A method for reconstructing soil in arid mining areas

Abstract

The present application relates to the technical field of environmental ecological restoration, and provides a dry mining area soil reconstruction method, comprising the following steps: sequentially arranging a lower water-resisting layer, an intermediate water storage layer and an upper gravel curtain layer on the surface of a dry mining area waste land, the lower water-resisting layer is a waterproof material layer or a clay layer, the soil used in the intermediate water storage layer is sandy soil or loamy sand, and the upper gravel curtain layer is formed by gravel with a particle size not less than 5 mm. In the present application, the upper gravel curtain layer can quickly infiltrate surface water into the soil, reduce the water evaporation speed of the lower soil, effectively store precipitation, and also increase the surface roughness and reduce soil wind erosion; the intermediate water storage layer can store the infiltrated surface water; and the lower water-resisting layer can prevent the water infiltration depth from exceeding the absorption range of the vegetation root system. The present application can effectively restore the vegetation in the dry mining area, has low restoration cost, short restoration time, and effectively solves the existing problems of the current vegetation restoration in the dry mining area.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental ecological restoration, and in particular to a method for reconstructing soil in a dry mining area. BACKGROUND

[0002] In the process of open-pit mining of mineral resources, the surface soil and overburden are stripped as a whole. After open-pit mining, the surface soil suitable for the growth of vegetation in the mining area is lost, and the vegetation is difficult to survive, forming a mine wasteland. To restore the ecological system of the mine wasteland, the soil layer suitable for the growth of local vegetation must be restored, that is, the soil layer must be reconstructed.

[0003] At present, a large number of soil layer reconstruction experiments and soil layer reconstruction engineering projects have been carried out on mine wastelands in humid and semi-humid regions. These soil layer reconstruction projects have reconstructed soil layers suitable for the growth of vegetation, and the vegetation has survived, and the ecological system of the mining area has gradually recovered. At present, the methods for reconstructing the soil layer include the following: the method of covering with imported soil, the method of deepening and shallowing, the method of stripping and interlacing and backfilling, the method of stacking ground soil, and the method of filling with fly ash. These soil reconstruction methods include engineering technical measures, physical measures, chemical measures, and biological measures. The reconstructed soil can effectively improve the water and fertilizer retention capacity of the surface soil, providing suitable substrate conditions for the survival of vegetation, and playing a key role in the restoration of vegetation in the mining area.

[0004] In arid regions, the wind speed is high, the evaporation is strong, the precipitation is scarce and unevenly distributed, and most of the effective precipitation that can be provided for plants is concentrated in a few short and heavy rainfall events. How to store this precipitation in the soil layer available to plants is the key to soil reconstruction for mine restoration in arid regions. The soil reconstruction methods in humid and semi-humid regions are to construct a soil surface layer suitable for the growth of vegetation, such as replacing the sandy gravel soil (stone) on the surface of the mining area with sandy loam or loam suitable for the growth of vegetation. This soil reconstruction method cannot store short and heavy rainfall in the soil, but on the contrary, it can cause serious soil erosion due to the lack of surface water infiltration capacity. Therefore, the soil reconstruction method in humid and semi-humid regions is not suitable for soil reconstruction in arid mining areas. SUMMARY

[0005] Therefore, the present application provides a method for reconstructing soil in a dry mining area. The soil reconstruction method provided by the present application has good vegetation restoration effect in arid mining areas, low restoration cost, and short restoration time, effectively solving the problems existing in the current vegetation restoration in arid mining areas.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] A method for reconstructing soil in a dry mining area, comprising the following steps:

[0008] The lower water-resisting layer, the intermediate water-storing layer and the upper gravel curtain layer are sequentially arranged on the surface of the abandoned land in the arid mining area.

[0009] The lower water-resisting layer is a waterproof material layer or a clay layer, and the compaction degree of the clay layer is greater than 85%; the soil used in the intermediate water-storing layer is sandy soil or loamy sandy soil, and the compaction degree of the intermediate water-storing layer is not more than 80%; the upper gravel curtain layer is formed by gravel with a particle size not less than 5 mm.

[0010] Preferably, the content of clay particles in the clay layer is greater than 30 wt%.

[0011] The waterproof material used in the waterproof material layer includes one or more of geomembrane, polyethylene membrane and polyurethane membrane.

[0012] Preferably, the lower water-resisting layer is omitted in the region where the depth of underlying bedrock is not more than 3 m or the depth of groundwater level is less than 3 m in the arid mining area.

[0013] Preferably, the content of sand particles in the soil used in the intermediate water-storing layer is 70-95 wt%, and the content of clay particles is 5-20 wt%.

[0014] The total N content of the soil used in the intermediate water-storing layer is greater than 0.2 g / kg, the total P content is greater than 0.5 g / kg, and the organic matter content is greater than 5 g / kg.

[0015] Preferably, when the restoration target is a desert herbaceous plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 15-20 wt%; when the restoration target is a desert shrub plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 10-18 wt%; and when the restoration target is a desert small arbor plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 5-15 wt%.

[0016] Preferably, in the region where the maximum wind speed is less than or equal to 17.2 m / s, the particle size of the gravel in the upper gravel curtain layer is 5-16 mm; in the region where the maximum wind speed is greater than 17.2 m / s and less than or equal to 20.8 m / s, the particle size of the gravel in the upper gravel curtain layer is 16-40 mm; in the region where the maximum wind speed is greater than 20.8 m / s and less than or equal to 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is 40-80 mm; and in the region where the maximum wind speed is greater than 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is greater than 100 mm.

[0017] Preferably, the thickness of the upper gravel curtain layer is 5-15 cm, the thickness of the intermediate water-storing layer is 50-300 cm, and the thickness of the clay layer is greater than 50 cm.

[0018] Preferably, when the target of the restoration is a desert herbaceous plant community, the thickness of the intermediate water storage layer is 50-80 cm; when the target of the restoration is a desert shrub plant community, the thickness of the intermediate water storage layer is 100-150 cm; and when the target of the restoration is a desert small arbor plant community, the thickness of the intermediate water storage layer is 200-300 cm.

[0019] Preferably, the gravel in the upper gravel curtain layer, the sand and clay particles in the soil used in the intermediate water storage layer, and the clay particles in the clay layer are obtained by crushing and sieving solid waste in arid mining areas.

[0020] Preferably, the gravel and sand are obtained by crushing and sieving waste residues in sandstone layers or limestone layers in arid mining areas; and the sand and clay particles are obtained by crushing and sieving waste residues in shale layers or mudstone layers in arid mining areas.

[0021] The present application provides a soil reconstruction method for arid mining areas, comprising the following steps: sequentially arranging a lower water-blocking layer, an intermediate water storage layer and an upper gravel curtain layer on the surface of a waste land in an arid mining area; the lower water-blocking layer is a waterproof material layer or a clay layer, and the compaction degree of the clay layer is > 85%; the soil used in the intermediate water storage layer is sandy soil or loamy sandy soil, and the compaction degree of the intermediate water storage layer is not more than 80%; and the upper gravel curtain layer is formed by gravel with a particle size not less than 5 mm. In the present application, the upper gravel curtain layer can quickly infiltrate surface water into the soil, reduce the water evaporation speed of the lower soil, and effectively store precipitation; at the same time, the upper gravel curtain layer can increase the surface roughness and reduce soil erosion; the intermediate water storage layer can store the infiltrated surface water; and the lower water-blocking layer can prevent the water infiltration depth from exceeding the absorption range of the plant roots. The results of the examples show that, by arranging the lower water-blocking layer, the intermediate water storage layer and the upper gravel curtain layer, the present application can effectively restore the vegetation in arid mining areas, has low restoration cost, short restoration time, and effectively solves the problems existing in the current vegetation restoration in arid mining areas. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A structural schematic diagram of the soil reconstruction layer constructed by the present application, wherein: 1-upper gravel curtain layer, 2-intermediate water storage layer, 3-lower water-blocking layer, and 4-lower overlying tailings residue layer or bedrock layer. DETAILED DESCRIPTION

[0023] The present application provides a soil reconstruction method for arid mining areas, comprising the following steps:

[0024] sequentially arranging a lower water-blocking layer, an intermediate water storage layer and an upper gravel curtain layer on the surface of a waste land in an arid mining area;

[0025] The lower water-resisting layer is a waterproof material layer or a clay layer, and the compaction degree of the clay layer is greater than 85%; the soil used in the middle water storage layer is sandy soil or loamy sand, and the compaction degree of the middle water storage layer is not more than 80%; the upper gravel curtain layer is formed by gravel with a particle size not less than 5 mm.

[0026] In the present application, the arid mining area specifically refers to a mining area located in a region with a ratio of annual precipitation to potential evaporation less than 0.25, and when the ratio of annual precipitation to potential evaporation is less than 0.05, it is an extremely arid area.

[0027] Figure 1 The structure diagram of the soil reconstruction layer constructed in the present application is shown in the following Figure 1 which will be described in detail.

[0028] In the present application, the surface of the waste land in the arid mining area is a tailings layer or a bedrock layer, and the lower water-resisting layer, the middle water storage layer and the upper gravel curtain layer are sequentially arranged on the surface of the tailings layer or the bedrock layer. In the specific embodiment of the present application, when the tailings layer is large rock fragments, the soil or sand is preferably used for leveling treatment, and then the soil reconstruction layer is constructed.

[0029] In the present application, the lower water-resisting layer is a waterproof material layer or a clay layer, and the compaction degree of the clay layer is greater than 85%, preferably 88-95%; the content of clay particles in the clay layer is preferably greater than 30wt%, more preferably 50-80wt%, and in the present application, the clay particle is a soil particle with a particle size less than 0.001 mm, which will not be described in detail hereinafter; the clay layer is specifically formed by compacting clay, and the thickness of the clay layer is preferably greater than 50 cm, more preferably greater than 50 cm and less than or equal to 100 cm, and further preferably 55-100 cm.

[0030] In the present application, the waterproof material used in the waterproof material layer preferably includes one or more of geomembrane, polyethylene membrane and polyurethane membrane; the thickness of the waterproof material layer is preferably 2-4 mm; in the specific embodiment of the present application, in the region where clay resources are seriously scarce, the waterproof material layer is preferably used as the lower water-resisting layer.

[0031] In the present application, the lower water-resisting layer can be omitted in the region where the depth of the underlying bedrock is not more than 3 m or the depth of the underground water level is less than 3 m in the arid mining area. Specifically, because the permeability of the bedrock is very low, it is equivalent to a water-resisting layer, so the lower water-resisting layer can be omitted; when the underground water level is less than 3 m, the plant root system can directly use the underground water, so the lower water-resisting layer can also be omitted in this case.

[0032] In the present application, the soil used in the intermediate water storage layer is sandy soil or loamy sandy soil; the total N content of the soil used in the intermediate water storage layer is preferably > 0.2 g / kg, more preferably 1.5-3.0 g / kg, the total P content is preferably > 0.5 g / kg, more preferably 1.0-2.0 g / kg, and the organic matter content is preferably > 5 g / kg, more preferably 15-30 g / kg; the present application controls the contents of total N, total P and organic matter within the above ranges, so that the soil in the intermediate water storage layer can meet the nutrient requirements of plant communities.

[0033] In the present application, the content of sand particles in the soil used in the intermediate water storage layer is preferably 70-95 wt%, and the content of clay particles is preferably 5-20 wt%; the sand particles specifically refer to soil particles with a particle size greater than 0.05 mm, specifically soil particles with a particle size greater than 0.05 mm and equal to or less than 2 mm; specifically, when the restoration target is a desert herbaceous plant community, the content of clay particles in the soil used in the intermediate water storage layer is preferably 15-20 wt%; when the restoration target is a desert shrub plant community, the content of clay particles in the soil used in the intermediate water storage layer is preferably 10-18 wt%; when the restoration target is a desert small tree plant community, the content of clay particles in the soil used in the intermediate water storage layer is preferably 5-15 wt%.

[0034] In the present application, the soil in the intermediate water storage layer is not suitable for compaction and needs to maintain appropriate aeration. In specific embodiments of the present application, the soil in the intermediate water storage layer is naturally piled and settled, and if there is a large amount of mechanical work, the compaction degree should not exceed 80%. In specific embodiments of the present application, the soil is preferably naturally piled and settled, and the surface is leveled with a bulldozer or a forklift, and the mechanical compaction degree of the surface layer is not more than 80%. In the present application, the thickness of the intermediate water storage layer is preferably 50-300 cm; in specific embodiments of the present application, the thickness of the intermediate water storage layer is preferably determined according to the root distribution depth of the restored vegetation; specifically, the root depth of desert herbaceous plant communities is relatively shallow, and the main root depth is generally 50-80 cm, specifically such as the Artemisia spiciformis community, the A. fruticosa community or the Stipa capillata community; the root depth of desert shrub plant communities is generally 100-150 cm, specifically such as the Cistanthe colubrina community, the Kandelia candel community; the root depth of desert small tree plant communities is generally more than 200 cm, specifically such as the Haloxylon ammodendron community, the H. persicum community, the Calligonum mongolicum community. Based on the above root distribution depth data, the present application controls the specific thickness of the intermediate water storage layer as follows: when the restoration target is a desert herbaceous plant community, the thickness of the intermediate water storage layer is preferably 50-80 cm; when the restoration target is a desert shrub plant community, the thickness of the intermediate water storage layer is preferably 100-150 cm; when the restoration target is a desert small tree plant community, the thickness of the intermediate water storage layer is preferably 200-300 cm.

[0035] In the present application, the upper gravel curtain layer is formed by gravel with a particle size of not less than 5 mm, and the gravel size of the upper gravel curtain layer is related to the maximum wind speed of the repair region, that is, the greater the maximum wind speed of the repair region, the greater the particle size of the gravel curtain layer. Specifically, in the region with a maximum wind speed of <17.2 m / s, the particle size of the gravel in the upper gravel curtain layer is preferably 5 mm to 16 mm, and more preferably 8 to 12 mm; in the region with a maximum wind speed greater than 17.2 m / s and less than or equal to 20.8 m / s, the particle size of the gravel in the upper gravel curtain layer is preferably 16 mm to 40 mm, and more preferably 20 to 35 mm; in the region with a maximum wind speed greater than 20.8 m / s and less than or equal to 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is preferably 40 mm to 80 mm, and more preferably 50 to 60 mm; in the region with a maximum wind speed greater than 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is preferably more than 100 mm, and more preferably 100 to 300 mm.

[0036] In the present application, the thickness of the upper gravel curtain layer is preferably 5 to 15 cm.

[0037] In the present application, when constructing the above-mentioned soil reconstruction layer, the gravel, sand and clay used are preferably locally sourced, and the solid waste in the mining area is fully utilized; specifically, the gravel in the upper gravel curtain layer, the sand and clay in the soil used in the intermediate water storage layer, and the clay in the clay layer are obtained by crushing and sieving the solid waste in the arid mining area; the gravel and sand are obtained by mechanically crushing and sieving the waste slag of the sandstone layer or the limestone layer in the arid mining area; and the sand and clay are obtained by mechanically crushing and sieving the waste slag of the shale layer or the mudstone layer in the arid mining area.

[0038] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] Embodiment 1

[0040] This embodiment provides a soil reconstruction method in an arid area, which is implemented in the Zhundong coal base.

[0041] Zhundong coal base is located in the southeast of Junggar Basin, is the 14th large coal base in China, and is the largest whole coal field in China. Zhundong coal base belongs to temperate continental climate and is located in inland arid area. The average annual precipitation of the region is 159.1 mm, the annual potential evaporation is 2090.4 mm, the average annual temperature is 5-6℃, the extreme maximum temperature is 41.6℃, the extreme minimum temperature is -36.6℃, the average annual wind speed is 3.6 m / s, and the extreme maximum wind speed can reach 18 m / s. The soil is mainly salinized sandy soil, sub-sandy soil and sandy clay, with a thickness of 1-2 m. The soil contains 0.4%-3% of soluble salt, and the highest reaches 7%, and the pH value is 7.5-8.6. The region belongs to desert and semi-desert area, and the main plant communities are Haloxylon ammodendron community, Ceratoides lanata community and Karelinia caspia community. The overall ecological carrying capacity is poor, and the environment is relatively fragile.

[0042] Zhundong coal base mainly adopts open-pit mining. During the open-pit mining of coal, the stripped overburden is stacked on the ground to form a high dump. Under the influence of drought, little rain and strong wind, the open-pit dump becomes a source of wind and sand, and the suspended particles in the air increase significantly, which needs to be treated. The surface of the dump formed by open-pit mining of coal is mainly broken coarse-grained rock debris or coal gangue, and plants cannot grow. Although the topsoil can be collected separately and stored during the stripping of the overburden, and then covered on the surface of the dump after the dump is closed, this method can help plants to re-settle on the dump to some extent; but this method often encounters that the collected topsoil is insufficient to cover the entire dump, and the thickness of the covered soil and the nature of the soil cannot meet the needs of plant re-settlement, and the soil layer needs to be reconstructed to meet the needs of plant recovery. The purpose of this soil reconstruction is to reconstruct the desert Ceratoides lanata community on the closed dump, and the specific implementation is as follows:

[0043] The surface of the closed dump is leveled with sand, and then a lower water barrier layer, an intermediate water storage layer and an upper gravel curtain layer are set from bottom to top, wherein:

[0044] The lower water barrier layer is formed by compaction of clay, with a thickness of 55 cm. The clay of the lower water barrier layer contains >30% of clay particles (particle size <0.001 mm). The clay of the lower water barrier layer is compacted by a road roller, and the soil compaction degree is >85%.

[0045] The thickness of the intermediate water storage layer is determined according to the root distribution depth of the restored vegetation, and is 100 cm; the soil used in the intermediate water storage layer is sand, wherein the content of sand particles (particle size > 0.05 mm) is between 80-90%, and the content of clay particles (particle size < 0.001 mm) is controlled to be between 10-15%; the soil in the intermediate water storage layer is naturally deposited and settled, and the surface is leveled by a bulldozer or a forklift, and the mechanical compaction degree of the surface layer is not more than 80%; the soil in the intermediate water storage layer in the above reconstructed soil layer needs to meet the nutrient requirements of the plant community growth. The total N content of the soil in the intermediate water storage layer is > 0.2 g / kg, the total P content is > 0.5 g / kg, and the organic matter content is > 5 g / kg.

[0046] The thickness of the upper gravel curtain layer is 5 cm, and the particle size of the gravel in the gravel curtain layer is 16-40 mm.

[0047] The gravel, sand particles and clay particles in the above reconstructed soil layer are preferably locally sourced, and the solid waste in the mining area is fully utilized. The waste slag in the sandstone layer in the mining area is mechanically crushed, and then particle size screening is performed to form the required gravel and sand particles for the reconstructed soil; the waste slag in the mudstone layer in the mining area is mechanically crushed, and then screening is performed to form the required sand particles and clay particles for the reconstructed soil.

[0048] From the implementation effect, the wind erosion amount of the coal mine dump site after the soil reconstruction is significantly reduced. In windy weather, no high-intensity dust is blown up in the soil reconstruction dump site, and the lower layer of soil is well protected by the surface gravel curtain layer. The survival rate of the planted Kochia prostrate in the soil reconstruction dump site reaches 85%, and the Kochia prostrate population gradually recovers. Artificial irrigation is performed in the first year of planting, and in the second year and thereafter, the natural rainfall can completely maintain the healthy growth of the Kochia prostrate population. The soil reconstruction method of the present application can fully utilize the waste from coal mining to reconstruct the soil required for the growth of vegetation in arid regions, and the cost required for this restoration method is only about 20% of that of the guest soil method. The method has a short artificial intervention time, and basically achieves a self-maintenance state of the ecological system after one year. This restoration method has great advantages in the restoration of vegetation in arid coal mines.

[0049] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method of reconstituting arid mine soils, characterized in that, The steps are: The lower water-resisting layer, the intermediate water-storing layer and the upper gravel curtain layer are sequentially arranged on the surface of the abandoned land in the arid mining area; The lower water-resisting layer is a waterproof material layer or a clay layer, and the compaction degree of the clay layer is greater than 85%; the soil used in the intermediate water-storing layer is sandy soil or loamy sandy soil, and the compaction degree of the intermediate water-storing layer is not more than 80%; the upper gravel curtain layer is formed by gravel with a particle size not less than 5 mm; The content of clay particles in the clay layer is greater than 30 wt%; When the repair target is a desert herbaceous plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 15-20 wt%; when the repair target is a desert shrub plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 10-18 wt%; when the repair target is a desert small arbor plant community, the content of clay particles in the soil used in the intermediate water-storing layer is 5-15 wt%; when the repair target is a desert herbaceous plant community, the thickness of the intermediate water-storing layer is 50-80 cm; when the repair target is a desert shrub plant community, the thickness of the intermediate water-storing layer is 100-150 cm; and when the repair target is a desert small arbor plant community, the thickness of the intermediate water-storing layer is 200-300 cm; In a region where the maximum wind speed is less than or equal to 17.2 m / s, the particle size of the gravel in the upper gravel curtain layer is 5-16 mm; in a region where the maximum wind speed is greater than 17.2 m / s and less than or equal to 20.8 m / s, the particle size of the gravel in the upper gravel curtain layer is 16-40 mm; in a region where the maximum wind speed is greater than 20.8 m / s and less than or equal to 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is 40-80 mm; and in a region where the maximum wind speed is greater than 28.5 m / s, the particle size of the gravel in the upper gravel curtain layer is more than 100 mm.

2. The method of reconstituting arid continental soils according to claim 1, characterised in that, The waterproof material used in the waterproof material layer includes one or more of geomembrane, polyethylene membrane and polyurethane membrane.

3. The method of reprofiling arid zone soils according to claim 1 or 2, characterised in that, In a region where the depth of the underlying bedrock is not more than 3 m or the depth of the underground water level is less than 3 m in the arid mining area, the lower water-resisting layer is omitted.

4. The method of reconstituting arid continental soils according to claim 1, wherein, The content of sand particles in the soil used in the intermediate water-storing layer is 70-95 wt%; The total N content of the soil used in the intermediate water-storing layer is greater than 0.2 g / kg, the total P content is greater than 0.5 g / kg, and the organic matter content is greater than 5 g / kg.

5. The method of reconstituting arid continental soils according to claim 1, wherein, The thickness of the upper gravel curtain layer is 5-15 cm, and the thickness of the clay layer is greater than 50 cm.

6. The method of reconstituting arid zone soils according to claim 1 or 4, wherein, The gravel in the upper gravel curtain layer, the sand particles and clay particles in the soil used in the intermediate water-storing layer, and the clay particles in the clay layer are obtained by crushing and sieving the solid waste in the arid mining area.

7. The method of reprofiling arid zone soils according to claim 6, characterised in that, The gravel and sand particles are obtained by mechanically crushing and sieving the waste slag of the sandstone layer or the waste slag of the limestone layer in the arid mining area; and the sand particles and clay particles are obtained by mechanically crushing and sieving the waste slag of the shale layer or the waste slag of the mudstone layer in the arid mining area.

Images