WO2019138538A1

WO2019138538A1 - Method for improving ground

Info

Publication number: WO2019138538A1
Application number: PCT/JP2018/000652
Authority: WO
Inventors: 下田政朗; 田中駿也; 島田聡之; 長澤浩司; なつみ北崎
Original assignee: 花王株式会社
Priority date: 2018-01-12
Filing date: 2018-01-12
Publication date: 2019-07-18
Also published as: JPWO2019138538A1; JP6487133B1

Abstract

The present invention is a method for improving ground, the method comprising introducing a hydraulic powder, at least one compound [hereinafter, referred to as compound (a)] selected from among sodium hydrogen carbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, and sodium pyrosulfite, and at least one compound [hereinafter, referred to as compound (b)] selected from among hydroxymethanesulfonic acid, salts thereof, hydroxymethanesulfinic acid, and salts thereof, into the soil, wherein the compound (a) is mixed with the compound (b) in a (compound (a))/(compound (b)) mass ratio of 50/50 to 99/1 and the compound (a) and compound (b) are incorporated in a total amount of 0.5-20.0 mass% with respect to the hydraulic powder.

Description

Ground improvement method

The present invention relates to a ground improvement method, a ground improvement body, an additive composition for ground improvement, a slurry for ground improvement, and a powder solidified material composition for ground improvement.

BACKGROUND ART As a method of improving the foundation to construct a structure, a method of improving ground in which a ground improvement column made of concrete or steel pipe is driven into the ground or injecting cement-based solidifying material such as cement milk while excavating the ground There is known a ground improvement method in which a column-shaped ground improvement formed by mixing excavated soil and the cement milk is formed directly in the ground.

In the case of ground improvement that modifies the ground by adding and mixing cement-based solidifying material with the soil, it is necessary to suppress the elution of environmental pollutants such as hexavalent chromium from the ground improvement body. In consideration of this, it is desirable to select an appropriate solidifying material, compounding ratio, additives and the like.
JP-A-2002-60751 discloses a cement composition containing a hexavalent chromium elution reducing agent containing a chelate compound and a cement.
JP-A-2012-201765 discloses a soil modifying composition which further comprises a reducing agent in a soil modifying composition for modifying an oil-contaminated soil having activated carbon and a cement-based solidifying agent.

Moreover, since the time which the intensity | strength and solidification of a ground improvement body require in the method of using the said cement milk is important, the technique for it is proposed conventionally variously.
JP-A-10-17864 discloses a ground containing a cement-based setting retarder and a cement-based hardening accelerator comprising one or more compounds selected from triethanolamine, diethanolamine and monoethanolamine. Improved formulations are disclosed.
JP-A-53-139633 discloses an accelerator for promoting the hardening of cement suitable for use in underground mining equipment, including triethanolamine, sodium carbonate and potassium carbonate.

SUMMARY OF THE INVENTION The present invention provides a method for improving the ground where the initial strength of the ground improvement body is high and elution of environmental contaminants such as hexavalent chromium from the ground improvement body is small.

The present invention relates to soil, hydraulic powder and at least one compound selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, and sodium pyrosulfite [hereinafter referred to as compound (a)] It is an improvement method of ground where a mixture of at least one compound selected from hydroxymethanesulfonic acid or a salt thereof and hydroxymethanesulfinic acid or a salt thereof (hereinafter referred to as a compound (b)) is mixed,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
It relates to the improvement method of ground.

Further, the present invention contains soil, hydraulic powder, compound (a) and compound (b), and the mass ratio of compound (a) / compound (b) is 1.0 or more and 99 or less. The present invention relates to a ground improvement body, wherein the total content of the compound (a) and the compound (b) relative to the content of the hydraulic powder is 0.5% by mass or more and 20.0% by mass or less.

Further, the present invention is a ground improvement body obtained by curing a mixture of a slurry containing water, hydraulic powder, a compound (a) and a compound (b), and the soil,
The slurry has a water / hydraulic powder mass ratio of 0.5 to 1.5,
The slurry has a compound (a) / compound (b) mass ratio of 1.0 or more and 99 or less,
In the slurry, the total content of the compound (a) and the compound (b) is 0.5% by mass or more and 20.0% by mass or less based on the content of the hydraulic powder,
The mixing amount of the slurry per 1 m ^{3 of} soil is 100 kg or more and 800 kg or less,
It relates to the ground improvement body.

Furthermore, the present invention contains the compound (a) and the compound (b), and the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less. About.

Moreover, this invention is a slurry for ground improvement materials containing water, hydraulic powder, a compound (a), and a compound (b), Comprising: The mass ratio of water / hydraulic powder is 0. 5 or more and 1.5 or less, the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less, and the total of the compound (a) and the compound (b) relative to the content of hydraulic powder The slurry for ground improvement whose content is 0.5 mass% or more and 20.0 mass% or less is related.

Further, the present invention contains a hydraulic powder, a compound (a) and a compound (b), and the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less, and water The present invention relates to a powder solidifying material composition for ground improvement, wherein the total content of the compound (a) and the compound (b) relative to the content of the hard powder is 0.5% by mass or more and 20.0% by mass or less.

ADVANTAGE OF THE INVENTION According to this invention, the initial stage strength of a ground improvement body is high, and the elution method of environmental pollutants, such as hexavalent chromium, from a ground improvement body is small, and the improvement method of a ground is provided.

It is a graph which shows the relationship between pH of imitation clay, and the relative intensity of a hardening object about a part of Example.

Mode for carrying out the invention (ground improvement method)
The soil improvement method of the present invention can target soils of various grounds.
In the ground improvement method of the present invention, preferably the soil is acidic soil. Here, the acidic soil refers to soil having a pH of 7 or less in the Geotechnical Engineering Society Standard (JGS0211-2009) “pH test method for soil suspension”.

In the ground improvement method of the present invention, preferably the soil is a soil containing allophane. In the soil containing allophane, the amount of allophane in the soil is 5.0% by mass or more, further 10.0% by mass or more, and 90.0% by mass or less, further 80.0% by mass based on the dry mass of the soil The following can be mentioned.
The ground improvement method of the present invention can also target acid soil containing allophane.

In the soil improvement method of the present invention, the soil is preferably at least one soil selected from an acid soil, a soil containing allophane, and an acid soil containing allophane.

The amount of allophane in the soil can be measured by the "acid-alkali alternate dissolution method" described in the following document (A).
Literature (A): Atsushi Kitagawa "Studies on the Determination of Allophane and Amorphous Inorganic Elements in Soil", Report of the Agricultural Technology Research Institute B No. 29, pages 1 to 48 (1977)

The soil improvement method of the present invention is effective even in acid soil, marine clay, and viscous soil containing allophane, ie, soil containing clay.
The ground improvement method of the present invention can also be used for the ground improvement of soil containing allophane and seawater, or marine cohesive soil containing allophane.

In the ground improvement method of the present invention, preferably, the soil is a soil selected from oxysol, Ultisol, and Andisol. These soils are soils classified based on the soil order of soil classification (Soil Taxonomy) by the USDA.

In the case of soil containing acidic soil or allophane, since the soil is rich in active aluminum components, the addition of the ground improvement additive composition of the present invention under the predetermined conditions makes the activity contained in these soils It is presumed that the strength of the ground improvement body is high because aluminum is efficiently converted to ettringite.

The hydraulic powder is a powder having physical properties that hardens by hydration reaction, and examples thereof include cement and gypsum. Preferably, cement is, for example, Portland cement such as ordinary Portland cement, belite cement, medium heat cement, early strength cement, ultra early strength cement, sulfate resistant cement, etc. In addition, blast furnace slag cement, fly ash cement, silica fume cement, etc. where powder having pozzolanic action such as blast furnace slag, fly ash, silica fume etc. and / or latent hydraulic property is added to cement etc., stone powder (calcium carbonate powder) etc. May be. The hydraulic powder is preferably a hydraulic powder containing portland cement.

In the present invention, the amount of hydraulic powder is the amount of powder having physical properties to be hardened by hydration reaction, but the hydraulic powder is a powder having pozzolanic action and a powder having latent hydraulic property. When the powder is selected from the body and stone powder (calcium carbonate powder), in the present invention, those amounts are also included in the amount of hydraulic powder.

The compound (a) is one or more compounds selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, and sodium pyrosulfite.
From the viewpoint of the strength of the ground improvement body which is a hardened body, the compound (a) is preferably at least one compound selected from sodium hydrogen carbonate and sodium sulfate.
The compound (a) is one or more selected from sodium thiosulfate, sodium dithionite, and sodium metabisulfite from the viewpoint of suppression of elution of environmental contaminants such as hexavalent chromium from the ground improvement body which is a hardened body Compounds are preferred.
In the present invention, two or more kinds of the compound (a) can be used. When two or more compounds (a) are used, one or more compounds selected from sodium hydrogencarbonate, sodium sulfate and sodium thiosulfate are preferably included in the compound (a), and sodium sulfate and sodium thiosulfate are preferably used. It is more preferable that the compound (a) contains one or more compounds selected from For example, when sodium sulfate and sodium thiosulfate are used as the compound (a), the sodium thiosulfate / sodium sulfate mass ratio is 0.10 or more, further 0.25 or more, and 9.0 or less, further 8.0 It can be selected from the following.

The compound (b) is at least one compound selected from hydroxymethanesulfonic acid or a salt thereof and hydroxymethanesulfinic acid or a salt thereof. Two or more types of compounds (a) can be used. The salts of hydroxymethanesulfonic acid and hydroxymethanesulfinic acid are preferably alkali metal salts and more preferably sodium salts. The hydroxymethanesulfonic acid and the salt of hydroxymethanesulfinic acid can be used in powder form of hydrate, respectively, but the amount is an anhydride equivalent.

In the ground improvement method of the present invention, from the viewpoint of strength development of the ground improvement body, the hydraulic powder and the hydraulic powder / soil mass ratio are preferably 0.01 or more, and more preferably soil. The mixing is preferably performed at 0.05 or more, more preferably 0.1 or more, and preferably 1.0 or less, more preferably 0.9 or less, and still more preferably 0.8 or less from the viewpoint of economy.

Moreover, in the improvement method of the ground of the present invention, the mass ratio of compound (a) / compound (b) is preferably 1.0 or more, preferably compound (a) and compound (b) from the viewpoint of strength development. Is mixed at 1.5 or more, more preferably 4.0 or more, and 99 or less, preferably 19 or less, more preferably 9.0 or less from the viewpoint of suppression of hexavalent chromium elution.

Moreover, in the improvement method of the ground according to the present invention, the compound (a) and the compound (b) in total are water from the viewpoint of strength development of the ground improvement body or suppression of hexavalent chromium elution from the ground improvement body. 0.5% by mass or more, preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and 20.0% by mass or less, preferably 10% by mass from the viewpoint of economy, with respect to the hard powder The content is mixed at not more than 0% by mass, more preferably not more than 8.0% by mass.

Among the compounds (b), hydroxymethanesulfonic acid or a salt thereof is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass, with respect to the hydraulic powder. % Or more, preferably 1.5% by mass or less, more preferably 1.0% by mass or less, still more preferably 0.8% by mass or less.
Among the compounds (b), hydroxymethanesulfinic acid or a salt thereof is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass, with respect to the hydraulic powder. % Or more, preferably 1.0% by mass or less, more preferably 0.8% by mass or less, still more preferably 0.5% by mass or less.
When using two or more compounds (b), it mixes so that the total mixing amount may become 0.01 mass% or more and 2.0 mass% or less with respect to hydraulic powder from these ranges.

The ground improvement method of the present invention can be applied to methods such as a surface layer improvement method, a deep layer improvement method, a steel pipe pile method, and a shield method. For example, the deep layer improvement method can be applied to the high pressure injection method, the TRD method, the SMW method, and the like.

The ground improvement method according to the present invention is a ground improvement method in which hydraulic powder, compound (a) and compound (b) are mixed in the soil,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
An improvement method of ground can be mentioned which reduces the amount of elution of hexavalent chromium from the ground improvement body.
Further, the present invention is a method for reducing the amount of elution of hexavalent chromium from a ground improvement body, comprising mixing hydraulic powder, compound (a) and compound (b) in soil,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
To provide a method of reducing the amount of elution of hexavalent chromium from a ground improvement body.
The matters described in the ground improvement method of the present invention can be appropriately applied to these methods.

In the ground improvement method of the present invention, it is preferable to mix the hydraulic powder, the compound (a) and the compound (b) with the soil by any of the following methods (I) and (II). From the viewpoint of the uniformity of the ground improvement body, the method (I) is preferred.
<Method (I)>
A slurry containing water, hydraulic powder, compound (a) and compound (b) and having a water / hydraulic powder mass ratio of 0.5 to 1.5 mixed with soil how to.
<Method (II)>
Method to mix hydraulic powder, compound (a), and compound (b) with soil with powder respectively.
Hereinafter, methods (I) and (II) will be described.

<Method (I)>
In the method (I), the mixing amount of the slurry per 1 m ^{3 of} soil is preferably 100 kg or more and 800 kg or less.
Moreover, in method (I), it is preferable that mass ratio of hydraulic powder / soil in a slurry is 0.01 or more and 1.0 or less.
In the method (I), either fresh water or seawater can be used as water used to prepare the slurry. At least a portion of the water of the slurry may be seawater.

A specific method of preparing a slurry by mixing water, hydraulic powder, compound (a) and compound (b) may be according to a known method of preparing a hydraulic composition such as cement milk.

In the method (I), the mass ratio of water / hydraulic powder in the slurry is 0.5 or more, preferably 0.6 or more, more preferably 0.8 or more from the viewpoint of the mixing property of cement milk and the ground. And, from the viewpoint of strength development of the ground improvement body, it is 1.5 or less, preferably 1.2 or less, more preferably 1.0 or less.

The specific method of injecting the slurry into the ground may be according to a known ground improvement method.
As a method of injecting the slurry into the ground, for example, a jet agitation method (one phase flow method, two phase flow method, three phase flow method) or a mechanical agitation method (CDM method etc.), and a continuous underground wall method (SMW method, TRD method etc.). Furthermore, in a system in which a compound (a) and a compound (b) are dry-blended in hydraulic powder, it can be used for shallow layer improvement using a powder mixing method DJM (Dry Jet Mixing) method or a stabilizer.

In the method (I), the amount of slurry mixed per 1 m ^{3 of} soil is 100 kg or more, preferably 150 kg or more, more preferably 200 kg or more, from the viewpoint of strength development of the ground improvement body; From the viewpoint of reducing the amount, it is 800 kg or less, preferably 700 kg or less, more preferably 600 kg or less.

The mixture of the slurry and the soil is solidified according to known ground improvement methods.

As a more specific example of the method (I), the ground improvement method having the following steps 1 to 3 can be mentioned.
<Step 1>
A step of mixing a water, a hydraulic powder, a compound (a) and a compound (b) to prepare a slurry, wherein the mass of water and hydraulic powder is the mass of the water / hydraulic powder. Mixing the compound (a) and the compound (b) at a mass ratio of compound (a) / compound (b) of 1.0 to 99, The hydraulic powder, the compound (a) and the compound (b) are mixed in a total proportion of the compound (a) and the compound (b) to the hydraulic powder of 0.5% by mass or more and 20.0% by mass or less Process <Process 2>
The step of injecting the slurry obtained in step 1 into the ground and mixing the slurry and the soil to obtain a mixture, wherein the mixing amount of the slurry per 1 m ^{3 of} soil is 100 kg or more and 800 kg or less, and water in the slurry Process in which the mass ratio of hard powder / soil is 0.01 or more and 1.0 or less <Process 3>
Solidifying the mixture of slurry and soil obtained in step 2

<Method (II)>
In the method (II), the hydraulic powder, the compound (a) and the compound (b) are each mixed with the soil in the form of powder. The powder of hydraulic powder, the powder of compound (a) and the powder of compound (b) may be separately mixed with the soil, or mixed with the soil as a powder mixture in which both are mixed beforehand. It is also good. In the powder mixture in which both are mixed in advance, the total content of the compound (a) and the compound (b) relative to the content of the hydraulic powder is preferably 0.5% by mass or more and 20.0% by mass or less This is a powder / solidifier composition for ground improvement of the present invention. In the method (II), it is preferable to mix the hydraulic powder with the soil at a mass ratio of hydraulic powder / soil of 0.01 to 1.0. Moreover, it is preferable that the said powder mixture is mixed with soil, and mass ratio of hydraulic powder / soil is 0.01 or more and 1.0 or less.

In method (II), for example, after soil treatment such as spreading or scraping, soil is treated with hydraulic powder, powder compound (a) and powder compound (b). It can be carried out in a compacting mode in which the soil, hydraulic powder, compound (a) and compound (b) are mixed by means of a mixing machine such as a stabilizer and the like. In addition, method (II) is carried out by spreading the external soil on the ground to be improved, and then spreading the soil, and then the hydraulic powder and powder compound (a) and powder compound (b) are applied to this soil And so-called in-situ mixing method. In addition, method (II) is to ground the soil, hydraulic powder, powder compound (a) and powder compound (b) in advance in an earth removal site etc. and then try to improve this So-called pre-mixing method. In any of the methods, mixing of the soil and the hydraulic powder and the powder compound (a) with the powder compound (b) can be carried out by a known method.

As a ground improvement method of the present invention, it is a ground improvement method in which a compound (a) and a compound (b) are mixed with acidic soil,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
The improvement method of the ground is mentioned.

According to the ground improvement method of the present invention, it is a ground improvement method in which a compound (a) and a compound (b) are mixed with soil containing allophane,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
The improvement method of the ground is mentioned.

The ground improvement method according to the present invention is a ground improvement method in which a compound (a) and a compound (b) are mixed with an acidic soil containing allophane,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
The improvement method of the ground is mentioned.

The ground improvement method according to the present invention is a ground improvement method in which a compound (a) and a compound (b) are mixed with soil.
The soil is a soil containing acidic soil and / or allophane,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
The improvement method of the ground is mentioned.

[Ground improvement body]
The ground improvement body of the present invention contains soil, hydraulic powder, compound (a) and compound (b), and the mass ratio of compound (a) / compound (b) is 1.0 or more and 99 It is the following, It is a ground improvement object whose sum total content of a compound (a) and a compound (b) to content of hydraulic powder is 0.5 mass% or more and 20.0 mass% or less. This ground improvement body may be a ground improvement body formed by curing a slurry containing a predetermined amount of soil, water, hydraulic powder, compound (a) and compound (b). The ground improvement body preferably has a hydraulic powder / soil mass ratio of 0.01 or more and 1.0 or less.
Accordingly, the present invention is a ground improvement body obtained by curing a mixture of a slurry containing water, hydraulic powder, compound (a) and compound (b) and soil,
The slurry has a water / hydraulic powder mass ratio of 0.5 to 1.5,
The slurry has a compound (a) / compound (b) mass ratio of 1.0 or more and 99 or less,
In the slurry, the total content of the compound (a) and the compound (b) is 0.5% by mass or more and 20.0% by mass or less based on the content of the hydraulic powder,
The mixing amount of the slurry per 1 m ^{3 of} soil is 100 kg or more and 800 kg or less,
A ground improvement body will also be provided. The mixture preferably has a hydraulic powder / soil mass ratio of 0.01 or more and 1.0 or less.

The ground improvement body of the present invention may be a ground improvement body formed by mixing soil and the powder solidifying material composition for ground improvement of the present invention described later.
The ground improvement body of the present invention may be a ground improvement body formed by mixing soil and the ground improvement slurry of the present invention described later.

The matters described in the ground improvement method of the present invention can be appropriately applied to the ground improvement body of the present invention.
In the ground improvement body of the present invention, concrete examples such as hydraulic powder, compound (a), compound (b), soil, preferred embodiments, and quantitative specifications such as respective mass ratios are also improvement of the ground of the present invention It is the same as the construction method. For example, the soil may be at least one soil selected from acidic soil, soil containing allophane, and acidic soil containing allophane.

[Additive composition for ground improvement]
The ground improvement additive composition of the present invention contains the compound (a) and the compound (b), and the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less. It is an additive composition for improvement. The ground improvement additive composition of the present invention may consist of the compound (a) and the compound (b). Two or more types of compound (a) and compound (b) can be used, respectively.

Such a ground improvement additive composition is an additive composition used for a ground improvement material to be mixed with soil for ground improvement, for example, a hydraulic composition such as cement milk. By using the additive composition for ground improvement of the present invention, it is possible to suppress the elution of environmental pollutants such as hexavalent chromium from the ground improvement body. That is, the present invention contains compound (a) and compound (b), and the mass ratio of compound (a) / compound (b) is 1.0 or more and 99 or less. An inhibitor composition can be provided.
The amount of the additive composition for ground improvement of the present invention can be set in consideration of the type of ground improvement material, the type of soil (ground), etc. However, the ground improvement method of the present invention and the ground improvement body of the present invention It is preferable that the amount is as stated in The matters described in the ground improvement method of the present invention can be appropriately applied to the ground improvement additive composition of the present invention.
The ground improvement additive composition of the present invention may be for acidic soil. The soil improvement additive composition of the present invention may be for soil containing allophane, and further for acidic soil containing allophane.

[Slurry for ground improvement]
The slurry for ground improvement according to the present invention is a slurry for ground improvement material containing water, hydraulic powder, compound (a) and compound (b), and the mass ratio of water / hydraulic powder Is 0.5 or more and 1.5 or less, the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less, and the compound (a) and the compound (b) with respect to the content of hydraulic powder The slurry for ground improvement whose total content of (a) is 0.5 mass% or more and 20.0 mass% or less. The slurry for ground improvement of the present invention is a slurry for ground improvement material formed by mixing water, hydraulic powder and an additive composition for ground improvement, and the mass ratio of water / hydraulic powder is It is 0.5 or more and 1.5 or less, the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less, and the compound (a) and the compound (b) with respect to the content of hydraulic powder The ground improvement slurry may have a total content of 0.5% by mass or more and 20.0% by mass or less. The slurry for ground improvement according to the present invention is preferably used in the method for improving ground according to the present invention. The matters described in the ground improvement method, ground improvement body, and ground improvement additive composition of the present invention can be applied to the ground improvement slurry of the present invention as appropriate. The ground improvement slurry of the present invention may be for acidic soil. In addition, the slurry for ground improvement of the present invention may be for soil containing allophane, and further for acidic soil containing allophane.

The slurry for ground improvement of the present invention is a slurry for ground improvement mixed with soil for ground improvement, for example, a hydraulic composition such as cement milk. By using the slurry for ground improvement of the present invention, it is possible to suppress the elution of environmental pollutants from the ground improvement body in the method for improving ground.
The usage amount of the slurry for ground improvement of the present invention can be set in consideration of the composition of the slurry for ground improvement, the type of soil (ground) and the like, but it is described in the ground improvement method of the present invention and the ground improvement body of the present invention It is preferable that the amount be different.
Soil improvement slurry of the present invention, soil 1 m ³ per 100kg or more, is preferably at least 150 kg, more preferably 200kg or more, and, 800 kg or less, preferably used is 700kg or less, more preferably mixed with soil below 600kg Is preferred. In the slurry for ground improvement of the present invention, the hydraulic powder / soil in the slurry has a hydraulic powder / soil mass ratio of 0.01 or more, preferably 0.05 or more, more preferably 0. It is preferably 1 or more and 1.0 or less, preferably 0.9 or less, more preferably 0.8 or less and used in combination with the soil.

[Powder-solidified material composition for ground improvement]
The powder solidifying material composition for ground improvement of the present invention contains hydraulic powder, compound (a) and compound (b), and the mass ratio of compound (a) to compound (b) is 1.0. Powdered solidified material for ground improvement, having a total content of the compound (a) and the compound (b) of not less than 99 and not more than 0.5 mass% and not more than 20.0 mass% with respect to the content of hydraulic powder It is a composition. The powder solidifying material composition for ground improvement of the present invention contains a hydraulic powder and the additive composition for ground improvement of the present invention, and the compound (a) and the compound (b (b) relative to the content of the hydraulic powder The powder solidifying material composition for ground improvement may have a total content of 0.5% by mass or more and 20.0% by mass or less. The powder solidifying material composition for ground improvement of the present invention is preferably used for the ground improvement method of the present invention. The matters described in the ground improvement method, the ground improvement body, the ground improvement additive composition, and the ground improvement slurry according to the present invention can be appropriately applied to the ground solidified powder solidified material composition according to the present invention. The powder-solidifier composition for ground improvement of the present invention may be for acidic soil. Further, the powder / solidifier composition for ground improvement of the present invention may be for soil containing allophane, and further for acidic soil containing allophane.

The powdery solidifying material composition for ground improvement of the present invention is a powdery solidifying material for ground improvement mixed with soil for ground improvement. By using the powder solidifying material composition for ground improvement of the present invention, elution of environmental pollutants from the ground improvement body can be suppressed.
The use amount of the powder solidifying material composition for ground improvement of the present invention can be set in consideration of the composition of the composition, the type of soil (ground), etc., but the method for improving the ground of the present invention or the ground improvement of the present invention It is preferable to be the amount stated in the body.
The powder solidifying material composition for ground improvement of the present invention has a hydraulic powder / soil mass ratio of 0.01 or more, preferably 0.05 or more, more preferably 0.1 or more, and 1.0 or less, It is preferably 0.9 or less, more preferably 0.8 or less, which is used by mixing with the soil.

Example <Soil cement slurry>
Soil cement slurries (I) and (II) were prepared using the components in Tables 1 and 2 and used in the following Examples and Comparative Examples. In addition, when producing soil cement slurry, the additives in Tables 3 to 12 were added to the water (mixing water) used for preparation of cement slurry so that the amount of addition to the powder would be as shown in Tables 3 to 12. Used. The pH of the simulated clay in Table 1 (1) was 6.4 as measured by the above method. In addition, the local soil in Table 2 (2) is a volcanic ash cohesive soil (Kanto loam), and the pH of the local soil was 6.2 as measured by the above method.

The powder used the following thing by the combination of the table of Table 3 or subsequent ones.
・ NC: Ordinary portland cement, manufactured by Sumitomo Osaka Cement Co., Ltd., specific gravity 3.15
・ SL: Blast furnace slag, Nippon Steel Sumikin Cement Co., Ltd. spirits 4000, specific gravity 2.91
Anhydrite: manufactured by Kokusai Shoji Co., Ltd.

Example 1 and Comparative Example 1
(1) Preparation of ground improvement body Soil cement slurry (I) of Table 1 was filled with the formwork (diameter 50 mm x height 100 mm). The filling was performed by filling the two layers for 15 seconds with a table vibrator. Four specimens were prepared. In addition, as soil cement slurry (I), the injection amount of the cement slurry per 1 m ^{3 of} soil used 400 kg.

(2) Measurement of the amount of elution of hexavalent chromium The mold filled with soil cement slurry (I) was allowed to stand at 20 ± 2 ° C., and after 7 days, it was demolded to obtain a cured product. The cured product was ground, passed through a 2 mm sieve, and the sieved material was allowed to air dry for 24 hours. 4.0 g of air-dried matter was collected in a 50 ml centrifuge tube, 40.0 g of distilled water adjusted to pH 6.0 was added, and the mixture was shaken for 6 hours with a tube rotator (50 rpm) manufactured by As One Corporation. After shaking, it was centrifuged at 3000 rpm for 3 minutes. The hexavalent chromium concentration in the supernatant was analyzed with a digital spectrophotometer "HI723" manufactured by Hannah Instruments Japan. The results are shown in Table 3.

(3) Measurement of 7-day strength The strength of the hardened body (ground improvement body) obtained in (2) was measured by a uniaxial compression tester. The results are shown in Table 3.

In Table 3, the addition amount is% by mass based on the powder, and (a) + (b) shows the total addition amount (% by mass) of the compound (a) and the compound (b) relative to the powder (the same applies hereinafter) ).

Example 2 and Comparative Example 2
A cured product was prepared in the same manner as in Example 1 except that the types and addition amounts of the additives were as shown in Table 4, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product were measured. The results are shown in Table 4. Table 4 also shows the results of a part of Example 1 and a part of Comparative Example 1.

Example 3 and Comparative Example 3
As in Example 1, however, the types and amounts of additives were as shown in Table 5, and the allophane content in the simulated clay used for preparation of soil cement slurry (I) was as shown in Table 5 ( The total amount of allophane and the amount of clay is kept constant to adjust the amount of the both), the cured product is prepared, and the amount of hexavalent chromium dissolved from the cured product and the strength of the cured product are measured. The results are shown in Table 5. Table 5 also shows the results of a part of Example 1 and a part of Comparative Example 1.

Example 4 and Comparative Example 4
A cured product is prepared in the same manner as in Example 1 except that the types of powder, and the types and addition amounts of additives are as shown in Table 6, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product are It was measured. The results are shown in Table 6.

Example 5 and Comparative Example 5
In the same manner as in Example 1, except that the amount of cement slurry injected in soil cement slurry (I), the type of powder, and the type and amount of additives are as shown in Table 7, a cured product is prepared and cured. The amount of leached hexavalent chromium from the mixture and the strength of the cured product were measured. The results are shown in Table 7.

Example 6 and Comparative Example 6
In the same manner as in Example 1, except that the amount of cement slurry injected in soil cement slurry (I), the type of powder, and the type and amount of additives are as shown in Table 8, a cured product is prepared and cured. The amount of leached hexavalent chromium from the mixture and the strength of the cured product were measured. The results are shown in Table 8.

Example 7 and Comparative Example 7
A cured product is prepared in the same manner as in Example 1 except that the types of powder and the types and addition amounts of additives are as shown in Table 9, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product are obtained. It was measured. The results are shown in Table 9.

Example 8 and Comparative Example 8
In the same manner as Example 1, but using the soil cement slurry (II) of Table 2 as the soil cement slurry, with the type of powder, and the type and addition amount of additives as shown in Table 10, the cured product is It was prepared, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product were measured. The results are shown in Table 10.

Example 9 and Comparative Example 9
As in Example 1, except that the soil cement slurry (II) in Table 2 is used as the soil cement slurry, and the type of powder, and the type and amount of additive added as shown in Table 11, the cured product is It was prepared, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product were measured. The results are shown in Table 11.

Example 10 and Comparative Example 10
In the same manner as Example 1, but using the soil cement slurry (II) of Table 2 as the soil cement slurry, with the type of powder, and the type and amount of additive added as shown in Table 12, the cured product was It was prepared, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product were measured. The results are shown in Table 12.

Examples 11 to 15 and Comparative Examples 11 to 15
As in Example 1, except that the pH of the simulated clay used to prepare the soil cement slurry (I) is changed with acetic acid and / or sodium hydroxide as shown in Tables 13 to 17 to prepare a cured product and cure it. The amount of hexavalent chromium dissolved from the body and the strength of the cured body were measured. The results are shown in Tables 13-17.
Although some examples and comparative examples were carried out with the same configuration as the previous example and comparative example, the test date is different (the cement lot, the time taken to prepare the simulated clay, etc. are different) , Have different measurement values. Relative values were compared on the basis of a comparative example on the same test day.

The results of Tables 13 to 17 are extracted, and the relationship between pH and strength (relative value) of the simulated clay is shown in the graph of FIG. The graph of FIG. 1 is based on the result of the sum total of 3.00 mass% of a compound (a) and a compound (b). It can be seen from FIG. 1 that the present invention is more effective and higher in relative strength when the pH of the simulated clay is low, that is, when using an acid soil.

Example 16 and Comparative Example 16
The soil cement slurry (III) in Table 18 below is used as the soil cement slurry as in Example 1, and the standing temperature of the mold filled with the soil cement slurry (III) is set to 28 to 32 ° C. A cured product was prepared, and the amount of eluted hexavalent chromium from the cured product and the strength of the cured product were measured. The results are shown in Table 19.

Claims

In the soil, hydraulic powder and at least one compound selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, and sodium pyrosulfite [hereinafter referred to as compound (a)], hydroxymethane A ground improvement method of mixing a sulfonic acid or a salt thereof and one or more compounds (hereinafter referred to as a compound (b)) selected from hydroxymethanesulfinic acid or a salt thereof,
The compound (a) and the compound (b) are mixed at a mass ratio of compound (a) / compound (b) of 1.0 or more and 99 or less,
The compound (a) and the compound (b) are mixed in total at 0.5% by mass or more and 20.0% by mass or less with respect to the hydraulic powder.
Ground improvement method.
The ground improvement method according to claim 1, wherein the compound (a) is one or more compounds selected from sodium hydrogen carbonate, sodium sulfate and sodium thiosulfate.
The improvement method of the ground according to claim 1 or 2, wherein the soil is an acidic soil.
The ground improvement method according to any one of claims 1 to 3, wherein the soil is a soil containing allophane.
The soil improvement method according to claim 4, wherein the amount of allophane in the soil is 5.0% by mass or more and 90.0% by mass or less.
The soil improvement method according to any one of claims 1 to 5, wherein the soil is a soil selected from oxysol, altisol, and andysol.
The ground improvement method according to any one of claims 1 to 6, wherein the compound (a) and the compound (b) are mixed in total at 1% by mass to 8% by mass with respect to the hydraulic powder. .
The ground improvement method according to any one of claims 1 to 7, wherein a mass ratio of the compound (a) to the compound (b) is 4 or more and 20 or less.
The ground according to any one of claims 1 to 8, wherein the hydraulic powder, the compound (a) and the compound (b) are mixed with the soil by any of the following methods (I) and (II): Improvement method.
<Method (I)>
A slurry containing water, hydraulic powder, compound (a) and compound (b) and having a water / hydraulic powder mass ratio of 0.5 to 1.5 mixed with soil how to.
<Method (II)>
Method to mix hydraulic powder, compound (a), and compound (b) with soil with powder respectively.
The method of mixing the hydraulic powder, the compound (a) and the compound (b) with the soil is the method of the above (I), and the mixing amount of the slurry per 1 m 3 of soil is 100 kg or more and 800 kg or less. The ground improvement method according to claim 9, wherein a mass ratio of hydraulic powder / soil in the slurry is 0.01 or more and 1.0 or less.
The method according to (9), wherein the method of mixing the hydraulic powder, the compound (a) and the compound (b) with the soil is the method of the above (I), and at least a part of the water is seawater. Ground improvement method.
The method of mixing the hydraulic powder, the compound (a) and the compound (b) with the soil is the method of the above (II), and the hydraulic powder has a mass ratio of hydraulic powder / soil of 0 The soil improvement method according to claim 9, wherein the soil is mixed with the soil at a temperature of not less than 01 and not more than 1.0.
The ground improvement method according to any one of claims 1 to 12, wherein the hydraulic powder comprises portland cement.
The ground improvement method according to any one of claims 1 to 13, wherein the hydraulic powder is mixed with the soil at a mass ratio of hydraulic powder / soil of 0.01 to 1.0.
One or more compounds selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, sodium pyrosulfite [hereinafter referred to as compound (a)], hydroxymethanesulfonic acid or a salt thereof, and hydroxymethanesulfinic acid Or one or more compounds selected from the salts thereof [hereinafter referred to as compound (b)], and the mass ratio of compound (a) / compound (b) is 1.0 or more and 99 or less, for ground improvement Additive composition.
A total content of the compound (a) and the compound (b) with respect to the content of the hydraulic powder is 0.5 mass containing the hydraulic powder and the additive composition for ground improvement according to claim 15 Powder solidified material composition for ground improvement which is% or more and 20.0 mass% or less.
Water, hydraulic powder, and one or more compounds selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, sodium pyrosulfite [hereinafter referred to as compound (a)], hydroxymethane sulfone It is a slurry for ground improvement materials containing an acid or its salt, and 1 or more types of compounds chosen from the hydroxy methane sulfinic acid or its salt [Hereinafter, it is called a compound (b)], and mass of water / hydraulic powder Ratio is 0.5 or more and 1.5 or less, the mass ratio of the compound (a) / the compound (b) is 1.0 or more and 99 or less, and the compound (a) and the compound ( A slurry for ground improvement, wherein the total content of b) is 0.5% by mass or more and 20.0% by mass or less.
Soil, hydraulic powder, and one or more compounds selected from sodium hydrogencarbonate, sodium sulfate, sodium thiosulfate, sodium dithionite, sodium pyrosulfite [hereinafter referred to as compound (a)], hydroxymethane sulfone And one or more compounds selected from an acid or a salt thereof and hydroxymethanesulfinic acid or a salt thereof [hereinafter referred to as a compound (b)], and the mass ratio of the compound (a) / the compound (b) is 1.0 The ground improvement body which is 99 or less and whose total content of a compound (a) and a compound (b) is 0.5 mass% or more and 20.0 mass% or less with respect to content of hydraulic powder.
The ground improvement body of Claim 18 which mixes soil and the powder-solidification material composition for ground improvement of Claim 16.
The ground improvement body of Claim 18 which mixes a soil and the slurry for ground improvement of Claim 17.