A method for producing a fluidized sand composition.

Abstract

To provide a fluidized sand composition which can obtain adequate strength and an accurate coefficient of water permeability according to applications after filling, and can surely prevent damage such as caving and the possibility of recurrence.SOLUTION: A method for manufacturing a fluidized sand composition for cavity filling, which is mixed with blast furnace slag fine powder as an additive to material sand, one or two kinds selected from slaked lime and gypsum, moisture content adjustment water, a fluidizing agent and a plasticizing agent, and exhibits appropriate strength after having been filled into a ground side cavity part, previously checks a coefficient of water permeability, in such a state that the addition amount of the plasticizing agent is increased / decreased, or in such a state that the addition amount of the blast furnace slag fine powder is increased / decreased, so as to satisfy adequate strength and a required coefficient of water permeability after the fluidized sand composition has been filled into the ground side cavity part, and adjusts the coefficient of water permeability to the required prescribed coefficient of water permeability with reference to the coefficient of water permeability.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for producing a fluidized sand composition for cavity filling to be injected into a cavity formed between the ground and a structure, for example. Regarding To do.

Background Art

[0002] In Japan, there are many cavities in the ground not only in mountainous areas but also in urban areas. In mountainous areas, underground cavities and spaces such as old coal and lignite mine waste pits, underground bunkers during the war, underground quarry sites, and abandoned underground buried objects are left unattended everywhere, and sometimes these suddenly collapse, causing disasters such as subsidence, settlement, and inclination of the ground surface and above-ground facilities. Also, in urban areas, underground structures such as buried pipes and underground tunnels, and pile structures such as river culvert pipes and bridge piers have cavities or loose areas directly below the structures, and there are concerns about settlement and damage caused by earthquakes associated with them.

[0003] Conventional countermeasures often involve drilling holes by boring from the ground or under the road in an existing structure and filling them from the holes. The filling material generally contains a cement-based solidifying material (a grout material, see, for example, Japanese Patent Application Laid-Open No. 2022-54928). However, since this grout material is impermeable, it is easy for a water passage to occur between the solidified filling portion and the existing ground over time, resulting in re-suction and the recurrence of cavities. Also, in river levees, if waterways occur similarly in the culvert pipes and sluice gates existing in the longitudinal direction, a piping phenomenon may occur during heavy rain, leading to levee breaches.

[0004] The applicants have developed fluidized sand (fluidized material) as a cavity-filling material other than grout, as described in Patent Document 1, etc., to fill cavities, and further developed fluidized sand compositions as described in Patent Document 2, etc., which have been improved to achieve a predetermined hardness after filling. The former is a fluidized sand composition in which sand is the main material, and fluidizing agents and plasticizers are included, so as to fill cavities with fluidized sand that does not solidify even after filling, and the fluidized sand is plasticized by natural standing. In this fluidized sand, when dewatered by injection pressure, it exhibits strength as sand, but in ground where drainage is not possible or in cases where injection dewatering is not performed, the strength becomes insufficient. Therefore, the latter is a fluidized sand composition in which blast furnace slag fine powder, one or two selected from slaked lime and gypsum as additives, water for adjusting the water content, and a fluidizing agent are mixed with the material sand, so as to ensure that appropriate strength is reliably exhibited after filling cavities. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5780714 [Patent Document 2] Patent No. 7231513 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0006] The above-mentioned fluidized sand composition can achieve any desired strength according to the purpose, even in areas where dewatering is not possible due to the ground properties. Incidentally, there are various forms of filling in cavities on the ground side, such as filling behind tunnel linings, filling in structural foundations, filling behind river revetments, filling behind existing slopes, filling for anchor fixing injection, filling for blocking underground buried pipes, and filling for open cracks in bedrock. The above-mentioned fluidized sand composition is easy to adjust the strength after filling to any value that allows for excavation as a filling material for each of these forms, has excellent filling operability into cavities, and is expected to have permeability that is not found in grout-type filling materials. Furthermore, as a fluid filling material mainly composed of sand particles, it blends well with the existing ground, is CO2-advantageous compared to grout-type filling materials, and has low CO2 emissions.

[0007] Through the implementation of the above-mentioned fluidized sand composition, the applicants have found that, for example, the permeability coefficient after filling and solidification changes depending on the origin of the material sand used, and that the permeability coefficient after filling and solidification increases with material sand that has a coarse particle size distribution, while it decreases with material sand that has a fine particle size distribution. Further investigations have been conducted to examine the relationship between particle size and permeability percentage for material sand from different origins, as shown in Figure 1, and to develop a manufacturing method that allows for the arbitrary adjustment and control of the permeability coefficient after filling and solidification as a physical property of the fluidized sand composition.

[0008] The object of the present invention is to provide a method for producing a fluidized sand composition that further improves upon the fluidized sand composition described in Patent Document 2, which is designed to obtain appropriate strength after filling a cavity in the ground, by obtaining not only appropriate strength after filling but also an appropriate permeability coefficient according to the application, thereby preventing damage such as subsidence and the risk of recurrence. Other or specific objects will be clarified in the following description. [Means for solving the problem]

[0009] To achieve the above objective, the invention of claim 1 is a method for producing a fluidized sand composition for cavity filling, in which blast furnace slag fine powder, one or two selected from slaked lime and gypsum, water for adjusting the water content, a fluidizer, and a plasticizer are mixed as additives to the material sand, and the fluidized sand composition exhibits appropriate strength after being filled into a cavity on the ground side, wherein the amount of plasticizer added is increased or decreased so that the fluidized sand composition satisfies the required permeability coefficient along with appropriate strength after being filled into a cavity on the ground side As such, the change in the permeability coefficient is obtained by including at least 0.05 to 0.1 parts by weight of the plasticizing agent per 100 parts by weight of the material sand. It is characterized by pre-determining the required hydraulic conductivity and adjusting it to the specified value based on that information. Furthermore, the invention of claim 2 is a method for producing a fluidized sand composition for cavity filling, in which blast furnace slag fine powder, one or two selected from slaked lime and gypsum, water for adjusting the water content, a fluidizer, and a plasticizer are mixed as additives to material sand, and the fluidized sand composition exhibits appropriate strength after being filled into a cavity on the ground side, characterized in that, in order for the fluidized sand composition to satisfy the required permeability coefficient along with appropriate strength after being filled into a cavity on the ground side, the amount of blast furnace slag fine powder added is increased or decreased, and the change in permeability coefficient is investigated in advance in a range in which the blast furnace slag fine powder is at least 1 to 5 parts by weight per 100 parts by weight of material sand, and the required permeability coefficient is adjusted by referring to the results.

[0010] The present invention was developed based on the recognition that if the permeability coefficient of a fluidized sand composition after filling and solidification could be adjusted in advance, it would be possible to create a filling material with a more appropriate permeability coefficient depending on the application, making it easier to eliminate damage such as sinkholes and the risk of recurrence.

[0011] (Example of Use) An example of the use of the fluidized sand composition produced by the present invention is as follows: It is used to fill cavities that have formed at the boundary between the ground and a structure (river embankments, slope backs, structural foundations, tunnels). Cavities that occur in such places often develop and expand due to the erosion of the ground by water flow. For example, if such a cavity is filled with grout, water flow will occur again at the boundary between the original ground and the filled area. In this case, the water flow will take the following characteristics depending on the difference in permeability between the filled area and the original ground. If the original ground has high permeability and the filling area has low permeability, water flow will be faster at the boundary. • If the original ground has high permeability and the filling area also has high permeability, the flow of water will slow down at the boundary. If the original ground has low permeability (mainly cohesive soil), erosion will not occur much, but voids will form between the structure and the ground due to settlement. Given this phenomenon, it is considered most rational for the filling material to have the same permeability coefficient as the ground in the end.

[0012] (Instructions for Use) The most preferred use and application method for the fluidized sand composition of the present invention is to use it in accordance with the permeability of the ground, as follows. A: When the permeability coefficient of the fluidized sand composition is high (for example, in the graphs in Figures 2 and 3, the permeability coefficient (m / s) is higher than 1.E-05), a suitable use case is to fill cavities generated by erosion, etc., at the boundary with a structure when the original ground is gravel or coarse sand. B: When the permeability coefficient of the fluidized sand composition is medium (for example, in the graphs in Figures 2 and 3, the permeability coefficient (m / s) is approximately 1.E-07 to 1.E-05), a suitable use case is when the original ground is fine sand and silt-mixed sand, and the composition is used to fill voids created by erosion, etc., at the boundary with a structure. Specific structures include tunnels, culverts, river revetment backs, and existing covered slope backs. C: When the permeability coefficient of the fluidized sand composition is low (for example, in the graphs in Figures 2 and 3, the permeability coefficient (m / s) is lower than 1.E-07), a suitable use case is to fill cavities, cracks in bedrock, or spaces surrounded by cement structures that have been created by the settlement of the original ground, etc. Specific structures include underground pits, inside buried pipes, anchoring structures, and cracks in bedrock.

[0013] (1) The specification of claim 1 is As can be seen from the graph in Figure 2, when the amount of plasticizer added is less than 1x the standard blend, i.e., less than 0.5g (0.05 parts by weight) per 1.000g of material sand, the permeability coefficient (m / s) becomes considerably smaller. Conversely, when the amount added exceeds 2x, i.e., 1g (0.1 parts by weight) per 1.000g of material sand, not much increase in the permeability coefficient (m / s) can be expected. In this range of plasticizer addition amounts, the permeability coefficient (m / s) varies depending on the origin of the material sand used, but is roughly around 1.E-07 to 1.E-3.5.

[0014] (2) The specification of claim 2 is As can be seen from the graph in Figure 3, when the amount of blast furnace slag fine powder added is less than 10g (1 part by weight) per 1,000g of material sand, which is the standard addition amount of 1%, the permeability coefficient (m / s) becomes considerably large. Conversely, when the addition amount exceeds 50g (5 parts by weight) per 1,000g of material sand, which is the addition amount of 5%, the permeability coefficient (m / s) becomes considerably small. In this range of blast furnace slag fine powder addition amounts, the permeability coefficient (m / s) varies depending on the origin of the material sand used, but is roughly around 1.E-08 to 1.E-04. [Effects of the Invention]

[0015] Claim 1 and 2In the inventive method, as the fluidized sand composition, the permeability coefficient can be selected within a wide range and can be created as any permeability coefficient, thereby improving the quality as a filler and being more useful in preventing damages such as subsidence and the risk of recurrence. That is, in the fluidized sand composition of the present invention, in the filled and solidified state, any strength and any water permeability (permeability coefficient) can be exhibited, and since it has fluidity during filling, it can surely fill every corner of various cavities. Here, any strength is as described in Patent Document 2. For any permeability coefficient, the permeability coefficient corresponding to the addition amount of the plasticizer or fine blast furnace slag powder is investigated in advance, and it is adjusted to the required permeability coefficient by referring to it. Note that grout-based fillers do not have water permeability because they are solidified with cement.

[0016] In addition, Claim 1 In the invention, in proportion to the blending amount of the plasticizer, the neutralization by the fluidizing agent becomes faster until solidification, and it solidifies in a state where the gaps are enlarged, resulting in a fluidized sand composition with a large permeability coefficient.

[0017] Claim 2 In the invention, for example, in proportion to the addition amount of fine blast furnace slag powder, the crystal structure within the fluidized sand interval due to solidification decreases, resulting in a fluidized sand composition with a small permeability coefficient.

[0018] By implementing each of the above inventions, Since it becomes a fluidized sand composition with the permeability coefficient adjusted and managed, it can obtain a high evaluation in surely preventing damages such as subsidence and the risk of recurrence.

Brief Description of Drawings

[0019] [Figure 1] It is a graph showing the relationship between the particle size and the passing mass percentage of sand by place of origin (material sand), which is the main material used in the fluidized sand composition. [Figure 2] It is a graph showing the variation of the permeability coefficient when the addition amount of the plasticizer is changed as the fluidized sand composition manufactured by applying the method of the present invention. [Figure 3]This graph shows the change in the hydraulic conductivity of a fluidized sand composition produced by applying the method of the present invention, when the amount of blast furnace slag fine powder added is changed. [Modes for carrying out the invention]

[0020] The fluidized sand composition of the present invention and its manufacturing method will be described in detail with reference to Figures 1 to 3 as necessary.

[0021] (Overall composition) The fluidized sand composition in question develops appropriate strength after being filled into a cavity in the ground. It is manufactured by mixing the main material sand with one or two additives selected from blast furnace slag fine powder, slaked lime, and gypsum, water for adjusting the water content, a fluidizing agent, and a plasticizing agent. This composition is substantially the same as that disclosed in Patent Document 2. In the manufacturing method of the present invention, as a configuration different from the manufacturing method of Patent Document 2, in order for the fluidized sand composition to satisfy an arbitrary required permeability coefficient along with appropriate strength after being filled into a cavity in the ground, the permeability coefficients in the manner in which the amount of plasticizing agent added is increased or decreased, or in the manner in which the amount of blast furnace slag fine powder added is increased or decreased, are investigated in advance, and the permeability coefficient is adjusted to the required predetermined value by referring to these values.

[0022] The following describes the constituent materials of the fluidized sand composition, then clarifies the manufacturing method of the fluidized sand composition, and finally clarifies the details through Example 1, which investigated the change in the permeability coefficient of fluidized sand compositions manufactured by changing the amount of plasticizer added (blending amount), and Example 2, which investigated the change in the permeability coefficient of fluidized sand compositions manufactured by changing the amount of blast furnace slag fine powder added (blending amount).

[0023] The constituent materials are as follows: (1) The material sand can be any type that has been used in the manufacture of conventional fluidized sand or fluidized sand compositions, and may contain some silt or gravel. The graph in Figure 1 shows the relationship between particle size and passing mass percentage for sands from production sites a to e. In Figure 1, in Examples 1 and 2 described later, sand e from Futaijima, sand d from Oga, and sand b from Hoki were used. Sand e from Futaijima has an appropriate moisture content of 30%, sand d from Oga has an appropriate moisture content of 25%, sand b from Hoki has an appropriate moisture content of 35%, and sand c from the lower reaches of the Kiso River has an appropriate moisture content of 30%. As material sand, a particle size of about 0.074 to 2.0 mm is preferable. The dashed lines on the left and right indicate the range permitted by the SCP (Sand Compaction Pile) method. Furthermore, the particle size accumulation curve generally indicates that compaction characteristics are good when the particle size is distributed over a wide area, as in sand e from Futaijima and sand d from Ogajima, while compaction characteristics are poor when the particle size is concentrated over a narrow area, as in sand b from Hoki. Also, the area from the left of sand b from Hoki to the right of sand d is the range of actual use in conventional fluidized sand and fluidized sand compositions, with the average particle size D 50 The particles are approximately 0.5 mm in size and have a fine particle content of Fc = 5% or less.

[0024] (2) Blast furnace slag fine powder is a granular by-product generated in the steelmaking process, and its main components are CaO, SiO2, Al2O3, and MgO. Blast furnace slag includes slag that has been cooled and granulated slag, of which granulated slag is preferred. Granulated slag is a glassy (amorphous) granular material produced by rapidly cooling molten blast furnace slag with pressurized water. Blast furnace slag fine powder has a specific surface area of ​​2,750 to 10,000 cm². 2 A product containing 1g is preferable.

[0025] The amount of blast furnace slag powder added significantly affects not only the hardness of the resulting fluidized sand composition but also its hydraulic conductivity. The amount is typically 0.5 to 5.5 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of material sand. As can be inferred from the graph in Figure 3, even with the same amount added, the hydraulic conductivity of the resulting fluidized sand composition varies depending on the material sand used. Therefore, in the design phase of production, the amount of blast furnace slag powder added is determined by referring to graphs like Figure 3, which are created in advance for each type of material sand used, to ensure that a fluidized sand composition with the desired or required hydraulic conductivity is obtained.

[0026] (3) One or two selected from slaked lime and gypsum. When blast furnace slag fine powder is added to, for example, known fluidized sand, the presence of slaked lime or gypsum promotes the reaction, accelerates solidification or hardening, and facilitates the development of appropriate strength. However, appropriate strength cannot be reliably achieved with blast furnace slag fine powder alone.

[0027] Slaked lime is calcium hydroxide, produced by quenching quicklime with water or steam. Commercially available powdered slaked lime for construction or industrial use is preferred. The amount of slaked lime to be added is 10 to 200 parts by weight, preferably 20 to 100 parts by weight, per 100 parts by weight of blast furnace slag fine powder. If the amount of slaked lime is too high, the pH of the fluidized sand composition becomes alkaline, and the leaching of alkaline components is undesirable in terms of environmental impact. If the amount is too low, the reaction with blast furnace slag fine powder will not be promoted.

[0028] Examples of gypsum include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum, of which hemihydrate gypsum is preferred due to its availability. Specific examples of gypsum include natural gypsum, gypsum produced as a by-product of flue gas desulfurization, natural anhydrous gypsum, and hydrofluoric acid anhydrous gypsum produced as a by-product in the hydrofluoric acid manufacturing process. The amount of gypsum to be added is 10 to 200 parts by weight, preferably 20 to 100 parts by weight, per 100 parts by weight of blast furnace slag fine powder. Too much gypsum is undesirable from an economic standpoint, while too little will not promote the reaction with the blast furnace slag fine powder.

[0029] The material may consist of three components as additives to the sand: blast furnace slag fine powder, slaked lime, and gypsum, or it may consist of two components as additives: blast furnace slag fine powder and either slaked lime or gypsum. In these configurations, the materials may be in powder form or dissolved in water.

[0030] (4) When adjusting the water content, it is preferable to use neutral tap water, avoiding industrial water or seawater that contains cations such as metal ions that particularly affect the fluidizing agent. The amount of water used is usually calculated to adjust the water content of the fluidized sand composition to be manufactured to a range of 25-40%. This water content should also be taken into consideration, as a higher water content will proportionally increase the volume that can be injected into the cavities.

[0031] (5) The fluidizing agent is an additive that increases the viscosity of the interpore water between sand particles, suppresses the separation of sand and water in a saturated state, and improves handling properties such as pumpability. Specifically, these include anionic polymer flocculants, nonionic polymer flocculants, and cationic polymer flocculants. Preferably, an anionic polymer agent is used to increase viscosity and suppress the settling and separation of sand particles. This is because the hydrophilic groups of the polymer have excellent water retention properties, and also bond sand particles or soil particles through the adhesive parts at the ends of the polymer. The amount of fluidizing agent to be blended or added is 0.01 to 2.0 parts by weight per 100 parts by weight of sand material, preferably 0.1 to 1.0 parts by weight. If the amount is too small, the sand material will not fluidize, and it will separate or clog in the pipes, making it impossible to pump. Conversely, if it is too large, the fluidization effect will not change and it will be a factor that increases costs. If there is too much fluidizing agent in the fluidized sand, it will also be a factor that reduces water permeability.

[0032] (6) The plasticizer has the effect of electrically neutralizing the fluidizer, making it impossible to retain the polymer of the fluidizer, and restoring friction between sand particles or soil particles, with a molecular weight of 10 4 ~10 7 Cationic polymer agents are preferred. Examples of such cationic polymer agents include polyethylene polyamine-dimethylamine-epichlorohydrin polycondensate. Plasticizers are sometimes also called slow-acting plasticizers.

[0033] The amount of plasticizer added significantly affects the permeability coefficient of the resulting fluidized sand composition, and is typically 0.05 to 0.1 parts by weight relative to the sand material. Too little plasticizer makes it difficult for the fluidized sand composition to plasticize, while too much causes premature plasticization, hindering the filling process. As can be inferred from the graph in Figure 2, even with the same amount of additive, the permeability coefficient of the fluidized sand composition varies depending on the sand material used. Therefore, in the design phase of manufacturing, the amount of plasticizer added is determined by referring to graphs like Figure 2, which are created in advance for each type of sand material used, to ensure that a fluidized sand composition with the desired or required permeability coefficient is obtained.

[0034] Next, the method for producing the fluidized sand composition according to the present invention will be explained with reference to Figures 2 and 3. This method is the same as the method described in Patent Document 2 in that it involves mixing blast furnace slag fine powder, one or two additives selected from slaked lime and gypsum, water for adjusting the water content, and a fluidizing agent with the raw material sand, and then filling and solidifying the resulting fluidized composition into a cavity on the ground side, after which it develops appropriate strength. However, it differs from the method described in Patent Document 2 in the following respects. In the method described in Example 1, the amount of plasticizer added is varied to change the permeability coefficient of the fluidized composition. In Example 2, the amount of blast furnace slag fine powder added is increased or decreased to change the permeability coefficient of the fluidized composition. These methods are performed for each type of sand from a different region, i.e., for each type of raw material sand used. Figure 2 shows the results of investigating the change in permeability coefficient (m / s) due to the amount (times) of plasticizer added in Example 1, and Figure 3 shows the results of investigating the change in permeability coefficient due to the amount (%) of blast furnace slag fine powder added in Example 2.

[0035] (Example 1) In this Example 1, the material sand is mixed in a mixing tank with blast furnace slag fine powder, one or two additives selected from slaked lime and gypsum, water for adjusting the water content, a fluidizer, and a plasticizer. Preferably, the process involves a first step of mixing the material sand with blast furnace slag fine powder and one or two additives selected from slaked lime and gypsum, a second step of mixing water for adjusting the water content and a fluidizer into the mixture obtained in the first step, and a third step of mixing a plasticizer into the mixture obtained in the second step.

[0036] Example 1 involves adding blast furnace slag fine powder (specific surface area 4.000 cm²) to the material sand. 2 The mixture consists of 1,000 g of sand, slaked lime, water for adjusting the water content, and an anionic polymer agent as a fluidizer, mixed in a standard proportion. Specifically, the proportions are: 1,000 g of material sand: 30 g of blast furnace slag powder: 10 g of slaked lime: 275 g of water for adjusting the water content (this is broken down as follows: 99 g of water content in the sand + 40 g of added water + 100 g of diluent for the fluidizer + 36 g of water for dissolving the solidifying agent): 6.4 g of fluidizer (amount of the original solution). In this example, only slaked lime was added, and gypsum was not used. However, gypsum may also be added. In contrast, the amounts of cationic polymer agent added as a plasticizer are 1x, 1.1x, 1.2x, and 2x. This value is based on a standard formulation of 0.5 g (0.05 parts by weight) of plasticizer per 1.000 g of material sand. In Example 1, this corresponds to 0.05 parts by weight for a 1x plasticizer addition, 0.055 parts by weight for a 1.1x addition, 0.06 parts by weight for a 1.2x addition, and 0.1 parts by weight for a 2x addition.

[0037] The fluidized sand compositions manufactured under the above conditions were filled and solidified into test ground cavities, and their permeability coefficients were measured. The results are summarized in Table 1. In Table 1, SR is an abbreviation for fluidized sand composition, and the P1 addition amount is the amount of plasticizer added. SR(d) is a fluidized sand composition using sand from Ogashima, SR(e) is a fluidized sand composition using sand from Futaijima, and SR(b) is a fluidized sand composition using sand from Hoki.

[0038] The method for determining the permeability coefficient of the solidified fluidized sand composition was based on the Japanese Industrial Standard for Soil Permeability Testing (JIS A1218:2020). This method includes a constant-level permeability test, which is suitable for cases with relatively high permeability coefficients, and a variable-level permeability test, which is suitable for cases with relatively low permeability coefficients. The fluidized sand composition in question was measured using the latter test. A detailed explanation of the measurement method is omitted here, but please refer to pages 467-489 of Volume 1 of Volume 2 of "Methods and Commentary on Geotechnical Material Testing," "First Revised Edition," published by Maruzen Publishing Co., Ltd. and the Japanese Geotechnical Society.

[0039] (Table 1) TIFF0007839595000001.tif67132 As described above, 1x the amount of P1 added corresponds to 0.05 parts by weight, 2x corresponds to 0.1 parts by weight, 1.1x corresponds to 0.055 parts by weight, and 1.2x corresponds to 0.06 parts by weight.

[0040] The graph in Figure 2 shows that when the amount of plasticizer added is 1x, i.e., less than 0.05 parts by weight per 1,000g of material sand, the permeability coefficient becomes quite small. Conversely, when the amount of plasticizer added exceeds 2x, i.e., more than 0.1 parts by weight per 1,000g of material sand, the increase in the permeability coefficient becomes gradual. In other words, it is presumed that the fluidized sand composition produced will be neutralized by the fluidizer more quickly in proportion to the amount of plasticizer added, hardening or solidifying with larger pores, resulting in a filler with a high permeability coefficient. The graph in Figure 2 also includes the estimated permeability coefficient when material sand with a 10% particle size is used. This was obtained by determining the particle size distribution using the Japanese Industrial Standards (JIS) soil particle size distribution test method (JIS A1204), and then using, for example, Hazen's formula from the obtained particle size distribution.

[0041] (Example 2) In this Example 2, the material sand was mixed with one or two additives selected from slaked lime and gypsum, water for adjusting the water content, an anionic polymer agent as a fluidizing agent, and a cationic polymer agent as a plasticizing agent in a standard proportion, and blast furnace slag fine powder (specific surface area 4,000 cm²) was added. 2 The amount of additive (%) ( / g) is increased or decreased. Specifically, the mixture is 1,000g of material sand: 10g, 30g, or 50g of blast furnace slag fine powder: 10g of slaked lime: 275g of water for adjusting the water content (this is broken down as follows: water content of sand 99g + added water 40g + diluent for fluidizer 100g + dissolving water for solidifying agent 36g): fluidizer 6.4g (amount of undiluted solution): plasticizer 0.5g. In this example, only slaked lime was added and gypsum was not used. However, gypsum may also be added. Here, the standard blend of 3% blast furnace slag fine powder is 30g (3 parts by weight) of blast furnace slag fine powder per 1,000g of material sand, and 1% blast furnace slag fine powder is 1 part by weight, and 5% is 5 parts by weight.

[0042] The fluidized sand composition produced under the above conditions was filled and solidified into a test ground cavity, and its permeability coefficient was measured. The results are listed in Table 2. In Table 2, SR, SR(d), SR(e), and SR(b) are the same as in Example 1.

[0043] (Table 2) TIFF0007839595000002.tif59115

[0044] The graph in Figure 3 shows that when the amount of blast furnace slag fine powder added is 1%, or less than 1 part by weight per 1,000 g of material sand, the permeability coefficient becomes quite large. Conversely, when the amount added exceeds 5%, or 5 parts by weight per 1,000 g of material sand, the permeability coefficient becomes quite small. In other words, the fluidized sand composition produced has a lower permeability coefficient because the amount of blast furnace slag fine powder added (blended amount) is inversely proportional to the amount of crystalline structure in the fluidized sand pores due to solidification.

[0045] Furthermore, the present invention only needs to have the configuration specified in each claim. The details can be developed in various ways based on these, for example, although gypsum was omitted and only slaked lime was added in each embodiment, slaked lime and gypsum may be mixed, or only gypsum may be added.

Claims

1. A method for producing a fluidized sand composition for filling cavities, which develops appropriate strength after being filled into a cavity on the ground side, by mixing blast furnace slag fine powder, one or two selected from slaked lime and gypsum, water for adjusting the water content, a fluidizing agent, and a plasticizing agent as additives to the material sand, A method for producing a fluidized sand composition, characterized in that, in order for the fluidized sand composition to satisfy the required permeability coefficient along with appropriate strength after being filled into a cavity on the ground side, the change in permeability coefficient in a range in which the amount of plasticizer added is at least 0.05 to 0.1 parts by weight of the plasticizer per 100 parts by weight of the material sand is investigated in advance, and the fluidized sand composition is adjusted to a predetermined permeability coefficient by referring to the results, in such a manner that the fluidized sand composition satisfies the required permeability coefficient along with appropriate strength.

2. A method for producing a fluidized sand composition for filling cavities, which develops appropriate strength after being filled into a cavity on the ground side, by mixing blast furnace slag fine powder, one or two selected from slaked lime and gypsum, water for adjusting the water content, a fluidizing agent, and a plasticizing agent as additives to the material sand, A method for producing a fluidized sand composition, characterized in that, in order for the fluidized sand composition to satisfy the required permeability coefficient along with appropriate strength after being filled into a cavity on the ground side, the permeability coefficient is determined by first investigating the change in permeability coefficient in a range in which the blast furnace slag fine powder is included in an amount of at least 1 to 5 parts by weight of the blast furnace slag fine powder per 100 parts by weight of the material sand, and adjusting the fluidized sand composition to the required predetermined permeability coefficient by referring to the results.

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