JP2017166231A - Ground improvement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground improvement device capable of shortening a construction period, by reducing the ground improvement number.SOLUTION: A ground improvement device 100 comprises a main hole drilling bit 30 arranged in a tip part of a main rotary shaft 20 having a coaxial double cylinder structure, a plurality of relative agitation blades 41, 42 and 43 arranged closer to the outer periphery of the main rotary shaft 20 on the base end side than this and mutually rotating in the opposite direction, four sub-rotary shafts 50 arranged so as to enclose the periphery of the main rotary shaft 20 closer to the base end side than these, a sub-hole drilling bit 51 arranged in its lower end part, fairing means 60 for fairing so that a shape of an area excavated by the plurality of hole drilling bits 51 on a virtual plane orthogonal to the main rotary shaft 20, forms a quadrangular shape with the main rotary shaft 20 as the center, agitation blades 23 and 52 respectively arranged on the outer periphery of the main rotary shaft 20 and the sub-rotary shaft 50 closer to the base end side than this, an anti-deflection member 80 and rotation transmission means 70 arranged closer to the base end side than these.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ground improvement device for use in a construction in which a solidified material is injected into soft ground and mixed with excavated soil to solidify the solidified material to improve the ground.

  Various types of equipment have been used in the past to inject solidified materials such as cement milk while excavating soft ground, stir and mix the excavated soil and solidified material, and create improved piles in the ground to strengthen the ground. However, as a thing relevant to this invention, there exists a "ground improvement apparatus" described in patent document 1, for example.

  This "ground improvement device" has an inner shaft and an outer shaft formed as inner and outer double shafts, and an excavation shaft body in which the inner shaft and the outer shaft can be rotated in reverse to each other. A relative agitation blade body attached so as to relatively reversely rotate the inner agitation blade and the outer agitation blade at the inner and outer positions. Further, in this “ground improvement device”, at least one of the inner stirring blade and the outer stirring blade is provided with a solidifying material discharge section for discharging the solidifying material.

  FIG. 10 is a plan view showing the ground surface during the soft ground improvement work using the “ground improvement device” described in Patent Document 1. A region surrounded by one of the plurality of circular portions R1 shown in FIG. 10 is a region that is agitated and mixed by inserting the excavation shaft body constituting the “ground improvement device” once into the ground ( (Hereinafter, the circular portion R1 may be referred to as an improved area per one).

  The diameter of the improvement area (circular portion R1) per one is determined by the outer diameter of the relative agitating blade attached to the tip of the excavation shaft constituting the “ground improvement device”. In general, however, the diameter of the circular portion R1 is about 2,260 mm.

  Further, when the soft ground is improved using the “ground improvement device”, adjacent agitation is performed as shown in FIG. 10 in order to avoid a region that is not stirred and mixed (improved) remaining in the ground. It is constructed so that parts of the mixed region (portion surrounded by the circular portion R1) wrap around each other. Specifically, the center-to-center distances Q1 and Q2 of the adjacent circular portions R1 are both smaller than the diameter of the circular portion R1, 2,260 mm, for example, about Q1 = 1,958 mm and Q2 = 1,695 mm. It is set and constructed.

Japanese Patent Laid-Open No. 2001-200531

  As described above, when the soft ground improvement work is performed using the “ground improvement device” described in Patent Document 1, the adjacent improvement region R1 (the portion surrounded by the circular portion R1 in FIG. 10). It is necessary to wrap some of them together and work without gaps. For this reason, the lap portion P1 shown in FIG. 10 is a waste of work (labor, energy, etc.).

  For example, using the “ground improvement device” described in Patent Document 1 for soft ground with an area of 1000 square meters, the ground improvement work was carried out under the working conditions in which the improvement area per one was as shown in FIG. In this case, in order to improve the target range without gaps, it is actually necessary to have about 300. For this reason, the larger the area of the land to be constructed, the greater the waste of labor and energy, which is also a factor in extending the construction period.

  Therefore, the problem to be solved by the present invention is to enlarge the improvement area by improving the efficiency of one ground improvement work, and further, by reconsidering the improvement area form, it is possible to perform construction without wrapping, and waste of labor and energy. An object of the present invention is to provide a ground improvement device capable of shortening the work period by reducing the number of ground improvements.

The ground improvement device of the present invention is
A main rotary shaft having a coaxial double cylinder structure in which a cylindrical inner shaft and an outer shaft can rotate in opposite directions around the same axis by rotating the base end side by a power source;
A main drilling bit arranged in a state of being connected to the inner shaft at the tip of the main rotating shaft;
A plurality of relative stirring blades arranged on the outer periphery of the main rotation shaft on the base end side from the main drilling bit and rotating in opposite directions;
At least four sub-rotating shafts arranged to surround the main rotating shaft in a posture substantially parallel to the main rotating shaft around the main rotating shaft on the proximal side from the relative stirring blade;
A sub-drilling bit disposed at the lower end of the sub-rotating shaft;
A shaping means for shaping a region where a plurality of sub-drilling bits of the sub-rotation shafts form a polygon centered on the main rotation axis on a virtual plane orthogonal to the main rotation axis;
A plurality of stirring blades disposed on the outer periphery of the main rotating shaft and the outer periphery of the auxiliary rotating shaft closer to the base end side than the shaping means;
Rotation transmission means for transmitting the rotation of the main rotation shaft to the sub rotation shaft.

here,
The relative stirring blades
Inner stirring blades arranged radially on the outer periphery of the outer shaft;
An intermediate stirring blade that is arranged in a substantially U shape on the outer periphery of the inner shaft and rotates outside the rotation region of the inner stirring blade in a direction opposite to the inner stirring blade;
It is desirable to include an outer stirring blade that is arranged in a substantially U-shape on the outer periphery of the outer shaft and rotates outside the rotation region of the intermediate stirring blade in a direction opposite to the intermediate stirring blade. .

in this case,
The inner stirring blade is a flat plate member erected radially from the outer periphery of the outer shaft,
The intermediate stirring blade connects a pair of horizontal blade portions standing from the outer periphery of the inner shaft at two positions separated in the axial direction of the inner shaft with the inner stirring blade interposed therebetween, and the tips of the horizontal blade portions. A longitudinal wing, and
The outer agitating blade connects a pair of horizontal wing portions standing from the outer periphery of the outer shaft at two positions separated in the axial direction of the outer shaft with the intermediate agitating blade interposed therebetween, and the tips of the horizontal wing portions. And a vertical wing portion.

On the other hand, the rotation transmission means includes a plurality of driving members arranged radially on the outer periphery of the outer shaft, and a plurality of driven members arranged radially on the outer periphery of the plurality of auxiliary rotating shafts,
It can be set as the structure arrange | positioned so that a part of said to-be-driven member may always exist in the position which can contact the said driving member in the rotation area | region of the said driving member.

Further, the drive member is a gate-shaped member having a pair of legs standing radially from the outer periphery of the outer shaft,
The driven member can be configured as a rod-like member erected radially from the outer periphery of the auxiliary rotating shaft.

  According to the present invention, the improvement area can be expanded by increasing the efficiency of one ground improvement work, and further, the construction without wrapping can be performed by reviewing the form of the improvement area, and the number of ground improvement works can be reduced except for waste of labor and energy. Thus, it is possible to provide a ground improvement device capable of shortening the work period.

It is a partially-omission perspective view which shows the use condition of the ground improvement apparatus which is embodiment of this invention. It is a partially-omission front view which looked at the ground improvement apparatus shown in FIG. 1 from the arrow X direction. FIG. 3 is a partially omitted cross-sectional view taken along line AA in FIG. 2. FIG. 3 is a partially omitted cross-sectional view taken along line BB in FIG. 2. FIG. 3 is a partially omitted cross-sectional view taken along line CC in FIG. 2. FIG. 3 is a partially omitted sectional view taken along line DD in FIG. 2. FIG. 3 is a partially omitted sectional view taken along line EE in FIG. 2. It is a top view which shows the ground surface improved with the ground improvement apparatus shown in FIG. It is a top view which shows the ground surface under improvement work by the ground improvement apparatus shown in FIG. It is a top view which shows the ground surface under improvement construction by the conventional ground improvement apparatus.

  Hereinafter, the ground improvement apparatus 100 which is embodiment of this invention is demonstrated based on FIGS. As shown in FIG. 1, the ground improvement device 100 is a fixed holder provided at a lower end portion of a leader 2 erected in the vertical direction in front of a machine body 1 of a pile driving machine 10 capable of self-propelled by an endless track 4. 3 is attached. A double pipe rod 5 that is parallel to the leader 2 is provided in front of the leader 2, and a drive motor and a counter rotating gear mechanism (not shown) are provided above the double pipe rod 5. . Below the double tube rod 5, a main rotating shaft 20 described later is integrally connected. The vertical upper side of the main rotating shaft 20 is referred to as a base end side (or upper end side), and the vertical lower side is referred to as a distal end side (or lower end side) (hereinafter the same).

  As shown in FIGS. 1 and 2, in the ground improvement device 100, the base end side is rotationally driven by a power source (drive motor), so that the cylindrical inner shaft 21 and the outer shaft 22 have the same axis 20c. A main rotary shaft 20 having a coaxial double cylinder structure that can rotate in directions opposite to each other is provided.

  A main drilling bit 30 is disposed in a propeller shape at the tip of the main rotating shaft 20 in a state of being connected to the inner shaft 21. The main drilling bit 30 has a comb blade shape. A plurality of relative stirring blades (an inner stirring blade 41, an intermediate stirring blade 42, and an outer rotating blade 43) that rotate in opposite directions are disposed on the outer periphery of the main rotating shaft 20 on the proximal end side of the main drilling bit 30. Thus, the relative stirring unit 40 is formed.

  Four sub-rotating shafts 50 are arranged around the main rotating shaft 20 on the base end side relative to the relative stirring unit 40 so as to surround the main rotating shaft 20 in a posture substantially parallel to the main rotating shaft 20. A comb-blade-shaped sub-drilling bit 51 is disposed in a propeller shape at the lower end of the sub-rotating shaft 50. In addition, in a portion of the sub-rotating shaft 50 on the base end side from the sub-drilling bit 51, an area where the sub-drilling bits 51 of the plurality of sub-rotating shafts 50 are excavated is on a virtual plane orthogonal to the main rotating shaft 20 Then, a shaping means 60 (an improved area securing plate) for shaping so as to form a regular square centered on the main rotation shaft 20 is disposed.

  A plurality of stirring blades 23 and 52 are arranged on the outer periphery of the main rotary shaft 20 and the outer periphery of the sub rotary shaft 50 on the proximal end side with respect to the shaping means 60, respectively, with a distance in the direction of the axis 20c. Further, an anti-blur member 80 is attached to the main rotary shaft 20 and the sub rotary shaft 50 on the base end side with respect to the stirring blades 23 and 52. Further, a rotation transmission means 70 is provided on the main rotating shaft 20 and the sub rotating shaft 50 on the proximal end side with respect to the anti-blur member 80.

  As shown in FIGS. 2 and 3, the relative stirring unit 40 includes a plurality of inner stirring blades 41, intermediate stirring blades 42, and outer stirring blades 43. The plurality of inner stirring blades 41 are radially arranged on the outer periphery of the outer shaft 22 of the main rotating shaft 20 at intervals of 180 degrees. The plurality of intermediate stirring blades 42 are arranged at intervals of 120 degrees so as to form a substantially U shape on the outer periphery of the inner shaft 21, and rotate outside the rotation region of the inner stirring blade 41 in the opposite direction to the inner stirring blade 41. The plurality of outer rotor blades 43 are arranged at 120 degree intervals so as to form a substantially U-shape on the outer periphery of the outer shaft 22, and the outer side of the rotation region of the intermediate stirring blade 42 is opposite to the intermediate stirring blade 42 (inner stirring). Rotate in the same direction as the wing 41).

  The inner stirring blade 41 is a flat plate member that radiates from the outer periphery of the outer shaft 22. The intermediate stirring blade 42 has a pair of horizontal blade portions 42a erected from the outer periphery of the inner shaft 21 at two positions separated in the direction of the axis 20c of the inner shaft 21 across the inner stirring blade 41, and a pair of horizontal blade portions 42a. Vertical wings 42b that connect the tips of the two. The outer agitating blade 43 includes a pair of horizontal wing portions 43a standing up from the outer periphery of the outer shaft 22 at two positions separated in the axial direction 20c of the outer shaft 22 with the intermediate agitating blade 42 interposed therebetween, and the tip of the horizontal wing portion 43a. And a vertical wing portion 43b that connects the two.

  Of the pair of horizontal blade portions 42a constituting the intermediate stirring blade 42, the horizontal blade portion 42a positioned below is 45 degrees around the axis 20c along the rotation direction of the intermediate stirring blade 42 from the upper horizontal blade portion 42a. Since it is provided at the advanced position, the vertical wing part 42b connecting the tips of the pair of horizontal wing parts 42a forms a part of a spiral drawn around the axis 20c.

  Similarly, of the pair of horizontal blade portions 43a constituting the outer stirring blade 43, the lower blade portion 43a positioned below the upper stirring blade 43a is arranged around the axis 20c in the rotational direction of the outer stirring blade 43a. Therefore, the vertical wing portion 43b that connects the tips of the pair of horizontal wing portions 43a forms a part of a spiral drawn around the axis 20c.

  As shown in FIG. 4, the shaping means 60 includes a bearing portion 61 that rotatably holds the inner shaft 21, four support members 62 that extend radially from the outer periphery of the bearing portion 61 at intervals of 90 degrees, A bearing 63 provided at the tip of the support member 62 to hold the sub-rotating shaft 50 rotatably, and a square inner frame member that holds the four bearings 63 so as to be positioned at the apex of a regular square. 64 and a square outer frame member 65 surrounding the frame member 64. Between the inner frame-shaped member 64 and the outer frame-shaped member 65, a plurality of reinforcing members 66 connecting the two are provided in a direction extending radially from the axis 20c.

  As shown in FIGS. 2 and 4, the length of one side of the outer frame-shaped member 65 of the shaping means 60 is equal to the rotation diameter of the main drilling bit 30 (the diameter of the drilling region 30x of the main drilling bit 30). It is. In addition, a part of the outer periphery of the drilling region 51 x of the four sub-drilling bits 51 is located inside the corner portion 67 of the outer frame member 65, and a part of the outer periphery is the outer frame member 65. It arrange | positions so that it may protrude from the edge part 68 of this.

  As shown in FIGS. 2 and 5, a plurality of stirring blades 52 are arranged in a propeller shape on the outer periphery of the auxiliary rotating shaft 50 on the base end side (the base end side of the shaping means 60) with respect to the sub drilling bit 51. . Further, on the outer periphery of the outer shaft 22 of the main rotary shaft 20 in the vicinity of the stirring blade 52 of the sub rotating shaft 50, a plurality of stirring blades 23 positioned above and below the stirring blade 52 of the sub rotating shaft 50 are arranged in a propeller shape. ing. An anti-blur member 80 for holding the plurality of sub-rotating shafts 50 around the main rotating shaft 20 in a fixed state at a position closer to the base end side than the stirring blades 23 and 52 of the main rotating shaft 20 and the sub-rotating shaft 50. Is arranged.

  As shown in FIG. 6, the anti-blur member 80 includes a bearing portion 81 that rotatably holds the inner shaft 21, and four support members 82 that extend radially from the outer periphery of the bearing portion 81 at intervals of 90 degrees. , And a bearing portion 83 provided at the distal end portion of the support member 82 for rotatably holding the auxiliary rotary shaft 50.

  As shown in FIG. 2, rotation transmission means 70 for transmitting the rotation of the main rotary shaft 20 to the four sub rotary shafts 50 is provided on the outer periphery of the sub rotary shaft 50 on the base end side with respect to the anti-blur member 80. It has been. As shown in FIGS. 2 and 7, the rotation transmitting means 70 includes a plurality of drive members 24 arranged radially on the outer periphery of the outer shaft 22 and a plurality of members arranged radially on the outer periphery of the four auxiliary rotating shafts 50. The driven member 53 is provided.

  As shown in FIG. 2, the drive member 24 has a pair of leg portions 24a erected radially from two positions separated from each other in the direction of the axis 20c on the outer periphery of the outer shaft 22, and the ends of the pair of leg portions 24a. It is a gate-shaped member having a connecting portion 24b connected in the direction of the center 20. The driven member 53 is a rod-like member that stands up radially from the outer periphery of the auxiliary rotary shaft 50. As shown in FIG. 7, reinforcing members 24c and 53a are provided between the driving members 24 adjacent to each other in the rotational direction and between the driven members 53 (in FIG. 2, the reinforcing members 24c and 53a is omitted).

  As shown in FIGS. 2 and 7, in the rotation transmitting means 70, a part (tip portion) of the driven member 53 always contacts the connecting portion 24 b of the driving member 24 in the rotation region 24 x of the driving member 24. It is arranged to exist in a possible position. When the plurality of driving members 24 rotate around the axis 20c due to the rotation of the outer shaft 22, the connecting portions 24b of the driving members 24 come into contact with the tip ends of the driven members 53 of the four auxiliary rotating shafts 50, By pressing this, the rotational force is transmitted to the sub-rotating shaft 50, so that the four sub-rotating shafts 50 rotate in the same direction. When the four sub rotating shafts 50 rotate, the plurality of sub drilling bits 51 and the stirring blades 52 provided on each of the sub rotating shafts 50 rotate.

  Next, ground improvement work using the ground improvement device 100 will be described based on FIGS. 1, 2, 8, and 9. As shown in FIG. 1, the ground improvement device 100 is used by being attached to the lower end portion of the leader 2 in front of the machine body 1 of the pile driving machine 10.

  An inner shaft 21 and an outer shaft 22 of the main rotary shaft 20 of the ground improvement device 100 attached to the front of the pile driving machine 10 carried into the ground improvement work site are provided as drive sources (not shown). 1), when the ground improvement device 100 is lowered toward the soft ground that is the object of the improvement work, the main drill bit 30 and the auxiliary drill bit 30 that rotate in the direction of the arrow in FIG. The ground is excavated by the drill bit 51 and the excavated soil is agitated by the relative agitating blades 41, 42, 43 and the agitating blades 23, 52.

  In FIG. 2, the portion indicated by “40x” indicates the vertical surface shape of the stirring region by the relative stirring unit 40. In FIG. 5, the portion indicated by “23x” indicates the horizontal plane shape of the stirring region by the stirring blade 23, and the portion indicated by “52x” indicates the horizontal plane shape of the stirring region by the stirring blade 52.

  In parallel with this, the solidification material (for example, cement milk etc.) was supplied and supplied to the upper end side of the double tube rod 5 from the solidification material supply part (not shown) arrange | positioned at the pile driving machine 10 side. The solidified material is discharged from the distal end portion 20a of the main rotating shaft 20 into the ground via the inside of the hollow portion of the inner shaft 21 of the main rotating shaft 20.

  When the above-described operation is performed while lowering the ground improvement device 100 toward the soft ground, the relative stirring blades 41, 42, and 43 are excavated while the ground is excavated by the main drilling bit 30 and the sub-drilling bit 51. In addition, since the excavated soil and the solidified material are agitated and mixed by the stirring blades 23 and 52 and a region in which the soil and the solidified material are uniformly mixed is formed in the soft ground, the solid ground after the solidified material is solidified. To be improved.

  As described above, the ground improvement device 100 includes the main drilling bit 30 and the four sub-drilling bits 51 having the function of excavating the ground, and the shaping means 60 (the improved area securing plate) having the function of securing the improved area. And. For this reason, an area as shown in FIG. 8 in the ground by one improvement work by the ground improvement apparatus 100 (one work of lifting the ground improvement apparatus 100 to a predetermined depth in the soft ground and then pulling it up). The ground can be improved.

  FIG. 8 is a plan view showing the ground surface improved by one improvement operation using the ground improvement device 100 shown in FIG. 1, and a portion indicated by “30x” is a main drilling bit of the ground improvement device 100. 30 shows a drilling region 30x, and the four parts indicated by "51x" show the drilling region 51x of the sub-drilling bit 51, respectively. A portion indicated by “60x” indicates an improved region (stirring and mixing region) secured (improved) by the ground improvement device 100 including the shaping means 60.

  As shown in FIGS. 1 and 2, the ground improvement device 100 includes four sub-drilling bits 51, a plurality of agitating blades 23 and 52, and shaping means 60 in addition to the main drilling bit 30 and the relative stirring unit 40. Therefore, as shown in FIG. 8, a ground improvement region 60x having a regular square horizontal plane shape can be constructed by one improvement work on the soft ground.

  Therefore, when performing improvement work on a soft ground having a large area, conventionally, as shown in FIG. 10, it is necessary to wrap a part of the adjacent stirring and mixing region (portion surrounded by the circular portion R1) without gaps. However, if the ground improvement device 100 of the present embodiment is used, it is not necessary to wrap a part of the adjacent improvement region 60x. For this reason, the labor and energy required for the ground improvement work can be reduced, and the construction period can be shortened.

  In the ground improvement apparatus 100, the rotation diameter of the main drilling bit 30 is 2000 mm, the rotation diameters of the sub-drilling bit 51 and the stirring blade 52 are 900 mm, and the rotation diameter of the stirring blade 23 is 1400 mm. The length of one edge portion 68 of the outer frame member 65 of the shaping means 60 is 2000 mm. Further, the interval between the sub-rotating shafts 50 adjacent to each other in the longitudinal direction of the edge portion 68 of the square outer frame member 65 is 1200 mm, and the interval between the sub-rotating shafts 50 facing the diagonal direction of the outer frame member 65 is 1700 mm. It is.

  Accordingly, when performing ground improvement work using the ground improvement device 100, as shown in FIG. 9, if construction is performed while moving the insertion points 20p of the main rotary shaft 20 at intervals of 2000 mm in the horizontal direction, adjacent improvement regions 60x. Part of the lap does not wrap, and the ground can be improved without gaps.

  Here, with reference to FIGS. 9 and 10, when the ground improvement device 100 in which the planar shape of the improved region is a square is used, and when the conventional ground improvement device in which the planar shape of the improved region is a circular shape is used. The difference in work efficiency will be described.

  For example, when the ground improvement work is performed on the soft ground having an area of 1000 square meters using the ground improvement device 100, the state shown in FIG. 9 (a state where a part of the adjacent improvement region 60x does not wrap) is shown. Since the improvement work can proceed, the number of ground improvement devices 100 inserted into the ground is 250.

  On the other hand, when the ground improvement work is performed on the soft ground having the same area as described above by using the conventional ground improvement device, as described above, the state shown in FIG. 10 (part of the adjacent improvement region R1). Therefore, the number of insertions of the ground improvement device into the ground is 300.

  As described above, when the ground improvement device 100 is used for the soft ground of 1000 square meters, the number of insertions into the ground can be reduced to about 17% compared to the conventional case. That is, by using the ground improvement device 100, the number of ground improvement can be reduced and the work period can be shortened.

  In addition, the ground improvement apparatus 100 demonstrated based on FIGS. 1-9 shows an example of this invention, and the ground improvement apparatus of this invention is not limited to the ground improvement apparatus 100 mentioned above.

  The ground improvement device of the present invention can be widely used in industrial fields such as civil engineering and construction for the purpose of strengthening soft ground and treating contaminated soil.

DESCRIPTION OF SYMBOLS 1 Machine main body 2 Leader 3 Fixed holder 4 Endless track 5 Double pipe rod 10 Pile driver 20 Main rotating shaft 20a Tip part 20c Axle 20p Insertion point 21 Inner shaft 22 Outer shaft 23,52 Stirring blade 23x, 40x, 52x Stirring Region 24 Driving member 24a Leg portion 24b Connecting portion 24c, 53a Reinforcement member 24x Rotating region 30 Main drilling bit 30x, 51x Drilling region 40 Relative stirring portion 41, 42, 43 Relative stirring blade 42a, 43a Horizontal blade portion 42b, 43b Longitudinal wing part 50 Sub rotating shaft 51 Sub drilling bit 60 Shaping member 60x Improvement area 61, 63, 81, 83 Bearing part 62, 82 Support member 64 Inner frame member 65 Outer frame member 66 Reinforcement member 67 Corner corner 68 Edge part 100 Ground improvement device

Claims (5)

A main rotary shaft having a coaxial double cylinder structure in which a cylindrical inner shaft and an outer shaft can rotate in opposite directions around the same axis by rotating the base end side by a power source;
A main drilling bit arranged in a state of being connected to the inner shaft at the tip of the main rotating shaft;
A plurality of relative stirring blades arranged on the outer periphery of the main rotation shaft on the base end side from the main drilling bit and rotating in opposite directions;
At least four sub-rotating shafts arranged to surround the main rotating shaft in a posture substantially parallel to the main rotating shaft around the main rotating shaft on the proximal side from the relative stirring blade;
A sub-drilling bit disposed at the lower end of the sub-rotating shaft;
A shaping means for shaping a region where a plurality of sub-drilling bits of the sub-rotation shafts form a polygon centered on the main rotation axis on a virtual plane orthogonal to the main rotation axis;
A plurality of stirring blades disposed on the outer periphery of the main rotating shaft and the outer periphery of the auxiliary rotating shaft closer to the base end side than the shaping means;
A ground improvement device comprising: a rotation transmission means for transmitting rotation of the main rotation shaft to the sub rotation shaft. The relative stirring blades
Inner stirring blades arranged radially on the outer periphery of the outer shaft;
An intermediate stirring blade that is arranged in a substantially U shape on the outer periphery of the inner shaft and rotates outside the rotation region of the inner stirring blade in a direction opposite to the inner stirring blade;
The ground according to claim 1, further comprising: an outer stirring blade that is disposed on the outer periphery of the outer shaft so as to have a substantially U-shape and rotates outside the rotation region of the intermediate stirring blade in a direction opposite to the intermediate stirring blade. Improved device. The inner stirring blade is a flat plate member erected radially from the outer periphery of the outer shaft,
The intermediate stirring blade connects a pair of horizontal blade portions standing from the outer periphery of the inner shaft at two positions separated in the axial direction of the inner shaft with the inner stirring blade interposed therebetween, and the tips of the horizontal blade portions. A longitudinal wing, and
The outer agitating blade connects a pair of horizontal wing portions standing from the outer periphery of the outer shaft at two positions separated in the axial direction of the outer shaft with the intermediate agitating blade interposed therebetween, and the tips of the horizontal wing portions. The ground improvement device according to claim 2, further comprising a vertical wing portion. The rotation transmission means includes a plurality of driving members arranged radially on the outer circumference of the outer shaft, and a plurality of driven members arranged radially on the outer circumference of the plurality of auxiliary rotating shafts,
The ground improvement device according to any one of claims 1 to 3, wherein a part of the driven member is arranged so as to always be in a position where it can contact the driving member in a rotation region of the driving member. . The driving member is a gate-shaped member having a pair of legs standing radially from the outer periphery of the outer shaft;
The ground improvement device according to claim 4, wherein the driven member is a rod-like member that rises radially from the outer periphery of the auxiliary rotating shaft.

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