An ecological self-repairing solidified soil and a preparation method and use method thereof

Abstract

This invention discloses an ecologically self-healing stabilized soil and its preparation and application methods, comprising the following components: finely ground dry soil, core-shell structured microbial slow-release particles, and water, with a mass ratio of (300-500):(20-30):(100-200). The stabilized soil of this invention significantly reduces pollution to the underground environment, with its 18-hour heavy metal ion leaching concentration being 5%-10% of that of cement-stabilized soil with the same stabilizer dosage; it exhibits low-carbon and energy-saving characteristics, with its life-cycle carbon emissions being 10%-15% of that of cement-stabilized soil with the same stabilizer dosage; it has good resistance to freeze-thaw cycles, with a strength loss rate of 25%-30% after 100 freeze-thaw cycles; and it demonstrates good resistance to wet-dry cycles, with a minimum strength loss rate of only 3.2% after 100 wet-dry cycles.

Description

Technical Field

[0001] This invention belongs to the field of building materials, and in particular relates to an ecological self-healing solidified soil and its preparation and application methods. Background Technology

[0002] Traditionally, using cement and industrial solid waste materials such as fly ash and slag to prepare solidified soil is a common method for realizing the resource utilization of engineering waste soil. However, this technology has significant limitations. First, heavy metal ions (such as lead, chromium, and cadmium) contained in cement and some industrial solid waste pose a risk of leaching under long-term hydrological conditions, potentially causing secondary pollution to the soil and groundwater surrounding the backfill area. Second, the production of traditional cement-based solidified soil relies on cement, and cement production is a typical high-energy-consuming and high-carbon-emission industry. This contradicts the current global advocacy of "carbon neutrality" and green sustainable development. Third, as a brittle material, cement-based solidified soil commonly experiences cracking during its service life due to factors such as its own drying shrinkage, temperature stress, or external loads. Once these cracks form, they not only reduce the overall strength and load-bearing capacity of the backfill but also become rapid channels for moisture and corrosive ions, seriously affecting its long-term durability. Moreover, traditional materials are difficult to effectively repair once cracked. Therefore, there is an urgent need to develop a new type of solidified soil material that is environmentally friendly, low-carbon, energy-saving, and has long-term durability.

[0003] While existing technologies utilize superabsorbent resins or microspheres to adsorb water and curing agents to prepare self-curing solidified soil (e.g., CN115784701B), the core purpose of these technologies is to address the issues of moisture evaporation and shrinkage during the initial hardening stage of the solidified soil. In these existing technologies, the loaded substances typically begin to be released at the initial mixing stage to assist the hydration reaction, and microorganisms are usually directly exposed to the matrix environment to participate in initial curing. However, for damage and cracking of solidified soil caused by environmental erosion or loads during long-term service, existing self-curing systems lack an intelligent repair mechanism that can remain dormant for a long time and be passively triggered when damage occurs, making it difficult to solve the durability problem throughout the material's entire life cycle. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide an ecological self-healing solidified soil and its preparation and application methods.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: An ecological self-healing type of solidified soil comprises the following components: finely ground dry soil, microbial slow-release particles with a core-shell structure, and water, wherein the mass ratio of the three components is (300-500):(20-30):(100-200). The core-shell structured microbial sustained-release particles are prepared by the following method: a) Dissolve Bacillus pasteurellii spores, urea, and calcium source in water to form a nutrient solution; b) Add superabsorbent resin powder to the nutrient solution to saturate it with adsorption and form gel particles; c) The saturated gel particles are rolled and wrapped in calcium source powder, or immersed in a cross-linking agent solution containing calcium salt for surface hardening, so that a shell layer is formed on the surface of the particles, resulting in microbial slow-release particles with a core-shell structure.

[0006] As a further improvement, the number of Bacillus pasteurellii spores in the nutrient solution is 1×10⁻⁶. 7 CFU / mL ~5×10 9 CFU / mL.

[0007] As a further improvement, the calcium source is at least one of calcium chloride, calcium acetate, calcium nitrate, or calcium lactate.

[0008] As a further improvement, the molar ratio of urea to calcium source in the nutrient solution is 1:1 to 1.2:1.

[0009] As a further improvement, the concentrations of urea and calcium source in the nutrient solution are both 0.5 mol / L to 1.5 mol / L.

[0010] As a further improvement, the nutrient solution also contains yeast extract at a concentration of 1 g / L to 5 g / L.

[0011] As a further improvement, the superabsorbent resin is sodium polyacrylate or polyacrylamide with a particle size of 200μm~500μm.

[0012] As a further improvement, the crosslinking agent solution is a calcium nitrate solution, calcium chloride solution, calcium acetate solution, or calcium lactate solution with a mass concentration of 5-15%.

[0013] A method for preparing the ecological self-healing solidified soil according to the present invention includes: mixing the core-shell structured microbial slow-release particles with finely ground dry soil evenly, and then adding water and stirring to form a solidified soil mixture.

[0014] The present invention discloses a method for using the ecological self-healing solidified soil, which is used for slope repair, foundation pit backfilling, or site reinforcement.

[0015] The principle of this invention: This invention utilizes Microbially Induced Calcite Precipitation (MICP) technology, innovatively introducing superabsorbent polymer (SAP) as a micro-carrier for loading microorganisms and nutrients to construct a dormant-activated self-healing system within the solidified soil. Furthermore, it constructs a microcapsule structure of SAP core-inorganic shell. Specifically, this invention transforms the open structure of SAP into a closed microcapsule by coating the surface of SAP saturated with bacterial solution with a dense inorganic powder shell (such as calcium source powder). During the mixing stage of the solidified soil, this shell prevents the exchange of nutrients between the SAP interior and the external mixing water, protecting the microorganisms from damage caused by complex chemical environments and mechanical stress, ensuring their long-term survival. When microcracks form in the solidified soil matrix due to drying shrinkage or external forces, the formation of these cracks destroys some particles with core-shell structures or provides channels for external moisture infiltration, thereby rapidly activating the dormant microorganisms. The activated microorganisms immediately utilize the nutrients stored in the SAP (Super Acid Processing Unit) for metabolism. Their secreted urease efficiently hydrolyzes urea to produce carbonate ions, which then react in situ with calcium ions provided by the calcium source to generate calcium carbonate crystals with adhesive strength. These generated calcium carbonate crystals effectively fill and cement cracks, restoring the material's integrity and impermeability, thus achieving self-repair and significantly improving its long-term durability and environmental friendliness.

[0016] This invention differs from traditional cement-based or solid waste-based solidified soil in that it fundamentally changes the repair model of solidified soil in response to damage and solves the core pain point of environmental friendliness. To achieve this goal, this invention includes an SAP component loaded with core nutrients such as Bacillus pasteurellii, urea, and calcium sources.

[0017] The entire process of the ecological self-healing solidified soil based on SAP-loaded microorganism-induced calcium carbonate precipitation can be divided into two stages: the initial solidification stage and the long-term self-healing stage.

[0018] In the initial solidification stage, after all components are mixed together to form a mixture and pumped to the backfill area, its initial hardening and strength establishment mainly depend on physical and biochemical reactions. Finely ground dry soil acts as the skeleton, its particles tightly packed under the influence of moisture. The friction and interlocking between particles provide the main shear strength, which is the primary source of the backfill's load-bearing capacity. On the other hand, pre-adsorbed saturated microbial slow-release particles, as hydrogel microcapsules, are uniformly distributed within the pores of the soil particles. Although their dense surface shell limits the early release of internal moisture to the surrounding soil to some extent (which also prevents premature nutrient loss), this closed structure effectively locks in the moisture inside the particles, preventing evaporation during the heat release or drying process of the solidified soil. This trapped moisture, together with the SAP gel, constitutes elastic, flexible micronodes, not only physically filling and reducing porosity but also reserving the necessary liquid environment for subsequent responsive water release remediation when cracks occur.

[0019] During the long-term self-healing phase, when microcracks develop in the hardened solidified soil due to various factors such as load, shrinkage, and freeze-thaw cycles, the SAP particles inside the solidified soil rupture, releasing the Pasteurella multocida and nutrients. Simultaneously, these microcracks provide a seepage channel for rainwater and groundwater from the external environment, allowing water to rapidly penetrate the cracks. This water intrusion is a crucial signal for awakening dormant Pasteurella multocida spores and dissolving the urea and calcium stored within the SAP (bacterial spores typically germinate when nutrients and water are abundant. However, inside the SAP hydrogel, most water molecules are bound by hydrogen bonds within the polymer chains, making it difficult for microorganisms to utilize this water for metabolic activities). The awakened spores germinate into metabolically active vegetative cells, which begin to secrete large amounts of urease as a highly efficient catalyst, rapidly hydrolyzing the urea in the cracks.

[0020] This reaction generates carbonate ions needed for repair, while the calcium ions provided by the dissolved calcium source react with the newly generated carbonate ions to form calcium carbonate precipitate.

[0021] The generated calcium carbonate crystals preferentially nucleate and grow on the surface of the crack. These crystals continue to grow and overlap, re-bonding the two walls of the crack together. Eventually, the entire crack is completely filled and sealed by dense calcium carbonate crystals, which not only restores the mechanical strength of the solidified soil but also isolates the channels for further erosion by external moisture and harmful ions, thus achieving the self-repair of the solidified soil.

[0022] This invention differs from simple mixing; instead, it utilizes SAP to construct a micro-bioreactor chamber. The three-dimensional mesh structure of SAP acts as a physical shield, isolating the reaction system from the soil matrix. This isolation ensures that: during the mixing period, microorganisms are prevented from being prematurely activated or damaged by mechanical forces; and during service life, the repair mechanism is only activated when cracks appear as a trigger signal. This slow-release characteristic is not found in ordinary self-healing materials.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The solidified soil of the present invention is a new type of backfill material. It is no longer limited to the field of traditional solidified soil, but can be used as an ecological restoration material. Under the premise of ensuring environmental friendliness, low carbon and energy saving and sufficient strength, it can also have good long-term durability.

[0024] (2) The core-shell structure of the present invention provides an independent pH buffer for microorganisms, avoiding the killing effect of mechanical shearing and complex chemical environment on spores in the early stage of mixing, and greatly improving the survival rate of microorganisms. Moreover, the microbial mineralization reaction rate of the core-shell structure particles of the present invention is less than 5% within 24 hours after mixing, and more than 90% of nutrients are retained for later crack repair.

[0025] (3) Compared with traditional backfill solidified soil, the solidified soil of the present invention: It greatly reduces pollution to the underground environment, and its 18-hour heavy metal ion leaching concentration is 5% to 10% of that of cement-stabilized soil with the same amount of solidifier. It features low carbon and energy saving, with its total life cycle carbon emissions being only 10% to 15% of those of cement-stabilized soil with the same amount of solidifying agent. It exhibits excellent resistance to freeze-thaw cycles, with a strength loss rate of 25%~30% after 100 freeze-thaw cycles, which is 31.25%~37.5% of that of cement-cured soil with the same curing agent dosage. It exhibits excellent resistance to wet-dry cycles. After 100 wet-dry cycles, the strength loss rate of this invention is as low as 3.2%, while the strength loss of cement-based solidified soil under the same conditions is as high as 65.2%, and the loss rate of the SAP-free system exceeds 80%.

[0026] This fully demonstrates that SAP is not merely a carrier; its dormancy-activation system, constructed with microorganisms, successfully blocks the path of microcracks developing into through cracks. Detailed Implementation

[0027] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0028] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0030] This invention provides an ecological self-healing solidified soil based on SAP-loaded microbial-induced calcium carbonate precipitation, as well as its preparation and application methods. While ensuring backfill strength, it reduces carbon emissions and environmental damage, and can self-repair after the backfill body cracks, thus serving as an ecological backfill material.

[0031] In some specific embodiments, the ecological self-healing solidified soil of the present invention comprises the following components: finely ground dry soil, microbial slow-release particles with a core-shell structure, and water, wherein the mass ratio of the three components is (300-500): (20-30): (100-200).

[0032] In some embodiments, the engineering soil sample is dried and ground to obtain finely ground dry soil. The engineering soil sample is taken according to the engineering requirements, and should be as free of impurities as possible, such as large stones and domestic waste, but retain residual vegetation roots and other humus in the soil sample. In some embodiments, the soil sample is dried at 105°C, then ground and sieved with a sieve aperture diameter of 1 mm.

[0033] In some embodiments, the microbial sustained-release particles with a core-shell structure are prepared by: a) Dissolve Bacillus pasteurellii spores, urea, and calcium source in water to form a nutrient solution.

[0034] In some embodiments, the number of Bacillus pasteurellii spores in the nutrient solution is 1 × 10⁻⁶. 7 CFU / mL ~5×10 9 CFU / mL, preferably 3×10 8 CFU / mL ~8×10 8 CFU / mL.

[0035] In some embodiments, the calcium source is at least one of calcium chloride, calcium acetate, calcium nitrate, or calcium lactate.

[0036] In some embodiments, the molar ratio of urea to calcium source in the nutrient solution is 1:1 to 1.2:1. The concentrations of both urea and calcium source in the nutrient solution are 0.5 mol / L to 1.5 mol / L, and it contains yeast extract at a concentration of 1 g / L to 5 g / L. Yeast extract, also known as yeast flavoring, is a commercially available nutrient.

[0037] In some embodiments, the mass ratio of Bacillus pasteurellii spore powder, urea, calcium source, and yeast extract is (0.01~0.05):(5~8):(15~20):(1.5~2.5).

[0038] b) Add superabsorbent polymer (SAP) powder to the nutrient solution to saturate it with adsorption and form gel particles.

[0039] In some embodiments, the superabsorbent polymer (SAP) is sodium polyacrylate or polyacrylamide with a particle size of 200 μm to 500 μm.

[0040] In some embodiments, the ratio of the mass of SAP to the volume of the nutrient solution is 20-30 g / L.

[0041] c) Surface coating treatment: The adsorption-saturated gel particles are placed in calcium source powder for rolling and coating, or immersed in cross-linking agent solution for surface hardening, until a non-sticky dense shell is formed on the particle surface, thus obtaining microbial slow-release particles with core-shell structure.

[0042] In some embodiments, the shell is made of one or more calcium source powders, and the shell thickness is 10 μm to 50 μm. The calcium source is at least one of calcium chloride, calcium acetate, calcium nitrate, or calcium lactate.

[0043] In some embodiments, the crosslinking agent solution is a calcium nitrate solution, calcium chloride solution, calcium acetate solution, or calcium lactate solution with a mass concentration of 5% to 15%. The calcium ions in the solution react rapidly with the polymer chains on the surface of the SAP particles to form a dense, crosslinked, hardened shell on the particle surface.

[0044] The microbial slow-release particles of the present invention have a core-shell structure and consist of a core and an outer shell. The core is a superabsorbent polymer (SAP) hydrogel that has absorbed a nutrient solution containing Bacillus pasteurellii spores, urea, and a calcium source. The outer shell is an inorganic powder coating layer or a gel hardening layer that coats the surface of the core. During the mixing stage of the solidified soil, the outer shell prevents the nutrients in the core from diffusing outward and only breaks to release the core material when it is torn by mechanical force during crack development or when water continues to penetrate.

[0045] Microbial slow-release particles, in a water-absorbing and swollen state, fill the pores of finely ground dry soil particles as flexible nodes, and Bacillus pasteurellii spores are protected in the microenvironment inside the microbial slow-release particles and do not participate in the cementation reaction in the initial solidification stage.

[0046] In some specific embodiments, the preparation method of the ecological self-healing solidified soil of the present invention includes the following steps: mixing the core-shell structured microbial slow-release particles with finely ground dry soil evenly, and then adding water and stirring to form a solidified soil mixture.

[0047] In some embodiments, the stirring speed is 800 rpm, the stirring time is 15 min, and the temperature of the stirring chamber is controlled at 25 ℃ during the stirring process.

[0048] In some specific embodiments, the method of using the ecological self-healing solidified soil of the present invention is to apply it to slope repair, foundation pit backfilling, or site reinforcement. The mixture is pumped to the backfill location, and after hardening, it forms a monolithic backfill with a certain strength.

[0049] In some embodiments, after the solidified soil is mixed, the solidified soil mixture is pumped to the backfill pit or slope surface.

[0050] The significant feature of the self-healing stabilized soil of this invention is its self-healing capability, resulting in significantly improved durability. When microcracks appear inside the matrix, it can actively trigger a microbial mineralization reaction, effectively filling and healing the cracks, thereby restoring the material's mechanical properties and impermeability. This fundamentally solves the problem of rapid performance degradation and difficulty in repair after cracking in traditional stabilized soils, significantly improving the long-term durability of the material and the reliability of engineering structures, effectively extending service life. It achieves true environmental friendliness and aligns with sustainable development.

[0051] This invention is an environmentally friendly ecological material with dual environmental advantages. First, it replaces traditional cement hydration with a biological reaction, and the core process does not rely on cement, fundamentally avoiding the high energy consumption and high carbon emissions associated with cement production. Second, the reaction process is mild, and the final product is calcium carbonate, which is stable in nature, non-toxic and harmless, avoiding the secondary pollution risks to soil and groundwater caused by the strong alkalinity of traditional solidified soil and the leaching of heavy metal ions from solid waste.

[0052] Experimental tests show that the ecological self-healing solidified soil backfilled by this invention has self-healing capabilities and significantly improved durability; it achieves true environmental friendliness and conforms to sustainable development; it reduces the total life cycle cost; it upgrades structural materials to smart materials, resulting in higher safety; it has strong process adaptability and broad application prospects.

[0053] Example 1 The solidified soil provided in this embodiment comprises the following components: Finely ground dry soil: Microbial slow-release particles: Water = 400:25:150.

[0054] The method for preparing finely ground dry soil is as follows: the engineering soil sample is dried at a temperature of 105℃, and then the soil sample is ground finely using a high-power pulverizer or ball mill and sieved through a sieve with a sieve hole diameter of 1 mm to obtain finely ground dry soil.

[0055] The raw materials for the microbial slow-release granules include: 0.01 parts of Bacillus pasteurellii spore powder (the concentration of the prepared bacterial solution is 1×10⁻⁶). 8 The microbial sustained-release granules were prepared by dissolving each component in 1000 parts of water to form a bacterial solution, which was then absorbed by 25 parts of SAP (sodium polyacrylate, 200μm~500μm) to form gel particles. After filtering out the excess liquid, the saturated gel particles were placed in a disc granulator, and 50 parts of finely ground calcium lactate powder were added for rolling and coating until a dense powder shell (shell thickness controlled at 10μm~50μm) formed on the particle surface. Excess powder was then sieved off, resulting in microbial sustained-release granules with a core-shell structure.

[0056] Then, the slow-release microbial granules, finely ground dry soil, and water are mixed in a specific ratio and stirred evenly using a soil solidification mixing device to form a uniform solidified soil mixture. The mixing speed is 800 rpm, the mixing time is 15 minutes, and the temperature of the mixing chamber is controlled at 25 ℃ during the mixing process.

[0057] Example 2 The solidified soil provided in this embodiment comprises the following components: Finely ground dry soil: Microbial slow-release particles: Water = 500:20:180.

[0058] The raw materials for the microbial sustained-release granules include: 0.01 parts of Bacillus pasteurellium spore powder (bacterial concentration 1×10⁻⁶). 8 The microbial sustained-release granules were prepared by dissolving each component in 1000 parts water to form a nutrient solution. Then, 20 parts of SAP (sodium polyacrylate, 200μm~500μm) were added to the solution until saturation, forming gel particles. A 10% (w / w) calcium nitrate solution was prepared as a cross-linking agent and placed in an impregnation tank. The saturated gel particles were placed in a stainless steel mesh basket and immersed in the cross-linking agent solution for 10~20 seconds. The particles were then removed, and excess surface moisture was drained to obtain microbial sustained-release granules with a core-shell structure.

[0059] The obtained granules are mixed with finely ground dry soil and water, and stirred evenly according to the process in Example 1.

[0060] Example 3 The solidified soil provided in this embodiment comprises the following components: Finely ground dry soil: Microbial slow-release particles: Water = 400:25:150.

[0061] The raw materials for the microbial sustained-release granules include: 0.05 parts of Bacillus pasteurellium spore powder (bacterial concentration 5×10⁻⁵). 8 (CFU / mL); 6 parts urea; 18 parts calcium chloride; 2 parts yeast extract.

[0062] The preparation method is as described in Example 1.

[0063] Comparative Example 1 The solidified soil (traditional cement-solidified soil) provided in this comparative example comprises the following components: Finely ground dry soil: cement (PO 42.5): water = 400:40:150.

[0064] Finely ground dry soil, cement, and water are mixed in a specific ratio and then stirred evenly using a soil hardening mixing device to form a uniform soil hardening mixture.

[0065] Comparative Example 2 The solidified soil (without microbial system) provided in this embodiment differs from that in Example 1 only in that: Slow-release granules (without added Bacillus pasteurization spore powder): 6 parts urea; 18 parts calcium lactate; 2 parts yeast extract.

[0066] Comparative Example 3 The solidified soil (nutrient-free system) provided in this embodiment differs from that in Example 1 only in that: Microbial sustained-release granules (without urea, calcium lactate, or yeast extract): 0.01 parts of Bacillus pasteurellium spore powder (bacterial concentration 1×10⁻⁶). 8 (CFU / mL).

[0067] Comparative Example 4 The solidified soil (without SAP system) provided in this embodiment includes the following components: Finely ground dry soil: water = 400:150.

[0068] 0.01 parts of Bacillus pasteurellium spore powder (bacterial concentration 1×10⁻⁶) 8 (CFU / mL); 6 parts urea; 18 parts calcium lactate; 2 parts yeast extract.

[0069] The above components are directly mixed and stirred evenly using a soil hardening mixing device to form a uniform soil hardening mixture. The mixing speed is 800 rpm, the mixing time is 15 minutes, and the temperature of the mixing chamber is controlled at 25 ℃ during the mixing process.

[0070] The composition of the solidified soil in the examples and comparative examples is shown in Table 1.

[0071] Table 1. Composition (parts) of the solidified soil in the examples and comparative examples

[0072] Note: In Examples 1-3, urea, calcium source and bacterial powder were loaded inside the microbial slow-release particles; in Comparative Example 4, they were directly incorporated.

[0073] The solidified soils of the comparative and examples described above were uniformly mixed using a concrete mixer to form a solidified soil mixture. This mixture was pumped into a pre-prepared mold and cured for 28 days. The compressive strength was then measured, along with the compressive strength after 100 freeze-thaw cycles and 100 wet-dry cycles after 28 days of curing (see Table 2). Simultaneously, the leaching amount of heavy metal ions from the mixture over 18 hours was measured, and the life-cycle carbon emissions of the solidified soil were calculated (see Table 2). The leaching amount of heavy metal ions was measured according to Chinese standard GB 5085.3-2007, and the life-cycle carbon emissions were measured according to international standard ISO 14040 / 14044.

[0074] In the freeze-thaw cycle test, the test blocks, after being cured for 28 days, were first saturated with water, then removed and dried. The conditions for a single cycle were: the test blocks were placed in a low-temperature chamber at -20℃±2℃ for 12 hours, then removed and cured in a constant-temperature water bath at 20℃±2℃ for 12 hours. This constituted one cycle, and a total of 100 cycles were performed. After the cycles were completed, the unconfined compressive strength of the test blocks was measured, and the strength loss rate was calculated.

[0075] The conditions for a single cycle of the wet-dry cycling test are as follows: the specimen is immersed in water at 20℃±2℃ for 24 hours, then removed and dried in an oven at 60℃±2℃ for 24 hours. This constitutes one cycle, and a total of 100 cycles are performed. After the cycles are completed, the unconfined compressive strength of the specimen is measured, and the strength loss rate is calculated.

[0076] To determine the leaching amount of heavy metal ions, solidified soil samples cured for 28 days were crushed and sieved (particle size <9.5 mm). A certain mass of the sample was weighed and placed in an extraction bottle. A sulfuric acid-nitric acid mixed extraction solvent (mass ratio 2:1, pH adjusted to 3.20±0.05) was added at a liquid-to-solid ratio of 10:1 (L / kg). The extraction bottle was fixed on a rotary shaker and shaken at 30±2 r / min for 18±2 h at an ambient temperature of 23±2℃. After shaking, the sample was allowed to stand and filtered through a 0.45 μm microporous membrane using a pressure filter, and the filtrate was collected. Finally, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to determine the Pb content in the filtrate. 2+ and Cr 6+ The concentration.

[0077] Table 2. Remaining compressive strength, ion leaching concentration, and life-cycle carbon emissions of the test blocks after 28 days and 100 freeze-thaw and wet-dry cycles.

[0078] Although the 28-day strength of the example group was lower than that of the cement-based Comparative Example 1, it fully met the requirements of most backfilling projects. More importantly, the example group effectively immobilized heavy metal ions in the soil, and its total life-cycle carbon emissions were only about 1 / 7 of those of the cement-based solution, demonstrating significant environmental and low-carbon advantages. Furthermore, the example group exhibited excellent freeze-thaw resistance. This is because the SAP hydrogel can convert free water in the pores into bound water, reducing the destructive stress caused by ice crystal frost heave. In contrast, Comparative Examples 2, 3, and 4, lacking a complete cementing or repair system, suffered severe structural damage under freeze-thaw conditions.

[0079] In particular, Example 3 showed minimal strength loss after wet-dry cycles. This is because the microcracks generated during the shrinkage and expansion process were promptly and effectively repaired by the self-healing system of the present invention, preventing the accumulation and expansion of damage. At the same time, its higher bacterial concentration made its implementation effect superior to that of Examples 1 and 2.

[0080] In contrast, under wet-dry cycling, microcracks continuously formed and developed in Comparative Example 1, leading to severe structural deterioration and a significant decrease in strength. Comparative Examples 2, 3, and 4, lacking or possessing only weak repair capabilities, rapidly deteriorated under wet-dry cycling.

[0081] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, 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 should fall within the protection scope of the present invention.

Claims

1. An ecologically self-healing stabilized soil, characterized in that, It includes the following components: finely ground dry soil, microbial slow-release particles with a core-shell structure, and water, in a mass ratio of (300-500):(20-30):(100-200); The core-shell structured microbial sustained-release particles are prepared by the following method: a) Dissolve Bacillus pasteurellii spores, urea, and calcium source in water to form a nutrient solution; b) Add superabsorbent resin powder to the nutrient solution to saturate it with adsorption and form gel particles; c) The saturated gel particles are rolled and wrapped in calcium source powder, or immersed in a cross-linking agent solution containing calcium salt for surface hardening, so that a shell layer is formed on the surface of the particles, resulting in microbial slow-release particles with a core-shell structure.

2. The ecological self-healing stabilized soil according to claim 1, characterized in that, The number of Bacillus pasteurellii spores in the nutrient solution is 1×10⁻⁶. 7 CFU / mL ~5×10 9 CFU / mL.

3. The ecological self-healing stabilized soil according to claim 1, characterized in that, The calcium source is at least one of calcium chloride, calcium acetate, calcium nitrate, or calcium lactate.

4. The ecological self-healing stabilized soil according to claim 1, characterized in that, In the nutrient solution, the molar ratio of urea to calcium source is 1:1 to 1.2:

1.

5. The ecological self-healing stabilized soil according to claim 1, characterized in that, In the nutrient solution, the concentrations of urea and calcium source are both 0.5 mol / L to 1.5 mol / L.

6. The ecological self-healing stabilized soil according to claim 1, characterized in that, The nutrient solution also contains yeast extract at a concentration of 1 g / L to 5 g / L.

7. The ecological self-healing stabilized soil according to claim 1, characterized in that, The superabsorbent resin is sodium polyacrylate or polyacrylamide, with a particle size of 200μm~500μm.

8. The ecological self-healing stabilized soil according to claim 1, characterized in that, The crosslinking agent solution is a calcium nitrate solution, calcium chloride solution, calcium acetate solution, or calcium lactate solution with a mass concentration of 5-15%.

9. A method for preparing the ecological self-healing solidified soil according to any one of claims 1 to 8, characterized in that, include: The core-shell structured microbial slow-release particles are mixed evenly with finely ground dry soil, and then water is added and stirred to form a solidified soil mixture.

10. A method of using the ecological self-healing stabilized soil according to any one of claims 1 to 8, characterized in that, It can be used for slope repair, foundation pit backfilling, or site reinforcement.

Images