A rain-erosion-resistant spray-seeding soil-fixing material and a spray-seeding soil-fixing method thereof

Abstract

This invention discloses a hydroseeding material and method for resisting rain erosion during the semi-solidification period, relating to the fields of slope ecological protection and soil stabilization technology. Addressing the problem of insufficient surface rain erosion resistance and seed and nutrient soil loss during the semi-solidification period after hydroseeding, before the soil stabilizing agent forms a film, this material comprises a main component and a rain-triggered component. The rain-triggered component includes slow-dissolving multivalent cation source micropowder coated with an amphiphilic slow-release carrier. In use, the main component is mixed with water to form a main slurry, and the rain-triggered component is enriched on the surface of the hydroseeded soil layer. During the semi-solidification period, once rainfall occurs, rainwater infiltration accelerates the dissolution of cation sources on the rain-affected surface, causing free multivalent cations on the rain-affected surface to exceed the gelation threshold and cross-link with anionic polymer ions, forming an in-situ rain-erosion-resistant sacrificial skin. This invention converts rainfall into a signal to trigger surface protection, resisting rain erosion during the semi-solidification period without physical covering, without damaging final permeability and seedling emergence. It can be used on bare slopes and other surfaces requiring hydroseeding for soil stabilization.

Description

Technical Field

[0001] This invention relates to the field of slope ecological protection and soil stabilization technology, and in particular to a sprayed soil stabilization material resistant to rain erosion during the semi-solidification period, and a sprayed soil stabilization method using the sprayed soil stabilization material. Background Technology

[0002] Highways, railways, mines, and water conservancy projects often leave large areas of exposed slopes after excavation. Hydroseeding is currently the most commonly used method for ecological protection and soil and water conservation on these slopes. During construction, plant seeds, fiber mulch, slow-release fertilizer, and a soil-stabilizing agent are mixed with water to form a slurry, which is then sprayed onto the slope. After the soil-stabilizing agent dehydrates and forms a film, it binds the surface soil particles and seeds together. Once the herbs and shrubs grow, their root systems take over from the soil-stabilizing agent to continue stabilizing the slope.

[0003] Soil stabilizing agents are crucial to this process. Early methods often used inorganic cementing materials like cement and water glass, which resulted in a hard and brittle film with poor air and water permeability, inhibiting seed germination. Later, water-soluble polymer soil stabilizing agents such as anionic polyacrylamide, sodium alginate, and modified starch were gradually adopted. These agents form flexible, permeable films that are seed-friendly and have become the mainstream. The film formation of these polymer soil stabilizing agents relies on the slow evaporation of water from the slurry and the cross-linking of molecular chains, a gradual process that requires time.

[0004] The root of the problem lies in the fact that polymer film formation takes time. After the hydroseeding material is sprayed onto the slope, some of the surface moisture evaporates, and the slurry loses its fluidity. However, the polymer molecular chains are far from being able to come together to form a continuous film—this period is generally referred to in the industry as the semi-curing period, which can range from a few hours to one or two days. The surface layer during the semi-curing period is in a very awkward state: it is no longer like freshly sprayed wet slurry, which can spread out again when exposed to water and smooth out any small pits washed out; yet it is far from having the strength of a fully cured layer, unable to withstand the impact of raindrops or the runoff collected on the slope. If rainfall occurs during this period, the semi-cured surface layer, along with the seeds and nutrient soil encased within, will be washed away, leaving gullies and large areas of exposed soil on the slope. The entire hydroseeding area is often rendered unusable and requires rework. In rainy areas of the south and during the rainy season, this situation of failure due to rainfall shortly after hydroseeding is particularly common.

[0005] To avoid rain erosion during the semi-curing period, three common methods are used on-site. One method is to quickly cover the slope with a layer of non-woven fabric or a protective net after spraying, relying on physical shielding to protect the surface from rain. However, this requires additional labor and materials, and the shading can affect seed germination; often, there isn't enough time to cover it during the rainy season when deadlines are tight. Another method is to simply increase the dosage of the soil-stabilizing agent or add quick-setting components to shorten the curing time and increase hardness. However, if the curing is too fast and too hard, the final film will become dense and compacted, reducing air and water permeability, making seed germination difficult, and increasing costs. A third method is to spray during weather-predicted dry periods; however, weather is unpredictable, and it's difficult to find consecutive sunny periods during the rainy season.

[0006] The aforementioned methods all focus on avoiding or passively enduring rainfall erosion during the semi-curing period, without addressing the semi-curing period itself. The root cause lies in the fact that existing soil stabilizing agent formulations and construction processes focus on the final strength after complete curing, treating the curing process as a spontaneous process requiring no intervention, neglecting the dynamic changes in the surface's rain erosion resistance over time. The semi-curing period, representing the lowest point of surface rain erosion resistance, has long been overlooked. How to enable the hydroseeded soil stabilizing layer to autonomously acquire rain erosion resistance within this most vulnerable window, without relying on physical covering or sacrificing final permeability and aeration, or seed germination rate, remains an unsolved technical problem in this field. Summary of the Invention

[0007] In view of the problems in the above-mentioned background technology, such as the lack of rain erosion resistance of the surface layer during the semi-curing period after hydroseeding and before the soil stabilizing agent has formed a film, and the loss of seeds and nutrient soil when exposed to rain, the present invention provides a hydroseeding soil stabilizing material resistant to rain erosion during the semi-curing period, and a hydroseeding soil stabilization method using the hydroseeding soil stabilizing material.

[0008] The core idea of ​​this invention is to pre-incorporate the rain-triggered component as part of the hydroseeding soil-stabilizing material, enriching it on the surface of the hydroseeding soil-stabilizing layer, and using rainfall itself as a signal to trigger surface protection. Once rain occurs during the semi-curing period, the rain-affected surface can in situ cross-link to form a sacrificial skin layer resistant to erosion. To this end, the main soil-stabilizing agent is a water-soluble polymer with anionic groups, and the rain-triggered component is a slow-dissolving multivalent cationic source micropowder coated with an amphiphilic slow-release carrier. By calibrating the slow-release rate to align with the semi-curing period window, and ensuring that the rain-triggered component forms a gradient distribution along the thickness direction of the hydroseeding soil-stabilizing layer, enriching on the surface and decreasing from the surface inwards, the protection precisely covers the most vulnerable semi-curing window, while using only a small amount of triggering material, without affecting the water and fertilizer retention and seedling emergence of the underlying layer.

[0009] The hydroseeding soil stabilization material of this invention comprises a main component and a rain-triggered component. The main component includes anionic water-soluble polymer soil stabilizing agent, plant seeds, fiber mulch, and slow-release fertilizer. The main component, when mixed with water, forms a main slurry for hydroseeding. The rain-triggered component comprises slow-dissolving multivalent cation source micropowder and an amphiphilic slow-release carrier coated on the outer surface of the slow-dissolving multivalent cation source micropowder.

[0010] The slow-release half-life of the amphiphilic slow-release carrier is not less than the time from the completion of spraying to the loss of fluidity of the surface of the sprayed soil-stabilizing layer, and not greater than the time from the completion of spraying to the initial film formation of the anionic water-soluble polymer soil-stabilizing agent. Based on the total solid mass of the main component and the rain-triggered component being 100%, the mass percentage of the anionic water-soluble polymer soil-stabilizing agent can be 3% to 12%, the mass percentage of the slow-dissolving multivalent cation source micropowder can be 5% to 20%, and the mass of the amphiphilic slow-release carrier can be 5% to 30% of the mass of the coated slow-dissolving multivalent cation source micropowder.

[0011] When using the above-mentioned hydroseeding soil stabilization material, the hydroseeding soil stabilization method for resisting rain erosion during the semi-solidification period includes: The main slurry is prepared by adding water to the main components. The main slurry includes anionic water-soluble polymer soil stabilizer, plant seeds, fiber mulch, slow-release fertilizer and water. The anionic water-soluble polymer soil stabilizer slowly cross-links to form a film after spraying and dehydration to establish final soil stabilization strength. Prepare or provide a rain-triggered component, wherein the rain-triggered component comprises a slow-dissolving multivalent cation source micropowder coated with an amphiphilic slow-release carrier, wherein the slow-release half-life of the amphiphilic slow-release carrier is not less than the time from the completion of spraying to the time when the surface of the sprayed soil stabilization layer loses its fluidity, and is not greater than the time from the completion of spraying to the time when the anionic water-soluble polymer soil stabilization agent initially forms a film. The main slurry and the rain-triggered component are sprayed onto the substrate to be stabilized, and the rain-triggered component is distributed in a gradient distribution along the thickness direction of the sprayed soil stabilization layer, with the surface concentration being higher than the bottom concentration. The sprayed soil-stabilizing layer is allowed to stand still and enter a semi-curing period. During the semi-curing period, the slow-dissolving multivalent cation source micro powder is dissolved at a limited rate by the amphiphilic slow-release carrier, so that the concentration of free multivalent cations in the sprayed soil-stabilizing layer is lower than the gelation threshold of the anionic water-soluble polymer soil-stabilizing agent. When rainfall occurs during the semi-curing period, rainwater infiltration accelerates the dissolution of the slow-dissolving polyvalent cation source micropowder in the rain-receiving surface layer, causing the concentration of free polyvalent cations in the rain-receiving surface layer to exceed the gelation threshold, and cross-linking with the anionic water-soluble polymer soil-stabilizing agent of the rain-receiving surface layer to form a sacrificial skin layer resistant to rain erosion in situ.

[0012] Therefore, this invention transforms rain during the semi-curing period into a signal to trigger surface protection: during the semi-curing period, as long as it rains, the rain-affected surface layer immediately cross-links into a sacrificial coat, absorbing raindrop impact and runoff erosion, protecting the underlying substrate that has not yet formed a film. This solves the problem of the surface layer lacking rain erosion resistance during the semi-curing period and losing seeds and nutrient soil upon rain, eliminating the need for additional physical covering and the need to rush the construction schedule based on weather conditions. The slow-release rate is aligned with the semi-curing window, allowing the protection to be triggered within the window and naturally recede outside, preventing premature cross-linking and hardening of the entire layer. The rain-triggered component is only enriched in the surface layer, saving on dosage, while the bottom layer remains breathable and permeable, without affecting seed germination and root growth. After the main soil-fixing agent forms a film, the sacrificial coat softens and degrades with the dry-wet cycle, restoring the surface layer to water and air permeability, without affecting later seedling emergence. Attached Figure Description

[0013] Figure 1 A flowchart of a spraying method for soil stabilization against rain erosion during the semi-curing period, provided as an exemplary embodiment of the present invention; Figure 2 A schematic diagram of the hydroseeding soil stabilization layer profile and the rain-triggered component gradient distribution provided as an exemplary embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the mechanism by which rain triggers surface ion crosslinking to form a sacrificial skin layer during the semi-curing period, as provided in an exemplary embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the alignment between the rain-triggered component release rate and the semi-curing period window, provided as an exemplary embodiment of the present invention. Figure 5 A comparison chart of surface sand yield and seed retention rate under simulated rainfall erosion during the semi-solidification period provided as an exemplary embodiment of the present invention; Figure 6 A comparison chart of permeability coefficient and seedling emergence rate of each group after 28 days of maintenance, provided as an exemplary embodiment of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. The specific component ratios, sustained-release half-lives, particle sizes, threshold values, and various values ​​in simulated rainfall experiments used in the following embodiments are all illustrative examples and do not constitute a limitation on the scope of protection of this invention; those skilled in the art can adjust the corresponding parameters according to actual slope conditions and climate, and the adjusted implementation methods still fall within the scope of protection of this invention. Several terms involved in this invention will be explained below, and then combined with… Figure 1 The steps of the method are explained step by step, followed by an explanation of the composition of the hydroseeding soil stabilization material, and finally, in conjunction with... Figure 5 , Figure 6 A complete implementation example and its simulated rainfall test results are given.

[0015] The semi-curing period refers to the time from when the sprayed material is applied to the slope and its surface loses its fluidity due to water loss, until the anionic water-soluble polymer soil-stabilizing agent initially cross-links and forms a film, achieving initial continuity of the surface. Initial continuity means that the surface shear strength reaches 0.5 kPa to 2.0 kPa, and when a 5 mm diameter glass rod is lightly pressed horizontally across the surface, the indentation depth does not exceed 2 mm, and the surface no longer disintegrates upon contact with water. During this period, the sprayed soil-stabilizing layer is in a precarious state: it is neither like freshly sprayed wet slurry, which can spread out and smooth out small pits when exposed to water, nor like a fully cured layer, which can withstand raindrop impact and runoff; it represents the weakest point in its resistance to rain erosion. The semi-curing period generally ranges from 2 hours to 36 hours, varying depending on slope temperature, wind speed, relative humidity, and the moisture content of the sprayed material—high temperatures, strong winds, and dry air result in a shorter semi-curing period; cold, damp conditions result in a longer period. The final soil stabilization strength refers to the mechanical strength achieved by the sprayed soil stabilization layer after the anionic water-soluble polymer soil stabilizing agent has been completely dehydrated and formed a film, which is sufficient for long-term stabilization of surface soil particles on a slope. It can be characterized by the surface shear strength or the sediment yield under simulated rainfall. The gelation threshold refers to the minimum concentration of free polyvalent cations required for the anionic water-soluble polymer soil stabilizing agent to transform from a flowable, water-redispersible sol state to a gel state that cannot be redispersed by water. When the concentration of free polyvalent cations is below this threshold, the polymer remains dispersible; once the concentration exceeds this threshold, it crosslinks in situ to form a gel. The gelation threshold varies with the type and concentration of the polymer and the cation valence state, and is determined as follows: At 25°C and pH 7.0, prepare 100 mL of a fixed concentration (e.g., 0.5 wt%) of anionic water-soluble polymer solution. Use 0.01 mol / L CaCl₂ solution as the titrant. Monitor the transmittance at 600 nm using a spectrophotometer. The threshold is the Ca²⁺ value corresponding to the transmittance decreasing to 50% of the initial value. + The concentration is the gelation threshold of the polymer-cationic system under these conditions; or the falling ball viscosity method is used, in which a glass ball with a diameter of 3 mm and a density of 2.5 g / cm³ is dropped onto the liquid surface, and the Ca² concentration corresponding to the sudden drop in falling velocity to less than 10% of the initial value is recorded. + The concentration is the gelation threshold. For example, for a 0.5 wt% sodium alginate solution, the gelation threshold for calcium ions is approximately 8-12 mmol / L.

[0016] The anionic water-soluble polymer soil stabilizer refers to polymers with anionic groups such as carboxyl and sulfonic acid groups on their molecular chains, which are soluble in water and form a film to stabilize soil particles after dehydration. Examples include anionic polyacrylamide, sodium alginate, xanthan gum, sodium carboxymethyl cellulose, and anionic modified starch. Their anionic groups can combine with polyvalent cations to form salt bridges and achieve ionic cross-linking, which is the chemical basis for triggering surface crust formation upon rain. The slow-dissolving polyvalent cation source refers to slightly soluble mineral salts that dissolve slowly in water and can continuously provide divalent or trivalent cations (calcium, magnesium, and aluminum ions), such as calcium carbonate, calcium sulfate, calcium hydroxide, and dolomite powder. The dissolution rate of these slightly soluble salts increases with the amount of water in contact and the degree of undersaturation of the water. Rainwater is fresh water that flows in in large quantities and is undersaturated with these salts, which is the physical basis for rainwater infiltration accelerating their dissolution. The slow-dissolving multivalent cation source micropowder refers to powder made from the slow-dissolving multivalent cation source with an average particle size of 5 to 80 micrometers. The amphiphilic slow-release carrier refers to a film-forming substance with one hydrophilic end and one hydrophobic end, which coats the outer surface of the slow-dissolving multivalent cation source micropowder to form a coating. When the slurry has a high moisture content, this coating restricts the rate of cation diffusion, suppressing release and achieving rate-limited release. Its hydrophilic end is rapidly wetted when rainwater infiltrates or the surface water flux increases sharply, providing a channel for accelerated dissolution. Examples include saponified plant waxes, multivalent metal salts of stearic acid, shellac, and polycaprolactone. The slow-release half-life refers to the time elapsed under specified leaching conditions when the slow-dissolving multivalent cation source coated by the amphiphilic slow-release carrier is cumulatively released to half of its total releaseable amount. The specified leaching conditions refer to immersing a quantitative amount of coated micropowder in water at 25°C and pH... The microparticles were leached in deionized water at a liquid-to-solid ratio of 100:1 (mL of leaching solution to grams of coated microparticles). Every 24 hours, all supernatant was collected and an equal amount of fresh deionized water was added. The amount of polyvalent cations released in each leaching was determined by EDTA complexometric titration or atomic absorption spectrometry, and the cumulative release amount was obtained by summing the results. The total release amount was calculated as the cumulative release amount when the cumulative release increment of the same batch of coated microparticles under the above conditions was less than 1% of the total release amount in two consecutive measurements. The sustained-release half-life was defined as the time when the cumulative release amount reached half of the total release amount. This time was determined by linear interpolation between two adjacent measurement time points that spanned half of the total release amount. The sustained-release half-life could be calibrated by adjusting the coating thickness, the hydrophilicity-to-hydrophobicity ratio of the carrier, and the particle size of the microparticles. The sacrificial skin refers to a dense, thin gel layer that cross-links in situ on the rain-affected surface during the semi-curing period and cannot be redispersed by water. For example, it has a thickness of 0.3 mm to 2.0 mm, a shear strength of 1.0 kPa to 5.0 kPa, and a mass loss rate of no more than 5% after 24 hours of exposure to water. During the most vulnerable semi-curing period, it withstands the impact of raindrops and runoff on the main body, hence the name sacrificial skin. After the main soil stabilizing agent forms a film, it will gradually soften and degrade with the wet-dry cycle, restoring the permeable and breathable surface layer.

[0017] For ease of understanding, the remaining terms involved in this invention are explained below. The "base surface to be stabilized" refers to the exposed soil surface that needs to be covered by a sprayed soil stabilization layer, including exposed slopes, road cut slopes, mine spoil heap surfaces, or other exposed engineering surfaces. The "sprayed soil stabilization layer" refers to the cover layer formed after the main slurry and the rain-triggered component are sprayed onto the base surface to be stabilized. The "gradient distribution" refers to the distribution of the rain-triggered component along the thickness direction of the sprayed soil stabilization layer, with a higher concentration at the surface and a decreasing concentration towards the interior. The surface layer refers to the area within the top 0.5cm to 1.0cm of the sprayed soil stabilization layer, and the bottom layer refers to the area within the sprayed soil stabilization layer within the lower 1.0cm to 2.0cm of the base surface to be stabilized, excluding the base surface itself. The total thickness of the sprayed soil stabilization layer is 3cm to 8cm. The "rain-receiving surface layer" refers to the outermost layer of the sprayed soil stabilization layer that is hit by raindrops and is the first layer through which rainwater infiltrates. The surface slurry refers to the slurry carrying the rain-triggered component and used to form the surface layer of the hydroseeding soil stabilization layer. It can be part of the main slurry or a diluted main slurry containing little or no plant seeds. The free polyvalent cations refer to divalent or trivalent cations dissolved in the pore water of the hydroseeding soil stabilization layer that have not yet combined with the polymer. The ionic crosslinking refers to the crosslinking method in which the carboxyl and sulfonic acid groups on the molecular chains of the anionic water-soluble polymer soil stabilizing agent combine with polyvalent cations to form salt bridges, thereby connecting the polymer molecular chains into a network. The fiber covering material refers to plant fibers, such as wood fiber, rice straw fiber, and coconut husk fiber, incorporated into the main slurry to increase water retention and form an erosion-resistant skeleton. The slow-release fertilizer refers to a fertilizer that releases nutrients slowly and can be continuously absorbed by plants. The coating refers to the rate-limiting release thin layer formed by the amphiphilic slow-release carrier coating the outer surface of the slow-dissolving polyvalent cation source micropowder.

[0018] The process of the hydroseeding soil stabilization method for resisting rain erosion during the semi-solidification period described in this invention is as follows: Figure 1 As shown, steps S1 to S5 are included. It should be noted that the numbering of S1 to S5 is for ease of reference only and does not constitute a strict limitation on the execution order of the steps: steps S1 and S2 are independent and can be executed in any order or simultaneously; steps S3 and S4 are performed sequentially, and step S5 is triggered when rainfall occurs during the semi-curing period. The following is in conjunction with… Figure 1 Each step will be explained step by step.

[0019] In step S1, the main slurry is prepared. The anionic water-soluble polymer soil-stabilizing agent, plant seeds, fiber mulch, and slow-release fertilizer from the main components are added to water and stirred until homogeneous to obtain a sprayable main slurry. The anionic water-soluble polymer soil-stabilizing agent should preferably be a blend of at least two of the aforementioned polymers. For example, anionic polyacrylamide can provide long-chain bridging, and sodium alginate can provide carboxyl sites that can be rapidly cross-linked by calcium ions. This blend balances film-forming flexibility and rain-triggered response speed. The soil-stabilizing agent's mass percentage can be 3% to 12% of the total solid mass of the main components and the rain-triggered component; the upper limit should be used for sandy or steep slopes, and the lower limit for soil slopes. The fiber mulch can be made of wood fiber, straw fiber, coconut fiber, etc., to increase the slurry's water retention and erosion resistance framework. The slow-release fertilizer and plant seeds can be configured according to the target vegetation community.

[0020] In step S2, the rain-triggered component is prepared. This is the first core step of the invention. Micronized powder of a slow-dissolving multivalent cation source is coated onto its surface with an amphiphilic slow-release carrier to form a film, thus obtaining the slow-release rain-triggered component. The slow-dissolving multivalent cation source can be at least one of calcium carbonate, calcium sulfate, calcium hydroxide, or dolomite powder, preferably a slightly soluble salt with a solubility of no more than 0.3 g per 100 g of water at 25°C, and an average particle size of 5 to 80 micrometers; its amount, based on the total mass of the main component and the rain-triggered component, can be 5% to 20%. The sustained-release half-life must fall within the window of the semi-curing period—the lower limit should not be less than the time from the completion of spraying to the loss of fluidity of the surface of the sprayed soil-stabilized layer (if earlier, the slurry can still flow, and the prematurely released cations will be diluted by the overall slurry and wasted, and may also cause premature cross-linking of the whole rather than the surface, resulting in loss of sprayability), and the upper limit should not be greater than the time when the soil-stabilizing agent initially forms a film (if later, the main soil-stabilizing agent has already formed a film on its own, and protection is no longer necessary). In engineering, the sustained-release half-life can be directly set to 0.5 to 1.5 times the semi-curing period: 0.5 times is earlier, triggering is more sensitive but with a small margin; 1.5 times is later, with a large margin but a slightly slower response; and 1.0 times is the recommended default method, where the half-release point is near the latter part of the semi-curing window, with a middle margin and sensitivity. The sustained-release half-life can be adjusted individually or in combination: Firstly, the coating thickness, calculated as the proportion of coating mass to the mass of the coated micropowder, can range from 5% to 30%; the thicker the coating, the longer the half-life. Secondly, the hydrophilicity-to-hydrophobicity ratio of the carrier; the more hydrophobic segments, the longer the half-life. Thirdly, the micropowder particle size; the larger the particle size, the longer the half-life. For example, on a slope with a semi-curing period of approximately 12 hours, the sustained-release half-life can be calibrated to approximately 12 hours (i.e., 1.0 times). This can be achieved by coating with saponified plant wax, accounting for approximately 15% of the micropowder mass, with an average micropowder particle size of approximately 40 micrometers. The resulting product is... Figure 4 The sustained-release curve shown is one where the half-release point falls within the semi-cured window. Figure 4The horizontal dashed line represents the reference line where the cumulative release rate reaches half-full release. The gray diagonal dashed line represents the control release curve with an excessively long sustained-release half-life, which results in insufficient release within the semi-curing period window, making it difficult for the surface cation concentration to exceed the gelation threshold in time when it rains. Considering the significant differences in semi-curing periods across different slopes, the sustained-release half-life does not need to be, and should not be, a fixed value. It should be calibrated based on the locally measured semi-curing period. This invention is not limited to any specific value.

[0021] In step S3, the main slurry and rain-triggered components are sprayed onto the substrate to be stabilized, ensuring that the rain-triggered components exhibit a gradient distribution within the sprayed soil stabilization layer, with a higher concentration at the surface and decreasing from the surface inwards. The resulting sprayed soil stabilization layer profile and the surface enrichment gradient of the rain-triggered components are as follows: Figure 2 As shown. The reason for creating a gradient is that rain hits the surface layer, and the surface layer needs protection. Pile the triggering components to the bottom layer, which is wasteful and causes premature cross-linking, hindering water and fertilizer retention and root development. Only by enriching it on the surface can the protective effect be concentrated in key areas with minimal material. There are two convenient on-site methods to achieve the gradient, which can be chosen or used in combination: The first is to spray in two passes. First, the main slurry is sprayed onto the substrate to be stabilized to form the base layer. Then, the rain-triggering component is sprayed onto the base layer surface along with a thin layer of topcoat slurry. The topcoat slurry carries the rain-triggering component and is used to form the surface layer of the sprayed soil stabilization layer, naturally concentrating the triggering component on the surface. The second is to spray in one pass, but increase the proportion of the rain-triggering component in the feed pump at the end of the main slurry spraying process, so that more rain-triggering component is sprayed out and falls into the outermost layer of slurry. Regardless of the method, the content of slow-dissolving polyvalent cation source per unit volume of the surface layer should be 2 to 8 times that of the bottom layer. If the multiple is too small, the gradient will not be obvious and the surface protection will be weak. If the multiple is too large, the surface material will be concentrated and attention should be paid to uniform spraying. 3 to 5 times is a commonly used range that balances protection and material saving.

[0022] In step S4, after spraying, the sprayed soil-stabilizing layer is allowed to stand still for a semi-curing period. During this time, when there is no rainfall, the coating slows down the dissolution of the slow-dissolving polyvalent cation source, and the concentration of free polyvalent cations in the sprayed soil-stabilizing layer remains below the gelation threshold of the soil-stabilizing agent. The polymer remains dispersible and does not undergo overall cross-linking. The soil-stabilizing agent continues to dehydrate and form a film at its own pace, accumulating final strength. When there is no rain, this triggering system is inactive, neither interfering with the film-forming process of the main soil-stabilizing agent nor prematurely cross-linking and hardening the entire layer. This helps maintain final air and water permeability and seedling emergence.

[0023] In step S5, if rainfall occurs during the semi-curing period, the triggering mechanism is activated. This is the second core aspect of the invention, and its mechanism is as follows: Figure 3As shown, rainwater falls and seeps into the surface layer, providing a large influx of fresh, unsaturated water to the slow-dissolving multivalent cation source powders on the surface. This rapidly wets and dissolves the channels formed by the hydrophilic ends of the amphiphilic slow-release carrier, disrupting the membrane structure and accelerating cation release. Simultaneously, it significantly increases the mass transfer driving force for dissolution, thus significantly accelerating the cation dissolution of the surface powders. Since the rain-triggered components are already enriched on the surface, the rainwater first contacts and continuously flows through this surface layer. The dissolved multivalent cations first reach a higher concentration locally on the surface layer, rather than being diluted as the water flows deeper. Within a short time, the concentration of free multivalent cations on the surface layer exceeds the gelation threshold, combining with the carboxyl and sulfonic acid groups of the anionic water-soluble polymer soil stabilizer enriched on the surface to form salt bridges and in-situ ionic cross-linking, resulting in a dense, sacrificial skin layer that can no longer be redispersed by water. This outer layer absorbs the kinetic energy of raindrop impacts and the shear force of runoff, protecting the underlying substrate, which has not yet formed a film, and the seeds and nutrient soil encased within. Since triggering only occurs on the surface layer that is hit by rain and seeped in by water, and this surface layer is already rich in rain-triggered components, it's a case of "where it rains, it hardens; the heavier the rain, the faster the surface cross-links"—the scouring energy of the rainwater is converted in situ into a signal that triggers protection. Optionally, after the main soil-stabilizing agent completes its final film formation and the stabilized substrate enters a normal wet-dry cycle, the sacrificial outer layer will gradually soften and degrade (its softening and degradation are considered complete when its thickness drops below 0.1 mm or its shear strength drops below 0.3 kPa), allowing the surface layer to re-permeable to water and air. The time from the formation of the sacrificial outer layer to its complete softening and degradation is generally 7 to 30 days, precisely covering the transition period after the semi-solidification period and before seedling emergence, without affecting seed emergence and subsequent growth.

[0024] The above is a general implementation of the method described in this invention. The composition of the hydroseeding soil-stabilizing material described in this invention is further explained below. Before adding water, the hydroseeding soil-stabilizing material can be divided into two parts: a main component and a rain-triggered component. The main component includes anionic water-soluble polymer soil-stabilizing agent, plant seeds, fiber mulch, and slow-release fertilizer; the rain-triggered component includes slow-dissolving multivalent cationic source micropowder coated with an amphiphilic slow-release carrier. Its slow-release half-life and semi-solidification period are matched, allowing the cationic source to release at a limited rate under normal conditions and accelerate dissolution and ionic cross-linking on the surface when rain infiltrates. Based on the total solid mass of the main component and the rain-triggered component being 100%, the anionic water-soluble polymer soil-stabilizing agent accounts for 3% to 12%, the slow-dissolving multivalent cationic source micropowder accounts for 5% to 20%, and the amphiphilic slow-release carrier accounts for 5% to 30% of the mass of the coated slow-dissolving multivalent cationic source micropowder. The specific amounts of fiber mulch, slow-release fertilizer, and plant seeds can be configured according to the target vegetation community, slope soil type, and construction moisture content. When using, add water to adjust the mixture to a sprayable consistency based on the condition of the substrate to be stabilized. This material can be either mixed as a whole and then adjusted at the end for surface enrichment, or it can be separated into main components and a topcoat slurry containing triggering components, packaged separately, and sprayed in stages on-site.

[0025] Example The following is a complete embodiment to illustrate the above method in detail, and provides the results of a simulated rainfall test during the semi-curing period. A highway cutting slope has a slope ratio of approximately 1:1.5 (slope angle of approximately 34 degrees), and the slope surface is sandy clay. The construction season is early summer, a rainy period. The solid components of the main material and the rain-triggered component are based on the total mass of the two solid components, as shown in the following example: approximately 4% anionic polyacrylamide, approximately 4% sodium alginate, approximately 45% wood fiber and straw fiber combined, approximately 6% slow-release compound fertilizer, approximately 1.5% mixed grass-shrub seeds (tall fescue, Amorpha fruticosa, etc.), approximately 12% calcium carbonate powder, and approximately 1.8% saponified palm wax coated on top (equivalent to 15% of the calcium carbonate mass). The remaining approximately 25.7% is topsoil matrix screened on-site. Water is added separately to adjust the consistency of the slurry and is not included in the total mass of the above solids. The rain-triggered component is prepared by coating calcium carbonate micropowder with an average particle size of approximately 40 micrometers with saponified palm wax to form a film, with a slow-release half-life of approximately 12 hours. Application: First, the main slurry is sprayed to form a base layer approximately 4 cm thick. Then, the rain-triggered component is sprayed onto the surface along with a thin layer of topcoat slurry. The measured calcium carbonate content of the surface layer is approximately four times that of the base layer. After spraying, the measured semi-curing period of the slope is approximately 11 hours (the surface layer loses its fluidity in approximately 0.8 hours, and the soil stabilizing agent initially forms a film after approximately 12 hours). The slow-release half-life is approximately 12 hours, about 1.0 times the duration of the semi-curing period, with the half-release point near the latter part of the semi-curing window.

[0026] To verify the effectiveness, a simulated rainfall erosion test was conducted on the slope and parallel test plots during the semi-solidification period. Six hours after hydroseeding (during the semi-solidification period), simulated rainfall of 60 mm / h for 30 minutes was applied using an artificial rain generator, and the surface sand yield and seed retention rate were measured. Surface permeability and germination rate were measured after 28 days of curing. Four groups were set up: the invention group was the above-described embodiment; Comparative Example 1 was conventional hydroseeding with the same formulation as the invention group but without the rain-triggered component; Comparative Example 2 was the existing "increased dosage acceleration" route, without the rain-triggered component, but with the soil-stabilizing agent dosage increased to 15% for faster solidification; and a non-triggered control group was set up with the same formulation as the invention group, but without rainfall during the semi-solidification period to verify whether the triggering system was inactive in the absence of rain.

[0027] The test results are as follows Figure 5 , Figure 6 As shown, Figure 5 The columnar shape corresponds to the surface sand yield during the semi-solidification period after rain, while the broken line corresponds to the seed retention rate. Figure 6 The columnar section corresponds to the permeability coefficient after 28 days of curing, and the broken line corresponds to the germination rate. All column points use the same abscissa. The following data are representative values ​​from three parallel experiments and include normal fluctuations. Comparative Example 1, i.e., conventional hydroseeding without rain-triggered components: during the semi-solidification period, when rain occurs, the surface sand yield is approximately 412 g / m², and the seed retention rate is approximately 58%. After 28 days of curing, the permeability coefficient is approximately 5.6 × 10⁻⁴ cm / s, and the germination rate is approximately 87%. This is because during the semi-solidification period of conventional hydroseeding, the surface film is not yet continuous. Raindrop impact and slope runoff directly wash away the unconsolidated surface layer along with the seeds, resulting in high sand yield and severe seed loss. While its permeability and germination are acceptable, the entire area is rendered unusable upon rain during the semi-solidification period. Comparative Example 2, which uses an accelerated solidification route with increased soil stabilizing agent dosage to 15% and no rain-triggered components, showed a reduction in sand yield to approximately 214 g / m², a seed retention rate of approximately 75%, and improved erosion resistance during the semi-solidification period. However, due to the excessive dosage of soil stabilizing agent and the resulting dense and compacted final film, the permeability coefficient dropped to approximately 2.3 × 10⁻⁴ cm / s after 28 days, and the germination rate was only about 46%. This demonstrates that while accelerated solidification with increased dosage can partially resist rain erosion, it sacrifices water permeability, air permeability, and germination. The present invention group showed a sand yield of approximately 63 g / m², a seed retention rate of approximately 93%, a 28-day permeability coefficient of approximately 5.9 × 10⁻⁴ cm / s, and a germination rate of approximately 88%. During the semi-solidification period, rain-triggered sand yield was reduced by approximately 80% compared to conventional hydroseeding, while the seed retention rate was significantly improved. Final water permeability and germination were essentially the same as conventional hydroseeding, significantly superior to the accelerated solidification route. The non-triggered control of this invention (no rainfall during the semi-curing period): after 28 days, the water permeability coefficient was approximately 6.1 × 10⁻⁴ cm / s, and the germination rate was approximately 90%, comparable to conventional hydroseeding. This demonstrates that the triggering system remains inactive in the absence of rain, preventing premature cross-linking and hardening of the entire layer and avoiding damage to germination. The above control indicates that the protection provided by this invention is triggered by rainfall and only occurs when needed.

[0028] Whether the sustained-release half-life falls within the semi-solidification window determines the success or failure of rain-triggered protection. A half-life that is too early will result in wasted resources, while a half-life that is too late will not allow for a response. To illustrate this point, a comparison was made based on the present invention group, only changing the sustained-release half-life: When the half-life is approximately 6 hours (approximately 0.5 times the semi-solidification period), the sand yield is approximately 71 g / m², and the seed retention rate is approximately 90%. The protection is effective, but due to the early release and the consumption of a small amount of cations in the later stages of semi-solidification, the germination rate after 28 days is slightly lower at approximately 85%. When the half-life is approximately 12 hours (approximately 1.0 times, with the half-release point near the latter part of the semi-solidification window), as described above, the present invention group is optimal overall. When the half-life is approximately 30 hours (approximately 2.5 times, exceeding the preferred range of the present invention), because the coating has not yet reached the state of accelerated dissolution upon rain, and the surface cations do not have time to cross the gelation threshold, the sand yield rebounds to approximately 188 g / m², and the protection is significantly weakened. It is evident that aligning the sustained-release half-life with the semi-curing window is crucial to the success of trigger protection; too early will lead to consumption, and too late will result in failure. This also confirms that the limitation on the range of sustained-release half-life values ​​in step S2 is not arbitrary.

[0029] It should be noted that the above-mentioned formulation, particle size, coating ratio, sustained-release half-life, and various test data are all illustrative examples for this specific slope. For slopes with different aspects, slope ratios, soil types, and climates, the semi-solidification period will vary. Those skilled in the art should first measure the local semi-solidification period, and then calibrate the sustained-release half-life nearby (taking 0.5 to 1.5 times the semi-solidification period). Based on the slope steepness, the dosage of the soil stabilizing agent and triggering component, as well as the surface enrichment factor, should be adjusted within the aforementioned range. The adjusted scheme still falls within the protection scope of this invention.

[0030] Regarding special circumstances, the following supplementary explanations are provided. First, if there is no rainfall for a long period after spraying: the triggering component remains unactivated, the main soil-stabilizing agent forms a film as usual, and this invention degenerates into conventional spraying. The addition of the triggering component will not adversely affect the final state, as evidenced by the data from the non-triggered component mentioned above. Second, if a heavy rainstorm occurs immediately after spraying and the surface has not yet lost its fluidity: at this time, the surface can still spread out again upon contact with water and partially heal itself. Furthermore, the coating has not yet reached the accelerated dissolution stage in this very early stage, and protection relies primarily on the initial water retention and corrosion resistance of the slurry itself. The slow-release half-life can be set near the lower limit of the preferred range, or the surface enrichment factor can be appropriately increased to achieve an earlier response. Third, if the semi-solidification period on a dry, high-temperature slope is very short (close to 2 hours): the slow-release half-life should be calibrated to near the lower limit, and smaller particle size micro-powder should be selected to accelerate the response to rain. Fourth, all thresholds and times mentioned should be based on local measurements. The value ranges given in this invention are illustrative engineering references and do not constitute limitations.

[0031] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features, and such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A sprayed soil stabilization material resistant to rain erosion during the semi-curing period, characterized in that, Includes main ingredient components and rain-triggered components; The main components include anionic water-soluble polymer soil stabilizer, plant seeds, fiber mulch, and slow-release fertilizer. When water is added to the main components, a main slurry is formed for hydroseeding. The rain-triggered component includes a slow-dissolving multivalent cation source micropowder and an amphiphilic slow-release carrier coated on the outer surface of the slow-dissolving multivalent cation source micropowder. The amphiphilic slow-release carrier is used to limit the dissolution rate of the slow-dissolving multivalent cation source micropowder when there is no rainfall, and to accelerate wetting when rainwater infiltrates so that the slow-dissolving multivalent cation source micropowder dissolves on the rain-affected surface. The rain-triggered component is used to form a gradient distribution in the hydroseeded soil stabilization layer where the concentration on the surface is higher than that on the bottom layer. This causes the concentration of free polyvalent cations on the rain-affected surface layer to exceed the gelation threshold of the anionic water-soluble polymer soil stabilization agent during the semi-curing period, and to cross-link with its ions, forming a sacrificial skin layer resistant to rain erosion.

2. The hydroseeding soil stabilization material according to claim 1, characterized in that, The anionic water-soluble polymer soil stabilizer is a compound of at least two of the following: anionic polyacrylamide, sodium alginate, xanthan gum, sodium carboxymethyl cellulose, and anionic modified starch.

3. The hydroseeding soil stabilization material according to claim 1, characterized in that, The slow-dissolving multivalent cation source micro powder is at least one of calcium carbonate, calcium sulfate, calcium hydroxide and dolomite powder, and the solubility of each selected micro powder in water at 25 degrees Celsius is no more than 0.3 grams per 100 grams of water, with an average particle size of 5 micrometers to 80 micrometers.

4. The hydroseeding soil stabilization material according to claim 1, characterized in that, Based on the total solid mass of the main component and the rain-triggered component being 100%, the mass percentage of the anionic water-soluble polymer soil stabilizer is 3% to 12%, and the mass percentage of the slow-dissolving multivalent cation source micro powder is 5% to 20%. The mass of the amphiphilic sustained-release carrier is 5% to 30% of the mass of the coated slow-dissolving multivalent cation source micropowder.

5. The hydroseeding soil stabilization material according to claim 1, characterized in that, The amphiphilic sustained-release carrier is at least one of saponified plant wax, a multivalent metal salt of stearic acid, shellac, and polycaprolactone. The sustained-release half-life of the amphiphilic sustained-release carrier is not less than the time from the completion of spraying to the loss of fluidity of the surface layer of the sprayed soil stabilization layer, and not greater than the time from the completion of spraying to the initial film formation of the anionic water-soluble polymer soil stabilization agent.

6. A method for hydroseeding soil stabilization using the hydroseeding soil stabilization material according to any one of claims 1 to 5, characterized in that, include: The main material components are mixed with water to prepare the main slurry, and the rain-triggered component is sprayed together with the main slurry or in sections onto the substrate to be stabilized, so that the rain-triggered component is distributed in a gradient with a higher concentration at the surface than at the bottom along the thickness direction of the formed sprayed soil stabilization layer. The sprayed soil-stabilizing layer is allowed to stand still and enter a semi-curing period. During the semi-curing period, the slow-dissolving multivalent cation source micro powder is dissolved at a limited rate by the amphiphilic slow-release carrier, so that the concentration of free multivalent cations in the sprayed soil-stabilizing layer is lower than the gelation threshold of the anionic water-soluble polymer soil-stabilizing agent. When rainfall occurs during the semi-curing period, rainwater infiltration accelerates the dissolution of the slow-dissolving polyvalent cation source micropowder in the rain-receiving surface layer, causing the concentration of free polyvalent cations in the rain-receiving surface layer to exceed the gelation threshold, and cross-linking with the anionic water-soluble polymer soil-stabilizing agent of the rain-receiving surface layer to form a sacrificial skin layer resistant to rain erosion in situ.

7. The hydroseeding method for soil stabilization according to claim 6, characterized in that, The gradient distribution can be formed in at least one of the first and second methods; The first method involves first spraying the main slurry onto the substrate to be stabilized to form a base layer, and then spraying the rain-triggered component along with the topcoat slurry to cover the surface of the base layer. The topcoat slurry is a slurry that carries the rain-triggered component and is used to form the surface layer of the sprayed soil stabilization layer. The second method involves increasing the feed ratio of the rain-triggered component at the end of the spraying of the main slurry; The content of the slow-dissolving polyvalent cation source micro powder per unit volume in the surface layer of the sprayed soil stabilization layer is 2 to 8 times that in the bottom layer per unit volume.

8. The hydroseeding method for soil stabilization according to claim 6, characterized in that, The semi-curing period is the time from when the surface of the sprayed soil layer loses its fluidity after spraying is completed until the anionic water-soluble polymer soil-fixing agent initially forms a film, and its duration is 2 hours to 36 hours. The sustained-release half-life of the amphiphilic sustained-release carrier is 0.5 to 1.5 times the duration of the semi-curing period.

9. The hydroseeding method for soil stabilization according to claim 6, characterized in that, After the anionic water-soluble polymer soil-stabilizing agent completes its final film formation, the sacrificial skin gradually softens and degrades with the wet-dry cycle of the substrate to be stabilized, restoring the surface of the sprayed soil-stabilizing layer to be permeable to water and air.

10. The hydroseeding method for soil stabilization according to claim 9, characterized in that, The time from the formation of the sacrificial skin to the completion of its softening and degradation is 7 to 30 days; wherein, the softening and degradation is considered to be complete when the thickness of the sacrificial skin drops to below 0.1 mm or the shear strength drops to below 0.3 kPa.

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