JP2897870B2 - Drilling equipment and medium digging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excavator for drilling in the ground like an earth auger used for foundation work and the like, and a method for excavating the earth using the excavator.

[0002]

2. Description of the Related Art In general, various methods are used in foundation works. Among them, a middle digging method is known as one of the embedding methods using a ready-made pile foundation. The above-mentioned mid-digging method is a method in which an auger is built in the hollow part of a pile body of a ready-made pile such as a tubular concrete pile or a steel pipe pile, and the pile penetrates to a predetermined depth while excavating the ground at the tip of the pile. This is a method that can be performed with low noise and low vibration.

FIG. 10 shows an outline of the above-mentioned inside digging method. For example, a general construction method of the inside digging method is as follows. First, the auger 4 having the shaft 3 with the excavating screw 2 is inserted into the hollow portion of the tubular ready-made pile 1, and the pile 1 and the auger 4 are built. Next, the auger 4 is rotated by the rotary drive device 5 to excavate the ground e at the lower end of the pile 1 and, at the same time, excavate the excavated soil, and perform the self-weight or the self-weight and press-fitting or tapping of the pile 1 and the associated equipment. The pile 1 is sunk together.

Next, as shown in FIG. 10, when the tip of the pile 1 reaches a support layer (not shown), the auger is pulled out and the middle digging step is completed. Then, in order to secure the supporting force of the tip of the pile 1, the head of the pile 1 is hit, or cement milk or concrete is injected, stirred or driven into the tip of the pile 1 to consolidate the root.

[0005] The auger 4 is a drilling device such as a so-called earth auger, which is pierced in the ground by being rotated by a rotary drive device 5 such as a motor and a speed reducer in a state of being built vertically. In addition to the above-mentioned digging method,
It is used for drilling vertical holes in the pre-boring method, the construction of cast-in-place piles, and the construction of underground diaphragm walls.

[0006]

In the above-mentioned middle digging method, an auger 4 having a screw 2 slightly smaller than the inner diameter of the ready-made pile 1 is used. Is required. For example, when embedding a pile 1 having an inner diameter of 800 mm, the diameter is 7 mm.
A screw 2 of about 40 mm is required.

Further, since there is not much difference between the inner diameter of the pile 1 and the diameter of the screw 2 as described above, when the screw 2 is rotated as shown in FIG.
Due to the excavated soil that is sandwiched between the inner surface and the inner surface, a large resistance is generated over the entire circumference of the screw 2,
A large torque is required to rotate the auger 4. Further, there was a case where a stone got stuck between the inner surface of the pile 1 and the screw 2 and rotation of the auger 4 was stopped. Note that, in FIG. 11, a portion where a large load is applied to the auger 4 is indicated by oblique lines.

[0008] Since the large-diameter screw 2 is required, the auger 4 itself is costly, and the rotation driving device 5 having a large output for rotating the auger 4 is required.
Is required, and equipment costs increase. In addition, the auger 4 is extracted after the pile 1 is embedded as described above. However, since the diameter of the screw 2 is large as described above, when the auger 4 is extracted, much of the excavated soil in the pile 1 is involved. As a result, a large amount of earth and sand is discharged from the pile 1, and there is a problem that a large amount of soil is discharged.

The present invention has been made in view of the above circumstances, and it is possible to reduce the equipment cost and to reduce the earth removal and prevent the stone from being entrapped when used in the middle digging method. It is an object of the present invention to provide a drilling device and a method of digging inside using the drilling device.

[0010]

An excavator according to claim 1 of the present invention is used for drilling underground, and comprises a long shaft having a drilling screw, and a rotary drive for rotating the shaft. Device, the shaft is connected to a fixed state in an eccentric state with respect to the rotation axis of the rotary drive device, and the axis is substantially parallel to the rotation axis, and the center of the rotation axis is The above-mentioned problem is solved by being able to orbit around the area.

[0011] According to the above configuration, when a shaft having a screw alone is used without being arranged in the internal space of the pile, when the hole is excavated, the orbiting screw is provided on the inner surface of the excavated hole. It becomes a state where the earth and sand are stuck, and the amount of excavated soil that has been kneaded and compressed can be reduced, and the strength of the inner wall surface of the drilled hole is increased, making the inner wall surface of the hole hard to collapse be able to.

The shaft having the screw is basically an auger for drilling underground, but the shape of the screw is not particularly limited. Further, the above-mentioned rotary drive device is basically a power device such as an electric motor or a hydraulic motor, but may include a speed reducer, a power transmission device, and other gear mechanisms.

According to a second aspect of the present invention, in the excavator, the shaft is connected to the rotary drive so as to be movable between a state in which the shaft is aligned with the rotary axis of the rotary drive and an eccentric state. The above-mentioned problem is solved by having a connecting means. According to the above configuration, not only can it be used as a device that moves around the shaft while being mounted in an eccentric state as described above, but also can be used as a normal non-eccentric excavator.

According to a third aspect of the present invention, in the excavator, a cylindrical pile is disposed so as to surround the shaft having the screw, and a center line of the cylindrical pile and the rotation axis are substantially coincident with each other. By decentering the shaft with respect to the rotation shaft, the shaft is shifted from the center line of the cylindrical pile,
A solution to the above problem is to have an embedding means for embedding the cylindrical pile in the ground in correspondence with excavation of the ground by the shaft.

According to the above configuration, when the above-mentioned excavator is used for the middle digging method, the long shaft having the excavation screw moves around, so that a hole larger than the diameter of the screw can be excavated. Thus, it is possible to cope with a shaft having a screw considerably smaller than the inner diameter of the cylindrical pile. In addition, since the shaft having the screw moves orbitally, the entire peripheral surface of the screw does not come close to the inner surface of the pile, and only a part of the outer periphery of the screw comes close to the inner surface of the pile. Therefore, a large load is applied only to the portion of the screw close to the inner surface of the pile, so that excavation can be performed with a relatively small torque.

Further, since the diameter of the screw can be reduced as described above, the amount of earth removal when the shaft is extracted after the pile is embedded can be reduced. In addition, when the shaft moves orbitally as described above, when the movement of the screw is viewed from one place on the inner surface of the pile, the screw moves closer to and away from the inner surface of the pile. When the stone is about to be caught in the pile, at a certain point, the screw moves away from the position on the inner surface of the pile where the stone is likely to be caught, making it difficult for the stone to be caught.

The embedding means may be, for example, a means for embedding the pile by its own weight of the pile and the rotary driving device, a means for inserting the pile by taking a reaction force from the pile already embedded in the ground, or an excavating apparatus. It is possible to use one that press-fits the pile by taking a reaction force from the overall weight, one that vibrates the pile, one that taps the pile, and the like.

According to a fourth aspect of the present invention, there is provided the excavator having a rotation means for rotating the rotating shaft around the center line of the shaft instead of fixing the shaft to the rotating shaft. This is means for solving the above problems. According to the above configuration, since the shaft having the screw moves around the rotation shaft of the rotary drive device and rotates, the excavation can be performed efficiently. The rotation means may have a power device such as a motor independently of the rotation drive device, or may transmit power from the rotation drive device via a power transmission device such as a gear mechanism to rotate the rotation drive device. The shaft may be rotated by the power of the device.

According to a fifth aspect of the present invention, there is provided a middle digging method using the digging device according to the third or fourth aspect, wherein the shaft having the screw is circulated in the cylindrical pile. The means for solving the above problem is to excavate the earth and sand at the tip portion of the cylindrical pile and to bury the cylindrical pile in the ground corresponding to the excavation of the earth and sand. According to the above configuration, it is possible to obtain an effect when the above-described excavator is used for the middle digging method.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of a digging apparatus according to the present invention and a middle digging method using the digging apparatus will be described with reference to the drawings. FIGS. 1, 2 and 3 show a first example of an excavator 10. 1, 2 and 3
As shown in the figure, the excavator 10 of the first example has a long shaft 11
And a well-known auger 13 comprising a drilling screw 12 provided on the shaft 11, a well-known rotation drive device 14 for rotating the auger 13, and a rotation shaft 14a of the auger 13 and the rotation drive device 14. And a connection unit 15 for connecting

The auger 13 is a well-known auger as described above, and various well-known augers 13 for underground drilling can be used in the present invention. Spiral (screw) screw 12
And an auger head 16 having a drill bit at the tip of the shaft. The rotation drive device 14 is a known device as described above, and includes a power device (not shown) such as a motor and a gear mechanism (not shown) such as a speed reducer, and is provided via a rotation shaft 14a. Auger 11
Is to rotate.

The connecting portion 15 includes a rail portion 15a fixed to the rotating shaft 14a of the rotary drive device 14, a moving portion 15b fixed to the auger 13 and movable along the rail portion 15a, The hydraulic jack 17 drives the moving unit 15b with respect to the unit 15a. The rail portion 15a is fixed to the distal end of the rotary shaft 14a in a state orthogonal to the rotary shaft 14a of the rotary drive device 14, and becomes horizontal when the rotary shaft 14a is arranged vertically. I have. And the rail part 15
As shown in FIG. 3A, the cross section is convex, and the moving portion 15b is movably fitted to the left and right protruding portion of the lower portion of the rail portion 15a. .

Also, at one end of the rail portion 15a,
The tip of the rod 17a of the hydraulic jack 17 is
It is fixed with a horizontal. The moving unit 15
As shown in FIG. 3, b has a C-shaped cross section, and is movably fitted to the lower portion of the rail portion 15a as described above, and the cylinder 17b of the hydraulic jack 17 is fixed.

The auger 13 is suspended from the lower surface of the moving portion 15b. The rotation of the rotating shaft 14a of the rotary driving device 14 causes the connecting portion 15 to rotate. 13 also rotates. The hydraulic jack 17 is provided on the rail 1 as described above.
When the rod 17a was extended and connected to the moving part 5a and the moving part 15b, as shown in FIG. 1, the auger 13 was eccentric with respect to the rotary shaft 14a of the rotary drive device 14, and the rod 17a was retracted. At this time, as shown in FIG. 2, the center line of the auger 13 and the rotating shaft 1 of the rotary driving device 14
4a coincides with the center line.

When the center line of the auger 13 and the center line of the rotating shaft 14a are matched by the connecting portion 15,
The auger 13 becomes rotatable around its center line, and becomes usable as a normal auger 13. Further, when the auger 13 is eccentric with respect to the rotation shaft 14a, the auger 13 moves around the rotation shaft 14a in a state where the auger 13 is arranged in parallel with the rotation shaft 14a.

The excavator 10 of the first example includes a support device and an embedding device (not shown). The above-mentioned supporting device is, for example, a well-known device including a crawler type cart and a crane device provided on the cart and supporting the auger 13, the connecting portion 15, and the rotary drive device 14 in a vertically erected state. It is. In the first example, the embedding apparatus uses a well-known pile press-in / pull-out machine capable of taking in a reaction force from the already buried pile 1 to press-fit or pull out the pile 1. The embedding device is not limited to the pile press-in and pull-out machine, but may be any device that can embed various types of piles 1 used in the middle digging method.

Next, a description will be given of a middle digging method using the digging device 10. First, the tubular ready-made stake 1 is erected, and the auger 13 connected to the rotary drive device 14 via the connection part 15 is sunk in the stake 1.
At this time, the center line of the pile 1 and the rotary shaft 14a of the rotary drive device 14 are made to substantially match. Also, the connection unit 15
In the above, the rod 17a of the hydraulic jack 17 is extended so that the auger 13 is eccentrically connected to the rotary shaft 14a of the rotary drive device 14. That is, as shown in FIG. 1, the auger 13 is shifted from the center line of the pile 1 in the pile 1.

Next, the rotation drive device 14 is operated to rotate the auger 13 in an eccentric state. In this case, the auger 13 includes a rotation shaft 14a of the rotation drive device 14,
In other words, here, it moves around the periphery of the pile 1 while being arranged parallel to the center line. Therefore, when there is not much difference between the inner diameter of the pile 1 and the diameter of the screw 12 of the auger 13, the auger 13 cannot move around inside the pile 1 and the diameter of the screw 12 of the auger 13 is
It is considerably smaller than the inner diameter of the pile 1. The actual diameter of the screw 12 of the auger 13 is determined by the inner diameter of the pile 1 and the degree of eccentricity of the auger 13.

The ground e immediately below the lower end of the pile 1 is excavated by the auger head 16 of the auger 13.
At this time, the auger 13 is rotated, and the auger 13 is pressed downward by the weight of the rotary driving device 14 and the like, and the auger 13 performs perforation downward. Then, as described above, the pile 1 excavated below is pressed downward by the embedding device, and the pile 1 is embedded in the ground corresponding to the excavation by the auger 13.

Then, by continuing the excavation by the auger 13, the auger 13 enters the ground, and the excavated soil is accumulated around the auger 13 inside the pile 1, and the screw of the rotating auger 13 is rotated. Excavated soil accumulated between the outer peripheral side of the pile 1 and the inner surface of the pile 1 causes a large resistance. However, as shown in FIG. Only a part of the outer periphery of is close to the inner surface of the pile 1,
Since the other part of the outer periphery is separated from the inner surface of the pile 1, the load applied to the auger 13 becomes smaller than when the inner surface of the pile 1 is approached over the entire circumference of the screw 12, and the rotation of the auger 13 is reduced. The torque can be reduced. In FIG. 4, a portion where a large resistance acts on the auger 13 is indicated by oblique lines.

Further, as the auger 13 orbits as described above, at one point on the inner surface of the pile 1, the auger 13 is moved.
, When the auger 13 is approaching,
In the case where the stone is about to bite between the auger 13 and the inner surface of the pile 1, the auger 13 approaches the part where the stone of the inner surface of the pile 1 is likely to bite. It is possible to prevent the stone from being bitten from leaving later.

When a stone is about to be caught between the auger 13 and the inner surface of the pile 1, the auger 13 basically moves along the inner circumference of the pile 1 and moves in the moving direction. On the side, since there is a relatively large distance between the inner surface of the pile 1 and the auger 13, it is possible for the stone pushed by the auger 13 to escape into the excavated soil on the front side of the auger 13, By running away, it is possible to prevent the stones from biting. From the above, it is possible to prevent the rotation of the auger from stopping due to the biting of the stone.

The excavation by the auger 13 and the press-fitting of the pile 1 by the embedding device bring the pile 1 into a state of being buried in the ground by the middle digging method. Then, when the embedding of the stake 1 is completed, the auger 13 is pulled up,
As described above, since the screw 12 is considerably smaller than the inner diameter of the pile 1, the soil discharge caused by lifting the auger 13 can be reduced.

In the embedded pile 1, a process for securing the supporting force at the tip of the pile 1 is performed by a known method, and the embedding of the pile 1 is completed. As described above, when the excavator 10 of the first example is applied to the middle digging method, the screw 12 of the auger 13 can be made considerably smaller than the inner diameter of the pile 1 and the rotation of the auger 13 can be reduced. By reducing the required torque, the equipment cost of the auger 13 and the rotary drive 14 can be reduced.

Further, as described above, the interruption of the work due to the biting of the stone can be prevented, and the construction period can be stabilized and shortened. In addition, by reducing the amount of earth removal as described above, labor required for processing the earth removal can be reduced, and labor can be saved. In the first example,
Although the above-described excavator 10 was used in an eccentric state, as shown in FIG.
Can be used even when the rotary shaft 14a of the auger 13 and the shaft 11 of the auger 13 are arranged on a straight line, so that it can also be used as a normal earth auger.

Further, the excavator 10 of the first example can be used, for example, in underground drilling other than the mid-digging method. For example, as shown in FIG. 5, in the construction of a well-known cast-in-place pile 24 constructed by excavating a vertical hole 21 in the ground e and then inserting a reinforced cage 22 into the vertical hole 21 and driving concrete 23. As shown in FIG. 6, the excavator 10 can be used to excavate the vertical hole 21.

When the vertical hole 21 is excavated by the excavator 10 of the first example with the auger 13 being eccentric, the auger 13 moves around along the inner wall surface of the excavated vertical hole 21. 13, the excavated soil is stuck to the inner wall surface of the vertical hole 21, and a part of the excavated soil is kneaded to the inner wall surface and compressed. Therefore, the amount of earth removal can be reduced, and the inner wall surface of the vertical hole 21 is reinforced, so that collapse of the inner wall surface can be prevented.

FIG. 7 shows a second example of an excavator 30 according to an embodiment of the present invention. The excavator 30 of the second example is a modification of the excavator 10 of the first example, and the same components as those of the first example are denoted by the same reference numerals and the description thereof will be omitted. Is omitted. Excavator 30 of the second example
Is provided with a second rotation driving device 31 having a motor or the like on the lower surface of the moving portion 15b of the connecting portion 15 fixed to the rotation shaft 14a of the rotation driving device 14, and the rotation shaft 31a of the second rotation driving device 31 Is connected to the shaft 11 of the auger 13.

Accordingly, the moving section 15b is moved to auger 1
In the case where the auger 3 is eccentric with respect to the rotation axis 14a of the rotation driving device 14, the auger 13 is driven by the rotation driving device 14 to orbit around the rotation shaft 14a of the rotation driving device 14 (orbit). The auger 13 is configured to rotate (self-rotate) around its axis by a second rotation driving device 31.

Therefore, the ground e can be efficiently excavated by revolving and rotating the auger head 16 during excavation. In the second example, two driving devices, the rotation driving device 14 and the second rotation driving device 31, are used. However, the rotation and rotation of the auger are performed by a well-known gear mechanism or other transmission mechanism. It is good also as a structure performed by one drive device.

FIGS. 8 and 9 show a third example of an excavator 40 according to an embodiment of the present invention. The third example of the excavator 40 is a modification of the first example of the excavator 10, and the same components as those of the first example are:
The same reference numerals are given and the description is omitted. The third example of the digging device 40 is an improved version of the connecting portion 14 of the first example of the digging device 10.
A first rotating body 42 fixed to the tip of the rotating shaft 14a of the rotary driving device 14, and a second rotating body 4 rotatably connected to the first rotating body 42 and to which the auger 13 is fixed.
And 3.

The first rotating body 42 is a plate fixed to the tip of the rotating shaft 14a of the rotary driving device 14 so as to be orthogonal to the rotating shaft 14a, so that the first rotating body 42 rotates integrally with the rotating shaft 14a. Has become. The second rotating body 43 is rotatably supported on the lower surface side of the first rotating body 42. The rotation axis (not shown) of the second rotating body 43 is arranged parallel to the rotation axis 14a of the rotation drive device 14, and
It is located at a shifted position.

A well-known stopper (not shown) for restricting the rotation of the second rotating body 43 at an arbitrary position and holding the second rotating body 43 fixed to the first rotating body 42. Is provided. The auger 13 is suspended from the side edge of the lower surface of the second rotating body 43.

When the second rotating body 43 is rotated with respect to the first rotating body 42 and fixed by the stopper at the position shown in FIG.
4 are arranged in a straight line with the rotation shaft 14a of the
0 can be used as a normal earth auger.
When the second rotating body 43 is rotated with respect to the first rotating body 42 and fixed at the position shown in FIG. 8 by the stopper, the auger 13 and the rotating shaft 14 of the rotation driving device 14 are rotated.
a and is arranged in an eccentric state deviating from a, so that the same operation and effects as those of the middle digging method and the construction of the cast-in-place pile described in the first example can be obtained.

That is, in the excavator 10 of the first example, the auger 13 and the rotary shaft 14a are moved from the state where the auger 13 and the rotary shaft 14a of the rotary drive device 14 are arranged in a straight line to the state where the auger 13 and the rotary shaft 14a are eccentric. While the auger 13 was slid, the excavator 40 of the third example changed the state in which the auger 13 and the rotary shaft 14a were arranged in a straight line.
The auger 13 is rotated to move the auger 13 and the rotary shaft 14a in an eccentric state.

In FIGS. 8 and 9, the first rotating body 42 and the second rotating body 43 are disc-shaped, but the first rotating body 42 and the second rotating body 43 Is not limited to a disk shape. In the present invention, a moving method for moving the auger 13 and the rotary shaft 14a from the state where the auger 13 and the rotary shaft 14a of the rotary drive device 14 are arranged in a straight line to the state where the auger 13 and the rotary shaft 14a are eccentric is particularly limited. Instead, a movement method other than the above-described slide movement and rotational movement may be used.

For example, by changing the connection position so that the auger 13 can be connected to a plurality of positions of the connection portion, the auger 13 and the rotating shaft 14a are arranged in a straight line.
The auger 13 and the rotating shaft 14a may be moved in an eccentric state. Further, in the present invention, the auger 13 and the rotary shaft 14a of the rotary drive device 14 may be fixed in an eccentric state in advance.

[0048]

As described above, according to the excavator of the first aspect of the present invention, when the shaft having the screw alone is used without being disposed in the internal space of the pile, the hole is formed. When excavating, the orbiting screw sticks the earth and sand to the inner surface of the excavated hole, the amount of excavated soil that has been kneaded and compressed can reduce the amount of excavated soil, and the inner wall surface of the excavated hole , The inner wall surface of the hole can be made hard to collapse.

According to the excavator according to the second aspect of the present invention, the excavator is not only used as an eccentrically mounted excavator as described above, but also used as a normal non-eccentric excavator. be able to. According to the excavator of the third aspect of the present invention, it is possible to cope with the shaft having a screw considerably smaller than the inner diameter of the cylindrical pile. In addition, since a large load is not applied to the entire circumference of the screw and a large load is applied only to a portion of the screw close to the inner surface of the pile, excavation can be performed with a relatively small torque.

Further, since the diameter of the screw can be reduced as described above, it is possible to reduce the amount of earth removal when the shaft is removed by embedding the pile. In addition, it is possible to prevent the stone from being caught between the screw and the inner surface of the pile to stop the screw.

According to the excavator of the fourth aspect of the present invention, the shaft having the screw orbits around the rotary shaft of the rotary drive device and rotates, thereby enabling efficient excavation. According to the middle digging method of the fifth aspect of the present invention, the effect when the above-mentioned digging device is used for the middle digging method can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view showing a digging device used in a first example of a middle digging method according to an embodiment of the present invention.

FIG. 2 is a front view showing a digging device used in the first example of the middle digging method.

FIG. 3 is a side view of a main part showing the first example of the excavator.

FIG. 4 is a plan view of an essential part for explaining the operation when the excavator of the first example is used for the middle digging method.

FIG. 5 is a cross-sectional view showing a cast-in-place pile constructed using the excavator of the first example.

FIG. 6 is a cross-sectional view showing a state where a vertical hole of a cast-in-place pile is formed using the excavator of the first example.

FIG. 7 is a front view showing a digging device used for a second digging method according to the embodiment of the present invention.

FIG. 8 is a main part perspective view showing a third example of the excavator according to the embodiment of the present invention.

FIG. 9 is a perspective view of a main part showing a third example of the excavator according to the embodiment of the present invention.

FIG. 10 is a front view showing a digging device used in a conventional middle digging method.

FIG. 11 is a plan view of a principal part for explaining an operation when a conventional excavator is used for a middle digging method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pile 10 Drilling device 11 Axis 12 Screw 13 Auger 14 Rotation drive device 14a Rotation shaft of a rotation drive device 15 Connection part (connection means) 30 Drilling device 31 Second rotation drive device (spinning means) 40 Drilling device 41 Connection part ( Connection means)

Claims (5)

(57) [Claims] 1. An excavator used for underground drilling, comprising: an elongate shaft having an excavation screw; and a rotation drive device for rotating the shaft. It is connected to a fixed state in an eccentric state with respect to the rotation axis of the device, and is capable of orbiting around the center of the rotation axis while the axis is substantially parallel to the rotation axis. Drilling rig. And a connecting means for movably connecting the shaft to the rotary driving device between a state in which the shaft is aligned with the rotary shaft of the rotary driving device and an eccentric state. The excavator according to claim 1. 3. A cylindrical pile is arranged so as to surround a shaft having the screw, a center line of the cylindrical pile is substantially coincident with the rotating shaft, and the shaft is eccentric with respect to the rotating shaft. With this configuration, there is provided an embedding unit that can embed the cylindrical pile in the ground in correspondence with excavation of the ground by the axis while the axis is shifted from a center line of the cylindrical pile. The excavator according to claim 1 or 2, wherein: 4. The rotating shaft according to claim 3, wherein said shaft is fixed to said rotating shaft, and said rotating means is provided with a rotating means for rotating said rotating shaft around a center line of said shaft. Drilling rig. 5. A middle digging method using the excavator according to claim 3 or 4, wherein a shaft having the screw is circulated in the cylindrical pile to form a tip of the cylindrical pile. A middle digging method characterized by excavating earth and sand, and burying the cylindrical pile in the ground in response to excavation of earth and sand.