Auxiliary agent for backfill injection liquid a and method for producing liquid a

Abstract

To provide an auxiliary material for a backfill injection liquid A which achieves carbon neutral or carbon negative while securing predetermined quality, and a method for producing the liquid A.SOLUTION: The auxiliary material for the backfill injection liquid A constitutes the backfill injection material by being mixed with the liquid B and is blended in the liquid A containing a hardening material and a stabilizer, and contains a clay mineral and bio-charcoal. The method for producing the liquid A includes a first step of mixing a clay mineral and biochar to obtain a first composition of a powdery assistant, a second step of adding water to the first composition to obtain a second composition which is a liquid composition, and a third step of mixing the second composition, a curing material, and a stabilizer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a backfill grout used when constructing a tunnel using an excavation machine such as a shield machine. [Background technology]

[0002] In recent years, there has been a demand for carbon-neutral or carbon-negative technologies that do not emit carbon dioxide, with the aim of reducing greenhouse gas emissions, and the same is true for construction work.

[0003] As an example of carbon neutral or carbon negative technology in construction work, Patent Document 1 proposes a premix mortar product containing cement and a low-carbon composite material made by blending at least two types of low-carbon materials in a mass ratio of 97:3 to 70:30 in order to reduce the amount of carbon dioxide emitted when manufacturing the premix mortar product.

[0004] Furthermore, Patent Document 2 proposes a hardenable cement composition containing cement, water, fine aggregate, coarse aggregate, and biochar as a carbon dioxide fixation material in order to reduce carbon dioxide emissions during production to a carbon neutral or carbon negative level.

[0005] In tunnel construction using a shield machine, backfill grout is injected into the tail void, which is the gap between the excavated ground and the segments. For backfill injection materials, a two-component mixture type is often used, in which liquid A and liquid B are produced outside the tunnel, pumped, and mixed just before being injected into the tail void. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-207686 [Patent Document 2] Japanese Patent Publication No. 2023-160056 Summary of the Invention [Problem to be solved by the invention]

[0007] The technologies described in Patent Documents 1 and 2 above relate to general cement products, and no proposals have been made to achieve carbon neutrality or carbon negativity for backfill injection materials.

[0008] The problem to be solved by the present invention is to provide a backfilling injection material that achieves carbon neutrality or carbon negative while ensuring a predetermined quality, in particular, an auxiliary material for backfilling injection A liquid and a method for producing A liquid. [Means for solving the problem]

[0009] The inventors of the present invention have conducted extensive research focusing on biochar, a carbon dioxide fixation material, and two-component mixed backfill injection materials, and have discovered that using biochar as an auxiliary material for backfill injection material A can produce a backfill injection material with assured quality, which has led to the completion of the present invention.

[0010] The invention of claim 1 is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized by containing clay minerals and biochar.

[0011] The invention of claim 2 is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized in that it contains clay minerals and wood charcoal as biochar.

[0012] The invention of claim 3 is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized in that it contains clay minerals and rice husk charcoal as biochar.

[0013] The invention of claim 4 is an auxiliary material for backfill injection A liquid described in any one of claims 1 to 3, characterized in that the blending ratio of the biochar to the clay mineral is 5 or less by weight on an absolute dry basis.

[0014] The invention of claim 5 is an auxiliary material for backfill injection A liquid described in any one of claims 1 to 3, characterized in that the blending ratio of the biochar to the clay mineral is 0.6 to 5 in terms of absolute dry weight ratio.

[0015] The invention according to claim 6 is the auxiliary material for backfilling injection A liquid according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 62% or less.

[0016] The invention according to claim 7 is an auxiliary material for backfilling injection A liquid according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 60% or less.

[0017] The invention of claim 8 is an auxiliary material for backfilling injection A liquid according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 10% or more and 62% or less.

[0018] The invention of claim 9 is a method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, characterized in that the method comprises: a first step of mixing a clay mineral and biochar to obtain a first composition of a powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0019] The invention of claim 10 is a method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, characterized in that the method comprises: a first step of mixing a clay mineral with wood charcoal as biochar to obtain a first composition of powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0020] The invention of claim 11 is a method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, characterized in that the method comprises: a first step of mixing clay mineral and rice husk charcoal as biochar to obtain a first composition of powdered auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0021] The invention of claim 12 is a method for producing liquid A described in any one of claims 9 to 11, characterized in that the blending ratio of the biochar to the clay mineral is 5 or less by weight on an absolute dry basis.

[0022] The invention of claim 13 is a method for producing liquid A described in any one of claims 9 to 11, characterized in that the blending ratio of the biochar to the clay mineral is 0.6 or more and 5 or less by weight on an absolute dry basis.

[0023] The invention according to claim 14 is the method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 62% or less.

[0024] The invention according to claim 15 is the method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 60% or less.

[0025] The invention according to claim 16 is the method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 10% or more and 62% or less. [Effects of the Invention]

[0026] According to the present invention, biochar, which has a high carbon dioxide emission reduction effect, is blended into the auxiliary material for backfill injection A liquid, making it possible to achieve a high level of carbon neutrality or carbon negativity. By mixing biochar with clay minerals to create an auxiliary material, it is less likely to separate than when biochar is added to A liquid alone or when it is mixed with a hardener and then added to A liquid, and it is less likely to become agglomerated over time, making it easier to transport and increasing its strength.

[0027] In addition, by blending biochar in an absolute dry weight ratio to clay minerals of 0.6 or more and 5 or less, it is possible to ensure carbon neutral or carbon negative levels while maintaining qualities such as flow value and bleeding.

[0028] In addition, by setting the weight moisture content of biochar to 10% or more, the risk of fire is reduced, and by setting it to 62% or less or 60% or less, it is less likely to aggregate over time, which means that it is less likely to clog transport equipment when transported. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic view of a liquid A manufacturing apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments. FIG. 1 is a schematic diagram of the liquid A manufacturing apparatus.

[0031] In this embodiment, the backfill injection material injected into the gap between the excavated ground and the segment is a two-component mixed type in which liquid A and liquid B are produced outside the tunnel or elsewhere, pumped, and mixed just before being injected into the tail void of the shield tunneling machine.

[0032] Liquid A contains a hardener, a stabilizer, an auxiliary material, and mixing water. Liquid B is an accelerator (plastic strength adjuster) that reacts with the hardener to gel and harden rapidly when mixed with Liquid A, and examples of such accelerators include water glass (sodium silicate). In this embodiment, Liquid B is preferably an aqueous solution containing at least one selected from the group consisting of sodium silicate, sodium polychloride, and compounds thereof.

[0033] The components of Solution A will be explained below. The hardening agent may be a commonly used cementitious material, such as blast furnace type B cement, ordinary Portland cement, high-early-strength cement, ground granulated blast furnace slag, fly ash, or a mixture thereof.

[0034] The stabilizer is a hardening retarder that slows the hardening of the hardener in order to pump the liquid A. Examples of the stabilizer include zinc oxide, silicon fluoride, borax, sugars or their derivatives, lignin sulfonates, and hydroxycarboxylates. The amount of stabilizer added can be adjusted depending on the usable time of solution A, but if the amount is too large, the viscosity may decrease, which may result in a decrease in strength.

[0035] Generally, the auxiliary material used is bentonite or methylcellulose resin, which has a thickening and solid-liquid separation suppression function to prevent separation and bleeding of materials and ensure viscosity during storage or pumping after production of Liquid A. In this embodiment, however, the auxiliary material used is a mixture of biochar and a clay mineral such as bentonite, which swells and imparts viscosity when water is added, i.e., the auxiliary material for Liquid A. Furthermore, the clay mineral may be a material whose main component is at least one smectite clay mineral selected from the group consisting of montmorillonite, beidellite, and saponite.

[0036] Biochar is made by carbonizing plants, which absorb carbon dioxide and store carbon during their growth, before they are burned or decayed, and the carbon is immobilized.By using this as a backfill injection material, it is possible to reduce carbon dioxide emissions.

[0037] Typical biochars that are effective in reducing carbon dioxide emissions include wood charcoal made by carbonizing wood, as well as rice husk charcoal. However, the carbon dioxide emission intensity, which is the carbon storage amount, is -1.60 (t-CO 2 / t), while wood charcoal is -2.87(t-CO 2 / t), so in this embodiment, wood charcoal will be used for explanation. Wood charcoal was used in powder form. The particle size distribution (weight) of the powdered wood charcoal was about 70% 425 μm or less, about 10% 425 to 700 μm, about 10% 700 μm to 1 mm, and about 10% 1 mm or more.

[0038] The carbon dioxide emission intensity, which is the amount of carbon stored, is expressed by the following formula. Carbon dioxide emission intensity = carbon content x carbon residue rate x conversion factor The carbon content was determined based on the results of component analysis (rice husk charcoal: 0.49, wood charcoal: 0.88). The carbon residual rate was set to a heating temperature of >600°C (0.89) in J Credit, assuming that the material will be used as a backfill injection material for shield construction, as the contact area with the soil will be large. The conversion factor is a coefficient that represents the ratio between the weight of carbon and the weight of carbon dioxide. Since 1 mole of carbon weighs 12g and 1 mole of carbon dioxide weighs 44g, the carbon weight is multiplied by 44 / 12 = 3.67 to calculate the amount of carbon dioxide emissions.

[0039] From this, the carbon dioxide emission intensity of rice husk charcoal is: 0.49×0.89×3.67=-1.60(t-CO 2 / t), The carbon dioxide emission intensity of wood charcoal is: 0.88×0.89×3.67=-2.87(t-CO2 / t), Wood charcoal is dominant.

[0040] If the only purpose of wood charcoal was to reduce carbon dioxide emissions, it could be added to Liquid A by adding water to the wood charcoal, but since its true specific gravity is light at around 0.8, it became necessary to confirm its mixability and handling.

[0041] Therefore, the measured bulk specific gravity was 0.164 g / cm 3 The kneading properties were evaluated when kneading water was added to dry wood charcoal with a measured moisture content of 31.5% by weight. In addition, the measured bulk specific gravity is 0.462 g / cm 3 The kneading properties were evaluated when kneading water was added to wet wood charcoal with a measured weight moisture content of 74.5%.

[0042] The test method involves adding an equal amount of mixing water to dry wood charcoal (5 to 50 kg) and wet wood charcoal equivalent to the weight of the dry wood charcoal, and checking viscosity, mixability, sedimentation, etc.

[0043] The kneadability was evaluated from the viewpoint of uniformity of solubility by kneading 1 L of the prepared solution for 30 seconds in a tabletop mixer (Model TMX20A, manufactured by Tescom), scraping it off, and kneading it for 1 minute. After mixing, the viscosity was measured using a No. 3 rotor (0.3 to 13 dPa·s) of a Riontec Co., Ltd. Visco Tester VT-06. The settling property was evaluated by stirring with a spatula after kneading and leaving to stand for 30 minutes, and observing the degree of adhesion.

[0044] Table 1 shows the relationship between the dissolved concentration and viscosity of dry wood charcoal. Table 2 shows the relationship between the dissolved concentration and viscosity of wet wood charcoal.

[0045] [Table 1]

[0046] [Table 2]

[0047] The results in Table 1 show that when dry wood charcoal is added alone, it immediately separates from the mixing water and settles, making it impossible to mix uniformly, and the results in Table 2 show that when wet wood charcoal is added alone, it forms agglomerates and is difficult to mix, meaning that in either case it is difficult to add wood charcoal alone to Liquid A. It was also confirmed that dry wood charcoal, in particular, is prone to generating dust when used alone.

[0048] It is also possible to premix wood charcoal and hardener and add it to Liquid A. Therefore, we used blast furnace cement type B as the hardening agent, and compared the properties of Liquid A, which was made by pre-mixing this hardening agent with wood charcoal (weight moisture content 31.5%) and then compounding it. We also compared the gel time and strength when sodium silicate was added to Liquid A as Liquid B, and the properties of Liquid A to which an auxiliary material made from a mixture of the clay mineral bentonite (particle size less than 75 μm) and wood charcoal was added, and the gel time and strength when sodium silicate was added to Liquid A as Liquid B.

[0049] The formulation of a premixed hardener (premixed hardener) prepared by mixing hardener and wood charcoal in advance is shown in Table 3. In the comparative example, the premixed hardener is mixed with auxiliary materials, mixing water, and stabilizer to prepare liquid A, which is then mixed with liquid B.

[0050] The mix was adjusted and set based on the mix of backfill injection material used in general shield construction. Specifically, when wood charcoal is added to the standard mix, the viscosity of Liquid A becomes high, the flow decreases, making it difficult to mix with Liquid B, and the gel time increases. Also, if the amount of auxiliary material (bentonite) is reduced and the stabilizer is increased to lower the viscosity of Liquid A, the viscosity is satisfied, but the gel time exceeds the limit. These factors were taken into consideration and the mix was set appropriately.

[0051] [Table 3]

[0052] In order to knead the auxiliary material (bentonite) in advance as an aqueous solution, the water for kneading the auxiliary material (200 L) was subtracted from the blending water (812 L) and kneaded. Comparative Examples 1 to 3 were prepared by varying the amount of stabilizer blended, 3 kg, 5 kg, and 10 kg.

[0053] The formulation of an example in which clay mineral and wood charcoal were mixed in advance (premix auxiliary material) is shown in Table 4. In the example, the hardener was kneaded with the premix auxiliary material, mixing water, and stabilizer to prepare liquid A, which was then mixed with liquid B.

[0054] [Table 4]

[0055] In order to prepare the premix auxiliary materials (bentonite and wood charcoal) as an aqueous solution and knead them with the hardener, the water for kneading the auxiliary materials (400 L) was subtracted from the blending water (812 L) before kneading. In the example, the amount of water for kneading the auxiliary materials was increased compared to the comparative example in order to use wood charcoal as the auxiliary material. Examples 1 to 3 were prepared using different stabilizer blends of 3 kg, 5 kg, and 10 kg.

[0056] The performance evaluations for the comparative examples and examples were as follows: as evaluation of Liquid A, the flow value immediately after production of Liquid A and the bleeding value after 1 hour; as evaluation of backfill injection material, the gel time after adding Liquid B to Liquid A and the uniaxial compressive strength of the backfill injection material after 28 days.

[0057] The flow value was measured by placing a cylinder with an inner diameter of 80 mm and a height of 80 mm on a horizontal acrylic plate, filling it with Liquid A, and then gently lifting the cylinder and measuring the diameter of Liquid A at that time.

[0058] The bleeding rate was determined by placing the thoroughly stirred and fused solution A in a 500 ml measuring cylinder, leaving it to stand and sealing it, and measuring the amount of bleeding water (supernatant).

[0059] The gel time was measured by adding Solution B to Solution A and immediately mixing for 5 seconds using a hand mixer (two-way type, manufactured by Familia Fellows).

[0060] The unconfined compressive strength was measured as the compressive strength after 28 days in accordance with JISA1216 "Unconfined Compression Test for Soil."

[0061] As with general shield backfill injection materials, the target performance is a flow value of 400±100mm for Liquid A, and a bleeding value of within 5%. Note that the flow value is an index used to grasp the consistency of Liquid A's fluidity, long-distance pumpability, viscosity, etc., while bleeding is an index used to grasp the material stability.

[0062] If the gel time is too long, it can have adverse effects such as allowing groundwater to seep in, so the target performance is within 20 seconds.

[0063] The unconfined compressive strength of backfill injection material is generally 1N / mm 2 However, to fix carbon dioxide permanently, it is necessary to double that to 2N / mm 2 It is desirable that it is at least that level.

[0064] Table 5 shows the performance evaluation of the comparative example, and Table 6 shows the performance evaluation of the example.

[0065] [Table 5]

[0066] [Table 6]

[0067] As is clear from Tables 5 and 6, the premix of bentonite and wood charcoal achieved the target for all evaluated performance, but the premix of hardener and wood charcoal did not achieve the target for gel time and uniaxial compressive strength.

[0068] This can be said to be because, in the case of a premix of hardener and wood charcoal, the cement component of the hardener weathered when it came into contact with the moisture in the wood charcoal, causing a decrease in cohesive strength, resulting in a delay in gel time and a decrease in strength.

[0069] Blast furnace cement has a pH of 12 to 13, while bentonite and wood charcoal both have a pH of around 10. Therefore, it is thought that a premix of bentonite and wood charcoal is less susceptible to ion exchange than a premix of blast furnace cement and wood charcoal, and is therefore easier to maintain stable properties.

[0070] A comparison of the carbon dioxide emissions of the backfill injection materials (liquid A and liquid B) in the above-mentioned Examples and Comparative Examples is shown in Table 7. Table 7 also shows the general mix of backfill injection materials for shield construction (Table 8) (general example).

[0071] [Table 7]

[0072] [Table 8]

[0073] With regard to the amount of carbon dioxide emitted, all of Examples 1 to 3 and Comparative Examples 1 to 3 have a carbon dioxide absorption effect.

[0074] When transporting premixed powder materials, if the particle size increases due to agglomeration or the like, there is a risk that the material will clog and block the pressure transport pipe. In a manufacturing plant for backfill injection materials, when a conveying device with a screw inside a casing is used to transport premixed powder materials, the clearance between the inner diameter of the casing and the outer diameter of the screw is approximately 5 mm, so it can be said that particles with a diameter of less than 5 mm can be pumped.

[0075] Therefore, we investigated the degree of agglomeration over time after premixing for a premix of hardener and wood charcoal (premix hardener) and a premix of clay minerals and wood charcoal (premix auxiliary).

[0076] The premix hardener was designated as Comparative Example 4, and the premix auxiliary material was designated as Example 4, and the compositions shown in Table 9 were prepared.

[0077] [Table 9]

[0078] Comparative Example 4 was based on the blending ratio of blast furnace cement type B and wood charcoal in Comparative Examples 1 to 3 (285 kg:73 kg (bone dry content 50 kg+moisture 23 L)) and was blended per ton. In Example 4, the blending ratio of bentonite and wood charcoal per ton was determined based on the blending ratio of Examples 1 to 3 (20 kg:73 kg (bone dry content 50 kg+moisture 23 L)).

[0079] The test method for Comparative Example 4 and Example 4 is to store the mixed samples sealed in a non-breathable container, and measure and evaluate the change over time in the passing status through a sieve with a mesh size of 4.75 mm, assuming a clearance of approximately 5 mm between the inner diameter of the casing and the outer diameter of the screw.

[0080] The residual rate is calculated using the following formula, and based on past performance data on crushed clay particle size, etc., the target control value is set at 5% or less. Residual mass of residual sample = (1,000 g of mixed sample) - (mass passing through sieve) Residual rate (%) = (g of residual sample) ÷ (1,000g of mixed sample) × 100

[0081] The residual mass and residual rate from immediately after mixing until 56 days later are shown in Table 10. The number of days elapsed was set to 56 days (8 weeks, approximately 2 months) at the longest, from the viewpoint of storage stability as a premix material.

[0082] [Table 10]

[0083] As is clear from Table 10, in Comparative Example 4, where hardener and wood charcoal were mixed, the residual rate increased significantly from the 28th day, and although it was slightly below the target residual rate of 5% after 56 days, it exceeded it thereafter. On the other hand, in Example 4, where bentonite and wood charcoal were mixed, the residual rate increased slightly from the 28th day even after 56 days had passed, but was still far below the target residual rate.

[0084] From the above, it was found that the premix auxiliary material had less agglomeration than the premix hardening material and was superior in terms of preservation.

[0085] Regarding the blending of wood charcoal in the premix auxiliary material, if the blending amount is small, the effect of suppressing carbon dioxide emissions will be reduced, so it is better to blend as much as possible within the range that ensures the performance of the premix auxiliary material in solution.

[0086] On the other hand, the premix auxiliary material is used in the form of a solution in the production of Liquid A, and in order to ensure mixing with hardeners, etc., it is desirable for the specific gravity to be 1.0 or more. In order to make the specific gravity of the premix auxiliary solution 1.0 or more, the total weight of the premix auxiliary solution must exceed the total volume.

[0087] If the weight ratio of wood charcoal to bentonite in an absolutely dry state is x, and the true specific gravity of bentonite is 2.6 and 0.82, respectively, then 1 + x ≥ 1 / 2.6 + x / 0.82, and x ≤ 2.8. In other words, in an absolutely dry state, it is desirable for the weight ratio of wood charcoal to bentonite to be a maximum of 2.8.

[0088] In addition, the performance of the premix auxiliary solution was evaluated in terms of flow value while changing the weight ratio of wood charcoal to bentonite on an absolute dry basis.

[0089] The flow value was measured by placing a cylinder with an inner diameter of 80 mm and a height of 80 mm on a horizontal acrylic plate, filling it with the premix auxiliary solution, and then gently lifting the cylinder and measuring the diameter of the premix auxiliary solution.From the perspective of handling, such as pumpability within the plant and kneadability of Liquid A, the target control value for the flow value of the premix auxiliary solution was set at 600±100 mm.

[0090] Table 11 shows the formulation of the premix auxiliary solution and the results of measuring the flow value.

[0091] [Table 11]

[0092] As is clear from Table 11, if the weight ratio of wood charcoal to bentonite on an absolute dry basis is 0.9 or more and 2.8 or less (the weight ratio of bentonite to wood charcoal on an absolute dry basis is 1:0.9 to 1:2.8), the flow value will be within the target control value of 600±100 mm, and it can be seen that it is desirable for the weight ratio of wood charcoal to bentonite on an absolute dry basis to be 0.9 or more and 2.8 or less.

[0093] Wood charcoal used as a premix auxiliary material may ignite depending on storage conditions if its moisture content by weight falls below 10%. Also, if the moisture content by weight falls below 10%, it is more likely to produce large amounts of dust.

[0094] Furthermore, as mentioned above, when transporting premixed powder materials, if the particle size increases due to agglomeration or the like, there is a risk that the pressure-transporting pipes will become clogged and blocked. In a manufacturing plant for backfill injection materials, when a conveying device with a screw inside a casing is used to transport premixed powder materials, the clearance between the inner diameter of the casing and the outer diameter of the screw is approximately 5 mm, so it can be said that particles with a diameter of less than 5 mm can be pumped.

[0095] Therefore, we investigated the aggregate formation over time after premixing clay minerals and wood charcoal (premix auxiliary material) by changing the moisture content of the wood charcoal by weight. Wood charcoal with a weight moisture content of 31.5% was watered to create samples with varying weight moisture contents as shown in Table 12, and these samples were mixed with bentonite as a clay mineral to prepare samples.

[0096] [Table 12]

[0097] The test method involves storing 1000g of mixed sample of each moisture content in a sealed, non-breathable container, and measuring and evaluating the change over time in the passing status through a 4.75mm sieve, which assumes a clearance of approximately 5mm between the inner diameter of the casing and the outer diameter of the screw.

[0098] The residual rate is calculated using the following formula, and based on past performance data on crushed clay particle size, etc., the target control value is set at 5% or less. Residual mass of residual sample = (1,000 g of mixed sample) - (mass passing through sieve) Residual rate (%) = (g of residual sample) ÷ (1,000g of mixed sample) × 100

[0099] The residual mass and residual rate from immediately after mixing until 56 days later are shown in Table 13. The number of days elapsed was set to 56 days (8 weeks, approximately 2 months) at the longest, from the viewpoint of storage stability as a premix material.

[0100] [Table 13]

[0101] As is clear from Table 13, the higher the weight moisture content of the wood charcoal, the faster the aggregation tended to proceed. When the moisture content of wood charcoal by weight was 60.0% or more, the target control value was exceeded immediately after mixing with bentonite, and when it was 50.0%, it exceeded the target control value after 3 days.

[0102] If the weight moisture content of wood charcoal is 44.4%, the target control value will be reached after 28 days, so if the weight moisture content of wood charcoal is 44%, the storage period can be set at 28 days.

[0103] When the moisture content of wood charcoal by weight is 41.2%, it falls below the target control value after 56 days. Therefore, if the moisture content of wood charcoal by weight is 41%, the storage period can be set at 56 days, and an even longer storage period can be expected.

[0104] When the moisture content of wood charcoal by weight is 37.5%, it falls below the target control value after 56 days. Therefore, if the moisture content of wood charcoal by weight is 37%, the storage period can be set at 56 days, and an even longer storage period can be expected.

[0105] When the moisture content of wood charcoal by weight is 31.5%, it falls below the target control value after 56 days. Therefore, if the moisture content of wood charcoal by weight is 31%, the storage period can be set at 56 days, and an even longer storage period can be expected.

[0106] From these results, it is desirable that the moisture content of wood charcoal by weight be 44% or less if the storage period of premixed materials is set to 28 days, and that the moisture content of wood charcoal by weight be 41% or less if the storage period of premixed materials is set to 56 days.

[0107] Furthermore, taking into consideration the risk of fire and the possibility of dust scattering mentioned above, it is desirable that the moisture content of wood charcoal used as premix auxiliary material be between 10% and 44% (if the storage period is set to 28 days) or between 10% and 41% (if the storage period is set to 56 days).

[0108] The method for producing Solution A will be described below. To produce the liquid A, a liquid A production device 1 as shown in FIG. 1 is used.

[0109] The liquid A manufacturing device 1 includes a premix auxiliary material silo 2, an auxiliary material mixer 3, an auxiliary material dissolving tank 4, a hardening material silo 5, a mortar mixer 6, and a liquid A agitator .

[0110] The premix auxiliary material silo 2 stores a powdery first composition, that is, an auxiliary material, which is a mixture of clay minerals such as bentonite and wood charcoal (containing moisture equivalent to the moisture content by weight).

[0111] The auxiliary material mixer 3 is charged with blending water for auxiliary material kneading and the first composition stored in the premix auxiliary material silo 2 by a conveying device such as a screw feeder (not shown) and kneaded to produce the second composition (auxiliary material solution).

[0112] The second composition formed in the auxiliary mixer 3 is introduced into the auxiliary dissolving tank 4 . The hardening material silo 5 stores hardening materials such as blast furnace cement type B.

[0113] The hardening material stored in the hardening material silo 5, the second composition contained in the auxiliary material dissolving tank 4, the stabilizer, and the blending water for mixing the liquid A are fed into the mortar mixer 6 and mixed to produce the liquid A.

[0114] Liquid A formed in the mortar mixer 6 is fed into the liquid A agitator 7 and agitated until it is supplied into the tunnel.

[0115] Solution A is produced through the following process. First, in the first step, clay mineral and wood charcoal are mixed to obtain a first composition of powdery auxiliary material. The auxiliary material for the first composition may be produced by mixing clay minerals and wood charcoal at the backfill injection plant at the shield construction site, or it may be produced in advance by mixing clay minerals and wood charcoal at another factory or the like and then transported.

[0116] The first composition is sent to the premix auxiliary material silo 2 by a conveying device (not shown).

[0117] Next, in the second step, blending water for mixing auxiliary materials is added to the first composition fed from the premix auxiliary material silo 2 to the auxiliary material mixer 3, and the mixture is mixed in the auxiliary material mixer 3 to obtain a second composition, which is a liquid composition. The second composition is introduced into the auxiliary material dissolving tank 4 .

[0118] Next, in the third step, the second composition supplied from the auxiliary material dissolving tank 4, the hardener charged from the hardener silo, the stabilizer, and the blending water for kneading the liquid A are mixed in the mortar mixer 6 to produce the liquid A.

[0119] The produced liquid A is sent to the liquid A agitator 7, where it is stirred while waiting, and then sent further into the tunnel, where it is mixed with liquid B just before being injected into the gap between the natural ground and the segments, to become the backfill material.

[0120] In another embodiment, performance evaluation was also carried out on a sample using rice husk charcoal as biochar in the same manner as for wood charcoal.

[0121] Table 14 shows the formulation of an example in which clay mineral and powdered rice husk charcoal (weight moisture content 30.6%) were mixed in advance (premix auxiliary). The formulations were changed (Examples 11 and 12) from the standard formulation shown in Table 8. In the examples, the premix auxiliary, mixing water, and stabilizer were kneaded with the hardener to create Liquid A, which was then mixed with Liquid B.

[0122] [Table 14]

[0123] The performance evaluation of the examples is shown in Table 15.

[0124] [Table 15]

[0125] As is clear from Table 15, rice husk charcoal also meets the target performance.

[0126] Table 16 shows a comparison of the carbon dioxide emissions of the backfill injection materials (liquid A and liquid B) in the above-mentioned rice husk charcoal examples (Examples 11 and 12) and the standard formulation of backfill injection material for shield construction (Table 8).

[0127] [Table 16]

[0128] The carbon dioxide emissions in Examples 11 and 12 were lower than in General Example 1, and although not as high as when wood charcoal was used, it was clear that the use of rice husk charcoal also had the effect of suppressing carbon dioxide emissions.

[0129] As a further embodiment, conditions for using rice husk charcoal as biochar were investigated, and performance evaluation was carried out in the same manner as for wood charcoal. Note that explanations of the same parts as in the previous embodiment may be omitted, and the following mainly describes the differences.

[0130] The rice husk charcoal used was in powder form. The particle size distribution (weight) of the powdered rice husk charcoal was approximately 20% below 425 μm, approximately 30% between 425 and 700 μm, approximately 20% between 700 μm and 1 mm, and approximately 30% above 1 mm.

[0131] To confirm the kneadability and handling of rice husk charcoal, the true specific gravity was 1.46 and the actual measured bulk specific gravity was 0.114 g / cm 3 The kneading ability was evaluated when kneading water was added to dried rice husk charcoal with a measured moisture content of 30.6% by weight. The test and evaluation methods were the same as those for wood charcoal.

[0132] Table 17 shows the relationship between the dissolved concentration and viscosity of dried rice husk charcoal.

[0133] [Table 17]

[0134] The results in Table 17 show that increasing the amount of dried rice husk charcoal used does not impart viscosity, and that, perhaps because the particle size of dried rice husk charcoal is large, increasing the amount of dried rice husk charcoal results in more floating matter, and it takes time for the solution to become hydrophilic. In addition, rice husk charcoal alone was difficult to dissolve because it separated from the mixing water and settled out.

[0135] Next, rice husk charcoal and auxiliary material were mixed in advance and added to liquid A, and the formulation of a premixed material (premix auxiliary material) made by premixing clay minerals and powdered rice husk charcoal (weight moisture content 30.6%) was investigated, resulting in the composition shown in Table 18.

[0136] When considering the formulation, it was decided to increase the amount of rice husk charcoal in order to further enhance the effect of suppressing carbon dioxide emissions (for example, to the same extent as in the case of wood charcoal mentioned above). Increasing the amount of rice husk charcoal has the advantage that the viscosity does not increase as much due to the rice husk charcoal's larger particle size compared to wood charcoal, but it was necessary to reduce the amount of bentonite to compensate for the increase in the amount of rice husk charcoal, and reducing the amount of bentonite resulted in significantly different properties. Specifically, the viscosity of Liquid A decreased, compromising its stability and reducing its strength. For this reason, a formulation was considered that took into account the stability and strength of Liquid A by increasing the amount of hardener and increasing the overall powder amount.

[0137] In the example, the hardener is mixed with a premixing aid, blending water, and a stabilizer to prepare liquid A, which is then mixed with liquid B.

[0138] [Table 18]

[0139] In order to prepare the premix auxiliary materials (bentonite and rice husk charcoal) as an aqueous solution in advance and knead them with the hardening agent, the water (400 L) used for kneading the auxiliary materials is subtracted from the blending water before kneading. Examples 21 to 23 were prepared using different stabilizer blends of 3 kg, 5 kg, and 10 kg.

[0140] The performance of Examples 21 to 23 was evaluated in the same way as that of wood charcoal, by evaluating the flow value immediately after production of Liquid A and the bleeding value after one hour as evaluations as Liquid A, and by evaluating the gel time after adding Liquid B to Liquid A as evaluations as backfill injection material, and the uniaxial compressive strength of the backfill injection material after 28 days. As with wood charcoal, the target performance of Liquid A is a flow value of 400±100 mm, a bleeding value of 5% or less, and a gel time of 20 seconds or less. The unconfined compressive strength is 2N / mm 2 It is desirable that it is at least that level.

[0141] The performance evaluations of Examples 21 to 23 are shown in Table 19.

[0142] [Table 19]

[0143] As is clear from Table 19, the premix of bentonite and rice husk charcoal achieved the target in all evaluated performances.

[0144] Blast furnace cement has a pH of 12 to 13, while bentonite and rice husk charcoal both have a pH of around 10, so it is thought that a premix of bentonite and rice husk charcoal is easier to maintain stable properties.

[0145] Table 20 shows a comparison of the carbon dioxide emissions from the backfilling injection materials (liquid A and liquid B) in Examples 21 to 23 described above.

[0146] [Table 20]

[0147] It can be seen that all of Examples 21 to 23 have a carbon dioxide absorption effect with respect to the amount of carbon dioxide emitted.

[0148] Next, we investigated the aggregation of clay minerals and rice husk charcoal over time after premixing (premixing aid).

[0149] A premix auxiliary material was prepared as Example 24 according to the formulation shown in Table 21.

[0150] [Table 21]

[0151] In Example 24, the blending ratio of bentonite and rice husk charcoal per ton was determined based on the blending ratio of Examples 21 to 23 (20 kg:130 kg (bone dry content 90 kg+moisture 40 L)).

[0152] The test and evaluation methods (residual mass and residual rate) shall be the same as those for wood charcoal, and the target control value for residual rate shall be 5% or less.

[0153] The residual mass and residual rate from immediately after mixing until 56 days later are shown in Table 22. The number of days elapsed was set to 56 days (8 weeks, approximately 2 months) at the longest, from the viewpoint of storage stability as a premix material.

[0154] [Table 22]

[0155] As shown in Table 22, in Example 24, in which bentonite and rice husk charcoal were mixed, the target residual rate of 5% was met even after 56 days.

[0156] Next, the performance of the premix auxiliary solution was evaluated in terms of flow value while changing the absolute dry weight ratio of rice husk charcoal to bentonite.

[0157] The flow value was measured by placing a cylinder with an inner diameter of 80 mm and a height of 80 mm on a horizontal acrylic plate, filling it with the premix auxiliary solution, and then gently lifting the cylinder and measuring the diameter of the premix auxiliary solution.From the perspective of handling, such as pumpability within the plant and kneadability of Liquid A, the target control value for the flow value of the premix auxiliary solution was set at 600±100 mm.

[0158] The formulation of the premix auxiliary solution and the results of flow value measurements are shown in Table 23.

[0159] [Table 23]

[0160] As is clear from Table 23, if the blending ratio of rice husk charcoal to bentonite is 0.6 or more and 5.0 or less in absolute dry weight (the absolute dry weight ratio of bentonite to rice husk charcoal is 1:0.6 to 1:5.0), the target control value of flow value is within the range of 600±100 mm, and it can be seen that it is desirable for the blending ratio of rice husk charcoal to bentonite to be 0.6 or more and 5.0 or less in absolute dry weight.

[0161] As with wood charcoal, rice husk charcoal used as a premix auxiliary material has the risk of catching fire depending on storage conditions if its moisture content by weight falls below 10%. Also, if its moisture content by weight falls below 10%, it is prone to scattering large amounts of dust.

[0162] Furthermore, when transporting premixed powder materials, if the particle size increases due to agglomeration or the like, there is a risk that the material may clog and block the pressure transport pipe. In a manufacturing plant for backfill injection materials, when a conveying device with a screw inside a casing is used to transport premixed powder materials, the clearance between the inner diameter of the casing and the outer diameter of the screw is approximately 5 mm, so it can be said that particles with a diameter of less than 5 mm can be pumped.

[0163] Therefore, we investigated the aggregate formation over time after premixing by varying the weight moisture content of the rice husk charcoal, which was a mixture of clay minerals and rice husk charcoal (premix aid). Water was added to rice husk charcoal with a weight moisture content of 30.6% to adjust the moisture content to 35-90%, and samples with different weight moisture contents were created as shown in Table 24, which were then mixed with bentonite as a clay mineral to prepare the samples.

[0164] [Table 24]

[0165] The test method and the method for calculating the residual rate are the same as those for wood charcoal. As with wood charcoal, the target control value for the residual rate is set at 5% or less.

[0166] The residual mass and residual rate from immediately after mixing until 56 days later are shown in Table 25. The number of days elapsed was set to 56 days (8 weeks, approximately 2 months) at the longest, from the viewpoint of storage stability as a premix material.

[0167] [Table 25]

[0168] At a weight moisture content of 80%, all samples exceeded the target control value, and at a weight moisture content of 90%, all samples had liquefied.

[0169] As is clear from Table 25, the higher the weight moisture content of rice husk charcoal, the faster it tends to form aggregates. When the moisture content of rice husk charcoal by weight was 70.0% or more, the target control value was exceeded immediately after mixing with bentonite, and when it was 65.0%, it exceeded the target control value after 28 days.

[0170] If the weight moisture content of rice husk charcoal is 62.5%, it will exceed the target control value after 56 days, so if the weight moisture content of rice husk charcoal is 62%, the storage period can be set at 28 days.

[0171] It was found that if the weight moisture content of rice husk charcoal was 60.0% or less, the target control value of 5% was met even after 56 days. When the moisture content of rice husk charcoal by weight is 60%, it falls below the target control value after 56 days. Therefore, if the moisture content of rice husk charcoal by weight is 60%, the storage period can be set at 56 days, and an even longer storage period can be expected.

[0172] From these results, it is desirable that the moisture content of rice husk charcoal by weight be 62% or less when the storage period for premixed materials is set to 28 days. Also, it is desirable that the moisture content of rice husk charcoal by weight be 60% or less when the storage period for premixed materials is set to 56 days.

[0173] Furthermore, considering the risk of fire and the possibility of dust scattering mentioned above, it is desirable that the rice husk charcoal used as a premix auxiliary material has a weight moisture content of 10% to 62% (if the storage period is set to 28 days) or 10% to 60% (if the storage period is set to 56 days).

[0174] [Other Modifications] The present invention is not limited to the above-described embodiment, and may also include the following, for example.

[0175] In the embodiment of the present application, the auxiliary material is formed by mixing bentonite and biochar, but other clay minerals can also be used instead of bentonite.

[0176] In the embodiment of the present application, blast furnace cement type B is used as the hardening agent, but other cement-based materials may also be used.

[0177] The technical matters in the embodiments including the modified examples may be combined and applied to other embodiments to form examples.

[0178] [Extractable inventions] Examples of inventions extracted from this specification include the following.

[0179] (1) This is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized by containing clay minerals and biochar.

[0180] (2) The backfill injection A liquid auxiliary material according to (1), characterized in that the blending ratio of the biochar to the clay mineral is 5 or less in absolute dry weight ratio.

[0181] (3) The backfill injection A liquid auxiliary material according to (1), characterized in that the blending ratio of the biochar to the clay mineral is 0.6 to 5 in terms of absolute dry weight.

[0182] (4) The backfill injection A liquid auxiliary material according to any one of (1) 1 to (3), characterized in that the biochar has a weight moisture content of 62% or less.

[0183] (5) The backfill injection A liquid auxiliary material according to any one of (1) to (3), characterized in that the biochar has a weight moisture content of 60% or less.

[0184] (6) The backfill injection A liquid auxiliary material according to any one of (1) to (3), characterized in that the biochar has a weight moisture content of 10% or more and 62% or less.

[0185] (7) A method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, comprising: a first step of mixing a clay mineral and biochar to obtain a first composition of powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0186] (8) The method for producing liquid A described in (7) is characterized in that the blending ratio of the biochar to the clay mineral is 5 or less in terms of absolute dry weight.

[0187] (9) The method for producing liquid A described in (7) is characterized in that the blending ratio of the biochar to the clay mineral is 0.6 or more and 5 or less by weight on an absolute dry basis.

[0188] (10) The method for producing liquid A according to any one of (7) to (9), characterized in that the biochar has a weight moisture content of 62% or less.

[0189] (11) The method for producing liquid A according to any one of (7) to (9), wherein the biochar has a weight moisture content of 60% or less.

[0190] (12) The method for producing liquid A according to any one of (7) to (9), wherein the biochar has a weight moisture content of 10% or more and 62% or less.

[0191] (13) This is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized by containing clay minerals and wood charcoal as biochar.

[0192] (14) The backfilling injection A liquid auxiliary material according to (13), characterized in that the blending ratio of the wood charcoal to the clay mineral is 2.8 or less in absolute dry weight ratio.

[0193] (15) The backfilling injection A liquid auxiliary material according to (13), characterized in that the blending ratio of the wood charcoal to the clay mineral is 0.9 to 2.8 in terms of absolute dry weight ratio.

[0194] (16) The auxiliary material for backfilling injection A liquid according to any one of (13) to (15), characterized in that the wood charcoal has a weight moisture content of 44% or less.

[0195] (17) The auxiliary material for backfilling injection A liquid according to any one of (13) to (15), characterized in that the wood charcoal has a weight moisture content of 41% or less.

[0196] (18) The auxiliary material for backfilling injection A liquid according to any one of (13) to (15), characterized in that the wood charcoal has a weight moisture content of 10% or more and 44% or less.

[0197] (19) A method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, comprising: a first step of mixing a clay mineral with wood charcoal as biochar to obtain a first composition of powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0198] (20) The method for producing Solution A according to (19), wherein the blending ratio of the wood charcoal to the clay mineral is 2.8 or less in terms of absolute dry weight.

[0199] (twenty one) The method for producing Solution A according to (19), wherein the blending ratio of the wood charcoal to the clay mineral is 0.9 or more and 2.8 or less by weight on an absolute dry basis.

[0200] (twenty two) The method for producing Solution A according to any one of (19) to (21), wherein the wood charcoal has a weight moisture content of 44% or less.

[0201] (twenty three) The method for producing Solution A according to any one of (19) to (21), wherein the wood charcoal has a weight moisture content of 41% or less.

[0202] (twenty four) The method for producing Solution A according to any one of claims (19) to (21), wherein the wood charcoal has a weight moisture content of 10% or more and 44% or less.

[0203] (twenty five) This is an auxiliary material for backfilling injection liquid A that is mixed with liquid B to form a backfilling injection material and is blended with liquid A that contains a hardener and a stabilizer, and is characterized by containing clay minerals and rice husk charcoal as biochar.

[0204] (26) The backfill injection A liquid auxiliary material according to (25), characterized in that the rice husk charcoal is blended in an absolute dry weight ratio of 5 or less to the clay mineral.

[0205] (27) The backfill injection A liquid auxiliary material according to (25), characterized in that the rice husk charcoal is blended in an absolute dry weight ratio of 0.6 to 5 with respect to the clay mineral.

[0206] (28) The backfill injection A liquid auxiliary material according to any one of (25) to (27), characterized in that the rice husk charcoal has a weight moisture content of 62% or less.

[0207] (29) The backfill injection A liquid auxiliary material according to any one of (25) to (27), characterized in that the rice husk charcoal has a weight moisture content of 60% or less.

[0208] (30) The backfill injection A liquid auxiliary material according to any one of (25) to (27), characterized in that the rice husk charcoal has a weight moisture content of 10% or more and 62% or less.

[0209] (31) A method for producing liquid A, which is mixed with liquid B to form a backfill injection material and contains a hardener and a stabilizer, comprising: a first step of mixing clay minerals with rice husk charcoal as biochar to obtain a first composition of powdered auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition, which is a liquid composition; and a third step of mixing the second composition obtained in the second step with the hardener and the stabilizer.

[0210] (32) The method for producing liquid A according to (31), characterized in that the rice husk charcoal is blended in an absolute dry weight ratio of 5 or less to the clay mineral.

[0211] (33) The method for producing liquid A according to (31), wherein the rice husk charcoal is blended in an absolute dry weight ratio of 0.6 to 5 with respect to the clay mineral.

[0212] (34) The method for producing liquid A according to any one of (31) to (33), wherein the rice husk charcoal has a weight moisture content of 62% or less.

[0213] (35) The method for producing liquid A according to any one of (31) to (33), wherein the rice husk charcoal has a weight moisture content of 60% or less.

[0214] (36) The method for producing liquid A according to any one of (31) to (33), wherein the rice husk charcoal has a weight moisture content of 10% or more and 62% or less. [Explanation of symbols]

[0215] 1 A liquid manufacturing equipment 2 Premix auxiliary material silo 3 Auxiliary material mixer 4 Auxiliary material dissolving tank 5 Hardening material silo 6 Mortar Mixer 7 Liquid A agitator

Claims

1. A backfill injection auxiliary material for backfill injection A liquid that is mixed with B liquid to form a backfill injection material and is blended with A liquid containing a hardener and a stabilizer, An auxiliary material for backfill injection A liquid, characterized by containing clay minerals and biochar.

2. A backfill injection auxiliary material for backfill injection A liquid that is mixed with B liquid to form a backfill injection material and is blended with A liquid containing a hardener and a stabilizer, An auxiliary material for backfill injection A liquid, characterized by containing clay minerals and wood charcoal as biochar.

3. A backfill injection auxiliary material for backfill injection A liquid that is mixed with B liquid to form a backfill injection material and is blended with A liquid containing a hardener and a stabilizer, An auxiliary material for backfill injection A liquid, characterized by containing clay minerals and rice husk charcoal as biochar.

4. The backfill injection A liquid auxiliary material according to any one of claims 1 to 3, characterized in that the blending ratio of the biochar to the clay mineral is 5 or less in terms of absolute dry weight ratio.

5. The backfill injection A liquid auxiliary material according to any one of claims 1 to 3, characterized in that the blending ratio of the biochar to the clay mineral is 0.6 to 5 in terms of absolute dry weight ratio.

6. The backfill injection A liquid auxiliary material according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 62% or less.

7. The backfill injection A liquid auxiliary material according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 60% or less.

8. The backfill injection A liquid auxiliary material according to any one of claims 1 to 3, characterized in that the biochar has a weight moisture content of 10% or more and 62% or less.

9. A method for producing a liquid A that is mixed with a liquid B to form a backfill injection material and contains a hardener and a stabilizer, A first step of mixing a clay mineral and biochar to obtain a first composition of a powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition which is a liquid composition; a third step of mixing the second composition obtained in the second step with the curing agent and the stabilizer. A method for producing solution A,

10. A method for producing a liquid A that is mixed with a liquid B to form a backfill injection material and contains a hardener and a stabilizer, A first step of mixing a clay mineral with wood charcoal as biochar to obtain a first composition of a powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition which is a liquid composition; a third step of mixing the second composition obtained in the second step with the curing agent and the stabilizer. A method for producing solution A,

11. A method for producing a liquid A that is mixed with a liquid B to form a backfill injection material and contains a hardener and a stabilizer, A first step of mixing a clay mineral with rice husk charcoal as biochar to obtain a first composition of a powdery auxiliary material; a second step of adding water to the first composition obtained in the first step to obtain a second composition which is a liquid composition; a third step of mixing the second composition obtained in the second step with the curing agent and the stabilizer. A method for producing solution A,

12. 12. The method for producing liquid A according to claim 9, wherein the biochar is blended in an amount of 5 or less by weight relative to the clay mineral in terms of absolute dry weight.

13. 12. The method for producing liquid A according to claim 9, wherein the biochar is blended in an amount of 0.6 or more and 5 or less by weight relative to the clay mineral in an absolute dry weight ratio.

14. The method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 62% or less.

15. The method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 60% or less.

16. The method for producing liquid A according to any one of claims 9 to 11, characterized in that the biochar has a weight moisture content of 10% or more and 62% or less.

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