Agitation head of ground improvement device

Abstract

To provide an agitation head of a ground improvement device that is less likely to cause co-rotation of a co-rotation prevention blade even in viscous soil.SOLUTION: Blades 62, 62 have a circular through-hole 64 formed at an inner peripheral side close to a bearing portion 61 and an elongated through-hole 65 formed at an outer peripheral side away from the bearing portion 61. An opening area of the elongated through-hole 65 at the outer peripheral side is larger than an opening area of the circular through-hole 64 at the inner peripheral side. Therefore, when a drive shaft 2 is rotated and an excavation blade 3 excavates a bottom of an excavation hole and the excavated soil and a ground improvement material are agitated, the excavated soil and the ground improvement material pass through the circular through-hole 64 and the elongated through-hole 65, thus ball-shaped lumps are less likely to adhere to a co-rotation prevention blade 6 and agitation resistance is reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mixing head for a ground improvement device used for improving soft ground. More specifically, the present invention relates to a mixing head for a ground improvement device that improves the ground by supplying soil improvement material to clayey soil while mixing it with mixing blades to form columnar improvement bodies in the ground, and that has an improved structure for preventing co-rotation of blades. [Background technology]

[0002] A known method for improving soft ground, such as clayey soil, involves mixing and stirring soil improvement materials with agitating blades. The excavated soil and soil improvement materials are mixed and stirred with the agitating blades, but sometimes the excavated soil clumps together, preventing smooth mixing. To prevent this, anti-rotation blades are used, which are rotatably attached to a drive shaft and fixed to the ground during ground improvement work. Even with these anti-rotation blades, the phenomenon of co-rotation can occur in soft clayey ground, or even if co-rotation does not occur, the excavated soil and soil improvement materials may not be mixed sufficiently. Therefore, in order to reliably fix the anti-rotation blades to the peripheral wall of the excavation hole, it has been proposed to increase the holding area by extending the tip of the anti-rotation blade vertically or horizontally, or by providing multiple tips, thereby increasing the resistance to co-rotation (see Patent Documents 1 and 2, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-313857 [Patent Document 2] Utility model registration No. 3231978 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if a large anti-rotation blade is used to increase the resistance to co-rotation, the resistance to penetration and pull-out increases, making workability difficult. Also, even if a large anti-rotation blade does not cause co-rotation, it may not mix the excavated soil and ground improvement material sufficiently, reducing the quality of the ground improvement work.

[0005] The present invention has been made in view of the above background to achieve the following objects. An object of the present invention is to provide a mixing head for a ground improvement device in which co-rotation of the anti-co-rotation blades is unlikely to occur even in clayey soil. Another object of the present invention is to provide an agitation head for a ground improvement device that does not degrade the quality of the ground improvement. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention employs the following means. In other words, the mixing head of the ground improvement device of the first invention comprises a drive shaft that is rotated by a rotary drive device and has a discharge hole for discharging ground improvement material, a mixing blade fixed to the drive shaft and mixing the excavated soil in the excavation hole, a drilling blade attached to the lower end of the drive shaft on the bottom side of the excavation hole and having multiple drilling blades for excavating the excavation hole, and a co-rotation prevention blade that is larger than the inner diameter of the excavation hole and is rotatably attached to the drive shaft between the mixing blade and the drilling blade, the outer end of which bites into the inner wall surface of the excavation hole to stop its rotation, and rotates relative to the rotation of the mixing blade and the drilling blade to mix and mix the excavated soil together with the ground improvement material, and is characterized in that the co-rotation prevention blade has a through hole formed therein that allows the excavated soil and the ground improvement material to pass through while the drive shaft is rotating.

[0007] The mixing head of the ground improvement apparatus of Invention 2 is Invention 1, characterized in that the outer peripheral end of the co-rotation prevention blade is parallel to a plane including the axis of the drive shaft. The mixing head of the ground improvement apparatus of Invention 3 is Invention 1 or 2, characterized in that the anti-co-rotation blade has a plurality of through holes arranged in the radial direction of the drive shaft. The mixing head of the ground improvement device of Invention 4 is characterized in that, in Invention 3, the opening area of the through hole on the outer periphery side of the anti-rotation blade is large and the opening area of the through hole on the inner periphery side of the anti-rotation blade is small. [Effects of the Invention]

[0008] The mixing head of the ground improvement device of the present invention has through holes in the anti-rotation blades, so the excavated soil and ground improvement material are less likely to adhere to the anti-rotation blades, and the mixing resistance is low, so the wall surface of the excavated hole is not damaged. As a result, the probability of the anti-rotation blades rotating together is reduced, and the excavated soil and ground improvement material are less likely to become clumped, which improves the mixing efficiency of the excavated soil and ground improvement material. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an overall perspective view showing a mixing head of a soil improvement apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the mixing head of FIG. [Figure 3] FIG. 3 is a right side view of the mixing head of FIG. [Figure 4] FIG. 4 is a front view of a comparative stirring head used in a comparative test of co-rotation prevention blades. [Figure 5] Figure 5 shows data showing the results of test installation of the anti-corotation blade. [Figure 6] FIG. 6 is an overall perspective view showing the mixing head of the soil improvement apparatus according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a front view of the mixing head of FIG. [Figure 8] FIG. 8 is a right side view of the mixing head of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes a mixing head of a ground improvement device according to a first embodiment of the present invention, with reference to the drawings. Fig. 1 is an overall perspective view of the mixing head of the ground improvement device according to the first embodiment of the present invention, Fig. 2 is a front view of the mixing head of Fig. 1, and Fig. 3 is a right side view of the mixing head of Fig. 2. As shown in Figs. 1 to 3, the mixing head 1 is mounted on the head (not shown) of a movable ground improvement machine and is driven to rotate. The drive shaft 2 of the mixing head 1 is connected to a rotary drive unit mounted on the head of the ground improvement machine and is driven to rotate. Ground improvement material pumped from the ground improvement machine body is injected into an injection hole 21 at the upper end of the hollow drive shaft 2. The injected ground improvement material is discharged from a discharge hole 22 at the lower end of the drive shaft 2 and mixed with the excavated soil in the excavated hole. A flat excavation blade 3 for excavating the excavated hole is fixed to the lower end (bottom side of the excavated hole) of the drive shaft 2 and is driven to rotate integrally with the drive shaft 2.

[0011] The excavation blade 3 is arranged in a linear manner in the diameter direction, perpendicular to the central axis of the drive shaft 2, and has multiple excavation blades 31 fixed to it. The maximum rotational outer diameter D1 of the excavation blade 31 matches the inner diameter of the excavated hole (the outer diameter of the ground improvement pillar). The excavation blade 3 is flat and attached so as to intersect with a plane including the central axis of the drive shaft 2. When the drive shaft 2 is rotated (forward rotation), the excavation blade 31 moves downward while scraping the bottom of the excavation hole, thereby excavating. The excavated soil is lifted to the ground by the inclined excavation blade 3. An upper mixing blade 4 and a lower mixing blade 5 are integrally fixed to the drive shaft 2 above the excavation blade 3 by welding or the like. The upper mixing blade 4 and the lower mixing blade 5 are spaced apart in the direction of the central axis of the drive shaft 2 (vertical direction) and are arranged 90 degrees out of phase with each other. The rotational outer diameter D2 of the upper stirring blade 4 and the rotational outer diameter D3 of the lower stirring blade 5 are equal to the maximum rotational outer diameter D1 of the digging blade 3 (digging blade 31) (see FIGS. 3 and 4).

[0012] The upper mixing blade 4 is flat and is attached so as to intersect with a plane including the central axis of the drive shaft 2. The inclination direction of the upper mixing blade 4 is the same as that of the excavation blade 3. The lower mixing blade 5 is also flat and is attached so as to intersect with a plane including the central axis of the drive shaft 2, but is inclined in the opposite direction to that of the excavation blade 3. When the drive shaft 2 is rotated (forward rotation), the upper mixing blade 4 lifts the excavated soil toward the ground while stirring it. When the drive shaft 2 is rotated (forward rotation), the lower mixing blade 5 pushes the excavated soil toward the bottom of the excavated hole while stirring it. A co-rotation prevention blade 6 is rotatably attached to the drive shaft 2 between the excavation blade 3 and the lower mixing blade 5. A bearing portion 61 at the center of the co-rotation prevention blade 6 is rotatably supported by upper and lower flange portions 23, 23 that are integral with the drive shaft 2.

[0013] Flat blades 62, 62 are fixed by welding to the outer peripheral surface of the bearing portion 61 at positions facing each other at 180 degrees. The blades 62, 62 are arranged linearly in the diameter direction, perpendicular to the central axis of the drive shaft 2. The blades 62, 62 are attached parallel to a plane including the central axis of the drive shaft 2. The outer rotation diameter D4 of the blades 62, 62 is larger than the maximum outer rotation diameter D1 of the excavation cutting edge 31. The tips (diametrically outer sides) of the blades 62, 62 have a vertical width W2 wider than the vertical width W1 of the blades 62, 62, and sharp axe-shaped portions 63, 63 are formed on both the top and bottom. Therefore, the axe-shaped portions 63, 63 of the anti-rotation blade 6 bite into the inner peripheral wall surface (not shown) of the excavation hole, and the anti-rotation blade 6 does not rotate even when the drive shaft 2 is rotated.

[0014] Each of the blades 62, 62 has a circular through-hole 64 on the inner periphery near the bearing portion 61 and an elongated through-hole 65 on the outer periphery away from the bearing portion 61. The opening area of the elongated through-hole 65 on the outer periphery is larger than the opening area of the circular through-hole 64 on the inner periphery. Therefore, when the drive shaft 2 is rotated and the excavation blade 3 excavates the bottom of the excavated hole and mixes the excavated soil and ground improvement material, the excavated soil and ground improvement material pass through the circular through-hole 64 and the elongated through-hole 65. This prevents clumps from adhering to the anti-rotation blade 6 and reduces mixing resistance, preventing damage to the wall of the excavated hole. As a result, the anti-rotation blade 6 is less likely to rotate and is less likely to clump, improving the mixing efficiency of the excavated soil and ground improvement material.

[0015] FIG. 5 shows data showing the results of test construction of the anti-rotation blade 6 of the mixing head 1 of the ground improvement device according to the first embodiment of the present invention. FIG. 4 is a front view of a comparative mixing head 10 used in a comparative test with the anti-rotation blade 6 of the first embodiment. As shown in FIG. 4, the comparative mixing head 10 differs from the mixing head 1 of the first embodiment only in the shape of the anti-rotation blade. Specifically, the upper mixing blade 4 and the lower mixing blade 5 are integrally fixed to the drive shaft 2 above the excavation blade 3 by welding or the like, and the anti-rotation blade 7 is rotatably attached to the drive shaft 2 between the excavation blade 3 and the lower mixing blade 5. A bearing 71 at the center of the anti-rotation blade 7 is rotatably supported by upper and lower flanges 23, 23 integral with the drive shaft 2. Flat blades 72, 72 are fixed to the outer periphery of the bearing 71 at positions 180 degrees opposite each other by welding.

[0016] The blades 72 are arranged linearly in the diameter direction, perpendicular to the central axis of the drive shaft 2. The blades 72 are attached parallel to a plane including the central axis of the drive shaft 2. The vertical width W3 of the blades 72 is the same as the vertical width W1 of the blades 62 of the mixing head 1 of the first embodiment. The outer rotation diameter D5 of the blades 72 is the same as the maximum outer rotation diameter D1 of the excavation blade 31. Figure 5 shows the core condition, uniaxial compression test results, and needle penetration test results of a core (specimen) taken from a columnar improvement body of the improved ground that was tested. In this test, the diameter of the columnar improvement body was 1200 mm, and a dry excavation was performed 1 m from the ground surface, and a 12 m long columnar improvement body was formed below it. The soil improvement material used was Solid Ace #100, with a mixing rate of 150 kg / m. 3 The water-cement ratio (W / C) was 100%, and the rotation speed of the drilling blade 3 was 400 rpm. The drilling blade 3 was rotated forward to excavate to the bottom of the columnar improvement body, and then the drilling blade 3 was rotated backward to pull it out to the ground surface.

[0017] The full-length core collection rate shown in Figure 5 was calculated by observing the entire length of the collected core, searching for areas that easily crumbled with finger pressure or water washing, and determining areas with a cross-sectional defect rate of 50% or more as unsolidified. The rate was 69.9% for the comparative mixing head 10, while it was 99.7% for the mixing head 1 of the first embodiment, demonstrating improved quality. The uniaxial compression test shown in Figure 5 was conducted by compressing a freestanding core without confining pressure and determining the uniaxial compressive strength (qu), which is the maximum compressive stress. As shown in Figure 5, the uniaxial compressive strength (qu) and coefficient of variation (total qu) of the mixing head 1 of the first embodiment were improved compared to the comparative mixing head 10. The needle penetration test shown in Figure 5 was conducted by penetrating a penetration needle into a columnar improved soil and measuring the penetration length L and the load P at the time of needle penetration to estimate the uniaxial compressive strength.

[0018] As shown in FIG. 5, the mixing head 1 of the first embodiment has improved needle-equivalent uniaxial compressive strength (qu) and coefficient of variation (total needle-equivalent qu) values compared to the mixing head 10 of the comparative example. FIG. 6 is an overall perspective view of the mixing head of a ground improvement device according to a second embodiment of the present invention, FIG. 7 is a front view of the mixing head of FIG. 6, and FIG. 8 is a right side view of the mixing head of FIG. 7. As shown in FIGS. 6 to 8, the mixing head 100 of the second embodiment differs from the mixing head 1 of the first embodiment only in the shape of the anti-rotation blade. Specifically, the upper mixing blade 4 and the lower mixing blade 5 are integrally fixed to the drive shaft 2 above the excavation blade 3 by welding or the like, and the anti-rotation blade 8 is rotatably attached to the drive shaft 2 between the excavation blade 3 and the lower mixing blade 5. The bearing portion 81 in the center of the anti-rotation blade 8 is rotatably supported by upper and lower flange portions 23, 23 integral with the drive shaft 2.

[0019] Flat blades 82, 82 are fixed by welding to the outer peripheral surface of the bearing portion 81 at positions facing each other at 180 degrees. The blades 82, 82 are arranged linearly in the diameter direction, perpendicular to the central axis of the drive shaft 2. The blades 82, 82 are attached parallel to a plane including the central axis of the drive shaft 2. The vertical width W4 of the blades 82, 82 is the same as the vertical width W2 of the axe-shaped portions 63, 63 of the mixing head 1 of the first embodiment. The rotational outer diameter D6 of the blades 82, 82 is larger than the maximum rotational outer diameter D1 of the digging blade 31 and is the same as the rotational outer diameter D4 of the blades 62, 62 of the mixing head 1 of the first embodiment. The vertical width of the blades 82, 82 is constant, and sharp axe-shaped portions 83, 83 are formed on both the upper and lower sides of the tips (diametrically outer) of the blades 82, 82. Therefore, the axe-shaped portions 83, 83 of the anti-rotation blade 8 bite into the inner peripheral wall surface of the excavation hole, and the anti-rotation blade 8 does not rotate even when the drive shaft 2 is driven to rotate.

[0020] Each of the wing bodies 82 has six circular through holes 84. The circular through holes 84 are linearly arranged, two in each direction parallel to the central axis of the drive shaft 2 and three in each direction perpendicular to the central axis of the drive shaft 2. The circular through holes 84 have the same opening area. The wing bodies 82 have a vertical width W4 that is wider over their entire length than the vertical width W1 of the wing bodies 62 of the first embodiment. Therefore, the opening area of the twelve circular through holes 84 in the wing bodies 82 is set to approximately twice the combined opening area of the two circular through holes 64 and the two oblong through holes 65 of the wing bodies 62 of the first embodiment. Therefore, when the drive shaft 2 of the mixing head 100 of the second embodiment is rotated and the excavation blade 3 excavates the bottom of the excavated hole, and the excavated soil and ground improvement material are mixed, the excavated soil and ground improvement material pass through the many circular through-holes 84, 84, making it difficult for clumps to adhere to the anti-rotation blade 8 and reducing mixing resistance, so the wall surface of the excavated hole is not destroyed. As a result, the probability of the anti-rotation blade 8 rotating together with the excavated soil decreases, making it difficult for clumps to form, and improving the mixing efficiency of the excavated soil and ground improvement material.

[0021] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, the circular through holes 64, the elongated through holes 65, and the circular through holes 84 in the above-described embodiments may have other shapes, such as an elliptical shape. Furthermore, the number of circular through holes 64, the elongated through holes 65, and the circular through holes 84 is not limited to these embodiments. Furthermore, the "through holes" referred to in the present invention may be in shapes other than circles and ellipses, such as squares and hexagons. [Explanation of symbols]

[0022] 1, 10, 100...mixing head 2...Drive shaft 21…Injection hole 22...Discharge hole 23...Flange 3...Drilling wing 31...Drilling blade 4...Top stirring blade 5…Lower stirring blade 6... Co-rotation prevention wing 61...Bearing part 62...wing body 63...axe-shaped part 64...Circular through hole 65...Slotted through hole 7... Co-rotation prevention wing 71...Bearing part 72...wing body 8... Co-rotation prevention wing 81...Bearing part 82...wing body 83...axe-shaped part 84...Circular through hole

Claims

1. A drive shaft that is rotationally driven by a rotary drive device and has a discharge hole for discharging the ground improvement material; A mixing blade fixed to the drive shaft for mixing the excavated soil in the excavated hole; A drilling blade provided at a lower end of the drive shaft on the bottom side of the drilling hole and having a plurality of drilling blades for drilling the drilling hole; a co-rotation prevention blade that is larger than the inner diameter of the excavated hole, is rotatably provided on the drive shaft between the mixing blade and the excavating blade, has an outer peripheral end that bites into the inner peripheral wall surface of the excavated hole to stop its rotation, and rotates relative to the rotation of the mixing blade and the excavating blade to mix and stir the excavated soil together with the ground improvement material; In the mixing head of the ground improvement device, The co-rotation prevention blade is formed with a through hole that allows the excavated soil and the ground improvement material to pass through while the drive shaft is rotating. A mixing head for a ground improvement device.

2. The mixing head of the ground improvement device according to claim 1, The outer peripheral end of the anti-co-rotation blade is parallel to a plane including the axis of the drive shaft. A mixing head for a ground improvement device.

3. The mixing head of the ground improvement device according to claim 1 or 2, The anti-co-rotation blade has a plurality of through holes arranged in the radial direction of the drive shaft. A mixing head for a ground improvement device.

4. The mixing head of the ground improvement device according to claim 3, The opening area of the through hole on the outer circumferential side of the anti-rotation blade is large, and the opening area of the through hole on the inner circumferential side of the anti-rotation blade is small. A mixing head for a ground improvement device.

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