Site Improvement Methods

Abstract

To provide a soil improvement method which can uniformly mix soil and a solidification material by reducing a clay lump when improving the soil containing clay by using the solidification material.SOLUTION: In a soil improvement method for mixing hydraulic setting powder (ii), a chemical compound (iii) expressed by the following general formula (1) and water (iv) to soil (i) which contains clay, the soil improvement method mixes the chemical compound (iii) to the soil (i) at a ratio of 0.01 mass% or higher, and 1 mass% of lower. R-O-(AO)m-H (1). (In the general formula (1), R expresses a hydrogen atom, or a hydrocarbon group whose carbon number is equal or larger than 1, and equal to or smaller than 4, AO expresses an oxyethylene group or an oxypropylene, and m expresses an average addition mole number of AO, and is a number equal to or larger than 20, and equal to or smaller than 25,000).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a ground improvement method and a ground improvement body. [Background technology]

[0002] In the fields of civil engineering and architecture, compositions containing various components such as soil and cement are used for various purposes. For example, soil cement is known as a composition used in ground improvement methods, earth retaining methods, foundation pile methods, backfilling methods, and the like. Soil cement is a mixture of soil and a cement-based solidification material or water added thereto. Soil cement used in the fields of civil engineering and architecture is often prepared by adding cement milk, which is a mixture of a cement-based solidification material and water, to soil. The required properties of soil cement, such as viscosity and fluidity, differ depending on the construction method. On the other hand, for ground improvement, for example, a columnar ground reinforcement method such as the so-called soil cement method in which cement milk is injected into the ground to construct a soil cement column in the ground, and a so-called replacement column method in which the ground soil is replaced with a solidification material are known.

[0003] Patent Document 1 discloses a method for constructing a hydraulic solidification material replacement column, which is characterized in that the tip of an excavation auger having a supply passage for hydraulic solidification material inside is provided with at least an excavation claw and a discharge port for the hydraulic solidification material, the excavation auger is excavated to a predetermined depth while rotating (forward or reverse) with a construction device equipped with an auger motor, and then the excavation auger is pulled up while rotating (forward or reverse) or without rotating while discharging hydraulic solidification material from the discharge port, and a predetermined section of the excavated part is filled with the hydraulic solidification material. In the embodiment, a slurry consisting of ordinary Portland cement, bentonite, and water is used as the hydraulic solidification material.

[0004] On the other hand, it is known that various components are added to soil cement used for ground improvement and to the cement-based solidification materials used in its preparation. Patent Document 2 discloses a soil cement containing a compound having an ortho-position polyhydric phenol skeleton. Patent Document 3 discloses an additive for soil cement that contains a phosphate polymer obtained by copolymerizing a specific monomer 1 having a polyoxyalkylene group, a phosphate monoester monomer 2, and a phosphate diester monomer 3 at a pH of 7 or less. Patent Document 4 discloses a powdered premixed cement composition for ground improvement, which contains 0.5 to 15 parts by mass of a powdered ground improvement additive composed of sodium lignin sulfonate, an alkali metal carbonate, and a specified polyether antifoaming agent per 100 parts by mass of a powdered cement-based solidifying material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-106253 A [Patent Document 2] JP 2020-26523 A [Patent Document 3] JP 2007-169547 A [Patent Document 4] JP 2009-286655 A Summary of the Invention [Problem to be solved by the invention]

[0006] Soil cement is obtained by mixing soil and a solidifying agent, but clay contained in the soil may remain in the form of lumps due to uptake from the soil or aggregation during mixing. If clay lumps remain in the soil cement, for example, the soil may easily adhere to the excavation blades and mixing blades of the excavation and mixing device, and the so-called co-rotation phenomenon may occur in which these blades and the soil rotate synchronously, and the soil and the solidifying agent may not be mixed uniformly. If fine particles such as clay are not mixed uniformly, clay lumps will be localized in the soil cement column, resulting in a decrease in strength. The present invention provides a ground improvement method that can reduce clay lumps and uniformly mix soil and a solidification material when improving soil containing clay with a solidification material. [Means for solving the problem]

[0007] The present invention relates to a method for improving ground, which comprises mixing a clay-containing soil (i) (hereinafter referred to as component (i)), a hydraulic powder (ii) (hereinafter referred to as component (ii)), a compound (iii) represented by the following general formula (1) (hereinafter referred to as component (iii)), and water (iv) (hereinafter referred to as component (iv)): The component (iii) is mixed in an amount of 0.01% by mass or more and 1% by mass or less with respect to the component (i); This relates to ground improvement methods. RO-(AO) m -H (1) (In general formula (1), R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, AO represents an oxyethylene group or oxypropylene, and m represents the average number of moles of AO added and is a number of 20 to 25,000.)

[0008] The present invention also relates to a ground improvement body containing component (i), component (ii), and component (iii), The component (iii) is contained in an amount of 0.01% by mass or more and 1% by mass or less relative to the component (i); Regarding ground improvement bodies. Effect of the Invention

[0009] According to the present invention, there is provided a ground improvement method capable of uniformly mixing clay-containing soil with a solidifying material in the ground improvement of clay-containing soil. Furthermore, in the present invention, a solidification material slurry having good fluidity and excellent handleability can be prepared from components (ii), (iii), and (iv), and therefore workability is also good. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Soil improvement method> The ground improvement method of the present invention is a method for mixing component (i) with component (ii), component (iii), and component (iv), in which component (iii) is mixed in a ratio of 0.01% by mass to 1% by mass relative to component (i). Specifically, for example, the method is a method for mixing component (i) with component (ii), component (iii), and component (iv) to obtain soil cement, which is poured into the ground.

[0011] The average particle size of the component (i) may be, for example, 1 μm or more, further 5 μm or more, and 150 μm or less, further 100 μm or less, further 50 μm or less. Here, the average particle size of the component (i) is measured, for example, by preparing a suspension in which particles are suspended in water, and measuring the change in density of the suspension over time to determine the particle size. Specifically, the average particle size of the component (i) can be measured, for example, by JIS A 1223 "Test method for fine particle content of soil", and the average particle size was measured by this method in the examples described later.

[0012] The (i) component may be soil in which the difference between the natural water content and the plastic limit is, for example, 15% or more, further 18% or more, and 80% or less, further 70% or less, further 60% or less, and further 50% or less. Here, the natural water content means the ratio of the mass of water contained divided by the dry mass of the clay, and can be measured, for example, by the "Test method for water content of soil" of JIS A 1203, and the natural water content was measured by this method in the examples described later. The plastic limit is the water content at the boundary when the soil changes from a plastic state to a semi-solid state, and may be, for example, the water content at which a lump of soil is kneaded well and rolled with the palm of the hand on a glass plate to a diameter of 3 mm, at which it just breaks into pieces. The plastic limit of the (i) component can be measured, for example, by the "Test method for liquid limit and plastic limit of soil" of JIS A 1205, and the plastic limit was measured by this method in the examples described later.

[0013] Component (i) preferably contains fine particles having a particle size of less than 75 μm. The classification criteria for soil as a ground material are summarized in the Geotechnical Society Standards (Geotechnical Society of Japan, 2009). According to these, particles with a particle size of 5 μm or more and less than 75 μm are classified as silt, and particles with a particle size of less than 5 μm are classified as clay. These fine particles are the components that give the soil its viscosity. According to the Geotechnical Society Standards, clayey soil, organic soil, and volcanic ash clayey soil are known as soils with a ratio of fine particles with a particle size of less than 75 μm of 50 mass % or more. Such soils can be targeted in the present invention. An example of component (i) is soil in which the proportion of fine particles having a particle size of less than 75 μm is preferably 40% by mass or more, 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 100% by mass or less.

[0014] Clay is mainly composed of hydrous silicate minerals (hereinafter referred to as clay minerals) having a layered structure, and examples of clay minerals contained as fine particles in this clay include kaolin (kaolinite, dickite, nacrite, etc.), serpentine (lizardite, antigorite, chrysotile, etc.), mica clay minerals (illite, sericite, glauconite, celadonite, etc.), chlorite, vermiculite, smectite (montmorillonite, beidellite, nontronite, saponite, hectorite, etc.). The types and amounts of clay contained in soil are diverse, but the present invention can target soil containing clay minerals selected from, for example, kaolin and smectite.

[0015] Component (i) may contain clay, for example, at least 30%, even at least 40%, even at least 50%, and at most 100%, even at most 95%, even at most 90% by weight.

[0016] The component (i) may be soil originating from volcanic ash. The component (i) may be volcanic ash clay, for example, tuffaceous clay. Tuffaceous clay is soil that has been converted into clay through weathering, hydrolysis, etc. of volcanic ash. Generally, tuffaceous clay has a milky white or milky gray appearance with little sand mixed in. Tuffaceous clay is a soil that is prone to clay lumps being mixed in and formed during the production of soil cement, but the clay lumps are difficult to deflocculate. In the present invention, even clay lumps originating from such tuffaceous clay can be easily deflocculated.

[0017] The component (i) has a dry density of, for example, 1.9 g / cm 3 Above that, an additional 2.0g / cm 3 Above, and 2.9g / cm 3 Below that, 2.8g / cm 3 Here, the dry density of the component (i) can be specifically measured, for example, by the method of JIS A 1224, and the dry density was also measured by this method in the examples described later.

[0018] The component (i) has a BET specific surface area of, for example, 10 m 2 / g or more, and 20m 2 / g or more, and 100m 2 / g or less, and 80m 2 / g or less. Here, the BET specific surface area of ​​component (i) is measured, for example, by a gas adsorption method, that is, a method in which gas molecules with a known adsorption area are adsorbed on the surface of soil particles, the specific surface area of ​​the sample is calculated from the amount of gas molecules adsorbed, and the pore distribution is measured from the condensation of the gas molecules. Specifically, the BET specific surface area of ​​component (i) can be measured, for example, by a one-point BET method using a fully automatic specific surface area measuring device (for example, MacSorb manufactured by Mountec Co., Ltd.). In the examples described later, a fully automatic specific surface area measuring device (MacSorb manufactured by Mountec Co., Ltd.) is used, and about 3 g of the sample is placed in a glass cell, and the adsorption gas (a mixed gas of nitrogen and helium in a ratio of 3:7) is injected at 60 cm into the sample cooled to liquid nitrogen temperature. 3 The gas was introduced at a flow rate of 100 / min and allowed to adsorb, and the amount of gas desorbed when the sample was returned to room temperature was measured. The specific surface area (single-point BET method) was obtained by dividing the amount by the sample mass.

[0019] Component (ii) is a hydraulic powder. The hydraulic powder of component (ii) is a powder having the physical property of hardening through a hydration reaction, and examples thereof include cement, gypsum, and the like. The hydraulic powder is preferably cement. The cement is, for example, Portland cement such as ordinary Portland cement, belite cement, moderate heat cement, early strength cement, ultra early strength cement, sulfate resistant cement, etc. The hydraulic powder contains cement, further Portland cement, 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.

[0020] 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.

[0021] 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.

[0022] The component (iii) is a compound represented by the following general formula (1). RO-(AO) m -H (1) (In general formula (1), R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, AO represents an oxyethylene group or oxypropylene, and m represents the average number of moles of AO added and is a number of 20 to 25,000.)

[0023] In the general formula (1), R is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. Examples of the hydrocarbon group include an alkyl group and an alkenyl group. R is preferably a hydrogen atom. In the general formula (1), AO is an oxyethylene group or an oxypropylene group, and AO is preferably an oxyethylene group. In the general formula (1), m represents the average number of moles of AO added and is a number of 20 to 25000. m is, for example, preferably 50 or more, preferably 100 or more, preferably 350 or more, preferably 500 or more, more preferably 2000 or more, more preferably 6000 or more from the viewpoint of reducing the clay lump residual rate, and from the viewpoint of reducing the fluidity of the solidification material slurry, it may be preferably 18000 or less, more preferably 16000 or less, more preferably 14000 or less, more preferably 12000 or less, more preferably 8000 or less, or more preferably 5000 or less.

[0024] The weight average molecular weight of the (iii) component is, for example, preferably 1000 or more, more preferably 1800 or more, more preferably 3000 or more, more preferably 5000 or more, more preferably 10000 or more, more preferably 15000 or more, and from the viewpoint of reducing the fluidity of the solidification material slurry, preferably 1000000 or less, more preferably 800000 or less, more preferably 400000 or less, more preferably 200000 or less, more preferably 50000 or less, more preferably 25000 or less. It is preferable to select m in the general formula (1) so that the (i) component has this weight average molecular weight.

[0025] In the ground improvement method of the present invention, from the viewpoint of obtaining a homogeneous solidification material mixture (meaning a mixture containing components (i), (ii), (iii) and water; the same applies below) with few clay lumps, component (iii) is mixed in a ratio of 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.03% by mass or more, and 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less, relative to component (i). This ratio is calculated by [amount of component (iii) / amount of component (i)]×100.

[0026] In the ground improvement method of the present invention, from the viewpoint of preparing a uniformly mixed cement slurry in a short time, the (iii) component is mixed in a ratio of preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.5 mass% or more, and preferably 12 mass% or less, more preferably 11 mass% or less, even more preferably 10 mass% or less, and even more preferably 1 mass% or less, relative to the (ii) component. This ratio is calculated by [amount of (iii) component / amount of (ii) component]×100.

[0027] In the ground improvement method of the present invention, from the viewpoint of achieving both the strength of the column and the reduction of the amount of sludge generated during construction, the (ii) component is mixed in a ratio of preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 5 mass% or more, and preferably 100 mass% or less, more preferably 50 mass% or less, even more preferably 30 mass% or less, even more preferably 15 mass% or less, relative to the (i) component. This ratio is calculated by [amount of (ii) component / amount of (i) component]×100.

[0028] In the ground improvement method of the present invention, from the viewpoint of achieving both the strength of the column and the reduction of the amount of sludge generated during construction, the (iv) component is mixed in a ratio of preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 100% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, based on the (ii) component. This ratio is calculated by [amount of (iv) component / amount of (ii) component]×100.

[0029] In the present invention, a water reducing agent (v) (hereinafter referred to as component (v)) may be mixed. Examples of the (v) component include polymer compounds having a group selected from a carboxyl group, a sulfonic acid group, and a phosphoric acid group. The weight-average molecular weight of the polymer compound may be 3,000 or more and 100,000 or less. Examples of the (v) component include polycarboxylic acid polymers, naphthalene polymers, and polymers of (hydroxyalkyl) methacrylic acid esters of phosphoric acid. Specifically, examples of the (v) component include polyalkylene glycol monoester monomers having an oxyalkylene group with 2 or 3 carbon atoms and acrylic acid polymers, polymers containing amide macromonomers, polymers containing polyethyleneimine, copolymers of polyalkylene glycol monoester monomers having an oxyalkylene group with 2 or 3 carbon atoms, di-[(2-hydroxyethyl) methacrylic acid] phosphate, and mono(2-hydroxyethyl) methacrylic acid phosphate, and naphthalene sulfonic acid formaldehyde condensates. Examples of the (v) component include melamine sulfonic acid formalin condensates, aminosulfonic acid, and the like. (v) Component can be a commercially available water reducing agent or high-performance water reducing agent. In the ground improvement method of the present invention, from the viewpoint of reducing the load on the cement milk pump, component (v) is mixed in a ratio of preferably 0.01 mass% or more, more preferably 0.02 mass% or more, even more preferably 0.03 mass% or more, and preferably 1 mass% or less, more preferably 0.5 mass% or less, even more preferably 0.2 mass% or less, relative to component (ii). This ratio is calculated by [amount of component (v) / amount of component (ii)]×100.

[0030] In the present invention, a defoaming agent (vi) (excluding component (iii)) (hereinafter referred to as component (vi)) may be mixed. Examples of the component (vi) include silicone-based defoamers, fatty acid ester-based defoamers, ether-based defoamers, aliphatic amine-based defoamers, etc. Dimethylpolysiloxane is more preferred among silicone-based defoamers, polyalkylene glycol fatty acid esters are more preferred among fatty acid ester-based defoamers, polyalkylene glycol alkyl ethers are more preferred among ether-based defoamers, and alkyldimethylamines or salts thereof are more preferred among aliphatic amine-based defoamers. In the ground improvement method of the present invention, from the viewpoint of preventing outflow of materials from the milk plant, the (vi) component is mixed with the (ii) component in a ratio of preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more, even more preferably 0.0003% by mass or more, and preferably 0.01% by mass or less, more preferably 0.005% by mass or less, even more preferably 0.001% by mass or less. This ratio is calculated by [amount of the (vi) component / amount of the (ii) component]×100.

[0031] In the present invention, it is preferable to mix a slurry containing components (ii), (iii), and (iv) with component (i). The slurry is a slurry containing components (ii), (iii), and (iv), and may be a solidifying material slurry such as so-called cement milk. The slurry may contain components (v) and (vi).

[0032] In the present invention, the component (i) can also be mixed with the components (ii), (iii) and (iv) separately.

[0033] In the ground improvement method of the present invention, the (i) component can be mixed with the (ii), (iii) and (iv) components in situ to prepare soil cement. As an example of the ground improvement method of the present invention, the prepared soil cement can be poured into the ground, and the soil cement hardens to become a ground improvement body, thereby improving the strength of the ground.

[0034] The ground improvement method of the present invention includes a construction method in which soil cement is poured into the ground. For example, the method can be implemented by a surface mixing method, a middle layer mixing method, a deep layer mixing method, a steel pipe pile method, a shield method, and the like. For example, the deep layer mixing improvement method includes a high pressure injection method, a TRD method, an SMW method, and the like. The method of the present invention is suitable for the deep layer mixing method.

[0035] In the ground improvement method of the present invention, it is preferable to use the above-mentioned slurry. In that case, the above-mentioned slurry can be mixed into the component (i) using a slurry mixing type agitator. Here, the slurry mixing type agitator is an agitator used in a construction method involving mechanical agitation of soil and slurry, and is an agitator that can inject a slurry containing hydraulic powder such as cement into soil and add mechanical agitation. Examples of construction methods using such an agitator include the mud stabilizer method, the ARM method, the LVM method, the FAM method, the mud mixer M-II method, the SCM method, the ISM method, the WILL method, the eye mark method II, the VMS method, and the ST column method. Examples of these include three-dimensional mixing method, power blender method, MMB method, MR-IIC method, twin blade mixing method, open wing method, double mixing method, USP method, MT-CMC method, Esmi column method, Three S G method, Soil Master method, CDM-SSC method, PROP method, CI-CMC method, Ascolumn method, DJM method, TRD method, Epo column method, NC column method, RAS column method, JST method, CDM-LODIC method, CDM-column method, CDM method, Teno column method, KS-B MIX method, CDM-Mega method, CDM-Land4 method, CDM-Lemni 2 / 3 method, CDM-FLOAT method, DCM-L method, DCS method, expansion and contraction column method, HEMS method, and MITS method.

[0036] In the present invention, from the viewpoint of achieving both the quality of the column and the shortening of the construction period, the number of times the blades are cut in the mixing by the agitator is preferably 100 times or more, more preferably 200 times or more, and preferably 1000 times or less, more preferably 500 times or less. It is preferable to use an agitator with a blade cutting number in this range. In general, an agitator used for ground improvement is equipped with agitating blades, and the number of blade cutting is set in consideration of the shape of the agitating blades, the number of agitating blades, the agitating force, the amount of soil, the quality of the soil, etc.

[0037] When using the slurry, the specific method of injecting the slurry into the ground (i) component may be in accordance with known ground improvement methods. Examples of methods for injecting the slurry into the ground include jet mixing methods (one-phase flow method, two-phase flow method, three-phase flow method), mechanical mixing methods (CDM method, etc.), and underground diaphragm wall methods (SMW method, TRD method, etc.). The solidification material mixture such as soil cement obtained by mixing the slurry with the (i) component can be solidified in accordance with known ground improvement methods.

[0038] In the present invention, the component (i) can be mixed and stirred while injecting the slurry into the ground, to form soil cement, and then a soil cement column can be constructed. In the present invention, the component (i) can be mixed with the slurry by rotating and drilling the ground while discharging the slurry from the tip of the mixing and stirring device. These methods can be combined. Such a method is suitable for a deep mixing treatment method.

[0039] The ground improvement method of the present invention includes a method of penetrating component (i) while rotating a rod equipped with an agitating blade and a slurry outlet, and injecting a slurry containing components (ii), (iii), and (iv) into component (i) from the outlet while stirring and mixing component (i) and the slurry with the agitating blade, in which component (iii) is mixed in a ratio of 0.01% by mass to 1% by mass relative to component (i). This method is also preferably performed at the original location of component (i). In general, when such a rod is used, component (i) and the slurry are stirred and mixed in an area shaped according to the rotation shape of the rod, for example, a circular area.

[0040] In the present invention, as the agitator for the slurry mixing method, for example, an earth auger for excavation having an auger rod, a nozzle for ejecting the solidification material (slurry) provided on the auger rod, an excavation blade provided on the auger rod, and an anti-corotation blade provided on the auger rod as necessary can be used. Such an earth auger for excavation can be any known one used in the method for constructing soil cement columns. The excavating earth auger is set at a predetermined position in the ground where a soil cement column is to be constructed, and excavation is performed to a predetermined dry excavation depth while rotating the mixing blade. During this process, the slurry is discharged from the auger rod while excavation is performed. Although excavation may be performed without discharging the slurry, when the predetermined depth is reached, the slurry is discharged while excavation is performed. When the injection excavation process (mixing and stirring) is completed, the discharge of the slurry is stopped, the rotation direction of the auger rod is reversed, and then lifting (mixing and stirring) is started. The auger is pulled out to complete the process. In this method, the number of times the blades are cut can be calculated from the rotation speed of the mixing blade. In the present invention, the clay lumps in the soil cement column are reduced, and the clay lumps that exist are small, so that the decrease in the strength of the soil cement column can be suppressed. The slurry can be prepared with excellent fluidity, so that the workability is improved.

[0041] <Ground improvement body> The present invention relates to a ground improvement body containing component (i), component (ii), and component (iii), and containing component (iii) in a ratio of 0.01% by mass to 1% by mass relative to component (i). 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. Specific examples and preferred examples of components (i), (ii), and (iii) in the ground improvement body of the present invention are also the same as those in the ground improvement method of the present invention.

[0042] The ground improvement body of the present invention may be a ground improvement body obtained by mixing component (i), component (ii), and component (iii), in which the mixing ratio of component (iii) is 0.01 mass% or more and 1 mass% or less relative to component (i). Furthermore, the ground improvement body of the present invention may be a ground improvement body obtained by hardening a mixture of components (i), (ii), (iii), and (vi), in which the mixing ratio of component (iii) is 0.01 mass % or more and 1 mass % or less relative to component (i).

[0043] The ground improvement product of the present invention contains component (iii) in a ratio of 0.01% by mass or more, preferably 0.02% by mass or more, more preferably 0.03% by mass or more, and 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less, relative to component (i). This ratio is calculated by [amount of component (iii) / amount of component (i)]×100.

[0044] The ground improvement product of the present invention contains component (iii) in a ratio of preferably 0.1 mass% or more, more preferably 0.2 mass% or more, even more preferably 0.5 mass% or more, and preferably 12 mass% or less, more preferably 11 mass% or less, even more preferably 10 mass% or less, and even more preferably 1 mass% or less, relative to component (ii). This ratio is calculated by [amount of component (iii) / amount of component (ii)]×100.

[0045] The ground improvement body of the present invention contains the component (ii) in a ratio of preferably 1 mass % or more, more preferably 3 mass % or more, even more preferably 5 mass % or more, and preferably 100 mass % or less, more preferably 50 mass % or less, even more preferably 30 mass % or less, even more preferably 15 mass % or less, based on the component (i). This ratio is calculated by [amount of component (ii) / amount of component (i)]×100.

[0046] When the ground improvement body of the present invention is a hardened product of a mixture obtained by mixing component (iv), the mixture contains component (iv) in a ratio of preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 100% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, based on component (ii). This ratio is calculated by [amount of component (iv) / amount of component (ii)]×100. EXAMPLES

[0047] The components (ii), (iii), and (iv) shown in the table were mixed in the amounts (g) shown in the table to prepare a solidification material slurry. Mixing was carried out using a hand mixer for 1 minute. The component (i) used here was the following soil. Average particle size: 13.5μm Difference between natural water content and plastic limit: 18.3% Clay content: 61% by weight Dry density: 2.45g / cm 3 BET specific surface area: 31.3m 2 / g The component (ii) used was Eustabiler 50, a special soil solidification material manufactured by Ube Mitsubishi Cement Co., Ltd.

[0048] The fluidity of the solidification material slurry (P funnel flow time) was measured in accordance with JSCE-F521-1999 "Fluidity test of injection mortar for prepacked concrete", and the results are shown in the table.

[0049] The soil cement was prepared by mixing the solidification material slurry with the (i) component in the amount shown in the table. The mixing was carried out for 1 minute using a mortar Hobart mixer. The soil cement was filled into a container (soft plastic cup) with a diameter of 10 cm and a height of 5 cm, and the container was tapped 10 times to remove any coarse voids.

[0050] While the soil cement was still unhardened, the container was filled with soil cement, and the container was cut at a position 2.5 cm from the bottom, and 1% phenolphthalein (90% ethanol) was sprayed onto the cut surface. The areas containing cement were stained, but the areas not containing cement were not stained. The areas not containing cement were unstained areas where clay lumps remained. A transparent 5mm square mesh was placed on the cross section after the dyeing process, and the number of unstained cells was counted. The clay lump residual rate was calculated using the following formula, which was used as an index of mixability. This formula assumes that a cell that is partially unstained is equivalent to 0.5 unstained cells. The smaller the clay lump residual rate, the more uniformly the soil and solidification material slurry are mixed. Clay lump remaining rate (%) = {(number of cells in the 5 mm grid that are all unstained) x 1 + (number of cells in the 5 mm grid that are partially unstained) x 0.5} / (total number of cells used in the measurement) In the table, the reduction value (difference) is shown as a relative value based on the clay lump residual rate of Comparative Example 4. The relative value was calculated by the following formula. Relative value (%) = {1 - (clay lump residual rate of each example / clay lump residual rate of Comparative Example 4)} x 100

[0051] [Table 1]

[0052] The symbols for component (iii) in the table have the following meanings. PEG: Polyethylene glycol PPG: Polypropylene glycol ·C4-PPG: Polypropylene glycol monobutyl ether

Claims

1. A method for improving ground comprising mixing a clay-containing soil (i) (hereinafter referred to as component (i)), a hydraulic powder (ii) (hereinafter referred to as component (ii)), a compound (iii) represented by the following general formula (1) (hereinafter referred to as component (iii)), and water (iv) (hereinafter referred to as component (iv)), The component (iii) is mixed in a ratio of 0.01% by mass or more and 1% by mass or less with respect to the component (i), and the weight average molecular weight of the component (iii) is 3,000 or more and 1,000,000 or less. Ground improvement method. R-O-(AO)m-H (1) (In general formula (1), R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, AO represents an oxyethylene group, and m represents the average number of moles of AO added and is a number of 20 to 25,000.)

2. 2. The method for improving ground according to claim 1, wherein a slurry containing the components (ii), (iii) and (iv) is mixed with the component (i).

3. 3. The method for improving ground according to claim 2, wherein the slurry is mixed with component (i) using a slurry mixing type agitator.

4. The ground improvement method according to claim 3, wherein the number of times the blades of the agitator are cut is 100 to 1,000 times.

5. The method for improving ground according to any one of claims 1 to 4, wherein the component (i) is mixed with the component (ii), the component (iii), and the component (iv) in situ.

6. The ground improvement method according to any one of claims 1 to 5, wherein the (ii) component is mixed in a ratio of 1 mass% to 100 mass% relative to the (i) component.

7. A ground improvement body containing clay-containing soil (i) [hereinafter referred to as component (i)], hydraulic powder (ii) [hereinafter referred to as component (ii)], and a compound (iii) represented by the following general formula (1) [hereinafter referred to as component (iii)]: The component (iii) is contained in an amount of 0.01% by mass or more and 1% by mass or less relative to the component (i), and the weight average molecular weight of the component (iii) is 3,000 or more and 1,000,000 or less. Ground improvement body. R-O-(AO)m-H (1) (In general formula (1), R represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms, AO represents an oxyethylene group, and m represents the average number of moles of AO added and is a number of 20 to 25,000.)

8. The ground improvement body according to claim 7, containing the component (iii) in a ratio of 0.007 mass% or more and 12 mass% or less relative to the component (ii).

9. 9. The ground improvement body according to claim 7 or 8, containing the component (ii) in a ratio of 1 mass% or more and 100 mass% or less relative to the component (i).

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