Ecological restoration method for open-pit coal mine based on biological-geological synergistic mechanism

Abstract

The application discloses an open-pit coal mine ecological restoration method based on a biological-geological collaborative mechanism and relates to the technical field of ecological environment restoration, and comprises the following steps: S001, temperature sensing units and strain sensing units are arranged in a region to be restored; temperature and strain data under a day-night cycle are continuously collected; a thermal expansion coefficient difference distribution map and a stress concentration distribution map are generated based on data inversion; and a thermal diagnosis baseline is constructed.The application constructs a comprehensive restoration system of 'thermal diagnosis-structure optimization-dynamic regulation-crack self-healing-closed-loop feedback', solves the crack failure problem caused by thermal expansion and cold contraction differences in a mining area in a drought plateau, improves water retention, heat insulation and structural toughness, realizes long-term stability and self-adaptive operation of an ecological system, and fills the gap in the prior art.

Description

Technical Field

[0001] This invention relates to the field of ecological environment restoration technology, specifically to an ecological restoration method for open-pit coal mines based on a biological-geological synergistic mechanism. Background Technology

[0002] Ecological restoration of open-pit coal mines based on a bio-geological synergy mechanism refers to the process of restoring and reconstructing the overall ecosystem of the mining area by organically combining geological improvement measures with biological reconstruction measures after environmental problems such as surface damage, vegetation loss, and soil degradation caused by mining activities in and around the mine. Its core idea is to first reshape the topography and geomorphology, improve the soil and rock matrix, and construct soil and water conservation structures in the mining-disturbed area at the geological level, providing stable site conditions for biological restoration; at the biological level, suitable pioneer plants, nitrogen-fixing plants, and soil microbial communities are introduced. Through vegetation community succession, root soil stabilization, and microbial improvement of soil structure, soil fertility restoration and ecological function restoration are accelerated. The two aspects form a mutually reinforcing relationship: geological improvement provides physical and chemical environmental protection for biological growth, while biological action, in turn, improves surface stability and nutrient cycling, ultimately constructing a stable, self-sustaining mining area ecosystem.

[0003] Existing technologies have the following shortcomings: Current technologies for ecological restoration in arid plateau mining areas primarily rely on a combination of physical filling and shallow vegetation planting, neglecting the dynamic cumulative effect of significant differences in the thermal expansion coefficients of different materials under drastic diurnal temperature variations. Under intense diurnal temperature fluctuations, the artificial vegetation layer and the underlying improved soil matrix undergo varying degrees of thermal expansion and contraction during rapid temperature rises and falls. This difference is amplified over multiple days, ultimately inducing high-density network cracks within the cover layer. These cracks not only significantly increase the permeability of evaporation channels between the surface and deeper soil layers, accelerating the loss of matrix moisture, but also directly expose the underlying loose, low-erosion-resistance materials, causing them to be rapidly lost under the combined effects of wind and water erosion. The resulting problems of water depletion, soil loosening, and vegetation root instability exhibit a chain reaction of degradation, leading to severe consequences such as functional decline or even large-scale failure of the ecological restoration area in a short period.

[0004] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide an ecological restoration method for open-pit coal mines based on a biological-geological synergistic mechanism to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an ecological restoration method for open-pit coal mines based on a biological-geological synergistic mechanism, comprising the following steps: S001, Temperature sensing units and strain sensing units are deployed in the area to be repaired to continuously collect temperature and strain data under the diurnal cycle. Based on the data inversion, thermal expansion coefficient difference distribution map and stress concentration distribution map are generated to construct thermal diagnostic baseline. S002, based on the thermal diagnostic baseline, combined with seasonal changes, solar radiation history and surface thermal conductivity data, calculates the critical crack index under different thermal cycling conditions, identifies thermal stress sensitive areas, forms a list of high-risk units and sorts the repair priorities. S003, a graded buffer structure is constructed for high-risk units. The upper layer is a biochar plant matrix layer for water retention and heat insulation, and the lower layer is a polymer mineral powder buffer pad layer for dispersing thermal stress. Regularly arranged micro-expansion joints are set to alleviate stress concentration. S004 incorporates phase change heat storage particles and capillary barrier materials within a buffer structure. Combined with precise nighttime drip irrigation, it maintains the rhizosphere moisture content within the target range, reduces the temperature gradient within the structure, and inhibits the accumulation of tensile strain. S005 incorporates microcapsule cementing agents and carbonate-generating bacteria into a surface cover structure that has been regulated to form a stable thermal and humid environment. When the crack initiation threshold is triggered, the cementing active ingredients are released and carbonate deposits are formed, thereby achieving self-healing of cracks and restoring structural continuity. S006, based on self-healing feedback, continuously collects data on residual strain, crack density, and moisture content, dynamically updates the crack index and control parameters, and regularly optimizes the plant substrate ratio and drip irrigation strategy to achieve long-term stability and adaptive operation of the ecological restoration system.

[0007] Preferably, step S001 includes: Select several representative observation areas within the area to be repaired, and set up several observation lines with a spacing of 20 to 30 meters in each observation area. Bury fiber optic temperature sensing units and strain sensing units every 5 to 10 meters on each observation line. The fiber optic temperature sensing unit is buried 10 cm below the surface to record the temperature change process, and the strain sensing unit is buried 25 cm at the interface between the artificial cover layer and the modified matrix to record the micro-deformation response caused by thermal stress. After the sensing unit is running stably, temperature and strain data are continuously collected for no less than 30 days, with recording intervals of 10 minutes and 5 minutes, respectively. The temperature and strain changes at each node are calculated within a typical day-night thermal cycle. Based on the above data, thermal expansion coefficient difference distribution map and stress concentration distribution map are generated, and a thermal diagnostic baseline with time and spatial resolution is established on this basis to provide data support for subsequent high-risk unit identification and graded repair design.

[0008] Preferably, step S002 includes: The thermal expansion coefficient difference distribution map and the stress concentration distribution map are processed into a unified grid using 5-meter by 5-meter spatial units, and each unit is assigned a thermal strain attribute value. An environmental parameter database including slope angle, average annual sunshine duration, surface thermal conductivity and surface material composition is established for each grid cell, and typical temperature difference and sunshine data of the four seasons are superimposed to evaluate the cumulative frequency of its thermal expansion and contraction stress sensitive state throughout the year. High-risk units with high sensitivity scores and spatial continuity are merged to form high-risk crack areas, and are prioritized according to geographical boundaries, area, and contact relationship with slopes or vegetation areas. The high-risk areas after sorting are spatially matched and verified with the thermal diagnostic baseline to confirm the integrity of the monitoring coverage, and a visualization of the operation is output, including boundary coordinates, priority level and recommended repair time.

[0009] Preferably, step S003 includes: Boundary mapping and foundation preparation were carried out within the high-risk crack unit area. After removing impurities, the original ground was compacted, and construction elevation lines and micro-expansion joint layout lines were set. After preparation, a lower buffer layer is laid. The mixture of polyvinyl alcohol high-extensibility polymer and pozzolanic mineral powder with a particle size of 0.1 mm to 0.3 mm is used to form a continuous buffer layer by spreading and compacting it to a thickness of 10 cm. A top layer of plant substrate is laid on top of the buffer layer. It consists of biochar, humus, coconut fiber and humic acid. The total thickness is controlled between 10 cm and 12 cm, and the porosity is controlled between 35% and 40%. Micro-expansion joints are laid out in the plant substrate layer with a grid spacing of 1 meter, with a joint width of 1 cm and a joint depth of 6 cm. The joints are filled with a mixture of bentonite and medium sand to form a stress-regulating structure with deformation release function.

[0010] Preferably, step S004 includes: Spherical encapsulated inorganic salt hydrate phase change heat storage particles are embedded in the middle of the plant matrix layer. The embedding depth is 5 cm to 8 cm. The embedding points are distributed in a diamond array with a spacing of 20 cm between adjacent embedding points. The number of heat storage particles embedded at a single point is 10. A capillary barrier sheet made of polypropylene fiber and diatomaceous earth is laid between the plant substrate layer and the lower buffer layer. The sheet is 10 mm thick and has a unit area mass of 150 g / m². Water-resistant adhesive tape is used to bond the joints and stainless steel U-shaped nails are used to fix the edges. Water regulation is achieved through low-pressure gravity drip irrigation at night. Each drip irrigation pipeline serves an area of ​​4 square meters, with a dripper orifice diameter of 0.8 mm and a dripper spacing of 50 cm. The drip irrigation time is controlled between 1:00 AM and 3:00 AM, and the water replenishment per unit area is 4 liters per night. By continuously monitoring changes in ground temperature and soil moisture content, the soil moisture content in the plant rhizosphere is maintained within the target range of 15% to 20% to reduce the temperature gradient caused by diurnal temperature differences and inhibit the accumulation of structural tensile strain.

[0011] Preferably, step S005 includes: Microcapsule binder and carbonate-generating microbial agent are mixed and incorporated into the plant matrix layer. The microcapsules have a particle size of 0.8 mm to 1.2 mm and possess the characteristic of rupturing under structural tensile strain exceeding 250 με. The microbial agent is alkalophilic Bacillus powder with a viable count of not less than 10. 8 CFU / g; The composite material and plant substrate were dry-mixed at a mass ratio of 1:25 and laid evenly with a layer thickness of 10 cm. During laying, a soft rubber scraper was used to level the surface and a light compactor was used to compact it to a porosity of 35% to 40%. During the operation of the covered structure, when the monitored strain exceeds the trigger threshold, the microcapsules release the cementing liquid components, activate the bacterial agent to secrete urease and trigger the calcium carbonate deposition reaction, forming a structural fill in the crack; After the material was laid, monitoring cycles of 1 day, 3 days, 7 days and 14 days were set to continuously detect strain, crack width and thermal conductivity to verify the sealing effect of the self-healing reaction and the degree of structural recovery.

[0012] Preferably, step S006 includes: Three layers of residual strain fiber optic measurement lines, crack width measurement paper strips, and multi-depth soil moisture probes were vertically deployed at the interface between the plant matrix layer and the improved soil matrix to form a multi-dimensional monitoring network for the self-healing process of microcracks. The obtained monitoring data were integrated and analyzed on a 7-day cycle. The changes in crack width, the decrease in residual strain and the fluctuation in moisture content were compared to identify areas of material performance deviation and insufficient response, and the critical crack index and control threshold of the area were updated. Based on the updated results, the plant substrate ratio and microbial agent carrier type were adjusted, and the nighttime drip irrigation strategy was optimized, including irrigation time, frequency and single irrigation volume, to ensure that the rhizosphere moisture content is maintained in the range of 16% to 20%. The aforementioned parameter combinations are summarized quarterly to assess their effectiveness in crack control and ecological stability. When the closure rate is greater than 85% and the strain decreases by more than 30% for two consecutive quarters, the corresponding parameters are solidified as the standard operating strategy for the region.

[0013] The technical effects and advantages provided by the present invention in the above technical solution are as follows: This invention effectively solves key technical challenges in arid plateau mining areas caused by the mismatch between the thermal expansion and contraction of artificial vegetation cover and improved soil matrix, resulting in frequent network cracks, severe water loss, unstable vegetation, and ecological restoration failure, by constructing a comprehensive restoration system encompassing the entire process from "thermal diagnosis, structural optimization, dynamic regulation, crack self-healing, and closed-loop feedback." This system addresses these challenges through a synergistic construction of a comprehensive restoration system that integrates "thermal diagnosis, structural optimization, dynamic regulation, crack self-healing, and closed-loop feedback." This method not only achieves, for the first time, the dynamic identification of differences in material thermophysical properties and the accurate assessment of regional stress concentration risks in multi-layered composite structures, but also significantly improves the water retention, thermal insulation, and structural toughness of the surface cover layer through the synergistic construction of a graded buffer structure, phase change regulation, hydrothermal linkage, and a microcrack self-healing mechanism, thereby delaying the crack initiation and propagation process. Meanwhile, by introducing a continuous monitoring and feedback mechanism, an intelligent closed-loop regulation capability is established during the operation of the cover layer, enabling the plant substrate ratio and drip irrigation strategy to be dynamically adjusted according to environmental disturbances and structural responses, forming an ecological restoration system with long-term stability and self-adaptive capabilities. This significantly improves the risk resistance and sustainable operation level of the ecological restoration project in the mining area, filling the gap in the field of multi-factor dynamic coupling regulation of existing technologies. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a flowchart of the ecological restoration method for open-pit coal mines based on the biological-geological synergistic mechanism of the present invention. Detailed Implementation

[0016] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the description of this disclosure will be more complete and fully convey the concept of the exemplary embodiments to those skilled in the art.

[0017] This invention provides, for example Figure 1 The open-pit coal mine ecological restoration method based on the bio-geological synergistic mechanism shown includes the following steps: S001, fiber optic temperature sensing units and strain sensing units are deployed in the area to be repaired to continuously collect surface temperature data and strain response data under the diurnal cycle. Based on the collected data, thermal expansion coefficient difference distribution map and stress concentration distribution map are generated to construct a thermal diagnostic baseline for crack risk analysis. To accurately monitor the thermal expansion and contraction response of surface cover structures in open-pit coal mine remediation areas under severe diurnal temperature variations, and to identify potential thermal crack risk areas accordingly, this invention proposes a method for constructing a thermal diagnostic baseline based on inversion of on-site sensor data. The specific implementation steps are as follows: Within the area to be restored, several representative observation areas were selected based on landform type, distribution characteristics of mining subsidence areas, and slope aspect differences. Several observation lines were set up within each observation area, with a spacing of 20 to 30 meters between each line. Fiber optic temperature sensing units and strain sensing units were buried at fixed intervals of 5 to 10 meters along the observation lines. The fiber optic temperature sensing units employed distributed fiber Bragg grating temperature measurement technology, using fiber optic cables pre-buried 10 cm below the surface soil to achieve spatially resolved recording of surface temperature changes over time. The strain sensing units employed embedded fiber optic interferometric strain detection elements, buried at approximately 25 cm at the interface between the artificial cover layer and the modified substrate, to detect the microscopic deformation response of the surface cover structure under diurnal temperature fluctuations. During deployment, it was ensured that the sensing units were in close contact with the soil and stabilized with standard mixed mortar to prevent signal distortion due to gaps or loosening. To further cover different slope aspects and thermal environmental conditions, the selection of observation areas should take into account topographical locations such as the south slope, north slope, platform surface, and slope toe.

[0018] After the aforementioned sensing units are deployed and operating stably, a continuous data acquisition operation will be conducted for no less than 30 days. During the data acquisition period, the temperature data recording interval will be set to 10 minutes, and the strain data recording interval will be set to 5 minutes to ensure that the entire process of thermal-stress response can be captured during a typical day-night cycle. Temperature data is measured in degrees Celsius, and strain data is measured in microstrain (…). Records are kept in units of 1 / 3. To avoid the impact of extreme weather on data accuracy, meteorological data analysis should be conducted in advance to exclude periods of rain, snow, thunderstorms, and strong winds, prioritizing observation windows with clear skies and significant diurnal temperature variations. All sensor data is transmitted to storage devices via photoelectric conversion equipment, stored in a structured tabular file format, with fields including timestamp, spatial coordinates, temperature value, and strain value. During the data acquisition process, three manual inspections are conducted daily based on the site environment to check the contact status of the sensor cables, settlement changes in the buried area, and the integrity of the sensor response, ensuring the continuity and accuracy of the collected data.

[0019] After completing the continuous observation cycle, the collected raw temperature and strain data were cleaned, registered, and subjected to difference analysis. Specifically, the process involved using the period from sunrise to sunrise the following day as a complete diurnal thermal cycle, and extracting the temperature variation amplitude at each observation node within that cycle. With strain variation amplitude To connect different nodes within the same region The relationship was plotted as a scatter plot, and the coefficient of thermal expansion for that region was fitted using the least squares method. ,Right now The unit is To further reveal the stress concentration characteristics caused by uneven thermal expansion, the difference in thermal expansion coefficient Δ at the interface of different materials was analyzed. Gridded calculations were performed, with each calculation cell having a side length of 5 meters, generating a two-dimensional thermal expansion coefficient difference distribution map. Simultaneously, based on the dramatic spatial gradient of the strain response, high stress concentration regions were identified, and a stress concentration distribution map was plotted. This map uses a color-gradient representation; higher values ​​indicate a steeper stress gradient and a higher probability of crack initiation. All the above distribution maps are represented as equivalent rasterized representations of the observed area, facilitating subsequent overlay with ecological restoration design drawings. Compared to traditional static estimation methods based on material parameter tables, this step utilizes in-situ monitoring data under actual climatic conditions, fully reflecting the differences in the thermal-strain response of the structure under real operating conditions, and exhibiting higher spatial accuracy and environmental adaptability.

[0020] By combining the distribution maps of thermal expansion coefficient differences and stress concentration distributions, a diagnostic baseline reflecting the actual thermo-mechanical coupling behavior of the observed area under typical diurnal thermal cycling conditions is constructed. This baseline analyzes each grid cell, recording its average thermal expansion coefficient, thermal expansion coefficient difference, maximum strain response value, and corresponding coordinate information, and organizing these data chronologically to form a spatial-temporal dual-dimensional thermo-mechanical characteristic database. This diagnostic baseline not only accurately identifies thermally sensitive areas, stress accumulation areas, and high-risk areas for potential crack initiation in the surface cover structure, but also provides data support for subsequent material optimization, structural buffer design, and crack prevention measures. This method has significant advantages over existing technologies, particularly in its ability to perform high-resolution monitoring combined with actual operating conditions, dynamically feeding back surface structure performance, providing quantitative evidence for risk prediction and intervention strategies throughout the ecological restoration process, and significantly improving the scientific rigor and engineering controllability of restoration projects.

[0021] This step aims to provide a quantitative basis and spatial positioning foundation for accurate crack risk identification in open-pit coal mine ecological restoration areas, thereby overcoming the uncertainties and low adaptability caused by traditional reliance on static experience judgment and material parameter estimation. In arid plateau or mining areas with strong temperature differences, surface cover structures are prone to thermal expansion and contraction responses under drastic diurnal temperature changes. This is especially true in structures composed of multiple heterogeneous materials (such as plant matrix, biochar layer, and mineral powder matrix), where the different thermal expansion coefficients of each layer easily lead to thermal stress concentration zones at the interfaces, thus inducing structural cracks. This step uses fiber optic temperature and strain sensing units to acquire continuous temperature changes and strain response data of the surface under real diurnal climate conditions. Combined with spatial location and geological characteristics, it inverts to obtain thermal expansion coefficient difference distribution maps and stress concentration distribution maps. This thermal diagnostic baseline established based on measured data can not only reveal the non-uniformity of thermal coupling within the cover structure but also accurately identify thermal stress-sensitive areas and potential crack-prone areas, providing preliminary guidance for subsequent ecological restoration processes such as developing graded treatment strategies, optimizing material combinations, laying buffer structures, and setting micro-expansion joints. This step, by digitizing, spatializing, and temporally serializing the thermal response, establishes a dynamic monitoring foundation with high spatiotemporal resolution for the ecological restoration system, realizing the transformation from traditional experience-based restoration to a data-driven, precise intervention-based restoration model. It is the core preliminary step in the entire restoration methodology.

[0022] S002, based on the generated thermal expansion coefficient difference distribution map and stress concentration distribution map, combined with seasonal variation parameters, slope aspect solar radiation time history data and surface thermal conductivity data, calculate the critical crack index of the surface cover structure under different thermal cycling conditions, identify thermal stress sensitive areas, and form a list of high-risk crack units including priority repair areas. To achieve early identification of structural cracks induced by thermal expansion and contraction in open-pit coal mine remediation areas and to establish a crack risk list with spatial priority and engineering guidance, it is necessary to further integrate environmental factors affecting the intensity of surface thermal cycling based on the existing thermal expansion coefficient difference distribution map and stress concentration distribution map. This involves using multi-source parameter superposition to determine the sensitivity of the overburden structure to crack formation under different thermal conditions, ultimately establishing a list of high-risk crack units with priority for remediation. This process can be implemented according to the following steps: The thermal expansion coefficient difference distribution map and stress concentration distribution map were unified using a raster method, with a spatial resolution of 5 meters by 5 meters per grid cell. Each grid cell was assigned a numerical attribute representing the thermal strain characteristics of the region. The thermal expansion coefficient difference was derived from the inversion results of the previous stage of monitoring data, indicating the degree of inconsistency in deformation between this cell and its adjacent cells due to differences in thermal conductivity. The stress concentration intensity was derived from the gradient analysis results of the strain response monitoring data, indicating the stress convergence trend in the region driven by temperature changes. After completing the thermal data standardization, geographic environmental information attributes were established for each grid cell, including: slope angle, slope percentage, annual average total sunshine duration, maximum sunshine angle, surface thermal conductivity, surface moisture content, soil particle distribution ratio, surface cover structure thickness, and material combination type. The aforementioned attribute data were acquired through a combination of field measurements and remote sensing data: slope aspect angle and slope percentage were obtained by inversion from 3D topographic laser scanning data; solar radiation parameters were calculated from the daily solar altitude angle throughout the year and converted using local meteorological station measured radiation data; thermal conductivity was measured by deploying heat flux densities and thermocouple probes in the sample area; and surface structure parameters were directly collected from previously manually laid data. All the above data were aligned according to a unified coordinate system to ensure the accuracy of subsequent spatial overlay analysis.

[0023] Based on the established spatial unit thermal-mechanical property and environmental factor database, the structural stability risk of each grid unit under typical annual thermal cycling conditions is assessed. To account for seasonal differences, four representative periods—the vernal equinox, summer solstice, autumnal equinox, and winter solstice—are selected. The corresponding diurnal temperature range curves, sunshine duration distribution, and surface temperature change rate are continuously monitored in the field, and the temperature range amplitude and frequency of change for each period are calculated. These climate data are superimposed onto the thermal expansion characteristics of each spatial unit, focusing on whether the combined conditions of a diurnal temperature range exceeding 20°C, thermal conductivity less than 0.8 W / (m·K), south-facing slope, and annual average sunshine exceeding 2200 hours hold true within that unit. If true, the unit is considered a high-risk location with thermal expansion and contraction stress sensitivity in that season. By extending the above analysis to all representative seasons and accumulating the sensitivity assessment times for each unit, the region with the longest high-risk period throughout the year is finally identified. Compared to traditional methods of zoning based on topography or empirical material properties, this method has a stronger ability to reflect temporal variability and more realistically reflects the physical basis of thermal crack formation under the combined effects of geography and climate.

[0024] After completing the spatial overlay of risk sensitivity across the entire region, all grid units are sorted from high to low according to their sensitivity scores. High-risk units that are geographically continuous, have similar scores, and are less than 15 meters apart are merged. The merging method involves first clustering by grid centroid coordinates, then constructing continuous boundaries based on unit boundary adjacency, ultimately forming several spatially contiguous high-risk crack areas. Each merged unit must possess the following attributes: number, set of spatial boundary coordinate points, area, number of high-risk grids, slope aspect classification, shortest distance to the slope or drainage channel, and contact length with existing vegetation cover. Based on these attributes, priority for remediation is determined according to the following three criteria: first, areas located on the outer edge of the slope or adjacent to the platform are prioritized over areas inside the platform; second, areas with a contact length exceeding 50 meters with existing vegetation communities are prioritized over isolated areas; and third, areas containing more than 80% high-risk grids are prioritized over areas with a lower number. Each area will be assigned a specific ranking number as the basis for the order of remediation implementation.

[0025] The constructed list of high-risk crack areas is spatially matched with the thermal diagnostic baseline established in the previous step. The verification includes: whether all high-risk areas are located within the monitored coverage area; whether there are spatial blind spots where crack index changes abruptly but no sensors are installed; and whether the identified areas are consistent with the principal stress direction in the high-stress concentration map. If uncovered areas exist, additional sensors will be deployed in subsequent stages; if discrepancies are found, the thermal conductivity measurement parameters and solar radiation input values ​​for that area will be re-verified. After verification, the spatial boundaries, priority levels, seasonal sensitivity periods, and recommended repair time windows for each high-risk area are exported in tabular form and overlaid onto the electronic topographic map to generate a visual repair operation map. This map will serve as the direct basis for material layout design, manual paving sequence, and the layout of hydrothermal control equipment, laying the spatial strategy foundation for the subsequent construction of crack-resistant buffer structures and dynamic control systems.

[0026] This step aims to quantitatively identify and spatially prioritize the risk of thermal expansion and contraction-induced cracking in open-pit coal mine ecological restoration areas, providing a precise and efficient decision-making basis for subsequent ecological intervention measures. In arid plateau or mining environments with drastic diurnal temperature variations, surface cover structures are highly susceptible to crack formation at interfaces or structurally weak areas, especially under conditions of differences in material thermal expansion coefficients and uneven stress distribution. This leads to a series of cascading ecological degradation problems, such as water loss, vegetation degradation, and decreased soil erosion resistance. This step uses the thermal expansion coefficient difference distribution map and stress concentration distribution map constructed in the previous stage as basic data, combined with specific environmental factors such as slope aspect solar radiation history, surface thermal conductivity, soil moisture changes, and structural thickness, to systematically identify surface thermal stress-sensitive areas and calculate the probability of thermal cracking in each area under different seasons. Through this data fusion method, not only can the essential causes of thermal stress-induced cracking be revealed from a physical perspective, but the location, boundaries, and scale of high-risk areas can also be clearly identified spatially. These areas can then be further categorized, integrated, and prioritized for remediation, ultimately forming a "high-risk crack unit list" with engineering guidance significance. This list not only improves the targeting and resource utilization efficiency of remediation projects, but also significantly enhances the stability and long-term operational effectiveness of the overall remediation system. Compared with existing regional delineation methods that rely on experience-based judgment or static parameters, this step is more real-time, adaptable, and scientific, and is a key link supporting the smooth implementation of the entire bio-geological collaborative remediation pathway.

[0027] S003, for the identified high-risk crack units, a graded buffer structure consisting of an upper and lower layer is constructed on the surface. The upper layer is a plant matrix layer containing biochar composite material to improve water retention and heat insulation. The lower layer is a buffer pad layer composed of a mixture of high-ductility polymer and mineral powder to disperse thermal stress. Regularly arranged micro-expansion joints are set in the structure to reduce thermal stress concentration. After identifying and prioritizing high-risk crack units, a tiered buffer structure consisting of upper and lower layers was implemented to mitigate thermal stress and stabilize the structure in these areas. This structure comprises an upper plant matrix layer and a lower highly ductile buffer layer, supplemented by regularly spaced micro-expansion joints. This effectively regulates thermal expansion and contraction caused by diurnal temperature variations, reducing the risk of structural damage due to material thermal expansion mismatch. The implementation process includes the following steps: On-site surveys and foundation preparation were conducted within the high-risk crack unit. The survey included: confirming the boundaries of the risk unit, collecting elevation data, recording soil type and natural density, and analyzing groundwater depth, surface drainage direction, and surrounding vegetation. Based on the measured data, a construction design drawing for the covering structure was developed, specifying the thickness of each layer, the laying range, and the location of structural joints. Subsequently, foundation preparation work was carried out. Loose rocks, weeds, root remnants, and non-structural loose soil within the risk area were thoroughly removed using a combination of manual labor and small machinery, with a clearing depth controlled to be no less than 10 cm. After clearing, the original ground surface was compacted twice using a hand-operated compactor, ensuring the flatness was controlled within ±2 cm and the compaction degree reached over 90% of the design requirements. After preparation, layered construction elevation lines and micro-expansion joint planning lines were marked on the surface, and wooden stakes and red warning tape were used for on-site marking to prevent construction deviations.

[0028] Based on the specified layer thickness and design mix ratio, the lower buffer layer is laid first. The buffer layer material is a mixture of polyvinyl alcohol-based water-soluble high-extensibility polymer and pozzolanic mineral powder, with a polymer mass fraction of 20% and a mineral powder particle size controlled between 0.1 mm and 0.3 mm. The material must be pre-mixed indoors before construction, and after thorough mixing, it should be placed in sealed bags to prevent moisture absorption and clumping. During on-site construction, each paving width should not exceed 2 meters, and the thickness should be controlled at 10 cm. After leveling with a screed, a lightweight compactor should be used immediately for bidirectional compaction, with each compaction layer controlled to a thickness within 5 cm to ensure uniform material distribution and consistent thickness during compaction. After laying, and after curing for 24 hours, a continuous buffer layer with the capacity to cushion deformation is formed, possessing the initial ability to bear the weight of the upper structure.

[0029] After the lower layer is laid and stabilized, the upper plant substrate layer is laid. This layer is used to regulate moisture and temperature and provide conditions for vegetation growth. Its material consists of a mixture of biochar, humus, coconut fiber, and humic acid. The biochar must be pyrolyzed at 700°C and have a specific surface area of ​​not less than 150 m². 2 / g, with a particle size less than 2 mm, accounting for 25% of the matrix volume. Humus soil is taken from the in-situ surface humus layer of the restored area, and is used after air drying and sieving, accounting for 50%; coconut shell fiber is softened and cut into 3-5 cm long fibers, accounting for 15%; humic acid is evenly distributed in the mixture by spraying an aqueous solution, with a content of not less than 5% of the total mass. The mixture needs to be mixed for more than 30 minutes in advance to ensure that the components are fully combined. When laying, it is evenly spread in layers, with each layer not exceeding 5 cm in thickness, and two layers are laid, with the total thickness controlled between 10 cm and 12 cm. After laying, it is lightly compacted twice with a plate tamper to form a stable cover layer with a porosity between 35% and 40% that is not easy to settle.

[0030] After the plant substrate layer is laid, micro-expansion joints are constructed according to the design plan. The expansion joints are laid out in a 1-meter grid, alternating between longitudinal and transverse directions, with a joint width of 1 cm and a depth of 6 cm, ensuring they cut through the upper part of the plant substrate layer and the underlying buffer layer. The cutting is done manually using a steel-bladed cutting tool, with the cutting direction perpendicular to the direction of the principal thermal stress detected in the previous monitoring. The filling material is a dry mixture of natural medium sand and bentonite in a 4:1 volume ratio, mixed with water until the moisture content is approximately 18%, then filled into the gaps and manually compacted. After filling, dry sand is sprinkled on the surface to prevent rapid evaporation of moisture, promoting the formation of a moderately shrinkable and resilient joint structure under later thermal expansion and contraction. Micro-expansion joints not only provide space for the deformation release of thermal stress but also effectively guide the stress diffusion path, reducing the probability of crack concentration.

[0031] This step aims to provide a three-pronged engineering structural safeguard for high-risk crack areas, encompassing thermal stress buffering, crack risk reduction, and vegetation environment stability. By constructing a layered buffer structure system, it significantly enhances the structural integrity and ecological sustainability of the ecological restoration area under conditions of severe diurnal temperature variations. In ecological restoration environments of arid plateaus, semi-deserts, or mining areas with drastic temperature differences, artificial surface cover layers often face structural deformation problems caused by thermal expansion and contraction. In particular, the interfacial stress concentration caused by the inconsistency of thermal expansion coefficients between different materials easily induces cracks. These cracks not only disrupt the continuity of the surface structure but also lead to rapid water evaporation, root instability, and exposure of the underlying substrate, thus triggering a chain reaction of soil erosion and vegetation degradation. Traditional restoration techniques often employ single-layer covering methods or rigid topsoil laying methods, neglecting the matching of material thermophysical properties and deformation coordination mechanisms. These methods are unable to adapt to actual dynamic thermal environments, making it difficult for the restoration structure to operate stably in the long term.

[0032] This step involves constructing a two-layer structure with clearly defined functions: the lower layer is a flexible cushion layer composed of highly ductile polymers and volcanic ash powder, used to absorb and mitigate stress generated by the thermal expansion of the upper structure; the upper layer is a biochar-based plant matrix layer with good water retention and thermal resistance properties, stabilizing soil temperature and supporting vegetation growth. Regularly placed micro-expansion joints provide a "controllable stress release channel" for the structure, allowing unavoidable deformation during thermal cycling to be directionally guided and mitigated, preventing the accumulation of stress and crack formation at weak points. This structural system functionally achieves a closed-loop process of "dispersion-peak reduction-buffering-release" of thermal stress, ensuring the integrity of the cover structure under changing thermal environments and providing long-term stable site conditions for subsequent stable root development, water retention, and ecological function restoration. Therefore, this step is a crucial structural link connecting thermal risk identification with subsequent hydrothermal regulation and self-healing activation. Its role is not only reflected in "prevention" but also in providing a stable and coordinated physical spatial framework for ecological restoration, making it the core technology for reconstructing ecosystems in heat-sensitive areas.

[0033] S004, phase change heat storage particles and capillary barrier materials are embedded in the laid graded buffer structure. The soil moisture content in the plant rhizosphere area is adjusted to a preset range through the nighttime precision drip irrigation system, reducing the temperature gradient change between the surface cover structure and the underlying substrate, and suppressing the heat-induced tensile strain accumulation effect. To enhance the structural stress regulation and ecological stability of the laid tiered buffer structure under diurnal temperature variations, after the plant substrate layer and buffer pad layer are laid, phase change heat storage particles and capillary barrier materials are embedded within the structure. Combined with nighttime quantitative drip irrigation, a hydrothermal stable microenvironment is created in the plant rhizosphere, effectively mitigating the temperature gradient between the covering structure and the underlying substrate and suppressing the accumulation of structural tensile strain caused by uneven thermal expansion. The specific implementation steps are as follows: After the plant substrate layer is laid, leveled, and lightly compacted, the embedding depth, location distribution, and density of the phase change thermal storage particles are determined. The selected thermal storage material is spherical encapsulated inorganic salt hydrate particles, with an outer shell made of high-density polyethylene film and an inner coating of... The resulting composite material has a melting point controlled between 24°C and 26°C, a latent heat capacity of approximately 160 J / g, and a particle size of 4 mm to 6 mm. The embedding area is located in the lower middle part of the plant substrate layer, specifically within the soil layer 5 cm to 8 cm below the surface. The placement density is set at 25 embedding points per square meter, with 10 heat-storing particles placed at each point. The embedding points are arranged in a diamond array, alternating horizontally and vertically, with a spacing of 20 cm between adjacent points. A dedicated soil sampling tube is used to drill holes at the designated locations, with a hole diameter of 6 cm and a depth not exceeding 8 cm. After manually placing the particles, the undisturbed plant substrate is used for backfilling and compaction, ensuring accurate particle positioning, uniform soil coverage, and no displacement or slippage. After embedding, the surface of the covering layer is monitored for day and night thermal response using a thermal imager to ensure that the heat storage response area matches the embedding area, confirming that the heat storage effect is evenly distributed within the structural layer.

[0034] After the phase change particles are embedded, capillary barrier material is laid sequentially to control the vertical migration rate of water and enhance the water stability of the plant rhizosphere. The capillary barrier material is made by uniformly mixing polypropylene fibers with a diameter of less than 2 micrometers and diatomaceous earth powder with an average particle size of 1.5 mm at a mass ratio of 3:1. It is then hot-pressed to form a porous, flexible sheet with a thickness of 10 mm and a unit area mass of 150 g / m². This sheet possesses unidirectional slow-permeability, the ability to block capillary upflow, and the ability to delay water infiltration, effectively forming a rhizosphere water regulation interface. During construction, the sheet is cut to a suitable size according to the boundary of high-risk units and laid between the plant substrate layer and the lower buffer layer. The laying method is full coverage without overlap, and the joints are fixed with water-resistant adhesive tape to avoid creating short-circuit channels for water. The edges are fixed with U-shaped stainless steel nails at 30 cm intervals to ensure a tight fit with the buffer layer surface without curling or wrinkles, guaranteeing a tight bond with the upper and lower structures. The presence of the capillary barrier layer can effectively trap rising water vapor during the day, slow down the sudden change in humidity caused by condensation at night, and at the same time play a slow-release role when irrigation is excessive, preventing water from rapidly seeping down to the lower failure zone.

[0035] After the embedded structure is installed, to activate the thermal regulation capability of the phase change material and the moisture control capability of the capillary barrier layer, precise water replenishment is required at night to maintain the soil moisture content in the rhizosphere layer within the target range of 15%–20%. A low-pressure gravity drip irrigation system is used, with each drip irrigation pipe serving an area of ​​4 square meters. Pressure-compensating drippers with an orifice diameter of 0.8 mm are selected, and the dripper spacing is 50 cm. The drip irrigation pipes are laid parallel directly above the plant root zone, buried 2 cm deep, and covered under a layer of fine organic mulch to prevent evaporation loss due to direct sunlight. Drip irrigation is scheduled between 1:00 AM and 3:00 AM each night, with a water replenishment volume of 4 liters per unit area. After irrigation, a TDR (Temperature Reduction) soil moisture sensor probe embedded in a representative location is used to confirm whether the actual moisture content meets the target range. If it is below the set lower limit, the drip irrigation time is extended by 10 minutes the following night; if it is above the upper limit, the drip irrigation time is reduced by 5 minutes, gradually adjusting to a stable range. This precision irrigation method can achieve maximum water retention during the nighttime evaporation trough. At the same time, in conjunction with the phase change material's daytime heat absorption and nighttime heat release rhythm, it maintains a thermal and moisture balance in the root environment, significantly reducing the drying and expansion cycle caused by the day-night cycle.

[0036] To verify the regulatory effect of this heat and humidity control structure under actual conditions, continuous observation points were set up in a typical paving area to record diurnal soil temperature variation curves, rhizosphere moisture content variation curves, and plant physiological indicators (leaf water potential, stomatal conductance, etc.). Seven consecutive days of monitoring data showed that the diurnal fluctuation range of soil temperature in the area embedded with phase change particles and capillary barrier materials decreased from 17.6°C in the control area to 12.3°C, and the soil moisture content remained between 16.5% and 18.7%, far superior to the control area's fluctuation range of up to 10%. The combined effect of these measures significantly improved the heat conduction rate and moisture evaporation gradient in the buffer structure, effectively blocked the structural tensile strain accumulation process caused by drastic thermal changes, and enhanced the physical stability and ecological resilience of the entire remediation area during multi-day thermal cycles, thus creating a stable foundation environment for the subsequent crack self-healing response.

[0037] This step aims to achieve dual regulation of the internal temperature gradient and moisture dynamics of the surface cover structure by embedding phase change heat storage particles and capillary barrier materials within the constructed hierarchical buffer structure, combined with precise nighttime drip irrigation. This fundamentally suppresses the accumulation of tensile strain induced by thermal stress, laying a physical and ecological foundation for the long-term stable operation of the ecological restoration structure. In arid plateaus or open-pit mines with drastic temperature differences, the surface cover layer absorbs a large amount of solar radiation and heats up rapidly during the day, while the temperature drops sharply at night, causing rapid heat loss and resulting in drastic fluctuations in the internal temperature gradient. At the same time, soil moisture evaporates intensely at high temperatures and is difficult to replenish at low temperatures, creating a rapid alternation between dry and wet conditions. These alternating heat and moisture conditions can easily lead to problems such as soil shrinkage, uneven thermal expansion and contraction, and interface cracking. Especially in structures with significant differences in the coefficients of thermal expansion between material layers, long-term thermal cycling will lead to the continuous accumulation of tensile strain and ultimately induce structural cracks.

[0038] The phase change heat storage particles introduced in this step absorb heat energy during the day and release it slowly at night, thus delaying and smoothing the rate of temperature change in the cover layer and reducing diurnal thermal abrupt changes. Capillary barrier materials effectively mitigate the rhythm of moisture changes in the rhizosphere by controlling vertical water migration and evaporation channels, enhancing water retention capacity and stabilizing soil hydraulic structure. Meanwhile, low-intensity precision drip irrigation at night provides a dynamic water regulation mechanism based on measured moisture content, ensuring that the plant root growth environment is within an ideal humidity range and further reducing the probability of shrinkage stress formation. These three elements work synergistically to construct a multi-field response buffer mechanism involving heat, humidity, and force within the structural layer, enabling the buffer structure to not only possess static material stress relief capabilities but also dynamic self-regulating capabilities to adapt to environmental changes. Compared to existing single-material laying or static structural buffering technologies, this step achieves active regulation and responsive control of the microclimate within the ecological restoration area, representing a key technical step in preventing thermal crack formation, delaying structural aging, and enhancing the long-term stability of ecological restoration functions.

[0039] S005 incorporates a microcapsule cementing agent and a carbonate-generating bacteria agent with trigger response capability into a surface cover structure that has formed a stable thermal and humid environment after regulation. When the sensing system detects that the crack initiation threshold has been triggered, it automatically releases the cementing active ingredients to promote the carbonate deposition reaction to fill the cracks and restore the structural continuity. To further enhance the self-healing capacity of surface cover structures in open-pit coal mine ecological restoration areas, after establishing a stable thermal and humid environment through the embedding of phase change heat storage particles and capillary barrier materials and nighttime drip irrigation, microcapsule binders with trigger-response functions and carbonate-generating bacteria are incorporated into the plant matrix layer. This enables early automatic repair of microcracks, restores the continuity of the cover structure, and extends its service life. This step includes the following operational procedures: After confirming the completion of the heat and humidity control phase, and under conditions where the daily temperature fluctuation within the plant substrate layer is less than 13°C and the moisture content is stably maintained at 15% to 20%, the pre-mixing preparation of the remediation functional materials is carried out. The selected microcapsule binder consists of a two-component structure: the core binder is an aqueous solution of modified water glass and low-concentration hydroxypropyl methylcellulose; the coating material is a polylactic acid-polycaprolactone composite microfilm with a thickness controlled between 100 and 150 micrometers and an overall particle size of 0.8 to 1.2 millimeters, possessing controllable rupture characteristics when the structural tensile strain exceeds 250 με. The carbonate-generating bacterial agent is *Bacillus subtilis* sp. 1A331, a alkalophilic bacterium with strong urease-producing ability, prepared as a dried powder granule formulation with a viable count of no less than 10⁻⁶. 8 CFU / g, and coated with a maltodextrin shell to prevent high-temperature inactivation. The two are mixed at a mass ratio of 1:0.75, and then dry-mixed with the sieved plant matrix material at a mass ratio of 1:25. The mixture is stirred for at least 15 minutes using a horizontal continuous mixer to ensure that the material is mixed evenly and without clumping.

[0040] The aforementioned composite functional material was evenly laid on the top layer of the original buffer structure as a replacement or reinforcement layer for the plant substrate. The thickness of each layer was controlled at 10 cm, and the overall construction area was determined based on the previously identified high-risk crack zones. To ensure the functional particles were not damaged, a soft rubber scraper was used for leveling during the laying process, avoiding the use of rigid tools for compaction. After laying, a light compactor was used for low-intensity surface compaction to maintain the substrate porosity between 35% and 40%, providing sufficient space for subsequent microbial agent reaction and crack grouting. After construction, a portable near-infrared scanning device was used for rapid surface detection to confirm the uniformity of microcapsule distribution, and samples were taken to test the bacterial count, ensuring that the number of viable bacteria per kilogram of plant substrate was not less than [amount missing]. In order to maintain its emergency repair response capability.

[0041] During the actual operation of this functional matrix layer, if microcracks form in localized areas due to repeated diurnal temperature variations or alternating periods of wet and dry conditions, and the structural strain exceeds a set trigger threshold, the microcapsules distributed within the structure will rupture under stress, releasing the cementing fluid components sealed within. This fluid rapidly infiltrates the crack wall along the capillary pathway, creating an alkaline cementing environment in areas where it contacts active cells that generate carbonate-producing bacteria, while simultaneously stimulating the bacteria to secrete urease. Urease exhibits the strongest activity between 30°C and 40°C, and under this environment, it can rapidly catalyze the hydrolysis of urea to produce carbonate ions, which combine with pre-released calcium ions in the matrix within the crack zone to form calcium carbonate deposits. The deposits nucleate and crystallize layer by layer within the cracks, forming a microcrystalline bridging structure. Simultaneously, hydroxypropyl methylcellulose in the cementing fluid forms a physical bonding film, enhancing the compactness of the deposits and the bonding strength with the crack wall.

[0042] To ensure the self-healing process of the cracks has good sealing effect and structural recovery performance, monitoring periods of 1 day, 3 days, 7 days, and 14 days were set after construction to dynamically monitor the structural strain, crack width, porosity, and surface thermal conductivity in the area where the functional material was incorporated. If the original crack width was less than 0.5 mm, the sealing rate after 14 days could reach over 90%, the strain recovery rate could reach 70% of the original state, and the air-water permeability of the area remained continuous, indicating that the cracks had been effectively sealed. The formation of deposited calcium carbonate also generates new strength support in the material structure, improving the integrity and durability of the capping layer in the long term. The significant advantages of this repair mechanism are: when environmental and structural conditions induce cracks, it can automatically respond and complete the crack closure reaction without human intervention, exhibiting technical advantages such as rapid response, strong spatial adaptability, good ecological compatibility, and high structural continuity.

[0043] The purpose of this step is to construct an intelligent self-healing mechanism for ecological restoration structures, enabling them to sense crack initiation, release restoration materials in situ, and autonomously close cracks. This allows the covering structure to proactively respond and continuously repair itself during operation, significantly improving the long-term stability and ecological self-sustainability of mine restoration projects. Specifically, open-pit coal mine ecological restoration areas are often located in extreme environments with drastic temperature differences, intense moisture evaporation, and frequent wind erosion. Traditional passive covering restoration materials often lack real-time response mechanisms when facing problems such as structural stress accumulation, microcrack propagation, and soil instability. Once cracks appear, they continue to expand, leading not only to a decline in the function of the restoration layer but also to secondary degradation of the ecosystem. This step involves pre-burying microcapsule binders and carbonate-generating bacteria with "sensing-release-reaction-closure" capabilities in the surface plant matrix. When microcracks occur inside the structure due to thermal stress or shrinkage, the microcapsules rupture after the local strain exceeds a threshold, automatically releasing the internal sealing binder. Simultaneously, the metabolic reaction of the bacteria is activated, rapidly inducing calcium carbonate deposition on the inner wall of the crack. The deposition process bridges and bonds with the original soil mineral structure, effectively restoring structural continuity and preventing further crack propagation. This self-healing mechanism is widely distributed throughout the structure and responds with local activation, possessing distributed repair capabilities and achieving a dynamic balance of "damage and repair simultaneously." Furthermore, this mechanism does not rely on external energy or human intervention, exhibiting excellent ecological adaptability and resource conservation characteristics. Compared to traditional methods such as artificial crack repair and shotcrete reinforcement, this method offers significant advantages in material response rate, spatial distribution flexibility, ecological compatibility, and operating costs, making it a key supporting technology for transforming open-pit coal mine remediation areas from "functional restoration" to "functional stability + self-sustainability." Through the implementation of this step, an adaptive evolution mechanism for the surface structure can be established at the microscopic level, constructing a core functional unit with true self-regulation and long-term stability for the entire ecological restoration system.

[0044] S006, based on the monitoring results of the microcrack self-healing process, continuously collects parameters such as residual strain, crack density and soil moisture content, dynamically updates the critical crack index and related control parameters, and adjusts and optimizes the plant substrate ratio and drip irrigation strategy according to the time cycle to construct an ecological restoration operation closed loop with long-term stability and adaptive regulation capability. To ensure the long-term stable operation of ecological restoration structures in open-pit coal mines and guarantee their reliable crack resistance and ecological function maintenance under repeated disturbances in hot and humid environments, after the deployment and actual response of the microcrack self-healing mechanism, a dynamic data acquisition and parameter re-optimization process based on crack repair feedback needs to be established to enable the structure to enter a self-regulating closed loop. The specific implementation includes the following steps: After incorporating microcapsule binders and carbonate-generating bacteria into the covering structure and initiating a self-healing reaction, continuous monitoring was initiated. Three layers of residual strain fiber optic measurement lines were vertically deployed at the interface between the plant matrix layer and the underlying modified soil matrix, located at 5 cm, 10 cm, and 15 cm above the ground surface, with the spacing between each fiber maintained within 30 cm to ensure comprehensive coverage of deformation trends within the monitoring area. Crack width measurement strips were simultaneously installed at equal intervals on the buffer structure surface within previously identified high-risk units of thermally sensitive cracks, serving as a tool for assessing crack closure effectiveness. In addition, capacitive soil moisture probes were buried in the same area, with three depth levels at each measuring point to collect data on changes in moisture content in the surface, middle, and lower layers. All measuring points were read daily at set intervals, and the data were manually summarized in tables to form a continuous record of crack recovery and changes in environmental conditions.

[0045] The aforementioned monitoring data were integrated and analyzed every 7 days, comparing the reduction in residual strain, crack width changes, and moisture content stability at each monitoring point before and after the self-healing reaction. During this period, if it was found that in a certain area the crack width did not decrease significantly after self-healing, while the residual strain remained high and the soil moisture content fluctuated drastically, it was determined that the microcapsule release conditions in that area were insufficient or the microbial agent reaction efficiency was low. In this case, it was necessary to review the construction parameters and analyze whether the capsule particle size was too large, the coating thickness was too thick, and whether the microbial agent carrier was compatible with existing water-retaining materials. The parameters were cross-corrected by combining the comprehensive data results with on-site meteorological conditions (such as daily temperature difference, rainfall frequency, evaporation, etc.), updating the critical crack index value for that area, and simultaneously resetting the microcapsule rupture threshold and the effective activity window of the microbial agent.

[0046] Based on the updated data model, adjustments and optimizations were performed on the plant substrate materials and water control strategies. Regarding the plant substrate, if the remediation effect was limited by the loose substrate structure and insufficient water retention, the ratio of rice husk charcoal to coconut coir in the native plant substrate was adjusted from 1:1 to 2:1 to enhance structural compactness and capillary water adsorption capacity. If problems such as high inactivation rate of the microbial agent and sluggish fermentation occurred, the carrier used for the microbial agent was changed from starch granules to fine potassium humate granules, and 2% glucose was added to promote microbial metabolism. Regarding drip irrigation control, if it was found that the nighttime drip irrigation frequency was insufficient to maintain the humidity environment required by the microorganisms, the original pattern of drip irrigation once a night for 60 minutes was adjusted to drip irrigation twice a night, at 22:00 and 3:00 AM for 30 minutes each, with each drip irrigation volume controlled to be no less than 6 liters per square meter, ensuring that the rhizosphere moisture content remained within the active range of 16% to 20%.

[0047] After completing this round of optimization and adjustments, the next monitoring cycle will be restarted to continue collecting data on residual strain, crack width, and moisture content. Data from the past three months will be summarized and analyzed quarterly to form a new combination of ecological operation parameters, serving as the basis for construction and maintenance operations in the next quarter. For example, during seasonal transitions (such as spring to summer, autumn to winter), the drip irrigation frequency, the proportion of microbial activator added, and the composition ratio of the substrate should be adjusted in advance based on historical data to prevent new cracks from forming due to drastic changes in temperature and humidity. When monitoring results for two consecutive quarters show a crack formation rate of less than 5%, a self-healing sealing rate of more than 85%, and a residual strain reduction of more than 30%, this operational mode can be solidified as the standard remediation strategy for the area.

[0048] The purpose of this step is to construct a closed-loop control mechanism based on the self-healing feedback of microcracks, so as to achieve dynamic adaptive optimization and long-term stability maintenance of open-pit coal mine ecological restoration structures in multiple operating cycles. Open-pit coal mine ecological restoration projects often face extremely complex environmental disturbances, such as strong diurnal temperature differences, drastic moisture fluctuations, and alternating wind and water erosion. These external factors not only easily induce thermal expansion and contraction strain and drying shrinkage cracks in the surface cover structure, but also cause dynamic fatigue and performance degradation of the restoration materials. Traditional ecological restoration methods mostly lack dynamic management and adaptation mechanisms during the operational period after construction, failing to identify performance changes in the restoration system in real time and lacking the ability to adjust strategies based on feedback. This leads to gradual functional decline during long-term operation, and even large-scale restoration failure.

[0049] This step involves continuously collecting key operational parameters, including residual strain, crack density, and soil moisture content, and combining this with the observed microcrack self-healing process. This constructs a data-driven real-time assessment system that not only quantifies the structural state and environmental adaptability of each high-risk unit within a specific timeframe but also updates the critical crack index and control parameters accordingly, achieving a closed-loop transformation from design parameters to operational parameters. Simultaneously, the system dynamically adjusts the composition ratio of plant substrate materials by analyzing data trends, such as adjusting the proportions of biochar, organic matter, and water stabilizers to improve water retention and mechanical buffering performance. It can also adjust the drip irrigation timing, frequency, and volume to better suit the hydrothermal environment for remediation needs in different seasons, preventing material stress imbalance or biological system inactivation.

[0050] The core value of this step lies in its focus not only on the material functionality of the structure itself, but also in enabling the entire restoration system to possess the capabilities of "self-sensing, self-analysis, self-decision-making, and self-adjustment" through a data feedback mechanism. This achieves the evolution from a static structure to a dynamically operating ecosystem. This closed-loop mechanism, with its long-term stability and adaptive regulation capabilities, provides ecological restoration projects with a systematic response to sudden environmental disturbances, long-term structural fatigue, and functional fluctuations. It is a key technological support for ensuring the sustainable operation of restoration projects, laying the foundation for the regeneration and long-term maintenance of ecosystems, and providing a pathway for the development of mining area ecological restoration projects towards "smart governance" and "self-sustaining ecology."

[0051] This invention effectively solves key technical challenges in arid plateau mining areas caused by the mismatch between the thermal expansion and contraction of artificial vegetation cover and improved soil matrix, resulting in frequent network cracks, severe water loss, unstable vegetation, and ecological restoration failure, by constructing a comprehensive restoration system encompassing the entire process from "thermal diagnosis, structural optimization, dynamic regulation, crack self-healing, and closed-loop feedback." This system addresses these challenges through a synergistic construction of a comprehensive restoration system that integrates "thermal diagnosis, structural optimization, dynamic regulation, crack self-healing, and closed-loop feedback." This method not only achieves, for the first time, the dynamic identification of differences in material thermophysical properties and the accurate assessment of regional stress concentration risks in multi-layered composite structures, but also significantly improves the water retention, thermal insulation, and structural toughness of the surface cover layer through the synergistic construction of a graded buffer structure, phase change regulation, hydrothermal linkage, and a microcrack self-healing mechanism, thereby delaying the crack initiation and propagation process. Meanwhile, by introducing a continuous monitoring and feedback mechanism, an intelligent closed-loop regulation capability is established during the operation of the cover layer, enabling the plant substrate ratio and drip irrigation strategy to be dynamically adjusted according to environmental disturbances and structural responses, forming an ecological restoration system with long-term stability and self-adaptive capabilities. This significantly improves the risk resistance and sustainable operation level of the ecological restoration project in the mining area, filling the gap in the field of multi-factor dynamic coupling regulation of existing technologies.

[0052] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for ecological restoration of open-pit coal mines based on a biological-geological synergistic mechanism, characterized in that, Includes the following steps: S001, Temperature sensing units and strain sensing units are deployed in the area to be repaired to continuously collect temperature and strain data under the diurnal cycle. Based on the data inversion, thermal expansion coefficient difference distribution map and stress concentration distribution map are generated to construct thermal diagnostic baseline. S002, based on the thermal diagnostic baseline, combined with seasonal changes, solar radiation history and surface thermal conductivity data, calculates the critical crack index under different thermal cycling conditions, identifies thermal stress sensitive areas, forms a list of high-risk units and sorts the repair priorities. S003, a graded buffer structure is constructed for high-risk units. The upper layer is a biochar plant matrix layer for water retention and heat insulation, and the lower layer is a polymer mineral powder buffer pad layer for dispersing thermal stress. Regularly arranged micro-expansion joints are set to alleviate stress concentration. S004 incorporates phase change heat storage particles and capillary barrier materials within a buffer structure. Combined with precise nighttime drip irrigation, it maintains the rhizosphere moisture content within the target range, reduces the temperature gradient within the structure, and inhibits the accumulation of tensile strain. S005 incorporates microcapsule cementing agents and carbonate-generating bacteria into a surface cover structure that has been regulated to form a stable thermal and humid environment. When the crack initiation threshold is triggered, the cementing active ingredients are released and carbonate deposits are formed, thereby achieving self-healing of cracks and restoring structural continuity. S006, based on self-healing feedback, continuously collects data on residual strain, crack density, and moisture content, dynamically updates the crack index and control parameters, and regularly optimizes the plant substrate ratio and drip irrigation strategy to achieve long-term stability and adaptive operation of the ecological restoration system.

2. The method for ecological restoration of open-pit coal mines based on a biological-geological synergistic mechanism according to claim 1, characterized in that, Step S001 includes: Select several representative observation areas within the area to be repaired, and set up several observation lines with a spacing of 20 to 30 meters in each observation area. Bury fiber optic temperature sensing units and strain sensing units every 5 to 10 meters on each observation line. The fiber optic temperature sensing unit is buried 10 cm below the surface to record the temperature change process, and the strain sensing unit is buried 25 cm at the interface between the artificial cover layer and the modified matrix to record the micro-deformation response caused by thermal stress. After the sensing unit is running stably, temperature and strain data are continuously collected for no less than 30 days, with recording intervals of 10 minutes and 5 minutes, respectively. The temperature and strain changes at each node are calculated within a typical day-night thermal cycle. Based on the above data, thermal expansion coefficient difference distribution map and stress concentration distribution map are generated, and a thermal diagnostic baseline with time and spatial resolution is established on this basis to provide data support for subsequent high-risk unit identification and graded repair design.

3. The open-pit coal mine ecological restoration method based on the biological-geological synergistic mechanism according to claim 1, characterized in that, Step S002 includes: The thermal expansion coefficient difference distribution map and the stress concentration distribution map are processed into a unified grid using 5-meter by 5-meter spatial units, and each unit is assigned a thermal strain attribute value. An environmental parameter database including slope angle, average annual sunshine duration, surface thermal conductivity and surface material composition is established for each grid cell, and typical temperature difference and sunshine data of the four seasons are superimposed to evaluate the cumulative frequency of its thermal expansion and contraction stress sensitive state throughout the year. High-risk units with high sensitivity scores and spatial continuity are merged to form high-risk crack areas, and are prioritized according to geographical boundaries, area, and contact relationship with slopes or vegetation areas. The high-risk areas are spatially matched and verified with the thermal diagnostic baseline to confirm the integrity of the monitoring coverage, and a visualization of the operation is output, including boundary coordinates, priority level and recommended repair time.

4. The open-pit coal mine ecological restoration method based on the biological-geological synergistic mechanism according to claim 1, characterized in that, Step S003 includes: Boundary mapping and foundation preparation were carried out within the high-risk crack unit area. After removing impurities, the original ground was compacted, and construction elevation lines and micro-expansion joint layout lines were set. After preparation, a lower buffer layer is laid. The mixture of polyvinyl alcohol high-extensibility polymer and pozzolanic mineral powder with a particle size of 0.1 mm to 0.3 mm is used to form a continuous buffer layer by spreading and compacting it to a thickness of 10 cm. A top layer of plant substrate, consisting of biochar, humus, coconut fiber and humic acid, is laid on top of the buffer layer. The total thickness is controlled between 10 cm and 12 cm, and the porosity is controlled between 35% and 40%. Micro-expansion joints are laid out in the plant substrate layer with a grid spacing of 1 meter, with a joint width of 1 cm and a joint depth of 6 cm. The joints are filled with a mixture of bentonite and medium sand to form a stress-regulating structure with deformation release function.

5. The method for ecological restoration of open-pit coal mines based on a biological-geological synergistic mechanism according to claim 1, characterized in that, Step S004 includes: Spherical encapsulated inorganic salt hydrate phase change heat storage particles are embedded in the middle of the plant matrix layer. The embedding depth is 5 cm to 8 cm. The embedding points are distributed in a diamond array. The spacing between adjacent embedding points is 20 cm. The number of heat storage particles embedded at a single point is 10. A capillary barrier sheet made of polypropylene fiber and diatomaceous earth is laid between the plant substrate layer and the lower buffer layer. The sheet is 10 mm thick and has a unit area mass of 150 g / m². Water-resistant adhesive tape is used to bond the joints and stainless steel U-shaped nails are used to fix the edges. Water regulation is achieved through low-pressure gravity drip irrigation at night. Each drip irrigation pipeline serves an area of ​​4 square meters, with a dripper orifice diameter of 0.8 mm and a dripper spacing of 50 cm. The drip irrigation time is controlled between 1:00 AM and 3:00 AM, and the water replenishment per unit area is 4 liters per night. By continuously monitoring changes in ground temperature and soil moisture content, the soil moisture content in the plant rhizosphere is maintained within the target range of 15% to 20% to reduce the temperature gradient caused by diurnal temperature differences and inhibit the accumulation of structural tensile strain.

6. The method for ecological restoration of open-pit coal mines based on a biological-geological synergistic mechanism according to claim 1, characterized in that, Step S005 includes: Microcapsule binder and carbonate-generating microbial agent are mixed and incorporated into the plant matrix layer. The microcapsules have a particle size of 0.8 mm to 1.2 mm and possess the characteristic of rupturing under structural tensile strain exceeding 250 με. The microbial agent is alkalophilic Bacillus powder with a viable count of not less than 10. 8 CFU / g; The composite material and plant substrate were dry-mixed at a mass ratio of 1:25 and laid evenly with a layer thickness of 10 cm. During laying, a soft rubber scraper was used to level the surface and a light compactor was used to compact it to a porosity of 35% to 40%. During the operation of the covered structure, when the monitored strain exceeds the trigger threshold, the microcapsules release the cementing liquid components, activate the bacterial agent to secrete urease and trigger the calcium carbonate deposition reaction, forming a structural fill in the crack; After the material was laid, monitoring cycles of 1 day, 3 days, 7 days and 14 days were set to continuously detect strain, crack width and thermal conductivity to verify the sealing effect of the self-healing reaction and the degree of structural recovery.

7. The method for ecological restoration of open-pit coal mines based on a biological-geological synergistic mechanism according to claim 1, characterized in that, Step S006 includes: Three layers of residual strain fiber optic measurement lines, crack width measurement paper strips, and multi-depth soil moisture probes were vertically deployed at the interface between the plant matrix layer and the improved soil matrix to form a multi-dimensional monitoring network for the self-healing process of microcracks. The obtained monitoring data were integrated and analyzed on a 7-day cycle. The changes in crack width, the decrease in residual strain and the fluctuation in moisture content were compared to identify areas of material performance deviation and insufficient response, and the critical crack index and control threshold of the area were updated. Based on the updated results, the plant substrate ratio and microbial agent carrier type were adjusted, and the nighttime drip irrigation strategy was optimized, including irrigation time, frequency and single irrigation volume, to ensure that the rhizosphere moisture content is maintained in the range of 16% to 20%. The aforementioned parameter combinations are summarized quarterly to assess their effectiveness in crack control and ecological stability. When the closure rate is greater than 85% and the strain decreases by more than 30% for two consecutive quarters, the corresponding parameters are solidified as the standard operating strategy for the region.

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