Coal mining subsidence reclaimed land waterlogging and salinization synergistic treatment process

Abstract

The present application provides a kind of coal mining subsidence reclaimed land waterlogging and salinization synergistic treatment process, by constructing waterlogging stress index, salinization stress index and synergistic risk index, the quantitative evaluation and dynamic classification of waterlogging and salinization synergistic risk are realized, by coal-based solid waste compound conditioner precise compounding and based on synergistic risk index optimization application decision, the precise regulation and control of conditioner application are realized, by microtopography reconstruction and the linkage of optimal calculation of buried pipe drainage spacing, the dynamic optimization of drainage system is realized, by double control test system and yield recovery rate, comprehensive soil fertility index dual evaluation path, the reliable verification of treatment effect is realized, so as to effectively solve the technical problems that waterlogging and salinization synergistic occurrence of high groundwater level coal mining subsidence reclaimed land is difficult to identify, conditioner application lacks precise decision basis, drainage system cannot dynamically respond and treatment effect is difficult to reliably verify in limited period.

Description

Technical Field

[0001] This invention relates to the field of environmental governance technology, and in particular to a synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas. Background Technology

[0002] Coal is my country's most important basic energy source, with approximately 90% extracted through underground mining. Large-scale underground mining has led to widespread surface subsidence; the area of ​​land subsidence caused by coal mining in my country has reached 2.33 million hectares. 2 And at an annual rate of 20,000-26,700 hectares 2 The rate of land subsidence continues to increase. Most of the coal mining subsidence areas were originally high-quality arable land. Mining subsidence easily leads to slopes, water accumulation, and uneven surfaces. Under the combined effects of rainwater, wind, and other factors, the surface suffers severe damage. As the focus of coal resource mining in eastern mining areas gradually shifts from mining to the management of coal mining subsidence areas, the reclamation of coal mining subsidence areas and the restoration of arable land have become urgent requirements for arable land protection and mining area environmental restoration in my country.

[0003] In mining areas with high groundwater levels, coal mining subsidence leads to a relative rise in the groundwater level, sometimes even exposing it to the surface. Combined with intense rainfall, the combined effects of subsidence micro-topography and poor drainage, the topsoil of reclaimed land is prone to prolonged dampness, reduced aeration, and surface salt accumulation. Existing technologies include solutions for controlling groundwater levels and reducing soil salinization in high groundwater level coal mining subsidence areas by constructing drainage ditches. Other studies have proposed using "water collection control engineering" to comprehensively balance water and soil resources in subsidence areas, achieving spatial regulation of water resources through the construction of dispersed collection pits and ponds, thus addressing the decline in farmland quality caused by poor drainage in subsidence areas. Furthermore, in terms of soil improvement, existing technologies utilize coal gangue, fly ash, and other coal-based solid waste to prepare soil conditioners for mining area reclamation. For example, coal gangue can be co-activated with phosphogypsum and other raw materials for saline-alkali land improvement.

[0004] However, the existing technologies still have the following shortcomings: First, existing technologies mostly treat waterlogging control and salinization control as independent problems, lacking a systematic identification of the synergistic mechanism of waterlogging and salinization under high groundwater levels, and failing to reveal the intrinsic relationship between groundwater level fluctuations driving vadose zone water and salt migration, thereby affecting the topsoil structure and root zone salinity environment. Second, the application of existing coal-based solid waste conditioners lacks a precise application decision model based on real-time monitoring data; the dosage is mostly determined empirically, making it difficult to accurately control based on the dynamic waterlogging and salinization risks of reclaimed land. Furthermore, there is a lack of a systematic evaluation system for the safety of conditioner raw materials, posing long-term environmental risks of heavy metal leaching and soluble salt accumulation. Third, existing treatment methods lack a closed-loop technical system of "monitoring-assessment-control-verification," making it difficult to reliably verify the effects of productivity restoration and soil fertility improvement within a limited period. Fourth, the design parameters of existing underground drainage systems are mostly static values, failing to form a linkage control with dynamic soil water and salt monitoring and waterlogging and salinization risk assessment results.

[0005] Therefore, there is an urgent need in this field to develop a coal mining subsidence reclamation land treatment technology that can achieve coordinated management of waterlogging and salinization, precise regulation based on dynamic monitoring data, and verifiable results. Summary of the Invention

[0006] The purpose of this invention is to provide a synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas, in order to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas, comprising the following steps: Step 1: Deployment of the monitoring system and data acquisition. Groundwater level observation wells and multi-depth soil sensors are deployed in the coal mining subsidence reclamation plots to be treated to monitor groundwater level depth, soil moisture content and electrical conductivity in real time. Soil samples at different depths are collected regularly to determine soil total salt content, ionic composition, pH, organic matter and nutrient indicators. Simultaneously, micro-topographic elevation measurements are carried out to generate a digital elevation model. Step 2: Collaborative risk assessment of waterlogging and salinization. Based on the data obtained in Step 1, calculate the waterlogging stress index and salinization stress index, and then construct a collaborative risk index to classify the reclaimed land plots by risk. Step 3: Precise formulation and application of coal-based solid waste composite conditioner. First, a safety assessment is conducted on the raw materials of coal gangue, fly ash, and desulfurization gypsum to eliminate high-risk batches. Then, the safe raw materials are compounded with organic materials and calcium-based materials in a certain proportion to prepare the coal-based solid waste composite conditioner. The application rate is optimized based on the synergistic risk index in Step 2. The conditioner is applied to the surface layer of the reclaimed land and mixed evenly with the soil. After application, water is irrigated to leach salt and the land is covered with mulch to retain moisture. Step 4: Micro-topography-drainage coordinated regulation. Based on the digital elevation model in Step 1 and the coordinated risk index in Step 2, micro-topography modification is implemented in high-risk areas. Drainage pipes are buried in the reclaimed land, and the spacing of the pipes is optimized based on the soil saturated hydraulic conductivity, the burial depth of the pipes, the design drainage time, and the dynamic calculation of the groundwater level. Step 5: Verify the effectiveness of the dual-control system. Set up a normal farmland control area, an unreclaimed obstacle control area, and a process treatment area. During the crop growing season, regularly monitor the groundwater level, soil water and salt profile, soil structure parameters, and crop physiological indicators in each treatment area. At harvest, measure yield and soil fertility indicators. Evaluate the treatment effect by the yield recovery rate and the multiple of improvement in the comprehensive soil fertility index.

[0008] Preferably, in step one, the soil multi-depth sensor is buried at 10cm, 30cm, 50cm and 80cm underground, and the depth of the groundwater level observation well is 2-3m below the water table; the periodic collection is to collect soil samples from three layers of soil at 0-20cm, 20-40cm and 40-60cm every half month.

[0009] Preferably, the formula for calculating the collaborative risk index in step two is: ; in, The waterlogging stress index, This is the salt stress index. , , The weighting coefficients are determined using the analytic hierarchy process (AHP). + + =1; <0.3 indicates low risk, 0.3≤ <0.6 indicates medium risk. A value of ≥0.6 indicates a high risk.

[0010] Preferably, the formula for calculating the waterlogging stress index is: ; in, The depth of the groundwater level. This is the critical groundwater depth. The slope coefficient of the waterlogging response. This represents the cumulative rainfall over the previous 30 days. This represents the average rainfall for the same period over many years. The formula for calculating the salinity stress index is as follows: ; in, The conductivity of the saturated soil extract. The critical electrical conductivity for crop salt damage. The threshold for severe salinization. , , These represent the concentrations of Na+, Ca2+, and Mg2+ in the soil solution, respectively.

[0011] Preferably, the safety evaluation in step three includes four dimensions: total risk evaluation, leaching risk evaluation, salinity risk evaluation, and farmland suitability evaluation. Batches with total heavy metal content exceeding the GB 15618 screening value, leaching concentration exceeding the GB5085.3 limit, or soluble salt content exceeding the standard are rejected.

[0012] Preferably, the optimized application rate of the coal-based solid waste-based composite conditioner in step three is dynamically adjusted based on the synergistic risk index and the soil sodium adsorption ratio. The higher the synergistic risk index or the greater the soil sodium adsorption ratio, the higher the application rate.

[0013] Preferably, the micro-topography modification in step four includes a raised field mode and a ridge cultivation mode. The raised field mode involves raising a local plot of land by 30-50cm in the catchment area to form a turtle-back shaped micro-elevation. The ridge cultivation mode involves creating ridges along the drainage direction, with a ridge height of 20-30cm and a ridge width of 60-80cm.

[0014] Preferably, the optimized spacing of the drainage pipes in step four is calculated according to the following formula: ; in, This refers to the spacing between concealed pipes. For soil saturated hydraulic conductivity, For the depth of the concealed pipe burial, To design drainage time, For soil effective porosity, For water supply degree, This represents the initial groundwater level depth. The target groundwater level depth after the designed drainage time.

[0015] Preferably, the formula for calculating the comprehensive soil fertility index in step five is as follows: ; in, For the first Measured values ​​of soil fertility index and These are the minimum and maximum reference values ​​for the indicator, respectively. For the first The weights of the indicators; the soil fertility indicators include soil organic matter, total nitrogen, available phosphorus, available potassium, pH, conductivity of saturated extract and soil bulk density.

[0016] Preferably, in step five, the yield recovery rate is the ratio of the yield in the treated area to the yield in the normal farmland control area multiplied by 100%; the acceptance standard is that the yield recovery rate in the treated area is not less than 80%, and the comprehensive soil fertility index is not less than twice that of the unreclaimed obstacle area.

[0017] The present invention achieves the following beneficial technical effects compared to the prior art: This invention provides a synergistic treatment technology for waterlogging and salinization in coal mining subsidence reclamation areas. It achieves quantitative assessment and dynamic classification of the synergistic risks of waterlogging and salinization by constructing waterlogging stress index, salinization stress index, and synergistic risk index. Precise control of conditioner application is achieved through precise formulation of coal-based solid waste-based composite conditioners and optimized application decisions based on the synergistic risk index. Dynamic optimization of the drainage system is achieved through the linkage of micro-topography modification and optimized calculation of underground pipe drainage spacing. Reliable verification of the treatment effect is achieved through a dual-control test system and a dual evaluation path of yield recovery rate and comprehensive soil fertility index. This effectively solves the technical problems of difficulty in identifying the synergistic occurrence of waterlogging and salinization in high-water-level coal mining subsidence reclamation areas, lack of precise decision-making basis for conditioner application, inability of the drainage system to respond dynamically, and difficulty in reliably verifying the treatment effect within a limited period. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The present invention provides a synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The purpose of this invention is to provide a synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas, in order to solve the problems existing in the prior art.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example 1: Please refer to Figure 1 The specific implementation process of the present invention is as follows.

[0024] The first step is to deploy the monitoring system and collect data. In the coal mining subsidence reclamation area to be treated, a representative area is selected as the core monitoring zone. Groundwater level observation wells are installed within this core zone, with a depth of 2-3 meters below the water table to ensure year-round monitoring of groundwater level fluctuations. Around the observation wells, multi-depth soil sensors are installed at depths of 10cm, 30cm, 50cm, and 80cm to monitor changes in soil moisture content and conductivity in real time. Sensor data is automatically recorded and wirelessly transmitted to the data center via a data acquisition device, with a collection frequency set to once per hour to capture rapid response processes under rainfall and evaporation conditions. Simultaneously, every two weeks, soil samples are collected from three depths (0-20cm, 20-40cm, and 40-60cm) within the core monitoring zone using a five-point sampling method. These samples are then taken to the laboratory to determine the total salt content and composition of the eight major ions (Na+, Na ... + K + Ca 2+ Mg 2+ Cl - SO4 2- HCO3 - CO3 2- Nutrient indicators such as pH value, organic matter content, alkaline nitrogen, available phosphorus, and available potassium were measured. Furthermore, RTK-GPS (Real-Time Dynamic Differential Positioning) was used to conduct 1:500 scale elevation measurements on the site to be treated. A digital elevation model was generated based on the measurement data. The model was used to analyze and identify catchment areas, waterlogged areas, and natural drainage paths within the site, providing fundamental data support for subsequent micro-topographical modifications. For larger treatment areas, measurement points were laid out at a grid density of 50m × 50m to ensure that the digital elevation model accurately reflects the micro-undulations of the surface.

[0025] The second step, a combined risk assessment of waterlogging and salinization, is then performed. Based on the data obtained from real-time monitoring and periodic sampling in the first step, the waterlogging stress index and salinization stress index are calculated separately. The calculation of the waterlogging stress index comprehensively considers both groundwater level depth and rainfall recharge, and its formula is as follows: ; in, The groundwater level depth (unit: m) is obtained for real-time monitoring. The critical groundwater depth (unit: m) is determined based on the root distribution depth and flood tolerance of the target crop. For example, the critical depth for wheat is usually 0.8-1.0 m, and for corn it is 0.9-1.2 m. The slope coefficient of waterlogging response reflects the sensitivity of crops to waterlogging stress caused by changes in groundwater level. It is obtained by fitting the correspondence between historical monitoring data and crop growth response, and is generally taken between 0.5 and 2.0. The cumulative rainfall over the previous 30 days (unit: mm) is obtained from small weather stations installed in the fields or nearby weather monitoring stations; The average rainfall over the same period over many years (unit: mm) is calculated based on meteorological statistics from the local meteorological department over the past 10-30 years. The first part of the formula is an S-shaped curve function. When the groundwater level is deeper than the critical depth, the waterlogging stress approaches 0; when the groundwater level is deeper than the critical depth, the waterlogging stress approaches 1. The rainfall correction coefficient in the second part reflects the amplification effect of short-term heavy rainfall on waterlogging risk.

[0026] The formula for calculating the salt stress index is: ; in, The electrical conductivity of the saturated soil extract (unit: dS / m) was obtained through laboratory testing. The critical electrical conductivity for crop salt damage (unit: dS / m) is determined based on the salt tolerance of the target crop. For example, it is usually taken as 4 dS / m for wheat and 3 dS / m for corn. The threshold for severe salinization (unit: dS / m) is generally taken as 8 dS / m. Soil exceeding this value is considered severely salinized, and crop growth is severely inhibited. , , Na in soil solution + Ca 2+ Mg 2+ The concentration (unit: meq / L) was determined by ion chromatography or atomic absorption spectrometry. The first part of the formula reflects the stress level of total soil salinity on crops, and the second part, the sodium adsorption ratio, reflects the specific harm of sodium ions to soil structure and crop roots. Multiplying the two parts makes the salinity stress index take into account both the influence of total salt content and the differences in salt composition.

[0027] After obtaining the waterlogging stress index and salinization stress index, a synergistic risk index is further constructed, and its calculation formula is as follows: ; in, , , Let be the weighting coefficient, satisfying + + =1, the specific value was determined by combining the analytic hierarchy process (AHP) with the experience of regional experts. For coal mining subsidence reclamation areas with high groundwater levels, waterlogging and salinization often occur simultaneously and exacerbate each other, and the synergistic term... weight Typically, a value between 0.2 and 0.4 is used to reflect the synergistic amplification effect of waterlogging and salinization. For example, when both the waterlogging stress index and the salinization stress index are 0.5, the synergistic contribution is 0.25, significantly higher than the sum of their independent contributions. This reflects the two-way positive feedback mechanism of salt accumulation on the surface with capillary water under waterlogging conditions, and salt inhibiting crop transpiration, thus exacerbating waterlogging. Based on the calculated synergistic risk index, the reclaimed land is divided into three risk levels: Areas with a density <0.3 are considered low-risk and can be managed using standard field practices; areas with a density ≤0.3 are considered low-risk. A reading of <0.6 indicates a medium-risk area, requiring the activation of early warning and control measures. Areas with a concentration of ≥0.6 are considered high-risk areas, and emergency collaborative governance plans should be activated immediately.

[0028] Step three involves the precise formulation and application of the coal-based solid waste-based composite conditioner. First, a systematic safety assessment is conducted on the coal gangue, fly ash, and desulfurization gypsum stockpiled in the mining area. This safety assessment includes four dimensions: First, total quantity risk assessment, determining the total amount of heavy metals (cadmium, mercury, arsenic, lead, chromium, copper, nickel, and zinc) in the raw materials according to GB 15618 "Soil Environmental Quality Standard for Agricultural Land Soil Pollution Risk Control," and eliminating batches exceeding the screening values; second, leaching risk assessment, conducting leaching tests using the sulfuric acid-nitric acid method to determine the concentration of each heavy metal in the leachate, and eliminating batches exceeding the limits of GB 5085.3 "Identification Standard for Hazardous Waste - Leaching Toxicity Identification"; third, salinity risk assessment, determining the soluble salt content of the raw materials, and rejecting batches exceeding the acceptable threshold; and fourth, farmland suitability assessment, including the basic physicochemical properties of the raw materials such as pH value, particle size distribution, and organic matter content. Only raw materials that pass the safety assessment can proceed to the compounding stage. In the compounding process, safe and qualified coal gangue (30%-50%), fly ash (15%-25%), desulfurized gypsum (10%-20%), and decomposed straw or other organic materials (15%-25%), as well as calcium-based materials such as limestone powder (5%-10%), are mixed and compounded according to the designed proportions. After crushing, sieving (2mm sieve aperture), and thorough stirring, the finished coal-based solid waste-based composite conditioner is obtained. The specific compounding ratio of the conditioner can be optimized through orthogonal experiments based on the characteristics of the raw materials and the treatment objectives to obtain the best soil improvement effect and economic benefits.

[0029] The dosage of the conditioner is dynamically determined based on the synergistic risk index calculated in step two, specifically using the following decision formula: ; in, The optimized application rate of conditioner (unit: t / ha). The baseline application rate (unit: t / ha) is the recommended application rate of each compound formulation under medium-risk conditions, determined through previous orthogonal experiments. This represents the current sodium adsorption ratio in the soil, determined by the Na+ concentration in the soil solution. + Ca 2+ and Mg 2+ Concentration was calculated; The target sodium adsorption ratio is usually set to less than 13 based on the improvement target. The critical sodium adsorption ratio is usually taken as 18. Exceeding this value indicates that the soil is severely sodium-damaged and that more conditioner needs to be added. , The weighting coefficients, determined through response surface methodology, reflect the influence of synergistic risk level and sodium toxicity severity on the application dosage, respectively. The basic principle of this formula is as follows: based on the baseline application rate, when the synergistic risk index exceeds the low-risk threshold of 0.3, the application rate is increased to address the increased risk; when the soil sodium adsorption ratio is higher than the target value, the application rate is further increased to accelerate sodium ion leaching and soil structure improvement. After determining the application rate, the conditioner is evenly spread on the top 0-20cm layer of the reclaimed land, followed by rotary tillage to ensure thorough mixing. Immediately after application, irrigation is carried out to leach salts, with the irrigation volume sufficient to wet the topsoil and allow excess water to drain away through underground pipes, generally controlled at 450-600m³. 3 / ha. After salt leaching, cover the surface with transparent mulch to retain moisture. Mulch can effectively reduce soil evaporation and salt return, while increasing soil temperature to promote the maturation of conditioners and the restoration of soil structure.

[0030] Step four involves coordinated regulation of micro-topography and drainage. Based on the digital elevation model generated in Step one, catchment low-lying areas and natural drainage channels within the site are identified. For the coordinated risk index... In high-risk areas with a risk level ≥0.5, differentiated micro-topographical modifications are implemented based on terrain conditions. For low-lying plots located in catchment areas, a raised-field model is adopted, where topsoil is stripped and piled in the central area of ​​the plot, raising the central part by 30-50cm above the original surface, forming a turtle-back shaped micro-elevation. Crops are planted on the raised turtle-back. Shallow drainage ditches are retained around the turtle-back to collect rainwater runoff and guide it to the drainage system. For plots with gentler slopes and poor drainage paths, a ridge-planting model is adopted, where ridges are created along the drainage direction (perpendicular to the contour lines), with a ridge height of 20-30cm and a ridge width of 60-80cm. Crops are planted on the top of the ridges, and the furrows serve as micro-channels for drainage. The two models can be flexibly combined according to the shape and area of ​​the plot. At the same time, drainage pipes are buried within the reclaimed plots. The pipes are made of corrugated plastic pipes with a filter layer, with a diameter of 80-100mm, and wrapped with a non-woven geotextile filter layer to prevent clogging. The burial depth of underground pipes is determined based on a combination of groundwater level control targets and crop root depth, generally ranging from 1.0 to 1.5 meters. The spacing between underground pipes is calculated using the following optimized formula: ; in, Soil saturated hydraulic conductivity (unit: m / d) was determined through a field double-ring infiltration test. Burial depth of concealed pipes (unit: m); The design drainage time (unit: d) is the time required for the groundwater level to drop from the initial level to the target level. It is determined based on the flood tolerance of the target crop and is generally taken as 2-3 days. Effective porosity of soil (dimensionless) refers to the proportion of soil pores from which gravity water can drain out to the total pores, and is determined by the indoor ring sampler method. The water yield (dimensionless) reflects the amount of water released per unit area of ​​soil when the groundwater level drops by a unit height. It is determined by pumping tests or indoor water release tests. The initial groundwater level depth (unit: m) is measured by the observation well. The target groundwater level depth (in meters) to be achieved after the designed drainage time is determined based on the maximum allowable groundwater level of the target crop. This formula is derived from the unsteady flow seepage theory, and its physical meaning is that the spacing between the underground pipes is positively correlated with the soil's water conductivity, drainage time requirements, and groundwater level drawdown, while it is negatively correlated with the soil's water holding capacity and water supply capacity. After the underground pipes are installed, their outlets are connected to a collection well or drainage ditch. A water level control gate is installed in the collection well, and the gate opening is dynamically adjusted to control the drainage speed based on real-time monitoring of groundwater level dynamics and changes in the collaborative risk index. When the risk level rises to medium or higher, increase the gate opening to accelerate drainage; when When the risk level drops to low, reduce the opening size appropriately to maintain suitable soil moisture.

[0031] Step five involves verifying the effectiveness of the dual-control system. After completing the aforementioned treatment measures, normal farmland control areas and unreclaimed obstacle control areas were established around the treated plots. The normal farmland control areas were adjacent, non-subsided, normally cultivated farmland with the same soil type and similar topography as the treated plots, representing the regional productivity baseline. The unreclaimed obstacle control areas were waterlogged or saline-alkali wasteland located within the same coal mining subsidence area that had not undergone any treatment measures, representing the initial obstacle level before treatment. All three areas (treatment area, normal farmland control area, and unreclaimed obstacle control area) maintained the same crop variety, sowing density, fertilization level, and field management practices throughout the crop growing season to ensure the scientific validity of the comparison. Monitoring was conducted every half month throughout the crop's growth period, including groundwater level depth, soil moisture content and electrical conductivity at each layer, soil structural parameters (bulk density, total porosity, capillary porosity), and crop physiological indicators (plant height, leaf area index, SPAD value). During the harvest period, yield sample plots were taken in each region using a five-point sampling method to determine the actual yield and yield components (number of ears, number of grains per ear, and thousand-grain weight). At the same time, topsoil samples were collected from each region to determine the various indicators included in the comprehensive soil fertility index.

[0032] The formula for calculating the comprehensive soil fertility index is: ; in, To account for the total number of soil fertility indicators included in the evaluation, this process selected seven core soil fertility indicators: soil organic matter (g / kg), total nitrogen (g / kg), available phosphorus (mg / kg), available potassium (mg / kg), pH value, saturated extract conductivity (dS / m), and soil bulk density (g / cm³). 3 ); For the first Measured values ​​of soil fertility index and These are the minimum and maximum reference values ​​for the indicator, respectively. For the first The weights of the indicators are determined using principal component analysis or analytic hierarchy process (AHP). It should be noted that for the two inverse indicators, saturated extract conductivity and soil bulk density (higher values ​​indicate poorer soil fertility), the numerator is adjusted to [value missing] during normalization. This is to ensure that the comprehensive soil fertility index and soil fertility level maintain a positive correlation.

[0033] The formula for calculating the yield recovery rate is: Yield Recovery Rate (%) = (Yield in the treated area / Yield in the normal farmland control area) × 100%. The acceptance criteria for this process are: the yield recovery rate in the treated area must be no less than 80% (i.e., reaching more than 80% of the normal farmland yield), and the comprehensive soil fertility index must be at least twice that of the unreclaimed obstacle control area. Only when both conditions are met simultaneously can the treatment effect be considered to have met the acceptance criteria. If the acceptance criteria are met in both years within a two-year verification period, it proves that this process has good stability and reliability; if the criteria are not met in any year, it is necessary to review the monitoring data, analyze the impact of factors such as groundwater level fluctuations, extreme weather events, or field management deviations, and make targeted adjustments to the conditioner application plan and drainage control strategy.

[0034] In summary, this invention achieves the synergistic management of waterlogging and salinization in high-water-level coal mining subsidence reclamation areas through a complete technical closed loop of "monitoring and sensing → risk assessment → precise regulation → effect verification." Starting with dynamic monitoring of groundwater levels and soil salinity, the risk levels of waterlogging and salinization are quantitatively identified through a synergistic risk index. Based on this, the precise application rate of conditioning agents and the micro-topography-drainage synergistic regulation scheme are determined. Finally, the effects of yield recovery and soil fertility improvement are reliably verified through a dual-control experimental system. The entire technical route is logically clear and interconnected, with well-defined parameter transfer and feedback adjustment mechanisms between each step. It overcomes the shortcomings of existing technologies, such as separate management of waterlogging and salinization, reliance on empirical conditioning agent application, static drainage design, and lack of control groups for effect verification. This invention demonstrates significant technological advancement and practical value.

[0035] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0036] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A synergistic treatment technology for waterlogging and salinization in coal mining subsidence reclamation areas, characterized in that, Includes the following steps: Step 1: Deployment of the monitoring system and data acquisition. Groundwater level observation wells and multi-depth soil sensors are deployed in the coal mining subsidence reclamation plots to be treated to monitor groundwater level depth, soil moisture content and electrical conductivity in real time. Soil samples at different depths are collected regularly to determine soil total salt content, ionic composition, pH, organic matter and nutrient indicators. Simultaneously, micro-topographic elevation measurements are carried out to generate a digital elevation model. Step 2: Collaborative risk assessment of waterlogging and salinization. Based on the data obtained in Step 1, calculate the waterlogging stress index and salinization stress index, and then construct a collaborative risk index to classify the reclaimed land plots by risk. Step 3: Precise formulation and application of coal-based solid waste composite conditioner. First, a safety assessment is conducted on the raw materials of coal gangue, fly ash, and desulfurization gypsum to eliminate high-risk batches. Then, the safe raw materials are compounded with organic materials and calcium-based materials in a certain proportion to prepare the coal-based solid waste composite conditioner. The application rate is optimized based on the synergistic risk index in Step 2. The conditioner is applied to the surface layer of the reclaimed land and mixed evenly with the soil. After application, water is irrigated to leach salt and the land is covered with mulch to retain moisture. Step 4: Micro-topography-drainage coordinated regulation. Based on the digital elevation model in Step 1 and the coordinated risk index in Step 2, micro-topography modification is implemented in high-risk areas. Drainage pipes are buried in the reclaimed land, and the spacing of the pipes is optimized based on the soil saturated hydraulic conductivity, the burial depth of the pipes, the design drainage time, and the dynamic calculation of the groundwater level. Step 5: Verify the effectiveness of the dual-control system. Set up a normal farmland control area, an unreclaimed obstacle control area, and a process treatment area. During the crop growing season, regularly monitor the groundwater level, soil water and salt profile, soil structure parameters, and crop physiological indicators in each treatment area. At harvest, measure yield and soil fertility indicators. Evaluate the treatment effect by the yield recovery rate and the multiple of improvement in the comprehensive soil fertility index.

2. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: In step one, the soil multi-depth sensors are buried at depths of 10cm, 30cm, 50cm, and 80cm. The depth of the groundwater level observation well is 2-3m below the water table. The periodic collection refers to collecting soil samples from three layers of soil at depths of 0-20cm, 20-40cm, and 40-60cm every half month.

3. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: The formula for calculating the collaborative risk index in step two is as follows: ； in, The waterlogging stress index, This is the salt stress index. , , The weighting coefficients are determined using the analytic hierarchy process (AHP), and + + =1; <0.3 indicates low risk, 0.3≤ <0.6 indicates medium risk. A value of ≥0.6 indicates a high risk.

4. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 3, characterized in that: The formula for calculating the waterlogging stress index is as follows: ； in, The depth of the groundwater level. This is the critical groundwater depth. The slope coefficient of the waterlogging response. This represents the cumulative rainfall over the previous 30 days. This represents the average rainfall for the same period over many years. The formula for calculating the salinity stress index is as follows: ； in, The conductivity of the saturated soil extract. The critical electrical conductivity for crop salt damage. The threshold for severe salinization. , , Na in soil solution + Ca 2+ Mg 2+ The concentration.

5. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: The safety assessment in step three includes four dimensions: total risk assessment, leaching risk assessment, salinity risk assessment, and farmland suitability assessment. Batches with total heavy metal content exceeding the GB 15618 screening value, leaching concentration exceeding the GB 5085.3 limit, or soluble salt content exceeding the standard will be rejected.

6. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 3, characterized in that: In step three, the optimal application rate of the coal-based solid waste-based composite conditioner is dynamically adjusted based on the synergistic risk index and the soil sodium adsorption ratio. The higher the synergistic risk index or the greater the soil sodium adsorption ratio, the higher the application rate.

7. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: The micro-topography modification in step four includes the raised field mode and the ridge mode. The raised field mode involves raising a local plot of land by 30-50cm in the catchment area to form a turtle-back shaped micro-elevation. The ridge mode involves creating ridges along the drainage direction, with a ridge height of 20-30cm and a ridge width of 60-80cm.

8. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: The optimized spacing of the drainage pipes in step four is calculated using the following formula: ； in, This refers to the spacing between concealed pipes. For soil saturated hydraulic conductivity, For the depth of the concealed pipe burial, To design drainage time, For soil effective porosity, For water supply degree, This represents the initial groundwater level depth. The target groundwater level depth after the designed drainage time.

9. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: The formula for calculating the comprehensive soil fertility index in step five is as follows: ； in, For the first Measured values ​​of soil fertility index and These are the minimum and maximum reference values ​​for the indicator, respectively. For the first The weights of the indicators; the soil fertility indicators include soil organic matter, total nitrogen, available phosphorus, available potassium, pH, conductivity of saturated extract and soil bulk density.

10. The synergistic treatment process for waterlogging and salinization in coal mining subsidence reclamation areas according to claim 1, characterized in that: In step five, the yield recovery rate is the ratio of the yield in the treated area to the yield in the normal farmland control area multiplied by 100%; the acceptance standard is that the yield recovery rate in the treated area is not less than 80%, and the comprehensive soil fertility index is not less than twice that of the unreclaimed obstacle area.

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