Microbial-based climate buffer and method of construction thereof

Abstract

The application discloses a kind of microbial-based climate buffer layer and its construction method.The construction method includes the following steps: S1, the mixture of basalt fiber and basalt sand is added to the mixed solution of bacterial solution and cementing fluid, so that the basalt fiber in it is dispersed in basalt;S2, the mixed material obtained in step S1 is laid on the surface of the soil to be treated, forming a granular medium layer;S3, bacterial solution and cementing fluid are applied to the surface of the granular medium layer for multiple rounds to obtain a microbial-based climate buffer layer;In each round, bacterial solution is applied first, and then cementing fluid is applied after the bacterial solution penetrates into the interior of the granular medium layer;In steps S1 and S3, the bacterial solution contains urease-producing bacteria, and the cementing fluid includes calcium ions and urea.The application uses basalt sand, basalt fiber and MICP process in coordination, which can form a cover layer with structural integrity, moderate permeability and hydrothermal buffering capacity, and also provide a stable microenvironment suitable for long-term survival, dormancy and reactivation of microorganisms.

Description

Technical Field

[0001] This invention relates to the field of geological disaster prevention and control technology, and in particular to a microbial-based climate buffer layer and its construction method. Background Technology

[0002] Global warming has led to a significant increase in extreme weather events such as extreme heat, torrential rain, drought, and frequent freeze-thaw cycles. This causes more severe disturbances to the moisture, heat, and structural stability of the Earth's surface, resulting in a series of geological and environmental problems such as slope instability, soil erosion, and topsoil erosion. As the primary energy exchange interface between the atmosphere and the subsurface environment, the soil surface's water and heat regulation characteristics directly affect surface stability and ecological recovery capacity. Therefore, there is an urgent need for a surface cover structure that can effectively mitigate atmospheric disturbances, maintain soil water and heat balance, and possess long-term stability.

[0003] Existing surface protection measures mainly include engineering rigid protective structures and ecological cover layers. While the former, such as concrete or masonry slope protection, possesses high strength, its poor permeability and thermal regulation capacity often disrupt the natural water and heat cycle of the soil and weaken its ecological functions. Ecological cover layers, such as vegetation restoration, vegetation mats, or biodegradable mulch, can improve the surface ecological environment to some extent, but they rely on plant growth or material degradation processes, have long construction cycles, are sensitive to moisture and climate conditions, have high construction and maintenance costs, and their structural integrity and protective stability are easily compromised under extreme climatic conditions.

[0004] Microbially Induced Calcite Precipitation (MICP) technology has been used for surface reinforcement in recent years. It involves microbial metabolism producing calcium carbonate, which forms a cemented structure in granular media. While this technology is environmentally friendly, self-growing, and potentially self-healing, its limitations stem from the poor pore connectivity and insufficient permeability of natural soil. MICP typically forms only a very thin, discontinuous mineralized layer on the soil surface, making it difficult to construct a cover structure of sufficient thickness and uniformity. Furthermore, the calcium carbonate layer formed by MICP is brittle and prone to micro-cracks and gradual peeling under wind and rain erosion, wet-dry cycles, or freeze-thaw cycles, weakening its long-term protective capabilities. Although microorganisms possess a dormancy-activation mechanism, allowing them to resume metabolism and induce new mineralization reactions under certain humidity and nutrient conditions, the existing soil structure lacks a stable microenvironment, making it difficult for microorganisms to persist long-term and sustain their potential for self-healing and long-term mineralization.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a microbial-based climate buffer layer and its construction method, which uses basalt sand, basalt fiber and MICP process in combination to form a cover layer with structural integrity, moderate permeability and hydrothermal buffering capacity, and provides a stable microenvironment suitable for long-term survival, dormancy and reactivation of microorganisms, thereby realizing the construction of a composite climate buffer layer with long-term effect.

[0007] The present invention adopts the following technical solution: A method for constructing a microbial-based climate buffer layer includes the following steps: S1. Add the mixture of basalt fiber and basalt sand to the mixed solution of bacterial solution and cementing solution, so that the basalt fiber is dispersed in the basalt. S2. The mixed material obtained in step S1 is laid on the surface of the soil to be treated to form a granular medium layer. S3. Apply bacterial solution and cementing liquid to the surface of the particulate media layer in multiple rounds to obtain the microbial-based climate buffer layer; in each round, apply bacterial solution first, and after the bacterial solution penetrates into the interior of the particulate media layer, apply cementing liquid. In steps S1 and S3, the bacterial solution contains urease-producing bacteria, and the cementing solution includes calcium ions and urea.

[0008] In a preferred embodiment, in step S3, the number of rounds is 2 to 10.

[0009] In a preferred embodiment, the basalt sand has a particle size of 0.2~2.5mm, and the number of cycles in step S3 is 3~6.

[0010] In a specific and more preferred embodiment, the basalt sand has a particle size of 0.25~0.5mm, and the number of cycles in step S3 is 3~4.

[0011] In a specific and more preferred embodiment, the basalt sand has a particle size of 0.5~1mm, and the number of cycles in step S3 is 4~5. In a specific and more preferred embodiment, the basalt sand has a particle size of 1-2 mm, and the number of cycles in step S3 is 5-6.

[0012] In a specific and preferred embodiment, the basalt sand has a particle size of 0.075~0.25mm, and the number of cycles in step S3 is 2~3.

[0013] In a more preferred embodiment, in each round, the bacterial solution is sprayed once and the cementing solution is sprayed once, with an interval of 30 to 120 minutes between spraying the bacterial solution and spraying the cementing solution; the interval between each round of spraying is 6 to 12 hours.

[0014] In a preferred embodiment, the porosity of the microbial-based climate buffer layer is 10-40%, and the average pore size is 20-400 μm.

[0015] In a preferred embodiment, the porosity of the microbial-based climate buffer layer is 10-40%, and the average pore size is 25-400 μm. In a more preferred embodiment, the porosity of the microbial-based climate buffer layer is 20-40%, and the average pore size is 50-400 μm.

[0016] In a preferred embodiment, in each round of step S3, a cementing liquid is applied when the bacterial solution has penetrated to the soil surface below the granular media layer.

[0017] In a preferred embodiment, the urease-producing bacteria includes Bacillus pasteurellii, and the viable count in the bacterial solution is 1.0~1.5×10⁹ CFU / mL; the cementing solution is a mixture of calcium chloride solution and urea solution, wherein the concentration of calcium chloride solution is 0.5~1 mol / L and the concentration of urea solution is 0.5~1 mol / L.

[0018] In a preferred embodiment, the basalt fiber has a monofilament diameter of 7-15 μm, a length of 3-12 mm, and is used in an amount of 0.2-2% of the volume of basalt sand.

[0019] In a preferred embodiment, in step S1 or S3, the volume ratio of bacterial solution, cementing solution and basalt sand is 0.1~0.2:0.1~0.2:1.

[0020] In a preferred embodiment, in step S2, the thickness of the mixed material is 5~50mm.

[0021] A microbial-based climate buffer layer, obtained by the aforementioned construction method, wherein the microbial-based climate buffer layer has a porosity of 10-40% and an average pore size of 20-400 μm.

[0022] The beneficial effects of this invention are as follows: This invention uses basalt sand and basalt fibers as the medium for microbial cementation (MICP). The excellent porosity of basalt sand significantly improves the permeability and uniformity of distribution of cementing solution and microorganisms within the capping layer, thereby effectively enhancing the treatment depth and mineralization continuity of MCP. The incorporation of basalt fibers into the sand layer constructs a three-dimensional support structure formed by the interaction of basalt fibers and calcium carbonate during mineralization. This results in a capping layer with significantly superior crack resistance, erosion resistance, and overall durability compared to structures formed by simple mineralization. Simultaneously, within the multi-scale porous system composed of basalt sand and fibers, microorganisms can survive long-term under the protection of the calcium carbonate mineralization framework. They enter dormancy under drought or low-temperature conditions and are reactivated by rainfall, increased humidity, or improved solute conditions, continuously inducing new calcium carbonate precipitation. This endows the capping layer with a certain degree of self-maintenance and local self-repair capabilities, further enhancing the long-term stability and service life of the structure. The resulting cover layer has moderate permeability, which can both suppress surface evaporation and reduce surface temperature fluctuations, while allowing rainwater infiltration, reducing slope runoff and soil erosion, and achieving effective buffering and regulation of soil hydrothermal conditions. At the same time, the construction process is simple, and a composite cover layer with a certain thickness, uniformity and stability can be constructed in a short time, overcoming the shortcomings of ecological cover methods that rely on plant growth, have long cycles and high maintenance costs.

[0023] In summary, the construction method provided by this invention can form a composite bio-based climate buffer layer on the soil surface that combines structural stability, self-healing potential, permeability regulation, hydrothermal buffering function, and carbon sequestration ecological value. It is suitable for scenarios such as slope protection, ecological restoration, and extreme climate disturbance prevention and control. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a microbial-based climate buffer layer according to an embodiment of the present invention.

[0026] Figure 2 This is an enlarged schematic diagram of a microbial-based climate buffer layer according to an embodiment of the present invention.

[0027] Figure label: 1. Slope; 2. Microbial-based climate buffer layer; 3. Basalt fiber; 4. Basalt sand; 5. Calcium carbonate; 6. Bacteria; 7. Soil particles. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more readily understood by those skilled in the art. It should be noted that the description of these embodiments is for the purpose of aiding understanding the present invention, but does not constitute a limitation thereof.

[0029] To address the shortcomings of existing surface protection technologies, such as insufficient hydrothermal regulation capabilities, limited structural stability, long construction periods, and difficulty in forming a mineralized overburden layer of sufficient thickness and uniformity on the soil surface, this invention proposes a method for constructing a climate buffer layer using microbial mineralization combined with the properties of basalt materials. This method aims to overcome the problems of shallow mineralization depth, uneven distribution, brittle mineralized structure, and difficulty in maintaining long-term microbial activity in traditional MIP (microbial microbial biochemical) technology. It also compensates for the deficiencies of ecological overburden layers, such as long construction periods, sensitivity to climate conditions, and limited durability.

[0030] Basalt sand possesses a favorable porous structure, which facilitates the infiltration and distribution of microbial solutions. During natural weathering, it can react with carbon dioxide in the environment, demonstrating potential for mineral weathering and carbon sequestration. Basalt fibers exhibit high strength and good durability, forming a stable spatial support structure within a particle packing system, thus improving the material's crack resistance and overall toughness. This paper proposes a method that synergistically utilizes basalt sand, basalt fibers, and the MICP process to create a capping layer with structural integrity, moderate permeability, and hydrothermal buffering capacity, while also providing a stable microenvironment suitable for the long-term survival, dormancy, and reactivation of microorganisms, thereby constructing a long-term composite climate buffer layer.

[0031] This invention provides a method for constructing a climate buffer layer using microbial mineralization and basalt materials, comprising the following steps: S1. Basalt Sand-Basalt Fiber Mixture: Basalt fiber and basalt sand are mixed in a predetermined ratio, and an appropriate amount of a mixed solution consisting of bacterial solution and cementing solution is added to the mixture. This allows the basalt fiber to be fully dispersed within the basalt sand under wetted conditions, forming a preliminary three-dimensional interwoven structure. The calcium carbonate precipitate induced by microorganisms in the mixed solution can form preliminary cementation between particles, improving the initial structural stability of the mixed material.

[0032] S2. Basalt sand-fiber mixed layer laying: Pretreated fiber-containing basalt sand is laid on the surface of the soil to be treated to form a granular medium layer with a certain thickness and suitable pore structure, which is conducive to the subsequent penetration, distribution and reaction of microbial solution and cementing liquid in the cover layer.

[0033] S3. Spraying of Bacterial Solution and Cementing Solution: Bacterial solution and cementing solution are sprayed onto the surface of the basalt sand-basalt fiber mixed layer. Spraying is carried out in rounds, each round consisting of one application of bacterial solution and one application of cementing solution. During spraying, the bacterial solution is sprayed first, allowing microorganisms to penetrate into the basalt sand-fiber mixed layer. The cementing solution is then applied as it penetrates to the surface of the underlying soil to ensure sufficient contact between the bacterial solution and the cementing solution within the cover layer and to facilitate calcium carbonate precipitation. The number of spraying rounds can be adjusted according to the mineralization degree and mechanical performance requirements of the cover layer on site to achieve the desired cementing effect and structural strength.

[0034] The bacterial solution contains urease-producing bacteria, and the cementing solution includes calcium ions and urea. During the MICP process, urease-producing bacteria act as the microbial pathway for calcium carbonate precipitation. The viable cell count in the bacterial solution is 1.0 ~ 1.5 × 10⁻⁶. 9 CFU / mL.

[0035] The *Pasteurella multocida* was cultured in a liquid culture medium containing 15.73 g / L Tris Base, 10 g / L ammonium sulfate, and 20 g / L yeast extract under general microbial culture conditions to obtain the bacterial solution.

[0036] Specifically, the cementing solution is a mixed solution composed of calcium chloride solution and urea solution, wherein the concentration of calcium chloride solution is 0.5-1 mol / L and the concentration of urea solution is 0.5-1 mol / L.

[0037] Preferably, the basalt sand has a particle size range of 0.075~2mm. Further, the basalt sand can have a particle size range of 0.075~0.25mm, 0.25~0.5mm, 0.5~1mm, or 1~2mm.

[0038] Preferably, the porosity of the basalt sand is 20-50%, more preferably 25-45%; and the average pore size is 20-800 μm, more preferably 50-800 μm. For example, the porosity of the basalt sand is 25-30%, and the average pore size is 50-100 μm; or, the porosity of the basalt sand is 30-35%, and the average pore size is 100-200 μm; or, the porosity of the basalt sand is 35-40%, and the average pore size is 20-400 μm; or, the porosity of the basalt sand is 40-45%, and the average pore size is 400-800 μm.

[0039] Preferably, the basalt fiber has a single filament diameter ranging from 7 to 15 μm, a length of 3 to 12 mm, and is used in an amount of 0.2 to 2% of the volume of basalt sand.

[0040] Preferably, in step S1, the volume ratio of the added bacterial solution: cementing solution: basalt sand is 0.1~0.2:0.1~0.2:1, wherein the volume ratio of the bacterial solution to the cementing solution is 1:1.

[0041] Preferably, in step S2, the thickness of the particulate medium layer is 5~50 mm.

[0042] Preferably, in step S3, the volume ratio of the sprayed bacterial solution, cementing solution and basalt sand is 0.1~0.2:0.1~0.2:1, and the volume ratio of the sprayed bacterial solution to the cementing solution is 1:1.

[0043] Preferably, in step S3, each round of spraying includes one spraying of bacterial solution and one spraying of cementing solution, with an interval of 30 to 120 minutes between spraying bacterial solution and spraying cementing solution; the interval between each round of spraying is 6 to 12 hours; and the number of spraying rounds is 2 to 6.

[0044] Furthermore, in step S3, the number of rounds is 2-3 times, 3-4 times, 4-5 times, or 5-6 times.

[0045] The obtained microbial-based climate buffer layer has a porosity of 10-40%, preferably 15-35%, more preferably 20-35%, and an average pore size of 20-400 μm, preferably 25-400 μm, more preferably 50-400 μm. For example, the microbial-based climate buffer layer has a porosity of 15-20% and an average pore size of 25-50 μm; or, the microbial-based climate buffer layer has a porosity of 20-25% and an average pore size of 50-100 μm; or, the microbial-based climate buffer layer has a porosity of 25-30% and an average pore size of 100-200 μm; or, the microbial-based climate buffer layer has a porosity of 30-35% and an average pore size of 200-400 μm.

[0046] This invention utilizes basalt sand as the application medium for nutrient solution-microorganism cultivation (MICP). Its excellent pore structure significantly improves the permeability and uniformity of distribution of nutrient solution and microorganisms within the capping layer, thereby effectively enhancing the treatment depth and mineralization continuity of MCP. By incorporating basalt fibers into the sand layer, a three-dimensional spatial support structure formed by the combined action of basalt fibers and calcium carbonate is constructed during the mineralization process. This results in a capping layer that exhibits significantly superior crack resistance, erosion resistance, and overall durability compared to structures formed through simple mineralization.

[0047] Basalt sand can react with carbon dioxide during natural weathering, possessing a certain potential for mineral weathering and carbon sequestration. This allows the caprock to not only perform hydrothermal regulation functions but also have a long-term geochemical carbon sequestration effect. Simultaneously, within the multi-scale porous system composed of basalt sand and fibers, microorganisms can survive for extended periods under the protection of the calcium carbonate mineralization framework. They enter dormancy under drought or low-temperature conditions but are reactivated when rainfall, increased humidity, or improved solute conditions occur, continuously inducing new calcium carbonate precipitation. This endows the caprock with a certain degree of self-maintenance and local self-repair capabilities, thereby further enhancing the long-term stability and service life of the structure.

[0048] The cover layer formed by this invention has moderate permeability, which can both inhibit surface evaporation and reduce surface temperature fluctuations, and allow rainwater infiltration, reducing slope runoff and soil erosion, thus achieving effective buffering and regulation of soil hydrothermal conditions. At the same time, the construction process of this invention is simple, and a composite cover layer with a certain thickness, uniformity and stability can be constructed in a short time, overcoming the shortcomings of ecological cover methods that rely on plant growth, have long cycles and high maintenance costs.

[0049] In summary, the construction method provided by this invention can form a composite climate buffer layer on the soil surface that combines structural stability, self-healing potential, permeability regulation, hydrothermal buffering function, and carbon sequestration ecological value, and is suitable for scenarios such as slope protection, ecological restoration, and extreme climate disturbance prevention and control.

[0050] The present invention will be further illustrated below through specific embodiments.

[0051] Example 1 Reference Figure 1 As shown, the treatment site is the slope surface of a certain slope 1, with a slope area of ​​approximately 10m². 2 The slope is approximately 30°. A microbial-based climate buffer layer 2 is constructed on this slope following the steps described below.

[0052] Step 1: Mix basalt sand and basalt fiber for pretreatment, add bacterial solution and cementing solution to fully disperse the basalt fiber inside the basalt sand, forming a basalt sand-fiber mixture.

[0053] In this step, 0.2 m³ of basalt sand with a particle size range of 0.075 ~ 0.25 mm is taken. 3 Basalt fiber, with a single filament diameter of 10 μm and a length of 9 mm, was added at a volume ratio of 0.4% of the basalt sand volume. After uniformly mixing the basalt sand and basalt fiber, the mixture was added to the solution at a volume ratio of bacterial solution: cementing solution: basalt sand = 0.15:0.15:1. The bacterial solution had a viable bacterial count of 1.2 × 10⁻⁶. 9The solution of *Pasteurella multocida* at CFU / mL was prepared by culturing *Pasteurella multocida* in a liquid medium containing 15.73 g / L Tris Base, 10 g / L ammonium sulfate, and 20 g / L yeast extract. The cementing solution was prepared by mixing equal volumes of calcium chloride solution and urea solution, both at a concentration of 1 mol / L.

[0054] After the mixed solution is added, it is thoroughly stirred to allow the basalt fibers to disperse evenly in a wetted state and form a preliminary three-dimensional interwoven structure with the sand grains. Simultaneously, microbially induced calcium carbonate forms a preliminary cement between the fibers and sand grains. Furthermore, the multi-scale porous structure of the basalt sand-fiber system provides a favorable microenvironment for microorganisms, allowing some cells to remain within the medium after the initial mineralization reaction, laying the foundation for subsequent reactivation and long-term mineralization.

[0055] Step 2: Evenly spread the pretreated basalt sand-fiber mixture on the slope surface to form a uniform cover layer of approximately 20 mm thickness, serving as the granular media layer. This thickness ensures that the mixture layer has a good porous structure to facilitate the penetration and reaction of subsequent spraying solutions.

[0056] After laying, the cover layer is lightly compacted to ensure full contact with the underlying soil and to form a continuous seepage path.

[0057] Step 3, MICP treatment: After the laying is completed, microbial mineralization consolidation is carried out by spraying bacterial solution and cementing solution at 60-minute intervals and in 3 spraying rounds.

[0058] Each round of spraying includes: first, spraying a bacterial solution with a volume ratio of 0.15:1 to basalt sand onto the surface of the overburden layer, allowing the solution to penetrate the entire mixed layer and reach the soil surface; then, spraying an equal volume ratio of cementing liquid, allowing the cementing liquid to penetrate along the same path, reacting with the microorganisms already distributed in the overburden layer to undergo urea hydrolysis and induce calcium carbonate precipitation. Each round of spraying is spaced 8 hours apart to ensure the mineralization reaction proceeds fully.

[0059] Reference Figure 2 After the spraying is completed, a continuous and dense calcium carbonate precipitate forms inside the basalt sand-fiber mixed layer. The basalt fiber (3), basalt sand (4), and calcium carbonate (5) together construct a stable three-dimensional composite framework structure, forming a climate buffer layer with good integrity, crack resistance, and erosion resistance. This significantly reduces slope runoff and the loss of fine soil particles (7) under heavy rainfall conditions. Some bacteria (6, Bacillus pasteurellii) can remain in the pore system of the climate buffer layer for a long time.

[0060] Example 2 Follow the steps below Figure 1 A microbial-based climate buffer layer was constructed on the slope shown.

[0061] Step 1: Mix basalt sand and basalt fiber for pretreatment, add bacterial solution and cementing solution to fully disperse the basalt fiber inside the basalt sand, forming a basalt sand-fiber mixture.

[0062] In this step, 0.2 m of basalt sand with a particle size range of 0.25 ~ 0.5 mm is taken. 3 Basalt fiber, with a single filament diameter of 10 μm and a length of 9 mm, was added at a volume ratio of 0.4% of the basalt sand volume. After uniformly mixing the basalt sand and basalt fiber, the mixture was added to the solution at a volume ratio of bacterial solution: cementing solution: basalt sand = 0.15:0.15:1. The bacterial solution had a viable bacterial count of 1.2 × 10⁻⁶. 9 The solution of *Pasteurella multocida* at CFU / mL was prepared by culturing *Pasteurella multocida* in a liquid medium containing 15.73 g / L Tris Base, 10 g / L ammonium sulfate, and 20 g / L yeast extract. The cementing solution was prepared by mixing equal volumes of calcium chloride solution and urea solution, both at a concentration of 1 mol / L.

[0063] After the mixed solution is added, it is thoroughly stirred to allow the basalt fibers to disperse evenly in a wetted state and form a preliminary three-dimensional interwoven structure with the sand grains. Simultaneously, microbially induced calcium carbonate forms a preliminary cement between the fibers and sand grains. Furthermore, the multi-scale porous structure of the basalt sand-fiber system provides a favorable microenvironment for microorganisms, allowing some cells to remain within the medium after the initial mineralization reaction, laying the foundation for subsequent reactivation and long-term mineralization.

[0064] Step 2: Evenly spread the pretreated basalt sand-fiber mixture on the slope surface to form a uniform cover layer of approximately 20 mm thickness, serving as the granular media layer. This thickness ensures that the mixture layer has a good porous structure to facilitate the penetration and reaction of subsequent spraying solutions.

[0065] After laying, the cover layer is lightly compacted to ensure full contact with the underlying soil and to form a continuous seepage path.

[0066] Step 3, MICP treatment: After the laying is completed, microbial mineralization consolidation is carried out by spraying bacterial solution and cementing solution at 60-minute intervals and in 4 spraying rounds.

[0067] Each round of spraying includes: first, spraying a bacterial solution with a volume ratio of 0.15:1 to basalt sand onto the surface of the overburden layer, allowing the solution to penetrate the entire mixed layer and reach the soil surface; then, spraying an equal volume ratio of cementing liquid, allowing the cementing liquid to penetrate along the same path, reacting with the microorganisms already distributed in the overburden layer to undergo urea hydrolysis and induce calcium carbonate precipitation. Each round of spraying is spaced 8 hours apart to ensure the mineralization reaction proceeds fully.

[0068] Example 3 Follow the steps below Figure 1 A microbial-based climate buffer layer was constructed on the slope shown.

[0069] Step 1: Mix basalt sand and basalt fiber for pretreatment, add bacterial solution and cementing solution to fully disperse the basalt fiber inside the basalt sand, forming a basalt sand-fiber mixture.

[0070] In this step, 0.2 m³ of basalt sand with a particle size ranging from 0.5 to 1.0 mm is taken. 3 Basalt fiber, with a single filament diameter of 10 μm and a length of 9 mm, was added at a volume ratio of 0.4% of the basalt sand volume. After uniformly mixing the basalt sand and basalt fiber, the mixture was added to the solution at a volume ratio of bacterial solution: cementing solution: basalt sand = 0.15:0.15:1. The bacterial solution had a viable bacterial count of 1.2 × 10⁻⁶. 9 The solution of *Bacillus pasteurellii* at CFU / mL was prepared by culturing *Bacillus pasteurellii* in a liquid medium containing 15.73 g / L Tris Base, 10 g / L ammonium sulfate, and 20 g / L yeast extract. The cementing solution was prepared by mixing equal volumes of calcium chloride solution and urea solution, both at a concentration of 1 mol / L.

[0071] After the mixed solution is added, it is thoroughly stirred to allow the basalt fibers to disperse evenly in a wetted state and form a preliminary three-dimensional interwoven structure with the sand grains. Simultaneously, microbially induced calcium carbonate forms a preliminary cement between the fibers and sand grains. Furthermore, the multi-scale porous structure of the basalt sand-fiber system provides a favorable microenvironment for microorganisms, allowing some cells to remain within the medium after the initial mineralization reaction, laying the foundation for subsequent reactivation and long-term mineralization.

[0072] Step 2: Evenly spread the pretreated basalt sand-fiber mixture on the slope surface to form a uniform cover layer of approximately 20 mm thickness, serving as the granular media layer. This thickness ensures that the mixture layer has a good porous structure to facilitate the penetration and reaction of subsequent spraying solutions.

[0073] After laying, the cover layer is lightly compacted to ensure full contact with the underlying soil and to form a continuous seepage path.

[0074] Step 3, MICP treatment: After the laying is completed, microbial mineralization consolidation is carried out by spraying bacterial solution and cementing solution at 60-minute intervals and in 5 spraying rounds.

[0075] Each round of spraying includes: first, spraying a bacterial solution with a volume ratio of 0.15:1 to basalt sand onto the surface of the overburden layer, allowing the solution to penetrate the entire mixed layer and reach the soil surface; then, spraying an equal volume ratio of cementing liquid, allowing the cementing liquid to penetrate along the same path, reacting with the microorganisms already distributed in the overburden layer to undergo urea hydrolysis and induce calcium carbonate precipitation. Each round of spraying is spaced 8 hours apart to ensure the mineralization reaction proceeds fully.

[0076] Example 4 Follow the steps below Figure 1 A microbial-based climate buffer layer was constructed on the slope shown.

[0077] Step 1: Mix basalt sand and basalt fiber for pretreatment, add bacterial solution and cementing solution to fully disperse the basalt fiber inside the basalt sand, forming a basalt sand-fiber mixture.

[0078] In this step, 0.2 m³ of basalt sand with a particle size ranging from 1.0 to 2.0 mm is taken. 3 Basalt fiber, with a single filament diameter of 10 μm and a length of 9 mm, was added at a volume ratio of 0.4% of the basalt sand volume. After uniformly mixing the basalt sand and basalt fiber, the mixture was added to the solution at a volume ratio of bacterial solution: cementing solution: basalt sand = 0.15:0.15:1. The bacterial solution had a viable bacterial count of 1.2 × 10⁻⁶. 9 The solution of *Bacillus pasteurellii* at CFU / mL was prepared by culturing *Bacillus pasteurellii* in a liquid medium containing 15.73 g / L Tris Base, 10 g / L ammonium sulfate, and 20 g / L yeast extract. The cementing solution was prepared by mixing equal volumes of calcium chloride solution and urea solution, both at a concentration of 1 mol / L.

[0079] After the mixed solution is added, it is thoroughly stirred to allow the basalt fibers to disperse evenly in a wetted state and form a preliminary three-dimensional interwoven structure with the sand grains. Simultaneously, microbially induced calcium carbonate forms a preliminary cement between the fibers and sand grains. Furthermore, the multi-scale porous structure of the basalt sand-fiber system provides a favorable microenvironment for microorganisms, allowing some cells to remain within the medium after the initial mineralization reaction, laying the foundation for subsequent reactivation and long-term mineralization.

[0080] Step 2: Evenly spread the pretreated basalt sand-fiber mixture on the slope surface to form a uniform cover layer of approximately 20 mm thickness, serving as the granular media layer. This thickness ensures that the mixture layer has a good porous structure to facilitate the penetration and reaction of subsequent spraying solutions.

[0081] After laying, the cover layer is lightly compacted to ensure full contact with the underlying soil and to form a continuous seepage path.

[0082] Step 3, MICP treatment: After the laying is completed, microbial mineralization consolidation is carried out by spraying bacterial solution and cementing solution at 60-minute intervals and in 6 rounds.

[0083] Each round of spraying includes: first, spraying a bacterial solution with a volume ratio of 0.15:1 to basalt sand onto the surface of the overburden layer, allowing the solution to penetrate the entire mixed layer and reach the soil surface; then, spraying an equal volume ratio of cementing liquid, allowing the cementing liquid to penetrate along the same path, reacting with the microorganisms already distributed in the overburden layer to undergo urea hydrolysis and induce calcium carbonate precipitation. Each round of spraying is spaced 8 hours apart to ensure the mineralization reaction proceeds fully.

[0084] The porosity characteristics of the climate buffer layers constructed in Examples 1 to 4 are shown in Table 1 below.

[0085] Table 1

[0086] According to Table 1, finer-grained basalt sand has lower pore size and porosity, requiring fewer MIP treatments. Conversely, coarser-grained basalt sand has higher pore size and porosity, requiring more treatments. By controlling the basalt sand grain size and the number of treatments, the pore structure of the climate buffer layer can be regulated. For example, using basalt sand with a grain size of 0.5–1 mm and performing 4–5 MIP treatments can help control the atmospheric-soil water and heat exchange.

[0087] Comparative Example right Figure 1 The slope shown was compared using the traditional MIP method. The specific steps are as follows: The slope surface is pretreated by removing the surface soil and retaining only the original soil without laying basalt sand or basalt fiber. The slope was subjected to microbial mineralization treatment, and the spraying method and spraying amount were the same as step 3 of Example 3.

[0088] After spraying, leave the slope surface exposed to complete the slope treatment.

[0089] In a comparative study, spraying pure MIP onto bare soil slopes resulted in the formation of a thin layer of calcium carbonate precipitate on the soil surface, improving short-term surface strength. However, this precipitate layer was only 1-3 mm thick, with a discontinuous, sheet-like structure lacking skeletal particle support and fiber reinforcement, resulting in poor overall integrity. Under natural wet-dry cycles, it was prone to cracking and peeling, leading to rapid strength decay. Furthermore, the thin layer had low and uneven porosity; while it could slightly reduce evaporation in the short term, its water retention capacity decreased rapidly as cracks formed, limiting its effectiveness in regulating hydrothermal conditions. During heavy rainfall, the calcium carbonate layer was easily splashed or completely stripped away, leading to fine particle loss from the exposed soil and significantly insufficient rain erosion protection.

[0090] Furthermore, due to the lack of a stable pore system in bare soil, microorganisms cannot survive for long periods. Most microorganisms become inactive or are washed away with changes in the external environment, failing to form a lasting self-repairing and remineralization capacity within the overburden layer. In addition, without the introduction of basalt materials with long-term slow-release weathering carbon sequestration potential, the treatment layer has almost no sustained carbon sequestration effect, and the calcium carbonate precipitate generated by MIP is also difficult to retain for long periods due to its easy detachment.

[0091] Referring to Table 2 below, the conventional MIP in the comparative examples exhibits limited treatment depth, discontinuous mineralization structure, and poor durability on bare soil slopes. Compared to the basalt sand-fiber-MICP composite buffer layer formed in the examples, it is significantly inferior in terms of crack resistance, overburden thickness stability, hydrothermal regulation capability, and erosion resistance. Furthermore, it lacks the long-term self-sustaining and remineralization capabilities of microorganisms and the mineral weathering and carbon sequestration effect, thus further demonstrating that the technical effect of this invention is significantly superior to existing technologies.

[0092] Table 1. Comparison of technical effects between the examples and comparative examples

[0093] In Examples 1 to 4, the cover layer maintains appropriate porosity, which can significantly reduce the slope evaporation rate and mitigate surface temperature fluctuations under extreme temperature conditions; at the same time, it retains a certain rainwater infiltration capacity, significantly reducing slope runoff and fine particle loss under heavy rainfall conditions. Some Bacillus pasteurellii can remain in the buffer layer's porous system for a long time (e.g., Figure 2 As shown, it can enter a dormant state under dry or low-temperature conditions, but can be reactivated when rainfall infiltrates, humidity increases, or nutrients are replenished, thereby inducing new local calcium carbonate precipitation inside the cover layer and giving the buffer layer a certain self-maintenance and microscale self-repair capability.

[0094] As the overburden is exposed to the natural environment over a long period, the basalt sand undergoes a slow mineral weathering reaction. The calcium, magnesium, and other cations contained in the basalt are gradually released under the influence of moisture and weak acids, and react with CO2 in the environment to undergo mineral carbonation, forming stable carbonate minerals while fixing carbon.

[0095] The composite buffer layer constructed in this embodiment has structural stability, hydrothermal regulation function, and certain self-healing and mineral weathering carbon fixation capabilities. The construction process is simple and the treatment efficiency is high. It can be applied to slope protection, ecological restoration and other scenarios that require rapid construction of surface protection structures.

[0096] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0097] As indicated in this specification and claims, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, and these steps and elements do not constitute an exclusive list; the method or apparatus may also include other steps or elements. The term "and / or" as used herein includes any combination of one or more of the associated listed items.

[0098] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0099] Any step described in any method or process claim may be performed in any order, and is not limited to the order presented in the claims. The limitation of method + function or step + function is used only if all of the following conditions are met in a particular claim: a) it expressly states "method for..." or "step for..."; b) it expressly states the corresponding function. Structures, materials, or actions supporting the method + function are expressly described in the description herein. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given herein.

[0100] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are preferred embodiments. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and they should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for constructing a microbial-based climate buffer layer, characterized in that, Includes the following steps: S1. Add the mixture of basalt fiber and basalt sand to the mixed solution of bacterial solution and cementing solution, so that the basalt fiber is dispersed in the basalt. S2. The mixed material obtained in step S1 is laid on the surface of the soil to be treated to form a granular medium layer. S3. Apply bacterial solution and cementing liquid to the surface of the particulate media layer in multiple rounds to obtain the microbial-based climate buffer layer; in each round, apply bacterial solution first, and after the bacterial solution penetrates into the interior of the particulate media layer, apply cementing liquid. In steps S1 and S3, the bacterial solution contains urease-producing bacteria, and the cementing solution includes calcium ions and urea.

2. The construction method according to claim 1, characterized in that, In step S3, the number of rounds is 2 to 10.

3. The construction method according to claim 1, characterized in that, The basalt sand has a particle size of 0.2~2.5mm, and the number of cycles in step S3 is 3~6.

4. The construction method according to claim 3, characterized in that, The basalt sand has a particle size of 0.25~0.5mm, and the number of cycles in step S3 is 3~4. Alternatively, the basalt sand has a particle size of 0.5~1mm, and the number of cycles in step S3 is 4~5; Alternatively, the basalt sand has a particle size of 1-2 mm, and the number of cycles in step S3 is 5-6.

5. The construction method according to claim 3, characterized in that, In each round, spray the bacterial solution once and the cementing solution once, with an interval of 30-120 minutes between spraying the bacterial solution and spraying the cementing solution; the interval between each round of spraying is 6-12 hours.

6. The construction method according to any one of claims 1 to 5, characterized in that, The porosity of the microbial-based climate buffer layer is 10-40%, and the average pore size is 20-400 μm.

7. The construction method according to claim 6, characterized in that, The porosity of the microbial-based climate buffer layer is 20-40%, and the average pore size is 50-400 μm.

8. The construction method according to any one of claims 1 to 5, characterized in that, In each round of step S3, a cementing solution is applied when the bacterial solution has penetrated to the soil surface below the granular media layer.

9. The construction method according to any one of claims 1 to 5, characterized in that, The urease-producing bacteria include Bacillus pasteurellii, and the viable count in the bacterial solution is 1.0 ~ 1.5 × 10⁻⁶. 9 CFU / mL; the cementing solution is a mixture of calcium chloride solution and urea solution, wherein the concentration of calcium chloride solution is 0.5~1 mol / L and the concentration of urea solution is 0.5~1 mol / L; The basalt fibers have a single filament diameter of 7~15μm and a length of 3~12mm, and are used in an amount of 0.2~2% of the volume of basalt sand. In step S1 or step S3, the volume ratio of bacterial solution, cementing solution and basalt sand is 0.1~0.2:0.1~0.2:1; In step S2, the thickness of the mixed material is 5~50mm.

10. A microbial-based climate buffer layer, characterized in that, It is obtained by the construction method as described in any one of claims 1 to 9, wherein the porosity of the microbial-based climate buffer layer is 10-40% and the average pore size is 20-400 μm.

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