Soil reconstruction method for dump of arid / semi-arid mining area

Abstract

The invention relates to the technical field of ecological environment restoration, in particular to an arid / semi-arid mining area waste dump soil reconstruction method which comprises the following steps: S1, stripping surface soil of a waste dump, and leveling and compacting the surface of the waste dump to obtain a parent material layer; s2, coal gangue and an ionic curing agent are mixed, the rotating speed is 50 rpm, stirring is conducted for 10 min, and a mixture is obtained; the parent material layer is covered with the mixture in a layered mode, the thickness of each layer is 15-20 cm, after the mixture is covered every time, the mixture is compacted, then the next layer of mixture is covered, and after the last layer of mixture is compacted, a water-resisting layer is obtained; s3, the water-resisting layer is covered with the water storage layer and laid flat; and S4, covering the water storage layer with the vegetation layer. Heavy metal pollutants in the coal gangue can be effectively fixed, surface water and surrounding soil are prevented from being polluted by leaching of the coal gangue, good durability is shown, and functions can be kept for a long time.

Description

Technical Field

[0001] The present invention relates to the technical field of ecological environment restoration, and more particularly to a soil reconstruction method for a waste dump in an arid / semi-arid mining area. Background Art

[0002] During open-pit mining, rock layers, overlying soil, and the green vegetation that supports them are removed, disrupting the soil's biological environment and natural stratification, which have been formed over countless years. Solid waste and mechanical compaction in spoil dumps disrupt the original pore structure and water cycle, significantly reducing vegetation and exposing the soil directly to sunlight and wind, accelerating water evaporation. Water retention capacity is significantly reduced, especially in arid and semi-arid regions where vegetation is sparse. Wind and water erosion further exacerbate soil erosion and nutrient loss. This not only removes nutrients from the soil but also damages the soil structure, further reducing water retention capacity. Furthermore, solid waste generated during mining increases the concentration of harmful substances such as heavy metals in the soil, increasing the risk of pollution. As soil water retention is one of the key drivers of vegetation restoration, it is urgent to strengthen it while preventing contamination from harmful substances in solid waste and restoring and sustaining vegetation in spoil dumps over the long term.

[0003] Land restoration, as a prerequisite for ecological restoration in mining areas, has received significant attention. For mine spoil dumps, soil reconstruction is often used for reclamation. The reconstructed soil is generally divided into a multi-layer soil structure, each layer of which has different functions. However, when repairing mine spoil dumps, the construction cost of the aquiclude is high, the material transportation is difficult, and it cannot effectively digest the original solid waste in the mining area, and the water retention performance is poor. Especially when applied to arid and semi-arid mining areas, it cannot effectively isolate water infiltration and nutrient loss. It is also not conducive to the long-term succession of the mining area and the utilization of mining solid waste. In particular, the improper use of low-value mining solid waste generated in open-pit mining poses a risk of secondary pollution.

[0004] Therefore, a method for constructing a water-blocking layer in a spoil dump is urgently needed. This method can rationally construct a water-blocking structure, adapt to local conditions, and use local materials to reconstruct the spoil dump water-blocking layer from the perspective of water flow and pore changes. This will achieve soil reconstruction in the spoil dump and the disposal and utilization of mining solid waste. Summary of the Invention

[0005] This invention addresses the challenges of existing technologies, such as the inability to effectively isolate soil moisture and nutrient loss, high remediation costs, and the accumulation of solid waste in mining areas, which can lead to land occupation and secondary pollution. By developing a new aquiclude and providing a method for reconstructing soil in arid / semi-arid mining dumps, this invention effectively addresses the issues of poor soil water retention, solid waste accumulation, and low utilization rates in mining areas. The reconstructed soil with the aquiclude can help restore ecosystems and prevent soil erosion.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A first aspect of the present invention provides a waterproof layer comprising 50 parts by weight of coal gangue and 4 to 5 parts of an ionic curing agent.

[0008] Preferably, the ionic curing agent includes, by weight, 45-50 parts of sulfonated oil, 30-35 parts of silane coupling agent, 10 parts of anionic polyacrylamide, 5 parts of environmentally friendly alkaline activator, 5 parts of environmentally friendly sulfate activator, 0.3-0.8 parts of dispersant, and 100 parts of water.

[0009] Preferably, the preparation method of the above-mentioned ionic curing agent comprises the following steps:

[0010] Step 1: Pour the above-mentioned alkaline activator and sulfate activator into a blender and mix them evenly. Stirring should be done indoors or at a temperature and humidity that is maintained indoors. The stirring rate should be 100 rpm and the stirring time should be 2 to 5 minutes.

[0011] Step 2: Pour the above amount of water into a blender and mix evenly. Stirring should be done indoors or in an environment that maintains room temperature and humidity. The stirring rate should be 150 rpm and the stirring time should be 2 to 5 minutes.

[0012] Step 3: Place the aforementioned portions of silane coupling agent, sulfonated oil, anionic polyacrylamide, and dispersant into a blender and mix uniformly. Stirring is performed indoors or at a temperature and humidity maintained indoors at a stirring rate of 300 rpm for 10 to 15 minutes to obtain an ionic curing agent.

[0013] Preferably, steps 1 to 3 are stirred under constant temperature and humidity conditions, with the stirring temperature being 60° C. and the humidity being 50%.

[0014] Preferably, the alkaline activator is Ca(OH)2.

[0015] Preferably, the environmentally friendly sulfate activator is CaSO4.

[0016] Preferably, the dispersant is paraffin.

[0017] Preferably, the particle size of the coal gangue does not exceed 0.4 cm, the calorific value is less than 2090 kJ / kg, the carbon content is less than 6%, and the strength is within 20 MPa.

[0018] The second aspect of the present invention provides a method for preparing the above-mentioned waterproof layer, comprising mixing coal gangue and ionic curing agent according to the above-mentioned weight parts, stirring at a rotation speed of 50 rpm for more than 10 minutes to obtain a mixture; leveling and compacting the mixture to a thickness of 15 to 20 cm to obtain a waterproof layer.

[0019] A third aspect of the present invention provides a method for soil reconstruction in an arid / semi-arid mining area dump using the aforementioned aquiclude, comprising the following steps:

[0020] S1. Stripping the surface soil of the dumping ground, leveling and compacting the surface of the dumping ground to obtain the parent material layer;

[0021] S2. Mix the gangue and the ionic curing agent according to the above weight parts, rotate at 50 rpm, and stir for 10 minutes to obtain a mixture; cover the mixture on the parent material layer in layers, with each layer having a thickness of 15 to 20 cm. After each covering of the mixture, compact the mixture and then cover it with the next layer of mixture. After the last layer of mixture is compacted, a water-proof layer is obtained;

[0022] S3. Lay the aquifer over the aquiclude;

[0023] S4. Cover the aquifer with a vegetation layer.

[0024] Preferably, the total thickness of the aquiclude is 40 to 60 cm, and the compaction degree of the soil aquiclude is not less than 95%.

[0025] Preferably, when compacting the mixture, the outer edges of the mixture are compacted first, and then the middle area of ​​the mixture is compacted.

[0026] Preferably, the aquifer is obtained by mixing gangue and soil, the mass ratio of gangue to soil is 1:6, the soil is sand and / or loam, and the compaction degree of the aquifer does not exceed 70%.

[0027] Preferably, the vegetation layer is the surface soil stripped from the spoil dump, and the thickness of the vegetation layer is not less than 30 cm.

[0028] The beneficial effects of the present invention are:

[0029] The coal gangue of the present invention comes from low-value coal gangue in mining areas that has low residual calorific value, low carbon content, and low strength after high-value utilization, and is difficult and costly to use in construction and industry. Its particle size is ≤0.4 cm. Using it in aquiclude construction can effectively solve its disposal problems while reducing its environmental pollution risk. The main components of the ionic curing agent used in the present invention are 45-50 parts of sulfonated oil, 30-35 parts of silane coupling agent, 10 parts of anionic polyacrylamide, 5 parts of environmentally friendly alkaline activator, 5 parts of environmentally friendly sulfate activator, and 0.3-0.8 parts of dispersant, which are added to 100 parts of water according to the weight ratio.

[0030] Ionic curing agents ionize in water to produce strong cations, some of which adsorb onto the negative charges of vacant gangue mineral crystal particles to form ionic bonds. Others replace weak cations originally adsorbed on the colloid surface, replacing weak cations on the gangue surface and between layers with strong cations. This reduces the negative charge on the surface, lowers its hydrophilicity and the content of surface-bound water, and enhances the gangue's hydrophobicity. The anionic end of the added sulfonated oil combines with the heavy metal ions in the gangue to form new chemical bonds, increasing the cohesive force between gangue particles while solidifying the metal ions in the gangue and reducing the escape or leaching of harmful substances.

[0031] Compared with the existing technology, the present invention uses coal gangue mixed with ionic curing agents to construct an aquiclude, which can effectively isolate soil moisture from infiltration and maintain soil moisture content. At the same time, it improves the utilization rate of coal gangue and effectively fixes heavy metal pollutants in coal gangue to prevent them from leaching and polluting surface water and surrounding soil. Laying reconstructed soil on the aquiclude has a good promoting effect on vegetation growth and microbial reproduction. It shows good durability and can maintain its function for a long time. It is suitable for soil reconstruction and improvement in arid / semi-arid mining areas. According to the "Soil Environmental Quality Standards", the quality of the reconstructed soil meets the requirements of Class 3 soil or above and does not cause harm or pollution to plants and the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a diagram of the mechanism of action of the aquiclude;

[0033] Figure 2 Schematic diagram of an implementation scheme of the water-barrier structure constructed in the present invention.

[0034] Figure 3 Reconstruct the soil moisture change map after precipitation.

[0035] Figure 4 This is a map showing the changes in vegetation coverage in the mining area's spoil dump after reconstruction of the aquiclude.

[0036] Figure 2 In the middle, 1-upper vegetation layer, 2-middle aquifer, 3-lower aquiclude. DETAILED DESCRIPTION

[0037] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0038] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. The experimental methods in the examples are conventional methods unless otherwise specified. Where specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0039] In order to solve the problems of poor soil water retention, low solid waste utilization rate and heavy metal pollution in arid / semi-arid mining dumps, the present invention reconstructs the dump aquifer by using coal gangue and ionic curing agent to construct an aquifer that can synergistically utilize water and solid waste, which is suitable for soil water retention in open-pit mining dumps.

[0040] To address the drawbacks of existing mine dump soil reconstruction aquicludes, such as high construction costs, difficulty in transporting materials, inability to effectively digest existing solid waste in the mine, poor water retention, inability to effectively isolate water and nutrient loss, and difficulty in timely water replenishment for vegetation. Furthermore, low-value mining solid waste generated in open-pit mining is difficult to utilize and poses a high risk of heavy metal ion contamination. The present invention provides an environmentally friendly method for solidifying low-value coal-based solid waste to reconstruct a soil aquiclude in arid / semi-arid mine dumps.

[0041] The present invention lays a gangue-solidified waterproof layer on the surface of the spoil dump in arid / semi-arid mining areas. The waterproof layer is composed of an ionic curing agent mixed with low-value gangue and fully compacted, and a soil reconstruction structure can be set thereon; the gangue is taken from the low-value gangue left after high-value utilization in the mining area, and the gangue particle size used for the waterproof layer is ≤0.4cm; the main component of the environmentally friendly ionic curing agent used is a self-developed strong cationic salt substance, which is non-toxic to the environment and organisms. The waterproof layer provided by the present invention stirs the gangue and the ionic curing agent to fully mix the curing agent and the gangue, avoiding the gangue agglomeration and inability to fully infiltrate. The stirred gangue and ionic curing agent are layered and compacted on the spoil dump, and compacted in three layers to avoid the waterproof layer being too thick to affect the compaction effect. The coal gangue is mixed with the curing agent and laid in the spoil yard, with a compaction degree of ≥95% and a permeability coefficient within 0.005m / d.

[0042] Example 1: Comparison of coal gangue properties before and after treatment

[0043] The ionic curing agent comprises, by weight, 50 parts of sulfonated oil, 30 parts of silane coupling agent, 10 parts of anionic polyacrylamide, 5 parts of environmentally friendly alkaline activator, 5 parts of environmentally friendly sulfate activator, 0.8 parts of dispersant and 100 parts of water.

[0044] The preparation method of the ionic curing agent comprises the following steps:

[0045] Step 1: Pour the above-mentioned alkaline activator and sulfate activator into a blender and mix them evenly. Stirring should be done indoors or at a temperature and humidity that is maintained indoors. The stirring rate should be 100 rpm and the stirring time should be 2 to 5 minutes.

[0046] Step 2: Pour the above amount of water into a blender and mix evenly. Stirring should be done indoors or in an environment that maintains room temperature and humidity. The stirring rate should be 150 rpm and the stirring time should be 2 to 5 minutes.

[0047] Step 3: Place the aforementioned portions of silane coupling agent, sulfonated oil, anionic polyacrylamide, and dispersant into a blender and mix uniformly. Stirring is performed indoors or at a temperature and humidity maintained indoors at a stirring rate of 300 rpm for 10 to 15 minutes to obtain an ionic curing agent.

[0048] The stirring temperature in steps 1 to 3 is controlled at 60° C. and the humidity is 50%. The alkaline activator is Ca(OH) 2 ; the environmentally friendly sulfate activator is CaSO 4 ; and the dispersant is paraffin.

[0049] Select coal gangue with a particle size of ≤0.4 cm, add 50 parts of coal gangue and 4 to 5 parts of ionic curing agent by weight into a forced mixer, rotate at 50 rpm, and stir for 10 minutes to allow the ionic curing agent to fully infiltrate the coal gangue to obtain treated coal gangue.

[0050] Untreated gangue with the same quality as the gangue before the above treatment was used as the blank control group, and the treated gangue was used as the experimental group. The gangue leachate was extracted according to the "Solid Waste Leaching Toxicity Leaching Method Horizontal Oscillation Method" (HJ557-2010). The concentrations of heavy metal element pollutants such as Mn (manganese), Cu (copper), Cd (cadmium), Cr (chromium), Ni (nickel), and Zn (zinc) in the gangue leachate before and after the curing agent treatment were determined by atomic absorption spectrometry (AAS). The test results are as follows:

[0051] For treated gangue samples, the leaching amounts of Mn (manganese), Cu (copper), Cd (cadmium), Cr (chromium), Ni (nickel), and Zn (zinc) were 34.12 μg / L, 46.61 μg / L, 1.83 μg / L, 2.15 μg / L, 3.02 μg / L, and 24.62 μg / L, respectively. For treated gangue samples, the leaching amounts of typical heavy metal ions Mn, Cu, and Zn decreased to 1.36 μg / L, 4.18 μg / L, and 1.69 μg / L, respectively. Monitoring values ​​for Cd, Cr, and Ni were below the detection limit. In its natural state, gangue solidified with an ionic solidifier has minimal impact on the aquatic environment, significantly reducing the risk of heavy metal toxicity from continued accumulation in the surrounding soil.

[0052] The experimental results show that the concentration of heavy metals in the treated gangue leachate is reduced by more than 90% compared with that before treatment, meeting environmental requirements and not causing leaching and pollution to the environment. Figure 1 As shown, the ionic curing agent used in the present invention mainly consists of sulfonated oil, silane coupling agent, anionic polyacrylamide, and a small amount of environmentally friendly alkaline activator, environmentally friendly sulfate activator, and dispersant. When mixed with water, it reacts with the surface of coal gangue, increasing the cohesion between coal gangue particles, reducing their hydrophilicity and the content of surface bound water. At the same time, it solidifies the metal ions in the coal gangue, reducing the escape or leaching of harmful substances.

[0053] Example 2: Reconstruction of the soil aquifer

[0054] The total thickness of the soil aquiclude constructed in this embodiment is 40 to 60 cm and is arranged on the surface of the spoil dump. The aquiclude is mainly composed of low-value coal gangue remaining after high-value utilization of coal gangue in the mining area mixed with an environmentally friendly ionic curing agent. The coal gangue is selected from low-value coal gangue in the mining area, which has low remaining heat, low carbon content, low strength after high-value utilization, and is difficult and costly to use in construction and industry. Its particle size is ≤0.4 cm. Using it to construct the aquiclude can effectively solve its disposal problem while reducing its risk of environmental pollution.

[0055] The selected gangue particles are well-graded, and the whole section is taken to reasonably control the content of gangue of each particle size, and the gangue with too large particle size is removed to avoid the gangue particles having the same size, which will lead to larger gaps.

[0056] Specifically, this example provides a preferred method for reconstructing a soil aquifer, including the following steps:

[0057] (1) Preparation of materials:

[0058] The ionic curing agent comprises, by weight, 45 parts of sulfonated oil, 35 parts of silane coupling agent, 10 parts of anionic polyacrylamide, 5 parts of environmentally friendly alkaline activator, 5 parts of environmentally friendly sulfate activator, 0.3 parts of dispersant and 100 parts of water.

[0059] The preparation method of the ionic curing agent comprises the following steps:

[0060] Step 1: Pour the environmentally friendly alkaline activator and the environmentally friendly sulfate activator into a blender and mix them evenly. Stirring is carried out indoors or the stirring environment is maintained at indoor temperature and humidity, with a stirring rate of 100 r / min and a stirring time of 2 to 5 minutes.

[0061] Step 2: Pour the water into a blender and mix evenly. Stirring is carried out indoors or the stirring environment is maintained at room temperature and humidity, with a stirring rate of 150 r / min and a stirring time of 2 to 5 minutes.

[0062] Step 3: Place the silane coupling agent, sulfonated oil, anionic polyacrylamide, and dispersant in a blender in sequence and mix them evenly. Stirring is performed indoors or at a temperature and humidity maintained indoors at a stirring rate of 300 rpm for 10 to 15 minutes to obtain an ionic curing agent.

[0063] Add 50 parts by weight of coal gangue (particle size ≤ 0.4 cm) and 4-5 parts of ionic curing agent into a forced mixer at a speed of 50 rpm and stir for 10 minutes to allow the ionic curing agent to fully infiltrate the coal gangue to obtain a mixture, which is set aside;

[0064] (2) Reconstruction of soil aquifer:

[0065] The mixture is covered on the surface of the mine spoil dump in three layers, with each layer being about 20 cm thick. After each layer is laid, the mixture is compacted by a roller. The speed of the roller is controlled at 9 to 15 km / h, and each layer is rolled more than 20 times. The next layer of mixture is then covered and the above compaction operation is repeated. After the last layer of mixture is compacted, a soil water-proof layer is formed.

[0066] The waterproof layer of the present invention is formed by rolling and compacting after the ionic curing agent is fully mixed with the low-value coal gangue. A forced mixer is used to stir the coal gangue and the ionic curing agent until the ionic curing agent fully infiltrates the coal gangue. The mixture is compacted in three layers to avoid the waterproof layer being too thick and affecting the compaction effect. Each layer is about 20 cm. The upper layer is compacted after the lower layer is fully compacted. A roller is used for compaction, and the speed of the roller is controlled to be maintained at 9 km / h to 15 km / h, and the rolling is performed more than 20 times. The permeability coefficient is within 0.005 m / d, and the compaction degree is ≥95%.

[0067] The above method is an environmentally friendly method for solidifying low-value coal-based solid waste to reconstruct the soil aquifer in arid / semi-arid mining area spoil dumps. The aquifer is formed by adding a special solidifying agent to coal gangue and fully mixing and compacting it. It effectively isolates water from infiltrating and losing during precipitation, and uses the capillary action of the isolated water to replenish the upper soil when there is a water shortage.

[0068] Example 3: Soil reconstruction in arid / semi-arid mining dumps

[0069] The present invention lays an impermeable layer on the mine dump to isolate the water from seeping into the upper soil layer, and the upper soil is sequentially provided with a reconstructed aquifer and vegetation layer. The selected dump is subjected to land preparation, and its terrain conditions are improved by engineering machinery to create conditions for the subsequent construction of the impermeable layer. At the same time, the stability of the site slope is improved, the slope area of ​​the mine dump is subjected to slope protection treatment, and the slope surface of the mine dump is constructed and repaired in combination with the specific terrain, so that the dump meets the subsequent construction conditions. The ionic curing agent, its preparation method, and the preparation method of the mixture in this embodiment are exactly the same as those in Example 2.

[0070] Specifically, if Figure 2 As shown, a soil reconstruction method for an arid / semi-arid mining area dump includes the following steps:

[0071] (1) After the soil and rock blocks of the spoil dump are compacted as a whole, mechanical leveling treatment is adopted. A road roller is used for compaction and the land is leveled at the same time to prevent the filler of the impermeable layer from penetrating into the spoil dump pile and being lost. The surface of the spoil dump after treatment is used as the structural parent material layer.

[0072] (2) After the surface of the spoil dump is leveled, a 40-60 cm thick aquiclude is laid. The aquiclude is made of low-value coal gangue after high-value utilization such as gangue power generation and high-value extraction, mixed with an ionic curing agent and compacted. Coal gangue with a particle size of ≤0.4 cm accumulated on site is used as the aquiclude material, and its particle size distribution is maintained well. A forced mixer is used to mix the coal gangue and the ionic curing agent so that the ionic curing agent fully penetrates the surface of the coal gangue.

[0073] The mixed material is spread on the surface of the treated spoil dump and mechanically compacted in layers. Compact in three layers, approximately 20 cm thick per layer. Compact the previous layer after the next layer is fully compacted. First, compact both sides of the aquiclude, then the center. Maintain a roller speed of 9 to 15 km / h. Roll back and forth in an "S" pattern for at least 20 times to achieve a compaction level of ≥95%, ensuring the spoil dump surface is as uniform as possible. If the compacted aquiclude surface is uneven, use a grader to smooth it out.

[0074] Since coal gangue contains certain clay mineral components and its chemical composition is mainly inorganic minerals, it is used instead of clay mixed with ionic curing agent as the raw material of the waterproof layer. After compaction under the action of the ionic curing agent, the permeability coefficient is within 0.005m / d.

[0075] (3) A 60cm thick aquifer is laid on top of the aquiclude to replace the original core soil destroyed by mining. This layer is made of sandy soil and loamy sand obtained from stripping the soil layer in the mining area, mixed with fine-grained coal gangue discarded in the mining area. The mass ratio of coal gangue to soil is 1:6. It has good porosity and greater permeability than the aquiclude, and the compaction degree does not exceed 70%. This layer can effectively improve the water storage capacity of the original soil structure. When the surface layer is short of water, plant roots can use this part of the water to achieve the purpose of water storage. This layer of soil is naturally piled up and leveled by a bulldozer, without the need for special machinery to roll and compact it.

[0076] (4) The top layer is a 30cm thick vegetation layer, which is made of topsoil with a certain amount of water-retaining agent and microbial fertilizer added. The topsoil comes from the original surface soil stored after stripping from the mining area, and contains a certain amount of humus. The water-retaining agent is a polyacrylamide functional polymer water-absorbing material.

[0077] Soil moisture and vegetation cover monitoring

[0078] The methods for monitoring soil moisture and vegetation coverage after reconstruction of the aquiclude in arid / semi-arid open-pit mines are as follows:

[0079] Frequency Domain Reflectometry (FDR) is a fast and accurate method for monitoring soil moisture at different depths. By measuring the differential echoes of electromagnetic waves emitted by the sensor in the soil, the dielectric properties of the soil are calculated, and the volumetric moisture content of the soil can be inferred.

[0080] Tubular soil moisture detectors are used to continuously monitor soil moisture at various depths. Observation points are set up beneath the soil, and hourly data is collected from the soil surface down to the bottom of the aquiclude. Monitoring and analysis are performed based on reconstructed soil moisture data at different depths, acquired in real time and at fixed locations in the dumping ground.

[0081] Using the soil reconstruction method described in Example 3, a small-scale comparative experiment was conducted to simulate soil moisture conditions after precipitation to illustrate the effect of aquitard reconstruction on soil moisture. Both the experimental and control groups were constructed using stripped soil retained from the mining area within the same region. The experiment lasted two months, from April to May. The experimental group constructed the aquitard using coal gangue treated with an ionic curing agent, while the control group constructed the aquitard using coal gangue not treated with an ionic curing agent.

[0082] like Figure 3As shown in the figure, the results show that under the influence of precipitation, soil moisture content increases rapidly within a certain period of time, and then gradually decreases over the subsequent monitoring period. The moisture content of the vegetation layer in the experimental group increased significantly, and its rate of decline was faster than that of the control group in the initial period after reaching the peak, indicating that the reconstructed lower aquifer has good porosity, which facilitates water flow. However, after a period of decline, the rate of decline slowed until it stabilized. In contrast, the moisture content of the vegetation layer in the control group continued to decline, with significant fluctuations. After a moderate rainfall, the moisture content of the central vegetation layer dropped from an initial moisture content of approximately 26.6% to approximately 18.2% within 7 days, a decrease of 8.4%. This indicates a significant loss of moisture, and compared with the experimental group, the moisture content continued to decline and lacked replenishment.

[0083] In the period after precipitation, the moisture content at the bottom of the aquifer in the control group was about 24%, which was higher than the 16% in the experimental group, and increased by about 8% compared with the control group. Combined with the conclusion that the moisture content in the vegetation layer of the experimental group decreased rapidly in the early stage after precipitation and then slowed down and stabilized in the later stage, it shows that the structure of the aquiclude can effectively block moisture, and the blocked moisture can move upward in the aquifer and be stored for a long time for vegetation use.

[0084] Vegetation coverage is an important indicator for measuring soil water retention and mining area ecological restoration after aquiclude reconstruction. Its dynamic monitoring is of great significance for evaluating aquiclude reconstruction methods and mining area ecology.

[0085] The present invention uses remote sensing imaging technology to monitor the overall growth status of vegetation in the spoil dump after soil reconstruction. Compared with traditional ground surveys, the monitoring range is larger and real-time data collection can be performed. Regular and periodic continuous observations are performed on the mine spoil dump that adopts the soil reconstruction method in Example 3.

[0086] The vegetation index uses the Normalized Difference Vegetation Index (NDVI), the most widely used in remote sensing monitoring. It can accurately reflect the vegetation status of the target area and quantifies vegetation by the ratio of the difference between the near-infrared band and the visible red band to the sum. The surface reflectance data required for NDVI calculation comes from the database collected by the Landsat series of satellites launched by the United States Geological Survey and NASA. The NDVI calculation formula is as follows:

[0087]

[0088] Where NDVI is the normalized difference vegetation index; NIR is the near-infrared band reflectance; and R represents the red light band reflectance.

[0089] NDVI is divided into 4 levels. When NDVI>0.2, it means there is plant growth. The specific classification is as follows:

[0090] High vegetation coverage area (NDVI>0.5), medium vegetation coverage area (0.3<NDVI≤0.5), low vegetation coverage area (0.2<NDVI≤0.3), and no low vegetation coverage area (NDVI≤0.2).

[0091] In order to eliminate the influence of winter snow in the area and effectively reduce the impact of clouds, atmosphere, snow, etc. on the images, the time was chosen to be July to August when vegetation respiration is vigorous and cloud cover is less than 10%.

[0092] By statistically analyzing the NDVI data of the mine dump at different times, the changes in the area proportion of each coverage area are analyzed to reflect the vegetation growth in the dump after the reconstruction of the aquiclude.

[0093] like Figure 4 As shown in the figure, the vegetation coverage monitoring data is statistically summarized, and the changes in the area of ​​each NDVI region are as follows:

[0094] The area without vegetation cover (NDVI ≤ 0.2) decreased from 42.35 km in 2010 to 2 Reduced to 9.56km in 2024 2 The proportion of the study area decreased from 47.06% to 10.62%, and the low vegetation coverage area (0.2<NDVI≤0.3) decreased from 23.58km in 2010 to 1.37km in 2011. 2 Reduced to 19.65km in 2024 2 The area proportion decreased from 26.2% to 21.83%; the area of ​​medium vegetation coverage (0.3<NDVI≤0.5) decreased from 15.49km in 2010 to 15.49km in 2011. 2 Increase to 29.65km by 2024 2 The area proportion increased from 17.21% to 32.95%; the high vegetation coverage area (NDVI>0.5) increased from 8.58km in 2010 to 1.37km in 2011. 2 Increase to 31.14km by 2024 2 , the area share increased from 9.53% to 34.6%.

[0095] The results show that the vegetation coverage of the spoil dump after reconstruction with the present invention's aquiclude has significantly improved over the years of restoration. The area without vegetation has been significantly reduced, while the area covered by dense medium and high vegetation has increased significantly, reaching a total proportion of over 65%, indicating good vegetation recovery.

[0096] The present invention provides a method for reconstructing an aquiclude based on curing gangue with a curing agent, which is used to solve the problems of poor water retention of the aquiclude, low solid waste utilization rate and heavy metal pollution during the reconstruction of soil in the dumping ground of semi-arid mining areas. The present invention treats the gangue with an environmentally friendly ionic curing agent to serve as the main material of the soil aquiclude in the mining dumping ground, effectively isolating water loss. The ionic curing agent acts on the surface of the mineral crystals of the gangue to thin the thickness of its weakly bound water film, reduce the repulsive force between the gangue particles, facilitate the compaction of the gangue and reduce its pore volume and porosity, making it more compact under mechanical external force compaction, thereby achieving the purpose of isolating water infiltration. Since the ionic curing agent can stabilize the harmful substances in the gangue and reduce its solubility and mobility, it can effectively block the infiltration of soil water, significantly improve the water retention performance of the soil in arid / semi-arid mining areas, and reduce the pollution risk of the gangue to the mining environment. Materials are obtained nearby, and while reconstructing the soil to accelerate the reclamation of the mining area, low-value solid waste generated by open-pit mining is well utilized.

[0097] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A water-proof layer, characterized in that: Calculated by weight, it comprises 50 parts of coal gangue and 4 to 5 parts of ionic curing agent.

2. The waterproof layer according to claim 1, characterized in that: The ionic curing agent comprises, by weight, 45 to 50 parts of sulfonated oil, 30 to 35 parts of silane coupling agent, 10 parts of anionic polyacrylamide, 5 parts of environmentally friendly alkaline activator, 5 parts of environmentally friendly sulfate activator, 0.3 to 0.8 parts of dispersant, and 100 parts of water.

3. The waterproof layer according to claim 2, characterized in that: The preparation method of the ionic curing agent comprises the following steps: Step 1: Mix an environmentally friendly alkaline activator and an environmentally friendly sulfate activator by weight at a speed of 100 r / min and stir for 2 to 5 minutes to obtain a first mixture; Step 2: Add water to the first mixture at a speed of 150 r / min and stir for 2 to 5 minutes to obtain a second mixture; Step 3: Add a silane coupling agent, sulfonated oil, anionic polyacrylamide and a dispersant to the second mixture in sequence, at a rotation speed of 300 r / min, and stir for 10 to 15 minutes to obtain an ionic curing agent; Steps 1 to 3 are stirred under constant temperature and humidity conditions, with the stirring temperature being 60° C. and the humidity being 50%; the alkaline activator is Ca(OH) 2 , the environmentally friendly sulfate activator is CaSO 4 , and the dispersant is paraffin.

4. The waterproof layer according to claim 1, characterized in that: The particle size of the gangue does not exceed 0.4 cm, the calorific value is less than 2090 kJ / kg, the carbon content is less than 6%, and the strength is within 20 MPa.

5. A method for preparing the water-proof layer according to any one of claims 1 to 4, characterized in that: The method comprises mixing gangue and an ionic curing agent according to the weight parts of any one of claims 1 to 4, stirring at a rotation speed of 50 rpm for more than 10 minutes to obtain a mixture; and leveling and compacting the mixture to a thickness of 15 to 20 cm to obtain a water-proof layer.

6. A soil reconstruction method for an arid / semi-arid mining area dump based on the aquiclude according to any one of claims 1 to 4, characterized in that: The steps include: S1. Stripping the surface soil of the dumping ground, leveling and compacting the surface of the dumping ground to obtain the parent material layer; S2. Mix the gangue and the ionic curing agent according to the weight parts of claim 1, rotate at 50 rpm, and stir for 10 minutes to obtain a mixture; cover the mixture on the parent material layer in layers, with each layer having a thickness of 15 to 20 cm. After each covering of the mixture, compact the mixture and then cover it with the next layer of mixture. After the last layer of mixture is compacted, a water-proof layer is obtained; S3. Lay the aquifer over the aquiclude; S4. Cover the aquifer with a vegetation layer.

7. The soil reconstruction method for an arid / semi-arid mining area dump according to claim 6, characterized in that: The total thickness of the aquiclude is 40 to 60 cm, and the compaction degree of the soil aquiclude is not less than 95%.

8. The soil reconstruction method for an arid / semi-arid mining area dump according to claim 6, characterized in that: When compacting the mixture, first compact the outer edges of the mixture, then compact the middle area of ​​the mixture.

9. The soil reconstruction method for an arid / semi-arid mining area dump according to claim 6, characterized in that: The aquifer is obtained by mixing coal gangue and soil, with the mass ratio of coal gangue to soil being 1:

6. The soil is sandy soil and / or loamy sand, and the compaction degree of the aquifer does not exceed 70%.

10. The soil reconstruction method for an arid / semi-arid mining area dump according to claim 6, characterized in that: The vegetation layer is the surface soil stripped from the spoil dump, and the thickness of the vegetation layer is not less than 30cm.

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