Soil improvement methods

Abstract

To provide a soil improvement method that can effectively modify water-containing soil to achieve soil that is easy to transport and handle quickly and inexpensively.SOLUTION: A soil improvement method for improving water-containing soil, includes: an addition step of adding a water-absorbing soil conditioner to the water-containing soil in an amount which is less than that required for almost completely absorbing moisture contained in the water-containing soil; and a stirring step of stirring the soil added with the soil conditioner, wherein the stirring is stopped before the soil condition stabilizes.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a soil improvement method for improving the quality of wet soil. [Background technology]

[0002] Soil generated by civil engineering, construction, railway construction, underground construction, tunnel excavation, etc. contains a relatively large amount of water and is therefore prone to flow, making it difficult to handle in its current state, such as by transporting it. Therefore, in order to improve the properties of such soil that contains a lot of water (hereinafter referred to as "wet soil"), soil improvement methods using soil conditioners have been used.

[0003] For example, there is a method that uses a mud modifier containing an inorganic coagulable compound and a water-soluble polymer compound (see, for example, Patent Document 1). The technology in Patent Document 1 is particularly aimed at modifying alkaline mud generated in construction work using alkaline civil engineering chemicals, and aims to make transportation easier by suppressing the fluidity of mud with a high water content.

[0004] There is also a method using a solidifying agent consisting of a water-soluble polymer compound such as polyacrylamide and a powder of a phyllosilicate mineral such as sodium montmorillonite (see, for example, Patent Document 2). The technology in Patent Document 2 aims to improve the solidification speed of wet soil using the same amount of solidifying agent as conventional ones. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-165998 [Patent Document 2] Japanese Patent Application Publication No. 4-103689 Summary of the Invention [Problem to be solved by the invention]

[0006] When improving moist soil, it is necessary to fully understand the properties of the moist soil to be improved and to carry out appropriate treatment accordingly. However, the inventors have discovered that in order to do so, the method of using the soil conditioner is extremely important, rather than the type of soil conditioner used (the specific details will be described in detail in the "Form for carrying out the invention" below).

[0007] However, in conventional soil improvement methods, including the techniques of Patent Documents 1 and 2, various considerations have been made regarding the components of the soil improvers used, but at present, sufficient consideration has not been given to how to use the soil improvers.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a soil improvement method that can effectively improve the quality of wet soil, thereby quickly and inexpensively producing soil that is easy to handle, such as for transportation. [Means for solving the problem]

[0009] The characteristic configuration of the soil improvement method according to the present invention for solving the above problems is as follows: A soil improvement method for improving the quality of wet soil, comprising: An addition step of adding a water-absorbent soil improver to the water-containing soil in an amount less than the required amount, which is an amount required for almost completely absorbing the water contained in the water-containing soil; A stirring step of stirring the soil to which the soil improver has been added; It encompasses In the stirring step, stirring is stopped before the state of the soil becomes stable.

[0010] In soil improvement work, when a water-absorbent soil conditioner is added to moist soil, a required amount is typically added, which is the amount required to nearly completely absorb the moisture contained in the moist soil. When the soil is stirred in this state, the moist soil gradually granulates. However, if the amount of soil conditioner added is less than the required amount, the moist soil gradually granulates as it is stirred. However, it has been found that stopping the stirring of the soil to which the soil conditioner has been added before the soil condition stabilizes unexpectedly results in soil that retains its properties to a degree that makes it easy to handle, such as for transportation. Therefore, in the stirring process, the soil stirring is stopped before the soil condition stabilizes. Therefore, the soil improvement method of this configuration enables effective modification of moist soil without using large amounts of chemicals or large-scale treatment equipment, which are required in conventional soil improvement methods, and allows for rapid and inexpensive production of soil that is easy to handle, such as for transportation.

[0011] In the soil improvement method according to the present invention, In the stirring step, it is preferable that the time from the start of stirring to the stop of stirring is 20 to 70 seconds.

[0012] According to the soil improvement method of this configuration, if the time from the start of stirring to the end of stirring is 20 to 70 seconds during the stirring process, the surface of the soil will remain temporarily solidified for a long period of time before the soil condition stabilizes (before the soil softens or fluidizes), and it is possible to reliably obtain soil that maintains a consistent state that allows it to be handled, such as for transportation.

[0013] In the soil improvement method according to the present invention, The water-containing soil preferably contains clay and sand in a weight ratio of 2:8 to 8:2, and the water content of the entire soil is preferably 15 to 30% by weight.

[0014] According to the soil improvement method of this configuration, the moist soil to be improved contains clay and sand in a ratio of 2:8 to 8:2 (by weight), and the moisture content of the entire soil is 15 to 30% by weight, so that most soil generated by civil engineering work, construction work, railway work, underground work, tunnel excavation work, etc. can be treated.

[0015] In the soil improvement method according to the present invention, It is preferable that the required amount of addition be determined based on the weight of the soil conditioner relative to the weight of water added at the time when water begins to seep out of the swollen gel formed by adding water to the soil conditioner in small amounts.

[0016] According to the soil improvement method of this configuration, the required amount of soil conditioner to be added is determined based on the weight of the soil conditioner relative to the weight of water added at the time when water begins to seep out of the swollen gel formed by adding water to the soil conditioner in small amounts, thereby making it possible to determine the optimal amount of soil conditioner to be added regardless of the type, characteristics, specifications, etc. of the soil conditioner.

[0017] In the soil improvement method according to the present invention, The soil conditioner preferably contains a hydrophilic polymer and / or a highly water-absorbent polymer.

[0018] According to the soil improvement method of this configuration, by using a soil conditioner containing a hydrophilic polymer and / or a highly water-absorbent polymer, it is possible to improve the quality of wet soil particularly effectively, and to achieve soil with the necessary and sufficient properties without using large amounts of chemicals or large-scale treatment equipment as in the past.

[0019] In the soil improvement method according to the present invention, The soil conditioner preferably further contains an inorganic filler.

[0020] According to the soil improvement method of this configuration, by using a soil conditioner that further contains an inorganic filler in addition to a hydrophilic polymer and / or a highly water-absorbent polymer, the dispersibility of the hydrophilic polymer and / or the highly water-absorbent polymer is improved, and the improvement of wet soil can be carried out more effectively. DETAILED DESCRIPTION OF THE INVENTION

[0021] An embodiment of the soil improving method of the present invention will be described below, however, the present invention is not limited to the following embodiments and examples.

[0022] <Hydrous soil> The soil improvement method of the present invention involves improving the quality of moist soil using a soil conditioner. The moist soil to be treated by the present invention has a moisture content of 5 to 50% by weight, preferably 10 to 30% by weight, and contains relatively small particles such as sand (average particle size of approximately 2 to 0.6 mm), silt (average particle size of approximately 0.6 to 0.004 mm), and clay (average particle size of approximately 0.004 mm or less) as its main components. However, soil containing relatively large particles such as gravel can also be treated by the present invention. Furthermore, the soil improvement method of the present invention is particularly suitable for treating soil containing a clay-to-sand ratio of 2:8 to 8:2 (by weight). Since such soils can be treated, most soils generated by civil engineering, construction, railway construction, underground construction, tunnel excavation, and other construction projects can be treated, and the soil improvement method of the present invention can be implemented at many sites.

[0023] <Soil conditioner> The soil conditioner used in the soil improvement method of the present invention is not particularly limited in type, but preferably contains a hydrophilic polymer and / or a superabsorbent polymer. The hydrophilic polymer and / or the superabsorbent polymer are components that mainly contribute to improving the quality of the wet soil. Furthermore, the soil conditioner more preferably further contains an inorganic filler in addition to the hydrophilic polymer and / or the superabsorbent polymer. The inorganic filler is a component that mainly contributes to improving the dispersibility of the hydrophilic polymer and / or the superabsorbent polymer added to the wet soil. In the soil improvement method of the present invention, the use of such a soil conditioner (chemical) can particularly effectively improve the properties (hardness, brittleness, shape retention, etc.) of the wet soil.

[0024] Examples of hydrophilic polymers include polyacrylic acid / polyacrylamide copolymers, polymethacrylic acid / polyacrylamide copolymers, polycarboxylic acid polymers, etc. Examples of highly water-absorbent polymers include polyacrylic acid polymers (e.g., sodium polyacrylate), polymethacrylic acid polymers, polyvinyl acetate polymers, polyvinyl alcohol polymers, carboxymethyl cellulose polymers, etc. Among these, preferred polymers are polyacrylic acid / polyacrylamide copolymers, which are a type of hydrophilic polymer, and sodium polyacrylate, which is a type of highly water-absorbent polymer, and more preferred polymer is sodium polyacrylate.

[0025] As the inorganic filler, salts of alkaline earth metals can be used, such as calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, calcium phosphate, magnesium phosphate, barium phosphate, etc. Among these, calcium carbonate is preferred as the inorganic filler, and crystalline calcium carbonate is more preferred. As the crystalline calcium carbonate, commercially available industrial chemicals can be used, but crushed marble containing crystalline calcium carbonate as the main component can also be used.

[0026] The blending ratio of the hydrophilic polymer and / or the highly water-absorbent polymer to the inorganic filler is preferably set to 10 / 90 to 30 / 70 by weight, and more preferably 15 / 85 to 20 / 80. When the blending ratio of the hydrophilic polymer and / or the highly water-absorbent polymer to the inorganic filler is set within the above range, the modification of the wet soil is further promoted, and soil that is easy to handle can be obtained.

[0027] The soil conditioner may contain other ingredients as needed, such as antifoaming agents, pH adjusters, solvents, thickeners, stabilizers, colorants, deodorizers, antibacterial agents, and antioxidants.

[0028] <Soil improvement method> The soil improving method of the present invention includes an adding step of adding a soil improver to wet soil and an agitating step of agitating the soil to which the soil improver has been added.

[0029] In the addition step, a water-absorbent soil conditioner is added to the hydrated soil in an amount less than the amount required to completely absorb the water contained in the hydrated soil (hereinafter referred to as the "required amount"). The required amount can be calculated based on the weight of the soil conditioner relative to the weight of water added at the point when water begins to seep out of the swollen gel formed by adding water to the soil conditioner in small amounts. For example, if 50 g of a soil conditioner containing commercially available industrial sodium polyacrylate (a highly absorbent polymer) with a claimed water absorption capacity of 300% and crystalline calcium carbonate (an inorganic filler) is used, adding water in small amounts to the soil conditioner will gradually swell as it absorbs water. Here, let's assume that the mixing ratio of sodium polyacrylate and crystalline calcium carbonate in the soil conditioner is 20 / 80 (i.e., 10g of sodium polyacrylate, 40g of crystalline calcium carbonate), and when the amount of water added reaches 20mL (≒20g), for example, the sodium polyacrylate can no longer absorb any more water and water begins to seep out from the swollen gel. In this case, the actual water absorption capacity of sodium polyacrylate is 200%, not 300%, so the amount of soil conditioner required to be added per 10g of water is: 10 × (100 / 200) × (50 / 10) = 25g By calculating the required amount of soil conditioner in this way, it is possible to determine the optimal amount of soil conditioner to be added, regardless of the type, characteristics, or advertised specifications of the soil conditioner. For example, when a soil conditioner is pulverized into fine particles, the initial specifications such as water absorption capacity may change, but even in such cases, it is possible to determine the optimal amount to be added for the current state of the soil conditioner.

[0030] In the mixing process, moist soil to which a soil conditioner has been added in an amount less than the required amount is mixed. During this process, the moist soil gradually granulates. If mixing continues, the granulated soil softens or fluidizes due to the presence of moisture not fully absorbed by the soil conditioner, and then stabilizes, remaining in a stable state with little change in state. However, we have found that stopping mixing before the soil stabilizes results in a unique phenomenon in which the moist soil retains a certain degree of its properties, resulting in soil that is easy to transport and handle. Therefore, the inventors decided to stop mixing soil to which a soil conditioner has been added in an amount less than the required amount before the soil stabilizes. Thus, the present invention goes beyond conventional wisdom and boldly performs insufficient mixing (low mixing), which was previously considered unacceptable, thereby enabling effective soil modification of moist soil. As a result, soil that is easy to transport and handle can be obtained quickly and inexpensively. Thus, the soil improvement method of the present invention can be said to be extremely valuable in that it can achieve soil with the necessary and sufficient properties without using large amounts of chemicals or large-scale treatment equipment as in the past.

[0031] Incidentally, the details of the phenomenon in which deliberately low agitation during the agitation process carried out in the soil improvement method of the present invention results in soil that retains properties that allow it to be handled for transportation, etc. are not yet clear, but one hypothesis is that this is because the hydrophilic polymer and / or highly water-absorbent polymer contained in the soil improver absorbs moisture from the hydrated soil and swells, engulfing the soil particles, causing the soil surface to temporarily (appear) harden; and if an inorganic filler is added, the inorganic filler acts as a nucleus to cause the soil particles to aggregate together, making the phenomenon of the soil surface temporarily hardening even more pronounced.

[0032] The stirring time (low stirring) in the stirring step is preferably 20 to 70 seconds from the start to the end of stirring, and more preferably 30 to 60 seconds. When the soil is stirred for the above stirring time, the soil surface remains temporarily solidified for a long time before the soil condition stabilizes (before the soil softens or fluidizes), and it is possible to reliably obtain soil that maintains a consistent state that allows it to be handled, such as for transportation. [Example]

[0033] To confirm the effectiveness of the soil improvement method of the present invention, soil improvement tests were conducted using simulated soil. A mixture of clay (average particle size of approximately 0.004 mm or less) and sand (average particle size of approximately 2 to 0.6 mm) was used as the simulated soil. The soil conditioners used were agents containing polyacrylic acid / polyacrylamide copolymer, a hydrophilic polymer (Examples 1 to 25), and agents containing sodium polyacrylate, a highly water-absorbent polymer (Examples 26 to 67). Crystalline calcium carbonate was blended as an inorganic filler in the soil conditioners of Examples 1 to 67. To evaluate the soil properties, the table flow value and cone index were measured, and the appearance of the soil was visually evaluated. The methods for measuring the table flow value and cone index, as well as the visual appearance evaluation criteria, are described below.

[0034] A table flow test was carried out in accordance with "12 Flow Test" in "Physical Testing Methods for Cement" specified in JIS R 5201. However, while JIS R 5201 stipulates that the number of drops must be 15 times in 15 seconds, in this example, the number of drops was set to 50 times in 50 seconds.

[0035] Specifically, a flow cone was placed in the center of the flow table and filled with simulated soil in two layers. The entire surface of each layer was poked 15 times with a poker, and the flow cone was appropriately replenished with simulated soil to level the surface. The flow cone was then quickly lifted vertically and allowed to fall 50 times in 50 seconds. The maximum diameter of the simulated soil spread on the flow table: a (mm) and the diameter in the direction perpendicular to the maximum diameter: b (mm) were measured, and this was taken as the table flow value: a (mm) x b (mm).

[0036] The testing device used to measure the table flow value was a plate testing machine (Mortar Flow Table SS-C-409) manufactured by Tokyo Shinohara Co., Ltd.

[0037] <Corn Index> The cone test was conducted in accordance with the "Cone Index Test Method for Compacted Soil" specified in JIS A 1228.

[0038] Specifically, the simulated soil was sieved through a 4.75 mm sieve, and the sample that passed through the sieve was divided into three layers and filled into a compaction test mold with an inner diameter of 100 mm. Each layer was dropped from a height of 30 cm with a 2.5 kg rammer, ramming each layer 25 times to create a test specimen.

[0039] Next, a cone penetrometer was set up vertically at the center of the top surface of the test specimen, and it was penetrated into the test specimen at a speed of 1 cm / sec. The penetration resistance was calculated when the tip of the cone penetrated 50 mm, 75 mm, and 100 mm from the top surface of the test specimen. The cone index was calculated by dividing the average of the penetration resistance forces at the three points by the base area of ​​the tip of the cone, as shown in the following formula (1). q c = Q c / A × 10 (1) q c : Cone index (kN / m 2 ) Q c :Average penetration resistance (N) A: Base area of ​​the cone tip (cm 2 )

[0040] The test equipment used to measure the cone index was a cone measuring instrument (construction management penetrometer SS-S-325), a paving rammer (SS-S-263), and a cone formwork (SS-S-263) manufactured by Tokyo Shinohara Co., Ltd.

[0041] <Visual appearance evaluation criteria> Regarding the appearance of the simulated soil (treated soil) immediately after stirring, soil in which no moisture was clearly visible on the soil surface was rated as "good," and soil in which moisture was visible seeping out from the soil surface was rated as "poor."

[0042] <1> Tests with soil conditioners containing polyacrylic acid / polyacrylamide copolymer (hydrophilic polymer) [Examples 1 to 4, Comparative Example 1] To 1 L of simulated soil (clay:sand = 2:8, moisture content approximately 20% by weight), 5 g or 10 g of a chemical agent (soil conditioner of the present invention) containing a polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate in a weight ratio of 20 / 80 was added, and the mixture was stirred in a Hobart mixer for 30 or 60 seconds (Examples 1 to 4). The required amount of chemical agent to be added to the simulated soil in Examples 1 to 4 was determined to be 30 g based on a separate chemical agent water absorption test (details omitted). For comparison, simulated soil without added chemical agent was also stirred in a Hobart mixer for 30 seconds (Comparative Example 1). The table flow value and cone index were then determined for the soil after each mixing (hereinafter referred to as "treated soil").

[0043] [Example 5, Comparative Example 2] To 1 L of simulated soil (clay:sand = 2:8, moisture content approximately 15% by weight), 1.25 g of a chemical agent (soil conditioner of the present invention) containing a polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate in a weight ratio of 20 / 80 was added, and the mixture was stirred for 30 seconds in a Hobart mixer. The required amount of chemical agent to be added to the simulated soil of Example 5 was determined to be 20 g based on a separate chemical agent water absorption test (details omitted). For comparison, simulated soil without added chemical agent was also stirred for 30 seconds in a Hobart mixer (Comparative Example 2). The table flow value and cone index were then determined for each treated soil.

[0044] [Examples 6 to 9, Comparative Example 3] To 1 L of simulated soil (clay:sand = 5:5, moisture content approximately 25% by weight), 15 g or 20 g of a chemical agent (soil conditioner of the present invention) containing a polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate in a weight ratio of 20 / 80 was added, and the mixture was stirred in a Hobart mixer for 30 or 60 seconds (Examples 6 to 9). The required amount of chemical agent to be added to the simulated soil in Examples 6 to 9 was determined to be 35 g based on a separate chemical agent water absorption test (details omitted). For comparison, simulated soil without added chemical agent was also stirred in a Hobart mixer for 30 seconds (Comparative Example 3). The table flow value and cone index were then determined for each treated soil.

[0045] [Examples 10 to 13, Comparative Example 4] To 1 L of simulated soil (clay:sand = 5:5, moisture content approximately 20% by weight), 10 g or 15 g of a soil conditioner (soil conditioner of the present invention) containing a 20 / 80 weight ratio of polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate was added, and the soil conditioner was mixed for 30 or 60 seconds in a Hobart mixer (Examples 10 to 13). The required amount of the agent to be added to the simulated soil in Examples 10 to 13 was determined to be 30 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 4). The table flow value and cone index were then determined for each treated soil.

[0046] [Examples 14 to 15, Comparative Example 5] Five grams of a soil conditioner (soil conditioner of the present invention) containing a 20 / 80 weight ratio of polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate was added to 1 L of simulated soil (clay:sand = 5:5, moisture content approximately 15% by weight), and the mixture was stirred in a Hobart mixer for 30 or 60 seconds (Examples 14-15). The required amount of the agent to be added to the simulated soil in Examples 14-15 was determined to be 25 g based on a separate water absorption test (details omitted). For comparison, simulated soil without added agent was also stirred in a Hobart mixer for 30 seconds (Comparative Example 5). The table flow value and cone index were then determined for each treated soil.

[0047] [Examples 16 to 19, Comparative Example 6] To 1 L of simulated soil (clay:sand = 8:2, moisture content approximately 30% by weight), 35 g or 40 g of a soil conditioner (soil conditioner of the present invention) containing a 20 / 80 weight ratio of polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate was added, and the soil conditioner was mixed for 30 or 60 seconds in a Hobart mixer (Examples 16 to 19). The required amount of the agent to be added to the simulated soil in Examples 16 to 19 was determined to be 45 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 6). The table flow value and cone index were then determined for each treated soil.

[0048] [Examples 20 to 23, Comparative Example 7] To 1 L of simulated soil (clay:sand = 8:2, moisture content approximately 25% by weight), 5 g or 10 g of a soil conditioner (soil conditioner of the present invention) containing a 20 / 80 weight ratio of polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate was added, and the soil conditioner was mixed for 30 or 60 seconds in a Hobart mixer (Examples 20 to 23). The required amount of the agent to be added to the simulated soil in Examples 20 to 23 was determined to be 35 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 7). The table flow value and cone index were then determined for each treated soil.

[0049] [Examples 24 to 25, Comparative Example 8] To 1 L of simulated soil (clay:sand = 8:2, moisture content approximately 20% by weight), 2.5 g of a chemical agent (soil conditioner of the present invention) containing a polyacrylic acid / polyacrylamide copolymer and crystalline calcium carbonate in a weight ratio of 20 / 80 was added, and the mixture was stirred in a Hobart mixer for 30 or 60 seconds (Examples 24-25). The required amount of chemical agent to be added to the simulated soil in Examples 24-25 was determined to be 30 g based on a separate chemical agent water absorption test (details omitted). For comparison, simulated soil without chemical agent was also stirred in a Hobart mixer for 30 seconds (Comparative Example 8). The table flow value and cone index were then determined for each treated soil.

[0050] The measurement results for Examples 1 to 25 and Comparative Examples 1 to 8 are shown in Tables 1 to 6 below. In each table, polyacrylic acid / polyacrylamide copolymer is abbreviated as "PA / PAA copolymer." The table flow value was judged to be good if it was within 120 mm x 120 mm, and the cone index was judged to be good if it was 200 kN / m 2 However, the overall evaluation was made on a three-point scale from A to C, taking into consideration the table flow value, cone index, and the appearance of the treated soil.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] [Table 5]

[0056] [Table 6]

[0057] From the test results shown in Tables 1 to 6 above, the following new findings were obtained regarding the soil improvement method of the present invention when using a soil improvement agent containing a polyacrylic acid / polyacrylamide copolymer (hydrophilic polymer).

[0058] (1-1) When soil with a clay:sand ratio of 2:8 and a moisture content of approximately 20% by weight was added with a soil conditioner at a concentration of 5 g / L or 10 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 1 to 4). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (Examples 2 and 4) than when it was set to 30 seconds (Examples 1 and 3). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 1).

[0059] (1-2) When soil with a clay:sand ratio of 2:8 and a moisture content of approximately 15% by weight was mixed with 1.25 g / L of soil conditioner, soil with good properties that were easy to handle, such as for transportation, was obtained with a mixing time of 30 seconds (Example 5). However, when the soil was further mixed, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). When no soil conditioner was added (Comparative Example 2), soil with good properties was not obtained.

[0060] (1-3) When soil with a clay:sand ratio of 5:5 and a moisture content of approximately 25% was added with a soil conditioner at a dosage of 15 g / L or 20 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 6 to 9). There was no significant difference in the properties of the soil between the cases where the mixing time was 30 seconds (Examples 6 and 8) and the cases where the mixing time was 60 seconds (Examples 7 and 9). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 3).

[0061] (1-4) When soil with a clay:sand ratio of 5:5 and a moisture content of approximately 20% by weight was added with a soil conditioner at a dosage of 10 g / L or 15 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 10 to 13). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (Examples 11 and 13) than when it was set to 30 seconds (Examples 10 and 12). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 4).

[0062] (1-5) When soil with a clay:sand ratio of 5:5 and a moisture content of approximately 15% by weight was added with a soil conditioner at a rate of 5 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 14-15). There was no significant difference in the properties of the soil between a mixing time of 30 seconds (Example 14) and a mixing time of 60 seconds (Example 15). However, when the soil was further mixed, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 5).

[0063] (1-6) In soil with a clay:sand ratio of 8:2 and a moisture content of approximately 30% by weight, adding a soil improver at a rate of 35 g / L or 40 g / L resulted in soil with good properties that were easy to handle, such as for transportation (Examples 16-19). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (Examples 17 and 19) than when the mixing time was set to 30 seconds (Examples 16 and 18). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil improver was added (Comparative Example 6).

[0064] (1-7) When soil with a clay:sand ratio of 8:2 and a moisture content of approximately 25% by weight was added with a soil conditioner at a concentration of 5 g / L or 10 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 20 to 23). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (Examples 21 and 23) than when it was set to 30 seconds (Examples 20 and 22). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 7).

[0065] (1-8) When soil with a clay:sand ratio of 8:2 and a moisture content of approximately 20% by weight was added with a soil conditioner at a rate of 2.5 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 24-25). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (Example 25) than when it was set to 30 seconds (Example 24). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 8).

[0066] <2> Tests with soil conditioners containing sodium polyacrylate (a superabsorbent polymer) [Examples 26 to 31, Comparative Example 9] To 1 L of simulated soil (clay:sand = 2:8, moisture content approximately 20% by weight), 5 g or 10 g of a soil conditioner (soil conditioner of the present invention) containing sodium polyacrylate and crystalline calcium carbonate in weight ratios of 20 / 80, 18 / 72, or 15 / 85 was added and mixed for 30 seconds in a Hobart mixer (Examples 26 to 31). The required amount of the agent to be added to the simulated soil in Examples 26 to 31 was determined to be 30 to 35 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 9). The table flow value and cone index were then determined for each soil after mixing (hereinafter referred to as "treated soil").

[0067] [Examples 32 to 43, Comparative Example 10] To 1 L of simulated soil (clay:sand = 5:5, moisture content approximately 25% by weight), 20 g or 30 g of a soil conditioner (soil conditioner of the present invention) containing sodium polyacrylate and crystalline calcium carbonate in weight ratios of 20 / 80, 18 / 72, or 15 / 85 was added, and the soil conditioner was mixed for 30 or 60 seconds in a Hobart mixer (Examples 32 to 43). The required amount of the agent added to the simulated soil in Examples 32 to 43 was determined to be 35 to 40 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 10). The table flow value and cone index were then determined for each soil after mixing (hereinafter referred to as "treated soil").

[0068] [Examples 44 to 49, Comparative Example 11] To 1 L of simulated soil (clay:sand = 5:5, moisture content approximately 20% by weight), 5 g, 10 g, or 20 g of a 20 / 80 weight ratio (soil conditioner of the present invention) of sodium polyacrylate and crystalline calcium carbonate was added, and the mixture was stirred in a Hobart mixer for 30 or 60 seconds (Examples 44 to 49). The required amount of the agent to be added to the simulated soil in Examples 44 to 49 was determined to be 25 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also stirred in a Hobart mixer for 30 seconds (Comparative Example 11). The table flow value and cone index were then determined for each soil after mixing (hereinafter referred to as "treated soil").

[0069] [Examples 50 to 61, Comparative Example 12] To 1 L of simulated soil (clay:sand = 8:2, moisture content approximately 30% by weight), 30 g or 40 g of a soil conditioner (soil conditioner of the present invention) containing sodium polyacrylate and crystalline calcium carbonate in weight ratios of 20 / 80, 18 / 72, or 15 / 85 was added and mixed for 30 or 60 seconds in a Hobart mixer (Examples 50-61). The required amount of the agent added to the simulated soil in Examples 50-61 was determined to be 40-50 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 12). The table flow value and cone index were then determined for each soil after mixing (hereinafter referred to as "treated soil").

[0070] [Examples 62 to 67, Comparative Example 13] To 1 L of simulated soil (clay:sand = 8:2, moisture content approximately 25% by weight), 10 g, 20 g, or 30 g of a 20 / 80 weight ratio (soil conditioner of the present invention) of sodium polyacrylate and crystalline calcium carbonate was added, and the soil conditioner was mixed for 30 or 60 seconds in a Hobart mixer (Examples 62 to 67). The required amount of the agent added to the simulated soil in Examples 62 to 67 was determined to be 30 g based on a separate water absorption test (details omitted). For comparison, simulated soil without the agent was also mixed for 30 seconds in a Hobart mixer (Comparative Example 13). The table flow value and cone index were then determined for each soil after mixing (hereinafter referred to as "treated soil").

[0071] The measurement results for Examples 26 to 67 and Comparative Examples 9 to 13 are shown in the following Tables 7 to 14. The table flow value was judged to be good if it was within 120 mm x 120 mm, and the cone index was 200 kN / m 2 However, the overall evaluation was made on a three-point scale from A to C, taking into consideration the table flow value, cone index, and the appearance of the treated soil.

[0072] [Table 7]

[0073] [Table 8]

[0074] [Table 9]

[0075] [Table 10]

[0076] [Table 11]

[0077] [Table 12]

[0078] [Table 13]

[0079] [Table 14]

[0080] From the test results shown in Tables 7 to 14 above, the following new findings were obtained regarding the soil improvement method according to the present invention when a soil improvement agent containing sodium polyacrylate (a highly water-absorbent polymer) was used.

[0081] (2-1) When soil with a clay:sand ratio of 2:8 and a moisture content of approximately 20% by weight was used, adding a soil conditioner at a rate of 5 g / L or 10 g / L resulted in soil with good properties that were easy to handle, including transportation (Examples 26 to 31). Also, soil conditioners with a higher content of sodium polyacrylate (Examples 26 and 27) tended to produce soil with good properties. However, when the soil was further stirred, the soil fluidized, making it difficult to handle, including transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 9).

[0082] (2-2) When soil with a clay:sand ratio of 5:5 and a moisture content of approximately 25% by weight was added with a soil conditioner at 20 g / L or 30 g / L, soil with good properties that were easy to handle, such as for transportation, was obtained (Examples 32 to 43). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (e.g., Example 35) than when it was set to 30 seconds (e.g., Example 34). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as for transportation (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 10).

[0083] (2-3) When soil with a clay:sand ratio of 5:5 and a moisture content of approximately 20% by weight was mixed with soil conditioner at 5 g / L, 10 g / L, or 20 g / L, soil with good properties and easy handling, such as transportation, was obtained (Examples 44 to 49). There was no significant difference in soil properties between the soil with a mixing time of 30 seconds (Examples 44, 46, and 48) and the soil with a mixing time of 60 seconds (Examples 45, 47, and 49). However, when the soil was further mixed, the soil became fluidized and became difficult to handle, such as transport (data not shown). Soil with good properties was not obtained without the addition of soil conditioner (Comparative Example 11).

[0084] (2-4) In soil with a clay:sand ratio of 8:2 and a moisture content of approximately 30% by weight, adding 30 g / L or 40 g / L of soil improver resulted in soil with good properties that were easy to handle, such as transport (Examples 50 to 61). Furthermore, soil with better properties was obtained when the mixing time was set to 60 seconds (e.g., Example 61) than when it was set to 30 seconds (e.g., Example 60). However, when the soil was further stirred, the soil became fluidized, making it difficult to handle, such as transport (data not shown). Soil with good properties was not obtained when no soil improver was added (Comparative Example 12).

[0085] (2-5) When soil with a clay:sand ratio of 8:2 and a moisture content of approximately 25% by weight was mixed with a soil conditioner at 10 g / L, 20 g / L, or 30 g / L, soil with good properties and easy handling, such as transportation, was obtained (Examples 62 to 67). There was no significant difference in soil properties between the cases where the mixing time was 30 seconds (Examples 62, 64, and 66) and the cases where the mixing time was 60 seconds (Examples 63, 65, and 67). However, when the soil was further mixed, the soil became fluidized and became difficult to handle, such as transport (data not shown). Soil with good properties was not obtained when no soil conditioner was added (Comparative Example 13). [Industrial Applicability]

[0086] The soil improvement method of the present invention can be used to improve various soils (especially water-containing soils) generated by civil engineering works, construction works, railway construction, underground construction, tunnel excavation works, etc.

Claims

1. A soil improvement method for improving the quality of wet soil, comprising: determining a required amount of additive to the water-containing soil, which is an amount of additive to be added so that the water contained in the water-containing soil is substantially completely absorbed; An addition step of adding a water-absorbent soil improver so that the amount added is less than the required amount; A stirring step of stirring the soil to which the soil improver has been added; It encompasses The required amount of addition is determined based on the weight of the soil improver relative to the weight of water added at the time when water begins to seep out of the swollen gel formed by adding water little by little to the soil improver, A soil improvement method, wherein the stirring step is stopped before the state of the soil becomes stable.

2. 2. The soil improving method according to claim 1, wherein the time from the start of stirring to the stop of stirring is 20 to 70 seconds in the stirring step.

3. 3. The soil improving method according to claim 1, wherein the water-containing soil contains clay and sand in a weight ratio of 2:8 to 8:2, and the water content of the entire soil is 15 to 30% by weight.

4. The soil improvement method according to any one of claims 1 to 3, wherein the soil improver contains a hydrophilic polymer and / or a highly water-absorbent polymer.

5. The soil improving method according to claim 4, wherein the soil improver further contains an inorganic filler.

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