JP7592540B2 - Pile driving casing and pile driving method - Google Patents

Description

The present invention relates to a pile driving casing and a pile driving method.

In recent years, there has been an increasing demand for wooden piles as support piles for small houses, as they are less expensive than steel pipe piles or concrete piles and are environmentally friendly as they are made from natural materials.

Wooden piles are weak against torsional forces, so they cannot be rotary pressed into the ground like steel pipe piles.
For this reason, a ground reinforcement method has been proposed in which a wooden pile with a drilling tool at the end is rotated and pressed into the ground together with a casing (sleeve pipe), and then only the casing is removed, leaving the wooden pile in place, as disclosed in Patent Document 1, for example.

JP 2012-214993 A

In the ground reinforcement method described in Patent Document 1, a gap is created between the ground and the surface of the wooden pile when the casing is removed, and there is a risk that the wooden pile will tilt within the gap during construction, making it unstable.

The present invention aims to provide a pile driving casing and pile driving method that can rotate and drive a pile into the pile while keeping it stable.

The first invention of the present application, made to achieve the above-mentioned object, provides a casing for driving piles, comprising a cylindrical casing body and a plurality of drilling fins arranged radially on the outer periphery near the lower end of the casing body, wherein the drilling fins have an inclined portion that slopes away from the casing body from bottom to top.
A second invention of the present application provides a casing for driving piles, characterized in that in the casing for driving piles of the first invention, a casing excavation blade is provided on the lower part of the casing body.
The third invention of the present application provides a casing for driving piles of the first or second invention, characterized in that the casing has a flat rolling blade protruding horizontally from the outer periphery of the casing body at the lower part of the drilling fin of the casing body.
The fourth invention of the present application provides a pile driving method using the pile driving casing of the first or second invention, characterized in that a pile having a tip drilling tool at its tip is inserted into the pile driving casing, the pile driving casing is rotated, the pile driving casing and the pile are penetrated into the ground, and only the pile driving casing is pulled up while being rotated, and the pile driving casing is pulled out while the drilling fins excavate and drop the soil around the penetrated pile, and the pile is left in the ground.
The fifth invention of the present application provides a pile driving method using the pile driving casing of the third invention, comprising: an insertion step of inserting a pile having a tip drilling tool at its tip into the pile driving casing; a penetration step of rotating the pile driving casing and penetrating the pile driving casing and the pile into the ground; an excavation step of lifting only the pile driving casing to a predetermined height while rotating and excavating and dropping the soil around the penetrated pile with the drilling fins ; a rolling step of pushing down the pile driving casing and rolling the soil around the pile with the rolling blades; and the excavation step and the rolling step are repeatedly performed over approximately the entire length of the pile left in the ground.

The present invention provides at least one of the following effects by solving the above-mentioned problems.
(1) The pile can be rotated and pressed into the pile together with the casing body and the tip drilling tool.
(2) The soil excavated by the drilling fin falls downward and fills the gap between the pile and the hole wall, restraining the pile with the soil and making it stable.

FIG. 1 is an explanatory diagram of a pile driving casing according to the present invention; FIG. 1 is an explanatory diagram of a pile driving casing and a pile according to the present invention; Plan view of the pile driving casing and tip drilling tool of the present invention (1) FIG. 1 is an explanatory diagram of a pile driving method using a pile driving casing according to the present invention. FIG. 2 is an explanatory diagram of the pile driving casing of the present invention. Plan view (2) of the pile driving casing and tip drilling tool of the present invention An explanatory diagram (2) of a pile driving method using the pile driving casing of the present invention FIG. 3 is an explanatory diagram of the pile driving casing of the present invention.

The following describes an embodiment of the present invention with reference to the drawings.

[Example 1]
[1] Configuration of the pile driving casing <1> Overall configuration The pile driving casing of the present invention comprises a casing body 1 and drilling fins 2 provided on the outer periphery of the casing body 1 (FIG. 1).
A wooden pile 3 is inserted into the casing body 1. A tip excavation tool 4 having a casing connecting part 42 is fixed to the tip (lower end) of the wooden pile 3, and the casing body 1 and the tip excavation tool 4 are engaged with each other by a configuration in which the casing connecting part 42 and a convex piece 11 provided on the casing body 1 are connected by forward rotation of the casing body 1 and are disconnected by reverse rotation. However, the engagement between the casing body 1 and the tip excavation tool 4 is not limited to this configuration, and any configuration can be used as long as the engagement between the casing body 1 and the tip excavation tool 4 is connected by forward rotation and disconnected by reverse rotation.
Each component will be explained below.
Although the present embodiment and a second embodiment described later are described as using wooden piles 3, the present invention is not limited to wooden piles, and can also be applied to piles made of steel pipes or concrete.

<2> Casing Body The casing body 1 is made of a steel pipe having an inner diameter that allows the wooden stake 3 to be inserted therein.
The casing body 1 is longer than the wooden piles 3 to be driven.

<3> Drilling Fins The drilling fins 2 are multiple metal members arranged radially around the outer periphery of the casing body 1 near the lower end.
The drilling fin 2 has a triangular cross section having an inclined portion 21 that is inclined from the bottom to the top in a direction away from the casing body 1.

[2] Pile driving method using a pile driving casing Next, a pile driving method using a pile driving casing of the present invention will be described.

<1> Wooden pile and tip excavation tool The wooden pile 3 is a conventional wooden pile made of cedar, Japanese larch or the like, and does not require any special processing.
The tip excavation tool 4 is a steel member into which the tip (lower end) of the wooden pile 3 is inserted and fixed.
In this embodiment, a helical drilling blade 41 is provided, but a tip blade member that has been conventionally used in rotary drive-in piles may also be used as appropriate.
However, the maximum drilling diameter r ₁ of the drilling fin 2 is made larger than the maximum drilling diameter r ₂ of the tip drilling tool 4 .

<2> Step <2.1> Penetration Step The wooden pile 3 is inserted, and the casing body 1 with its lower end connected to the tip drilling tool 4 is gripped by a pile driver (not shown) and rotated forward while being pressed into the ground. The wooden pile 3 is inserted into the casing body 1, and is penetrated together with the casing body 1 and the tip drilling tool 4.
Since the tip drilling tool 4 is connected to the lower end of the casing body 1, the tip drilling tool 4 also rotates as the casing body 1 rotates, thereby excavating the ground and easily performing rotational pressing.
The torsional force during rotary press-in acts on the casing body 1 held by the pile driver and the tip drilling tool 4 connected to the casing body 1, but does not act on the wooden pile 3 not held by the pile driver. Since the casing body 1 and the tip drilling tool 4 are both made of steel, they will not deform or break due to the torsional force, and the wooden pile 3 can be rotary pressed in together with the casing body 1 and the tip drilling tool 4. Furthermore, because it is rotary press-in, pre-digging is not required, no soil is discharged, and construction can be carried out without noise or vibration.
The drilling fins 2 provided on the outer periphery of the casing body 1 have inclined portions 21 that incline toward the casing body 1 from top to bottom, so that the surrounding ground is not disturbed more than necessary.

<2.2> Process of excavating the surrounding ground using the casing body The casing body 1 is rotated and pressed in until the tip drilling tool 4 reaches the supporting layer, and then the casing body 1 is rotated in the reverse direction to release the connection with the tip drilling tool 4.
Then, the casing body 1 is rotated while being pulled up, whereby the surrounding ground is excavated by the excavation fins 2.
Since the wooden pile 3 is inserted into the casing body 1 and the tip drilling tool 4 is also larger in diameter than the wooden pile 3, if the casing body 1 is pulled up as is, a gap will be created between the wooden pile 3 and the hole wall created by the drilling, and the wooden pile 3 may tilt in the gap and become unstable. In the present invention, the soil excavated by the large-diameter drilling fin 2 falls downward to fill the gap and restrain the wooden pile 3, so that the wooden pile 3 becomes stable.

[Example 2]
<1> Rolling fin The casing body 1 of the pile driving casing may be provided with a rolling fin 5 below the drilling fin 2 (FIG. 5).
The rolling blade 5 is a flat metal plate that protrudes horizontally from the outer periphery of the casing body 1. The maximum diameter _r3 of the rolling blade 5 is smaller than the maximum excavation diameter _r1 of the excavation fin 2 and is approximately the same as the maximum excavation diameter _r2 of the tip excavation tool 4 (FIG. 6).
The rolling blades 5 are not continuous in the circumferential direction of the casing body 1 but are spaced apart from each other by a gap S.

<2> Compaction process by rolling blades When the rolling blades 5 are provided on the pile driving casing, the casing body 1 is first rotated and pressed in until the tip drilling tool 4 reaches the supporting layer to drive the wooden pile 3 into the ground, and then the casing body 1 is rotated in the reverse direction to release the connection with the tip drilling tool 4, and the casing body 1 is pulled up and rotated to excavate the surrounding ground with the drilling fins 2 (FIG. 7(a)). The rolling blades 5 are erected with a gap S between them, so the soil excavated by the drilling fins 2 falls downward through the gap S to fill the gap between the wooden pile 3 and the hole wall.
After the casing body 1 is raised to a predetermined height, it is pushed down and the soil below the rolling blades 5 is rolled by the rolling blades 5 (FIG. 7(b)). By rolling the soil, the binding force of the wooden piles 3 is increased, making it possible to achieve a more stable condition.
After compaction, the casing body 1 is rotated while being raised to a position higher than the previous time, the surrounding ground is excavated by the excavation fins 2 (FIG. 7(c)), and the casing body 1 is pushed down and compaction is performed by the rolling blades 5 (FIG. 7(d)). Since the rolling blades 5 are erected with a spacing S between them, by rotating the casing body 1 and adjusting the position of the rolling blades 5 to the location where the spacing S was during the previous compaction, the area around the wooden pile 3 can be compacted more uniformly.
By repeating the excavation process and compaction process around the wooden pile 3, the surrounding soil and sand can be compacted over the entire length of the wooden pile 3, increasing the binding force of the soil and sand on the wooden pile 3 and creating a stable support structure.

[Example 3]
<1> Casing Excavation Blade A casing excavation blade 6 may be provided at the bottom of the casing body 1 (FIG. 8).
The maximum drilling diameter of the casing drilling blade 6 is made smaller than that of the drilling fin.

Reference Signs List 1: Casing body, 11: Convex piece 2: Excavation fin, 21: Inclined portion 3: Wooden stake 4: Tip excavation tool, 41: Excavation blade, 42: Casing connecting portion 5: Rolling blade 6: Casing excavation blade

Claims (5)

A cylindrical casing body;
A plurality of drilling fins are provided radially on the outer periphery near the lower end of the casing body,
The drilling fin has a triangular cross section having an inclined portion inclined from the bottom to the top in a direction away from the casing body.
Casing for driving piles. The pile driving casing according to claim 1,
A casing excavation blade is provided at the lower part of the casing body.
Casing for driving piles. The pile driving casing according to claim 1 or 2,
The lower part of the drilling fin of the casing body has a flat rolling blade protruding horizontally from the outer periphery of the casing body.
Casing for driving piles. A pile driving method using the pile driving casing according to claim 1 or 2,
A pile having a tip drilling tool at its tip is inserted into the pile driving casing,
The pile driving casing is rotated, and the pile driving casing and the pile are inserted into the ground.
The pile driving casing is pulled up while rotating, and the pile driving casing is pulled out while the soil around the penetrated pile is excavated and dropped by the excavation fin , and the pile is left in the ground.
Pile driving method. A pile driving method using the pile driving casing according to claim 3,
An insertion step of inserting a pile having a tip drilling tool at its tip into the pile driving casing;
A penetration step of rotating the pile driving casing and penetrating the pile driving casing and the pile into the ground;
An excavation process in which only the pile driving casing is rotated while being raised to a predetermined height, and the excavation fin excavates and drops the soil around the penetrated pile;
A rolling process in which the pile driving casing is pushed down and the soil around the pile is rolled by the rolling blade;
The excavation step and the rolling step are repeated over substantially the entire length of the pile left in the ground.
Pile driving method.

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