Ground improvement methods

Abstract

To provide a ground improvement method capable of efficiently excavating hard ground containing clay.SOLUTION: In a ground improvement method, copolymer (ii) of monomers containing a monomer represented by a specific general formula (iia) and a monomer represented by a specific general formula (iib) and water (iii) are mixed into soil containing clay with a cone index of 200 kN / m2 or more (i).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a ground improvement method and an additive for a ground improvement method.

Background Art

[0002] For the purpose of ground improvement, geological survey, etc., the ground is excavated to perform predetermined operations. When excavating the ground, a boring machine called an auger is used to make holes in the ground. At that time, a drilling fluid is used in combination to make the excavation proceed more smoothly or reinforce the periphery of the hole. Various drilling fluids are known, such as water and chemicals obtained by adding a polymer compound to water. On the other hand, as the ground to be improved, cohesive soil, and so-called hard cohesive soil in which the cohesive soil is further hardened are known.

[0003] In Patent Document 1, when solidifying and improving a ground having a hard ground layer such as a cohesive ground or a gravelly ground, without using an antifoaming agent, by reducing the excavation stirring resistance, the construction cost is suppressed, and a solid pile is quickly formed. For the purpose of providing an excavation stirring method, a solidifying material is discharged from a first discharge nozzle port attached to a predetermined position of a rotating shaft into the ground in the rotation area of a stirring blade provided at the lower part of the rotating shaft, and the in-situ soil is stirred and mixed to form a solidified treatment pile. The target ground has a hard ground layer, and in the hard ground layer, an aqueous solution of sodium polyacrylate or polyacrylamide, which is an excavation stirring resistance reducing agent, is discharged from the first discharge pipe or a second discharge nozzle port of a path different from the first discharge pipe. An excavation stirring method is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a ground improvement method capable of efficiently excavating a hard ground containing clay.

Means for Solving the Problems

[0006] The present invention relates to a ground improvement method in which a copolymer (ii) containing a monomer represented by the following general formula (iia) and a monomer represented by the following general formula (iib) and water (iii) are mixed with soil (i) containing clay having a cone index of 200 kN / m , , , 2 ,

[0009] , 7 , , , , r , , , 5 , , , , 2 , 6 , ,

[0010] , , r , or more.

[0007]

Chemical formula

[0008] [In the formula, R 1 , R 2 : may be the same or different, and is a hydrogen atom or a methyl group R 3 : a hydrogen atom or -COO(AO) n R 4 [[ID=AA]] R 4 : a hydrogen atom or an alkyl group having 1 to 4 carbon atoms AO: a group selected from an ethyleneoxy group and a propyleneoxy group n: the average number of added moles of AO, and is a number from 1 to 300 q: a number from 0 to 2 p: 0 or 1 is shown. ]

[0009]

Chemical formula

[0010] [In the formula, R 5 , R 6 , R 7 [[ID=BB]] r : may be the same or different, and is a hydrogen atom, a methyl group or (CH2) r COOM 2 and (CH2) r COOM 2 is COOM It should be noted that there may be some inaccuracies in the translation due to the complexity of chemical formulas and specific technical terms. It is recommended to double-check with relevant professionals for accurate understanding in a patent context.1 or other (CH2) r COOM 2 They may also form anhydrous compounds, in which case the M of those groups 1 M 2 It does not exist. M 1 M 2 : They may be the same or different, and include hydrogen atoms, alkali metals, alkaline earth metals (1 / 2 atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroalkyl groups, or alkenyl groups. r: A number between 0 and 2 (inclusive) This indicates...

[0011] Furthermore, the present invention relates to an additive for a ground improvement method, comprising a monomer copolymer (ii) [hereinafter referred to as component (ii)] containing a monomer represented by the general formula (iia) and a monomer represented by the general formula (iib) and water (iii) [hereinafter referred to as component (iii)], wherein the cone index is 200 kN / m 2 The above relates to an additive for ground improvement methods used in clay-containing soil (i) [hereinafter referred to as component (i)]. [Effects of the Invention]

[0012] According to the present invention, a ground improvement method is provided that can efficiently excavate hard ground containing clay. [Modes for carrying out the invention]

[0013] <Soil improvement method> The ground improvement method of the present invention has a cone index of 200 kN / m 2 The above describes a ground improvement method in which components (ii) and (iii) are mixed with component (i), which contains clay.

[0014] (i) The component has a cone index of 200 kN / m 2 That's all; for example, 220 N / m 2 In addition to the above, 250 N / m 2 That's all, and 500 N / m 2 Below, a further 400 N / m 2The following may apply. Here, the cone index for component (i) is measured using the cone penetrator penetration test method or the Yamanaka soil hardness test method.

[0015] (i) The average particle size of component (i) may be, for example, 1 μm or more, 5 μm or more, 150 μm or less, 100 μm or less, and 50 μm or less. Here, the average particle size of component (i) is measured, for example, by creating 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 component (i) can be measured, for example, by JIS A 1223 "Test method for fine particle content of soil".

[0016] (i) The component preferably contains fine particles with a particle size of less than 75 μm. The classification criteria for soil as a ground material are summarized in the Japanese Geotechnical Society Standards (Japanese Geotechnical Society, 2009). According to these standards, particles with a diameter of 5 μm or more and less than 75 μm are classified as silt, and particles with a diameter of less than 5 μm are classified as clay. These fine particles are the components that give viscosity to the soil. Furthermore, according to the aforementioned Japanese Geotechnical Society Standards, soils with a proportion of fine particles with a diameter of less than 75 μm of 50% by mass or more include clayey soil, organic soil, and volcanic ash clayey soil. This invention can target such soils. (i) Examples of components include soil in which the proportion of fine particles with 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.

[0017] Clay is mainly composed of hydrated silicate minerals with a layered structure (hereinafter referred to as clay minerals). 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, erythrolith, celadonite, etc.), chlorite, vermiculite, and smectite (montmorillonite, beidelite, nontronite, saponite, hectorite, etc.). The types and amounts of clay contained in soil vary, but in this invention, for example, soil containing clay minerals selected from kaolin and smectite can be targeted.

[0018] (i) The component may be soil containing halloysite. (i) The component may contain halloysite in amounts of, 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.

[0019] (i) The components may contain clay in amounts of, for example, 15% by mass or more, 20% by mass or more, 25% by mass or more, and 100% by mass or less, 95% by mass or less, and 90% by mass or less.

[0020] (i) The component may be soil originating from volcanic ash. The component may be volcanic ash clay, for example, tuffaceous clay. Tuffaceous clay is soil in which volcanic ash has been weathered, sedimented, etc. and turned into clay. Generally, tuffaceous clay has little sand mixed in and has a milky white to milky white appearance. Tuffaceous clay is a soil in which clay lumps are easily mixed and formed during the manufacture of soil cement, but these clay lumps are difficult to disintegrate. However, in the present invention, even clay lumps from such tuffaceous clay can be easily disintegrated. The component may contain tuffaceous clay in amounts of, for example, 5% by mass or more, further 10% by mass or more, further 15% by mass or more, and 50% by mass or less, further 40% by mass or less, and further 30% by mass or less.

[0021] (i) The dry density of component (i) is, for example, 1.9 g / cm³.3 In addition, 2.0 g / cm³ 3 And so, 2.9 g / cm³ 3 The following is an additional 2.8 g / cm³ 3 The following may apply: (i) The dry density of component (i) was measured by the method of JIS A 1224.

[0022] (ii) Component is a monomer copolymer containing the monomer represented by the general formula (iia) (hereinafter also referred to as monomer (iia)) and the monomer represented by the general formula (iib) (hereinafter also referred to as monomer (iib)).

[0023] In general formula (iia), R 1 From the viewpoint of fluidity, hydrogen atoms are preferred. In general formula (iia), R 2 From the viewpoint of fluidity, a methyl group is preferred. In general formula (iia), R 3 From the viewpoint of fluidity, hydrogen atoms are preferred. In general formula (iia), R 4b From the viewpoint of fluidity, a hydrogen atom or a methyl group is preferred. In general formula (iia), when p is 0, R 4 A hydrogen atom is preferred. In general formula (iia), AO is preferably an ethyleneoxy group from the viewpoint of fluidity. AO is preferably an ethyleneoxy group. In the general formula (iia), n is the average number of moles of AO added, and from the viewpoint of fluidity, it is 1 or more, preferably 5 or more, more preferably 7 or more, and 300 or less, preferably 250 or less, more preferably 200 or less, even more preferably 150 or less, even more preferably 100 or less, even more preferably 70 or less, even more preferably 50 or less, and even more preferably 30 or less. In general formula (iia), from the viewpoint of fluidity, p is preferably 0. When p is 0, q is preferably 1 or 2. When p is 1, q is preferably 0.

[0024] In the general formula (iib), from the standpoint of liquidity, R 5 A hydrogen atom is preferred. In the general formula (iib), from the standpoint of liquidity, R 6 A hydrogen atom or a methyl group is preferred. In the general formula (iib), from the standpoint of liquidity, R 7 A hydrogen atom is preferred. (CH2) r COOM 2 Regarding COOM 1 or other (CH2) r COOM 2 They may also form anhydrous compounds, in which case the M of those groups 1 M 2 It does not exist. M 1 and M 2 These may be the same or different, and are a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroalkyl group, or alkenyl group. M 1 M 2 The alkyl group, hydroalkyl group, and alkenyl group each preferably have 1 to 4 carbon atoms. M 1 and M 2 These may be the same or different, and are preferably a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, or alkylammonium group; more preferably a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), or ammonium group; even more preferably a hydrogen atom, alkali metal, or alkaline earth metal (1 / 2 atom); and even more preferably a hydrogen atom or alkali metal. From a liquidity standpoint, (CH2) in general formula (iib) r COOM 2 The value of r is preferably 1.

[0025] (ii) From the viewpoint of fluidity, the total amount of monomer (iia) and monomer (iib) in the constituent monomer is preferably 90% by mass or more, more preferably 92% by mass or more, even more preferably 95% by mass or more, and preferably 100% by mass or less. This total amount may be 100% by mass.

[0026] (ii) The proportion of monomer (iib) in the total of monomer (iia) and monomer (iib) of component (ii) may be, for example, 40 mol% or more, 95 mol% or less, further 90 mol% or less, further 85 mol% or less, and further 80 mol% or less, from the viewpoint of the fluidity of the hydraulic composition.

[0027] (ii) The weight-average molecular weight of component is preferably 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, and preferably 100,000 or less, more preferably less than 100,000, and even more preferably 80,000 or less, from the viewpoint of the fluidity of the hydraulic composition.

[0028] (ii) The weight-average molecular weight and number-average molecular weight of the components were measured by gel permeation chromatography (GPC) under the following conditions, respectively. *GPC conditions Equipment: GPC (HLC-8320GPC), manufactured by Tosoh Corporation. Columns: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN=9 / 1 Flow rate: 1.0mL / min Column temperature: 40℃ Detection: RI Sample size: 0.2 mg / mL Standard substances: Polyethylene glycol equivalent (monodisperse polyethylene glycols with known molecular weights: 87,500, 250,000, 145,000, 46,000, 24,000)

[0029] (ii) The component may also consist of two or more copolymers with different average moles of AO added, and different ratios of monomer (iia) and monomer (iib).

[0030] In the present invention, component (ii) can be used in amounts of 0.01% by mass or more, further 0.2% by mass or more, 1% by mass or less, and further 0.8% by mass or less, relative to component (iii).

[0031] (iii) Component is water. Tap water, river water, lake water, groundwater, etc. can be used. In the present invention, it is preferable to mix a mixture containing component (ii) and component (iii) with component (i). That is, it is preferable to mix component (ii) and component (iii) beforehand and then mix them with component (i). Hereinafter, the mixture containing component (ii) and component (iii) will also be referred to as drilling fluid.

[0032] In the present invention, component (iii) can be used in amounts of 10% by mass or more, further 15% by mass or more, 30% by mass or less, and further 25% by mass or less, relative to component (i).

[0033] In the present invention, component (i) may be mixed with component (ii) and component (iii) and hydraulic powder (iv) [hereinafter referred to as component (iv)]. Component (iv) may be added to the drilling fluid. That is, the drilling fluid may contain component (iv). By including hydraulic powder in the drilling fluid, it can also function as a solidifying agent for ground improvement. In the ground improvement method according to the present invention, component (ii), which has a group selected from ethyleneoxy group and / or propyleneoxy group, is mixed in, which is thought to increase the distance between hydraulic powder particles and improve the permeability of hydraulic powder into soil particles. (iv) The hydraulic powder component is a powder that has the property of hardening through a hydration reaction, and examples include cement and gypsum. The hydraulic powder is preferably cement. The cement is, for example, Portland cement such as ordinary Portland cement, beelite cement, moderate heat cement, rapid-hardening cement, ultra-rapid-hardening cement, sulfate-resistant cement, etc. The hydraulic powder contains cement, and more preferably Portland cement, in amounts of 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, and even more preferably 85% by mass or less.

[0034] Furthermore, the hydraulic powder may contain powders having pozzolanic and / or latent hydraulic properties, such as blast furnace slag, fly ash, and silica fume, as well as stone powder (calcium carbonate powder). Cement may also contain blast furnace slag cement, fly ash cement, silica fume cement, etc., in which these are added. From the viewpoint of providing an aluminum ion source for ettringite, which is a hydration product, the hydraulic powder preferably contains blast furnace slag. When the hydraulic powder contains blast furnace slag, its content is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 60% by mass or less, and more preferably less than 50% by mass, in the hydraulic powder.

[0035] In this invention, the amount of hydraulic powder is the amount of powder having physical properties that harden through a hydration reaction, such as cement or gypsum. However, if the hydraulic powder includes powders selected from powders having pozzolanic properties, powders having latent hydraulic properties, and stone powder (calcium carbonate powder), the amounts of these are also included in the amount of hydraulic powder in this invention.

[0036] When using component (iv), in the ground improvement method of the present invention, in order to achieve both the strength of the column and the reduction of the amount of excavated mud generated during construction, component (iv) is mixed with component (i) in a ratio of preferably 18% by mass or less. This ratio is preferably 3% by mass or more, more preferably 3.2% by mass or more, even more preferably 4% by mass or more, more preferably 5% by mass or more, even more preferably 6% by mass or more, even more preferably 8% by mass or more, and more preferably 15% by mass or less, even more preferably 12% by mass or less, even more preferably 11% by mass or less, and even more preferably 10% by mass or less. This ratio is calculated as [amount of component (iv) / amount of component (i)] × 100.

[0037] Furthermore, when using component (iv), in the ground improvement method of the present invention, from the viewpoint of ensuring the fluidity of the drilling fluid containing component (iv) and reducing the amount of excavated mud, component (iii) is mixed with component (iv) in a ratio of preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, preferably 250% by mass or less, more preferably 150% by mass or less, even more preferably 100% by mass or less, and even more preferably 80% by mass or less. This ratio is calculated as [amount of component (iii) / amount of component (iv)] × 100.

[0038] When using component (iv), in the present invention, it is preferable to mix component (i) with a drilling fluid containing components (ii), (iii), and (iv). The drilling fluid may be a solidifying agent slurry such as so-called cement milk. The drilling fluid may contain other optional components such as component (v) described later.

[0039] In the present invention, a defoaming agent (v) [hereinafter referred to as component (v)] may be mixed with component (i) together with component (ii), component (iii), and any component (iv). (v) Examples of components include silicone-based defoamers, fatty acid ester-based defoamers, ether-based defoamers, and aliphatic amine-based defoamers. 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 alkyldimethylamine or its salts are more preferred among aliphatic amine-based defoamers. In the ground improvement method of the present invention, from the viewpoint of preventing material outflow at the milk plant, component (v) can be mixed with component (iii) in proportions of, for example, 0.005% by mass or more, further 0.01% by mass or more, further 0.02% by mass or more, and 2% by mass or less, further 1% by mass or less, and further 0.5% by mass or less. This proportion is calculated as [amount of component (v) / amount of component (iii)] × 100.

[0040] In this invention, component (i) can be mixed separately with component (ii), component (iii), and any additional components (iv) and (v).

[0041] In the ground improvement method of the present invention, soil cement can be prepared by mixing component (i) in situ with component (ii) and component (iii), and further adding any components (iv) and (v). An example of the ground improvement method of the present invention using component (iv) is to pour the prepared soil cement into the ground, and the soil cement hardens to form a ground improvement body, thereby improving the strength of the ground.

[0042] (iv) The ground improvement method of the present invention using component (iv) includes a construction method in which soil cement is poured into the ground. For example, it can be carried out by methods such as surface mixing method, intermediate mixing method, deep mixing method, steel pipe pile method, and shield tunneling method. For example, deep mixing improvement methods include high-pressure injection method, TRD method, and SMW method. The method of the present invention is suitable for deep mixing methods.

[0043] In the ground improvement method of the present invention using component (iv), it is preferable to use the drilling fluid. In this case, the drilling fluid can be mixed with component (i) using a slurry mixing type agitator. Here, a slurry mixing type agitator is an agitator used in construction methods that involve mechanical stirring of soil and slurry, and is an agitator that can inject a slurry containing a hydraulic powder such as cement into the soil and add mechanical stirring. Examples of construction methods using such an agitator include the Mud Stabilizer method, ARM method, LVM method, FAM method, Mud Mixer M-II method, SCM method, ISM method, WILL method, Imark method II, VMS method, and ST Column method. Examples of construction methods include the 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, 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, 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, expanding / contracting column method, HEMS method, and MITS method.

[0044] In this invention, from the viewpoint of achieving both column quality and shortened construction period, the number of blade cuts in the mixing by the agitator is preferably 100 times or more, more preferably 200 times or more, and preferably 1000 times or less, and more preferably 500 times or less. It is preferable to use an agitator with a blade cut count within this range. Generally, agitators used for ground improvement are equipped with stirring blades, and the number of blade cuts is set considering the shape of the stirring blades, the number of stirring blades, the stirring force, the amount of soil, the quality of the soil, etc.

[0045] When using the drilling fluid containing component (iv), the specific method for injecting the drilling fluid into the ground (i) may be in accordance with known ground improvement methods. Examples of methods for injecting the drilling fluid into the ground include injection mixing methods (single-phase flow method, two-phase flow method, three-phase flow method), mechanical mixing methods (CDM method, etc.), and diaphragm wall methods (SMW method, TRD method, etc.). The solidification material mixture, such as soil cement, obtained by mixing the drilling fluid and component (i) can be solidified in accordance with known ground improvement methods.

[0046] In this invention, the drilling fluid containing component (iv) is injected into the ground while component (i) is mixed and stirred to form soil cement, after which a soil cement column can be constructed. In this invention, the drilling fluid can be discharged from the tip of the mixing and stirring device while the ground is rotated and drilled, and component (i) and the drilling fluid can be mixed. These methods can be combined and implemented. Such methods are suitable for deep mixing treatment.

[0047] The present invention's ground improvement method using component (iv) includes a method in which a rod equipped with a stirring blade and a drilling fluid nozzle is rotated and penetrated into component (i), and a drilling fluid containing components (ii), (iii), and (iv) is injected into component (i) from the nozzle while the stirring blade stirs and mixes component (i) and the drilling fluid; and a further ground improvement method in which component (iv) is mixed with component (i) at a ratio of preferably 18% by mass or less. These methods are also preferably performed in situ with component (i). Generally, when such a rod is used, component (i) and the drilling fluid are stirred and mixed in a region with a shape corresponding to the rotation shape of the rod, for example, a circular region.

[0048] In the present invention, as a slurry mixing type agitator, for example, an earth auger for drilling can be used, which is equipped with an auger rod, a drilling fluid outlet provided on the auger rod, drilling blades provided on the auger rod, and, if necessary, anti-rotation blades provided on the auger rod. Such an earth auger for drilling can be one known from methods for constructing soil-cement columns. The excavation earth auger is set in a predetermined position in the ground where the soil-cement column will be constructed, and excavated to a predetermined depth while rotating the mixing blades. During this process, the excavation fluid is discharged from the auger rod. Excavation may be carried out without discharging the excavation fluid, but once the predetermined depth is reached, the excavation fluid is discharged while excavating. Once the injection excavation process (mixing and stirring) is completed, the discharge of the excavation fluid is stopped, the rotation direction of the auger rod is reversed, and then the pulling up process (mixing and stirring) is started. The auger is withdrawn to complete the process. In this method, the number of blade cuts can be calculated from the number of rotations of the mixing blades. In this invention, the amount of clay lumps in the soil-cement column is reduced, and the size of the existing clay lumps is also reduced, thereby suppressing a decrease in the strength of the soil-cement column. The drilling fluid has excellent fluidity, which also improves workability.

[0049] When component (iv) is used, the present invention provides a ground improvement body containing component (i), component (ii), and component (iv). 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 (iv) in the ground improvement body of the present invention are the same as those in the ground improvement method of the present invention. The ground improvement body of the present invention may be a ground improvement body obtained by mixing component (i), component (ii), and component (iv). Furthermore, the ground improvement body of the present invention may be a ground improvement body obtained by hardening a mixture obtained by mixing component (i), component (ii), and component (vi).

[0050] <Additives for ground improvement methods> The present invention relates to an additive for a ground improvement method, comprising a monomer copolymer (ii) [component (ii)] containing a monomer represented by the general formula (iia) and a monomer represented by the general formula (iib), and water (iii) [component (iii)], wherein the cone index is 200 kN / m 2 The above relates to an additive for ground improvement methods used in soil containing clay [component (i)]. The additive for the ground improvement method of the present invention can be appropriately adapted to the matters described in the ground improvement method of the present invention. Specific examples and preferred examples of components (i), (ii), (iii), etc., in the additive for the ground improvement method of the present invention are the same as those in the ground improvement method of the present invention.

[0051] The additive for the ground improvement method of the present invention may contain component (ii) in amounts of, for example, 20% by mass or more, more 30% by mass, and 99% by mass or less, and more 50% by mass or less.

[0052] The additive for the ground improvement method of the present invention may contain component (iii) in an amount such that the total composition of the additive is 100% by mass. The additive for the ground improvement method of the present invention may contain component (iii) in amounts of, for example, 5% by mass or more, further 20% by mass, 80% by mass or less, and further 70% by mass or less.

[0053] The additive for the ground improvement method of the present invention may contain an antifoaming agent which is component (v). When the additive for the ground improvement method of the present invention contains component (v), the additive may contain component (v) in proportion to component (ii) of, for example, 0.1% by mass or more, further 0.5% by mass or more, further 1% by mass or more, and 10% by mass or less, further 8% by mass or less, and further 6% by mass or less. [Examples]

[0054] (1) Preparation of drilling fluid The drilling fluid was prepared by mixing components (ii), (iii), and (iv) shown in the table in the proportions indicated in the table. Mixing was performed using a hand mixer for 1 minute. The components used in the table are as follows. The (iii) / (iv) ratio in the table is a mass % calculated by [amount of component (iii) / amount of component (iv)] × 100. • Cement: A blended cement made by mixing ordinary cement manufactured by Taiheiyo Cement Corporation and ordinary cement manufactured by Sumitomo Osaka Cement Co., Ltd. in a 1:1 (mass ratio). • Copolymer (1): Methacrylic acid (methoxypolyethylene glycol 120 mol) ester [monomer represented by general formula (iia), in general formula (iia), R 1 is a hydrogen atom, R 2 is a methyl group, R 3 is a hydrogen atom, R 4 A copolymer obtained by copolymerizing a monomer (hereinafter referred to as MEPEG120 ester) with methacrylic acid (a monomer represented by general formula (iib)) in a molar ratio of MEPEG120 ester / methacrylic acid = 5 / 95, where is a methyl group, AO is an ethylene oxy group, n is 120, q is 0, and p is 1, and methacrylic acid is represented by general formula (iib), with a weight-average molecular weight of 29800. • Copolymer (2): A copolymer obtained by copolymerizing MEPEG120 ester and methacrylic acid in a molar ratio of MEPEG120 ester / methacrylic acid = 20 / 80, with a weight-average molecular weight of 36500. • Copolymer (3): A copolymer obtained by copolymerizing MEPEG120 ester and methacrylic acid in a molar ratio of MEPEG120 ester / methacrylic acid = 35 / 65, with a weight-average molecular weight of 36300. • Copolymer (4): Acrylic acid (methoxypolyethylene glycol 87 mol) ester [monomer represented by general formula (iia), in general formula (iia), R 1 is a hydrogen atom, R 2 is a methyl group, R 3 is a hydrogen atom, R 4 A copolymer obtained by copolymerizing a monomer (hereinafter referred to as MEPEG87 ester) with acrylic acid (a monomer represented by general formula (iib)) in a molar ratio of MEPEG87 ester / methacrylic acid = 40 / 60, with a weight-average molecular weight of 56,000. • Copolymer (5): Methacrylic acid (methoxypolyethylene glycol 48 mol) ester [monomer represented by general formula (iia), in general formula (iia), R 1 is a hydrogen atom, R 2 is a methyl group, R 3 is a hydrogen atom, R 4A copolymer obtained by copolymerizing a monomer (hereinafter referred to as MEPEG48 ester) with methacrylic acid (a monomer represented by general formula (iib)) in a molar ratio of MEPEG48 ester / methacrylic acid = 26 / 74, with a weight-average molecular weight of 42,000. • Copolymer (6): Methacrylic acid (methoxypolyethylene glycol 23 mol) ester [monomer represented by general formula (iia), in general formula (iia), R 1 is a hydrogen atom, R 2 is a methyl group, R 3 is a hydrogen atom, R 4 A copolymer obtained by copolymerizing a monomer (hereinafter referred to as MEPEG23 ester) with methacrylic acid (a monomer represented by general formula (iib)) in a molar ratio of MEPEG23 ester / methacrylic acid = 27 / 73, with a weight-average molecular weight of 40,000. NSF: Naphthalene sulfonate formaldehyde condensate sodium salt, weight-average molecular weight 10,000

[0055] (2) Preparation of test soil Clay (Kasaoka clay, Kanesan Kogyo Co., Ltd., moisture content 10%) and sand (No. 6 silica sand, Tohoku Silica Sand Co., Ltd.), totaling 200g in the mass ratio shown in the table, were placed into a tin-plated concrete specimen mold (Summit Mold, manufactured by Sumisho Cement Co., Ltd., 5φ × 100mm), and compacted as necessary to prepare the test soil [(i) component] with the cone index shown in the table.

[0056] (3) Measurement of the minimum needle penetration value 40 g of the drilling fluid prepared in (1) above was added to the test soil in the mold prepared in (2) above. Immediately after adding the entire amount of drilling fluid, the minimum needle penetration value of the test soil was measured using a penetration tester. A hydraulic Proctor penetration tester was used as the penetration tester. The penetration resistance value was measured when the spiral step drill (Fujiwara Sangyo Co., Ltd., SK-11, SSD-3), which is the penetration jig of the penetration tester, was penetrated to a depth of 15 mm from the surface of the test soil (speed 5 mm / min). Measurements were taken three times at arbitrary locations, and the average value is shown in the table. A larger minimum needle penetration value indicates a higher degree of softening of the test soil and easier drilling. In addition, the relative value was calculated with the penetration resistance value of a blank test soil with the same cone index set to 100, and judged as "○" if the relative value was 80 or less, "△" if it was between 80 and 91, and "×" if it was 91 or more.

[0057] [Table 1]

[0058] [Table 2]

[0059] Table 1 shows a cone index of 300 kN / m 2 Alternatively, see Table 2 for 200 kN / m 2 In the case of clay-containing soil, mixing copolymer (ii) and water (iii) results in a penetration resistance value of 84% or less relative to the blank value, indicating efficient excavation. On the other hand, a cone index of 100 kN / m 2 In the case of clay-containing soil, even when copolymer (ii) and water (iii) are mixed, the penetration resistance is 92% relative to the blank value, even at the lowest point of reduction, and the cone index is 200 kN / m 2 Excavation cannot be performed as efficiently as in the cases described above.

[0060] Copolymer (ii) is known, for example, as a cement dispersant, see Table 1. and 2 Furthermore, when using naphthalene sulfonic acid formaldehyde condensate sodium salt, which is also known as a cement dispersant, the cone index value is 100-300 kN / m 2 In this case, the penetration resistance value does not change significantly, remaining at around 91-94% relative to the blank value.

Claims

1. The cone index is 200 kN / m ２ The above is a ground improvement method comprising mixing clay-containing soil (i) [hereinafter referred to as component (i)] with a monomer copolymer (ii) [hereinafter referred to as component (ii)] containing a monomer represented by the following general formula (iia) and a monomer represented by the following general formula (iib) [hereinafter referred to as component (ii)] and water (iii) [hereinafter referred to as component (iii)]. 【Chemistry 1】 [During the ceremony, R １ , R ２ : They may be the same or different, and may be a hydrogen atom or a methyl group R ３ : Hydrogen atom or -COO(AO) ｎ R ４ R ４ : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: A group selected from ethyleneoxy group and propyleneoxy group. n: The average number of moles of AO added, a number between 1 and 300. q: A number between 0 and 2 (inclusive) p: 0 or 1 This indicates... 【Chemistry 2】 [During the ceremony, R ５ 、R ６ 、R ７ : may be the same or different, and is a hydrogen atom, a methyl group or (CH ２ ) ｒ COOM ２ where (CH ２ ) ｒ COOM ２ may form an anhydride with COOM １ or another (CH ２ ) ｒ COOM ２ In that case, M １ , M ２ of these groups do not exist. M １ M ２ : They may be the same or different, and include hydrogen atoms, alkali metals, alkaline earth metals (half an atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroalkyl groups, or alkenyl groups. r: A number between 0 and 2 (inclusive) This indicates...

2. The ground improvement method according to claim 1, wherein component (ii) is mixed with component (iii) in an amount of 0.01% by mass or more and 1% by mass or less.

3. The ground improvement method according to claim 1 or 2, wherein component (i) is mixed with component (ii) and component (iii) in situ.

4. The ground improvement method according to claim 1 or 2, wherein (i) component is mixed with (iv) hydraulic powder.

5. (i) The ground improvement method according to claim 1 or 2, wherein a defoaming agent (v) is mixed with component (i).

6. An additive for a ground improvement method, comprising a monomer copolymer (ii) containing a monomer represented by the following general formula (iia) and a monomer represented by the following general formula (iib), and water (iii), wherein the cone index is 200 kN / m ２ The above describes an additive for ground improvement methods used in soils containing clay. 【Transformation 3】 [During the ceremony, R １ , R ２ : They may be the same or different, and may be a hydrogen atom or a methyl group R ３ : Hydrogen atom or -COO(AO) ｎ R ４ R ４ : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: A group selected from ethyleneoxy group and propyleneoxy group. n: The average number of moles of AO added, a number between 1 and 300. q: A number between 0 and 2 (inclusive) p: 0 or 1 This indicates... 【Chemistry 4】 [During the ceremony, R ５ , R ６ , R ７ : They may be the same or different, and may be a hydrogen atom, a methyl group or (CH ２ ) ｒ COOM ２ (CH ２ ) ｒ COOM ２ COOM １ or other (CH ２ ) ｒ COOM ２ They may also form anhydrous compounds, in which case the M of those groups １ M ２ It does not exist. M １ M ２ : They may be the same or different, and include hydrogen atoms, alkali metals, alkaline earth metals (half an atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroalkyl groups, or alkenyl groups. r: A number between 0 and 2 (inclusive) This indicates...

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