JP7811161B2 - Existing pile removal method - Google Patents

Description

This invention relates to a method for removing existing piles by pulling them out from the ground and then backfilling the holes formed in the ground.

One example of a method for removing existing piles is described in Patent Document 1 by the same applicant. This method involves digging around 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 isolate the existing pile from the ground. This liquid 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. Then, new self-hardening stabilizer is injected into the hole, where the injected self-hardening stabilizer has accumulated, to fill the remaining hole. The existing pile is extracted by hooking it with a wire. Patent Document 2 also describes a method (chucking method) in which the existing pile is extracted using a casing by hooking it onto a chuck claw protruding from the inside of the bottom end of the casing.

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 evenly.

However, with the configuration described in Patent Document 1, which deals with mixing, the casing used to pull out the existing piles must be removed from the construction equipment (such as heavy construction machinery) on which it was installed and the auger screw must then 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 with an auger screw. As a result, mixing using conventional methods requires a lot of time and money.

Japanese Patent Application Laid-Open No. 2020-23788 Patent No. 3052135

The present invention aims to provide a method for removing existing piles that minimizes the increase in the number of processes.

This invention is a method for removing existing piles, which includes the following steps: a cutting process in which a cylindrical casing with 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 self-hardening liquid around the existing pile, thereby surrounding the existing pile with the casing; an extraction process in which movable claws attached to the lower end of the casing are moved to position the movable claws below the lower end of the existing pile or to align them with the lower end, and then the casing is moved upward to extract the existing pile from the ground; and a stirring process in which the casing, from which the existing pile has been removed, is re-placed in the hole remaining after the existing pile has been extracted, additional self-hardening liquid is supplied, and the casing is moved up and down multiple times to stir the soil and self-hardening liquid inside the remaining hole.

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 inside the remaining hole during the mixing process. This eliminates the need to change jigs on the construction equipment for mixing, as was the case with conventional auger screws.

The casing may also include a cylindrical main body and stirring blades that protrude radially from the main body and stir the soil and the self-hardening stabilizer liquid as the casing moves up and down during the stirring process.

With this configuration, the casing is equipped with agitating blades, allowing for efficient mixing of the soil and self-hardening stabilizer during the mixing process.

Furthermore, the movable claw, which is in the same state as when it was moved in the pulling-out process, can be used as the stirring blade.

With this configuration, the movable claws on the casing are used as stirring blades, eliminating the need for special stirring components.

The present invention eliminates the need to change jigs for mixing in construction equipment, thereby minimizing the increase in the number of processes.

This 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. 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. (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). 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. 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. 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.

The present invention will be explained below with reference to drawings, focusing on one embodiment of a method for removing existing piles P. The directions in the following explanation refer to the directions when the method is being carried out.

The construction method of this embodiment mainly comprises the edge-cutting process, the extraction process, and the mixing process, which are carried out in the order listed. 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 machinery. A tubular (specifically, cylindrical) casing 1 is attached to the construction equipment.

The casing 1 of the construction equipment is capable of vertical movement and axial rotation under the driving force of 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. The lower end of the casing 1 is formed with a drilling blade 2 that can excavate the ground G by rotating the casing 1. Because each figure is a schematic view, 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 extending circumferentially from the casing 1 (main body 11). The lower end of the casing 1 is provided with a liquid supply unit 3 that dispenses self-hardening stabilizer L to the outside of the casing 1. The liquid supply unit 3 is connected to a pipe (not shown) that supplies the self-hardening stabilizer L, which is connected to aboveground equipment (tanks, pumps, etc. that constitute the plant that supplies the self-hardening stabilizer L). 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. Additives can also be added to adjust the properties of the self-hardening stabilizer L.

Mountable claws 4 are provided at the lower end of the casing 1. The movable claws 4 are provided in the cylindrical main body of the casing 1 so as to be openable and closable, extending and retracting from 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. If 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 circumferential intervals. In this embodiment, the movable claws 4 rotate about a rotation axis that runs circumferentially relative to the main body 11 of the casing 1, and are configured to extend and retract radially relative to the inner circumferential surface of the main body 11 of the casing 1. The direction in which the movable claws 4 extend and retract is not limited to this, and they may be configured to extend and retract in a direction inclined relative to the radial and circumferential directions. When the movable claws 4 protrude radially inward (closed state), they can be positioned below the lower end of the existing pile P. The existing pile P can be hooked (caught) by the movable claws 4 in the closed state and pulled upward together with the casing 1. In other words, the existing pile P is pulled out of the ground G by pulling up the casing 1 with the construction equipment.

Next, each step in the construction method of this embodiment will be explained. As a preliminary step, as shown in Figure 1, the ground G around the existing pile P is excavated using a hydraulic excavator or similar tool so that the top end of the existing pile P is exposed above the ground G.

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 continues until the bottom end of the casing 1 reaches a position lower than the bottom end of the existing pile P. This causes the casing 1 to surround the entire lateral periphery of the existing pile P. The casing 1 is inserted while the self-hardening stabilizer L is sprayed from the liquid supply unit 3 to supply the self-hardening stabilizer L around the existing pile P.

During 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 Figures 3(a) and 3(b), the movable claws 4 are positioned below the lower end of the existing pile P. Then, as shown in Figures 4 and 5, the construction equipment 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 Figures 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 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. Self-hardening stabilizer L (mixed with soil and sand S) accumulates at the bottom of the remaining hole H. After the casing 1 is pulled out of 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 soil S and self-hardening stabilizer L under the intended conditions.

In the mixing process, as shown in Figure 6, the casing 1, from which the existing pile P has been removed, is re-placed in the hole H remaining after the existing pile P has been extracted. Additional self-hardening stabilizer L is supplied, and the casing 1 is 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 (total of the amount supplied in the edge-cutting and mixing processes). 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 the same opening as the closed state in the extraction process. In other words, the movable claws 4 are set to the closedest position within their movable range.

During the mixing process, for example, the casing 1 is moved up and down three times. Additional self-hardening stabilizer L is supplied during the first round trip. The range of vertical movement can be set appropriately to provide effective mixing force to the soil S and self-hardening stabilizer L. To ensure reliable mixing, for example, it is set 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 vertical movement causes the upper and lower surfaces of the movable claws 4 to scrape the mixture M of soil S and self-hardening stabilizer L, thereby achieving effective mixing. The casing 1 is also rotated in conjunction with the vertical movement. By rotating the casing 1, the sides of the movable claws 4 also scrape the mixture M of soil S and self-hardening stabilizer L, further enhancing mixing. Rotating the casing 1 also allows the excavation blades 2 to contribute to mixing. When the existing pile P is pulled out, a space is created in the remaining hole H, so 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 can be carried out immediately after the pulling out process, or 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 inside the remaining hole H is less than the planned amount, self-hardening stabilizer L is supplied as needed to make up for it.

Here, in the conventional "chucking method" (described, for example, in Patent Document 2), 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 had the following problem. Specifically, when pulling up the existing pile, this method involves the muddy water mixed with fresh water and soil between the casing and the existing pile falling into the remaining hole when the existing pile is removed, and not completely mixing with the self-hardening stabilizer, resulting in an uneven backfill. As a result, when a new pile hole is excavated and an area that has previously been backfilled is hit, the strength of that area is weak, so there is a risk that the pile hole will collapse and become filled up.

In contrast, in the construction method of this embodiment, the casing 1 is used to cut the edge while supplying self-hardening stabilizer L instead of fresh water from the liquid supply unit 3 installed in the casing 1. Then, after the existing pile P is extracted, the movable claws 4 are closed and stirring is performed while supplying self-hardening stabilizer L. By using self-hardening stabilizer L instead of fresh water to cut the edge, improved soil containing soil (cement-bentonite improved soil) is produced rather than simple muddy water. Furthermore, after the existing pile P is extracted, supplying self-hardening stabilizer L into the remaining hole H while stirring thoroughly ensures that the hardened mixture M of soil and sand S and self-hardening stabilizer L has uniform strength within the remaining hole H.

As described above, according to this embodiment, the casing 1 used in the edge-cutting and extraction processes can be used as is to mix the soil S and self-hardening stabilizer L inside the remaining hole H in the mixing process. Therefore, unlike the auger screw used in the past, there is no need to change jigs on the construction equipment for mixing. This prevents the number of processes from increasing, thereby saving time and money.

The present invention has been described above using one embodiment, but the present invention is not limited to this embodiment and various modifications are possible without departing from the spirit of the present invention.

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 self-hardening stabilizer L as the casing 1 moves up and down during the agitation process. By including the agitating blades in the casing 1, the soil S and self-hardening stabilizer L can be agitated efficiently during the agitation process. The agitating blades may be separate, detachable plates (thin blades) or blocks (thick blades) that can be 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 both catch the existing pile P and also function as the agitating blades. Therefore, in this embodiment, the casing 1 configuration used in the "chucking method" can be used as is to perform the agitation function, eliminating the need for a special (separate) agitation component, which is advantageous in terms of cost. Furthermore, while detachable agitator blades have the risk of falling off the casing 1, using movable claws 4 as agitator blades reduces the possibility of them falling off the main body 11 of the casing 1.

In the above embodiment, the casing 1 was rotated and moved up and down during the stirring process, but it can also be moved up and down without rotating. In the above embodiment, the movable claws 4 were closed to the maximum extent, but stirring can be performed in an intermediate closed state, for example, to adjust the stirring intensity. In the above embodiment, additional self-hardening stabilizer L was supplied during the first reciprocation, but 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 was supplied continuously, but it can also be supplied intermittently. Additional self-hardening stabilizer L may also 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 by ejecting air in parallel during the stirring process, stronger stirring may be achieved.

1 Casing 2 Excavation blade 3 Liquid supply part 4 Movable claw 11 Casing main body P Existing pile G Ground H Remaining hole L Self-hardening stabilized liquid S Soil and sand M Mixture

Claims (3)

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. The existing pile removal method described in 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. The existing pile removal method described in claim 2, wherein the movable claw, which has been moved in the same state as when it was moved in the extraction process, is used as the mixing blade.