Biological composite modified anti-scouring spray-seeding base material and preparation method thereof

Abstract

The invention relates to a biological composite modified anti-scouring spray seeding base material based on biological slurry, biochar and xanthan gum and a preparation method of the biological composite modified anti-scouring spray seeding base material. According to the base material, through the synergistic effect of the three, the stability and vegetation adaptability of the base material are remarkably improved, and the slope ecological restoration effect in the southern rainy environment is improved. In the mixing stage, xanthan gum is subjected to a hydration gel reaction, and soil macropores are filled to construct an initial skeleton; then, urease-producing bacteria in the biological slurry hydrolyze urea to induce calcium carbonate deposition and mineralization, and the mineralization process lags behind a hydration gel reaction of xanthan gum, so that secondary filling of residual tiny pores is realized, and the stability of the pore structure is improved. Meanwhile, the porous structure of the biochar obviously enhances the water and fertilizer retention capacity of the base material, a favorable environment is provided for microbial activity, and the mineralization effect is further promoted. The spray-seeding base material has good water stability and nutrient interception capability, and provides a good environment and a stable foundation for growth of plant seeds.

Description

Technical Field

[0001] This invention belongs to the field of slope ecological restoration technology, and more specifically relates to a bio-composite modified erosion-resistant spraying substrate based on bio-slurry, xanthan gum and biochar and its preparation method. Background Technology

[0002] Hydroseeding, a common method for slope ecological restoration, aims to revegetate and restore the ecosystem on barren slopes by creating a suitable substrate layer for vegetation growth. However, existing technologies face a significant challenge in practical application: the erosion resistance of the hydroseeding substrate is generally insufficient. After hydroseeding, the substrate is easily eroded by rainfall, leading to vegetation establishment failure and low coverage. This often necessitates secondary or even multiple re-seeding operations, significantly increasing costs and affecting the timeliness and overall effectiveness of ecological restoration. This problem is particularly pronounced in rainy and typhoon-prone areas such as the southeastern coastal regions, resulting in low initial slope establishment rates and severely restricting the long-term protective effect and ecological sustainability of slopes, greatly limiting the widespread application of hydroseeding technology in these areas. Therefore, to address the critical technical bottleneck of insufficient erosion resistance of hydroseeding substrates, it is urgent to optimize them through material composite and functional modification, and develop new substrates that not only have excellent erosion resistance but also meet the needs of vegetation growth and construction convenience. This will improve the success rate, durability, and environmental adaptability of slope ecological restoration, and promote the reliable application of hydroseeding technology in slope ecological restoration under various erosion environments. Summary of the Invention

[0003] In view of the above-mentioned technical problems, this invention provides a bio-composite modified erosion-resistant hydroseeding substrate and its preparation method. Based on the principles of environmental protection and ecological slope stabilization, this invention combines biomineralization technology with xanthan gum-biochar to develop a novel hydroseeding substrate that combines excellent vegetation adaptability, high water stability, and low cost. This solves the problem of insufficient erosion resistance in traditional topsoil hydroseeding technology and improves the reliability and long-term benefits of topsoil hydroseeding technology for slope ecological restoration in various erosion environments.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a bio-composite modified erosion-resistant spray seeding substrate, comprising the following steps:

[0005] S1. Mix the bacterial solution and the first cementing solution in a certain volume ratio, stir evenly, and let stand for a period of time. Remove the upper transparent liquid obtained after standing and stratification to obtain biological mud.

[0006] S2. Mix xanthan gum, biochar, and soil in a certain mass ratio and stir evenly to obtain a dry soil mixture. Then, add a certain mass or volume ratio of biological mud, second cementing liquid, water, and plant seeds to the dry soil mixture and stir evenly to obtain a bio-composite modified erosion-resistant spraying substrate.

[0007] Optionally, in the above technical solutions, the biological mud can be prepared in advance, stored at 4°C, transported to the construction site, and diluted with tap water at the construction site before use.

[0008] Preferably, the bacterial solution is a Bacillus pasteurellii bacterial solution.

[0009] In some preferred embodiments, both the first and second cementing solutions are prepared from equimolar concentrations of calcium chloride solution and urea solution. The cementing solution is prepared from equimolar concentrations of calcium chloride and urea under stirring conditions of 600 rpm and stirring time of 12 h.

[0010] In some preferred embodiments, the molar concentrations of calcium chloride and urea solutions in the first cementing solution are 1.0 mol / L to 2.0 mol / L, and the molar concentrations of calcium chloride and urea solutions in the second cementing solution are 0.3 mol / L to 0.6 mol / L. A high molar concentration of 1.0 mol / L to 2 mol / L is required when preparing the raw materials for concentrated urease bacterial solution. When the dry soil mixture, bio-slurry, second cementing solution, water, and plant seeds are mixed thoroughly, calcium ions, as the ions required for subsequent biomineralization processes, need to be maintained at a low concentration (0.3 mol / L to 0.6 mol / L) to ensure that bacterial activity is not affected, while providing a calcium source for subsequent calcium carbonate formation, thus effectively reducing the cost of microbial-induced calcium carbonate precipitation technology in engineering mineralization.

[0011] In some preferred embodiments, in step S1, the bacterial solution and the first cementing solution are mixed evenly at a volume ratio of 4:1 to obtain a mixed solution; the mixed solution is left to stand at room temperature for 6-10 hours to separate into layers.

[0012] In some preferred embodiments, the soil has a particle size of less than 2 mm, and the mass ratio of xanthan gum to biochar is 1% to 1.5%.

[0013] In some preferred embodiments, in step S2, when adding the biological mud and the second cementing liquid to the dry soil mixture, the biological mud and the second cementing liquid are mixed with the dry soil mixture at a mass ratio of 1:1.

[0014] In some preferred embodiments, in step S2, the biological slurry, the second cementing liquid, and water are added to the dry soil mixture, with the moisture content controlled at 70% to 75%. In both of the above preferred embodiments, the pH value of the biological slurry needs to be adjusted to 5.5 to 6.5 to remove white flocculent precipitates, thereby delaying the formation of calcium carbonate and allowing sufficient operating time for subsequent mixing with the dry soil mixture, the second cementing liquid, and other materials, and facilitating the mixing operation.

[0015] In some preferred embodiments, in step S2, the plant seeds are selected from one or more of ryegrass, tall fescue, bermudagrass, carpet grass, and zoysia grass, and the dosage is 30 g / m² to 40 g / m².

[0016] A second aspect of the present invention provides a bio-composite modified erosion-resistant spray seeding substrate, which is prepared by the preparation method described in the first aspect of the present invention.

[0017] Unlike existing technologies, the technical solution of this invention innovatively combines bio-slurry, xanthan gum, and biochar, significantly improving the overall performance of the topsoil spraying substrate through their synergistic effect. During the mixing stage, xanthan gum first undergoes a hydration-gel reaction, absorbing water and swelling to effectively fill the large pores in the soil. Subsequently, urease-producing bacteria in the bacterial solution further catalyze the hydrolysis of urea in the second cementing solution, inducing the precipitation of calcium carbonate crystals and achieving a biomineralization process. This mineralization process slightly lags behind the gelation reaction of xanthan gum, thus providing secondary filling of the remaining micropores, forming a stable calcium carbonate cemented structure, and greatly enhancing the overall stability of the pores.

[0018] Meanwhile, biochar, with its abundant porous structure, significantly enhances the water and fertilizer retention capacity of the substrate, creating favorable conditions for microbial activity and further promoting the effective functioning of biomineralization. This invention optimizes the filling efficiency of soil pores by constructing a "stepwise cementation" mechanism, effectively overcoming the defect of matrix layer shrinkage and cracking caused by the single use of xanthan gum, while significantly reducing the permeability and porosity of the matrix layer.

[0019] Compared to ordinary hydroseeding substrates, the bio-composite modified erosion-resistant hydroseeding substrate provided by this invention exhibits superior water stability. During vegetation growth, plant roots can form a composite reinforcement with this substrate, further enhancing the overall stability of the slope. Furthermore, this substrate layer also possesses excellent nutrient retention capacity, providing a solid foundation for subsequent plant seed growth and long-term ecological maintenance.

[0020] In terms of economy and environmental protection, the materials used in this invention have low cost, the preparation process does not rely on large-scale machinery and equipment, and it has low-carbon and environmentally friendly characteristics, and has good prospects for promotion and application.

[0021] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0022] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of this application and other related content, and should not be considered as limitations on this application.

[0023] In the accompanying drawings of the instruction manual:

[0024] Figure 1 This is a flowchart illustrating the practical engineering application of the method for preparing a biocomposite modified erosion-resistant hydroseeding substrate using a combination of biomineralization technology and xanthan gum-biochar.

[0025] Figure 2 This is a real-life photograph of the sedimentation of biological mud slurry in the method for preparing biocomposite modified erosion-resistant spray seeding substrate using a combination of biomineralization technology and xanthan gum-biochar according to the present invention.

[0026] Figure 3 This is a real-life photo of the dilution of biological mud solution in the method for preparing biocomposite modified erosion-resistant spray seeding substrate using a combination of biomineralization technology and xanthan gum-biochar according to the present invention.

[0027] Figure 4 This is a real-life photo of the mixing process for a method of preparing a biocomposite modified erosion-resistant spray seeding substrate using a combination of biomineralization technology and xanthan gum-biochar according to the present invention.

[0028] Figure 5 This is a real-life photo of a method for preparing a biocomposite modified erosion-resistant hydroseeding substrate using a combination of biomineralization technology and xanthan gum-biochar, according to the present invention.

[0029] Figure 6 This invention relates to a method for preparing a biocomposite modified erosion-resistant spray seeding substrate using biomineralization technology combined with xanthan gum and biochar. The image shows actual soil erosion on a slope.

[0030] Figure 7 This invention relates to a method for preparing a biocomposite modified erosion-resistant hydroseeding substrate using biomineralization technology combined with xanthan gum-biochar. The image shows a real-world example of slope matrix erosion.

[0031] Figure 8 The image shows actual plant growth of a method for preparing a biocomposite modified erosion-resistant hydroseeding substrate using a combination of biomineralization technology and xanthan gum-biochar, according to the present invention.

[0032] Figure 9 The image shows a disintegration test of a method for preparing a biocomposite modified erosion-resistant spray seeding substrate using a combination of biomineralization technology and xanthan gum-biochar, according to the present invention. Detailed Implementation

[0033] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0034] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0035] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0036] In the description of this application, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" logical relationship.

[0037] In this application, terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy or order relationship between these entities or operations.

[0038] Unless otherwise specified, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this application is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a list of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.

[0039] As understood in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments in this application, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.

[0040] In the description of the embodiments of this application, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the purpose of describing the specific embodiments of this application or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0041] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this application, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this application pertains, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0042] Hydroseeding, a common method for slope ecological restoration, aims to revegetate and restore the ecosystem on barren slopes by creating a suitable substrate layer for vegetation growth. However, existing technologies face a significant challenge in practical application: the erosion resistance of the hydroseeding substrate is generally insufficient. After hydroseeding, the substrate is easily eroded by rainfall, leading to vegetation establishment failure and low coverage. This often necessitates secondary or even multiple re-seeding operations, significantly increasing costs and affecting the timeliness and overall effectiveness of ecological restoration. This problem is particularly pronounced in rainy and typhoon-prone areas such as the southeastern coastal regions, resulting in low initial slope establishment rates and severely restricting the long-term protective effect and ecological sustainability of slopes, greatly limiting the widespread application of hydroseeding technology in these areas. Therefore, addressing the critical technical bottleneck of insufficient erosion resistance in hydroseeding substrates, it is urgent to optimize the technology through material composites and functional modifications. The aim is to develop novel substrates that possess both excellent erosion resistance and meet the needs of vegetation growth while also offering ease of construction. This would improve the success rate, durability, and environmental adaptability of slope ecological restoration, and promote the reliable application of hydroseeding technology in various erosion environments. In this regard, following the principles of environmental protection and ecological slope stabilization, this invention proposes a method for preparing a bio-composite modified erosion-resistant hydroseeding substrate using a combination of biomineralization technology and xanthan gum-biochar.

[0043] The *Pasteurella multocida* used in this embodiment of the invention was purchased from the China General Microbiological Culture Collection Center as a urease-producing bacterium. While *Pasteurella multocida* is used in this embodiment, the type of strain is not limited thereto. The calcium chloride and urea used in this embodiment were purchased from Xilong Chemical Co., Ltd. All plant seeds used were purchased from Shangming Seed Industry Co., Ltd. Xanthan gum was purchased from Shandong Fufeng Fermentation Co., Ltd. Biochar was purchased from Chengdu Daqi Technology Co., Ltd.

[0044] The Bacillus pasteurellium culture was obtained through the following preparation steps:

[0045] 1) Prepare Bacillus pasteurellium liquid culture medium: Add 20 g / L yeast extract, 15 g / L ammonium chloride, and 0.1 mM nickel chloride to a solution with 5 mol / L sodium hydroxide solution to adjust the pH to 9.25. The remainder is deionized water. Mix well and sterilize at 121℃.

[0046] 2) In a clean bench, inoculate the *Bacillus pasteurellii* strain into the above-mentioned liquid culture medium;

[0047] 3) Place the inoculated culture medium in a constant temperature and speed (30℃, 150 rpm) shaker for 20-22 hours to obtain Bacillus pasteurellus culture.

[0048] Example 1: A method for preparing a bio-composite modified erosion-resistant hydroseeding substrate

[0049] Please see Figure 1 The flowchart shown illustrates the actual engineering application of the preparation method for the bio-composite modified erosion-resistant hydroseeding substrate. The preparation method in this embodiment specifically includes the following steps:

[0050] S0. Preparation of *Bacillus pasteurellii* bacterial culture: *Bacillus pasteurellii* was inoculated into a liquid culture medium sterilized at 121℃ and cultured in a constant temperature shaking incubator at 30℃ and 150 rpm for 22 h to obtain the *Bacillus pasteurellii* bacterial culture. The bacterial activity was measured to be 10 mM / min. The above liquid culture medium was prepared as follows: 20 g / L yeast extract, 15 g / L ammonium chloride, and 0.1 mM nickel chloride were added, and the pH was adjusted to 9.25 with 5 mol / L sodium hydroxide solution. The remainder was deionized water. The mixture was then thoroughly mixed.

[0051] S1. Mix and stir the Bacillus pasteurellium bacterial solution with the first cementing solution. The volume of the first cementing solution added is 1 / 4 of the volume of the Bacillus pasteurellium bacterial solution. The first cementing solution is prepared by mixing calcium chloride solution and urea solution with equimolar concentration (2.0 mol / L) to obtain a mixed solution.

[0052] S2. The mixture was stirred at 25°C for 12 hours, and then allowed to stand at room temperature for 6 hours. Layering was observed in the mixture. Figure 2 The upper layer is a brown, transparent solution, and the lower layer is a white, flocculent precipitate, with the lower white flocculent precipitate occupying about 1 / 4 of the total solution volume. This phenomenon indicates that the Bacillus pasteurellium solution has completed sedimentation. Remove the upper brown, transparent liquid, leaving the white, flocculent, concentrated urease solution for later use. Add water or deionized water (tap water can be used for dilution, considering the convenience of the construction site) to this white, flocculent, concentrated urease solution until the volume of the original mixed solution is reached, thus obtaining biological mud. Figure 3 Then, adjust the pH of the biological mud to 6.0 with 2 mol / L hydrochloric acid, at which point the white flocculent precipitate will disappear.

[0053] S3. Weigh 1 kg of dry residual soil from granite with a particle size of less than 2 mm, and mix it evenly with 10 g of biochar and 10 g of xanthan gum to obtain a dry soil mixture of xanthan gum, biochar and granite residual soil.

[0054] S4. A mixture of biological mud with a pH of 6.0 and 0.3 mol / L secondary cementing agent (obtained by mixing equimolar concentrations of 0.3 mol / L calcium chloride solution and urea solution) at a 1:1 mass ratio is added to the dry soil mixture to replace 40% of the initial moisture content. Figure 4Add water to adjust the moisture content to 70%, sprinkle in drought-resistant plant seeds such as ryegrass and tall fescue, and mix evenly to obtain a bio-composite modified anti-erosion spraying substrate with a seed density of 30~40 g / m².

[0055] Example 2: A method for preparing a bio-composite modified erosion-resistant hydroseeding substrate

[0056] The difference from Example 1 is that, in preparing the dry soil mixture, 1 kg of dry granite residual soil particles with a particle size of less than 2 mm was weighed, and 10 g of biochar and 5 g of xanthan gum were added to obtain the dry soil mixture. All other operations were the same as in Example 1.

[0057] Example 3: A method for preparing a bio-composite modified erosion-resistant hydroseeding substrate

[0058] The difference from Example 1 is that the second cementing solution used in S4 is prepared by mixing calcium chloride solution and urea solution with equimolar concentration (0.6 mol / L) to obtain a mixed solution.

[0059] Application Example 1

[0060] Please see Figure 5 The bio-composite modified erosion-resistant hydroseeding substrate obtained in Example 1 was sprayed onto the surface of the slope model using a small hydroseeding machine. Vegetation maintenance was carried out regularly, and germination began after 7 days, with a germination rate of 83%. Figure 8 A disintegration test was conducted on the bio-composite modified erosion-resistant spray seeding substrate, and the disintegration rate was 0% after 24 hours. Figure 9 A scouring test was conducted on the substrate layer at a slope of 45°. A water discharge device was used to simulate rainfall of 2.5 L / min for 20 minutes, resulting in a scouring loss rate of 2.3%. Figure 7 Therefore, it can be seen that the bio-composite modified erosion-resistant hydroseeding substrate provided in Example 1 can effectively provide the nutrients required for plant growth and has good water stability.

[0061] In the application embodiment of the present invention, the germination rate is calculated as follows: Germination rate = Number of germinated seeds within a certain period of time / Total number of seeds * 100%.

[0062] The disintegration test is conducted in water: after the soil sample is prepared, it is soaked in water for a certain period of time, and the soil sample is observed to see if it crumbles; the disintegration rate is determined and calculated by the change in the reading of a tensile tester. Specifically, the formula for calculating the disintegration rate (DR) is:

[0063] DR t = [(W0-(W) t - Wb)) / W0] × 100%

[0064] Among them: DR t W: Disintegration rate at time t (%); W0: Initial dry weight of soil clods (g); W t Wb: Total mass (g) of "net basket + undisintegrated wet soil" at time t; Wb: Weight of the net basket (g); t - Wb): The mass of the wet soil in the undisintegrated portion at time t.

[0065] The method for determining the scour loss rate is as follows: collect the water-soil mixture slurry lost through scour, dry it, leave the dry soil, weigh it, and then divide it by the total mass of the slope soil to obtain the scour loss rate.

[0066] Application Example 2

[0067] The bio-composite modified erosion-resistant hydroseeding substrate obtained in Example 2 was sprayed onto the surface of a slope model using a small hydroseeding machine. Regular vegetation maintenance was carried out, and germination began after 7 days, with a germination rate of 82%. A disintegration test was conducted on the bio-composite modified erosion-resistant hydroseeding substrate, and the 24-hour disintegration rate was 2.1%. Figure 9 A scouring experiment was conducted on the substrate layer with a slope of 45° and a simulated rainfall of 2.5 L / min for 20 minutes using a water discharge device. The scouring loss rate was 5.3%. This demonstrates that the bio-composite modified scouring-resistant hydroseeding substrate provided in Example 2 can effectively provide the nutrients needed for plant growth and also exhibits a certain degree of water stability.

[0068] Comparative Example 1

[0069] A control test was conducted using untreated residual granite soil, specifically including the following steps:

[0070] Step 1): Take 1 kg of dried granite residual fine-grained soil and mix it with deionized water to replace 70% of the initial moisture content;

[0071] Step 2): Sprinkle drought-resistant plant seeds such as ryegrass and tall fescue into the mixed soil, with a seed density of 30~40 g / m² to obtain the sprayed vegetative substrate;

[0072] Step 3): Using a small hydroseeding machine, the sprayed vegetation substrate is sprayed onto the surface of the slope model. Regular vegetation maintenance is carried out. Germination begins after 7 days, with a germination rate of 80%. Figure 8 The substrate was subjected to a disintegration test, and the disintegration rate was 100% after 24 hours. Figure 9 A scouring test was conducted on the substrate layer at a slope of 45° and a rainfall rate of 2.5 L / min for 20 minutes. The scouring loss rate was 86.7%. Figure 6 This result indicates that the spray-mixed vegetative substrate in Comparative Example 1 can effectively provide nutrients for plant growth, but its water stability is relatively poor.

[0073] Comparative Example 2

[0074] A control experiment was conducted by mixing granite residual soil with xanthan gum, specifically including the following steps:

[0075] Step 1): Take 1 kg of dried granite residual fine soil and mix it evenly with 10 g of xanthan gum. Add deionized water and mix to replace 70% of the initial moisture content.

[0076] Step 2): Sprinkle drought-resistant plant seeds such as ryegrass and tall fescue into the mixed soil, with a seed density of 30~40 g / m² to obtain the sprayed vegetative substrate;

[0077] Step 3): Using a small hydroseeding machine, the hydro-mixed vegetation substrate from Comparative Example 2 was sprayed onto the surface of the slope model. Vegetation maintenance was carried out regularly. Germination began after 7 days, with a germination rate of 72%. A disintegration test was conducted on the substrate, and the 24-hour disintegration rate was 8.1%. Figure 9 A scouring experiment was conducted on the substrate layer at a slope of 45° and a rainfall rate of 2.5 L / min for 20 minutes, resulting in a scouring loss rate of 9.3%. This result indicates that the spray-mixed vegetation substrate in Comparative Example 2 can effectively provide nutrients for plant growth, but its water stability is relatively poor.

[0078] Comparative Example 3

[0079] A control experiment was conducted by mixing granite residual soil with biological mud, specifically including the following steps:

[0080] Step 1): Take 1 kg of dried granite residual fine soil, mix it with biological mud and 0.3 mol / L cementing liquid in a 1:1 ratio to replace 70% of the initial moisture content;

[0081] Step 2): Sprinkle drought-resistant plant seeds such as ryegrass and tall fescue into the mixed soil, with a seed density of 30~40 g / m² to obtain the sprayed vegetative substrate;

[0082] Step 3): Using a small hydroseeding machine, the hydro-mixed vegetation substrate of Comparative Example 3 was sprayed onto the surface of the slope model. Vegetation maintenance was carried out regularly. Germination began after 7 days, with a germination rate of 71%. A disintegration test was conducted on the substrate, and the disintegration rate was 50% after 24 hours. Figure 9 A scouring experiment was conducted on the substrate layer at a slope of 45° and a rainfall rate of 2.5 L / min for 20 minutes, resulting in a scouring loss rate of 16.5%. This result indicates that the spray-mixed vegetation substrate in Comparative Example 3 can effectively provide nutrients for plant growth, but its water stability is relatively poor.

[0083] Comparative Example 4

[0084] A control experiment was conducted by mixing granite residual soil with biochar, specifically including the following steps:

[0085] Step 1): Take 1 kg of dried granite residual fine soil and mix it evenly with 10 g of biochar. Add deionized water and mix to replace 70% of the initial moisture content.

[0086] Step 2): Sprinkle drought-resistant plant seeds such as ryegrass and tall fescue into the mixed soil, with a seed density of 30~40 g / m² to obtain the sprayed vegetative substrate;

[0087] Step 3): Using a small hydroseeding machine, the sprayed vegetation substrate was sprayed onto the surface of the slope model. Regular vegetation maintenance was carried out. Germination began after 7 days, with a germination rate of 74%. A disintegration test was conducted on the substrate, and the 24-hour disintegration rate was 52%. Figure 9 A scouring experiment was conducted on the substrate layer at a slope of 45° and a rainfall of 2.5 L / min for 20 minutes, resulting in a scouring loss rate of 11.8%. This result indicates that the spray-mixed vegetation substrate in Comparative Example 4 can effectively provide nutrients for plant growth, but its water stability is relatively poor.

[0088] From the above embodiments and comparative examples, it can be seen that the technology of the present invention has the following beneficial effects compared with ordinary spraying substrates:

[0089] 1. The core mechanism of this hydroseeding substrate is significant, with the incorporated bio-slurry (containing high levels of urease-producing bacteria), biochar, and xanthan gum exhibiting excellent synergistic effects. During the mixing stage, xanthan gum undergoes a hydration-gel reaction, absorbing water and swelling to initially fill the large pores in the soil. Subsequently, the urease-producing bacteria in the bio-slurry hydrolyze urea in the second cementing solution, inducing mineralization to form calcium carbonate crystals. This mineralization process lags behind the gelation reaction of xanthan gum, thus achieving secondary filling of the remaining micropores in the soil and forming a stable calcium carbonate cemented structure. The two components reinforce intermolecular connections, enhancing the stability of the soil pore structure. Simultaneously, the porous structure of biochar significantly enhances the substrate's water and fertilizer retention capacity, providing a favorable environment for microbial activity and further promoting the biomineralization process. The stepwise cementing mechanism of this invention improves the pore-filling efficiency. The addition of bio-slurry and biochar effectively overcomes the defect of xanthan gum as a single additive, which easily leads to shrinkage and cracking of the matrix layer, reducing the permeability and porosity of the matrix layer.

[0090] 2. Compared to traditional ordinary concrete spraying substrates, this hydroseeding substrate boasts advantages such as high water stability, porous structure, and eco-friendliness. Traditional ordinary concrete substrates, designed for strength, form a dense, rigid structure that isolates water and air exchange, inhibiting plant growth. This bio-composite modified hydroseeding substrate organically combines the advantages of soil with bio-slurry, biochar, and xanthan gum, establishing a "stepwise cementation, ecological symbiosis" structural system. It establishes a "first gel, then mineralize" stepwise cementation mechanism, efficiently filling soil pores and significantly improving the substrate's erosion resistance. Simultaneously, the substrate's rich porous structure provides excellent water and fertilizer retention for plant growth, creating a favorable environment for vegetation planting. This substrate overcomes the inherent defects of traditional substrates, such as ecological isolation and brittle cracking, thus significantly enhancing the erosion resistance of the hydroseeding substrate while meeting plant growth requirements, effectively improving the ecological protection and greening effect of hydroseeding on slopes in rainy southern environments.

[0091] 3. The "gel-mineralization" composite structure formed within the hydroseeding substrate, with its multi-level pores and stable cemented interface, provides ideal anchoring points for the penetration and fixation of plant roots. As the vegetation grows, the dense root network intertwines and anchors with the substrate, transforming the originally loose substrate into a reinforced "root-substrate composite." Through the synergistic effect of vegetation and engineering materials, dynamic and continuous enhancement of slope stability is achieved, with its protective effect continuously improving with the plant growth cycle.

[0092] 4. This hydroseeding substrate offers significant long-term economic benefits, exhibiting lower equipment dependence and stronger practical applicability compared to ordinary substrates. The bacterial cells in this bio-composite modified hydroseeding substrate, which utilize a large amount of bio-mud, are identical to those in the original bacterial solution, avoiding the limitations of high-speed centrifugation that causes bacterial cell compression and deformation. It has virtually no impact on cell activity, and dilution can be achieved using tap water at the construction site. The preparation process of the bio-mud is simple, requiring only the addition of a suitable amount of low-concentration calcium ion solution to the original bacterial solution. After thorough stirring and standing for a period, bio-mud with one-quarter the volume of the original bacterial solution can be obtained. In practical engineering applications, this method avoids the cumbersome operation and equipment investment required for transporting and storing large quantities of original bacterial solution, simplifying operation and significantly improving efficiency. Simultaneously, calcium ions are required for subsequent biomineralization processes; the low concentration of calcium ions does not affect bacterial activity and provides a calcium source for subsequent calcium carbonate formation, effectively reducing the cost of microbial-induced calcium carbonate precipitation technology in engineering mineralization.

[0093] Based on experimental data from numerous slope models, this invention provides a proven and mature formulation and preparation process for biomineralized sprayed vegetation substrates, offering significant guidance for practical engineering applications. Furthermore, the bio-composite modified erosion-resistant sprayed substrate provided by this invention exhibits improved water stability compared to other topsoil sprayed substrates, and the plant roots formed during subsequent plant growth can form a composite reinforcement with the ecological substrate, further enhancing slope stability. The bio-composite modified erosion-resistant sprayed substrate layer of this invention possesses strong nutrient retention capacity, providing a favorable environment and stable foundation for plant seed growth. In addition, the bio-composite modified erosion-resistant sprayed substrate of this invention is lower in carbon footprint and more environmentally friendly than ordinary sprayed vegetation substrates, requiring no large-scale machinery for preparation, and overall offers significant economic, environmental, and social benefits.

[0094] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for preparing a bio-composite modified erosion-resistant hydroseeding substrate, characterized in that, Includes the following steps: S1. Mix the bacterial solution and the first cementing solution in a certain volume ratio, stir evenly, and let stand for a period of time. Remove the upper transparent liquid obtained after standing and stratification to obtain biological mud. S2. Mix xanthan gum, biochar, and soil in a certain mass ratio and stir evenly to obtain a dry soil mixture. Then, add a certain mass or volume ratio of biological mud, second cementing liquid, water, and plant seeds to the dry soil mixture and stir evenly to obtain a bio-composite modified erosion-resistant spraying substrate.

2. The preparation method according to claim 1, characterized in that, The bacterial solution is a Bacillus pasteurellii bacterial solution.

3. The preparation method according to claim 1, characterized in that, Both the first and second cementing solutions are mixtures containing equimolar concentrations of calcium chloride and urea.

4. The preparation method according to claim 3, characterized in that, The molar concentrations of calcium chloride solution and urea solution in the first cementing solution are 1.0 mol / L to 2.0 mol / L, and the molar concentrations of calcium chloride solution and urea solution in the second cementing solution are 0.3 mol / L to 0.6 mol / L.

5. The preparation method according to claim 1, characterized in that, In step S1, the bacterial solution and the first cementing solution are mixed in a volume ratio of 3:1 to 4:

1. In step S1, the mixed solution is left to stand at room temperature for 6 to 10 hours to separate into layers.

6. The preparation method according to claim 1, characterized in that, The soil particles were less than 2 mm in size, and the mass ratio of xanthan gum to biochar was 1.0% to 1.5%.

7. The preparation method according to claim 1, characterized in that, In step S2, when adding the biological mud and the second cementing liquid to the dry soil mixture, the biological mud and the second cementing liquid are mixed with the dry soil mixture at a mass ratio of 1:

1.

8. The preparation method according to claim 7, characterized in that, In step S2, the biological mud, the second cementing liquid, and water are added to the dry soil mixture, with the moisture content controlled at 70% to 75%.

9. The preparation method according to claim 1, characterized in that, In step S2, the plant seeds are selected from one or more of ryegrass, tall fescue, bermudagrass, carpet grass, and zoysia grass, and the dosage is 30-40 g / m².

10. A bio-composite modified erosion-resistant spray seeding substrate, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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