JP7255442B2 - drilling stirrer - Google Patents

Description

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

When constructing a building on soft ground, a binder (solidifying material) such as cement milk is injected into the excavated soil while a vertical hole is being excavated, and the excavated soil and binder are stirred and mixed to solidify into a columnar shape. A ground improvement method is known in which a columnar improvement body called a "pile" is constructed in the ground to increase the bearing capacity of the ground. With regard to such a ground improvement method, for example, because the soil of the ground is organic soil, the solidification strength of the mixed soil does not reach the required level, or the site is narrow and only a small base machine can be introduced. In some cases, sufficient bearing capacity of the cylindrical improved body cannot be obtained due to the fact that the soil cannot be uniformly solidified due to the low stirring capacity of the base machine. In order to solve this problem, in Patent Document 1, a cylindrical improvement body made of a solidified mixture of excavated soil and a binding material is additionally formed with a core body made of only a binding material at the center part of the cylindrical improvement body. A construction method for increasing the supporting strength of the body is disclosed. Furthermore, the present applicant also proposed a construction method improved from the construction method described in Patent Literature 1 in Patent Literature 2, and is trying to put it into practical use.

The outline of the ground improvement method disclosed in Patent Document 2 and the excavation stirrer used in the method is shown in FIGS. 7 and 8. FIG. In this ground improvement method, an excavation stirrer 1, also called a "head" or "bit", is attached to the tip of a rod 21 that is rotationally driven by an auger device (not shown) mounted on a base machine. While excavating a vertical hole, the excavated soil and binder are stirred and mixed. As shown in FIG. 7, the excavation stirrer 1 includes a body tube portion (“body shaft portion” in Patent Document 2) 22 which is connected to a rod 21 and rotates integrally with the rod 21, and a lower end of the body tube portion 22. An excavation blade 24 provided so as to protrude radially outward of the main body tubular portion 22 from the vicinity, a stirring blade 26 provided above the digging blade 24 in the main body tubular portion 22, the digging blade 24 and the agitating blade 26. and a co-rotation prevention wing 25 provided to be relatively rotatable with respect to the main body cylindrical portion 22 between the It is configured. A binder injection port (nozzle) 221 is provided laterally in the vicinity of the lower end of the main body cylindrical portion 22 , and the binder supplied through a 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 excavating blades 24 and the stirring blades 26 .

8A and 8B are diagrams showing the order of steps when the ground improvement method is carried out using this excavation stirring device 1. As shown in FIG. An exemplary process is performed as follows.

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

[S2] As the excavated hole 40 is dug down, the excavated soil remains inside. The binder is discharged into the excavated hole 40 from a binder injection port 221 provided at the lower end of the excavation stirrer 1 and stirred and mixed with the excavated soil by the rotation of the excavation blades 24 and the stirring blades 26 . At this time, the anti-co-rotation wing 25, which is slightly longer than the excavation wing 24, bites into the hole wall of the excavation hole 40 at its tip, so that the rod is moved deep into the excavation hole 40 without rotating itself. 21, and resists co-rotation of the excavated soil and binder and the excavating blades 24 and stirring blades 26 to assist in their mixing. In this way, the unsolidified mixture 5 is generated substantially uniformly within the drilled hole 40 . When the excavation hole 40 reaches a predetermined depth, the excavation stirrer 1 is rotated and slightly moved up and down a plurality of times to treat the bottom, and then the rotation and vertical movement are stopped.

[S3] Next, while rotating the rod 21 in the reverse direction, the excavation stirrer 1 is gradually raised. Injection and agitation of the binder can also take place during this rise. Then, the excavation stirrer 1 is once completely pulled up from the excavation hole 40 , the excavation blade 24 is removed from the body cylindrical portion 22 , and replaced with the extension nozzle 27 . As shown in FIG. 7 , the extension nozzle 27 is a substantially cylindrical member having a binder flow path 270 therein, and its upper end is connected to the lower end of the main body tubular portion 22 . To enable this replacement, the excavating wing 24 is configured to be separable from the main tubular portion 22 . The lower end of the extension nozzle 27 is open downward, and this opening becomes a new binder injection port 271, thereby substantially moving the binder injection position downward.

Then, the core bottom cover member 3 is attached to the lower end of the extension nozzle 27 so as to block the binder injection port 271 . The core-bottom lid member 3 is a substantially circular member in a plan view and made of metal, hard synthetic resin, concrete, or the like. The core bottom lid member 3 is formed by, for example, engaging an engaging concave portion 39 formed by notching the peripheral edge thereof with an engaging convex portion 272 protruding from the lower end of the extension nozzle 27, so that the extension nozzle 27 is closed. Temporarily fixed at the bottom end.

[S4] The excavation stirrer 1 attached with the extension nozzle is put into the excavation hole 40 again, and the rod 21 is lowered while rotating forward. The core bottom cover member 3 attached to the lower end of the extension nozzle 27 is pushed into the unsolidified mixture 5 while rotating integrally with the extension nozzle 27 . When the lower end of the extension nozzle 27 reaches near the bottom 41 of the excavation hole 40, the excavation stirrer 1 stops descending.

[S5] The delivery of the binder is resumed at the stop position, and the binder is injected into the center of the unsolidified mixture 5 from the binder injection port 271 at the lower end of the extension nozzle 27 . While injecting the binder, the rod 21 is reversely rotated to gradually raise the excavation stirrer 1 . Due to the additionally injected binder, an unsolidified core 6 consisting of only the binder is gradually formed in the center of the unsolidified mixture 5 from bottom to top. The core bottom cover material 3 attached to the lower end of the extension nozzle 27 is detached from the extension nozzle 27 when the discharge of the binder is started, and left near the bottom 41 of the excavation hole 40 to be injected into the core 6. It receives the binder that is applied and prevents the binder from spreading and flowing out into the unsolidified mixture 5 and the soil. By attaching the extension nozzle 27, there is a difference in height between the rotational position of the stirring blade 26 and the binder injection port 271. Also, the binder discharged from the extension nozzle 27 is less likely to be affected by stirring, and the shape of the core portion 6 is preferably maintained.

[S6] After pulling up the excavation stirrer 1, the unsolidified mixture 5 and the unsolidified core 6 are solidified through a predetermined curing period. Thus, a double-structured columnar improved body is constructed, which includes the solidified mixture 50 formed in a columnar shape up to the bottom 41 of the excavation hole 40, and the core body 60 formed at the center thereof and made only of the binder. be done.

JP 2016-20621 A Japanese Patent No. 6216477

In the ground improvement method disclosed in Patent Document 2, the first half step ([S1] to [S3]) of generating an unsolidified mixture 5 in which the excavated soil and binder are stirred and mixed in the excavated hole 40 and , and the second half step ([S4] to [S5]) of additionally forming a core body 60 made of only a binder in the central portion of the mixture 5, the excavation stirrer 1 is once pulled up from the excavation hole 40. , removing the excavating blade 24, replacing it with the extension nozzle 27, and mounting the core bottom cover member 3 on the lower end thereof. Pulling up the excavation stirring device 1 from the lowest part 41 of the excavation hole 40 to the ground, replacing the members, and then lowering it to the lowest part 41 again causes a large loss in the process, and the weight of the replaced members is several tens of kg or more. Therefore, the work is also dangerous.

The invention disclosed in the present application is capable of integrally constructing a column made of a mixture of excavated soil and a binder and a core made of only the binder without pulling it up from an excavated hole or replacing members. Specifically, the core and bottom cover material is attached to the cylindrical body for constructing the core body, and the core and bottom lid material is attached in advance to the bottom of the borehole. The object to be solved is to accurately remove the core bottom cover material from the cylindrical body near the bottom and leave it in the excavation hole.

In order to achieve the above object, the excavation agitator of the invention disclosed by the present application has a cylindrical hollow portion serving as a flow path for a binding material inside a main body tubular portion that holds an excavation blade, an agitation blade, and a co-rotation prevention blade. is provided, the hollow portion opens downward at the bottom portion of the main body tubular portion, and a hollow cylindrical inner cylinder for core body construction is inserted into the inner side of the hollow portion to extend below the main tubular portion A core bottom cover member is held so as to be able to appear and disappear, and the lower end of the core body construction inner cylinder is opened downward, and the core bottom cover member having a shape to close the opening is provided via the holding means provided in the main body cylindrical portion. is held in the vicinity of the bottom portion of the main body tubular portion, and when the core-body-building inner cylinder housed in the main-body tubular portion is protruded downward, the lower end of the core-body-building inner cylinder acts on the holding means, The core bottom cover member is separated from the holding means and attached to the lower end of the inner cylinder for core body construction.

That is, in this excavation agitating device, when the core body construction inner cylinder housed in the body cylinder part is projected downward from the body cylinder part, the core bottom cover material held in the vicinity of the bottom part of the body cylinder part moves to the body cylinder part. Since it is configured to be detached from the bore hole, if the binder is injected while the inner cylinder for core body construction is protruding when the bore hole is dug, the core bottom cover material can be left at an arbitrary position in the bore hole. can be done.

In this excavation agitator, the core-bottom cover member has an inverted cone-shaped bottom and a brim-shaped portion provided on the periphery of the bottom, and the bottom is provided with a binder injection port, Practically, a portion of said collar is held by said holding means.

Engagement means are provided on the upper surface of the core bottom lid member and the lower end of the core body construction inner cylinder to engage with each other in an uneven manner to transmit rotational force around the axis. It is more preferable that the core bottom cover member separated from the core is attached to the lower end of the core body-constructing inner cylinder via the engaging means.

As a specific aspect of the engaging means, an engaging convex portion protruding upward from the peripheral edge of the core bottom cover member and an engaging concave portion formed at the lower end of the core body-constructing inner cylinder are composed of the core. The engaging convex portion and the engaging concave portion are configured to be able to engage with each other in the axial direction of the inner cylinder for body construction, and in a state in which the inner cylinder for core body construction is accommodated in the main body tubular portion. The core-bottom lid material may be held by the holding means so as to be circumferentially aligned and shallowly engaged.

Further, the holding means includes a holding member which is biased in a direction of protruding radially inward of the main body tubular portion from the inner peripheral surface of the main tubular portion and appears and disappears, and the tip end side of the protruding direction of the holding member is provided. is formed with a grasping portion that can be engaged with and disengaged from the peripheral edge of the core bottom lid material, and a sliding contact slope that slopes downward toward the tip end in the projecting direction is formed on the upper surface of the holding member, and is accommodated in the main body cylindrical portion. When the core-body-building inner cylinder is protruded downward, the lower end of the core-body-building inner cylinder comes into contact with the slidable contact slope, causing the holding member to retreat in the radially outer direction of the main body cylindrical portion. It is more preferable that the core bottom cover member is detached from the gripping portion.

Furthermore, the lower surface of the holding member may be formed with a facing slope that slopes upward toward the leading end in the projecting direction.

Further, the holding member is accommodated in a box assembled by opening a peripheral wall of the main body cylindrical portion surrounding the hollow portion, and the outer wall portion of the box is flush with the outer peripheral surface of the main body cylindrical portion. It is also preferred that a biasing member is interposed within a watertight chamber aligned and formed between the outer wall of the box and the retaining member.

In the excavation agitator according to the invention disclosed in the present application, when the inner cylinder for core body construction housed in the main tubular part is protruded downward from the main tubular part, the core bottom cover material held near the bottom of the main tubular part is opened. is detached from the main body tube portion, when the bore hole is dug to a predetermined depth, by injecting the binder while protruding the inner tube for core body construction, the core bottom lid material can be removed from the bore hole. can be accurately left in the vicinity of the bottom of the Therefore, if this excavation stirrer is used, the process of injecting a binder while digging an excavation hole and stirring and mixing the excavated soil and the binder (the ground improvement method described in Patent Document 2 described in the Background Art section (Fig. Following the step [S2] in 8)), the core bottom cover material is left near the bottom of the drilled hole, and the excavator is raised while the binder is injected above it, so that the excavator is made of only the binder. The step of forming the core portion (same, step [S5]) can be carried out continuously. Since the process of pulling up the excavator from the excavation hole, replacing the member, and attaching the core bottom cover material to the lower end thereof can be omitted, the ground for constructing a cylindrical improved body having a core made of only a binder in the center part. The construction efficiency of the improved construction method is greatly improved.

1 is a front view of an excavation stirrer according to an embodiment of the invention disclosed by the present application; FIG. Fig. 2 is a longitudinal cross-sectional view of the front side showing the internal structure of the excavation agitating device, in which (a) shows a state in which the inner cylinder for core body construction is housed in the main body cylinder, and (b) shows the inner cylinder for core body construction placed downward. , respectively. Fig. 3 is a longitudinal cross-sectional view of the side surface showing the internal structure of the excavation agitating device, in which (a) shows a state in which the inner cylinder for core body construction is housed in the main body cylinder part, and (b) shows that the inner cylinder for core body construction is placed downward. , respectively. It is a trihedral view which shows the form of the core-bottom cover material used for the said excavation stirring apparatus, Comprising: (a) is a top view, (b) is a front view, (c) is a side view. FIG. 5 is a five-sided view showing an enlarged specific configuration of a core-bottom cover material holding means in the excavation agitator, wherein (a) is a front view, (b) is a top view, (c) is a bottom view, ( d) is an inner side view, and (e) is an outer side view. It is process explanatory drawing of the ground improvement method using the excavation stirrer based on invention which this application discloses. It is a front view of the excavation stirrer used for the ground improvement method disclosed by patent document 2. FIG. It is process explanatory drawing of the ground improvement method disclosed by patent document 2. FIG.

Hereinafter, embodiments of the invention disclosed by 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 operation, the vertical direction and horizontal direction are specified based on the mode of use in which the ground is being excavated. In addition, constituent elements having functions or actions common to the conventional excavation agitating device and ground improvement method using the device shown in FIGS.

FIG. 1 shows the appearance of an excavation stirrer according to an embodiment of the invention disclosed by the present application. The excavation stirring 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 tube portion 22 having a substantially cylindrical shape. The upper end of the body cylindrical portion 22 is connected to a rod 21 (see FIG. 7) and driven to rotate by an auger device or the like. A cylindrical hollow portion 220 that serves as a flow path for the binder is provided in the axial center portion of the main tubular portion 22 . The lower end of the hollow portion 220 opens downward at the bottom portion of the main tubular portion 22 .

The excavation wing 24 is provided so as to protrude from the vicinity of the lower end of the main tubular portion 22 in the radially outer direction of the main tubular portion 22 and rotate integrally with the main tubular portion 22 . A plurality of digging blades 241 for digging the ground are projected from the lower surface of the digging wing 24 . The stirring blades 26 are provided so as to protrude radially outward of the main tubular portion 22 from near the middle and near the upper end of the main tubular portion 22 and rotate integrally with the main tubular portion 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 blades 25 are arranged between the excavation blades 24 and the lower stage stirring blades 26 and between the lower stage stirring blades 26 and the upper stage stirring blades 26, respectively. overhanging. The co-rotation prevention blade 25 is formed so that its rotation diameter is slightly larger than the rotation diameters of the excavation blade 24 and the stirring blade 26, and is attached to the main body cylindrical portion 22 so as to be capable of relative rotation (idling). In the exemplified embodiment, the co-rotation prevention blades 25 and the stirring blades 26 are provided in two stages, but in the present invention, their arrangement and the number of stages are not particularly limited. Also, 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 body tube portion 22 in the excavation stirring device 10. FIG. Inside the hollow portion 220 formed in the main tubular 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 core body construction is held so as to be able to advance and retreat in the axial direction of the main body cylinder portion 22 using an appropriate driving means. The driving means for advancing and retracting the core body construction inner cylinder 23 is not particularly limited in the present specification, but may be, for example, a cylinder piston mechanism using hydraulic pressure, gas pressure, water pressure, or the like, an electric motor, a gear, a cam, a belt, a chain, or the like. Appropriate driving means including known techniques such as a power transmission mechanism or a sliding mechanism combining the above can be employed.

As shown in FIGS. 2(a) and 3(a), when the core-body-constructing inner cylinder 23 is at the highest position, the lower end of the core-body-constructing inner cylinder 23 reaches above the bottom of the main body cylindrical portion 22. As shown in FIGS. Immerse yourself. As shown in FIGS. 2(b) and 3(b), most of the core-body-constructing inner cylinder 23 protrudes downward from the main tubular portion 22 at the lowest position of the core-body-constructing inner cylinder 23. . The forward/backward stroke is set to be approximately the same as the rotational diameter of the excavation blade 24 .

The upper end of the core-constructing inner cylinder 23 opens upward and communicates with the flow path in the hollow portion 220 . The lower end of the core-constructing inner cylinder 23 is opened downward, and a core-bottom lid member 30 having a shape that closes the opening is held near the bottom of the main body cylindrical portion 22 .

FIG. 4 shows the form of the core bottom cover member 30. As shown in FIG. The core bottom lid member 30 is a member made of, for example, metal or a hard synthetic resin material, and includes a bottom portion 31 having an inverted conical shape and a brim portion 32 provided on the periphery thereof. A binder injection port 33 is formed in the bottom portion 31 and is opened obliquely. A held portion 34 held by a holding member 28 (to be described later) is formed at two opposing locations of the brim portion 32 sandwiching the axis of the cone so that the outer peripheral edge thereof is slightly cut off. Approximately rectangular parallelepiped engaging protrusions 35 protrude upward at two opposite locations orthogonal to the held portion 34 when viewed from the axial direction of the cone. On the other hand, an engaging concave portion 231 that can be engaged with the engaging convex portion 35 is formed at the lower end of the core-constructing inner cylinder 23 .

The core bottom cover member 30 is held in the vicinity of the bottom portion of the main body tubular portion 22 via holding means provided on the main tubular portion 22 in a state in which the core body construction inner cylinder 23 is accommodated in the main tubular portion 22 . be. FIG. 5 shows a specific configuration of the holding means. This holding means comprises a holding member 28 projecting radially inwardly from the inner peripheral surface of the main tubular portion 22 . The holding member 28 is a block-shaped member made of metal, hard synthetic resin, or the like, and is housed in a box 29 having a simple watertight structure. This box 29 is assembled by opening the peripheral walls at two locations opposite to each other across the axis in the vicinity of the bottom of the tubular body 22 . It is fixed to the main body tubular portion 22 by screwing to the outer peripheral surface of the . The outer peripheral surface of the main body tubular portion 22 is counterbored to a depth corresponding to the thickness of the outer wall portion 291 of the box body 29, so that the outer surface of the outer wall portion 291 and the outer peripheral surface of the main tubular portion 22 are aligned. They are aligned flush. An urging member 292 made of a compression coil spring or the like is interposed inside the box 29 to urge the holding member 28 to protrude radially inward of the main tubular portion 22 .

A gripping portion 281 having a U-shape in a side view that can be engaged with and disengaged from the held portion 34 of the core bottom cover member 30 is formed on the tip side of the holding member 28 in the projecting direction. The upper surface of the holding member 28 is formed with a slidable contact slope 282 that slopes downward toward the distal end in the projecting direction. Further, the lower surface of the holding member 28 is formed with a facing slope 283 that slopes upward toward the distal end in the projecting direction.

The core bottom cover member 30 is attached to the holding member 28 from below. When the held portion 34 formed on the brim portion 32 of the core bottom cover member 30 is aligned with the position of the holding member 28 and pressed against the facing slope 283 of the holding member 28 , the holding member 28 resists the biasing member 292 . When the held portion 34 of the core bottom cover member 30 is accommodated in the grip portion 281, the holding member 28 protrudes radially inward again. In this way, the movement of the core bottom cover member 30 in the axial direction is restrained. At this time, at the same time, the engaging projection 35 projecting from the brim 32 of the core bottom cover member 30 and the engaging recess 231 formed at the lower end of the core-constructing inner cylinder 23 are shallow in the axial direction. When engaged, the rotation of the core bottom cover member 30 about the axis is also restrained.

When the core-construction inner cylinder 23 is projected downward from the state in which the core-bottom lid member 30 is held by the main-body cylinder portion 22 in this manner, the lower end of the core-construction inner cylinder 23 is pushed out of the holding member 28 . It abuts on the slidable contact slope 282 and retracts the holding member 28 in the radially outward direction against the biasing member 292 . In order to facilitate this operation, the outer edge of the lower end of the core-building inner cylinder 23 is chamfered or rounded. The core bottom lid member 30, which has lost the holding force of the holding member 28, is pushed downward by the core-construction inner cylinder 23, and attached to the lower end of the core-construction inner cylinder 23 so as to be pulled up. At this time, the state of engagement between the engaging convex portion 35 of the core bottom cover member 30 and the engaging concave portion 231 of the core-constructing inner cylinder 23 also deepens.

FIG. 6 shows the steps of the ground improvement method implemented using this excavation stirrer 10 . This step is performed as follows.

[S10] With the core body construction inner tube 23 housed in the main tube portion 22 in advance, the core bottom cover member 30 is attached to the holding portion of the main tube portion 22 . The rod 21 to which the excavation stirrer 10 is attached is installed at a predetermined position, and is gradually lowered while being rotated forward to start excavation of the ground.

[S20] While excavating the excavation hole 40 by rotating the excavation stirrer 10 in the forward direction, a binder is supplied into the main body cylindrical portion 22 and injected into the excavation hole 40 from the binder injection port 33 formed in the core bottom lid member 30. A binding material is injected, and the excavated soil and the binding material are stirred and mixed to form an unsolidified mixture 5 in the excavated hole 40 . When the excavation hole 40 reaches a predetermined depth, the excavation stirrer 10 is rotated in the forward direction and moved slightly up and down a plurality of times to treat the bottom, after which the rotation and vertical movement are stopped. Since the core bottom cover member 30 is firmly held by the holding member 28 up to this stage, it does not come off from the main tube portion 22 even if the excavation stirring device 10 is moved up and down. In the first half of the process up to this point, except that the core bottom cover material 30 is attached to the excavation stirrer 10, [S1] to [S1] in the ground improvement method described in Patent Document 2 (FIG. This is substantially the same as the step [S2].

[ S<b>30 ] The driving device is operated in the vicinity of the bottommost portion of the excavation hole 40 to project the core-constructing inner cylinder 23 downward, thereby removing the core-bottom lid member 30 from the body cylinder portion 22 . When the inner cylinder 23 for core body construction reaches a predetermined depth, the excavation stirrer 10 is rotated in the reverse direction to gradually raise it, and the injection of the binder is restarted. Then, the core bottom cover member 30 engaged with the core body construction inner cylinder 23 at its lower end is separated from the core body construction inner cylinder 23 by the injection pressure of the bonding material, and left near the bottom of the excavation hole 40. be done. If the injection of the binder is continued while pulling up the excavation stirrer 10 , the unsolidified core 6 made of only the binder is gradually formed above the core bottom cover member 30 . When the core portion 6 is formed, the core-constructing inner cylinder 23 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 likely to be affected by agitation, the core portion 6 becomes denser, and the shape is favorably retained.

[S40] After pulling up the excavation stirrer 10, the unsolidified mixture 5 and the unsolidified core 6 are solidified through a predetermined curing period. Thus, a double-structured columnar improved body is constructed, which includes the solidified mixture 50 formed in a columnar shape up to the bottom 41 of the excavation hole 40, and the core body 60 formed at the center thereof and made only of the binder. be done. The latter half of the process 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 art section.

As described above, the excavation stirring device 10 according to the invention disclosed in the present application is attached near the bottom of the main body tubular portion 22 by causing the core body construction inner tube 23 housed in the main tubular portion 22 to protrude downward. The core bottom lid material 30 can be removed at any position. Therefore, if excavation is started with the core-bottom lid member 30 attached in advance to the excavation stirrer 10, the binder is injected while the excavation hole is dug down to a predetermined depth, and the excavated soil and the binder are stirred and mixed in the first half. Following the process, the inner cylinder 23 for core body construction is protruded in the vicinity of the bottommost portion of the excavation hole to remove the core bottom cover material 30, and the excavating stirrer 10 is raised while injecting the binder above it. The latter half of the process of forming the core portion 6 made of chisel can be carried out continuously without interruption. Since it is possible to omit the trouble of pulling up the excavation stirring device 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 used in the center part. The construction efficiency of the ground improvement method for constructing a cylindrical improvement body having a core made of is remarkably improved. In particular, when a plurality of cylindrical improved bodies are collectively and continuously constructed, the effect of reducing man-hours becomes remarkable.

The technical scope of the present invention should not be limitedly interpreted 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 cover member and members constituting its holding means may be modified as appropriate within the range in which substantially the same effects as those of the exemplary embodiment can be obtained. I don't mind. In addition, the detailed shape of the construction machine and excavator and agitator, the type and composition of the binder, the operation procedure for raising and lowering the excavator and agitator, the timing of injecting the binder, etc., can be appropriately modified according to the construction environment. be.

10 Excavation stirrer 21 Rod 22 Main tube portion 220 Hollow portion 23 Core body construction inner cylinder 231 Engagement concave portion 24 Excavation blade 241 Excavation blade 25 Co-rotation prevention blade 26 Stirring blade 28 Holding member 281 Grasping portion 282 Sliding slope 283 Welcome Slope 29 Box 291 Outer wall 292 Biasing member 30 Core bottom cover member 31 Bottom 32 Flange 33 Bonding material injection port 34 Retained portion 35 Engagement projection 4 Ground 40 Excavation hole 41 Bottom 5 Unsolidified mixture 50 solidified mixture 6 unsolidified core 60 core

Claims (7)

A cylindrical hollow portion serving as a flow path for the binder is provided inside the body cylindrical portion that holds the excavating blade, the stirring blade, and the co-rotation preventing blade,
the hollow portion opens downward at the bottom of the main tubular portion;
A hollow cylinder-shaped inner cylinder for core body construction is inserted into the hollow part and held so as to be able to appear and disappear below the main body cylinder part,
The lower end of the inner tube for core body construction is opened downward, and a core bottom cover member having a shape to close the opening is placed in the vicinity of the bottom portion of the main tube portion via holding means provided on the main tube portion. held in
When the core body-building inner cylinder housed in the main body tube 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 excavating and stirring device characterized by being attached to the lower end of the inner cylinder for core body construction. The drilling agitator according to claim 1,
The core-bottom lid member has an inverted cone-shaped bottom and a brim-shaped portion provided on the periphery of the bottom, and the bottom is provided with a binder injection port,
An excavation stirrer, wherein a part of the brim portion is held by the holding means. In the drilling agitator according to claim 1 or 2,
Engagement means are provided on the upper surface of the core bottom lid material and the lower end of the core body construction inner cylinder to engage with each other in an uneven manner to transmit rotational force around the axis,
The excavation stirrer according to claim 1, wherein the core bottom lid member separated from the holding means of the main body tube portion is attached to the lower end of the core body construction inner cylinder via the engaging means. In the drilling agitator according to claim 3,
The engaging means includes an engaging convex portion projecting upward from the peripheral edge of the core bottom cover member and an engaging concave portion formed at the lower end of the core body constructing inner cylinder. configured to be engaged in the axial direction of
In a state in which the inner cylinder for core body construction is housed in the main body cylinder part, the core bottom lid is arranged so that the engaging convex part and the engaging concave part are aligned with each other in the circumferential direction and are shallowly engaged with each other. An excavation stirrer, wherein a material is held by said holding means. In the excavation stirrer according to any one of claims 1 to 4,
The holding means includes a holding member that appears and disappears when biased in a direction of protruding radially inward of the main tubular portion from an inner peripheral surface of the main tubular portion,
A gripping portion that can be engaged and disengaged from the peripheral edge of the core bottom cover member is formed on the tip end side of the holding member in the projecting direction,
The upper surface of the holding member is formed with a slidable contact slope that slopes downward toward the leading end in the projecting direction,
When the core-body-building inner cylinder housed in the main-body tubular portion is projected downward, the lower end of the core-body-building inner cylinder comes into contact with the slidable inclined surface, causing the holding member to move toward the diameter of the main-body tubular portion. The excavation agitator, wherein the core bottom cover member is separated from the gripping portion by retracting outward. In the drilling agitator according to claim 5,
An excavation stirrer, wherein a facing slope is formed on the lower surface of the holding member so as to be inclined upward toward the leading end of the projecting direction. In the drilling agitator according to claim 5 or 6,
The holding member is housed in a box assembled by opening a peripheral wall of the main body cylindrical portion surrounding the hollow portion,
The outer wall portion of the box body is flush with the outer peripheral surface of the main body cylindrical portion,
An excavation stirrer, wherein an urging member is interposed in a watertight chamber formed between an outer wall portion of the box and the holding member.

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