JP7152899B2 - Extraction method for existing piles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for pulling out an existing pile that consistently performs from pulling out an existing pile buried in the ground to backfilling a construction hole after the pulling out.

BACKGROUND ART Conventionally, when rebuilding a building such as an apartment complex or a building, dismantling and removal of the existing structure and removal of the piles of the structure (hereinafter also referred to as "existing piles") have been performed. Existing piles have been cut off and pulled out from the ground by a pulling device such as a casing that excavates the ground, for example. However, in places where the ground is hard, excavation may take a long time, and excavation may generate vibration and noise.

Therefore, Patent Document 1 discloses a technique for softening the ground and reducing friction between the extraction device and the ground by ejecting water from a jetting nozzle provided near the tip of the extraction device during excavation. . In this method, a self-hardening stabilizing liquid is injected when pulling up existing piles and pulling equipment to reduce the friction between the pulling equipment and the ground.

JP-A-55-85734

However, in the technique disclosed in Patent Document 1, the water spouted out during excavation of the ground dilutes the concentration of the self-hardening stabilizer that is injected during backfilling of the construction hole. In other words, after a few weeks, the self-hardening stabilizer, which was formulated to harden to the desired strength, was diluted by the jetted water, so the strength of the backfilling part of the construction hole decreased, and there was no difference in the strength of the ground. occur. As a result, there is a risk that the backfilling part of the construction hole will collapse when the new pile is buried.

Furthermore, the self-hardening stabilizing liquid used in Patent Document 1 aims at reducing the friction between the side surface of the extraction device and the inner surface of the ground. That is, by injecting the self-hardening stabilizing liquid while pulling up the pulling device, the self-hardening stabilizing liquid intervenes between the side of the pulling device and the inner side of the ground, so that the inner side of the ground directly hits the side of the pulling device. It is intended to avoid the occurrence of friction, and is not used to backfill the construction hole.

As described above, the self-hardening stabilizer not only takes several weeks to develop the desired strength after being injected into the construction hole, but also has the problem that it becomes difficult to develop the desired strength if it is diluted with water or the like. The inventors have arrived at the fact that it should be used not only to soften the ground during excavation but also not to adversely affect the components of the self-hardening stabilizer injected after excavation.

Therefore, the object of the present invention is to improve work efficiency by promoting excavation of the ground when pulling out existing piles, and to reduce the difference between the strength of the ground and the strength of the part where the construction hole is backfilled with the self-hardening stabilizer. To provide a pull-out method for existing piles which is made as small as possible to improve construction quality.

That is, the method for pulling out existing piles according to the present invention is to spray the self-hardening stabilizing liquid that fills the construction hole after pulling out the existing pile in the ground from near the tip of the cylindrical casing, and the existing frame with the casing. When the tip of the casing reaches at least the lower end of the existing frame, the casing and the existing pile are pulled out, respectively, and further into the construction hole where the sprayed self-hardening stabilizing liquid is staying. The construction hole is filled by injecting the new self-hardening stabilizer.

It is desirable to stir the self-hardening stabilizer in the construction hole.

It is desirable that the properties of the self-hardening stabilizer are determined based on the properties of the ground.

According to the existing pile extraction method according to the present invention, the excavation of the ground is promoted during the extraction of the existing pile to improve work efficiency, and the strength of the ground and the strength of the part where the construction hole is backfilled by the self-hardening stabilizer. It is possible to provide an existing pile extraction method that minimizes the difference between the existing pile and improves the construction quality.

1 is a diagram conceptually showing flows (a) to (g) of an existing pile extraction method according to an embodiment of the present invention. FIG.

Hereinafter, referring to FIG. 1, an existing pile extraction method according to an embodiment of the present invention (hereinafter also referred to as "existing pile extraction method") will be described.
It should be noted that in these figures, there are portions where only one portion is numbered for a plurality of identical portions. For convenience of explanation, predetermined parts and their lead lines are indicated by dashed lines or imaginary lines (two-dot chain lines), and some cross-sectional parts are indicated by hatching.

First, the premise of this existing pile extraction method will be explained.

As shown in FIG. 1(a), this existing pile extraction method is carried out when the existing piles S of a demolished housing complex or the like are buried in the ground G. As shown in FIG. The existing pile S corresponds to, for example, a PC pile having a diameter of 0.3 m and a length of 15 m driven into the ground G by a press-fitting method.
Before the construction of this existing pile extraction method, the characteristics of the ground G were changed to the deformation coefficient of the ground, the strength of the soil layer of the ground (N value), and the uniaxial compressive strength of the soil layer (N/mm ² ). can be guided based on Specifically, based on the relationship between the soil layer strength and the soil layer strength derived from the relationship between the ground deformation coefficient and the soil layer strength and the relationship between the ground deformation coefficient and the soil layer uniaxial compressive strength, The uniaxial compressive strength may be calculated with respect to the layer strength (target value).

As shown in FIG. 1(b), the casing 1 is made of metal and has a cylindrical shape with an inner diameter larger than the existing pile 1 in order to cut off the edge of the existing pile 1 from the ground G. Those that move up and down in the direction correspond. A single or a plurality of claws 11 for excavating the ground G are provided at the tip of the casing 1 (lower end at the time of construction of this existing pile extraction method). In the vicinity of the tip of the casing 1, an injection port 12 is provided for injecting the self-hardening stabilizer 2 to fill the construction hole after the existing pile S in the ground G is pulled out.
In addition, the casing 1 may be moved by a crane truck or the like, and is rotated and moved up and down by a motor, an engine, a cylinder, or a drive device that is an appropriate combination of these, which is already installed in the crane truck or prepared separately from the crane truck or the like. You may The casing 1 may have a structure capable of gripping the existing pile S when pulled up. The injection port 12 may be an opening provided in the casing 1 or a nozzle-like one, and may be provided at the tip of the claw portion 11 or between the claw portions 11 .

The self-hardening stabilizer 2 is, for example, a mixture of bentonite (clay) and cement milk (cement and water necessary for solidifying the cement) in order to fill the construction hole after the existing pile S in the ground G is pulled out. ) in a predetermined ratio (also referred to as “cement bentonite improved soil”).
The characteristics of the self-hardening stabilizer 2 may be determined based on the characteristics of the ground G described above. Specifically, the uniaxial compressive strength of the soil layer composed of the self-hardening stabilizing liquid 2 is set in view of the coefficients related to safety and the variation in the strength developed due to the above-mentioned ratio and mixing condition. The strength of the soil layer of the ground G (target value) may be substituted for the relationship between the strength and the unconfined compressive strength.

Next, the construction procedure of this existing pile extraction method will be explained.

First, as shown in FIG. 1(a), the ground G is dug up so that the upper ends of the existing piles S are exposed. Moreover, based on the characteristics of the ground G, the self-hardening stabilizer 2 is mixed in advance.

Next, as shown in FIG. 1(b), the casing 1 surrounds the existing pile S while rotating around the axis of the existing pile S, and excavates the existing pile S from the ground S so as to cut off the edge. The self-hardening stabilizer 2 is injected from the injection port 12 so that the claw portion 11 can easily excavate the ground. When at least the tip of the casing 1 reaches the lower end of the existing pile 1, the excavation of the ground G is completed.
In addition, the amount of the self-hardening stabilizer 2 to be injected may be appropriately controlled according to each soil layer of the ground G.

Then, when the casing 1 is lifted from the ground G as shown in FIG.
In addition, while the casing 1 is being pulled up, the self-hardening stabilizer 2 may be sprayed. In this case, the self-hardening stabilizer 2 may be used to reduce the frictional resistance from the inner surface of the construction hole H applied to the casing 1 .

Furthermore, as shown in FIG. 1(d), the existing pile S is pulled up by hooking the existing pile S with a wire (not shown) hung from the upper part of the construction hole H. Then, as shown in FIG. After pulling up the existing pile S, the self-hardening stabilizer 2 mixed with earth and sand accumulates at the bottom of the construction hole H.
Incidentally, the existing pile S may be pulled up at the same time as the casing 1 is pulled up.

After that, as shown in FIG. 1(e), a new self-hardening stabilizing liquid 2 is injected from above the construction hole H by the pump P until it reaches the same height as the surface of the ground G. Then, as shown in FIG.
The amount of newly injected self-hardening stabilizer 2 may be determined based on the relationship between the amount of self-hardening stabilizer 2 ejected during excavation and the volume of the hole H to be drilled.

Finally, as shown in FIG. 1( f ), the self-hardening stabilizer 2 mixed with earth and sand staying on the lower side of the construction hole H and the newly injected self-hardening stabilizer 2 staying on the upper side is stirred by the auger screw 3, the earth and sand are mixed with the self-hardening stabilizer 2 as a whole, so that the strength of the self-hardening stabilizer 2 is increased in the construction hole H as shown in FIG. 1(g). can be homogenized.
For stirring the self-hardening stabilizer 2, for example, a method of introducing air by air blow may be employed.

Therefore, according to this existing pile extraction method, since the self-hardening stabilizer 2 is injected from the casing 1 during excavation, not only the ground G becomes softer and easier to excavate, but also the self-hardening stability retained in the construction hole H Even if the liquid 2 and the self-hardening stabilizer 2 injected when filling the construction hole H are mixed, the concentration will not be diluted and the desired strength can be expressed, so even if the construction hole of the new pile is excavated, it will not collapse easily. can do.

REFERENCE SIGNS LIST 1 casing 11 claw 12 injection port 2 self-hardening stabilizer 3 auger screw G ground S existing pile H construction hole P pump

Claims (2)

By operating the cylindrical casing while spraying a self-hardening stabilizer with characteristics selected based on the characteristics of the construction ground from near the tip of the casing, the existing pile is cut off from the ground. and _
a step of creating a construction hole by pulling out the casing and the existing pile after the tip of the casing reaches at least the lower end of the existing pile in the digging step ;
In the construction hole where the self-hardening stabilizer sprayed in the digging process stays ,
a step of filling the construction hole by further injecting the self-hardening stabilizer used in the digging step ;
Extraction method of existing piles, including 2. The method of pulling out an existing pile according to claim 1, wherein the self-hardening stabilizing liquid in the construction hole is agitated.

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