JP7745341B2 - Pile hole excavation bucket and pile hole excavation method - Google Patents

Description

The present invention relates to a pile hole drilling bucket and a pile hole drilling method.

Patent Document 1 below describes a wide-bottom bucket equipped with two wide-bottom blades. In this excavation bucket, the wide-bottom blades open to expand the diameter of the wide-bottom bucket and widen the excavation hole.

JP 2014-141844 A

The excavation bucket in Patent Document 1 above is equipped with two widening wing sections. When excavating the ground using these two widening wing sections, there are two points of contact between the excavation hole and the excavation bucket, but the excavation bucket is prone to swinging in directions other than the points of contact, making it difficult to stabilize its planar position. If the planar position of the excavation bucket is unstable, it is difficult to ensure the excavation accuracy of the excavation hole (pile hole).

In consideration of the above, the present invention aims to provide a pile hole excavation bucket and pile hole excavation method that can improve pile hole excavation accuracy.

One embodiment of a pile hole drilling bucket comprises a rotating shaft that is inserted into the ground, and three drilling blades that are attached to the rotating shaft and rotate around an axis that runs vertically while swiveling, thereby being pushed out horizontally and expanding in diameter to excavate the ground.

One embodiment of the pile hole excavating bucket is attached to a rotary shaft and can excavate the ground using three excavating blades that expand as they rotate. As a result, the three excavating blades form a surface, making it easier to stabilize the planar position of the rotary shaft compared to when excavating with two excavating blades. This results in higher pile hole excavation accuracy. In addition, the weight of the pile hole excavating bucket can be reduced compared to when excavating with four or more excavating blades.

In one embodiment of the pile hole excavation bucket, the three excavation blades are each connected to a fixed link fixed to the rotating shaft, and to three expansion links connected to the shaft as a connecting part, and the three expansion links are connected by a synchronization link that synchronizes and expands the diameters of the three expansion links, and at least one extension device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link to which the synchronization link is connected, and which extends and contracts to rotate the expansion links and the excavation blades.

In one embodiment of the pile digging bucket, three digging blades are connected to three expansion links, respectively. The three expansion links are connected by a synchronization link that synchronizes the expansion of the three expansion links. Therefore, the expansion amounts of the three digging blades are equal.

In addition, by attaching an extension device to one expansion link and expanding the expansion link, the diameters of the three expansion links can be expanded. This allows the three excavation blades to expand in unison. Furthermore, if an extension device is attached to each of the three expansion links, the three excavation blades can still rotate and expand even if one or two of the extension devices fail.
The pile excavation bucket of claim 1 comprises a rotating shaft that is inserted into the ground, and three excavation blades that are attached to the rotating shaft and pushed out horizontally while rotating to expand in diameter and excavate the ground, the three excavation blades are each connected to three expansion links that are connected to a fixed link fixed to the rotating shaft, the three expansion links are connected by a synchronization link that expands the diameters of the three expansion links in unison, and at least one extension device is provided that has one end connected to the fixed link and the other end connected to the expansion link and that extends and contracts to rotate the expansion link and the excavation blade, and three extension devices are provided, each connected to three different expansion links.

The pile hole drilling bucket of claim 2 is the pile hole drilling bucket of claim 1 , further comprising a plurality of anti-vibration bars attached to the rotary shaft above the drilling blades and extending toward the hole wall.

In the excavation bucket according to claim 2 , a plurality of anti-sway bars extend toward the hole wall. This increases the number of fulcrums at which the excavation bucket comes into contact with the hole wall, enhancing the anti-sway effect. This improves the excavation accuracy of the pile hole.

The pile hole excavation bucket of claim 3 is the pile hole excavation bucket of claim 1 or 2 , and further comprises a bottom cover attached to the lower end of the rotating shaft for collecting mud generated when the excavation blades excavate the ground, and an opening/closing mechanism for opening and closing the bottom cover.

The pile hole excavating bucket according to claim 3 has a bottom cover attached to the lower end of the rotary shaft for collecting mud generated when the excavating blades excavate the ground. When the pile hole excavating bucket is pulled out of the pile hole with the mud collected in the bottom cover, the bottom cover is opened at a position offset from the pile hole, and the mud is discharged from the pile hole. This allows the mud to be discharged from the pile hole more efficiently than when there is no bottom cover.

A pile hole drilling method according to claim 4 comprises the steps of: inserting a rotary shaft having three excavation blades attached thereto, into the ground; excavating the ground with the excavation blades while rotating the rotary shaft, thereby forming a shaft portion having a constant pile diameter; and rotating the excavation blades around a vertical axis while pivoting them according to the insertion depth of the rotary shaft into the ground, thereby extruding the excavation blades horizontally and expanding their diameters to form an expanded diameter portion having a larger drilling width than the shaft portion, wherein the three excavation blades are respectively connected to three expansion links which are connected to a fixed link fixed to the rotary shaft, and the three expansion links are connected by synchronization links which synchronize and expand the diameters of the three expansion links, and at least one extension device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link, and which extends and contracts to rotate the expansion link and the excavation blades, and three extension devices are provided, each connected to three different expansion links .

In the pile hole drilling method described in claim 4 , the ground is excavated by three excavation blades attached to a rotary shaft and expanding their diameter while rotating. This makes it easier to stabilize the position of the rotary shaft compared to when excavating with two excavation blades. This results in high excavation accuracy of the pile hole. Furthermore, the weight of the pile hole excavation bucket can be reduced compared to when excavating with four or more excavation blades.

In addition, depending on the depth to which the rotary shaft is inserted into the ground, the diameter of the three drilling blades is expanded to form an expanded diameter section with a larger drilling width than the shaft section. This allows the rotary shaft to excavate with less vibration than when drilling with two drilling blades, making it possible to form an expanded diameter section in the pile hole with high dimensional accuracy.

A pile hole drilling method according to claim 5 comprises the steps of: excavating the ground while rotating a pile hole drilling bucket to form a shaft portion having a constant pile diameter; and rotating an excavation blade attached to a rotating shaft around a vertical axis while pivoting it in accordance with the insertion depth of the rotating shaft into the ground, thereby pushing out the blade in the horizontal direction and expanding its diameter to form an expanded diameter portion having a larger drilling width than the shaft portion, wherein the three excavation blades are respectively connected to three expansion links which are connected to a fixed link fixed to the rotating shaft, and the three expansion links are connected by synchronization links which synchronize and expand the diameters of the three expansion links, and at least one extension device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link, and which extends and contracts to rotate the expansion link and the excavation blade, and three extension devices are provided, each connected to three different expansion links .

In the pile hole drilling method of claim 5 , the diameters of the three excavation blades are expanded depending on the insertion depth of the rotary shaft into the ground to form an expanded diameter section with a larger drilling width than the shaft section. This makes it easier to stabilize the position of the rotary shaft compared to when the expanded diameter section is excavated with two excavation blades. This allows for high pile hole excavation accuracy and the formation of an expanded diameter section with high dimensional accuracy. Furthermore, the weight of the pile hole excavation bucket can be reduced compared to when the expanded diameter section is excavated with four or more excavation blades.

This invention enables higher drilling accuracy for pile holes.

FIG. 1 is a plan view showing a pile hole boring bucket according to an embodiment of the present invention. 1 is an elevational view of a pile hole boring bucket according to an embodiment of the present invention; FIG. FIG. 1A is an elevation view showing a state in which a rotary shaft is inserted into the ground in a pile hole drilling method according to an embodiment of the present invention; FIG. 1B is an elevation view showing a state in which the ground is excavated by an excavation blade to form a pile hole; FIG. 1C is an elevation view showing a state in which the excavation blade is expanded to form an expanded diameter portion in the pile hole; and FIG. 1D is an elevation view showing a state in which the excavation blade is further expanded to adjust the expanded diameter width of the expanded diameter portion. FIG. 10 is an elevation view showing a state in which, when forming an enlarged diameter portion in the middle part of a pile hole, the pile hole below the enlarged diameter portion is formed first. FIG. 10 is an elevation view showing the state in which an attachment is attached to the excavation blade to form the enlarged diameter portion after forming a pile hole below the enlarged diameter portion.

The pile hole drilling bucket and pile hole drilling method according to an embodiment of the present invention will be described below with reference to the drawings. Components indicated with the same reference numerals in each drawing are the same components. However, unless otherwise specified in the specification, each component is not limited to one and may exist in multiple numbers. Furthermore, explanations of duplicated components and reference numerals in each drawing may be omitted. Note that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications, such as omitting components or replacing them with different components, within the scope of the object of the present invention.

<Pile hole digging bucket>
As shown in FIG. 1 , a pile hole excavating bucket 10 (hereinafter referred to as the “bucket 10”) according to an embodiment of the present invention includes a rotating shaft 20, a fixed link 30, an expansion link 32, excavating wings 40, an extension device 50, and a synchronization link 60.

As shown in Figure 2, the bucket 10 also includes a stabilizer 70 and a bottom cover 80. Note that Figure 2 shows a simplified configuration to make it easier to understand the connection state of the rotating shaft 20, fixed link 30, expansion link 32, excavator blade 40, extension device 50, and synchronization link 60.

(rotation axis)
The rotating shaft 20 is a rod-shaped shaft that is inserted into the ground G (see Figure 3), and when this rotating shaft 20 rotates, the drilling blade 40 rotates, allowing the ground G to be excavated and a pile hole H to be formed.

(fixed link, expansion link, excavation blade)
The fixed link 30 is a flat metal plate fixed to the rotary shaft 20 and rotates integrally with the rotary shaft 20. The fixed link 30 is substantially triangular in plan view, and is formed radially in three directions from the rotary shaft 20. An expansion link 32 is rotatably connected to each of the apexes of the triangular fixed link 30.

The expansion link 32 is a flat metal plate connected to the fixed link 30. One end of the expansion link 32 is connected to the fixed link 30, and as shown by arrow N1, it is rotatable relative to the fixed link 30 around the connection point L1 with the fixed link 30. When the expansion link 32 rotates around one end connected to the fixed link 30 as an axis extending in the vertical direction, the other end moves toward or away from the rotating shaft 20.

A digging blade 40 is fixed to the other end of the expansion link 32. The digging blade 40 is a metal plate formed in a roughly arc shape in plan view (when viewed from above in the position for digging the pile hole H, or when viewed from the direction along the axial direction of the rotation shaft 20), and a digging blade 42 is formed at the tip fixed to the expansion link 32.

The excavation blade 40 expands or contracts in diameter as the expansion link 32 rotates around the connecting portion L1.

Note that "the excavation wing 40 expands in diameter" means that the excavation wing 40 moves away from the rotation shaft 20 so that the diameter of the pile hole H formed by the excavation blade 42 of the excavation wing 40 expands. Similarly, "the excavation wing 40 contracts in diameter" means that the excavation wing 40 moves closer to the rotation shaft 20 so that the diameter of the pile hole H formed by the excavation wing 40 contracts.

There are three expansion links 32, each connected to the top of a fixed link 30. A drilling wing 40 is fixed to each expansion link 32. That is, the drilling wing 40 is attached to the rotating shaft 20 via the fixed link 30 and the expansion link 32. Therefore, when the rotating shaft 20 rotates, the drilling wing 40 pivots around the rotating shaft 20.

In this embodiment, the digging blades 42 of the three digging blades 40 are positioned approximately 120° apart when viewed from the axial direction of the rotation shaft 20. In other words, the three digging blades 42 are positioned at the vertices of a roughly equilateral triangle.

As shown in Figure 2, the excavation blade 40 has a vertical section 40A and a sloped section 40B in an elevation view (viewed from the side in the position in which the pile hole H is being excavated). The excavation blade 42 is attached to both the vertical section 40A and the sloped section 40B.

The vertical section 40A of the drilling wing 40 is the section that extends in the up-down direction, and is used to drill the pile hole H. The sloped section 40B of the drilling wing 40 is formed above the vertical section 40A and slopes upward from the upper end of the vertical section 40A toward the rotation shaft 20. This sloped section 40B is used to drill part of the enlarged diameter section HL (see Figure 3) of the pile hole H.

(Expansion device)
1, the extension device 50 is a hydraulic cylinder having one end connected to the fixed link 30 (connection L2) and the other end connected to the expansion link 32 (connection L3). Three extension devices 50 are provided, and each is connected to a different expansion link 32.

The extension device 50 is connected to the fixed link 30 and the expansion link 32 at connection points L2 and L3, respectively, so that it can rotate around connection points L2 and L3. The extension device 50 is extendable and retractable along its axial direction, as indicated by arrow N2, and the amount of extension and retraction can be freely set and maintained by the operator of the pile hole drilling bucket 10.

As the extension device 50 extends or retracts in the direction indicated by arrow N2, the expansion link 32 and excavation blade 40 rotate in the direction indicated by arrow N1, expanding or contracting in diameter.

(Synchronized link)
The synchronization link 60 is a link mechanism that synchronizes and expands the diameters of the three diameter expansion links 32. The synchronization link 60 is formed by including an interlocking link 62 and a restricting link 64.

The interlocking link 62 is roughly triangular in plan view, and is formed radially in three directions from the rotation shaft 20. The interlocking link 62 is rotatably connected to the rotation shaft 20. A restricting link 64 is rotatably connected to each of the apexes of the triangular interlocking link 62.

There are three restriction links 64, one end of each of which is rotatably connected to the top of the interlocking link 62 (connection part L4). The other end of each restriction link 64 is rotatably connected to the expansion link 32 (connection part L5).

At the three connection points L4, the connection angles (opening angles) of the three regulating links 64 relative to the interlocking link 62 are all set to be equal. In other words, when one regulating link 64 rotates relative to the interlocking link 62, the other two regulating links 64 also rotate in unison so that the connection angles are equal. The regulating links 64 rotate in conjunction with the extension and contraction of the extension device 50, and the amount of rotation of the regulating links 64 depends on the amount of extension and contraction of the extension device 50.

(stabilizer)
As shown in Fig. 2, the stabilizer 70 is attached to the rotary shaft 20 above the excavation blade 40, and is a stabilizing device equipped with a plurality of arms (anti-vibration rods) 72. The arms 72 extend toward the wall of the pile hole H formed by the excavation blade 40 excavating the ground G (see Fig. 3).

The length of the arm 72, i.e., the distance W1 from the center line CL of the rotation shaft 20 to the tip of the arm 72, is adjusted according to the diameter of the pile hole to be drilled. It is preferable to set this distance W1, for example, to be approximately 2 to 6 cm shorter than the radius W2 of the pile hole H. This allows the rotation shaft 20 to be positioned at the center of the pile hole H, while preventing the arm 72 from interfering with the pile hole H and making it difficult to excavate the pile hole H.

As shown in Figure 1, three arms 72 are provided, and each arm 72 extends in a different direction from the excavating wing 40 in a plan view. Specifically, the arm 72 and the excavating blade 42 of the excavating wing 40 are positioned approximately 60° apart from each other when viewed from the rotation axis 20. The three arms 72 are positioned approximately 120° apart from each other.

(bottom lid)
2, the bottom cover 80 is a metal tray attached to the lower end of the rotary shaft 20. The bottom cover 80 collects mud generated when the excavating blade 40 excavates the ground G.

The bottom cover 80 is equipped with an opening/closing mechanism 82. The opening/closing mechanism 82 includes a hinge 82A that holds the bottom cover 80 at the lower end of the rotating shaft 20 and serves as the rotating shaft when the bottom cover 80 is opened and closed, and a latch 82B that holds the bottom cover 80 at the lower end of the rotating shaft 20 and can be switched between locked and unlocked when the bottom cover 80 is opened and closed.

When mud has accumulated in the bottom cover 80, the bucket 10 is pulled out of the pile hole H and the bottom cover 80 is opened at a position offset from the pile hole H in plan view, thereby discharging the mud from the pile hole H. This allows mud to be discharged from the pile hole H more efficiently than when the bottom cover 80 is not provided.

<Pile hole drilling method>
To excavate a pile hole H using the bucket 10, first, as shown in Fig. 3(A), the rotary shaft 20 to which the excavating blade 40 is attached is inserted into the ground G. Then, while rotating the rotary shaft 20, the excavating blade 40 excavates and bores the ground G. As a result, a pile hole H (shaft portion with a fixed pile diameter) is formed as shown in Fig. 3(B). In addition, in consideration of excavation efficiency, an excavation blade may be provided on the bottom surface of the bottom cover 80.

Next, as necessary, an enlarged diameter portion HL is formed in the pile hole H as shown in Figure 3(C). The enlarged diameter portion HL is formed at a predetermined depth in the ground G. When the insertion depth of the rotary shaft 20 reaches the predetermined depth, the drilling blade 40 is rotated to enlarge the diameter. This forms the enlarged diameter portion HL, which is a portion in the pile hole H with a larger diameter than the rest of the pile hole.

The expanded diameter section HL is formed by the vertical section 40A and the sloped section 40B of the excavation blade 40. Of these, the sloped section 40B forms an inclined section in the expanded diameter section HL where the lower diameter is larger than the upper diameter. Furthermore, the vertical section 40A forms a vertical section below the sloped section where the lower diameter is equal to the upper diameter.

Once a sloped section with a depth corresponding to the height H1 of the sloped section 40B of the excavating wing 40 has been formed, the pile hole H is excavated and the bucket 10 is lowered by height H1 (or a predetermined height lower than height H1) as shown in Figure 3(D). The excavating wing 40 is then expanded to adjust the excavation width and further expand the expanded diameter section HL.

By repeating the expansion of the excavation wing 40 and the lowering of the bucket 10 a desired number of times in this manner, an expansion section HL of any size can be formed, which has an inclined section with an angle equal to that of the inclined section 40B of the excavation wing 40.

The enlarged diameter section HL may be formed at the tip (lower end) of the pile hole H, or in the middle of the pile hole H. When the enlarged diameter section HL is formed in the middle of the pile hole H, for example, after the state shown in Figure 3(B) is reached, the pile hole H is excavated to a point below the portion where the enlarged diameter section HL will be formed (the portion shown by the dashed line in Figure 4), as shown in Figure 4.

The bucket 10 is then temporarily lifted above ground level, and the attachment 40C shown in Figure 5 is fixed to the lower end of the excavation wing 40. The attachment 40C is inclined downward and toward the rotation shaft 20 from the lower end of the vertical section 40A. The excavation wing 40 to which this attachment 40C is fixed is then used to form the expanded diameter section HL, as described using Figures 3(C) and (D). This allows for the formation of an inclined section at the lower end of the expanded diameter section HL, where the upper diameter is larger than the lower diameter.

If the expanded diameter section HL is to be formed not only in the middle of the pile hole H but also at the tip (lower end) of the pile hole H, the expanded diameter section HL is formed in the middle of the pile hole H as shown in Figure 5, and then the bucket 10 is raised to the ground again and the attachment 40C is removed. Then, as explained using Figures 3(C) and (D), the expanded diameter section HL is formed at the tip of the pile hole H.

In order to form an inclined portion at the lower end of the expanded diameter section HL where the upper diameter is larger than the lower diameter, the entire excavation wing 40 may be replaced with a different excavation wing rather than fixing the attachment 40C to the excavation wing 40.

<Action and effect>
In the bucket 10 and pile hole drilling method according to the embodiment of the present invention, as shown in FIG. 1, the ground G (see FIG. 3) can be excavated by three excavation blades 40 attached to a rotating shaft 20 and expanding in diameter as it rotates.

As a result, the three excavation blades 40 form a surface that contacts the pile hole H at three points, making it easier to stabilize the planar position of the rotation shaft 20 compared to when excavating with two excavation blades. This increases the excavation accuracy of the pile hole H. In addition, the weight of the bucket 10 can be reduced compared to when excavating with four or more excavation blades.

In addition, in the bucket 10 according to an embodiment of the present invention, the three excavating blades 40 are connected to three expansion links 32, respectively. The three expansion links 32 are connected by a synchronization link 60 that synchronizes the expansion of the three expansion links 32. As a result, the expansion amounts of the three excavating blades 40 are the same.

Furthermore, because an extension device 50 is attached to each of the three expansion links 32, even if one or two of the extension devices 50 fail, the three excavation blades 40 can still be rotated and expanded.

The expansion device 50 may be configured to be attached to only one expansion link 32. Even in this configuration, if a synchronization link 60 is provided, the diameter of this expansion link 32 can be expanded to expand the diameter of all three expansion links 32.

Note that while the bucket 10 is equipped with both the extension device 50 and the synchronization link 60, this is not a limitation of the present invention. If an extension device 50 is provided on each of the three expansion links 32, each expansion link 32 can be expanded, so the synchronization link 60 may be omitted.

In addition, the bucket 10 according to the embodiment of the present invention is provided with a stabilizer 70, and three arms 72 acting as anti-vibration rods extend from the rotation shaft 20 in a direction different from that of the excavating blade 40 in a plan view.

As a result, compared to when the arm 72 is extended in the same direction as the excavation wing 40, the bucket 10 has more fulcrums at which it comes into contact with the pile hole H in plan view, providing a stronger anti-vibration effect. This allows for higher excavation accuracy in the pile hole H.

The number of arms 72 is not limited to three. For example, it may be two, or four or more. By providing at least two arms 72, it is possible to obtain an anti-sway effect for the rotating shaft 20. Also, for example, the stabilizer 70 may be omitted. Even if the stabilizer 70 is omitted, the rotating shaft 20 is less likely to vibrate because three excavating blades 40 are provided.

In addition, in the pile hole drilling method according to an embodiment of the present invention, the diameter of the three drilling blades 40 is expanded to adjust the drilling width depending on the insertion depth of the rotary shaft 20 into the ground G. This allows drilling to be performed with the rotary shaft 20 less likely to vibrate than when drilling with two drilling blades, making it possible to form an expanded diameter portion HL in the pile hole H with high dimensional accuracy.

In addition, in this embodiment, the shaft portion, which has a constant pile diameter in the pile hole H, and the expanded diameter portion HL are formed using the same excavation blade 40, but this is not a limitation of the present invention. For example, the shaft portion and the expanded diameter portion HL may be formed using different excavation blades.

Specifically, a known non-expanding drilling blade may be fixed to the rotating shaft 20 to form the shaft portion of the pile hole H, and then the known drilling blade may be replaced with the drilling blade 40 to form the expanded diameter portion HL. Two or four or more known drilling blades may be used.

Furthermore, the shaft portion of the pile hole H and the enlarged diameter portion HL may be formed using different pile hole excavation buckets. That is, the shaft portion of the pile hole H may be formed using a known pile hole excavation bucket, and only the enlarged diameter portion HL may be formed using bucket 10.

10 Excavation bucket 20 Rotation shaft 30 Fixed link 32 Expansion link 40 Excavation wing 50 Telescopic device 60 Synchronization link 72 Arm (anti-vibration rod)
80 Bottom cover 82 Opening/closing mechanism G Ground

Claims (5)

A rotating shaft inserted into the ground;
Three excavation blades attached to the rotary shaft, which are pushed out horizontally while rotating to expand their diameters and excavate the ground;
Equipped with
The three excavation blades are respectively connected to three expansion links connected to a fixed link fixed to the rotating shaft,
The three diameter expansion links are connected by a synchronization link that synchronizes the diameter expansion of the three diameter expansion links,
At least one telescopic device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link, and which extends and contracts to rotate the expansion link and the excavation blade;
Three of the expansion devices are provided, and each is connected to three different expansion links.
Pile hole drilling bucket. A plurality of anti-vibration rods attached to the rotating shaft above the drilling blade and extending toward the hole wall;
2. The pile hole drilling bucket of claim 1 , comprising: a bottom cover attached to a lower end of the rotating shaft and configured to collect mud generated when the excavation blade excavates the ground;
an opening/closing mechanism for opening and closing the bottom cover;
3. A pile hole boring bucket according to claim 1 or 2 , comprising: a step of inserting a rotary shaft having three excavation blades attached thereto, capable of excavating the ground, into the ground;
A step of excavating the ground with the excavation blade while rotating the rotation shaft to form a shaft portion having a constant pile diameter;
A process of rotating the drilling blade around a vertical axis while rotating it according to the insertion depth of the rotating shaft into the ground, thereby pushing it out horizontally and expanding its diameter to form an expanded diameter portion having a drilling width larger than that of the shaft portion;
Equipped with
The three excavation blades are respectively connected to three expansion links connected to a fixed link fixed to the rotating shaft,
The three diameter expansion links are connected by a synchronization link that synchronizes the diameter expansion of the three diameter expansion links,
At least one telescopic device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link, and which extends and contracts to rotate the expansion link and the excavation blade;
The pile hole drilling method , wherein three of the expansion devices are provided and connected to three different expansion links, respectively . A step of excavating the ground while rotating the pile hole excavation bucket to form a shaft portion of a pile with a constant diameter;
a step of rotating three drilling blades attached to a rotary shaft around a vertical axis while rotating them in accordance with the insertion depth of the rotary shaft into the ground, thereby pushing them out horizontally and expanding their diameter to form an expanded diameter portion having a drilling width larger than that of the shaft portion;
Equipped with
The three excavation blades are respectively connected to three expansion links connected to a fixed link fixed to the rotating shaft,
The three diameter expansion links are connected by a synchronization link that synchronizes the diameter expansion of the three diameter expansion links,
At least one telescopic device is provided, one end of which is connected to the fixed link and the other end of which is connected to the expansion link, and which extends and contracts to rotate the expansion link and the excavation blade;
The pile hole drilling method , wherein three of the expansion devices are provided and connected to three different expansion links, respectively .