JP2020076245A - Ground improvement device, and ground improvement method - Google Patents

Abstract

To provide a ground improvement device with a high material discharge capacity and an excellent maintenance property.SOLUTION: A ground improvement device 4 includes a taper-shaped tip screw 10 provided at a tip of a casing pipe 3 so as to integrally rotate and formed to become larger in diameter as going from an upper part to a lower part, and pushes out materials discharged from the tip of the casing pipe 3 to a lower part. The tip screw 10 is substantially the same in diameter as the casing pipe 3 at its upper part and larger in diameter than the casing pipe 3 at its lower part. Since the tip screw 10 is provided just below the casing pipe 3, function of pressing out the materials discharged downward from the tip is improved, construction time is shortened, and compaction area is enlarged, thus, a secure improvement body can be constructed. In a penetration step, screwing-in effect by the tip screw 10 in accordance with rotational penetration of the casing pipe 3 is presented, the tip screw 10 moves sediment upward while disentangling natural ground wider than a diameter of the casing pipe 3, and friction in a side face of the casing pipe 3 is reduced, thus penetration force is improved.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a ground improvement device for discharging a ground improvement material into the ground to form a ground improvement body such as a sand pile, and a ground improvement method using the ground improvement device, and particularly to low vibration and low noise. The present invention relates to the technology of the static compaction method for forming a ground improvement body.

  Patent Document 1 is a conventional technique proposed by the applicant of the present application, in which a ground improvement material (sand pile material such as recycled sand or recycled crushed stone) is filled into the ground to form an underground pile. An improved device is described.

The ground improvement device described in Patent Document 1, as shown in FIG.
A casing pipe 3 made of a cylindrical steel pipe that penetrates to a predetermined depth in the ground;
A screw type bottom surface claw 91 provided below the tip of the casing pipe 3,
A movable excavating claw 93 that is rotatable and is provided on the outer peripheral surface of the casing pipe 3 on the tip side.

  The casing pipe 3 is configured such that the sand pile material can be put inside the casing pipe 3 and that the sand pile material can be discharged in a state of penetrating the ground.

  The bottom surface claw 91 is composed of a screw that rotates integrally with the casing pipe 3. Downward stress is applied to the sand pile material discharged from the opening portion at the tip of the casing pipe by the fin of the screw forming the bottom surface claw 91. Further, by applying downward stress to the discharged sand pile material in this way, the sand pile material in the ground is compacted.

  The movable excavation claw 93 is rotatably provided (expandable / contractible) between a vertically oriented “reduced position” and a horizontally oriented “expanded position”. According to the description of Patent Document 1, the movable excavating claw 93 has a function of exerting a lateral pressure on the ground to move the movable excavating claw 93 when the movable excavating claw 93 is in the expanded diameter position, as one of its functions. Further, as another function, it plays a role of guiding the sand pile material discharged from the front end opening portion of the casing pipe 3 toward the bottom surface claw 91 without escaping to the side.

JP, 2016-145514, A

  However, the conventional technique disclosed in Patent Document 1 has the following problems.

  Regarding the ground improvement device of Patent Document 1, when the applicant of the present application conducted an experiment to verify the capability, it was revealed that the material discharge capability was significantly inferior to the expected level and that the target construction capability was not reached. Became.

  In addition, in the experiment, it became clear that the base ground was clogged between the movable excavating claw and the casing pipe, and there was a case where the original function was not fulfilled due to this clogging. Therefore, in order to maintain the function of the ground improvement device of Patent Document 1, it is necessary to frequently perform cleaning such as soil removal and operation confirmation, and the work for maintaining the function is extremely complicated.

  Further, since the movable excavating claw is adopted, there is a risk that the excavating claw may fall off during construction depending on the strength and durability of the metal fitting at the connecting portion between the excavating claw and the casing pipe.

  Therefore, in view of the above-described problems, an object of the present invention is to provide a new ground improvement device and a ground improvement method, which have a better material discharging capacity than conventional ones, and also have a simple structure and excellent maintainability. It is in.

The above purpose is
A device used as a ground improvement method for forming a ground improvement body for compacting the ground in the ground,
A casing pipe that can discharge sand pile material from the tip while penetrating the ground,
Provided at the tip of the casing pipe so as to be rotatable integrally, and a tip screw for pushing down the sand pile material discharged from the tip of the casing pipe,
This is achieved by a ground improvement device in which the tip screw is formed so that its diameter increases from top to bottom.

  In the ground improvement device, the tip screw has an upper portion having substantially the same diameter as the casing pipe and a lower portion having a diameter exceeding the diameter of the casing pipe.

  Further, the ground improvement device further has an air injection portion for intermittently injecting air that prompts the discharge of the sand pile material from the tip of the casing pipe, which is located near the tip inside the casing pipe. It is provided.

  Further, the ground improvement device further has a measuring means for measuring the top end position of the sand pile material in the casing pipe.

  Further, the ground improvement device further includes a side screw for suppressing soil discharge that may occur along the side surface of the casing pipe or the vicinity thereof, and the side screw is provided on the side surface of the casing pipe.

  In addition, the above-mentioned object is to use a casing pipe capable of discharging sand pile material to promote the discharge of sand pile material from the tip of the casing pipe in the method of constructing a ground improvement body for compacting the ground in the ground. This is achieved by intermittently injecting air.

The ground improvement device according to the present invention has a tip screw integrally rotatably provided at the tip of the casing pipe. This tip screw has a taper shape formed so that the diameter gradually increases from the top to the bottom, and the sand pile material discharged from the tip of the casing pipe (in this application, simply referred to as “ (Also referred to as “material”).
By providing the tip screw (taper type screw) with such features just below the casing pipe, the function of pushing more material discharged from the tip of the casing pipe downward in the process of constructing the ground improvement body is improved. However, the time required for forming the ground improvement body can be shortened, and the construction period can be shortened. Furthermore, the compaction effect (range of compaction) of the ground improvement body is expanded, so that a reliable ground improvement body can be created.

Further, the ground improvement device according to the present invention does not have the movable excavating claw as seen in the technique of Patent Document 1, and therefore has a simpler structure than the related art, and as a result, maintenance work can be reduced.
Further, in the case of Patent Document 1, the material discharge capacity is affected by the position of the movable excavating claw (horizontal direction during construction), but in the case of the present invention, there is no such movable excavating claw. A stable material discharge capacity can be maintained regardless of the position.

Further, in the present invention, the tapered tip screw has an upper portion having a diameter substantially the same as the diameter of the casing pipe and a lower portion having a diameter exceeding the diameter of the casing pipe.
By providing the tip screw having such characteristics, in the penetration step of the ground improvement device, the "screw-in effect" by the screw is exhibited with the rotation penetration of the casing pipe. In addition, the tip screw moves the earth and sand upward while loosening the original ground having a diameter larger than that of the casing pipe, and reduces the friction on the side surface of the casing pipe, thereby improving the penetration force.
Further, the screw diameter of the tip screw increases as it goes downward, and has a maximum diameter exceeding the diameter of the casing pipe at the lowermost portion. Therefore, the range in which the torque (force) of the motor can be directly transmitted to the ground improvement body by the screw bottom surface is expanded, and the compaction effect is improved.

Further, in the present invention, the air injection unit is provided near the inner tip of the casing pipe, and the air for injecting the material from the tip of the casing pipe is intermittently ejected from this air injection unit.
It should be noted that FIG. 2B of Patent Document 1 discloses an air injection unit (inner jet 31) provided inside the casing pipe, so that air is simply continuously injected from this air injection unit. Is becoming However, in the "static compaction method" that creates a ground improvement body with low vibration and low noise, there is no vibration due to the vibro hammer, and when the casing pipe is rotated, the centrifugal force in the horizontal direction is applied to the material inside the casing pipe. Acts to increase the frictional resistance between the material and the casing pipe, and the casing pipe and the material are integrated. Even under such a circumstance, even if the air is simply continuously jetted (continuously jetted), the pressure inside the tip of the casing pipe becomes stable and the discharge speed of the material decreases.
Therefore, in the present invention, air is intermittently jetted from an air jet portion provided near the tip inside the casing pipe. The action of the intermittent air causes a pulsation in the pressure acting on the material near the tip inside the casing pipe (that is, the material in front of the tip opening of the casing pipe), and the pressure change due to this pulsation promotes the discharge of the material. The material in the pipe can be discharged continuously without delay. That is, stable material discharge is achieved in the process of forming the ground improvement body.

  Further, in the present invention, depending on the type of material to be used (sand, recycled sand, recycled crushed stone, etc., when constructing a sand pile as a ground improvement body, for example), filling of compressed air into the casing pipe or its exhaust Dust is generated in the casing pipe. Therefore, a measurement means having a function of withstanding the internal pressure of the casing pipe and a function of transmitting dust in the casing pipe to measure the material top end in real time is required. Therefore, the ground improvement device of the present invention provides a measuring means capable of reliably and stably measuring the material top end position in the casing pipe regardless of the situation in the casing pipe (filling of compressed air, generation of dust, etc.). I have it.

Further, in the ground improvement device of the present invention, as described above, the compressed air is filled into the casing pipe, and intermittent air is jetted from the air jetting portion near the tip inside the casing pipe, and the material is fed from the casing pipe tip. Is discharged. However, when this material is discharged, excess air leaks from the tip of the casing pipe and is discharged to the ground along the side surface of the casing pipe. Then, soil is discharged along with the air exhausted to the ground.
Therefore, in the ground improvement device of the present invention, a side screw is provided on the side surface of the casing pipe for the purpose of suppressing soil discharge when constructing the ground improvement body. Specifically, a screw is installed at a position higher than the tip of the casing pipe in the direction of pushing it down (the same winding direction as the tip screw) during the building process. The effect of this side screw is that the air passage along the side of the casing pipe (air escape path to the ground) is agitated and the earth and sand to be discharged can be moved downward, suppressing the discharge of earth. Especially.
Further, along with the above-mentioned suppression of soil removal, an excellent effect that the effect of increasing the density by the ground improvement body formed in the ground can be enhanced is also achieved.

Further, the ground improvement method according to the present invention relates to a method for forming a ground improvement body for compacting the ground in the ground by using a casing pipe capable of discharging a sand pile material, and sand from the tip of the casing pipe. It is designed to inject air intermittently to expel pile material.
This causes pulsation in the pressure acting on the material near the tip inside the casing pipe (that is, the material in front of the tip opening of the casing pipe), and due to the pressure change due to this pulsation, the pressure in the casing pipe in the ground improvement body construction step is increased. Material can be discharged continuously without delay.

It is a side view and an outline front view showing an example of a construction machine provided with a ground improvement device. It is a figure which shows roughly the structure by the side of the tip of the casing pipe with which the ground improvement device is provided, (a) is a side view and (b) is a top view of (a). It is a figure which shows roughly the structure by the side of the tip of the casing pipe with which the ground improvement device is provided, (a) is a side view and (b) is a top view of (a). It is a perspective view which shows roughly the internal structure by the side of the tip of the casing pipe with which the ground improvement device is provided, and is a perspective view which looked at the ground improvement device from the side. It is a perspective view which shows roughly the internal structure by the side of the tip of the casing pipe with which the ground improvement device is provided, and is a perspective view which looked at the ground improvement device from the side. It is a perspective view showing a state where the top end position of the sand pile material in the casing pipe is measured by using the measuring means included in the ground improvement device, and is a perspective view of the ground improvement device seen from the side. .. (A) exemplifies measurement by a microwave type level meter, (b) exemplifies measurement by a laser radar range finder, and (c) exemplifies measurement by a weight type sand surface meter. There is. It is a figure which shows roughly the structure of the side screw with which the ground improvement apparatus is equipped, (a) is a side view, (b) is a top view of (a). It is a process drawing which shows the ground improvement method. It is a schematic diagram which shows the effect of an inner jet in the process of process d-f shown in FIG. It is a graph which shows the experimental result in an Example. It is a graph which shows the experimental result in an Example. It is a figure which shows roughly the structure by the side of the tip of the casing pipe with which the conventional ground improvement device is provided, (a) is a side view and (b) is a top view of (a).

(Ground improvement device)
First, the structure of the ground improvement device will be described.
The ground improvement device of the present embodiment is a device used for carrying out a static compaction method (ground improvement method) for constructing compaction piles with low vibration and low noise to increase the density of the ground. Further, in the present embodiment, sand pile materials such as sand, recycled sand and recycled crushed stone are used as the ground improvement material.

As shown in FIG. 1, the construction machine 1 used in the static compaction method mainly
・ Crawler-type base machine 2 that can move freely on the ground,
A ground improvement device 4 having a casing pipe 3 made of a cylindrical steel pipe,
A columnar leader 5 that supports the ground improvement device 4 so that it can move up and down.
A rotation drive device 6 that moves up and down along the leader 5 to rotate the casing pipe 3 around an axis;
A hopper 7 for feeding the sand pile material into the inner space of the casing pipe 3,
It has an air valve 8 which is configured to be openable and closable and is closed when the pressure inside the casing pipe 3 is increased.

Then, the ground improvement device 4 according to the present embodiment, as shown mainly in FIG. 1 and FIG.
・ Casing pipe 3 capable of discharging sand pile material from the tip opening,
A tip screw 10 provided below the tip of the casing pipe 3,
An outer jet 21 provided near the tip on the outside of the casing pipe 3,
An inner jet 31 provided near the tip inside the casing pipe 3 (see FIG. 4),
A measuring means for measuring the top position of the sand pile material in the casing pipe (see FIG. 6),
・ The side screw 40 provided on the side surface of the casing pipe 3 (see FIG. 7)
I have it.

  The casing pipe 3 is configured such that the sand pile material can be charged inside the casing pipe 3, and the sand pile material can be discharged from the tip opening portion of the casing pipe 3 in a state of penetrating into the ground. The sand pile material charged into the casing pipe 3 is discharged from the tip opening of the casing pipe 3 by the pressure adjustment in the casing pipe 3 and the discharge promoting action by the intermittent air from the inner jet 31, as described later. ..

  In addition, in the present embodiment, the inner screw as disclosed in FIG. 9 of Patent Document 1 is not provided inside the casing pipe 3.

  The tip screw 10 is located below the tip opening of the casing pipe 3 and is provided so as to rotate integrally with the casing pipe. The tip screw 10 is fixed to the casing pipe 3 so as to maintain an upright posture in a state of protruding downward from the tip of the casing pipe 3.

  The tip screw 10 has a function of pushing down the sand pile material discharged from the tip of the casing pipe 3, and also a role of expanding and compacting the sand pile material discharged from the tip of the casing pipe 3. ing. The specific configuration of the tip screw 10 will be described later.

As shown in FIG. 2, the outer jet 21, which is the first air injection unit, has a flow passage arranged along the outer peripheral surface near the tip of the casing pipe 3 and an injection port located at the tip of this flow passage. It is configured to include. The base end side of the flow path connected to the outer jet 21 is connected to an air compressor (not shown).
The outer jet 21 can inject an air jet from an injection port at the tip of the outer jet 21 as needed, and plays a role of assisting penetration of the casing pipe 3 (a role of relaxing penetration resistance).

The inner jet 31, which is the second air injection unit, is configured to include a flow passage arranged along the inner peripheral surface of the casing pipe 3 and an injection port located at the tip of this flow passage. The injection port at the tip of the inner jet 31 is located in front of the tip opening of the casing pipe 3 (above the opening), and the base end side of the flow path connected to the inner jet 31 is not shown. It is connected to the air compressor.
The inner jet 31 can intermittently jet an air jet from the opening at the tip thereof, if necessary. The intermittent air causes pulsation in the pressure acting on the sand pile material near the tip inside the casing pipe (that is, the sand pile material in front of the tip opening of the casing pipe 3), and the pressure change due to this pulsation causes the casing to change. The sand pile material in the pipe 3 can be continuously discharged without delay.

  It should be noted that the specific configuration of the air jet unit that constitutes the inner jet 31 is not particularly limited, and for example, a nozzle type air jet unit as illustrated in FIG. 4 or a block type air jet as illustrated in FIG. Departments can be employed. In addition, the control method of the air injection unit forming the inner jet 31 is not particularly limited, and for example, a control method using a generally known solenoid valve or ON / OFF control device can be adopted.

Further, the ground improvement device 4 according to the present embodiment includes a measuring means for measuring the top end position (that is, the sand surface) of the sand pile material in the casing pipe 3. As the sand surface measuring means, for example, a non-contact type sand surface measuring apparatus or a contact type sand surface measuring apparatus can be used.
Specific examples of sand surface measurement using a non-contact type sand surface measuring device include a microwave level meter as shown in Fig. 6 (a) and a sand using a laser radar range finder as shown in Fig. 6 (b). The sand surface measurement by surface measurement can be mentioned.
As a specific example of the sand surface measurement using the contact type sand surface measuring apparatus, there is a sand surface measurement by a weight type sand surface measuring instrument as shown in FIG. 6 (c).

  The microwave type level meter used in the sand surface measurement illustrated in FIG. 6A transmits a microwave signal toward the sand surface. This measuring means does not require operator's operation like the laser radar rangefinder.

  The laser radar rangefinder used in the sand surface measurement illustrated in FIG. 6 (b) does not require operator's operation because it uses laser light.

  The weight type sand surface meter used in the sand surface measurement illustrated in Fig. 6 (c) requires a winch operation by an operator for hoisting before sand supply and unwinding after sand supply. It is possible to measure even under the conditions of dust and high pressure.

In addition, in the present embodiment, as shown in FIG. 7, a side surface screw 40 is provided on the side surface of the casing pipe 3, and this is a member that is responsible for suppressing soil discharge during sand pile construction.
As described above, in the present embodiment, the compressed air is filled into the casing pipe 3, and the intermittent air is jetted from the inner jet 31 near the tip inside the casing pipe to discharge the material from the tip of the casing pipe. However, when this material is discharged, excess air leaks from the tip of the casing pipe and is discharged to the ground along the side surface of the casing pipe. Then, soil is discharged along with the air exhausted to the ground.
Therefore, in the present embodiment, the side surface screw 40 is provided on the side surface of the casing pipe 3 for the purpose of suppressing the soil discharge when constructing the sand pile. The effect of the side screw 40 is to stir the air passage formed along the side surface of the casing pipe and move the earth and sand to be discharged downward to suppress the discharge of soil.
Further, along with the above-described suppression of earth removal, an excellent effect that the density increasing effect of the compacted sand pile formed in the ground can be enhanced is also achieved.

  The installation position of the side surface screw 40 is not particularly limited as long as it is a side surface (peripheral surface) of the casing pipe 3 and is capable of exhibiting earth removal suppression. In the embodiment illustrated in FIG. 7, about 1 m above the tip end of the casing pipe 3 is equipped with about two 1 / 4-turn screws in the direction of pushing downward during the building process (the same winding direction as the tip screw). is doing.

(Tip screw)
Next, a specific configuration of the tip screw 10 provided immediately below the tip opening of the casing pipe 3 will be described with reference to FIGS. 2 and 3.

  As shown in FIG. 2, in the present embodiment, the tip screw 10 has a shaft member 11 coaxial with the center of the casing pipe 3, and the shaft member 11 is inserted into the inner space of the casing pipe 3. The shaft member 11 included in the tip screw 10 has its upper end side fixed to the inner peripheral surface of the casing pipe 3 via a fixing member 13. That is, the tip screw 10 is indirectly fixed to the inner peripheral surface of the casing pipe 3 through the beam-shaped fixing member 13. As a result, when the casing pipe 3 rotates, the tip screw 10 rotates integrally. To do.

The attachment mode of the tip screw 10 is not limited to the embodiment shown in FIG. 2, and it is also possible to adopt the mode shown in FIG. 3, for example.
In the embodiment shown in FIG. 3, the ground improvement device 4 has a pair of fixing members 15 parallel to the casing pipe 3, and the upper side of the fixing members 15 is welded to the side surface of the tip of the casing pipe. The lower side of the fixing member 15 is welded to the fin of the tip screw 10. That is, in the embodiment shown in FIG. 3, the tip screw 10 is indirectly fixed to the outer peripheral surface of the casing pipe via the pair of fixing members 15, and as a result, when the casing pipe 3 rotates, the tip screw 10 is rotated. The screw 10 rotates integrally.

Further, the tip screw 10 has a tapered shape whose fins are formed so as to gradually expand in diameter from top to bottom.
By providing the tip screw (taper type screw) having such a shape just below the tip of the casing pipe 3, the function of pushing out more of the material discharged from the tip of the casing pipe in the sand pile building process is improved. However, the sand pile construction time can be shortened, and the construction period can be shortened.
Further, the fins of the tip screw 10 rotating integrally with the casing pipe 3 can apply downward stress to the sand pile material discharged from the tip opening of the casing pipe. By applying such downward stress to the discharged sand pile material, the compaction effect (compaction range) on the sand pile to be constructed is expanded, and as a result, the sand pile of the designed quality is ensured. Can be created.

Further, in the present embodiment, as shown in FIG. 2, the tapered tip screw 10 has an upper portion having a diameter substantially the same as the diameter of the casing pipe 3 and a lower portion having a diameter exceeding the diameter of the casing pipe 3. Have
By providing the tip screw 10 having such characteristics, in the penetration step of the ground improvement device 4, the "threading effect" by the screw is exhibited as the casing pipe 3 rotates and penetrates. Further, the tip screw 10 moves the earth and sand upward while loosening the original ground having a diameter equal to or larger than the diameter of the casing pipe 3 to reduce the friction on the side surface of the casing pipe, thereby improving the penetration force.

(Ground improvement method)
Next, a ground improvement method using the above-described ground improvement device will be described based on FIGS. 8 and 9 with reference to the device configurations shown in FIGS. 1 to 7.
Note that steps a to h described below correspond to steps (a) to (h) shown in FIG. 8, respectively.

  The ground improvement method of the present embodiment is a construction method of constructing sand piles in the ground by pulling out continuous casing pipes without hammering back the penetrated casing pipes. The main steps of this ground improvement method will be described below.

<Step a>
The casing pipe 3 is guided on the ground at the planned construction position of the sand pile (ground improvement body).
Then, a sand pile material (point sand) is put into the casing pipe 3 in order to prevent the intrusion of the raw ground soil.

<Step b>
Next, the casing drive pipe 3 is rotated in the forward direction by the rotation drive device 6 to start penetration of the casing pipe.
In the process of penetrating into the ground, the casing pipe 3 is penetrated to a specified depth along the leader 5 while using the outer jet 21, which is a penetration assisting device, etc., if necessary.
In the process of penetrating the casing pipe 3, the sand pile material blocks the tip opening of the casing pipe 3, so that the entry and mixing of earth and sand into the casing pipe is prevented.

<Process c>
When the lower end of the casing pipe 3 reaches the target depth, the penetration is finished. When the outer jet 21 is also used, the injection of the air jet is stopped.
Next, the sand pile material is put into the casing pipe 3 through the hopper 7. Specific examples of the material for the sand pile include sand, recycled sand, recycled crushed stone, and the like.

<Process d>
Subsequently, compressed air is fed into the casing pipe with the air valve 8 above the casing pipe 3 closed to increase the internal pressure of the casing pipe 3. Then, the top end of the sand pile material in the casing pipe is confirmed by the measuring means (see FIG. 6 (a)) such as the microwave type level meter described above.
Further, an air jet is intermittently jetted by the inner jet 31 to cause pulsation in the sand pile material near the tip inside the casing pipe 3 to promote discharge of the sand pile material from the tip opening portion of the casing pipe 3. .. As a result, it is possible to prevent the sand pile material from stagnating at the tip opening portion of the casing pipe 3 and to promptly discharge the sand pile material.
Further, while the casing pipe 3 is rotated in the reverse direction (rotated in the direction opposite to the rotation direction shown in FIGS. 8B and 8C) by the rotation drive device 6, the casing winch 3 is pulled out by the hoisting winch.

<Process e>
Then, in the process of pulling out the casing pipe 3 along the leader 5 while operating the inner jet 31 and the rotation drive device 6, the sand pile material is discharged from the lower end of the casing pipe. Further, the top end of the sand pile material in the casing pipe 3 is followed by the measuring means.

<Process f>
When the casing pipe 3 reaches the specified depth, the withdrawal of the casing pipe is stopped.
Subsequently, the inner jet 31 and the rotary drive device 6 are operated to discharge the sand pile material, and further compaction is performed.
In addition, as shown in FIG. 9, the compressed air by the inner jet is discharged together with the sand pile material in the steps d to f, thereby increasing the pore water pressure and increasing the progress of compaction as the effective stress is reduced. The effect is obtained.

<Process g>
The top end of the sand pile material in the casing pipe 3 is measured by a measuring means to check whether a specified amount of the sand pile material has been discharged from the casing pipe 3.

<Process h>
When the casing pipe 3 is pulled out to the improved crown height by repeating the supply of the sand pile material and the steps d to g, the construction of the compacted sand pile (ground improvement body of specified length) is completed.

  Next, specific examples of the present invention including the above-mentioned tip screw will be described.

  An actual machine experiment was conducted for the purpose of verifying the penetration capability of the ground improvement device in the penetration process and the material discharge capability in the construction process.

(Ground improvement device used in the experiment)
A ground improvement device having the features shown in FIG. 2 was used as an example.
A ground improvement device having the features shown in FIG. 12 was used as a comparative example.

  The ground improvement device according to the example and the ground improvement device according to the comparative example are different in the following points, and have other common points such as the diameter of the casing pipe.

  As shown in FIG. 2, the ground improvement device of the example was equipped with a tip screw for pushing down the sand pile material discharged from the tip of the casing pipe. This tip screw was integrally rotatably provided at the tip of the casing pipe.

The ground improvement device of the comparative example is, as shown in FIG.
A screw type bottom surface claw 91 provided below the tip of the casing pipe 3,
A rotatable movable excavating claw 93 provided on the outer peripheral surface of the casing pipe 3 on the front end side was provided.

(experimental method)
In the experiment for verifying the penetration capability, the motor output was set to the same value in the example and the comparative example, and the penetration input for the same motor output was compared.

  In the experiment for verifying the material discharge capacity, a plurality of depths were set in the example and the comparative example, and the material discharge rates were compared for each depth.

(Experimental result)

The result of the penetration capability verification experiment was as shown in FIG.
That is, in the example in which the taper type screw is provided just below the tip of the casing pipe, the penetration force for the same motor output is increased (compared to the comparative example), which leads to an improvement in the penetration speed of about 1.5 to 1.7 times. It was

The result of the verification experiment of the material discharge capacity is as shown in FIG.
That is, it was found that in the example in which the taper type screw was provided just below the tip of the casing pipe, the material discharge capacity was improved by about 1.5 to 2.5 times (compared with the comparative example). It was also found that the construction speed increases as the discharge capacity improves.

1 Construction Machine 2 Base Machine 3 Casing Pipe 4 Ground Improvement Device 5 Leader 6 Rotation Drive Device 7 Hopper 8 Air Valve 10 Tip Screw (Tapered Screw)
11 shaft member 13 fixed member 15 fixed member 21 outer jet (air injection part)
31 Inner jet (air injection part)
40 Side Screw 91 Bottom Claw 93 Movable Excavator Claw

Claims (6)

A device used as a ground improvement method for forming a ground improvement body for compacting the ground in the ground,
A casing pipe that can discharge the ground improvement material from the tip while penetrating the ground,
A tip screw for rotatably provided at the tip of the casing pipe and pushing out the ground improvement material discharged from the tip of the casing pipe,
The ground improvement device, wherein the tip screw is formed so that a diameter thereof increases from top to bottom. The tip screw is
The upper part has a diameter substantially the same as the diameter of the casing pipe,
The lower portion has a diameter exceeding the diameter of the casing pipe,
The ground improvement device according to claim 1, wherein: An air injection unit provided near the inner tip of the casing pipe for intermittently injecting air that prompts the discharge of the ground improvement material from the tip of the casing pipe,
The ground improvement device according to claim 1 or 2, further comprising: Measuring means for measuring the top end position of the ground improvement material in the casing pipe,
The ground improvement device according to any one of claims 1 to 3, further comprising: A side screw provided on the side surface of the casing pipe and for suppressing the soil discharge that may occur along the side surface of the casing pipe or in the vicinity thereof,
The ground improvement device according to any one of claims 1 to 3, further comprising: Using a casing pipe capable of discharging the ground improvement material, in a method of forming a ground improvement body for compacting the ground in the ground,
A ground improvement method characterized by intermittently injecting air to promote discharge of the ground improvement material from the tip of the casing pipe.