JPH06128932A - Poor subsoil improvement method - Google Patents

Abstract

PURPOSE:To organically combine a sand drain method with a deep stirring and mixing method of soil stabilization to promote the effect of improvement of the poor subsoil. CONSTITUTION:After a large number of sand piles are developed at a specific pitch in a poor subsoil to carry out a primary soil improvement by a drain method, sand of sand piles, ground soil and hardener are stirred and mixed to a secondary soil improvement is made by additional hardener. Under such a method, a construction period is reduced in comparison with a drain method only, and a consumed amount of the hardener is reduced in comparison with a a hardener addition method only. The sand of the sandpiles is used for aggregate in the secondary soil improvement, so that effective soil improvement is rationally executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved construction method for cohesive soil-based soft ground (including peat-based soft ground).

[0002]

2. Description of the Related Art There are two methods for improving cohesive soil-based soft ground: a vertical drain method typified by a sand drain method and a deep soil stabilization treatment method (deep agitation mixing treatment method) by adding various solidifying materials. However, there is no known conventional example in which the above-mentioned construction methods having different characteristics are organically combined to enhance the improvement effect.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new soft ground improvement method in which the sand drain method and the deep agitation mixing treatment method are organically combined to rationally enhance the improvement effect.

[0004]

According to the first aspect of the present invention, the soft ground improvement method is characterized in that a large number of sand piles are formed on the soft ground at a predetermined pitch to improve the first ground by the drainage method. After that, the sand of the sand pile, the ground soil, and the solidifying material are stirred and mixed to perform the secondary ground improvement by adding the solidifying material, and the soft ground according to claim 2 of the present invention. The structural feature of the improved construction method is that, in the soft ground improvement construction method according to claim 1, the sand of the sand pile and the ground soil around the sand pile are passed through the rotary shaft of a single-axis stirring and mixing processor in the center of the sand pile. The point is to stir and mix with the solidifying material.

As is clear from the above characteristic points of the structure,
In the soft ground improvement method of the present invention, the first ground improvement is carried out for a while, and then the second ground improvement is performed. Moreover, in the second ground treatment, the first ground improvement is performed. The sand of the sand pile used for the drainage is mixed with the ground soil and the solidifying material by stirring to effectively improve the soft ground.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, first, a large number of sand piles are formed on a soft ground at a predetermined pitch to perform a first ground improvement by a drainage method. Sand sand is used as a constituent material of the sand pile. In addition to the sand, slag that can be used for both the drain material and the aggregate can be used.

There is no particular limitation on the method for forming the sand pile, and any known method using a casing may be used.

When performing the first ground improvement, it is optional whether or not preload is applied to promote drainage.

After the first ground improvement, the sand of the sand pile, the ground soil, and the solidifying material are mixed by stirring to perform the second ground improvement by adding the solidifying material.
Using a conventionally known single-screw type or multi-screw type agitation / mixing processor in which agitating blades are radially provided on the lower end of the rotary shaft to supply the solidifying material to the rotating region of the agitating blades. Also, cement or the like is used as the solidifying material.

A large number of solidified piles are formed in the ground by the above-mentioned stirring and mixing treatment. Since sand of sand pile is mixed as aggregate in the solidified pile, the strength thereof is the same as that of the conventional deep layer stirring and mixing. This is larger than the case of the solidified pile formed by the processing method, and if the strength is the same, the solidified material can be saved.

In the above-mentioned second ground improvement, when the sand of the sand pile and the ground soil and the solidifying material around the sand pile are stirred and mixed through the rotary shaft of the single-axis type stirring and mixing processor in the center of the sand pile, Regardless of the pitch of the sand pile,
The sand of the sand pile can be mixed into the solidified pile without waste and relatively uniformly.

The above-mentioned stirring and mixing treatment may be carried out over the entire length of the sand pile, or may be carried out partially such as in the upper part or the middle part.

[0013]

The soft ground improvement method of the present invention is as described above. Therefore, after the ground is improved by the first drainage method, the ground is improved by adding the second solidifying material. As a result, the construction period can be shortened compared to the case of only the drainage method, and the amount of the solidifying material used can be smaller than that of the case of only adding the solidifying material. By using the sand of the used sand pile as an aggregate in the second ground improvement, the first ground improvement and the second ground improvement are organically linked,
A peculiar effect that ground improvement is reasonably effective can be expected.

Claims (2)

[Claims] 1. A large number of sand piles are formed on a soft ground at a predetermined pitch to carry out a first ground improvement by a drainage method, and then sand of the sand pile, ground soil and a solidifying material are mixed by stirring. The second method is to improve the soft ground by adding a solidifying material. 2. The sand of the sand pile, the ground soil around the sand pile, and the solidifying material are agitated and mixed by passing through the rotating shaft of a single-axis type agitation and mixing processor at the center of the sand pile.
The soft ground improvement method described.