Composite salt water-retaining material for ecological restoration of strip mine and preparation method of composite salt water-retaining material

Abstract

The invention discloses a composite salt water-retaining material for ecological restoration of strip mines and a preparation method, and belongs to the technical field of ecological restoration. The composite salt water retention material is of a core-control-protection-shell four-layer composite structure and comprises a core layer, a control layer wrapping the core layer, a protection layer wrapping the control layer and an outer shell layer wrapping the protection layer. The comprehensive technical effects of efficient moisture absorption and water retention, precise salt control and slow release, soil synergistic improvement, stable and long-acting environment and flexible scene adaptation are successfully achieved, and the method is a new foundation for ecological restoration of drought and water-deficient mining areas, especially open pit coal mine waste dump and rock slopes with severe site conditions. An efficient, reliable and sustainable moisture management core material and technical support are provided, and the success rate and quality of ecological restoration are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of ecological restoration technology, and specifically relates to a composite salt-water-retaining material for ecological restoration of open-pit mines and its preparation method. Background Technology

[0002] Ecological restoration in open-pit coal mining generally faces dual stresses from water and soil, severely restricting vegetation restoration and ecological reconstruction. Currently, most open-pit coal mines are located in arid and semi-arid regions such as Inner Mongolia and Xinjiang, where natural rainfall is scarce and evaporation is intense. The loose substrate and poor water-holding capacity of spoil heaps lead to rapid water seepage and intense evaporation, resulting in severely insufficient soil moisture, becoming a major bottleneck restricting plant establishment and growth. This problem is particularly severe on rock slopes formed by open-pit mining due to water scarcity. Reconstructed soil from spoil heaps often contains large amounts of gravel and slag, with a loose structure, lack of organic matter, and poor aggregate stability, making it difficult to effectively retain limited water and nutrients. Rock slopes, on the other hand, completely lack an effective substrate layer for plant growth.

[0003] Currently, water-retaining materials used for ecological restoration are relatively limited, such as superabsorbent polymers and polyacrylamide. In the extreme environments of mining areas, characterized by strong evaporation, high salinity, and intense ultraviolet radiation, problems such as severe salinization, uncontrollable water release rates, high costs, and potential secondary pollution often arise. Furthermore, these methods only address the water issue and have limited effectiveness in soil improvement. Measures such as mulching and soil covering are easily blown away by the wind, degrade easily, and cannot actively absorb and utilize air humidity, resulting in limited effectiveness under extreme drought conditions. Existing technologies fail to systematically solve these complex problems, either focusing solely on water retention while neglecting soil improvement and environmental adaptability, or being too costly for large-scale application, or unsuitable for the harsh site conditions of mining areas. (1) Applying highly hygroscopic salts directly to the soil can lead to soil salinization, increase soil electrical conductivity, and affect the ecological restoration effect.

[0004] (2) Under the strong ultraviolet radiation, wet-dry cycle, freeze-thaw cycle, wind and rain erosion and soil mechanical stress in open-pit mines, conventional water-retaining materials are prone to physical disintegration, chemical degradation or rapid functional failure, making it difficult to ensure that they continue to play a role during the repair cycle. (3) In arid and semi-arid mining areas, relying solely on limited precipitation is insufficient to meet the needs of ecological restoration. Existing technologies lack the ability to actively capture and utilize atmospheric water vapor (humidity), and cannot convert air humidity during non-precipitation periods into usable soil moisture, resulting in the waste of precious water resources.

[0005] (4) Traditional single water-retaining materials or bare salt often have problems such as excessively rapid water release or excessively high instantaneous salt release concentration in extreme environments in mining areas, and lack the ability to coordinate and accurately control the release rate of water and salt.

[0006] (5) Rock slopes lack an effective soil layer, and conventional soil covering and water retention techniques are costly, difficult, and prone to erosion. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a composite salt-water-retaining material for ecological restoration of open-pit mines and its preparation method.

[0008] The technical solution adopted in this invention is: a composite salt-water-retaining material for ecological restoration of open-pit mines. Its key technical feature is the use of a four-layer composite structure of "core-control-protection-shell," comprising, by weight: Core layer: 35-40 parts, a strongly hygroscopic salt composed of 60-70 parts calcium chloride and 30-40 parts magnesium chloride; The control layer covering the core layer consists of 25 to 35 parts of a controlled-release, water-retaining, and soil-improving composite material composed of 7 to 10 parts bentonite, 10 to 15 parts carbonaceous mudstone, and 4 to 7 parts polyacrylamide. A protective layer covering the control layer: 10-15 parts, consisting of 8-15 parts of open-pit coal mine clay and 5-10 parts of sub-clay, forming a buffer isolation layer; The outer shell layer covering the protective layer: 10 to 15 parts, an anti-corrosion coating formed of 5 to 10 parts polyvinyl alcohol and 5 to 10 parts silanized starch.

[0009] Furthermore, the control layer is uniformly composited from bentonite, carbonaceous mudstone, and polyacrylamide through hydration.

[0010] Furthermore, in the outer shell layer, polyvinyl alcohol and silanized starch are cross-linked by hot melt to form a weather-resistant coating.

[0011] A method for preparing a multifunctional composite salt water-retaining material, the key technical points of which include the following steps: (1) Core layer preparation: calcium chloride and magnesium chloride are melt-blended and granulated and dried into solid spherical particles using a fluidized bed spray granulation dryer; (2) Control layer coating: bentonite, sieved carbonaceous mudstone and polyacrylamide are mixed, water is added to make a slurry, sprayed onto the surface of the core layer particles and dried; (3) Protective layer coating: sieved clay and sub-clay are mixed, water is added to make a slurry, sprayed onto the surface of the control layer and dried; (4) Outer layer coating: polyvinyl alcohol is dissolved in hot water at 85-95℃, silanized starch is added and mixed evenly, cooled and sprayed onto the surface of the protective layer and cured.

[0012] Furthermore, the amount of water added in step (2) is twice the total mass of the control layer solids.

[0013] Furthermore, the amount of water added in step (3) is twice the total mass of the protective layer solid.

[0014] Application of multifunctional composite salt-water-retaining materials in ecological restoration of open-pit coal mines.

[0015] Furthermore, the application involves mixing the multifunctional composite salt-water-retaining material with reclaimed soil at a mass ratio of 2% to 5%, and then backfilling it onto the open-pit coal mine spoil heap platform.

[0016] Furthermore, the application involves encapsulating the multifunctional composite salt-water-retaining material in a non-woven bag to form a modular water storage belt, and burying and anchoring the water storage belt to the slope of an open-pit coal mine spoil heap.

[0017] Furthermore, the application is for the revegetation of rocky slopes in open-pit coal mines. Specifically, a planting trench is opened on the rocky slope, and 2% to 3% of the multifunctional composite salt-water-retaining material is added to the backfill soil in the trench, along with the plants. After planting, a 10cm thick layer of the multifunctional composite salt-water-retaining material is then placed on the surface.

[0018] The beneficial effects of this invention are as follows: The composite salt-water-retaining material and its preparation method for open-pit mine ecological restoration are multi-level composite systems consisting of a core, control layer, protective layer, and shell. This allows for the sequential release of functions. The core layer rapidly captures moisture, while the control layer, through mineral adsorption, pore channeling, and a polymer gel network, precisely regulates the slow-release rate of moisture and salt in the core layer, preventing instantaneous water loss and a sudden increase in salt concentration. The protective layer buffers external environmental impacts, further stabilizing water transport. The outer shell provides mechanical protection and an environmental barrier, ensuring the orderly coordination and efficient integration of functions such as moisture absorption, water retention, controlled release, isolation, and protection in time and space. The core salt efficiently absorbs moisture from the soil and air, significantly increasing the available water volume in the restoration area, especially during non-rainfall periods. The multi-layered barrier works synergistically to effectively isolate the direct contact between highly hygroscopic salts and plant roots, and through a control layer, precisely regulates the release of water and salt, significantly reducing the risk of soil salinization and maintaining a suitable rhizosphere environment. In practical applications on open-pit coal mine spoil heap platforms, slopes, and hard rock slopes, the addition of this material significantly improves seed germination rate, seedling survival rate, and vegetation coverage, accelerating the ecological restoration process. This invention, applied to limited trench topsoil and as a surface cover, creates and maintains crucial water retention capacity for plants on rock walls, solving the water supply problem under soil-free or low-soil conditions on hard rock slopes. Through its unique multi-level structural design and component coupling, this invention successfully achieves comprehensive technical effects of "highly efficient hygroscopic water retention, precise salt control and slow release, synergistic soil improvement, long-term environmental stability, and flexible adaptation to various scenarios." It provides an efficient, reliable, and sustainable core material and technical support for water management in arid and water-scarce mining areas, especially in open-pit coal mine spoil heaps and rock slopes with harsh site conditions, significantly improving the success rate and quality of ecological restoration. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the composite salt water-retaining material structure in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the direct mixing and application of the mixture with reclaimed soil in Embodiment 8 of the present invention. Figure 3 This is a schematic diagram illustrating the direct mixing and application of the mixture with reclaimed soil in Embodiment 9 of the present invention. Figure 4 This is a schematic diagram of the modular water storage belt structure in Embodiment 7 of the present invention; Figure 5 for Figure 4 AA diagram; Figure 6 This is a schematic diagram of the nonwoven tape connection structure according to an embodiment of the present invention; The numbers in the diagram are explained as follows: 1 Outer shell layer, 2 Protective layer, 3 Control layer, 4 Core layer, 5 Backfill soil, 6 Composite salt-water-retaining material, 7 Modular water storage belt, 8 Steel anchor bolt, 9 Non-woven bag. Detailed Implementation

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the following description is provided in conjunction with the accompanying drawings. Figures 1-4 The present invention will be further described in detail below with reference to specific embodiments. Example 1:

[0022] The composite salt-water-retaining material used in this embodiment has the following composition ratio based on a total mass of 100 parts: Core layer: 35 parts, including 21.0 parts (60%) of calcium chloride and 14.0 parts (40%) of magnesium chloride; both calcium chloride and magnesium chloride are highly hygroscopic salts, mainly absorbing moisture from the soil and air.

[0023] The control layer, covering the core layer, consists of 25 parts and primarily functions to control salt release, temperature control, and water retention. It comprises 7 parts bentonite, 10 parts carbonaceous mudstone, and 4 parts polyacrylamide. The bentonite mainly controls temperature and increases soil cohesion. The carbonaceous mudstone provides a certain carbon source and good water channels. The polyacrylamide acts as a binder and also adsorbs water, controlling the rate of water loss and absorption.

[0024] The protective layer covering the control layer consists of 10 parts, of which 8 parts are clay and 2 parts are siliceous clay. In cases where clay is scarce in the mine, siliceous clay can be used as a substitute. It mainly serves to isolate the control layer from the outer shell layer and buffer the rate of moisture migration.

[0025] The outer shell layer, covering the protective layer, comprises 10 parts, including 5 parts polyvinyl alcohol and 5 parts silanized starch. Its main function is to resist soil erosion, increase the strength of the water-retaining material, and ensure the integrity of the multifunctional composite salt-water-retaining material.

[0026] The preparation steps of the composite salt water-retaining material in this embodiment are as follows: Core layer preparation: Weigh 21.0 g of calcium chloride and 14.0 g of magnesium chloride, and add them sequentially to the melting device, prioritizing the addition of field-grade magnesium chloride followed by calcium chloride to reduce the influence of moisture absorption. Under nitrogen protection, heat to 450–500 °C at 5–10 °C / min and hold for 60–90 min, continuously stirring at 200–300 rpm until the system is completely melted and forms a homogeneous eutectic. Granulate and dry the melt into solid spherical particles using a fluidized bed spray dryer.

[0027] Control layer coating: Weigh 7g of bentonite, 10g of carbonaceous mudstone sieved to a particle size <1cm, and 4g of polyacrylamide. Mix them evenly, then add 42g of water and stir to form a fluid slurry. Spray this slurry onto the surface of the core layer particles to form a primary encapsulation.

[0028] Protective layer coating: Weigh 8g of clay with a particle size of <1cm and 2g of sub-clay, mix them evenly, add 20g of water, stir to form a fluid slurry, and spray it onto the surface of the control layer to form a secondary embedding.

[0029] Outer shell coating: Weigh 5g of polyvinyl alcohol and slowly add it to 50g of deionized water heated to 90℃, stirring until completely dissolved. Add 5g of silanized starch, stir evenly, and cool to room temperature. Spray this onto the surface of the protective layer to obtain the water-retaining material. Example 2:

[0030] The composite salt-water-retaining material used in this embodiment has the following composition ratio based on a total mass of 100 parts: Core layer: 40 parts, including 28.0 parts (70%) of calcium chloride and 12.0 parts (30%) of magnesium chloride; Control layer: 35 parts, including 10 parts bentonite, 15 parts carbonaceous mudstone, and 7 parts polyacrylamide; Protective layer: 15 parts, of which 10 parts are clay and 5 parts are silty clay; Outer shell layer: 15 parts, of which 10 parts are polyvinyl alcohol and 5 parts are silanized starch.

[0031] The steps for preparing multifunctional composite salt water-retaining materials are as follows: Core layer preparation: Weigh 28.0g of calcium chloride and 12.0g of magnesium chloride, melt-blend them, and then granulate them into solid spherical particles using a fluidized bed spray granulation dryer.

[0032] Control layer coating: Weigh 10g of bentonite, 15g of carbonaceous mudstone sieved to a particle size <1cm, and 7g of polyacrylamide. Mix them and add 64g of water to form a slurry. Spray the slurry onto the core layer.

[0033] Protective coating: Weigh 10g of clay (sieved to a particle size <1cm) and 5g of sub-clay, add 30g of water to form a slurry. Spray onto the control layer.

[0034] Outer layer coating: Weigh 10g of polyvinyl alcohol, add 50g of deionized water, heat to 95℃ to dissolve, add 5g of silanized starch, stir evenly and cool. Spray onto the protective layer and air dry for 24 hours to cure. Example 3:

[0035] The composite salt-water-retaining material used in this embodiment has the following composition ratio based on a total mass of 100 parts: Core layer: 38 parts, including 26.6 parts (70%) of calcium chloride and 11.4 parts (30%) of magnesium chloride; Control layer: 30 parts, including 8.5 parts bentonite, 12.5 parts carbonaceous mudstone, and 5.0 parts polyacrylamide; Protective layer: 12 parts, of which 10 parts are clay and 2 parts are silty clay; Outer shell: 12 parts, of which 6 parts are polyvinyl alcohol and 6 parts are silanized starch.

[0036] Preparation steps: Core layer preparation: Weigh 26.6g of calcium chloride and 11.4g of magnesium chloride, melt-blend and granulate into solid spherical particles.

[0037] Control layer coating: Weigh 8.5g of bentonite, 12.5g of carbonaceous mudstone sieved to a particle size <1cm, and 5.0g of polyacrylamide. Mix them and add 52g of water to form a slurry. Spray the slurry onto the core layer and allow it to dry.

[0038] Protective coating: Weigh 10g of clay and 2g of siliceous clay sieved to a particle size <1cm, add 24g of water to form a slurry. Spray onto the control layer and allow to dry.

[0039] Outer layer coating: Weigh 6g of polyvinyl alcohol, add 54g of deionized water, heat to 90℃ to dissolve, add 6g of silanized starch, stir evenly and cool. Spray onto the protective layer and air dry to cure. Example 4:

[0040] The composite salt-water-retaining material used in this embodiment has the following composition ratio based on a total mass of 100 parts: Core layer: 37 parts, including 25.9 parts calcium chloride and 11.1 parts magnesium chloride; Control layer: 26 parts, including 7 parts bentonite, 11 parts carbonaceous mudstone, and 5 parts polyacrylamide; Protective layer: 10 parts, of which 5 parts are clay and 3 parts are silty clay; Outer shell layer: 10 parts, of which 5 parts are polyvinyl alcohol and 5 parts are silanized starch.

[0041] Preparation steps: Core layer preparation: Weigh 25.9g of calcium chloride and 11.1g of magnesium chloride, melt-blend and granulate into solid spheres.

[0042] Control layer coating: Weigh 7g of bentonite, 11g of carbonaceous mudstone, and 5g of polyacrylamide, add 50g of water to form a slurry, spray and dry.

[0043] Protective coating: Weigh 10g of clay and 3g of siliceous clay, add 26g of water to form a slurry, spray and dry.

[0044] Outer shell coating: Weigh 7g of polyvinyl alcohol, add 63g of deionized water, heat to 90℃ to dissolve, add 6g of silanized starch, cool, spray and air dry.

[0045] The water-retaining material prepared in this embodiment is mixed with sieved topsoil at a mass ratio of 5% and then the platform is restored.

[0046] Technical effects: The high application rate further enhanced the water retention effect. Under strong evaporation conditions, the soil moisture retention time was extended by approximately 40%, and the seedling survival rate increased to over 80%.

[0047] Example 5: Directly mixed with reclaimed soil and applied.

[0048] The composite salt-water-retaining material 6 prepared in this embodiment is uniformly mixed with sieved topsoil at a mass ratio of 2% before platform backfilling. First, the topsoil is sieved to remove excess gravel, controlling the topsoil particle size to be less than 2cm. 1000kg of sieved topsoil is taken, and 20kg of water-retaining material is added. The mixture is thoroughly mixed using mechanical mixing equipment before platform backfilling. Topsoil backfilling reduces transpiration, especially in arid areas, as the composite salt-water-retaining material can draw moisture from the air, reducing water loss. Example 6:

[0049] The difference between this embodiment and Embodiment 5 is that the water-retaining material is uniformly mixed with the reclaimed topsoil at a mass ratio of 5%. Take 1000 kg of sieved topsoil, add 50 kg of water-retaining material, and use a special mixing device to thoroughly stir the mixture to ensure that the material is evenly distributed before platform reclashing.

[0050] Example 7: Modular application of composite salt water-retaining materials for organized water storage.

[0051] The water-retaining material prepared in this embodiment is encapsulated in a 3.5m × 10cm × 10cm non-woven bag 9 to form a modular water storage strip 7. This strip is buried 3cm deep on the slope and fixed with steel anchor rods 8, each 1.5m long and 1.5cm in diameter, at 1.5m intervals. Each module is laid out along the slope at 5m intervals, thus achieving both soil and water conservation and the absorption of moisture from the air.

[0052] Example 8: Composite salt-water-retaining material applied to soilless planting technology.

[0053] A 1m×1m×1m planting trench is constructed on the rock slope. When backfilling the trench, 2% of the water-retaining material of this embodiment is mixed in with the total mass of the topsoil and thoroughly mixed. Backfill soil is then laid in the trench. In arid areas, 2% of the total mass of the topsoil composite salt-water-retaining material 6 can be added to the backfill soil. Subsequently, reclaimed plants are planted in the soil, leaving a 10cm space above the trench. After the plants are planted, they are covered with the composite salt-water-retaining material 6 to retain moisture and absorb water. Example 9:

[0054] The difference between this embodiment and Embodiment 8 is that: a vertically drilled trench with dimensions of 1m × 1m × 1m is made on the rock slope. Backfill soil 5 is laid in the trench, and water-retaining material of 3% of the total mass of topsoil is added to the backfill soil and thoroughly mixed. Subsequently, reclaimed plants are planted in the soil, leaving a 10cm space above the trench. After the plants are planted, they are covered with water-retaining material with a thickness of 10cm.

[0055] Soil improvement and water retention effect test of spoil heap platform Newly constructed spoil heap platforms with consistent site conditions were selected and divided into four 20m × 50m experimental plots. Group T1 (materials of this invention): The material prepared in Example 1 was uniformly mixed with the cover soil at a 3% mass ratio and backfilled, with a cover soil thickness of 50cm. Group T2 (commercially available water-retaining agent group): An equal mass of commercially available polyacrylamide water-retaining agent was mixed with the cover soil and backfilled. Group T3 (bare salt control group): An equal mass of uncoated physical mixed salt of calcium chloride and magnesium chloride (in the same proportion as the core layer) was mixed with the cover soil and backfilled. Group CK (blank control group): Only ordinary spoil heap cover soil was backfilled. All plots used the same mixed sowing method of alfalfa, saxaul, and caragana. During the first growing season after sowing, from June to September, soil moisture dynamics showed that during a drought period of 15 consecutive days without rainfall in June, the average volumetric water content of the 0-20cm soil layer in Group T1 remained at 12.5%, significantly higher than that of Group CK (6.8%), Group T2 (9.2%), and Group T3 (7.1%). Soil moisture content in group T1 was approximately 84% higher than in group CK, with a significantly longer moisture retention time. A survey 45 days after sowing showed that the average emergence rate of grasses and legumes in group T1 reached 76%, with a seedling survival rate of 85%. In contrast, the emergence rate in group CK was only 38%, with a survival rate of 45%. Group T2 had an emergence rate of 65%, but seedlings wilted during the mid-dry season. Group T3 suffered from salt damage, resulting in an emergence rate below 10% and all seedlings dying. At the end of the growing season, the aboveground dry matter accumulation per unit area in group T1 was 2.3 times that of group CK and 1.5 times that of group T2.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite salt-water-retaining material for ecological restoration of open-pit mines, characterized in that, It adopts a four-layer composite structure of "core-control-protection-shell", which includes, by mass parts: Core layer: 35-40 parts, a strongly hygroscopic salt composed of 60-70 parts calcium chloride and 30-40 parts magnesium chloride; The control layer covering the core layer consists of 25 to 35 parts of a controlled-release, water-retaining, and soil-improving composite material composed of 7 to 10 parts bentonite, 10 to 15 parts carbonaceous mudstone, and 4 to 7 parts polyacrylamide. A protective layer covering the control layer: 10-15 parts, consisting of 8-15 parts of open-pit coal mine clay and 5-10 parts of sub-clay, forming a buffer isolation layer; The outer shell layer covering the protective layer: 10 to 15 parts, an anti-corrosion coating formed of 5 to 10 parts polyvinyl alcohol and 5 to 10 parts silanized starch.

2. The multifunctional composite salt-water-retaining material according to claim 1, characterized in that, The control layer is uniformly composited from bentonite, carbonaceous mudstone, and polyacrylamide through hydration.

3. The multifunctional composite salt-water-retaining material according to claim 1, characterized in that, The outer shell layer contains polyvinyl alcohol and silanized starch that are cross-linked by hot melt to form a weather-resistant coating.

4. A method for preparing the multifunctional composite salt-water-retaining material as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Core layer preparation: Calcium chloride and magnesium chloride are melt-blended and granulated into solid spheres using a fluidized bed spray granulation dryer; (2) Control layer coating: Bentonite, sieved carbonaceous mudstone and polyacrylamide are mixed, water is added to make a slurry, and the slurry is sprayed onto the surface of the core layer spheres and dried; (3) Protective layer coating: Sieve-blended clay and sub-clay are mixed, water is added to make a slurry, and the slurry is sprayed onto the surface of the control layer and dried; (4) Outer layer coating: Polyvinyl alcohol is dissolved in hot water at 85-95℃, silanized starch is added and mixed evenly, and after cooling, it is sprayed onto the surface of the protective layer and cured.

5. The method for preparing multifunctional composite salt-water-retaining materials according to claim 4, characterized in that, The amount of water added in step (2) is twice the total mass of the control layer solid.

6. The method for preparing multifunctional composite salt-water-retaining materials according to claim 4, characterized in that, The amount of water added in step (3) is twice the total mass of the protective layer solid.

7. The application of the multifunctional composite salt-water-retaining material according to any one of claims 1-3 in the ecological restoration of open-pit coal mines.

8. The application according to claim 7, characterized in that, The application involves mixing the multifunctional composite salt-water-retaining material with reclaimed soil at a mass ratio of 2% to 5%, and then backfilling it onto the open-pit coal mine spoil heap platform.

9. The application according to claim 7, characterized in that, The application involves encapsulating the multifunctional composite salt-water-retaining material in a non-woven bag to form a modular water storage belt, and then burying and anchoring the water storage belt to the slope of an open-pit coal mine spoil heap.

10. The application according to claim 7, characterized in that, The application is for the revegetation of rocky slopes in open-pit coal mines. Specifically, a planting trench is opened on the rocky slope, and 2% to 3% of the multifunctional composite salt-water-retaining material is added to the backfill soil in the trench. After planting plants, the surface is covered with a 10cm thick layer of the multifunctional composite salt-water-retaining material.

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