Soil conditioner and soil improvement method

Abstract

The present invention provides a soil conditioner that facilitates handling, such as transportation, by modifying water-containing soil, particularly construction sludge and other soils that are difficult to solidify, as the target soil for treatment. [Solution] A soil conditioner for modifying water-containing soil present in civil engineering works, construction works, or soil improvement work, comprising a volume-reducing agent that reduces the volume of the modified soil by reducing the amount of inorganic preparation used for the water-containing soil, wherein the volume-reducing agent is a polymer preparation, and the polymer preparation is at least one selected from the group consisting of hydrophilic polymers, water-absorbing polymers, and polymer flocculants, and the inorganic preparation comprises at least one selected from the group consisting of cement, quicklime, gypsum, paper sludge ash, and magnesium oxide.

Description

Technical Field

[0001] The present invention relates to a soil conditioner for modifying water-containing soil existing in civil engineering work, construction work, or soil improvement work, and a soil improvement method.

Background Art

[0002] Soil (hereinafter referred to as "construction sludge, etc.") generated in civil engineering work, construction work, soil improvement work, etc. often contains a large amount of moisture, and the difficulty of handling the soil due to the moisture has reduced the transportation efficiency of construction sludge, etc. In order to improve the transportation efficiency of water-containing soil such as construction sludge, it is required to modify (solidify or harden) the soil using a soil conditioner.

[0003] As a soil conditioner for water-containing soil, those mainly composed of inorganic materials have been conventionally known. For example, there are those that use inorganic fired powder containing volcanic ash, fly ash, silica fume, and paper sludge as a soil conditioner (see Patent Document 1).

[0004] According to Patent Document 1, by simply adding and mixing a small amount of this soil conditioner to water-containing soil, the components contained in the soil are solidified by a pozzolanic reaction, and the fluidity of the water-containing soil is lost and it can be modified into a sandy soil state.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, as described in the examples, Patent Document 1 uses a sample of water-containing soil with only cement added as a baseline, and examines the effects of adding both cement and a soil conditioner to water-containing soil. In other words, the soil conditioner in Patent Document 1 is intended to be used in combination with cement, and does not attempt to modify (solidify) water-containing soil with the soil conditioner alone. Furthermore, since cement is a type of inorganic material, if we consider cement as a type of soil conditioner, then Patent Document 1 would be using a considerable amount of soil conditioner. In addition, the water-containing soil tested in Patent Document 1 is not the extremely difficult soil described as "soft soil requiring soil modification" according to the Ministry of Land, Infrastructure, Transport and Tourism's recycling guidelines. Therefore, the soil conditioner in Patent Document 1 cannot be said to take into account the high-moisture soil that actually occurs at construction sites, etc.

[0007] This invention has been made in view of the above-mentioned problems, and aims to provide a soil conditioner and a soil conditioner method that facilitates handling, such as transportation, by modifying water-containing soil, particularly construction sludge and other soils that are difficult to solidify, as the soil to be treated. [Means for solving the problem]

[0008] The characteristic configuration of the soil conditioner according to the present invention, which solves the above problems, is as follows: A soil conditioner for modifying water-containing soil present in civil engineering works, construction works, or soil improvement work, The invention includes a volume-reducing agent that reduces the volume of the modified soil by reducing the amount of inorganic preparation used in the aforementioned water-containing soil.

[0009] This soil conditioner formulation, compared to conventional soil conditioners primarily composed of inorganic preparations (inorganic materials), includes a volume-reducing agent that reduces the amount of inorganic preparations used. As a result, the increase in the overall volume and weight of the soil is suppressed by the reduced amount of inorganic preparations used. Consequently, soil modified with this soil conditioner has a reduced volume compared to soil modified with conventional soil conditioners, making it easier to handle during transportation and other processes.

[0010] In the soil conditioner according to the present invention, The volume-reducing agent is preferably a polymer formulation.

[0011] With this soil conditioner configuration, by using a polymer formulation as a volume-reducing agent, even if the soil to be modified is a construction sludge or similar material that is difficult to handle due to its high moisture content, when this soil conditioner configuration is mixed with the construction sludge or similar material and stirred, the polymer formulation and inorganic formulation work together to efficiently absorb or separate the large amount of water contained in the construction sludge or similar material, causing the soil to solidify and its volume to be reduced.

[0012] In the soil conditioner according to the present invention, The polymer formulation is preferably at least one selected from the group consisting of hydrophilic polymers, water-absorbing polymers, and polymer flocculants.

[0013] According to this soil conditioner configuration, by using at least one selected from the group consisting of hydrophilic polymers, water-absorbing polymers, and polymer flocculants as the polymer formulation, moisture (especially free water) contained in the water-containing soil is absorbed or separated from the soil by the polymer formulation. As a result, the moisture content of the modified soil decreases, and the increase in the overall volume and weight of the soil can be suppressed.

[0014] In the soil conditioner according to the present invention, The inorganic preparation preferably contains at least one selected from the group consisting of cement, quicklime, gypsum, paper sludge ash, and magnesium oxide.

[0015] According to this soil conditioner configuration, the inorganic preparation to be combined with the soil conditioner is at least one selected from the group consisting of cement, quicklime, gypsum, paper sludge ash, and magnesium oxide. When the soil conditioner is added and mixed with water-containing soil, the soil conditioner absorbs or separates moisture from the water-containing soil, and crystal nuclei of the inorganic preparation, which serve as the starting point for solidification, are formed in the soil. Subsequently, crystals grow in the soil, and as the pozzolanic reaction, hydration reaction, or exothermic reaction progresses, the inorganic preparation and the volume-reducing agent work together to solidify the entire soil.

[0016] In the soil conditioner according to the present invention, The amount of volume-reducing agent added to the aforementioned water-containing soil is 0.5 to 10 kg / m³. 3 Therefore, the amount of inorganic preparation added is 50-500 kg / m³. 3 It is preferable that the amount of the volume-reducing agent and / or the inorganic preparation is set so as to result in the above.

[0017] According to this soil conditioner composition, if the proportions of the volume-reducing agent and / or inorganic preparation are set to meet the above conditions, the modified soil will have a strength of at least that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism (cone index of 200 kN / m²). 2 The above-mentioned properties will be expressed, making it possible to transport soil with reduced volume.

[0018] In the soil conditioner according to the present invention, The cone index, as measured by the cone index test in accordance with JIS A 1228, is 200 kN / m. 2 It is preferable to modify the water-containing soil in such a manner as described above.

[0019] According to this soil conditioner formulation, the cone index of the soil after modification is 200 kN / m³. 2 If the soil meets the above criteria, it will be classified as Type 4 improved soil or higher as defined by the Ministry of Land, Infrastructure, Transport and Tourism, making it possible to transport the reduced-volume soil.

[0020] In the soil conditioner according to the present invention, In accordance with JIS R 5201, it is preferable to modify the water-containing soil so that the table flow value obtained in a table flow test, in which the fall rate is changed to 1 time / second and the number of falls to 50 times, is 110 mm × 110 mm or less.

[0021] With this soil conditioner, if the table flow value of the modified soil is 110 mm x 110 mm or less, it will be classified as soil of Class 4 or higher as defined by the Ministry of Land, Infrastructure, Transport and Tourism, making it possible to transport the reduced-volume soil.

[0022] In the soil conditioner according to the present invention, It is preferable to modify the water-containing soil so that the slump value obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020 is 3.0 cm or less, or so that the mini-slump value obtained by a mini-slump test using a mini-slump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm) is 1.5 cm or less.

[0023] With this soil conditioner composition, if the slump value of the modified soil is 3.0 cm or less, or the mini-slump value is 1.5 cm or less, it will be classified as Type 4 improved soil or better as defined by the Ministry of Land, Infrastructure, Transport and Tourism, making it possible to transport the reduced-volume soil.

[0024] The characteristic configuration of the soil improvement method according to the present invention, which solves the above problems, is as follows: A soil improvement method for modifying water-containing soil present in civil engineering works, construction works, or soil improvement work, The process includes an addition step of adding one of the above soil conditioners to the aforementioned water-containing soil. The water-containing soil to which the soil conditioner has been added is subject to the following conditions immediately after or one day after the addition of the soil conditioner: (a) The cone index measured in the cone index test in accordance with JIS A 1228 is 200 kN / m 2 That's all. (b) The table flow value measured by a table flow test in accordance with JIS R 5201 is 110 mm x 110 mm or less. (c) A slump value of 3.0 cm or less obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020, or a minislump value of 1.5 cm or less obtained by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm) conforming to JIS A 1101:2020. The goal is to satisfy this condition.

[0025] This soil improvement method, unlike conventional methods that use soil conditioners primarily composed of inorganic preparations (inorganic materials), adds a volume-reducing agent that reduces the amount of inorganic preparations used. As a result, the increase in the overall volume and weight of the soil is suppressed by the reduction in the amount of inorganic preparations used. Consequently, soil modified using this method is less voluminous than soil modified using conventional methods, making it easier to transport and handle. Furthermore, if the water-containing soil to which the soil conditioner has been added meets the above conditions immediately after or one day after the addition of the soil conditioner, the (a) cone index, (b) table flow value, and (c) slump value or mini-slump value will be classified as Type 4 improved soil or higher as defined by the Ministry of Land, Infrastructure, Transport and Tourism, making it possible to transport the reduced-volume soil.

[0026] In the soil improvement method according to the present invention, The soil conditioner is configured to include the inorganic preparation, The addition step is preferably carried out so that the volume-reducing agent and the inorganic preparation are added to the water-containing soil simultaneously, or so that the volume-reducing agent is added to the water-containing soil first, and then the inorganic preparation is added.

[0027] According to this soil improvement method, by simultaneously adding a volume-reducing agent and an inorganic preparation to water-containing soil, or by adding the volume-reducing agent and the inorganic preparation in that order, the soil conditioner first absorbs or separates water from the water-containing soil, causing the soil to be subdivided and reduced in size. Crystal nuclei of the inorganic preparation, which serve as the starting point for solidification, are then formed in the subdivided soil. Subsequently, crystals grow in the soil, and as the pozzolanic reaction, hydration reaction, or exothermic reaction progresses, the solidification of the subdivided soil is completed. In this way, according to this soil improvement method, the inorganic preparation and the volume-reducing agent work together to solidify the entire soil. [Brief explanation of the drawing]

[0028] [Figure 1] Figure 1 is an illustrative diagram illustrating the mechanism by which water-containing soil solidifies using the soil conditioner of the present invention. [Modes for carrying out the invention]

[0029] The present invention aims to facilitate handling, such as transportation, of water-containing soil present in civil engineering works, construction works, or soil improvement work by modifying it. The soil conditioner and soil improvement method according to the present invention will be described below. However, the present invention is not limited to the configurations described in the embodiments and examples below.

[0030] <Hydrous soil> The construction sludge and other materials intended for treatment by this invention are water-containing soils. Water-containing soils have a water content of 10 to 60% by weight (11 to 122% as a water content ratio) and mainly consist of relatively small particles such as sand (average particle size approximately 2 to 0.6 mm), silt (average particle size approximately 0.6 to 0.004 mm), and clay (average particle size approximately 0.004 mm or less). Specifically, they are "soft soils requiring soil modification" according to the Ministry of Land, Infrastructure, Transport and Tourism's recycling guidelines. However, soils containing relatively large particles such as gravel can also be treated by this invention.

[0031] Construction sludge and the like generally have a high water content, making them difficult to handle during transportation and other processes. Therefore, the inventors recognized that improving the properties of construction sludge and the like is necessary to facilitate their handling during transportation and other processes, and have come up with a soil conditioner that is particularly suitable for modifying construction sludge and the like, which have a high water content.

[0032] The soil conditioner of the present invention contains, for example, clay and silt and sand in a ratio of 2:8 to 8:2 (by weight) as solid components, and can suitably treat waterlogged soil with a moisture content of 45 to 50% by weight (82 to 100% as a water content ratio). Since waterlogged soil with such properties is contained in most construction sludge generated by civil engineering works, construction works, underground works, tunnel excavation works, or soil improvement work, the soil conditioner of the present invention can be used at many construction sites and work sites.

[0033] <Soil conditioner> The soil conditioner of the present invention comprises at least a volume-reducing agent and optionally an inorganic preparation. Alternatively, it may be a combination of a volume-reducing agent and an inorganic preparation (whether one or two agents). First, the mechanism of solidification of water-containing soil by the soil conditioner of the present invention will be explained.

[0034] Figure 1 is an illustrative diagram illustrating the mechanism by which water-containing soil solidifies using the soil conditioner of the present invention. When a volume-reducing agent is added to water-containing soil (Figure 1(a)), the water-containing soil solidifies to a certain extent due to the action of the volume-reducing agent (absorbing or separating water from the soil) (Figure 1(b)), and the soil fragments and shrinks (Figure 1(c)). Fragmentation will be described later in the section on volume-reducing agents. Next, when an inorganic preparation is added (Figure 1(d)), the inorganic preparation penetrates the fragmented soil and generates crystal nuclei (Figure 1(e)). After about one day, crystals grow in the fragmented soil (Figure 1(f)), and solidification is completed as the pozzolanic reaction, hydration reaction, or exothermic reaction progresses. In this way, the soil conditioner of the present invention solidifies water-containing soil through the cooperation of a volume-reducing agent and an inorganic preparation. With the soil conditioner of the present invention, the amount of inorganic preparation used is reduced compared to conventional methods, thus suppressing the increase in the overall volume and weight of the soil. As a result, soil modified with the soil conditioner of the present invention has a reduced volume compared to soil modified with conventional soil conditioners, making it easier to handle, such as during transportation.

[0035] The following describes the volume-reducing agent, which is the main component of the soil conditioner of the present invention, and inorganic formulations that can be used in combination with the volume-reducing agent.

[0036] [Volume-reducing agent] Volume-reducing agents are components that contribute to reducing the volume of modified soil by reducing the amount of inorganic preparations used in water-containing soil. Polymeric preparations are preferred as volume-reducing agents, and polymeric preparations having affinity for water are particularly preferred. When a polymeric preparation is added to water-containing soil and mixed, the water content of the water-containing soil decreases, and the soil becomes fragmented (granulated) and shrinks, either by the absorption of water contained in the water-containing soil by the polymeric preparation or by the release of water contained in the water-containing soil due to the action of the polymeric preparation.

[0037] Examples of polymer formulations include hydrophilic polymers, superabsorbent polymers (SAP), and polymer flocculants. Of these, hydrophilic polymers and superabsorbent polymers have the effect of absorbing moisture (free water) present around soil particles. Polymer flocculants have the effect of gathering moisture (free water) present around the soil together with the soil (isolating it from the surroundings). Polymer formulations may contain hydrophilic polymers, superabsorbent polymers, or polymer flocculants individually, or they may be mixtures of two or more of these.

[0038] Examples of hydrophilic polymers include polyacrylic acid / polyacrylamide copolymers, polymethacrylic acid / polyacrylamide copolymers, and polycarboxylic acid polymers. Of these, the preferred hydrophilic polymer is the polyacrylic acid / polyacrylamide copolymer.

[0039] Examples of superabsorbent polymers include polyacrylic acid polymers, polymethacrylic acid polymers, polyvinyl acetate polymers, polyvinyl alcohol polymers, and carboxymethylcellulose polymers. Of these, a preferred superabsorbent polymer is sodium polyacrylate, which is a representative polyacrylic acid polymer.

[0040] Any of the following polymer flocculants can be used: anionic polymer flocculants, cationic polymer flocculants, amphoteric polymer flocculants, and nonionic polymer flocculants. However, anionic polymer flocculants are preferred due to their excellent ability to prevent soil adhesion and their low environmental impact. Among amphoteric polymer flocculants, anion-rich amphoteric polymer flocculants, which have more anionic groups than cationic groups, can also be used in the same way as anionic polymer flocculants. In other words, polymer flocculants containing anionic groups in their molecular structure (anionic polymer flocculants, or anion-rich amphoteric polymer flocculants) are preferred.

[0041] Examples of anionic polymer flocculants include polycarboxylates or copolymers of polycarboxylates and acrylamide, polysulfonates or copolymers of polysulfonates and acrylamide, and derivatives thereof. Examples of polycarboxylic acids for forming polycarboxylates include acrylic acid, methacrylic acid, itaconic acid, and maleic acid. Examples of polysulfonic acids for forming polysulfonates include acrylamide 2-methylpropanesulfonic acid, vinylsulfonic acid, and styrenesulfonic acid.

[0042] Examples of cationic polymer flocculants include alkylaminoacrylate polymers or copolymers of alkylaminoacrylate polymers and acrylamide, alkylaminomethacrylate polymers or copolymers of alkylaminomethacrylate polymers and acrylamide, and derivatives thereof. Examples of alkylaminoacrylate polymers include dimethylaminoethyl acrylate, dimethylaminopropyl acrylamide, acryloyloxyethyltrimethylammonium chloride, acryloylaminopropyltrimethylammonium chloride, and acryloyl 2-hydroxypropyl lide. Examples of alkylaminomethacrylate polymers include dimethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide, methacryloyloxyethyltrimethylammonium chloride, methacryloylaminopropyltrimethylammonium chloride, and methacryloyl 2-hydroxypropyl lide.

[0043] As amphoteric polymer flocculants, there are random copolymers, alternating copolymers, block copolymers, and graft copolymers of anionic monomers which are the constituent units of anionic polymer flocculants, cationic monomers which are the constituent units of cationic polymer flocculants, and nonionic monomers (if necessary). From the viewpoint of stability, random copolymers or alternating copolymers are preferred. The polymerization ratio of the anionic monomer and the cationic monomer is such that the anionic group is 30 to 45 mol%, preferably 35 to 42 mol%, the cationic group is 0.1 to 10.0 mol%, preferably 0.1 to 4.0 mol%, and the balance is a nonionic group. The amphoteric polymer flocculant has an anionic group of the anionic polymer flocculant and a cationic group of the cationic polymer flocculant present in the same polymer structure, and does not phase-separate like a mixture of an anionic polymer flocculant and a cationic polymer flocculant, so that stable performance can be exhibited.

[0044] The molecular weight of the polymer preparation is preferably 1.0×10 7 ~2.5×10 7 and more preferably 1.3×10 7 ~2.2×10 7 If the molecular weight of the polymer preparation is within the above range, it has excellent water absorption or isolation ability for the water-containing soil, and is also easy to handle as a volume reduction agent. The content of the polymer preparation in the volume reduction agent is not particularly limited and can be arbitrarily set within the range of 0.1 to 100% by weight.

[0045] The dosage form of the polymer preparation may be powdery or liquid dissolved or dispersed in a solvent such as water. In the case of a liquid polymer preparation, the solid content is preferably 10 to 80% by weight, more preferably 20 to 60% by weight, and even more preferably 40 to 50% by weight.

[0046] The addition amount of the volume reduction agent to the water-containing soil is determined in relation to the addition amount of the inorganic preparation described later, and is preferably 0.5 to 10 kg / m 3 However, when the volume reduction agent is a powdery polymer preparation, it is 0.5 to 4 kg / m3 Preferably, the concentration is 1 to 10 kg / m³, and if it is a liquid polymer formulation, the concentration is 1 to 10 kg / m³. 3 It is preferable that the soil after modification has a strength (cone index of 200 kN / m²) of at least that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 The above-mentioned properties will be expressed, making it possible to transport soil with reduced volume. [Inorganic preparations] Inorganic preparations are components used to solidify water-containing soil. When inorganic preparations are added to and mixed with water-containing soil, as described above, crystal nuclei of the inorganic preparation, which serve as the starting point for solidification, are formed in the water-containing soil. Subsequently, through crystal growth, the components contained in the water-containing soil are solidified as the pozzolanic reaction, hydration reaction, or exothermic reaction progresses.

[0047] Inorganic preparations include cement, quicklime, gypsum, paper sludge ash, and magnesium oxide. Cement mainly consists of calcium silicate and calcium aluminate and hardens by the pozzolanic reaction. Quicklime mainly consists of calcium oxide and hardens by the pozzolanic reaction and an exothermic reaction. Gypsum mainly consists of calcium sulfate (hemihydrate gypsum) and hardens by a hydration reaction. Paper sludge ash mainly consists of calcium oxide, silicon oxide, and cellulose and hardens by the pozzolanic reaction. Magnesium oxide hardens by a hydration reaction.

[0048] The amount of inorganic preparation added to water-containing soil is determined in relation to the amount of volume-reducing agent added, as mentioned above, and is typically 50-500 kg / m³. 3 It is preferable that the soil after modification has a strength (cone index of 200 kN / m²) of at least that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 The above-mentioned properties will be expressed, making it possible to transport soil with reduced volume.

[0049] [Other ingredients] Soil conditioners may also contain other ingredients as needed. These other ingredients may include defoamers, pH adjusters, solvents, thickeners, stabilizers, colorants, deodorizers, antibacterial agents, and antioxidants. These ingredients may be used individually or in combination.

[0050] [Performance of soil conditioners] According to the soil conditioner of the present invention, water-containing soil can be modified to the following properties. (a) The cone index measured in the cone index test in accordance with JIS A 1228 is 200 kN / m 2 That's all. (b) The table flow value measured by a table flow test in accordance with JIS R 5201 is 110 mm x 110 mm or less. (c) A slump value of 3.0 cm or less obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020, or a minislump value of 1.5 cm or less obtained by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm) conforming to JIS A 1101:2020.

[0051] Soils possessing the properties described in (a) to (c) above are equivalent to soils classified as Type 4 or higher improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. The soil modification test for water-containing soils will be explained in the examples below.

[0052] <Soil Improvement Methods> The soil improvement method of the present invention modifies water-containing soil present in civil engineering works, construction works, or soil improvement work using the above-mentioned soil conditioner, and involves performing an addition step of adding the above-mentioned soil conditioner to the water-containing soil.

[0053] The addition process may involve adding the volume-reducing agent and the inorganic preparation simultaneously to the water-containing soil, or the volume-reducing agent may be added first, followed by the inorganic preparation. In the diagram illustrating the mechanism of soil solidification shown in Figure 1, the volume-reducing agent is added first, followed by the inorganic preparation. However, even when the volume-reducing agent and the inorganic preparation are added simultaneously, the solidification rate due to the volume-reducing agent is greater than the crystallization rate due to the inorganic preparation, so soil solidification proceeds as shown in the mechanism in Figure 1.

[0054] When the above addition process is carried out, the water-containing soil to which the soil conditioner has been added will have the following conditions immediately after or one day after the addition of the soil conditioner: (a) The cone index measured in the cone index test in accordance with JIS A 1228 is 200 kN / m 2 That's all. (b) The table flow value measured by a table flow test in accordance with JIS R 5201 is 110 mm x 110 mm or less. (c) A slump value of 3.0 cm or less obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020, or a minislump value of 1.5 cm or less obtained by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm) conforming to JIS A 1101:2020. Solidification proceeds to satisfy the conditions.

[0055] The soil improvement method of the present invention, unlike conventional soil improvement methods that use soil conditioners mainly composed of inorganic preparations (inorganic materials), adds a volume-reducing agent that has the effect of reducing the amount of inorganic preparations used. As a result, the increase in the overall volume and weight of the soil can be suppressed by reducing the amount of inorganic preparations used. Consequently, the soil improved by the soil improvement method of the present invention is less voluminous than the soil improved by conventional soil improvement methods, making it easier to handle, such as during transportation. Furthermore, when the water-containing soil to which the soil conditioner has been added satisfies the above conditions for (a) cone index, (b) table flow value, and (c) slump value or mini-slump value immediately after or one day after the addition of the soil conditioner, it becomes soil of Class 4 improved soil or higher as defined by the Ministry of Land, Infrastructure, Transport and Tourism, making it possible to transport the voluminous soil.

[0056] Furthermore, by simultaneously adding a volume-reducing agent and an inorganic preparation to water-containing soil, or by adding the volume-reducing agent and the inorganic preparation in that order, the soil conditioner first absorbs or separates moisture from the water-containing soil, causing the soil to be subdivided and reduced in size. Crystal nuclei of the inorganic preparation, which serve as the starting point for solidification, are then formed in the subdivided soil. Subsequently, crystals grow in the soil, and as the pozzolanic reaction, hydration reaction, or exothermic reaction progresses, the solidification of the subdivided soil is completed. In this way, with this soil improvement method, the inorganic preparation and the volume-reducing agent can work together to solidify the entire soil. [Examples]

[0057] To confirm the performance of the soil conditioner of the present invention, various tests were conducted using (1) a high-moisture-content organic clay layer and (2) simulated soils that represent the soil contained in the high-moisture-content clay layer. Examples and other details are described below.

[0058] (1) High water content organic clay <Simulated soil> High-moisture organic clay found in high-moisture organic clay layers is a soil with a high water content (water ratio), contains organic matter, and has low strength. In this example, in order to simulate high-moisture organic clay, we used the "Standards for the Use of Excavated Soil" (National Government Technical No. 112, National Government General No. 309, dated August 10, 2006) issued by the Ministry of Land, Infrastructure, Transport and Tourism, which specifies a cone index of 200 kN / m 2 We recreated organic clayey soil that is less than 100% mud and has a water content of approximately 80% or more.

[0059] Specifically, Kasaoka clay (clay from Kasaoka City, Okayama Prefecture) and black soil (topsoil from Kanuma City, Tochigi Prefecture) were mixed in a weight ratio of 5:5. Then, water was added until the moisture content reached approximately 100%, and the mixture was stirred until no lumps remained. After standing for two days, the moisture content was measured, and if it remained above 80%, it was used as a simulated soil that mimicked high-moisture organic clay. The properties of the simulated soil actually prepared were a moisture content of 100%, a specific gravity of 1.45, and a minislump value of 11 cm. The moisture content was measured using a heated drying type moisture meter (model: MF-50, manufactured by A&D Co., Ltd.). The specific gravity was calculated from the volume and weight of the simulated soil placed in a beaker (500 mL). The minislump value was measured using a minislump test with a minislump cone (upper inner diameter 50 mm × lower inner diameter 100 mm × height 150 mm).

[0060] <Soil conditioner> The ingredients (chemicals) used as soil conditioners are as follows: [Volume-reducing agent] • Powdered polymer formulation (main component: acrylic acid compound, manufactured by Technica LLC, "TG Lock") (hereinafter referred to as "PAM"). • Liquid polymer formulation (main component: acrylic acid compound, solid content: 40% by weight, manufactured by Technica LLC, "TG Lock L") (hereinafter referred to as "PAML"). [Inorganic preparations] • Cement: UBE Mitsubishi Cement Co., Ltd. "Yustabilizer 60" • Quicklime manufactured by Kawai Lime Industry Co., Ltd. • Gypsum (hemihydrate gypsum) manufactured by E-Plus Co., Ltd. • Paper sludge ash, manufactured by Jaiwat Co., Ltd., "Wattle" • Magnesium oxide, manufactured by Ube Materials Co., Ltd., "Green Lime NP"

[0061] (1-0) Soil solidification test using only volume-reducing agent First, as a reference example, a soil solidification test was conducted using only the volume-reducing agent, which is the main component of the soil conditioner of the present invention, to confirm the extent to which simulated soil could be solidified. In this reference example, the amount of volume-reducing agent (PAM or PAML) added to the simulated soil (high-water-content organic clay) was changed as shown in Table 1 below, and the minislump value, table flow value, and cone index were measured immediately after addition and one day after addition, respectively.

[0062] The minislump value was determined by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm). The table flow value was determined according to JIS R 5201, but with the drop speed changed to 1 time / second and the number of drops to 50. The cone index was determined by a cone index test in accordance with JIS A 1228. If the fluidity of the simulated soil was too high to measure, it was indicated as "-". These procedures were followed in subsequent tests as well. The test results are shown in Table 1 below.

[0063] [Table 1]

[0064] As shown in Table 1, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the minislump value and table flow value, but the cone index did not improve when either PAM or PAML was added alone, as defined by the Ministry of Land, Infrastructure, Transport and Tourism as having a strength of 200 kN / m² or higher (cone index of 200 kN / m²). 2 The above results could not be achieved. Therefore, in subsequent soil solidification tests using inorganic formulations and volume reducers in combination, the solidification state of the simulated soil was evaluated using the cone index.

[0065] (1-1) Soil solidification test using cement and volume reducer in combination The amounts of cement and volume reducer (PAM or PAML) added to the simulated soil were changed as shown in Table 2 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 2 below.

[0066] [Table 2]

[0067] As shown in Table 2, when the amount of cement added to the simulated soil was kept constant, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, cement alone would require 200 kg / m³ 3 The above amounts of additives are necessary, but if cement is used in combination with PAM or PAML, the amount of cement to be added is 100 kg / m³. 3 The study showed that anything above this level is sufficient, and that it may be possible to reduce the amount of cement added by at least 50%. Incidentally, the strength (cone index of 400 kN / m²) of improved soil (Type 3 soil) as defined by the Ministry of Land, Infrastructure, Transport and Tourism is sufficient. 2 To achieve the above, cement alone would require 200 kg / m³ 3 The above amounts of additives are necessary, but when cement is used in combination with PAM or PAML, the amount of cement to be added is 150 kg / m³. 3 Anything above that is acceptable.

[0068] (1-2) Soil solidification test using quicklime and volume reducer in combination The amounts of quicklime and volume reducer (PAM or PAML) added to the simulated soil were changed as shown in Table 3 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 3 below.

[0069] [Table 3]

[0070] As shown in Table 3, when the amount of quicklime added to the simulated soil was kept constant, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, quicklime alone is required at a rate of 150 kg / m³. 3 The above amounts of additives are necessary, but if quicklime is used in combination with PAM or PAML, the amount of quicklime to be added is 100 kg / m³. 3 The study showed that any of the above conditions would suffice, potentially reducing the amount of quicklime added by at least 30%. Incidentally, the strength of the soil (cone index of 400 kN / m²) is equivalent to or greater than that of Type 3 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, quicklime alone would require 200 kg / m³ 3 The above amounts of additives are necessary, but when quicklime is used in combination with PAM or PAML, the amount of quicklime to be added is 150 kg / m³. 3 Anything above that is acceptable.

[0071] (1-3) Soil solidification test using gypsum and volume reducer in combination The amounts of gypsum and volume reducer (PAM or PAML) added to the simulated soil were changed as shown in Table 4 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 4 below.

[0072] [Table 4]

[0073] As shown in Table 4, when the amount of gypsum added to the simulated soil was kept constant, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2To achieve the above, gypsum alone is not sufficient, but when gypsum is used in combination with PAM or PAML, the amount of gypsum added is 200 kg / m³. 3 The above is sufficient, and it has been shown that gypsum, which cannot be used alone with high-moisture-content organic clay, may be usable.

[0074] (1-4) Soil solidification test using paper sludge ash and volume reducer in combination The amounts of paper sludge ash and volume reducer (PAM or PAML) added to the simulated soil were changed as shown in Table 5 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 5 below.

[0075] [Table 5]

[0076] As shown in Table 5, when the amount of paper sludge ash added to the simulated soil was kept constant, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, paper sludge ash alone requires 200 kg / m³ 3 The above amounts of additives are necessary, but if paper sludge ash is used in combination with PAM or PAML, the amount of paper sludge ash to be added is 100 kg / m³. 3 The above is sufficient, and it has been shown that it may be possible to reduce the amount of paper sludge ash added by at least 50%. Incidentally, the strength (cone index of 400 kN / m²) of improved soil (Type 3 soil or higher) as defined by the Ministry of Land, Infrastructure, Transport and Tourism is sufficient. 2 To achieve the above, paper sludge ash alone requires 200 kg / m³ 3 The above amounts of additives are necessary, but when paper sludge ash is used in combination with PAM or PAML, the amount of paper sludge ash to be added is 150 kg / m³. 3 Anything above that is acceptable.

[0077] (1-5) Soil solidification test using magnesium oxide and volume reducer in combination The amounts of magnesium oxide and volume reducer (PAM or PAML) added to the simulated soil were changed as shown in Table 6 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 6 below.

[0078] [Table 6]

[0079] As shown in Table 6, when the amount of magnesium oxide added to the simulated soil was kept constant, gradually increasing the amount of PAM or PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, magnesium oxide alone would require 200 kg / m³ 3 The above amounts are necessary, but if magnesium oxide is used in combination with PAM or PAML, the amount of magnesium oxide to be added is 150 kg / m³. 3 The above is sufficient, and it was shown that it may be possible to reduce the amount of magnesium oxide added by at least 25%.

[0080] (2) High water content clay <Simulated soil> High-water-content clay found in high-water-content clay layers is a soil with a high water content (water ratio) and low strength. In this example, in order to simulate high-water-content clay, the cone index of 200 kN / m² was used, as specified in the "Standards for the Use of Excavated Soil" (National Government Technical No. 112, National Government General No. 309, dated August 10, 2006) issued by the Ministry of Land, Infrastructure, Transport and Tourism. 2 We recreated clayey soil that is less than 100% mud and has a water content of approximately 80% or more.

[0081] Specifically, Kasaoka clay (clay from Kasaoka City, Okayama Prefecture) and bentonite were mixed in a weight ratio of 9:1, and then water was added until the moisture content reached approximately 100%, and the mixture was stirred until no lumps remained. After standing for two days, the moisture content was measured, and if it remained above 80%, it was used as a simulated soil that mimicked high-moisture clay. The properties of the simulated soil actually prepared were a moisture content of 100% and a specific gravity of 1.44. The method for measuring moisture content and specific gravity was the same as the method for measuring high-moisture organic clay described above.

[0082] <Soil conditioner> The components (chemicals) used as soil conditioners are the same as those used on the high-moisture-content organic clay mentioned above.

[0083] (2-0) Soil solidification test using only volume-reducing agent Similar to the reference example conducted for the high-water-content organic clay mentioned above, the amount of volume-reducing agent (PAML) added to the simulated soil (high-water-content clay) was changed as shown in Table 7 below, and the minislump value, table flow value, and cone index were measured immediately after addition and one day after addition, respectively. In the case of the high-water-content organic clay mentioned above, either PAM or PAML was used as the volume-reducing agent, but since similar trends (effects) were observed for both, only PAML was used as the volume-reducing agent for the high-water-content clay. The test results are shown in Table 7 below.

[0084] [Table 7]

[0085] As shown in Table 7, gradually increasing the amount of PAML added to the simulated soil tended to improve the minislump value and table flow value, but the cone index did not improve with PAML alone, which is equivalent to or greater than the strength of Type 4 improved soil defined by the Ministry of Land, Infrastructure, Transport and Tourism (cone index of 200 kN / m²). 2 The above results could not be achieved. Therefore, in subsequent soil solidification tests using inorganic formulations and volume reducers in combination, the solidification state of the simulated soil was evaluated using the cone index.

[0086] (2-1) Soil solidification test using cement and volume reducer in combination The amounts of cement and volume reducer (PAML) added to the simulated soil were changed as shown in Table 8 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 8 below.

[0087] [Table 8]

[0088] As shown in Table 8, when the amount of cement added to the simulated soil was kept constant, gradually increasing the amount of PAML added to the simulated soil tended to improve the cone index. Furthermore, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, cement alone can only provide 75 kg / m³ 3 The above amounts of additives are necessary, but if cement is used in combination with PAML, the amount of cement to be added is 50 kg / m³. 3 The study showed that any of the above would suffice, potentially reducing the amount of cement added by at least 30%. Incidentally, the strength of the soil (cone index of 400 kN / m²) is equivalent to or greater than that of Type 3 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, cement alone would require 100 kg / m³ 3 The above amounts of additives are necessary, but when cement is used in combination with PAML, the amount of cement to be added is 75 kg / m³. 3 Anything above that is acceptable.

[0089] (2-2) Soil solidification test using quicklime and volume reducer in combination The amounts of quicklime and volume reducer (PAML) added to the simulated soil were changed as shown in Table 9 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 9 below.

[0090] [Table 9]

[0091] As shown in Table 9, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, quicklime alone would require 200 kg / m³ 3 The above amounts of additives are necessary, but if quicklime is used in combination with PAML, the amount of quicklime to add is 75 kg / m³. 3 The study showed that the above is sufficient, and that it may be possible to reduce the amount of quicklime added by at least 60%. Incidentally, the strength (cone index of 400 kN / m²) of improved soil (Type 3 soil) as defined by the Ministry of Land, Infrastructure, Transport and Tourism is 400 kN / m² or higher. 2 To achieve the above, quicklime alone would require 300 kg / m³ 3 The above amounts of additives are necessary, but when quicklime is used in combination with PAML, the amount of quicklime to be added is 150 kg / m³. 3 Anything above that is acceptable.

[0092] (2-3) Soil solidification test using gypsum and volume reducer in combination The amounts of gypsum and volume reducer (PAML) added to the simulated soil were changed as shown in Table 10 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 10 below.

[0093] [Table 10]

[0094] As shown in Table 10, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, gypsum alone requires 600 kg / m³ 3 The above amounts of additives are necessary, but if gypsum is used in combination with PAML, the amount of gypsum to be added is 300 kg / m³. 3 The study showed that any of the above would suffice, and that it could potentially reduce the amount of gypsum added by at least 50%. Incidentally, the strength of the soil (cone index of 400 kN / m²) is equivalent to or greater than that of Type 3 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2To achieve the above, gypsum alone is insufficient, but when gypsum is used in combination with PAML, the amount of gypsum added is 500 kg / m³. 3 Anything above that is acceptable.

[0095] (2-4) Soil solidification test using paper sludge ash and volume reducer in combination The amounts of paper sludge ash and volume reducer (PAML) added to the simulated soil were changed as shown in Table 11 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 11 below.

[0096] [Table 11]

[0097] As shown in Table 11, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, paper sludge ash alone would require 600 kg / m³ 3 The above amounts of additives are necessary, but if paper sludge ash is used in combination with PAML, the amount of paper sludge ash to be added is 300 kg / m³. 3 The above is sufficient, and it has been shown that it may be possible to reduce the amount of paper sludge ash added by at least 50%. Incidentally, the strength (cone index of 400 kN / m²) of improved soil (Type 3 soil or higher) as defined by the Ministry of Land, Infrastructure, Transport and Tourism is sufficient. 2 To achieve the above, paper sludge ash alone is not sufficient, but when paper sludge ash is used in combination with PAML, the amount of paper sludge ash added is 400 kg / m³. 3 Anything above that is acceptable.

[0098] (2-5) Soil solidification test using magnesium oxide and volume reducer in combination The amounts of magnesium oxide and volume reducer (PAML) added to the simulated soil were changed as shown in Table 12 below, and the cone index was measured immediately after addition and one day after addition. The test results are shown in Table 12 below.

[0099] [Table 12]

[0100] As shown in Table 12, one day after addition to the simulated soil, the strength (cone index of 200 kN / m²) was equal to or greater than that of Type 4 improved soil as defined by the Ministry of Land, Infrastructure, Transport and Tourism. 2 To achieve the above, magnesium oxide alone would require 500 kg / m³ 3 The above amounts are necessary, but if magnesium oxide is used in combination with PAML, the amount of magnesium oxide to be added is 400 kg / m³. 3 The above is sufficient, and it has been shown that it may be possible to reduce the amount of magnesium oxide added by at least 20%. Incidentally, the strength (cone index of 400 kN / m²) of improved soil of type 3 or higher as defined by the Ministry of Land, Infrastructure, Transport and Tourism 2 To achieve the above, magnesium oxide alone would require 600 kg / m³ 3 The above amounts of additives are necessary, but when magnesium oxide is used in combination with PAML, the amount of magnesium oxide to be added is 500 kg / m³. 3 Anything above that is acceptable.

[0101] (3) Summary From the above examples, the soil conditioner of the present invention has a formulation that includes a volume-reducing agent that has the effect of reducing the amount of inorganic preparation used. As a result, the increase in the overall volume and weight of the soil can be suppressed by reducing the amount of inorganic preparation used. Consequently, soil modified with the soil conditioner of the present invention is smaller in volume compared to soil modified with conventional soil conditioners, making it easier to handle during transportation. This can also contribute to reducing transportation costs and carbon dioxide emissions associated with transportation. [Industrial applicability]

[0102] The soil conditioner and soil conditioner method of the present invention can be used to improve construction sludge (water-containing soil) that contains a large amount of water generated by civil engineering works, construction works, etc.

Claims

1. A soil conditioner for modifying water-containing soil present in civil engineering works, construction works, or soil improvement work, A soil conditioner comprising a volume-reducing agent that reduces the volume of the modified soil by reducing the amount of inorganic preparation used in the aforementioned water-containing soil.

2. The soil conditioner according to claim 1, wherein the volume-reducing agent is a polymer formulation.

3. The soil conditioner according to claim 2, wherein the polymer formulation is at least one selected from the group consisting of hydrophilic polymers, water-absorbing polymers, and polymer flocculants.

4. The soil conditioner according to claim 1, wherein the inorganic preparation comprises at least one selected from the group consisting of cement, quicklime, gypsum, paper sludge ash, and magnesium oxide.

5. The amount of volume-reducing agent added to the aforementioned water-containing soil is 0.5 to 10 kg / m³. ３ Therefore, the amount of inorganic preparation added is 50 to 500 kg / m³. ３ The soil conditioner according to claim 1, wherein the amount of the volume-reducing agent and / or the inorganic preparation is set to such an extent.

6. The cone index, measured according to the cone index test in accordance with JIS A 1228, is 200 kN / m. ２ A soil conditioner according to any one of claims 1 to 5, which modifies the water-containing soil as described above.

7. A soil conditioner according to any one of claims 1 to 5, wherein the water-containing soil is modified such that the table flow value in a table flow test, in which the falling speed is changed to 1 time / second and the number of falls to 50 times, is 110 mm x 110 mm or less.

8. A soil conditioner according to any one of claims 1 to 5, which modifies the water-containing soil so that the slump value obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020 is 3.0 cm or less, or so that the minislump value obtained by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm) is 1.5 cm or less.

9. A soil improvement method for modifying water-containing soil present in civil engineering works, construction works, or soil improvement work, The method includes an addition step of adding a soil conditioner according to any one of claims 1 to 5 to the aforementioned water-containing soil, The water-containing soil to which the soil conditioner has been added exhibits the following conditions immediately after or one day after the addition of the soil conditioner: (a) The cone index measured in the cone index test in accordance with JIS A 1228 is 200 kN / m ２ That's all. (b) The table flow value measured by a table flow test in accordance with JIS R 5201 is 110 mm x 110 mm or less. (c) A slump value of 3.0 cm or less obtained by a slump test using a slump cone (upper inner diameter 100 mm x lower inner diameter 200 mm x height 300 mm) conforming to JIS A 1101:2020, or a minislump value of 1.5 cm or less obtained by a minislump test using a minislump cone (upper inner diameter 50 mm x lower inner diameter 100 mm x height 150 mm). A soil improvement method that satisfies the requirements.

10. The soil conditioner is configured to include the inorganic preparation, The soil improvement method according to claim 9, wherein the addition step is carried out so that the volume reducing agent and the inorganic preparation are added to the water-containing soil simultaneously, or so that the volume reducing agent is added to the water-containing soil and then the inorganic preparation is added.

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