 2 is formed at the lower end of the casing 1, allowing the casing 1 to excavate the ground G by rotating the casing 1. Because each figure is a schematic diagram, the drilling blade 2 is shown formed only on the lower end surface of the casing 1 (main body 11). However, this is not limited to this, and the drilling blade 2 may be formed to extend circumferentially from the casing 1 (main body 11). A liquid supply unit 3 is also provided at the lower end of the casing 1, which supplies the self-hardening stabilizer L to the outside of the casing 1. A piping (not shown) for supplying the self-hardening stabilizer L is connected to the liquid supply unit 3, and this piping is connected to aboveground equipment (tanks, pumps, etc., constituting the plant for supplying the self-hardening stabilizer L). The self-hardening stabilizer L is a liquid that is mixed with soil and sand S to harden the mixture M, and can be, for example, a mixture of bentonite (clay) and cement milk (a mixture of cement, which is a hardener, and water). The composition of the self-hardening stabilizer L is not limited to this, and liquids with various hardening properties can be used. Also, additives can be added to adjust the properties of the self-hardening stabilizer L.

[0018] In addition, a movable claw 4 is provided at the lower end of the casing 1. The movable claw 4 is provided in the cylindrical main body of the casing 1 so as to be openable and closable so as to protrude and retract into the internal space of the casing 1. In this embodiment, two movable claws 4 are provided radially opposite each other, but the number is not particularly limited. When multiple movable claws 4 are provided, they are preferably provided at fixed axial positions on the main body 11 of the casing 1 and at equal intervals in the circumferential direction. In this embodiment, the movable claw 4 rotates about a rotation axis along the circumferential direction relative to the main body 11 of the casing 1 and is configured to protrude and retract radially relative to the inner circumferential surface of the main body 11 of the casing 1. Note that the protruding and retracting direction of the movable claw 4 is not limited thereto, and the movable claw 4 may be configured to protrude and retract in a direction inclined relative to the radial and circumferential directions. When the movable claw 4 protrudes radially inward (closed state), it can be positioned below the lower end of the existing pile P. The existing pile P can be hooked (caught) by the movable claw 4 in the closed state and pulled upward together with the casing 1. That is, the existing pile P is pulled out from the ground G by pulling up the casing 1 with the construction equipment.

[0019] Next, each step in the construction method of this embodiment will be described. As a preliminary preparation, as shown in Figure 1, the ground G around the existing pile P is excavated using a hydraulic excavator or the like so that the upper end of the existing pile P is exposed from the ground G.

[0020] In the edge separation process, as shown in Figures 1 and 2, the casing 1 is inserted into the ground G in which the existing pile P is buried. The insertion is continued until the bottom end of the casing 1 reaches a position lower than the bottom end of the existing pile P. In this way, the entire lateral periphery of the existing pile P is surrounded by the casing 1. The insertion of the casing 1 is carried out while the self-hardening stabilizing liquid L is sprayed from the liquid supply unit 3 to supply the self-hardening stabilizing liquid L around the existing pile P.

[0021] In the extraction process, the movable claws 4 of the casing 1 are moved to a closed position protruding into the internal space of the casing 1. As shown in FIGS. 3(a) and 3(b), the movable claws 4 are positioned below the lower end of the existing pile P. Then, as shown in FIGS. 4 and 5, the construction device is driven to move the casing 1 upward, thereby extracting the existing pile P from the ground G. In this embodiment, the movable claws 4 are in the most closed position within their movable range. Note that FIGS. 3(a) and 3(b) show a case where the lower end of the existing pile P is flat. If the lower end of the existing pile P is pointed (not shown), part of the pointed portion may be located below the movable claws 4. In other words, in this case, the movable claws 4 are aligned with the lower end of the existing pile P. After the extraction process is completed, a remaining hole H excavated by the casing 1 is formed in the ground G. Furthermore, the bottom of the remaining hole H is filled with self-hardening stabilizer L (mixed with soil and sand S). After the casing 1 is pulled out from the ground G, the movable claws 4 are retracted from the internal space of the casing 1 to open it. This allows the existing pile P to be removed (pulled out) from the casing 1. As much soil S as possible adhering to the casing 1 and the existing pile P is collected and returned to the remaining hole H. This is to harden the mixture M of the soil S and self-hardening stabilizing liquid L under the assumed conditions.

[0022] In the mixing process, as shown in Figure 6, the casing 1 from which the existing pile P has been removed is placed again in the hole H remaining after the existing pile P has been extracted, and additional self-hardening stabilizer L is supplied. The casing 1 is then moved up and down multiple times to mix the fluid soil S located inside (space) of the remaining hole H with the self-hardening stabilizer L (the total amount supplied in the edge-cutting process and the mixing process). Prior to placing the casing 1 in the remaining hole H, the movable claws 4 are returned from the open state to the closed state. This closed state is set to the same opening degree as the closed state in the extraction process. In other words, the movable claws 4 are set to the closed state to the maximum extent within their movable range.

[0023] During the mixing process, the casing 1 is moved up and down three times. Additional self-hardening stabilizer L is supplied during the first movement. The range of the up and down movement can be appropriately set to provide effective mixing force to the soil S and the self-hardening stabilizer L. To ensure reliable mixing, the range is set, for example, so that the lower end of the casing 1 moves back and forth between the top and bottom of the remaining hole H. The time required for the mixing process is not particularly limited, but it can be performed for, for example, three minutes or more. The up and down movement causes the upper and lower surfaces of the movable claws 4 to scrape the mixture M of soil S and the self-hardening stabilizer L, thereby effectively mixing the mixture. The casing 1 is also rotated in conjunction with the up and down movement. By rotating the casing 1, the sides of the movable claws 4 also scrape the mixture M of soil S and the self-hardening stabilizer L, thereby further improving mixing. Rotating the casing 1 also allows the excavation blades 2 to contribute to mixing. Since a space is created in the remaining hole H when the existing pile P is pulled out, an additional volume of self-hardening stabilizer L is supplied that is at least greater than the volume of the existing pile P. This stirring process may be carried out immediately after the pulling out process, or may be carried out after a certain amount of time has passed (preferably within the same day as the pulling out process). If the self-hardening stabilizer L overflows from the remaining hole H during the stirring process and the amount of self-hardening stabilizer L inside the remaining hole H falls short of the planned amount, the self-hardening stabilizer L is supplied as needed to make up for it.

[0024] In the conventional "chucking method" (described in Patent Document 2, for example), excavation is performed around the existing pile while spraying fresh water using a casing similar to that of this embodiment, thereby separating the existing pile from the ground. The existing pile is then caught by the lower end of the casing and pulled up together with the existing pile (while simultaneously injecting self-hardening stabilizer). However, this method has the following problems. Specifically, when pulling up the existing pile, this method involves the muddy water (a mixture of fresh water and soil) between the casing and the existing pile falling into the remaining hole after the existing pile is removed and not completely mixing with the self-hardening stabilizer, resulting in an uneven backfill. Therefore, when a new pile hole is excavated and the previously backfilled area is encountered, the previously backfilled area has a low strength, which can cause the pile hole to collapse and become filled up.

[0025] In contrast, in the construction method of this embodiment, the casing 1 is used to perform edge cutting while supplying self-hardening stabilizer L instead of fresh water from the liquid supply unit 3 provided in the casing 1. Then, after the existing pile P is pulled out, the movable claws 4 are closed and stirring is performed while supplying the self-hardening stabilizer L. By performing edge cutting using the self-hardening stabilizer L instead of fresh water, improved soil containing soil (cement-bentonite improved soil) is produced rather than simple muddy water. Furthermore, after the existing pile P is pulled out, the self-hardening stabilizer L is supplied into the remaining hole H while being thoroughly stirred, thereby ensuring uniform strength within the remaining hole H of the hardened product formed by the mixture M of soil and sand S and the self-hardening stabilizer L.

[0026] As described above, according to this embodiment, the casing 1 used in the edge-cutting process and the extraction process can be used as is to mix the soil S and the self-hardening stabilizer L inside the remaining hole H in the mixing process. Therefore, unlike the auger screw that has been used conventionally, it is not necessary to change the jig for mixing in the construction equipment. This prevents an increase in the number of processes, thereby saving time and costs.

[0027] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0028] For example, the casing 1 may be configured to include a cylindrical main body 11 and agitating blades that protrude radially (inner or outer) from the main body 11 and agitate the soil S and the self-hardening stabilizer L as the casing 1 moves up and down during the agitation process. By providing the agitating blades in the casing 1, the soil S and the self-hardening stabilizer L can be agitated efficiently during the agitation process. The agitating blades may be separate, thin-walled plates (such as blades) or blocks (thick-walled) that can be detachably attached to the main body 11 of the casing 1, or they may be attached so that they can be extended or retracted from the main body 11 of the casing 1. The movable claws 4 in the above embodiment can be said to have the function of catching the existing pile P and also function as the agitating blades. Therefore, in this embodiment, the configuration of the casing 1 used in the "chucking method" can be used as is to perform the agitation function, eliminating the need for a special (separate) configuration for agitation, which is advantageous in terms of cost. Furthermore, with detachable agitating blades, there is a risk that they may fall off from the casing 1, but if the movable claws 4 are used as agitating blades, the possibility of them falling off from the main body 11 of the casing 1 can be reduced.

[0029] In the stirring process, the casing 1 is rotated and moved up and down in the above embodiment, but it can also be moved up and down without rotating. In the above embodiment, the movable claws 4 are closed at their maximum, but stirring may be performed in an intermediate closed state, for example, to adjust the stirring intensity. In the above embodiment, additional self-hardening stabilizer L is supplied during the first reciprocation, but the self-hardening stabilizer L may be supplied during the second reciprocation, or even the third reciprocation and beyond. In the above embodiment, the self-hardening stabilizer L is supplied continuously, but it can also be supplied intermittently. Additional self-hardening stabilizer L may be supplied directly to the remaining hole H without using the liquid supply unit 3 of the casing 1. For example, the liquid supply unit 3 may be configured to eject air, and the air may be ejected in parallel during the stirring process, thereby achieving stronger stirring. [Explanation of symbols]

[0030] 1 casing 2 Digging blade 3 Liquid supply section 4 Movable claws 11 Casing body P Existing pile G Ground H remaining hole L Self-hardening stabilizer S. Soil M mixture

Claims

1. a cutting-edge process in which a cylindrical casing having an inner diameter larger than the outer diameter of the existing pile is inserted into the ground in which the existing pile is buried while supplying a self-hardening stabilizing liquid around the existing pile, and the existing pile is surrounded by the casing; a pulling-out process in which a movable claw provided at the lower end of the casing is moved to position the movable claw below the lower end of the existing pile or to align the movable claw with the lower end, and then the casing is moved upward to pull out the existing pile from the ground; a stirring step of relocating the casing from which the existing piles have been removed into the hole remaining after the existing piles have been pulled out, supplying additional self-hardening liquid, and moving the casing up and down multiple times to stir the soil and the self-hardening liquid inside the remaining hole; A method for removing existing piles.

2. 2. The method for removing existing piles according to claim 1, wherein the casing comprises a cylindrical main body and mixing blades that protrude radially from the main body and mix the soil and the self-hardening stabilizing liquid as the casing moves up and down during the mixing process.

3. The existing pile removal method according to claim 2, wherein the movable claw is used as the stirring blade in the same state as when it was moved in the pulling-out process.

Images