Overly wet soil composite improvement material and overly wet soil dewatering and consolidation method

Abstract

The application discloses a kind of over-wet soil composite improvement material and over-wet soil precipitation consolidation method, it is related to soil remediation improvement and solid waste treatment technical field.Over-wet soil composite improvement material includes solid waste base improvement material and microbial improvement material;According to mass fraction, solid waste base improvement material includes ceramic powder 35~40 parts, red mud 20~30 parts, flue gas desulfurization reducing agent residue 10~15 parts and magnesium base paper fiber waste 20~25 parts;Microbial improvement material includes pasteur bacillus liquid culture.The over-wet soil composite improvement material of the application makes full use of solid waste, can realize over-wet soil rapid precipitation, and enhances soil compactness and compressive strength.

Description

Technical Field

[0001] This invention relates to the fields of soil remediation and solid waste treatment, and in particular to a composite amendment for excessively wet soil and a method for consolidating excessively wet soil after precipitation. Background Technology

[0002] In road engineering, the raw soil required for foundation treatment and subgrade filling is generally taken from the in-situ soil surrounding the project site. Due to groundwater soaking or rainfall, this soil typically has a high moisture content, often remaining excessively wet or even saturated. This is particularly true in southern my country, where the rainy season is long and rainfall is heavy, coupled with a high groundwater level, resulting in soil that is frequently excessively wet or even near saturation. Directly using excessively wet soil as foundation soil or subgrade filling material can easily lead to problems such as roadbed softening, subgrade slope collapse, backfill settlement of structures, and seepage across the foundation, causing engineering losses. Therefore, before foundation construction and subgrade filling, excessively wet soil needs to be dewatered to ensure it meets construction requirements.

[0003] To effectively reduce the moisture content of excessively wet soil, traditional methods typically involve natural sun-drying or mixing with lime (cement, lime). However, natural sun-drying is limited by weather conditions, inefficient, and time-consuming, especially in humid and rainy areas where insufficient sunlight makes it difficult to effectively reduce the moisture content of excessively wet soil. While mixing with lime can reduce water content to some extent, the effect is still poor, particularly when treating near-saturated soil. The high moisture content of the mixture and the damaged capillary pores of soil particles hinder water penetration and dissipation, resulting in minimal treatment benefits. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a composite amendment for excessively wet soil, which can achieve rapid water reduction in excessively wet soil and enhance soil density and compressive strength.

[0005] The technical problem to be solved by the present invention is to provide a method for consolidating excessively wet soil after dewatering. By using the above-mentioned composite amendment for excessively wet soil, rapid dewatering of excessively wet soil can be achieved, and the soil density and compressive strength can be enhanced.

[0006] To address the aforementioned technical problems, this invention provides a composite amendment for overly wet soil, comprising a solid waste-based amendment and a microbial amendment. According to the mass fractions, the solid waste-based modified material includes 35-40 parts of ceramic powder, 20-30 parts of red mud, 10-15 parts of flue gas denitrification reducing agent residue, and 20-25 parts of magnesium-based paper fiber waste. The microbial improver includes Bacillus pasteurellium culture medium.

[0007] As an improvement to the above technical solution, the ceramic powder comprises the following chemical components by mass percentage: CaO 1%~5%, SiO2 72%~85%, Al2O3 12%~21%, Fe2O3 1%~3%, Na2O 1%~3%, MgO 1%~5%, and LOI 2%~5%.

[0008] As an improvement to the above technical solution, the red mud, by mass percentage, comprises the following chemical components: CaO 45%~50%, SiO2 25%~35%, Al2O 35%~10%, Fe2O 35%~7wt%, Na2O 1%~3wt%, MgO 1%~5wt%, and LOI 1%~5wt%.

[0009] As an improvement to the above technical solution, the flue gas denitrification reducing agent residue, by mass percentage, includes the following elements: Ca 18%~25%, O 25%~35%, N 45%~55%, H 5%~10wt%, Ti 1%~2wt%, Cu 1%~2wt%, Al 1%~3wt%.

[0010] As an improvement to the above technical solution, the magnesium-based paper fiber waste includes the following chemical components by mass percentage: CaO 1%~5%, SiO2 10%~15%, Al2O3 1%~3%, Fe2O3 1%~3wt%, MgO 50%~60wt%, SO3 5%~10%, LOI 20%~25wt%.

[0011] As an improvement to the above technical solution, the bacterial concentration OD of the *Bacillus pasteurellium* bacterial solution is... 600 The value is 1.5~2.0.

[0012] As an improvement to the above technical solution, the urease activity in the Bacillus pasteurellium culture is ≥6mM / min.

[0013] The activation steps of the Bacillus pasteurellii are as follows: (1) Preparation of culture medium: Prepare solid culture medium with 25-30 g / L agar, 28-30 g / L yeast extract, 10-15 g / L peptone, 5-7 g / L urea and 8-12 g / L ammonium sulfate. Adjust the pH of the culture medium to 7.3-7.5 and sterilize it. Dispense the culture medium into conical flasks, seal them with sealing film and wrap them with newspaper for later use; (2) Sterilization treatment: Add an appropriate amount of deionized water to the sterilizer, put in the wrapped conical flasks and experimental equipment, and set the sterilization conditions to 121°C for 30 minutes; (3) Treatment of bacteria: Wipe the outer wall of the ampoule containing Bacillus pasteurellii bacteria with 75% alcohol in the ultra-clean workbench, and break it after scratching the tube with a grinding wheel. Before operation, glass shards must be removed and the solution disinfected; (4) Preparation of bacterial suspension: Add 0.5 mL of cooled and sterilized deionized water to the ampoule, mix the lyophilized powder thoroughly to form a uniform suspension; (5) Inoculation: Take 0.2 mL of bacterial suspension and spread it evenly on the surface of the solid culture medium. Repeat the operation to prepare two culture dishes; (6) Incubation: Place the inoculated culture dishes in a 30°C biochemical incubator and incubate for 36 hours until colonies form; (7) Preservation: After the sterilized material has cooled, take 1 mL of 10% glycerol solution and 1 mL of bacterial solution into a cryovial. When taking the bacterial solution, shake the conical flask while operating to ensure that the bacterial solution concentration is uniform. Before freezing at 80°C, shake the cryovials repeatedly to ensure the mixture is thoroughly mixed. Cryopreservation can typically preserve the microbial culture for 1-2 years. Before each use, remove the cryovials from the freezer and thaw them in a water bath to prevent thawing at room temperature.

[0014] As an improvement to the above technical solution, the particle size of the ceramic powder is ≤75μm; The particle size of the red mud is ≤100μm; The particle size of the flue gas denitrification reducing agent residue is ≤100μm; The particle size of the magnesium-based paper fiber waste is ≤100μm.

[0015] Accordingly, the present invention also provides a method for consolidating excessively wet soil after precipitation, using the above-mentioned excessively wet soil composite amendment, comprising the following steps: (1) Add the solid waste-based amendment to the wet soil to be treated and mix evenly to obtain the first mixed soil; (2) Add the microbial amendment to the first mixed soil and stir evenly to obtain the second mixed soil. Wait for the moisture content of the second mixed soil to decrease. When the moisture content of the second mixed soil decreases to the preset moisture content, the dewatering treatment of the overly wet soil can be completed and the amended soil can be collected.

[0016] As an improvement to the above technical solution, in step (1), the amount of solid waste-based amendment is 5% to 25% of the mass of the wet soil to be treated; In step (2), the amount of microbial amendment added is 0.5 kg to 3 kg per cubic meter of wet soil to be treated.

[0017] Implementing this invention has the following beneficial effects: 1. Through the synergistic effect of solid waste-based amendments and microbial amendments, not only can rapid dewatering of excessively wet soil be achieved, but soil density and compressive strength can also be significantly enhanced without the need for high-cost materials such as cement and lime. Specifically, the red mud in the solid waste-based amendment, when mixed with excessively wet soil, consumes the moisture in the soil while increasing the pH value of the reaction system. The active SiO2 and Al2O3 within the ceramic powder and magnesium-based paper fiber waste dissolve in an alkaline environment, consuming water to generate cementing products such as hydrated calcium silicate and hydrated calcium aluminosilicate, establishing a network structure, initially cementing soil particles, and forming a skeletal structure. The MgO in the magnesium-based paper fiber waste reacts with free water in the excessively wet soil under alkaline conditions to generate magnesium hydroxide, which has an expansive effect, increasing soil density. Furthermore, the fibers in the magnesium-based paper fiber waste can form bridges with the soil, resisting the generation and development of cracks and improving the toughness of the amended soil. Urea in the flue gas denitrification reducing agent residue can react with calcium ions to produce soluble double salts, regulate the crystallization rate of hydration products, improve the early strength of improved soil, and provide a growth environment for Bacillus pasteurellii, ultimately hydrolyzing into NH4+. 3+ and HCO 3- At the same time, OH is generated - This increases the pH value of the reaction system and combines with calcium ions formed by the hydration of red mud to generate calcium carbonate, which fills the capillary structure.

[0018] 3. Bacillus pasteurellii possesses a urea-hydrolyzing mechanism, capable of converting dissolved heavy metal ions in red mud into insoluble minerals, consuming internal moisture in overly wet soil, and simultaneously increasing the pH value of the reaction system. Furthermore, the negatively charged microbial cells adsorb and accumulate calcium ions on their cell walls, reacting with carbonate ions to form calcium carbonate crystal precipitates, thus increasing soil strength.

[0019] 2. The raw materials of the solid waste-based amendment include ceramic powder, red mud, flue gas denitrification reducing agent residue, and magnesium-based paper fiber waste. It makes full use of solid waste, alleviates the problem of solid waste accumulation and disposal to a certain extent, improves the utilization rate of solid waste, and has good economic and environmental benefits. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below. This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this invention.

[0021] Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0022] This embodiment provides a composite amendment for overly wet soil, including a solid waste-based amendment and a microbial amendment; According to the mass fractions, the solid waste-based modified material includes 35-40 parts of ceramic powder, 20-30 parts of red mud, 10-15 parts of flue gas denitrification reducing agent residue, and 20-25 parts of magnesium-based paper fiber waste. The microbial improver includes Bacillus pasteurellium culture medium.

[0023] It is worth noting that the raw materials of the solid waste-based soil amendment in this embodiment include ceramic powder, red mud, flue gas denitrification reducing agent residue, and magnesium-based paper fiber waste. This fully utilizes solid waste, alleviating the problems of solid waste accumulation and disposal to a certain extent, improving the utilization rate of solid waste, and demonstrating good economic and environmental benefits. When the red mud in the solid waste-based soil amendment is mixed with excessively wet soil, the calcium oxide in the red mud reacts with the water in the excessively wet soil to generate calcium hydroxide, consuming water and increasing the pH value of the reaction system. The active SiO2 and Al2O3 inside the ceramic powder and magnesium-based paper fiber waste dissolve in an alkaline environment, consuming water to generate hydrated calcium silicate, hydrated calcium aluminosilicate, and other cementing products, establishing a network structure, initially cementing soil particles, and forming a skeletal structure. The MgO in the magnesium-based paper fiber waste reacts with free water in the excessively wet soil under alkaline conditions to generate magnesium hydroxide, which has an expansion effect and improves soil compaction. Furthermore, the fibers in the magnesium-based paper fiber waste can also form bridges with the soil, resisting the generation and development of cracks and improving the toughness of the amended soil. The urea in the flue gas denitrification reducing agent residue can react with calcium ions to produce soluble double salts, regulate the crystallization rate of hydration products, and improve the early strength of improved soil. It can also provide a growth environment for Bacillus pasteurellii, and ultimately hydrolyze into NH4+. 3+ and HCO 3- At the same time, OH is generated - This process increases the pH of the reaction system and combines with calcium ions formed during the hydration of red mud to generate calcium carbonate, filling the capillary structure. *Bacillus pasteurellii* possesses a urea-hydrolyzing mechanism, capable of converting dissolved heavy metal ions in red mud into insoluble minerals, consuming internal moisture in overly wet soil, and simultaneously increasing the pH of the reaction system. Furthermore, negatively charged microbial cells adsorb and accumulate calcium ions on their cell walls, reacting with carbonate ions to form calcium carbonate crystal precipitates, thus increasing soil strength.

[0024] It is worth noting that red mud is an industrial solid waste discharged during the extraction of alumina in aluminum profile production. This embodiment uses red mud as an alkali activator. Red mud has a porous structure, high specific surface area, high water absorption rate, and high water retention capacity. Simultaneously, red mud can consume water in overly wet soil to generate calcium hydroxide, providing an alkaline environment for the reaction system. This embodiment uses red mud as an alkali activator, which, while providing an alkaline environment, also consumes water, thus reducing the water content of the overly wet soil. Compared to conventional alkali activators such as sodium silicate, although sodium silicate can provide higher strength to the reaction system, it forms silica-rich gel during hydration. This silica-rich gel, with its high water content, undergoes significant shrinkage after dehydration. Furthermore, it does not consume water in the system when mixed with overly wet soil, making it difficult to achieve efficient water reduction, and it also has disadvantages such as higher cost.

[0025] Specifically, red mud can be classified into sintering red mud, Bayer process red mud, and combined process red mud according to the production process. This embodiment preferably uses Bayer process red mud. The Bayer process is widely used in the alumina industry. Under high temperature and pressure, a certain concentration of sodium hydroxide is added to dissolve bauxite, yielding a sodium aluminate solution. The residue obtained after filtration is Bayer red mud. Because the chemical alkali bound to red mud is difficult to remove and has a high content, and also contains heavy metals and other impurities, the current disposal method for red mud is mainly seabed or land-based stockpiling, which easily causes soil alkalization and groundwater pollution. The main chemical component of red mud is calcium oxide. The calcium oxide in red mud can react with water in overly wet soil to generate calcium hydroxide, consuming water and simultaneously increasing the pH value of the system. This facilitates the reaction of active SiO2 and Al2O3 within the system to generate hydrated calcium silicate and hydrated calcium aluminosilicate, which have a cementing effect.

[0026] In one embodiment, the red mud comprises the following chemical components by mass percentage: CaO 45%~50%, SiO2 25%~35%, Al2O3 5%~10%, Fe2O3 5%~7wt%, Na2O 1%~3wt%, MgO 1%~5wt%, and LOI 1%~5wt%. It should be noted that the red mud also contains trace amounts of heavy metals, but since the heavy metal content is in the milligram range and constitutes a very small percentage, they are not shown in the above chemical composition of the red mud.

[0027] In one embodiment, the red mud has a particle size ≤100μm.

[0028] Further explanation: the ceramic powder is waste residue powder from sanitary or building ceramics, possessing high pozzolanic activity. The main components of the ceramic powder are SiO2 and Al2O3. The ceramic powder contains sufficient active substances to react with calcium hydroxide to produce hydrated calcium silicate, hydrated calcium aluminate, and other products, which cement soil particles and improve soil strength.

[0029] In one embodiment, the ceramic powder comprises the following chemical components by mass percentage: CaO 1%~5%, SiO2 75%~85%, Al2O3 12%~21%, Fe2O3 1%~3%, Na2O 1%~3%, MgO 1%~5%, and LOI 2%~5%.

[0030] In one embodiment, the particle size of the ceramic powder is ≤75μm. Preferably, the particle size of the ceramic powder is 20μm~30μm. The smaller particle size of the ceramic powder allows it to fill pores and improve soil density through physical filling.

[0031] To further explain, the flue gas denitrification reducing agent residue is used in the aluminum electrolysis stage of aluminum profile production. Selective catalytic reduction technology is employed, using urea as a reducing agent, to treat nitrogen oxides (NOx) in the exhaust gas emitted from the electrolysis workshop. The residue produced after the reaction mainly consists of unreacted urea and residual ammonium salts. The ammonium salts in the flue gas denitrification reducing agent residue generate ammonia in an alkaline environment, which combines with moisture in the overly wet soil to produce hydroxide ions, further increasing the pH of the reaction system. The urea in the residue acts as an early agent, regulating the crystallization rate of the hydration products and improving early-stage strength. Simultaneously, it provides a growth environment for Bacillus pasteurella, consuming system moisture, generating calcium carbonate, and filling the capillary structure.

[0032] In one embodiment, the flue gas denitrification reducing agent residue comprises the following elements by mass percentage: Ca 18%~25%, O 25%~35%, N 45%~55%, H 5%~10wt%, Ti 1%~3wt%, Cu 1%~3wt%, Al 1%~5wt%.

[0033] In one embodiment, the particle size of the flue gas denitrification reducing agent residue is ≤100μm.

[0034] To further explain, magnesium-based paper fiber waste is a waste product generated during the production and processing of magnesium compound cementitious materials (magnesium oxide, magnesium hydroxide) and special paper materials made from wood pulp and plant fibers. Its main components are MgO and residual plant fibers. MgO can be activated by calcium hydroxide produced during the hydration of red mud, undergoing a chemical reaction to generate magnesium hydroxide with expanding properties, which fills the pores inside the soil and improves the solidification strength. Furthermore, the large amount of plant fibers contained in magnesium-based paper fiber waste can improve the engineering properties of soil through physical reinforcement.

[0035] In one embodiment, the magnesium-based paper fiber waste comprises the following chemical components by mass percentage: CaO 1%~5%, SiO2 10%~15%, Al2O3 1%~3%, Fe2O3 1%~3wt%, MgO 50%~60wt%, SO3 5%~10%, and LOI 20%~25wt%. In one embodiment, the particle size of the magnesium-based paper fiber waste is ≤100μm, and the average particle size is 70μm~80μm.

[0036] Specifically, the preparation method of the solid waste-based improver in this embodiment is as follows: according to the mass parts, 35-40 parts of ceramic powder, 20-30 parts of red mud, 10-15 parts of flue gas denitrification reducing agent residue and 20-25 parts of magnesium-based paper fiber waste are mixed evenly to obtain the solid waste-based improver.

[0037] In one embodiment, the microbial improver comprises Bacillus pasteurellium culture medium.

[0038] *Pasteurella multocida* is a non-pathogenic Gram-positive bacterium isolated from soil. Belonging to the order Bacillus, it possesses strong survival capabilities and can continue to survive as spores even in the absence of nutrients. *Pasteurella multocida* produces urease, a nickel-containing metalloenzyme that specifically catalyzes the breaking of the amide bond in the urea (CO(NH2)2) molecule, initiating a hydrolysis reaction. Urease decomposes urea into carbonate and ammonium ions, which then react with calcium ions to form calcium carbonate crystals. Specifically, the urease produced by *Pasteurella multocida* can hydrolyze unreacted urea in flue gas denitrification reducing agent residue into carbamic acid and ammonia. On one hand, the generated ammonia reacts with water to produce ammonium and hydroxide ions, consuming the internal moisture of the overly wet soil and simultaneously increasing the pH of the reaction system. On the other hand, carbamic acid is extremely unstable in water and reacts rapidly with water to produce carbon dioxide and ammonia. Due to the high water content of excessively wet soil, ammonia dissolves in water to form ammonium ions, carbon dioxide reacts with water to form carbonic acid, and carbonic acid decomposes into water-soluble bicarbonate ions, releasing hydrogen ions. The bicarbonate ions react with hydrogen and hydroxide ions in the system to produce carbonate ions and water. With the addition of calcium ions produced during red mud hydration, negatively charged microbial cells adsorb and accumulate calcium ions on their cell walls, reacting with carbonate ions to form calcium carbonate crystal precipitates, thus increasing soil strength.

[0039] In one embodiment, the bacterial concentration OD of the Bacillus pasteurellium culture is... 600 The value is 1.5~2.0.

[0040] As an improvement to the above technical solution, the bacterial concentration OD of the *Bacillus pasteurellium* bacterial solution is... 600The value is 1.5~2.0. When the bacterial concentration is too low, insufficient urease is produced, resulting in insufficient carbonate ions. This leads to insufficient urea utilization in the flue gas denitrification reducing agent residue, ultimately resulting in insufficient calcium carbonate production and low soil strength. When the bacterial concentration is too high, a large amount of urease is usually produced. At this time, the urease decomposed by bacteria will accumulate in large quantities on the surface of the flue gas denitrification reducing agent residue. When the soil and amendment are not fully mixed, a large amount of carbonate ions are produced. After combining with urea, a large amount of calcium carbonate will accumulate in the flue gas denitrification reducing agent residue, hindering further chemical reactions between the flue gas denitrification reducing agent residue and other materials.

[0041] Specifically, the bacterial concentration test method for the *Bacillus pasteurellii* bacterial suspension is the turbidimetric method. A model 752N spectrophotometer is used, and the measurement is performed at a wavelength of 600 nm. The spectrophotometer is preheated for 30 minutes. The wavelength is adjusted to 600 nm for calibration. The bacterial suspension and deionized water are mixed evenly at a ratio of 1:9 and then poured into a cuvette to 2 / 3 full. The outside of the cuvette is wiped with lens paper. The cuvette is then placed in the spectrophotometer for measurement and reading. The measured absorbance OD is... 600 The value needs to be multiplied by the dilution factor.

[0042] In one embodiment, the urease activity in the Bacillus pasteurellium culture is ≥6 mM / min.

[0043] Specifically, the urease activity in the *Bacillus pasteurellii* bacterial culture can be tested using the conductivity method: Under room temperature conditions, 2 mL of the test solution is pipetted into 18 mL of a 1.11 mol / L urea solution and mixed with the mixture while observing the conductivity value. The start time is recorded when the value stops fluctuating and rises steadily. After 5 minutes, the final value is recorded. The difference between the final and initial values ​​represents the change in conductivity in the mixture. The urease activity in the *Bacillus pasteurellii* bacterial culture is expressed as the average amount of urea hydrolyzed per minute.

[0044] Accordingly, the present invention also provides a method for consolidating excessively wet soil after precipitation, using the above-mentioned excessively wet soil composite amendment, comprising the following steps: (1) Add the solid waste-based amendment to the wet soil to be treated and mix evenly to obtain the first mixed soil; (2) Add the microbial amendment to the first mixed soil and stir evenly to obtain the second mixed soil. Wait for the moisture content of the second mixed soil to decrease. When the moisture content of the second mixed soil decreases to the preset moisture content, the dewatering treatment of the overly wet soil can be completed and the amended soil can be collected.

[0045] The method for dewatering and consolidating excessively wet soil in this embodiment uses MICP combined with solid waste-based amendments to treat the excessively wet soil. It makes full use of solid waste, enables rapid dewatering of excessively wet soil, and can enhance soil density and compressive strength without adding cement and lime, thereby reducing the cost of treating excessively wet soil.

[0046] In one embodiment, in step (1), the amount of solid waste-based amendment is 5% to 25% of the mass of the wet soil to be treated, for example 5%, 10%, 12%, 15%, 18%, 20%, 22% or 25%, but not limited thereto.

[0047] In one embodiment, in step (2), the amount of microbial amendment added is 0.5 kg to 3 kg per cubic meter of wet soil to be treated, for example 0.5 kg, 0.8 kg, 1.0 kg, 1.2 kg, 1.5 kg, 1.8 kg, 2 kg, 2.5 kg or 3 kg, but not limited thereto.

[0048] The technical solution of the present invention will be further described below through embodiments and comparative examples.

[0049] Example 1 This embodiment provides a composite amendment for overly wet soil, including a solid waste-based amendment and a microbial amendment; Based on mass percentages, the solid waste-based amendment comprises 40 parts ceramic powder, 25 parts red mud, 15 parts flue gas denitrification reducing agent residue, and 20 parts magnesium-based paper fiber waste. Specifically, the chemical composition of the ceramic powder in this embodiment, calculated by mass percentage, is: CaO 1.79wt%, SiO2 74.49wt%, Al2O3 12.61wt%, Fe2O3 2.12wt%, Na2O 2.85wt%, MgO 3.47wt%, LOI 2.67wt%; the chemical composition of the red mud is: CaO 48.34wt%, SiO2 32.44wt%, Al2O3 7.89wt%, Fe2O3 6.18wt%, Na2O 1.47wt%, MgO 2.45wt%, LOI 1.23wt%; and the chemical elements of the flue gas denitrification reducing agent residue are: Ca 19.57wt%, O 25.28wt%, N 46.27wt%, H... 5.31wt%, Ti 1.10wt%, Cu 1.29wt%, Al 1.18wt%; The chemical composition of magnesium-based paper fiber waste is CaO 2.75wt%, SiO2 10.55wt%, Al2O3 1.13wt%, Fe2O3 1.34wt%, MgO 55.41wt%, SO3 7.79%, LOI 21.03wt%.

[0050] The microbial amendment was a Bacillus pasteurellium bacterial solution, added at a rate of 0.6 kg per cubic meter of the wet soil to be treated. The bacterial concentration (OD) of the Bacillus pasteurellium solution was [not specified]. 600 The value was 1.6, and the urease activity was 6.34 mM / min.

[0051] Example 2 This embodiment provides a super-wet soil composite amendment. The difference between the super-wet soil composite amendment in Embodiment 2 and the super-wet soil composite amendment in Embodiment 1 is that the super-wet soil composite amendment in Embodiment 2 includes 35 parts of ceramic powder, 30 parts of red mud, 10 parts of flue gas denitrification reducing agent residue, and 25 parts of magnesium-based paper fiber waste. The rest are the same as in Embodiment 1.

[0052] Example 3 This embodiment provides a super-wet soil composite amendment. The difference between the super-wet soil composite amendment of Example 3 and Example 1 is that the bacterial concentration OD of the Bacillus pasteurization solution in Example 3 is higher. 600 The value was 1.8, the urease activity was 7.34 mM / min, and the rest were the same as in Example 1.

[0053] Application Example 1 This application example provides a method for consolidating excessively wet soil after precipitation, including the following steps: (1) Add the solid waste-based amendment to the wet soil to be treated and stir evenly. The stirring method is to stir slowly at 300 rpm for 1 min and then stir quickly at 1000 rpm for 1 min to obtain the first mixed soil. (2) Add the microbial amendment to the first mixed soil and stir evenly. The stirring method is to stir slowly at 300 rpm for 1 min, and then stir quickly at 1000 rpm for 1 min to obtain the second mixed soil. Wait for the moisture content of the second mixed soil to decrease.

[0054] In this application example, the solid waste-based amendment and microbial amendment used are the same as those in Example 1.

[0055] Application Example 2 This application embodiment provides a method for consolidating overly wet soil after dewatering. The difference between the overly wet soil consolidation method in application embodiment 2 and application embodiment 1 is that the solid waste-based amendment and microbial amendment used in application embodiment 2 are the same as those in application embodiment 2. All other aspects are the same as in application embodiment 1.

[0056] Application Example 3 This application embodiment provides a method for consolidating overly wet soil after dewatering. The difference between the overly wet soil consolidation method in application embodiment 3 and application embodiment 1 is that the solid waste-based amendment and microbial amendment used in application embodiment 3 are the same as those in application embodiment 3. All other aspects are the same as in application embodiment 1.

[0057] Comparative Example 1 This comparative example provides a method for dewatering overly wet soil. The method for dewatering overly wet soil in Comparative Example 1 is basically the same as that in Application Example 1, except that no microbial amendment is added in the method for dewatering overly wet soil in Comparative Example 1, while the remaining steps are the same as those in Application Example 1.

[0058] Comparative Example 2 This comparative example provides a method for dewatering excessively wet soil. The method for dewatering excessively wet soil in Comparative Example 2 is basically the same as that in Application Example 1, except that in step (1), the method for dewatering excessively wet soil in Comparative Example 2 uses PO42.5 cement instead of solid waste-based amendment. The basic properties of PO42.5 cement are shown in Table 1.

[0059] Table 1 Physical properties of cement used in Comparative Example 2

[0060] Comparative Example 3 This comparative example provides a method for dewatering overly wet soil. The method for dewatering overly wet soil in Comparative Example 3 is basically the same as that in Application Example 1, except that: in step (1), the method for dewatering overly wet soil in Comparative Example 3 uses lime instead of solid waste-based amendment. The lime used in Comparative Example 3 is industrial grade lime with a CaO content ≥95wt%.

[0061] Comparative Example 4 This comparative example provides a method for dewatering excessively wet soil. Comparative example 4 only involves placing excessively wet soil indoors in an open environment to allow it to air dry naturally.

[0062] Specifically, rapid precipitation consolidation tests were conducted on wetted soil using the methods of Application Examples 1 to 3 and Comparative Examples 1 to 4, respectively. The specific steps are as follows: (1) Soil extraction Soil samples were taken from a construction site in Foshan City at a depth of 2m. The samples were immediately sealed in polyethylene bags after excavation to prevent moisture loss during storage. Basic performance indicators of the soil samples are shown in Table 2.

[0063] Table 2 Basic Properties of Soil Samples

[0064] (2) Excessive moisture in soil The mixing of excessively wet soil was carried out in accordance with JGJ / T 233-2011 "Specification for Cement-Soil Mix Design". The dosage of solid waste-based amendment, cement, and lime was 12% of the mass of the excessively wet soil. 0.6 kg of microbial amendment was sprayed per cubic meter of excessively wet soil. After mixing, the soil samples were placed open in an environment of 25℃ and a humidity range of 35%RH~45%RH. The soil moisture content was tested at 1, 2, and 3 days, according to GB / T 50123-2019 "Standard for Geotechnical Testing Methods". The soil samples after 1, 2, and 3 days of open mixing were molded, and their shear strength and permeability coefficient were tested. The molding and testing methods were in accordance with GB / T 50123-2019 "Standard for Geotechnical Testing Methods". The test results are shown in Table 3.

[0065]

[0066] Table 3 Test results of various properties of the excessively wet soil samples Furthermore, to verify the effect of microbial amendments on the fixation of heavy metals contained in red mud, leaching toxicity tests were conducted on the amended soil after wet soil treatment. The test methods were in accordance with the "Leaching Toxicity of Solid Waste - Horizontal Oscillation Method" (HJ577-2010) and "Determination of Petroleum in Soil - Infrared Spectrophotometry" (HJ 1051-2019). Crushed test blocks were taken after 3 days of shear strength testing for testing. The test results are shown in Table 4.

[0067] Table 4. Test results of heavy metal content in overly wet soil samples

[0068] Note: ND in Table 4 indicates not detected.

[0069] The results show that this invention uses ceramic powder, red mud, flue gas denitrification reducing agent residue, and magnesium-based paper fiber waste to prepare solid waste-based soil amendment, making full use of solid waste and alleviating the problems of solid waste accumulation and disposal to a certain extent, thus improving the utilization rate of solid waste. Calcium oxide in the red mud reacts with hydration in overly wet soil to form calcium hydroxide, consuming the internal moisture of the overly wet soil and simultaneously increasing the pH value of the reaction system. This provides an alkaline environment for the active SiO2 and Al2O3 within the ceramic powder and magnesium-based paper fiber waste, generating stable hydration products such as hydrated calcium silicate and hydrated calcium aluminosilicate, establishing a network structure, initially cementing soil particles, and forming a skeletal structure. MgO in the magnesium-based paper fiber waste reacts with free water in the overly wet soil under alkaline conditions to generate magnesium hydroxide, which has an expanding effect, improving soil compaction. Furthermore, the fibers in the magnesium-based paper fiber waste can also form bridges with the soil, resisting the generation and development of cracks and improving the toughness of the amended soil. Urea in the residue of flue gas denitrification reducing agent can react with calcium ions to produce soluble double salts, regulating the crystallization rate of hydration products and improving the early strength of improved soil. It can also provide a growth environment for Bacillus pasteurellii, ultimately hydrolyzing into NH4+. 3+ and HCO 3- At the same time, OH is generated - The process increases the pH of the reaction system and combines with calcium ions formed during the hydration of red mud to generate calcium carbonate, filling the capillary structure. *Bacillus pasteurellii* possesses a urea-hydrolyzing mechanism, capable of converting dissolved heavy metal ions in red mud into insoluble minerals, reducing heavy metal pollution caused by red mud accumulation, and consuming internal moisture in overly wet soil while simultaneously increasing the pH of the reaction system. Furthermore, negatively charged microbial cells adsorb and accumulate calcium ions on their cell walls, reacting with carbonate ions to form calcium carbonate crystal precipitates, increasing soil strength.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A composite amendment for overly wet soil, characterized in that, Including solid waste-based amendments and microbial amendments; According to the mass fractions, the solid waste-based modified material includes 35-40 parts of ceramic powder, 20-30 parts of red mud, 10-15 parts of flue gas denitrification reducing agent residue, and 20-25 parts of magnesium-based paper fiber waste. The microbial improver includes Bacillus pasteurellium culture medium.

2. The composite amendment for overly wet soil according to claim 1, characterized in that, The ceramic powder comprises the following chemical components by mass percentage: CaO 1%~5%, SiO2 72%~85%, Al2O3 12%~21%, Fe2O3 1%~3%, Na2O 1%~3%, MgO 1%~5%, and LOI 2%~5%.

3. The composite amendment for overly wet soil according to claim 1, characterized in that, The red mud comprises the following chemical components by mass percentage: CaO 45%~50%, SiO2 25%~35%, Al2O 35%~10%, Fe2O 35%~7wt%, Na2O 1%~3wt%, MgO 1%~5wt%, and LOI 1%~5wt%.

4. The composite amendment for overly wet soil according to claim 1, characterized in that, The flue gas denitrification reducing agent residue comprises the following elements by mass percentage: Ca 18%~25%, O 25%~35%, N 45%~55%, H 5%~10wt%, Ti 1%~2wt%, Cu 1%~2wt%, Al 1%~3wt%.

5. The composite amendment for overly wet soil according to claim 1, characterized in that, The magnesium-based paper fiber waste comprises the following chemical components by mass percentage: CaO 1%~5%, SiO2 10%~15%, Al2O3 1%~3%, Fe2O3 1%~3wt%, MgO 50%~60wt%, SO3 5%~10%, and LOI 20%~25wt%.

6. The composite amendment for overly wet soil according to claim 1, characterized in that, The bacterial concentration (OD) of the *Bacillus pasteurellium* culture was... 600 The value is 1.5~2.

0.

7. The composite amendment for overly wet soil according to claim 1, characterized in that, The urease activity in the *Bacillus pasteurellii* bacterial culture was ≥6 mM / min.

8. The composite amendment for overly wet soil according to claim 1, characterized in that, The ceramic powder has a particle size ≤75μm, and the red mud has a particle size ≤100μm.

9. The composite amendment for overly wet soil according to claim 1, characterized in that, The particle size of the flue gas denitrification reducing agent residue is ≤100μm, and the particle size of the magnesium-based paper fiber waste is ≤100μm.

10. A method for consolidating excessively wet soil after dewatering, characterized in that, Using the overly wet soil composite amendment according to any one of claims 1-9 includes the following steps: (1) Add the solid waste-based amendment to the wet soil to be treated and mix evenly to obtain the first mixed soil; (2) Add the microbial amendment to the first mixed soil and stir evenly to obtain the second mixed soil. Wait for the moisture content of the second mixed soil to decrease. When the moisture content of the second mixed soil decreases to the preset moisture content, the dewatering treatment of the overly wet soil can be completed and the amended soil can be collected.

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