JP3523051B2 - Ground improvement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a columnar reinforcing member in the ground to improve soft ground.

[0002]

2. Description of the Related Art Conventionally, a technique of burying concrete piles in the ground using a pile driver has been known, but this construction method requires large-scale equipment and causes large noise and vibration. There was a problem. Therefore, in recent years, a low-noise / low-vibration method has been widely adopted in which a columnar reinforcing body is formed by mixing the current soil with a solidifying material in a hole excavated in the ground.
This method is roughly classified into a wet method using cement milk as a solidifying material and a dry method using cement powder.

In the wet method, cement milk is injected while excavating the ground with an excavator, the present soil and cement milk are stirred and mixed to produce slurry-like improved soil, and the improved soil is solidified to form a columnar reinforcement. The body is constructed, and it has the advantage that a homogeneous and high-strength improved ground can be obtained. On the other hand, the dry method excavates the ground with a screw auger, adds cement powder to the excavated current soil to generate dry improved soil, and backfills the improved soil with a compaction to Since it is solidified with water to form a columnar reinforcing body, it has the advantage that it can be constructed with a relatively small-scale facility.

[0004]

However, according to the conventional wet method, it is necessary to use a large excavator and a high-performance milk pumping device, which results in high construction cost, poor maneuverability, and small land area. It was not suitable for improvement work. Moreover, according to the conventional dry method, uneven mixing of the cement powder and uneven rolling of the improved soil are liable to occur, resulting in uneven strength of the reinforcing body, resulting in insufficient strength, and large vibration during rolling of the improved soil. There was a problem such as occurrence.

Therefore, an object of the present invention is to provide a new ground improvement method by which a high-quality columnar reinforcing member can be easily formed with a small-scale facility.

[0006]

In order to solve the above problems, the ground improvement method of the present invention is to excavate the ground with a screw auger to form a vertical hole, and mix the cement-based solidifying material with the excavated current soil. To produce dry modified soil,
Backfill in the vertical hole and screw the backfilled dry improved soil
Stir further with an auger, and stir the dry modified soil on the surface.
The dry modified soil and the water or cement-containing water carried out were kneaded with a screw auger in a vertical hole to produce a slurry-like wet modified soil, and the wet modified soil was solidified to form a columnar reinforcement in the ground. It is characterized by being formed (Claim 1).

Further, in the production of the wet improved soil, the screw auger is raised stepwise so that the dry improved soil and water or cement-containing water can be uniformly mixed, and the kneading work is carried out in several steps. Is preferable (Claim 2).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In the improvement work of soft ground, first, the predetermined initial setup work is performed, such as setting the position of the construction site and determining the finished height of the reinforcing body. Next, as shown in FIG. 1, an excavating machine (not shown) such as a construction wheel truck, a mini-pile driver, and a truck auger is carried into the construction site, and the screw auger 1 is attached to the excavation machine and set at a construction site.

Next, as shown in FIG. 2, the screw auger 1 is normally rotated and the ground is excavated to form a vertical hole 2. At this time, the powdery cement-based solidifying material 4 is added to the existing soil 3, and the existing soil 3 and the solidifying material 4 are mixed by utilizing the rotation of the screw auger 1 to generate the dry improved soil 5. In addition,
As the solidifying material 4, an inorganic material containing cement as a main component and containing an additive such as an alumina-based mineral, gypsum or slag powder can be preferably used. The standard content of the solidifying material 4 with respect to the current soil 3 is 200 to 300 Kg / m3, but it can be arbitrarily changed according to the soil quality of the current soil 3 and the amount of groundwater.

When the vertical hole 2 has been excavated to the required depth in this way, the screw auger 1 is taken out from the vertical hole 2 as shown in FIG. 3, and then the dry improved soil 5 is backfilled in the vertical hole 2 as shown in FIG. . Then, as shown in FIG. 5, the dry improved soil 5 is stirred by the screw auger 1 to uniformly mix the existing soil and the cement-based solidifying material. And
As shown in FIG. 6, the dry improved soil 5 that has been stirred is carried to the surface of the ground, and the screw auger 1 is taken out from the vertical hole 2.

Next, as shown in FIG. 7, the screw auger 1 is rotated in the reverse direction, the dry improved soil 5 is carried into the vertical hole 2, and the cement milk 6 is fed into the small plant mixer 7.
To the vertical hole 2. Cement milk 6 is cement-containing water obtained by dissolving a cement-based solidifying material in water.
It is produced by the plant mixer 7 with a cement content of about 100 to 700 kg / m3. Then, by rotating the screw auger 1 in the reverse direction, the dry improved soil 5 and the cement milk 6 are kneaded and compacted in the vertical holes 2 to produce a slurry-like wet improved soil 8. At this time, the screw auger 1 is raised stepwise at a predetermined pitch so that the dry improved soil 5 and the cement milk 6 can be mixed evenly, and the kneading operation is performed in several steps. Thereafter, as shown in FIG. 8, the wet modified soil 8 is cured and solidified to form a columnar reinforcing body 9 having a required height in the ground.

According to the above-mentioned ground improvement method, the dry type improved soil 5 is transformed into the slurry type wet improved soil 8 to form the columnar reinforcing body 9, so that the following advantages can be obtained. (1) Compared with the conventional wet method, small excavators and plant mixers can be used, construction costs are low, maneuverability is excellent, and it is suitable for improvement work on narrow land. (2) Compared with the conventional dry method, the current soil and cement components can be evenly mixed, and a homogeneous and high-strength columnar reinforcement can be formed. (3) Unlike the conventional dry method, the improved soil in the form of slurry is compacted with a screw auger, so that it is possible to suppress the occurrence of vibration, and it is difficult to affect the adjacent land and the adjacent objects.

In the above embodiment, the cement-containing water is used to generate the wet improved soil, but water containing no cement may be added to the dry improved soil to produce the slurry wet improved soil. However, in this case, it is necessary to set the compounding amount of the cement-based solidifying material to be added to the existing soil to be larger than usual in the step of producing the dry improved soil. In addition, the present invention is not limited to the above embodiment,
It is also possible to appropriately change the materials used and the procedure without departing from the spirit of the present invention.

[0014]

As described in detail above, according to the ground improvement method of the present invention, it is possible to easily produce a high-quality columnar reinforcing body with a small-scale facility.

[Brief description of drawings]

FIG. 1 is an elevational view showing a screw auger setting step in a ground improvement method of the present invention.

FIG. 2 is an elevational view showing an excavation process and a dry improved soil generation process.

FIG. 3 is an elevational view showing a completed form of excavation.

FIG. 4 is an elevational view showing a backfilling process of dry improved soil.

FIG. 5 is an elevational view showing a stirring process of dry improved soil.

FIG. 6 is an elevational view showing a stirring completion mode.

FIG. 7 is an elevational view showing a step of producing wet improved soil.

FIG. 8 is an elevational view showing a completed form of a columnar reinforcing body.

[Explanation of symbols]

1 ・ ・ Screw auger 2 ・ ・ Vertical hole 3 ・ ・ Current soil 4 ・ ・ Cement-based solidifying material 5 ・ ・ Dry improved soil 6 ・
・ Cement milk, 7 ・ ・ Plant mixer, 8 ・ ・ Wet modified soil, 9 ・ ・ Columnar reinforcement.

Claims (2)

(57) [Claims] 1. The ground is excavated with a screw auger to form a vertical hole, and the excavated current soil is mixed with a cement-based solidifying material to generate dry improved soil, and the dry improved soil is backfilled in the vertical hole.
And then backfill the dry improved soil with a screw auger.
Agitated, and carry out the dry improved soil that has been agitated to the surface of the earth, and carry it out.
A soil improvement method for kneading dry improved soil and water or cement-containing water with a screw auger in a vertical hole to produce a wet improved soil in the form of a slurry, and solidifying the wet improved soil to form a columnar reinforcement in the ground. . 2. The ground improvement method according to claim 1, wherein when the wet improved soil is produced, the screw auger is raised stepwise in the vertical hole and the kneading operation is performed in several steps.