Repair structure and repair method for one-wall type landform remodeling

Abstract

The invention provides a one-wall type landform remodeling repairing structure and method, and relates to the technical field of industrial by-product ardealite reutilization, the one-wall type landform remodeling repairing structure comprises a one-wall type landform stope, a drainage layer is arranged on a foundation of the one-wall type landform stope, an impermeable layer is arranged on the drainage layer, a gypsum filling body is arranged on the impermeable layer, and the gypsum filling body is arranged on the gypsum filling body. A water-resisting layer is arranged on the side, close to one wall type landform stope, of the gypsum filling body, a seepage water pressure drainage system is arranged in the water-resisting layer, a step-shaped water-resistant gypsum side slope is arranged on the free face of the gypsum filling body, and a planting soil layer covers the step-shaped water-resistant gypsum side slope. The method aims to restore the landform, eliminate hidden dangers and improve the land utilization rate, and the ecological environment of the mining area is restored by arranging the vegetation restoration layer on the top of the restoration body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of recycling of industrial by-products phosphogypsum, and particularly to a one-face-wall type landform remodeling repair structure and a repair method. BACKGROUND

[0002] With the rapid development of China's mining industry, the exploration technology of mineral resources is also constantly progressing. Many regions in China have excellent ore-forming conditions and rich mineral resources, and the dominant mineral species in different regions are also different. The exploitation of dominant mineral species has greatly promoted the rapid development of local economy.

[0003] However, due to the single and extensive mining method, economic interest driving, inadequate supervision and management, and insufficient technology and awareness, the frequent occurrence of the mine stope landform formed by the "one-face-wall" type digging and excavation in many mining areas has caused great hidden dangers to human safety activities. The vibration during the mining process causes cracks in the mountain rocks, and the excavation of the slope angle and the formation of the high and steep slope directly destroy the stress balance of the rock mass, forming a typical "cantilever beam" and "vertical face" dangerous rock structure, which is prone to geological disaster hazards such as relaxation and tensile cracking, creep, collapse, and landslide, as well as ecological environment destruction.

[0004] However, the high and steep slope has not been substantially solved by using the traditional direct green covering or grouting, anchor rod reinforcement and stabilization repair methods. Under the long-term penetration of water pressure on the ground surface, relaxation and tensile cracking, creep, collapse, and landslide are prone to occur. The traditional slope cutting treatment and repair method has a large amount of engineering and is extremely destructive to the ecology, and a large amount of waste rock cannot be handled. The traditional waste rock backfill repair method is more suitable for backfilling in concave areas, and the strength of the waste rock backfill is lacking. Blindly stacking high to repair high and steep slopes will only increase the geological landslide disaster.

[0005] The by-product hemihydrate phosphogypsum of the semi-wet process phosphoric acid system in phosphorus chemical industry has potential cementitious activity, and can be prepared into a gypsum-based ecological repair material after alkali activation and modification. The gypsum-based ecological repair material can be quickly coagulated and hardened after stirring with water, has the advantage of high strength, and can be applied to waste mine ecological repair filling, paste filling, underground filling, etc. However, when the gypsum-based ecological repair material is used to remodel the "one-face-wall, half-mountain" type mine landform and repair the mountain structure, the structure is not designed systematically according to the characteristics of the gypsum-based ecological repair material. Therefore, there is an urgent need for a technical means that can fully absorb phosphogypsum and solve the problem of collapse and landslide of the "one-face-wall, half-mountain" type stope slope. SUMMARY

[0006] This invention provides a one-wall-style landform reshaping restoration structure and method. The aim is to address the performance of air-hardening gypsum-based ecological restoration materials and the application characteristics of "one-wall" style high-steep slope mining environment reshaping. This invention proposes a one-wall-style landform reshaping restoration structure and method, which incorporates a structural functional layer design to solve problems such as water pressure seepage landslides in both new and old mountain areas, and slope weathering and rainwater erosion.

[0007] The present invention provides the following technical solution to achieve the above objectives: A restoration structure for reshaping a one-wall-type landform includes a one-wall-type landform mining area. A drainage layer is provided on the foundation of the one-wall-type landform mining area. An impermeable layer is provided on the drainage layer. A gypsum fill body is provided on the impermeable layer. A water-proof layer is provided on the side of the gypsum fill body adjacent to the one-wall-type landform mining area. A seepage water pressure drainage system is provided in the water-proof layer. A stepped water-resistant gypsum slope is provided on the free surface of the gypsum fill body. A planting soil layer is provided on the stepped water-resistant gypsum slope.

[0008] Furthermore, the permeable water pressure drainage system includes steel porous water collection pipes arranged vertically and horizontally along the height direction of the one-wall-type terrain mining area, and the steel porous water collection pipes are wrapped with geotextile.

[0009] Furthermore, a compacted clay layer is provided within the steps of the stepped water-resistant gypsum slope.

[0010] A method for reshaping a single-wall-like landform includes the following steps: A. Pre-treatment of the single-wall type mining area, including clearing dangerous rocks, slag and water accumulation; treatment based on the slope of the original foundation of the mining area. If the slope is less than 1:5, the foundation is compacted. If the slope is between 1:2.5 and 1:5, the slope is cleared into steps and then the foundation is compacted; finally, a drainage layer and an impermeable layer are laid on the pre-treated foundation in sequence. B. A permeable water pressure drainage system is installed along the steep slope of the wall-type terrain mining area. The bottom of the permeable water pressure drainage system is buried in the drainage layer, and a water-proof layer is filled in layers on the permeable water pressure drainage system. C. Along the height direction of the single-wall-type terrain mining area, from low to high, gypsum-based ecological restoration materials are used to successively compact and slope the gypsum fill body in layers to form a gypsum fill body; on the free face of the gypsum fill body, water-resistant gypsum composite cementitious material is used for layered filling and compaction to form a graded stepped water-resistant gypsum slope. D. Cover the stepped, water-resistant gypsum slope with soil and plant shallow-rooted vegetation.

[0011] Furthermore, in step A, the drainage layer is formed by laying 30cm of crushed stone, and the seepage prevention layer is formed by laying 80cm of compacted clay.

[0012] Furthermore, in step B, the waterproof layer is formed by layering and compacting water-resistant gypsum composite cementitious material, and the thickness of the waterproof layer is not less than 0.75m.

[0013] Furthermore, in step B, the permeable water pressure drainage system is constructed synchronously as the filling elevation of the gypsum fill increases.

[0014] Furthermore, in step C, the stepped water-resistant gypsum slope is constructed synchronously with the increase in the filling elevation of the gypsum fill body. Compared with the prior art, the present invention has the following beneficial effects: 1. This invention significantly improves geological safety and structural stability. Traditional restoration methods (such as direct revegetation and grouting anchoring) can only provide short-term or surface reinforcement, failing to fundamentally solve the problems of rock mass stress imbalance and steep slopes caused by "one-wall" mining. This invention uses gypsum-based materials with considerable strength to reshape the landform, providing effective support for the slope, restoring rock mass stress balance, and thus eliminating the hidden dangers of geological disasters such as collapse and landslides. Unlike traditional waste rock backfilling which lacks strength, the gypsum-based ecological restoration material used in this invention has high compressive and shear strength, resulting in structural stability. Stability calculations show that under normal and seismic conditions, the slope sliding safety factor can reach 1.712 and 1.462, respectively, meeting the safety requirements of a Class I slope.

[0015] 2. This invention designs a water-impermeable layer between old and new mountain slopes, a drainage system for permeable water pressure, and a water-resistant slope. This systematic structure solves the problems of landslides caused by rainwater infiltration and slope collapse due to weathering and rainwater erosion, avoiding collapses caused by increased internal water pressure or material erosion. Furthermore, during the large-scale piling and filling process of air-hardening gypsum material, the material gradually mineralizes (lithifies) over time due to temperature changes, pressure from the piling, and natural wind erosion within the fill body. Impurity ions are highly complexed and solidified, although this process is slow. The drainage system, water-impermeable layer, and water-resistant slope ensure good water-impermeability before the formation of dense gypsum-like minerals, guaranteeing stability during lithification. After the air-hardening gypsum material lithifies, a permanent gypsum-like mineral mountain is formed. Even if the water-impermeable layer is damaged, secondary landslides and slope instability will not occur under rainwater erosion, thus obtaining high-quality artificial gypsum mineral resources.

[0016] 3. Compared to traditional slope-cutting methods, which involve massive engineering work and are extremely destructive to the ecosystem, this invention avoids the severe damage to the ecosystem caused by secondary excavation. This invention uses phosphogypsum, a byproduct of phosphate chemical industry, as the main raw material to prepare remediation materials, transforming industrial solid waste into valuable remediation materials and achieving effective resource utilization. By setting up water-resistant slopes and a systematic seepage-proof and drainage structure, the pollutant concentration in the surface runoff water of the remediated landform can reach the Class III standard for surface water one year after backfilling, effectively avoiding the heavy metal pollution or gypsum leaching pollution problems that may occur with traditional backfilling methods. This invention aims to restore landforms, eliminate hidden dangers, improve land utilization, and restore the ecological environment of the mining area by setting a vegetation restoration layer on top of the remediation body.

[0017] 4. This invention provides an effective solution for steep, "one-wall" slope mining areas where traditional waste rock backfilling is difficult to handle. Compared to similar technical solutions that fail to systematically design ecological restoration structures and functional layers, this invention features a detailed structural and functional layer design for the restoration system (such as waterproofing layers, drainage systems, and water-resistant slopes), solving several key technical challenges. Compared to the low strength and poor stability of traditional dihydrate gypsum backfilling, the multiphase gypsum and other materials used in this invention have higher strength and are better suited to the mechanical performance requirements of steep slope restoration. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall repair structure of the present invention; Figure 2 This is a calculation diagram for the safety, stability, and anti-slip resistance of the repair structure in this invention (under normal working conditions). Figure 3 This is a calculation diagram for the structural safety, stability, and anti-slip resistance of the repair structure in this invention (under seismic conditions). Attached diagram labels: 1-Drainage layer; 2-Impering layer; 3-Gypsum fill; 4-Waterproof layer; 5-Permeable water pressure drainage system; 6-Stepped water-resistant gypsum slope; 7-Planting soil layer. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0020] It should be noted that the terms "vertical," "horizontal," "up," "down," "left," "right," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] A wall-like landscape reshaping and restoration structure, structural reference. Figure 1 The site includes a one-wall-type terrain mining area. A drainage layer 1 is set on the foundation of the one-wall-type terrain mining area. An anti-seepage layer 2 is set on the drainage layer 1. A gypsum fill body 3 is set on the anti-seepage layer 2. A water-proof layer 4 is set on the side of the gypsum fill body 3 adjacent to the one-wall-type terrain mining area. A seepage water pressure drainage system 5 is set in the water-proof layer 4. A stepped water-resistant gypsum slope 6 is set on the free surface of the gypsum fill body 3. A planting soil layer 7 is covered on the stepped water-resistant gypsum slope 6.

[0023] The permeable water pressure drainage system includes steel porous water collection pipes arranged vertically and horizontally along the height direction of the one-wall-type terrain mining area, and the steel porous water collection pipes are wrapped with geotextile. The stepped water-resistant gypsum slope is provided with a compacted clay layer 8 inside the steps; the compacted clay layer 8 is provided to prevent rainwater, flash floods and other factors from excessively eroding and damaging the stepped water-resistant gypsum slope. The gypsum-filled body 3 is formed by filling with gypsum-based ecological restoration materials. These materials are derived from phosphogypsum, a byproduct of phosphate chemical enterprises, and comprise: hemihydrate gypsum composite cementitious material, multiphase gypsum cementitious material, and dihydrate gypsum filler. The hemihydrate gypsum cementitious material's main component is CaSO4·1 / 2H2O; the multiphase gypsum cementitious material's main component is a composite phase of CaSO4·1 / 2H2O and CaSO4·2H2O; and the dihydrate gypsum filler's main component is CaSO4·2H2O. After compaction and hardening, the gypsum composite cementitious material exhibits water resistance, with a softening coefficient ≥0.8. The leaching toxicity of the gypsum-based ecological restoration materials meets the backfilling requirements of the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025).

[0024] Safety, stability and anti-slip analysis of gypsum-filled structures Core samples were taken from the air-hardening gypsum fill. According to the Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering (JTG 3441—2024), the 7-day unconfined compressive strength was 4.21 MPa. After continuous soaking for one month, the unconfined compressive strength decreased to 2.3 MPa. Simultaneously, the shear strength of the fill was tested under saturated conditions according to the Test Procedure for Highway Geotechnical Engineering (JTG3430-2020), as follows: Safety stability and anti-slip analysis under normal operating conditions, such as Figure 2 As shown; Safety and stability anti-sliding analysis under seismic conditions, such as Figure 3 As shown; According to the Technical Specification for Slope Engineering of Buildings (GB 50330-2013), slope stability analysis was conducted. After calculation, when the slope ratio was 1:1.75, the slope stability sliding safety factor of phosphogypsum cementitious material was 1.712 and 1.462 under general mining conditions and seismic conditions after long-term water immersion (28 days). This meets the requirements of the Technical Specification for Slope Engineering of Buildings (GB 50330-2013) that the safety level of Grade I slopes under general mining conditions and seismic conditions is greater than 1.35 and 1.15, respectively.

[0025] However, as can be seen from the above data, although the air-hardening gypsum material used in this invention has good cementing properties (its main component is hemihydrate gypsum) and an unconfined compressive strength of 4.21 MPa, the prepared fill material, after simulating continuous immersion in water for 28 days, showed a decrease in unconfined compressive strength to 2.3 MPa, and its cohesion C decreased from 0.490 MPa to 0.260 MPa, indicating a decrease. Nevertheless, it still meets the slope stability requirements under general mining conditions and seismic conditions. Figure 2 , Figure 3 However, when not soaked by rainwater, the calcium sulfate hemihydrate can absorb most of the free water inside the fill due to the process of converting calcium sulfate dihydrate to calcium sulfate dihydrate. During the long-term hydration and evaporation process, the fill gradually tends to dry out (measured free water content of 1.08% after 180 days of natural curing). Compared with the saturated water state, the compressive strength (measured unconfined compressive strength of 6.89 MPa after 180 days of natural curing) and shear strength show a significant increase.

[0026] Therefore, in the process of layered stacking and filling of bulk air-hardening gypsum materials, the design of drainage system, water-proof layer and water-resistant slope can ensure that the air-hardening gypsum materials are always in a dry state with low moisture content, and ensure that they play a good role in water isolation and drainage before the formation of dense gypsum-like minerals, thus ensuring the safety and stability of the lithification process of the gypsum filling body.

[0027] A method for reshaping a single-wall-like landform includes the following steps: A. Pre-treatment of the single-wall type mining area, including clearing dangerous rocks, slag and water accumulation; treatment based on the slope of the original foundation of the mining area. If the slope is less than 1:5, the foundation is compacted. If the slope is between 1:2.5 and 1:5, the slope is cleared into steps and then the foundation is compacted; finally, a drainage layer and an impermeable layer are laid on the pre-treated foundation in sequence. B. A permeable water pressure drainage system 5 is installed along the steep slope of the one-wall-type terrain mining area. The bottom of the permeable water pressure drainage system 5 is buried in the drainage layer 1, and a water-proof layer 4 is filled in layers on the permeable water pressure drainage system 5. By burying the bottom of the permeable water pressure drainage system 5 in the drainage layer 1, it is convenient for water flowing down the one-wall-type terrain mining area to enter the permeable water pressure drainage system 5 and be discharged through the drainage layer 1, thus avoiding water erosion of the gypsum fill 3. C. Along the height direction of the wall-type mining area, from low to high, gypsum-based ecological restoration materials are used to successively compact and slope the gypsum fill body 3 in layers; on the free face of the gypsum fill body 3, water-resistant gypsum composite cementitious material is used for layered filling and compaction to form a graded stepped water-resistant gypsum slope 6. The gypsum fill 3 is obtained by layering and compacting gypsum-based ecological restoration materials to form a slope. The compaction degree is ≥90% and the strength is ≥1.5MPa. Under normal mining conditions and seismic conditions, the slope sliding safety factor is greater than 1.35 and 1.15, respectively, which meets the requirements of the first-level slope safety level. The water-resistant gypsum composite cementitious material used in the stepped water-resistant gypsum slope 6 is selected with a water resistance coefficient ≥0.8 and a permeability coefficient ≤1*10. -5 Materials with a strength of ≥3MPa and a strength of cm / s; D. Cover the stepped water-resistant gypsum slope 6 with soil and plant shallow-rooted vegetation; In step A, the drainage layer 1 is formed by laying 30cm of crushed stone, and the seepage-proof layer 2 is formed by laying 80cm of compacted clay. In step B, the waterproof layer 4 is formed by layering and compacting a water-resistant gypsum composite cementitious material, with a thickness of not less than 0.75m. The water-resistant gypsum composite cementitious material is selected with a water resistance coefficient ≥0.8 and a permeability coefficient ≤1*10. - 5 Materials with a speed of cm / s.

[0028] In step B, the permeable water pressure drainage system 5 is constructed synchronously with the rise of the filling elevation of the gypsum fill body 3; In step C, the stepped water-resistant gypsum slope 6 is constructed synchronously with the rise of the filling elevation of the gypsum fill body 3; Example 1. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0029] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0030] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6 cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm, consistent with the thickness of the main filling area. Before the gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connection is formed, preventing structural cracks caused by the two different material formulations on the slope. The above material is cyclically spread and compacted in layers until a cumulative thickness of 1m is reached. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 1.75m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped area. The same cyclical construction method is used to obtain a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope was naturally cured for 7 days. Core samples showed a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0031] 4) The materials from step 3) are used for cyclic filling construction until the set elevation for landform restoration is reached, resulting in a stepped slope with a gradient of 1:1.75. A 4-meter-wide walkway is constructed with each step being 6 meters wide. The constructed water-resistant stepped slope is covered with soil to a thickness of 1.5 meters, grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0032] Example 2. A method for reshaping a single-wall-like landform, comprising: 1) Pre-treatment of the single-wall-type mining area includes clearing unstable rocks, slag layers, and accumulated water. The original foundation slope at the bottom of the mining area is between 1:2.5 and 1:5. The foundation slope needs to be cleared into steps and then compacted. After pre-treatment, a 30cm thick gravel drainage layer is installed at the bottom of the mining area; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0033] The difference from step 1) in Example 1 is that the slope of the original mining site foundation has an important impact on the safety and stability of the fill body. When the slope is steeper than 1:5, if the original soil foundation is not treated in a stepped manner, it will increase the slip coefficient of the entire gypsum backfill body. Under long-term self-weight conditions, it will creep and eventually lead to landslide.

[0034] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0035] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm, consistent with the thickness of the main filling area. Before the gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connection is formed, preventing structural cracks caused by the two different material formulations on the slope. The above material is cyclically spread and compacted in layers until a cumulative thickness of 1m is reached. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 1.75m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped area. The same cyclical construction method is used to obtain a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope was naturally cured for 7 days. Core samples showed a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0036] 4) The materials from step 3) are used for cyclic filling construction until the set elevation for landform restoration is reached, resulting in a stepped slope with a gradient of 1:1.75. A 4-meter-wide walkway is constructed with each step being 6 meters wide. The constructed water-resistant stepped slope is covered with soil to a thickness of 1.5 meters, grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0037] Example 3. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0038] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0039] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6 cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm, consistent with the thickness of the main filling area. Before the gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connection is formed, preventing structural cracks caused by the two different material formulations on the slope. The above material is cyclically spread and compacted in layers until a cumulative thickness of 1m is reached. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 1.5m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped area. The same cyclical construction method is used to obtain a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope was naturally cured for 28 days. Core samples showed a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0040] 4) The materials from step 3) are used for cyclic filling construction until the set elevation for landform restoration is reached, resulting in a stepped slope with a gradient of 1:1.50. A 4-meter-wide walkway is constructed with each step being 6 meters long. The constructed water-resistant stepped slope is covered with soil to a thickness of 1.5 meters, grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0041] The difference from steps 3) and 4) in Example 1 is that the slope steps increase the slope from 1:1.75 to 1:1.50, making the slope steeper. While ensuring the safety and stability slip coefficient, more slope voids can be saved and the gypsum filling rate can be increased.

[0042] Example 4. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0043] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0044] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6 cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 0.5m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm, consistent with the thickness of the main filling area. Before the gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connection is formed, preventing structural cracks caused by the two different material formulations on the slope. The above material is cyclically spread and compacted in layers until a cumulative thickness of 0.5m is reached. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 0.9m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped area. The same method is used for cyclical construction, resulting in a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope was naturally cured for 28 days. Core samples showed a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0045] The difference from step 3) in Example 1 is that although the slope of the slope remains unchanged from 1:1.75, the width and height of the steps are reduced. Compared with the traditional natural slope brushing method, it can still effectively increase the stability of the soil cover, but it is not as stable as the soil cover of the steps in step 3) in Example 1.

[0046] 4) The materials from step 3) are used for cyclic filling construction until the set elevation for landform restoration is reached, resulting in a stepped slope with a gradient of 1:1.75. A 4-meter-wide walkway is constructed with each step being 6 meters wide. The constructed water-resistant stepped slope is covered with soil to a thickness of 1.5 meters, grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0047] Comparative Example 1. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0048] 2) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm, consistent with the thickness of the main filling area. Before the gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connection is formed, preventing structural cracks caused by the two different material formulations on the slope. The above material is cyclically spread and compacted in layers until a cumulative thickness of 1m is reached. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 1.75m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped area. The same cyclical construction method is used to obtain a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope was naturally cured for 7 days. Core samples showed a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0049] 3) The materials from step 3) are cyclically filled to the set elevation for landform restoration, resulting in a stepped slope with a gradient of 1:1.75. A 4m wide walkway is constructed with each 6m step as a grade. The constructed water-resistant stepped slope is then covered with 1.5m thick soil, sown with grass seeds, and covered with biodegradable mesh to prevent soil erosion.

[0050] The difference from Example 1 is that no mountain seepage water pressure drainage system was installed. Although this case restored the slope through gypsum fill, providing the mechanical balance needed to prevent landslides, in areas or seasons with concentrated heavy rainfall, rainwater seeps into the mountain. Because the mountain has fissures and detachment layers from long-term mining, the rainwater infiltration will increase the mountain's weight and provide creep sliding force, leading to cracks in both the old and new mountain sections. In this vicious cycle, the original mountain or gypsum fill is continuously eroded, eventually causing a collapse.

[0051] Comparative Example 2. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0052] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0053] 3) After laying a crushed stone drainage layer and an anti-seepage layer at the bottom of the pre-treated abandoned mine site, the multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm and compacted on a slope. Two meters from the slope edge, steel molds are used for support, each mold being 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is then filled into the support molds at a loose height of 45cm, consistent with the thickness of the main filling area. Before the multiphase gypsum and gypsum composite cementitious material harden, compaction is carried out simultaneously, achieving a compaction degree of 94%. After hardening, a complete connected body is formed, preventing structural cracks caused by the two different material formulations on the slope. The above-mentioned materials are cyclically layered, spread, and compacted until a cumulative thickness of 1m is achieved. After curing for 3 days and hardening, the formwork is removed, and the platform is stepped back 1.75m inward. Support for the next step's steel formwork then begins, with steel tripods erected on the surface of the stepped area. This cyclical construction method yields a stepped slope that forms an integral connection with the main filling area. The prepared stepped slope is naturally cured for 28 days. Core sampling shows a strength of 15.68 MPa and a permeability coefficient of 1.98 × 10⁻⁶. -6 cm / s.

[0054] 4) The materials from step 3) are used for cyclic filling construction until the set elevation for landform restoration is reached, resulting in a stepped slope with a gradient of 1:1.75. A 4-meter-wide walkway is constructed with each step being 6 meters wide. The constructed water-resistant stepped slope is covered with soil to a thickness of 1.5 meters, grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0055] The difference from Example 1 is that no waterproof layer was installed between the mountain and the gypsum fill. Although a permeable water pressure drainage system was installed between the mountain and the gypsum fill to prevent large amounts of seepage water from eroding the gypsum fill, the gypsum fill, being an air-hardening cementitious material, will gradually be hollowed out by the slow erosion of some of the seepage water. This will create gaps between the old and new mountain structures, increasing the amount of rainwater seeping in and ultimately leading to a landslide.

[0056] Comparative Example 3. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0057] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0058] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, multiphase gypsum filling construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area. Simultaneous compaction is ensured, achieving a compaction degree of 93%. After hardening, it forms a complete connection with the main filling area, thus obtaining a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68 MPa and a permeability coefficient of 6.98*10. -6 cm / s.

[0059] 4) Circulate and fill the material from step 3) to the set elevation for landform restoration, with a slope of 1:1.75, and set up 4m wide walkways in 6m increments. Cover the slopes of the water-resistant steps with soil to a thickness of 1.5m, sow grass seeds, and cover the surface with biodegradable mesh to prevent soil erosion.

[0060] The difference from Example 1 is that: no trapezoidal water-resistant gypsum slope was set up. Instead, multiphase gypsum was used to naturally brush the slope in the traditional way and then cover it with soil. Since the gypsum filling is an air-hardening cementitious material, it has a certain strength and can meet the requirements of safety, stability and anti-slip coefficient. However, the slope is a weak area in the compaction process, which is difficult to compact and is not water-resistant. At the same time, the slope has a large water catchment area, which will be continuously eroded and seeped into the slope, eventually leading to the collapse of the slope.

[0061] Comparative Example 4. A method for reshaping a single-wall-like landform, comprising: 1) The single-wall-type mining area undergoes pretreatment, including the removal of unstable rocks, spoil layers, and accumulated water. The original foundation slope at the bottom of the mining area is less than 1:5, requiring only compaction. After pretreatment, a 30cm thick gravel drainage layer is installed at the bottom; the impermeable layer is an 80cm layer of compacted clay, with a permeability coefficient of 1.76*10⁻⁶. -6 The permeability is cm / s, which meets the requirement that the saturated permeability coefficient of the base layer should not exceed 1.0 × 10⁻⁶ cm / s in the "Technical Specification for Pollution Control of Utilization and Harmless Storage of Phosphogypsum" (HJ 1415—2025). -5 The speed requirement is cm / s, and the thickness is not less than 0.75 m.

[0062] 2) A permeable water pressure drainage system will be installed along the steep slope of the abandoned mine, connected to the seepage prevention layer below the pit, and discharged through the crushed stone drainage layer. Specifically, 273mm Q235B steel porous water collection pipes will be vertically buried in the crushed stone drainage layer and fixed along the vertical slope of the mine. The system will be laid out as the height of the fill increases. The seepage prevention layer will be welded. A vertical steel porous water collection pipe will be installed every 8m wide, and a horizontal steel porous water collection pipe will be installed every 8m high. The surface of the pipes will be filled with crushed stone to ensure permeability and prevent blockage.

[0063] 3) After laying a crushed stone drainage layer and an impermeable layer at the bottom of the pre-treated abandoned mine site, dihydrate gypsum fill construction is carried out, with each layer loosely laid at 45cm intervals and compacted on a slope. At a distance of 2m from the mountain wall, gypsum composite cementitious material is used for backfilling, with the backfill thickness consistent with the single-layer backfill thickness of the main filling area, achieving a compaction degree of 94%. This provides a gypsum waterproof layer. After 28 days of natural curing, core sampling showed a strength of 13.68MPa and a permeability coefficient of 6.98*10. -6 cm / s. At a depth of 2 meters from the slope edge, steel formwork is used for support. Each formwork is 3m long and 1m high, supported by steel tripods, and arranged in a cyclical manner. Gypsum composite cementitious material is filled into the support formwork, with a loose layer height of 45cm and a compaction degree of 93%. This material is cyclically spread and compacted in layers until a cumulative thickness of 1m is achieved. After curing for 3 days and hardening, the formwork is removed, and the slope is stepped back 1.75m inward. Support for the next step of steel formwork begins, with steel tripods erected on the surface of the stepped section. The same cyclical construction method is used to obtain a stepped slope. The prepared stepped slope is naturally cured for 7 days. Core sampling shows a strength of 15.68MPa and a permeability coefficient of 1.98*10. -6 cm / s.

[0064] 4) The materials from step 3) are cyclically filled to the set elevation for landform restoration, resulting in a stepped slope with a gradient of 1:1.75. A 4m wide walkway is constructed with 6m increments as each step. The water-resistant stepped slope is then filled with soil at the corners, compacted to form an uneven surface, and then loosely covered with 0.5m of soil. Grass seeds are sown, and biodegradable mesh is used to cover the surface to prevent soil erosion.

[0065] The difference from Example 1 is that low-strength dihydrate gypsum was used for the compaction of the main area. Although the bearing capacity of the dihydrate gypsum compacted fill is similar to that of traditional soil backfill (22.78%), in the case of a one-wall type mountain restoration, the mountain is steep, with only one side backed by the mountain and the other three sides exposed with little support. Traditional low-strength soil backfill requirements are not applicable, and the safety and stability gradually deteriorate as the filling height increases. Furthermore, dihydrate gypsum has low strength and is not water-resistant. Although a mountain permeable drainage system, a waterproof layer, and a water-resistant slope were installed, the weight of rainwater during the rainy season increases the sliding force, making the low-strength gypsum fill prone to landslides.

[0066] Flushing water index The restored landforms formed in Examples 1-4 and Comparative Examples 1-4 were used to collect surface erosion data one year after soil cover by setting up gentle slopes, collecting ditches, and collecting ponds. The characteristic pollutants tested are as follows: The leachate prepared by gypsum-based materials according to HJ557-2010 "Solid Waste - Leaching Toxicity Leaching Method" can meet the requirements for the concentration of characteristic pollutants of phosphogypsum when used for ecological restoration and backfilling of open-pit abandoned mines in GB-T 32124-2024 "Specifications for Treatment and Disposal of Phosphogypsum" and HJ 1415-2025 "Technical Specifications for Pollution Control in Utilization and Harmless Storage of Phosphogypsum".

[0067] However, during the backfilling process of gypsum-based materials, the concentration of characteristic pollutants in the leaching and flushing water is difficult to meet the Class III surface water standard, and in most cases, it cannot be discharged and needs to be collected for use. In contrast, the ecological restoration systems described in Examples 1-4, Comparative Examples 1 and 4 of this paper, after backfilling, show that the surface flushing water meets the Class III surface water standard. However, in Comparative Examples 2-3, after backfilling, due to the lack of a trapezoidal slope waterproofing layer and a waterproofing layer between the mountain and the gypsum fill, the collected infiltration water and surface flushing water samples do not meet the Class III surface water standard.

[0068] Obviously, the above description is only a part of the embodiments of the present invention, and not all of the embodiments. The above embodiments are not intended to limit the present invention, and various modifications and variations can be made to the present invention by those skilled in the art. Any combination, modification, equivalent substitution, improvement, and all other embodiments that can be made by those skilled in the art within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. A restoration structure for reshaping a single-wall-type landform, comprising a single-wall-type landform mining site, characterized in that: A drainage layer (1) is provided on the foundation of the one-wall-type landform mining site. An anti-seepage layer (2) is provided on the drainage layer (1). A gypsum fill body (3) is provided on the anti-seepage layer (2). A water-proof layer (4) is provided on the side of the gypsum fill body (3) adjacent to the one-wall-type landform mining site. A seepage water pressure drainage system (5) is provided in the water-proof layer (4). A stepped water-resistant gypsum slope (6) is provided on the free surface of the gypsum fill body (3). A planting soil layer (7) is provided on the stepped water-resistant gypsum slope (6).

2. The repair structure according to claim 1, characterized in that: The permeable water pressure drainage system includes porous water collection pipes arranged vertically and horizontally along the height direction of the one-wall-type terrain mining area, and the porous water collection pipes are wrapped with geotextile.

3. The repair structure according to claim 1, characterized in that: The stepped water-resistant gypsum slope has a compacted clay layer (8) inside the steps.

4. A method for reshaping a single-wall-like landform, accomplished using the method described in claim 1, characterized in that, Includes the following steps: A. Pre-treatment of the single-wall type mining area, including clearing dangerous rocks, slag and water accumulation; treatment based on the slope of the original foundation of the mining area. If the slope is less than 1:5, the foundation is compacted. If the slope is between 1:2.5 and 1:5, the slope is cleared into steps and then the foundation is compacted; finally, a drainage layer and an impermeable layer are laid on the pre-treated foundation in sequence. B. A permeable water pressure drainage system is installed along the steep slope of the wall-type terrain mining area. The bottom of the permeable water pressure drainage system is buried in the drainage layer, and a water-proof layer is filled in layers on the permeable water pressure drainage system. C. Along the height direction of the single-wall-type terrain mining area, from low to high, gypsum-based ecological restoration materials are used to successively compact and slope the gypsum fill body in layers to form a gypsum fill body; on the free face of the gypsum fill body, water-resistant gypsum composite cementitious material is used for layered filling and compaction to form a graded stepped water-resistant gypsum slope. D. Cover the stepped, water-resistant gypsum slope with soil and plant shallow-rooted vegetation.

5. The repair method according to claim 4, characterized in that: In step A, the drainage layer is formed by laying 30cm of crushed stone, and the seepage prevention layer is formed by laying 80cm of compacted clay.

6. The repair method according to claim 4, characterized in that: In step B, the waterproof layer is formed by layering and compacting water-resistant gypsum composite cementitious material, and the thickness of the waterproof layer is not less than 0.75m.

7. The repair method according to claim 4, characterized in that: In step B, the permeable water pressure drainage system is constructed synchronously as the filling elevation of the gypsum fill increases.

8. The repair method according to claim 4, characterized in that: In step C, the stepped water-resistant gypsum slope is constructed synchronously with the increase in the filling elevation of the gypsum fill body.

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