JP2022183826A - Soil improvement method - Google Patents

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, and can obtain a soil-improved body which is excellent in rigidity.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 (ii) to (i) at a ratio equal to or lower than 18 mass%, and in the method, (i) is the soil whose uniformity coefficient (D50/D10) is equal to or higher than 2.6, and equal to or lower than 8.0: 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 to or larger 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 18,000.)SELECTED DRAWING: None

Description

The present invention relates to a ground improvement method.

In fields such as civil engineering and construction, 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 method, earth retaining method, foundation pile method, backfilling method and the like. Soil cement is a mixture of soil with a cement-based solidifying material or water added thereto. Soil cement used in the fields of civil engineering and construction is often prepared by adding cement milk, which is a mixture of a cement-based solidifying material and water in advance, to soil. Soil cements have different physical properties, such as viscosity and fluidity, due to differences in construction methods. Cement milk and soil cement are used, for example, in a columnar ground reinforcement construction method such as the so-called soil cement construction method in which cement milk is injected into the ground to construct a soil cement column in the ground. Also known is a so-called replacement column method in which ground soil is replaced with a solidification material.

Patent Document 1 discloses an excavation auger having a supply passage for a hydraulic solidification liquid inside thereof, and having at least an excavation claw and a discharge port for the hydraulic solidification liquid at the tip thereof, and the excavation auger equipped with an auger motor. Excavate to a predetermined depth while rotating (forward or reverse rotation) with the construction device, and then rotate (forward or reverse rotation) the excavation auger while discharging the hydraulic solidification material liquid from the discharge port, or A method for constructing a hydraulic solidifying material replacement column is disclosed, which is characterized by pulling up the column without rotating it and filling a predetermined section of an excavated portion with the hydraulic solidifying material liquid.

On the other hand, it is known to add various components to cementitious solidifying materials.
Patent Document 2 discloses a soil cement containing a compound having an ortho-position polyhydric phenol skeleton.
In Patent Document 3, phosphoric acid obtained by copolymerizing a specific monomer 1 having a polyoxyalkylene group, a phosphoric acid monoester monomer 2, and a phosphoric acid diester monomer 3 at pH 7 or less A soil cement additive containing an ester polymer is disclosed.
In Patent Document 4, 0 parts of a powdery soil improvement additive consisting of sodium lignin sulfonate, alkali metal carbonate, and a predetermined polyether antifoaming agent is added per 100 parts by mass of a powdery cement-based solidifying material. A powdery premixed cement composition for soil improvement comprising 0.5 to 15 parts by weight is disclosed.

JP 2011-106253 A JP 2020-26523 A JP 2007-169547 A JP 2009-286655 A

In soil cement, clay may exist as clumps due to incorporation from the soil or agglomeration during mixing. If clay lumps remain in the soil cement, for example, the soil tends to adhere to the excavating blades and mixing blades of the excavating and mixing device, causing the so-called co-rotation phenomenon in which these blades and the soil rotate synchronously. It may occur and the soil and solidification material may not be stirred and mixed uniformly. If the fine particles such as clay are not uniformly mixed, clay lumps will be localized in the soil cement column, resulting in a decrease in the strength of the soil improvement material, which is the hardened material of the soil cement.
INDUSTRIAL APPLICABILITY The present invention is a ground improvement method that can uniformly mix the soil and the solidifying material by reducing clay lumps when soil containing clay is improved using a solidifying material, and obtains a soil improvement body with excellent strength. I will provide a.

The present invention comprises clay-containing soil (i) [hereinafter referred to as component (i)], hydraulic powder (ii) [hereinafter referred to as component (ii)], and general formula (1) below. A soil improvement method for mixing compound (iii) [hereinafter referred to as (iii) component] and water (iv) [hereinafter referred to as (iv) component],
(i) the component is soil with a uniformity coefficient (D50/D10) of 2.6 or more and 8.0 or less;
(ii) component is mixed in a ratio of 18% by mass or less with respect to (i) component,
It relates to a ground improvement method.
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 added moles of AO.)

According to the present invention, when soil containing clay is improved using a solidification material, clay lumps can be reduced and the soil and the solidification material can be uniformly mixed, and a ground improvement body having excellent strength can be obtained. An improved method is provided.

<Soil Improvement Method>
In the ground improvement method of the present invention, the (i) component having a uniformity coefficient (D50/D10) of 2.6 or more and 8.0 or less is mixed with the (ii) component, the (iii) component, and the (iv) component. It is a ground improvement method, wherein the component (ii) is mixed with the component (i) in a ratio of 18% by mass or less.

The component (i) is clay-containing soil having a uniformity coefficient (D50/D10) of 2.6 or more and 8.0 or less. (i) The uniformity factor (D50/D10) of the component is the effective diameter D50 (particle diameter at a passing mass percentage of 50%) obtained by the method of JIS A 1204 with the effective diameter D10 (particle diameter at a passing mass percentage of 10%). It is calculated by dividing The uniformity coefficient was calculated by this method also in the examples described later. (i) The uniformity coefficient (D50/D10) of the component is 2.6 or more, preferably 2.8 or more, from the viewpoint that the strength of the soil improvement material can be improved by reducing the sand component and making the grains dense. It is more preferably 3.0 or more and 8.0 or less, preferably 7.6 or less, more preferably 7.0 or less, still more preferably 6.0 or less.

Component (i) may be soil having a natural water content of 35% or more and 85% or less, from the viewpoint of increasing the uniformity of mixing and the adhesion strength of particles through water. (i) The natural water content of the component means the ratio obtained by dividing the mass of water contained in the soil by the dry mass of the soil, and is calculated by the soil water content test method of JIS A 1203. . The natural water content ratio was also measured by this method in the examples described later. The natural water content of component (i) is more preferably 40% or more, still more preferably 45% or more, and more preferably 80% or less, still more preferably 75% or less.

The component (i) may be soil having a BET specific surface area of 30 m ² /g or more and 70 m ² /g or less from the viewpoint of securing adhesion points between particles and increasing strength. The BET specific surface area of component (i) is more preferably 35 m ² /g or more, still more preferably 40 m ² /g or more, and more preferably 65 m ² /g or less, still more preferably 60 m ² /g or less. The BET specific surface area of component (i) is determined by a method of adsorbing gas molecules with a known adsorption area on the surface of soil particles, determining the specific surface area of the sample from the amount, and measuring the pore distribution from the condensation of the gas molecules. Calculated. Specifically, the BET specific surface area of component (i) can be measured, for example, by a single-point BET method using a fully automatic specific surface area measuring device (eg, 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.) was used, about 3 g of a sample was placed in a glass cell, and the sample cooled to the temperature of liquid nitrogen was added with an adsorption gas (nitrogen and helium). 3:7 mixed gas) is introduced at a flow rate of 60 cm ³ /min for adsorption, the amount of gas desorbed when the sample is returned to room temperature is measured, and the specific surface area ( 1-point BET method) was obtained.

The component (i) may be soil having a pore distance of 7 nm or more and 20 nm or less from the viewpoint of increasing the strength by cross-linking the particles with the compound (iii). The pore distance of component (i) is calculated by dividing the volume of water contained in the soil by the BET specific surface area. The pore distance of component (i) is more preferably 8 nm or more, still more preferably 9 nm or more, and more preferably 18 nm or less, still more preferably 16 nm, from the viewpoint of the short distance that compound (iii) can crosslink. It is below.

The component (i) may be soil in which the difference between the natural water content and the plastic limit is 0% or more and 80% or less, from the viewpoint that the compound (iii) fixes water on the surface of the particles and increases the strength. Here, the plastic limit is the water content ratio at the boundary when the soil changes from a plastic state to a semi-solid state. In addition, it may be the water content ratio when it is just cut off. Specifically, the plastic limit of the component (i) can be measured, for example, by JIS A 1205 “Liquid limit/plastic limit test method for soil”, and the plastic limit is measured by this method in the examples described later. did. The difference between the natural water content of component (i) and the plastic limit is more preferably 20% or more, more preferably 40% or more, and more preferably 70%, from the viewpoint of increasing the concentration of compound (iii) and mixing uniformity. % or less, more preferably 60% or less.

In the present invention, each physical property (uniformity coefficient, etc.) for the component (i) is obtained by using soil (in situ soil) as a sample for performing the soil improvement method of the present invention. For example, the uniformity factor may be determined for the soil in situ.

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The uniformity factor, natural water content, and BET specific surface area of component (i) can be adjusted, for example, by kneading industrial sand, sand for grain size adjustment, and water.

Component (i) may have an average particle size of, 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 float in water and measuring changes in the density of the suspension over time to determine the particle size. be. Specifically, the average particle size of the component (i) can be measured, for example, according to JIS A 1223 "Testing method for content of fine particles in soil".

Component (i) preferably contains fine particles having a particle size of less than 75 μm.
Criteria for classifying soil as a geotechnical material are summarized as criteria of the Geotechnical Society (Geotechnical Society of Japan, 2009). According to this, 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 grain fractions are components that give viscosity to the soil. Further, according to the Japanese Geotechnical Society standards, cohesive soil, organic soil, and volcanic cohesive soil are known as soils in which the ratio of fine particles having a particle size of less than 75 μm is 50% by mass or more. In the present invention, such soil can be targeted.
As an example of component (i), 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, still more preferably 60% by mass or more, and even more preferably 70% by mass. above, and preferably below 100% by mass.

Clay is mainly composed of hydrous silicate minerals (hereinafter referred to as clay minerals) having a layered structure, and 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.). There are various types and amounts of clay contained in soil, but the present invention can target soil containing clay minerals selected from kaolin and smectite, for example.

The (i) component may be soil containing halloysite. Component (i) contains, for example, 5% by mass or more, 10% by mass or more, 15% by mass or more, and 50% by mass or less, 40% by mass or less, and 30% by mass or less of halloysite. It's okay.

Component (i) contains, for example, 15 mass % or more, further 20 mass % or more, further 25 mass % or more, and 100 mass % or less, further 95 mass % or less, further 90 mass % or less of clay. It's okay.

The (i) component may be soil originating from volcanic ash. The (i) component may be a volcanic cohesive soil, such as a tuffaceous clay. Tuffaceous clay is soil made from volcanic ash that has turned into clay through weathering and hydration. In general, tuffaceous clays have a low sand content and a milky or milky white appearance. Tuff clay is a soil in which clay lumps are easily mixed and formed during the production of soil cement, but the clay lumps are difficult to deflocculate. It can be deflocculated easily. Component (i) contains, for example, 5 mass% or more, further 10 mass% or more, further 15 mass% or more, and 50 mass% or less, further 40 mass% or less, further 30 mass% or less of tuff clay. can be anything.

Component (i) may have a dry density of, for example, 1.9 g/cm ³ or more, further 2.0 g/cm ³ or more, and 2.9 g/cm ³ or less, further 2.8 g/cm ³ or less. . Here, the dry density of component (i) is measured by the method of JIS A 1224.

(ii) component is a hydraulic powder. Hydraulic powder as component (ii) is a powder having a physical property to harden by hydration reaction, and examples thereof include cement and gypsum.
The hydraulic powder is preferably cement. Cement includes, for example, Portland cement such as ordinary Portland cement, belite cement, moderate heat cement, high-early-strength cement, super-early-strength cement, sulfate-resistant cement, and the like. Hydraulic powder contains cement, more preferably Portland cement, preferably 25% by mass or more, more preferably 35% by mass or more, still more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass. % by mass or more, preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, and even more preferably 85% by mass or less.

Moreover, the hydraulic powder can contain powder having pozzolanic action and/or latent hydraulicity such as blast furnace slag, fly ash, silica fume, and stone powder (calcium carbonate powder). Blast-furnace slag cement, fly ash cement, silica fume cement, etc. to which these are added to cement may also be used. The hydraulic powder preferably contains blast furnace slag from the viewpoint of supplying aluminum ions for ettringite, which is a hydration product. When the hydraulic powder contains blast furnace slag, the content is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, more preferably 60% by mass or less, more preferably It is less than 50% by mass.

In the present invention, the amount of hydraulic powder is the amount of powder having a physical property to harden by hydration reaction, for example, the amount of cement or gypsum. , latent hydraulic powder, and stone powder (calcium carbonate powder), the amount thereof is also included in the amount of hydraulic powder in the present invention.

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 added moles of AO.)
In general formula (1), R is a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. Hydrocarbon groups include alkyl groups and alkenyl groups. R is preferably a hydrogen atom.
In general formula (1), AO is an oxyethylene group or oxypropylene. AO is preferably an oxyethylene group.
In general formula (1), m represents the average added mole number of AO. m may be, for example, a number of 50 or more, further 100 or more, further 150 or more, and 50,000 or less, further 25,000 or less, further 12,500 or less.

The weight average molecular weight of component (iii) may be, for example, 1,000 or more, further 2,000 or more, further 3,000 or more, and 2,000,000 or less, further 1,000,000 or less, further 500,000 or less, further 200,000 or less. It is preferable to select m in the general formula (1) so that the component (i) has this weight average molecular weight.

In the ground improvement method of the present invention, the component (ii) is mixed with the component (i) in a ratio of 18% by mass or less from the viewpoint of achieving both the strength of the column and the reduction of the amount of sludge generated during construction. . This proportion is preferably 3% by mass or more, more preferably 3.2% by mass or more, still more preferably 4% by mass or more, more preferably 5% by mass or more, even more preferably 6% by mass or more, and even more preferably 8% by mass or more, preferably 15% by mass or less, more preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less. This ratio is calculated by [amount of component (ii)/amount of component (i)]×100.

In the ground improvement method of the present invention, from the viewpoint of obtaining a uniform solidification material mixture (meaning a mixture containing (i) component, (ii) component, (iii) component and water, hereinafter the same) with less clay lumps , Component (iii) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, still more preferably 0.03% by mass or more, and preferably 1% by mass, relative to component (i) % or less, more preferably 0.5 mass % or less, and still more preferably 0.2 mass % or less. This ratio is calculated by [amount of component (iii)/amount of component (i)]×100.

In the ground improvement method of the present invention, the component (iii) is preferably 0.007% by mass or more, more preferably 0.007% by mass or more, more preferably 0.007% by mass or more, based on the component (ii), from the viewpoint of preparing a uniformly mixed cement slurry in a short time. 008% by mass or more, more preferably 0.009% by mass or more, and preferably 12% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. This ratio is calculated by [amount of component (iii)/amount of component (ii)]×100.

In the ground improvement method of the present invention, from the viewpoint of ensuring the fluidity of the cement slurry and reducing the amount of sludge discharged, the component (iv) is preferably 40% by mass or more, more preferably 50% by mass, based on the component (ii). Above, more preferably 60% by mass or more, preferably 250% by mass or less, more preferably 150% by mass or less, and even more preferably 80% by mass or less are mixed. This ratio is calculated by [amount of component (iv)/amount of component (ii)]×100.

In the present invention, a water reducing agent (v) [hereinafter referred to as component (v)] may be mixed with component (i).
Component (v) includes polymer compounds having groups selected from carboxyl groups, sulfonic acid groups and phosphoric acid groups. The weight average molecular weight of the polymer compound may be 3,000 or more and 100,000 or less. Examples of component (v) include polycarboxylic acid-based polymers, naphthalene-based polymers, and polymers of phosphoric acid (hydroxyalkyl) methacrylic acid) esters. Specifically, a polyalkylene glycol monoester-based monomer and an acrylic acid-based polymer into which an oxyalkylene group having 2 or 3 carbon atoms is introduced, a polymer containing an amide-based macromonomer, a polymer containing polyethyleneimine, Polyalkylene glycol monoester-based monomer into which an oxyalkylene group having 2 or 3 carbon atoms is introduced, phosphoric acid di-[(2-hydroxyethyl) methacrylic acid] ester, and phosphoric acid mono(2-hydroxyethyl) methacrylic acid Copolymers with acid esters, naphthalene sulfonic acid formaldehyde condensates, and the like are included. In addition, melamine sulfonic acid-formalin condensates, aminosulfonic acid systems, and the like can also be used as the component (v). A commercially available water reducing agent or a high performance water reducing agent can be used as the component (v).
In the soil improvement method of the present invention, from the viewpoint of reducing the load on the cement milk pump, the component (v) is preferably 0.01% by mass or more, more preferably 0.02% by mass, relative to the component (ii). Above, more preferably 0.03% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.2% by mass or less are mixed. This ratio is calculated by [amount of component (v)/amount of component (ii)]×100.

In the present invention, an antifoaming agent (vi) [excluding component (iii)] [hereinafter referred to as component (vi)] may be mixed with component (i).
Component (vi) includes silicone antifoaming agents, fatty acid ester antifoaming agents, ether antifoaming agents, and aliphatic amine antifoaming agents. Dimethylpolysiloxane is more preferable as a silicone antifoaming agent, polyalkylene glycol fatty acid ester is more preferable as a fatty acid ester antifoaming agent, polyalkylene glycol alkyl ether is more preferable as an ether antifoaming agent, and an aliphatic amine antifoaming agent. Alkyldimethylamine or a salt thereof is more preferred as the agent.
In the soil improvement method of the present invention, from the viewpoint of preventing the outflow of materials in the milk plant, the component (vi) is preferably 0.0001% by mass or more, more preferably 0.0002% by mass, based on the component (ii). % by mass or more, more preferably 0.0003% by mass or more, and preferably 0.01% by mass or less, more preferably 0.005% by mass or less, and even more preferably 0.001% by mass or less. This ratio is calculated by [amount of component (vi)/amount of component (ii)]×100.

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

In the present invention, component (ii), component (iii), and component (iv) can be separately mixed with component (i).

In the ground improvement method of the present invention, soil cement can be prepared by mixing component (i) with component (ii), component (iii) and component (iv) in situ with component (i). . As the soil improvement method of the present invention, for example, the prepared soil cement is placed in the ground, and the soil cement hardens to become a soil improvement body to improve the strength of the ground.

The ground improvement method of the present invention includes a construction method of placing soil cement in the ground. For example, it can be implemented by construction methods such as a surface layer mixing method, an intermediate layer mixing method, a deep layer mixing method, a steel pipe pile construction method, and a shield construction method. For example, the deep 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 deep mixing processing methods.

In the soil improvement method of the present invention, it is preferable to use the slurry. In that case, the slurry can be mixed with component (i) using a slurry mixing type stirrer. Here, the slurry mixing type agitator is an agitator used in a construction method involving mechanical agitation of soil and slurry, and can add slurry containing hydraulic powder such as cement to soil and add mechanical agitation. A stirrer. Examples of construction methods using such stirrers include the Mud Stubby construction method, ARM construction method, LVM construction method, FAM construction method, Mud Mixer M-II construction method, SCM construction method, ISM construction method, WILL construction method, Eye Mark construction method II, VMS construction method, ST column method. 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, 3S G method, soil master method , CDM-SSC method, PROP method, CI-CMC method, As-column method, DJM method, TRD method, Epo-column method, NC-column method, RAS-column method, JST method, CDM-LODIC method, CDM-column method, CDM method, Tenocolumn method, KS-B・MIX method, CDM-Mega method, CDM-Land4 method, CDM-Lemni 2/3 method, CDM-FLOAT method, DCM-L method, DCS method, Scaling column method, HEMS method, MITS method can be mentioned.

In the present invention, from the viewpoint of both the quality of the column and the shortening of the construction period, in the mixing with the stirrer, the number of times of blade cutting is preferably 100 times or more, more preferably 200 times or more, and preferably 1000 times or less. It is preferably 500 times or less. It is preferable to use a stirrer with blade cutting times within this range. In general, the agitator used for soil improvement is equipped with agitating blades, and the blade cutting frequency is set in consideration of the shape of the agitating blade, the number of agitating blades, the agitation power, the amount of soil, the quality of the soil, etc. .

When the slurry is used, a specific method of injecting the slurry into the ground component (i) may be according to a known ground improvement method. As a method of injecting the slurry into the ground, for example, injection stirring method (single-phase flow method, two-phase flow method, three-phase flow method), mechanical stirring method (CDM method, etc.), underground continuous wall method (SMW method) , TRD method, etc.). A solidification material mixture such as soil cement obtained by mixing the slurry and component (i) can be solidified according to a known ground improvement method.

In the present invention, the component (i) is mixed and agitated while injecting the slurry into the ground to obtain soil cement, and then the soil cement column can be constructed. In the present invention, it is possible to mix the component (i) with the slurry by rotating and excavating the ground while discharging the slurry from the tip of the mixing and stirring device. These can be implemented in combination. Such methods are suitable for deep mixing processes.

As the ground improvement method of the present invention, a rod equipped with a stirring blade and a slurry ejection port is rotated and penetrated into the component (i) to contain the component (ii), the component (iii) and the component (iv). A ground improvement method for stirring and mixing the (i) component and the slurry with the stirring blade while injecting the slurry into the (i) component from the spout, wherein the (ii) component is added to the (i) component and mixing at a ratio of 18% by mass or less, a ground improvement method. This method is also preferably performed in situ with component (i). In general, when such a rod is used, the component (i) and the slurry are stirred and mixed in a region having a shape corresponding to the rotational shape of the rod, such as a circular region.

In the present invention, as a slurry mixing type stirrer, for example, an auger rod, a solidifying material (said slurry) ejection port provided on the auger rod, an excavating blade provided on the auger rod, and if necessary, on the auger rod An earth auger for excavation with provided anti-rotation wings can be used. Such excavating earth augers can be used in a manner known in the art for constructing soil-cement columns.
The earth auger for excavation is set at a predetermined position for constructing a soil cement column in the ground, and excavation is performed to a predetermined dry excavation depth while rotating the stirring blade. At that time, the excavation is carried out while discharging the slurry from the auger rod. The trench may be excavated without discharging the slurry, but when the predetermined depth is reached, the excavation is carried out while discharging the slurry. After the pouring and advancing step (mixing and stirring) is completed, the discharge of the slurry is stopped, and after the rotation direction of the auger rod is reversed, lifting (mixing and stirring) is started. Withdraw the auger to complete the process. In such a method, the number of blade cutting times can be calculated from the rotation speed of the stirring blade.
In the present invention, the clay lumps in the soil cement column are reduced, and the existing clay lumps are also small, so that the deterioration of the strength of the soil cement column can be suppressed. Since the slurry has excellent fluidity, workability is also improved.

<Soil improvement material>
The present invention is a soil improvement material containing components (i), (ii), and (iii), wherein the component (i) has a uniformity coefficient (D50/D10) of 2.6 or more and 8 It relates to a soil improvement material having a soil of .0 or less and containing component (ii) in a ratio of 18% by mass or less with respect to component (i). The items described in the soil improvement method of the present invention can be appropriately applied to the soil improvement body of the present invention. Specific examples and preferred examples of components (i), (ii), and (iii) in the soil improvement material of the present invention are also the same as those of the soil improvement method of the present invention.

The soil improvement material of the present invention is a soil improvement material obtained by mixing components (i), (ii), and (iii), wherein the component (i) has a uniformity coefficient (D50/D10) is 2.6 or more and 8.0 or less, and the mixing amount of component (ii) is 18% by mass or less with respect to the mixing amount of component (i).
Further, the soil improvement material of the present invention is a soil improvement material obtained by curing a mixture obtained by mixing components (i), (ii), (iii), and (vi), (i) component is soil with a uniformity coefficient (D50/D10) of 2.6 or more and 8.0 or less, and the content of component (ii) in the mixture is the content of component (i) in the mixture It may be a soil improvement material that is 18% by mass or less with respect to the amount.

(1) Preparation of Solidifying Material Slurry Components (ii), (iii) and (iv) shown in the table were mixed to prepare a solidifying material slurry. Mixing was performed with a hand mixer for 1 minute. At that time, the component (iii) was mixed so that the ratio to the component (ii) was as shown in the table. In addition, component (iv) was mixed so as to be 60% by mass with respect to component (ii).

(2) Measurement of residual clay area ratio A soil cement was prepared by mixing the component (i) shown in the table with a solidifying agent slurry. Mixing was performed using a mortar Hobart mixer for 1 minute. At that time, the solidifying material slurry was used so that the ratio of component (ii) to component (i) was as shown in the table.
The soil cement was filled into a container (soft plastic cup) having a diameter of 10 cm and a height of 5 cm, and rough voids were removed by tapping 10 times.

With the soil cement unhardened, the soil cement filled with the container was cut vertically from the outside of the container at a position 2.5 cm from the bottom of the container, and 1% phenolphthalein (90% ethanol) was sprayed. The part containing cement is dyed, but the part without cement is not dyed. Cement-free locations are unstained locations where clay mass remains.
A transparent plate of mesh of 5 mm grid was placed on the section after the dyeing treatment, and the number of unstained cells was counted, and the clay mass residual rate was calculated by the following formula and used as an index of the mixing property. In this calculation formula, a partially unstained cell corresponds to 0.5 unstained cells. It means that the smaller the value of the residual clay mass ratio, the more uniformly the soil and the solidifying material slurry are mixed.
Clay mass residual rate (%) = {(Number of unstained cells in all 5 mm squares) × 1 + (Number of unstained cells in part of 5 mm squares) × 0.5} / (Number of all cells used for measurement )

(3) Measurement of Minimum Needle Penetration Value The upper portion of the soil cement cut in (2) above was cured at 20° C. for 24 hours in a container. At that time, in order to prevent drying of the cross section, the cross section of the soil cement was covered with a wet towel for curing. After curing, the minimum needle penetration value was measured using a penetrometer. A prescribed penetration needle (hereinafter referred to as a needle) was used for the penetration tester. Here, the needle was made of stainless steel (SUS440C defined in JIS G 4303), had a conical tip, had a length of 40 mm, a diameter of 1 mm, and was not rusted or bent. The surface roughness of the taper portion of the needle was 0.3 μm or less when measured according to JIS B 0651.
After confirming that the total mass of the loading part (needle, needle holder, weight) of the penetration tester shows the specified mass (100 g), the weight (50 ± 0.05 g) is placed on the penetration tester. Attached to the needle holder. Also, the clasp was pressed and the needle holder immediately dropped. The sample after curing was measured with a needle penetration tester to measure the distance until the needle stops. This measurement was performed at five randomly selected locations on the sample surface. The smallest of these distances is shown in the table as the minimum needle penetration value. The smaller the minimum needle penetration value, the higher the strength of the cured product.

* 1 Prepared product is commercially available Kasaoka clay (manufactured by Kasanen Factory, trade name Kasaoka clay (powder) (250 mesh)), No. 6 silica sand, and water, Kasaoka clay / silica sand / water = 10/70/ Soil prepared by mixing at 20 (mass ratio).

Claims (11)

Soil (i) containing clay [hereinafter referred to as component (i)], hydraulic powder (ii) [hereinafter referred to as component (ii)], and compound (iii) represented by the following general formula (1) [hereinafter referred to as component (iii)] and water (iv) [hereinafter referred to as component (iv)] are mixed,
(i) the component is soil with a uniformity coefficient (D50/D10) of 2.6 or more and 8.0 or less;
(ii) component is mixed in a ratio of 18% by mass or less with respect to (i) component,
Soil improvement method.
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 added moles of AO.) The soil improvement method according to claim 1, wherein the component (i) is soil having a natural water content of 35% or more and 85% or less. The ground improvement method according to claim 1 or 2, wherein the component (i) is soil having a BET specific surface area of 30 m ² /g or more and 70 m ² /g or less. (i) The soil improvement method according to any one of claims 1 to 3, wherein the component is soil having a pore distance of 7 nm or more and 20 nm or less. (i) The soil improvement method according to any one of claims 1 to 4, wherein the component is soil with a difference between the natural water content and the plastic limit of 0% or more and 80% or less. (i) The soil improvement method according to any one of claims 1 to 5, wherein the component is soil containing halloysite. (i) The soil improvement method according to any one of claims 1 to 6, wherein the component is soil containing tuffaceous clay. The ground improvement method according to any one of claims 1 to 7, wherein the component (iv) is mixed with the component (ii) in a proportion of 40% by mass or more and 250% by mass or less. (iii) The soil improvement method according to any one of claims 1 to 8, wherein the weight average molecular weight of the component is 1000 or more and 2000000 or less. The soil improvement method according to any one of claims 1 to 9, wherein the component (i) is mixed with a water reducing agent (v). The ground improvement method according to any one of claims 1 to 10, wherein the component (i) is mixed with an antifoaming agent (vi).