JP6045907B2 - Anti-rotation blade for agitator and mixer - Google Patents

Description

  The present invention relates to an agitating and mixing apparatus for constructing a cylindrical soil cement column in the ground by injecting solidified material such as cement milk into the ground being excavated and stirring and mixing the excavated soil and the solidified material. As for the co-rotation preventing wing attached to the base, it is possible to reduce the ground excavation resistance by thinning and increasing the strength of the co-rotation preventing wing end and to efficiently construct the soil cement column.

  As a general deep mixing method, a cylindrical soil cement column is built in the ground by injecting solidified material such as cement milk into the ground being excavated and stirring and mixing the excavated soil and the solidified material. Ground improvement methods are known.

  In this construction method, for example, as shown in FIG. 8, a drilling blade 2 that rotates together with the drilling rod 1, a drilling soil excavated by the drilling blade 2, and a solidified material such as cement milk injected into the drilling soil. A stirring and mixing device provided with a stirring blade 3 for stirring and mixing is used.

  During the construction of the soil cement column by this construction method, especially in the viscous ground with high adhesive strength, the so-called co-rotation phenomenon occurs in which the excavated soil adheres to the excavating blade 2 and the agitating blade 3 and rotates synchronously with these blades. As a result, the excavated soil and the solidified material may not be uniformly mixed.

  For this type of problem, the applicant attaches a co-rotation preventing blade 15 longer than the excavation diameter to the excavation rod 1 so as to be rotatable as shown in FIG. By inserting 15a into the ground outside the hole wall surface of the excavation hole excavated by the excavation blade 2, the co-rotation prevention blade 15 does not rotate in synchronism with the excavation blade 2 and the agitation blade 3 in the excavation hole. We have developed a co-rotation prevention wing that prevents the co-rotation phenomenon of excavated soil by stopping (see Patent Document 1).

  In this case, the thickness b and height h of the overhanging portions 15a, 15a of the co-rotation preventing wing 15 are such that the co-rotation preventing wing can perform its function without synchronous rotation, and can be used for underground troubles. It is empirically formed to be about 18 to 50 mm and about 100 to 200 mm so as not to be damaged even if it collides.

  Further, instead of the co-rotation preventing wing 15, a co-rotation preventing wing 16 configured in a box shape when viewed from the side as shown in FIG. The co-rotation prevention blade 16 includes a pair of upper and lower blade bodies 16a and 16a attached to both upper and lower sides of the stirring blade 3 attached immediately above the excavation blade 2 with the stirring blade 3 interposed therebetween, and the blade bodies 16a and 16a. A pair of left and right overhang portions 16b and 16b attached across the stirring blade 3 between the left and right end portions of the left and right ends are configured in a box shape when viewed from the side, and the left and right overhang portions 16b and 16b do not hit the stirring blade 3 As seen from the side, it is formed in a U shape.

  In Patent Document 2, the anti-rotation wing is attached to the excavation rod in a side view, and a resistance flange that bites into the hole wall ground of the excavation hole is attached to the outside of the vertical piece, and this resistance flange is attached to the excavation rod. A co-rotation preventing wing is disclosed in which the resistance resistance of the resistance flange in hard ground is reduced by raising and lowering along a vertical piece.

  Further, in Patent Document 3, the co-rotation preventing wing is attached to the excavation rod so as to be rotatable about a horizontal axis, and the co-rotation prevention wing is returned to the original position by a coil spring, so that A co-rotation preventing wing designed to reduce digging resistance is disclosed.

  Patent Document 4 discloses a soil constructed by increasing the gripping force of the co-rotation preventing wing against the hole wall surface by attaching a Y-shaped tip portion that contacts the hole wall surface of the excavation hole to the tip of the co-rotation preventing wing. A co-rotation preventing wing is disclosed which improves the vertical accuracy of a cement pillar.

Japanese Patent Publication No.58-29374 JP 2011-1686 Japanese Patent Laid-Open No. 11-061800 JP 2010-37730 A

  However, in the co-rotation preventing wing disclosed in Patent Document 1, both ends projecting portions 15a and 15a of the co-rotation preventing wing 15 inserted into the ground outside the hole wall of the excavation hole are grounded outside the hole wall along with the excavation. Therefore, especially in hard ground, the resistance to digging at both ends 15a, 15a is increased, so it takes a long time to build the soil cement column, or it is extremely difficult to build the soil cement column. Furthermore, there was a problem that the soil cement column assumed in the design could not be built because the drilling was substantially impossible.

  Further, in the co-rotation preventing wing disclosed in Patent Documents 2 and 3, even if the resistance to the ground outside the hole wall can be reduced, the co-rotation preventing wing needs to be movably attached in the ground. In addition to the problem that the structure is complicated and the manufacturing cost is increased, there is a problem that it is not possible to confirm whether or not the co-rotation preventing wing operates as designed in the ground.

  In the co-rotation preventing wing described in Patent Document 4, synchronous rotation with the excavation rod of the co-rotation prevention wing is prevented by the gripping force on the hole wall surface of the Y-shaped tip that contacts the hole wall surface of the excavation hole. As a result, the synchronous rotation of the co-rotation preventing blade may not be completely prevented.

  The present invention has been made to solve the above-mentioned problems, and reduces the ground excavation resistance at the end overhanging portion of the anti-rotation blade attached to the stirring and mixing device for constructing the cylindrical soil cement column. It is an object of the present invention to provide an anti-rotation blade for a stirring and mixing device that can efficiently construct a soil cement column particularly in hard ground.

  The co-rotation preventing wing of the stirring and mixing apparatus according to the present invention is a co-rotation preventing wing that is attached to a rotatable drilling rod together with the drilling wing and the stirring wing. The overhanging portion is composed of a prevention wing body, and an overhanging portion that is attached to an end of the co-rotation prevention wing main body, and a part or all of which is inserted into the ground outside the excavation hole excavated by the excavation blade. Is formed thinner than the co-rotation preventing wing body and made of a material having a higher strength than the material of the co-rotation prevention wing body.

  The present invention provides an anti-rotation blade for an agitating and mixing device for constructing a cylindrical soil cement column in the ground by stirring and mixing excavated soil and a solidified material. By reducing the excavation resistance of the ground, the soil cement column can be constructed efficiently.

  That is, by reducing the thickness of the cross-sectional direction of the overhanging portion of both ends of the co-rotation preventing wing thinner than that of the co-rotation preventing wing body, the digging speed is reduced particularly in hard ground by reducing the digging resistance of the ground generated in the bulging portion It is possible to prevent the phenomenon of lowering and to build the soil cement column assumed in the design very efficiently.

  Here, the hard ground is assumed to be a ground having an N value of about 10 or more for viscous ground and an N value of about 30 or more for sandy ground.

  In addition, even a construction machine operator who does not have a skilled technique can shorten the time required for the construction of the soil cement column, and can prevent the situation where the construction of the soil cement column becomes impossible. As a result, it is possible to reduce the psychological anxiety of the construction engineer that the design support power cannot be secured.

  In addition, because the construction time can be stably shortened, it is possible to reduce the fatigue and stress of workers such as construction machine operators. Can be prevented.

  Furthermore, it is possible to reduce the load, impact, etc. generated on the construction machine main body, auger motor, excavation rod, excavation blade, agitation blade, etc., greatly reduce repairs due to failure, etc., and extend the service life.

  In addition, by forming V-shaped cross-sectional blade shapes (knife-shaped blade shapes) at the upper and lower end portions of the overhang portion, the ground resistance generated in the overhang portion during excavation and lifting can be further reduced.

  Further, by reducing the resistance of the ground generated in the overhanging portion during excavation and lifting, it becomes possible to use a small construction machine and to construct a large-diameter soil cement column.

  In particular, it has been confirmed that the overhanging part is prone to shear deformation and bending deformation by the construction test. Therefore, in order to reduce the digging resistance by thinning the overhanging part, shear deformation and bending deformation can be performed with a little force. It is necessary to form the overhanging portion with a hard steel material so as not to occur.

  For the material of the overhanging portion, it is possible to select ultra high strength steel such as spring steel (SUP material), hardx (abrasion resistant steel plate), weldox (high tensile steel plate) and the like.

Yield point of these steels, compared rolled steel for general structure that is 245 N / mm ^2, a spring steels (SUP material) 1080N / mm ^2, Hadokkusu (abrasion steel) is 1000~1300N / mm ² Weldox (high tensile steel plate) is 700 N / mm ² . Hardx and Weldox are collectively called Swedish steel, both of which are products of Swedish Steel.

  When considering the strength of rolled steel for general structure, considering the workability such as cutting, grinding and polishing, availability such as delivery date, and cost such as material cost and processing cost, etc. What has the yield point of about 2.5 to 4.0 times of steel materials is desirable.

  In addition, the thickness b of the overhang is preferably as thin as possible from the viewpoint of reducing ground excavation resistance, and may be 4.5 mm or more for spring steel materials or Swedish steel materials. In consideration of the above, about 10 mm is desirable.

  Also, the length of the overhanging part inserted into the ground outside the hole wall of the excavation hole is such that the resistance moment obtained from the passive resistance of the overhanging part exceeds the rotation moment of the co-rotation prevention wing determined from the rotation of the excavation rod. Or about 10 cm empirically, but generally the rotation moment of the co-rotation prevention wing due to the rotational force of the drilling rod increases in proportion to the drilling diameter. It is necessary to change the lateral length and height h of the overhang portion in proportion to the diameter of the projection.

  For this reason, the overall length of the overhanging part is usually 10 cm in length of the part inserted into the ground outside the hole wall of the excavation hole, and the part of the part bolted by overlapping the end of the co-rotation prevention wing body. A total of about 20 cm, 10 cm in length, is sufficient.

  Moreover, the length of the portion inserted into the ground outside the hole wall can be freely set by forming it longer than this, and further, it can be replaced by bolting or the like, depending on the target ground It can be changed to the optimum dimensions.

  For example, when the rotational moment of the co-rotation preventing blade due to the rotational force of the excavating rod becomes larger than expected, the length of the portion inserted into the ground outside the hole wall surface can be freely set and replaced.

  Moreover, the co-rotation prevention blade can further enhance the co-rotation prevention effect by attaching one on each of the upper and lower sides of the stirring blade.

  Furthermore, by attaching the overhanging part between the tip parts of the co-rotation prevention wing body and connecting the upper and lower co-rotation prevention wings to form a box shape when viewed from the side, it not only improves the co-rotation prevention effect but also advances By preventing the excavation rods from shaking, the soil cement column can be built vertically and the construction accuracy can be improved.

  According to the present invention, as an anti-rotation blade of an agitating and mixing device for constructing a cylindrical soil cement column in the ground by agitating and mixing excavated soil and solidified material, the end overhang of the anti-rotation blade is provided. By making the thickness of the cross section in the cross-sectional direction thinner than the co-rotation prevention wing body, it is possible to reduce the ground excavation resistance acting on the overhanging part, thereby making the construction of the cylindrical soil cement column extremely efficient Can be done.

  In addition, it is possible to reduce the fatigue and stress of workers during excavation, thereby preventing accidents and injury of workers. Further, it is possible to reduce the load and impact generated on the construction machine main body, the auger motor, the excavating rod, the excavating blade, the agitating blade, etc., greatly reduce repairs due to failure, etc., and extend the service life. Furthermore, stable construction is possible even in the construction of soil cement columns on hard ground.

FIG. 1 shows a stirring and mixing device equipped with a co-rotation prevention blade of the present invention, FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (c), (d), and (e) are a front view, a side view, and a plan view, respectively, showing the co-rotation preventing wing of the present invention. FIG. 1 shows a stirring and mixing device equipped with a co-rotation prevention blade of the present invention, FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (c), (d), (e) are a front view, a side view, and a plan view, respectively, showing another embodiment of the co-rotation preventing wing of the present invention. FIG. 1 shows a stirring and mixing device equipped with a co-rotation prevention blade of the present invention, FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (c), (d), (e) are a front view, a side view, and a plan view, respectively, showing another embodiment of the co-rotation preventing wing of the present invention. FIG. 1 shows a stirring and mixing device equipped with a co-rotation prevention blade of the present invention, FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (c), (d), (e) are a front view, a side view, and a plan view, respectively, showing another embodiment of the co-rotation preventing wing of the present invention. FIG. 1 shows a stirring and mixing device equipped with a co-rotation prevention blade of the present invention, FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (c), (d), (e) are a front view, a side view, and a plan view, respectively, showing another embodiment of the co-rotation preventing wing of the present invention. Comparison of excavation status as a relationship diagram of depth and construction time when building a cylindrical soil cement column using conventional anti-rotation blades and building a soil cement column using co-rotation prevention blades of the present invention It is a graph. This is a graph comparing the excavation energy by the depth distribution when the cylindrical soil cement column is built using the conventional anti-rotation blade and when the cylindrical soil cement column is built using the anti-rotation blade of the present invention. is there. FIG. 1 shows a conventional stirring / mixing device equipped with a co-rotation prevention blade, and FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (d), (e) are a front view, a side view, and a plan view, respectively, showing a conventional co-rotation preventing wing. FIG. 1 shows a conventional stirring / mixing device equipped with a co-rotation prevention blade, and FIG. (A) is a front view showing the positional relationship of a drilling rod, a drilling blade, a stirring blade and a co-rotation prevention blade, and FIG. (B) is a diagram (a). (A), (d), (e) are a front view, a side view, and a plan view, respectively, showing a conventional co-rotation preventing wing.

  1 (a) to 1 (e) show an embodiment of a co-rotation preventing wing according to the present invention. In the figure, a digging wing 2 is attached to the tip of a digging rod 1, and a plurality of stirrings are provided above it. Wings 3 are attached at regular intervals in the axial direction of the excavation rod 1. Further, the co-rotation prevention blade 4 of the present invention is attached between the excavation blade 2 and the stirring blade 3 attached immediately above.

  The excavation rod 1 has an excavation bit 5 and a solidified material discharge port 6 at the tip, and rotates by an auger motor (not shown) and moves up and down by an elevator (not shown) to excavate the ground.

  The excavating blade 2 and the agitating blade 3 are formed to have substantially the same length, and both of them rotate synchronously with the excavating rod 1 so that the excavating blade 2 excavates the ground in cooperation with the excavating bit 5. Then, the excavated soil excavated by the excavating bit 5 and the cement milk discharged from the solidified material discharge port 6 are stirred and mixed. The excavation blades 2 and the stirring blades 3 project radially in a plurality of directions on a plane.

  Cement milk is manufactured at an above-ground plant facility (not shown), pumped from a grout pump or the like (not shown), and injected through an injection material injection path (not shown) provided in the excavating rod 1, and It is discharged from the solidified material discharge port 6 to the ground under excavation.

  The co-rotation prevention blade 4 includes a co-rotation prevention blade body (hereinafter referred to as a “blade body”) 7 that is formed to have substantially the same length as the excavation blade 2 and the stirring blade 3 and an overhang projecting from the tip of the blade body 7. Part 8.

  The wing body 7 is integrally formed from a cylindrical circumscribed portion 7a circumscribed by the excavating rod 1 and a plurality of wing portions 7b projecting outside the circumscribed portion 7a.

  The overhanging portion 8 is formed such that the thickness b in the cross-sectional direction is thinner than the thickness in the cross-sectional direction of the wing body 7 and a blade shape (knife shape of a knife) 8a having a substantially V-shaped cross section is formed at both upper and lower ends. . In addition, as the steel material forming the overhanging portion 8, super high strength steel such as spring steel material (SUP material), hardx (abrasion resistant steel plate), weldox (high tensile steel plate) is used, and the yield point of these steel materials is It has a strength of about 2.5 to 4.0 times the yield point of the general structural rolled steel forming the blade body 7.

  The overhang 8 formed in this way is detachably attached by overlapping the side surface of the base end side 8b with the side surface of the tip end of the wing body 7 for a predetermined length and bolting. If necessary, the mounting plate 10 may be used together.

  The embodiment illustrated in FIGS. 2A to 2E shows an example in which the overhang portion 8 is attached to both ends of the blade body 7 by welding, and the overhang portion 8 is attached by welding. Except for this, it is almost the same as the embodiment described in FIGS.

  In such a configuration, the circumscribed portion 7 a of the blade body 7 is rotatably circumscribed on the excavation rod 1, and all of the overhang portion 8 or a part of the tip of the excavation hole is excavated by the excavation blade 2 and the excavation bit 5. The co-rotation prevention wing 4 is fixed in the excavation hole by being inserted into the ground outside the hole wall surface.

  Then, the co-rotation preventing blade 4 remains stationary in the excavation hole without rotating synchronously with the excavation rod 1, and only the excavation blade 2 and the stirring impeller 3 rotate synchronously with the excavation rod 1. This prevents the excavated soil from adhering to the excavated blade 2 and the agitating blade 3 and prevents the “synchronous phenomenon of excavated soil” rotating with the excavated blade 2 and the agitated blade 3. Stir and mix.

  Further, the thickness b in the cross-sectional direction of the overhanging portion 8 is formed to be thinner than the thickness in the cross-sectional direction of the wing body 7, and the blade shape 8 a having a substantially V-shaped cross section is formed at the upper and lower end portions of the overhanging portion 8. As a result, the excavation resistance of the ground in the overhang portion 8 is greatly reduced, so that the excavation speed can be stabilized and the soil cement column can be built very efficiently.

  3 (a) to 3 (e) show other embodiments of the present invention. In the figure, a drilling blade 2 is attached to the tip of the drilling rod 1, and a plurality of stirring blades 3 are provided above the drilling rod 1. It is attached at regular intervals in the axial direction. Further, a co-rotation preventing blade 11 is attached immediately above the excavating blade 2.

  The co-rotation prevention blade 11 is provided between the tip ends of the left and right ends of a pair of upper and lower blade bodies 7 and 7 attached to both the upper and lower sides of the stirring blade 3 attached immediately above the excavation blade 2 with the stirring blade 3 interposed therebetween. A pair of left and right overhanging portions 12 and 12 attached across the stirring blade 3 is formed in a box shape when viewed from the side.

  The thickness b in the cross-sectional direction of the overhanging portion 12 is thinner than the thickness in the cross-sectional direction of the blade body 7, and the yield point of the steel material forming the overhanging portion 12 is 2.5 to less than the yield point of the steel material forming the blade body 7. It is about 4.0 times stronger.

  Furthermore, blade shapes (knife blade shapes) 12a and 12a having a substantially V-shaped cross section are formed at both upper and lower ends, respectively, and the overhanging portion 12 is provided with the overhanging portion 12 on the side surfaces of the tip portions of the upper and lower blade bodies 7 and 7. The side surface of the base end side 12b is attached by being overlapped with a predetermined length and bolted. Other configurations are almost the same as those of the embodiment described with reference to FIGS.

  By being configured in this way, the co-rotation prevention blade 12 not only prevents the occurrence of the co-rotation phenomenon of the excavated soil, but also the effect of increasing the construction accuracy by preventing the excavation rod from shaking during excavation. It also has.

  FIGS. 4 (a) to 4 (e) show another embodiment of the present invention, and in the embodiment described in FIGS. 3 (a) to 3 (e), in particular, the overhang portion of the co-rotation preventing wing The shape is different.

  In the figure, the co-rotation preventing blades 13 are provided at the left and right ends of a pair of upper and lower blade bodies 7 and 7 respectively attached on both upper and lower sides of the stirring blade 3 attached immediately above the excavation blade 2 with the stirring blade 3 interposed therebetween. A pair of left and right overhang portions 14 and 14 attached across the stirring blade 3 between the tip portions are configured in a box shape when viewed from the side.

  Further, in particular, the overhanging portion 14 protrudes horizontally between the upper and lower blade bodies 7 and 7 from the upper and lower ends of the vertical flange 14a and the vertical flange 14a extending in the vertical direction in the vicinity of the stirring blade 3, respectively. The horizontal flanges 14b and 14b are formed in a substantially U shape when viewed from the front.

  The overhanging portion 14 overlaps the upper and lower horizontal flanges 14b and 14b on the side surfaces of the end portions of the upper and lower blade bodies 7 and 7 by a predetermined length, and is bolted with a plurality of mounting bolts 9 to the tip portions of the blade bodies 7 and 7. It is attached detachably. If necessary, the mounting plate 10 may be used together.

  5 (a) to 5 (e) show an example in which the overhang portion 14 is attached to both ends of the upper and lower blade bodies 7, 7 by welding, and the overhang portion 14 is welded. Except for being attached, it is almost the same as the embodiment described in FIGS. 4 (a) to 4 (e).

  As shown in FIG. 5, the overhanging portion 14 is formed in a U-shape when viewed from the front by a simple method such as notching a part of the side so that the tip of the stirring blade 3 does not hit. Can do.

  The graph of FIG. 6 and Table 1 show the state of digging when a cylindrical soil cement column is constructed using the conventional anti-rotation blade and when a soil cement column is constructed using the anti-rotation blade according to the present invention. Is a comparison.

  The target soil is GL-0.8m from the top, loam with N value of 3-5 to GL-2.8m, fine sand with N value of 5-13 to GL-8.5m, sand mixed silt, fine sand Fine sand with N value of 15 to 32 mixed with silt with GL-11.8m, fine sand with N value of 12 to 56 accumulated to GL-20.8m, and has a water level in the hole at GL-3.8m. .

  As shown in FIG. 6, when the conventional anti-rotation blade is used, the hard ground at the tip of the soil cement column requires the excavation rod to be repeatedly moved up and down, while the anti-rotation blade according to the present invention is used. For example, it was possible to dig without moving the excavating rod up and down. Further, as apparent from Table 1, the construction time could be shortened by about 4 minutes on average per one.

 As a result, it was possible to reduce the fatigue and stress of the workers during the construction, thereby preventing accidents and injury of the workers.

  7 and Table 2 show a case where a cylindrical soil cement column is constructed using a conventional anti-rotation blade and a case where a cylindrical soil cement column is constructed using the anti-rotation blade according to the present invention. The drilling energy is compared by depth distribution.

  When the co-rotation preventing wing according to the present invention was used, the excavation energy could be reduced by 32% in the middle part of the soil cement column compared to the conventional co-rotation preventing wing and by 90% at the tip. As a result, the load applied to the stirring and mixing device particularly in hard ground is reduced, so that the failure of the stirring and mixing device is reduced, the service life is extended, and it is considered that construction with a small construction machine is also possible.

  The energy required to excavate the ground can be expressed by indentation energy and rotational energy, and the excavation energy (E) was defined as in equation (1).

E = (α · E _TV + β · E _TR ) / V (kN) (1)
Also, E _TV and E _TR were defined as shown in equations (2) and (3), respectively.
E _TV = P ・ V (kN ・ m / min) ...... (2)
E _TR = 2π ・ T ・ R (kN ・ m / min) (3)
here,
E _TV : Pushing energy per unit time E _TR : Rotational energy per unit time P: Pushing force (kN)
V: Drilling speed (m / min)
T: Torque (kN · m)
R: Number of revolutions (rpm)
α, β: Drilling efficiency for each energy (α = 1, β = 1 this time)

  Table 3 shows the allowable bending moment of the overhang portion in the conventional co-rotation preventing wing, and Table 4 shows the allowable bending moment of the overhang portion in the co-rotation preventing wing of the present invention.

  As is apparent from Tables 3 and 4, the allowable bending moment was 7.4 to 10.2 kN · m in the conventional anti-corotation blade. Assuming that the lower limit of the allowable allowable bending moment for the co-rotating blade according to the present invention is 7.4 kN · m, the lower limit of the allowable bending moment in Table 4 is 7.5 kN · m. The lower limit of b is up to 4.5 mm.

  Table 5 shows the ground excavation resistance force received by the overhang portion of the conventional co-rotation prevention wing, and Table 6 shows the hard ground parameters for calculating the ground excavation resistance force (extreme support force (qd)). Table 7 shows the excavation resistance of the ground when the thickness b of the overhanging portion is changed.

  When the thickness b of the overhanging portion of the conventional co-rotation preventing wing was 18 mm to 25 mm, the excavation resistance of the ground was 23.80 to 33.06 kN. As shown in Table 7, in order to reduce the ground excavation resistance force 33.06 kN by half, the thickness b of the overhanging portion is 12 mm. Therefore, the upper limit value of the thickness b of the overhang portion targeted in the present invention is set to 12 mm.

  From the above examination results, the thickness b of the overhang portion can be calculated from 4.5 mm to 12 mm, and it is desirable to make it as thin as possible from the viewpoint of reducing the excavation resistance of the ground. In consideration of the above, about 10 mm is desirable.

  Moreover, the yield point of the steel material forming the overhang portion may be any material having a strength about 2.5 to 4.0 times that of the general structural rolled steel material, based on the yield point of the general structural rolled steel material. In view of workability such as grinding and polishing, availability such as delivery date, and costs such as material costs and processing costs, it is desirable that the steel has a strength approximately 4.0 times that of general structural rolled steel.

  The present invention reduces the digging resistance of the ground in the overhanging portion of the both ends of the co-rotation preventing blade installed in the stirring and mixing device for constructing the cylindrical soil cement column in the ground by thinning the overhanging portion. In particular, it is possible to efficiently construct the soil cement column in the hard ground.

DESCRIPTION OF SYMBOLS 1 Drilling rod 2 Drilling blade 3 Agitation blade 4 Co-rotation prevention blade 5 Drilling bit 6 Solidification material discharge port 7 Blade body (co-rotation prevention blade body)
7a Outer part
7b Wings 8 Overhang
8a Blade shape
8b Base end side 9 Mounting bolt
11 Co-rotation prevention wing
12 Overhang part
12a Blade shape
12b Base end
13 Co-rotation prevention wing
14 Overhang part
14a Vertical flange
14b Horizontal flange
14c Blade type

Claims (3)

A co-rotation preventing wing of a stirring and mixing device attached to a rotatable excavation rod together with an excavation blade and an agitation blade, the co-rotation prevention wing body attached to the excavation rod so as not to rotate synchronously with the excavation rod, and the co-rotation prevention wing A projecting portion that is attached to an end portion of the main body, and a part or all of the projecting portion is inserted into the ground outside the hole wall surface of the excavation hole excavated by the excavating blade. A co-rotation preventing blade of a stirring and mixing device, characterized in that it is formed of a steel material that is thinner and has a yield point that is 2.5 times or more than the yield point of the steel material forming the co-rotation prevention blade body. 2. The co-rotation prevention blade of the stirring and mixing apparatus according to claim 1, wherein a blade shape having a substantially V-shaped cross section is formed at a lower end portion or an upper and lower end portion of the overhanging portion. Wings. The co-rotation preventing wing of the stirring and mixing device according to claim 1 or 2 , wherein the co-rotation preventing wing main body is respectively attached to the upper and lower sides of one or a plurality of stirring wings, and the overhanging portion is a tip of the co-rotation preventing wing main body. An anti-rotation blade for a stirring and mixing device, characterized in that it is mounted in between.

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