Slope ecological restoration substrate based on multi-stage collaborative curing and layered spray seeding method

Abstract

This invention discloses a slope ecological restoration substrate based on multi-level synergistic solidification and a layered spraying method, belonging to the field of geotechnical engineering and ecological restoration technology. This invention proposes a three-layer synergistic substrate system and dynamic construction process. In the substrate, the bottom layer uses modified volcanic ash and nano-silica sol as cementing materials to enhance rock surface penetration and adhesion; the middle layer uses chitosan slow-release particles and a gradient moisture content design to achieve phased nutrient release and interlayer stress buffering; the surface layer combines a 3D honeycomb biochar carrier and a biodegradable PLA grid, simultaneously loading grass seeds and mycorrhizal fungi to form a "physical-biological" composite anchoring structure. The construction method of this invention includes high-frequency micro-vibration infiltration, layered gradient spraying, and photosensitive non-woven fabric covering technology to ensure the substrate's resistance to rain erosion and rapid vegetation cover. This invention combines mechanical stability and ecological compatibility, is suitable for the restoration of steep rock slopes, and significantly reduces maintenance costs and environmental pollution risks.

Description

Technical Field

[0001] This invention relates to the fields of geotechnical engineering and ecological restoration technology, and in particular to a slope ecological restoration substrate based on multi-level synergistic solidification and a layered spraying method. Background Technology

[0002] Slope ecological restoration technologies mainly include methods such as topsoil spraying, vegetation concrete, and eco-bags. The core objective is to achieve soil stability and vegetation restoration through substrate improvement. In recent years, related research has focused on the following directions: 1) Using cement-organic polymer composite cementitious materials to improve the strength of the substrate in the short term, but excessive cement content (>15%) can easily lead to soil alkalization (pH>9.0), inhibiting plant root development; 2) Proposing "fiber-reinforced spraying substrate", which improves tensile strength by adding polypropylene fibers (0.5-1.5%), but the bonding force between the fiber and the substrate interface is insufficient, and it is easy to delaminate under heavy rain; 3) Designing a layered spraying process (bottom bonding layer + middle nutrient layer), but the consistent moisture content of each layer and the difference in curing shrinkage lead to interlayer cracking, resulting in a cracking rate of >30% after 60 days.

[0003] In the field of slope ecological restoration substrates, seeking cementitious materials to replace cement can help reduce the cost and adverse effects of ecological restoration. However, the substrates currently used in this field are still dominated by cement-based cementitious systems. Volcanic ash is a low-cost and widely available material. In the similar field of concrete, there are studies on using volcanic ash and silica sol to partially replace cement or as concrete additives to improve performance. For example, Chinese invention patent CN114477828A provides a concrete waterproofing, densifying, and shrinkage-reducing agent and its preparation method, using nano-silica sol, volcanic ash, zeolite powder, sodium carbonate, sodium silicate, nano-alumina, and water as raw materials to improve the impermeability of concrete and reduce early shrinkage. Another example is Chinese patent CN118851682A, which uses volcanic ash active substances as auxiliary cementitious materials, while utilizing the coagulation effect of silica sol and the filling and sintering effect of nanoparticles, combined with fiber toughening materials, to improve the impermeability of cementitious substrates. However, conventional volcanic ash has low cementitious activity, poor adhesion strength, and an underdeveloped pore structure, making it difficult to completely replace cement materials. Furthermore, considering slope restoration applications and ecological factors, in addition to meeting the physical and chemical performance indicators of the substrate, it is also necessary to take into account specific functions such as plant compatibility, heavy metal adsorption, and carbon emission reduction. These targeted design requirements further increase the difficulty of developing corresponding slope ecological restoration substrates.

[0004] In summary, existing technologies suffer from three major defects: 1) Poor ecological compatibility of cementitious materials: Traditional cement or chemical binders cause soil compaction (porosity <35%) and pH imbalance (8.5-10.0), resulting in vegetation survival rates below 50%; 2) Limited erosion resistance structure: Relying on surface cover nets or randomly distributed fibers, it is impossible to form a "physical-biological" synergistic anchoring system, leading to substrate loss >10 kg / m³ under 50 mm / h rainfall. 2 3) Mismatch between nutrient supply and plant needs: Ordinary slow-release fertilizers have a fixed release cycle (e.g., 30 days), which cannot match the nutrient needs of plants at different growth stages (e.g., high nitrogen is needed during budding, and high phosphorus is needed during root expansion). Therefore, developing a cement-free slope ecological restoration substrate that reduces construction costs, solves the problem of easy loss of traditional substrates, and achieves both rapid greening and zero pollution is of great significance to the field of slope ecological restoration. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, in a first aspect of the present invention, a slope ecological restoration substrate that is not easily lost, rapidly greens, is biodegradable, and low-cost is provided, comprising a bottom substrate, a middle substrate, and a top substrate; each substrate layer comprises the following raw materials in the following proportions by weight:

[0006] (a) The underlying substrate includes 25-35 parts of modified volcanic ash, 3-7 parts of nano-silica sol, 45-55 parts of crushed stone aggregate, 3-7 parts of humic acid, and 0.5-1.5 parts of pH adjuster; wherein, the modified volcanic ash is calcined basalt volcanic ash;

[0007] (b) The middle layer substrate includes 15-25 parts of coconut shell fiber, 8-12 parts of chitosan slow-release granules, 20-30 parts of bentonite, 10-20 parts of organic fertilizer, and 3-7 parts of water-retaining agent;

[0008] (c) The surface substrate comprises the following components by weight: 10-20 parts of 3D printed honeycomb biochar carrier, 2-5 parts of plant seeds, 1-3 parts of arbuscular mycorrhizal fungi powder, and 8-12 parts of vermiculite.

[0009] Preferably, in the underlying substrate, the modified volcanic ash is basalt volcanic ash calcined at 600-800 ℃, with a specific surface area ≥200 m². 2 / g.

[0010] Preferably, in the underlying substrate, the SiO2 content of the nano-silica sol is 20 wt.%-30 wt.%, and the particle size is 10-50 nm.

[0011] Preferably, the pH of the underlying substrate is 6.5-7.2 and the porosity is 45%-50%.

[0012] Preferably, in the intermediate substrate, the chitosan slow-release particles are made by blending and granulating chitosan and humic acid at a weight ratio of 1.5-3:1, with a particle size of 2-5 mm and a slow-release period of 60-90 days.

[0013] Preferably, in the surface substrate, the 3D printed honeycomb biochar carrier is made by carbonizing crop straw under anaerobic conditions at 500-600 ℃, with a pore size of 0.5-2 mm and a porosity of ≥70%.

[0014] In a second aspect of the present invention, a convenient, easy-to-implement, and low-cost method for layered hydroseeding for slope ecological restoration is provided, using the slope ecological restoration substrate of the first aspect of the present invention, comprising the following steps:

[0015] (1) Clean the slope surface, spray the base substrate to a thickness of 3-5 cm, apply high frequency micro-vibration to form a base substrate penetration and curing layer;

[0016] (2) After the bottom substrate has initially set, the middle substrate is sprayed in two stages. The gradient moisture content design of the middle substrate is divided into a lower moisture-bearing layer and an upper moisture-bearing layer. The moisture content of the lower moisture-bearing layer is 20%-25%, and the moisture content of the upper moisture-bearing layer is 35%-40%. The first spraying is 50%-60% of the total amount of the middle substrate to prepare the lower moisture-bearing layer. After standing for 3-5 hours, a semi-cured layer is formed. The remaining part is then sprayed to a total thickness of 5-8 cm to prepare the upper moisture-bearing layer, and finally the middle gradient water-retaining layer is formed.

[0017] (3) The surface substrate and the biodegradable polylactic acid (PLA) fiber mesh are sprayed simultaneously, and deep-rooted shrub seedlings are planted at the mesh nodes to form a surface biochar-plant symbiotic layer.

[0018] (4) Cover with photosensitive degradable nonwoven fabric to complete the construction of the slope ecological restoration structure.

[0019] Preferably, in step (1), the high-frequency micro-vibration is achieved by an eccentric wheel vibrator attached to the spraying equipment, with the vibration direction at an angle of 10°-30° to the normal direction of the slope; the applied frequency of the high-frequency micro-vibration is 20-40 Hz, the amplitude is 0.5-1 mm, and the duration is 5-15 min.

[0020] After the bottom layer is sprayed, high-frequency micro-vibration is applied to allow the cementitious material to penetrate into the rock fissures, increasing the penetration depth by 2.3 times compared to conventional processes.

[0021] In the intermediate substrate, the moisture content of each layer is controlled by a water-retaining agent (such as polyacrylamide-attapulgite composite) and a gradient spraying volume. The intermediate substrate is sprayed in two stages, first forming a semi-cured layer and then spraying the remaining part, which helps to avoid overall shrinkage and cracking.

[0022] Preferably, in step (3), the degradation cycle of the biodegradable polylactic acid fiber mesh is 150-200 days, the degradation products are carbon dioxide and water, the mesh spacing is 15 cm×15 cm to 25 cm×25 cm, the mesh tensile strength is ≥50 MPa, and planting holes with a diameter of 3-5 cm are provided at the nodes. The biodegradable polylactic acid fiber mesh and the root system of deep-rooted shrub seedlings form a spatially interwoven anchoring network with an anchoring depth ≥30 cm.

[0023] Preferably, in step (4), the degradation conditions for the photosensitive nonwoven fabric are a cumulative ultraviolet irradiation of 200-300 MJ / m. 2 The degradation cycle is 25-35 days.

[0024] In a third aspect of the invention, a slope ecological restoration structure is provided, which is made using the slope ecological restoration layered spraying method as described in the second aspect of the invention.

[0025] Preferably, the slope ecological restoration structure has a substrate loss of ≤3.5 kg / m³ under a 50 mm / h rainstorm. 2 The period during which vegetation coverage reaches over 80% is 60-90 days.

[0026] Based on the above technical solutions, the design concept and principle of this invention are as follows:

[0027] This invention employs modified volcanic ash and nano-silica sol to form an inorganic-nano composite cementing system in the bottom substrate, eliminating the need for cement and enhancing penetration and adhesion to the rock surface. This results in a bottom substrate with pH and porosity within target ranges, providing space for plant root expansion. In the middle substrate, chitosan slow-release particles combined with a gradient moisture content design reduce interlayer shear stress differences, increasing interlayer bonding strength to 45-50 kPa, achieving nutrient release in stages and interlayer stress buffering. A 3D-printed honeycomb biochar carrier and biodegradable PLA mesh simultaneously load arbuscular mycorrhizal fungi and drought-resistant grasses, combined with photosensitive degradation, forming a "physical-biological" composite anchoring structure. This addresses the application requirements of rapid vegetation cover and strong ecological compatibility, achieving rapid greening with zero pollution. The modified volcanic ash / straw biochar replaces expensive materials, and combined with a layered vibration spraying process, reduces rework and maintenance frequency, resulting in significant economic benefits.

[0028] To replace cement, this invention designs a modified volcanic ash and nano-silica sol to form a cementing system, significantly improving its cementing strength and making it irreplaceable by ordinary volcanic ash. The modified volcanic ash exhibits higher cementing activity, with an activity index (28 days) ≥85%, compared to ≤65% for ordinary volcanic ash. Calcination disrupts the basalt crystal structure, releasing more cementing active substances; high-temperature calcination removes volatile impurities, optimizes pore size distribution, and reduces defects. Furthermore, when synergistically combined with nano-silica sol, the adhesion strength reaches 3.0-3.5 MPa, higher than that of ordinary volcanic ash; while using volcanic ash alone as a cementing material results in an adhesion strength as low as <1.5 MPa. The modified volcanic ash possesses a unique multi-level porosity (micropores + mesopores) with a porosity of 45%-50%, while ordinary volcanic ash has a single pore size distribution and a porosity <35%, making it unsuitable for slope ecological restoration.

[0029] This invention employs a modified volcanic ash and nano-silica sol cementing system, a specific choice for slope ecological benefits. Considering the plant compatibility of slopes, modified volcanic ash is more conducive to promoting root development; in practical applications, root length can increase by up to 40%. In contrast, the alkaline environment and harmful impurities in ordinary volcanic ash easily inhibit plant root growth. Regarding heavy metal absorption, the porous structure of modified volcanic ash is more effective at absorbing heavy metals such as Pd. 2+ Cd 2+ Plasma has an adsorption rate >90%, while ordinary volcanic ash has <50%. Ordinary volcanic ash needs to be mixed with cement materials, resulting in poor emission reduction. The cementitious system designed in this invention can completely replace cement, reducing CO2 emissions by up to 35 kg / m³. 3 It has an outstanding contribution to carbon emission reduction.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] This invention provides a slope ecological restoration substrate that combines mechanical stability and ecological compatibility, making it suitable for the restoration of steep rock slopes and significantly reducing maintenance costs and environmental pollution risks.

[0032] This invention provides a layered spraying method for ecological restoration of slopes, which has the advantages of being convenient, easy to implement, and having low construction costs.

[0033] This invention provides a slope ecological restoration structure with strong resistance to rainstorm erosion, solving the problem of easy loss of traditional slope substrate. It has the advantages of rapid vegetation coverage, strong ecological compatibility and low cost, and has broad application prospects in the field of slope ecological restoration. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the implementation of the present invention. Detailed Implementation

[0035] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0036] Example 1

[0037] This embodiment provides a slope ecological restoration substrate, which is prepared using the following component ratio and method:

[0038] (a) Preparation of the base material: Basalt volcanic ash (particle size ≤ 0.075 mm) was calcined at 750 ℃ ​​for 2 h. After cooling, 30 parts of modified volcanic ash were mixed with 5 parts of nano silica sol (SiO2 content 25 wt.%), 50 parts of crushed stone aggregate (5-10 mm gradation), and 5 parts of humic acid (decomposition degree ≥ 80%). Water was added to a moisture content of 18%-20%, and the mixture was stirred for 10 min to form a slurry.

[0039] (b) Preparation of intermediate substrate: Chitosan (degree of deacetylation ≥90%) and humic acid are mixed at a ratio of 2:1 and granulated into chitosan slow-release granules with a diameter of 3 mm; 10 parts of chitosan slow-release granules, 20 parts of coconut shell fiber (length 10-20 mm), 25 parts of bentonite (cation exchange capacity ≥70 mmol / 100 g), 15 parts of organic fertilizer (NPK=8-5-6) and 5 parts of water-retaining agent are mixed, and water is added to divide them into component A (moisture content 25%) and component B (moisture content 40%).

[0040] (c) Preparation of surface substrate: Corn stalks were carbonized at 550 °C under anaerobic conditions for 2 h, crushed and then 3D printed into a honeycomb carrier (pore size 1 mm, wall thickness 0.2 mm). 15 parts of the 3D printed honeycomb biochar carrier were soaked in an arbuscular mycorrhizal fungal spore suspension (spore concentration ≥50 spores / g) for 24 h, dried and then mixed with 3 parts of grass seeds, 2 parts of fungal agent powder and 10 parts of vermiculite.

[0041] Example 2

[0042] This embodiment provides a layered hydroseeding method for slope ecological restoration, using the slope ecological restoration substrate from Embodiment 1 for construction, including the following steps:

[0043] (1) Slope treatment: After cleaning the loose rocks, drill holes in the slope (10 mm in diameter, 50 cm in depth, 1 m × 1 m spacing), insert Φ8 mm steel anchor rods and fix them with grout;

[0044] Underlying layer spraying: Use a wet spraying machine (working pressure 0.6 MPa) to spray the underlying substrate to a thickness of 4 cm, and immediately start the eccentric wheel vibrator (frequency 35 Hz, amplitude 0.8 mm, angle with the slope normal 20°) to vibrate for 10 min to form a penetrating and curing layer of the underlying substrate;

[0045] (2) Intermediate layer spraying: The first spraying of intermediate layer A component (moisture content 25%) to a thickness of 3 cm, and letting it stand for 4 h; the second spraying of component B (moisture content 40%) to a total thickness of 7 cm, and covering with a moisturizing film for 24 h after spraying to form a intermediate layer gradient water retention layer.

[0046] (3) Surface construction: The surface substrate and PLA grid (20 cm × 20 cm, with 4 cm diameter planting holes pre-drilled at the nodes) are sprayed simultaneously, and Amorpha fruticosa seedlings (15-20 cm tall) are planted to form a surface biochar-plant symbiotic layer;

[0047] (4) Cover with photosensitive biodegradable nonwoven fabric (30 g / m²) 2 ), and complete the construction of the slope ecological restoration structure.

[0048] This process reduces construction costs by 58%, using modified volcanic ash / straw biochar to replace expensive materials, and combining layered vibration spraying technology to reduce rework rate and maintenance frequency. The overall cost is only 0.5 million yuan / mu·year (compared to 1.2 million yuan / mu·year for traditional methods).

[0049] Example 3

[0050] This embodiment verifies the application effect of the slope ecological restoration structure constructed based on the layered hydroseeding method under extreme conditions. The experimental steps of this embodiment are as follows:

[0051] 1. Slope model preparation:

[0052] Clean the surface of the test tank and spray a waterproof coating to prevent water seepage from the side walls.

[0053] Spray the substrate (bottom layer → middle layer → top layer) according to the process of this invention, and cure for 7 days until fully cured;

[0054] 2. Simulated rainfall activation:

[0055] Adjust the nozzle pressure to 0.15 MPa and calibrate the rainfall intensity to 55 mm / h (verify uniformity using a rain gauge with multiple measurements).

[0056] Start the runoff collection system (with a V-shaped guide channel and a collection bucket installed at the bottom of the trough);

[0057] 3. Monitoring of the flushing process:

[0058] Runoff volume and turbidity were recorded every 30 minutes.

[0059] The changes in slope erosion depth were monitored using a laser scanner (accuracy 0.1 mm).

[0060] 4. Experiment Termination and Data Acquisition:

[0061] After rinsing, collect all lost substrate (sediment in the collection bucket), dry at 105 ℃ to constant weight, and weigh to calculate the loss (kg / m³). 2 );

[0062] Measure the maximum depth (cm) of the erosion gully and the percentage of the eroded area (%).

[0063] Under steep rock slope conditions (70°), using the substrate and process of this invention, vegetation coverage reached 85% after 90 days, PLA mesh completely degraded, and shrub roots penetrated to the underlying substrate, with an anchoring depth of 38 cm. In a rainstorm erosion test (60 mm / h), the substrate loss was 4.1 kg / m³. 2 It meets the requirements for Class I slope protection.

[0064] Example 4

[0065] To further optimize the mixing ratio parameters and verify the erosion resistance and vegetation coverage, this embodiment conducted substrate mixing ratio optimization experiments, rainstorm erosion resistance simulation experiments, and vegetation coverage verification experiments.

[0066] Experiment 1: Optimization Experiment of Substrate Proportion

[0067] The experiment used orthogonal experimental design to determine the optimal ratio of the bottom, middle and top layers of substrate, focusing on optimizing parameters such as compressive strength, permeability coefficient and water retention rate.

[0068] The experimental design is as follows:

[0069] 1. Underlying substrate variables (L9(3) 4 (orthogonal array):

[0070] Factor A: Volcanic ash content (25%, 30%, 35%);

[0071] Factor B: Amount of nano-silica sol added (3%, 5%, 7%);

[0072] Factor C: Humic acid ratio (3%, 5%, 7%);

[0073] Response indicators: adhesion strength (MPa), pH value, 28-day compressive strength (MPa).

[0074] 2. Variables in the middle layer substrate:

[0075] Factor D: Proportion of chitosan sustained-release particles (8%, 10%, 12%);

[0076] Factor E: Gradient moisture content design (20-30%, 25-35%, 30-40%);

[0077] Response indicators: interlaminar shear strength (kPa), nutrient slow release period (days).

[0078] 3. Surface substrate variables:

[0079] Factor F: Porosity of 3D biochar carrier (65%, 75%, 85%);

[0080] Factor G: Mycorrhizal fungi addition amount (1%, 2%, 3%);

[0081] Response indicators: seed germination rate (%), mycorrhizal infection rate (%).

[0082] Experiment 2: Simulation Experiment of Resistance to Torrential Rain Erosion

[0083] The experiment simulated rainfall intensity of 55 mm / h, continuous scouring for 6 hours, with a slope model of 1:1.5 (approximately 33.7°) and a substrate spraying thickness of 10 cm.

[0084] Experimental group: Substrate of this invention, 20 cm × 20 cm PLA mesh;

[0085] Comparative group: The substrate of this invention has no PLA mesh;

[0086] Control group: Traditional cement substrate + ordinary hydroseeding, without PLA mesh; the components of the traditional cement substrate are as follows: silicate cement (15%-25%), sandy aggregate (50%-70%), crushed stone (5-10 mm) (10%-20%), polypropylene fiber (0.1%-0.5%), cellulose ether (0.2%-0.8%), and organic polymer latex (2%-5%).

[0087] Experiment 3: Verification Experiment of Vegetation Coverage

[0088] The experimental setup was as follows: Plant species: tall fescue (Festuca arundinacea) + Amorpha fruticosa; Observation period: Coverage was recorded on days 7, 30, 60, and 90 after hydroseeding; Environmental conditions: natural light, average daily temperature 20-25 ℃, simulated drought cycle (watering stopped for 7 days every 15 days).

[0089] The above experiments verified the optimized substrate ratio parameters, erosion resistance, vegetation coverage, compressive strength and ecological indicators of different substrate ratios. The results are shown in Tables 1-4.

[0090] Table 1: Substrate Proportioning Parameters

[0091]

[0092] Table 2: Erosion Resistance

[0093]

[0094] Table 3: Vegetation Coverage

[0095]

[0096] Table 4: Compressive strength and ecological indicators of different substrate ratios

[0097]

[0098] Based on the above test results, it can be seen that the erosion resistance of the substrate of this invention is significantly better than that of traditional materials, with a 74% reduction in erosion. The addition of PLA mesh further reduces erosion by 44%. The resistance to torrential rain erosion is improved by 74%. The multi-stage cured substrate (modified volcanic ash + nano-silica sol) and PLA mesh anchoring work synergistically, resulting in a substrate erosion of only 3.2 kg / m³ under a 55 mm / h rainstorm. 2 (Traditional technology 12.5 kg / m) 2 This invention solves the problem of easy loss of traditional substrates. The 3D biochar carrier significantly improves the early germination rate, and arbuscular mycorrhizal fungi promote root development under drought conditions. The coverage rate only decreases by 7% during the water outage period (compared to 35% for traditional substrates). This invention achieves rapid vegetation coverage and strong ecological compatibility. The combination of 3D biochar carrier and mycorrhizal fungi enables a 93% vegetation coverage rate in 90 days, and the zero cement addition and PLA fully degradable design balance rapid greening with zero pollution.

[0099] In summary, this invention addresses the problems of poor substrate adhesion, weak erosion resistance, and low vegetation survival rate in existing technologies by proposing a three-layer synergistic substrate system and dynamic construction process. In the substrate, the bottom layer uses modified volcanic ash and nano-silica sol as cementing materials to enhance rock surface penetration and adhesion; the middle layer employs chitosan slow-release particles and a gradient moisture content design to achieve phased nutrient release and interlayer stress buffering; the surface layer combines a 3D honeycomb biochar carrier and a biodegradable PLA grid, simultaneously loading grass seeds and mycorrhizal fungi to form a "physical-biological" composite anchoring structure. The construction method of this invention includes high-frequency micro-vibration infiltration, layered gradient spraying, and photosensitive non-woven fabric covering processes to ensure the substrate's resistance to torrential rain erosion and rapid vegetation cover. This invention combines mechanical stability and ecological compatibility, making it suitable for the restoration of steep rock slopes and significantly reducing maintenance costs and environmental pollution risks.

[0100] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A layered hydroseeding method for ecological restoration of slopes, characterized in that, The use of slope ecological restoration substrate includes the following steps: (1) Clean the slope surface, spray the base substrate to a thickness of 3-5 cm, apply high frequency micro-vibration to form a base substrate penetration and curing layer; (2) After the bottom substrate has initially set, the middle substrate is sprayed in two stages. The gradient moisture content design of the middle substrate is divided into a lower moisture-bearing layer and an upper moisture-bearing layer. The moisture content of the lower moisture-bearing layer is 20%-25%, and the moisture content of the upper moisture-bearing layer is 35%-40%. The first spraying is 50%-60% of the total amount of the middle substrate to prepare the lower moisture-bearing layer. After standing for 3-5 hours, a semi-cured layer is formed. The remaining part is then sprayed to a total thickness of 5-8 cm to prepare the upper moisture-bearing layer, thus forming the middle gradient moisture-retaining layer. (3) The surface substrate and the biodegradable polylactic acid fiber mesh are sprayed simultaneously, and deep-rooted shrub seedlings are planted at the mesh nodes to form a surface biochar-plant symbiotic layer; (4) Cover with photosensitive degradable nonwoven fabric to complete the construction of the slope ecological restoration structure; The slope ecological restoration substrate includes a bottom substrate, a middle substrate, and a top substrate; by weight, each substrate layer comprises the following raw materials in the following proportions: (a) The underlying substrate comprises 25-35 parts modified volcanic ash, 3-7 parts nano-silica sol, 45-55 parts crushed stone aggregate, 3-7 parts humic acid, and 0.5-1.5 parts pH adjuster; wherein the modified volcanic ash is calcined basalt volcanic ash; the modified volcanic ash is calcined basalt volcanic ash at 600-800 ℃ with a specific surface area ≥200 m². 2 / g; the SiO2 content of the nano-silica sol is 20 wt.%-30 wt.%; (b) The middle layer substrate includes 15-25 parts of coconut shell fiber, 8-12 parts of chitosan slow-release granules, 20-30 parts of bentonite, 10-20 parts of organic fertilizer, and 3-7 parts of water-retaining agent; (c) The surface substrate comprises the following components by weight: 10-20 parts of 3D printed honeycomb biochar carrier, 2-5 parts of plant seeds, 1-3 parts of arbuscular mycorrhizal fungi powder, and 8-12 parts of vermiculite; the 3D printed honeycomb biochar carrier is made by carbonizing crop straw under anaerobic conditions at 500-600 ℃.

2. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In the underlying substrate, the particle size of the nano-silica sol is 10-50 nm; the pH of the underlying substrate is 6.5-7.2, and the porosity is 45%-50%.

3. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In the intermediate substrate, the chitosan slow-release particles are made by blending and granulating chitosan and humic acid at a weight ratio of 1.5-3:1, with a particle size of 2-5 mm and a slow-release period of 60-90 days.

4. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In the surface substrate, the 3D printed honeycomb biochar carrier has a pore size of 0.5-2 mm and a porosity of ≥70%.

5. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In step (1), the high-frequency micro-vibration is achieved by an eccentric wheel vibrator attached to the spraying equipment. The vibration direction is at an angle of 10°-30° to the normal direction of the slope. The applied frequency of the high-frequency micro-vibration is 20-40 Hz, the amplitude is 0.5-1 mm, and the duration is 5-15 min.

6. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In step (3), the degradation cycle of the biodegradable polylactic acid fiber mesh is 150-200 days, the degradation products are carbon dioxide and water, the mesh spacing is 15cm×15cm to 25cm×25cm, the mesh tensile strength is ≥50 MPa, and planting holes with a diameter of 3-5cm are provided at the nodes. The biodegradable polylactic acid fiber mesh and the root system of deep-rooted shrub seedlings form a spatially interwoven anchoring network with an anchoring depth ≥30cm.

7. The layered hydroseeding method for slope ecological restoration according to claim 1, characterized in that: In step (4), the degradation conditions for the photosensitive nonwoven fabric are a cumulative ultraviolet irradiation of 200-300 MJ / m. 2 The degradation cycle is 25-35 days.

8. A slope ecological restoration structure, characterized in that: It is prepared using the layered spraying method for slope ecological restoration as described in any one of claims 1-7.

9. The slope ecological restoration structure according to claim 8, characterized in that: The slope ecological restoration structure exhibits a substrate loss of ≤3.5 kg / m² under a 50 mm / h rainstorm. 2 The period during which vegetation coverage reaches 80% or more is 60-90 days.

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