Integrated toughness ecological restoration and reinforcement method for expansive soil side slope

Abstract

The invention relates to the technical field of ecological restoration, and discloses an integrated toughness ecological restoration and reinforcement method for an expansive soil side slope, which sequentially comprises a deep crack restoration layer (1), a shallow barrier layer (2) and a surface ecological layer (3) from inside to outside in the depth direction of the expansive soil side slope, and the three layers form a protection system; from the overall view of the scheme, the fundamental problem of slope structure stability is solved through deep reinforcement, the reason that expansive soil swells when encountering water is cut off through shallow water blocking, long-term ecological restoration and surface protection are achieved through surface ecology, and full-dimensional toughness protection of deep stability control, shallow water control and surface ecology control is formed through a three-layer system. And finally, the core problems that in traditional expansive soil slope restoration, the short-term effect is obvious, but the long-term effect is prone to losing efficacy, and structural reinforcement and ecological restoration are difficult to consider at the same time are solved, and the double sustainable targets of slope safety stability and ecological environment restoration are achieved.

Description

Technical Field

[0001] This invention relates to the field of ecological restoration technology, specifically to an integrated resilient ecological restoration and reinforcement method for expansive soil slopes. Background Technology

[0002] Expansive soils, rich in hydrophilic minerals, are prone to developing fissures under wet-dry cycles, forming a three-dimensional fissure network. This leads to soil strength degradation and increased rainwater infiltration, causing slope instability. Traditional protection methods have significant drawbacks: deep repair often uses cement or chemical grouting, which has high viscosity, requires high-pressure injection, easily disturbs the slope, and pollutes the environment; shallow protection often involves a single geomembrane or plain soil cover, with limited seepage prevention and prone to failure due to soil expansion and contraction; surface vegetation protection lacks synergistic design with deep structures and is difficult to cope with extreme rainfall conditions. Among existing technologies, microbial induced calcium carbonate precipitation (MICP) technology has ecological advantages, but its application alone suffers from insufficient grout penetration depth and uneven solidification; capillary retaining layers can delay infiltration, but lack integration with biomineralization, resulting in unstable long-term seepage prevention performance. Therefore, there is an urgent need to construct an integrated protection system that combines deep fissure repair, shallow seepage prevention reinforcement, and surface ecological regulation to achieve long-term safe protection of expansive soil slopes. Summary of the Invention

[0003] This invention aims to solve the problems of incomplete repair of deep cracks, poor synergy between shallow seepage prevention and surface ecology, and insufficient overall protection durability in existing expansive soil slope protection technologies. It provides a tough ecological protection structure and construction method that can achieve synergistic effects of "deep-shallow-surface".

[0004] The technical solution adopted by this invention to solve its technical problem is: an integrated tough ecological restoration and reinforcement method for expansive soil slopes, which includes, from the inside to the outside, a deep crack repair layer, a shallow barrier layer and a surface ecological layer along the depth direction of the expansive soil slope, forming a protective system. The deep fracture repair layer is constructed using a targeted injection composite mineralization slurry. The composite mineralization slurry is composed of MICP reaction solution, crude urease solution, calcium-based bentonite modified with γ-polyglutamic acid, and Aspergillus fungal spores. The MICP reaction solution contains urease solution containing bacterial cells and a cementing solution. The cementing solution is an aqueous solution containing 0.8%-1.5% urea and 0.8%-2.0% calcium chloride by mass. The concentration of Aspergillus fungal spores relative to the total mass of the composite mineralization slurry is 0.1%-0.5%. After injection, a CaCO3 solidification network is formed in the deep fracture. The shallow barrier layer consists of a capillary barrier layer and a biomineralization layer from bottom to top. The capillary barrier layer is laid in layers of coarse and fine particles. The coarse particle layer is continuously graded gravel with a particle size of 20mm-50mm and a mud content of ≤3%. The fine particle layer is silt with a particle size of 0.005mm-0.075mm. The biomineralization layer contains rain-sensing microbial capsules, which encapsulate bacterial cells, nutrients, and humidity-sensitive hydrogel in a mass ratio of 1:10:50. The surface ecological layer comprises a planting layer and an ecological landscape layer. The planting layer is an improved planting soil containing humus and a water-retaining agent. The humus is derived from peat moss or well-rotted straw with an organic matter content ≥30%. The water-retaining agent is sodium polyacrylate with a water absorption ratio of 300-500 times, and its mass percentage in the improved planting soil is 0.12%-0.5%. The pH value of the improved planting soil is controlled at 6.8-7.5. The ecological landscape layer consists of a vegetation community and ecological bags. The vegetation community uses a mixture of bermudagrass and alfalfa at a mass ratio of 1-2:1. The bermudagrass seeds have a purity ≥95% and a germination rate ≥85%, and the alfalfa seeds have a purity ≥95% and a germination rate ≥85%. The total sowing amount is 20-30 g / m². 2 The eco-bags are made of polypropylene and weigh 100-150g / m³. 2 The tensile strength is ≥10kN / m. The bags are filled with improved planting soil and grass seeds that are consistent with the composition of the planting layer. The grass seeds are bermudagrass seeds or alfalfa seeds. The ecological bags are laid along the contour lines of the slope. The bags are fixed together by double tenon fasteners made of PP material to form a grid-like constraint structure. The double tenon fasteners are 20-30mm long and 15-20mm wide. The grid side length of the grid-like constraint structure is 50cm-100cm.

[0005] As a further technical solution, the Aspergillus spores in the deep fissure repair layer are either Aspergillus niger spores or Aspergillus flavus spores.

[0006] As a further technical solution, in the composite mineralized slurry of the deep fracture repair layer, the crude urease solution is derived from sword bean extract and soybean extract, with the crude urease solution extracted from sword bean having an extraction rate of ≥80% and the crude urease solution extracted from soybean having an extraction rate of ≥75%, and the enzyme activity of the crude urease solution from all sources being ≥1000U / g; the volume ratio of crude urease solution to urease solution containing bacterial cells is 1:2-5.

[0007] As a further technical solution, the preparation method of the calcium-based bentonite modified with γ-polyglutamic acid is as follows: the calcium-based bentonite has a montmorillonite content ≥70% and a cation exchange capacity ≥80meq / 100g, and is soaked in a γ-polyglutamic acid aqueous solution with a mass concentration of 0.5%-2%, wherein the γ-polyglutamic acid in the aqueous solution has a molecular weight of 50-100kDa and a purity ≥90%; the soaking process is carried out at 25-35℃ and pH 6.0-7.0 for 12-24h, and then the soaked calcium-based bentonite is dried at 60-80℃ until the moisture content is ≤10%, and then pulverized and passed through a 20-50 mesh sieve.

[0008] As a further technical solution, in the shallow barrier layer, the coarse-grained layer has a thickness of 15cm-30cm and a compaction degree of ≥90%; the fine-grained layer has a thickness of 5cm-15cm and a compaction degree of ≥90%.

[0009] As a further technical solution, in the biomineralized layer, the rain-sensing microbial capsules have a particle size of 1-5 mm and a particle size deviation of ≤ ±0.5 mm, and a capsule wall thickness of 0.1-0.3 mm; CaCO3 crystals fill the internal pores of the biomineralized layer through a mineralization reaction, and after filling, the porosity of the biomineralized layer is reduced to below 15%.

[0010] As a further technical solution, the nutrient is a deionized aqueous solution containing 1%-5% urea, 0.5%-3% calcium chloride, and 0.1%-0.5% yeast extract by mass concentration, and the humidity-sensitive hydrogel is a poly(N-isopropylacrylamide) hydrogel that swells and ruptures when the ambient humidity is ≥80%RH.

[0011] As a further technical solution, in the planting layer of the surface ecological layer, the humus accounts for 8%-15% of the mass of the improved planting soil; the dry density of the improved planting soil is 1.3-1.5 g / cm³. 3 Furthermore, the porosity is 35%-45%; the water-retaining agent has a dispersion uniformity of ≥90% in the improved planting soil.

[0012] As a further technical solution, in the ecological landscape layer, the mixed sowing of bermudagrass and alfalfa adopts a row sowing method with a row spacing of 20-30cm and a sowing depth of 1-2cm; the size of the ecological bags is 40cm×60cm with a size deviation of ±2cm, and the compaction degree of the filling material in the bags is ≥85%; the insertion depth of the double tenon connector is ≥10mm and the connection strength is ≥500N / each; the grid side length deviation of the grid-like constraint structure is ≤±5cm, and the flatness of the ecological bag slope laying is ≤5cm / 2m.

[0013] As a further technical solution, the bacterial cells are Bacillus spheroidae; the concentration of the bacterial cells in the urease solution is 10. 6 -108 CFU / mL; pH of the urease-containing bacterial solution is 7.0-7.5.

[0014] The beneficial effects of this invention are as follows: 1. This invention constructs a full-depth protection system consisting of a deep fissure repair layer, a shallow barrier layer, and a surface ecological layer. The core features of each layer form a progressive synergy from the microscopic mechanism of action to the macroscopic protection effect, effectively solving the problems of disconnect between reinforcement and ecology and insufficient long-term stability in traditional expansive soil slope repair. In the deep fracture repair layer, the multi-component combination of the composite mineralization slurry has a clear microscopic functional orientation: Bacillus spheroidae provides a functional source for the MIP reaction, and its metabolic process can react with urea and calcium chloride in the cementing solution to generate calcium carbonate crystals. The crude urease solution can accelerate this reaction through enzymatic action, significantly shortening the natural mineralization cycle and preventing the fractures from remaining unfilled for a long time. γ-polyglutamic acid modified calcium-based bentonite, with the high molecular adsorption and dispersibility of γ-polyglutamic acid, not only enhances the bonding stability of the slurry during the injection process and prevents the slurry from flowing along the fractures, but also guides the orderly growth of calcium carbonate crystals, avoiding the disordered accumulation of crystals that form new pores. Aspergillus fungal spores can grow slowly after injection according to environmental conditions, further filling the micro fractures not covered by MIP mineralization, forming a dual fracture repair mechanism of bacterial mineralization and fungal filling. It is the synergistic effect of these microscopic components that enables the composite mineralized slurry to form a continuous and dense CaCO3 solidification network within deep fissures. This network fills the pores and fissures between soil particles at the microscopic level, enhancing the cementation strength between particles. This solves the problems of poor overall integrity and easy rainwater infiltration along fissures leading to deep softening in expansive soil slopes caused by fissure development. Macroscopically, it reduces the impermeability coefficient of deep soil to 10. -7 With a strength at the cm / s level, the unconfined compressive strength is increased to over 780 kPa, laying a deep foundation for the structural stability of the entire slope.

[0015] 2. The shallow barrier layer, through the synergistic combination of physical capillary retraction and chemical-biomineralization, constructs a dual barrier against water infiltration, overcoming the shortcomings of traditional single physical barriers or chemical reinforcement. In the capillary retraction layer, the coarse-grained layer, with its large pore structure, enables rapid drainage of surface rainwater, preventing water accumulation on the shallow soil surface. The fine-grained layer utilizes the capillary properties of fine particles to form a capillary water uplift fracture zone between the coarse-grained layer and the deeper soil, microscopically blocking capillary water migration to deeper layers through the water potential difference generated by the gradation difference, achieving preliminary water blocking at the physical level. Meanwhile, the rain-sensing microbial capsules in the biomineralization layer have environmentally responsive characteristics. When the ambient humidity is ≥80%RH, the poly(N-isopropylacrylamide) hydrogel swells and ruptures, releasing bacteria and nutrients that rapidly undergo a mineralization reaction. The generated CaCO3 crystals microscopically fill any tiny pores that may exist in the capillary retraction layer, reducing the porosity of the biomineralization layer to below 15%. This synergistic effect of physical water blocking and chemical pore sealing not only solves the problem of water blocking failure caused by construction gaps or particle size distribution deviations due to physical barriers alone, but also avoids the shortcomings of chemical mineralization alone, which cannot respond to changes in environmental humidity and has a delayed mineralization timing. Macroscopically, it effectively reduces the fluctuation of moisture content in shallow soil, inhibits the volume expansion of expansive soil caused by changes in moisture content, and improves the shear strength of shallow soil. This reduces the pressure of water infiltration for deep protection systems, forming a progressive protection logic of shallow water blocking and deep reinforcement.

[0016] 3. The surface ecological layer achieves integrated ecological restoration and surface reinforcement through the ecological-structural synergy of improved planting soil, ecological bags, and vegetation communities, breaking the limitations of traditional restoration methods that prioritize ecology over reinforcement or vice versa. In the improved planting soil, humus improves soil particle structure at the microscopic level, enhancing soil aeration and fertility, providing basic conditions for vegetation growth; sodium polyacrylate water-retaining agent maintains stable soil moisture content through microscopic water absorption and slow release, preventing sudden changes in moisture caused by drought or rain erosion; ecological bags are laid along slope contour lines and connected by double tenons to form a grid-like constraint structure, physically encapsulating the surface soil at the microscopic level, preventing surface soil from peeling off due to rain erosion or gravity; the mixed sowing of bermudagrass and alfalfa allows their roots to interweave between soil particles at the microscopic level during growth, forming a biological root network, further enhancing the bonding strength of the surface soil. The synergistic effect of these features provides multiple safeguards at the micro level, including soil fertility, moisture stability, physical constraints, and biological soil stabilization. At the macro level, it increases vegetation coverage to over 88% while enhancing the erosion resistance of the topsoil. From an overall perspective, deep reinforcement addresses the fundamental issue of slope structural stability, shallow water blocking eliminates the incentive for expansive soil to swell when exposed to water, and surface ecology enables long-term ecological restoration and surface protection. This three-layer system forms a comprehensive, resilient protection system encompassing deep stability control, shallow water control, and surface ecological control. Ultimately, it solves the core problems of traditional expansive soil slope restoration—where short-term effects are significant but long-term failures are common, and structural reinforcement and ecological restoration are difficult to achieve simultaneously. This approach achieves the dual sustainable goals of slope safety and stability and ecological environment restoration. Attached Figure Description

[0017] Figure 1 This is a diagram illustrating an integrated, resilient, ecologically sound structure for the restoration and reinforcement of expansive soil slopes. 1. Deep fissure repair layer; 2. Shallow barrier layer; 3. Surface ecological layer; 4. CaCO3 crystals; 5. Bacterial cells; 6. Ecological landscape layer; 7. Biomineralization layer; 8. Planting layer; 9. Fine-grained layer; 10. Coarse-grained layer; 11. CaCO3 solidification network. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] An integrated resilient ecological restoration and reinforcement method for expansive soil slopes includes, from the inside to the outside, a deep fissure repair layer 1, a shallow barrier layer 2, and a surface ecological layer 3 along the depth direction of the expansive soil slope. The three layers work together to form a comprehensive protection system of "repair-seepage prevention-ecology". The deep fracture repair layer 1 is constructed using a targeted injection composite mineralization slurry. The composite mineralization slurry is composed of MICP reaction solution, crude urease solution, calcium-based bentonite modified with γ-polyglutamic acid γ-PGA, and Aspergillus spores. The MICP reaction solution contains urease solution containing bacterial cells 5 and a cementing solution. The cementing solution is an aqueous solution containing 0.5%-1.5% urea and 0.8%-2.0% calcium chloride by mass. The concentration of Aspergillus spores relative to the total mass of the composite mineralization slurry is 0.1%-0.5%. After injection, a CaCO3 solidification network 11 is formed in the deep fracture. The shallow barrier layer 2 consists of a capillary retardation layer and a biomineralization layer 7, arranged from bottom to top. The capillary retardation layer is laid in two layers: a coarse-grained layer 10 and a fine-grained layer 9. The coarse-grained layer 10 is continuously graded gravel with a particle size of 20mm-50mm and a mud content of ≤3%. The fine-grained layer 9 is silt with a particle size of 0.005mm-0.075mm and a plasticity index IP=10-17. The biomineralization layer 7 contains rain-sensing microbial capsules, which encapsulate bacterial cells 5, nutrients, and humidity-sensitive hydrogel. The mass ratio is 1:10:50. The nutrients are a deionized aqueous solution containing 1%-5% urea, 0.5%-3% calcium chloride, and 0.1%-0.5% yeast extract. The humidity-sensitive hydrogel is a poly(N-isopropylacrylamide) PNIPAM-based hydrogel, which swells and ruptures when the ambient humidity is ≥80%RH. The rain-sensing microbial capsule swells and ruptures when rainwater seeps in, causing the ambient humidity to be ≥80%RH, releasing internal components to initiate a mineralization reaction and generate CaCO3 crystals. The surface ecological layer 3 includes a planting layer 8 and an ecological landscape layer 6. Planting layer 8 is an improved planting soil containing humus and a water-retaining agent. The humus is derived from peat moss or well-rotted straw with an organic matter content ≥30%. The water-retaining agent is sodium polyacrylate with a water absorption ratio of 300-500 times that of deionized water. At 25℃, the water-retaining agent accounts for 0.12%-0.5% of the improved planting soil by mass, and the pH value of the improved planting soil is controlled at 6.8-7.5. Ecological landscape layer 6 consists of a vegetation community and ecological bags. The vegetation community uses a mixture of bermudagrass and alfalfa at a mass ratio of 1:1-2:1. The bermudagrass seeds have a purity ≥95% and a germination rate ≥85%, and the alfalfa seeds have a purity ≥95% and a germination rate ≥85%. The total sowing amount is 20-30 g / m². 2 The eco-bags are made of polypropylene and weigh 100-150g / m³. 2 Furthermore, the tensile strength is ≥10kN / m. The bags are filled with improved planting soil and grass seeds that are consistent with the 8 components of the planting layer. The grass seeds are bermudagrass seeds or alfalfa seeds with the same parameters as mentioned above. The ecological bags are laid along the contour lines of the slope. The bags are fixed together by double tenon fasteners made of PP material to form a grid-like constraint structure. The double tenon fasteners are 20-30mm long and 15-20mm wide. The grid side length of the grid-like constraint structure is 50cm-100cm.

[0020] In the deep fracture repair layer 1, the Aspergillus fungal spores are either Aspergillus niger spores or Aspergillus flavus spores. The Aspergillus niger spores are strain CGMCC No. 40231 (refer to 202211635261.1, A type of Aspergillus niger and its application), and the Aspergillus flavus spores are strain CGMCC No. 23268 (refer to 202111501827.7, A type of Aspergillus flavus and its application). After germination in the composite mineralization slurry, the fungal spores form a three-dimensional hyphal network. This hyphal network works synergistically with the CaCO3 solidification network 11 to enhance the integrity of the deep soil through a biological reinforcement effect. At the same time, the fungi produce oxalic acid through metabolism. The oxalic acid combines with calcium ions in the environment to form calcium oxalate. This calcium oxalate and the calcium carbonate in the CaCO3 solidification network 11 constitute a mixed mineralization system.

[0021] In the composite mineralized slurry of the deep fracture repair layer 1, the crude urease solution was derived from sword bean extraction, soybean extraction, or microbial fermentation. The extraction rate of crude urease solution from sword bean extraction was ≥80%, and the extraction rate of crude urease solution from soybean extraction was ≥75%. The crude urease solution from microbial fermentation was produced by Bacillus pasteurellii, and the enzyme activity of the fermentation broth was ≥1500 U / mL. The enzyme activity of crude urease solution from all sources was ≥1000 U / g. The volume ratio of crude urease solution to urease bacterial solution containing 5 bacterial cells was 1:2-5. The calcium-based bentonite modified with γ-polyglutamic acid was used in the preparation... The preparation method is as follows: the calcium-based bentonite has a montmorillonite content ≥70% and a cation exchange capacity ≥80 meq / 100g. The calcium-based bentonite is soaked in a 0.5%-2% (w / w) γ-polyglutamic acid aqueous solution. The γ-polyglutamic acid in the aqueous solution has a molecular weight of 50-100kDa and a purity ≥90%. The soaking process is carried out at 25-35℃ and pH 6.0-7.0 for 12-24 hours. Then, the soaked calcium-based bentonite is dried at 60-80℃ until the moisture content is ≤10%. After pulverizing, it is passed through a 20-50 mesh sieve.

[0022] The CaCO3 solidification network 11 formed in the deep fracture repair layer 1 is tightly bonded to the fracture wall, improving the properties of the deep soil through the "crusting effect" and "reinforcement effect". The "crusting effect" is manifested in the formation of a dense solidified layer with a thickness of 1-3 mm on the fracture surface, and the "reinforcement effect" is manifested in the formation of a solidified body that penetrates the fracture with a diameter of 2-5 mm. The shear strength of the soil after repair is increased by 30%-50% compared with that before repair. The shear strength test is a direct shear test with a vertical pressure of 100 kPa. The fracture rate of the soil after repair is the volumetric fracture rate and is reduced to below 5%.

[0023] In the shallow barrier layer 2, the coarse-grained layer 10 has a thickness of 15cm-30cm, a compaction degree of ≥90%, and the compaction degree test adopts the heavy compaction standard with a maximum dry density of 1.9-2.1g / cm³.3 The fine-grained layer 9 is laid with a thickness of 5cm-15cm, and the compaction degree is ≥90%. The compaction degree test adopts the heavy compaction standard, and the maximum dry density is 1.6-1.8g / cm³. 3 The capillary force difference at the interface between coarse and fine particles hinders the downward infiltration of rainwater, and the capillary force difference is manifested as a capillary rise height ≥20cm.

[0024] In the biomineralized layer 7, the rain-sensing microbial capsules have a particle size of 1-5 mm with a particle size deviation ≤ ±0.5 mm, and a capsule wall thickness of 0.1-0.3 mm; the mass ratio of nutrients to bacterial cells 5 is 6-10:1; CaCO3 crystals 4 fill the internal pores of the biomineralized layer 7 through a mineralization reaction, reducing the porosity of the biomineralized layer 7 to below 15% after filling; after the mineralization reaction, the permeability coefficient of the shallow soil decreases to 1×10⁻⁶. -6 For flow rates below cm / s, the permeability coefficient is tested using a variable head permeability test.

[0025] In the planting layer 8 of the top ecological layer 3, humus accounts for 8%-15% of the mass of the improved planting soil; the dry density of the improved planting soil is 1.3-1.5 g / cm³. 3 Furthermore, the porosity is 35%-45%; the water-retaining agent has a dispersion uniformity of ≥90% in the improved planting soil, and the dispersion uniformity is tested by random sampling with a coefficient of variation ≤10%; the water-retaining agent is used to provide continuous water supply for the growth of vegetation communities in ecological landscape layer 6, and the water retention period is ≥7 days after a single watering.

[0026] In ecological landscape layer 6, the mixed sowing of bermudagrass and alfalfa is carried out using row sowing, with a row spacing of 20-30cm and a sowing depth of 1-2cm. The size of the ecological bags is 40cm×60cm with a dimensional deviation of ±2cm. The compaction degree of the filling material in the bags is ≥85%, and the compaction degree test uses the dry density index with a dry density of 1.2-1.4g / cm³. 3 The insertion depth of the double tenon connector is ≥10mm and the connection strength is ≥500N / piece; the grid side length deviation of the grid-like constraint structure is ≤±5cm, and the flatness of the ecological bag slope laying is ≤5cm / 2m.

[0027] Bacterial cell 5 was a *Bacillus spheroidae* strain with preservation number GDMCC No: 64032 (refer to 202410104404.9, A *Bacillus spheroidae* and its application); the concentration of bacterial cell 5 in the urease solution was 10. 6 -10 8CFU / mL, concentration was determined using plate counting; the pH of the urease bacterial solution was 7.0-7.5, and the shelf life was ≥30 days under storage conditions of 2-8℃; in the deep fracture repair layer 1, bacterial cells 5 were responsible for long-term sustainable mineralization, with a mineralization duration of ≥90 days, to maintain the structural stability of the CaCO3 solidification network 11, and the compressive strength of the CaCO3 solidification network 11 was ≥1.5MPa; in the biomineralization layer 7, bacterial cells 5 participated in the immediate mineralization reaction, with a mineralization initiation time of ≤24h, to rapidly generate CaCO3 crystals 4, and the amount of CaCO3 crystals 4 generated within 24h was ≥0.5g / cm³. 3 .

[0028] The shallow barrier layer 2 blocks rainwater infiltration pathways through a synergistic "blocking-storage-drainage" effect: the capillary barrier layer composed of the coarse-grained layer 10 and the fine-grained layer 9 slows down the infiltration rate of rainwater; the CaCO3 crystals 4 generated in the biomineralization layer 7 enhance the seepage prevention effect, with a stable permeability coefficient ≤1×10 -6 cm / s; the ecological landscape layer 6 of the surface ecological layer 3 reduces the soil moisture content of the planting layer 8 to 15%-20% through vegetation transpiration; the grid structure formed by the ecological bags inhibits the development of surface soil fissures, and the surface fissure rate is ≤2%; the CaCO3 solidification network 11 of the deep fissure repair layer 1, the seepage prevention system of the shallow barrier layer 2, and the ecological regulation system of the surface ecological layer 3 work together to achieve an overall stability coefficient of ≥1.3 for the expansive soil slope. The stability coefficient is calculated using the limit equilibrium method and is based on rainstorm conditions, achieving long-term safety protection for the expansive soil slope with a protection period of ≥5 years.

[0029] The following are specific examples: Example 1: Construction of deep fracture repair layer: (1) Preparation of MICP reaction solution: Bacillus spheroidae was selected as the bacterial cells, and urease bacterial solution was prepared by liquid fermentation. The concentration of bacterial cells in the urease bacterial solution was controlled to be 10 by counting with a hemocytometer. 7 CFU / mL; adjust the pH of the urease-containing bacterial solution to 7.2 using a pH adjuster (0.1 mol / L HCl or NaOH solution). Prepare the cementing solution: measure 1000 mL of deionized water, add 12 g of urea and 14 g of calcium chloride, and stir with a magnetic stirrer at 500 rpm for 30 min until completely dissolved. Control the mass concentration of urea to 1.2% and the mass concentration of calcium chloride to 1.4% to obtain the cementing solution. Pour the urease-containing bacterial solution and the cementing solution into a mixing tank at a volume ratio of 1:1, and stir for 15 min to mix thoroughly to obtain the MICP reaction solution.

[0030] (2) Preparation of crude urease solution: Fresh sword beans were selected, washed, and crushed. 0.02 mol / L phosphate buffer (pH 7.0) was added at a solid-liquid ratio of 1:5, and the mixture was extracted at 30℃ for 2 hours. The mixture was then filtered through gauze, and the filtrate was centrifuged (4000 r / min, 15 min). The supernatant was taken as the crude urease solution. The extraction rate of this crude urease solution was 82%, and the enzyme activity was 1050 U / g as determined by the urea colorimetric method. 300 mL of the crude urease solution was prepared at a volume ratio of 1:3 (crude urease solution to urease bacteria solution).

[0031] (3) Preparation of γ-polyglutamic acid modified calcium-based bentonite: Select calcium-based bentonite with 75% montmorillonite content and 85 meq / 100g cation exchange capacity. Prepare γ-polyglutamic acid aqueous solution: Measure 1000mL of deionized water, add 12g of γ-polyglutamic acid (γ-polyglutamic acid molecular weight 100kDa, purity 95%), stir to dissolve, and control the mass concentration of γ-polyglutamic acid aqueous solution to 1.2%. Weigh 500g of calcium-based bentonite and add it to the above γ-polyglutamic acid aqueous solution, and let it stand for 18h in a constant temperature water bath at 30℃ and pH 6.5. After standing, take out the calcium-based bentonite, put it in an oven, and dry it at 70℃. Check the moisture content every 2h until the moisture content drops to 8%. After drying, pulverize it with a universal pulverizer and pass it through a 30-mesh standard sieve to obtain γ-polyglutamic acid modified calcium-based bentonite.

[0032] (4) Preparation of composite mineralization slurry: Measure 1000 mL of MICP reaction solution and 300 mL of crude urease solution and pour them into a mixing tank. Add 200 g of calcium-based bentonite modified with γ-polyglutamic acid and 4.5 g of Aspergillus niger spores (the concentration of Aspergillus niger spores relative to the total mass of the composite mineralization slurry is 0.3%). Adjust the speed of the mixing tank to 300 r / min and stir for 20 min to ensure that all components are mixed evenly to obtain the composite mineralization slurry.

[0033] (5) Targeted grouting: Using a high-pressure targeted grouting device (model GP-30), the composite mineralized grout is injected into the deep fissures of the expansive soil slope. The grouting pressure is controlled at 0.3 MPa, and the grouting speed is 50 mL / min to ensure that the grout fills the fissures. After grouting, the soil is left to cure for 7 days to allow the mineralization reaction to complete and form a CaCO3 solidified network in the deep fissures, thus completing the construction of the deep fissure repair layer.

[0034] Shallow barrier layer laying: (1) Laying the capillary retardant layer: First, lay the coarse-grained layer, selecting continuously graded gravel, screening gravel with a particle size of 25mm to 40mm using a standard sieve, and testing the mud content using the water washing method to ensure it is 2.5%. Lay the gravel evenly along the shallow layer of the slope according to the requirement of a 20cm paving thickness. During the paving process, use a small road roller (model YZC10) to compact the gravel at a speed of 2km / h, and compact it 3 times to control the compaction degree to 92% (tested using the ring cutter method). After the coarse-grained layer is laid, lay the fine-grained layer, selecting silt with a particle size of 0.01mm to 0.06mm, and lay it according to the requirement of a 10cm paving thickness. After laying, use a small road roller to compact the gravel to control the compaction degree to 92%, thus completing the capillary retardant layer paving.

[0035] (2) Laying the biomineralization layer: Prepare rain-sensing microbial capsules. The capsules are filled using a capsule filling machine (model NJP-400) at a mass ratio of bacterial cells (Bacillus spheroidae), nutrients, and humidity-sensitive hydrogel (poly(N-isopropylacrylamide) hydrogel) of 1:10:50. The capsule particle size is controlled to be 3 mm (measured with calipers), with a particle size deviation of ±0.3 mm and a capsule wall thickness of 0.2 mm. Prepare the nutrients: Measure 1000 mL of deionized water, add 30 g of urea, 18 g of calcium chloride, and 3 g of yeast extract, stir to dissolve, and control the urea mass concentration to be 3%, the calcium chloride mass concentration to be 1.8%, and the yeast extract mass concentration to be 0.3%. Weigh 100 kg of biomineralization layer matrix (silt with the same composition as the fine-grained capillary barrier layer), add 5000 rain-sensing microbial capsules, stir evenly, and disperse at a density of 500 capsules per square meter. Then, lay the matrix containing the rain-sensing microbial capsules along the top of the capillary barrier layer to a thickness of 8 cm. After being laid and left to stand, the hydrogel swelled and ruptured when the ambient humidity reached 85%RH (measured with a thermometer and hygrometer), releasing bacterial cells and nutrients, and undergoing a mineralization reaction to generate CaCO3 crystals. After 14 days of curing, the porosity of the biomineralized layer was measured using mercury intrusion porosimetry, and the result was 12%, completing the laying of the shallow barrier layer.

[0036] Surface ecological layer construction: (1) Preparation of improved planting soil: 800 kg of ordinary planting soil (taken from the perimeter of the experimental site) was weighed, and 120 kg of humus (from peat moss, with an organic matter content of 35%, tested using the potassium dichromate oxidation-external heating method) and 2.76 kg of sodium polyacrylate water-retaining agent (water absorption ratio of 400 times, calculated based on a water-retaining agent mass ratio of 0.3%) were added. All components were poured into a mixer (model JS500) and stirred for 30 min at a stirring speed of 200 r / min. After stirring, the uniformity of water-retaining agent dispersion was tested using a random sampling method, and the result was 93%. The pH value of the improved planting soil was adjusted to 7.0 using 0.1 mol / L HCl or NaOH solution (tested using a pH meter), and the dry density was tested using the ring cutter method, which showed a density of 1.4 g / cm³. 3The porosity was found to be 40% using the drainage method, indicating that the soil was an improved planting soil.

[0037] (2) Construction of ecological landscape layer: Plant community sowing: Bermuda grass seeds (purity 96%, germination rate 88%, both tested according to GB / T2930.1-2017) and alfalfa seeds (purity 97%, germination rate 87%, tested according to GB / T2930.1-2017) were selected and mixed at a mass ratio of 1.5:1. The total sowing amount was calculated to be 25g / m². 2 Sowing was carried out using a row seeder (model 2BXF-10), with the row spacing adjusted to 25cm and the sowing depth to 1.5cm, to complete the sowing of the vegetation community. Ecological bags were laid: polypropylene ecological bags were selected, with a measured weight of 120g / m³. 2 The tensile strength is 12kN / m, and the dimensions are 40cm×60cm (measured with a tape measure), with a dimensional deviation of ±1.5cm. Each eco-bag is filled with 15kg of improved planting soil (identical to the planting layer composition) and 50g of Bermuda grass seeds. After filling, it is compacted using a compactor, controlling the compaction degree to be 88% (measured using the ring cutter method). Eco-bags are laid along the contour lines of the slope. After each row is laid, the bags are secured with PP double-tenon fasteners. The double-tenon fasteners are 25mm long, 18mm wide (measured with calipers), and have an insertion depth of 12mm. The connection strength is measured at 550N / fastener using a tensile tester. After fixing, a grid-like constraint structure is formed, controlling the grid side length to be 80cm (measured with a tape measure), with a side length deviation of ±3cm. The flatness of the eco-bag slope laying is measured at 4cm / 2m using a 2m straightedge, completing the construction of the surface ecological layer.

[0038] Example 2: Construction of a deep fracture repair layer: (1) Preparation of MICP reaction solution: Bacillus spheroidae was selected as the bacterial cells to prepare urease bacterial solution, and the concentration of bacterial cells in the urease bacterial solution was controlled at 10. 8 Adjust the pH of the urease-containing bacterial solution to 7.5 using CFU / mL. Prepare the cementing solution: Measure 1000 mL of deionized water, add 15 g of urea and 20 g of calcium chloride, stir to dissolve, and control the mass concentration of urea to 1.5% and the mass concentration of calcium chloride to 2.0% to obtain the cementing solution. Mix the urease-containing bacterial solution and the cementing solution at a volume ratio of 1:1, stir for 15 min, and obtain the MICP reaction solution.

[0039] (2) Preparation of crude urease solution: Crude urease solution was extracted from sword beans. The extraction rate was 85% and the enzyme activity was 1100 U / g. 500 mL of crude urease solution was prepared according to the volume ratio of crude urease solution to urease bacteria solution of 1:5.

[0040] (3) Preparation of calcium-based bentonite modified with γ-polyglutamic acid: Calcium-based bentonite with 80% montmorillonite content and 90 meq / 100g cation exchange capacity was selected. Aqueous solution of γ-polyglutamic acid (γ-polyglutamic acid molecular weight 100kDa, purity 95%) was prepared, and the mass concentration was controlled at 2.0%. The calcium-based bentonite was added to the aqueous solution and allowed to stand for 24h at 35℃ and pH 7.0. After standing, it was dried at 80℃ to a moisture content of 7%, pulverized, and passed through a 50-mesh sieve to obtain modified calcium-based bentonite.

[0041] (4) Preparation of composite mineralization slurry: Measure 1000mL MICP reaction solution and 500mL crude urease solution, add 250g modified calcium-based bentonite, and then add 7.5g Aspergillus flavus spores (concentration 0.5%). Stir at 350r / min for 25min until the mixture is homogeneous to obtain composite mineralization slurry.

[0042] (5) Targeted injection: High-pressure targeted injection equipment is used to inject composite mineralized slurry into deep fractures. The injection pressure is 0.4MPa and the injection speed is 60mL / min. After injection, the slurry is cured for 7 days to form a CaCO3 solidification network and complete the construction of the deep fracture repair layer.

[0043] Shallow barrier layer laying: (1) Laying the capillary barrier layer: Select continuously graded gravel with a particle size of 35mm to 50mm and a mud content of 2.8%, lay it with a thickness of 30cm, and compact it to a degree of 93% after rolling. Then lay silt with a particle size of 0.04mm to 0.075mm, with a thickness of 15cm, and compact it to a degree of 93% after rolling to complete the laying of the capillary barrier layer.

[0044] (2) Laying the biomineralization layer: Prepare rain-sensing microbial capsules (particle size 5 mm, deviation ±0.5 mm, wall thickness 0.3 mm), with urea mass concentration of 5%, calcium chloride 3.0%, and yeast extract 0.5% in the nutrients. Disperse the capsules in the matrix at a density of 600 capsules per square meter, lay a thickness of 10 cm, and after curing for 14 days, the porosity is tested and found to be 10%, thus completing the laying of the shallow barrier layer.

[0045] Surface ecological layer construction: (1) Preparation of improved planting soil: Measure 750 kg of ordinary planting soil, add 150 kg of humus (derived from decomposed straw, organic matter content 38%) and 4.5 kg of water-retaining agent (water absorption ratio 500 times, mass percentage 0.5%), stir for 35 min, and the dispersion uniformity is 95%. Adjust the pH value to 7.5 and test the dry density to 1.5 g / cm³. 3 With a porosity of 35%, improved planting soil was obtained.

[0046] (2) Constructing the ecological landscape layer: Select bermudagra seeds (purity 96%, germination rate 88%) and alfalfa seeds (purity 97%, germination rate 87%), mix them at a mass ratio of 2:1, and sow a total of 30g / m². 2 The row spacing for sowing is 30cm, and the sowing depth is 2cm. Polypropylene eco-bags (weight 150g / m²) are selected. 2 The soil (tensile strength 13kN / m) is filled with improved planting soil and alfalfa seeds, and compacted to 90%. It is laid along the slope and fixed with double tenon connectors (length 30mm, width 20mm, insertion depth 15mm, connection strength 600N / each) to form a grid structure with a side length of 100cm (deviation ±5cm). The flatness of the laying is 5cm / 2m, thus completing the construction of the surface ecological layer.

[0047] Example 3: Construction of a deep fracture repair layer: (1) Preparation of MICP reaction solution: Bacillus spheroidae was selected as the bacterial cells to prepare urease bacterial solution, and the bacterial cell concentration was controlled at 10. 6 CFU / mL, pH 7.0. Preparation of cementing solution: Measure 1000mL of deionized water, add 8g of urea and 8g of calcium chloride, stir to dissolve, the mass concentration of urea is 0.8% and the mass concentration of calcium chloride is 0.8%. Mix the urease bacteria solution with the cementing solution at a ratio of 1:1 to obtain the MICP reaction solution.

[0048] (2) Preparation of crude urease solution: Crude urease solution was extracted from soybeans with an extraction rate of 75% and an enzyme activity of 1000 U / g. 200 mL was measured at a volume ratio of 1:2 for later use.

[0049] (3) Preparation of calcium-based bentonite modified with γ-polyglutamic acid: Calcium-based bentonite with 70% montmorillonite content and 80 meq / 100g cation exchange capacity was selected, and γ-polyglutamic acid aqueous solution (γ-polyglutamic acid molecular weight 100kDa, purity 95%) was prepared with a mass concentration of 0.5%. The calcium-based bentonite was added to the aqueous solution, and allowed to stand for 12h at 25℃ and pH 6.0. It was then dried at 60℃ to a moisture content of 10%, pulverized and passed through a 20-mesh sieve to obtain modified calcium-based bentonite.

[0050] (4) Preparation of composite mineralization slurry: Measure 1000mL of MICP reaction solution and 200mL of crude urease solution, add 150g of modified calcium-based bentonite, and then add 1.5g of Aspergillus niger spores (concentration 0.1%). Stir at 250r / min for 15min to obtain composite mineralization slurry.

[0051] (5) Targeted infusion: Infusion pressure 0.2MPa, speed 40mL / min, curing for 7 days to form a CaCO3 solidification network and complete the construction of deep fracture repair layer.

[0052] Shallow barrier layer laying: (1) Laying capillary barrier layer: Select gravel with a particle size of 20mm to 30mm and a mud content of 2.2%, lay it with a thickness of 15cm and a compaction degree of 90%; then lay silt with a particle size of 0.005mm to 0.03mm, a thickness of 5cm and a compaction degree of 90%, to complete the laying of capillary barrier layer.

[0053] (2) Laying the biomineralization layer: Prepare rain-sensing microbial capsules (particle size 1 mm, deviation ±0.2 mm, wall thickness 0.1 mm), with 1% urea, 0.5% calcium chloride and 0.1% yeast extract in the nutrients, dispersed at a density of 400 particles per square meter, laid with a thickness of 6 cm, and after curing for 14 days, the porosity is 14%, thus completing the laying of the shallow barrier layer.

[0054] Surface ecological layer construction: (1) Preparation of improved planting soil: Measure 870 kg of ordinary planting soil, add 80 kg of humus (peat source, organic matter content 30%) and 1.14 kg of water-retaining agent (water absorption ratio 300 times, mass percentage 0.12%), stir for 25 min, and the dispersion uniformity is 90%. Adjust the pH value to 6.8 and test the dry density to 1.3 g / cm³. 3 With a porosity of 45%, improved planting soil was obtained.

[0055] (2) Constructing the ecological landscape layer: Select bermudagra seeds (96% purity, 88% germination rate) and alfalfa seeds (97% purity, 87% germination rate), mix them at a mass ratio of 1:1, and sow a total of 20g / m². 2 The row spacing for sowing is 20cm, and the sowing depth is 1cm. Polypropylene eco-bags (100g / m²) are selected. 2 The soil is filled with improved planting soil and bermudagrass seeds, with a compaction degree of 85%. It is fixed with double tenon connectors (length 20mm, width 15mm, insertion depth 10mm, connection strength 500N / each) to form a grid structure with a side length of 50cm (deviation ±2cm). The flatness of the laying is 3cm / 2m, and the surface ecological layer is completed.

[0056] Verification test on the effect of integrated toughness ecological restoration and reinforcement of expansive soil slopes: Test Samples: Expansive soil slope samples from Examples 1, 2, and 3 that underwent repair and reinforcement were selected. Each sample measured 1m × 1m × 0.5m (length × width × height). Three parallel samples were prepared for each group. Samples were taken from the same expansive soil slope site to ensure consistent initial soil properties (initial expansion rate 9.2%, unconfined compressive strength 380kPa, permeability coefficient 9.5 × 10⁻⁶). -5 (cm / s).

[0057] Comparative sample: Comparative Example 1: Using the same process as Example 1, but without constructing a deep crack repair layer, only a shallow barrier layer and a surface ecological layer were retained, and 1m×1m×0.5m samples were prepared, with 3 parallel samples.

[0058] Comparative Example 2: Using the same process as Example 1, but without constructing a shallow barrier layer, only retaining the deep crack repair layer and the surface ecological layer, a 1m×1m×0.5m sample was prepared, with 3 parallel samples.

[0059] Comparative Example 3: A traditional hydroseeding ecological restoration method was used (only the surface layer was hydroseeded with a mixture of bermudagrass and alfalfa, the seed ratio and dosage were the same as in Example 1, without deep or shallow protection), and 1m×1m×0.5m samples were prepared, with 3 parallel samples.

[0060] Test method: Swelling rate test: Refer to the "Standard for Geotechnical Testing Methods" (GB / T50123-2019). Cut each sample into ring specimens with a diameter of 61.8 mm and a height of 20 mm. Take 3 ring specimens for each sample and place them in a WG type dilatometer. Add distilled water to immerse the specimens and record the initial reading. Then, take readings every 1 hour. Stop taking readings after 24 hours. Calculate the swelling rate according to the formula "Swelling rate = (Swelling height - Initial height) / Initial height × 100%" and take the average value of 3 parallel specimens.

[0061] Unconfined compressive strength test: Refer to the "Standard for Geotechnical Testing Methods" (GB / T50123-2019). Cut each specimen into a cylindrical specimen with a diameter of 50 mm and a height of 100 mm. Take 3 cylindrical specimens for each sample. Use a YAW-300B compression testing machine and apply a uniform loading rate of 1 mm / min. Record the maximum pressure at specimen failure. Calculate the strength value according to the formula "Unconfined compressive strength = Maximum pressure / Specimen cross-sectional area". Take the average value of 3 parallel specimens.

[0062] Permeability coefficient test: Refer to the "Standard for Geotechnical Testing Methods" (GB / T50123-2019). Cut each sample into a cylindrical specimen with a diameter of 100 mm and a height of 50 mm. Take 3 cylindrical specimens for each sample and install them in a TST-55 variable head permeameter. Apply a constant head difference of 50 cm and record the initial head height and initial time. Then record the head height and time every 5 minutes for 30 minutes. Calculate the permeability coefficient according to the variable head permeability coefficient formula and take the average value of 3 parallel specimens.

[0063] Vegetation coverage test: Referencing the "Technical Specification for Ecological Restoration of Slopes" (GB / T28577-2012), five 10cm × 10cm square quadrats were evenly set up within each 1m × 1m sample area. Each quadrat was covered with transparent graph paper (1mm accuracy). The number of grid squares covered by vegetation was counted. The vegetation coverage rate for each quadrat was calculated using the formula: "Vegetation coverage rate = (Number of covered squares / Total number of squares) × 100%". The average of the five quadrats was taken. The test was conducted 60 days after restoration (to ensure stable vegetation growth). The results are as follows: Table 1

[0064] As shown in the table above, the expansion rates of Examples 1, 2, and 3 are all below 3%, which is much lower than the initial expansion rate of 9.2%, indicating that the method of the present invention can effectively suppress the expansion characteristics of expansive soil; the unconfined compressive strength is above 750 kPa, which is significantly higher than the initial strength of 380 kPa, demonstrating a good reinforcement effect and effectively reducing the permeability of the slope; the vegetation coverage is above 85%, achieving a good ecological restoration effect.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated, resilient, ecological restoration and reinforcement method for expansive soil slopes, characterized in that, Along the depth direction of the expansive soil slope, from the inside to the outside, there are three layers: a deep crack repair layer (1), a shallow barrier layer (2), and a surface ecological layer (3), which together form a protective system. The deep fracture repair layer (1) is constructed using a targeted injection composite mineralization slurry. The composite mineralization slurry is composed of MICP reaction solution, crude urease solution, calcium-based bentonite modified with γ-polyglutamic acid, and Aspergillus fungal spores. The MICP reaction solution contains urease solution containing bacterial cells (5) and a cementing solution. The cementing solution is an aqueous solution containing 0.8%-1.5% urea and 0.8%-2.0% calcium chloride by mass. The concentration of Aspergillus fungal spores relative to the total mass of the composite mineralization slurry is 0.1%-0.5%. After injection, a CaCO3 solidification network (11) is formed in the deep fracture. The shallow barrier layer (2) consists of a capillary barrier layer and a biomineralization layer (7) from bottom to top. The capillary barrier layer is laid in layers of coarse-grained layer (10) and fine-grained layer (9). The coarse-grained layer (10) is continuously graded gravel with a particle size of 20mm-50mm and a mud content of ≤3%. The fine-grained layer (9) is silt with a particle size of 0.005mm-0.075mm. The biomineralization layer (7) contains rain-sensing microbial capsules, which encapsulate bacterial cells (5), nutrients, and humidity-sensitive hydrogel in a mass ratio of 1:10:

50. The surface ecological layer (3) includes a planting layer (8) and an ecological landscape layer (6). The planting layer (8) is an improved planting soil containing humus and a water-retaining agent. The humus comes from peat moss or decomposed straw and has an organic matter content of ≥30%. The water-retaining agent is sodium polyacrylate and has a water absorption ratio of 300-500 times. The water-retaining agent accounts for 0.12%-0.5% of the mass of the improved planting soil. The pH value of the improved planting soil is controlled at 6.8-7.

5. The ecological landscape layer (6) consists of a vegetation community and ecological bags. The vegetation community is a mixture of bermudagrass and alfalfa at a mass ratio of 1-2:

1. The bermudagrass seeds have a purity of ≥95% and a germination rate of ≥85%. The alfalfa seeds have a purity of ≥95% and a germination rate of ≥85%. The total sowing amount is 20-30g / m². 2 The eco-bags are made of polypropylene and weigh 100-150g / m³. 2 And the tensile strength is ≥10kN / m. The bag is filled with improved planting soil and grass seeds with the same composition as the planting layer (8). The grass seeds are bermudagrass seeds or alfalfa seeds. The ecological bags are laid along the contour lines of the slope. The bags are fixed together by PP material double tenon fasteners to form a grid-like constraint structure. The double tenon fasteners are 20-30mm long and 15-20mm wide. The grid side length of the grid-like constraint structure is 50cm-100cm.

2. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the deep fissure repair layer (1), the Aspergillus fungal spores are either Aspergillus niger spores or Aspergillus flavus spores.

3. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the composite mineralized slurry of the deep fracture repair layer (1), the crude urease solution is derived from sword bean extract and soybean extract. The crude urease solution extracted from sword bean has an extraction rate of ≥80%, and the crude urease solution extracted from soybean has an extraction rate of ≥75%. The enzyme activity of the crude urease solution from all sources is ≥1000U / g. The volume ratio of the crude urease solution to the urease solution containing bacterial cells (5) is 1:2-5.

4. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, The preparation method of the calcium-based bentonite modified with γ-polyglutamic acid is as follows: the calcium-based bentonite has a montmorillonite content ≥70% and a cation exchange capacity ≥80 meq / 100g. The calcium-based bentonite is soaked in a γ-polyglutamic acid aqueous solution with a mass concentration of 0.5%-2%, the γ-polyglutamic acid in the aqueous solution has a molecular weight of 50-100kDa and a purity ≥90%. The soaking process is carried out at 25-35℃ and pH 6.0-7.0 for 12-24h. Then, the soaked calcium-based bentonite is dried at 60-80℃ until the moisture content is ≤10%, pulverized and passed through a 20-50 mesh sieve.

5. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the shallow barrier layer (2), the coarse-grained layer (10) has a laying thickness of 15cm-30cm and a laying compaction degree of ≥90%; the fine-grained layer (9) has a laying thickness of 5cm-15cm and a laying compaction degree of ≥90%.

6. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the biomineralized layer (7), the particle size of the rain-sensing microbial capsule is 1-5 mm and the particle size deviation is ≤ ±0.5 mm, and the capsule wall thickness is 0.1-0.3 mm; CaCO3 crystals (4) fill the internal pores of the biomineralized layer (7) through mineralization reaction, and the porosity of the biomineralized layer (7) is reduced to below 15% after filling.

7. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 6, characterized in that, The nutrients are a deionized aqueous solution containing 1%-5% urea, 0.5%-3% calcium chloride, and 0.1%-0.5% yeast extract by mass concentration. The humidity-sensitive hydrogel is a poly(N-isopropylacrylamide) hydrogel, which swells and ruptures when the ambient humidity is ≥80%RH.

8. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the planting layer (8) of the surface ecological layer (3), the mass ratio of humus in the improved planting soil is 8%-15%; the dry density of the improved planting soil is 1.3-1.5 g / cm³. 3 Furthermore, the porosity is 35%-45%; the water-retaining agent has a dispersion uniformity of ≥90% in the improved planting soil.

9. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, In the ecological landscape layer (6), the mixed sowing of bermudagrass and alfalfa is carried out by row sowing, with a row spacing of 20-30cm and a sowing depth of 1-2cm; the size of the ecological bag is 40cm×60cm with a size deviation of ±2cm, and the compaction degree of the filling material in the bag is ≥85%; the insertion depth of the double tenon connection buckle is ≥10mm and the connection strength is ≥500N / each; the grid side length deviation of the grid-like constraint structure is ≤±5cm, and the flatness of the ecological bag slope is ≤5cm / 2m.

10. The integrated resilient ecological restoration and reinforcement method for expansive soil slopes according to claim 1, characterized in that, The bacterial cell (5) is a spherical Bacillus; the concentration of the bacterial cell (5) in the urease solution is 10. 6 -10 8 CFU / mL; pH of the urease-containing bacterial solution is 7.0-7.5.

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