JPS6116809B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves inserting a rotating shaft equipped with stirring blades into soft ground so as to be able to penetrate and pull it out, and discharging a ground improvement agent into the ground from inside the rotating shaft. This invention relates to the provision of a new device for soil improvement that mixes and consolidates clayey soil (sludge).

By forcibly stirring and mixing various ground improvement agents, including chemical improvers such as quicklime and cement, with viscous soil (sludge) for soft ground, and creating column-shaped solidified parts in the ground, it is possible to improve soft ground. The ground improvement method has already been established as a new method in the recent construction foundation industry with many achievements, and it is also known that many new proposals regarding construction methods and equipment have been made along with this. be. These various methods and devices can be broadly classified in terms of the improving agents used, devices, machine mechanisms, and especially the means of discharging and supplying the improving agents. Those that use the improver as is (a) and those that use the improver in the form of a slurry such as cement milk or mortar (b) are classified into two categories. From the perspective of the supply means, a so-called batch method in which an improver such as quicklime is stored in a pourable pouring pipe that can be freely penetrated and withdrawn, and then discharged into the ground from the lower end of the pouring pipe using a screw feeder, etc. inside the pouring pipe...(a), Slurry A system in which a solid improver is conveyed in a circular manner through piping and supplied from a pouring pipe...(b) A rotary system that uses pressurized air to convey a solid improver in an air conveyor and is equipped with a stirring blade. Discharge and supply method from inside the shaft...Classified as (c). Various current construction methods and devices combine the above (a), (b), and (c) to emphasize their unique effects, but generally (b) - ( The majority of methods are of the combination method b), and recently, the injection agitation method, which is a combination method of (a) and (c), has also been put into practical use, and their contents are wide-ranging. In either type, it is necessary to continuously supply the improver (low b).
Even in the combination type, a rotating shaft (stirring shaft) equipped with stirring blades can be used without using a pouring pipe.
The slurry improver can be used as a hollow shaft and the slurry improver can be flowed into the hollow part and discharged near the stirring blade, or a dedicated supply pipe can be provided and the dedicated supply pipe can be opened near the stirring blade to improve the slurry. New types that do not use conventional pouring pipes have also been developed, such as those that discharge the agent.

In any case, the aim of these new construction methods and equipment is to improve construction efficiency and quality after ground improvement, but based on the construction experience and construction results to date,
In order to obtain improved quality and consistency over a certain value, it is necessary to satisfy the number of times of stirring per hour by the stirring blade, and to improve construction efficiency, it is necessary to It is necessary to increase the speed, and for this the rotating shaft (stirring shaft)
By increasing the number of stirring blades by arranging them in multiple vertical and multi-tiered configurations, and as a result increasing and maintaining the number of times of stirring per hour, effective results can be obtained with the lowest power consumption. At this time, improvements such as increasing the rotational speed of a single stirring blade or increasing the blade width have little effect in terms of power consumption, and even with current construction methods and equipment of this type, multi-stage stirring blades are not possible in most areas. This is the situation. However, even in those using multiple and multistage stirring blades,
They have common drawbacks, such as the occurrence of an unimproved layer at the tip of the rotating shaft, and the inability to supply the improving agent at all when the rotating shaft penetrates the ground.

The present invention examines the problems and shortcomings of these conventional soil improvement methods and devices, and in order to satisfy the demands of improving construction efficiency and improving quality after improvement, the present invention uses a plurality of upper and lower multi-stage stirring blades, and By making it possible to discharge and supply the ground improvement agent near the stirring blades at different vertical positions during both the reciprocating process of penetrating into the ground and pulling out the rotating shaft, which is the rotating base that supports the stirring blades, it is possible to It exhibits an excellent improvement effect that could not be attempted with other methods, and if it is difficult to supply and stir the improvement agent during penetration due to soil conditions, etc., it is possible to discharge the improvement agent during extraction, which is conventionally done. This method can also be used to completely resolve only the unimproved layer at the tip, and also eliminates temporary defects such as pits that occur on the surface of the improved ground during pulling out. The chamber includes a rotating shaft outer cylinder that can be raised and lowered and rotatably equipped with a plurality of stirring blades arranged in the radial direction in multiple stages above and below, and a rotary shaft outer cylinder that is inserted into the outer cylinder so that it can accompany the outer cylinder and is independent of the outer cylinder. a rotary shaft inner cylinder that is movable in position and also serves as a supply path for the improving agent; and a improving agent supply nozzle that is provided on the counter-rotation direction side of the rotary shaft at the attachment base of the upper and lower stirring blades of the rotary shaft outer cylinder. , is slidably held in the inner cylinder of the rotating shaft, and communicates with the supply nozzle on the lower stirring blade side when the rotating shaft penetrates underground, and communicates with the supply nozzle on the lower stirring blade side when the rotating shaft is pulled out of the ground, through the positional change of the inner cylinder with respect to the outer cylinder. A telescoping inner cylinder having a changeover supply hole for improving agent, which is provided so as to be able to communicate with the supply nozzle on the wing side, and an action disk provided at the lower end of the telescoping inner cylinder and closing the lower end of the rotary shaft inner cylinder. The switching valve is elastically supported along the rotating shaft inner cylinder so as to be able to rise and fall freely, and the lower surface of the disc having a smaller diameter than the outer cylinder diameter is used as a surface on which soil resistance reaction force acts when the rotating shaft penetrates underground. It is at a point that includes the body.

The present invention will be described in detail below based on the illustrated embodiments. Figures 1 and 2 are both longitudinal sectional front views of the main part of the rotating shaft equipped with stirring blades according to the present invention, and Figure 3 is the opposite view of the present invention. A longitudinal sectional front view of one example of a stirring blade rotating shaft using a switching valve plate with a larger diameter than the rotating shaft outer cylinder, and FIG. For convenience, the stirring blade rotating shaft shown in FIG. 3 will be explained prior to the present invention.
In addition to using a plurality of stirring blades in multiple vertical stages, a ground improvement agent is applied near the stirring blades at different vertical positions during both the reciprocating strokes of the rotating shaft, which is the rotating body that supports the stirring blades, penetrating into the ground and pulling out. The stirring blade rotating shaft 30 has a composite tube rotation form consisting of a rotating shaft outer cylinder 31 and a rotating shaft inner cylinder 34 that is concentrically installed inside the outer cylinder 31. 2 to 31 protruding in the radial direction on the lower end circumferential side of 31.
Three-bladed stirring blades 5a, 5b, and 5c are arranged in a vertically multistage manner. Although the upper part of the outer cylinder 31 is omitted in this figure, as will be understood in the entire improved device described later in FIG. The parts are continuous to form a rotating shaft 30 of a required length, and
The rotational motion is transmitted and provides stirring torque to the stirring blades 5a to 5c. Although the upper part of the inner cylinder 34 is not shown, it is assumed to have the same length as the outer cylinder 31.
As shown in the embodiment of the apparatus shown in FIG. 4, the ground improvement agent is supplied from the upper end and is pumped through the inner cylinder 34 as a passage. A working disk 37a having a large diameter and protruding from the lower end of the outer cylinder 31, and a switching valve plate 37 having a pointed head 37b for penetration at the lower end of the working disk 37a are fixedly installed. Further, the lower end circumferential side of the inner cylinder 34 is engaged with a straight groove-shaped guide notch 40 provided on the inner surface of the outer cylinder 31 to prevent free rotation of the inner cylinder 34 in the planar direction, and to guide the inner cylinder 34 in a straight direction in the vertical direction. A key-shaped regulation guide 39 that serves as a stopper that also serves as a nozzle alignment for the upper blade when moving downward.
By providing this, the rotating shaft inner cylinder 34 rotates together with the rotation of the rotating shaft outer cylinder 31, and the inner cylinder 34 can independently move its position relative to the outer cylinder 31 in the vertical direction. It is provided so that it can be varied.

Moreover, the multi-stage stirring blades 5a to 5 in the outer cylinder 31
In c, at each mounting position of the upper stirring blade 5a and the lower stirring blade 5c except for the middle stirring blade 5b, the rotation shaft 30 is attached to the mounting base of each stirring blade 5a, 5c on the circumferential side of the outer cylinder 31. Improving agent injection nozzles 32 and 33 that open toward the opposite direction are opened, respectively. Furthermore, these upper and lower injection nozzles 32, 33
On the other hand, on the circumferential side of the rotating shaft inner cylinder 34, the inner cylinder 34
For example, switching supply holes 35 and 36 are provided in the upper and lower portions for supplying the improver that is pumped together with pressurized air. That is, the upper switching supply hole 35 corresponding to the injection nozzle 32 in the upper stirring blade 5a and the injection nozzle 33 in the lower stirring blade 5c
The lower switching supply hole 36 corresponding to the inner cylinder 34
When the rotary shaft 30 penetrates or pulls out the ground to be improved, the inner cylinder 3
Working disk 37a of switching valve plate 37 at the lower end of 4
The inner cylinder 34 is made to slide vertically independently with respect to the outer cylinder 31 using the resistance of the ground cohesive soil acting on both the upper and lower sides of the rotary shaft 30 by changing the position of the switching supply holes 35 and 36. When penetrating underground, the lower switching supply hole 36 coincides with the injection nozzle 33 of the lower stirring blade 5c as shown in the figure, and the improving agent in the inner cylinder 34 is sprayed and supplied from this position into the target ground.
On the contrary, when the rotating shaft 30 is pulled upward from the target ground, the upper switching supply hole 35 coincides with the injection nozzle 32 of the upper stirring blade 5a, and the improvement agent is sprayed and supplied into the ground at this position. So do it. FIG. 3 shows a state in which the rotary shaft 30 has penetrated into the target ground. At the time of penetration, the reaction force of the ground cohesive soil acts on the lower surface of the operating disk 37a of the switching valve plate 37, so the operating disk 37a is always pressed against the outer cylinder surface a side throughout the entire penetration stroke, and the lower switching supply passage 36 coincides with the injection nozzle 33 of the lower stirring blade 5c, and the air is forced into the inner cylinder 34 together with pressurized air. The improving agent is ejected from the same nozzle 33, and is stirred and mixed by the lower stirring blade 5c, and the stirring and mixing is repeated by the subsequent intermediate stirring blade 5b and upper stirring blade 5a. This makes it possible to discharge and mix the improving agent during the underground penetration process of the rotary shaft 30, which has not been possible in the past. At the time of this penetration, the upper switching supply passage hole 35 is not in communication with the injection nozzle 32 of the upper stirring blade 5a, so that sludge and water are prevented from entering the interior. In this way, the rotating shaft 30 that has penetrated to a predetermined depth in the ground to be improved rises from the same point and is pulled out above the ground surface, but in this pulling process, the resistance of the cohesive soil in the ground to be improved is The upper surface of 37a, to be more precise, the outer diameter of outer cylinder 31 and the working disk 37a
As a downward reaction force acts on the upper surface of the cylindrical portion corresponding to the difference between the outer diameter of
is out of communication with the injection nozzle 33 of the lower stirring blade 5c, and conversely, the upper switching supply hole 35 is lowered and coincides with the injection nozzle 32 on the upper stirring blade 5a side, and the improver in the inner cylinder 34 is It is ejected into the ground from the nozzle 32, and is mixed and stirred by the upper stirring blade 5a, and is repeatedly stirred and mixed by the subsequent intermediate stirring blade 5b and lower stirring blade 5c. This working state will continue for a long time. At this time, the clayey soil resistance acting on the cylindrical portion due to the difference in the outer diameter of the working disk 37a is, for example, the outer diameter of the outer cylinder 31 is 200φ, and the outer diameter of the working disk 37a is 200φ.
When the diameter is 300φ, the adhesive force of clayey soil is 3 tons/m ²
The weight reaches approximately 100 kg, so it is sufficiently possible for the inner cylinder 34 to move downward alone. Further, the regulation guide 39 that engages with the guide notch 40 described above
In the penetration and withdrawal strokes, each nozzle 32,
33 and each of the through holes 35 and 36 at a specified position, and the inner cylinder 34 freely rotates to prevent misalignment between the nozzle and the through holes in the plane direction. Further, in the upper and lower stirring blades 5a, 5c, the outer cylinder 3
1. In other words, the injection nozzles 32 and 33 are opened toward the rear in the counter-rotational direction of the rotating shaft 30 at the attachment root of the blade on the rotating shaft. In the case of jetting, the improvement agent is injected along the back surface of the blades immediately after the stirring blades 5a and 5c rotate, so the improvement agent can be improved in the ground within the diameter range of the blades 5a and 5c with relatively low air pressure. At this time, the agent reaches the soil through the nozzles 32 and 33, and due to the change in flow velocity, the pressurized air and the improving agent are separated, and the improving agent diffuses well into the gaps in the soil. ,
The forced stirring by the blades ensures solidification with the clay soil, and the pressurized air that has reached the tips of the blades can be moved through air recovery passages and guides formed on one side of the top of the blades as necessary. or even without it, due to the gap with the soil caused by core vibration of the rotating shaft, etc.
It can be easily collected along the outer circumference of the outer cylinder 31.
The improving agents used include powder and granules, powdered cement, quicklime, removed gypsum, and slag slag.
Slurry-like materials such as cement milk and mortar are used.

An example of an overall soil improvement device incorporating the stirring blade rotating shaft 30 shown in FIG. 3 is shown in FIG. 4. That is, the apparatus shown in FIGS. 4 and 4 is an example of a dual type rotary shaft 30 and one that uses a powder improver. A slide pedestal 3 is mounted on the pedestal 3 so that it can move up and down in a straight line via an appropriate slide guide, and two stirring blade rotating shafts 30 are rotatably provided on the pedestal 3 and protrude downward. In order to raise and lower the frame 2, a driven wheel 6, a driving wheel 7, and an endless band 8 stretched between the two wheels are provided above and below the frame 2, and a part of the endless band 8 is connected to the frame 3 via a connecting part 9. The driving wheel 1 is connected to the driving wheel 1 from the prime mover 12 provided with the driving wheel 11 of the drive shaft 10 on the driving wheel 7 side on the base 1.
By driving through three belts 14, the frame 3 is moved up and down through the forward and reverse circulation of the endless band 8, and the rotating shaft 30 is moved up and down. The mount 3 is provided with a rotation motor 15 for the rotation shaft 30, and the rotation is applied to the rotation shaft outer cylinder 31 through an appropriate transmission mechanism, whereby the rotation shaft 30 consisting of the outer cylinder 31 and the inner cylinder 34 While rotating, it penetrates into the ground to be improved, reaches a required depth point, and is pulled out from this point, and a improving agent blowing supply port 17 is provided at the upper end of the inner cylinder 34 of the rotating shaft 30. . Furthermore, an air ring feed pipe 18 is connected to the base 1 as a device for supplying cement, quicklime, and other soil improvement agents together with pressurized air into the inner cylinder 34. A screw conveyor 21 that communicates with the hopper 19 via a rotary valve 20, and a distribution feeder 22 that communicates with the discharge port of the conveyor 21 are provided. Two supply ports 2
3, 23 and the blowing supply ports 17, 17 to the inner cylinders 34, 34 of the two rotating shafts 30, 30 are connected by feed pipes 24, 24. According to this, the powdered improver that is forced into the hopper 19 from the air ring feed pipe 18 is supplied to the screw conveyor 21 through the opening of the rotary valve 20, and from the conveyor 21 to the supply port of the distribution feeder 22. 23, 23 feeding pipes 24, 24 to the inner cylinders 34, 3 of each rotating shaft 30
4 through the blowing supply ports 17, 17, and when the rotary shaft 30 penetrates into the ground, it is injected into the target ground through the injection nozzle 33 on the lower stirring blade 5c side. stirring blades 5c, 5
b, 5a repeatedly performs the stirring and mixing, and when pulling out underground after reaching the required depth, the upper stirring blade 5a
The soil improvement agent is injected into the target ground through the injection nozzle 32 on the side, and the stirring blades 5a, 5b, and 5c repeatedly stir and mix the soil. This results in a ground improvement work in which the powder is supplied and mixed with the ground by repeating this using the upper and lower multi-stage stirring blades 5a to 5c. However, in addition to this upper drive type, the device as a whole is equipped with a rotational drive mechanism on the base 1 side, into which the stirring blade rotating shaft 30 is inserted and supported so as to be able to move up and down and rotate, thereby making it possible to penetrate underground and withdraw. There is also a lower drive type, so the overall design of the improved device is not limited to the illustrated example.

As shown in FIG. 3, a rotating shaft outer cylinder 31, a rotating shaft inner cylinder 34, upper and lower multi-stage stirring blades 5a to 5c, upper and lower injection nozzles 33, 34 for supplying improver, upper and lower switching supply holes 35, 36. According to the stirring blade rotating shaft 30 having the switching valve plate 37, in the soft ground improvement work, the improving agent can be switched and supplied during both the underground penetration and extraction process of the rotating shaft 30, and the stirring blades 5a~ 5
By repeating forced stirring and mixing in step c, the number of times of stirring using the stirring blade will naturally double, thereby improving the quality of the improved soil and ensuring improved soil with uniform, stable, and dense consolidated structure without any variation. It can be easily obtained, and it is expected that the construction speed and efficiency will be significantly improved. Valve plate 3
7, new problems may arise depending on the soil quality of the target ground. That is, the operating disk 37a is closed by the switching valve plate 37, which has an operating disk 37a that closes the lower end of the inner cylinder 34 and has a larger diameter than the outer cylinder 31 and is secured to the lower end of the outer cylinder 31 in an overhanging manner. Moving the inner cylinder 34 up and down using earth pressure acting on the upper and lower surfaces is advantageous in that it requires no power at all, but on the other hand, the switching valve plate 37, which has a larger diameter than the outer cylinder 31, is essential. As a result, a concave hole is formed on the ground surface side at the end of the drawing stroke of the rotating shaft 30. As mentioned earlier as an example, while the diameter of the outer cylinder 31 is 200φ, the diameter of the operating disk 37a in this switching valve plate 37 is 300φ.
Since it is necessary to have a large diameter such as φ, a relatively large concave hole is generated after the construction is completed when the rotating shaft 30 is pulled out from the ground surface.
Depending on the moisture content and strength of the soil in the target ground, these holes may be filled with soil from the surrounding area, or they may remain as they are; It is inconvenient to do so, and adjustments are required after the fact.

The present invention has been made to solve this problem, and for this reason, in the present invention, the rotary shaft inner cylinder 34 and its switching valve plate 37 are constructed as shown in the embodiments shown in FIGS. 1 and 2. This is a new proposed configuration. That is, in the embodiment shown in FIG. 1, the same longitudinal sectional front view as in FIG. 3 and the sectional view taken along line A-A in FIG. Upper and lower stirring blades 5a, 5c are arranged in rows as multi-stage stirring blades on the lower end circumferential side of the outer cylinder 31, and these stirring blades 5a, 5
Injection nozzles 32 and 33 for improving agent that open toward the side opposite to the rotational direction of the rotating shaft 30 are inserted into the circumferential side of the outer cylinder 31, which is the mounting base of c. The closed bottom of the tube 31 is shown. On the other hand, the rotating shaft inner cylinder 34 of the present invention has its lower end on the bottom 40 side of the outer cylinder 31, with a seal 41,
A retractable inner cylinder 34a is fixed by a fixing member 42 such as a bolt, and is inserted into the lower end of the inner cylinder 34 corresponding to the injection nozzles 32, 33 so as to be movable up and down. Bottom portion 4 of the outer cylinder 31
A switching valve body 43 having a disc 43a that is locked at 0 and stopped at a bottom diameter, that is, an outer diameter smaller than the diameter of the outer cylinder 31, is attached in a closed state by screw fitting or the like. Both nozzles 32 and 3 are provided on the circumferential side of the fixed-side inner cylinder 34 that corresponds to the injection nozzles 32 and 33.
3 are formed with fitting diameters 44 and 45,
The injection nozzle 3 is provided on the upper and lower peripheral sides of the telescopic inner cylinder 34a.
2, 33 and corresponding upper and lower switching supply holes 35, 3
As is clear from the figure, a plurality of support and stopper brackets 46 are arranged radially on the lower end circumferential side of the telescopic inner cylinder 34a, and each of these brackets 46 connects to the inner cylinder 34 on the fixed side. A spring 48 is slidably engaged with a guide notch 47 provided on the circumferential side of the bracket, and a spring 48 is tensioned between each bracket 46 and the bottom 40 of the outer cylinder 31 to push down and elastically support the telescopic inner cylinder 34a. 49
1 shows a fixing device such as a bolt for attaching each injection nozzle 32, 33 to the outer cylinder 31.

Further, in the embodiment shown in FIG. 2, the stirring blade rotating shaft 30 includes a rotating shaft outer cylinder 31 having upper and lower multi-stage stirring blades 5a, 5c, and a circumference of the outer cylinder 31 at the attachment base of each stirring blade 5a, 5c. The injection nozzles 32 and 33 for the improver are inserted through the fixtures 49 on the side opposite to the rotating direction of the rotating shaft, respectively, as in the embodiment shown in FIG. 1, but the inner cylinder 34 of the rotating shaft is As shown in the figure, it is fixed via a steady rest bracket 50 installed radially between the outer cylinder 31 and its lower end is inserted downward from the closed bottom part 40 of the outer cylinder 31, and the injection nozzles 32, 33 The fitting opening tube 44,
45, and the outer cylinder 31 is fitted to the lower end of the telescopic inner cylinder 34a, which is inserted into the inner cylinder 34 so as to be able to rise and fall freely.
A switching valve plate 43 having a disc 43a smaller in diameter than the diameter of
The valve body 43 and the inner cylinder 3 on the fixed side are installed in a closed state.
A spring 48 that presses the telescopic inner cylinder 34a downward is elastically intervened between the lower end of 5 and the lower end of 5.
Reference numeral 1 denotes a rotation prevention pin protruding from the circumferential side of the telescopic inner cylinder 34a, and the pin 51 is slidably engaged with a guide notch 52 provided on the circumferential side of the fixed inner cylinder 34.
is an air nozzle installed at the bottom 40 of the outer cylinder 31. This nozzle uses the double pipe section between the outer cylinder 31 and the inner cylinder 34 to forcibly inject pressurized air into the soil to emit effluent. It is a nozzle for discharging air to produce an effect, and 54 is an outer cylinder 3 of the bracket 50.
The fixing device on the first side, 55, indicates the seals of the necessary parts.

According to the stirring blade rotating shaft 30 of the present invention, the rotating shaft 3
The switching supply of the improving agent in each of the underground penetration and extraction steps of 0, and the repeated continuous stirring using the upper and lower multi-stage stirring blades are performed as follows. In other words, although the embodiment shown in FIG. 1 shows the state of penetration into the ground, when the stirring blade rotating shaft 30 penetrates to the required depth in the soil to be improved, as explained in FIG. Disk 4 of switching valve plate 43 of cylinder 34a
The earth pressure of the cohesive soil acts as a reaction force on the lower surface of 3a, and this force overcomes the force of the spring 48, pressing the switching valve plate 43 against the bottom 40 side of the outer cylinder 31 and causing the telescopic inner cylinder 34a to rise. As a result, the lower switching supply hole 36 of the inner cylinder 34a is integrally connected to the fixed inner cylinder 34 side of the lower injection nozzle 33.
The improving agent that has been forced into the inner cylinder 34 together with pressurized air is injected into the ground from the lower injection nozzle 33, and is repeatedly stirred and mixed in this order by the stirring blades 5c and 5a. It will be done. During the extraction process of the rotary shaft 30 after reaching a predetermined depth point, the disc 4
3a has a smaller diameter than the outer cylinder 31, so
Although it is not expected that the reaction force due to the earth pressure will act on the upper surface of the disk 43a, the spring 45
As a result, the telescopic inner cylinder 34a is moved straight down through the guide of the bracket 46 and the guide notch 47, and the upper switching supply hole 35 matches the upper injection nozzle 32, and the improving agent is switched into the ground through this nozzle 32. This results in continuous and repeated stirring by the stirring blades 5a and 5c. Although the embodiment shown in FIG. 2 shows the pulled out state, during the underground penetration process, the reaction force of the ground cohesive soil is applied to the disc 43 of the switching valve plate 43.
a, the valve body 43 is pushed upward toward the lower end of the fixed-side inner cylinder 34 by overcoming the force of the spring 48, and as a result, the telescopic inner cylinder 34a rises and the lower switching supply passage 36 communicates with the lower injection nozzle 33 to inject the improving agent into the ground, which is repeatedly stirred by the stirring blades 5c and 5a in this order. In addition, during the illustrated drawing stroke, the switching valve plate 43 telescopic inner cylinder 34a is lowered by the spring 48, and the upper switching supply hole 35 is aligned with the upper injection nozzle 32, so that the improver is ejected from the nozzle 32. , stirring blade 5a,
Repeated stirring in the order of 5c will be obtained as well.

According to the present invention, compared to what is shown in FIG.
The disc 43a that acts as an earth pressure acting surface in the switching valve body 43 can be made small enough to close the lower end of the inner cylinder 34 by having a diameter smaller than that of the outer cylinder 31, so that the underground extraction process is completed. It is possible to eliminate the occurrence of depressions on the surface of the improved ground at the time of completion of the improvement construction. Telescopic inner cylinder 34a
Since the lower end of the disc 43a is pulled out later than the outer cylinder 31 together with the valve body 43, the diameter of the disc 43a is small. It is the size of the diameter itself, and even though a switching mechanism was installed inside so that there would be no problems with conventional ones, no problems occurred at all.

At this time, in the present invention, the lowering for switching during the drawing stroke is performed by separating and forming a short telescopic inner cylinder 34a having switching supply holes 35, 36, and applying a simple and small external force such as a spring 48. This is easily possible. In other words, the double tube bearing support structure and prevention of core wobbling in the upper part of the outer cylinder 31 and the inner cylinder 34 are facilitated, and the inner cylinder 34 on the fixed side is connected to the fitting opening cylinders 44 and 45 as shown in the figure. If the structure is such that it fits and supports the injection nozzles 32 and 33, the inner cylinder 34 and the retractable inner cylinder 34a can be easily taken out from the outer cylinder 31 by removing the fixture 49 and pulling out the nozzles 32 and 32. Maintenance is easy, and only the telescopic inner cylinder 34a can be converted, and the double pipe connection structure at the upper part of the outer cylinder 31 and the inner cylinder 34 can also be constructed using screws, flexible hoses, etc. It is also advantageous in terms of simplifying the structure, and includes a rotary shaft outer cylinder 31, a rotary shaft inner cylinder 34 whose vertical position can be moved with respect to the rotary shaft outer cylinder 31, and upper and lower injection nozzles 32, 33 that can be continuously cut off between the two cylinders. and switching supply hole 3
5, 36, underground penetration by upper and lower multistage stirring blades 5a and 5c, switching spouting of each improving agent during the drawing process, and increasing the number of stirrings by continuous multistage repeated stirring and mixing, thereby improving the quality of the improved ground ,
This method produces an effect that cannot be obtained with conventional methods by producing a uniform and stable consolidated structure, and contributes significantly to ground improvement work.

[Brief explanation of the drawing]

1 and 2 are both longitudinal sectional front views of the main parts of an embodiment of the apparatus of the present invention, FIG. 3 is a longitudinal sectional front view of the main parts of the apparatus having a switching valve plate having a diameter larger than the diameter of the outer cylinder, and FIG. 4 is an explanatory diagram of the entire ground improvement device. 30... Stirring blade rotating shaft, 31... Rotating shaft outer cylinder,
32, 33... Injection nozzle, 34... Rotating shaft inner cylinder, 34a... Telescopic inner cylinder, 35, 36... Switching supply hole, 43... Switching valve body, 43a... Disk, 4
8... Spring, 5a, 5b, 5c... Stirring blade.

Claims (1)

[Claims] 1. A rotary shaft outer cylinder that can be raised and lowered and is rotatably equipped with a plurality of stirring blades provided in the radial direction and in multiple stages above and below;
A rotary shaft inner cylinder which is inserted into the outer cylinder so as to be able to accompany the outer cylinder and whose position can be varied independently with respect to the outer cylinder, and which also serves as a supply path for the improving agent, and attachment of upper and lower stirring blades of the rotary shaft outer cylinder. When the rotary shaft penetrates underground, the improvement agent supply nozzle is installed at the base on the opposite rotational direction side of the rotary shaft, and is slidably held in the inner cylinder of the rotary shaft, and through positional changes with respect to the inner cylinder. A telescoping inner cylinder having an improving agent switching supply hole that communicates with the supply nozzle on the stirring blade side and can communicate with the supply nozzle on the upper stirring blade side when pulled underground; The working disk is provided with a working disk that closes the lower end of the inner cylinder of the rotating shaft, and is elastically supported along the inner cylinder of the rotating shaft so as to be able to rise and fall freely, and the lower surface of the disk having a diameter smaller than that of the outer cylinder is connected to the ground of the rotating shaft. A ground improvement device characterized by comprising a switching valve body that acts as an action surface of soil resistance reaction force during intermediate penetration.