JPH0931970A - Ground improvement method and ground improvement device - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a ground improvement method and a ground improvement device for improving soft ground by excavating soft ground, injecting a stabilizer into the excavated soil, and stirring and mixing. SOLUTION: The upper end of a stirring and excavating shaft 2 having a stirring blade 3 and a excavating cutter 4 is connected to a lower end of a screw-equipped drive shaft 1 to which a screw 1'is attached in a spiral shape in a reverse winding to a forward rotation. , The screw drive shaft 1 is normally rotated and penetrated vertically into the soft ground to excavate the ground without injecting the stabilizer, and when the excavation reaches the planned depth, the screw drive is performed. The shaft 1 is reversely rotated at that position to forcibly discharge the in-situ soil in an amount equivalent to the amount of the stabilizer injected, and then the drive shaft with screw 1 is rotated in the same direction as when the penetration was made. While stirring, the stabilizer is injected from the injection hole 7 in the upper part of the stirring excavation shaft 2 and stirred and mixed, and then lifted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention excavates a soft ground, pours a ground stabilizing material or a hardening material (hereinafter collectively referred to as "stabilizing material") into the excavated soil, and stirs and mixes the soft ground. The present invention relates to a ground improvement method for improvement treatment and a ground improvement device used for implementing the method.

[0002]

2. Description of the Related Art Conventionally, various ground improvement methods and devices for improving soft ground by excavating soft ground, injecting a stabilizer into the excavated soil and stirring and mixing have been developed and widely implemented. . In particular, in order to solve the problem that the injected stabilizer increases the volume in the soil and causes horizontal ground displacement, which adversely affects the underground structure, in order to solve the problem that the amount of stabilizer injected is equal to the original position. Means have been proposed to remove the soil and prevent an increase in volume in the soil. For example, in Japanese Examined Patent Publication No. 5-62167, a screw rod having a stirring head at its tip is rotationally penetrated into soft ground, and soil is discharged simultaneously with pulling and stirring, and a stabilizer is jetted from the lower end of the screw rod. It describes the construction method and equipment for pouring into the soil in situ to improve the ground. Further, in Japanese Examined Patent Publication No. 4-57805, a screw for earth removal is provided on the outer circumference of two rotary shafts, each of which has a stirring blade attached to the tip thereof. The soil improvement method and apparatus are described, in which the soil is soiled and the stirrer is agitated and mixed while the rotary shaft is reversed while the rotary shaft is pulled out.

[0003]

Generally, it is said that the amount of discharged soil changes depending on the discharged area of the screw, the pitch of the screw, the number of rotations per unit time, and the working time. However, the soil condition to be improved is deep,
It is a well-known fact that the penetration speed of the rotating shaft is fast or slow depending on the soil condition and is not constant depending on the place and the like.

However, the above-mentioned ground improvement method is
It is extremely difficult to control the amount of soil discharged to an amount equivalent to the amount of soil injected because the soil is discharged and discharged at the same time. In addition, since the soil improvement method described above is configured to discharge soil at the same time as excavation and penetration, the amount of soil discharged is directly affected by the penetration speed of the screw rod, and it is extremely difficult to properly control the amount of soil discharged. In addition, since the required injection amount of the stabilizer is often set according to each soil condition, the injection amount cannot be changed by increasing or decreasing the amount of soil discharged, and there is a problem that ground displacement eventually occurs.

Therefore, it is an object of the present invention to precisely discharge the soil in an amount corresponding to the amount of the stabilizer injected when the stabilizer is injected and mixed by stirring to improve the soft ground.
Therefore, it is to provide a ground improvement method for reliably preventing ground displacement. A further object of the invention is, after excavation penetration,
It is an object of the present invention to provide a ground improvement method in which a soil unloading step is independently provided as a step prior to drawing and stirring.

[0006]

As means for solving the above-mentioned problems, the ground improvement method according to the invention described in claim 1 has an upper end of an agitation excavation shaft 2 having an agitation blade 3 and an excavation cutter 4. Is connected to the lower end of the drive shaft with screw 1 in which a screw 1'is attached in a spiral shape that is reverse-wound to the direction of normal rotation, and the drive shaft with screw 1 is rotated in the normal rotation and vertically into soft ground. The ground is excavated without penetrating into the ground and the stabilizer is injected, and when the excavation reaches the planned depth, the screw-equipped drive shaft 1 is rotated in reverse at that position to obtain the amount of the stabilizer injected. A corresponding amount of in-situ soil is forcibly discharged, and then the stabilizer is injected from the injection hole 7 above the stirring excavation shaft 2 while rotating the drive shaft with screw 1 in the same direction as when the penetration was performed. Lift while stirring and mixing It is characterized by

Next, in the ground improvement device according to a second aspect of the present invention, a single or a plurality of screw drive shafts 1 are rotatably supported while maintaining a vertical posture with high accuracy, and the screw drive shafts are supported. 1, a screw 1'is attached in a spiral shape that is reverse-wound with respect to normal rotation and intrusion rotation, and an excavation cutter 4 for excavating soft ground is attached to the lower end of the drive shaft 1 with screw. Agitating and excavating shaft 2 having a plurality of agitating blades 3 horizontally arranged above it
Are connected in series, and an injection hole 7 for injecting the stabilizer into the tip and the upper part of the stirring and excavating shaft 2 is introduced.
Are respectively provided.

A switching valve 5 is provided at a position above the stirring blade 3 above the stirring blade 3 and above the stirring excavation shaft 2 to enable switching between tip injection and upper injection of the stabilizer. It is also characterized by being present.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ground improvement method of the present invention is carried out by a single axis ground improving apparatus or a multi-axis ground improving apparatus having two or more axes. The tip end injection and the upper part injection of the stabilizer are performed by switching the rotation direction of the drive shaft with screw 1 in the forward and reverse directions, thereby applying the inertial force of the valve element to perform switching, or by applying the action of earth pressure. This is done by a switching valve mechanism.

In the earth unloading process, the tip is improved (consolidation) after the drive shaft with screw 1 that has penetrated into the excavation reaches the planned depth.
As a process prior to the treatment and pulling and stirring, the designed earth removal amount is accurately executed by immobilizing the height of the drive shaft 1 with a screw and only rotating it. After the stirring excavation shaft 2 and the drive shaft with screw 1 reach the planned depth, the stirring excavation shaft 2
It is also possible to form the root-consolidated portion by repeatedly raising and lowering the screw-equipped drive shaft 1 by a height corresponding to the root-consolidated portion, and then injecting a stabilizer with it.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B show a step of excavating soft ground from the ground to a predetermined depth with a drive shaft 1 with a screw having a stirring excavation shaft 2 at the tip. A stirring excavation shaft 2 is connected in series to the lower end of the drive shaft 1 with a screw.

In the case of the illustrated example, the drive shafts with screws are two, and the lower parts of the respective shafts are mutually restrained by the connecting metal fittings 6 to keep the relative positions of both shafts, and the vertical posture can be maintained with high precision and rotatable. Supported by. The screw 1'of the drive shaft with screw 1 is mounted in a spiral shape that is reverse-wound to the forward rotation. Therefore, no soil is discharged during the excavation. The reason is that the screw 1'of the drive shaft with screw 1 is attached in the reverse winding of the normal rotation and the penetration rotation,
Since the screw 1 ′ has a function of pushing the excavated soil downward, no soil is discharged except for the naturally rising soil at the time of intrusion. An excavation cutter 4 for excavating soft ground is attached to the lower end of the agitation excavation shaft 2, and a plurality of agitation blades 3 that agitate excavated soil and mix a stabilizer are horizontally attached above the excavation cutter 4. . The stirring excavation shaft 2
An injection hole 7 for injecting the stabilizer is provided at a position slightly higher than the tip end portion and the stirring blade. A switching valve 5 is provided near the upper end of the stirring excavation shaft 2 above the stirring blade 3 to switch the flow path for supplying the stabilizer to the two injection holes 7. The outer diameter of the screw 1 ′ is smaller than the outer diameters of the stirring blade 3 and the excavation cutter 4.

In FIG. 1A, the screw drive shaft 1 is rotated in the normal direction and a downward pushing force is applied to vertically penetrate into the soft ground to advance excavation. With the forward rotation of the drive shaft with screw 1, the excavation cutter 4 of the stirring excavation shaft 2 integrally rotates in the same direction to excavate the soft ground. No stabilizer is injected at this stage. If necessary, bentonite muddy water is poured out, but dry drilling is also performed without supplying any liquid.

FIG. 1B shows a stage in which the drive shaft with screw 1 reaches a predetermined depth. At this stage, the rotation is stopped once and the excavation of soft ground is stopped. Next, FIG. 2 shows a process of removing the in-situ soil excavated by the drive shaft with screw 1 that has reached the planned depth position. The drive shaft with screw 1 is rotated in the opposite direction to that at the time of penetration. Therefore, the screw 1'is wound in the normal direction of rotation, and the screw 1'is
The excavation soil pushes the excavated soil to the ground, and the excavated soil is smoothly discharged to the ground. The rotation is stopped when the amount of soil equivalent to the designed amount of stabilizer injected is discharged.

FIGS. 3A and 3B show the steps from the planned depth position of FIG. 2 until the stirring excavation shaft 2 and the drive shaft with screw 1 are pulled out to the ground. At this time, the drive shaft with screw 1 is rotated in the normal direction, the switching valve 5 opens the flow path to the injection hole 7 at a nearby position, and stirs and mixes while injecting the stabilizer upward. Thus, drive shaft with screw 1
Improving body 8 can be made in the mark of pulling out.

With the above process, the two partially improved bodies 8, 8 are completed, and thereafter, the same process is repeated over the entire area of the soft ground to carry out the improvement treatment. Note that FIG.
After the forced soil removal of No. 3, as shown in FIG. 4A, while stabilizing the drive shaft with screw 1 and lifting it up to a height equivalent to that of the stirring excavation shaft 2, the stabilizer is top-poured through the pouring hole 7 provided at the top of the stirring excavation shaft 2. After stirring and mixing, as shown in FIG. 4B, the rotating direction of the drive shaft with screw 1 is reversed and lowered, and the stabilizer is fed from the injection hole 7 provided at the tip of the stirring excavation shaft 2 to a predetermined depth. It is also possible to perform stirring and mixing while injecting at the tip, and then repeating the same process to form a root-hardening part. In this case, it is also necessary to consider the amount of forced earth removal in FIG.

[0017]

According to the ground improvement method and the ground improvement apparatus of the present invention, the amount of the stabilizer injected is designed only by the rotation of the drive shaft with the screw without the action of excavation penetration or lifting stirring. Since the amount of soil that can be removed is forcibly discharged forcibly, there is no adverse effect such as ground displacement on the surrounding ground, and pollution-free ground improvement is achieved.

[Brief description of drawings]

1A to 1C are explanatory views showing a process of advancing ground improvement from the ground surface to reaching a planned depth according to the present invention.

FIG. 2 is a front view showing a step of discharging in-situ soil excavated by the drive shaft with a screw that has reached a planned depth position according to the present invention.

FIG. 3A and FIG. 3B are explanatory views showing steps from the state where the planned depth is reached according to the present invention to the step of pulling out the screw-equipped drive shaft with the stirring excavation shaft to the ground.

4A and 4B are explanatory views showing a process of forming a root consolidation portion of soft ground.

[Explanation of symbols]

 3 stirring blade 4 excavation cutter 2 stirring excavation shaft 1'screw 1 drive shaft with screw 7 injection hole 5 switching valve

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[Procedure amendment]

[Submission date] November 13, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

[1] A, B is an explanatory view showing a step of advancing the soil improvement from the ground according to the invention the scheduled depth reached.

Claims (3)

[Claims] 1. A ground improvement method for excavating a soft ground, injecting a stabilizer into an in-situ excavated soil, stirring and mixing with the soil to improve the soft ground, and stirring agitation having a stirring blade and a drilling cutter. The upper end of the shaft is connected to the lower end of a screw-equipped drive shaft that has a screw that is spirally wound in the direction opposite to that of the normal rotation intrusion rotation, and the drive shaft with screw is rotated vertically in the normal rotation and penetrates into soft ground. The ground is excavated without penetrating and injecting stabilizer, and when the excavation reaches the planned depth, it corresponds to the amount of stabilizer injected designed by rotating the drive shaft with screw in reverse at that position. The amount of in-situ soil is forcibly discharged,
Then, the ground improvement method is characterized in that while the drive shaft with screw is rotated in the same direction as when it is penetrated, a stabilizer is injected from an injection hole in the upper part of the stirring excavation shaft, and the mixture is lifted while stirring and mixing. 2. A ground improvement device for excavating soft ground, injecting a stabilizer into excavated soil at an in-situ position, stirring and mixing with the soil to improve the soft ground, wherein a drive shaft with a screw or screws is provided. It is supported rotatably while maintaining a vertical posture with high precision, and a screw is attached to the same drive shaft with a screw in a spiral shape that is reverse-wound with respect to the forward rotation, and at the lower end of the drive shaft with a screw. , An excavation cutter for excavating soft ground is attached to the lower end, and a plurality of stirring blades with a plurality of stirring blades attached in a horizontal arrangement are connected in series thereabove, at the tip and the upper portion of the stirring excavation shaft. A ground improvement device, characterized in that it is provided with injection holes for injecting the stabilizer at the tip and at the top, respectively. 3. A switching valve is provided above the stirring blade according to claim 2 and above the stirring excavation shaft, the switching valve being capable of switching between tip injection and upper injection of the stabilizer. The ground improvement device.