Mineral heat co-mining three-field coupling test system and test method thereof

Abstract

The invention provides an ore-heat co-production three-field coupling test system. The ore-heat co-production three-field coupling test system comprises a main body structure, a stress loading module, a bottom heating module, an injection-production-extraction module, a temperature monitoring network and a data acquisition control module, a heat-resistant transparent observation window is arranged on the front side of the main body structure, and a working space for accommodating a rock sample is formed inside; the stress loading module comprises a vertical loading system and a horizontal loading system, the vertical loading system applies vertical stress through an independent servo loading unit, and the horizontal loading system integrates injection-production holes and applies controllable horizontal stress; the bottom heating module comprises an electric hot plate array and a temperature control system and is used for zone temperature control; the injection-extraction module is connected to an injection-extraction hole of the horizontal loading system through a constant-temperature water tank and a high-precision plunger pump, and fluid extraction is achieved through a vacuum pump. The temperature monitoring network comprises a small-diameter armored probe pre-embedded in the sample and an infrared thermal imager arranged outside the observation window; the data acquisition control module synchronously acquires stress, seepage and temperature data and controls the modules to operate cooperatively.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering and geothermal extraction technology, specifically a three-field coupled test system and test method for co-mining geothermal resources. Background Technology

[0002] As shallow mineral resources become increasingly depleted, mining operations are gradually extending to deeper areas. However, deep mining faces a complex geological environment characterized by "three highs and one disturbance," namely, high ground stress, high ground temperature, high osmotic pressure, and intense mining disturbance, with the high ground temperature problem being particularly prominent.

[0003] The high-temperature environment in deep mines is mainly due to the influence of the geothermal gradient; generally, the ground temperature increases by 2.5-3.0℃ for every 100m of depth. When the mining depth reaches 2000m, the rock temperature can reach 60-80℃. High temperatures not only seriously threaten the lives and health of miners but also significantly increase the cost of mine ventilation and cooling, reducing mining efficiency. It is estimated that cooling costs in deep mines account for 15-25% of production costs, and in some high-temperature mines, this figure even exceeds 30%.

[0004] At the same time, deep, high-temperature rock masses also contain abundant geothermal energy resources. Based on a geothermal gradient of 30℃ / km, the rock temperature at a depth of 1000m is approximately 40℃, and at a depth of 2000m it is approximately 70℃, possessing the basic conditions for geothermal development. If mining and geothermal extraction can be combined to achieve co-extraction of minerals and heat, not only can the heat hazard problem in deep mines be solved, but geothermal energy can also be recovered and utilized, achieving comprehensive resource utilization and energy conservation and emission reduction.

[0005] Co-mining involves complex multi-physics coupling processes. Stress redistribution caused by mining disturbances can induce surrounding rock fracturing, forming new seepage channels; the migration of high-temperature fluids within the fracture network alters the temperature field distribution of the rock mass; and temperature changes, in turn, cause thermal stress and deformation in the rock mass, further affecting the stress and seepage fields. This stress-seepage-temperature (THM) three-field coupling mechanism is complex and represents a core scientific problem in co-mining technology.

[0006] Existing experimental research methods have many shortcomings. Traditional rock mechanics testing machines mainly focus on stress-strain relationships and lack the function of coupling temperature field and seepage field; geothermal mining experimental devices focus on simulating heat and mass transfer processes and do not adequately consider mining-induced stress; although mine floor water inrush experimental devices consider the coupling of stress and seepage, they ignore the influence of temperature field.

[0007] Specifically, the existing technology has the following problems:

[0008] (1) Incomplete physical field coupling. Most experimental systems can only achieve single physical field or two-field coupling, and cannot truly simulate the interaction of stress-seepage-temperature three fields. The few systems that claim to achieve three-field coupling are simply superimposed and lack a real coupling mechanism.

[0009] (2) Low level of visualization. Traditional experimental devices use steel sealed containers, which cannot directly observe the internal processes. Even if observation windows are installed, they are mostly small-sized glass, which limits the observation range. Moreover, the glass is prone to breakage under high temperature and pressure, posing a safety hazard.

[0010] (3) The injection and extraction modes are limited. The injection and extraction locations of the existing equipment are fixed, making it impossible to simulate different injection and extraction configurations. In actual mines, the arrangement of injection and extraction wells has a significant impact on thermal extraction efficiency, requiring experimental optimization.

[0011] (4) Poor system integration. Each functional module operates independently, lacking a unified control platform, making data synchronization difficult and resulting in low experimental efficiency.

[0012] Therefore, there is an urgent need to develop an experimental system capable of achieving true coupling of the stress-seepage-temperature three fields, with high visualization, high monitoring accuracy, flexible injection-production modes, and co-mining of mineral and thermal resources, providing a scientific experimental platform for the management of thermal hazards in deep mines and the coordinated exploitation of geothermal resources. A variable experimental system for co-mining of mineral and thermal resources is needed. Summary of the Invention

[0013] The main objective of this invention is to provide a three-field coupling test system and test method for co-mining mineralized thermal mining that can achieve real coupling of stress, seepage and temperature fields, has high visualization and high monitoring accuracy.

[0014] The three-field coupled experimental system for co-mining mineralization and thermal mining provided by this invention includes a main structure, a stress loading module, a bottom heating module, an injection-production-extraction module, a temperature monitoring network, and a data acquisition and control module. The main structure has a heat-resistant transparent observation window on its front side, forming a working space to accommodate rock samples. The stress loading module includes a vertical loading system and a horizontal loading system. The vertical loading system applies vertical stress through an independent servo loading unit, while the horizontal loading system integrates injection-production holes and applies controllable horizontal stress. The bottom heating module includes a heating plate array and a temperature control system for zoned temperature control. The injection-production-extraction module is connected to the injection-production holes of the horizontal loading system via a constant-temperature water tank and a high-precision plunger pump, and achieves fluid extraction through a vacuum pump. The temperature monitoring network includes a fine-diameter armored probe pre-embedded inside the sample and an infrared thermal imager positioned outside the observation window. The data acquisition and control module synchronously acquires stress, seepage, and temperature data and controls the coordinated operation of each module.

[0015] In one embodiment of the above-mentioned test system, the horizontal loading system includes multiple adjustable loading rods, each with an injection / sampling port equipped with an independent flow control valve, a pressure sensor, and a temperature sensor.

[0016] In one embodiment of the above-mentioned test system, the heating plate array is divided into multiple independent temperature control zones. The temperature of each temperature control zone is adjusted by a PID control strategy, and a multi-layer insulation system is provided at the bottom. The multi-layer insulation system includes, from bottom to top, aluminum silicate fiber felt, nano aerogel felt and stainless steel reflector.

[0017] In one embodiment of the above-mentioned test system, the injection-production-extraction module supports switching between multiple injection-production modes, including well-to-well injection-production mode, in-seam injection-production mode, and distributed injection-production mode; in the well-to-well injection-production mode, water is injected through one injection-production hole and extracted through the other extraction hole; in the in-seam injection-production mode, a parallel flow field is formed through multiple injection-production holes on the same side; in the distributed injection-production mode, one injection for multiple extractions or multiple injections for one extraction is achieved through independent valve control.

[0018] In one embodiment of the above-mentioned test system, the heat-resistant transparent observation window is composed of a heat-resistant quartz glass plate and an outer nano-aerogel layer, and the glass plate is connected to the main structure through an elastic sealing system.

[0019] In one embodiment of the above-mentioned test system, a tunnel cavity is pre-embedded inside the main structure. The tunnel cavity is made of high thermal conductivity ceramic material, with an air inlet and an air outlet connected at both ends, and the bottom is open to simulate heat transfer from the rock mass.

[0020] In one embodiment of the above-mentioned test system, the temperature monitoring network further includes fiber optic temperature sensors and miniature wind speed sensors arranged in the tunnel cavity to monitor the axial temperature gradient and cross-sectional flow field distribution of the tunnel.

[0021] In one embodiment of the above-mentioned test system, the bottom heating module is equipped with a safety protection system, including a thermocouple for real-time temperature monitoring; a leakage protection switch and an emergency stop button for circuit protection; and a temperature fuse that automatically cuts off the power supply when the temperature exceeds the limit.

[0022] A method for conducting a co-mining experiment using the above-mentioned experimental system, comprising the following specific steps:

[0023] 1. Sample preparation and system initialization

[0024] Based on similarity theory, model similarity criteria were determined, and similarity parameters for rock mass, roadway, pillar, goaf, and backfill were identified. Rock similarity material samples were prepared using cement, quartz sand, and gypsum, with dimensions matching the working space of the main structure. Fine-diameter armored temperature probes were pre-embedded inside the samples at key monitoring points. Fiber optic temperature sensors were arranged along the axial direction of the roadway cavity. Miniature wind speed sensors were placed at the roadway cross-section and air inlet and outlet. The samples were then installed into the main structure, sealed with heat-resistant quartz glass plates, and fitted with a nano-aerogel insulation layer. The injection and extraction modules were connected, and finally, the data acquisition and control module was activated to calibrate all sensors.

[0025] 2. Initial Three Fields Construction

[0026] Stress field loading: Adjust the pressure of the servo loading unit and the flexible airbag to apply gradient loading to the target value to complete the vertical stress loading; then apply non-uniform stress by the adjustable loading rod of the horizontal loading system to simulate the actual ground stress field and complete the horizontal stress loading.

[0027] Temperature field establishment: Start the electric heating plate array, control the temperature in zones through the temperature control system, and set up a multi-layer insulation system;

[0028] Initialization of seepage field: The constant temperature water tank is turned on and the sample is injected through a high-precision plunger pump; the vacuum pump maintains negative pressure at the extraction end to form a stable seepage field; the electromagnetic flowmeter monitors the flow rate in real time.

[0029] 3. Mining disturbance simulation and three-field coupled monitoring

[0030] Dynamic mining disturbance: The vertical stress is unloaded in a stepwise manner by a servo control system to simulate the mining stress relief process; the horizontal loading system synchronously adjusts the stress distribution to induce the propagation of surrounding rock fissures.

[0031] Three-field coupled data acquisition: pressure sensors monitor stress redistribution caused by fracture development to complete stress field acquisition; fluid channel sensors record flow and pressure changes in the fracture network, and combined with infrared thermal imagers to observe heat flow migration paths to complete seepage field acquisition; armored probes acquire internal point temperatures; infrared thermal imagers scan the surface temperature field; fiber optic sensors monitor the temperature gradient within the tunnel to complete temperature field acquisition.

[0032] 4. Injection and Propagation Mode Switching

[0033] By combining different injection and extraction modules, multiple injection and extraction modes can be achieved; by switching injection and extraction modes, tests of different modes can be completed.

[0034] 5. Thermal extraction experiment and parameter optimization

[0035] Different mining layouts were simulated based on predetermined roadway spacing, pillar width, backfill width, and goaf height. Thermal extraction experiments were conducted on the ore body mining and injection-production processes to analyze heat recovery efficiency. Based on the collected monitoring data such as stress, temperature, and seepage, a multi-field coupled numerical model was established to compare and analyze different roadway-pillar-backfill layouts and injection-production schemes, and to optimize the ore-thermal co-mining parameters and heat recovery strategies.

[0036] The beneficial effects of this invention are as follows:

[0037] 1. By integrating injection and production boreholes within the horizontal loading system, the physical coupling of stress and seepage fields is achieved; combined with the bottom electric heating plate array for zoned temperature control and the roadway ventilation simulation structure, a foundation for the dynamic interaction of stress, seepage, and temperature fields is established; breaking through the coupling limitations of traditional devices, the fully coupled process of "mining-induced stress-induced fractures → seepage channel formation → thermal migration feedback rock mass deformation" in deep mines is realistically reproduced for the first time in experiments; modular design enhances the system's scalability and supports complex working condition simulation of multi-scale rock mass samples;

[0038] 2. A heat-resistant quartz glass plate + nano-aerogel composite window is adopted, combined with a fine-diameter armored temperature probe and an infrared thermal imager for non-contact monitoring, forming a dual temperature field acquisition scheme of internal point measurement and surface scanning; full-process visualization is achieved in extreme environments, and crack propagation and heat flow are directly observed; the infrared thermal imaging and embedded sensor work together to improve the spatial resolution of the temperature field to the millimeter level, providing high-precision data for the verification of coupled models;

[0039] 3. Based on the reconfigurable injection-production hole array and independent valve control unit, it supports rapid switching between different injection and production modes; combined with the adjustable parameters module of roadway-pillar-filling body, it realizes dynamic optimization of mining layout. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure of the experimental system of the present invention;

[0041] Figure 2 for Figure 1 Schematic diagram of the structure of the middle tunnel cavity;

[0042] Figure 3 for Figure 1 A schematic diagram of the structure of the electric heating plate array;

[0043] Figure 4 for Figure 3 Schematic diagram of a multi-layer thermal insulation system;

[0044] Figure 5 for Figure 1 A schematic diagram of the structure of the central security protection system;

[0045] Figure 6 for Figure 1 Schematic diagram of the lateral structure of the injection well;

[0046] Figure 7 This is a schematic diagram of the temperature monitoring network in this embodiment;

[0047] Figure 8 This is a schematic diagram of the data acquisition control module in this embodiment;

[0048] Figure 9 This is a schematic diagram of the structure of the large-size rock sample in this embodiment;

[0049] Figure 10 This is a schematic diagram of different injection and extraction modes of the present invention.

[0050] The attached figures are labeled as follows:

[0051] 1. Main structure; 2. Stress loading module; 3. Bottom heating module; 4. Injection and extraction module; 5. Temperature monitoring network; 6. Data acquisition and control module; 11. Heat-resistant quartz glass plate; 12. Air inlet; 13. Tunnel cavity; 14. Air outlet; 21. Vertical loading system; 22. Flexible airbag; 23. Gas storage tank; 24. Servo control system; 25. Horizontal loading system; 31. Heating plate array; 32. Safety protection system; 33. Temperature control system; 34. Multi-layer insulation system; 41. Constant temperature water tank; 42. High-precision plunger pump; 43. Electromagnetic flowmeter; 4 4. Injection / Production Port; 45. Vacuum Pump; 46. Glass Collection Tank; 5. Temperature Monitoring Network; 51. Fine-diameter Armored Probe; 52. Infrared Thermal Imager; 61. Temperature Acquisition System; 62. Temperature Display Computer; 131. Fiber Optic Temperature Sensor; 132. Miniature Wind Speed ​​Sensor; 321. Thermocouple; 322. Leakage Protection Switch; 323. Emergency Stop Button; 324. Temperature Fuse; 341. Thick Alumina Silicate Fiber Felt; 342. Thick Nano-Aerogel Felt; 343. Stainless Steel Reflector; 441. Injection / Production Outlet; 442. Extraction / Production Outlet; 443. Fluid Channel Sensor. Detailed Implementation

[0052] The relevant technical solutions will now be clearly and completely described with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only a part of the embodiments, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] like Figure 1As shown, the three-field coupled experimental system for co-mining mineralization and thermal energy disclosed in this embodiment includes a main structure 1, a stress loading module 2, a bottom heating module 3, an injection-production extraction module 4, a temperature monitoring network 5, and a data acquisition and control module 6. These modules work together to achieve dynamic coupled simulation of the stress field, seepage field, and temperature field through physical connection.

[0054] The main structure 1 serves as the basic frame. The stress loading module 2 is installed on the top and sides of the main structure 1. The bottom heating module 3 is fixed below the bottom plate of the main structure 1. The injection and extraction module 4 is integrated into the horizontal loading system 25 of the stress loading module 2. The temperature monitoring network 5 is distributed inside and on the surface of the sample and is connected to the data acquisition and control module 6 through data cables. The data acquisition and control module 6 communicates with all monitoring and control units through a bus system to achieve synchronous data acquisition and real-time control.

[0055] The main structure 1 is a rectangular box welded from high-strength metal materials, which forms a working space inside that can accommodate large-sized rock-like material samples.

[0056] A high-transmittance heat-resistant quartz glass plate 11 is installed on the front side of the main structure 1. This glass plate is connected to the main structure through an elastic sealing system to ensure airtightness and thermal expansion adaptability under high-temperature environments. Furthermore, a high-performance insulation layer such as nano-aerogel is installed on the outer side of the glass plate to enhance overall insulation performance. The rear side of the main structure uses a metal plate with an air inlet 12 and an air outlet 14. The air inlet and outlet are made of corrosion-resistant metal materials and equipped with flange interfaces and controllable valves for connecting to external air sources.

[0057] like Figure 2 As shown, the main structure 1 also has a pre-embedded tunnel cavity 13, which is made of high thermal conductivity and high temperature resistant ceramic material and is reliably connected to the main structure 1 through multiple sealing structures. The two ends of the tunnel cavity 13 are respectively connected to the air inlet 12 and the air outlet 14, and sealing gaskets are set at the interface to improve the overall sealing of the ventilation system; the bottom of the tunnel cavity is empty to simulate the heat transfer process of the bottom rock mass.

[0058] The tunnel cavity 13 is equipped with sensor components, including an optical fiber temperature sensor 131 arranged along the tunnel axis to obtain the temperature distribution inside the tunnel; miniature wind speed sensors 132 arranged at different positions on the tunnel cross section to monitor the flow field distribution inside the tunnel; in addition, wind speed sensors are set at the air inlet 12 and the air outlet 14 to monitor the ventilation wind speed and heat exchange efficiency of the tunnel in real time.

[0059] The stress loading module 2 includes a vertical loading system 21 and a horizontal loading system 25.

[0060] The vertical loading system 21 is installed on top of the main structure 1 and consists of multiple independent servo loading units, flexible airbags 22, air tanks 23, and a servo control system 24. The flexible airbags 22 are connected to the air tanks 23 via pipelines, and the servo control system 24 adjusts the vertical stress applied by the servo loading units. The vertical loading system can continuously and adjustably apply vertical stress within a preset range and precisely control the loading process to simulate the ground stress state under different deep burial conditions.

[0061] The horizontal loading system 25 is installed on the left and right sides of the main structure 1. It consists of multiple adjustable loading rods. The adjustable loading rods apply controllable horizontal stress to the sample, making the loading point position and loading form adjustable, thereby simulating the complex horizontal stress field distribution.

[0062] The horizontal loading system 25 is equipped with an independent servo control system 24, including pressure sensors and displacement sensors, for real-time monitoring and feedback control of the horizontal stress state.

[0063] The horizontal loading system 25 also integrates the injection and extraction holes 44 of the injection and extraction module 4. The left loading rod is drilled for water injection, and the right loading rod is drilled for extraction. The two are connected by fluid pipelines to realize the comprehensive simulation of horizontal stress and seepage field.

[0064] The bottom heating module 3 is fixed below the base plate of the main structure 1, and includes an electric heating plate array 31, a safety protection system 32, a temperature control system 33, and a multi-layer insulation system 34.

[0065] like Figure 3 As shown, the heating plate array 31 consists of multiple carbon fiber heating plates, one end of which is covered by a multi-layer insulation system, enabling adjustable heating within a certain temperature range. Each carbon fiber heating plate uses high-temperature resistant heating elements and is encapsulated with an insulation layer. The surface temperature can be adjusted within a preset range to create different bottom temperature field distributions. Gaps are reserved between the heating plates to facilitate thermal expansion and maintenance / replacement.

[0066] The heating plate array 31 covers the bottom area of ​​the sample and is connected to the safety protection system 32 and the temperature control system 33 via cables. The temperature control system adopts a PID control strategy, dividing the heating plate array into several control zones. The heating plates in each control zone are adjusted in conjunction to achieve fine adjustment of the bottom temperature field.

[0067] like Figure 4 As shown, the multi-layer insulation system 34 comprises, from bottom to top, a thick aluminum silicate fiber felt 341, a thick nano-aerogel felt 342, and a stainless steel reflector 343. The multi-layer insulation system is used to reduce heat loss and improve heating efficiency and temperature field stability.

[0068] like Figure 5As shown, the safety protection system 32 includes a thermocouple 321, a leakage protection switch 322, an emergency stop button 323, and a temperature fuse 324. It is connected to the heating plate array 31 and the temperature control system 33 through a circuit to realize over-temperature protection and emergency shutdown.

[0069] Each control zone is equipped with an independent temperature fuse 324 and thermocouple 321 for temperature monitoring. When the temperature exceeds the preset safety threshold, the heating power supply is automatically cut off. The main circuit is equipped with a leakage protection switch 322 and an emergency stop button 323. When leakage is detected or the emergency stop button is triggered in an emergency, the system immediately cuts off the relevant power supply and triggers the alarm device, thereby ensuring the safety of experimental personnel and equipment.

[0070] like Figure 6 As shown, the injection-production-extraction module 4 is implemented based on the drilling of the horizontal loading system 25, and includes a left-side injection-production system and a right-side extraction system.

[0071] The injection and extraction system consists of a constant-temperature water tank 41, a high-precision plunger pump 42, an electromagnetic flowmeter 43, and an injection / extraction port 44, all connected sequentially via pipelines. The extraction system consists of a vacuum pump 45, a glass collection tank 46, and an extraction port 44, also connected via pipelines. It is used to achieve constant-temperature injection, stable delivery, precise metering, extraction, and collection of fluids.

[0072] The injection-production port 44 is divided into an injection-production outlet port 441 and a extraction outlet port 442. Each port is equipped with an independent flow control valve, pressure sensor and temperature sensor, which can be finely adjusted and monitored in real time within the preset flow and pressure range to adapt to different injection-production conditions.

[0073] Fluid channel sensors 443 are arranged at key locations in the injection and production ports 44, including at least the injection port, the extraction port, and the junction of the main flow channels, to monitor the flow rate, pressure, and temperature changes of the fluid during the injection and production process, and to realize the visualization analysis of the seepage channels and seepage process.

[0074] The injection / production port 44 is made of stainless steel with an inner diameter of 6mm and is equipped with quick connectors for easy pipeline connection. Because multiple sets of injection / production ports are configured, several injection / production channels can be formed, supporting various injection / production modes such as well-to-well injection / production, in-seam injection / production, and cross-injection / production. In well-to-well injection / production mode, water is injected through one injection / production port and extracted through the other extraction port; in-seam injection / production mode, multiple injection / production ports on the same side form a parallel flow field; and in distributed injection / production mode, independent valve control enables one injection for multiple extractions or multiple injections for one extraction.

[0075] like Figure 7 As shown, the temperature monitoring network 5 consists of two parts: internal point measurement and surface scanning.

[0076] Internal point measurements utilize a small-diameter armored probe 51, pre-embedded inside the sample and fluid channels. It is connected to the data acquisition and control module 6 via a small hole filled with sealing material. The sealing material is similar to the thermal properties of the rock mass to minimize disturbance to fluid flow and heat transfer, ensuring that the monitoring process does not significantly alter the original multi-field coupling characteristics. A multi-wire connection method is preferred for the lead wires to reduce the influence of conductor resistance on the measurement results.

[0077] The surface scanning is performed using an infrared thermal imager 52, which is positioned on the outside of the heat-resistant quartz glass plate 11 at the front of the main structure 1, to monitor the sample surface temperature non-contactly and continuously. The infrared thermal imager can acquire the spatiotemporal changes of the large-scale temperature field, complementing the multi-point temperature sensors deployed inside the rock mass, thereby achieving coordinated monitoring of the internal and surface temperature fields of the sample, thus improving the completeness and visualization effect of the temperature field acquisition.

[0078] The fiber optic temperature sensor 131 and the miniature wind speed sensor 132 inside the tunnel cavity 13 are also connected to the temperature monitoring network 5.

[0079] like Figure 8 As shown, the data acquisition and control module 6 includes a temperature acquisition system 61 and a temperature display computer 62. The temperature acquisition system connects all temperature sensors and the infrared thermal imager 52 via data cables, supporting multi-channel synchronous acquisition. The temperature display computer 62 connects to the temperature acquisition system 61, the servo control system 24, and the temperature control system 33 via a bus system, enabling real-time data display and program control.

[0080] The overall structure of this invention serves to simulate the stress-seepage-temperature three-field coupling phenomenon during the deep mine thermal mining process. This is achieved by: applying controllable vertical and horizontal stresses through the stress loading module 2 to simulate the geostress field and induce rock mass fractures; providing zoned temperature-controlled heat sources through the bottom heating module 3 to construct a temperature gradient; injecting and extracting fluids through the injection-production-extraction module 4 to form a seepage field and promote heat migration; and acquiring multi-field data in real time through the temperature monitoring network 5 and the data acquisition and control module 6. Combined with the visualization design of the heat-resistant quartz glass plate 11, the propagation of fractures and the movement of heat flow are directly observed. Ultimately, this achieves a fully coupled process of fracture induction by mining stress, seepage channel formation, and heat migration feedback to rock mass deformation.

[0081] like Figure 9 As shown, the large-size rock sample in this experimental system has multiple parallel roadways and several pillars arranged in the center of the model. A goaf is formed between the roadways and pillars. Filling material can be optionally placed within the goaf to simulate different mining methods and filling processes. The roadway spacing S1 and pillar width B are shown. p , width of filling body B f and the height H of the goaf mAll parameters are set to adjustable and can be configured and adjusted during model design and construction according to experimental needs, thereby enabling the reproduction of various roadway layouts, such as strip mining, room-and-pillar method, backfilling method, and different pillar-backfill combinations.

[0082] Injection and extraction wells 441 and evacuation wells 442 are arranged on both sides of the model, connecting to the roadway and goaf, forming a visible network of seepage channels within the fractured seepage layer under the action of water injection and extraction. The top vertical loading system 21 applies a downward vertical stress σ. v The horizontal loading system 25 on both sides applies a controllable horizontal stress σ. h The lower part is provided with a local heat source by the bottom heating module 3, forming an upward heat flow q, realizing the real coupling evolution of stress field, seepage field and temperature field. By adjusting the roadway spacing, pillar width, filling body parameters and injection-production hole combination, the thermal-hydraulic-mechanical coupling effect and heat recovery efficiency in the mineral-thermal co-mining process under different mining layouts and filling schemes can be systematically studied.

[0083] Figure 9 The diagram illustrates how the system provides a heat source through the bottom heating module 3, realizes fluid injection and extraction through the injection-extraction module 4, and applies force load through the stress loading module 2, thereby realistically reproducing the thermal-water-force coupling phenomenon in deep mines, including the dynamic processes of fracture propagation, thermal migration, and fluid transport, providing a visual basis for optimizing mining parameters and analyzing heat recovery efficiency.

[0084] To simulate different mining layout schemes, the layout parameters of roadways, pillars, and backfill in the model are all adjustable. Before the experiment, multiple roadway and pillar layout schemes are pre-designed in the mining layer. By changing the centerline spacing of the roadways, the number of roadways, the width of the pillars, and whether backfill is provided, different combinations of mining structures can be simulated. The geometric dimensions and positions of the roadways and pillars can be determined according to different schemes when the model is formed. During the experiment, the model or local structure of the corresponding scheme is selected according to the target working conditions to change the roadway spacing and pillar width. The parameters of the backfill can be adjusted by adjusting the backfill material ratio, density, and thickness.

[0085] The aforementioned adjustable layout allows the model to reproduce various roadway-pillar-fill combinations from actual mines, improving the system's adaptability to on-site conditions.

[0086] A method for conducting a co-mining experiment using this experimental system, comprising the following specific steps:

[0087] 1. Sample preparation and system initialization

[0088] Based on similarity theory, model similarity criteria were determined, and similarity parameters for rock mass, roadway, pillar, goaf, and filling body were determined. Rock similarity material samples were prepared using cement, quartz sand, and gypsum, with dimensions matching the working space of the main structure 1. Fine-diameter armored temperature probes 51 were pre-embedded inside the samples at key monitoring points. Fiber optic temperature sensors 131 were arranged along the axial direction of the roadway cavity 13. Miniature wind speed sensors 132 were placed at the roadway cross-section and air inlet and outlet.

[0089] Next, the sample is loaded into the main structure 1, the heat-resistant quartz glass plate 11 is sealed, and the nano-aerogel insulation layer is installed; the injection and extraction module 4 is connected, and finally the data acquisition and control module 6 is started to calibrate all sensors.

[0090] 2. Initial Three Fields Construction

[0091] Stress field loading: The pressure of the servo loading unit and the flexible airbag 22 is adjusted by the servo control system 24 to load the target value in a gradient manner, thus completing the vertical stress loading; then, the adjustable loading rod of the horizontal loading system 25 applies non-uniform stress to simulate the actual stress field, thus completing the horizontal stress loading.

[0092] Temperature field establishment: Start the electric heating plate array 31, control the temperature in zones through the temperature control system 33, and set up a multi-layer insulation system 34 to reduce heat loss;

[0093] Initialization of seepage field: The constant temperature water tank 41 is turned on, and the sample is injected through the high-precision plunger pump 42; the vacuum pump 45 maintains the negative pressure at the extraction end to form a stable seepage field; the electromagnetic flowmeter 43 monitors the flow rate in real time.

[0094] 3. Mining disturbance simulation and three-field coupled monitoring

[0095] Dynamic mining disturbance: The vertical stress is unloaded in a step-by-step manner by the servo control system 24 to simulate the mining stress relief process; the horizontal loading system 25 synchronously adjusts the stress distribution to induce the expansion of surrounding rock fractures.

[0096] Three-field coupled data acquisition: The pressure sensor monitors the stress redistribution caused by fracture development and completes the stress field acquisition; the fluid channel sensor 443 records the flow and pressure changes in the fracture network, and combined with the infrared thermal imager 52 to observe the heat flow migration path and complete the seepage field acquisition; the armored probe 51 acquires the internal point temperature; the infrared thermal imager 52 scans the surface temperature field; and the fiber optic sensor 131 monitors the temperature gradient in the tunnel and completes the temperature field acquisition.

[0097] 4. Injection and Propagation Mode Switching

[0098] like Figure 10 As shown, various injection and extraction modes can be achieved through different combinations of the injection and extraction modules 4:

[0099] (1) Well injection and production mode: Water is injected into one side of the borehole and extracted from the other side, forming a countercurrent flow field across the sample;

[0100] (2) In-bedding injection-production mode: Injection-production pairs are formed between boreholes at different locations, creating a flow field that is approximately in the bedding direction;

[0101] (3) Multi-point distributed injection and production mode: Each borehole works independently, which can realize complex injection and production combination modes such as one injection and multiple production, multiple injection and one production, and multiple injection and multiple production, thereby simulating the complex injection and production network structure in actual mines.

[0102] Therefore, the injection and extraction modes were switched to complete the tests of different modes.

[0103] 5. Thermal extraction experiment and parameter optimization

[0104] According to the predetermined roadway spacing S1 and pillar width B p , width of filling body B f and the height H of the goaf m Simulate different mining layouts, conduct thermal extraction experiments on ore body mining and injection-production processes, and analyze heat recovery efficiency; and establish a multi-field coupled numerical model based on the collected monitoring data such as stress, temperature and seepage, to compare and analyze different roadway-pillar-backfilling layouts and injection-production schemes, and optimize ore-thermal co-mining mining parameters and heat recovery strategies.

[0105] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-field coupled test system for co-mining mineralized and thermal mining, characterized in that: It includes the main structure, stress loading module, bottom heating module, injection and extraction module, temperature monitoring network, and data acquisition and control module; The main structure has a heat-resistant transparent observation window on the front, forming a working space to accommodate the rock sample. The stress loading module includes a vertical loading system and a horizontal loading system. The vertical loading system applies vertical stress through an independent servo loading unit, while the horizontal loading system integrates injection and extraction holes and applies controllable horizontal stress. The bottom heating module includes an electric heating plate array and a temperature control system for zoned temperature control. The injection and extraction module is connected to the injection and extraction holes of the horizontal loading system through a constant temperature water tank and a high-precision plunger pump, and achieves fluid extraction through a vacuum pump. The temperature monitoring network includes a fine-diameter armored probe pre-embedded inside the sample and an infrared thermal imager set outside the observation window. The data acquisition and control module synchronously acquires stress, seepage, and temperature data and controls the coordinated operation of each module.

2. The three-field coupling test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The horizontal loading system includes multiple adjustable loading rods, each with an injection / sampling port equipped with an independent flow control valve, pressure sensor, and temperature sensor.

3. The three-field coupled test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The heating plate array is divided into multiple independent temperature control zones. Each temperature control zone adjusts its temperature through a PID control strategy. The bottom is equipped with a multi-layer insulation system, which includes aluminum silicate fiber felt, nano aerogel felt, and stainless steel reflector from bottom to top.

4. The three-field coupling test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The injection-production-extraction module supports switching between multiple injection-production modes, including well-to-well injection-production mode, in-seam injection-production mode, and distributed injection-production mode. In the well-to-well injection-production mode, water is injected through one injection-production hole and extracted through the other extraction hole. In the in-seam injection-production mode, multiple injection-production holes on the same side form a parallel flow field. In the distributed injection-production mode, one injection is used to achieve multiple extractions or multiple injections are used to achieve one extraction.

5. The three-field coupled test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The heat-resistant transparent observation window is composed of a heat-resistant quartz glass plate and an outer nano-aerogel layer, and the glass plate is connected to the main structure through an elastic sealing system.

6. The three-field coupling test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The main structure has a pre-embedded tunnel cavity, which is made of high thermal conductivity ceramic material. The two ends are connected to the air inlet and the air outlet, respectively, and the bottom is open to simulate the heat transfer of the rock mass.

7. The three-field coupling test system for co-mining mineral and thermal mining as described in claim 6, characterized in that: The temperature monitoring network also includes fiber optic temperature sensors and miniature wind speed sensors arranged in the tunnel cavity to monitor the axial temperature gradient and cross-sectional flow field distribution of the tunnel.

8. The three-field coupling test system for co-mining mineral and thermal mining as described in claim 1, characterized in that: The bottom heating module is equipped with a safety protection system, including thermocouples for real-time temperature monitoring; leakage protection switches and emergency stop buttons for circuit protection; and a temperature fuse that automatically cuts off the power supply when the temperature exceeds the limit.

9. A method for conducting a co-mining test using the test system as described in any one of claims 1-8, characterized in that, The specific steps are as follows: (1) Sample preparation and system initialization Based on similarity theory, model similarity criteria were determined, and similarity parameters for rock mass, roadway, pillar, goaf, and backfill were identified. Rock similarity material samples were prepared using cement, quartz sand, and gypsum, with dimensions matching the working space of the main structure. Fine-diameter armored temperature probes were pre-embedded inside the samples at key monitoring points. Fiber optic temperature sensors were arranged along the axial direction of the roadway cavity. Miniature wind speed sensors were placed at the roadway cross-section and air inlet and outlet. The samples were then installed into the main structure, sealed with heat-resistant quartz glass plates, and fitted with a nano-aerogel insulation layer. The injection and extraction modules were connected, and finally, the data acquisition and control module was activated to calibrate all sensors. (2) Initial three-field construction Stress field loading: Adjust the pressure of the servo loading unit and the flexible airbag to apply gradient loading to the target value to complete the vertical stress loading; then apply non-uniform stress by the adjustable loading rod of the horizontal loading system to simulate the actual ground stress field and complete the horizontal stress loading. Temperature field establishment: Start the electric heating plate array, control the temperature in zones through the temperature control system, and set up a multi-layer insulation system; Initialization of seepage field: The constant temperature water tank is turned on and the sample is injected through a high-precision plunger pump; the vacuum pump maintains negative pressure at the extraction end to form a stable seepage field; the electromagnetic flowmeter monitors the flow rate in real time. (3) Mining disturbance simulation and three-field coupled monitoring Dynamic mining disturbance: The vertical stress is unloaded in a stepwise manner by a servo control system to simulate the mining stress relief process; the horizontal loading system synchronously adjusts the stress distribution to induce the propagation of surrounding rock fissures. Three-field coupled data acquisition: pressure sensors monitor stress redistribution caused by fracture development to complete stress field acquisition; fluid channel sensors record flow and pressure changes in the fracture network, and combined with infrared thermal imagers to observe heat flow migration paths to complete seepage field acquisition; armored probes acquire internal point temperatures; infrared thermal imagers scan the surface temperature field; fiber optic sensors monitor the temperature gradient within the tunnel to complete temperature field acquisition. (4) Switching between injection and extraction modes By combining different injection and extraction modules, multiple injection and extraction modes can be achieved; by switching injection and extraction modes, tests of different modes can be completed. (5) Thermal extraction experiment and parameter optimization Different mining layouts were simulated based on predetermined roadway spacing, pillar width, backfill width, and goaf height. Thermal extraction experiments were conducted on the ore body mining and injection-production processes to analyze heat recovery efficiency. Based on the collected monitoring data such as stress, temperature, and seepage, a multi-field coupled numerical model was established to compare and analyze different roadway-pillar-backfill layouts and injection-production schemes, and to optimize the ore-thermal co-mining parameters and heat recovery strategies.

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