Waste mine goaf water storage and heat recovery multi-field coupling simulation test system and method

Abstract

The invention discloses a waste mine goaf water storage and heat recovery multi-field coupling simulation test system and method. A bearing cavity with an opening in the upper end is defined by a bearing box; a test sample is filled in the bearing cavity; the formation pressure loading mechanism is positioned above the test sample; the ground temperature simulation heating assembly is laid at the bottom of the bearing cavity; the recharge well and the water pumping and heat collecting well penetrate through the formation pressure loading mechanism and then extend into the test sample; the recharge assembly is connected with the recharge well; the water pumping and heat collecting assembly is connected with the water pumping and heat collecting well; the plurality of liquid pressure sensors are embedded in the test sample at intervals; the thin film distributed pressure sensor is laid at the bottom of the test sample; the plurality of temperature sensors are embedded in the test sample at intervals; the displacement sensor is arranged at the upper end of the bearing box body and is connected with the loading plate; and the industrial camera is supported on one side outside the bearing box body. According to the invention, comprehensive simulation of evolution of a seepage field, a temperature field and a structure field in the water storage and heat recovery process of the abandoned coal mine goaf can be realized.

Description

Technical Field

[0001] This invention belongs to the field of water storage and heat recovery technology in abandoned coal mine goaf areas, specifically relating to a multi-field coupled simulation test system and method for water storage and heat recovery in abandoned mine goaf areas. Background Technology

[0002] With the continuous increase in the depth of coal mining in my country, coal mining is gradually shifting towards deeper levels. As of 2015, approximately 47 coal mines nationwide had depths exceeding 1000 meters, and the mining depth is increasing at a rate of about 10-25 meters per year. Under deep mining conditions, the temperature of the surrounding rock in the mine rises significantly, with an average geothermal gradient of about 1-3℃ / 100m. When the mine depth reaches the kilometer level, the temperature of the surrounding rock is typically between 35-45℃. Meanwhile, affected by the depletion of coal resources and industrial restructuring, it is estimated that by 2030, the number of abandoned coal mines in my country will reach approximately 15,000. These abandoned mines contain a large amount of untapped geothermal resources, mine water resources, and underground space resources.

[0003] Current statistics show that about one-third of the coal mines that have ceased operation in my country were water-rich mines, leaving behind an underground space volume of approximately 80 m³. 3 This provides abandoned coal mines with excellent conditions for water storage and heat extraction. Underground coal mines generally employ the total caving method to manage the roof. After the coal face is mined, the overlying strata collapse, forming large-scale goaf areas. These goaf areas are filled with broken coal and rock blocks, characterized by high porosity (generally reaching 30%-45%), large specific surface area, and excellent heat exchange conditions. Therefore, abandoned mine water storage and heat extraction technology, using goaf areas as heat storage space and mine water as the heat transfer medium, is considered a highly promising method for utilizing geothermal resources and has positive significance for promoting the "dual carbon" target (carbon reduction and carbon emission reduction).

[0004] However, in actual operation, the fractured rock mass in the goaf is subjected to long-term erosion by mine water seepage, pressure from overlying strata, and geothermal temperature, resulting in significant spatial heterogeneity in its internal structure. Under the coupled effects of seepage, temperature, and formation pressure, the contact relationships between rock blocks and the load-bearing framework structure are constantly adjusted. Furthermore, the fractured rock mass is prone to secondary fracturing during long-term service, generating a large number of fine particles. These particles detach and migrate under the influence of mine water flow, accumulating in pores or fracture throats, leading to narrowing of seepage channels and even blockage, which in turn causes a decline in the permeability and reinjection capacity of the goaf.

[0005] Furthermore, the processes of rock fragmentation and particle transport not only degrade seepage performance but may also weaken the overall load-bearing framework of the fractured rock mass in the goaf. In extreme cases, it can even induce secondary subsidence of the overlying strata, adversely affecting the safety of the shaft structure. Therefore, to achieve efficient, safe, and controllable operation of water storage and heating projects in abandoned coal mine goafs, it is urgent to systematically study the evolution of the spatial structure of the fractured rock mass in the goaf under the multi-field coupling of seepage, temperature, and formation pressure, reveal the mechanisms of particle transport and blockage formation, effectively assess blockage risks, predict potential blockage areas, and provide a scientific basis for the design optimization and operational control of water storage and heating projects. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a multi-field coupled simulation test system and method for water storage and heat recovery in abandoned mine goaf areas. This system is simple in structure, low in manufacturing cost, and convenient to operate. It can effectively simulate the formation pressure exerted by the overlying strata on the test samples in the goaf area and can achieve comprehensive online observation of structural changes in the test samples under visual conditions, providing a good experimental basis for subsequent structural sampling and CT three-dimensional scanning reconstruction analysis. The method is simple to implement and low in cost. It can comprehensively simulate the evolution of the seepage field, temperature field, and structural field during water storage and heat recovery in abandoned coal mine goaf areas, and can accurately capture and quantify the structural response and blockage characteristics under thermo-fluid-structure interaction.

[0007] To achieve the above objectives, the present invention provides a multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas, including a load-bearing box, test samples, a formation pressure loading mechanism, a geothermal simulation heating component, a seepage circulation mechanism, a multi-parameter monitoring unit, and a sampling and post-processing unit. The support box is a transparent structure, and a support cavity with an opening at the top is defined inside it; The test sample was filled into the support cavity; The formation pressure loading mechanism is installed in the bearing cavity and located above the test sample. The formation pressure loading mechanism includes counterweights, a loading plate and a flexible pad distributed from top to bottom, and multiple counterweights are evenly distributed on the upper end of the loading plate. The geothermal simulation heating component is laid at the bottom of the bearing cavity; The seepage circulation mechanism includes a reinjection well, a pumping and heating well, a reinjection assembly, and a pumping and heating assembly. The reinjection well and the pumping and heating well are spaced apart on the left and right sides, and both extend into the test sample after passing through the formation pressure loading mechanism. The reinjection assembly is connected to the inlet end of the reinjection well for injecting seepage fluid. The pumping and heating assembly is connected to the outlet end of the pumping and heating well for pumping out seepage fluid. The multi-parameter monitoring unit includes a liquid pressure sensor, a thin-film distributed pressure sensor, a temperature sensor, a displacement sensor, and an industrial camera. Multiple liquid pressure sensors are embedded at intervals in different spatial locations within the test sample. The thin-film distributed pressure sensor is laid at the bottom of the test sample. Multiple temperature sensors are embedded at intervals in different spatial locations within the test sample. The displacement sensor is mounted on the upper end of the support box and connected to the loading plate. The industrial camera is mounted on one side of the outside of the support box.

[0008] In this invention, the test sample is filled into the bearing cavity of the bearing box, which facilitates the simulation of the spatial structure and seepage environment of the fractured rock mass in the goaf of an abandoned coal mine, thereby facilitating the investigation of the formation pressure effect of the overlying strata on the test sample. Making the bearing box a transparent structure effectively withstands the water pressure and loading stress generated during the test, while also allowing for direct observation of changes in the test sample inside the bearing box. Furthermore, by mounting an industrial camera on one side of the bearing box, the changes in the test sample during the entire test can be recorded. By laying a geothermal simulation heating component at the bottom of the bearing cavity, a stable and controllable heat source can be provided to the fractured coal and rock mass of the test sample via wall heating, thereby achieving the loading of temperature boundary conditions and effectively simulating the geothermal conditions of the surrounding rock in the goaf. In the formation pressure loading mechanism, counterweights, a loading plate, and a flexible pad are arranged sequentially from top to bottom. The flexible pad forms a buffer layer between the loading plate and the test sample, thus preventing secondary fracture of the test sample due to stress concentration during loading. The loading plate, positioned above the flexible pad, fully utilizes its flexibility and rigidity to evenly transfer the load of the counterweights to the test sample, effectively ensuring the consistency of stress conditions and guaranteeing the test results. The evenly distributed counterweights above the loading plate allow for convenient changes in the applied vertical load by adjusting the weight and number of counterweights, and facilitate the even transfer of the applied equivalent vertical pressure to the test sample through the loading plate. This makes it easier to maintain a specific vertical load state, effectively simulating the formation pressure effect of the overlying rock in the goaf on the test sample. By interspersing reinjection wells and pumping wells within the test sample, a seepage channel under goaf water storage and heating conditions can be easily constructed inside the sample. This facilitates the injection of seepage fluid into the sample via reinjection wells and the extraction of seepage fluid via pumping wells. Multiple liquid pressure sensors embedded at different locations within the test sample allow for real-time monitoring of liquid pressure signals at various spatial locations during the experiment. A thin-film distributed pressure sensor at the bottom of the test sample enables real-time monitoring of stress signals at the bottom, facilitating the real-time perception of the spatial distribution characteristics of the sample's stress load. This, in turn, helps to accurately obtain the spatial force distribution and its changing characteristics under the multi-dimensional coupling of seepage, heat, and stress. Multiple temperature sensors embedded at different locations within the test sample allow for real-time monitoring of temperature signals at various spatial locations during the experiment. The placement of position sensors facilitates real-time acquisition of the settlement displacement signals of the loading plate. An industrial camera is mounted on one side of the outer casing to facilitate continuous image recording of the structural evolution and particle breakage and movement of the test sample during the seepage process.

[0009] The system is simple in structure, low in manufacturing cost, and easy to operate. It can effectively simulate the formation pressure of overlying rock in goaf areas on test samples and can realize comprehensive online observation of structural changes of test samples under visual conditions, which can provide a good experimental basis for subsequent structural sampling and CT three-dimensional scanning reconstruction analysis.

[0010] Furthermore, to facilitate data acquisition, storage, and rapid analysis and processing of experimental data, the multi-parameter monitoring unit also includes a data processing terminal; the data processing terminal is connected to a liquid pressure sensor, a thin-film distributed pressure sensor, a temperature sensor, a displacement sensor, an industrial camera, a geothermal simulation heating component, a reinjection component, and a pumped heating component.

[0011] Furthermore, in order to facilitate rapid drainage after the test and to facilitate convenient maintenance of the test system, the bearing box includes a support frame and a transparent water tank. The transparent water tank is installed in the support frame, and a drain outlet is provided at the bottom of one side of the transparent water tank, with a plug installed at the drain outlet.

[0012] In this technical solution, the drainage outlet facilitates the rapid discharge of residual seepage fluid or mine water from the test chamber after the test. By installing a support frame on the outside of the transparent water tank, the overall stability and load-bearing capacity are greatly improved through circumferential support, effectively preventing the risk of tank deformation and enhancing the reliability of the seal.

[0013] Furthermore, to prevent deformation of the loading plate during loading and to ensure that the pressure is evenly transmitted to the test sample, the loading plate is made of stainless steel; and to effectively provide cushioning protection, the flexible pad is made of silicone.

[0014] Furthermore, in order to facilitate precise injection of seepage fluid, the reinjection assembly includes a reinjection tank, an electric motor, and a reinjection pump; The reinjection tank stores seepage fluid; the drive shaft of the reinjection pump is coaxially connected to the output shaft of the motor, its inlet is connected to the reinjection tank through a replenishment pipeline, and its outlet is connected to the inlet of the reinjection well through a filling pipeline. The multi-parameter monitoring unit also includes an electromagnetic flowmeter and a pressure transmitter; the electromagnetic flowmeter and the pressure transmitter are connected in sequence to the filling pipeline.

[0015] In this technical solution, the installation of motor one facilitates the driving of the reinjection pump, thereby providing power for the injection of seepage fluid. The installation of pressure transmitter one facilitates real-time monitoring of the injection pressure signal of the seepage fluid in the injection pipeline, thus enabling real-time acquisition of injection pressure data. The installation of electromagnetic flowmeter one facilitates real-time monitoring of the instantaneous flow rate signal of the seepage fluid in the injection pipeline, thereby enabling not only real-time acquisition of instantaneous injection flow rate data but also the generation of cumulative injection flow rate data based on the instantaneous injection flow rate data.

[0016] Furthermore, in order to facilitate the precise extraction of seepage fluid, the pumping and heating assembly includes an extraction tank, an electric motor, and an extraction pump. The drive shaft of the extraction pump is coaxially connected to the output shaft of the second motor. Its inlet is connected to the outlet of the pumping and heating well through the extraction pipeline, and its outlet is connected to the extraction water tank through the discharge pipeline. The multi-parameter monitoring unit also includes an electromagnetic flowmeter II and a pressure transmitter II; the electromagnetic flowmeter II and the pressure transmitter II are connected in sequence to the extraction pipeline.

[0017] In this technical solution, the installation of motor two facilitates the driving of the extraction pump, thereby providing power for the extraction of seepage fluid. The installation of pressure transmitter two facilitates real-time monitoring of the extraction pressure signal of the seepage fluid in the extraction pipeline, thus facilitating the real-time acquisition of extraction pressure data. The installation of electromagnetic flowmeter two facilitates real-time monitoring of the instantaneous flow rate signal of the seepage fluid in the extraction pipeline, thereby enabling not only real-time acquisition of instantaneous extraction flow rate data but also the retrieval of cumulative extraction flow rate data based on the instantaneous extraction flow rate data.

[0018] Furthermore, in order to effectively simulate the formation pressure effect of the overlying rock in the goaf on the test sample, the test sample is a fractured coal and rock mass; in order to facilitate intuitive observation of internal changes while ensuring effective bearing strength, the transparent water tank is made of acrylic material.

[0019] This invention also provides a multi-field coupled simulation test method for water storage and heat recovery in abandoned mine goaf areas, employing a multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas, comprising the following steps: S1: Determine the test operating conditions and set the test parameters; S2: Preparation of test samples; S3: Assembly and testing of the test system; S4: Establish stress and temperature field; load multiple counterweights in an array on the loading plate, and collect stress signals at the bottom of the test sample in real time through a thin-film distributed pressure sensor until the stress value inside the test sample reaches the target loading stress value range; at the same time, start the ground temperature simulation heating component to heat until the internal temperature of the test sample reaches the preset ground temperature boundary value. S5: Water storage and heating operation test; Start the reinjection component and the pumping heating component to make the test system run stably according to the preset operating conditions and simulate the actual water storage and heating process; During the simulation, the injection flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 1, the injection pressure signal of the seepage liquid is collected in real time by pressure transmitter 1, the extraction flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 2, the extraction pressure signal of the seepage liquid is collected in real time by pressure transmitter 2, the hydraulic pressure signal at different spatial positions in the test sample is collected in real time by liquid pressure sensor, the stress signal at the bottom of the test sample is collected in real time by thin film distributed pressure sensor, the temperature signal at different spatial positions in the test sample is collected in real time by temperature sensor, the displacement signal of the loading plate is collected in real time by displacement sensor, and the image data of the seepage process and structural changes are collected in real time by industrial camera; S6: Test termination and unloading; When the preset termination conditions are met, control the reinjection component and the pumping heating component to stop, control the ground temperature simulation heating component to stop industrial operation, remove the plug in the drain outlet to carry out drainage operation, and then unload the counterweight in stages. S7: Formation of in-situ solidified body; The heated and melted impregnated solidified structural material is injected into the bearing cavity by partial or complete injection. Capillary action and gravity are used to allow the impregnated solidified material to enter the pores of the sample and wrap the particles, forming a solidified body that maintains the in-situ structure. S8: Grid-based sampling and three-dimensional quantitative characterization; S81: Spatial positioning sampling of the solidified body according to the pre-designed grid coordinates; During the sampling process, the principle of in-situ and low disturbance is followed to obtain the original structural samples at each sampling location; S82: The original structural samples are scanned using CT scanning technology, and the pore structure parameters and particle spatial distribution characteristics of the samples are obtained through three-dimensional reconstruction analysis methods to achieve quantitative characterization of the blockage area and structural evolution.

[0020] Furthermore, to facilitate accurate identification of rock mass migration, deposition, and secondary fragmentation behavior, the sample preparation process in S2 is as follows: First, coal and rock samples were collected from the site and crushed using a jaw crusher to prepare crushed coal and rock particles. Then, the crushed coal and rock particles were screened and graded to obtain crushed coal and rock particles of different sizes. Subsequently, the surfaces of the crushed coal and rock particles of different sizes were dyed with different colors of water-resistant dyes, and then naturally air-dried and dried to form traceable test samples.

[0021] As a preferred option, the assembly and testing process of the test system in S3 is as follows: S31: Install a ground temperature simulation heating component at the bottom of the bearing cavity in the bearing box, and lay a thin film distributed pressure sensor above the ground temperature simulation heating component; S32: The test sample is loaded into the bearing cavity using a layered loading method, and multiple liquid pressure sensors and multiple temperature sensors are embedded in predetermined positions. S33: Lay a flexible pad and a loading plate on top of the test sample in sequence; at the same time, install a displacement sensor on the upper end of the bearing box and connect it to the loading plate; S34: Make the lower ends of the reinjection well and the pumping heating well pass through the flexible pad and the loading plate and extend into the test sample, and make the reinjection assembly connect to the reinjection well and the pumping heating assembly connect to the pumping heating well. S35: Start the reinjection assembly and the pumping heat extraction assembly, and run them in a cycle for 20 to 30 minutes under the set flow conditions to ensure that there is no leakage in any part of the system and that the operating conditions are stable.

[0022] This invention provides a multi-field coupled physical test method for seepage, temperature, and formation pressure under water storage and heating conditions in abandoned coal mine goaf areas. During the establishment of the stress-temperature field, an array of equations is used to load the counterweight blocks, ensuring that the applied equivalent vertical pressure is uniformly transmitted to the test sample through the loading plate, thus ensuring the reliable establishment of the stress field. This allows for a more realistic simulation of the gravity distribution of the overlying rock and soil. A geothermal simulation heating component provides a stable and controllable heat source to the fractured coal and rock mass of the test sample via wall heating, achieving reliable loading of temperature boundary conditions. This effectively simulates the geothermal conditions of the surrounding rock in the goaf area, ensuring the reliable establishment of the temperature field. This facilitates the revelation of the effects of temperature changes on fluid viscosity, mineral dissolution / precipitation, and particle migration. Activating the reinjection and pumping heating components effectively simulates the actual water storage and heating process. Simultaneously, electromagnetic flowmeters one and two collect injection and extraction flow signals respectively, enabling real-time sensing of injection and extraction flow data. Similarly, pressure transmitters one and two collect injection and extraction pressure signals respectively, enabling real-time sensing of injection and extraction pressure data. Multiple liquid pressure sensors allow for the acquisition of temperature signals at different spatial locations within the test sample during the experiment, thus enabling real-time sensing of temperature data at different locations within the sample. A thin-film distributed pressure sensor allows for the real-time acquisition of stress signals at the bottom of the test sample, facilitating real-time sensing of the spatial distribution characteristics of the stress borne by the sample. This helps in accurately acquiring the spatial force distribution state and its changing characteristics under the multi-dimensional coupling of seepage, heat, and stress. An industrial camera captures real-time image data of the seepage process and structural changes of the test sample during the experiment, enabling real-time acquisition of structural changes in the fractured coal and rock mass and the movement of small particles generated by secondary crushing. After the experiment is terminated, the residual seepage liquid in the bearing cavity is first drained through the drain outlet. This effectively reduces the free water content in the pores of the test sample and minimizes the adverse effects of the mixing of the fixed structure and the aqueous phase on the structural fidelity during the subsequent impregnation and consolidation process. Then, the counterweight is removed using a staged unloading method to avoid any adverse effects on the test sample during unloading. Adding molten impregnation and consolidation material to the test sample effectively encapsulates the particles, maintaining the stability of the in-situ structure and ensuring that the complete in-situ structure is still visible after sampling. The networked sampling process facilitates the reconstruction of the original spatial positions of several samples by numbering, enabling a more accurate reconstruction of the spatial structural characteristics of the test sample. This facilitates the subsequent creation of porosity variation cloud maps or blockage distribution maps, clearly demonstrating the characteristics of the blockage distribution.By using CT scanning technology to obtain pore structure parameters and particle spatial distribution, the blockage analysis can be elevated from qualitative description to three-dimensional theorem characterization, thereby enabling precise calculation of the volume and location of the blockage zone and its actual impact on the pore network.

[0023] This method can effectively simulate the real boundary environment under controllable conditions, simulating the combined effects of mine water seepage, geothermal activity, and overlying rock pressure. Under multi-field coupling, it can reproduce key changes such as compaction and rearrangement of the bearing skeleton of broken coal and rock mass in goaf, secondary crushing, and particle shedding, migration, deposition, and blockage. It can achieve simultaneous monitoring and data acquisition of seepage parameters, temperature field, and stress / deformation response, thereby quantitatively characterizing the attenuation of permeability and the evolution of blockage.

[0024] This method is simple to implement and has low implementation costs. Through the reliable establishment of temperature and stress fields, spatial grid sampling, structural stabilization processing, and precise perception using 3D imaging methods such as CT, it can achieve spatial distribution identification and quantitative analysis of experimental particle accumulation, blockage areas, and pore structures. It can provide reliable experimental basis and methodological support for blockage risk assessment, blockage area prediction, and operational parameter optimization of goaf water storage and heating systems. Thus, it realizes the comprehensive simulation of the evolution of seepage field, temperature field, and structural field during the goaf water storage and heating process in abandoned coal mines, and can accurately capture and quantify the structural response and blockage characteristics under the action of thermal-fluid-structure interaction. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the experimental system in this invention; Figure 2 This is an assembly diagram of the load-bearing box, formation pressure loading mechanism, reinjection well, and pumping and heating well in this invention. Figure 3 This is a schematic diagram showing the state of the test sample being filled in the load-bearing box in this invention; Figure 4 This is a schematic diagram of the arrangement structure of the multi-parameter monitoring unit in this invention; Figure 5 This is a schematic diagram of the test sample meshing and CT three-dimensional reconstruction process in this invention; Figure 6 This is a flowchart of the experimental method in this invention.

[0026] In the diagram: 1. Test sample, 2. Transparent water tank, 3. Flexible pad, 4. Loading plate, 5. Counterweight, 6. Geothermal simulation heating component, 7. Reinjection well, 8. Pumping and heating well, 9. Reinjection water tank, 10. Motor 1, 11. Reinjection pump, 12. Electromagnetic flowmeter 1, 13. Pressure transmitter 1, 14. Liquid pressure sensor, 15. Temperature sensor, 16. Thin-film distributed pressure sensor, 17. Industrial camera, 18. Data processing terminal, 19. Drain outlet, 20. Support frame, 21. Displacement sensor, 22. Consolidated stable sample, 23. Pumping water tank, 24. Motor 2, 25. Pumping pump, 26. Electromagnetic flowmeter 2, 27. Pressure transmitter 2, 28. Liquid replenishment pipeline, 29. Filling pipeline, 30. Pumping pipeline, 31. Drainage pipeline, 32. Support box. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figures 1 to 4 As shown, the present invention provides a multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas, including a bearing box 32, a test sample 1, a formation pressure loading mechanism, a geothermal simulation heating component 6, a seepage circulation mechanism, a multi-parameter monitoring unit, and a sampling and post-processing unit; The bearing box 32 is a transparent structure, and a bearing cavity with an opening at the top is defined inside it; The test sample 1 was filled into the bearing cavity; The formation pressure loading mechanism is installed in the bearing cavity and located above the test sample 1. The formation pressure loading mechanism includes counterweights 5, loading plates 4 and flexible pads 3 arranged from top to bottom. The flexible pad 3 is in direct contact with the upper end of the test sample 1. The size of the loading plate 4 is adapted to the cross-sectional size of the bearing cavity and is horizontally arranged above the flexible pad 3. Multiple counterweights 5 are evenly distributed in an array on the upper end of the loading plate 4.

[0029] The geothermal simulation heating component 6 is laid at the bottom of the bearing cavity; The seepage circulation mechanism includes a reinjection well 7, a pumping and heating well 8, a reinjection assembly, and a pumping and heating assembly. The reinjection well 7 and the pumping and heating well 8 are spaced apart on the left and right sides, and both extend into the test sample 1 after passing through the formation pressure loading mechanism, which is used to construct the seepage and extraction channels for mine water in the fractured coal and rock mass of the test sample 1. The reinjection assembly is connected to the inlet end of the reinjection well 7 for injecting seepage fluid. The pumping and heating assembly is connected to the outlet end of the pumping and heating well 8 for extracting seepage fluid. The multi-parameter monitoring unit includes a liquid pressure sensor 14, a thin-film distributed pressure sensor 16, a temperature sensor 15, a displacement sensor 21, and an industrial camera 17. Multiple liquid pressure sensors 14 are embedded at different spatial locations within the test sample 1, spaced apart from each other. The thin-film distributed pressure sensor 16 is laid at the bottom of the test sample 1. Multiple temperature sensors 15 are embedded at different spatial locations within the test sample 1, spaced apart from each other. The displacement sensor 21 is installed at the upper end of the support box 32 and connected to the loading plate 4. Preferably, the displacement sensor 21 is a dial indicator; after installation, the dial indicator's probe rests on the upper end of the loading plate 4 to effectively monitor the settlement of the loading plate 4 during the test. The industrial camera 17 is mounted on one side outside the support box 32, preferably directly in front of the support box 32, to collect image data of the test sample 1 within the support box 32, thereby obtaining information on the structural changes of the crushed coal and rock mass and the movement of small particles generated by secondary crushing. In this invention, the test sample is filled into the bearing cavity of the bearing box, which facilitates the simulation of the spatial structure and seepage environment of the fractured rock mass in the goaf of an abandoned coal mine, thereby facilitating the investigation of the formation pressure effect of the overlying strata on the test sample. Making the bearing box a transparent structure effectively withstands the water pressure and loading stress generated during the test, while also allowing for direct observation of changes in the test sample inside the bearing box. Furthermore, by mounting an industrial camera on one side of the bearing box, the changes in the test sample during the entire test can be recorded. By laying a geothermal simulation heating component at the bottom of the bearing cavity, a stable and controllable heat source can be provided to the fractured coal and rock mass of the test sample via wall heating, thereby achieving the loading of temperature boundary conditions and effectively simulating the geothermal conditions of the surrounding rock in the goaf. In the formation pressure loading mechanism, counterweights, a loading plate, and a flexible pad are arranged sequentially from top to bottom. The flexible pad forms a buffer layer between the loading plate and the test sample, thus preventing secondary fracture of the test sample due to stress concentration during loading. The loading plate, positioned above the flexible pad, fully utilizes its flexibility and rigidity to evenly transfer the load of the counterweights to the test sample, effectively ensuring the consistency of stress conditions and guaranteeing the test results. The evenly distributed counterweights above the loading plate allow for convenient changes in the applied vertical load by adjusting the weight and number of counterweights, and facilitate the even transfer of the applied equivalent vertical pressure to the test sample through the loading plate. This makes it easier to maintain a specific vertical load state, effectively simulating the formation pressure effect of the overlying rock in the goaf on the test sample. By interspersing reinjection wells and pumping wells within the test sample, a seepage channel under goaf water storage and heating conditions can be easily constructed inside the sample. This facilitates the injection of seepage fluid into the sample via reinjection wells and the extraction of seepage fluid via pumping wells. Multiple liquid pressure sensors embedded at different locations within the test sample allow for real-time monitoring of liquid pressure signals at various spatial locations during the experiment. A thin-film distributed pressure sensor at the bottom of the test sample enables real-time monitoring of stress signals at the bottom, facilitating the real-time perception of the spatial distribution characteristics of the sample's stress load. This, in turn, helps to accurately obtain the spatial force distribution and its changing characteristics under the multi-dimensional coupling of seepage, heat, and stress. Multiple temperature sensors embedded at different locations within the test sample allow for real-time monitoring of temperature signals at various spatial locations during the experiment. The placement of position sensors facilitates real-time acquisition of the settlement displacement signals of the loading plate. An industrial camera is mounted on one side of the outer casing to facilitate continuous image recording of the structural evolution and particle breakage and movement of the test sample during the seepage process.

[0030] The system is simple in structure, low in manufacturing cost, and easy to operate. It can effectively simulate the formation pressure of overlying rock in goaf areas on test samples and can realize comprehensive online observation of structural changes of test samples under visual conditions, which can provide a good experimental basis for subsequent structural sampling and CT three-dimensional scanning reconstruction analysis.

[0031] To facilitate data acquisition, storage, and rapid analysis and processing of experimental data, the multi-parameter monitoring unit also includes a data processing terminal 18; the data processing terminal 18 is connected to a liquid pressure sensor 14, a thin-film distributed pressure sensor 16, a temperature sensor 15, a displacement sensor 21, an industrial camera 17, a ground temperature simulation heating component 6, a reinjection component, and a pumping and heating component.

[0032] To facilitate rapid drainage after the test and to facilitate convenient maintenance of the test system, the bearing box 32 includes a support frame 20 and a transparent water tank 2. The transparent water tank 2 is installed in the support frame 20. A drain outlet 19 is provided at the bottom of one side of the transparent water tank 2, and a plug is installed at the drain outlet 19. The drain outlet 19 is used to quickly drain the mine water in the bearing cavity. In this technical solution, the drainage outlet facilitates the rapid discharge of residual seepage fluid or mine water from the test chamber after the test. By installing a support frame on the outside of the transparent water tank, the overall stability and load-bearing capacity are greatly improved through circumferential support, effectively preventing the risk of tank deformation and enhancing the reliability of the seal.

[0033] To prevent deformation of the loading plate during loading and to ensure that the pressure is evenly transmitted to the test sample, the loading plate 4 is made of stainless steel. To effectively provide buffer protection, the flexible pad 3 is made of silicone. The flexible pad 3 is located between the loading plate 4 and the test sample 1 to avoid secondary breakage caused by local stress concentration. To facilitate precise injection of seepage fluid, the reinjection assembly includes a reinjection tank 9, a motor 10, and a reinjection pump 11. The reinjection tank 9 stores seepage fluid; the drive shaft of the reinjection pump 11 is coaxially connected to the output shaft of the motor 10, its inlet is connected to the reinjection tank 9 through the replenishment pipeline 28, and its outlet is connected to the inlet end of the reinjection well 7 through the injection pipeline 29. The multi-parameter monitoring unit also includes an electromagnetic flowmeter 12 and a pressure transmitter 13; the electromagnetic flowmeter 12 and the pressure transmitter 13 are connected in sequence to the filling pipeline 29.

[0034] In this technical solution, the installation of motor one facilitates the driving of the reinjection pump, thereby providing power for the injection of seepage fluid. The installation of pressure transmitter one facilitates real-time monitoring of the injection pressure signal of the seepage fluid in the injection pipeline, thus enabling real-time acquisition of injection pressure data. The installation of electromagnetic flowmeter one facilitates real-time monitoring of the instantaneous flow rate signal of the seepage fluid in the injection pipeline, thereby enabling not only real-time acquisition of instantaneous injection flow rate data but also the generation of cumulative injection flow rate data based on the instantaneous injection flow rate data.

[0035] To facilitate precise extraction of seepage fluid, the pumping and heating assembly includes a water extraction tank 23, an electric motor 24, and an extraction pump 25. The drive shaft of the pumping pump 25 is coaxially connected to the output shaft of the motor 24. Its inlet is connected to the outlet of the pumping and heating well 8 through the pumping pipeline 30, and its outlet is connected to the pumping water tank 23 through the drain pipeline 31. The multi-parameter monitoring unit also includes an electromagnetic flowmeter 26 and a pressure transmitter 27; the electromagnetic flowmeter 26 and the pressure transmitter 27 are connected in sequence to the extraction pipeline 30.

[0036] In this technical solution, the installation of motor two facilitates the driving of the extraction pump, thereby providing power for the extraction of seepage fluid. The installation of pressure transmitter two facilitates real-time monitoring of the extraction pressure signal of the seepage fluid in the extraction pipeline, thus facilitating the real-time acquisition of extraction pressure data. The installation of electromagnetic flowmeter two facilitates real-time monitoring of the instantaneous flow rate signal of the seepage fluid in the extraction pipeline, thereby enabling not only real-time acquisition of instantaneous extraction flow rate data but also the retrieval of cumulative extraction flow rate data based on the instantaneous extraction flow rate data.

[0037] To effectively simulate the formation pressure exerted by the overlying rock of the goaf on the test sample, the test sample 1 is a fractured coal and rock mass. To ensure effective load-bearing strength while facilitating direct observation of internal changes, the transparent water tank 2 is preferably made of acrylic material. To ensure effective load-bearing strength while facilitating direct observation of internal changes, the structural strength of the transparent water tank 2 must meet the experimental requirements under seepage, loading, and heating conditions. Thus, the supporting tank 32 can not only support the fractured coal and rock mass of the test sample 1 but also provide visual observation conditions.

[0038] like Figure 6 As shown, the present invention also provides a multi-field coupled simulation test method for water storage and heat recovery in abandoned mine goaf areas, employing a multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas, comprising the following steps: S1: Determine the test operating conditions and set the test parameters; Specifically, the test operation conditions are determined, including constant flow rate, constant pressure, pulse injection, and backwashing conditions. Simultaneously, test parameters were set, including boundary conditions and sensor layout schemes; boundary conditions included vertical loading stress and ground temperature boundaries; sensor layout schemes included pressure parameters, temperature parameters, displacement parameters, and monitoring points and sampling frequencies that affect acquisition accuracy. S2: Preparation of test sample 1; S3: Assembly and testing of the test system; S4: Establish stress and temperature field; load multiple counterweights 5 in an array on loading plate 4, and collect stress signals at the bottom of test sample 1 in real time through thin-film distributed pressure sensor 16 until the stress value inside test sample 1 reaches the target loading stress value range; at the same time, start the ground temperature simulation heating component 6 to heat until the internal temperature of test sample 1 reaches the preset ground temperature boundary value. S5: Water storage and heat extraction operation test; The reinjection and pumping heat recovery components are started to make the test system operate stably according to the preset operating conditions, simulating the actual water storage and heat recovery process. During the simulation, the injection flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 12, the injection pressure signal of the seepage liquid is collected in real time by pressure transmitter 13, the extraction flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 26, the extraction pressure signal of the seepage liquid is collected in real time by pressure transmitter 27, the hydraulic pressure signal at different spatial positions in the test sample 1 is collected in real time by liquid pressure sensor 14, the stress signal at the bottom of the test sample 1 is collected in real time by thin-film distributed pressure sensor 16, the temperature signal at different spatial positions in the test sample 1 is collected in real time by temperature sensor 15, the displacement signal of the loading plate 4 is collected in real time by displacement sensor 21, and the image data of the seepage process and structural changes are collected in real time by industrial camera 17. S6: Trial Termination and Unloading; When the preset termination condition is reached, the reinjection component and the pumping heating component are shut down, the ground temperature simulation heating component 6 is stopped from operation, the plug in the drain outlet 19 is removed for drainage, and then the counterweight block 5 is unloaded in stages, and the loading plate 4 and the flexible pad 3 are removed in sequence, so that the test sample 1 is in a sampleable state. Then, the sample is left to stand for a set time under natural ventilation to dry it, so as to effectively reduce the free water content in the pores and reduce the adverse effect of the mixing of the consolidation material and water phase on the structural fidelity during the subsequent impregnation and consolidation process. In order to improve the drying efficiency, the ground temperature simulation heating component 6 can be turned on to use the heat source provided by the ground temperature simulation heating component 6 to quickly dry the sample 1. S7: Formation of in-situ solidified body; The heated and melted impregnated solidified structural material (such as: melted paraffin, agar, gel or low viscosity epoxy resin) is injected into the bearing cavity by partial or whole injection. The impregnated solidified material enters the pores of the sample 1 and wraps the particles by capillary action and gravity. After the solidified material cools and solidifies, an integral solidified body that maintains the in-situ structure is formed to ensure the stability of the sample in the subsequent analysis process. S8: Grid-based sampling and three-dimensional quantitative characterization, such as Figure 5 As shown; S81: Spatial positioning sampling of the solidified body is performed according to the pre-designed grid coordinates (the planar areas are numbered using a combination of letters and numbers). During the sampling process, a sampler can be used, preferably a cuboid sampling box with a square cross-section. Sampling is performed by pressing until the sampler reaches the bottom of the solidified body and stops, and the sample is taken out. At the same time, following the principle of in-situ and low disturbance, the original structural samples at each sampling position are obtained so as to obtain representative structurally stable samples at each position. Considering the potential local disturbances and tertiary breakage that may occur at the outer edge of the target sample during cutting / removal, a secondary sampling method can be adopted after the initial sampling: specifically, a cuboid sample can be cut with a tool to form a cylindrical sample, in order to reduce the impact of edge disturbances on the quantitative results of pore structure and particle spatial distribution, and improve the reliability of structural characterization; S82: The sample is sent into the CT system, and the original structural sample is scanned using CT scanning technology to obtain a tomographic image sequence. Through image segmentation and three-dimensional reconstruction analysis methods, the pore structure parameters (such as porosity, connectivity, pore throat scale distribution, blockage zone morphology, etc.) and particle spatial distribution characteristics of the sample are obtained, so as to achieve quantitative characterization of the blockage area and structural evolution.

[0039] Furthermore, for comparative verification of particle size distribution or particle migration, the consolidated material in the CT-scanned samples can be removed: for paraffin-consolidated samples, the paraffin can be removed by dissolution / melting; for gel-consolidated samples, the consolidated material can be removed by peeling or swelling. After removing the consolidated material, the particles can be sieved and statistically analyzed to obtain particle size distribution characteristics. Combined with the spatial distribution records of stained graded particles, the mechanisms of particle migration, deposition, and blockage can be further analyzed. Simultaneously, the enrichment / migration characteristics of unstained, fractured, fine particles can be identified to characterize the migration and deposition distribution patterns of secondary fragmentation products.

[0040] To facilitate accurate identification of rock mass migration, deposition, and secondary fragmentation behavior, the preparation process of test sample 1 in S2 is as follows: First, coal and rock samples were collected from the site and crushed using a jaw crusher to prepare crushed coal and rock particles. Then, the crushed coal and rock particles were screened and graded to obtain crushed coal and rock particles of different sizes. Subsequently, in order to facilitate the identification of particle migration and secondary crushing process, the surfaces of crushed coal and rock particles of different sizes were dyed with different colors of water-resistant dyes. Then, they were naturally air-dried and dried to form traceable test samples 1.

[0041] As a preferred option, the assembly and testing process of the test system in S3 is as follows: S31: Install the transparent water tank 2 in the support frame 20 to form a bearing box 32; install the ground temperature simulation heating component 6 at the bottom of the bearing cavity in the bearing box 32, and lay a thin film distributed pressure sensor 16 above the ground temperature simulation heating component 6 to monitor the stress distribution at the bottom of the test sample 1 in real time. S32: The test sample 1 is loaded into the bearing cavity by a layered filling method, and multiple liquid pressure sensors 14 and multiple temperature sensors 15 are respectively embedded in the predetermined positions; S33: A flexible pad 3 and a loading plate 4 are laid on top of the test sample 1 in sequence; the loading plate 4 can realize the uniform transmission of loading force and effectively ensure the test effect; at the same time, a displacement sensor 21 is installed on the upper end of the bearing box 32 and connected to the loading plate 4. S34: Make the lower ends of the reinjection well 7 and the pumping heating well 8 pass through the flexible pad 3 and the loading plate 4 and extend into the test sample 1, and make the reinjection assembly connect to the reinjection well 7 and the pumping heating assembly connect to the pumping heating well 8. S35: Start the reinjection assembly and the pumping heat extraction assembly, and run them in a cycle for 20 to 30 minutes under the set flow conditions to ensure that there is no leakage in any part of the system and that the operating conditions are stable.

[0042] This invention provides a multi-field coupled physical test method for seepage, temperature, and formation pressure under water storage and heating conditions in abandoned coal mine goaf areas. During the establishment of the stress-temperature field, an array of equations is used to load the counterweight blocks, ensuring that the applied equivalent vertical pressure is uniformly transmitted to the test sample through the loading plate, thus ensuring the reliable establishment of the stress field. This allows for a more realistic simulation of the gravity distribution of the overlying rock and soil. A geothermal simulation heating component provides a stable and controllable heat source to the fractured coal and rock mass of the test sample via wall heating, achieving reliable loading of temperature boundary conditions. This effectively simulates the geothermal conditions of the surrounding rock in the goaf area, ensuring the reliable establishment of the temperature field. This facilitates the revelation of the effects of temperature changes on fluid viscosity, mineral dissolution / precipitation, and particle migration. Activating the reinjection and pumping heating components effectively simulates the actual water storage and heating process. Simultaneously, electromagnetic flowmeters one and two collect injection and extraction flow signals respectively, enabling real-time sensing of injection and extraction flow data. Similarly, pressure transmitters one and two collect injection and extraction pressure signals respectively, enabling real-time sensing of injection and extraction pressure data. Multiple liquid pressure sensors allow for the acquisition of temperature signals at different spatial locations within the test sample during the experiment, thus enabling real-time sensing of temperature data at different locations within the sample. A thin-film distributed pressure sensor allows for the real-time acquisition of stress signals at the bottom of the test sample, facilitating real-time sensing of the spatial distribution characteristics of the stress borne by the sample. This helps in accurately acquiring the spatial force distribution state and its changing characteristics under the multi-dimensional coupling of seepage, heat, and stress. An industrial camera captures real-time image data of the seepage process and structural changes of the test sample during the experiment, enabling real-time acquisition of structural changes in the fractured coal and rock mass and the movement of small particles generated by secondary crushing. After the experiment is terminated, the residual seepage liquid in the bearing cavity is first drained through the drain outlet. This effectively reduces the free water content in the pores of the test sample and minimizes the adverse effects of the mixing of the fixed structure and the aqueous phase on the structural fidelity during the subsequent impregnation and consolidation process. Then, the counterweight is removed using a staged unloading method to avoid any adverse effects on the test sample during unloading. Adding molten impregnation and consolidation material to the test sample effectively encapsulates the particles, maintaining the stability of the in-situ structure and ensuring that the complete in-situ structure is still visible after sampling. The networked sampling process facilitates the reconstruction of the original spatial positions of several samples by numbering, enabling a more accurate reconstruction of the spatial structural characteristics of the test sample. This facilitates the subsequent creation of porosity variation cloud maps or blockage distribution maps, clearly demonstrating the characteristics of the blockage distribution.By using CT scanning technology to obtain pore structure parameters and particle spatial distribution, the blockage analysis can be elevated from qualitative description to three-dimensional theorem characterization, thereby enabling precise calculation of the volume and location of the blockage zone and its actual impact on the pore network.

[0043] This method can effectively simulate the real boundary environment under controllable conditions, simulating the combined effects of mine water seepage, geothermal activity, and overlying rock pressure. Under multi-field coupling, it can reproduce key changes such as compaction and rearrangement of the bearing skeleton of broken coal and rock mass in goaf, secondary crushing, and particle shedding, migration, deposition, and blockage. It can achieve simultaneous monitoring and data acquisition of seepage parameters, temperature field, and stress / deformation response, thereby quantitatively characterizing the attenuation of permeability and the evolution of blockage.

[0044] This method is simple to implement and has low implementation costs. Through the reliable establishment of temperature and stress fields, spatial grid sampling, structural stabilization processing, and precise perception using 3D imaging methods such as CT, it can achieve spatial distribution identification and quantitative analysis of experimental particle accumulation, blockage areas, and pore structures. It can provide reliable experimental basis and methodological support for blockage risk assessment, blockage area prediction, and operational parameter optimization of goaf water storage and heating systems. Thus, it realizes the comprehensive simulation of the evolution of seepage field, temperature field, and structural field during the goaf water storage and heating process in abandoned coal mines, and can accurately capture and quantify the structural response and blockage characteristics under the action of thermal-fluid-structure interaction.

Claims

1. A multi-field coupled simulation test system for water storage and heat extraction in abandoned mine goaf areas, comprising a support box (32) and a test sample (1), characterized in that, It also includes a formation pressure loading mechanism, a geothermal simulation heating component (6), a seepage circulation mechanism, a multi-parameter monitoring unit, and a sampling and post-processing unit; The carrier box (32) is a transparent structure, and a carrier cavity with an opening at the top is defined inside it; The test sample (1) was filled into the bearing cavity; The formation pressure loading mechanism is installed in the bearing cavity and located above the test sample (1). The formation pressure loading mechanism includes counterweights (5), loading plates (4) and flexible pads (3) distributed from top to bottom, and multiple counterweights (5) are evenly distributed on the upper end of the loading plate (4). The ground temperature simulation heating component (6) is laid at the bottom of the bearing cavity; The seepage circulation mechanism includes a reinjection well (7), a pumping and heating well (8), a reinjection assembly, and a pumping and heating assembly; the reinjection well (7) and the pumping and heating well (8) are distributed on the left and right sides at intervals, and both extend into the test sample (1) after passing through the formation pressure loading mechanism; the reinjection assembly is connected to the inlet end of the reinjection well (7) for injecting seepage fluid; the pumping and heating assembly is connected to the outlet end of the pumping and heating well (8) for pumping out seepage fluid; The multi-parameter monitoring unit includes a liquid pressure sensor (14), a thin-film distributed pressure sensor (16), a temperature sensor (15), a displacement sensor (21), and an industrial camera (17); multiple liquid pressure sensors (14) are embedded at different spatial locations within the test sample (1) at intervals; the thin-film distributed pressure sensor (16) is laid at the bottom of the test sample (1); multiple temperature sensors (15) are embedded at different spatial locations within the test sample (1) at intervals; the displacement sensor (21) is installed at the upper end of the support box (32) and connected to the loading plate (4); the industrial camera (17) is supported on one side outside the support box (32).

2. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The multi-parameter monitoring unit also includes a data processing terminal (18); the data processing terminal (18) is connected to a liquid pressure sensor (14), a thin-film distributed pressure sensor (16), a temperature sensor (15), a displacement sensor (21), an industrial camera (17), a ground temperature simulation heating component (6), a reinjection component, and a pumping heating component.

3. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The supporting box (32) includes a support frame (20) and a transparent water tank (2). The transparent water tank (2) is installed in the support frame (20), and a drain outlet (19) is provided at the bottom of one side of the transparent water tank (2), and a plug is installed at the drain outlet (19).

4. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The loading plate (4) is made of stainless steel; the flexible pad (3) is made of silicone.

5. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The recharge assembly includes a recharge tank (9), an electric motor (10), and a recharge pump (11). The reinjection tank (9) stores seepage fluid; the drive shaft of the reinjection pump (11) is coaxially connected to the output shaft of the motor (10), its inlet is connected to the reinjection tank (9) through the replenishment pipeline (28), and its outlet is connected to the inlet end of the reinjection well (7) through the injection pipeline (29); The multi-parameter monitoring unit also includes an electromagnetic flowmeter (12) and a pressure transmitter (13); the electromagnetic flowmeter (12) and the pressure transmitter (13) are connected in sequence to the filling pipeline (29).

6. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The pumping and heating assembly includes a pumping tank (23), a second electric motor (24), and a pumping pump (25). The drive shaft of the pump (25) is coaxially connected to the output shaft of the second motor (24). Its inlet is connected to the outlet of the pumping and heating well (8) through the pumping pipeline (30), and its outlet is connected to the pumping water tank (23) through the drain pipeline (31). The multi-parameter monitoring unit also includes an electromagnetic flowmeter (26) and a pressure transmitter (27); the electromagnetic flowmeter (26) and the pressure transmitter (27) are connected in sequence to the extraction pipeline (30).

7. The multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas according to claim 1, characterized in that, The test sample (1) is a broken coal and rock mass; the transparent water tank (2) is made of acrylic material.

8. A multi-field coupled simulation test method for water storage and heat recovery in abandoned mine goaf areas, employing the multi-field coupled simulation test system for water storage and heat recovery in abandoned mine goaf areas as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Determine the test operating conditions and set the test parameters; S2: Preparation of test sample (1); S3: Assembly and testing of the test system; S4: Establish stress and temperature field; load multiple counterweights (5) in an array on the loading plate (4), and collect stress signals at the bottom of the test sample (1) in real time through a thin-film distributed pressure sensor (16) until the stress value inside the test sample (1) reaches the target loading stress value range; at the same time, start the ground temperature simulation heating component (6) to heat until the internal temperature of the test sample (1) reaches the preset ground temperature boundary value. S5: Water storage and heating operation test; start the reinjection assembly and the pumping heating assembly to make the test system run stably according to the preset operating conditions and simulate the actual water storage and heating process; during the simulation, the injection flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 1 (12), the injection pressure signal of the seepage liquid is collected in real time by pressure transmitter 1 (13), the extraction flow rate of the seepage liquid is collected in real time by electromagnetic flowmeter 2 (26), the extraction pressure signal of the seepage liquid is collected in real time by pressure transmitter 2 (27), the hydraulic pressure signal at different spatial positions in the test sample (1) is collected in real time by multiple liquid pressure sensors (14), the stress signal at the bottom of the test sample (1) is collected in real time by thin film distributed pressure sensor (16), the temperature signal at different spatial positions in the test sample (1) is collected in real time by temperature sensor (15), the displacement signal of the loading plate (4) is collected in real time by displacement sensor (21), and the image data of the seepage process and structural changes are collected in real time by industrial camera (17). S6: Test termination and unloading; When the preset termination conditions are met, control the reinjection component and the pumping heating component to stop, control the ground temperature simulation heating component (6) to stop industrial operation, remove the plug in the drain outlet (19) to carry out drainage operation, and then unload the counterweight block (5) in stages. S7: Formation of in-situ solidified body; The heated and melted impregnated solidified structural material is injected into the bearing cavity by partial or complete injection. Capillary action and gravity are used to make the impregnated solidified material enter the pores of the sample (1) and wrap the particles to form a solidified body that maintains the in-situ structure. S8: Grid-based sampling and three-dimensional quantitative characterization; S81: Spatial positioning sampling of the solidified body according to the pre-designed grid coordinates; During the sampling process, the principle of in-situ and low disturbance is followed to obtain the original structural samples at each sampling location; S82: The original structural samples are scanned using CT scanning technology, and the pore structure parameters and particle spatial distribution characteristics of the samples are obtained through three-dimensional reconstruction analysis methods to achieve quantitative characterization of the blockage area and structural evolution.

9. The multi-field coupled simulation test method for water storage and heat recovery in abandoned mine goaf areas according to claim 8, characterized in that, In S2, the preparation process of test sample (1) is as follows: First, coal and rock samples were collected on site and crushed using a jaw crusher to prepare crushed coal and rock particles. Then, the crushed coal and rock particles were screened and graded to obtain crushed coal and rock particles of different sizes. Subsequently, the surfaces of the crushed coal and rock particles of different sizes were dyed with different colors of water-resistant dyes, and then naturally air-dried and dried to form traceable test samples (1).

10. The multi-field coupled simulation test method for water storage and heat recovery in abandoned mine goaf areas according to claim 9, characterized in that, In S3, the assembly and testing process of the experimental system is as follows: S31: Install a ground temperature simulation heating component (6) at the bottom of the bearing cavity in the bearing box (32), and lay a thin film distributed pressure sensor (16) above the ground temperature simulation heating component (6). S32: The test sample (1) is loaded into the bearing cavity by layered loading, and multiple liquid pressure sensors (14) and multiple temperature sensors (15) are buried at predetermined positions respectively. S33: A flexible pad (3) and a loading plate (4) are laid on top of the test sample (1) in sequence; at the same time, a displacement sensor (21) is installed on the upper end of the bearing box (32) and connected to the loading plate (4); S34: Make the lower ends of the reinjection well (7) and the pumping heating well (8) pass through the flexible pad (3) and the loading plate (4) and extend into the test sample (1), and make the reinjection assembly connect to the reinjection well (7) and the pumping heating assembly connect to the pumping heating well (8). S35: Start the reinjection assembly and the pumping heat extraction assembly, and run them in a cycle for 20 to 30 minutes under the set flow conditions to ensure that there is no leakage in any part of the system and that the operating conditions are stable.

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