Method for repairing open-pit mine dump by using salt and alkali tolerant shrubs and herbaceous plants

Abstract

The present application relates to the technical field of mine ecological restoration, and discloses a method for repairing a strip mine dump by using salt-tolerant shrubs and herbs in combination, which comprises the following steps: constructing a root base layer by pre-planting salt-tolerant shrub seeds on the bottom layer; respectively preparing an anti-reverse base slurry, an alkaline cross-linking trigger phase and an herb seed auxiliary phase; pumping the three-phase materials through independent channels, controlling the pipeline pressure of the alkaline cross-linking trigger phase and the herb seed auxiliary phase to be greater than the pumping pipeline pressure of the anti-reverse base slurry, and mixing the three phases into a mixed jet flow at the end of the pipeline; spraying the mixed jet flow above the base layer, triggering delayed cross-linking after landing to form a hydrogel surface layer for limiting the growth of herb root systems, and reacting with the soil to generate microcrystals to block capillary channels. By establishing a physical layer position isolation of shrubs and herbs, the nutrient competition between the herbs and the shrubs is relieved, and the multi-channel positive pressure confluence process eliminates the mechanical and chemical damage to the seeds.

Description

Technical Field

[0001] This invention relates to the field of mine ecological restoration technology, specifically a method for restoring open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs. Background Technology

[0002] Due to severe topsoil erosion, loose physical structure, and varying degrees of salinization, ecological restoration of open-pit mine spoil heaps has always been a key focus of mine area environmental management. Currently, the industry commonly uses hydroseeding or hydrogel spraying techniques for the rapid reconstruction of surface vegetation on spoil heaps. These techniques mainly involve mixing plant seeds, water-retaining agents, polymer binders, and nutrient substrates with water to create a slurry, which is then sprayed onto the surface of the slope or flat area to be restored using high-pressure pumping equipment. This forms a substrate layer that can adhere to the topsoil in a relatively short time, providing initial moisture and nutrient support for seed germination.

[0003] However, long-term engineering practice has revealed limitations in conventional hydroseeding techniques when faced with complex vegetation restoration needs. In material transport, existing equipment often uses centrifugal pumps for single-line delivery, and the high-speed rotating impellers cause direct physical shear damage to plant seed coats. To achieve rapid solidification of the substrate after landing, seeds are often mixed with a strong alkaline cross-linking agent in the same container or pipeline for extended periods. The continuous erosion by the alkaline components reduces seed embryo vigor and germination rate. Regarding vegetation establishment, to balance initial green coverage and later ecological community succession, herbaceous plants and deep-rooted shrub seeds are typically mixed and hydroseeded in the same substrate layer. Because herbaceous plants germinate early and have extremely rapid root growth, they quickly intertwine in the shallow layer to form a dense root network, intercepting most of the environmental moisture and nutrients. This causes relatively slow-growing shrub seeds to face severe nutrient competition and physical space compression in the early stages of germination, resulting in a generally low establishment rate of the shrub community later on.

[0004] Furthermore, the unique geographical and climatic environment of spoil heaps places high demands on the long-term resilience of hydroseeding remediation substrates. Mining areas are often located in high-altitude, cold regions with large diurnal temperature variations and intense ultraviolet radiation. Conventional hydrogel substrates are prone to internal water freezing and expansion, as well as polymer chain degradation, under these conditions, leading to premature degradation of the substrate's physical structure and water retention capacity. Simultaneously, soluble salts contained in the deep soil layers of spoil heaps migrate and accumulate to the surface along the capillary channels as surface water evaporates. Conventional surface covering substrates cannot block the upward flow of underground salts. Over time, the continuously increasing salt concentration in the shallow layer will cause salt stress toxicity to newly emerging plant seedlings, affecting the long-term stability of ecological restoration.

[0005] Therefore, the present invention provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, in order to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs. This method solves the problems of seed susceptibility to mechanical cutting by pumps and corrosion from alkaline cross-linking agents in traditional hydroseeding processes, low shrub establishment rates due to nutrient competition caused by the co-sowing of herbaceous plants and deep-rooted shrubs, poor stress resistance of hydrogel matrices in the cold and saline-alkali environment of mines, and the continuous upward flow of deep salts through soil capillary pores.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, employing the following technical solution: A method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs includes the following steps: S1. Sub-bottom pre-planting: Mix the seeds of at least one salt-tolerant shrub selected from Amorpha fruticosa, Caragana korshinskii, Hippophae rhamnoides, Salix matsudana or Tamarix chinensis with imported soil and lay it on the surface of the spoil heap to build a base layer for shrub rooting. S2. Material preparation: Prepare stress-resistant base slurry, alkaline crosslinking trigger phase and herbaceous seed auxiliary phase separately; the stress-resistant base slurry contains polyvinyl alcohol, a delayed crosslinking precursor formed by boric acid and glycerol, free glycerol, sodium lignosulfonate and potassium humate; the alkaline crosslinking trigger phase contains sodium silicate; the herbaceous seed auxiliary phase contains water and herbaceous seeds selected from at least one of alfalfa, tall fescue, alfalfa or ryegrass; S3, Multi-channel confluence spraying: The above three-phase materials are pumped through independent channels, and the herbaceous seed auxiliary phase is transported through a peristaltic pump or a non-impeller low-shear channel; the pumping pipeline pressure of the alkaline crosslinking trigger phase and the herbaceous seed auxiliary phase is controlled to be greater than the pumping pipeline pressure of the stress-resistant base slurry, so that the three-phase materials are confluenced and mixed into a mixed jet at the end of the pipeline for a short time before being sprayed out. S4. Spatial Isolation Covering: The mixed jet is sprayed onto the surface of the shrub root base layer. After the mixed jet lands, it triggers a delayed cross-linking and curing reaction, forming a hydrogel surface layer that encapsulates the herb seeds. At the same time, the alkaline cross-linking trigger phase infiltrates with water, and sodium silicate is used to form a salt-blocking zone that seals the capillary pores in the shallow layer of the spoil heap.

[0008] By adopting the above technical solution, and through the combination of bottom pre-planting and multi-channel confluence spraying, the material is controlled to cross-link and form a spatial isolation covering layer after landing, thus achieving the following effects: This solution establishes a three-channel independent pumping system using fluid control technology. During material transport, the pipeline pressure between the alkaline crosslinking trigger phase and the herbaceous seed auxiliary phase is consistently greater than the pipeline pressure of the stress-resistant base slurry, thus creating a unidirectional positive pressure differential at the pipeline confluence. This pressure differential design, along with the independent transport of herbaceous seeds as an auxiliary phase, significantly inhibits the reverse flow of strongly alkaline materials at the mixing point into the stress-resistant base slurry and herbaceous seed auxiliary phase channels. This completely avoids premature contact of herbaceous seeds with large amounts of alkaline components, reducing the risk of seed embryo tissue inactivation due to chemical erosion.

[0009] After instantaneous mixing at the end of the pipeline, the jet containing herbaceous seeds covers the base layer pre-planted with shrub seeds. The jet material then falls to the ground and undergoes a cross-linking phase transition to form a gel network. This structure restricts the downward extension of the herbaceous plant's fibrous roots, causing them to grow primarily within the hydrogel surface layer. Meanwhile, the deep-rooted shrub seeds in the lower soil layer develop and independently root downwards. This spatial isolation helps to mitigate the rapid depletion of moisture and nutrients from the lower soil by the herbaceous plants, alleviates the suppressive effect of the rapidly developing herbaceous community on shrub growth, and provides the necessary living space for the long-term establishment of the shrubs.

[0010] Meanwhile, during the initial landing phase of the mixed jet, some fluid components within the alkaline cross-linking trigger phase will infiltrate downwards with the water, entering the shallow surface layer of the high-salt soil in the spoil heap. The sodium silicate introduced into the formulation system reacts with calcium and magnesium ions rising from the soil capillaries with the water, undergoing an in-situ inorganic precipitation reaction to generate insoluble crystal particles. The specific reaction formula is as follows: Na2SiO3+Ca 2+ →CaSiO3↓+2Na + ; Na2SiO3+Mg 2+ →MgSiO3↓+2Na + ; The generated calcium silicate and magnesium silicate microcrystals can be retained in situ in the capillary pores of the soil, which can physically block the channels through which groundwater carries salt to the surface, thereby slowing down the process of surface soil salinization due to water evaporation.

[0011] Preferably, in step S2, the raw materials of the stress-resistant base slurry include, by weight: 8-15 parts polyvinyl alcohol, 0.5-2.5 parts boric acid, 6-15 parts glycerol, 1-4 parts sodium lignosulfonate, 0.5-3 parts potassium humate, and 100-120 parts water; wherein, the boric acid combines with a portion of the glycerol to form the delayed crosslinking precursor, and the remaining glycerol is the free glycerol; the alkaline crosslinking trigger phase includes the following raw materials by weight: 2-8 parts sodium silicate (solids) and 10-20 parts water; the herbaceous seed auxiliary phase includes the following raw materials by weight: 1-3 parts herbaceous seeds and 10-20 parts water. The degree of alcoholysis of the polyvinyl alcohol is 85%-90%, and the degree of polymerization is 1700-2400; the sodium lignosulfonate is a high molecular weight compound containing an aromatic ring structure, and the potassium humate is a small molecule highly active component containing a conjugated polyphenol structure.

[0012] By employing the above technical solution, polyvinyl alcohol provides the polymer backbone, boric acid provides the chemical cross-linking nodes, and sodium silicate serves as the alkali source and precipitant for the cross-linking reaction. Furthermore, the sodium lignosulfonate used in conjunction contains aromatic rings, and potassium humate contains conjugated polyphenol structures; both tend to arrange themselves around the polyvinyl alcohol backbone, acting as a kind of physical barrier. This macromolecular structure helps absorb some external ultraviolet radiation and converts it into heat energy through intramolecular vibrations, thereby reducing the probability of the polyvinyl alcohol backbone breaking down and degrading due to ultraviolet light absorption. On the other hand, the sulfonic acid groups attached to the structures of sodium lignosulfonate and potassium humate provide certain steric hindrance and electrostatic repulsion, which can appropriately slow down the damage to the polyvinyl alcohol hydration layer when faced with high concentrations of external free cations, thus helping the hydrogel matrix maintain its internal water storage space under saline-alkali conditions.

[0013] Preferably, in step S2, the specific preparation method of the stress-resistant basic slurry includes: first, pre-reacting the boric acid with glycerol accounting for 30%-40% of the total glycerol content under acidic conditions with a pH of 3.5-5.5 to prepare a delayed crosslinking precursor formed by boric acid and glycerol; then, dissolving the polyvinyl alcohol in hot water at 85-95°C and stirring to gelatinize it; when the system cools down to 50-60°C, adding the above-prepared delayed crosslinking precursor formed by boric acid and glycerol and reacting for 30-45 minutes; then adding the remaining amount of glycerol, sodium lignosulfonate and potassium humate, and stirring evenly at room temperature of 20-30°C to obtain the liquid stress-resistant basic slurry.

[0014] By employing the above technical solution and using a batch-addition of glycerol, the first batch of added glycerol undergoes a moderate pre-esterification reaction with the side-chain hydroxyl groups of polyvinyl alcohol under the action of boric acid, thus constructing a relatively loose initial polymer network. The remaining glycerol is then added; this portion does not participate in the initial pre-esterification reaction but remains primarily in a free state within the gaps of the polymer network. These free glycerol molecules, through their polyhydroxyl structure, can bind with water molecules within the gel to form hydrogen bonds. This hydrogen bond interaction interferes with the crystallization process of water molecules, lowering the freezing point of free water within the matrix. When exposed to external cooling, this can mitigate, to some extent, the physical damage to the material structure caused by the expansion of internal water upon freezing.

[0015] Preferably, in step S3, the stress-resistant base slurry is pumped through a centrifugal mud pump in the main channel, the herbaceous seed auxiliary phase is pumped independently through a peristaltic pump in the side channel, and the alkaline crosslinking trigger phase is pumped independently through a metering pump in another side channel. During the pumping process, the pumping pressure in each side channel is controlled to be 0.15-0.55 MPa higher than the average back pressure in the main channel. The mixing process is carried out in a static mixer installed at the end of the pipeline, and the residence time of the three-phase materials in the static mixer is controlled to be 0.5-1.5 seconds.

[0016] By adopting the above technical solution, a peristaltic pump is introduced to independently transport the herbaceous seed auxiliary phase containing herbaceous seeds. This mainly utilizes the fluid compression and propulsion mode within the flexible tube, avoiding the physical shear force generated by the high-speed rotation of the impeller in a conventional centrifugal water pump. This helps reduce the risk of mechanical breakage of plant seeds during pumping. Using a metering pump to transport the alkaline trigger phase ensures the precise proportioning of the crosslinking agent. Simultaneously, controlling the fluid residence time of the three-phase materials in the static mixer to approximately 0.5 to 1.5 seconds provides basic uniform mixing conditions and prevents premature deep solidification of the materials within the pipeline due to excessive fluid residence time, thereby reducing the probability of pipe blockage during construction.

[0017] Preferably, in step S4, after the mixed jet lands, the pH value of its system rises to 8.5-10.0, and cross-linking and solidification are completed within 10-30 seconds to form the hydrogel surface layer with a three-dimensional network structure, and the free glycerol is locked inside the three-dimensional network structure; the alkaline cross-linking trigger phase penetrates downward to a depth of 2 cm below the surface of the waste disposal site, and the increase in the electrical conductivity of the surface soil in the 0-2 cm layer is controlled to be between 0.11-0.22 mS / cm after 30 days of treatment under continuous evaporation test conditions on day 0 after the in-situ cross-linking and solidification of the hydrogel surface layer.

[0018] By employing the above technical solution, the sodium silicate component in the mixture releases hydroxide ions, making the local fluid environment alkaline. When the system pH reaches the range of 8.5 to 10.0, it accelerates the multidimensional complexation and cross-linking reaction between borate and polyvinyl alcohol, causing the polymer chains to intertwine and form a three-dimensional network structure within a short time after landing. As the phase change process progresses, the free glycerol and other components reserved in the system are encapsulated and confined within the network, allowing the surface material to be formed in situ and exert a physical sealing effect.

[0019] Preferably, in step S2, the herbaceous seed auxiliary phase or alkaline crosslinking trigger phase further contains highly water-retaining plant cellulose and a compound microbial agent, which have a water absorption ratio of 20-50 times their own weight in a pure water medium at 25°C. The amount of highly water-retaining plant cellulose added is 2%-5% of the total weight before the addition of the corresponding phase region, and the amount of the compound microbial agent added is 0.1%-0.5% of the total weight before the addition of the corresponding phase region.

[0020] By adopting the above technical solution, the addition of plant cellulose increases the physical adsorption porosity of the substrate surface layer, which is beneficial for providing the necessary moisture support for the initial germination of herbaceous seeds. After the compound microbial agent is fixed inside the gel system, as the polymer matrix components naturally degrade later, the microbial community will gradually be released into the surrounding soil. This helps to replenish the trace elements in the local soil and regulate the community structure of the surrounding microhabitat to a certain extent.

[0021] This invention provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs. It offers the following advantages: 1. This invention establishes a stratified isolation of the community in physical space through a process that combines pre-planting shrub seeds at the bottom layer with spraying a mixture of herbaceous plants on the surface. The three-dimensional hydrogel network formed after the jet material undergoes a phase change upon landing restricts the growth of herbaceous plant roots within the surface layer, allowing the shrub seeds at the bottom layer to develop independently and take root downwards in the lower soil layer, free from the pressure and entanglement of herbaceous roots. This stratified spatial arrangement blocks the rapid absorption channels of deep water and nutrients by herbaceous plants, alleviating nutrient competition and shading suppression of deep-rooted shrubs by herbaceous plants in the early stages of growth. While ensuring initial surface vegetation coverage, it significantly improves the long-term establishment rate of shrubs.

[0022] 2. This invention utilizes multi-channel positive pressure confluence fluid control technology, employing a flexible peristaltic pump to independently deliver the alkaline cross-linking trigger phase containing herbaceous seeds. The flexible confluence extrusion propulsion mode avoids the mechanical cutting damage to the seed coat caused by the high-speed rotation of the impeller in conventional mud pumps. Simultaneously, maintaining a unidirectional positive pressure differential at the confluence of the alkaline cross-linking trigger phase channel against the reverse base slurry channel effectively prevents the reverse backflow of the strongly alkaline cross-linking material from a kinetic perspective. This avoids prolonged immersion of the herbaceous seeds within the confluence, preventing erosion by alkaline substances and effectively protecting the initial embryonic vigor and germination rate of the seeds.

[0023] 3. This invention retains free glycerol in the stress-resistant base slurry and introduces a polymer compound with a macromolecular barrier structure. It utilizes multi-hydroxyl hydrogen bonding to lower the system's freezing point and relies on the aromatic ring structure to dissipate ultraviolet light energy, thus improving the structural stability of the hydrogel matrix under high-altitude and high-light radiation environments. After the material lands, the sodium silicate, which infiltrates with water, further undergoes an inorganic precipitation reaction with calcium and magnesium ions rising through capillary channels in high-salt soil. The in-situ generated insoluble microcrystalline particles intercept and physically block the capillary pores of the shallow soil layer, thereby reducing the rate at which underground salts migrate to the surface with water evaporation and improving the microenvironment for seed establishment. Attached Figure Description

[0024] Figure 1 The figures show the structural characterization of the delayed crosslinking precursor and the rheological properties of the crosslinking reaction system of the present invention. Among them, (a) is the ATR-FTIR infrared absorption spectrum of the reference sample and the liquid delayed crosslinking precursor obtained in Preparation Example 1, and (b) is the curve of the storage modulus of Example 1, Comparative Example 1 and Comparative Example 2 changing with test time. Figure 2 The diagram shows the changes in conveying pressure and pumping energy consumption per unit volume under different conveying methods of the present invention. (a) is a graph showing the relationship between the average back pressure of the main channel and the pumping energy consumption per unit volume, and (b) is a graph showing the trend of pipeline pressure changes in Example 1 and Comparative Example 4 within a representative operating range. Figure 3 This is a trend diagram showing the change in soil electrical conductivity from 0 to 2 cm in the surface layer of the soil column as a function of continuous evaporation time. Figure 4 This is a trend diagram showing the change of temperature difference between the matrix center and the environment inside the chamber under simulated illumination conditions as a function of illumination time. Figure 5 This is a schematic diagram illustrating the relationship between the germination rate of herbaceous seeds recovered after spraying and the number of surviving shrubs after 90 days, according to the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0027] Polyvinyl alcohol, CAS No. 9002-89-5, chemical name is high molecular linear homopolymer polyvinyl alcohol, the molecular structure is composed of repeating ethylene alcohol structural units linked together, the degree of alcoholysis is 88%, the degree of polymerization is 1700 to 2400, the weight average molecular weight distribution ranges from 75kDa to 105kDa, and it is a white powder at room temperature.

[0028] Sodium-based bentonite, CAS No. 85049-30-5, passes through a 200-mesh standard sieve, with an average particle size of less than 74 μm and a cation exchange capacity greater than 80 mmol / 100g.

[0029] Sodium lignosulfonate, CAS No. 8061-51-6, has a weight-average molecular weight range of 8kDa to 10kDa and a sulfonic acid mass fraction of 8% to 10%.

[0030] Potassium humate is a small-molecule, highly active component extracted from natural humic acid. Its weight-average molecular weight is less than 1 kDa, its water solubility is greater than 95%, and its appearance is a dark brown powder.

[0031] Sodium silicate, CAS No. 1344-09-8, is used in an aqueous solution with a mass concentration of 20% to 25%, provided that the molar ratio of silicon dioxide to sodium oxide is limited to 2.8 to 3.3.

[0032] For routine chemical reagents, commercially available analytical grade products were used, including boric acid with CAS number 10043-35-3 and a purity greater than 99.5%, glycerol with CAS number 56-81-5 and a purity greater than 99.0%, potassium dihydrogen phosphate with CAS number 7778-77-0 and a purity greater than 99.0%, and an aqueous solution of phosphoric acid with CAS number 7664-38-2 and a mass concentration of 10%.

[0033] The shrub seeds were sand willow seeds and Amorpha fruticosa seeds, which were soaked in 25℃ warm water for 24 hours before sowing to promote germination. The herbaceous plant seeds were tall fescue seeds, alfalfa seeds and ryegrass seeds. Among them, ryegrass seeds were used for representative field plot verification experiments, and the germination rate of all of them was greater than 85%.

[0034] Preparation Example 1: This preparation example provides a method for preparing a delayed crosslinking precursor, including the following steps: (1) Add 22 mL of water and 27.6 g of glycerin to a mixing jar equipped with a constant temperature water bath, turn on the stirring and heat to 60 °C; (2) Add 6.2g of powdered boric acid in batches at a uniform rate. At this time, the molar ratio of boric acid to glycerol in the system is 1:3. (3) Stir at 200 rpm for 30 min to allow the two to undergo esterification complexation until the system becomes transparent and homogeneous and no crystals precipitate. Cool down to room temperature to obtain a liquid delayed crosslinking precursor for later use.

[0035] Preparation Example 2: This preparation example provides a method for preparing a delayed crosslinking precursor, including the following steps: (1) Add 26 mL of water and 32.2 g of glycerin to a mixing jar with a constant temperature water bath, turn on the stirring and heat to 62 °C; (2) Add 6.2g of powdered boric acid in batches at a uniform rate. At this time, the molar ratio of boric acid to glycerol in the system is 1 to 3.5. (3) Stir at 250 rpm for 38 min to allow the two to undergo esterification complexation until the system becomes transparent and homogeneous and no crystals precipitate. Cool down to room temperature to obtain a liquid delayed crosslinking precursor for later use.

[0036] Preparation Example 3: This preparation example provides a method for preparing a delayed crosslinking precursor, including the following steps: (1) Add 29 mL of water and 36.8 g of glycerin to a mixing tank with a constant temperature water bath, turn on the stirring and heat to 65 °C; (2) Add 6.2g of powdered boric acid in batches at a uniform rate. At this time, the molar ratio of boric acid to glycerol in the system is 1:4. (3) Stir at 300 rpm for 45 min to allow the two to undergo esterification complexation until the system becomes transparent and homogeneous and no crystals precipitate. Cool down to room temperature to obtain a liquid delayed crosslinking precursor for later use.

[0037] Example 1: This embodiment provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, including the following steps: Step 1: Preparation of the stress-resistant base slurry: Inject 100 kg of water into a reactor equipped with a variable frequency stirrer and a temperature control jacket, start the stirrer and heat to 88°C; slowly add 5.5 kg of polyvinyl alcohol, stir at a constant temperature until it is completely dissolved into a homogeneous transparent sol; circulate cooling water through the jacket to cool the material to 38°C, add 1.2 kg of sodium lignosulfonate, 0.5 kg of potassium humate and 15.0 kg of sodium bentonite, increase the speed to 220 rpm for strong dispersion for 35 min; add 0. 3 kg of potassium dihydrogen phosphate was used to adjust the pH of the system to 5.2; the temperature was maintained at no higher than 40℃, and shrub seeds were not added to the stress-resistant base slurry; finally, all the delayed crosslinking precursors prepared by scaling up the preparation method according to Preparation Example 2 were added using 0.3 kg of boric acid as raw material and mixed evenly to obtain the stress-resistant base slurry; before spraying, 2.0 kg of germinated sand willow seeds were evenly pre-distributed in the surface soil of the slope of the spoil heap to be repaired, so that the sand willow seeds were located in the soil layer below the hydrogel surface layer to be sprayed later; Step 2: Preparation of alkaline crosslinking trigger phase and herbaceous seed auxiliary phase: Prepare 10.0 kg of sodium silicate aqueous solution with a mass concentration of 22% as alkaline crosslinking trigger phase; mix 0.75 kg of tall fescue seeds with 0.75 kg of water evenly to obtain herbaceous seed auxiliary phase with a total mass of 1.5 kg; Step 3, Multi-channel positive pressure delivery and delayed cross-linking spraying: The stress-resistant base slurry obtained in Step 1 is delivered to the main channel of the multi-channel manifold valve block at an outlet pressure of approximately 0.9 MPa using a high-pressure centrifugal mud pump; simultaneously, the herbaceous seed auxiliary phase is injected into side channel A at a positive pressure of 1.35 MPa using a peristaltic pump, and the alkaline cross-linking trigger phase is injected into side channel B at a positive pressure of 1.35 MPa using a high-pressure diaphragm metering pump; after the three fluids merge, they are forcibly pushed into a large-diameter static mixer with a length of 0.65 m by the positive pressure of the system. The residence time of the fluid in the mixer is controlled to be 0.6 s. After mixing, the fluid flows out of the spray gun, stays in the air for 4 s after spraying, and then contacts the slope surface. The pH value of the system after the mixed jet lands is measured to be 8.8, and in-situ cross-linking and curing are completed within 18 seconds.

[0038] Example 2: This embodiment provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, including the following steps: Step 1: Preparation of the stress-resistant base slurry: 100 kg of water was injected into a reactor equipped with a variable frequency stirrer and a temperature control jacket. The stirrer was turned on and the temperature was raised to 85°C. 3.0 kg of polyvinyl alcohol was slowly added and stirred at a constant temperature until it was completely dissolved into a homogeneous transparent sol. The temperature was lowered to 35°C, and 0.5 kg of sodium lignosulfonate, 0.2 kg of potassium humate and 10.0 kg of sodium bentonite were added. The stirring speed was increased to 200 rpm and the mixture was strongly dispersed for 30 min. 0.1 kg of potassium dihydrogen phosphate was added to adjust the pH of the system to 5.0. The temperature was maintained at no higher than 40°C, and no shrub seeds were added to the stress-resistant base slurry. Finally, all the delayed crosslinking precursors prepared by scaling up the preparation method according to Example 1 using 0.1 kg of boric acid as raw material were added and mixed evenly to obtain the stress-resistant base slurry. Before spraying, 1.0 kg of germinated Salix psammophila seeds were evenly pre-distributed in the surface soil of the slope of the spoil heap to be repaired, so that the Salix psammophila seeds were located in the soil layer below the hydrogel surface layer to be sprayed. Step 2: Preparation of alkaline crosslinking trigger phase and herbaceous seed auxiliary phase: Prepare 5.0 kg of 20% sodium silicate aqueous solution as alkaline crosslinking trigger phase; mix 0.5 kg of alfalfa seeds with 0.5 kg of water evenly to obtain a total mass of 1.0 kg of herbaceous seed auxiliary phase; Step 3, Multi-channel positive pressure delivery and delayed cross-linking spraying: The stress-resistant base slurry obtained in Step 1 is delivered to the main channel of the multi-channel manifold valve block at an outlet pressure of approximately 0.8 MPa using a high-pressure centrifugal mud pump; simultaneously, the herbaceous seed auxiliary phase is injected into side channel A at a positive pressure of 1.2 MPa using a peristaltic pump, and the alkaline cross-linking trigger phase is injected into side channel B at a positive pressure of 1.2 MPa using a high-pressure diaphragm metering pump; after the three fluids merge, they are forcibly pushed into a large-diameter static mixer with a length of 0.5 m. The residence time of the fluid in the mixer is controlled to be 0.5 s. After mixing, the fluid flows out of the spray gun, stays in the air for 3 s after spraying, and then contacts the slope surface. The pH value of the system after the mixed jet lands is measured to be 8.5, and in-situ cross-linking and curing are completed within 25 seconds.

[0039] Example 3: This embodiment provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, including the following steps: Step 1: Preparation of the stress-resistant base slurry: 100 kg of water was injected into a reactor equipped with a variable frequency stirrer and a temperature control jacket. The stirrer was turned on and the temperature was raised to 90°C. 8.0 kg of polyvinyl alcohol was slowly added and stirred at a constant temperature until it was completely dissolved into a homogeneous transparent sol. The temperature was lowered to 40°C, and 2.0 kg of sodium lignosulfonate, 0.8 kg of potassium humate, and 20.0 kg of sodium bentonite were added. The stirring speed was increased to 250 rpm and the mixture was strongly dispersed for 40 min. 0.5 kg of potassium dihydrogen phosphate was added to adjust the pH of the system to 5.5. The temperature was maintained at no higher than 40°C, and no shrub seeds were added to the stress-resistant base slurry. Finally, all the delayed crosslinking precursors prepared by scaling up the preparation method according to Example 3 using 0.5 kg of boric acid as raw material were added and mixed evenly to obtain the stress-resistant base slurry. Before spraying, 3.0 kg of germinated Amorpha fruticosa seeds were evenly pre-distributed in the surface soil of the slope of the spoil heap to be repaired, so that the Amorpha fruticosa seeds were located in the soil layer below the hydrogel surface layer to be sprayed. Step 2: Preparation of alkaline crosslinking trigger phase and herbaceous seed auxiliary phase: Prepare 15.0 kg of sodium silicate aqueous solution with a mass concentration of 25% as alkaline crosslinking trigger phase; mix 1.0 kg of tall fescue seeds with 1.0 kg of water evenly to obtain herbaceous seed auxiliary phase with a total mass of 2.0 kg; Step 3, Multi-channel positive pressure delivery and delayed cross-linking spraying: The stress-resistant base slurry obtained in Step 1 is delivered to the main channel of the multi-channel manifold valve block at an outlet pressure of approximately 1.0 MPa using a high-pressure centrifugal mud pump; simultaneously, the herbaceous seed auxiliary phase is injected into side channel A at a positive pressure of 1.5 MPa using a peristaltic pump, and the alkaline cross-linking trigger phase is injected into side channel B at a positive pressure of 1.5 MPa using a high-pressure diaphragm metering pump; after the three fluids merge, they are forcibly pushed into a large-diameter static mixer with a length of 0.8 m. The residence time of the fluid in the mixer is controlled to be 0.9 s. After mixing, the fluid flows out of the spray gun, stays in the air for 5 s after spraying, and then contacts the slope surface. The pH value of the system after the mixed jet lands is measured to be 9.5, and in-situ cross-linking and curing are completed within 12 seconds.

[0040] Example 4: This embodiment provides a method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, including the following steps: Step 1: Preparation of the stress-resistant base slurry: Inject 100 kg of water into a reactor equipped with a variable frequency stirrer and a temperature control jacket, start the stirrer and heat to 88°C; slowly add 6.0 kg of polyvinyl alcohol, stir at a constant temperature until it is completely dissolved into a homogeneous transparent sol; cool to 38°C, add 1.5 kg of sodium lignosulfonate, 0.8 kg of potassium humate and 18.0 kg of sodium bentonite, increase the speed to 230 rpm for strong dispersion for 35 min; add 0.4 kg of 10% dilute phosphorus solution. The pH of the acid-adjusted system was adjusted to 5.2; the temperature was maintained at no higher than 40℃, and shrub seeds were not added to the stress-resistant base slurry; finally, all the delayed crosslinking precursors prepared by scaling up the preparation method according to Preparation Example 3 were added using 0.4 kg of boric acid as raw material and mixed evenly to obtain the stress-resistant base slurry; before spraying, 2.5 kg of germinated mixed seeds of Salix psammophila and Amorpha fruticosa were evenly pre-distributed in the surface soil of the slope of the spoil heap to be repaired, so that the mixed seeds of Salix psammophila and Amorpha fruticosa were located in the soil layer below the hydrogel surface layer to be sprayed later; Step 2: Preparation of the alkaline crosslinking trigger phase and the herbaceous seed auxiliary phase: Prepare 12.0 kg of a 25% sodium silicate aqueous solution as the alkaline crosslinking trigger phase, and add 0.36 kg of high water-retaining plant cellulose and 0.036 kg of compound microbial agent to the alkaline crosslinking trigger phase, so that the addition amount accounts for 3% and 0.3% of the total weight of the phase before addition, respectively; mix 0.8 kg of alfalfa seeds with 0.8 kg of water evenly to obtain a herbaceous seed auxiliary phase with a total weight of 1.6 kg; Step 3, Multi-channel positive pressure delivery and delayed cross-linking spraying: The stress-resistant base slurry obtained in Step 1 is delivered to the main channel of the multi-channel manifold valve block at an outlet pressure of approximately 0.9 MPa using a high-pressure centrifugal mud pump; simultaneously, the herbaceous seed auxiliary phase is injected into side channel A at a positive pressure of 1.4 MPa using a peristaltic pump, and the alkaline cross-linking trigger phase is injected into side channel B at a positive pressure of 1.4 MPa using a high-pressure diaphragm metering pump; after the three fluids merge, they are forcibly pushed into a large-diameter static mixer with a length of 0.7 m. The residence time of the fluid in the mixer is controlled to be 0.7 s. After mixing, the fluid flows out of the spray gun, stays in the air for 4 s after spraying, and then contacts the slope surface. The pH value of the system after the mixed jet lands is measured to be 9.2, and in-situ cross-linking and curing are completed within 15 seconds.

[0041] Comparative Example 1: Compared to Example 1, the difference lies in the altered cross-linking triggering sequence and pumping process. 10.0 kg of sodium silicate aqueous solution was directly added to the stress-resistant base slurry in the reactor, stirred to pre-cross-link and solidify into a high-viscosity hydrogel, and then herbaceous seeds were mixed in as a cofactor. Finally, the entire mixture was pumped and sprayed using a high-pressure centrifugal mud pump. The *Salix psammophila* seeds were pre-placed in the surface soil of the slope to be restored before spraying, as in Example 1. Everything else remained the same.

[0042] Comparative Example 2: Compared to Example 1, the difference lies in the change of the molar ratio during the preparation of the delayed crosslinking precursor. In preparing this crosslinking precursor, the molar ratio of boric acid to glycerol was adjusted to 1:1, meaning that only the basic esterification complexation consumption was met, and there was no excess free glycerol residue in the system. Everything else remained the same.

[0043] Comparative Example 3: Compared to Example 1, the difference lies in the removal of the synergistic components of sodium lignosulfonate and potassium humate. In the preparation steps of the stress-resistant base slurry, sodium lignosulfonate and potassium humate are not added; instead, sodium-based bentonite is directly added for dispersion. All other steps are the same.

[0044] Comparative Example 4: Compared to Example 1, the differences lie in the simultaneous alteration of the spatial arrangement of the seeds and the terminal confluence method. Germinated *Salix psammophila* seeds and tall fescue seeds were simultaneously mixed into the stress-resistant base slurry, without pre-laying shrub seeds at the bottom of the slope; the multi-channel confluence valve block and the positive pressure pump side channel were removed at the end, replaced by a negative pressure Venturi jet injector, utilizing the negative pressure suction effect generated by the main flow velocity to draw in sodium silicate aqueous solution. This comparative example was used to evaluate the failure under the combined conditions of shrub-grass co-layer sowing and negative pressure suction confluence. All other aspects remained the same.

[0045] Comparative Example 5: The difference from Example 1 is that the chemical substance of the alkaline crosslinking trigger phase was replaced. The 22% sodium silicate aqueous solution was replaced with a sodium hydroxide aqueous solution with the same pH value as the alkaline crosslinking trigger phase, and the added mass of the alkaline crosslinking trigger phase remained 10.0 kg. Everything else was the same.

[0046] Test Example 1: Experimental Description: Fourier transform infrared spectroscopy was used to characterize the structural changes of the crosslinking precursor, and a rotational rheometer was used to monitor the change of the storage modulus of the crosslinking reaction system over time, in order to evaluate the crosslinking induction time and delayed crosslinking characteristics of the crosslinking reaction system.

[0047] Experimental steps: (1) The liquid crosslinking precursor prepared in Preparation Example 1 was used as the test sample. Boric acid and glycerol were directly stirred and mixed at room temperature (25°C) according to the feeding ratio in Preparation Example 1. This liquid-solid mixture without isothermal esterification complexation treatment was used as the reference sample. Fourier transform infrared spectroscopy was performed using an attenuated total reflectance accessory at a resolution of 4 cm⁻¹. -1 Scanning range 4000cm -1 Up to 500cm -1 Under the conditions, the ATR-FTIR infrared absorption spectra of the two samples were recorded.

[0048] (2) Use a rotational rheometer, configure a coaxial cylindrical measuring rotor, and keep the temperature of the test system constant at 25℃.

[0049] (3) For Example 1 and Comparative Example 2, 40 mL of the stress-resistant base slurry without the addition of the alkaline crosslinking trigger phase was measured and placed in a cylindrical sample cell. The rheometer was set to time-scan mode, and a constant strain of 1% and a test frequency of 1 Hz were applied. At the same time as starting the shear measurement, the corresponding proportion of the alkaline crosslinking trigger phase was rapidly injected into the cylinder through a syringe and mixed. The evolution data of the storage modulus and loss modulus of the system over time were recorded in real time. The time when the storage modulus produces a step increase and exceeds the loss modulus was defined as the crosslinking induction time.

[0050] (4) For Comparative Example 1, take the hydrogel sample obtained by pre-crosslinking and curing in the reactor, cut an appropriate amount and put it into the sample cell, run time scanning under the same test conditions, and record its initial and subsequent energy storage modulus data.

[0051] The experimental data are shown in Table 1: Table 1. Test data of cross-linking curing rheological parameters: Note: Comparative Example 1 is in a pre-crosslinked state, exhibiting high-modulus gel characteristics from the start of the test, and has no induction period data.

[0052] See Table 1 and Figure 1 Infrared spectroscopy results showed that, compared with the reference sample that had not undergone isothermal esterification complexation treatment, the liquid crosslinking precursor obtained in Preparation Example 1 exhibited better performance at 1380 cm⁻¹. -1 A BOC bond-related absorption peak appeared nearby, at 1420 cm⁻¹. -1 The intensity of the absorption peaks associated with free boric acid decreased. These results indicate that, under the test conditions, a boric acid-glycerol esterified complex structure may have formed between boric acid and glycerol. This structure helps to reduce the degree to which boric acid directly participates in the rapid crosslinking of polyvinyl alcohol in the system, thus providing a reaction basis for subsequent delayed crosslinking.

[0053] Rheological testing results showed that in Example 1, after the addition of the alkaline crosslinking trigger phase, the storage modulus increased significantly after approximately 3.8 seconds and gradually reached a stable level, indicating that the system has a certain crosslinking induction time. In Comparative Example 2, the storage modulus increased rapidly after approximately 0.6 seconds, indicating that its crosslinking and curing process was faster. Based on the formulation analysis, the relatively excessive glycerol in Example 1 may have a competitive or buffering effect on the crosslinking reaction between polyvinyl alcohol and boric acid, thereby prolonging the crosslinking induction time. This delayed crosslinking characteristic helps reduce the risk of premature curing of materials in pipelines or static mixers.

[0054] Comparative Example 1, employing a pre-crosslinking process, achieved a storage modulus of 9214.1 Pa at the start of the test, exhibiting a high-modulus gel state. In contrast, Example 1, before the addition of the alkaline crosslinking trigger phase, had an initial storage modulus of 15.2 Pa, indicating that the stress-resistant base slurry maintained a low-modulus flow state before triggering crosslinking. This state is beneficial for reducing flow resistance during transport and provides an operational time window for the stress-resistant base slurry, herbaceous seed auxiliary phase, and alkaline crosslinking trigger phase to be fully mixed at the end of the pipeline.

[0055] Test Example 2: Experimental Description: This test involves building a pilot-scale pipeline test bench to monitor pipeline pressure changes, alkaline crosslinking trigger phase injection status, and pumping energy consumption per unit volume under different delivery modes. This is used to evaluate the delivery stability and engineering applicability of the multi-channel positive pressure anti-backflow design.

[0056] Experimental steps: (1) Construct a multi-channel hydroseeding pilot test system. The main channel is equipped with a centrifugal mud pump, and the side channels are equipped with a peristaltic pump and a diaphragm metering pump, respectively. The end of each channel is connected to a large-diameter static mixer. Pressure transmitters and power monitoring meters are installed at the pump outlets of the main channel, the pump outlets of the side channels, and the inlet of the static mixer.

[0057] (2) For Examples 1 to 4, prepare the stress-resistant base slurry, alkaline crosslinking trigger phase, and herbaceous seed auxiliary phase according to the corresponding schemes, and pump them into the corresponding silos respectively. Start the control system and run the test system continuously for 120 minutes according to the set operating parameters. Record the average back pressure of the main channel and the actual injection pressure of the alkaline crosslinking trigger phase during stable operation. Extract the data from the power monitoring meter to calculate the pumping energy consumption per cubic meter of slurry per unit volume, and count the number of times the end mixer and pipeline were blocked during operation.

[0058] (3) For Comparative Example 1, the hydrogel that had been cross-linked and cured in the reactor was put into the main material silo, and the main channel centrifugal slurry pump was turned on for single-channel delivery, maintaining the same flow parameters as in the example. The system back pressure, pumping energy consumption per unit volume, and pipe blockage were recorded over 120 minutes.

[0059] (4) For Comparative Example 4, a negative pressure Venturi jet injector was installed at the end of the main pipeline to replace the multi-channel positive pressure manifold. The anti-reverse base slurry was transported through the main pipeline, and the alkaline crosslinking trigger phase was drawn in by the negative pressure of the Venturi jet injector. The pressure data fluctuations during operation were recorded, and the reading of the pressure gauge at the suction end was used to characterize the suction stability of the alkaline crosslinking trigger phase. The backflow phenomenon of the suction pipeline was observed, and the number of pipe blockages and power consumption were counted.

[0060] The experimental data are shown in Table 2: Table 2 Test Data of Delivery Pressure and Pumping Energy Consumption per Unit Volume: According to Table 2 and Figure 2 Data shows that different material states have a certain impact on conveying pressure and pumping energy consumption per unit volume. Comparative Example 1 uses pre-crosslinked hydrogel for single-channel conveying; during the test, the average back pressure of the main channel was 3.65 MPa, and the pumping energy consumption per unit volume of slurry was 9.14 kWh·m³. -3 In Examples 1 to 4, no alkaline crosslinking trigger phase was introduced during the long-distance transport stage. The stress-resistant basic slurry remained in a flowing state, the average back pressure in the main channel was 0.82 MPa to 1.05 MPa, and the pumping energy consumption per unit volume of slurry was 1.31 kWh·m³. -3 Up to 1.72 kWh·m -3 The above results indicate that, compared to the pre-crosslinked gel single-path delivery method, the delayed crosslinking spraying method is beneficial for reducing pipeline resistance and energy consumption during the delivery process.

[0061] From the injection status of the alkaline crosslinking trigger phase, in Comparative Example 4, when using the Venturi negative pressure suction method, the pressure gauge reading at the suction end was 0.38 MPa, accompanied by certain pressure fluctuations, and a significant fluid backflow phenomenon was observed during operation. This phenomenon may be related to the back pressure of the end static mixer, fluctuations in the main pipe pressure, and insufficient Venturi suction capacity. Examples 1 to 4 used a multi-channel positive pressure delivery method, and the actual injection pressure of the alkaline crosslinking trigger phase was 1.21 MPa to 1.48 MPa, which was generally higher than the average back pressure of the corresponding main channel. This positive pressure difference is beneficial for the alkaline crosslinking trigger phase to enter the end mixing area in a set proportion and reduces the risk of material backflow into the suction pipe or side channel.

[0062] The pipe blockage statistics showed that Comparative Example 1 and Comparative Example 4 experienced 3 and 2 blockages respectively during 120 minutes of continuous operation; Examples 1 to 4 did not record any blockages within the same test time. Combined with pressure data analysis, the high flow resistance during pre-crosslinked gel delivery, as well as the backflow and proportion fluctuations during Venturi negative pressure suction, may increase the risk of premature crosslinking or material retention. The examples employed a multi-channel positive pressure delivery and delayed crosslinking spraying method, ensuring that the materials of each phase mainly contact each other in the final mixing area and continue to complete crosslinking and curing after spraying, which is beneficial for improving the operational stability of the continuous spraying process.

[0063] Test Example 3: Experimental Description: This test is used to simulate temperature alternation, high salinity and high evaporation environmental conditions to monitor the physicochemical properties of the solidified gel matrix and soil column model, in order to evaluate the system's performance in resisting frost heave, moisture absorption and water retention, resisting salt precipitation and dehydration, and in situ blocking the upward movement of soil salts.

[0064] Experimental steps: (1) Preparation of test matrix and simulated extract. According to the proportions of Examples 1 to 4, Comparative Examples 2, 3 and 5, after deducting the plant seeds, weigh the corresponding stress-resistant basic slurry, alkaline crosslinking trigger phase and seedless auxiliary phase blank liquid, wherein the seedless auxiliary phase blank liquid is water, and the amount added is the same as the mass of water in the corresponding herb seed auxiliary phase; mix the above non-plant components evenly, and let it stand at room temperature for 24 hours to allow it to be completely crosslinked and solidified, and cut it into solidified gel matrix samples.

[0065] (2) Collect highly saline-alkali soil from the mine site, soak and filter it with deionized water, and prepare a simulated high-salt leachate with a total dissolved solids content of 15 g / L. This leachate contains Na + Ca 2+ Mg 2+ Cl - SO4 2- and HCO3 - The main salt ions, including Ca 2+ With Mg 2+ This is used to simulate a divalent cation environment in saline-alkali soil of spoil heaps that easily induces polymer salting-out shrinkage and participates in silicate precipitation reactions.

[0066] (3) Test the resistance to frost heave and moisture absorption and retention. Weigh a portion of the solidified gel matrix sample and place it in a high and low temperature alternating test chamber. Set the temperature cycling curve to -20℃ for 8 hours, raise the temperature to 15℃ and hold for 8 hours, and perform 10 freeze-thaw cycles continuously. Measure the volume change of the sample before and after freeze-thaw and calculate the freeze-thaw volume expansion rate.

[0067] (4) Take another portion of the initially dry cured gel matrix sample and place it in a constant temperature and humidity chamber. Set the ambient temperature to 25℃ and the relative humidity to 30%. After 72 hours, weigh it and calculate the moisture absorption weight gain based on the mass change before and after placement.

[0068] (5) Testing the resistance to salting out and swelling retention. Equal amounts of each group of dried and cured gel matrix samples were weighed. One group was immersed in deionized water, and the other group was immersed in a prepared simulated high-salt extract. After soaking at 25°C for 48 hours, the swelling mass was weighed. The salt water swelling retention rate was calculated by comparing the swelling ratio in the salt water environment with the swelling ratio in the deionized water environment. This was used to evaluate the effect of the high-salt environment on the water absorption and swelling performance of the gel.

[0069] (6) Test the in-situ salt barrier performance of the soil column. Cut a 10 cm inner diameter polyvinyl chloride pipe, lay a quartz sand filter layer at the bottom, fill the pipe with collected highly saline-alkali soil, and make a simulated soil column with a height of 40 cm.

[0070] (7) The seedless stress-resistant base slurry, seedless auxiliary phase blank liquid, and alkaline crosslinking trigger phase of each group were pre-measured according to the mass ratio of the corresponding embodiment or comparative example. The seedless auxiliary phase blank liquid was clean water with the same water content as the herbaceous seed auxiliary phase. Then, the three were quickly mixed to form a spraying liquid to be solidified, and immediately and evenly sprayed to cover the top surface of the corresponding soil column, so that it crosslinked and solidified in situ on the surface of the soil column. All soil columns were placed in an artificial climate chamber, the top was turned on with infrared irradiation lamps to simulate a dry evaporation environment, and the bottom was regularly replenished with deionized water to maintain the set groundwater depth.

[0071] (8) Using a soil conductivity meter, record the soil conductivity of the soil column at a depth of 0 to 2 cm on the 0th day after the in-situ cross-linking and curing of the cover layer and after 30 days of continuous evaporation, and the increase in soil conductivity of the 0-2 cm layer.

[0072] The experimental data are shown in Table 3: Table 3. Test data on the physical and chemical resistance to extreme habitats and the in-situ salt barrier performance of soil columns: According to Table 3 and Figure 3 The data show that the freeze-thaw volume expansion rates of Examples 1 to 4 were 3.1% to 5.6%, and the moisture absorption weight gain rates were 15.3% to 21.4%. The freeze-thaw volume expansion rate of Comparative Example 2 was 28.7%, and the moisture absorption weight gain rate was 3.2%. These results indicate that under the test conditions, the system in the examples exhibited minimal volume change after freeze-thaw cycles and demonstrated a certain capacity for moisture absorption and weight gain in low-humidity environments. Based on the formulation analysis, the relatively excessive glycerol in the examples may have been retained as a small-molecule moisturizing component in the cross-linked network, influencing the internal moisture state of the gel through hydrogen bonding, thereby helping to reduce the impact of freeze-thaw cycles on the gel's volume stability.

[0073] The brine swelling retention rate data can be used to evaluate the effect of high-salt environment on the swelling performance of gel. In Examples 1 to 4, the brine swelling retention rate in simulated high-salt extract was 85.1% to 92.4%, while in Comparative Example 3, the brine swelling retention rate was 35.8%. These results indicate that the addition of sodium lignosulfonate and potassium humate is beneficial to improving the swelling retention capacity of the gel in a high-salt environment. Combined with component structure analysis, the sulfonic acid groups in sodium lignosulfonate and the oxygen-containing functional groups in potassium humate may weaken the adverse effects of divalent Ca and Mg cations on the polymer hydration state through electrostatic repulsion, complexation, or steric hindrance, thereby reducing the tendency for salting out and dehydration.

[0074] The increase in surface electrical conductivity of a soil column can be used to reflect the degree of salt migration to the surface under continuous evaporation conditions. In Comparative Example 5, after replacing the alkaline crosslinking trigger phase with an aqueous sodium hydroxide solution of the same pH, the increase in electrical conductivity of the top 0-2 cm soil was 2.45 mS·cm.-1 The increase in electrical conductivity of the top 0-2 cm soil layer in Examples 1 to 4 was 0.11 mS·cm. -1 Up to 0.22 mS·cm -1 The above results indicate that, under local column simulation conditions, the example system using sodium silicate as the alkaline crosslinking trigger phase has a certain inhibitory effect on the increase in surface soil conductivity. This may be because, in addition to providing an alkaline triggering environment, sodium silicate may also form a sparingly soluble silicate deposition phase with Ca and Mg divalent cations in saline-alkali soil or upwelling brine. This deposition phase helps reduce the connectivity of capillary pores in the surface soil, thereby slowing down the rate at which salts migrate to the surface with water evaporation.

[0075] Test Example 4: Experimental Description: This test is used to evaluate the mechanical retention properties of the cured substrate under continuous ultraviolet irradiation and to examine the photothermal heating performance of the substrate under simulated light conditions and its impact on the local temperature environment.

[0076] Experimental steps: (1) Take the mixture of Example 1, Example 4 and Comparative Example 3, and mix the stress-resistant base slurry, alkaline crosslinking trigger phase and seedless auxiliary phase blank liquid according to the corresponding ratio without adding plant seeds. Then, inject the mixture into a standard cylindrical mold and allow it to stand for crosslinking and curing. Demold the mold to obtain the cured gel matrix sample. All cured gel matrix samples are divided into two groups and used for ultraviolet aging test and photothermal temperature rise test, respectively.

[0077] (2) Take the first group of cured gel matrix samples and use a universal testing machine to determine the initial unconfined compressive strength. Then, place the cured gel matrix samples in an ultraviolet aging test chamber and irradiate them continuously for 300 hours under UV-A ultraviolet light at 50 watts per square meter. Take out the aged cured gel matrix samples, measure the compressive strength again, record the data and calculate the compressive strength retention rate.

[0078] (3) The second set of samples was placed in a low-temperature light chamber with a constant ambient temperature of 5°C. A thermocouple probe was pre-embedded in the geometric center of the sample, and an ambient temperature probe was set in the chamber. The full-spectrum simulated sun lamp on the top of the chamber was turned on for irradiation, and the data of the ambient temperature and the center temperature of the matrix were continuously recorded for 120 minutes. The maximum temperature difference between the center temperature of the matrix and the ambient temperature inside the chamber was calculated.

[0079] The experimental data are shown in Table 4: Table 4. Test data on UV aging resistance and photothermal temperature regulation: According to Table 4 and Figure 4Data from Comparative Example 3, after removing sodium lignosulfonate and potassium humate, showed that its unconfined compressive strength decreased from 46.5 kPa to 5.8 kPa after 300 hours of UV-A irradiation, with a compressive strength retention rate of 12.5%. The compressive strength retention rates for Examples 1 and 4 under the same UV irradiation conditions were 88.3% and 93.7%, respectively. These results indicate that under the test conditions, the gel matrix containing sodium lignosulfonate and potassium humate exhibits a high mechanical strength retention rate after UV irradiation.

[0080] Based on component structure analysis, the aromatic ring structure in sodium lignosulfonate and the conjugated polyphenol structure in potassium humate may have a certain absorption or shielding effect on ultraviolet light, thereby reducing the adverse effects of ultraviolet irradiation on the polyvinyl alcohol matrix structure. In Example 4, the amount of potassium humate was higher than that in Example 1, and its compressive strength retention rate was relatively higher, indicating that increasing the potassium humate content may be beneficial to improving the mechanical retention properties of the matrix under ultraviolet irradiation conditions.

[0081] The photothermal temperature rise test results showed that during 120 minutes of full-spectrum simulated sunlight irradiation, the maximum temperature difference between the matrix center temperature and the ambient temperature inside the chamber in Comparative Example 3 was 0.5℃; the maximum temperature differences in Examples 1 and 4 were 4.6℃ and 6.4℃, respectively. These results indicate that the example systems exhibit a certain photothermal temperature rise capability under low-temperature light irradiation conditions, with Example 4 showing a relatively higher temperature rise.

[0082] Based on the analysis of the material composition, the aromatic structures, conjugated structures, and oxygen-containing functional groups in sodium lignosulfonate and potassium humate may participate in light absorption and convert some of the absorbed light energy into heat energy through non-radiative relaxation, causing a certain temperature rise inside the gel matrix. This photothermal warming effect helps to improve the local low-temperature environment of herbaceous seeds in the hydrogel surface layer and shrub seeds below the hydrogel surface layer, thus providing more favorable microenvironmental conditions for seed germination and emergence under low-temperature conditions.

[0083] Test Example 5: Experimental Description: This test evaluated the effects of different transport and confluence methods on the viability of herbaceous seeds by extracting herbaceous seeds from the substrate after hydroseeding and monitoring their growth in field plots. It also investigated the effects of the hydrogel surface layer on the spatial distribution and growth competition between herbaceous and shrub plants.

[0084] Experimental steps: (1) Prepare the slope test area and divide it into independent test plots with an area of ​​4 square meters. Ryegrass was selected as the herbaceous test plant and Amorpha fruticosa as the shrub test plant. The two were used to representatively evaluate the spatial distribution and co-growth of herbaceous and shrub plants.

[0085] (2) For Examples 1 to 4, in order to reduce the impact of differences in different plant species on the field statistical results, each group used Amorpha fruticosa as a uniform shrub representative plant and ryegrass as a uniform herb representative plant.

[0086] (3) Mix Amorpha fruticosa seeds with the topsoil of the experimental area and place them in the soil below the hydrogel surface layer of each experimental plot. Using a multi-channel spraying platform, mix ryegrass seeds with water to form a herbaceous seed auxiliary phase, and inject it into the end of the pipeline through the side channel A by a peristaltic pump; use sodium silicate aqueous solution as an alkaline crosslinking trigger phase, and inject it into the end of the pipeline through the side channel B by a high-pressure diaphragm metering pump; after the herbaceous seed auxiliary phase, alkaline crosslinking trigger phase and the main channel stress-resistant base slurry are mixed at the end, they are sprayed to cover the soil surface where Amorpha fruticosa seeds are pre-placed.

[0087] (4) For Comparative Example 1, a representative verification was conducted by referring to the pre-crosslinking pumping method of Comparative Example 1. Ryegrass seeds and Amorpha fruticosa seeds were directly mixed with the pre-crosslinked hydrogel and sprayed through the main channel mud pump in a single channel. For Comparative Example 4, a representative verification was conducted by referring to the mixed sowing of shrubs and grasses in the same layer and the negative pressure suction confluence method of Comparative Example 4. Ryegrass seeds and Amorpha fruticosa seeds were mixed into the stress-resistant base slurry at the same time, without pre-laying the Amorpha fruticosa seeds under the hydrogel surface layer; at the same time, a negative pressure Venturi jet device was used to suction sodium silicate aqueous solution for spraying.

[0088] (5) During each spraying operation, freshly sprayed gel matrix was randomly collected from the surface of the sprayed cover layer. The collected gel matrix was washed in room temperature deionized water, and ryegrass seeds were extracted by sieving. This was used to evaluate the effects of different transport and confluence methods on the mechanical damage to herbaceous seeds and the contact of the alkaline cross-linking trigger phase. The extracted ryegrass seeds were placed in petri dishes lined with moistened filter paper and cultured in a light incubator at 25°C with a 12-hour light cycle. The number of germinations was continuously observed and counted over 14 days, and the germination rate of the herbaceous seeds was calculated.

[0089] (6) Each experimental plot in the slope test area was kept in the open air under natural conditions. The vegetation growth of each experimental plot was recorded on the 90th day. The herbaceous plant cover of each experimental plot was measured and calculated using the diagonal grid method, and the number of surviving Amorpha fruticosa plants in each experimental plot was manually counted and recorded.

[0090] The experimental data are shown in Table 5: Table 5. Germination rate of herbaceous seeds and spatial distribution of shrubs and grasses: According to Table 5 and Figure 5Data shows that different transport and confluence methods have a certain impact on the germination rate of herbaceous seeds after hydroseeding. In Comparative Example 1, a main channel mud pump was used for total mixing transport. Ryegrass seeds, transported along with pre-crosslinked hydrogel through the pump, had a germination rate of 14.3% after spraying and recovery, and the herbaceous plant cover was 11.5% after 90 days. This result indicates that when the pre-crosslinked gel and seeds are transported together through the main channel, the seeds may be adversely affected by pump shearing, compression, or the high viscosity resistance of the gel. In this representative verification experiment, Amorpha fruticosa seeds were also transported along with pre-crosslinked hydrogel through the main channel; the number of surviving shrubs after 90 days was 16, lower than in the example group.

[0091] Comparative Example 4, using a mixed-layer sowing of shrubs and grasses with a negative-pressure Venturi inhalation and confluence method, achieved a germination rate of 68.7% for recovered herbaceous seeds after spraying. Analysis of operational phenomena suggests that backflow and pressure fluctuations during the negative-pressure inhalation and confluence process may cause some herbaceous seeds to prematurely contact the alkaline cross-linking trigger phase, thus adversely affecting seed viability. Examples 1 to 4, employing an independent herbaceous seed and auxiliary phase delivery method, achieved germination rates of 86.1% to 91.5% for recovered herbaceous seeds after spraying. These results indicate that peristaltic pump delivery and a multi-channel positive-pressure confluence method are beneficial in reducing mechanical damage to herbaceous seeds during delivery and the risk of backflow contact with the alkaline cross-linking trigger phase.

[0092] Based on the 90-day vegetation growth results, the herbaceous plant cover in Examples 1 to 4 ranged from 79.2% to 85.6%, with 35 to 42 surviving shrubs. In Comparative Example 4, the herbaceous plant cover was 86.4%, with only 3 surviving shrubs. Although Comparative Example 4 still achieved a high herbaceous plant cover, the ryegrass seeds and Amorpha fruticosa seeds were located in the same physical layer. During germination and early growth stages, the herbaceous plants may have competed with the Amorpha fruticosa seedlings for nutrients, root space, and above-ground shading, thus affecting the survival of the shrub seedlings.

[0093] The embodiment employs a combination of a hydrogel surface layer and pre-placed shrub seeds beneath it, ensuring that herbaceous seeds are primarily distributed within the hydrogel surface layer, while shrub seeds are mainly distributed in the soil beneath. This spatial arrangement facilitates the formation of a cover by herbaceous plants on the slope surface, while simultaneously reducing early competition between herbaceous plants and shrub seedlings, providing more favorable conditions for shrub seedling survival and subsequent plant community establishment.

[0094] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs, characterized in that, Includes the following steps: S1. Sub-bottom pre-planting: Mix the seeds of at least one salt-tolerant shrub selected from Amorpha fruticosa, Caragana korshinskii, Hippophae rhamnoides, Salix matsudana or Tamarix chinensis with imported soil and lay it on the surface of the spoil heap to build a base layer for shrub rooting. S2. Material preparation: Prepare stress-resistant base slurry, alkaline crosslinking trigger phase and herbaceous seed auxiliary phase separately; the stress-resistant base slurry contains polyvinyl alcohol, a delayed crosslinking precursor formed by boric acid and glycerol, free glycerol, sodium lignosulfonate and potassium humate; the alkaline crosslinking trigger phase contains sodium silicate; the herbaceous seed auxiliary phase contains water and herbaceous seeds selected from at least one of alfalfa, tall fescue, alfalfa or ryegrass; S3, Multi-channel confluence spraying: The above three-phase materials are pumped through independent channels, and the herbaceous seed auxiliary phase is transported through a peristaltic pump or a non-impeller low-shear channel; the pumping pipeline pressure of the alkaline crosslinking trigger phase and the herbaceous seed auxiliary phase is controlled to be greater than the pumping pipeline pressure of the stress-resistant base slurry, so that the three-phase materials are confluenced and mixed into a mixed jet at the end of the pipeline for a short time before being sprayed out. S4. Spatial Isolation Covering: The mixed jet is sprayed onto the surface of the shrub root base layer. After the mixed jet lands, it triggers a delayed cross-linking and curing reaction, forming a hydrogel surface layer that encapsulates the herb seeds. At the same time, the alkaline cross-linking trigger phase infiltrates with water, and sodium silicate is used to form a salt-blocking zone that seals the capillary pores in the shallow layer of the spoil heap.

2. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 1, characterized in that, In step S2, the raw materials of the stress-resistant base slurry include, by weight: 8-15 parts polyvinyl alcohol, 0.5-2.5 parts boric acid, 6-15 parts glycerol, 1-4 parts sodium lignosulfonate, 0.5-3 parts potassium humate, and 100-120 parts water; wherein, the boric acid combines with some of the glycerol to form the delayed crosslinking precursor, and the remaining glycerol is the free glycerol.

3. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 2, characterized in that, The alkaline crosslinking trigger phase comprises the following raw materials in parts by weight: 2-8 parts sodium silicate and 10-20 parts water (based on solids); the herbaceous seed auxiliary phase comprises the following raw materials in parts by weight: 1-3 parts herbaceous seeds and 10-20 parts water.

4. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 2, characterized in that, The degree of alcoholysis of the polyvinyl alcohol is 85%-90%, and the degree of polymerization is 1700-2400; the sodium lignosulfonate is a high molecular weight compound containing an aromatic ring structure, and the potassium humate is a small molecule highly active component containing a conjugated polyphenol structure.

5. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 2, characterized in that, The specific preparation method of the stress-resistant basic slurry includes: First, the boric acid and glycerol (30%-40% of the total glycerol content) are pre-reacted under acidic conditions with a pH of 3.5-5.5 to prepare a delayed crosslinking precursor formed by boric acid and glycerol. Then, the polyvinyl alcohol is dissolved in hot water at 85-95°C and stirred to gelatinize. When the system is cooled to 50-60°C, the delayed crosslinking precursor formed by boric acid and glycerol is added and reacted for 30-45 minutes. Then, the remaining amount of glycerol, sodium lignosulfonate and potassium humate are added and stirred evenly at room temperature of 20-30°C to obtain the liquid stress-resistant basic slurry.

6. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 1, characterized in that, In step S3, the stress-resistant base slurry is pumped through the centrifugal mud pump in the main channel, the herbaceous seed auxiliary phase is pumped independently through the peristaltic pump in the side channel, and the alkaline crosslinking trigger phase is pumped independently through the metering pump in the other side channel. During the pumping process, the pumping pressure of each side channel is controlled to be 0.15-0.55 MPa higher than the average back pressure of the main channel.

7. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 1, characterized in that, In step S3, the mixing process is carried out in a static mixer installed at the end of the pipeline, and the residence time of the three-phase materials in the static mixer is controlled to be 0.5-1.5 seconds.

8. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 2, characterized in that, In step S4, after the mixed jet lands, the pH value of its system rises to 8.5-10.0, and cross-linking and curing are completed within 10-30 seconds to form the hydrogel surface layer with a three-dimensional network structure, and the free glycerol is locked inside the three-dimensional network structure.

9. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 2, characterized in that, In step S4, the alkaline crosslinking trigger phase penetrates downwards to a depth of 2 cm below the surface of the waste dump. After 30 days of treatment under continuous evaporation test conditions on day 0 after the in-situ crosslinking and curing of the hydrogel surface layer, the increase in the electrical conductivity of the surface soil in the 0-2 cm layer is controlled to be between 0.11 and 0.22 mS / cm.

10. The method for remediating open-pit mine spoil heaps using a combination of salt-tolerant shrubs and herbs according to claim 3, characterized in that, In step S2, the herbaceous seed auxiliary phase or alkaline cross-linking trigger phase also contains highly water-retaining plant cellulose and a compound microbial agent, which have a water absorption ratio of 20-50 times their own weight in a pure water medium at 25°C. The amount of highly water-retaining plant cellulose added is 2%-5% of the total weight before the corresponding phase region is added, and the amount of the compound microbial agent added is 0.1%-0.5% of the total weight before the corresponding phase region is added.

Images