Reclamation double-surface soil key layer in semi-arid mining area and refined construction method of reclamation double-surface soil key layer

Abstract

The invention relates to the technical field of semi-arid mining area land reclamation and ecological restoration, and discloses a semi-arid mining area reclamation double-surface-soil key layer and a refined construction method thereof.The semi-arid mining area reclamation double-surface-soil key layer comprises a wind-erosion-resistant key layer and a water and fertilizer maintaining key layer which are arranged from top to bottom; the anti-wind-erosion key layer comprises a coarse particle windproof layer and a fine particle cementing layer which are arranged from top to bottom; the water and fertilizer maintenance key layer is prepared from the following raw materials: fine sand or original sandstorm surface soil, a clay mineral-based physical structure regulator, an organic water-retaining agent and a biological enhancement matrix material; the raw materials of the coarse particle windproof layer comprise gravel and coarse sand; the raw materials of the fine particle cementation layer comprise fine sand or original sandstorm surface soil, a clay mineral-based physical structure regulator and an organic water retention capacity cementing agent. The reclamation double-surface soil key layer for the semi-arid mining area can effectively resist natural erosion, improve the soil structure, improve the water and fertilizer retention capability and promote the recovery of local host plants.

Description

Technical Field

[0001] The present invention belongs to the technical field of land reclamation and ecological restoration in semi-arid mining areas, and particularly relates to a double topsoil key layer for reclamation in semi-arid mining areas and a fine construction method thereof. Background Art

[0002] The exploitation of mineral resources damages land and seriously destroys soil at the same time. Soil reconstruction has become the key and core of land reclamation and ecological restoration in mining areas. In semi-arid regions of China, the climate conditions are harsh, with less annual precipitation, large evaporation, and strong wind erosion, resulting in poor soil fertility, loose structure, poor water and fertilizer retention performance, and low vegetation coverage, making soil reconstruction in mining areas face huge challenges. As the topsoil key layer in the reconstructed soil profile, the structural distribution, component combination, and performance optimization of the plant growth medium layer are the keys to determining its functional adaptation and improvement. Therefore, a high-quality, efficient, and durable topsoil key layer structure and a fine construction method have crucial practical significance for land reclamation and ecological restoration in semi-arid open-pit mining areas.

[0003] Traditional soil reconstruction methods mostly adopt simple topsoil covering, topsoil improvement, and vegetation planting. These methods have their own characteristics and are suitable for improving soil quality or screening dominant plants under a single reconstruction goal (such as only achieving wind erosion resistance or fertility improvement or water retention). Although topsoil plays a key role in the overall function of the reconstructed soil profile, in a strong drought and wind erosion environment, directly exposing the fine-grained topsoil with high nutrient content on the surface is likely to cause severe evaporation of soil moisture, accelerate soil degradation, and reduce the durability of plant growth. The reason is the lack of adaptability to natural environment and climate conditions and the consideration of the functionality of the reconstructed soil layer. Therefore, aiming at the problems existing in semi-arid open-pit mining areas, such as the lack of high-quality topsoil resources, the acceleration of soil degradation under natural stress conditions of drought and wind erosion, and the high failure rate of ecological restoration, there is an urgent need for a special topsoil key layer fine construction method guided by the principles of ecological niche and key layer, aiming at reconstructing soil functions and with the fine description of key layer structure and materials as the core. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related technologies to some extent. To this end, an embodiment of the present invention provides a double topsoil key layer for reclamation in semi-arid mining areas, which can effectively resist natural erosion, improve soil structure, enhance water and fertilizer retention capacity, and promote the restoration of local host plants.

[0005] The double topsoil key layer for reclamation in semi-arid mining areas of the present invention includes a wind erosion resistance key layer and a water and fertilizer retention key layer arranged from top to bottom. The wind erosion resistance key layer includes a coarse-grained wind protection layer and a fine-grained cementing layer arranged from top to bottom;

[0006] The raw materials of the key water and fertilizer retention layer include fine sand or original wind-blown sand surface soil, clay mineral-based physical structure regulator, organic water-retaining agent and biological reinforcement matrix material;

[0007] The raw materials of the coarse-grained windbreak layer include gravel and coarse sand;

[0008] The raw materials of the fine-grained cementing layer include fine sand or original wind-blown sand surface soil, a clay mineral-based physical structure regulator and an organic water-retaining binder.

[0009] Optionally, in the water and fertilizer retention key layer, the mass ratio of the fine sand or original wind-blown sand surface soil, the clay mineral-based physical structure regulator, the organic water-retaining agent and the bioreinforcement matrix material is 1: (0.04-0.15): (0.002-0.005): (0.02-0.05);

[0010] and / or, the fine sand or original wind-blown sand surface soil in the key water and fertilizer retention layer has a sand content of 35 to 85 wt%;

[0011] And / or, the clay mineral-based physical structure regulator comprises montmorillonite and kaolin, and the mass ratio of the montmorillonite to the kaolin is 1:(1-3);

[0012] And / or, the organic water-retaining agent comprises natural plant gum and water, and the mass ratio of the natural plant gum to water is 1:(0.2-0.5);

[0013] And / or, the bio-enhanced matrix material includes biochar, plant fiber and earthworm castings, and the mass ratio of the biochar, plant fiber and earthworm castings is (1-3):(1-3):(1-3).

[0014] Optionally, the particle size of the montmorillonite and / or kaolin is ≤150 μm;

[0015] and / or, the particle size of the organic water-retaining agent in the solid state is ≤150 μm;

[0016] and / or the particle size of the biochar, plant fiber and earthworm castings is ≤1000 μm;

[0017] And / or, the particle size of the plant fiber is ≤1 mm.

[0018] Optionally, the natural plant gum includes at least one of xanthan gum or guar gum;

[0019] And / or, the plant fiber includes at least one of corn straw or wheat straw.

[0020] Optionally, the mass ratio of gravel to coarse sand is (3-5):1;

[0021] And / or, the particle size of the gravel is 15 to 50 mm, and the gravel is shale or mudstone;

[0022] And / or, the sand content of the coarse sand is ≥ 85 wt%.

[0023] Optionally, in the fine particle cementing layer, the mass ratio of the fine sand or the original aeolian sandy soil, the clay mineral-based physical structure regulator, and the organic water retention cementing agent is 1:(0.04 - 0.08):(0.001 - 0.003);

[0024] And / or, the sand content of the fine sand or the original aeolian sandy soil in the fine particle cementing layer is ≥ 60 wt%;

[0025] And / or, the organic water retention cementing agent includes a water retaining agent and water, the mass ratio of the water retaining agent and water is 1:0.2 - 0.5, and the particle size of the water retaining agent in the solid state is ≤ 150 μm.

[0026] Optionally, the water retaining agent includes at least one of modified ammonium carboxymethyl cellulose or polyacrylamide.

[0027] Optionally, the thickness of the wind erosion resistance key layer is 5 - 15 cm, and the thickness of the water and fertilizer retention key layer is 15 - 30 cm;

[0028] And / or, the thickness of the coarse particle windproof layer is 3 - 5 cm, and the thickness of the fine particle cementing layer is 2 - 10 cm.

[0029] Optionally, the compaction coefficient of the wind erosion resistance key layer is 0.8 - 0.85, the coverage is ≥ 75%, and the compaction coefficient of the water and fertilizer retention key layer is 0.75 - 0.8.

[0030] The present invention provides a refined construction method for the double topsoil key layer in the reclamation of semi-arid mining areas, including the following steps:

[0031] (1) Mix montmorillonite and kaolin in a designed ratio to obtain a clay mineral-based physical structure regulator; mix natural plant gum and water in a designed ratio to obtain an organic water retaining agent; mix biochar, plant fiber, and earthworm manure in a designed ratio to obtain a bio-enhanced matrix material; mix a water retaining agent and water in a designed ratio to obtain an organic water retention cementing agent;

[0032] (2) Mix fine sand or original aeolian sandy soil, clay mineral-based physical structure regulator, organic water retaining agent, and bio-enhanced matrix material in a designed ratio to obtain a water and fertilizer retention material, lay the water and fertilizer retention material on the original aeolian sandy soil section of the open-pit mine waste dump in the semi-arid aeolian area after leveling, tamp it, keep the surface moist, and cure for one week to obtain a water and fertilizer retention key layer;

[0033] (3) fine sand or original wind-blown sand surface soil, clay mineral-based physical structure regulator and organic water-retention performance binder are mixed in a designed proportion to obtain a fine-grained binder material, the fine-grained binder material is laid on top of the water and fertilizer retention key layer, the surface is kept moist, and the binder is cured for one week to obtain a fine-grained binder layer;

[0034] (4) Gravel and coarse sand are mixed in a designed proportion to obtain a coarse-grained gravel layer material, and the coarse-grained gravel layer material is laid on top of the fine-grained cementing layer to obtain a coarse-grained windbreak layer. The coarse-grained windbreak layer and the fine-grained cementing layer are jointly constructed to obtain a key layer for resisting wind erosion.

[0035] The technical effects of the double topsoil key layer for reclamation of semi-arid mining areas of the present invention are as follows:

[0036] (1) The "coarse at the top and fine at the bottom" physical structure constructs an adaptive moisture regulation-bioreinforcement matrix quality improvement structure, making full use of local sandy soil matrix and weathering products, solid waste produced by open-pit coal mining, and the main clay minerals missing from the original sandy surface soil as the reconstruction matrix and physical structure improvement matrix. Agricultural solid waste such as plant fiber and earthworm manure are selected as the bioreinforcement matrix. More than 85% of the materials used for reconstruction are the original sandy soil, mining solid waste and agricultural solid waste in the mining area. Local materials are used and waste is utilized, which has great economic benefits.

[0037] (2) In the double-topsoil key layer composite structure proposed by the present invention, the coarse sand and gravel used in the anti-wind erosion key layer can effectively resist the wind erosion of the wind-blown sandy topsoil layer; the addition of organic water-retaining agents enables the water-fertilizer retention key layer to produce a certain degree of self-cementation; the full mixing of clay minerals kaolin and montmorillonite can effectively prevent the evaporation of water in the topsoil while improving the physical structure of the wind-blown sandy soil; the "coarse particle-fine particle" matrix is distributed up and down, and the gravel blocks with sufficient coverage are closely combined with the cementing layer, which increases the threshold friction speed of sand particles between coarse particles, effectively inhibits wind erosion, and avoids the difficulty of water infiltration in the anti-wind erosion key layer, so as to further ensure the reconstruction effect of the water-fertilizer retention function of the lower layer;

[0038] (3) The lower layer of the double topsoil key layer structure is the water and fertilizer retention key layer, which uses natural plant gums and clay minerals, showing excellent microaggregate structure improvement and mineral composition replenishment effects, which can directly affect the stability of aeolian sandy soil and significantly improve water retention and fertilizer retention performance; through the addition of plant fibers and bio-organic materials, the nutrient content is improved while increasing soil activity;

[0039] (4) The materials used in this double topsoil key layer composite structure enable the water and fertilizer retention key layer to play the role of a "sponge" - the functions of waterlogging drainage, regulation and capillary water supply for water infiltration and water retention. The wind erosion resistance key layer, due to its relatively high spatial position, can better provide the basic guarantee for water movement while resisting wind erosion and preventing evaporation, effectively inhibiting the evaporation of deep - layer water, and is the core of the refined reconstruction of the key layer composite structure;

[0040] (5) The system of the present invention comprehensively identifies the functions of the topsoil key layer, improves the functions and obtains the inter - layer coupling relationship. Compared with other methods that adopt single - target reconstruction such as improving nutrient components, reducing water evaporation or improving physical structure in the reclamation topsoil reconstruction of semi - arid mining areas, the entire double topsoil key layer composite structure, through the synergistic effect of material combination between layers and reasonable combinations of texture, thickness and quantity, achieves good wind erosion resistance and anti - evaporation effects, high water and fertilizer retention performance, and obvious increase in plant biomass. It can more efficiently and highly reflect the overall natural stress elimination process and dynamic water and fertilizer balance of the reconstructed soil key layer, and is more adaptable to the restoration and improvement of the soil ecological functions in semi - arid sandy open - pit mining areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the double topsoil key layer composite structure for reclamation in a semi - arid mining area constructed in Embodiment 1 of the present invention;

[0042] Figure 2 It is a schematic diagram of the wind tunnel test device in the embodiment of the present invention;

[0043] Figure 3 It is a schematic diagram of the infiltration and evaporation device for the double topsoil key layer in the embodiment of the present invention (the infiltration and evaporation device schematic diagram of the wind erosion resistance key layer is Figure 3 (a), and the infiltration and evaporation device schematic diagram of the water and fertilizer retention key layer is Figure 3 (b));

[0044] Figure 4 It is a schematic diagram of the above - ground and underground plant biomass during the growth cycle in the embodiment of the present invention;

[0045] Figure 5 It is a schematic diagram of the device for the characteristics of soil water movement between layers in the physical simulation of the soil column in the embodiment of the present invention. In the figure, the soil from top to bottom is the coarse - grained wind - proof layer, the fine - grained cemented layer, the water and fertilizer retention layer, and the original same - layer - position sandy soil;

[0046] Figure 6 It is a curve graph of the water infiltration characteristics of the reconstructed soil profile of the double topsoil key layer in the embodiment of the present invention;

[0047] Figure 7This is an example diagram of soil water content during the infiltration process of the double topsoil key layer and the reconstructed profile of the original aeolian sandy soil in the embodiments of the present invention (the example diagram of soil water content in the reconstructed profile of the original aeolian sandy soil is Figure 7 (a), and the example diagram of soil water content in the reconstructed profile of the double topsoil key layer is Figure 7 (b));

[0048] In the figure, 1 - wind erosion resistance key layer, 1-1 - coarse particle windproof layer, 1-2 - fine particle cementing layer, 2 - water and fertilizer retention key layer, 3 - original aeolian sandy soil layer, 4 - high-speed camera, 5 - sample placement location, 6 - wind speed sensor, 7 - engine, 8 - fan device, 9 - placement rack, 10 - air outlet, 11 - rubber plug for micro soil column, 12 - micro soil column, 13 - permeable bottom plate hole, 14 - Mariotte bottle, 15 - infrared heat preservation lamp, 16 - filter screen, 17 - rubber plug for medium soil column, 18 - water sensor, 19 - data collector, 20 - small aperture gravel, 21 - infiltrated water collection device. Specific Embodiments

[0049] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0050] The double topsoil key layer for reclamation in semi-arid mining areas of the present invention includes a wind erosion resistance key layer and a water and fertilizer retention key layer arranged from top to bottom. The wind erosion resistance key layer includes a coarse particle windproof layer and a fine particle cementing layer arranged from top to bottom;

[0051] The raw materials of the water and fertilizer retention key layer include fine sand or original aeolian sandy topsoil, clay mineral-based physical structure regulator, organic water retention agent, and biological strengthening matrix material;

[0052] The raw materials of the coarse particle windproof layer include gravel and coarse sand;

[0053] The raw materials of the fine particle cementing layer include fine sand or original aeolian sandy topsoil, clay mineral-based physical structure regulator, and organic water retention performance cementing agent.

[0054] In some embodiments, optionally, in the water and fertilizer retention key layer, the mass ratio of the fine sand or original aeolian sandy topsoil, clay mineral-based physical structure regulator, organic water retention agent, and biological strengthening matrix material is 1:(0.04 - 0.15):(0.002 - 0.005):(0.02 - 0.05);

[0055] And / or, the sand particle content of the fine sand or original aeolian sandy topsoil in the water and fertilizer retention key layer is 35 - 85 wt%;

[0056] And / or, the clay mineral-based physical structure regulator comprises montmorillonite and kaolin, and the mass ratio of the montmorillonite to the kaolin is 1:(1-3);

[0057] And / or, the organic water-retaining agent comprises natural plant gum and water, and the mass ratio of the natural plant gum to water is 1:(0.2-0.5);

[0058] And / or, the bio-enhanced matrix material includes biochar, plant fiber and earthworm castings, and the mass ratio of the biochar, plant fiber and earthworm castings is (1-3):(1-3):(1-3).

[0059] In the embodiment of the present invention, the mass ratio of each substance in the key water and fertilizer retention layer is limited, which is beneficial to improving the water holding capacity, fertilizer retention performance and soil activity of the key water and fertilizer retention layer.

[0060] In some embodiments, optionally, the particle size of the montmorillonite and / or kaolin is ≤150 μm;

[0061] and / or, the particle size of the organic water-retaining agent in the solid state is ≤150 μm;

[0062] and / or the particle size of the biochar, plant fiber and earthworm castings is ≤1000 μm;

[0063] And / or, the particle size of the plant fiber is ≤1 mm.

[0064] In the embodiment of the present invention, the particle size range of each substance in the key water and fertilizer conservation layer is limited, which is conducive to making the key water and soil conservation layer play the role of a "sponge" and have better water infiltration and water retention functions.

[0065] In some embodiments, optionally, the natural plant gum includes at least one of xanthan gum or guar gum;

[0066] And / or, the plant fiber includes at least one of corn straw or wheat straw.

[0067] In some embodiments, optionally, the mass ratio of the gravel to the coarse sand is (3-5):1;

[0068] and / or, the particle size of the gravel is 15 to 50 mm, and the gravel is shale or mudstone;

[0069] And / or, the sand content of the coarse sand is ≥85wt%.

[0070] In the embodiment of the present invention, the mass ratio of gravel to coarse sand and the particle size of gravel are limited, which is beneficial to further improve the wind erosion resistance of the key wind erosion resistance layer.

[0071] In some embodiments, optionally, in the fine particulate cemented layer, the mass ratio of the fine sand or the original aeolian sandy soil, the clay mineral-based physical structure regulator, and the organic water retention cementing agent is 1:(0.04 - 0.08):(0.001 - 0.003);

[0072] and / or, the sand content of the fine sand or the original aeolian sandy soil in the fine particulate cemented layer is ≥60 wt%;

[0073] and / or, the organic water retention cementing agent includes a water retention agent and water, the mass ratio of the water retention agent to water is 1:0.2 - 0.5, and the particle size of the water retention agent in the solid state is ≤150 μm.

[0074] In the embodiments of the present invention, the contents of various substances in the fine particulate cemented layer are defined, which can better provide a basic guarantee for water migration while resisting wind erosion and preventing evaporation, effectively inhibit the evaporation of deep-layer water, and ensure the smooth infiltration of water.

[0075] In some embodiments, optionally, the water retention agent includes at least one of modified ammonium carboxymethyl cellulose or polyacrylamide.

[0076] In some embodiments, optionally, the thickness of the key wind erosion resistance layer is 5 - 15 cm, and the thickness of the key water and fertilizer retention layer is 15 - 30 cm;

[0077] and / or, the thickness of the coarse particulate wind prevention layer is 3 - 5 cm, and the thickness of the fine particulate cemented layer is 2 - 10 cm.

[0078] When the thickness ranges of the key wind erosion resistance layer and the key water and fertilizer retention layer are 5 - 15 cm and ≥15 cm respectively, and the textures are sandy soil - sandy loam and silty loam - loam respectively, the functions of resisting wind erosion and retaining water and fertilizer can be maximally realized;

[0079] When the thickness range of the key wind erosion resistance layer is 5 - 15 cm, the fine particulate cemented layer is ≥3 - 10 cm, and the texture is sandy soil - sandy loam, it can resist a maximum wind speed range of 10 - 15 m / s, and the cumulative wind erosion amount is 20 - 68 g / m2;

[0080] When the thickness range of the key water and fertilizer retention layer is ≥15 cm and the texture is silty loam - loam, the water content during the profile infiltration process is 23.5% - 68.7%, the cumulative evaporation amount is 39.2 - 86.6%, the organic matter content is 28.9% - 45.3%, and the above-ground and underground biomass of plants both exceed the control by more than 30%.

[0081] In some embodiments, optionally, the compaction coefficient of the key wind erosion resistance layer is 0.8 - 0.85, the coverage is ≥75%, and the compaction coefficient of the key water and fertilizer retention layer is 0.75 - 0.8.

[0082] The present invention also provides a method for the refined construction of the double topsoil key layer in the semi-arid mining area, comprising the following steps:

[0083] (1) Mix montmorillonite and kaolin in a designed ratio to obtain a clay mineral-based physical structure regulator; mix natural plant gum and water in a designed ratio to obtain an organic water-retaining agent; mix biochar, plant fiber, and earthworm manure in a designed ratio to obtain a bio-enhanced matrix material; mix a water-retaining agent and water in a designed ratio to obtain an organic water-retaining performance binder;

[0084] (2) Mix fine sand or the original aeolian sandy soil, the clay mineral-based physical structure regulator, the organic water-retaining agent, and the bio-enhanced matrix material in a designed ratio to obtain a water and fertilizer retention material, lay the water and fertilizer retention material on the original aeolian sandy soil section of the open-pit mine waste dump in the semi-arid aeolian area after leveling, tamp it, keep the surface moist, and cure for one week to obtain a water and fertilizer retention key layer;

[0085] (3) Mix fine sand or the original aeolian sandy soil, the clay mineral-based physical structure regulator, and the organic water-retaining performance binder in a designed ratio to obtain a fine particle cementing material, lay the fine particle cementing material above the water and fertilizer retention key layer, keep the surface moist, and cure for one week to obtain a fine particle cementing layer;

[0086] (4) Mix gravel and coarse sand in a designed ratio to obtain a coarse particle gravel layer material, lay the coarse particle gravel layer material above the fine particle cementing layer to obtain a coarse particle windproof layer, and jointly construct the coarse particle windproof layer and the fine particle cementing layer to obtain an anti-wind erosion key layer.

[0087] The technical effects of the double topsoil key layer for the reclamation of the semi-arid mining area of the present invention are as follows:

[0088] (1) The "coarse on the top and fine on the bottom" physical structure constructs a self-adaptive water regulation - bio-enhanced matrix quality improvement structure, making full use of local aeolian sandy soil matrix and weathered materials, solid wastes produced by open-pit coal mine mining, and materials lacking main clay minerals in the original aeolian sandy soil as reconstruction matrix and physical structure improvement matrix, selecting agricultural solid wastes such as plant fiber and earthworm manure as bio-enhanced matrix. More than 85% of the materials used for reconstruction are the original aeolian sandy soil, mining solid wastes, and agricultural solid wastes in the mining area. The materials are locally sourced and waste is utilized, having great economic benefits;

[0089] (2) In the double-topsoil key layer composite structure proposed by the present invention, the coarse sand and gravel used in the anti-wind erosion key layer can effectively resist the wind erosion of the wind-blown sandy topsoil layer; the addition of organic water-retaining agents enables the water-fertilizer retention key layer to produce a certain degree of self-cementation; the full mixing of clay minerals kaolin and montmorillonite can effectively prevent the evaporation of water in the topsoil while improving the physical structure of the wind-blown sandy soil; the "coarse particle-fine particle" matrix is distributed up and down, and the gravel blocks with sufficient coverage are closely combined with the cementing layer, which increases the threshold friction speed of sand particles between coarse particles, effectively inhibits wind erosion, and avoids the difficulty of water infiltration in the anti-wind erosion key layer, so as to further ensure the reconstruction effect of the water-fertilizer retention function of the lower layer;

[0090] (3) The lower layer of the double topsoil key layer structure is the water and fertilizer retention key layer, which uses natural plant gums and clay minerals, showing excellent microaggregate structure improvement and mineral composition replenishment effects, which can directly affect the stability of aeolian sandy soil and significantly improve water retention and fertilizer retention performance; through the addition of plant fibers and bio-organic materials, the nutrient content is improved while increasing soil activity;

[0091] (4) The materials used in the double topsoil key layer composite structure enable the water and fertilizer retention key layer to play the role of a "sponge" - drainage and storage - capillary water supply and water infiltration function, while the wind erosion resistance key layer, due to its higher spatial position, can better play the basic guarantee of water migration while resisting wind erosion and preventing evaporation, effectively inhibiting deep water evaporation, and is the core of the refined reconstruction of the key layer composite structure.

[0092] (5) The present invention systematically and comprehensively identifies the functions of the topsoil key layer, improves its functions, and obtains the coupling relationship between layers. Compared with other methods that use a single target reconstruction in the reconstruction of topsoil in semi-arid mining areas, namely, improving the nutrient content or reducing water evaporation or improving the physical structure, the entire double-topsoil key layer composite structure achieves good wind erosion and evaporation resistance, high water and fertilizer retention performance, and significant plant biomass increase through the synergistic effect of inter-layer material combination and reasonable texture, thickness, and quantity combination. It can more efficiently and accurately reflect the natural stress elimination process and dynamic water and fertilizer balance of the entire soil key layer, and is more suitable for the restoration and improvement of soil ecological functions in semi-arid wind and sand open-pit mining areas.

[0093] The technical solution of the present invention is described in detail below with reference to specific embodiments and drawings.

[0094] Example 1

[0095] 1. Constructing the key layer for water and fertilizer maintenance:

[0096] (1) fully mixing montmorillonite and kaolin in a mass ratio of 1:3 to obtain a clay mineral-based physical structure regulator, wherein the particle size range of the montmorillonite and kaolin is ≤150 μm;

[0097] (2) adding xanthan gum to water so that the mass ratio of xanthan gum to water is 1:0.2 to obtain an organic water-retaining agent, wherein the particle size range of the organic water-retaining agent in the solid state is ≤150 μm;

[0098] (3) fully mixing biochar, corn straw and earthworm castings in a mass ratio of 2:2:2 to obtain a bioreinforced matrix material, wherein the particle size of the biochar, corn straw and earthworm castings is ≤1000 μm;

[0099] (4) The original sandy topsoil, clay mineral-based physical structure regulator, organic water-retaining agent and bioreinforced matrix material are fully mixed in a mass ratio of 1:0.06:0.002:0.02 to obtain a water and fertilizer retention material; the sand content of the original sandy topsoil is 74.1 wt%, and the sandy soil within 15 cm below 10 cm from the top of the topsoil is selected as the reconstructed matrix of the key layer of water and fertilizer retention;

[0100] (5) laying the water and fertilizer retention material of step (4) on the original sandy soil profile of the open-pit mine dump in the arid and semi-arid sandy area after leveling, tamping, with a compaction coefficient of 0.75, keeping the surface moist, and curing for one week to obtain a water and fertilizer retention key layer with a thickness of 15 cm;

[0101] 2. Constructing a key layer to resist wind erosion

[0102] (6) fully mixing montmorillonite and kaolin in a mass ratio of 1:2 to obtain a clay mineral-based physical structure regulator, wherein the particle size range of the montmorillonite and kaolin is ≤150 μm;

[0103] (7) adding modified carboxymethyl cellulose ammonium to water so that the mass ratio of modified carboxymethyl cellulose ammonium to water is 1:0.3, thereby obtaining an organic water-retaining binder, wherein the particle size range of the water-retaining binder in the solid state is ≤150 μm;

[0104] (8) The original wind-blown sand surface soil, clay mineral-based physical structure regulator and organic water-retention performance binder are fully mixed in a mass ratio of 1:0.04:0.002 to obtain a fine-grained cementing material; the sand content of the original wind-blown sand surface soil is 85.61 wt%, and the wind-blown sand soil within 10 cm from the top surface soil is selected as the reconstructed matrix of the fine-grained cementing layer in the key layer of wind erosion resistance. If fine sand material is selected as the reconstructed matrix to replace the original wind-blown sand surface soil, the sand content range thereof can be controlled;

[0105] (9) laying the fine-grained cementing material on top of the key layer for water and fertilizer retention, keeping the surface moist, and curing for one week to obtain a fine-grained cementing layer with a thickness of 7 cm;

[0106] (10) gravel and coarse sand are fully mixed in a mass ratio of 3:1 to obtain a coarse-grained gravel layer material, wherein the particle size of the gravel is controlled to be 30 to 50 mm, and the sand content of the coarse sand matrix is 85.61 wt%;

[0107] (11) A coarse-grained gravel layer material is laid on the fine-grained cementing layer and compacted with a compaction coefficient of 0.85 and a coverage of 75% to obtain a coarse-grained windbreak layer with a thickness of 3 cm. Together with the fine-grained cementing layer below, a key layer of wind-resistant topsoil with a thickness of 10 cm is constructed.

[0108] The structure of the key double topsoil layer for reclamation of semi-arid mining areas constructed in this embodiment is as follows: Figure 1 As shown, 1 is the key layer of topsoil that resists wind erosion, 1-1 is the coarse-grained windbreak layer, 1-2 is the fine-grained cementing layer, 2 is the key layer for water and fertilizer retention, and 3 is the original aeolian sandy soil layer.

[0109] Use Figure 2 The wind tunnel test device shown verifies the wind erosion resistance function of the key layer of wind erosion resistance. The fan device 8 and the air outlet 10 are respectively placed on the placement rack 9 at the same height. The fan device 8 and the air outlet 10 are connected through the sample placement 5. The double topsoil key layer sample of the semi-arid mining area reclamation prepared in Example 1 is placed on the sample placement 5. The engine 7 is turned on to drive the fan device 8. The wind speeds of different intensities are set at 1m / s, 3m / s, 5m / s, 7m / s, 10m / s, 12m / s and 15m / s. The wind speed can be adjusted by the data displayed by the wind speed sensor 6, and the state of the sample is monitored by the high-speed camera 4. The blowing is continuously turned on for 10 minutes at each set wind speed, and the mass of the soil samples of the key layer of wind erosion resistance topsoil before and after the simulated wind erosion is measured, and the mass loss after the wind tunnel test is calculated. Finally, the cumulative wind erosion of the key layer of wind-erosion-resistant topsoil at wind speeds of 1 to 12 m / s was reduced by more than 50% compared with the original wind-blown sand topsoil control treatment, and it can withstand a maximum wind speed of 12 m / s.

[0110] Use Figure 3 The infiltration and evaporation device shown verifies the water retention function of the key layer for resisting wind erosion and the water evaporation prevention function of the key layer for retaining water and fertilizer, wherein Figure 3 (a) is a schematic diagram of the infiltration and evaporation apparatus for the key layer of anti-wind erosion. The reconstructed soil for the key layer of anti-wind erosion prepared in Example 1 is placed in a container with a permeable bottom plate hole 13 at the bottom to form a micro-soil column 12. A soil moisture sensor is inserted into a hole at the midpoint of the micro-soil column 12, and a micro-soil column rubber plug 11 is used to block the sensor insertion gap to prevent water outflow during the test. The entire process of the infiltration and evaporation test of the key layer of anti-wind erosion soil is completed by connecting a soil moisture data collector. Figure 3(b) Schematic diagram of the infiltration and evaporation device for the key layer of water and fertilizer retention. The reconstructed soil of the key layer of water and fertilizer retention prepared in Example 1 was filled into a container with a permeable bottom plate hole 13 at the bottom to form a micro soil column 12. Two soil moisture sensors were inserted by drilling holes at one-third and two-thirds of the total thickness of the set key layer respectively. Two micro soil column rubber plugs 11 were used to block the gaps where the sensors were inserted to prevent water from flowing out during the test. The whole process of soil infiltration and evaporation test of the key layer of water and fertilizer retention was completed by cooperating with 1 soil moisture data collector. During the test, the water content of the infiltrated soil was measured and obtained per minute. When the water moved down and flowed out, the infiltration test was immediately stopped. Finally, it was obtained that the cumulative water holding capacity of the key layer of water and fertilizer retention increased by 29.37 mm compared with the original aeolian sandy topsoil, the cumulative evaporation decreased by 23.21 mm, the water holding capacity of the key layer of wind erosion resistance increased by 18.06 mm compared with the original aeolian sandy topsoil after the infiltration and drainage were completed, and the cumulative evaporation ratio decreased by 14.32% compared with the original aeolian sandy topsoil, further proving that the key layer of wind erosion resistance can still ensure the infiltration of soil moisture to a certain extent while resisting wind erosion.

[0111] To verify the fertility retention and nutrient improvement functions of the key layer of water and fertilizer retention, local perennial carbon-fixing herbaceous plants in a semi-arid open-pit mining area were selected, and an indoor host plant cultivation experiment was carried out. Through the observation of the growth cycle of germination, emergence, and growth for a total of 9 weeks after planting, the biomass data graph as Figure 4 shown was obtained. Finally, it was obtained that the above-ground biomass of the plants during the growth period increased by 177.12% compared with the original aeolian sandy topsoil, even exceeding 44.35% of the normal topsoil of the surrounding grassland undamaged by mining, and the underground biomass exceeded 30% of the control.

[0112] Adopt as Figure 5The device shown simulates the interlayer soil water migration. Before the start of the experiment, a filter paper is placed on the orifice plate at the bottom of the soil column device. After calculating the required weight for each layer (5 cm) according to the bulk density of each reconstructed topsoil key layer, the device is filled layer by layer from bottom to top in the order of gravel with small holes 20, three layers of original aeolian sandy soil collected in the field, the water and fertilizer retention key layer, the fine-grained cemented layer, and the coarse-grained windproof layer. Before filling each layer of soil, the surface of each layer of soil needs to be roughened. Finally, another filter screen 16 is placed above the coarse-grained windproof layer, that is, on the surface of the soil column, to prevent the surface reconstructed soil from being impacted by water during the infiltration process and increasing the experimental error. A Mariotte bottle 14 is installed above the device. The experiment is carried out by the 3-cm constant head method. Moisture sensors 18 are inserted at the midpoint of each soil layer and connected to the soil moisture data collector 19. The position where the moisture sensor 18 is installed is sealed with a medium-sized soil column rubber stopper 17 to prevent water evaporation from affecting the experimental results. The soil moisture content is monitored at regular intervals in minutes. When the water moves down and flows into the water collection device 21 at the bottom, the infiltration experiment is immediately stopped. After complete drainage for at least 48 hours, an infrared heat preservation lamp 15 is installed to ensure that the daily simulated light time is about 8 hours, and the weighing method is used to record and calculate the water evaporation amount; through monitoring the soil profile water infiltration and evaporation experiment with a total period of 32 days, the interlayer coupling relationship and characteristic parameters of the double topsoil key layers are accurately obtained. Finally, it is found that when the thickness ratio of the upper and lower layers of the double topsoil key layers is 1:1.5, and the texture of the wind erosion resistance key layer is sandy loam and the texture of the water and fertilizer retention key layer is silty loam, the wetting front reaches the upper interface of the water and fertilizer retention key layer in a relatively short time, the moisture content during the profile infiltration process is 43.9%, and the cumulative infiltration amount is small, further proving that the wind erosion resistance key layer has a small hindrance effect on the downward movement of soil water, and the cumulative infiltration amount of the lower water and fertilizer retention layer is high and the water holding capacity is strong, which can significantly change the water infiltration and capillary water action of the surface soil and effectively inhibit the evaporation of deep water.

[0113] Refer to the soil mechanics test method to measure the soil moisture characteristic curve of the reconstructed soil profile of the double topsoil key layers in Example 1. The results are as Figure 6 shown. Under different soil water suction conditions, the soil volume water content of the reconstructed soil profile of the double topsoil key layers far exceeds that of the original aeolian sandy soil profile, and is infinitely close to or even exceeds the normal grassland soil profile when the soil water suction < 600 kPa.

[0114] During the infiltration process, the soil moisture content of the reconstructed soil profile of the double topsoil key layers and the original aeolian sandy soil profile in Example 1 is as Figure 7As shown in the figure, the soil infiltration moisture content of the double topsoil key layers exceeds that of the original aeolian soil at the same level (total thickness 25 cm), and the soil infiltration moisture content of the original aeolian soil layer 3 of the two profiles is quite different. The soil moisture content of the original aeolian soil layer 3 below the water and fertilizer conservation key layer is lower, and the time for the soil moisture in the lower soil layer to enter the stable saturation stage during the infiltration process is effectively delayed, which promotes the moisture retention of the topsoil key layer. This further verifies that the reconstructed profile of the double topsoil key layer can have good water retention performance and effectively hinder water infiltration.

[0115] Example 2

[0116] 1. Constructing the key layer for water and fertilizer maintenance:

[0117] (1) fully mixing montmorillonite and kaolin in a mass ratio of 1:2 to obtain a clay mineral-based physical structure regulator, wherein the particle size of the montmorillonite and kaolin is ≤150 μm;

[0118] (2) adding guar gum to water so that the mass ratio of guar gum to water is 1:0.2 to obtain an organic water-retaining agent, wherein the particle size range of the organic water-retaining agent in the solid state is ≤150 μm;

[0119] (3) fully mixing biochar, wheat straw and earthworm castings in a mass ratio of 2:2:2 to obtain a bioreinforced matrix material, wherein the particle size of the biochar, wheat straw and earthworm castings is ≤1000 μm;

[0120] (4) The original sandy topsoil, clay mineral-based physical structure regulator, organic water-retaining agent and bioreinforced matrix material are fully mixed in a mass ratio of 1:0.04:0.002:0.02 to obtain a water and fertilizer retention material; the sand content of the original sandy topsoil is 74.1 wt%, and the sandy soil within 20 cm below 10 cm from the top surface soil is selected as the reconstructed matrix of the key layer of water and fertilizer retention;

[0121] (5) laying the water-fertilizer retention material of step (4) on the original sandy soil profile of the open-pit mine dump in the arid and semi-arid sandy area after leveling, tamping, with a compaction coefficient of 0.8, keeping the surface moist, and curing for one week to obtain a water-fertilizer retention key layer with a thickness of 20 cm;

[0122] 2. Constructing a key layer to resist wind erosion

[0123] (6) fully mixing montmorillonite and kaolin in a mass ratio of 1:3 to obtain a clay mineral-based physical structure regulator, wherein the particle size range of the montmorillonite and kaolin is ≤150 μm;

[0124] (7) Add polyacrylamide to water so that the mass ratio of polyacrylamide to water is 1:0.3 to obtain an organic water-retaining binder. The particle size range of the water-retaining agent in the solid state is ≤150 μm;

[0125] (8) Thoroughly mix the original aeolian sandy soil, clay mineral-based physical structure regulator, and organic water-retaining binder in a mass ratio of 1:0.04:0.002 to obtain a fine-grained cementitious material; the sand content of the original aeolian sandy soil is 85.61 wt%, and the aeolian sandy soil within 10 cm from the topsoil is selected as the reconstruction matrix for the fine-grained cementitious layer in the key wind erosion resistance layer. If fine sand material is selected as the reconstruction matrix to replace the original aeolian sandy soil, only control its sand content range;

[0126] (9) Lay the fine-grained cementitious material above the key layer for water and fertilizer retention, keep the surface moist, and cure for one week to obtain a fine-grained cementitious layer with a thickness of 6 cm;

[0127] (10) Thoroughly mix gravel and coarse sand in a mass ratio of 3:1 to obtain a coarse-grained gravel layer material. The particle size of the gravel is controlled within 30 - 50 mm, and the sand content of the coarse sand matrix is 85.61 wt%;

[0128] (11) Lay the coarse-grained gravel layer material on the fine-grained cementitious layer, tamp it, with a compaction coefficient of 0.8 and a coverage of 75% to obtain a coarse-grained windproof layer with a thickness of 4 cm, and jointly construct a key wind erosion resistance topsoil layer with a thickness of 10 cm with the underlying fine-grained cementitious layer.

[0129] Use the same method as in Example 1 to verify the wind erosion resistance function of the key wind erosion resistance layer. Finally, it is obtained that the cumulative wind erosion amount of the key wind erosion resistance topsoil layer after 10 minutes of erosion at a wind speed of 12 m / s is reduced by 93.51% compared with the control treatment of the original aeolian sandy soil, showing strong wind erosion resistance performance.

[0130] Use the same method as in Example 1 to verify the water retention function of the key wind erosion resistance layer and the function of preventing water evaporation of the key layer for water and fertilizer retention. Finally, it is obtained that the cumulative water holding capacity of the key layer for water and fertilizer retention increases by 24.62 mm compared with the original aeolian sandy soil, the cumulative evaporation amount decreases by 26.33 mm, the water holding capacity of the key wind erosion resistance layer after infiltration and drainage increases by 19.12 mm compared with the original aeolian sandy soil, and the cumulative evaporation ratio decreases by 15.39% compared with the original aeolian sandy soil, further proving that the key wind erosion resistance layer can still ensure the infiltration of soil moisture to a certain extent while resisting wind erosion.

[0131] The same method as in Example 1 was used to verify the fertility retention and nutrient enhancement functions of the key water and fertilizer retention layer. Finally, it was obtained that the aboveground biomass of the plants during the growth period increased by 132.39% compared with the original aeolian sandy topsoil, and even exceeded 32.16% of the normal topsoil of the undamaged surrounding grassland near the mining area. The underground biomass exceeded 25% of the control in all cases.

[0132] The same method as in Example 1 was used to simulate the interlayer soil water migration. Through the soil profile water infiltration and evaporation test with a total monitoring period of 32 days, the interlayer coupling relationship and characteristic parameters of the double topsoil key layers were accurately obtained. Finally, it was found that when the thickness ratio of the upper and lower layers of the double topsoil key layer was 1:2, and the texture of the key wind erosion resistance layer was sandy loam and the texture of the key water and fertilizer retention layer was silty loam, the wetting front reached the upper interface of the key water and fertilizer retention layer in a relatively short time. The water content during the profile infiltration process was 38.75%, and the cumulative infiltration amount was relatively small. This further proved that the key wind erosion resistance layer had a relatively small hindrance effect on the downward movement of soil water, and the cumulative infiltration amount of the underlying key water and fertilizer retention layer was relatively high and the water retention ability was relatively strong. It could significantly change the water infiltration and capillary water action of the surface soil and effectively inhibit the evaporation of deep water.

[0133] Referring to the soil mechanics test method, the soil water characteristic curve of the reconstructed soil profile of the double topsoil key layer in this Example 2 was measured. It was found that the soil volume water content of the reconstructed soil profile of the double topsoil key layer far exceeded that of the original aeolian sandy soil profile under different soil water suction conditions, and was infinitely close to or even exceeded the normal grassland soil profile when the soil water suction < 700 kPa.

[0134] The measurement results of the soil water content during the infiltration process of the reconstructed soil profile of the double topsoil key layer and the original aeolian sandy soil profile in this Example 2 showed that the double topsoil key layer exceeded the soil infiltration water content of the original aeolian sandy soil in the same layer (total thickness 30 cm) of the surface soil layer. Moreover, the soil infiltration water content of the original aeolian sandy soil layer 3 in the two profiles differed greatly. The soil water content of the original aeolian sandy soil layer 3 below the key water and fertilizer retention layer was relatively low, and the time for the soil water in the underlying soil layer to enter the stable saturation stage during the infiltration process was effectively delayed, which promoted the water retention of the key surface soil layer. This further verified that the reconstructed profile of the double topsoil key layer could have good water retention performance and effectively hinder the downward infiltration of water.

[0135] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples.

[0136] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Variations, modifications, substitutions, and variations made by those of ordinary skill in the art to the above embodiments are all within the scope of protection of the present invention.

Claims

1. A key layer of double topsoil for reclamation in semi-arid mining areas, characterized in that, It includes a wind erosion resistance key layer and a water and fertilizer retention key layer arranged from top to bottom. The wind erosion resistance key layer includes a coarse particle windproof layer and a fine particle cementing layer arranged from top to bottom; The raw materials of the water and fertilizer retention key layer include fine sand or original aeolian sandy soil, a clay mineral-based physical structure regulator, an organic water retainer, and a biological strengthening matrix material; The raw materials of the coarse particle windproof layer include gravel and coarse sand; The raw materials of the fine particle cementing layer include fine sand or original aeolian sandy soil, a clay mineral-based physical structure regulator, and an organic water retention performance cementing agent.

2. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 1, characterized in that In the water and fertilizer retention key layer, the mass ratio of the fine sand or original aeolian sandy soil, the clay mineral-based physical structure regulator, the organic water retainer, and the biological strengthening matrix material is 1:(0.04 - 0.15):(0.002 - 0.005):(0.02 - 0.05); And / or, the sand particle content of the fine sand or original aeolian sandy soil in the water and fertilizer retention key layer is 35 - 85 wt%; And / or, the clay mineral-based physical structure regulator includes montmorillonite and kaolin, and the mass ratio of the montmorillonite to the kaolin is 1:(1 - 3); And / or, the organic water retainer includes natural plant gum and water, and the mass ratio of the natural plant gum to the water is 1:(0.2 - 0.5); And / or, the biological strengthening matrix material includes biochar, plant fiber, and earthworm cast, and the mass ratio of the biochar, the plant fiber, and the earthworm cast is (1 - 3):(1 - 3):(1 - 3).

3. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 2, characterized in that, The particle size of the montmorillonite and / or kaolin ≤ 150 μm; And / or, the particle size of the organic water retainer in the solid state ≤ 150 μm; And / or, the particle sizes of the biochar, the plant fiber, and the earthworm cast ≤ 1000 μm; And / or, the particle size of the plant fiber ≤ 1 mm.

4. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 2, characterized in that, The natural plant gum includes at least one of xanthan gum or guar gum; And / or, the plant fiber includes at least one of corn straw or wheat straw.

5. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 1, characterized in that, The mass ratio of the gravel to the coarse sand is (3 - 5):1; And / or, the particle size of the gravel is 15 - 50 mm, and the gravel is shale or mudstone; And / or, the sand particle content of the coarse sand ≥ 85 wt%.

6. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 1, wherein In the fine particle cementing layer, the mass ratio of the fine sand or original aeolian sandy soil, the clay mineral-based physical structure regulator, and the organic water retention performance cementing agent is 1:(0.04 - 0.08):(0.001 - 0.003); And / or, the sand particle content of the fine sand or original aeolian sandy soil in the fine particle cementing layer ≥ 60 wt%; And / or, the organic water retention performance cementing agent includes a water retainer and water, the mass ratio of the water retainer to the water is 1:0.2 - 0.5, and the particle size of the water retainer in the solid state ≤ 150 μm.

7. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 6, characterized in that, The water retainer includes at least one of modified ammonium carboxymethyl cellulose or polyacrylamide.

8. The double topsoil key layer for reclamation in semi-arid mining areas according to any one of claims 1 to 7, characterized in that, The thickness of the wind erosion resistance key layer is 5 - 15 cm, and the thickness of the water and fertilizer retention key layer is 15 - 30 cm; And / or, the thickness of the coarse particle windproof layer is 3 - 5 cm, and the thickness of the fine particle cementing layer is 2 - 10 cm.

9. The double topsoil key layer for reclamation in semi-arid mining areas according to claim 8, characterized in that, The compaction coefficient of the key wind erosion control layer is 0.8 - 0.85, and the coverage is ≥ 75%. The compaction coefficient of the key water and fertilizer retention layer is 0.75 - 0.

8.

10. The refined construction method of the double topsoil key layer for reclamation in semi-arid mining areas according to any one of claims 1 to 9, characterized in that, It includes the following steps: (1) Mix montmorillonite and kaolin in a designed ratio to obtain a clay mineral-based physical structure regulator; mix natural plant gum and water in a designed ratio to obtain an organic water retainer; mix biochar, plant fiber and earthworm manure in a designed ratio to obtain a bio-enhanced matrix material; mix the water retainer and water in a designed ratio to obtain an organic water retention binder. (2) Mix fine sand or the original aeolian sand soil surface, the clay mineral-based physical structure regulator, the organic water retainer and the bio-enhanced matrix material in a designed ratio to obtain a water and fertilizer retention material. Lay the water and fertilizer retention material on the original aeolian sand soil section of the open-pit mine waste dump in the semi-arid aeolian region after leveling, tamp it, keep the surface moist, and cure for one week to obtain the key water and fertilizer retention layer. (3) Mix fine sand or the original aeolian sand soil surface, the clay mineral-based physical structure regulator and the organic water retention binder in a designed ratio to obtain a fine-grained binder material. Lay the fine-grained binder material above the key water and fertilizer retention layer, keep the surface moist, and cure for one week to obtain the fine-grained binder layer. (4) Mix gravel and coarse sand in a designed ratio to obtain a coarse-grained gravel layer material. Lay the coarse-grained gravel layer material above the fine-grained binder layer to obtain a coarse-grained wind erosion control layer. The coarse-grained wind erosion control layer and the fine-grained binder layer jointly construct the key wind erosion control layer.

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