Excavation / agitation tool

Abstract

To provide an excavation / agitation tool that has a simple configuration but can reliably make an improvement material reach an outer periphery of an improvement diameter and can uniformly agitate and knead excavated soil and an improvement material.SOLUTION: An excavation / agitation tool A1 for improving the ground by kneading excavated soil with a slurry-like improvement material while excavating and agitating the ground, comprises: an excavation / agitation shaft 1 extending in the vertical direction; an excavating blade 2 provided at a lower end of the excavation / agitation shaft 1 and excavating the ground; and a discharge portion 3 having a discharge port that discharges a slurry-like improvement material supplied via an improvement material supply path provided within the excavation / agitation shaft 1. An opening face of the discharge port is inclined with respect to a discharge axis Q that passes through the center of the discharge port and intersects with an axis S of rotation of the excavation / agitation shaft 1. A flap-shaped valve body that covers the discharge port is provided in the discharge portion 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an excavating and mixing tool for soil improvement equipment that performs 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 carried out as a preventative measure against the structure's settlement and tilting. The ground improvement equipment used for ground improvement is equipped with an excavator and mixer with a discharge port that discharges a slurry-like improvement material whose main component is cement-based solidification material. The excavated soil and improvement material are mixed while excavating the ground to form a columnar improved body.

[0003] The improvement material passes through an improvement material supply passage provided within the rotating shaft of the excavating and mixing tool, whose axial direction is vertical, and is discharged to the outside from a discharge port provided at a predetermined position on the excavating and mixing tool. A check valve is provided at the discharge port to cover the outlet in order to prevent the improved soil from flowing back, and the check valve is configured to open due to discharge pressure when the improvement material is being discharged from the discharge port, and to close the discharge port when not being discharged (see Patent Documents 1 to 4).

[0004] In addition, a ground improvement device has been proposed in which the discharge nozzle of the excavating / mixing tool is tilted so that it faces diagonally downward relative to the rotation axis, thereby promoting the softening of the ground by the improvement material and improving mixing properties (see Patent Document 5). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-156208 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-277983 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-234557 [Patent Document 4] Utility Model Registration No. 3148363 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-119733 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional ground improvement work, in which excavated soil and improvement material are mixed to create a columnar improvement body, a mismatch between the orientation of the opening of the discharge port relative to the rotation axis and the actual discharge direction of the improvement material has prevented the improvement material from reaching the outer periphery of the rotating agitator blade, resulting in a deterioration in the quality of the columnar improvement body due to poor mixing of the excavated soil and improvement material.

[0007] In the technology described in Patent Document 1, a roughly box-shaped adapter is attached to the drilling shaft, covering the area around the circular improvement material outlet. The adapter redirects the discharge flow of improvement material injected into the adapter from a direction perpendicular to the axial direction of the rotating shaft toward a discharge port on the adapter, which opens diagonally upward or downward relative to the axial direction, thereby changing the discharge direction of the improvement material to the desired direction. Meanwhile, the opening of the flap-shaped valve body covering the discharge port on the adapter changes depending on the discharge pressure of the improvement material. In other words, if the discharge rate of improvement material per unit time is low and the discharge pressure is low, the discharge port will not fully open, and the valve body will further change the discharge direction of the improvement material to a direction different from the desired direction. This results in poor mixing of the excavated soil and improvement material, resulting in a deterioration in the quality of the columnar improvement body.

[0008] In the technology disclosed in Patent Document 2, the direction perpendicular to the axial direction of the rotating shaft is the discharge direction of the improvement material, and the valve body for preventing backflow is installed so as to face the discharge direction. The fixed end of the valve body is installed on the left side as seen from the front in the width direction of the rotating shaft, and if the improvement material cannot be discharged with the discharge pressure when the valve body is fully opened, the improvement material discharged from the gap on the outer surface of the excavation shaft, which is formed on the right side of the valve body opened at a predetermined angle, will remain around the excavation shaft without reaching the outer periphery of the improvement diameter, resulting in poor mixing of the excavated soil and improvement material.

[0009] In the technology of Patent Document 3, a valve body is provided on the circumferential surface of the conical head to prevent backflow, but the supply channel for the improving agent in the conical head is inclined so that the axis of the supply channel is perpendicular to the inclination of the circumferential surface of the conical head. Therefore, the valve body is provided so as to face the discharge direction of the improving agent. For this reason, the technology of Patent Document 3 also has the same problems as the technology of Patent Document 2.

[0010] In the technology of Patent Document 4, the direction perpendicular to the axial direction of the rotating shaft is the discharge direction of the improvement material, and the valve element for preventing backflow is installed facing the discharge direction with its lower side as the fixed end. The valve element for preventing backflow disclosed in Patent Document 4 is configured to guide the improvement material upward where the agitator blades are located by opening the valve element to a predetermined aperture so that the improvement material flows along the outer periphery of the improvement diameter along the agitator blades. The valve element for preventing backflow disclosed in Patent Document 4 cannot allow the improvement material to flow to the outer periphery of the improvement diameter unless the discharge pressure is insufficient and an appropriate aperture is achieved. In other words, the same problems as those of the technologies of Patent Documents 2 and 3 occur.

[0011] The above-mentioned problems have been pointed out in soil improvement work with a large improvement diameter (for example, an improvement diameter of 1600 mm), but with the recent improvement in the solidification performance of improvement materials and the increase in ground improvement work using improvement materials with low solidification agent content in pursuit of economy, the problems have become more apparent regardless of the size of the improvement diameter, and there is a growing demand for improvement.

[0012] The technology described in Patent Document 5 includes a nozzle for discharging improvement material, which is positioned on a rotating shaft with its outlet facing diagonally downward, allowing the improvement material to be discharged diagonally downward. The technology described in Patent Document 5 does not have a valve body covering the outlet, as disclosed in Patent Documents 1-4. Such a valve body does not change the direction of the improvement material's discharge, but whether the improvement material can reach the outer periphery of the improvement diameter depends on the discharge pressure due to the supply flow rate from the improvement material supply side. Therefore, when using a device configured as described in Patent Document 5 for ground improvement work using improvement materials with low solidification content, which have a low supply rate per unit time, insufficient discharge pressure can result in poor mixing of the excavated soil and improvement material. Furthermore, the technology described in Patent Document 5 does not have a backflow prevention measure at the tip of the nozzle, making it prone to nozzle clogging with improvement material. Once the nozzle outlet becomes clogged, maintenance requires a significant amount of effort.

[0013] Installing a valve to prevent backflow at the discharge outlet of an excavation tool is an effective measure to prevent clogging with improved soil. However, because the opening and direction of the valve vary depending on the discharge pressure, it is not possible to flow the improvement material in the desired direction and have it reach the outer periphery of the improvement diameter. For this reason, there is a demand for technology that can both install a valve to prevent backflow at the discharge outlet and flow the improvement material in the desired direction.

[0014] The present invention has been made in consideration of the above circumstances, and provides an excavating and mixing tool that has a simple configuration but can reliably allow the improvement material to reach the outer periphery of the improvement diameter and can uniformly mix and knead the excavated soil and improvement material. [Means for solving the problem]

[0015] In order to solve the above-mentioned problems of the related art, an excavating and stirring tool according to one embodiment of the present invention is (1) an excavating and stirring tool for carrying out ground improvement by mixing excavated soil and improvement material while excavating and stirring the ground, the excavating and stirring tool comprising: an excavating and stirring shaft extending in a vertical direction; an excavating blade provided at the lower end of the excavating and stirring shaft; an improvement material supply passage provided inside the excavating and stirring shaft for supplying improvement material to the lower end side of the excavating and stirring shaft; and a discharge part provided at the lower end side of the excavating and stirring shaft and having a discharge port for discharging the improvement material supplied via the improvement material supply passage to the outside of the excavating and stirring shaft, The discharge port is provided at the lower end of the material supply passage, in communication with a discharge passage extending from the axis of the excavation / mixing shaft toward the outer periphery, with the opening surface of the discharge port inclined with respect to the discharge direction of the improvement material determined by the discharge passage, and a flap-shaped valve body is provided at the discharge port, with the fixed end being the side where the length of the discharge passage becomes shorter due to the inclination of the opening surface in a side view, so that it can be attached to and detached from the discharge port depending on the discharge pressure of the improvement material, and the valve body is configured so that when the improvement material passes through the discharge port, the tip portion of the valve body opposite the fixed end is separated from the discharge port.

[0016] Furthermore, in another aspect of the present invention, the drilling and stirring tool is characterized in that (2) the discharge portion is provided on the rear side of the drilling blade in the direction of drilling rotation. [Effects of the Invention]

[0017] With the drilling and mixing tool according to the present invention, the valve body for preventing backflow is positioned at a predetermined inclination relative to the direction of discharge of the slurry improvement material, making it possible to discharge the improvement material at a predetermined discharge pressure regardless of the valve body opening. This allows the improvement material to reach the outer periphery of the improvement diameter and be dispersed uniformly in the excavated soil, improving the quality of the columnar improved body. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a side view schematically showing the configuration of a drilling and stirring tool according to a first embodiment of the present invention. [Figure 2] 1 is a bottom view schematically showing the configuration of a drilling and stirring tool according to a first embodiment of the present invention.

[0023] FIG. [Figure 3] 1 is a front view showing the configuration of the vicinity of a discharge part of a drilling and stirring tool according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram illustrating the state of discharging improvement material in the drilling and stirring tool according to the first embodiment of the present invention. [Figure 5] 1 is a cross-sectional outline view showing a discharge part of a drilling and stirring tool according to a first embodiment of the present invention.

[0023] FIG. [Figure 6] 1 is a cross-sectional outline view showing a discharge part of a drilling and stirring tool according to a first embodiment of the present invention.

[0023] FIG. [Figure 7] FIG. 4 is a side view schematically showing the configuration of a drilling and stirring tool according to a second embodiment of the present invention. [Figure 8] FIG. 4 is a bottom view schematically showing the configuration of a drilling and stirring tool according to a second embodiment of the present invention. [Figure 9] FIG. 10 is an explanatory diagram illustrating the function and effect of the drilling and stirring tool according to the second embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram illustrating the function and effect of the drilling and stirring tool according to the second embodiment of the present invention. [Figure 11] 1 is a schematic diagram of a ground improvement device to which an excavating and stirring tool according to the present invention is applied. [Figure 12] FIG. 10 is a side view illustrating the discharge portion of the excavating and stirring tool according to the comparative example. [Figure 13] FIG. 10 is a schematic cross-sectional view illustrating the discharge portion of a drilling and stirring tool according to a comparative example. [Figure 14] FIG. 10 is a schematic cross-sectional view illustrating the discharge portion of a drilling and stirring tool according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention relates to an excavation and mixing tool for ground improvement equipment that performs ground improvement by mixing excavated soil and improvement material while excavating and mixing the ground, and is configured with multiple mixing blades. By devising the configuration of the improvement material discharge section located at the lower end of the excavation and mixing shaft, it is possible to improve the diffusion efficiency of the improvement material and the quality of the columnar improved body. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] <1.Soil improvement device> The configuration of a ground improvement device equipped with an excavating and mixing tool according to the present invention will be described. Fig. 11 shows a ground improvement device K equipped with an excavating and mixing tool A according to the present invention. As shown in Fig. 11, the main equipment parts of the ground improvement device K are installed on the ground surface of the improved portion of the ground G.

[0021] 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 move up and down freely, an excavation and stirring shaft 1 that is formed to extend 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.

[0022] The improvement material supply unit 230, located at the rear of the base machine body 200, supplies a slurry-based improvement material into the borehole. The improvement material supply unit 230 is connected to the improvement material supply path 11 inside the drilling / mixing shaft 1, which is connected to the rotation drive unit 220 via an improvement material supply pipe 231.

[0023] 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, and other solidification materials other than cement-based materials, admixtures, additives, neutralizing agents, pharmaceuticals, chemical agents, etc. can also be added depending on the purpose of the ground improvement.

[0024] The improvement material supplied from the improvement material supply section 230 passes through the improvement material supply path in the excavation / mixing shaft 1, is discharged from the discharge port formed in the excavation / mixing tool A, is spread and diffused into the excavated ground and soil, and is mixed together with the excavated soil by the excavation / mixing tool A.

[0025] The rotation drive unit 220 is capable of moving up and down 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 .

[0026] One end of the hanging wire 221 is connected to the driving rotary drum, the middle part is passed through the top of the leader 210 and wound around a pulley 222 provided on the upper part of the rotary drive part 220, and the other end is fixed to the upper end of the leader 210.

[0027] 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.

[0028] A driving machine (not shown) is mounted inside the rotary driving section 220, and the excavating / mixing shaft 1 is connected at its base end to the driving machine and driven to rotate.

[0029] The driver inside the rotation drive unit 220 may be any driver that applies a driving force as a rotational force to the excavation / agitation shaft. Furthermore, the rotation drive unit 220 and the driver inside it are not limited to those corresponding to a single-shaft excavation / agitation shaft 1, but 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.

[0030] The ground improvement device K configured in this manner is provided with an excavating and mixing tool A, which is a main part that performs ground improvement by mixing the excavated soil with improvement materials while excavating and mixing the ground.

[0031] 2. First Embodiment [Overall structure] The configuration of the drilling and stirring tool A1 according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a side view schematically showing the configuration of the drilling and stirring tool A1 according to this embodiment, and FIG. 2 is a bottom view thereof. FIG. 3 is a side schematic view showing an enlarged view of the vicinity of the discharge port of the drilling and stirring tool A1. In FIGS. 1 and 2, the wall surface 9 of the imaginary drilled hole is indicated by a two-dot chain line. In addition, in FIG. 2, the stirring blade 4 and the anti-co-rotation blade 5 other than the drilling blade 2 are not shown.

[0032] The excavating and mixing tool A1 of this embodiment is used to improve the 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 that extends in the vertical direction, an excavating blade 2 that is attached to the lower end of the excavating and mixing shaft 1 and excavates the ground, a plurality of mixing blades 4, and a co-rotation prevention blade 5.

[0033] An improvement material supply passage 11 extends inside the drilling / mixing shaft 1 along the axis S of the drilling / mixing shaft 1. At the lower end of the improvement material supply passage 11, a discharge passage 11a is provided that is bent at approximately 90 degrees to form an opening on the side of the drilling / mixing shaft 1. That is, the discharge passage 11a of the improvement material supply passage 11 is provided from the axis S of the drilling / mixing shaft 1 toward the outer periphery, thereby defining the discharge direction X of the improvement material (see FIG. 5). Furthermore, the discharge passage 11a is provided inside the drilling / mixing shaft 1 so that the discharge direction X of the improvement material is perpendicular to the axis S.

[0034] The side surface of the lower end of the drilling / mixing shaft 1 is provided with a discharge section 3 having a discharge port 31 formed therein for discharging improvement material. The discharge section 3 is connected to the discharge passage 11a at the terminal end of the improvement material supply passage 11, the base end of which opens on the outer surface of the drilling / mixing shaft 1. It is a cylindrical section that protrudes outward from the side surface of the drilling / mixing shaft 1. The cylindrical discharge section 3 has the same inner diameter as the improvement material supply passage 11. The tip of the discharge section 3 is inclined at a predetermined angle relative to the protruding direction of the cylindrical section in side view. The discharge port 31 is an inclined cross section at the tip end of the cylindrical member in side view, and is an opening that communicates with the improvement material supply passage 11. The discharge port 31 opens so as to face diagonally downward relative to the axis S of the drilling / mixing shaft 1. In other words, the upper end of the discharge port 31 is inclined further outward. The discharge direction X of the improvement material up to the discharge port 31 is determined by the discharge axis Q, which is a straight line that passes through the center of the ellipse (circle when viewed from the front) described by the discharge port 31 and is perpendicular to the axis S of the excavation and mixing shaft 1. In other words, the improvement material flows from top to bottom through the improvement material supply path 11, and changes its flow by approximately 90 degrees toward the outer periphery of the excavation and mixing shaft 2 by flowing into the discharge path 11a at the lower end. Thereafter, the improvement material flows in the discharge direction X, which is the horizontal direction along the discharge axis Q, and hits the valve body 32.

[0035] The discharge section 3 is provided with a valve element 32 that covers the discharge port 31. The valve element 32 is a plate-shaped member formed of a flexible material, such as an elastic rubber plate or resin, having a predetermined thickness. As shown in FIGS. 5 and 6 , the valve element 32 is attached to the discharge port 31 with a fixed end 32a at the end of the discharge path 11a where the length in the direction from the axis S of the drilling / mixing shaft 1 toward the outer periphery is shorter, by providing an inclined opening surface 31a of the discharge port 31 in a side view. More specifically, the lower end of the valve element 32 is fixed to the lower end of the discharge port 31 by a fixing member 33 such as a screw. The valve element 32 closes the oval opening of the discharge port 31 and fixes the lower end with the fixing member 33, so that the plate surface of the valve element 32 is inclined at a predetermined angle θ with respect to the discharge axis Q (see FIG. 5 ).

[0036] The flap-shaped valve element 32 is adapted to move toward and away from the opening surface 31a (see FIG. 6) of the discharge port 31 in response to the discharge pressure of the improvement material. When the improvement material supply unit 230 is driven and the improvement material is being supplied to the improvement material supply path 11 at a predetermined flow rate (e.g., 50 to 200 L / min), the valve element 32 is deformed by the discharge pressure of the improvement material, so that the tip portion 32b of the valve element 32, which is opposite the fixed end 32a, is turned up. As the tip portion 32b moves away from the opening surface 31a of the discharge port 31, the valve element 32 opens the discharge port 31 at an opening angle corresponding to the discharge pressure. When the drive of the improvement material supply unit 230 is stopped and the improvement material is not flowing in the improvement material supply path 11, the valve element 32 comes into contact with the opening surface 31a of the discharge port 31 due to its elasticity (restoring force) to seal the discharge port 31 and prevent the improved soil from flowing back into the improvement material supply path 11.

[0037] The drilling blade 2 has a strip-shaped drilling blade main body 21 extending radially outward from the drilling / mixing 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 / mixing shaft 1 with its lower end inclined at a predetermined angle forward in the drilling rotation direction. The multiple bits 22 are arranged on the drilling blade main body 21 at predetermined intervals along the blade length direction.

[0038] Furthermore, a discharge section 3 for discharging improvement material is provided near the lower end of the drilling blade main body 21 on the lower end side of the drilling / mixing shaft 1. The discharge section 3 is positioned so that the center of a discharge port 31 formed at the tip end coincides with the rotation axis S of the drilling / mixing shaft 1 when viewed from the front (see FIG. 3). The discharge port 31 is configured to open from the outer circumferential surface of the drilling / mixing shaft 1 along the extension direction of the drilling blade 2 when discharging improvement material. The drilling blade 2 is supported on the drilling / mixing shaft 1 with the drilling blade main body 21 tilted at a predetermined angle, so that while the bit 22 excavates the ground, it discharges soil and sand upward together with the improvement material discharged from the discharge port 31.

[0039] In this embodiment, two excavation blades 2 are provided at the lower end of the excavation / mixing shaft 1 in point symmetry with respect to the axis S (see FIG. 1). In other words, the two excavation blades 2 are provided on both the left and right sides of the outer periphery of the excavation / mixing shaft 1 in a plan view, arranged with a phase difference of 180 degrees from each other. The number of excavation blades 2 provided on the excavation / mixing 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 excavation / mixing shaft 1. Furthermore, the blade length, blade width, and blade thickness of the excavation blades 2 can be selected appropriately according to the desired improvement diameter and / or the type of ground to be improved.

[0040] A plurality of mixing blades 4 provided above the excavation blade 2 mix the soil and sand excavated by the excavation blade 2 and discharged upward with the improvement material discharged from the discharge port 31 .

[0041] The agitator blades 4 are formed in the shape of a strip, 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 / mixing shaft 1, with one end supported by the drilling / mixing shaft 1. Multiple agitator blades 4 (four blades) are provided on the drilling / mixing shaft 1. The four agitator blades 4 are arranged in pairs, which are arranged point-symmetrically around the axis S of the drilling / mixing shaft 1 in plan view, and the two sets of agitator blades 4 are supported on the drilling / mixing shaft 1 in two rows, one above the other, so that their rotation phases around the axis S differ by 90 degrees.

[0042] The blade length of the agitator impeller 4 is such that the length from the axis S of the drilling / stirring shaft 1 to its tip is approximately the same as that of the drilling impeller 2. The agitator impeller 4 is a driven agitator impeller that rotates integrally with the drilling / stirring shaft 1 as one end is supported by the drilling / stirring shaft 1. The number of agitator impellers 4 is not particularly limited, and for example, multiple agitator impellers may be arranged radially from the outer circumferential surface in a plan view, and in a spiral shape with a predetermined rotation phase in the vertical direction.

[0043] The anti-corotation blade 5 is formed in the shape of a strip, and one end is supported by the boss portion 7. The boss portion 7 is a cylindrical member with an inner diameter slightly larger than that of the drilling and mixing shaft 1, and is loosely fitted onto the drilling and mixing shaft 1. This prevents the boss portion 7 from rotating with the drilling and mixing shaft 1. A pair of stoppers 8, 8 are disposed above and below the boss portion 7 on the drilling and mixing shaft 1 to restrict the boss portion 7 from moving up and down. Each of the pair of stoppers 8, 8 is a flange-shaped member fixed to the drilling and mixing shaft 1. The boss portion 7 is positioned at a predetermined height position on the drilling and mixing shaft 1 by being supported with its cylindrical periphery in sliding contact with the opposing flange surfaces of the pair of stoppers 8, 8.

[0044] The length of the anti-rotation blade 5 from the axis S of the drilling / mixing shaft 1 to its tip is longer than that of the drilling blade 2. The anti-rotation blade 5 rotates at a different speed from the drilling / mixing shaft 1, which is stationary or rotates at a predetermined speed within the drilling hole, by having its tip dig into and come into contact with the wall surface 9 of the drilling hole. The anti-rotation blade 5 shears soil and sand, and prevents the mixing blade 4 and the improved soil from forming a lump and rotating together. There is no particular limit to the number of anti-rotation blades 5; for example, four may be arranged to form an approximate cross in plan view.

[0045] In the drilling and stirring tool A1 according to this embodiment, the drilling blade 2, the anti-corotation blade 5, and the stirring blade 4 are arranged in this order from the bottom end upward.

[0046] 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 mechanism 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 the improvement material.

[0047] Comparative Example The excavating and mixing tool A1 according to this embodiment has a feature different from conventional tools in that the outlet 31 of the discharge section 3 that discharges the improvement material is an opening facing diagonally downward, and the plate surface of the plate-shaped valve body 32 that covers the outlet 31 is inclined at an angle θ with respect to the discharge axis Q. Problems with conventional outlets will be explained below with reference to the comparative example shown in Figs. 12 to 14. Fig. 12 is a side view illustrating the outlet 131 of an excavating and mixing tool B according to the comparative example. Figs. 13 and 14 are schematic cross-sectional views thereof. In the excavating and mixing tool B according to the comparative example shown in Figs. 12 to 14, the same reference numerals are used to designate equivalent components for ease of comparison with this embodiment.

[0048] The discharge part 130 of the drilling and mixing tool B according to the comparative example has a discharge port 131 that opens in a cross section perpendicular to a discharge axis Q that is perpendicular to the axis S of the drilling and mixing shaft 1 in a side view, and a valve body 132 that covers the discharge port 131. The lower end side of the valve body 132 is fixed by a fixing member 133 such as a screw member. Therefore, when improvement agent is supplied through the improvement agent supply path 11, the valve body 132 is curved and deformed so that the upper side of the valve body 132 is turned up, and the discharge port 131 is opened to an opening degree corresponding to the discharge pressure.

[0049] In the discharge part 130 of the excavating and mixing tool B according to the comparative example, the valve body 132 that closes the discharge port 131 is disposed so that its plate surface is perpendicular to the discharge axis Q (see FIG. 13). Therefore, the valve body 132 faces the flow of improvement material (indicated by the white arrow in FIG. 13) that flows through the improvement material supply path 11 toward the discharge port 131.

[0050] Assume that the valve element 132 is configured so that the discharge port 131 is fully open when improvement agent is supplied from the improvement agent supply unit 230 to the improvement agent supply path 11 at a flow rate of, for example, 200 L / min. Here, the fully open discharge port 131 refers to a state in which the valve element 132 is deformed, as shown by the dashed line in FIG. 14 . When improvement agent is supplied from the improvement agent supply unit 230 to the improvement agent supply path 11 at a flow rate of 200 L / min or slightly less (e.g., 150 L / min), the valve element 132 deforms at least to a position below the discharge axis Q to open the discharge port 131. In this case, the improvement agent flows along the underside of the drilling blade main body 21 approximately along the discharge axis Q and can reach the tip of the drilling blade 2.

[0051] On the other hand, when improvement agent is supplied from the improvement agent supply unit 230 to the improvement agent supply line 11 at a flow rate significantly lower than 200 L / min (e.g., 50 L / min), only the upper end of the valve element 132 deforms due to the discharge pressure, as shown by the solid line in Figure 14, and the opening of the discharge port 131 is approximately one-third of its full opening. In other words, because the valve element 132 faces the discharge direction X1 of the improvement agent as shown in Figure 13, the flow of improvement agent collides head-on with the valve element 132, causing a decrease in the discharge pressure of the improvement agent. Therefore, the improvement agent is not discharged in the direction along the discharge axis Q, but rather sprays out from the gap between the valve element 132 and the discharge port 131 (shown by the hollow arrow in Figure 14). The discharge port 131 is located below the inclined lower surface of the drilling blade main body 21, which is supported by the drilling / mixing shaft 1 at a predetermined angle of the drilling blade 2. Therefore, the improvement material discharged upward from the discharge port 131, which is open only on the upper side due to the deformation of the valve body 132, hits the inclined surface on the back side of the excavation blade main body 21, and changes its flow direction downward as shown by the white arrow in Figure 12 without reaching the outer circumferential end (tip) of the excavation blade 2. This causes the improvement material to not be sufficiently dispersed in the excavated soil, which causes poor quality of the columnar improvement body.

[0052] [Details and effects of the discharge section] The drilling and stirring tool A1 according to this embodiment overcomes the problems described with reference to the comparative example by employing a discharge part 3, which will be described in detail below. Figures 5 and 6 are cross-sectional outline views that schematically show the discharge part 3 of the drilling and stirring tool A1.

[0053] In this embodiment, the discharge port 31 of the discharge part 3 is formed with its opening surface 31a inclined at a predetermined angle θ with respect to the discharge axis Q. Therefore, the valve body 32 covering the inclined discharge port 31 is also disposed with its plate surface inclined at the predetermined angle θ with respect to the discharge axis Q. The predetermined angle θ is preferably an acute angle of about 15 to 75 degrees, and in this embodiment, the predetermined angle θ is set to approximately 45 degrees.

[0054] In this embodiment, unlike the comparative example shown in FIGS. 13 and 14 , the flow of improvement material supplied to the improvement material supply path 11 and proceeding toward the discharge port 13 strikes the inclined surface of the valve body 32, which is disposed at an angle relative to the discharge axis Q. Of the improvement material flowing along the discharge axis Q, the improvement material that strikes the lower side of the valve body 32 (the side closer to the fixed end 32a of the fixing member 33) before the improvement material flowing below the discharge axis Q and above the discharge axis Q flows toward the upper side of the discharge port 31 along the inclined surface of the valve body 32. In other words, the flow of improvement material is focused toward the outermost protruding portion of the discharge port 31. In this way, by concentrating the flow of improvement material along the inclined valve body 32 diagonally upward from the discharge port 31 in side view, the flow of improvement material from the upper part of the opened discharge port 31 toward the outside is substantially increased by deforming the valve body 32. In other words, it is possible to reduce the difference in the opening angle of the valve element 32 according to the discharge amount derived from the supply flow rate, and it is successful in minimizing the loss of discharge energy by the valve element 32. Therefore, when the improvement material is discharged from the discharge port 31, a discharge pressure is obtained that allows it to reach the outer periphery of the improvement diameter.

[0055] As shown in FIG. 6, the improvement material is guided diagonally forward by the fan-like shape formed by the inclined opening surface 31a of the discharge port 31 and the deformed valve body 32 in a side view. The discharge section 3 of this embodiment prevents the improvement material from scattering upward through the gap between the discharge port 131 and the valve body 132, colliding with the back surface of the excavation blade main body 21, and then moving downward, as in the comparative example. Even when the improvement material is supplied from the improvement material supply section 230 to the improvement material supply path 11 at a low flow rate (e.g., 50 L / min), the discharge section 3 of this embodiment can ensure that the improvement material reaches the wall surface 9 of the excavated hole, which is the outer periphery of the improvement diameter, as shown by the white arrow in FIG. 4. This allows the improvement material to be uniformly dispersed, improving the quality of the columnar improvement body.

[0056] Furthermore, by configuring the discharge part 3 in the present embodiment, it is possible to reduce the difference in the opening angle due to differences in the material of the valve element 32 (differences in flexibility, fixing mode of the valve element, etc.). This increases the options for the material of the valve element 32. Furthermore, by widening the range of flow rates that can be handled, the work of replacing the valve element 32 with one having a different flexibility according to different flow rates can be reduced.

[0057] Furthermore, in the discharge unit 3 of this embodiment, a flexible flap-shaped valve body 32 is attached by a fixing member 33, but this is not limiting. As the flexible plate-shaped member, hard rubber or the like can be used, but a hard material that does not have flexibility can also be used. For example, a hard material such as metal, plastic, or casting having a hinge portion can also be used. Furthermore, as a method for attaching a plate-shaped object having the same function as the flap-shaped valve body, an attachment method such as welding or bolting can be appropriately selected depending on the respective material.

[0058] 3. Second Embodiment Next, a drilling and stirring tool A2 according to a second embodiment of the present invention will be described with reference to FIGS. 7 to 10. FIG. 7 is a front view schematically illustrating the configuration of the drilling and stirring tool A2 according to this embodiment, and FIG. 8 is a bottom view thereof. FIGS. 9 and 10 are diagrams illustrating further functions and effects of the drilling and stirring tool A2. FIG. 9 is an enlarged view of area D surrounded by a dashed line in FIG. 7, and FIG. 10 is a partially enlarged view of the drilling impeller 2 and the flow straightener 23 when the discharge port 31 is viewed from the front. In addition, in FIG. 8, the agitating impeller 4 and the anti-corotation impeller 5 other than the drilling impeller 2 are not shown. In addition, in FIG. 10, the flow straightener 23, which is located on the front side of the paper relative to the discharge section 3, is indicated by a dashed line. Note that components equivalent to those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0059] 7, the second embodiment is similar to the first embodiment in that the drilling and stirring tool A2 has a drilling and stirring shaft 1, a drilling impeller 2 for drilling the ground, a stirring impeller 4, and a co-rotation prevention impeller 5, one end of which is supported by a boss portion 7 loosely fitted to the drilling and stirring shaft 1. On the other hand, the second embodiment differs from the first embodiment in that a flow regulator 23 is provided at the end of the drilling impeller 2.

[0060] The flow regulator 23 is a plate-like member provided at the tip of the excavation blade main body 21 of the excavation blade 2, protruding rearward in the direction of excavation rotation from the back side thereof, and is arranged so that the plate thickness surface faces the direction of excavation rotation. The flow regulator 23 has the function of adjusting the flow direction of the excavated soil cut by the bit 22 of the excavation blade 2 (see Figure 10).

[0061] As shown in FIG. 8, as the drilling blade 2 equipped with the flow straightener 23 rotates, a continuous, approximately fan-shaped space (negative pressure space R) is formed in a bottom or plan view on the radially center side of the drilling blade 2 relative to the flow straightener 23, with the rear side open in the rotation direction. The negative pressure space R is a low-pressure region where the pressure is lower than that of the area of ​​the excavation surface G1 before it is cut by the bit 22, and is formed behind the drilling blade 2, with the rotation direction of the drilling blade 2 being the front. As shown in FIG. 10, the flow straightener 23 utilizes the pressure difference between the front and rear of the drilling blade 2, which is created by forming the negative pressure space R behind the drilling blade 2, to generate a wake flow BF, which is a slow-flowing vortex flow that can wrap around behind the drilling blade 2. As a result, on the back side of the drilling blade 2 above the excavation surface G2 after excavation, the improvement material discharged from the discharge port 31 is uniformly dispersed and mixed into the excavated soil that has flowed behind the drilling blade 2 due to the vortex flow of the wake flow BF.

[0062] 9, the flow regulator 23 not only regulates the flow of excavated soil, but also serves as a physical barrier that causes the improvement material, which is discharged from the opening between the discharge port 31 of the discharge section 3 and the valve body 32 and reaches the outer periphery of the excavation blade 2, to flow back toward the excavation / agitation shaft 1. Therefore, in this embodiment, the improvement material discharged from the discharge section 3 is further diffused by the action of the vortex caused by the pressure difference before and after the excavation blade 2, which is brought about by the flow regulator 23, and the return action of the improvement material toward the excavation / agitation shaft 1. This further improves the quality of the columnar improved body.

[0063] It goes without saying that the shape of the flow regulator 23 can be changed within a predetermined range as long as it can function as a flow regulator.

[0064] It can be said that the excavating and stirring tools (A1, A2) of the first and second embodiments having the above-mentioned configuration have the following configuration. That is, the excavating and stirring tools (A1, A2) for performing ground improvement by mixing excavated soil and improvement material while excavating and stirring the ground have the following configuration: The excavating and stirring tools (A1, A2) include an excavating and stirring shaft 1 extending in the vertical direction, an excavating blade 2 provided at the lower end of the excavating and stirring shaft 1, an improvement material supply passage 11 provided inside the excavating and stirring shaft 1 and supplying improvement material to the lower end side of the excavating and stirring shaft 1, and a discharge section 3 provided at the lower end side of the excavating and stirring shaft 1 and having a discharge port 31 for discharging the improvement material supplied to the lower end side of the excavating and stirring shaft 1 via the improvement material supply passage 11 to the outside of the excavating and stirring shaft 1, and the discharge section 3 is provided at the lower end side of the improvement material supply passage 11 in communication with a discharge passage 11a extending from the axis S of the excavating and stirring shaft 1 toward the outer periphery. The opening surface 31a of the discharge port 31 is inclined with respect to the discharge direction X of the improvement material defined by the discharge path 11a, and the discharge port 31 is provided with a flap-shaped valve body 32 whose fixed end 32a is on the side where the length of the discharge path 11a becomes shorter due to the inclination of the opening surface 31a in a side view, so that the valve body 32 can be moved toward and away from the discharge port 31 depending on the discharge pressure of the improvement material, and the valve body 32 is configured so that when the improvement material passes through the discharge port 31, the tip portion 32b of the valve body 32, which is on the opposite side to the fixed end 32a, moves away from the discharge port 31.

[0065] Furthermore, the drilling and mixing tools (A1, A2) of the first and second embodiments having the above-described configurations can also be said to have the following configuration: That is, the discharge section 3 is provided with an opening surface 31a of the discharge port 31 inclined with respect to a discharge axis Q that passes through the center of the discharge port 31 and intersects with the axis S of the drilling and mixing shaft 1, and the discharge port 31 is provided with a flap-shaped valve body 32 that moves in and out of contact with the discharge port 31 depending on the discharge pressure of the improvement material.

[0066] Here, the discharge axis Q, which passes through the center of the discharge port 31 and intersects with the axis S of the drilling / mixing shaft 1, not only intersects with the axis S of the drilling / mixing shaft 1 at a right angle, as shown in each embodiment, but also intersects with the axis S of the drilling / mixing shaft 1 at a predetermined inclination angle. Furthermore, the term "orthogonal" does not necessarily mean perfectly perpendicular, but also means allowing for a deviation of, for example, about ±5 degrees. Furthermore, the term "orthogonal" also includes cases where the axis S and the discharge axis Q do not intersect at a single point, but are approximately perpendicular in side view within the radius of the improvement agent supply channel 11. In other words, the relationship between the axis S and the discharge axis Q, which is determined by the positional relationship between the improvement agent supply channel 11 and the discharge section 3, naturally includes tolerances allowed in the design and the assembly and installation process of each component.

[0067] Furthermore, the valve body 32, which is arranged at an angle relative to the discharge axis Q, may be arranged at an angle upward or horizontally, other than the angle facing diagonally downward as in each of the above-described embodiments, and may be inclined in any direction as long as it is arranged at an angle relative to the discharge axis Q.

[0068] With this configuration, a flap-shaped valve element 32 is provided at the discharge port 31 to prevent backflow of the improvement material, and the valve element 32 is provided at an angle with respect to the discharge direction X, thereby reducing the drop in discharge pressure caused by the valve element 32. As a result, the improvement material discharged from the discharge section 3 does not remain around the drilling / mixing shaft 1, but reaches the outer peripheral end of the drilling blade 2 (the tip of the drilling blade main body 21). By efficiently and reliably diffusing the improvement material in this way, the quality of the columnar improvement body can be improved.

[0069] Moreover, the excavating and stirring tool (A1, A2) according to this embodiment is characterized in that the discharge part 3 is provided on the rear side of the excavating blade 2 in the excavating rotation direction.

[0070] With this configuration, the improving agent can be diffused more efficiently.

[0071] The above-mentioned embodiments have been described using as examples the case where a columnar improvement body is constructed by supplying a slurry-like improvement material as a ground improvement method, but it goes without saying that the present invention is applicable to excavation and mixing tools used in ground improvement methods where a columnar improvement body is constructed by supplying a powder-like improvement material.

[0072] Finally, the above-described embodiments are merely examples of the present invention, and are not limited to the above-described embodiments and variations thereof. The present invention also includes configurations in which the components disclosed in the above-described embodiments are substituted or combined with each other, configurations in which the components disclosed in the publicly known technologies and the above-described embodiments are substituted or combined with each other, and other configurations. Furthermore, the present invention is not limited to the above-described embodiments, and various modifications are possible depending on the design, etc., as long as they do not deviate from the technical concept of the present invention. Furthermore, the present invention also covers matters described in the claims and their equivalents. Furthermore, the effects described in this disclosure are merely examples and are not intended to be limiting, and other effects may also be present. [Explanation of symbols]

[0073] A, A1, A2 Drilling and Mixing Tools 1 Drilling and stirring shaft 2 Drilling Wing 3 Discharge part 4. First mixing blade 5 Anti-corotation blade 7 Boss section 8 Stopper 9. Wall of the drilling hole 11 Improved material supply route 11a Discharge path 21 Excavation wing body 22-bit 31 Discharge port 31a Opening surface 32 Valve body 32a fixed end 32b Tip part 33 Fixing member S axis Q Discharge axis X Discharge direction

Claims

1. An excavation and mixing tool for improving ground by mixing excavated soil with improvement materials while excavating and mixing the ground. A drilling and stirring shaft extending in the vertical direction; A drilling blade provided at the lower end of the drilling / agitation shaft; an improvement material supply passage provided inside the excavation / agitation shaft and supplying improvement material to the lower end side of the excavation / agitation shaft; A discharge part provided on the lower end side of the drilling / agitation shaft and having a discharge port for discharging the improvement material supplied through the improvement material supply path to the outside of the drilling / agitation shaft; Equipped with The discharge portion is provided at the lower end side of the improvement material supply path in communication with a discharge path extending from the axis of the excavation / agitation shaft toward the outer periphery, and the opening surface of the discharge port is inclined with respect to the discharge direction of the improvement material defined by the discharge path, The discharge port is provided with a flap-shaped valve body, the fixed end of which is the side where the length of the discharge path is shortened by inclining the opening surface in a side view, so as to be able to come into and out of contact with the discharge port in accordance with the discharge pressure of the improvement material, The valve body is configured so that when the improvement material passes through the discharge outlet, the tip portion of the valve body opposite the fixed end is separated from the discharge outlet.

2. The excavating and stirring tool according to claim 1, wherein the discharge portion is provided on the rear side of the excavating blade in the excavating rotation direction.

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