An Ecological Restoration Method for Engineering Accumulations in Hot and Dry Valleys Based on EICP Technology

Abstract

This invention discloses an ecological restoration method for engineering deposits in arid and hot river valleys based on EICP technology. The core of this method involves pre-treating the engineering deposits and using them as the main material, mixing them with functional components such as planting soil and plant fibers, and then combining this with an EICP reaction system composed of plant-derived urease (adhesive A solution) and a urea-calcium chloride mixture (adhesive B solution) to prepare an ecological restoration substrate, which is then laid and maintained on-site. This method achieves resource utilization of the engineering deposits, the EICP reaction is environmentally friendly with zero carbon emissions, the substrate pH remains stable at 6.5-7.5, vegetation coverage reaches 87%-93% after 30 days, and the unconfined compressive strength is ≥1.6 MPa. It meets the requirements for high and steep slope protection while solving problems such as alkaline stress and poor vegetation recovery associated with traditional cement restoration, making it suitable for ecological restoration in arid and hot river valleys.

Description

Technical Field

[0001] This invention belongs to the field of ecological restoration technology, specifically to the field of soil conditioner manufacturing technology, and particularly relates to an ecological restoration method for engineering deposits in arid and hot valley areas based on EICP technology. Background Technology

[0002] Dry-hot river valleys (such as the Jinsha River basin) are important areas in my country's energy strategy. Large-scale hydropower development and other engineering projects have generated a large amount of engineering debris, mostly exposed steep rock slopes or gravel deposits. This not only occupies vast amounts of land resources but also easily triggers dust pollution, soil erosion, and even geological disasters such as landslides, severely disrupting the region's fragile ecosystem. This region constantly faces extreme climatic conditions such as strong winds, water scarcity, and large diurnal temperature variations. The surface soil is scarce and has extremely poor water, fertilizer, and moisture retention capabilities. Native plant species are limited and fragile, making ecological restoration extremely difficult.

[0003] Currently, the methods for handling engineering stockpiles in the dry-hot valley area have significant limitations: First, the use of retaining walls, active protective nets, and other methods to reinforce the stockpiles is not only costly and land-consuming, but also prone to secondary dust pollution in windy weather; Second, after screening the stockpiles, hard stones are taken for pouring frame beams, but the remaining fine dust particles will form PM2.5 pollution, and the overall utilization rate is low and the screening cost is high.

[0004] In the field of ecological restoration substrates, existing technologies also have many shortcomings: On the one hand, traditional substrates mostly use cementitious materials such as silicate cement for consolidation, resulting in high carbon emissions and energy consumption, and are prone to soil compaction and pH imbalance, inhibiting plant growth, which does not conform to the concept of green and low-carbon development; on the other hand, existing substrates are mostly not optimized for the extreme environment of arid and hot river valleys, have insufficient water and fertilizer retention capacity, are difficult to adapt to the granular structure of engineering accumulation bodies, and have poor vegetation adaptability, resulting in fragile and monotonous vegetation after restoration and poor ecosystem stability. In addition, although some ecological restoration technologies have attempted to use cementation systems, they have problems such as poor controllability of reaction, insufficient nucleation sites, and poor cementation uniformity, which cannot meet the strength requirements of ecological protection of high and steep slopes and the environmental needs of plant growth.

[0005] EICP (urease-induced calcium carbonate precipitation) technology, as a novel biomineralization technology, achieves cementation by catalyzing the hydrolysis of urea with free urease to generate calcium carbonate precipitate. It requires no microbial cultivation, offers strong reaction controllability, and is environmentally friendly, demonstrating potential in soil reinforcement and pollution control. However, current technologies have not yet integrated EICP technology with the resource utilization of engineering deposits in arid and hot river valleys. There is a lack of EICP reaction systems and ecological restoration substrate formulations optimized for the extreme environment of this region (drought, severe wind erosion, and poor soil), failing to address the dual challenges of efficient and harmless utilization of engineering deposits and regional ecological restoration.

[0006] In summary, existing technologies cannot simultaneously achieve the resource utilization of engineering deposits in arid and hot river valleys, as well as the environmental friendliness and stability of ecological restoration. There is an urgent need for an ecological restoration solution that is adapted to the environment of the region, combines the advantages of EICP technology, and takes into account both reinforcement effects and vegetation growth needs, in order to solve the core problems of existing technologies, such as poor environmental friendliness, insufficient adaptability, weak water and fertilizer retention capacity, and poor vegetation restoration effect. Summary of the Invention

[0007] To address the problems in the prior art, this invention provides a method for ecological restoration of engineering deposits in arid and hot valley areas based on EICP technology, the method comprising the following steps: Step 1: Raw material pretreatment: The engineering stockpile is crushed and screened to a particle size ≤50mm, the planting soil is air-dried to a moisture content ≤8% and screened to a particle size ≤10mm, the plant fiber is treated to be filaments with a diameter ≤1mm and a length ≤50mm, and the plant seeds are soaked in warm water at 25-30℃ for 4-6 hours to promote germination. Step 2: Preparation of EICP reaction system: a. Preparation of adhesive solution A: Soybeans are dried at 40℃ for 3-6 hours until the moisture content is 15%-20%, ground through a 100-mesh sieve to obtain soybean flour, mixed with deionized water at a material-to-liquid ratio of 1:25 and shaken for 1-1.5 hours, refrigerated at 4℃ for 24 hours, centrifuged at 4500rpm and 20℃ for 40 minutes, filtered, and prepared into a 60g / L urease solution, stored at 4℃ in the dark and used within 5 days; b. Preparation of adhesive solution B: Prepare 1.5 mol / L urea stock solution and 1.0 mol / L calcium chloride stock solution, mix them at a volume ratio of 1:1, add 0.05-0.1% auxiliary agent, shake for 20-30 minutes, and adjust the pH to 7.2-7.8 with a pH adjuster to prepare a 1.25 mol / L adhesive solution; Step 3: Preparation of ecological restoration substrate: a. Dry material mixing: Weigh out 30-50 parts by weight of the engineering stockpile and 40-60 parts by weight of the planting soil, mix and stir for 5-8 minutes, then add 4-6 parts by weight of plant fiber, 1.2-1.8 parts by weight of ordinary fertilizer, 0.5-0.9 parts by weight of slow-release fertilizer, 1-3 parts by weight of organic matter, 0.2-0.6 parts by weight of modifier, 0.1-0.3 parts by weight of water-retaining agent, and 0.1-0.3 parts by weight of activating bacteria agent, and continue stirring for 10-12 minutes to obtain the dry material; b. Preparation of wet material: Take 0.19-0.24 parts of adhesive B by weight, take water at 25-32% of the total weight of dry material, dilute adhesive B with half of the water, and spray it evenly into the dry material and stir to obtain wet material. c. EICP reaction triggering: Take 0.133-0.2 parts of adhesive solution A by weight, dilute adhesive solution A with the remaining half of the water, stir the wet material with the germinated plant seeds for 2-3 minutes, then add the diluted adhesive solution A, stir at 25-30℃ for 3-5 minutes to obtain the ecological restoration substrate; Step 4: On-site construction: Clean the slope and trim it to a slope of ≤45°. Use a wet spraying machine to evenly lay the ecological restoration substrate on the slope, with a thickness of 8-15cm, and lightly compact it to a porosity of ≥27%. Step 5: Post-construction maintenance and monitoring: For 1-15 days after construction, replenish water every morning and evening until the substrate moisture content is 20-25%. Regularly remove weeds and use biological pesticides to control pests. Monitor substrate porosity, pH value, vegetation germination rate and slope erosion modulus.

[0008] In a preferred embodiment, in step 2a, the source of urease may also include sword beans or peas, and the supernatant after centrifugation is filtered through qualitative filter paper to remove insoluble impurities.

[0009] In a preferred embodiment, in step 2b, the auxiliary agent is one or more of skim milk powder, chitosan, or soil particles with a particle size of 20-50 μm, and the pH adjuster is a 0.1-1.0 mol / L NaOH solution or HCl solution.

[0010] In a preferred embodiment, in step 3a, the nitrogen-phosphorus-potassium ratio of the ordinary fertilizer is 1.2-1.8:1.2-1.8:2.2-2.8, and the nitrogen-phosphorus-potassium ratio of the long-acting fertilizer is 2.5-3.5:2.5-3.5:4.5-5.5.

[0011] In a preferred embodiment, in step 3b, the adhesive liquid B is diluted by spraying it evenly while stirring, ensuring that the material does not clump and dissipates heat quickly.

[0012] In the preferred embodiment, in step 4, the thickness of the substrate is 12-15cm when the slope is 30-45° and 8-10cm when the slope is ≤30°. For steep slopes, the substrate is laid in two layers, and the second layer is laid after curing for 3 days after the first layer is laid.

[0013] In the preferred embodiment, in step 5, the monitoring indicators meet the following requirements: porosity ≥27% and pH 6.5-7.5 within 7-30 days; germination rate ≥75%; vegetation coverage ≥85% and unconfined compressive strength of the substrate ≥1.6MPa within 3-6 months; and erosion modulus ≤100g under 90mm / h rainfall intensity per year. min -1 m -2 .

[0014] In a preferred embodiment, in step 1, the plant seeds are one or more of the following ultra-xerophytic plant seeds: basil, alfalfa, and saxaul, with a seed content of 0.3 kg / 100 kg of wet ecological restoration substrate.

[0015] In a more preferred embodiment, the auxiliary agent is preferably skim milk powder, and its dosage is 0.05-0.1% of the total mass of the cementitious liquid.

[0016] In a more preferred embodiment, the pH adjuster is selected as a 0.5 mol / L NaOH solution or a 0.5 mol / L HCl solution, and the pH of the cementitious solution is stabilized at 7.5-7.6 after adjustment.

[0017] The beneficial effects of this invention are: (1) This invention uses engineering stockpiles in dry-hot valley areas as the main material. After crushing and screening, the stockpiles are directly incorporated into the ecological restoration substrate, achieving efficient and harmless utilization of the engineering stockpiles with a utilization rate of 30%-50%. This avoids the problems of land occupation and dust pollution caused by traditional stockpiling treatment methods (such as retaining wall stockpiling and screening utilization), and reduces the cost of purchasing planting soil, thus lowering the economic investment in ecological restoration projects. At the same time, the crushed stone particles of the engineering stockpiles provide a stable framework for the substrate, enhancing the slope's resistance to wind and water erosion, and achieving synergy between "waste treatment" and ecological protection. (2) EICP technology uses plant-derived urease as a catalyst to replace silicate cement with high carbon emissions. It has no secondary pollution and the reaction process is controllable. It will not cause soil pH imbalance, which is in line with the concept of green and low-carbon ecological restoration. (3) This invention organically integrates EICP technology with plant fiber reinforcement, activated bacterial agent improvement, and stepped nutrient supply technologies. It is not only applicable to the slope repair of hydropower engineering accumulation bodies in dry and hot river valleys, but can also be extended to the ecological restoration of engineering accumulation bodies generated by road construction and mine management. It provides a replicable and scalable technical solution for the resource utilization and ecological restoration of engineering waste in similar ecologically fragile areas.

[0018] In summary, the present invention provides an ecological restoration method for engineering deposits in arid and hot river valleys based on EICP technology. This method enables efficient, harmless, and resource-based utilization of engineering deposits, combining the concepts of resource utilization and ecological protection. The resulting ecological restoration substrate exhibits excellent physical and biological properties and is suitable for the ecological restoration of steep slopes. By utilizing engineering deposits in arid and hot river valleys in the field of ecological restoration, this invention solves the problems of fragile ecological environments and insufficient water, fertilizer, and moisture retention capacity in existing arid and hot river valley areas, thus achieving the goal of green development through ecological restoration. Attached Figure Description

[0019] Figure 1 This is a photograph of the sample site before restoration according to the present invention.

[0020] Figure 2 This is a photograph of the restored sample plot of the present invention.

[0021] Figure 3 These are comparison photos of the plot before and after remediation according to the present invention (Example 2).

[0022] Explanation of reference numerals in the figures: S1, Example 2 plot; S2, Example 3 plot; S3, Example 4 plot; D1, Comparative Example 1 plot; D2, Comparative Example 2 plot; D3, Comparative Example 3 plot. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments.

[0024] This invention is based on the ecological restoration experiment of the high slope of the Benzilan Hydropower Station and the research on the degradation degree and quality improvement technology of the topsoil of the engineering accumulation carried out by the State Energy Group on the upper reaches of the Jinsha River. A series of experimental studies have been carried out, resulting in the following examples.

[0025] Example 1 An ecological restoration method for engineering deposits in arid and hot river valleys based on EICP technology includes the following steps: Step 1: Raw material pretreatment: The engineering stockpile is crushed and screened to a particle size ≤50mm, the planting soil is air-dried to a moisture content ≤8% and screened to a particle size ≤10mm, the plant fiber is treated to be filaments with a diameter ≤1mm and a length ≤50mm, and the plant seeds are soaked in warm water at 25-30℃ for 4-6 hours to promote germination. Step 2: Preparation of EICP reaction system: a. Preparation of adhesive solution A: Soybeans are dried at 40℃ for 3-6 hours until the moisture content is 15%-20%, ground through a 100-mesh sieve to obtain soybean flour, mixed with deionized water at a material-to-liquid ratio of 1:25 and shaken for 1-1.5 hours, refrigerated at 4℃ for 24 hours, centrifuged at 4500rpm and 20℃ for 40 minutes, filtered, and prepared into a 60g / L urease solution, stored at 4℃ in the dark and used within 5 days; b. Preparation of adhesive solution B: Prepare 1.5 mol / L urea stock solution and 1.0 mol / L calcium chloride stock solution, mix them at a volume ratio of 1:1, add 0.05-0.1% auxiliary agent, shake for 20-30 minutes, and adjust the pH to 7.2-7.8 with a pH adjuster to prepare a 1.25 mol / L adhesive solution; Step 3: Preparation of ecological restoration substrate: a. Dry material mixing: Weigh out 30-50 parts by weight of the engineering stockpile and 40-60 parts by weight of the planting soil, mix and stir for 5-8 minutes, then add 4-6 parts by weight of plant fiber, 1.2-1.8 parts by weight of ordinary fertilizer, 0.5-0.9 parts by weight of slow-release fertilizer, 1-3 parts by weight of organic matter, 0.2-0.6 parts by weight of modifier, 0.1-0.3 parts by weight of water-retaining agent, and 0.1-0.3 parts by weight of activating bacteria agent, and continue stirring for 10-12 minutes to obtain the dry material; b. Preparation of wet material: Take 0.19-0.24 parts of adhesive B by weight, take water at 25-32% of the total weight of dry material, dilute adhesive B with half of the water, and spray it evenly into the dry material and stir to obtain wet material. c. EICP reaction triggering: Take 0.133-0.2 parts of adhesive solution A by weight, dilute adhesive solution A with the remaining half of the water, stir the wet material with the germinated plant seeds for 2-3 minutes, then add the diluted adhesive solution A, stir at 25-30℃ for 3-5 minutes to obtain the ecological restoration substrate; Step 4: On-site construction: Clean the slope and trim it to a slope of ≤45°. Use a wet spraying machine to evenly lay the ecological restoration substrate on the slope, with a thickness of 8-15cm, and lightly compact it to a porosity of ≥27%. Step 5: Post-construction maintenance and monitoring: For 1-15 days after construction, replenish water every morning and evening until the substrate moisture content is 20-25%. Regularly remove weeds and use biological pesticides to control pests. Monitor substrate porosity, pH value, vegetation germination rate and slope erosion modulus.

[0026] Furthermore, in step 2a, the source of urease also includes sword beans or peas, and the supernatant after centrifugation is filtered through qualitative filter paper to remove insoluble impurities.

[0027] Further, in step 2b, the auxiliary agent is one or more of skim milk powder, chitosan or soil particles with a particle size of 20-50 μm, and the pH adjuster is a 0.1-1.0 mol / L NaOH solution or HCl solution.

[0028] Further, in step 3a, the nitrogen-phosphorus-potassium ratio of the ordinary fertilizer is 1.2-1.8:1.2-1.8:2.2-2.8, and the nitrogen-phosphorus-potassium ratio of the long-acting fertilizer is 2.5-3.5:2.5-3.5:4.5-5.5.

[0029] Furthermore, in step 3b, the adhesive liquid B is diluted by spraying it evenly while stirring, ensuring that the material does not clump and dissipates heat quickly.

[0030] Furthermore, in step 4, the substrate thickness is 12-15cm when the slope is 30-45°, and 8-10cm when the slope is ≤30°.

[0031] Furthermore, in step 5, the monitoring indicators must meet the following requirements: porosity ≥27% and pH 6.5-7.5 within 7-30 days; germination rate ≥75%; vegetation coverage ≥85% and unconfined compressive strength of substrate ≥1.6MPa within 3-6 months; and erosion modulus ≤100g under 90mm / h rainfall intensity per year. min -1 m -2 .

[0032] Furthermore, in step 1, the plant seeds are one or more of the following ultra-drought-tolerant plant seeds: basil, alfalfa, and saxaul, with a seed content of 0.3 kg / 100 kg of wet ecological restoration substrate.

[0033] Furthermore, the auxiliary agent is preferably skim milk powder, and its dosage is 0.05-0.1% of the total mass of the cementitious liquid.

[0034] Furthermore, the pH adjuster is selected from 0.5 mol / L NaOH solution or 0.5 mol / L HCl solution, and the pH of the cementitious solution is stabilized at 7.5-7.6 after adjustment.

[0035] Example 2 The specific implementation process of the above-mentioned ecological restoration method is as follows: (1) Raw material pretreatment The piled-up crushed stone excavated from the hydropower project is put into a crusher, crushed and then screened through a 10-mesh sieve (particle size ≤ 50mm) to remove large impurities and collect qualified particles for later use. Collect topsoil from within 1m of the ground surface, spread it out in a ventilated place to air dry naturally for 3-5 days, turning it over regularly during this period until the moisture content is ≤8%. Then, sieve it through a 20-mesh sieve (particle size ≤10mm) to remove weeds, roots, and stones, and set it aside for later use. Palm or pine fiber is fed into a pulverizer, crushed, and then pre-screened through a 100-mesh sieve. It is then treated by an air-heating method to finally obtain filamentous fibers with a diameter ≤1mm and a length ≤50mm, which are then ready for use. Soak the mixed seeds in warm water at 25-30℃ for 4-6 hours, stirring twice during the process. After draining the water, place them in a constant temperature incubator at 25℃ for 12 hours to germinate. Rice husks or sawdust (organic matter) are dried to a moisture content of ≤10%; straw biochar (modifier) ​​is crushed to a particle size of ≤2mm; water-retaining agent (anionic polyacrylamide, molecular weight 10 million-15 million, solid content not less than 90%) and activating agent (Bacillus subtilis, effective live bacteria count not less than 50 billion / gram) are stored at room temperature in a sealed container to avoid moisture.

[0036] (2) Preparation of EICP reaction system (adhesive solution A and solution B must be prepared and used immediately, and construction should be completed within 2 hours after mixing to avoid a decrease in urease activity) ①Preparation of adhesive solution A Remove impurities from soybeans and dry them in a 40℃ constant temperature oven for 4 hours, controlling the moisture content to 18% (the optimal activity state in the laboratory). The dried soybeans are ground into powder using a grinder, and then sieved through a 100-mesh sieve to collect the soybean powder. Add soybean powder and deionized water to a sealed container at a material-to-liquid ratio of 1:25 (1g soybean powder: 25g deionized water), place the container in a shaker, and shake at 200 rpm for 1.2 hours. Remove the container and refrigerate at 4°C for 24 hours. Pour the refrigerated liquid into centrifuge tubes, place them in a centrifuge, set the centrifuge to 4500 rpm and 20°C, and centrifuge for 40 minutes to separate the supernatant. The supernatant was filtered through qualitative filter paper to remove insoluble impurities. The filtrate was then placed in a black, light-proof bottle and refrigerated at 4°C for later use. (Use within 5 days of preparation, otherwise the urease activity will gradually decrease. Urease is also very expensive to purchase. The price of urease on mainstream online shopping platforms is concentrated between 100 and 300 yuan / g (urease activity > 1 u / mg), with some prices exceeding 1000 yuan / g.)

[0037] ②Preparation of adhesive solution B Prepare 1.5 mol / L urea stock solution and 1.0 mol / L calcium chloride stock solution using deionized water; Measure out urea mother liquor and calcium chloride mother liquor by volume ratio of 1:1, add them to a sealed container, and add 0.1% of the total mass of skim milk powder at the same time. Place the container in a shaker and shake at 150 rpm for 25 minutes to mix thoroughly; Adjust the pH of the mixture to 7.5 (the optimal pH for urease) with 0.5 mol / L NaOH solution to obtain adhesive solution B, which is then ready for use.

[0038] (3) Preparation of ecological restoration substrate Add 30kg of pretreated engineering stockpile and 60kg of planting soil into a horizontal mixer and mix for 6 minutes until evenly mixed. Add 4kg of plant fiber, 1.2kg of ordinary fertilizer, 0.5kg of slow-release fertilizer, 1kg of organic matter, 0.2kg of modifier, 0.1kg of water-retaining agent, and 0.1kg of activating bacteria agent in sequence, and continue stirring for 11 minutes to obtain a uniform dry material for ecological restoration substrate; Measure 12kg of water and 0.19kg of adhesive B solution, and apply them evenly during the mixing of the dry ecological restoration substrate to prepare the wet ecological restoration substrate. Mix the above-mentioned wet ecological restoration substrate with 0.3 kg of plant seeds for 2-3 minutes. Then measure 12 kg of water and 0.133 kg of the prepared adhesive A solution and mix them. Add the diluted adhesive A solution to the wet substrate and stir for 3-5 minutes to obtain the ecological restoration substrate with the engineering accumulation body as the main material.

[0039] (4) On-site construction The prepared ecological restoration substrate was evenly laid on the slope surface using a wet spraying machine, with a thickness of 14cm. After laying, a light compaction device was used to lightly compact the substrate from top to bottom along the slope, controlling the porosity of the substrate to 30% (to ensure sufficient EICP reaction and facilitate seed germination). After compaction, the surface of the substrate was trimmed with a scraper to ensure flatness without obvious depressions or protrusions.

[0040] (5) Post-construction maintenance and monitoring ①Water management: 1-15 days after construction (critical curing period): Spray clean water once in the morning and once in the evening, using a fine mist nozzle, to control the moisture content of the substrate to 23% and avoid water accumulation. 16-90 days: Rehydrate every 3 days to maintain a moisture content of 18-20%; 90 days later: Replenish water according to rainfall, and replenish water once every 7 days during the drought period.

[0041] ②Weed removal: Remove weeds from the substrate surface once a month after construction to avoid competition for nutrients with the target plants.

[0042] ③ Pest and disease control: If aphids, powdery mildew, etc. appear, use biological pesticides (such as matrine, Bacillus subtilis preparations) for spraying and control, and spray preventively once a month.

[0043] Subsequently, the substrate porosity, pH value, vegetation germination rate, and slope erosion modulus were monitored regularly. The monitoring data are shown in Table 1.

[0044] Example 3 The overall steps are the same as in Example 2, except that the composition of the ecological restoration substrate is different. Specifically, it consists of: 40 kg of engineering stockpile, 50 kg of planting soil, 0.16 kg of adhesive A solution, 0.22 kg of adhesive B solution, 5 kg of plant fiber, 1.5 kg of ordinary fertilizer, 0.7 kg of slow-release fertilizer, 2 kg of organic matter, 0.4 kg of modifier, 0.2 kg of water-retaining agent, 0.2 kg of activating bacteria agent, and 28 kg of water.

[0045] The monitoring data is shown in Table 1.

[0046] Example 4 The overall steps are the same as in Example 2, except that the composition of the ecological restoration substrate is different. Specifically, it consists of: 50 kg of engineering stockpile, 40 kg of planting soil, 0.2 kg of adhesive A solution, 0.24 kg of adhesive B solution, 6 kg of plant fiber, 1.8 kg of ordinary fertilizer, 0.9 kg of slow-release fertilizer, 3 kg of organic matter, 0.6 kg of modifier, 0.3 kg of water-retaining agent, 0.3 kg of activating bacteria agent, and 32 kg of water.

[0047] The monitoring data is shown in Table 1.

[0048] Comparative Example 1 Take 30 kg of engineering stockpile, 60 kg of planting soil, 4 kg of silicate cement (P.O42.5), 4 kg of plant fiber, 1.2 kg of ordinary fertilizer, 0.5 kg of slow-release fertilizer, 1 kg of organic matter, 0.2 kg of pH adjuster (mainly HCl solution (0.1-1.0 mol / L) to lower the pH value after cement hydration), 0.1 kg of water-retaining agent, and 0.1 kg of activating bacteria agent.

[0049] First, the engineering stockpile and planting soil are initially mixed. Then, 4 kg of silicate cement (P.O42.5), plant fiber, ordinary fertilizer, slow-release fertilizer, organic matter, pH adjuster, water-retaining agent, and activating bacteria agent are added in sequence and mixed and stirred for 10-12 minutes to obtain the dry material of ecological restoration substrate. Then add water and continue stirring to prepare a wet ecological restoration substrate with a moisture content of 25-32%. Finally, the above-mentioned wet ecological restoration substrate was mixed evenly with 0.3 kg of plant seeds to obtain silicate cement-based ecological restoration substrate group one. The prepared ecological restoration substrate was evenly laid on the slope surface using a wet spraying machine with a thickness of 14 cm. After the laying was completed, a light compaction device was used to lightly compact the slope from top to bottom.

[0050] Subsequent maintenance and monitoring were the same as in Example 1, and the monitoring data are shown in Table 2.

[0051] Comparative Example 2 The steps are the same as those in Comparative Example 1, except that the composition of the ecological restoration substrate is different. Specifically, it consists of: 30 kg of engineering stockpile, 60 kg of planting soil, 6 kg of silicate cement (P.O42.5), 4 kg of plant fiber, 1.2 kg of ordinary fertilizer, 0.5 kg of slow-release fertilizer, 1 kg of organic matter, 0.3 kg of pH adjuster, 0.1 kg of water-retaining agent, and 0.1 kg of activating bacteria agent.

[0052] The monitoring data is shown in Table 2.

[0053] Comparative Example 3 The steps are the same as those in Comparative Example 1, except that the composition of the ecological restoration substrate is different. Specifically, it consists of: 30 kg of engineering stockpile, 60 kg of planting soil, 8 kg of silicate cement (P.O42.5), 4 kg of plant fiber, 1.2 kg of ordinary fertilizer, 0.5 kg of slow-release fertilizer, 1 kg of organic matter, 0.4 kg of pH adjuster, 0.1 kg of water-retaining agent, and 0.1 kg of activating bacteria agent.

[0054] The monitoring data is shown in Table 2.

[0055] Table 1 Comparison of test results in Examples 2-4

[0056] Table 2 Comparison of experimental results of Comparative Examples 1-3

[0057] As shown in Tables 1-2 above, the soil pH value after traditional cement remediation was significantly higher (pH reached 8.3-8.9 after 7 days in Comparative Examples 1-3). This highly alkaline environment inhibits seed germination and root growth, and even with the addition of pH adjusters, long-term stability is difficult. The pH of the EICP reaction system in this application is stable at 6.5-7.5, which highly matches the suitable pH range for plant growth (6.0-7.5), requiring no additional adjustment and fundamentally avoiding the inhibition of vegetation by alkaline stress. After 30 days, the vegetation coverage of traditional cement remediation was only 63% at most (Comparative Example 1), and the germination rate was extremely low (in some groups). (Less than 10%), the vegetation coverage of this application can reach 87%-93% after 30 days, with a germination rate of ≥75%. It has strong adaptability to ultra-xerophytic plants and can quickly form vegetation cover. The compressive strength of the substrate of traditional cement repair is too high (comparative examples 1-3, 7-day compressive strength 3.57-4.94MPa), which is easy to crack and fall off, and has poor compatibility with soil. It is prone to hollowing and peeling in the long term. The unconfined compressive strength of the substrate of this application is ≥1.6MPa, which can not only meet the protection requirements of steep slopes with a slope of ≤45°, but also has a certain degree of flexibility, good compatibility with the particle structure of the engineering accumulation, and strong long-term stability.

[0058] Traditional cement leaves alkaline residues in the soil for a long time, continuously affecting the activity of soil microorganisms. The EICP reaction of this application leaves no harmful residues, and the calcium carbonate precipitate generated can be used as a supplement to soil minerals. The activating agent can also regulate the soil microbial community and improve soil compaction. In the long run, it can continuously improve soil quality, rather than simply "solidification and protection".

Claims

1. A method for ecological restoration of engineering deposits in arid and hot river valleys based on EICP technology, characterized in that, Includes the following steps: Step 1: Raw material pretreatment: The engineering stockpile is crushed and screened to a particle size ≤50mm, the planting soil is air-dried to a moisture content ≤8% and screened to a particle size ≤10mm, the plant fiber is treated into filaments with a diameter ≤1mm and a length ≤50mm, and the plant seeds are soaked in warm water to promote germination. Step 2: Preparation of EICP reaction system: 2a. Preparation of adhesive solution A: Soybeans are dried to a moisture content of 15%-20%, ground and sieved to obtain soybean flour. The soybean flour is mixed with deionized water and shaken, then refrigerated and stored. After centrifugation and filtration, a urease solution is prepared, stored away from light and used within 5 days. 2b. Preparation of adhesive solution B: Prepare 1.5 mol / L urea stock solution and 1.0 mol / L calcium chloride stock solution, mix them at a volume ratio of 1:1, add 0.05-0.1% auxiliary agent, shake and mix evenly, adjust the pH to 7.2-7.8 with a pH adjuster, and prepare a 1.25 mol / L adhesive solution. Step 3: Preparation of ecological restoration substrate: 3a. Dry material mixing: Weigh out 30-50 parts by weight of the engineering stockpile and 40-60 parts by weight of the planting soil, mix and stir for 5-8 minutes, then add 4-6 parts by weight of plant fiber, 1.2-1.8 parts by weight of ordinary fertilizer, 0.5-0.9 parts by weight of slow-release fertilizer, 1-3 parts by weight of organic matter, 0.2-0.6 parts by weight of modifier, 0.1-0.3 parts by weight of water-retaining agent, and 0.1-0.3 parts by weight of activating bacteria agent, and continue stirring for 10-12 minutes to obtain the dry material; 3b. Preparation of wet material: Take 0.19-0.24 parts by weight of adhesive B liquid, take water at 25-32% of the total weight of dry material, take half of the water to dilute adhesive B liquid, spray it evenly into the dry material and stir to obtain wet material; 3c. EICP reaction triggering: Take 0.133-0.2 parts of adhesive A solution by weight, dilute adhesive A solution with the remaining half of the water, stir the wet material with the germinated plant seeds for 2-3 minutes, then add the diluted adhesive A solution, stir at 25-30℃ for 3-5 minutes to obtain the ecological restoration substrate; Step 4: On-site construction: Clean the slope and trim it to a slope of ≤45°. Use a wet spraying machine to evenly lay the ecological restoration substrate on the slope, with a thickness of 8-15cm, and lightly compact it to a porosity of ≥27%. Step 5: Post-construction maintenance and monitoring: For 1-15 days after construction, replenish water every morning and evening until the substrate moisture content is 20-25%. Regularly remove weeds and use biological pesticides to control pests. Monitor substrate porosity, pH value, vegetation germination rate and slope erosion modulus.

2. The ecological restoration method according to claim 1, characterized in that, In step 2a, the urease source also includes sword beans or peas, and the supernatant after centrifugation is filtered through qualitative filter paper to remove insoluble impurities.

3. The ecological restoration method according to claim 1, characterized in that, In step 2b, the auxiliary agent is one or more of skim milk powder, chitosan or soil particles with a particle size of 20-50 μm, and the pH adjuster is a 0.1-1.0 mol / L NaOH solution or HCl solution.

4. The ecological restoration method according to claim 1, characterized in that, In step 3a, the nitrogen-phosphorus-potassium ratio of the ordinary fertilizer is 1.2-1.8:1.2-1.8:2.2-2.8, and the nitrogen-phosphorus-potassium ratio of the long-acting fertilizer is 2.5-3.5:2.5-3.5:4.5-5.

5.

5. The ecological restoration method according to claim 1, characterized in that, In step 3b, the adhesive liquid B is diluted by spraying it evenly while stirring, ensuring that the material does not clump and dissipates heat quickly.

6. The ecological restoration method according to claim 1, characterized in that, In step 4, the substrate thickness is 12-15cm when the slope is 30-45°, and 8-10cm when the slope is ≤30°.

7. The ecological restoration method according to claim 1, characterized in that, In step 5, the monitoring indicators must meet the following requirements: porosity ≥27% and pH 6.5-7.5 within 7-30 days; germination rate ≥75%; vegetation coverage ≥85% and unconfined compressive strength of substrate ≥1.6MPa within 3-6 months; and erosion modulus ≤100g under 90mm / h rainfall intensity per year. min -1 m -2 .

8. The ecological restoration method according to claim 1, characterized in that, In step 1, the plant seeds are one or more of the following ultra-xerophytic plant seeds: basil, alfalfa, and saxaul, with a seed content of 0.3 kg / 100 kg of wet ecological restoration substrate.

9. The ecological restoration method according to claim 3, characterized in that, The auxiliary agent is preferably skim milk powder, and its dosage is 0.05-0.1% of the total mass of the cementitious liquid.

10. The ecological restoration method according to claim 3, characterized in that, The pH adjuster is selected from 0.5 mol / L NaOH solution or 0.5 mol / L HCl solution, and the pH of the cementitious solution is stabilized at 7.5-7.6 after adjustment.

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