JP4472373B2 - Widening drilling rig - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a widening excavator, and more particularly, a widened excavation blade after an excavation of a full length applied to a foundation of a building or the like, or an embedded pile or a cast-in-place concrete pile partially having a diameter-expanded portion, and a pile. The present invention relates to a widening excavator that can be suitably used for the construction of embedded piles, cast-in-place concrete piles, etc. that have been reliably reduced in diameter and easily pulled up.

  Conventionally, in order to construct the soil cement synthetic pile which is a typical example of the embedded pile applied to the foundation etc. of a building, the soil cement synthetic pile construction apparatus as shown in FIG. 7 is used (for example, Patent Document 1).

  This soil cement synthetic pile building device has a predetermined gap that allows the flow of excavated soil from the tip of the hollow tube 104 at the bottom of the excavating rod 101 inserted into the hollow tube 104 such as a steel pipe, and is hollow. A plurality of sets of excavation blades 102 extending in the circumferential direction from the outer diameter of the pipe 104 are swung via a shaft 122 to a bracket 111 formed on the excavation rod 101 with a base end 121 of each excavation blade 102. A predetermined gap allowing the flow of excavated soil is provided between the excavating blades 102 and 102, and is fixedly disposed on the excavating rod 101. Further, the base end 121 of each excavating blade 102 and By arranging the shear pin P between the bracket 111 formed on the excavation rod 101, the base end portion 121 of each excavation blade 102 is arranged to be swingable to the bracket 111 formed on the excavation rod 101 via the shaft 122. Set up The Kezutsubasa 102, is configured to be temporarily fixed in a substantially horizontal position extending in the circumferential direction than the outer diameter of the hollow tube 104.

  And this soil cement synthetic | combination pile construction apparatus is the hardening formed in the front-end | tip of the excavation rod 101, rotating the excavation blade 102 by rotating the excavation rod 101 in the state which expanded the excavation blade 102 from the beginning. The hollow tube 104 and the excavation rod 101 are lowered while injecting the curable injecting material into the excavated soil from the injection port 112 of the permeable injecting material and stirring the excavated soil and the curable injectable material to form a soil cement Then, the ground is excavated to a predetermined depth and stirred to create a soil cement composite pile. Thereafter, when collecting the excavation rod 101 and the excavation blade 102, the tip of the hollow tube 104 is brought into contact with the excavation blade 102, and as shown by the left half chain line in FIG. The shear pin P disposed between the base end portion 121 and the bracket 111 formed on the excavation rod 101 is cut so that the excavation blade 102 can be swung and reduced in diameter so that it can pass through the hollow tube 104. The excavation rod 101 is pulled out with the hollow tube 104 left, and the excavation blade 102 is recovered together with the excavation rod 101 to the ground.

  In this way, the soil cement synthetic pile building apparatus creates a soil cement column having a constant outer diameter which is larger than the outer diameter of the hollow tube 104 and embeds the hollow tube 104 in the soil cement column. By remaining in a state, a soil cement composite pile applied to the foundation of a building is efficiently created.

  By the way, in the conventional soil cement synthetic pile building device described above, the shear pin P is disposed between the base end portion of the excavating blade 102 and the bracket 111 formed on the excavating rod 101, whereby the base end portion of each excavating blade 102 is obtained. Can be temporarily fixed at a substantially horizontal position extending in the circumferential direction from the outer diameter of the hollow tube 104. The excavating blade 102 is swingably disposed on a bracket 111 formed on the excavating rod 101 via a shaft 122. However, the shear pin P used for temporarily fixing the excavating blade 102 needs to be broken and renewed every time a single soil cement composite pile is constructed, and therefore the workability is lowered. There was a problem.

  In order to cope with this problem, the widening excavation blade is arranged on a swing shaft provided to be inclined with respect to the rotation axis of the excavation rod, and the widening excavation blade is expanded by changing the rotation direction of the excavation rod. A widening excavator thus constructed has been proposed (see, for example, Patent Document 2).

  The widening excavator can smoothly and surely expand the diameter of the widened excavating blade by disposing the widened excavating blade on the swing shaft provided inclined with respect to the rotating shaft of the excavating rod. There is an advantage that the excavating rod can be driven to rotate without the eccentricity of the rotating shaft.

  However, since this widening excavator is formed so that the tip side of the widening excavation blade extends in a direction orthogonal to the swing axis, the diameter of the widening excavation blade is limited (specifically, widening excavation). There was a problem that the widening excavation of a large diameter could not be performed because of the expansion radius of the blade ≦ (outer diameter of the excavation blade−outer diameter of the excavation rod) × 1/2).

Japanese Patent Laid-Open No. 3-221506 JP 2003-239669 A

  In view of the problems of the conventional widening excavator, the present invention allows the widening excavator blades to be smoothly and reliably expanded or contracted so that the excavating rod can be driven to rotate without the eccentricity of the rotating shaft. An object of the present invention is to provide a widening excavator capable of carrying out large-diameter widening excavation.

  In order to achieve the above object, the widening excavator of the first aspect of the present invention is provided by disposing a widening excavating blade on a excavating rod provided with an excavating blade via a swing shaft and changing the rotation direction of the excavating rod. In the widening excavator configured to expand the diameter of the widening excavation blade, the swing shaft is provided to be inclined with respect to the rotation axis of the excavation rod, and the longitudinal direction of the rotation shaft of the excavation rod is closed with the widening excavation blade closed The base end portion of the widening excavation blade is bent so as to be positioned along the axis, and is pivotally attached to the swinging shaft, so that the distal end side of the widening excavation blade extends outside the excavation blade with the widening excavation blade opened. It is characterized by that.

In this case, the outer edge of the widening excavation blade can be positioned inside the excavation blade with the widening excavation blade closed.

  Further, the excavation bit disposed on the widening excavation blade with the widening excavation blade open can be positioned at least above the widening excavation blade.

  In order to achieve the object, the widening excavator according to the second aspect of the present invention arranges the widening excavation blade via the swing shaft on the excavation rod provided with the excavation blade, and changes the rotation direction of the excavation rod. In the widening excavator configured to reduce the diameter of the widening excavator blade, the swing shaft is provided to be inclined with respect to the rotary shaft of the excavation rod, and the longitudinal axis of the rotary shaft of the excavation rod is closed with the widening excavator blade closed. The base end of the widening excavation blade is bent so as to be positioned along the direction, and is pivotally attached to the swing shaft, and the distal end side of the widening excavation blade is extended outside the excavation blade with the widening excavation blade opened. It is characterized by doing so.

  In this case, the excavation bit disposed on the widening excavation blade with the widening excavation blade opened can be positioned at least on the lower side of the widening excavation blade.

  Then, with the widening excavation blade closed, the tip side of the widening excavation blade can be positioned below the swing shaft, or the tip side of the widening excavation blade can be positioned above the swing shaft.

  Moreover, the shape of the widening excavation blade can be formed so that the earth pressure received during rotation varies depending on the rotation direction.

  Further, the auxiliary widening excavation blade can be detachably disposed at the tip of the widening excavation blade.

  According to the widening excavator of the first aspect of the invention, the widening excavation blade is disposed on the excavation rod provided with the excavation blade via the swing shaft, and the widening excavation blade is expanded by changing the rotation direction of the excavation rod. In the widening excavator configured to have a diameter, the swing shaft is provided to be inclined with respect to the rotation axis of the excavation rod, and is positioned along the longitudinal direction of the rotation shaft of the excavation rod with the widening excavation blade closed. Since the base end of the widening excavation blade is bent and pivotally attached to the swing shaft, the widening excavation blade has its distal end extended outside the excavation blade with the widening excavation blade open. By changing the direction of rotation of the excavation rod, it is possible to ensure stable behavior of the widening excavation blade, to smoothly and reliably expand the diameter of the widening excavation blade, and to rotationally drive the excavation rod without the eccentricity of the rotating shaft, Large diameter widening excavation can be carried out.

In addition, with the widened excavating blade closed, the outer edge of the widened excavating blade is positioned inside the excavating blade, so that more stable behavior of the widened excavating blade can be ensured.

  Moreover, widening excavation can be carried out smoothly while pulling up the excavation rod by positioning the excavation bit disposed on the widening excavation blade with the widening excavation blade open.

  Further, according to the widening excavator of the second invention, the widening excavation blade is provided by disposing the widening excavation blade via the swing shaft on the excavation rod provided with the excavation blade, and changing the rotation direction of the excavation rod. In the widening excavator configured to reduce the diameter, the swing shaft is provided to be inclined with respect to the rotation axis of the excavation rod, and the widening excavation blade is closed along the longitudinal direction of the rotation axis of the excavation rod. The base end portion of the widening excavation blade is bent so as to be positioned and pivotally attached to the swing shaft, and the distal end side of the widening excavation blade is extended to the outside of the excavation blade with the widening excavation blade opened. Therefore, by changing the rotation direction of the excavation rod, stable behavior of the widening excavation blade can be ensured, and the widening excavation blade can be reduced in diameter smoothly and reliably, and large-diameter widening excavation can be performed.

  Moreover, widening excavation can be carried out smoothly while lowering the excavation rod by disposing the excavation bit disposed on the widening excavation blade with the widening excavation blade open.

  And in this 1st invention and 2nd invention, by making the front end side of a widening excavation blade be located below a rocking axis in the state where a widening excavation blade was closed, more stable behavior of a widening excavation blade was achieved. By ensuring that the tip side of the widening excavator blade is positioned above the swinging shaft, the distance between the excavating blade and the swinging shaft of the widening excavator blade can be set small and widened to a position near the excavating blade. It becomes possible to excavate, and it is possible to minimize the slackness of the ground at the bottom and to develop a large support force.

  In addition, by forming the shape of the widening excavation blade so that the earth pressure received during rotation varies depending on the rotation direction, it ensures a more stable behavior of the widening excavation blade and smoothly and reliably expands the diameter of the widening excavation blade Can do.

  Furthermore, widening excavation of an arbitrary diameter can be implemented only by selectively disposing the auxiliary widening excavation blade by disposing the auxiliary widening excavation blade in a detachable manner at the tip of the widening excavation blade.

  Hereinafter, embodiments of the widening excavator of the present invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of the widening excavator of the present invention.
In this embodiment, the widening excavator of the present invention is applied to a soil cement synthetic pile building device.

This soil cement synthetic pile construction device is provided with a widening excavator at the tip of the excavation rod 1 inserted through a hollow tube 4 such as a steel pipe.
In addition, the stabilizer 5 which prevents that the center axis | shaft of the excavation rod 1 and the hollow tube 4 decenters is arrange | positioned at the excavation rod 1 above a widening excavation apparatus.

  The widening excavator is provided with the excavating blade 3 disposed at the tip of the excavating rod 1, and the widened excavating blade 2 is disposed on the excavating rod 1 thereabove via the swing shaft 21. 1 is changed (in FIG. 1 (b), switching from forward rotation to reverse rotation) so that the widened excavation blade 2 is expanded in diameter (K1 in FIG. 1 (b) is the expanded widened width). K2 indicates the rotation trajectory of the outer edge of the excavation blade, and K2 indicates the rotation trajectory of the outer edge of the widened excavation blade whose diameter has been expanded.) Further, the rotation direction of the excavation rod 1 is changed (in FIG. By switching from rotation to normal rotation), the widened excavation blade 2 is reduced in diameter.

In this case, the swing shaft 21 of the widening excavation blade 2 is provided with an inclination of a predetermined angle θ1 with respect to the rotation axis L of the excavation rod 1 and the rotation shaft of the excavation rod 1 with the widening excavation blade 2 closed. A base end portion 22 of the widening excavation blade 2 is bent and attached to the swing shaft 21 so that the outer edge of the widening excavation blade 2 is positioned inside the excavation blade 3 along the longitudinal direction of L, With the widening excavation blade 2 opened, the tip side of the widening excavation blade 2 is extended to the outside (outer peripheral side) of the excavation blade 3.
Here, “along the longitudinal direction of the rotation axis L of the excavation rod 1 with the widening excavation blade 2 closed” means that the angle between the rotation axis L of the excavation rod 1 and the widening excavation blade 2 is 0 to 30 °. The degree, preferably about 0 to 20 °. In the case of the present embodiment, it is 0 ° (the rotation axis L of the excavation rod 1 and the widened excavation blade 2 are parallel).
Further, as means for bending the base end portion 22 of the widening excavation blade 2, the base end portion 22 of the widening excavation blade 2 made of a rod-like body or a plate-like body such as metal is bent or bent from the plate-like body. Any method such as cutting into a shape or joining a rod-like body or a plate-like body into a bent shape by welding, bolts / nuts, rivets or the like can be employed.

The inclination angle θ1 of the swing shaft 21 of the widening excavation blade 2 can be arbitrarily set in the range of 10 to 80 °, more preferably 30 to 60 °.
In the present embodiment, the inclination angle θ1 is set to 45 °, whereby the widening excavation blade 2 is closed from the closed state along the longitudinal direction of the rotation axis L of the excavation rod 1 so that the expansion angle θ2 is 90. It can be shifted to a horizontally open state.
Note that the second embodiment of the widening excavator of the present invention shown in FIG. 2 shows an example in which the inclination angle θ1 is set to 35 °, whereby the widening excavation blade 2 is connected to the longitudinal axis of the rotation axis L of the excavating rod 1. It is possible to shift from a closed state along the direction to an open state where the expansion angle θ2 is 70 °.

As described above, the swing shaft 21 is provided so as to be inclined with respect to the rotation axis L of the excavation rod 1, and along the longitudinal direction of the rotation axis L of the excavation rod 1 with the widening excavation blade 2 closed, In addition, the base end portion 22 of the widening excavation blade 2 is bent so that the outer edge of the widening excavation blade 2 is located inside the excavation blade 3, and is attached to the swing shaft 21, and the widening excavation blade 2 is opened. Since the distal end side 23 of the widening excavation blade 2 is extended outside the excavation blade 3, by changing the rotation direction of the excavation rod 1, a stable behavior of the widening excavation blade 2 is secured and widening is performed. The diameter of the excavating blade 2 can be smoothly and reliably expanded.
That is, in the present embodiment, the widening excavation blade 2 is opened so that the tip side 23 of the widening excavation blade 2 extends outside the excavation blade 3 from a closed state along the longitudinal direction of the rotation axis L of the excavation rod 1. At this time, the widening excavation blade 2 does not move in a plane perpendicular to the rotation axis L of the excavation rod 1 but is inclined with respect to the oscillation shaft 21 in an oblique direction. The widened excavating blade 2 itself is rotated 90 to 180 °, preferably 120 to 180 ° (about 165 ° in the present embodiment) while drawing the trajectory of the shape. Sufficient earth pressure required for expanding the diameter can be ensured, and even when the widening excavation blade 2 moves up and down as the excavation rod 1 moves up and down, stable behavior of the widening excavation blade can be ensured.

  In particular, in the present embodiment, the widening excavation blade 2 is closed, the tip side 23 of the widening excavation blade 2 is positioned below the swing shaft 21, and the excavation disposed on the widening excavation blade 2. The bit piece of the bit 24 is located on the rear end side in the forward rotation direction of the widening excavation blade 2, and the bit piece of the excavation bit 24 is located at least above the widening excavation blade 2 with the widening excavation blade 2 opened. By doing so, widening excavation can be carried out while pulling up the excavation rod 1, and the earth pressure received by the excavation bit 24 is small in the case of normal rotation, and the earth pressure received by the excavation bit 24 is increased in the case of reverse rotation. Thus, a more stable behavior of the widening excavation blade can be secured.

  By these, stable behavior of the widening excavation blades 2 (uniform behavior of the plural widening excavation blades 2) is ensured, and the diameter of the widening excavation blades 2 can be expanded smoothly and reliably, so that the rotation axis L is eccentric. The excavation rod 2 can be driven without rotation, and wide excavation with a large diameter can be performed without being restricted by the outer diameter of the excavation blade 3 or the outer diameter of the excavation rod 2.

In this embodiment, the widening excavation blade 2 is formed of a steel material having a rectangular cross-sectional shape. For example, as shown in the third embodiment of the widening excavation apparatus of the present invention shown in FIG. The cross-sectional shape is trapezoidal or triangular, and a clearance surface is provided, and the cross-sectional area is gradually reduced toward the tip side 23, so that the widening excavation blade 2 is improved in the case of normal rotation while improving the excavation performance. On the other hand, in order to reduce the earth pressure received, in the case of reverse rotation, the earth pressure received by the widening excavation blade 2 is increased to ensure a more stable behavior of the widening excavation blade, and the widening excavation blade is smooth and reliable. The diameter can be expanded.
In this third embodiment, the angle θ3 formed by the rotation axis L of the excavation rod 1 and the widening excavation blade 2 with the widening excavation blade 2 closed is about 10 °. 2 is satisfied along the longitudinal direction of the rotation axis L of the excavating rod 1 in a closed state, and is not excluded from the present invention.
In the first embodiment, the bit piece of the excavation bit 24 disposed on the widening excavation blade 2 is positioned only above the widening excavation blade 2 with the widening excavation blade 2 opened. For example, as shown in FIG. 3 (h), the excavation bit 24 includes a lower bit piece 24b in addition to the upper bit piece 24a of the widened excavation blade 2, and further to the side. Of the excavation bit 24 (in this case, the excavation bit 24 is arranged on the tip side 23 of the wide excavation blade 2 so that the bit pieces 24a, 24b, 24c of the excavation bit 24 protrude from the tip side 23 of the wide excavation blade 2). The excavation performance can be improved.

Furthermore, as shown in the fourth embodiment of the widening excavator of the present invention shown in FIG. 4, the auxiliary widening excavation blade 2 </ b> A can be detachably disposed at the tip of the widening excavation blade 2.
As the fixing means 25 for fixing the auxiliary widening excavation blade 2A to the widening excavation blade 2, any fixing means such as screwing or insertion of a joint pin (not shown) directly or via an auxiliary plate (not shown) is adopted. can do.
Then, a plurality of types of auxiliary widening excavation blades having different lengths are prepared as the auxiliary widening excavation blade 2A, and an appropriate length can be arbitrarily selected from these.
Further, similarly to the widened excavation blade 2, the excavation bit 24 is disposed on the auxiliary widening excavation blade 2A. In this case, one excavation bit 24 can be disposed across the widening excavation blade 2 and the auxiliary widening excavation blade 2A.
As described above, the auxiliary widening excavation blade 2A is detachably disposed at the tip of the widening excavation blade 2, so that the widening excavation with an arbitrary diameter can be performed only by selectively arranging the auxiliary widening excavation blade 2A. (K3 in FIG. 4 (b) indicates the rotation trajectory of the outer edge of the widened excavating blade having an enlarged diameter).

By the way, in each of the above-described embodiments, the distal end side 23 of the widening excavation blade 2 is positioned below the swing shaft 21, but the present invention is not limited to this, and the second widening excavator of the present invention shown in FIG. As shown in the fifth embodiment, the distal end side 23 of the widened excavation blade 2 may be positioned above the swing shaft 21.
As a result, it is possible to ensure a more stable behavior of the widening excavation blade, and it is possible to perform widening excavation to a position near the excavation blade 3 by setting the distance between the excavation blade 3 and the swing shaft 21 of the widening excavation blade 2 small. Thus, it is possible to minimize the slackness of the ground at the bottom and to develop a large support force.

  Further, in each of the above embodiments, the diameter of the widening excavation blade 2 is increased by changing the rotation direction of the excavation rod 1 (switching from forward rotation to reverse rotation). As shown in the sixth embodiment of the widening excavator of the present invention shown in FIG. 6, the rotation direction of the excavating rod 1 is changed (in FIG. 6 (b), switching from forward rotation to reverse rotation) to widen. The diameter of the excavating blade 2 is reduced (K1 in FIG. 6 (b) is the rotation trajectory of the outer edge of the expanded wide excavating blade, and K2 is the rotational trajectory of the outer edge of the expanded wide excavating blade, Respectively.)

  In this embodiment, the bit piece of the excavation bit 24 is positioned at least below the wide excavation blade 2 with the wide excavation blade 2 opened (here, the wide excavation blade 2 of the wide excavation blade 2). In addition to the lower bit piece 24b, an upper bit piece 24a and further a side bit piece 24c are provided, and the widening excavation blade 2 is opened (the widening excavation blade 2 is initially installed). Widening excavation can be carried out while lowering the excavation rod 1 in the state of expanded diameter).

  In addition, the structure of the widening excavation apparatus of each said Example and the effect which a widening excavation apparatus show | play are the same as that of the widening excavation apparatus of 1st Example or 3rd Example unless there is particular description.

As described above, the widening excavator of the present invention has been described based on a plurality of embodiments in which the widening excavator is applied to a soil cement synthetic pile building device, but the application object of the widening excavator of the present invention is a soil cement synthetic pile building Without being limited to the equipment, the widening excavation blade is surely reduced in diameter after the excavation of the full length applied to the foundation of the building, etc. Thus, it can be widely used for the construction of buried piles and cast-in-place concrete piles that are easily lifted.
Further, the present invention is not limited to the configurations described in the above embodiments, and the configurations can be appropriately changed without departing from the spirit thereof, such as appropriately combining the configurations described in the embodiments. is there.

  The widening excavator of the present invention is capable of smoothly and surely expanding or reducing the diameter of the widened excavating blade so that the excavating rod can be rotationally driven without the eccentricity of the rotating shaft and capable of carrying out large diameter widening excavation. Therefore, after the excavation of the entire length applied to the foundation of the building, etc. In addition to being able to be used suitably for the construction of easy embedded piles and cast-in-place concrete piles, it can be widely used for other various excavating devices.

The 1st Example of the widening excavation apparatus of this invention is shown, (a) is a front view, (b) is a top view. It is a front view of 2nd Example of the widening excavation apparatus of this invention. 3 shows a third embodiment of the widening excavator of the present invention, (a) is a plan view, (b) is a front view, (c) is an explanatory view of a swing shaft and widened excavating blades, and (d) (e) ( (f) is explanatory drawing of a widening excavation blade, (g) is explanatory drawing of a excavation bit. The 4th Example of the widening excavation apparatus of this invention is shown, (a) is a front view, (b) is a top view, (c) is explanatory drawing of an auxiliary widening excavation blade. The 5th Example of the widening excavation apparatus of this invention is shown, (a) is a top view, (b) is a front view. The 6th Example of the widening excavation apparatus of this invention is shown, (a) is a front view, (b) is a top view. It is a front view which shows the conventional soil cement synthetic | combination pile construction apparatus.

DESCRIPTION OF SYMBOLS 1 Excavation rod 2 Widening excavation blade 2A Auxiliary widening excavation blade 21 Oscillation shaft 22 Base end part 23 Front end side 24 Excavation bit 25 Fixing means 3 Excavation blade 4 Hollow tube 5 Stabilizer θ1 Inclination of the oscillation shaft with respect to the rotation axis Angle θ2 Widening angle of the widening excavation blade with respect to the rotation axis of the excavation rod θ3 Angle between the rotation axis of the excavation rod and the widening excavation blade when the widening excavation blade is closed L Rotation trajectory K2 Rotation trajectory of the outer edge of the widened excavating blade with expanded diameter K3 Rotation trajectory of the outer edge of the expanded widening excavating blade

Claims (9)

  In the widening excavator in which the widening excavating blade is disposed on the excavating rod provided with the excavating blade via the swing shaft, and the diameter of the widening excavating blade is increased by changing the rotation direction of the excavating rod. The moving shaft is inclined with respect to the rotation axis of the excavation rod, and the base end of the widening excavation blade is bent so as to be positioned along the longitudinal direction of the rotation axis of the excavation rod with the widening excavation blade closed. A widening excavator characterized in that the tip end side of the widening excavation blade is extended to the outside of the excavation blade while the widening excavation blade is opened and attached to the swing shaft. 2. The widening excavator according to claim 1, wherein the outer edge of the widened excavating blade is positioned inside the excavating blade with the widened excavating blade closed.   The widening excavator according to claim 1 or 2, wherein the excavation bit disposed on the widening excavation blade in a state where the widening excavation blade is opened is positioned at least on the upper side of the widening excavation blade.   In the widening excavator in which the widening excavation blade is disposed on the excavation rod provided with the excavation blade via the swing shaft, and the diameter of the widening excavation blade is reduced by changing the rotation direction of the excavation rod. The moving shaft is inclined with respect to the rotation axis of the excavation rod, and the base end of the widening excavation blade is bent so as to be positioned along the longitudinal direction of the rotation axis of the excavation rod with the widening excavation blade closed. A widening excavator characterized in that the tip end side of the widening excavation blade is extended to the outside of the excavation blade while the widening excavation blade is opened and attached to the swing shaft.   5. The widening excavator according to claim 4, wherein the excavation bit disposed on the widening excavation blade in a state where the widening excavation blade is opened is positioned at least on the lower side of the widening excavation blade.   6. The widening excavator according to claim 1, wherein a tip side of the widening excavation blade is positioned below the swing shaft in a state where the widening excavation blade is closed.   6. The widening excavator according to claim 1, wherein a tip side of the widening excavation blade is positioned above the swing shaft in a state where the widening excavation blade is closed.   8. The widening excavator according to claim 1, wherein the widening excavation blade is formed such that earth pressure received during rotation varies depending on the rotation direction.   9. The widening excavator according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein an auxiliary widening excavation blade is detachably disposed at a tip of the widening excavation blade.

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