JP2021127392A - Ground improvement method - Google Patents

Abstract

To provide a ground improvement method whereby it becomes possible to improve the compressive strength of soil cement even when a soil comprising an acidic soil containing an organic substance such as humic acid, fulvic acid, humin and bitumen is used.SOLUTION: A ground improvement method comprises mixing a soil having an organic substance fraction of 30% or more as determined by an ignition loss method with a hydraulic powder, water and a component (A) mentioned below, wherein the component (A) is mixed in an amount of 0.5 to 10 mass% relative to the amount of the hydraulic powder. The component (A): at least one compound which serves as a supply source capable of releasing an aluminum ion and/or a calcium ion and a chloride ion in water (excluding the hydraulic powder).SELECTED DRAWING: None

Description

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

As a method of improving the ground of the foundation for constructing a building, there is a ground improvement method in which a concrete or steel pipe ground improvement column is driven into the ground, or a cement-based solidifying material such as cement milk is injected while excavating the ground to excavate soil. A ground improvement method is known in which a column-shaped ground improvement body formed by mixing and the cement milk is directly formed in the ground.

In ground improvement, which modifies the ground by adding and mixing cement-based solidifying material with soil, appropriate solidifying material, compounding ratio, additives, etc. are taken into consideration, such as the nature of the soil to be mixed and the type of construction method for ground improvement. It is desirable to select. In particular, when the soil to be mixed is acidic soil containing a large amount of organic substances such as humic acid, the hydration reaction of the cement is hindered by the adsorption of the organic substances on the cement surface, so that the desired strength can be obtained even if a cement solidifying material is used. However, it may be difficult to improve the ground.

Patent Document 1 describes 20 to 30 parts by weight of sodium chloride and 20 to 30 parts by weight of magnesium chloride with respect to the Portorand cement sprayed on the soil in the soil improvement method of arranging Portorand cement on the soil and solidifying the soil. An additive containing 35 to 45 parts by weight of potassium chloride, 5 to 15 parts by weight of calcium chloride and 4 to 8 parts by weight of citric acid as main components is added to 100 parts by weight of the Portoland cement in the state of an aqueous solution. A soil improvement method is disclosed, in which the solid content of the agent is added so as to be 0.1 to 1 part by weight, the soil is stirred and mixed together, and the soil is pressurized from above to solidify the soil. ..
In Patent Document 2, 20 to 40 parts by weight of calcium chloride and 30 to 50 parts by weight of magnesium chloride are described in the soil generated at the site excavated from the ground to be constructed, with respect to 1000 parts by weight of wood chip material, cement and water. A construction method characterized by adding and mixing an aqueous hardener containing 15 to 30 parts by weight of aluminum chloride and 0.1 to 3 parts by weight of cobalt chloride and then supplementing this mixture to the excavated ground to be constructed is disclosed. Has been done.

Japanese Unexamined Patent Publication No. 60-229984 Japanese Unexamined Patent Publication No. 2006-169065

The present invention provides a ground improvement method capable of increasing the compressive strength of soil cement even when using acidic soil containing organic substances such as humic acid, fulvic acid, humin, and bitumen.

The present invention is a ground improvement method in which a water-hard powder, water, and the following component (A) are mixed in soil having an organic mass of 30% or more required by the ignition loss method. The present invention relates to a ground improvement method in which the component (A) is mixed so as to be 0.5% by mass or more and 10% by mass or less with respect to the water-hard powder.
Component (A): One or more compounds serving as a source for releasing aluminum ions and / or calcium ions and chloride ions in water (excluding water-hard powder)

The present invention is an additive for ground improvement containing the component (A), and is used for soil improvement in which the amount of organic matter required by the ignition loss method is 30% or more. Regarding additive composition.

Further, the present invention is a ground improvement body containing soil, a water-hard powder, water, and the above-mentioned component (A) having an organic content of 30% or more required by the ignition loss method, wherein the component (A) is used. The present invention relates to a ground improvement body containing 0.5% by mass or more and 10% by mass or less with respect to the water-hard powder.

According to the present invention, there is provided a ground improvement method capable of increasing the compressive strength of soil cement even when using acidic soil containing organic substances such as humic acid, fulvic acid, humin, and bitumen.

[Ground improvement method]
The ground improvement method of the present invention is effective even if the soil has an organic matter content of 30% or more required by the ignition loss method.
Further, in the ground improvement method of the present invention, the soil is soil in which the organic content required by the ignition loss method is 30% or more, and the soil suspension is measured by the method specified by the Japanese Geotechnical Society Standard JGS0211-2009. The effect is exhibited even in soil where the pH of the turbid liquid is 6 or less.

The mechanism by which the present invention exerts its effect is not clear, but it is presumed as follows. It is known that supplying aluminum ions and / or calcium ions to the soil in addition to the hydraulic powder promotes the hydration reaction of the hydraulic powder and contributes to the improvement of the strength of soil cement. Excessive addition of ions and / or calcium ions causes abnormal hydration (rapid hydration progresses and pseudo-coagulation) and causes a decrease in strength. Therefore, usually, a large amount of aluminum ion and / or calcium ion was not added. However, the present invention targets soils of acidic soil containing organic substances such as humic acid, fulvic acid, humin, and bitumen, and a large amount of aluminum ions and / or calcium ions are added to the soil in addition to the water-hard powder. When supplied to, a large amount of organic substances that inhibit the hydration reaction of the water-hard powder form a complex with the supplied aluminum ions and / or calcium ions, which prevents the organic substances from adsorbing on the cement surface and alleviates the hydration inhibition. , The present inventor has found that it is possible to improve the strength of soil cement. At the same time, the present inventor has also found that the presence of chloride ions has the effect of further promoting the effect.

The soil has an organic content of 30% or more, preferably 35% or more, more preferably 40% or more, and preferably 90% or less, more preferably 80% or less, which is determined by the ignition loss method. Here, the ignition loss method is a method specified in the Japanese engineering standard JIS A1226: 2009.
Examples of the organic matter contained in the soil include one or more kinds of organic matter selected from humic acid, humin, bitumen, and fulvic acid.

The soil is an acidic soil having a pH of the soil suspension measured by the method specified by the Japanese Geotechnical Society Standard JGS0211-2009, preferably 6 or less, more preferably 5.5 or less, still more preferably 5 or less. good.

The hydraulic powder used in the present invention is a powder having a physical property that is cured by a hydration reaction, and examples thereof include cement (however, the component (B) described later is excluded). From the viewpoint of improving the strength of soil cement containing acidic soil, the water-hard powder is preferably cement, for example, Portland cement such as ordinary Portland cement, belite cement, moderate heat cement, fast-strength cement, ultra-fast-strength cement, etc. Cement such as sulfate-resistant cement. The hydraulic powder is a blast furnace slag cement in which blast furnace slag, steelmaking slag, fly ash, silica fume and other pozzolanic and / or latent hydraulic powders and stone powder (calcium carbonate powder) are added to cement and the like. , Steelmaking slag cement, fly ash cement, silica fume cement and the like may be used. The hydraulic powder is preferably one or more selected from ordinary Portland cement, blast furnace slag cement, and steelmaking slag cement.

In the present invention, the amount of the water-hard powder is the amount of the powder having physical properties to be cured by the hydration reaction, but the water-hard powder is a powder having a pozolan action or a powder having latent water hardness. When powders selected from body and stone powder (calcium carbonate powder) are included, in the present invention, those amounts are also included in the amount of water-hard powder (however, the amount of component (B) described later is excluded). ..

The component (A) of the present invention is one or more compounds serving as a source for releasing aluminum ions and / or calcium ions and chloride ions in water. However, the hydraulic powder is excluded from the component (A).
Examples of the compound serving as a source for releasing aluminum ions include one or more selected from aluminum chloride, aluminum sulfate, aluminum lactate, alum, and aluminum nitrate from the viewpoint of improving the strength of soil cement containing acidic soil.
Examples of the compound serving as a supply source for releasing calcium ions include one or more selected from calcium chloride, calcium nitrate, and calcium thiocyanate from the viewpoint of improving the strength of soil cement containing acidic soil.
Examples of the compound serving as a source for releasing chloride ions include one or more selected from aluminum chloride, calcium chloride, sodium chloride, and potassium chloride from the viewpoint of improving the strength of soil cement containing acidic soil.

The component (A) is preferably the following component (A1) or component (A2) from the viewpoint of improving the strength of the soil cement containing acidic soil.
(A1) component: One or more compounds selected from calcium chloride salt or aluminum chloride salt having a solubility in water at 20 ° C. of 20 g / 100 ml or more (A2) component: (A21) alkali metal chloride salt, And one or more compounds selected from alkaline earth metal chloride salts (hereinafter referred to as (A21) component), and (A22) aluminum salts having a solubility in water at 20 ° C. of 20 g / 100 ml or more (however, (However, Excluding A21) component, hereinafter referred to as (A22) component)

The component (A1) may be one or more selected from calcium chloride and aluminum chloride from the viewpoint of improving the strength of soil cement containing acidic soil.

Among the components (A2), one or more selected from sodium chloride, potassium chloride, and calcium chloride can be mentioned as the component (A21) from the viewpoint of improving the strength of soil cement containing acidic soil, which is preferable from the viewpoint of safety. Is one or more selected from sodium chloride and calcium chloride.
From the viewpoint of improving the strength of soil cement containing acidic soil among the components (A2), the component (A22) includes one or more selected from aluminum lactate, alum, aluminum sulfate, and aluminum nitrate, and improves the strength of soil cement. From the viewpoint of, preferably one or more selected from alum and aluminum sulfate.

In the ground improvement method of the present invention, the water-hard powder is added to the soil, and the weight ratio of the water-hard powder / soil is preferably 0.01 or more, more preferably 0. 1 or more, more preferably 0.25 or more, and from the viewpoint of workability of soil cement, preferably 0.6 or less, more preferably 0.5 or less, still more preferably 0.45 or less.

In the ground improvement method of the present invention, from the viewpoint of workability of soil cement, the mass ratio of water / water-hard powder is preferably 40% by mass or more, more preferably 50% by mass of water-hard powder and water. % Or more, more preferably 60% by mass or more, and preferably 150% by mass or less, more preferably 120% by mass or less, still more preferably 100% by mass or less. This mass ratio is calculated by (amount of water / amount of hydraulic powder) × 100.

In the ground improvement method of the present invention, from the viewpoint of improving the strength of the soil cement containing acidic soil, the component (A) is added to the water-hard powder in an amount of 0.5% by mass or more, preferably 1.0% by mass. As described above, the mixture is more preferably 2.0% by mass or more, further preferably 3.0% by mass or more, and 10% by mass or less, preferably 8.0% by mass or less, more preferably 6.0% by mass or less. ..

In the ground improvement method of the present invention, when the component (A1) is used as the component (A), the component (A1) is preferably used with respect to the water-hard powder from the viewpoint of improving the strength of the soil cement containing acidic soil. Is 0.5% by mass or more, more preferably 1.0% by mass or more, still more preferably 2.0% by mass or more, still more preferably 3.0% by mass or more, and preferably 10% by mass or less, more preferably. Is mixed in an amount of 8.0% by mass or less, more preferably 6.0% by mass or less.

In the ground improvement method of the present invention, when the component (A2) is used as the component (A), from the viewpoint of improving the strength of the soil cement containing acidic soil, the component (A2) (component (A21) and component (A22)) Total) is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 3.0% by mass or more, based on the water-hard powder. , And preferably 10% by mass or less, more preferably 8.0% by mass or less.
In the ground improvement method of the present invention, when the component (A2) is used as the component (A), the component (A21) is preferably used with respect to the water-hard powder from the viewpoint of improving the strength of the soil cement containing acidic soil. Is 0.25% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, still more preferably 2.0% by mass or more, and preferably 6.0% by mass or less. More preferably 5.0% by mass or less, further preferably 4.0% by mass or less, the component (A22) is preferably 0.25% by mass or more, more preferably 0.5% by mass, based on the water-hard powder. Mass% or more, more preferably 1.0% by mass or more, still more preferably 2.0% by mass or more, and preferably 6.0% by mass or less, more preferably 5.0% by mass or less, still more preferably 4 Mix at 0.0% by mass or less.
In the ground improvement method of the present invention, when the component (A2) is used as the component (A), the component (A21) and the component (A22) are combined with the component (A21) from the viewpoint of improving the strength of the soil cement containing acidic soil. The mass ratio (A21) / (A22) of and the component (A22) is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1.0 or more, and preferably 10 or less, more preferably. Is 5.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less.

In the ground improvement method of the present invention, at least one or more selected from anhydrous gypsum, dihydrate gypsum, hemihydrate gypsum and sodium sulfate as the component (B) from the viewpoint of improving the strength of soil cement containing acidic soil. It is preferable to mix the compounds.
In the ground improvement method of the present invention, when the component (B) is used, the component (B) is preferably 0.1% by mass or more with respect to the water-hard powder from the viewpoint of improving the initial strength of the soil cement. More preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, still more preferably 3.0% by mass or more, still more preferably 5.0% by mass or more, still more preferably 7.0% by mass. % Or more, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less.

In the ground improvement method of the present invention, a cement dispersant may be mixed from the viewpoint of further improving the fluidity of the soil cement. As the cement dispersant, one or more selected from a polycarboxylic acid-based dispersant and a naphthalene sulfonic acid formaldehyde condensate-based dispersant are preferable.

The ground improvement method of the present invention can be applied to a method 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.

In the ground improvement method of the present invention, the soil, the water-hard powder, the component (A), optionally the component (B), and water can be mixed with the soil by the method (I) below. It is preferable from the viewpoint of uniformity of the improved product.
<Method (I)>
A slurry containing water, a water-hard powder, a component (A), and optionally a component (B), wherein the component (A) is 0.5% by mass or more and 10% by mass with respect to the water-hard powder. A method of mixing a slurry containing% or less with soil.

The method (I) will be described below.
In the method (I), ^{the mixing amount of the slurry per 1 m 3 of} soil is preferably 150 kg or more and 800 kg or less from the viewpoint of improving the strength of the soil cement containing acidic soil.
Further, in the method (I), from the viewpoint of improving the strength of the soil cement containing acidic soil, the mass ratio of the water-hard powder / soil in the soil cement is preferably 0.01 or more and 0.6 or less.
Further, in the method (I), either fresh water or seawater can be used as the water used for preparing the slurry. At least part of the water in the slurry may be seawater.

A specific method for preparing a slurry by mixing water, a hydraulic powder, a component (A), and an optional component (B) is based on a known method for preparing a hydraulic composition such as cement milk. good.

In the method (I), from the viewpoint of workability, the mass ratio of water / water-hard powder in the slurry is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and It is preferably 150% by mass or less, more preferably 120% by mass or less, and even more preferably 100% by mass or less.

The specific method for injecting the slurry into the ground may be based on a known ground improvement method.
As a method of injecting the slurry into the ground, for example, an injection stirring method (one-phase flow method, two-phase flow method, three-phase flow method), a mechanical stirring method (CDM method, etc.), and an underground continuous wall method (SMW method, SMW method, etc.) TRD method, etc.). Furthermore, in a system in which the component (A) and the component (B) are optionally dry-blended into a hydraulic powder, it is also used for the DJM (Dry Jet Mixing) method of powder mixing method and shallow layer improvement using a stabilizer or the like. can.

In the method (I), from the viewpoint ^{of mixability, the mixing amount of the slurry per 1 m 3 of} soil is preferably 150 kg or more, more preferably 200 kg or more, further preferably 250 kg or more, and from the viewpoint of workability of soil cement. , Preferably 800 kg or less, more preferably 500 kg or less, still more preferably 400 kg or less.

The mixture of slurry and soil is solidified according to a known ground improvement method.

As a more specific example of the method (I), which is the ground improvement method of the present invention, there is a ground improvement method having the following steps 1 to 3.
<Step 1>
A step of preparing a slurry by mixing water, a water-hard powder, a component (A), and an optional component (B), wherein the component (A) is 0.5 with respect to the water-hard powder. Step of preparing a slurry by mixing so as to be by mass% or more and 10% by mass or less <Step 2>
In the step of injecting the slurry obtained in step 1 into the ground and mixing the slurry and soil to obtain a mixture, ^{the mixing amount of the slurry per 1 m 3 of} soil is 150 kg or more and 800 kg or less, and water in the mixture. Step where the mass ratio of hard powder / soil is 0.01 or more and 0.6 or less <Step 3>
Step of solidifying the mixture of slurry and soil obtained in step 2

[Additive composition for ground improvement]
The ground improvement additive composition of the present invention is a ground improvement additive composition containing the component (A), and the amount of organic matter required for the soil of the ground by the ignition loss method is 30% or more. An additive composition for ground improvement used in a certain soil.
The ground improvement additive composition of the present invention can further contain the component (B). The ground improvement additive composition of the present invention may consist of the component (A) and the component (B).

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.
The amount of the additive composition for ground improvement of the present invention to be used can be set in consideration of the type of ground improvement material, the type of soil (ground), etc., but the ground improvement method of the present invention and the ground improvement body of the present invention can be set. It is preferable that the amount is as described 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.

[Slurry for ground improvement]
The ground improvement slurry of the present invention is a ground improvement slurry containing water, a water-hard powder, and a component (A), and the component (A) is 0.5% by mass with respect to the water-hard powder. This is a ground improvement slurry used for soil containing% or more and 10% by mass or less and having an organic content of 30% or more determined by the ignition loss method. The slurry has a water / hydraulic powder mass ratio of preferably 40% by mass or more and 150% by mass or less. The ground improvement slurry of the present invention may be a ground improvement slurry obtained by mixing water, a water-hard powder, and the ground improvement additive composition of the present invention. The ground improvement slurry of the present invention is preferably used in the ground improvement method of the present invention. In addition, the ground improvement slurry of the present invention can further contain (B). The matters described in the ground improvement method and the ground improvement additive composition of the present invention can be appropriately applied to the ground improvement slurry of the present invention.

The ground improvement slurry of the present invention is a ground improvement slurry that is mixed with soil for ground improvement, for example, a hydraulic composition such as cement milk.
The amount of the ground improvement slurry used of the present invention can be set in consideration of the composition of the ground improvement slurry, the type of soil (ground), etc., but will be 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 is large.
From the viewpoint of improving the strength of soil cement containing acidic soil, the ground improvement slurry of the present invention preferably contains 150 kg or more, more preferably 200 kg or more, still more preferably 250 kg or more, and preferably 800 kg or less per ^{1 m 3 of soil.} It is more preferably 500 kg or less, still more preferably 400 kg or less, and is used by mixing with soil. Further, in the ground improvement slurry of the present invention, the mass ratio of the water-hard powder / soil in the slurry is preferably 0.01 or more, more preferably 0.1 or more, and further. It is preferably mixed with soil at 0.25 or more, preferably 0.6 or less, more preferably 0.5 or less, still more preferably 0.45 or less.

[Ground improvement body]
The ground improvement body of the present invention is a ground improvement body containing soil, a water-hard powder, water, and a component (A) having an organic content of 30% or more required by the ignition loss method, and is (A). It is a ground improvement body containing 0.5% by mass or more and 10% by mass or less of the components with respect to the water-hard powder. From the viewpoint of improving the strength of soil cement containing acidic soil, this ground improvement body preferably has a water-hard powder / soil mass ratio of 0.01 or more and 0.6 or less. The ground improvement body may be a ground improvement body obtained by curing a slurry containing the soil, water, hydraulic powder, and the component (A).
The ground improvement body of the present invention may be a ground improvement body formed by mixing the soil and the ground improvement slurry of the present invention.

The matters described in the ground improvement method of the present invention, the additive composition for ground improvement, and the slurry for ground improvement can be appropriately applied to the ground improvement body of the present invention. The ground improvement body of the present invention can further contain the component (B).
Specific examples of the water-hard powder, the component (A), the component (B), the soil, etc. in the ground improvement body of the present invention, preferred embodiments, and quantitative provisions such as mass ratios of the present invention are also provided. It is the same as the improvement method, the additive composition for ground improvement, and the slurry for ground improvement.

<Ingredients>
The components used in the following examples, comparative examples, and reference examples are shown below.
(A) Ingredient (A1) Ingredient-Calcium chloride: Wako Pure Chemical Industries, Ltd., solubility in water at 20 ° C. 74.5 g / 100 ml
-Aluminum chloride: manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., solubility in water at 20 ° C. 45.8 g / 100 ml
(A2) Ingredients (A21) Ingredients-Sodium chloride: Fuji Film Wako Pure Chemical Industries, Ltd.-Calcium chloride: Fuji Film Wako Pure Chemical Industries, Ltd. (A22) Ingredients-Aluminum sulfate: Fuji Film Wako Pure Chemical Industries, Ltd., 20 Solubility in water at ° C 87g / 100ml
-Aluminum lactate: manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., solubility in water at 20 ° C, 30.8 g / 100 ml
-Alum: Wako Pure Chemical Industries, Ltd., Wako Pure Chemical Industries, Ltd., solubility in water at 20 ° C, 40.9 g / 100 ml

(B) Ingredients ・ Anhydrous gypsum: manufactured by Sanes Gypsum Co., Ltd. ・ Nisui Gypsum: manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.

Hydraulic powder / ordinary Portland cement: Made by Taiheiyo Cement Co., Ltd.

As the soil, peat and smikley muddy water shown in Table 1 were used. The organic content of peat and smikley muddy water was measured by the method specified in Japanese Industrial Standard JIS A1226: 2009. The pH of the soil suspension of peat and smikley muddy water was measured by the method specified by the Japanese Geotechnical Society standard JGS0211-2009. The pH of the peat soil suspension was 4.2, and the pH of the smikley muddy water soil suspension was 7.

<Examples, Comparative Examples and Reference Examples>
Soil cement was prepared using the soil shown in Table 1, and the soil cement was evaluated as follows. The results are shown in Tables 2 and 3.

(1) Preparation of soil cement First, cement milk was prepared by the following procedure. The water-hard powder, the component (A), and the component (B) were mixed in a 500 ml plastic cup (500 mL disposable cup, Nikko Hansen Co., Ltd.). Water was added to the mixture and kneaded with a hand mixer for 1 minute to prepare a cement slurry.
Tap water was used as the water for preparing the cement slurry. The water-hard powder and water were used so that the mass ratio of water / water-hard powder was 60% by mass.
The components (A) and (B) were used so that the amounts added to the hydraulic powder were as shown in Tables 2 and 3.
Then, the soil was poured into another 500 ml plastic cup, and the cement slurry was charged so as to have the injection amount shown in Tables 2 and 3 (water-hard powder / soil mass ratio = 0.38). Soil cement was prepared by stirring with a hand mixer for 3 minutes. After stirring, the upper surface was leveled by applying vibration, sealed with a wrap film, and allowed to stand at 22 ° C. for a predetermined time.

(2) Evaluation The strength of the ground improvement body obtained by using the prepared soil cement was evaluated by the following method. Soil cement was filled in a mold (diameter 50 mm × height 100 mm). Filling was done with a table vibrator for 30 seconds in two layers. Two specimens were prepared. The strength of the cured product (ground improvement product) of the specimen obtained above in air at 20 ° C. for 7 days was measured by a uniaxial compression tester. Tables 2 and 3 show the average value of the intensities of the two specimens as the intensities for 7 days.

In the comparative example in which the 7-day strength was described as 0 in Table 2, the strength was not measured because the soil cement could not be removed from the mold because it did not harden.

In Table 2, in Comparative Example 1 in which the component (A) is not mixed with the peat which is the soil of acidic soil containing organic substances only with the hydraulic powder, the soil cement cannot be hardened, but the peat is mixed with the hydraulic powder. It can be seen that the soil cement can be hardened in Examples 1 to 12 of the present invention in which the body and the component (A) are mixed in a specific amount.
Further, from the results in Table 3, even if the hydraulic powder and the component (A) were added to the smikley muddy water, which is a soil containing no organic substances, the 7-day strength of the soil cement was not improved, and the ground of the present invention was found. It can be seen that the improved construction method of is effective only for specific soils.

Claims (15)

This is a ground improvement method in which water-hard powder, water, and the following component (A) are mixed in soil with an organic content of 30% or more required by the ignition loss method. Is mixed so as to be 0.5% by mass or more and 10% by mass or less with respect to the water-hard powder, which is a method for improving the ground.
Component (A): One or more compounds serving as a source for releasing aluminum ions and / or calcium ions and chloride ions in water (excluding water-hard powder) The ground improvement method according to claim 1, wherein the pH of the soil suspension measured by the method specified by the Japanese Geotechnical Society Standard JGS0211-2009 is 6 or less. The ground improvement method according to claim 1 or 2, wherein the component (A) is one or more compounds selected from the following component (A1) and the component (A2).
(A1) component: One or more compounds selected from calcium chloride salt or aluminum chloride salt having a solubility in water at 20 ° C. of 20 g / 100 ml or more (A2) component: (A21) alkali metal chloride salt, And one or more compounds selected from alkaline earth metal chloride salts (hereinafter referred to as (A21) component), and (A22) aluminum salts having a solubility in water at 20 ° C. of 20 g / 100 ml or more (however, (However, Excluding A21) component, hereinafter referred to as (A22) component) The ground improvement method according to claim 3, wherein the soil, the hydraulic powder, water, and the component (A1) are mixed. The ground improvement method according to claim 4, wherein the component (A1) is at least one selected from calcium chloride and aluminum chloride. The ground improvement method according to claim 4 or 5, wherein the component (A1) is mixed with the hydraulic powder in an amount of 0.5% by mass or more and 10% by mass or less. The ground improvement method according to claim 3, wherein the soil, the hydraulic powder, water, and the component (A2) are mixed. According to claim 7, the component (A21) is one or more selected from sodium chloride, potassium chloride and calcium chloride, and the component (A22) is one or more selected from aluminum lactate, alum, and aluminum sulfate. The described ground improvement method. The ground improvement method according to claim 7 or 8, wherein the component (A2) is mixed with the hydraulic powder in an amount of 0.5% by mass or more and 10% by mass or less. The ground improvement method according to any one of claims 7 to 9, wherein the mass ratio (A21) / (A22) of the component (A21) to the component (A22) is 0.1 or more and 10 or less. Further, according to any one of claims 1 to 10, at least one compound (hereinafter referred to as (B) component) selected from (B) anhydrous gypsum, dihydrate gypsum, hemihydrate gypsum and sodium sulfate is mixed. The described ground improvement method. The ground improvement method according to claim 11, wherein the component (B) is mixed with the hydraulic powder in an amount of 0.1% by mass or more and 30% by mass or less. The ground improvement method according to any one of claims 1 to 12, wherein the hydraulic powder is one or more selected from ordinary Portland cement, blast furnace slag cement, and steelmaking slag cement. An additive composition for ground improvement containing the following component (A), which is used for soil in which the amount of organic matter required by the ignition loss method is 30% or more. Composition.
Component (A): One or more compounds serving as a source for releasing aluminum ions and / or calcium ions and chloride ions in water (excluding water-hard powder) A ground improvement body containing soil, water-hard powder, water, and the following component (A) having an organic content of 30% or more required by the ignition loss method, and the component (A) is the water-hard powder. A ground improvement body containing 0.5% by mass or more and 10% by mass or less.
Component (A): One or more compounds serving as a source for releasing aluminum ions and / or calcium ions and chloride ions in water (excluding water-hard powder)