JP2021059856A - Excavation agitator - Google Patents

Abstract

To provide an excavation agitator capable of integrally constructing a columnar improved body and a core body without pulling up from an excavation hole or replacing members when constructing a core body consisting only of a binder in a central part of the columnar improved body composed of a solidified mixture of an excavated soil and the binder.SOLUTION: A hollow portion 220 that serves as a flow path for a binder is provided in a main body cylinder portion 22, and a core body construction inner cylinder 23 is inserted into the hollow portion and is held so as to be able to appear and disappear downward. A core bottom lid material 30 that closes a lower end opening of the core body construction inner cylinder 23 is held in the vicinity of the bottom portion of the main body cylinder portion 22 via a holding member 28 provided on the main body cylinder portion 22. When an excavation hole 40 is dug in this state and the core body construction inner cylinder 23 is projected downward at a predetermined position, the core bottom lid material 30 is separated from the main body cylinder portion 22 and attached to a lower end of the core body construction inner cylinder 23. When an excavation agitator 10 is pulled up while additionally injecting the binder, the core bottom lid material 30 is left at an arbitrary position.SELECTED DRAWING: Figure 3

Description

The present application relates to an excavation agitator capable of efficiently carrying out a ground improvement method for constructing a columnar improved body by injecting a binder into the excavated soil while excavating a vertical hole in the ground and stirring and mixing the mixture.

When building a building on soft ground, inject a binder (solidifying material) such as cement milk into the excavated soil while excavating a vertical hole, and stir and mix the excavated soil and the binder to solidify them into columns. Therefore, a ground improvement method is known in which a columnar improved body called a "pile" is constructed in the ground to increase the bearing capacity of the ground. Regarding such a ground improvement method, for example, because the soil of the ground is organic soil, the solidification strength of the agitated soil does not reach the required level, or because the site is small and only a small base machine can be introduced, a columnar improved body with a small diameter. In some cases, the support capacity of the columnar improved body cannot be sufficiently obtained due to circumstances such as the fact that it can only be constructed, or the stirring capacity of the base machine is low and the stirring soil is not uniformly solidified. In order to solve such a problem, in Patent Document 1, the columnar improvement is performed by additionally forming a core body consisting of only the binder in the central portion of the columnar improved body made of a solidified mixture of the excavated soil and the binder. A construction method for increasing the support strength of the body is disclosed. Further, the applicant also proposes in Patent Document 2 a construction method which is an improvement of the construction method described in Patent Document 1, and is trying to put it into practical use.

The ground improvement method disclosed in Patent Document 2 and the outline of the excavation agitation device used in the method are shown in FIGS. 7 to 8. In this ground improvement method, an excavation agitator 1 also called a "head" or a "bit" is attached to the tip of a rod 21 which is rotationally driven by an auger device (not shown) mounted on a base machine. While excavating the vertical hole, the excavated soil and the binder are agitated and mixed. As shown in FIG. 7, the excavation agitator 1 has a main body cylinder portion (“main body shaft portion” in Patent Document 2) 22 which is connected to the rod 21 and rotates integrally with the rod 21, and a lower end of the main body cylinder portion 22. The excavation blade 24 provided so as to project from the vicinity in the radial direction of the main body cylinder portion 22, the stirring blade 26 provided above the excavation blade 24 in the main body cylinder portion 22, and the excavation blade 24 and the stirring blade 26. The ground is excavated by a plurality of excavation blades 241 projecting from the lower surface of the excavation blade 24, which is provided with a co-rotation prevention blade 25 provided so as to be rotatable relative to the main body cylinder portion 22. It is configured. A binder injection port (nozzle) 221 is provided laterally near the lower end of the main body cylinder portion 22, and the binder supplied through the flow path 220 formed inside the rod 21 is excavated from the binder injection port 221. It is discharged into the soil and mixed with the excavated soil by the rotation of the excavation blade 24 and the stirring blade 26.

FIG. 8 is a diagram showing steps in order when the ground improvement method is carried out using the excavation agitation device 1. The illustrated steps are carried out as follows.

[S1] The rod 21 to which the excavation agitator 1 is attached is installed vertically at a predetermined position, and is gradually lowered while rotating in the positive direction to start excavation of the ground 4.

[S2] As the excavation hole 40 is dug down, excavated soil remains inside the excavation hole 40. In parallel with this, a binder such as cement milk is injected into the excavation hole 40. The binder is discharged into the excavation hole 40 from the coupling material injection port 221 provided at the lower end of the excavation stirring device 1, and is agitated and mixed with the excavated soil by the rotation of the excavation blade 24 and the stirring blade 26. At this time, the co-rotation prevention blade 25, which is slightly longer than the excavation blade 24, has its tip bitten into the hole wall of the excavation hole 40, so that the rod moves to the deep part of the excavation hole 40 without rotating itself. It acts as a steady rest of the rotation of 21 and resists the excavated soil and binder and the excavation blades 24 and 26 from trying to rotate together, helping to mix them. In this way, the uncured mixture 5 is formed substantially uniformly in the excavation hole 40. When the excavation hole 40 reaches a predetermined depth, the excavation stirring device 1 is rotated and slightly moved up and down a plurality of times to perform bottom treatment, and then the rotation and the up and down movement are stopped.

[S3] Next, the excavation stirring device 1 is gradually raised while rotating the rod 21 in the reverse direction. Even during this rise, the binder can be injected and stirred. Then, the excavation stirring device 1 is once completely pulled up from the excavation hole 40, the excavation blade 24 is removed from the main body cylinder portion 22, and the excavation nozzle 27 is replaced with the extension nozzle 27. As shown in FIG. 7, the extension nozzle 27 is a substantially cylindrical member having a flow path 270 of a binder inside, and the upper end thereof is connected to the lower end of the main body tubular portion 22. In order to enable this replacement, the excavation blade 24 is configured to be separable from the main body cylinder portion 22. The lower end of the extension nozzle 27 is opened downward, and when this opening becomes a new binder injection port 271, the injection position of the binder is substantially moved downward.

Then, the core bottom lid material 3 is attached to the lower end of the extension nozzle 27 so as to close the binder injection port 271. The core bottom lid material 3 is a member having a substantially circular shape in a plan view, which is made of metal, a hard synthetic resin, concrete, or the like. The core bottom lid material 3 is formed by, for example, engaging an engaging recess 39 formed by cutting out the peripheral edge thereof with an engaging convex portion 272 projecting from the lower end of the extension nozzle 27, thereby engaging the extension nozzle 27. Temporarily fixed to the lower end.

[S4] The excavation stirring device 1 to which the extension nozzle is attached is put into the excavation hole 40 again, and the rod 21 is lowered while rotating in the forward direction. The core bottom lid material 3 attached to the lower end of the extension nozzle 27 is pushed into the uncured mixture 5 while rotating integrally with the extension nozzle 27. Then, when the lower end of the extension nozzle 27 reaches the vicinity of the bottommost portion 41 of the excavation hole 40, the descent of the excavation stirring device 1 is stopped.

[S5] The delivery of the binder is restarted at the stop position, and the binder is injected from the binder injection port 271 at the lower end of the extension nozzle 27 into the center of the uncured mixture 5. The rod 21 is rotated in the reverse direction while injecting the binder, and the excavation stirring device 1 is gradually raised. The additionally injected binder gradually forms an uncured core 6 consisting only of the binder in the center of the uncured mixture 5 from bottom to top. The core bottom lid material 3 attached to the lower end of the extension nozzle 27 is disengaged from the extension nozzle 27 when the ejection of the binder is started, is left in the vicinity of the bottommost portion 41 of the excavation hole 40, and is injected into the core portion 6. It receives the binder and prevents the binder from diffusing and flowing out into the unsolidified mixture 5 and soil. Since the height difference between the rotation position of the stirring blade 26 and the binder injection port 271 is generated by attaching the extension nozzle 27, the stirring blade 26 is rotated when the excavation stirring device 1 is raised. However, the binder discharged from the extension nozzle 27 is less affected by stirring, and the shape of the core portion 6 is preferably maintained.

[S6] After the excavation agitator 1 is pulled up, the uncured mixture 5 and the uncured core 6 are solidified after a predetermined curing period. Thus, a double-structured columnar improved body including a solidified mixture 50 formed in a columnar shape up to the bottom 41 of the excavation hole 40 and a core body 60 formed only of a binder formed in the central portion thereof is constructed. Will be done.

Japanese Unexamined Patent Publication No. 2016-20621 Japanese Patent No. 6216477

In the ground improvement method disclosed in Patent Document 2, the first half step ([S1] to [S3]) of producing an unsolidified mixture 5 in which the excavated soil and the binder are stirred and mixed in the excavation hole 40. The excavation stirring device 1 is temporarily pulled up from the excavation hole 40 between the latter half steps ([S4] to [S5]) of additionally forming the core body 60 composed of only the binder in the central portion of the mixture 5. It is necessary to remove the excavation blade 24, replace it with the extension nozzle 27, and attach the core bottom lid material 3 to the lower end thereof. Pulling up the excavation agitator 1 from the bottom 41 of the excavation hole 40 to the ground to replace the member, and then lowering it to the bottom 41 again causes a large loss in the process, and the weight of the replacement member is several tens of kg or more. Therefore, the work is also dangerous.

The invention disclosed in the present application integrally constructs a pillar body made of a mixture of excavated soil and a binder and a core body made of only a binder without pulling up from the excavation hole or replacing members. It was made to realize an excavation agitator that can be used, and in detail, it digs to the bottom of the excavation hole with the core bottom lid material attached to the cylinder for constructing the core body in advance. The solution is to accurately separate the core bottom lid material from the cylinder near the bottom and leave it in the excavation hole.

The excavation agitator of the invention disclosed in the present application for achieving the above-mentioned object is a cylindrical hollow portion that serves as a flow path for a binder inside a main body cylinder portion that holds an excavation blade, a stirring blade, and a co-rotation prevention blade. Is provided, the hollow portion opens downward at the bottom of the main body cylinder portion, and an inner cylinder for building a core body having a hollow cylindrical shape is inserted inside the hollow portion to be below the main body cylinder portion. A core bottom lid material, which is held so as to be able to appear and disappear, has a shape in which the lower end of the inner cylinder for building the core body opens downward and closes the opening, is provided via a holding means provided in the main body cylinder portion. When the inner cylinder for building the core body, which is held near the bottom of the main body cylinder and is housed in the cylinder of the main body, is projected downward, the lower end of the inner cylinder for building the core acts on the holding means. The core bottom lid material is characterized as being detached from the holding means and attached to the lower end of the core body construction inner cylinder.

That is, in this excavation agitator, when the inner cylinder for building the core body housed in the main body cylinder is projected below the main body cylinder, the core bottom lid material held near the bottom of the main body cylinder is the main body cylinder. Since it is configured to separate from the excavation hole, if the binder is injected while the inner cylinder for core body construction is projected when the excavation hole is dug, the core bottom lid material can be left at an arbitrary position in the excavation hole. Can be done.

In this excavation agitator, the core bottom lid material includes a bottom portion having an inverted conical shape and a collar-shaped portion provided on the peripheral edge of the bottom portion, and the bottom portion is provided with a binder injection port. It is practical that a part of the brim-shaped portion is held by the holding means.

Further, an engaging means is provided on the upper surface of the core bottom lid material and the lower end of the inner cylinder for building the core body by engaging with each other in an uneven manner to transmit the rotational force around the axis, and the holding means of the main body cylinder portion. It is more preferable that the core bottom lid material separated from the core body is attached to the lower end of the core body construction inner cylinder via the engaging means.

As a specific embodiment of the engaging means, the core includes an engaging convex portion protruding upward from the peripheral edge of the core bottom lid material and an engaging concave portion formed at the lower end of the core body construction inner cylinder. The engaging convex portion and the engaging concave portion are configured so as to be able to engage in the axial direction of the body building inner cylinder, and the core body building inner cylinder is housed in the main body cylinder portion. It is also possible that the core bottom lid material is held by the holding means so as to match the positions in the circumferential direction and engage shallowly.

Further, the holding means includes a holding member that is urged to project from the inner peripheral surface of the main body cylinder portion in the inward direction of the main body cylinder portion, and is provided on the tip side of the holding member in the protruding direction. A grip portion that can be engaged and disengaged is formed on the peripheral edge of the core bottom lid material, and a sliding contact slope that is inclined downward toward the tip end side in the protruding direction is formed on the upper surface of the holding member and is housed in the main body cylinder portion. When the core body construction inner cylinder is projected downward, the lower end of the core body construction inner cylinder abuts on the sliding contact slope and the holding member is retracted in the outer diameter direction of the main body cylinder portion. Therefore, it is more preferable that the core bottom lid material is separated from the grip portion.

Further, the lower surface of the holding member may be formed with a welcoming slope that inclines upward toward the tip end side in the protruding direction.

Further, the holding member is housed in a box body assembled by opening the peripheral wall of the main body cylinder portion surrounding the hollow portion, and the outer wall portion of the box body is flush with the outer peripheral surface of the main body cylinder portion. It is also preferable that the urging member is interposed in the watertight chamber formed between the outer wall portion of the box body and the holding member.

In the excavation agitation device according to the invention disclosed in the present application, when the inner cylinder for building a core body housed in the main body cylinder portion is projected below the main body cylinder portion, the core bottom lid material held in the vicinity of the bottom portion of the main body cylinder portion is held. Is configured to separate from the main body cylinder, so if the coupling material is injected while the inner cylinder for core body construction is projected when the excavation hole is dug to a predetermined depth, the core bottom lid material can be excavated. It can be accurately left near the bottom of the. Therefore, if this excavation agitator is used, a step of injecting a binder while digging a drill hole to agitate and mix the excavated soil and the binder (the ground improvement method described in Patent Document 2 described in the background technology column (FIG. FIG. Following the step (S2) in 8), the core bottom lid material is left near the bottom of the excavation hole, and the excavation stirring device is raised while injecting the binder material above the core bottom lid material, and the excavation stirring device is composed of only the binder material. The step of forming the core portion (same as the step of [S5]) can be continuously carried out. Since the process of pulling up the excavation agitator from the excavation hole, replacing the members, and attaching the core bottom lid material to the lower end can be omitted, the ground for constructing a columnar improved body having a core body consisting only of the binder in the central part. The construction efficiency of the improved construction method will be significantly improved.

It is a front view of the excavation agitation device which concerns on one Embodiment of the invention disclosed in this application. It is a vertical cross-sectional view of the front side which shows the internal structure of the excavation agitator. The state in which they are projected to each other is shown. It is a vertical cross-sectional view of the side surface which shows the internal structure of the excavation agitator. The state in which they are projected to each other is shown. It is a three-view view which shows the form of the core bottom lid material used for the excavation agitator, (a) is a top view, (b) is a front view, and (c) is a side view. FIG. 5 is an enlarged five-view view showing a specific configuration of a core bottom lid material holding means in the excavation agitator, in which (a) is a front view, (b) is a top view, and (c) is a bottom view. d) is an inner side view, and (e) is an outer side view. It is a process explanatory drawing of the ground improvement method using the excavation agitation device which concerns on the invention disclosed in this application. It is a front view of the excavation agitator used in the ground improvement construction method disclosed in Patent Document 2. It is a process explanatory drawing of the ground improvement method disclosed in Patent Document 2.

Hereinafter, embodiments of the invention disclosed in the present application will be described with reference to the drawings. In the following description, when specifying the positional relationship of parts / members and the direction of movement, the vertical direction and the horizontal direction are specified with reference to the usage mode in which the ground is excavated. Further, the components having the same function or action as the conventional excavation agitation device shown in FIGS. 7 to 8 and the ground improvement method using the device are designated by a common reference numeral to simplify their description.

FIG. 1 shows the appearance of an excavation agitator according to an embodiment of the invention disclosed in the present application. The excavation agitation device 10 is configured by attaching an excavation blade 24, a co-rotation prevention blade 25, a stirring blade 26, and the like around a main body cylinder portion 22 having a substantially cylindrical shape. The upper end of the main body cylinder 22 is connected to a rod 21 (see FIG. 7) and is rotationally driven by an auger device or the like. A cylindrical hollow portion 220 that serves as a flow path for the binder is provided at the axial center portion of the main body tubular portion 22. The lower end of the hollow portion 220 is opened downward at the bottom of the main body cylinder portion 22.

The excavation blade 24 is provided so as to project from the vicinity of the lower end of the main body cylinder portion 22 in the outer diameter direction of the main body cylinder portion 22, and rotates integrally with the main body cylinder portion 22. A plurality of excavation blades 241 for excavating the ground are projected on the lower surface of the excavation blade 24. The stirring blade 26 is provided so as to project from the vicinity of the middle of the main body cylinder 22 and the vicinity of the upper end in the outer diameter direction of the main body 22 and rotates integrally with the main body 22. The rotating diameter of the stirring blade 26 is substantially the same as the rotating diameter of the excavating blade 24.

The co-rotation prevention blade 25 is arranged between the excavation blade 24 and the lower stirring blade 26, and between the lower stirring blade 26 and the upper stirring blade 26, respectively, in the out-of-diameter direction of the main body cylinder portion 22. Overhanging. The co-rotation prevention blade 25 is formed so that its rotation diameter is slightly larger than the rotation diameter of the excavation blade 24 and the stirring blade 26, and is attached so as to be able to rotate (idle) relative to the main body cylinder portion 22. In the illustrated embodiment, the co-rotation prevention blade 25 and the stirring blade 26 are provided in two stages each, but in the present invention, the arrangement and the number of stages thereof are not particularly limited. Further, the detailed shapes of the excavation blade 24 and the excavation blade 241 are not particularly limited.

2 and 3 show the internal structure of the main body cylinder portion 22 in the excavation agitator 10. Inside the hollow portion 220 formed in the main body cylinder portion 22, a hollow cylindrical core body construction inner cylinder 23 having an outer diameter slightly smaller than the inner diameter of the hollow portion 220 is inserted from below. The inner cylinder 23 for building the core body is held so as to be able to move forward and backward in the axial direction of the main body cylinder portion 22 by using an appropriate driving means. The driving means for advancing and retreating the inner cylinder 23 for building the core body is not particularly limited in this specification, but for example, a cylinder piston mechanism using hydraulic pressure, gas pressure, water pressure, etc., a gear, a cam, a belt, a chain for an electric motor, etc. It is possible to adopt an appropriate driving means including a known technique such as a power transmission mechanism and a sliding mechanism in which the above are combined.

As shown in FIGS. 2 (a) and 3 (a), at the position where the core body building inner cylinder 23 is most raised, the lower end of the core body building inner cylinder 23 extends above the bottom of the main body cylinder portion 22. Immerse yourself. As shown in FIGS. 2 (b) and 3 (b), at the position where the core body building inner cylinder 23 is most lowered, most of the core body building inner cylinder 23 protrudes below the main body cylinder portion 22. .. The advance / retreat stroke is set to be about the same as the rotation diameter of the excavation blade 24.

The upper end of the core body construction inner cylinder 23 is opened upward and communicates with the flow path in the hollow portion 220. The lower end of the inner cylinder 23 for building the core body opens downward, and the core bottom lid material 30 having a shape for closing the opening is held in the vicinity of the bottom portion of the main body cylinder portion 22.

FIG. 4 shows the form of the core bottom lid material 30. The core bottom lid material 30 is a member made of, for example, a metal or a hard synthetic resin material, and includes a bottom portion 31 having an inverted conical shape and a collar-shaped portion 32 provided on the periphery thereof. A binder injection port 33 is formed in the bottom portion 31 and opens diagonally. In the flange-shaped portion 32, the held portion 34 held by the holding member 28, which will be described later, is formed at two opposite positions sandwiching the axial center of the pyramid so as to slightly cut off the outer peripheral edge. Further, substantially rectangular parallelepiped engaging convex portions 35 are projected upward at two opposing positions orthogonal to the held portion 34 when viewed from the axial direction of the pyramid. On the other hand, at the lower end of the core body construction inner cylinder 23, an engaging recess 231 capable of engaging with the engaging convex portion 35 is formed.

The core bottom lid material 30 is held in the vicinity of the bottom portion of the main body cylinder portion 22 via a holding means provided in the main body cylinder portion 22 in a state where the core body construction inner cylinder 23 is housed in the main body cylinder portion 22. To. FIG. 5 shows a specific configuration of the holding means. This holding means includes a holding member 28 that appears and disappears in the radial direction from the inner peripheral surface of the main body cylinder portion 22. The holding member 28 is a block-shaped member made of, for example, a metal or a hard synthetic resin material, and is housed in a box body 29 having a simple watertight structure. The box body 29 is assembled by opening two opposing peripheral walls that sandwich the axial center in the vicinity of the bottom portion of the main body cylinder portion 22, and the outer wall portion 291 protruding from the outer surface of the box body 29 is attached to the main body cylinder portion 22. It is fixed to the main body cylinder 22 by screwing it to the outer peripheral surface of the body. The outer peripheral surface of the main body cylinder 22 is subjected to counterbore processing to a depth corresponding to the thickness of the outer wall 291 of the box body 29, so that the outer surface of the outer wall 291 and the outer peripheral surface of the main body 22 are formed. They are flush with each other. An urging member 292 made of a compression coil spring or the like is interposed inside the box body 29 to urge the holding member 28 so as to protrude inward in the diameter of the main body cylinder portion 22.

On the tip side of the holding member 28 in the protruding direction, a side view U-shaped grip portion 281 that can be engaged with and disengaged from the held portion 34 of the core bottom lid member 30 is formed. A sliding contact slope 282 is formed on the upper surface of the holding member 28 so as to be inclined downward toward the tip end side in the protruding direction. Further, on the lower surface of the holding member 28, a welcoming slope 283 that inclines upward toward the tip end side in the protruding direction is formed.

The core bottom lid member 30 is attached to the holding member 28 from below. When the held portion 34 formed on the flange-shaped portion 32 of the core bottom lid member 30 is pressed against the receiving slope 283 of the holding member 28 in accordance with the position of the holding member 28, the holding member 28 opposes the urging member 292. When the held portion 34 of the core bottom lid member 30 is accommodated in the grip portion 281, the holding member 28 projects again in the inward diameter direction. In this way, the movement of the core bottom lid member 30 in the axial direction is restricted. At the same time, at the same time, the engaging convex portion 35 projecting from the flange-shaped portion 32 of the core bottom lid material 30 and the engaging concave portion 231 formed at the lower end of the core body construction inner cylinder 23 are shallow in the axial direction. By engaging, the rotation of the core bottom lid member 30 around the axis is also restrained.

When the core body construction inner cylinder 23 is projected downward from the state where the core bottom lid material 30 is held by the main body cylinder portion 22 in this way, the lower end of the core body construction inner cylinder 23 is the holding member 28. It abuts on the sliding contact slope 282 and retracts the holding member 28 in the out-diameter direction against the urging member 292. In order to facilitate this operation, the outer edge of the lower end of the core body construction inner cylinder 23 is chamfered or rounded. The core bottom lid material 30 that has lost the holding force of the holding member 28 is pushed downward by the core body construction inner cylinder 23, and is attached so as to be taken up by the lower end of the core body construction inner cylinder 23. At this time, the engagement state between the engaging convex portion 35 of the core bottom lid material 30 and the engaging concave portion 231 of the core body construction inner cylinder 23 is also deepened.

FIG. 6 shows the process of the ground improvement method carried out by using the excavation agitation device 10. This step is carried out as follows.

[S10] With the inner cylinder 23 for building the core body housed in the main body cylinder portion 22 in advance, the core bottom lid material 30 is attached to the holding portion of the main body cylinder portion 22. The rod 21 to which the excavation agitator 10 is attached is installed at a predetermined position and gradually lowered while rotating forward to start excavation of the ground.

[S20] While rotating the excavation agitator 10 in the forward direction to dig down the excavation hole 40, the binder is supplied into the main body cylinder portion 22 and from the binder injection port 33 formed in the core bottom lid material 30 into the excavation hole 40. The binder is injected and the excavated soil and the binder are stirred and mixed to form an uncured mixture 5 in the excavation hole 40. When the excavation hole 40 reaches a predetermined depth, the excavation stirring device 10 is rotated in the forward direction and slightly moved up and down a plurality of times to perform bottom treatment, and then the rotation and the up and down movement are stopped. Since the core bottom lid material 30 is firmly held by the holding member 28 up to this stage, it does not fall off from the main body cylinder portion 22 even if the excavation stirring device 10 is moved up and down. In the first half steps up to this point, [S1] to [S1] in the ground improvement method (FIG. 8) described in Patent Document 2 described in the background technology column, except that the core bottom lid material 30 is attached to the excavation agitator 10. It is substantially the same as the step of [S2].

[S30] By operating the drive device near the bottom of the excavation hole 40, the inner cylinder 23 for building the core body is projected downward, and the core bottom lid material 30 is separated from the main body cylinder portion 22. When the core body construction inner cylinder 23 reaches a predetermined depth, the excavation agitator 10 is rotated in the reverse direction and gradually raised to restart the injection of the binder. Then, the core bottom lid material 30 that is engaged with the inner cylinder 23 for building the core body at the lower end is separated from the inner cylinder 23 for building the core body due to the injection pressure of the coupling material, and is left in the vicinity of the bottommost portion of the excavation hole 40. Will be done. When the injection of the binder is continued while pulling up the excavation agitator 10, an uncured core portion 6 composed of only the binder is gradually formed above the core bottom lid material 30. When the core portion 6 is formed, the inner cylinder 23 for building the core body extends downward, which causes a difference in height between the rotational position of the stirring blade 26 and the binder injection port 33. The injected binder is less affected by stirring, the core portion 6 becomes dense, and the shape is suitably maintained.

[S40] After the excavation agitator 10 is pulled up, the uncured mixture 5 and the uncured core 6 are solidified after a predetermined curing period. Thus, a double-structured columnar improved body including a solidified mixture 50 formed in a columnar shape up to the bottom 41 of the excavation hole 40 and a core body 60 formed only of a binder formed in the central portion thereof is constructed. Will be done. This latter half step is substantially the same as the steps [S5] to [S6] in the ground improvement method (FIG. 8) described in Patent Document 2 described in the background technology column.

As described above, the excavation agitation device 10 according to the invention disclosed in the present application is attached to the vicinity of the bottom portion of the main body cylinder portion 22 by projecting the core body construction inner cylinder 23 housed in the main body cylinder portion 22 downward. The core bottom lid material 30 can be detached at an arbitrary position. Therefore, if excavation is started with the core bottom lid material 30 attached to the excavation stirring device 10 in advance, the coupling material is injected while digging the excavation hole to a predetermined depth, and the excavated soil and the coupling material are agitated and mixed in the first half. Following the process, the core body construction inner cylinder 23 is projected near the bottom of the excavation hole to separate the core bottom lid material 30, and the excavation agitator 10 is raised while injecting the binder material above the binder material. The latter half step of forming the core portion 6 made of only chisel can be continuously carried out without interruption. Since it is possible to save the trouble of pulling up the excavation agitator 10 from the excavation hole and replacing the members (steps [S3] to [S4] in the ground improvement method (FIG. 8) described in Patent Document 2), only the binder is provided in the central portion. The construction efficiency of the ground improvement method for constructing a columnar improved body having a core body made of the above is significantly improved. In particular, when a plurality of columnar improved bodies are continuously constructed together, the effect of reducing man-hours becomes remarkable.

The technical scope of the present invention should not be construed in a limited manner by the illustrated embodiments, but should be conceptually interpreted based on the description of the claims. In carrying out the present invention, the detailed shape, structure, arrangement, etc. of the core bottom lid material and the members constituting the holding means thereof are appropriately modified within a range in which substantially the same effects as those of the illustrated embodiment can be obtained. It doesn't matter. In addition, the detailed shape of the construction machine and excavation agitator, the type and composition of the binder, the operation procedure for raising and lowering the excavation agitator, the timing of injecting the binder, etc. can be appropriately modified according to the construction environment, etc. is there.

10 Excavation agitator 21 Rod 22 Main body Cylinder 220 Hollow part 23 Core body construction inner cylinder 231 Engagement recess 24 Excavation blade 241 Excavation blade 25 Co-rotation prevention blade 26 Stirring blade 28 Holding member 281 Grip part 282 Sliding slope 283 Slope 29 Box body 291 Outer side wall part 292 Biasing member 30 Core bottom lid material 31 Bottom part 32 Flute-shaped part 33 Coupling material injection port 34 Held part 35 Engagement convex part 4 Ground 40 Excavation hole 41 Bottom part 5 Unsolidified mixture 50 Solidified mixture 6 Unsolidified core 60 Core

Claims (7)

A cylindrical hollow portion that serves as a flow path for the binder is provided inside the main body cylinder that holds the excavation blade, stirring blade, and co-rotation prevention blade.
The hollow portion opens downward at the bottom of the main body cylinder portion, and the hollow portion opens downward.
An inner cylinder for building a core body having a hollow cylindrical shape is inserted inside the hollow portion and held so as to appear and disappear below the main body cylinder portion.
The lower end of the inner cylinder for building the core body is opened downward, and a core bottom lid material having a shape for closing the opening is provided in the vicinity of the bottom portion of the main body cylinder portion via a holding means provided in the main body cylinder portion. Held in
When the core body building inner cylinder housed in the main body cylinder portion is projected downward, the lower end of the core body building inner cylinder acts on the holding means, and the core bottom lid material is separated from the holding means. An excavation agitation device characterized in that it is attached to the lower end of the inner cylinder for building a core body. In the excavation agitator according to claim 1,
The core bottom lid material includes a bottom portion having an inverted conical shape and a collar-shaped portion provided on the peripheral edge of the bottom portion, and the bottom portion is provided with a binder injection port.
An excavation agitation device characterized in that a part of the brim-shaped portion is held by the holding means. In the excavation agitator according to claim 1 or 2.
Engagement means is provided on the upper surface of the core bottom lid material and the lower end of the inner cylinder for building the core body by engaging with each other in an uneven manner to transmit a rotational force around the axis.
An excavation agitation device characterized in that the core bottom lid material separated from the holding means of the main body cylinder portion is attached to the lower end of the core body construction inner cylinder via the engaging means. In the excavation agitator according to claim 3,
In the engaging means, the engaging convex portion protruding upward from the peripheral edge of the core bottom lid material and the engaging concave portion formed at the lower end of the core body building inner cylinder form the core body building inner cylinder. It is configured to be able to engage in the axial direction of
In a state where the inner cylinder for building the core body is housed in the main body cylinder portion, the core bottom lid is shallowly engaged so that the engaging convex portion and the engaging concave portion are aligned in the circumferential direction and engaged shallowly. An excavation agitator, characterized in that the material is held by the holding means. In the excavation stirring device according to any one of claims 1 to 4.
The holding means includes a holding member that is urged to project from the inner peripheral surface of the main body cylinder portion in the inward direction of the main body cylinder portion and appears and disappears.
A grip portion that can be engaged and disengaged is formed on the peripheral edge of the core bottom lid material on the tip side in the protruding direction of the holding member.
A sliding contact slope is formed on the upper surface of the holding member so as to be inclined downward toward the tip side in the protruding direction.
When the core body construction inner cylinder housed in the main body cylinder portion is projected downward, the lower end of the core body construction inner cylinder abuts on the sliding contact slope to hold the holding member with the diameter of the main body cylinder portion. An excavation agitation device characterized in that the core bottom lid material is separated from the grip portion by retracting outward. In the excavation agitator according to claim 5,
An excavation agitation device characterized in that a welcoming slope that inclines upward toward the tip end side in the protruding direction is formed on the lower surface of the holding member. In the excavation agitator according to claim 5 or 6,
The holding member is housed in a box assembled by opening the peripheral wall of the main body cylinder portion surrounding the hollow portion.
The outer wall portion of the box body is aligned with the outer peripheral surface of the main body cylinder portion,
An excavation agitation device characterized in that an urging member is interposed in a watertight chamber formed between the outer wall portion of the box body and the holding member.

Images