Ground improvement method

Abstract

To provide a ground improvement method capable of improving a compressive strength of soil cement even when soil containing organic matter is used.SOLUTION: A ground improvement method comprises mixing soil containing an organic matter with hydraulic powder, water, and a polymer having a structural unit represented by the following general formula (A) or a salt thereof. [In the formula, R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms].SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a soil improvement method and a soil improvement additive. [Background technology]

[0002] Known methods for improving the ground for the foundations of buildings include a ground improvement method in which concrete or steel pipe ground improvement columns are driven into the ground, and a ground improvement method in which a cement-based solidification material such as cement milk is injected while excavating the ground, and a column-shaped ground improvement body is formed directly in the ground by mixing the excavated soil with the cement milk.

[0003] In ground improvement work, where soil is modified by adding and mixing cement-based solidification materials, it is desirable to select an appropriate solidification material, mix ratio, additives, etc., taking into consideration the properties of the soil to be mixed and the type of construction method used for the ground improvement. In particular, when the soil to be mixed contains a lot of organic matter, such as organic soil, the organic matter is adsorbed onto the cement surface, inhibiting the hydration reaction of the cement, so that even if a cement-based solidification material is used, the desired strength cannot be obtained, and ground improvement may be difficult.

[0004] Patent Document 1 discloses a soil improvement method using a polymeric soil improvement material with the objective of forming and maintaining the soil's granular structure and ensuring water permeability, the method comprising the steps of mixing a cement-based solidification material with the soil and stirring it, spraying an aqueous solution containing a polymer compound as a soil improvement material onto the soil and stirring it, spreading and compacting the soil, and spraying the aqueous solution containing the polymer compound after the compaction, wherein the polymer compound is a polymer compound consisting of a complex of a magnesium salt of an acrylic acid-dimethylaminoethyl methacrylate copolymer and polyethyleneimine. Furthermore, Patent Document 2 discloses a ground hardening method in which an aqueous solution hardening liquid is injected into the ground to harden the ground, the method having an object of providing a ground hardening method that inhibits acid corrosion of equipment used in the operation of injecting a hardening liquid into the ground and extends its lifespan, the method using a corrosion inhibitor together with the hardening liquid, the aqueous solution hardening liquid being an aqueous solution of an acidic silica sol and an alkaline agent, and the corrosion inhibitor being a polyamine-based compound having a weight-average molecular weight of 300 to 150,000 and having two or more amino groups in the molecule, or a salt thereof. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2002-13102 A [Patent Document 2] JP 2002-155279 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a ground improvement method that can increase the compressive strength of soil cement even when soil containing organic matter is used. [Means for solving the problem]

[0007] The present invention relates to a method for improving ground, which comprises mixing a hydraulic powder, water, and (A) a polymer having a constitutional unit represented by the following general formula (A) or a salt thereof (hereinafter referred to as component (A)) with soil containing organic matter.

[0008] [ka] [In the formula, R 1 , R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0009] The present invention also relates to a soil improvement additive that contains a polymer having a structural unit represented by the above general formula (A) or a salt thereof and is used in a soil improvement method in which soil containing organic matter is mixed with hydraulic powder and water to solidify the soil. Effect of the Invention

[0010] According to the present invention, a method for improving ground can be provided that can increase the compressive strength of soil cement even when soil containing organic matter is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] When soil containing organic matter, such as organic soil, is improved with hydraulic powder such as cement, some of the organic matter present in the soil may be adsorbed to the hydraulic powder, inhibiting its hydration reaction and causing a significant decrease in strength development. For example, in a slurry in which hydraulic powder such as cement, water, and soil containing organic matter are mixed, the organic matter in the soil is adsorbed to calcium ions on the surface of the hydraulic powder via anionic functional groups such as carboxylate groups. The above component (A) is thought to electrically bond and block the anionic functional groups of the organic matter in soil containing organic matter, and further aggregate the organic matter by entangling the polymer chains, thereby reducing the contact area with the hydraulic powder and suppressing the adsorption of the organic matter to the surface of the hydraulic powder. On the other hand, cationic polymers having cis-diamine groups such as polyethyleneimine also adsorb to hydraulic powders due to the chelating effect, suppressing the hydration reaction of the hydraulic powder and reducing the compressive strength. Therefore, by using component (A), which is a cationic polymer that does not have cis-diamine groups and has a structure that is difficult to adsorb to cement, it is believed that a hardened body with high compressive strength can be obtained without suppressing the hydration reaction of the hydraulic powder. However, the present invention is not limited to this mechanism of action.

[0012] <Soil improvement method> The present invention provides a method for improving ground, which comprises mixing a hydraulic powder, water, and (A) a polymer having a structural unit represented by the above general formula (A) or a salt thereof (hereinafter referred to as component (A)) with soil containing organic matter. The structural unit represented by general formula (A) may be cationized at the nitrogen atom to form a salt with an anion. Examples of the salt include hydrochloride, acetate, and amidosulfate. That is, component (A) may be a polymer having a structural unit represented by the above general formula (A) (hereinafter referred to as component (A)) or a salt thereof. The ground improvement method of the present invention may be a ground improvement method for strengthening the ground by forming a hardened body in the ground.

[0013] In general formula (A), R 1 , R 2 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 1 , R 2 From the viewpoint of obtaining a hardened body having high compressive strength, each of them is preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 carbon atom, and even more preferably a hydrogen atom. In general formula (A), R 1 , R 2 The combination of R 1 , R 2 However, from the viewpoint of obtaining a hardened body with high compressive strength, a combination of a hydrogen atom and a hydrogen atom, a combination of a hydrogen atom and an alkyl group having 1 carbon atom, or a combination of an alkyl group having 1 carbon atom and an alkyl group having 1 carbon atom is preferred, and a combination of a hydrogen atom and a hydrogen atom is more preferred.

[0014] The component (A) may have a structural unit (X) other than the structural unit represented by general formula (A) (hereinafter referred to as other structural unit (X)). Examples of the other structural unit (X) include one or more types selected from the following general formulae (X1), (X2), (X3) and (X4). The proportion of the structural unit represented by the general formula (A) in all structural units of the component (A) may be, for example, 85 mol% or more, further 90 mol% or more, further 95 mol% or more, and may be 100 mol% or less, from the viewpoint of flocculating organic matter in the soil with a smaller amount of addition. The proportion of the structural unit represented by the general formula (A) in all structural units of the component (A) may be 100 mol%.

[0015] [ka]

[0016] [ka] [In the formula, R 3 , R 4 , R 5 each independently represents an alkyl group having 1 to 3 carbon atoms. - is one or more anions selected from a chloride ion, an acetate ion, and an amidosulfate ion.

[0017] [ka] [In the formula, R 6 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.]

[0018] [ka] [In the formula, R 7 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. - is one or more anions selected from a chloride ion, an acetate ion, and an amidosulfate ion.

[0019] (A) The weight average molecular weight of the component, from the viewpoint of aggregating the organic matter in the soil with a smaller addition amount, is preferably 800 or more, more preferably 1,000 or more, still more preferably 3,000 or more, and from the viewpoint of ensuring the fluidity of the slurry in which the soil containing organic matter, hydraulic powder, and water are mixed, it is preferably 30,000 or less, more preferably 20,000 or less, still more preferably 15,000 or less. The weight average molecular weight of the (A) component is a value measured by gel permeation chromatography (GPC).

[0020] (A) The weight average molecular weight of the component is measured by gel permeation chromatography (GPC) under the following conditions. <GPC conditions> · Column: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation) · Eluent: 0.2M phosphate buffer / acetonitrile = 7 / 3 (volume ratio) · Standard substance: Monodisperse polyethylene glycol with known molecular weight

[0021] (A) The component is preferably polyallylamine or a salt thereof from the viewpoint of improving the strength of the improved body in which the soil containing organic matter, hydraulic powder, and water are mixed. As the (A) component of polyallylamine or a salt thereof, commercially available products can be used. Examples of commercially available products include the "PAA (registered trademark)-HCL" series manufactured by Nitto Boseki Co., Ltd.

[0022] The hydraulic powder is a powder having physical properties that harden by a hydration reaction, and examples thereof include cement, gypsum, etc. The hydraulic powder is preferably cement. The cement may be, for example, Portland cement such as ordinary Portland cement, belite cement, blast furnace slag cement, moderate heat cement, early strength cement, ultra-early strength cement, sulfate-resistant cement, etc. The hydraulic powder may contain cement, preferably Portland cement, in an amount of preferably 25% by mass or more, more preferably 35% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, and preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, even more preferably 85% by mass or less.

[0023] The hydraulic powder may contain powders having pozzolanic action and / or latent hydraulic properties, such as blast furnace slag, fly ash, and silica fume, and stone powder (calcium carbonate powder). These may be added to cement, such as blast furnace slag cement, fly ash cement, and silica fume cement. The hydraulic powder preferably contains blast furnace slag from the viewpoint of an aluminum ion source for ettringite, which is a hydration product. When the hydraulic powder contains blast furnace slag, the content of the slag in the hydraulic powder is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably less than 50% by mass.

[0024] In the present invention, the amount of hydraulic powder is the amount of powder having the physical property of hardening through a hydration reaction, such as the amount of cement or gypsum. However, in cases where the hydraulic powder includes a powder selected from a powder having pozzolanic action, a powder having latent hydraulic properties, and stone powder (calcium carbonate powder), the amounts of these powders are also included in the amount of hydraulic powder in the present invention.

[0025] The water that can be used may be tap water, lake water, river water, groundwater, or the like.

[0026] Examples of soil containing organic matter include black soil, peat soil, etc. The organic matter may be humus, humic acid, fulvic acid, humin, bitumen, or cellulose or lignin derived from plants. In order to achieve a significant effect of the present invention, the organic matter content of the soil as determined by the loss on ignition method is preferably 10% or more, more preferably 30% or more, even more preferably 35% or more, even more preferably 40% or more, and preferably 90% or less, more preferably 80% or less. Here, the loss on ignition method is a method specified in the Japanese Engineering Standard JIS A 1226:2009.

[0027] The ground improvement method of the present invention will be described in detail. Note that the ground improvement method of the present invention is not limited to the following embodiment.

[0028] The ground improvement method of the present invention includes a step 1 of mixing hydraulic powder, water, and component (A) to obtain a hydraulic slurry, a step 2 of mixing soil containing organic matter with the hydraulic slurry to obtain a mixture of the soil and the hydraulic slurry, and a step 3 of curing the mixture of the soil and the hydraulic slurry. The mixture of the soil and the hydraulic slurry may be soil cement.

[0029] In step 1, from the viewpoint of strengthening the aggregation of organic matter in the soil, the (A) component can be mixed in the hydraulic slurry at a concentration of preferably 0.0125% by mass or more, more preferably 0.025% by mass or more, and even more preferably 0.04% by mass or more, and from the viewpoint of preventing thickening of the slurry, i.e., deterioration of workability, the (A) component can be mixed at a concentration of preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.8% by mass or less. When the (A) component is a salt, the mass is calculated as that of an unneutralized product (no salt is formed).

[0030] From the viewpoint of ensuring the strength of the hardened soil cement body, the hydraulic powder can be mixed in the mixed components of the hydraulic slurry at preferably 25 mass % or more, more preferably 30 mass % or more, and even more preferably 40 mass % or more, and from the viewpoint of maintaining the viscosity of the slurry within a workable range, the hydraulic powder can be mixed in at preferably 75 mass % or less, more preferably 65 mass % or less, and even more preferably 60 mass % or less.

[0031] From the viewpoint of strengthening the aggregation of the organic matter, the (A) component can be mixed in an amount of preferably 0.05 part by mass or more, more preferably 0.1 part by mass or more, and even more preferably 0.5 part by mass or more, per 100 parts by mass of the hydraulic powder, and from the viewpoint of ensuring the strength of the hardened soil cement, the (A) component can be mixed in an amount of preferably 3 parts by mass or less, more preferably 2 parts by mass or less, even more preferably 1.2 parts by mass or less, and even more preferably 1 part by mass or less.

[0032] The mass ratio [(W) / (C)] of the amount of water (W) mixed in the hydraulic slurry to the amount of hydraulic powder (C) mixed in the hydraulic slurry is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.55 or more, from the viewpoint of maintaining a low viscosity of the slurry and ensuring workability, and is preferably 3 or less, more preferably 2.5 or less, even more preferably 2 or less, and even more preferably 0.8 or less, from the viewpoint of ensuring the strength of the hardened soil cement body.

[0033] In step 2, the hydraulic slurry is mixed with soil containing organic matter. In step 2, hydraulic powder is applied to 1 m of soil in order to obtain the desired improvement strength while being affected by various types and physical properties of soil. 3 For example, the load may be preferably 100 kg or more, more preferably 200 kg or more, even more preferably 300 kg or more, and preferably 800 kg or less, more preferably 700 kg or less, even more preferably 600 kg or less. In step 2, 1 m of soil 3 It is preferable to mix the soil and the hydraulic slurry so that the mass of the hydraulic powder relative to the soil falls within the above range. In addition, the amount of soil containing organic matter mixed in step 2 is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of hydraulic powder from the viewpoint of obtaining an improved effect of improving the improved strength, and is preferably 65 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 45 parts by mass or less, from the viewpoint of obtaining a desired improved strength. The soil and hydraulic slurry can be mixed so that the amount of soil containing organic matter mixed relative to 100 parts by mass of hydraulic powder falls within the above range. In the present invention, the improved strength may be the strength of a hardened body of a mixture of hydraulic slurry and soil (the same applies hereinafter).

[0034] In step 2, from the viewpoint of further flocculating the organic matter in the soil, the amount of component (A) mixed per 100 parts by mass of soil is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and even more preferably 1.0 part by mass or more, and from the viewpoint of smoothly carrying out the hydration reaction of the cement, the soil can be mixed with the hydraulic slurry so that the amount is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.

[0035] In step 3, the mixture of the soil containing organic matter and the hydraulic slurry is cured to obtain a hardened body of the mixture of the soil containing organic matter and the hydraulic slurry. The curing temperature is preferably 15° C. or more, more preferably 18° C. or more, and preferably 40° C. or less, more preferably 30° C. or less, from the viewpoint of obtaining a strength at which the hardened body does not easily deform. The curing period is preferably 1 day or more, more preferably 3 days or more, from the viewpoint of obtaining a desired improved strength in addition to the above viewpoint, further preferably 7 days or more, and further preferably 28 days or more.

[0036] The ground improvement method of the present invention can be preferably applied to various shallow, medium and deep mixing treatment methods using cement-based solidification materials, and can perform stable ground reinforcement. Specific examples of the methods include the DCS method, the CDM method, the jet grout method and the power blender method.

[0037] <Soil improvement additive> The present invention provides a soil improvement additive that contains a polymer having a structural unit represented by the above general formula (A) [component (A)] and is used in a soil improvement method in which soil containing organic matter is mixed with hydraulic powder and water to solidify the soil. The soil improvement additive of the present invention may be a soil improvement additive for a soil improver, which is mixed into a mixture of soil, a hydraulic composition, and water when the mixture is solidified to form a soil improver. Component (A) is the same as component (A) described in the above ground improvement method. The soil improvement additive of the present invention may be a soil improvement additive used in a soil improvement method in which soil containing organic matter is mixed with hydraulic powder and water to solidify the soil. The soil improvement additive of the present invention may also be a hydraulic slurry additive for soil improvement, which is a hydraulic slurry obtained by mixing hydraulic powder and water and is mixed with soil containing organic matter.

[0038] <Powder composition for hydraulic composition> The present invention provides a powder composition for hydraulic compositions, which contains a polymer having a structural unit represented by the above general formula (A) [component (A)] and a hydraulic powder. The powder composition for hydraulic compositions of the present invention may be a soil improvement solidification material. The powder composition for hydraulic compositions of the present invention may be a premix for hydraulic compositions. The powder composition for hydraulic composition of the present invention may be a composition used in a ground improvement method in which the composition is mixed with soil containing organic matter and hardens the soil. That is, the powder composition for hydraulic composition of the present invention may be a powder composition for hydraulic composition for soil improver. The preferred embodiments of the component (A) and the hydraulic powder in the powder composition for hydraulic composition of the present invention are the same as those described above in the ground improvement method of the present invention.

[0039] <Composition and other components of powder composition for hydraulic composition> The powder composition for hydraulic composition of the present invention may contain the (A) component in an amount of preferably 0.05% by mass or more, more preferably 0.08% by mass or more, and even more preferably 0.1% by mass or more from the viewpoint of firmly agglomerating organic matter, and in an amount of preferably 3% by mass or less, more preferably 2% by mass or less, even more preferably 1.2% by mass or less, and even more preferably 1% by mass or less from the viewpoint of smoothly carrying out the hydration reaction of cement.

[0040] The powder composition for hydraulic compositions of the present invention may contain hydraulic powder in an amount of preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, from the viewpoint of ensuring the strength of the hardened soil cement body, and may contain preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of adding powders other than the hydraulic powder to adjust the viscosity when the powder composition for hydraulic compositions is made into a slurry.

[0041] In the powder composition for hydraulic composition of the present invention, the content of component (A) is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of hydraulic powder, from the viewpoint of firmly agglomerating organic matter, and from the viewpoint of smoothly carrying out the hydration reaction of cement, it is preferably 3 parts by mass or less, more preferably 2 parts by mass or less, even more preferably 1.2 parts by mass or less, and even more preferably 1 part by mass or less.

[0042] The powder composition for hydraulic compositions of the present invention may optionally contain a cement dispersant, a retarder and an antifoaming agent.

[0043] <Hydraulic slurry> The present invention provides a hydraulic slurry containing a polymer having a structural unit represented by the above general formula (A) [component (A)], a hydraulic powder, and water. The hydraulic slurry of the present invention may be a hydraulic slurry containing the powder composition for hydraulic compositions of the present invention and water. The hydraulic slurry of the present invention may be a hydraulic slurry for a soil improver, which is formed by mixing the hydraulic slurry with soil to form a mixture (soil cement) and solidifying the mixture to form a soil improver. The preferred embodiment of the hydraulic slurry of the present invention is the same as the hydraulic slurry described in the above-mentioned ground improvement method. In addition, the hydraulic slurry can contain any of the optional components described in the above-mentioned powder composition for hydraulic composition of the present invention. EXAMPLES

[0044] <Examples 1 to 3, Comparative Examples 1 and 3, and Reference> (1) Preparation of hydraulic slurry The hydraulic slurry was prepared by mixing the (A) component (polyallylamine hydrochloride, manufactured by Nittobo Medical Co., Ltd.) and water shown in Tables 1 to 3 in the ratios shown in Tables 1 to 3, and further mixing with ordinary cement (a mixture of ordinary cement manufactured by Pacific Cement Corporation and ordinary cement manufactured by Sumitomo Osaka Cement Co., Ltd. in a mass ratio of 50 / 50). The (A) component and water were stirred with a glass rod until they were visually uniform and transparent. In addition, the mixture of water and ordinary cement containing the (A) component was stirred with a hand mixer for 30 seconds. The hydraulic slurry was prepared so that the parts by mass of the (A) component per 100 parts by mass of ordinary cement (C) were the parts by mass shown in Tables 1 to 3. For the sake of convenience, the polyethyleneimine, which is a comparative component of the (A) component, is also listed in the same column for the soil improvement additives in Table 1. In addition, in Table 3, soil cements with the same amount of peat mixed were prepared as test groups A to D, respectively. In each of the test groups A to D, Examples 3-1 to 3-4 in which component (A) was mixed and Comparative Examples 3-1 to 3-4 in which component (A) was not mixed were prepared. The reference examples in Table 3 are evaluations of the case in which the amount of peat mixed was 0, that is, the case in which only hydraulic slurry was used.

[0045] (2) Compressive strength measurement (2-1) Preparation of specimen Soil cement was produced by mixing the hydraulic slurry prepared in (1) above with soil containing organic matter (peat soil collected in Ishikari City, Hokkaido (organic matter content 66.4%)). The soil cement was mixed for 30 seconds using a mortar Hobart mixer. The hydraulic slurry was used so that the parts by mass of peat per 100 parts by mass of ordinary cement (C) was the parts by mass shown in the table. The soil cement was immediately filled into the formwork (diameter 50 mm x height 100 mm). The filling was done in two layers for 15 seconds using a table vibrator. Two specimens were made. (2-2) Measurement of hardened body strength The formwork filled with soil cement was left to stand at 20±2°C for curing, and demolded after 28 days. The strength of the resulting hardened body (ground improvement body) was measured in accordance with JIS A 1216 Soil Uniaxial Compression Test Method. The compressive strength measurement results are shown in Tables 1 to 3. In addition, in Table 3, the strength ratio (Example / Comparative Example) between the strength of the hardened body of the Example and the strength of the hardened body of the Comparative Example was calculated for each of test groups A to D. This strength ratio shows that the hardened body of soil cement containing component (A) has improved strength compared to the hardened body of soil cement not containing (A).

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

Claims

1. A method for improving ground, comprising mixing soil containing organic matter, the organic matter content of which is 10% or more and 90% or less as determined by the loss on ignition method, with hydraulic powder containing cement, water, and (A) a polymer or a salt thereof having a constituent unit represented by the following general formula (A) (hereinafter referred to as component (A)): 【Chemistry 1】 [In the formula, R １ , R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

2. A ground improvement method as described in claim 1, wherein the mixed amount of the soil is 5 parts by mass or more and 65 parts by mass or less per 100 parts by mass of the hydraulic powder.

3. 3. The method for improving ground according to claim 1 or 2, wherein the weight average molecular weight of component (A) is 800 or more and 30,000 or less.

4. A step of mixing the hydraulic powder, water, and component (A) to obtain a hydraulic slurry; mixing the soil with a hydraulic slurry to obtain a mixture of the soil and the hydraulic slurry; curing the mixture of soil and hydraulic slurry; The ground improvement method according to any one of claims 1 to 3, comprising:

5. The ground improvement method according to any one of claims 1 to 4, wherein the (A) component is mixed in a ratio of 0.05 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the hydraulic powder.

6. A soil improvement additive for use in a soil improvement method in which soil containing organic matter, the organic matter content of which is 10% or more and 90% or less as determined by a loss on ignition method, is mixed with hydraulic powder containing cement and water to solidify the soil, the soil containing a polymer having a structural unit represented by the following general formula (A) or a salt thereof: 【Chemistry 2】 [In the formula, R １ , R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

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