Solidification method

Abstract

To provide a solidification treatment method for a soil containing an organic substance (in which, for example, the organic carbon content is 5 mass% or more, and the ignition loss is 10 mass% or more) capable of heightening a strength (for example, a uniaxial compressive strength) of a solidification-improved soil after solidification treatment even under a high temperature environment (to be more precise, even if an average value of temperatures of upward and vicinity parts of the surface of the solidification-improved soil until seven days are passed after feeding a soil improvement material to an unimproved soil is 24°C or higher).SOLUTION: A solidification treatment method includes: feeding a soil improvement material to an unimproved soil containing an organic substance; and mixing to obtain a solidification-improved soil, where the soil improvement material contains a cement-based solidification material, and a porous material, and is a powder or a slurry, and an average value of temperatures of upward and vicinity parts of the surface of the solidification-improved soil until seven days are passed after feeding the soil improvement material to the unimproved soil is 24°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a solidification method. [Background technology]

[0002] Conventionally, various soil improvement materials have been proposed. For example, Patent Document 1 describes a cement-based solidification material used for solidifying and improving various types of soil, such as highly organic soil and highly water-containing soil, which is characterized by containing 100 parts by weight of one or more of ordinary cement, blast furnace cement, high-early-strength cement, and Irwin cement, and 3 to 100 parts by weight of gypsum. Furthermore, Patent Document 2 describes a solidification material for highly organic soil or humus soil that contains cement, ground granulated blast furnace slag, and anhydrous gypsum as a solidification material that can solidify highly organic soil with a high content of organic acids (humic substances such as humic acid and fulvic acid) and a high water content, characterized in that the total amount of the ground granulated blast furnace slag and anhydrous gypsum relative to the total amount of the cement, ground granulated blast furnace slag, and anhydrous gypsum is 15 to 40 mass%, and the ground granulated blast furnace slag is 10 mass% or more relative to the total amount of the cement, ground granulated blast furnace slag, and anhydrous gypsum. Furthermore, Patent Document 3 discloses a soil strengthening material that can increase the strength of the ground despite the presence of hydration inhibitors (e.g., organic substances), which includes a cement-based solidification material and a BET specific surface area of ​​30 m 2 The article describes a soil strengthening material containing porous powder with a water content of 1000 to 10000 kJ / g or more, which is characterized in that it is used for soil containing organic matter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-137950 [Patent Document 2] Japanese Patent Application Publication No. 2018-193515 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-008765 Summary of the Invention [Problem to be solved by the invention]

[0004] When soil containing a large amount of organic matter is solidified in a high-temperature environment, there is a problem that the strength (e.g., uniaxial compressive strength) of the solidified soil (hereinafter also referred to as "solidified improved soil") decreases. The object of the present invention is to provide a solidification method that can increase the strength (e.g., uniaxial compressive strength) of solidified improved soil after solidification treatment, even when the soil contains organic matter (e.g., an organic carbon content of 5% by mass or more and an ignition loss of 10% by mass or more) and is in a high-temperature environment (specifically, the average temperature above and near the surface of the solidified improved soil for 7 days after the application of a soil improvement agent to unimproved soil is 24°C or higher). [Means for solving the problem]

[0005] As a result of extensive research into solving the above-mentioned problems, the inventors have discovered that the above-mentioned object can be achieved by a method of supplying and mixing unimproved soil with a soil improvement agent to obtain solidified and improved soil, wherein the soil improvement agent contains a cement-based solidification material and a porous material and is in the form of a powder or slurry, and wherein the average temperature above and near the surface of the solidified and improved soil is 24°C or higher for 7 days after the soil improvement agent is supplied to the unimproved soil, and thus completed the present invention. That is, the present invention provides the following [1] to [7]. [1] A solidification treatment method in which a soil improvement material is supplied to unimproved soil containing organic matter, and mixed to obtain solidified improved soil, wherein the soil improvement material contains a cement-based solidification material and a porous material, and is a powder or slurry, and wherein the average temperature above and near the surface of the solidified improved soil is 24°C or higher for 7 days after the soil improvement material is supplied to the unimproved soil. [2] The solidification method according to [1], wherein the proportion of the cement-based solidification material is 70 to 99 mass% and the proportion of the porous material is 1 to 30 mass% in 100 mass% of the solid content of the soil improvement material. [3] The solidification method according to [1] or [2], wherein the cement-based solidification material contains cement and gypsum but does not contain ground granulated blast furnace slag, or contains cement, gypsum, and ground granulated blast furnace slag, and the cement-based solidification material contains 20 to 90% by mass of the cement, 5 to 30% by mass of the gypsum in anhydrous equivalent, and 0 to 60% by mass of the ground granulated blast furnace slag.

[0006] [4] The solidification method according to any one of [1] to [3], wherein the porous material is at least one material selected from the group consisting of zeolite, opal A, opal CT, smectite, sepiolite, diatomaceous earth, siliceous shale, bentonite, and activated clay. [5] The solidification method according to any one of [1] to [4], wherein the unimproved soil has an organic carbon content of 5% by mass or more and an ignition loss of 10% by mass or more according to "JGS 0231-2020 (Testing method for organic carbon content of soil)". [6] The solidification method according to any one of [1] to [5], wherein the water content of the unimproved soil is 100% or more. [7] 1 m of the above unimproved soil 3 The method for improving ground according to any one of [1] to [6] above, wherein the amount of the soil improvement material supplied to the soil is 200 kg or more in terms of solid content. [Effects of the Invention]

[0007] According to the solidification treatment method of the present invention, the strength (e.g., uniaxial compressive strength) of the solidified improved soil after solidification treatment can be increased even when the soil contains organic matter (e.g., an organic carbon content of 5% by mass or more and an ignition loss of 10% by mass or more) and is in a high-temperature environment (specifically, the average temperature above and near the surface of the solidified improved soil is 24°C or more for 7 days after the soil improvement agent is supplied to the unimproved soil). DETAILED DESCRIPTION OF THE INVENTION

[0008] The solidification treatment method of the present invention is a solidification treatment method in which a soil improvement material is supplied to unimproved soil containing organic matter (hereinafter simply referred to as "unimproved soil") and mixed to obtain solidified and improved soil, wherein the soil improvement material contains a cement-based solidification material and a porous material, and is a powder or slurry, and the average temperature above and near the surface of the solidified and improved soil is 24°C or higher for 7 days after the soil improvement material is supplied to the unimproved soil. In the present invention, the unimproved soil to be solidified contains organic matter (for example, humic substances). Generally, organic matter inhibits the hydration reaction of cement, so when solidification treatment of unimproved soil containing organic matter is performed using cement-based solidification materials (especially in a high-temperature environment), the strength of the solidified improved soil (soil after solidification treatment) may not be sufficiently high. Examples of soils containing organic matter include peat, andosol, paddy soil, black mud soil, and podzols.

[0009] The organic carbon content of unimproved soil according to "JGS 0231-2020 (Testing Method for Organic Carbon Content of Soil)" is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 25% by mass or more, and particularly preferably 30% by mass or more. The organic carbon content is the ratio of the mass of carbon derived from organic matter to the furnace-dry mass of the soil, and it can be determined that the higher the organic carbon content, the greater the amount of organic matter in the unimproved soil. According to the method of the present invention, it is possible to increase the strength of the solidified and improved soil even for unimproved soil with a high organic matter content, such as an organic carbon content of 5% by mass or more. However, when the organic carbon content is less than 5% by mass, the strength of the solidified and improved soil can be sufficiently increased even by solidification treatment methods using general soil improvement agents, so there is little need to use the method of the present invention.

[0010] The ignition loss of unimproved soil is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more. Ignition loss refers to the ratio of the mass loss when ignited at 750±50°C to the oven-dry mass of the soil. It can be determined that the greater the ignition loss, the greater the amount of organic matter in the unimproved soil. According to the method of the present invention, it is possible to increase the strength of the solidified and improved soil even for unimproved soil with a high organic matter content, such as soil with an ignition loss of 10% or more by mass. However, when the ignition loss is less than 10% by mass, the strength of the solidified and improved soil can be sufficiently increased even by solidification treatment methods using ordinary soil improvement agents, and there is little need to use the method of the present invention.

[0011] The moisture content of unimproved soil is preferably 100% or more, more preferably 150 to 1,000%, even more preferably 300 to 900%, still more preferably 500 to 850%, and particularly preferably 650 to 800%. Generally, when the water content of unimproved soil is 100% or more, the strength development of soil improvement materials is low, but according to the method of the present invention, it is possible to increase the strength of the solidified and improved soil even for unimproved soil with a water content of 100% or more.In addition, when the water content is less than 100%, the strength of the solidified and improved soil can be sufficiently increased even with solidification treatment methods using general soil improvement materials, so there is little need to use the method of the present invention. The "moisture content" (unit: %) refers to the percentage of the mass of water contained in unimproved soil relative to the mass of solids contained in the unimproved soil (water / solids x 100%).

[0012] The soil improvement material used in the present invention includes cement-based solidification materials and porous materials. In this specification, the cement-based solidifying material refers to a powdery material containing cement and optionally containing an admixture. Examples of cements used in cement-based solidification materials include various types of Portland cement such as ordinary Portland cement, high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement; blended cements such as blast-furnace cement, fly ash cement, and silica cement; ecocement; white cement; and ultra-rapid-hardening cement. Among these, ordinary Portland cement, high-early-strength Portland cement, and blast-furnace cement are preferred from the viewpoint of strength development and the like. The cement content in the cement-based solidification material is preferably 20 to 95% by mass, more preferably 30 to 90% by mass, even more preferably 50 to 85% by mass, even more preferably 60 to 85% by mass, and particularly preferably 70 to 85% by mass. If the content is 20% by mass or more, the strength (e.g., uniaxial compressive strength) of the solidified improved soil can be increased. Furthermore, if the content is 95% by mass or less, material costs can be reduced and the amount of waste-derived raw materials used can be increased.

[0013] Furthermore, from the viewpoint of further improving workability, the cement-based solidification material preferably contains gypsum as an admixture. The proportion of gypsum in the cement-based solidification material is preferably 5 to 30 mass%, more preferably 8 to 28 mass%, and particularly preferably 10 to 25 mass%, calculated as anhydrous. The above gypsum ratio does not include the gypsum contained in the cement. Examples of the gypsum include anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum, and mixtures thereof.

[0014] The cement-based solidification material may contain ground granulated blast furnace slag as an admixture from the viewpoint of increasing the strength (e.g., unconfined compressive strength) of the solidified improved soil, reducing material costs, and promoting the use of ground granulated blast furnace slag. The proportion of ground granulated blast furnace slag in the cement-based solidification material is preferably 60% by mass or less, more preferably 10 to 55% by mass, even more preferably 20 to 45% by mass, and particularly preferably 25 to 35% by mass. If the proportion is 60% by mass or less, the amount of cement is relatively large, and the strength (e.g., unconfined compressive strength) of the solidified improved soil can be increased. In addition, when the cement contained in the cement-based solidification material is blast furnace cement, the ground granulated blast furnace slag contained in the blast furnace cement is included in the above ratio. Examples of admixtures other than gypsum and ground granulated blast furnace slag include quicklime, slaked lime, fly ash, ground limestone, silica fume, etc. These may be used alone or in combination of two or more. The proportion of admixtures other than gypsum and ground granulated blast furnace slag in the cement solidification material (the total of all admixtures if two or more types of admixtures are included) is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, from the viewpoint that the proportion of cement is relatively high and the strength of the solidified improved soil can be increased.

[0015] Examples of porous materials include zeolite, opal A, opal CT, smectite, sepiolite, diatomaceous earth, siliceous shale, bentonite, activated clay, etc. These may be used alone or in combination of two or more. Among these, sepiolite is preferred from the viewpoint of increasing the strength of the solidified improved soil. The porous material is usually in the form of a powder.

[0016] The proportion of cement-based solidification material in 100% by mass of the solid content of the soil improvement material is preferably 70 to 99% by mass, more preferably 75 to 97% by mass, even more preferably 82 to 94% by mass, and particularly preferably 86 to 92% by mass. If the proportion is 70% by mass or more, the strength of the solidified improved soil can be increased. If the proportion is 99% by mass or less, the proportion of porous material becomes relatively large, so the strength of the solidified improved soil can be increased even when the water content of the unimproved soil is high or when the solidification treatment is performed in a high-temperature environment. The proportion of porous material in 100% by mass of the solid content of the soil improvement material is preferably 1 to 30% by mass, more preferably 3 to 25% by mass, even more preferably 6 to 18% by mass, and particularly preferably 8 to 14% by mass. If the proportion is 1% by mass or more, the strength of the solidified and improved soil can be increased even when the water content of the unimproved soil is high or when the solidification treatment is carried out in a high-temperature environment. If the proportion is 30% by mass or less, the proportion of cement-based solidification material becomes relatively large, and the strength of the solidified and improved soil can be increased.

[0017] The soil improvement agent may be added and mixed in the form of a powder (dry addition method), or may be added and mixed in the form of a slurry (slurry addition method). For example, when the moisture content of unimproved soil is low (for example, when the moisture content is less than 300%) or when the amount of organic matter contained in unimproved soil is large ( Organic carbon content In cases such as those where the porosity is 25% by mass or more and the ignition loss is 70% by mass or more, it is preferable to supply the soil improvement material in a slurry state to the unimproved soil in order to increase the strength of the solidified and improved soil. In this case, the cement-based solidification material, porous material, and water are mixed in advance to form a slurry, and then the slurry is supplied to the unimproved soil. Alternatively, the powdered soil improvement agent and water may be supplied separately to the unimproved soil. The powdered soil improvement agent can usually be obtained by mixing the powdered materials except for water. When the soil improvement material is used in the form of a slurry, the water-to-powder ratio (the mass ratio of water to powder (a mixture of cement-based solidification material and porous material) ("water / powder" expressed as a percentage) is preferably 50 to 200%, more preferably 60 to 150%, and particularly preferably 70 to 120%, from the viewpoints of the strength development of the soil improvement material and ease of mixing with unimproved soil.

[0018] By adding soil improvement materials to unimproved soil containing organic matter and mixing it, solidified improved soil can be obtained. After the soil improvement agent is applied to unimproved soil, the average temperature above and near the surface of the solidified and improved soil for 7 days is at least 24°C, preferably at least 25°C, and more preferably at least 28°C. If the average temperature is less than 24°C, the strength of the solidified and improved soil can be sufficiently increased even by solidification treatment methods using ordinary soil improvement agents, and there is little need to carry out the method of the present invention. The temperature above and near the surface of the solidified and improved soil is the temperature measured at a height preferably within 5 cm, more preferably 0.5 to 4 cm, and particularly preferably 1 to 3 cm, vertically upward from the surface of the solidified and improved soil. The temperature of the solidified improved soil immediately after supplying and mixing the soil improvement agent is preferably 24° C. or higher, more preferably 26° C. or higher, and particularly preferably 28° C. or higher. If the temperature is below 24° C., the strength of the solidified improved soil can be sufficiently increased even by a solidification treatment method using a general soil improvement agent, and there is little need to carry out the method of the present invention. According to the solidification method of the present invention, the strength (for example, unconfined compressive strength) of the improved soil can be increased.

[0019] 1m of unimproved soil 3 The amount of soil improvement material supplied to the soil varies depending on the properties of the unimproved soil, the construction conditions, and the strength required for the solidified improved soil obtained after treatment, but it is recommended to use a volume of 1 m of unimproved soil. 3 The solid content is preferably 200 kg or more, more preferably 250 to 600 kg, more preferably 300 to 500 kg, and particularly preferably 320 to 450 kg. If the amount of supply is 200 kg or more, the strength of the solidified improved soil can be increased. If the amount of supply is 600 kg or less, an excessive increase in costs can be prevented. [Example]

[0020] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Cement 1: Ordinary Portland cement manufactured by Taiheiyo Cement Corporation (2) Cement 2: High-early-strength Portland cement manufactured by Taiheiyo Cement Corporation (3) Ground granulated blast furnace slag (referred to as "blast furnace slag" in Tables 2 and 4); manufactured by DC Corporation, trade name "Cerament" (4) Gypsum 1: Anhydrous gypsum (shown as "anhydrous" in Tables 2 to 4). (5) Gypsum 2: Gypsum hemihydrate (shown as "hemihydrate" in Tables 2 to 4). (6) Gypsum 3; Gypsum dihydrate (indicated as "dihydrate" in Tables 2 to 4) (7) Porous material A: Zeolite (8) Porous material B; siliceous shale (9) Porous material C: Bentonite (10) Porous material D: activated clay (11) Organic soil 1-3; details are shown in Table 1.

[0021] [Table 1]

[0022] [Examples 1 to 3] The materials used included the types of cement and gypsum shown in Table 2, as well as blast furnace slag powder, and the cement-based solidification material, with the proportions of each material in the cement-based solidification material shown in Table 2, was mixed with the types of porous material shown in Table 2 in amounts that would result in the mass ratios shown in Table 2 to obtain a powdered soil improvement material. In an environment of 26°C, organic soil 1m 3Powdered soil improvement material was added and mixed in the amounts shown in Table 2 to obtain solidified improved soil. The temperature of the solidified improved soil immediately after mixing (shown as "mixed temperature" in Table 2) was measured. The obtained solidified and improved soil was cured for 7 days in a constant temperature room at 26°C, and then the unconfined compressive strength of the solidified and improved soil was measured in accordance with JIS A 1216:2020 (Unconfined compression test method for soil). In addition, the temperature was measured every two hours at a height of 2 cm vertically upward from the surface of the solidified improved soil until the material was 7 days old, and the average value (shown as "average temperature" in Table 2) was calculated. [Comparative Examples 1 to 2] Solidified improved soil was obtained in the same manner as in Example 1, except that no porous material was used and a cement-based solidification material was used as the soil improvement material. Unconfined compressive strength and other properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[0023] [Table 2]

[0024] [Examples 4 to 5] A cement-based solidification material in which the proportions of ordinary Portland cement and anhydrous gypsum are shown in Table 3 was mixed with the types of porous material shown in Table 3 in amounts that would result in the mass ratios shown in Table 3 to obtain a powdered soil improvement material. Next, the powdered soil improvement material was mixed with water of the same mass as the soil improvement material to obtain a slurry with a water-powder ratio (the mass ratio of water to powdered soil improvement material expressed as a percentage) of 100%. In an environment of 30°C, organic soil 2, organic soil 1m 3 The above slurry was added and mixed to obtain solidified improved soil, with the amount of soil improvement material (solid content) per unit being as shown in Table 3. The temperature of the solidified improved soil immediately after mixing (shown as "mixed temperature" in Table 3) was measured. The obtained solidified and improved soil was cured for 7 days in a constant temperature room at 30°C, and then the unconfined compressive strength of the solidified and improved soil was measured in accordance with JIS A 1216:2020 (Unconfined compression test method for soil). In addition, the temperature was measured every two hours at a height of 2 cm vertically upward from the surface of the solidified improved soil until the material was 7 days old, and the average value (shown as "average temperature" in Table 3) was calculated. Comparative Example 3 Solidified improved soil was obtained in the same manner as in Example 4, except that no porous material was used and a cement-based solidification material was used as the soil improvement material. Unconfined compressive strength and other properties were measured in the same manner as in Example 1. The results are shown in Table 3.

[0025] [Table 3]

[0026] [Example 6] A cement-based solidification material containing ordinary Portland cement, blast furnace slag powder, and anhydrous gypsum in the proportions shown in Table 4 was mixed with the types of porous material shown in Table 4 in the mass ratios shown in Table 4 to obtain a powdered soil improvement material. Next, the powdery soil improvement material was mixed with water to obtain a slurry with a water-powder ratio (the mass ratio of water to powdery soil improvement material expressed as a percentage) of 80%. In an environment of 28°C, organic soil 3, organic soil 1m 3 The above slurry was added and mixed to obtain solidified improved soil, with the amount of soil improvement material (solid content) per unit being as shown in Table 4. The temperature of the solidified improved soil immediately after mixing (shown as "mixed temperature" in Table 4) was measured. The obtained solidified and improved soil was cured for 7 days in a constant temperature room at 28°C, and then the unconfined compressive strength of the solidified and improved soil was measured in accordance with JIS A 1216:2020 (Unconfined compression test method for soil). In addition, the temperature was measured every two hours at a height of 2 cm vertically upward from the surface of the solidified improved soil until the material was 7 days old, and the average value (shown as "average temperature" in Table 4) was calculated. Comparative Example 4 Solidified improved soil was obtained in the same manner as in Example 6, except that no porous material was used and a cement-based solidification material was used as the soil improvement material. Unconfined compressive strength and other properties were measured in the same manner as in Example 6. Comparative Example 5 The unconfined compressive strength and other properties were measured in the same manner as in Comparative Example 4, except that the obtained solidified improved soil was cured in a thermostatic chamber at 16°C for 7 days in an environment at 16°C. Comparative Example 6 The unconfined compressive strength and other properties were measured in the same manner as in Example 6, except that the obtained solidified and improved soil was cured in a thermostatic chamber at 16°C for 7 days in an environment at 16°C. The results are shown in Table 4.

[0027] [Table 4]

[0028] Comparing Examples 1 to 3 with Comparative Examples 1 and 2 in Table 2, it can be seen that the method of the present invention can increase the unconfined compressive strength of the solidified improved soil. A similar tendency was also seen in the comparison of Examples 4 to 5 with Comparative Example 3 in Table 3, and in the comparison of Example 6 with Comparative Example 4 in Table 4. Furthermore, a comparison of Comparative Examples 5 and 6 in Table 4 shows that when the temperature near the surface of the solidified and improved soil is 16°C, the uniaxial compressive strength of the solidified and improved soil when only cement-based solidification material is used (Comparative Example 5) is similar to that when cement-based solidification material and porous material are used (Comparative Example 6).

Claims

1. A solidification treatment method in which a soil improvement material is supplied to unimproved soil containing organic matter and mixed to obtain solidified improved soil, The unimproved soil has an organic carbon content of 25% by mass or more and an ignition loss of 70% by mass or more according to "JGS 0231-2020 (Testing method for organic carbon content of soil)". The soil improvement material includes a cement-based solidification material and a porous material, In 100% by mass of the solid content of the soil improvement material, the proportion of the cement-based solidification material is 70 to 99% by mass, and the proportion of the porous material is 1 to 30% by mass; The cement-based solidification material contains cement and gypsum but does not contain ground granulated blast furnace slag, or contains cement, gypsum, and ground granulated blast furnace slag, In the cement-based solidifying material, the proportion of the cement is 20 to 90 mass%, the proportion of the gypsum is 5 to 30 mass% in terms of anhydrous, and the proportion of the ground granulated blast furnace slag is 0 to 60 mass%, The soil improvement material is supplied to the unimproved soil in the form of a slurry premixed with water, A solidification treatment method characterized in that the average temperature measured at a height of 0.5 to 4 cm in the vertical upward direction from the surface of the solidified and improved soil is 28°C or higher for 7 days after the supply of the soil improvement agent to the unimproved soil.

2. 2. The solidification method according to claim 1, wherein the water-powder ratio of the slurry is 50 to 200%.

3. 3. The solidification method according to claim 1, wherein the porous material is at least one material selected from the group consisting of zeolite, opal A, opal CT, smectite, sepiolite, diatomaceous earth, siliceous shale, bentonite, and activated clay.

4. The solidification method according to any one of claims 1 to 3, wherein the water content of the unimproved soil is 100% or more.

5. 1 m of the above unimproved soil ３ 5. The solidification method according to claim 1, wherein the amount of the soil improvement agent supplied to the soil is 200 kg or more in terms of solid content.

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