Excavation and mixing tool

Abstract

To provide an excavation and mixing tool which has a simple structure and is capable of uniformly mixing and kneading excavated soil and improvement material by preventing co-rotation.SOLUTION: An excavation and mixing tool A1 is used to improve ground by mixing excavated soil with a slurry-like improvement material while excavating and mixing the ground, and comprises an excavation and mixing shaft 1 extending in the vertical direction, an excavation blade 2 attached to a lower end of the excavation and mixing shaft 1 and used to excavate the ground, a first mixing blade 4 extending radially relative to an axis S of the excavation and mixing shaft 1, a second mixing blade 5 attached via a boss portion 7 loosely fitted around an outer periphery of the excavation and mixing shaft 1 and extending radially relative to the axis S of the excavation and mixing shaft 1, and an adhesion removal blade 6 attached near the excavation and mixing shaft 1 with its blade length aligned along the excavation and mixing shaft 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an excavation and mixing tool of a ground improvement device for carrying out ground improvement by mixing excavated soil with an improvement material while excavating and mixing the ground. [Background technology]

[0002] Conventionally, when constructing a structure on soft ground, ground improvement has been performed as a preventive measure against the subsidence or tilting of the structure. Ground improvement equipment for constructing columnar improved bodies by excavating the ground and mixing the excavated soil with an improvement material mainly composed of a cement-based solidification material is equipped with an excavation and mixing tool. As for the excavation and mixing tool, in addition to a driving mixing blade that rotates integrally with the excavation and mixing shaft to mix the excavated soil, improvement material, improved soil, etc. (hereinafter simply referred to as improved soil), various types of tools have been proposed that are equipped with a co-rotation prevention blade that prevents the excavated and improved soil from rotating together in order to improve the excavation and mixing efficiency.

[0003] Generally, there are two types of anti-rotation blades: those that are immobile in the direction of rotation of the drilling / mixing shaft by engaging and fixing the blade tip to the inner wall of the drilling hole (hereinafter simply referred to as the surrounding ground), and those that rotate freely relative to the drilling / mixing shaft, thereby moving differently from the driven mixing blade (for example, with delayed rotation).

[0004] This type of anti-rotation impeller provides resistance to the excavated and improved soil against the rotation of the driven impeller and also exerts a shearing effect on the excavated and improved soil, thereby enabling effective mixing and kneading of the excavated and improved soil without it rotating together with the driven impeller.

[0005] However, if the excavated and improved soil is a clayey soil with strong adhesion, the excavated and improved soil will adhere to each impeller and swell (hereinafter referred to as soil adhesion), forming a soil lump. Such soil lumps will become integrated with the anti-rotation impeller and the driving impeller, and will be carried around as the driving impeller rotates, resulting in the phenomenon of co-rotation. When the phenomenon of co-rotation occurs, the effectiveness of mixing and kneading will be significantly reduced.

[0006] As a countermeasure against soil adhesion to the impeller, for example, an excavation and mixing tool has been proposed that is equipped with an ultrasonic oscillator on the impeller and emits ultrasonic waves from the ultrasonic oscillator to the excavated and mixed soil near the impeller (see, for example, Patent Documents 1 and 2).

[0007] As a measure to prevent soil from adhering to the drilling / agitating shaft, for example, a drilling / agitating tool has been proposed which has a ring body (ring-shaped collar) loosely inserted on the drilling / agitating shaft between vertically spaced agitating blades so that it can move up and down (see, for example, Patent Documents 3 and 4).

[0008] In addition, an apparatus has been proposed that is equipped with an excavating / mixing tool in which multiple auxiliary mixing members are provided on the mixing blade and the anti-rotation blade (see, for example, Patent Document 5), and an apparatus has been proposed that is equipped with an excavating / mixing tool in which a flexible auxiliary blade is attached to the anti-rotation blade (see Patent Document 6).

[0009] These excavation and mixing tools are said to be able to prevent soil from adhering to the mixing blades and excavation / mixing shaft and to prevent the co-rotation phenomenon by vibrating the excavated / mixed soil near the blades, by sliding parts around the excavation / mixing shaft, or by breaking up the soil lumps using auxiliary parts attached to the mixing blades and / or the anti-co-rotation blades.

[0010] Patent Document 7 discloses an apparatus equipped with an excavating / agitating tool having a plurality of agitating blades above and below a co-rotation prevention blade, with a protruding member provided on the anti-rotation blade so as to protrude toward the agitating blade, and Patent Document 8 discloses an apparatus equipped with an excavating / agitating tool having a blade provided on a boss portion to which the base end of the anti-rotation blade is fixed and loosely fitted in the anti-rotation blade or the rotating shaft (excavating / agitating shaft). Furthermore, Patent Document 9 discloses an apparatus equipped with an excavating / agitating tool having a blade extending vertically fixed to a boss portion to which the anti-rotation blade is fixed.

[0011] These excavating and mixing tools are said to be able to prevent soil lumps from adhering near the base end of the anti-rotation wing by providing a protruding member or blade that extends vertically relative to the horizontally extending anti-rotation wing. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2002-105948 A [Patent Document 2] JP 2004-339798 A [Patent Document 3] Japanese Utility Model Application Publication No. 56-73744 [Patent Document 4] Japanese Patent Application Publication No. 58-54121 [Patent Document 5] JP 2011-140790 A [Patent Document 6] JP 2010-180647 A [Patent Document 7] JP 2004-169374 A [Patent Document 8] JP 2015-218530 A [Patent Document 9] JP 2023-72747 A Summary of the Invention [Problem to be solved by the invention]

[0013] However, according to the above-mentioned conventional techniques, the following problems may occur when the improvement material is diffused or dispersed in the soil.

[0014] In other words, in the technologies disclosed in Patent Documents 1 and 2, not only is the installation of the ultrasonic oscillator while taking into consideration waterproofing, and the routing of the electric wires to the power source that supplies the driving current to the ultrasonic oscillator complicated, but the costs are also high.

[0015] In the techniques of Patent Documents 3 and 4, in order to obtain the effect of preventing soil from adhering to the excavation / agitation shaft, it is necessary to constantly move a ring body (ring-shaped collar) loosely inserted into the excavation / agitation shaft up and down, which creates a problem in feasibility. Also, the technique of Patent Document 3 discloses an example in which a spring is interposed between the agitation blade and the ring body on the excavation / agitation shaft in order to assist the up and down movement of the ring body (see Fig. 6 of Patent Document 3), but this can actually cause the improved soil to become clogged in the spring, which not only makes it impossible to obtain the effect of preventing soil from adhering to the excavation / agitation shaft, but also creates the problem of spending a lot of money and time to remove the clogged improved soil.

[0016] The technologies disclosed in Patent Documents 5 and 6 aim to prevent the phenomenon of co-rotation by breaking down the soil lumps into fine particles using auxiliary members attached to the agitator blades and / or anti-co-rotation blades. However, this creates problems in that the structure of the agitator blades becomes complicated, resulting in significant costs and time spent on maintenance work.

[0017] In the technology according to Patent Document 7 and Patent Document 8, the protruding member or blade (hereinafter referred to as the blade, etc.) is arranged with its width direction aligned with the radial direction of the excavation / mixing shaft and its plate surface facing the rotation direction of the excavation / mixing shaft. In other words, the parts of the blade, etc. that make up the blade face the flow of improved soil caused by the rotation of the excavation / mixing shaft. In addition, when the blade, etc. is fixed to the anti-rotation blade, the plate area of ​​the anti-rotation blade is substantially enlarged, and more load is applied to the anti-rotation blade when the excavation / mixing shaft rotates. For this reason, the anti-rotation blade is subjected to a greater force (moment of force) that tries to rotate the anti-rotation blade around the axis of the excavation / mixing shaft through the improved soil when the excavation / mixing shaft is rotated than when the blade is not provided. For this reason, the engagement between the blade tip of the anti-rotation blade and the ground around the excavation hole is released, inducing the phenomenon of the anti-rotation blade being dragged around the soil mass by the rotation of the excavation / mixing shaft. That is, these blades and the like do not function effectively as blades, and a phenomenon of co-rotation occurs.

[0018] Furthermore, in the arrangement of the blades and the like disclosed in Patent Documents 7 and 8, the direction in which a load acts on the blades and the like due to the rotation of the excavation / agitation shaft is a direction in which the cross section of the components constituting the blades and the like is bent about the weak axis (weak axis direction), causing damage such as bending to the blades and the like.

[0019] In the technology described in Patent Document 9, the blade is fixed to a boss portion equipped with anti-rotation blades, and the blade surface of the blade can be brought into contact with the lumps of soil adhering to the mixing blades to remove them. However, this technique gives rise to the same problems as the blade described in Patent Document 8.

[0020] The present invention has been made in consideration of the above circumstances, and provides an excavating and mixing tool that has a simple configuration and is capable of uniformly mixing and kneading excavated soil and improvement materials by preventing them from rotating together. [Means for solving the problem]

[0021] In order to solve the above-mentioned problems, an excavating and mixing tool according to one embodiment of the present invention is (1) a tool for improving ground by mixing excavated soil and improvement material while excavating and mixing the ground, the tool having an excavating and mixing shaft extending in a vertical direction, an excavating blade provided at the lower end of the excavating and mixing shaft, a plurality of mixing blades arranged above the excavating blades, a cylindrical member into which the excavating and mixing shaft is rotatably inserted, and a blade main body part whose blade length direction extends along the axis of the excavating and mixing shaft, and an adhesion remover wing for removing improved soil adhering to the cylindrical member, and the cross-sectional shape of the wing main body of the adhesion remover wing is characterized in that, in the cross-sectional plane, the width in the direction along a radial line of the outer circumferential circle of the excavation / mixing shaft is defined as a vertical width W1, and the width in the direction along a line perpendicular to the radial line of the outer circumferential circle is defined as a horizontal width W2, and the horizontal width W2 is equal to or greater than the vertical width W1, and the horizontal width W2 is equal to or less than the length of a chord of an arc with a central angle of 90 degrees on the outer circumferential circle of the excavation / mixing shaft or cylindrical member.

[0022] In addition, in the drilling and stirring tool according to another aspect of the present invention, (2) the adhesion drop blade is such that the horizontal width W2 is longer than the vertical width W1.

[0023] In addition, in another aspect of the present invention, in the drilling / mixing tool, (3) in the blade main body portion of the adhesion removal blade, a tapered surface is formed on the side end facing the rotation direction of the drilling / mixing shaft, which continues to the outer surface of the blade main body portion along the blade length direction.

[0024] In addition, in another aspect of the drilling / mixing tool of the present invention, (4) the adhesion removal blade is arranged, in a plan view, within the larger of either an imaginary circle centered on the axis of the drilling / mixing shaft and spaced 150 mm from the outer peripheral surface of the drilling / mixing shaft or the outer peripheral surface of the tubular member, or an imaginary circle with a radius of 1 / 2 the rotation radius of the drilling blade. Effect of the Invention

[0025] The drilling and mixing tool according to the present invention is provided with adhesion removal blades for removing improved soil that adheres to the drilling and mixing shaft or the cylindrical member into which the drilling and mixing shaft is rotatably inserted, so that the improved soil adhering to the shaft can be efficiently removed and the co-rotation phenomenon can be prevented. This makes it possible to improve the mixing efficiency of the improved soil and enhance the quality of the columnar support. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a front view showing a schematic configuration of a drilling and stirring tool according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a side view showing a schematic configuration of a drilling and stirring tool according to a first embodiment of the present invention. [Diagram 3] FIG. 1 is a perspective view showing the configuration of the vicinity of a sticking removal blade of a drilling and stirring tool according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing a schematic configuration of a drilling and stirring tool according to a first embodiment of the present invention. [Diagram 5] FIG. 2 is an explanatory diagram of the function and effect of the drilling and stirring tool according to the first embodiment of the present invention. [Figure 6] FIG. 2 is an explanatory diagram of the function and effect of the drilling and stirring tool according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a plan view showing a schematic arrangement of adhesion remover blades. [Figure 8] FIG. 2 is a plan view showing a schematic arrangement of adhesion remover blades. [Figure 9] FIG. 2 is an explanatory diagram of the cross-sectional shape of the blade body of the adhesion drop blade. [Figure 10] FIG. 2 is an explanatory diagram of the action and effect of the cross-sectional shape of the blade body of the adhesion drop blade. [Figure 11] 13 is an explanatory diagram showing a cross-sectional shape of another modified example of the blade body of the adhesion drop blade. FIG. [Figure 12] FIG. 1 is a front view showing a schematic configuration of a first modified example of the drilling and stirring tool according to the first embodiment of the present invention. [Figure 13] FIG. 4 is a front view showing a schematic configuration of a second modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 14] FIG. 4 is a side view showing a schematic configuration of a second modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 15] FIG. 4 is an explanatory diagram showing the configuration of a third modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 16] FIG. 11 is an explanatory view showing the configuration of a fourth modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 17] FIG. 11 is an explanatory view showing the configuration of a fifth modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 18] FIG. 13 is an explanatory view showing the configuration of a sixth modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 19] FIG. 13 is an explanatory view showing the configuration of a seventh modified example of the drilling and stirring tool related to the first embodiment of the present invention. [Figure 20] FIG. 4 is a front view showing a schematic configuration of a drilling and stirring tool according to a second embodiment of the present invention. [Figure 21] FIG. 5 is a cross-sectional view showing a schematic arrangement of adhesion drop-off blades according to a second embodiment of the present invention. [Figure 22] FIG. 11 is a side view showing a schematic arrangement of adhesion drop-off blades according to a second embodiment of the present invention. [Figure 23] FIG. 11 is a front view showing a schematic configuration of a drilling and stirring tool according to a third embodiment of the present invention. [Figure 24] FIG. 11 is a side view showing a schematic configuration of a drilling and stirring tool according to a third embodiment of the present invention. [Diagram 25] FIG. 11 is a front view showing a schematic configuration of a drilling and stirring tool according to a fourth embodiment of the present invention. [Figure 26] FIG. 11 is a front view showing a schematic configuration of a drilling and stirring tool according to a fifth embodiment of the present invention. [Figure 27] FIG. 13 is a front view showing a schematic configuration of a drilling and stirring tool according to a sixth embodiment of the present invention. [Figure 28] FIG. 1 is an explanatory diagram showing the configuration of a ground improvement device equipped with an excavation and mixing tool according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The present invention relates to an excavation and mixing tool of a ground improvement device that performs ground improvement by mixing excavated soil and improvement materials while excavating and mixing the ground, and in a configuration with multiple mixing blades, the device is provided with adhesion drop blades to reduce adhesion of soil lumps to the mixing blades and excavation and mixing shaft, and to prevent the excavated and improved soil from rotating together. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0028] <1.Soil improvement device> The configuration of a ground improvement device equipped with an excavator / mixer according to the present invention will be described. Fig. 28 shows a ground improvement device K equipped with an excavator / mixer A according to the present invention. As shown in Fig. 28, the main equipment parts of the ground improvement device K are installed on the ground surface of the improved portion of the ground G.

[0029] The ground improvement device K is basically configured to include a leader 210 that is mounted on a self-propelled base machine body 200 and extends in the vertical direction, a rotary drive unit 220 that is attached to the leader 210 so as to be able to rise and fall freely, an excavation and mixing shaft 1 that is formed by extending in the vertical direction and attached to the lower end of the rotary drive unit 220, and an improvement material supply unit 230 that supplies improvement material.

[0030] The improvement material supplying section 230 arranged at the rear of the base machine body 200 supplies a slurry-based improvement material into the borehole. The improvement material supplying section 230 is in communication with an improvement material supply passage inside the drilling / mixing shaft 1 connected to the rotary drive section 220 via an improvement material supplying pipe 231.

[0031] Improvement materials are materials that are mixed with excavated soil to improve the ground. They are slurry-like mixtures whose main components are water and cement-based solidification materials. Other solidification materials, admixtures, additives, neutralizing agents, medicines, chemical agents, etc. other than cement-based solidification materials can also be added depending on the purpose of the ground improvement.

[0032] The improvement material supplied from the improvement material supply section 230 passes through the improvement material supply passage in the excavation / mixing shaft 1, is discharged from a discharge port formed in the excavation / mixing tool A, is dispersed and spread into the excavated ground and soil, and is mixed together with the excavated soil by the excavation / mixing tool A.

[0033] The rotary drive unit 220 enables vertical movement along the extension direction of the leader 210 via a hanging wire 221 by a drive rotary drum built into the base machine body 200 .

[0034] One end of the hanging wire 221 is connected to the driving rotary drum, the middle part is passed through the top part of the leader 210 and wound around a pulley 222 provided on the upper part of the rotary driving part 220 , and the other end is fixed to the upper end part of the leader 210 .

[0035] In other words, the hanging wire 221 converts the rotational driving force of the driving rotary drum into a vertical lifting force along the leader 210 of the rotary driving unit 220, enabling the drilling and mixing tool A to move up and down when penetrating and extracting in ground improvement work.

[0036] A driving machine (not shown) is mounted inside the rotary drive unit 220, and the drilling / agitation shaft 1 is coupled at its base end to the driving machine and driven to rotate.

[0037] The driver inside the rotation drive unit 220 may be any driver that applies a driving force as a rotational force for the excavation / agitation shaft. The rotation drive unit 220 and the driver inside it are not limited to those corresponding to the single-shaft excavation / agitation shaft 1, and may be, for example, a driver corresponding to a multi-shaft excavation / agitation shaft having two or more rotating shafts, or a dual driver corresponding to an excavation / agitation shaft having a dual-shaft structure in which the shafts are driven relative to one another.

[0038] The ground improvement device K thus constructed is provided with an excavation and mixing tool A which is a main part for carrying out ground improvement by mixing the excavated soil with improvement materials while excavating and mixing the ground.

[0039] 2. First embodiment The configuration of the drilling and stirring tool A1 according to the first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 and Fig. 2 are front views each showing a schematic configuration of the drilling and stirring tool A1 according to this embodiment, and Fig. 2 is a side view thereof. Fig. 3 is an enlarged perspective view showing the periphery of the adhesion removing blade 6 of the drilling and stirring tool A1. Fig. 4 is a cross-sectional view cut along line BB in Fig. 1. In these figures, the wall surface 9 of the imaginary drilled hole is shown by a two-dot chain line.

[0040] The excavating and mixing tool A1 in this embodiment is used to improve ground by mixing excavated soil with a slurry-like improvement material while excavating and mixing the ground, and is equipped with an excavating and mixing shaft 1 extending in the vertical direction, an excavating blade 2 attached to the lower end of the excavating and mixing shaft 1 for excavating the ground, a number of mixing blades, and an adhesion removing blade 6 for removing improved soil adhering to the excavating and mixing shaft 1 or members attached to the outer periphery of the excavating and mixing shaft 1.

[0041] The drilling blade 2 has a strip-shaped drilling blade main body 21 extending radially outward from the drilling / agitation shaft 1, and a plurality of bits 22 protruding forward from the lower end of the drilling blade main body 21. The drilling blade main body 21 is supported by the drilling / agitation shaft 1 with its lower end inclined at a predetermined angle toward the front side in the drilling rotation direction. The multiple bits 22 are disposed on the drilling blade main body 21 at predetermined intervals along the blade length direction.

[0042] Further, a discharge port 3 for discharging the improvement material is formed at a position near the lower end of the drilling blade main body 21 on the lower end side of the drilling / mixing shaft 1. The discharge port 3 is arranged so that the center of the discharge port 3 coincides with the axis S of rotation of the drilling / mixing shaft 1, and opens from the outer circumferential surface of the drilling / mixing shaft 1 along the extension direction of the drilling blade 2. The drilling blade 2 is supported by the drilling / mixing shaft 1 with the drilling blade main body 21 inclined at a predetermined angle, so that the drilling blade 2 excavates the ground with the bit 22 and discharges soil and sand upward together with the improvement material discharged from the discharge port 3.

[0043] In this embodiment, two drilling blades 2 are provided at the lower end of the drilling / agitation shaft 1 in point symmetry with respect to the axis S (see FIG. 4). In other words, two drilling blades 2 are provided on both the left and right sides of the outer periphery of the drilling / agitation shaft 1 in a state of being arranged with a phase difference of 180 degrees from each other in a plan view. The number of drilling blades 2 provided on the drilling / agitation shaft 1 is not particularly limited, and for example, there may be multiple blades (three or more) radially arranged from the outer periphery of the drilling / agitation shaft 1. Furthermore, the blade length, blade width, and blade thickness of the drilling blade 2 can be appropriately selected according to the desired improvement diameter and the type of ground to be improved.

[0044] The multiple mixing blades provided above the excavation blade 2 mix the soil excavated by the excavation blade 2 and discharged upward with the improvement material discharged from the discharge port 3. The multiple mixing blades include a first mixing blade 4 whose base end is supported on the outer circumferential surface of the excavation / agitation shaft 1, and a second mixing blade 5 whose base end is supported on a boss portion 7 serving as a cylindrical member provided around the outer periphery of the excavation / agitation shaft 1.

[0045] The first agitating blade 4 is formed in a band-like plate shape, and in side view the blade surface forms an inclined surface that is inclined at a predetermined angle relative to the axis S of the drilling / agitation shaft 1, with one end supported by the drilling / agitation shaft 1. A plurality of first agitating blades 4 (four blades) are provided on the drilling / agitation shaft 1. The four first agitating blades 4 are arranged in pairs, each pair being arranged point-symmetrically about the axis S of the drilling / agitation shaft 1 in plan view, and the two pairs of first agitating blades 4 are supported by the drilling / agitation shaft 1 in two upper and lower stages so that their rotation phases around the axis S differ by 90 degrees.

[0046] The blade length of the first agitating blade 4 is such that the length from the axis S of the drilling / agitating shaft 1 to its tip is approximately the same as that of the drilling blade 2. The first agitating blade 4 is a driven agitating blade that rotates integrally with the drilling / agitating shaft 1 as one end is supported by the drilling / agitating shaft 1. The number of first agitating blades 4 is not particularly limited, and for example, multiple first agitating blades 4 may be arranged radially from the outer circumferential surface in a plan view and in a spiral shape at a predetermined rotation phase in the vertical direction.

[0047] The second agitating blade 5 is formed in a strip shape, and one end is supported by the boss portion 7. The boss portion 7 is a cylindrical member whose inner diameter is slightly larger than that of the drilling / agitation shaft 1, and is loosely fitted to the drilling / agitation shaft 1. In other words, the boss portion 7 is a support member that supports one end of the second agitating blade 5 on its outer circumferential surface, and is also a cylindrical member into which the drilling / agitation shaft 1 is inserted so as to be freely rotatable. As a result, the boss portion 7 can freely rotate around the outer periphery of the drilling / agitation shaft 1 without following the rotational motion of the drilling / agitation shaft 1, and the second agitating blade 5 supported by the boss portion 7 is freely rotatable relative to the drilling / agitation shaft 1. A pair of stoppers 8, 8 that restrict the vertical movement of the boss portion 7 are disposed above and below the boss portion 7 on the drilling / agitation shaft 1. Each of the pair of stoppers 8, 8 is a flange-shaped member fixed to the drilling / agitation shaft 1. The boss portion 7 is disposed at a predetermined height position of the drilling / agitation shaft 1 by its cylindrical peripheral portion being supported in sliding contact with the opposing flange surfaces of a pair of stoppers 8, 8.

[0048] The second agitating blade 5 is configured such that the length from the axis S of the drilling / agitating shaft 1 to the tip is longer than that of the drilling blade 2. In this embodiment, two second agitating blades 5 are arranged point-symmetrically around the axis S of the drilling / agitating shaft 1 in a plan view, and the blade plate surface of the second agitating blade 5 is arranged along the drilling / agitating shaft 1. The second agitating blade 5 rotates at a speed different from that of the drilling / agitating shaft 1, which is stationary or rotates at a predetermined speed in the drilling hole, by making its tip bite into or abut against the wall surface of the drilling hole. In other words, the second agitating blade 5 rotates at a non-constant speed along the flow direction of the improved soil caused by the rotation of the drilling blade 2 and the first agitating blade 4. As a result, the second agitating blade 5 shears the soil and sand, and functions as a co-rotation prevention blade that prevents the agitating blade and the improved soil from becoming a lump and rotating together. The number of second agitating blades 5 is not particularly limited, and for example, four second agitating blades may be arranged to form an approximately cross shape in a plan view.

[0049] In the drilling and mixing tool A1 according to this embodiment, the drilling blade 2, the second mixing blade 5, and the first mixing blade 4 are arranged in this order from the bottom end toward the top.

[0050] The adhesion remover blade 6 is provided along the drilling / mixing shaft 1 with the blade length direction parallel to the axis S of the drilling / mixing shaft 1, and has a blade main body 6a and a connection part 12. That is, the adhesion remover blade 6 is made up of a straight plate part 11 as the blade main body 6a constituting the blade plate part, and a connection part 12 provided on the back side of the straight plate part 11.

[0051] The straight plate portion 11 is a plate-like member having a long rectangular shape and a cross-sectional shape of approximately rectangular shape with the long dimension being the blade length direction. The straight plate portion 11 has a length in the blade length direction that is at least longer than the distance between the pair of upper and lower stoppers 8, 8 on the drilling / agitation shaft 1. In addition, in order to avoid contact between the drilling blade 2 and the first agitation blade 4, the straight plate portion 11 is set to a length shorter than the distance between the drilling blade 2 and the first agitation blade 4 arranged at the lowest position.

[0052] The connecting portion 12 is a portion for attaching the adhesion removing blade 6 to the boss portion 7 , and is provided in a protruding manner at the center of the rear side of the straight plate portion 11 .

[0053] The adhesion remover blade 6 is arranged along the drilling / mixing shaft 1 with one plate surface of the straight plate portion 11 facing the drilling / mixing shaft 1 and the boss portion 7 by fixing the connecting portion 12 to the outer peripheral surface of the boss portion 7, for example, by screwing, and is supported rotatably relative to the drilling / mixing shaft 1. Note that the adhesion remover blade 6 does not necessarily have to have the straight plate portion 11 formed from a single plate body, and may have a vertical length sufficient to cover at least a pair of upper and lower stoppers 8, 8, for example, by arranging plates half the length of the straight plate portion 11 symmetrically in a vertical direction. Also, it may be on either the top or bottom side.

[0054] The thus configured adhesion remover blade 6 is arranged with the blade length direction aligned with the excavation / mixing shaft 1 and one plate surface of the straight plate section 1 facing the excavation / mixing shaft 1 and the outer peripheral surface of the boss section 7, thereby performing the function of removing improved soil adhering to the excavation / mixing shaft 1 in the vicinity of the excavation blade 2 and the first mixing blade 4 in the excavation / mixing shaft 1.

[0055] In the excavating and mixing tool A1 having the above-described configuration, the base end of the excavating and mixing shaft 1 is connected to a drive machine inside the rotary drive unit 220 of the ground improvement device K, and the excavating and mixing shaft 1 is rotated, thereby excavating the ground and mixing the excavated soil with improvement material.

[0056] The action and effect of the adhesion and removal of improved soil from the excavation and mixing shaft 1 by the adhesion remover blade 6 will be described with reference to Figs. 5 and 6. Fig. 5 is a cross-sectional view taken along the line BB in Fig. 1, similar to Fig. 4. In Fig. 5, the wall surface 9 of the imaginary excavation hole is shown by a two-dot chain line, and the movement trajectories of the excavation blade 2 and the adhesion remover blade 6 are shown by a broken line. Fig. 6 is a side view similar to Fig. 2. In Fig. 6, the wall surface 9 of the imaginary excavation hole is shown by a two-dot chain line, and the positions of the excavation blade 2, the first mixing blade 4, and the second mixing blade 5 shown by solid lines in the figure are shown by broken lines when rotated approximately 90 degrees around the axis S of the excavation and mixing shaft 1. Furthermore, in Figs. 5 and 6, improved soil obtained by mixing the excavated soil and the improvement material is shown by dots.

[0057] When the excavation and mixing tool A1 according to this embodiment is used to excavate the ground to be improved and mix the excavated soil with the improvement material by mixing, the rotational force of the excavation and mixing shaft 1 is transmitted to the excavation blade 2 and the first mixing blade 4, and the excavation blade 2 and the first mixing blade 4 rotate together with the excavation and mixing shaft 1. The excavated soil excavated by the excavation blade 2 and the improvement material discharged from the discharge port 3 flow upward from the excavation blade 2 due to the inclination of the excavation blade main body 21 of the excavation blade 2 and the discharge pressure from the discharge port 3. The improved soil mixed with the excavated soil and improvement material that has flowed upward from the excavation blade 2 is pushed by the blade plate of the first mixing blade 4 and flows. At this time, the second mixing blade 5 is in a stationary state with respect to the flow of the improved soil because its tip is bitten into and contacts the wall surface 9 of the excavation hole. The adhesion drop blade 6 supported by the boss portion 7, like the second mixing blade 5, is also in a stationary state with respect to the flow of the improved soil.

[0058] When the drilling blade 2 rotates, the pressure becomes higher toward the radial outside of the excavation hole due to centrifugal force. At this time, the slurry-like improvement material discharged from the discharge port 3 is shear-mixed from the inside to the outside by the centrifugal force of the drilling blade 2, and the remaining slurry-like improvement material is ejected toward the radial inside of the excavation hole where the pressure is lower, that is, upward along the drilling and mixing shaft 1. If the mixability is poor due to a clayey soil layer, the improved soil will adhere to the rotating drilling and mixing shaft 1. If the amount of improved soil adhering to the drilling and mixing shaft 1 continues to increase, the improved soil will adhere from the drilling and mixing shaft 1 to the drilling blade 2 and the first mixing blade 4, forming a large soil lump. Then, the mixing blade's shear mixing function will be lost. After that, the large soil mass blocks the discharge path of the improvement material around the drilling and mixing shaft 1, which was in a low pressure area, and the slurry-like improvement material, which has higher fluidity than the excavated soil, is discharged to the ground side along the outer ground of the excavated hole, bypassing the large soil mass, as an excess fluid that did not mix with the excavated soil. Therefore, the slurry-like improvement material tends to accumulate on the outer periphery of the excavated hole. This reduces the peripheral adhesion of the improved soil to the wall surface 9 of the excavated hole, and a gap is created between the wall surface 9 of the excavated hole and the improved soil, making it easier for so-called edge cutting to occur. In other words, it is easier for the improved soil to rotate together with the rotation of the drilling and mixing shaft 1.

[0059] In this embodiment, the blade body 6a of the adhesion remover blade 6 always scrapes the improved soil around the excavation / mixing shaft 1 (the area of ​​the double circle shown by the broken line in Fig. 5) against the flow of the improved soil, so that it is possible to reliably prevent the improved soil adhering to the excavation / mixing shaft 1 from growing and increasing with the rotation. Furthermore, since the amount of improved soil in contact with the outer circumferential surface of the excavation / mixing shaft 1 can be reduced, the transmission of the rotational motion of the excavation / mixing shaft 1 to the improved soil can be suppressed, and the occurrence of co-rotation can be reduced. In addition, since the adhesion remover blade 6 improves the mixing performance, the improved material does not accumulate on the outer circumferential side of the rotational locus of the excavation blade 2, and the peripheral adhesive force that does not cause edge cutting is maintained, especially in the area of ​​the improved soil shown by dots in Figs. 5 and 6. In other words, the area shown by dots in Figs. 5 and 6 is in a state close to a stationary state with respect to the rotational motion of the excavation / mixing shaft 1. In other words, the improved soil comes into contact with the wall surface 9 of the excavation hole, which is the inner peripheral surface of the unimproved soil part and forms the boundary surface with the cylindrical improved body of the ground, with a certain degree of adhesive force, so that the improved soil does not rotate at the same speed as the excavation / mixing shaft 1, and the phenomenon of co-rotation is prevented.

[0060] Furthermore, whereas the second agitating blade 5 is a horizontal blade extending in a horizontal direction (ground surface) perpendicular to the axis S of the excavation / mixing shaft 1, the adhesion drop blade 6 is a straight blade whose blade main body 6a extends in a vertical direction along the axis S of the excavation / mixing shaft 1. By providing the excavation / mixing tool A1 with agitating blades whose blade plate extension directions differ from those of the excavation / mixing shaft 1 in this way, it is possible to prevent co-rotation, improve the mixing efficiency of the excavated soil and improvement material, and make it possible to obtain a columnar improved body in which the improvement material is uniformly mixed into the excavated soil.

[0061] In this embodiment, the adhesion remover blade 6 is supported by the boss portion 7 at a position where the rotation phase around the axis S differs from that of the second agitating blade 5 by 90 degrees in plan view, but this is not limited to this. As long as an appropriate distance can be ensured from the second agitating blade 5, the adhesion remover blade 6 may be supported at a position where the rotation phase around the axis S differs by 60 degrees, for example. Furthermore, although an example in which a single adhesion remover blade 6 is provided has been described in this embodiment, the number of adhesion remover blades 6 provided on the boss portion 7 is not particularly limited, and there may be, for example, a plurality of adhesion remover blades.

[0062] The arrangement of the adhesion remover blade 6 will be further described with reference to Figs. 7 and 8. Figs. 7 and 8 are plan schematic diagrams showing the arrangement range of the adhesion remover blade 6. In these figures, the drilling blade 2, the first agitating blade 4, the second agitating blade 5 and the adhesion remover blade 6 are omitted. In these figures, the drilling diameter circle corresponding to the wall surface 9 of the drilled hole drawn by the radially outer end of the drilling blade 2 by the rotation of the drilling / agitation shaft 1 is shown by a two-dot chain line, the imaginary circle P with a distance d of 150 mm from the outer circumferential surface of the drilling / agitation shaft 1 or the cylindrical member (boss portion 7) provided on the drilling / agitation shaft 1 and into which the drilling / agitation shaft 1 is rotatably inserted is shown by a dashed line, and the imaginary circle Q with a radius of 1 / 2 the rotation radius r of the drilling blade 2 is shown by a one-dot chain line.

[0063] As explained above with reference to Figures 5 and 6, in order to obtain the effect of the adhesion remover blade 6 removing improved soil adhering to the outer peripheral surface of the drilling / mixing shaft 1 and / or boss portion 7, the blade main body portion 6a of the adhesion remover blade 6 needs to be positioned at a position where, when viewed in a plane, the distance from the outer peripheral surface of the drilling / mixing shaft 1 or the outer peripheral surface of the tubular member (boss portion 7) is within a specified range.

[0064] On the other hand, in the ground improvement method in which a columnar improvement body is constructed underground, an excavation blade 2 having a rotation radius r according to the diameter of the columnar improvement body to be constructed (hereinafter referred to as the improvement diameter) is selected. The improvement diameter is selected according to the scale of the building to be constructed, for example, within the range of 600 mm to 2000 mm. Figure 7 shows an example in which the shaft diameter of the excavation / mixing shaft 1 is 150 mm and the improvement diameter is 800 mm, while Figure 8 shows an example in which the shaft diameter of the excavation / mixing shaft 1 is 200 mm and the improvement diameter is 1600 mm. The reason for arranging the adhesion drop blade 6 within a predetermined range is as follows.

[0065] In the case of highly adhesive ground such as silt or clayey soil layers, when the adhesion of the improved soil to the outer periphery of the excavation / mixing shaft 1 exceeds half the improvement diameter, the shearing effect of the first mixing blade 4 and the second mixing blade 5 decreases, and the mixing efficiency drops significantly. This causes the adhesion of the improved soil to the outer periphery of the excavation / mixing shaft 1 to increase further, causing the co-rotation phenomenon in which the improved soil and the mixing blades rotate together. Taking this phenomenon into consideration, it is preferable to place the adhesion remover blade 6 within an imaginary circle Q whose radius, equivalent to half the improvement diameter, is 1 / 2 the rotation radius r of the excavation blade 2 (see Figure 8).

[0066] On the other hand, if the ground to be improved is a layer of boulders or gravel, or an alternating layer of these, it is considered that the small stones or gravel are sandwiched between the outer circumferential surface of the excavation / mixing shaft 1 or the outer circumferential surface of the boss 7 and the adhesion drop blade 6, and the excavation / mixing shaft 1 and the boss 7 are no longer loosely fitted, and are fixed in place, which drives the excavation / mixing shaft 1 and the boss 7, increasing the adhesion of the improved soil to the outer circumferential surface and causing a co-rotation phenomenon. The typical gravel diameter of gravel contained in gravel layers is 30mm to 40mm, but in actual ground improvement, it is necessary to consider that the maximum gravel diameter (maximum gravel diameter) is about three times the typical gravel diameter. For this reason, if the maximum gravel diameter is 120mm (40mm x 3), it is preferable that the distance d between the outer circumferential surface of the excavation / mixing shaft 1 or the outer circumferential surface of the boss 7 and the adhesion drop blade 6 is 150mm, which allows the largest gravel to pass through.

[0067] 7, when the improved diameter is small (e.g., less than 900 mm) and the imaginary circle Q is smaller than the imaginary circle P, the adhesion drop vane 6 may be disposed outside the imaginary circle Q but within the imaginary circle P. When the improved diameter is large (e.g., 900 mm or more) and the imaginary circle Q is larger than the imaginary circle P, the adhesion drop vane 6 may be disposed outside the imaginary circle P but within the imaginary circle Q.

[0068] That is, the predetermined range for arranging the blade main body 6a of the adhesion remover blade 6 is preferably within the larger of an imaginary circle P centered on the axial center (axis S) of the drilling / mixing shaft 1 in a plan view, with a distance d of 150 mm from the outer circumferential surface of the drilling / mixing shaft 1 or the outer circumferential surface of the cylindrical member (boss portion 7), or an imaginary circle Q with a radius of 1 / 2 the rotation radius of the excavating blade 2. Note that "within a circle" here includes a state in which the part of the adhesion remover blade 6 closest to the drilling / mixing shaft 1 (for example, the inner blade plate surface) is located on the circumference.

[0069] The arrangement of the adhesion remover blades 6 can be freely changed according to the ground and improvement diameter to be applied within a predetermined range defined by the larger of the imaginary circles P and Q. For example, the distance between the outer circumferential surface of the drilling / mixing shaft 1 or the outer circumferential surface of the cylindrical member (boss portion 7) and the adhesion remover blades 6 may be zero. The distance between the outer circumferential surface of the drilling / mixing shaft 1 or the outer circumferential surface of the cylindrical member (boss portion 7) and the blade main body portion 6a of the adhesion remover blades 6 may be set to a distance (e.g., 20 mm) that allows sand to pass but does not trap gravel.

[0070] The cross-sectional shape of the blade main body 6a of the adhesion remover blade 6 will be further described with reference to Figures 9 and 10. Figure 9 is a cross-sectional view taken along line CC in Figure 1. Figure 10 is a schematic diagram illustrating the effect of preventing improved soil from adhering to the excavation / mixing shaft 1 due to differences in the arrangement of a plate-like member (hereinafter referred to as a blade 101) equivalent to a conventional adhesion remover blade and the blade main body 6a.

[0071] The blade body 6a of the adhesion remover blade 6 supported by a cylindrical member such as the boss portion 7 is stationary with respect to the flow of improved soil caused by the rotation of the excavation / mixing shaft 1. The adhesion remover blade 6 is preferably a member having a predetermined width and thickness as the cross-sectional shape of the blade body in order to efficiently scrape off the improved soil (hereinafter referred to as adhering soil) adhering to the excavation / mixing shaft 1 and the cylindrical member (boss portion 7), which causes them to rotate together. Furthermore, the parts constituting the blade body are required to be arranged in a direction that can withstand the load in the direction of the flow of improved soil relative to the excavation / mixing shaft 1 and the cylindrical member (boss portion 7).

[0072] The cross-sectional shape of the blade main body 6a of the adhesion removal blade 6 shown by a solid line in Figure 9 is such that a tapered surface 6c that continues to the outer surface 6b of the blade main body 6a along the blade length is formed at the side end facing the rotational direction of the drilling / mixing shaft 1.

[0073] In addition, the cross-sectional shape of the blade body 6a of the adhesion remover blade 6 shown by the solid line in Fig. 9 is such that the width (plate thickness) in the direction along the radial line y1 of the outer circumferential circle (circle centered on the axis S) of the excavation / mixing shaft 1 is the vertical width W1, and the width in the direction along the line (tangent x1 tangent to the outer circumferential circle) perpendicular to the radial line y1 of the outer circumferential circle is the horizontal width W2, and the horizontal width W2 is longer than the vertical width W1. In other words, the surface on the vertical width W1 side, where the area exposed to the flow of improved soil is narrower, is arranged facing the flow of improved soil. As a result, the direction of the horizontal width W2, which is longer than the vertical width W1 (direction along the tangent x1), becomes the strong axis direction in the members constituting the blade body 6a, and the blade body 6a becomes less likely to deform under the load Q in the direction of the flow of improved soil as shown by the arrow in Fig. 9.

[0074] Furthermore, the cross-sectional shape of the blade body 6a of the adhesion removal blade 6 is adjusted so that the width W2 is within a range in which the central angle of the outer circumferential circle of the excavation / mixing shaft 1 or the cylindrical member (boss portion 7) is equal to or less than the length of the chord of a circular arc with a central angle of 90 degrees, as shown in the blade body 6a indicated by the two-dot chain line in Fig. 9. If the width W2 exceeds this range, improved soil will adhere to the outward surface of the blade body 6a, and the effect of scraping off the improved soil adhering to the excavation / mixing shaft 1 and boss portion 7 will be impaired.

[0075] Further, as shown in Fig. 10(a), the conventional soil discharging plate 101 (see Patent Documents 7 and 8) is arranged with its plate surface facing the flow of improved soil. Taking the fulcrum as the axis S, the force point on the wing body part 6a side as F1, the force point on the soil discharging plate 101 side as F2, the distance from the fulcrum to the force point F1 as L1, and the distance from the viewing point to the force point P2 as L2, when the load applied to the force point F1 is P1 and the load applied to the force point F2 is P2, comparing the conventional soil discharging plate 101 with the wing body part 6a of the landing wing 6 of the present embodiment, for the moment M1 = L1×P1 acting on the wing body part 6a and the moment M2 = L2×P2 acting on the soil discharging plate 101, since it is obvious that L1 < L2, the relationship M1 < M2 holds. That is, a force that tries to rotate the soil discharging plate 101 around the axis of the excavation and agitation shaft 1 through the improved soil acts more on the soil discharging plate 101 when the excavation and agitation shaft 1 is rotated.

[0076] Furthermore, since the conventional soil discharging plate 101 is arranged such that both side end faces of the plate are along the straight line in the radial direction of the outer peripheral circle of the excavation and agitation shaft 1 and the plate surface faces the flow direction of the improved soil, adhesion of the improved soil and re - adhesion of the adhered soil scraped off from around the excavation and agitation shaft 1 by the soil discharging plate 101 are likely to occur on the plate surface with an area larger than the side end face of the plate. As shown by hatching in Fig. 10(b), the adhered soil G1 that could not be completely scraped off by the soil discharging plate 101 remains in the gap between the soil discharging plate 101 and the excavation and agitation shaft 1. Such adhered soil G1 around the excavation and agitation shaft 1 becomes integrated with the adhered soil G2 of the soil discharging plate 101, and it becomes impossible to resist the rotation of the excavation and agitation shaft 1. As a result, the engagement between the wing end of the second agitation wing 5 and the surrounding ground of the excavation hole may be disengaged, and the members supported by the boss part 7 may also rotate together with the soil mass.

[0077] In the landing wing 6 according to the present embodiment, the wing body part 6a (linear plate part 11) is located on the circumference that is concentric with the outer peripheral circle of the excavation and agitation shaft 1 with both side ends of the plate separated from the excavation and agitation shaft 1 by a predetermined distance, and the side end face of the plate with a smaller surface area than the plate surface is arranged to face the flow direction of the improved soil. For this reason, the adhered soil G3 adhering to the wing body part 6a is significantly less than before. Therefore, the co - rotation phenomenon is prevented.

[0078] Furthermore, in the conventional arrangement of the blade 101 relative to the excavation / mixing shaft 1, the load P2 is a load in the weak axial direction, which is weak in bending and prone to breakage. In contrast, in the arrangement of the blade body 6a of the adhesion removing blade 6, the load P1 is a load in the strong axial direction, which is strong in bending and prevents breakage of the blade body 6a.

[0079] Fig. 10(c) is an enlarged view of region D enclosed by a rectangle in Fig. 10(b). Fig. 10(c) shows an example in which the cross-sectional shape of the blade body 6a of the adhesion drop blade 6 has a tapered surface 6c that continues to the outer surface 6b of the blade body 6a over the blade length direction at the side end facing the rotation direction of the drilling / mixing shaft 1, as shown in Fig. 9. As shown in Fig. 10(c), by providing the tapered surface 6c, the amount of adhering soil G4 on the blade body 6a can be made smaller than the amount of adhering soil G3 adhering to the side end face of the rectangular cross section shown by the two-dot chain line.

[0080] Another modified example of the cross-sectional shape of the blade body 6a of the adhesion drop blade 6 will be further described with reference to Fig. 11. In Fig. 11, the X direction is the direction along the horizontal width W2, and the Y direction is the direction along the vertical width W1.

[0081] As explained with reference to Fig. 9, the cross-sectional shape of the blade body 6a of the adhesion remover blade 6 can be modified in various ways as long as the width W2 is equal to or greater than the length of the chord of an arc having a central angle of 90 degrees on the outer circumferential circle of the drilling / mixing shaft 1 or cylindrical member (boss portion 7). Furthermore, the blade width, blade thickness and shape of the adhesion remover blade 6 can be appropriately selected according to the geology of the application ground.

[0082] For example, the cross-sectional shape of the blade body 6a of the adhesion drop blade 6, i.e., the member constituting the blade plate portion, may be a rectangle (FIG. 11(a)), a square (FIG. 11(b)), a triangle (FIGS. 11(c), (d)), a polygon, a trapezoid, a circle (FIG. 11(g)), a semicircle (FIGS. 11(e), (f)), a horseshoe, a crescent, or the like. More specifically, when the cross-sectional shape is a rectangle (FIG. 11(a)), the vertical width W1 can be 15 mm, and the horizontal width W2 can be 40 mm to 60 mm. When the cross-sectional shape is a square (FIG. 11(b)), the vertical width W1 can be 25 mm, and the horizontal width W2 can be 25 mm. When the cross-sectional shape is a circle (FIG. 11(g)), the vertical width W1 can be 20 mm, and the horizontal width W2 can be 20 mm. When the cross-sectional shape is triangular (FIGS. 11(c) and (d)), the vertical width W1 can be 20 mm and the horizontal width W2 can be 40 mm to 60 mm. When the cross-sectional shape is semicircular (FIGS. 11(e) and (f)), the vertical width W1 can be 15 mm and the horizontal width W2 can be 40 mm to 60 mm. Note that the weight of the blade main body 6a can be reduced by bending a thin plate into an L-shape to form a triangular cross-sectional shape as shown in FIG. 11(c), or by bending a thin plate into an approximately U-shape to form a semicircular cross-sectional shape as shown in FIG. 11(e).

[0083] Also, the blade main body 6a can be made by bending a plate material along the arc of the outer circumferential circle of the drilling / mixing shaft 1 or the boss portion 7 so that the width W2 of the cross-sectional shape is equal to or less than the length of the chord of an arc with a central angle of 90 degrees on the outer circumferential circle centered on the axis S (see FIG. 9).

[0084] In addition, the cross-sectional shape of the blade body 6a of the adhesion remover blade 6 is preferably one that has little resistance in the direction of rotation. As shown in Fig. 11(h), the cross-sectional shape of the blade body 6a of the adhesion remover blade 6 is formed by chamfering the two corners of the square shape that are farther from the excavation / mixing shaft 1, so that the soil scraped off from the outer circumferential surface of the excavation / mixing shaft 1 can flow smoothly without being blocked by the blade body 6a. In addition to providing a tapered surface at the corners, the cross-sectional shape of the blade body 6a of the adhesion remover blade 6 may be formed by rounding the corners.

[0085] As shown in Fig. 11(b) and (g), a round bar or a square bar with a cross-sectional shape of the blade main body 6a having a vertical width W1 = horizontal width W2 can be used as the blade main body 6a. Furthermore, by making the cross-sectional shape thinner, with the vertical width W1 shorter than the horizontal width W2, the area of ​​the vertical width W1 side facing the flow of improved soil can be reduced, and the load that the blade main body 6a receives through the improved soil due to the rotation of the excavation / mixing shaft 1 can be reduced. In the arrangement of the blade main body 6a such that the surface on the vertical width W1 side faces the flow of improved soil, if the vertical width W1 is equal to or smaller than the horizontal width W2, at least the load in the weak axis direction does not act on the blade main body 6a, and sufficient strength can be ensured.

[0086] In the cross-sectional shape of the blade main body 6a shown by the solid line in Figure 9 and the cross-sectional shape in Figure 11(h), tapered surfaces are provided at symmetrical positions on the left and right sides of the paper in Figures 9 and 11 so that the resistance to the flow of the improved soil is further reduced by the tapered surfaces regardless of whether the excavating / mixing shaft 1 rotates clockwise or counterclockwise.

[0087] The blade body 6a of the adhesion drop wing 6 according to this embodiment is made of steel, but is not limited to this. The adhesion drop wing 6 can be made of metal, plastic, or other materials as long as they are strong enough not to be easily broken even when hit by gravel, etc. The adhesion drop wing 6 may be manufactured by integral molding, such as casting, or may be manufactured by a processing method suitable for the material, such as welding or bending.

[0088] <3. Modifications of the drilling and mixing tool according to the first embodiment> A modified example of the drilling and stirring tool A1 according to the first embodiment of the present invention will be described.

[0089] [First Modification] As shown in Fig. 12, the first modified drilling and mixing tool A1 has a configuration including an adhesion remover blade 6, in which the upper and lower ends of a straight plate portion 11 are held by a pair of auxiliary members 13, 13. Fig. 12(a) is a partial front view showing the attachment portion of the adhesion remover blade 6 to the boss portion 7, and Fig. 12(b) is a partial side view thereof.

[0090] The pair of upper and lower auxiliary members 13, 13 are, for example, wires formed into a substantially elliptical shape. In this modification, the auxiliary members 13 are shaped so as to be loosely fitted onto the drilling / agitation shaft 1, and are provided individually for the adhesion dropping blades 6.

[0091] In addition, when two adhesion remover blades 6 are provided point symmetrically around the axis S of the drilling and mixing shaft 1, the wire may be formed into a substantially annular shape, and a pair of auxiliary members 13, 13 may be connected to the corresponding positions of the adhesion remover blades 6. In other words, the pair of auxiliary members 13, 13 may support the upper and lower ends of the adhesion remover blades 6 without directly engaging with the drilling and mixing shaft 1. More specifically, the upper auxiliary member 63 may connect the upper ends of the straight plate portions 11 of the adhesion remover blades 6 arranged point symmetrically around the axis S of the drilling and mixing shaft 1, and the lower auxiliary member 13 may connect the lower ends of the straight plate portions 11 of the adhesion remover blades 6 arranged point symmetrically around the axis S of the drilling and mixing shaft 1.

[0092] According to the configuration of the first modified example, the upper and lower ends of the straight plate portion 11 of the adhesion removal blade 6 are connected to the excavation / mixing shaft 1 via auxiliary members 13, 13, thereby making it possible to prevent the end of the straight plate portion 11 from being deformed toward the outer periphery when it is hit by, for example, coarse gravel or larger stones.

[0093] [Second modified example] As shown in FIGS. 13 and 14, the excavating and stirring tool A 1 of the second modified example has an adhesion drop wing 16 having a shape different from that of the adhesion drop wing 6 .

[0094] In the second modified example, the adhesion removing blade 16 has a vertically elongated straight plate portion 17 with its long side in the direction of the axis S of the drilling / mixing shaft 1, end plate portions 18a, 18b extended with steps at the upper and lower ends of the straight plate portion 17, and a connection portion 19 provided on the back side of the straight plate portion 17. The end plate portions 18a, 18b are provided closer to the drilling / mixing shaft 1 than the radial protrusion length of the flanges of the stoppers 8, 8 from the outer circumferential surface of the drilling / mixing shaft 1, and are provided in a stepped shape with respect to the straight plate portion 17 in a side view.

[0095] The adhesion remover blade 16 is provided with its blade length direction parallel to the axis S of the drilling / agitation shaft 1. The blade length along the drilling / agitation shaft 1, which is the sum of the straight plate portion 17 of the adhesion remover blade 16 and the upper and lower end plate portions 18a, 18b, is set to a length such that both ends do not come into contact with the drilling blade 2 and the second agitation blade 5. The length along the drilling / agitation shaft 1 of the straight plate portion 17 of the adhesion remover blade 6 is set to be longer than the distance between a pair of upper and lower stoppers 8, 8 on the drilling / agitation shaft 1. The adhesion remover blade 16 is supported rotatably relative to the drilling / agitation shaft 1, similar to the second agitation blade 5, by fixing the connection portion 19 to the boss portion 7 by welding or screw fastening.

[0096] The length of the upper end plate portion 18a is set in consideration of the distance between the upper stopper 8 and the first agitating blade 4. The length of the lower end plate portion 18b is set in consideration of the distance between the lower stopper 8 and the excavating blade 2. That is, the pair of end plate portions 18a, 18 do not have to be the same length.

[0097] According to the configuration of the second modified example, by arranging the adhesion remover blade 16 along the drilling / agitating shaft 1, the adhesion remover blade 16 can effectively prevent improved soil from adhering to the drilling / agitating shaft 1 in the vicinity of the drilling blade 2 and the first agitating blade 4, where the adhesion remover blade 16 has a diameter smaller than the outer periphery of the boss portion 7.

[0098] Furthermore, according to the configuration of the second modified example, end plate portions 18 are provided at the upper and lower ends of the adhesion removal blade 16, which are positioned closer to the drilling / mixing shaft 1 than the straight plate portion 17, thereby making it possible to avoid deformation of the corners of the blades of the adhesion removal blade 16 due to, for example, being hit by coarse gravel or larger stones.

[0099] [Third modified example] As shown in Fig. 15, the drilling and mixing tool A1 of the third modified example has an adhesion drop blade 26 having a different shape from the adhesion drop blade 6. Fig. 15(a) is a partial front view showing the attachment portion of the adhesion drop blade 26 to the boss portion 7, and Fig. 15(b) is a partial side view thereof.

[0100] In the third modified example, the adhesion removal blade 26 comprises a vertically elongated straight plate portion 27 whose long side runs in the direction of the axis S of the drilling / mixing shaft 1, an upper protrusion 28a protruding toward the outer periphery from the upper end of the straight plate portion 27, a lower protrusion 28b protruding toward the outer periphery from the lower end of the straight plate portion 27, and a connection portion 29 provided on the back side of the straight plate portion 27.

[0101] The length of the straight plate portion 27 of the adhesion removing blade 26 along the drilling / agitating shaft 1 is set to be longer than the distance between a pair of upper and lower stoppers 8, 8 on the drilling / agitating shaft 1 and shorter than the distance between the drilling blade 2 and the first agitating blade 4 located at the lowest position.

[0102] The upper protrusion 28a and the lower protrusion 28b are provided horizontally from the upper and lower ends of the straight plate portion 27 toward the outside in the radial direction of the drilling and mixing shaft 1. The length of the upper protrusion 28a and the lower protrusion 28b is not particularly limited, but for example, the length is set so that the tip of each of them reaches a position from the axis S of the drilling and mixing shaft 1 to about one-third to one-half of the radius of the drilled hole defined by the blade length of the drilling blade 2. As shown in FIG. 15(b), in this modified example, the upper protrusion 28a and the lower protrusion 28b have different lengths, but they may be the same length. Also, either the upper protrusion 28a or the lower protrusion 28b may be omitted.

[0103] The adhesion removing impeller 26 is rotatably supported on the drilling / agitation shaft 1 in the same manner as the second agitation impeller 5 by fixing the connection part 29 to the boss part 7 by welding or screw fastening.

[0104] According to the configuration of the third modified example, the adhesion remover blade 26 has the protrusions 28a, 28b, so that the improved soil can be sheared by the protrusions 28a, 28b in the vicinity of the excavation / mixing shaft 1, thereby improving the mixing efficiency.

[0105] [Fourth Variation] As shown in Fig. 16, the drilling and mixing tool A1 of the fourth modified example has an adhesion drop blade 31 having a shape different from that of the adhesion drop blade 6. Fig. 16(a) is a partial front view showing the attachment portion of the adhesion drop blade 31 to the boss portion 7, and Fig. 16(b) is a partial side view thereof.

[0106] In the fourth modified example, the adhesion remover wing 31 can be said to have a shape obtained by dividing the adhesion remover wing 16 of the second modified example at the center from above to below. The adhesion remover wing 31 is composed of a pair of upper and lower wings 31a, 31b. Each of the pair of upper and lower wings 31a, 31b has a vertically elongated straight plate section 32 with its long side extending along the axis S of the drilling and mixing shaft 1, an end plate section 33 extended from one end of the straight plate section 32 with a step so as to be closer to the drilling and mixing shaft 1 than the straight plate section 32, and a connection section 25 provided at the other end (base end) of the straight plate section 32 toward the drilling and mixing shaft 1 so as to be approximately perpendicular to the plate surface of the straight plate section 32.

[0107] The adhesion removing blade 31 is rotatably supported on the drilling / agitation shaft 1 in the same manner as the second agitation blade 5, by fixing the connection parts 25 of each blade portion 31a, 31b to the boss portion 7 by welding or screw fastening. Also, by arranging each blade portion 31a, 31b symmetrically above and below so that the connection parts 25 face each other, each of the end plate portions 33 of the upper and lower blade portions 31a, 31b is provided closer to the drilling / agitation shaft 1 than the radial protrusion length of the flanges of the stoppers 8, 8 from the outer circumferential surface of the drilling / agitation shaft 1.

[0108] Furthermore, according to the configuration of the fourth modified example, as in the second modified example, the adhesion remover blade 31 is provided with an end plate portion 33 that is positioned closer to the drilling / mixing shaft 1 than the straight plate portion 32, thereby making it possible to avoid deformation of the corners of the blade of the adhesion remover blade 16 due to, for example, hitting coarse gravel or larger stones. [Fifth Variation] As shown in Fig. 17, the drilling and mixing tool A1 of the fourth modified example has an adhesion drop blade 34 having a different shape from the adhesion drop blade 6. Fig. 17(a) is a partial front view showing the attachment portion of the adhesion drop blade 34 to the boss portion 7, and Fig. 17(b) is a partial side view thereof.

[0109] In the fifth modified example, the adhesion remover blade 34 is composed of a pair of upper and lower blades 34a, 34b, similar to the adhesion remover blade 31 in the fourth modified example. Each of the pair of upper and lower blades 34a, 34b has an elongated shape with its long side in the direction of the axis S of the drilling and mixing shaft 1 in a front view, and has an inclined plate portion 35 inclined so that its tip approaches the drilling and mixing shaft 1 in a side view, and a connection portion 39 provided on the inclined plate portion 35 toward the drilling and mixing shaft 1 so as to form an acute angle with the plate surface of the inclined plate portion 35.

[0110] The adhesion removing blade 34 is supported rotatably on the drilling / agitation shaft 1 in the same manner as the second agitation blade 5, by fixing the connection parts 39 of each blade portion 34a, 34b to the boss portion 7 by welding or screwing. Also, by arranging each blade portion 34a, 34b symmetrically above and below so that the connection parts 39 face each other, the respective tips of the inclined plate portions 35 of the upper and lower blade portions 31a, 31b are closer to the drilling / agitation shaft 1 than the radial protrusion length of the flanges of the stoppers 8, 8 from the outer circumferential surface of the drilling / agitation shaft 1.

[0111] Like the inclined plate portion 35 of the adhesion removing blade 34 , a member serving as a blade may be provided at an incline with respect to the excavation / agitation shaft 1 .

[0112] [Sixth Variation] As shown in FIG. 18, the drilling and stirring tool A 1 of the sixth modified example has a sticking drop blade 36 having a shape different from that of the sticking drop blade 6 .

[0113] In the sixth modified example, the adhesion drop blade 36 has a rocking plate portion 37 pivotally attached to a support shaft 45 protruding from the outer peripheral surface of the boss portion 7, and a pair of springs 38, 38 connected to one end side of the rocking plate portion 37. The rocking plate portion 37 is a substantially rectangular plate-shaped member, with one end being a fixed end supported by the support shaft 45 and the other end being a free end. The free end side of the rocking plate portion 37 is formed into a semicircular shape by corner rounding or the like. The length from the support shaft 45 of the rocking plate portion 37 to the edge of the free end is at least a length that covers the stopper 8. In addition, the length from the support shaft 45 of the rocking plate portion 37 to the edge of the free end is a length that does not contact the excavation blade 2 or the first mixing blade 4.

[0114] The pair of springs 38, 38 are provided symmetrically on either side of the support shaft 45 at a position closer to the edge of the fixed end than the support shaft 45. Each of the pair of springs 38, 38 is interposed between the oscillating plate portion 37 and the boss portion 7, and holds the oscillating plate portion 37 in a position in which its length direction is along the axis S of the excavation / mixing shaft 1. When the oscillating plate portion 37 is pushed by gravel or the like and rotates around the support shaft 45 (arrow R in FIG. 18), one of the pair of springs 38, 38 receives the load in the compression direction, and the other spring 38 expands. When the pressure on the oscillating plate portion 37 is released, the urging force of the spring returns the oscillating plate portion 37 to its original position.

[0115] In this modified example, two adhesion drop wings 36 having such a configuration are arranged on the boss portion 7 via a support shaft 45 and a pair of springs 38, 38, with the free end of the adhesion drop wing 36 on the left side of the paper in Figure 18 facing upward, and the free end of the oscillating plate portion 37 on the right side of the paper facing downward.

[0116] According to the configuration of the sixth modified example, in the event of a collision with rough gravel or the like, the oscillating plate portion 37 can be oscillated around the support shaft 45 as shown by arrow R while the springs 38, 38 absorb the impact, thereby avoiding damage to the oscillating plate portion 37, i.e., damage to the adhesion removal blade 36.

[0117] [Seventh Variation] As shown in Fig. 19, the drilling and mixing tool A1 of the seventh modified example has an adhesion remover blade 46. This modified example has a oscillating plate section 37 of the same shape as the adhesion remover blade 36. Meanwhile, in this modified example, the two oscillating plate sections 37, together with the support shafts 45 that support the respective oscillating plate sections 37, are arranged on the same straight line parallel to the axis S of the drilling and mixing shaft 1, and the two oscillating plate sections 37 are connected by a single spring 48.

[0118] The adhesion removal blade 46 has a single spring 48 interposed between the opposing fixed ends of the two oscillating plate sections 37, and holds the two oscillating plate sections 37, each supported by a support shaft 45, in a position along the axis S of the drilling / mixing shaft 1.

[0119] When the oscillating plate portion 37 is pushed by gravel or the like and oscillates around the support shaft 45 (arrow R in Figure 19), the spring 48 receives the load in the compressive direction and deforms, and when the pressure on the oscillating plate portion 37 is released, the spring force causes the oscillating plate portion 37 to return to its original position.

[0120] According to the configuration of the seventh modified example, in the event of a collision with rough gravel or the like, the oscillating plate portion 37 can be oscillated around the support shaft 45 as indicated by arrow R while the spring absorbs the impact, thereby avoiding damage to the oscillating plate portion 37, i.e., damage to the adhesion removal blades 46.

[0121] 3. Second embodiment Next, a drilling and stirring tool A2 according to a second embodiment of the present invention will be described. Note that the same members as those in the first embodiment are given the same reference numerals and detailed descriptions thereof will be omitted.

[0122] In the second embodiment, as shown in FIG. 20 , the drilling and stirring tool A2 has a drilling and stirring shaft 1, a drilling blade 2 for excavating the ground, a first stirring blade 4 having one end supported on the outer peripheral surface of the drilling and stirring shaft 1, and a plurality of second stirring blades 5 having one end supported on a boss portion 7 loosely fitted into the drilling and stirring shaft 1, which is similar to the first embodiment.

[0123] On the other hand, the second embodiment differs from the first embodiment in that the adhesion dropping blade 56 , whose blade length direction is provided along the drilling / agitation shaft 1 , is supported by the second agitation blade 5 .

[0124] The adhesion removing blade 56 is a rod-like body having a length longer than the distance between a pair of upper and lower stoppers 8, 8 on the drilling / agitation shaft 1. The blade length of the adhesion removing blade 56 is set to be shorter than the distance between the drilling blade 2 and the first agitation blade 4 located at the lowest position in order to avoid contact with the drilling blade 2 and the first agitation blade 4.

[0125] The adhesion remover blade 56 is fixed at its side end near the center of its rod-shaped body to the blade surface of the second agitating blade 5 without any particular connection. The adhesion remover blade 56 can be fixed by welding or screw fastening using fasteners. In other words, the adhesion remover blade 56 is supported by the boss portion 7 via the second agitating blade 5. Therefore, the adhesion remover blade 56 is arranged along the drilling / agitation shaft 1 and is supported rotatably relative to the drilling / agitation shaft 1.

[0126] The adhesion remover blade 56 configured in this manner is arranged along the excavation / mixing shaft 1, thereby fulfilling the function of removing improved soil adhering to the excavation / mixing shaft 1. To fulfill this function, it is sufficient that one adhesion remover blade 56 is arranged on either one of the two second agitating blades 5 that are positioned point-symmetrically about the axis S, but it may also be provided on each of the two second agitating blades 5.

[0127] The attachment position of the adhesion remover blade 56 in the second agitating blade 5 will be further described. Figures 21 and 22 are diagrams showing the arrangement of the adhesion remover blade 56. Figure 21 is a cross-sectional view taken along the line EE in Figure 20, and Figure 22 is a side view. In these figures, the wall surface 9 of the imaginary drilling hole is shown by a two-dot chain line, and the adhesion remover blade 57, which is a modified example of the adhesion remover blade 56, is shown by a two-dot chain line with a different pitch from the two-dot chain line showing the wall surface 9 of the drilling hole. In Figure 16, the drilling blade 2 is omitted, and a virtual circle P with a distance d of 150 mm from the outer peripheral surface of the boss portion 7 is shown by a dashed line, and a virtual circle Q with a radius of 1 / 2 the rotation radius r of the drilling blade 2 is shown by a one-dot chain line.

[0128] The adhesion remover blade 56 supported by the boss section 7 via the second agitating blade 5 in the second embodiment is also arranged within the larger of an imaginary circle P centered on the axial center (axis line S) of the drilling / agitation shaft 1 in plan view and spaced 150 mm from the outer circumferential surface of the drilling / agitation shaft 1 or the outer circumferential surface of the boss section 7, or an imaginary circle Q with a radius half the rotation radius of the drilling blade 2, in the same manner as the arrangement of the adhesion remover blades described with reference to Figures 7 and 8. Note that "within a circle" here includes a state in which the part (surface) of the adhesion remover blade 56 closest to the drilling / agitation shaft 1 is located on the circumference (see Figures 21 and 22).

[0129] Furthermore, it goes without saying that the arrangement of the adhesion drop blades 56 can be freely changed within a predetermined range defined by the larger of the imaginary circles P and Q, depending on the application ground and improvement diameter.

[0130] Although the adhesion drop wing 56 is composed of a single member, the adhesion drop wing 57 may be composed of two members, an upper wing portion 57a ​​and a lower wing portion 57b, as in the adhesion drop wing 57 shown by the two-dot chain line in Fig. 22. Even in this case, the adhesion drop wing is disposed within a predetermined range defined by the larger of the imaginary circles P and Q.

[0131] According to the configuration of the second embodiment, since the adhesion removing blades 56, 57 are attached to the second agitator blade 5, an extremely simple configuration is possible in which there is no need to provide a connection part of a length equivalent to the separation distance between the boss portion 7 and the blade plate, thereby reducing the manufacturing costs of the adhesion removing blades.

[0132] <4. Third embodiment> Next, a description will be given of a drilling and stirring tool A3 according to a third embodiment of the present invention. Note that the same members as those in the first embodiment are given the same reference numerals and detailed descriptions thereof will be omitted.

[0133] The third embodiment differs from the first and second embodiments in that, as shown in Figures 23 and 24, it has a boss portion 77 which is longer in the vertical direction than the boss portion 7 in the drilling and mixing tools A1, A2, and in that an adhesion removal blade 66 is provided for each of a pair of upper and lower stoppers 8, 8.

[0134] The adhesion drop wing 66 has a straight plate portion 67 which is a rectangular plate-like body, and a connection portion 68 which is connected at a substantially right angle to one end of the straight plate portion 67. The straight plate portion 67 and the connection portion 68 are integrally formed, and the adhesion drop wing 66 has a substantially L-shape in side view (see FIG. 24).

[0135] The adhesion removing impeller 66 is attached to a pair of upper and lower stoppers 8, 8 fixed to the drilling / agitation shaft 1, and therefore rotates integrally with the drilling / agitation shaft 1, without being synchronized with the rotation of the second agitating impeller 5 supported by a boss portion 77 loosely fitted in the drilling / agitation shaft 1. Therefore, the length of the straight plate portion 67 of the adhesion removing impeller 66 is set so that, when each is attached to a pair of upper and lower stoppers 8, 8, the tip of the straight plate portion 67 does not interfere with the rotation of the second agitating impeller 5 supported on the outer peripheral surface near the center in the vertical direction of the boss portion 77.

[0136] The straight plate portions 67, 67 of the adhesion removing blades 66 attached to the upper and lower stoppers 8, 8 respectively are arranged along the drilling / mixing shaft 1 with a gap between their tips to avoid collision with the second mixing blade 5 shown by the dashed line in Figure 24.

[0137] In this embodiment, the two adhesion removing blades 66 are arranged in pairs above and below on the same straight line parallel to the axis S of the drilling / mixing shaft 1, but this is not limited to this. The two adhesion removing blades 66 may be arranged at different positions above and below the second mixing blade 5.

[0138] In this embodiment, the tip of the second agitating impeller 5 bites into the ground outside the wall surface 9 of the excavation hole, so that the second agitating impeller 5 and the boss portion 77 are stationary, and the adhesion removing impeller 66 rotates integrally with the rotation of the drilling / agitating shaft 1. In other words, since it revolves around the boss portion 77 at a position spaced a predetermined distance from the outer circumferential surface of the boss portion 77, the improved soil adhering to the boss portion 77 can be reliably removed.

[0139] The adhesion remover impeller 66 configured in this way is supported by the excavation / agitation shaft 1 via stoppers 8, 8, which are members that move (rotate) differently from the second agitation impeller 5, and thereby performs the function of removing improved soil that has adhered to the excavation / agitation shaft 1 in the vicinity of the excavation / agitation shaft 1 between the excavation impeller 2 and the first agitation impeller 4 in the vertical direction. In other words, by arranging the adhesion remover impeller so that it moves (rotates) differently from either the first agitation impeller 4 or the second agitation impeller 5, it is possible to perform the function of removing improved soil and prevent them from rotating together.

[0140] <5. Fourth embodiment> Next, a drilling and stirring tool A4 according to a fourth embodiment of the present invention will be described. Note that the same members as those in the first embodiment are given the same reference numerals and detailed descriptions thereof will be omitted.

[0141] In the fourth embodiment, as shown in FIG. 25, the drilling and mixing tool A4 is a two-shaft drilling and mixing tool having two parallel drilling and mixing shafts 1 extending in the vertical direction and configured so that the two drilling and mixing shafts 1 are rotated in opposite directions to each other.

[0142] The drilling / mixing tool A4 has a configuration in which, from the lower end side, the drilling blade 2, boss portion 7, first mixing blade 4, boss portion 7, and first mixing blade 4 are arranged on each drilling / mixing shaft 1. The drilling / mixing tool A4 has two boss portions 7 for each drilling / mixing shaft 1, and an anti-sway plate 41 is installed between the boss portions 7 of the two drilling / mixing shafts 1 at the same height position.

[0143] The anti-vibration plate 41 is intended to keep the relative positions of the two drilling / agitation shafts 1 constant by connecting them to each other via the boss portion 7. The anti-vibration plate 41 has the same blade width and blade thickness as the second agitation impeller 5 and is formed in a band-like shape. Both ends of the anti-vibration plate 41 are located at positions 180 degrees opposite to the support positions of the second agitation impeller 5 at each boss portion 7. Therefore, like the second agitation impeller 5, the anti-vibration plate 41 functions as a co-rotation prevention blade and exerts a shearing action on the improved soil.

[0144] In the drilling and mixing tool A4, the adhesion drop blades 6 explained in the first embodiment are arranged for each boss portion 7.

[0145] In this embodiment, the boss portion 7 loosely fitted to each excavation / agitation shaft 1 is connected by the anti-vibration plate 41, so that the second agitation impeller 5 and the boss portion 7 are stationary relative to the rotating excavation / agitation shaft 1. The excavation / agitation shaft 1 rotates relative to the stationary soil removal impeller 66, so that improved soil adhering to the excavation / agitation shaft 1 can be reliably removed.

[0146] In the excavating / mixing tool A4 configured in this manner, the adhesion remover blade 66 is arranged along the excavating / mixing shaft 1 with its blade length direction parallel to the axial direction of the excavating / mixing shaft 1, so that the adhesion remover blade 66 functions to remove improved soil adhering to the excavating / mixing shaft 1 in the vicinity of the excavating / mixing shaft 1 between the excavating blade 2 and the first mixing blade 4.

[0147] <6. Fifth embodiment> Next, a drilling and stirring tool A5 according to a fifth embodiment of the present invention will be described. Note that the same members as those in the first and third embodiments are given the same reference numerals and detailed descriptions thereof will be omitted.

[0148] In the fifth embodiment, as shown in FIG. 26, the drilling and mixing tool A5 has a drilling and mixing shaft 1 extending in the vertical direction and an outer shaft 51 fitted onto the drilling and mixing shaft 1, and is a dual-shaft drilling and mixing tool configured so that rotations in opposite directions are transmitted to the drilling and mixing shaft 1 and the outer shaft.

[0149] The drilling and stirring tool A5 also differs from the drilling and stirring tools A1 to A4 according to the first to fourth embodiments in that it has a second stirring blade 52 formed in a band-shaped arc shape. The drilling and stirring tool A5 has a configuration in which the drilling blade 2, boss portion 7, first stirring blade 4, and outer shaft 51 are arranged in this order from the lower end side of the drilling and stirring shaft 1.

[0150] The second agitating impeller 52 has a strip-shaped impeller main body 52a having an arc-shaped outer shape, and a pair of upper and lower impeller support parts 52b, 52b that extend through a bent part toward the outer shaft 51 and the boss part 7 and are connected to the outer peripheral surfaces of the outer shaft 51 and the boss part 7, respectively. That is, in this embodiment, the outer shaft 51 is a support member that supports at least one end of the second agitating impeller 52, similar to the boss part 7. The boss part 7, loosely fitted in the drilling / agitating shaft 1, is connected to the outer shaft 51 via the second agitating impeller 52, and rotates integrally with the outer shaft 51.

[0151] In the drilling and mixing tool A5, the adhesion remover blade 6 described in the first embodiment is arranged on the outer peripheral surface of the boss portion 7, and the adhesion remover blade 66 described in the third embodiment is arranged on the outer peripheral surface of the outer shaft 51, which serves as a support member supporting the second mixing blade 52.

[0152] The first agitating impeller 4 has a blade length that does not contact the blade body 52a of the second agitating impeller 52, and one end of the first agitating impeller 4 is supported on the outer peripheral surface between the upper end of the adhesion removing blade 6 provided on the boss portion 7 of the drilling / agitation shaft 1 and the lower end of the adhesion removing blade 66 provided on the outer shaft 51. In Fig. 22, the position of the first agitating impeller 4 when rotated approximately 90 degrees around the axis S of the drilling / agitation shaft 1 is shown by a dashed line.

[0153] As the drilling / agitation shaft 1 and the outer shaft 51 rotate in opposite directions, the second agitation blade 5 and the adhesion removal blades 6, 66 rotate in the opposite direction (e.g., counterclockwise) to the rotation direction (e.g., clockwise) of the drilling blade 2 and the first agitation blade 4.

[0154] In this embodiment, the adhesion remover blade 6 on the boss portion 7 and the adhesion remover blade 66 on the outer shaft 51 are arranged on the same straight line parallel to the axis S of the drilling / mixing shaft 1, but this is not limiting. The adhesion remover blade 6 and the adhesion remover blade 66 may be arranged at different positions around the axis above and below the second mixing blade 5.

[0155] In the excavating / mixing tool A5 configured in this manner, the adhesion remover blades 6, 66 are arranged along the excavating / mixing shaft 1 with their blade length direction parallel to the axial direction of the excavating / mixing shaft 1, so that the adhesion remover blades 6, 66 function to remove improved soil adhering to the excavating / mixing shaft 1 in the vicinity of the excavating / mixing shaft 1 between the excavating blade 2 and the first mixing blade 4.

[0156] <7. Sixth embodiment> Next, a drilling and stirring tool A6 according to a sixth embodiment of the present invention will be described. Note that the same members as those in the first and fifth embodiments are given the same reference numerals and detailed descriptions thereof will be omitted.

[0157] In the sixth embodiment, as shown in FIG. 27, the drilling and mixing tool A6 is a dual-shaft drilling and mixing tool similar to the drilling and mixing tool A5 described with reference to FIG. 26, which has a drilling and mixing shaft 1 extending in the vertical direction and an outer shaft 51 fitted onto the drilling and mixing shaft 1, and is configured so that rotations in opposite directions are transmitted to the drilling and mixing shaft 1 and the outer shaft 51.

[0158] The second agitating blade 55 is disposed on the outer peripheral surface of the outer shaft 51 as a support member for supporting the second agitating blade 52. In addition, the outer peripheral surface of the outer shaft 51 supports the first agitating blade 4 and the adhesion removing blade 66 described in the third embodiment.

[0159] The second agitating impeller 55 differs from the second agitating impeller 5 described in the first to third embodiments in that the length from the axis S of the drilling / agitating shaft 1 is equal to that of the drilling impeller 2. As a result, the tip of the second agitating impeller 55 does not pierce the wall surface 9 of the drilling hole, and rotates integrally with the outer shaft 51.

[0160] As the drilling / agitation shaft 1 and the outer shaft 51 rotate in opposite directions to each other, the first agitation blade 4, the second agitation blade 55 and the adhesion removal blade 66 rotate in the opposite direction (e.g., counterclockwise) to the rotation direction of the drilling blade 2 (e.g., clockwise).

[0161] In the drilling / mixing tool A6 configured in this manner, the adhesion remover blade 66 is arranged along the drilling / mixing shaft 1 with its blade length direction parallel to the axial direction of the drilling / mixing shaft 1, so that it functions as an adhesion remover blade that removes improved soil adhering to the drilling / mixing shaft 1 in the vicinity of the drilling / mixing shaft 1 between the drilling blade 2 and the first mixing blade 4.

[0162] As explained above, according to the present invention, by providing the excavation and mixing tools (A1, A2, A3, A4, A5, A6) with adhesion drop-off blades (6, 16, 26, 31, 34, 36, 46, 56, 66) along the excavation and mixing shaft 1, it is possible to drop the improved soil adhering to the excavation and mixing shaft 1 and reliably prevent it from rotating together with the shaft. This improves the mixing efficiency of the excavated soil and improvement material, makes it possible to obtain a columnar improved body in which the improvement material is uniformly dispersed, and improves the quality of the columnar improved body.

[0163] The drilling and mixing tools (A1, A2, A3, A4, A5, A6) of the present embodiment having the above-mentioned configuration can be said to have the following configuration. That is, the drilling and mixing tool (A1, A2, A3, A4, A5, A6) comprises a drilling and mixing shaft 1 extending in the vertical direction, a drilling blade 2 provided at the lower end of the drilling and mixing shaft 1, a plurality of mixing blades (first mixing blade 4, second mixing blade 5) arranged above the drilling blade 2, a tubular member (boss portion 7, 77, outer shaft 51) into which the drilling and mixing shaft 1 is inserted so as to be able to rotate freely, and an adhesion drop blade (boss portion 7, 77, outer shaft 51) having a blade main body portion (6a, straight plate portion 11, 17, 32, inclined plate portion 35, oscillating plate portion 37, adhesion drop blade 56, upper blade portion 57a, lower blade portion 57b, straight plate portion 67) whose blade length direction extends along the axis S of the drilling and mixing shaft 1, and for dropping improved soil adhering to the drilling and mixing shaft 1 and / or the tubular member (boss portion 7, 77, outer shaft 51).

[0164] Here, the cylindrical member is configured so that the drilling / agitation shaft 1 is inserted into it so as to be freely rotatable, and is configured to correspond to boss portions 7, 77 which are loosely fitted onto the drilling / agitation shaft 1, and an outer shaft 51 which is fitted onto the outside of the drilling / agitation shaft 1 and rotates relative to the drilling / agitation shaft 1.

[0165] In addition, in the drilling and mixing tools (A1, A2, A3, A4, A5, A6) of this embodiment, the cross-sectional shape of the blade main body portion (6a, straight plate portion 11, 17, 32, inclined plate portion 35, oscillating plate portion 37, adhesion removal blade 56, upper wing portion 57a, lower wing portion 57b, straight plate portion 67) in the adhesion removal blade (6, 16, 26, 31, 34, 36, 46, 56, 66) is such that, in the cross-sectional plane, the width in the direction along the radial line y1 of the outer peripheral circle of the drilling and mixing shaft 1 is the vertical width W1, and the width in the direction along the line x1 perpendicular to the radial line of the outer peripheral circle is the horizontal width W2, and the horizontal width W2 is equal to or greater than the vertical width W1, and the horizontal width W2 is equal to or less than the length of the chord of an arc with a central angle of 90 degrees on the outer peripheral circle of the drilling and mixing shaft 1 or the cylindrical member (boss portion 7, 77, outer shaft 51).

[0166] With this configuration, the wing main body portion (6a, straight plate portion 11, 17, 32, inclined plate portion 35, oscillating plate portion 37, adhesion removal wing 56, upper wing portion 57a, lower wing portion 57b, straight plate portion 67) faces the flow of improved soil at the end face on the vertical width W1 side, so that the wing main body portion is not subjected to load in the weak axis direction, which prevents damage to the wing main body portion and efficiently scrapes off soil adhering to the excavation / mixing shaft 1 or cylindrical member, thereby preventing the co-rotation phenomenon.

[0167] In the drilling and stirring tools (A1, A2, A3, A4, A5, A6) according to the present embodiment, the adhesion removing blades (6, 16, 26, 31, 34, 36, 46, 56, 66) have a width W2 of the blade main body that is longer than a length W1.

[0168] With this configuration, the wing main body portion (6a, straight plate portion 11, 17, 32, inclined plate portion 35, oscillating plate portion 37, adhesion drop wing 56, upper wing portion 57a, lower wing portion 57b, straight plate portion 67) of the adhesion drop wing is always loaded in the strong axis direction, which makes it possible to better prevent damage to the wing main body portion.

[0169] In addition, in the drilling and mixing tools (A1, A2, A3, A4, A5, A6) of this embodiment, the blade main body portion (6a, straight plate portion 11, 17, 32, inclined plate portion 35, oscillating plate portion 37, adhesion removal blade 56, upper blade portion 57a, lower blade portion 57b, straight plate portion 67) of the adhesion removal blade (6, 16, 26, 31, 34, 36, 46, 56, 66) has a tapered surface 6c that connects to the outer surface of the blade main body portion along the blade length at the side end facing the rotation direction of the drilling and mixing shaft 1.

[0170] With this configuration, the area of ​​the end face of the blade body on the vertical width W1 side facing the flow of improved soil is reduced, and the tapered surface 6c receives and deflects the flow of improved soil, thereby reducing the load on the blade body. This makes it possible to prevent damage to the blade body more effectively, and also ensures that the end face of the blade body on the vertical width W1 side facing the excavation / mixing shaft 1 scrapes off soil adhering to the excavation / mixing shaft 1 and the cylindrical member, preventing them from rotating together.

[0171] In addition, in the drilling and mixing tools (A1, A2, A3, A4, A5, A6) of this embodiment, the adhesion removal blades (6, 16, 26, 31, 34, 36, 46, 56, 66) are arranged with their blade length direction along the axis S of the drilling and mixing shaft, whichever is larger, either an imaginary circle P centered on the axis (axis S) of the drilling and mixing shaft 1 in a plan view and spaced 150 mm from the outer peripheral surface of the drilling and mixing shaft 1 or the outer peripheral surface of the cylindrical member, or an imaginary circle Q with a radius of 1 / 2 the rotation radius of the drilling blade 2.

[0172] The adhesion remover blades (6, 16, 26, 31, 34, 36, 46, 56, 66) are supported by the drilling / mixing shaft 1 or the cylindrical member (boss portion 7, 77, outer shaft 51), but the term "supported" here includes both direct and indirect support by the drilling / mixing shaft 1 or the cylindrical member (boss portion 7, 77, outer shaft 51). In other words, the adhesion remover blades (6, 16, 26, 31, 34, 36, 46, 56, 66) may be supported via a member fixed to the drilling / mixing shaft 1 or the cylindrical member.

[0173] Moreover, the adhesion remover blades (6, 16, 26, 31, 34, 36, 46, 56, 57) may be provided only on either the top or bottom along the excavation / mixing shaft 1. Even with such an arrangement, the adhesion remover blades (6, 16, 26, 31, 34, 36, 46, 56, 57) are effective in preventing the co-rotation phenomenon and improving mixing performance.

[0174] The adhesion removing blades (6, 16, 26, 31, 34, 36, 46, 56, 66) are provided between the drilling blade 2 and the lowest stirring blade supported by the drilling / agitation shaft 1. Here, the lowest stirring blade supported by the drilling / agitation shaft corresponds to the first stirring blade 4 located at the lowest position among the first stirring blades 4 which are driving stirring blades that rotate integrally with the drilling / agitation shaft 1 by being supported by the drilling / agitation shaft 1. Note that, in the case where the drilling / agitation shaft is a double shaft like the drilling / agitation tool A6 of the sixth embodiment, it may be the stirring blade located at the lowest position among the driving stirring blades that rotate integrally with the outer shaft.

[0175] In addition, the deeper the position, closer to the excavation blade 2, the more uneven the mixture of the excavated soil and improvement material immediately after it is excavated, and the more likely it is that the soil adhering to the excavation / mixing shaft 1 or cylindrical member will thicken, which will cause the co-rotation phenomenon. Therefore, providing the adhesion removal blades (6, 16, 26, 31, 34, 36, 46, 56, 66) between the excavation blade 2 and the lowest mixing blade supported by the excavation / mixing shaft 1 is more effective in preventing the co-rotation phenomenon.

[0176] The above-mentioned embodiments and modified examples have been explained using as examples a ground improvement method in which a slurry-like improvement material is supplied to construct a columnar improvement body, but it goes without saying that the present invention is applicable to excavation and mixing tools used in a ground improvement method in which a powder-like improvement material is supplied to construct a columnar improvement body.

[0177] Finally, the description of each embodiment described above is an example of the present invention, and is not limited to the above-mentioned embodiments and modifications, and includes configurations in which the configurations disclosed in the above-mentioned embodiments and modifications are replaced with each other or the combination is changed, configurations in which the configurations disclosed in the publicly known technology and the above-mentioned examples are replaced with each other or the combination is changed, etc. Also, the present invention is not limited to the above-mentioned embodiments, and it is of course possible to make various modifications according to the design, etc., as long as they do not deviate from the technical idea of ​​the present invention. And, it extends to the matters described in the claims and their equivalents. Also, the effects described in this disclosure are merely examples and are not limited, and other effects may be present. [Explanation of symbols]

[0178] A1~A6 Drilling and mixing tools 1 Drilling and mixing shaft 2. Drilling Wing 3 outlet 4. First mixing blade 5. Second mixing blade 6. Adhesion removal wing 6a Wing body 6c Tapered surface 7 Boss 8 Stopper 9. Wall of the drilling hole 11 Straight plate section (wing body section) 12 Connection 13 Auxiliary materials 16 Adhesion removal wing 17 Straight plate section (wing body section) 18a,18b End plate part 21 Drilling wing main body 22-bit 26 Adhesion removal wing 27 Straight plate section (wing body) 28a,28b protrusion 31 Adhesion removal wing 34 Adhesion removal wing 36 Adhesion removal wing 37 Swing plate section (wing main body section) 38 Spring 41 Vibration prevention plate 45 Spindle 46 Adhesion removal wing 48 Spring 51 Outer shaft 52 Second mixing blade 55 Second mixing blade 56 Adhesion removal wing 66 Adhesion removal wing 77 Boss

Claims

1. This excavation and mixing tool is used to improve ground by excavating and mixing the ground while mixing the excavated soil with improvement materials. A drilling and stirring shaft extending in the vertical direction; A drilling blade provided at the lower end of the drilling / agitation shaft; A plurality of stirring blades arranged above the excavation blade; A cylindrical member into which the drilling / agitation shaft is rotatably inserted; A blade body portion having a blade length direction extending along the axis of the excavation / mixing shaft, for removing improved soil adhering to the excavation / mixing shaft and / or the cylindrical member; Equipped with The cross-sectional shape of the blade main body of the adhesion drop blade is such that, in a cross-sectional plane, the width in a direction along a radial straight line of the outer circumferential circle of the drilling / agitation shaft is a vertical width W1, and the width in a direction along a straight line perpendicular to the radial straight line of the outer circumferential circle is a horizontal width W2, and the horizontal width W2 is equal to or greater than the vertical width W1, and the horizontal width W2 is equal to or less than the length of a chord of an arc having a central angle of 90 degrees on the outer circumferential circle of the drilling / agitation shaft or cylindrical member. A drilling and mixing tool characterized by the above.

2. 2. The excavating and mixing tool according to claim 1, wherein the horizontal width W2 of the adhesion removing blade is longer than the vertical width W1.

3. The drilling / mixing tool described in claim 1, characterized in that in the blade main body of the adhesion removal blade, a tapered surface is formed on the side end facing the rotational direction of the drilling / mixing shaft, which connects to the outer surface of the blade main body along the blade length.

4. The adhesion drop blade is arranged within a virtual circle having a center of the axis of the drilling / agitation shaft and a distance of 150 mm from the outer circumferential surface of the drilling / agitation shaft or the outer circumferential surface of the cylindrical member, or a virtual circle having a radius of 1 / 2 the rotation radius of the drilling blade, whichever is larger, in a plan view. The drilling and mixing impeller according to any one of claims 1 to 3.

Images