A comprehensive test platform for detecting hidden fire sources of deep-mine coal spontaneous combustion

Abstract

This invention discloses a comprehensive experimental platform for detecting concealed fire sources of spontaneous combustion in deep-well coal, comprising an experimental system, a pressurization system, and a temperature control and measurement system. It can conduct large-volume single-bearing pressure tests, and its side plates are designed with inner and outer layers of specific materials, enabling the platform to withstand high lateral stresses while also conducting demanding measurement tests such as ultrasonic testing. This tightly fitted double-layer design helps to understand the evolution mechanism of various parameters in the entire process of coal pillar from compression and fracturing to oxidative spontaneous combustion. Furthermore, a specific sensor grid, constructed in a three-dimensional mesh structure within the experimental chamber of the experimental system, facilitates data acquisition during the test. Through their combined operation, the platform enables in-situ simulation of the entire process of real-time loading and pressure on a coal pillar in a goaf, leading to fracture development and spontaneous combustion grouting; providing equipment support for studying the evolution of coal fracturing, spontaneous combustion, and grouting seepage processes.

Description

Technical Field

[0001] This invention relates to an underground integrated testing platform, specifically an integrated testing platform for detecting concealed fire sources of spontaneous combustion in deep coal mines. Background Technology

[0002] Spontaneous combustion of coal is a complex physicochemical process and a crucial aspect of mine fire control and management. This problem has long plagued humanity; spontaneous combustion underground not only poses a significant threat to the lives of miners but also results in substantial resource waste and property damage. Consequently, methods for detecting spontaneous combustion have been developed to help observe and understand the characteristics of the entire combustion process. Applying these characteristics to field practice allows for the timely identification of potential spontaneous combustion hazards, providing a basis for implementing effective prevention and control measures. This helps reduce the occurrence of spontaneous combustion accidents, ensures safe production in coal mines, and mitigates economic losses and the risk of casualties.

[0003] Due to the uncertainty and concealment of coal spontaneous combustion, traditional detection methods such as thermometry and indicator gas methods have limitations, making it difficult to accurately monitor the ignition of coal spontaneous combustion. With technological advancements, coal spontaneous combustion detection technology is constantly improving. Currently, in addition to traditional detection methods, technologies such as ultrasonic detection and resistivity detection have emerged, providing more means and methods for coal spontaneous combustion detection. Since one important cause of coal spontaneous combustion is air leakage through coal fissures, leading to an increase in internal oxygen and subsequent coal oxidation and heating, the primary method to reduce air leakage is currently grouting into the fissures to seal them, thereby slowing down the rate of coal oxidation. However, understanding the seepage pattern of the grout within the coal column is crucial for achieving better sealing results. Currently, there is no experimental platform capable of testing resistivity-based coal spontaneous combustion detection methods and determining the seepage pattern within the coal column after grouting.

[0004] Based on this, the research direction of this invention is to provide a new comprehensive test platform that can help understand the continuous development of internal fractures of coal pillars before and after entering the goaf, help understand the evolution mechanism of various parameters in the entire process of coal pillar from compression crushing to oxidation and spontaneous combustion, as well as the seepage law of grout inside the coal pillar when grouting is used to reinforce the coal pillar, and be able to use a resistivity detection system to study the synchronous response law of resistivity to the above coal crushing, coal spontaneous combustion and grouting seepage process. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines, which can effectively solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines, including a test system, a pressurization system, and a temperature control and measurement system;

[0007] The test system shown includes a base, columns, and a base plate. The base plate is fixed on the base to ensure that it is level with the ground and has a certain gap. Multiple columns are vertically fixed on the base plate, and the upper ends of each column are fixedly connected by a first connecting plate. Side plates are installed between adjacent columns to form a test chamber with multiple first connecting plates, multiple columns, multiple side plates, and the base plate, and to divide the interior of the test chamber into a coal pillar area and a goaf area.

[0008] The pressurization system includes a support truss, two hydraulic cylinders, and two pressure plates. A second connecting plate is mounted on the lower part of the support truss. The support truss is mounted above the test system and fixed by the first and second connecting plates. The two hydraulic cylinders are mounted on the support truss and are positioned directly above the coal pillar area and the goaf area, respectively. The two pressure plates are mounted on the extended ends of the two hydraulic cylinders, with one pressure plate having an area equal to the opening area at the top of the coal pillar area, and the other pressure plate having an area equal to the opening area at the top of the goaf area. When the two hydraulic cylinders extend, they can move their corresponding pressure plates towards the coal pillar area or the goaf area to apply pressure.

[0009] The temperature control and measurement system includes a sensor grid, heating elements, temperature sensors, gas concentration sensors, an ultrasonic transmitter and receiver, and a resistivity testing device. The sensor grid is installed inside the test chamber, and multiple heating elements, temperature sensors, and gas concentration sensors are mounted on the sensor grid. The heating elements are used to regulate the ambient temperature, while the temperature sensors and gas concentration sensors are used to collect ambient temperature and gas concentration data. The heating elements, temperature sensors, and gas concentration sensors are all connected to the outside of the test chamber through connecting lines inside the sensor grid for heating control and data transmission. The ultrasonic transmitter and receiver is used to perform ultrasonic detection on the coal pillar before and after pressure, and the resistivity testing device is used to test the resistivity of the coal pillar before and after grouting.

[0010] Furthermore, the test system also includes a top plate. When the pressure plate of the pressurization system is at its highest position, the top plate can be installed at the upper opening of the test chamber to seal the inside of the test chamber. When the pressurization system is required to conduct a pressure test, the top plate is removed.

[0011] Furthermore, the side plate consists of an inner plate and an outer plate arranged in parallel to each other. The inner plate is made of plexiglass, which facilitates ultrasonic testing. The outer plate is made of steel plate and can be detached and fixed. When it is detached, it is used for ultrasonic testing. Multiple grouting holes are opened on the inner plate in the goaf area for grouting testing.

[0012] Furthermore, the pressurization system also includes multiple guide rods. One end of a portion of the guide rods is perpendicular to and fixedly connected to the upper surface of one of the pressure plates, and the other end of a portion of the guide rods is perpendicular to and fixedly connected to the upper surface of another pressure plate. All guide rods pass through the support truss, and the movement of the guide rods is limited by the support truss, thereby ensuring the uniformity of pressure applied at different positions when the two pressure plates descend to apply pressure.

[0013] Furthermore, the base plate is provided with a threaded opening for the connecting wire to pass through, and is equipped with a screw of the same diameter. When no connecting wire passes through, the screw is fixed in the screw hole to seal it.

[0014] Furthermore, the sensor network frame includes hollow connecting rods, hollow connecting blocks, and plugs. The hollow connecting blocks are rectangular with connection ports on each side. The hollow connecting rods have ports at both ends. The ports of the hollow connecting rods are inserted into one of the connection ports of the hollow connecting blocks, so that the hollow connecting rods communicate with the interior of the hollow connecting blocks. The required number of hollow connecting rods and hollow connecting blocks are selected to form the sensor network frame. The plugs are installed on the connection ports where the hollow connecting rods are not inserted to seal them.

[0015] Furthermore, the heating element is a heating ball. Using this component ensures heating stability.

[0016] Furthermore, both the hollow connecting rod and the hollow connecting block are wrapped with a heat insulation layer. This heat insulation layer protects the internal connecting wires from the temperature fluctuations within the test chamber, thus ensuring the stability of data transmission.

[0017] Compared with existing technologies, the present invention combines a testing system, a pressurization system, and a temperature control and measurement system, which has the following advantages:

[0018] 1. This invention enables large-volume single-bearing pressure tests. Currently, large-volume coal pillar pressure crushing platforms cannot meet research needs, and purely theoretical research is unlikely to achieve significant breakthroughs. Furthermore, pressure crushing occurring underground in mines is uncontrollable and has poor utilization effects, while also posing significant risks. This invention facilitates a series of related studies.

[0019] 2. This invention, by designing the side plates to consist of an inner and outer layer of specific materials, enables the platform to withstand high lateral stress while also conducting demanding measurement tests such as ultrasonic testing. Because the outer steel plate significantly attenuates ultrasonic signals, while the inner plexiglass plate cannot withstand high stress but reduces friction with the coal pillar surface during compression displacement, facilitating the displacement of the coal pillar, this tightly fitted double-layer design completely solves this problem, aiding in understanding the evolution mechanism of various parameters throughout the entire process of coal pillar compression and spontaneous combustion.

[0020] 3. The present invention constructs a high-temperature resistant and portable sensor grid frame. The sensor grid frame is characterized by easy construction, flame retardancy, and high temperature resistance. It is built in the test chamber of the test system in the form of a three-dimensional mesh structure, which allows for the arbitrary placement of sensors inside the test platform without affecting the filling of materials, and facilitates the collection of data during the test.

[0021] 4. This invention enables in-situ simulation of the entire process of real-time loading and pressure on a coal pillar in a goaf, leading to fracture development and spontaneous combustion grouting. The invention fills the cavity of the coal pillar area with large coal blocks to simulate a coal pillar, and fills the goaf area with similar materials. Since the structures of the coal pillar and the goaf are different in actual conditions, and the loads they experience are also different, the pressurization system for the goaf and coal pillar areas of this invention can independently apply pressure to each area, or apply pressure simultaneously. Furthermore, the subsequent grouting test is conducted under pressure without any modification to the test specimen, thus better reflecting actual conditions.

[0022] 5. This invention can evaluate the entire experimental process using multiple indicators. By utilizing sensors, electromagnetic methods, resistivity methods, ultrasonic methods, and other detection methods, it evaluates and studies the continuous development of internal fractures in coal pillars under pressure, thereby helping to understand the evolution mechanism of various parameters in the entire process of coal pillars from compression and crushing to oxidation and spontaneous combustion, as well as the seepage law of grout inside the coal pillar during grouting reinforcement. Attached Figure Description

[0023] Figure 1 This is a front view of the assembled invention;

[0024] Figure 2 This is a side view of the assembled invention;

[0025] Figure 3 This is a top view of the assembled invention;

[0026] Figure 4 This is a three-dimensional schematic diagram of the coal pillar region of the present invention;

[0027] Figure 5 This is a three-dimensional schematic diagram of the hollow connecting rod of the present invention;

[0028] Figure 6 This is a three-dimensional schematic diagram of the hollow connecting block of the present invention;

[0029] Figure 7 This is a three-dimensional schematic diagram of the plug of the present invention.

[0030] In the diagram: 1. Base; 2. Side plate; 3. Column; 4-1. First connecting plate; 4-2. Second connecting plate; 5. Support truss; 6. Guide rod; 7. Hydraulic cylinder; 8. Pressure plate; 9. Threaded opening; 10. Base plate; 11. Steel plate; 12. Acrylic glass plate; 13. Grouting hole; 14. Hollow connecting rod; 15. Insulation layer; 16. Plug; 17. Flange; 18. Hollow connecting block; I. Test system; II. Pressurization system; A. Coal pillar area; B. Goaf area. Detailed Implementation

[0031] The present invention will be further described below.

[0032] like Figures 1 to 3 As shown, the present invention includes a test system I, a pressurization system II, and a temperature control and measurement system;

[0033] The test system I shown includes a base 1, columns 3, and a base plate 10. The base plate 10 is fixed to the base 1 to ensure that it is level with the ground and has a certain gap for easy wiring. Multiple columns 3 are vertically fixed to the base plate 10, and the upper ends of each column 3 are fixedly connected by a first connecting plate 4-1. Side plates 2 are installed between adjacent columns 3 to form a test chamber with the multiple first connecting plates 4-1, multiple columns 3, multiple side plates 2, and the base plate 10, dividing the interior of the test chamber into a coal pillar area A and a goaf area B. Figure 4 As shown, the side plate 2 consists of an inner plate and an outer plate arranged in parallel to each other. The inner plate is an organic glass plate 12, which facilitates ultrasonic testing. The outer plate is a steel plate 11, and the outer plate can be detached and fixed. When it is detached, it is used for ultrasonic testing. Multiple grouting holes 13 are opened on the inner plate located in the goaf area B for grouting testing.

[0034] The pressurization system II includes a support truss 5, two hydraulic cylinders 7, and two pressure plates 8. A second connecting plate 4-2 is mounted on the lower part of the support truss 5. The support truss 5 is mounted above the test system I and fixed by a first connecting plate 4-1 and a second connecting plate 4-2. The two hydraulic cylinders 7 are mounted on the support truss 5 and are positioned directly above the coal pillar area A and the goaf area B, respectively. The two pressure plates 8 are mounted on the extended ends of the two hydraulic cylinders 7, with one pressure plate 8 having the same area as the opening at the upper end of the coal pillar area A, and the other pressure plate 8 having the same area as the opening at the upper end of the goaf area B. When the two hydraulic cylinders 7 extend, they can move their corresponding pressure plates 8 towards the coal pillar area A or the goaf area B to apply pressure.

[0035] The temperature control and measurement system includes a sensor grid, heating elements, temperature sensors, gas concentration sensors, an ultrasonic transmitter and receiver, and a resistivity testing device. The sensor grid is installed inside the test chamber, and multiple heating elements, temperature sensors, and gas concentration sensors are mounted on it. The heating elements regulate the ambient temperature, while the temperature and gas concentration sensors collect ambient temperature and gas concentration data. All components—heating elements, temperature sensors, and gas concentration sensors—are connected to the outside of the test chamber via internal wiring within the sensor grid for heating control and data transmission. The ultrasonic transmitter and receiver performs ultrasonic detection on the coal pillar before and after pressure application, and the resistivity testing device tests the resistivity of the coal pillar before and after grouting. Figures 5 to 7 As shown, the sensor frame includes hollow connecting rods 14, hollow connecting blocks 18, and plugs 16. The hollow connecting blocks 18 are rectangular with connection ports on each side. The hollow connecting rods 14 have ports at both ends. The ports of the hollow connecting rods 14 are inserted into one of the connection ports of the hollow connecting blocks 18, allowing communication between the hollow connecting rods 14 and the interior of the hollow connecting blocks 18. The required number of hollow connecting rods 14 and hollow connecting blocks 18 can be selected to form the sensor frame. The plugs 16 are installed at the connection ports where no hollow connecting rods 14 are inserted to seal them. The hollow connecting blocks 18 have flanges 17 inside to facilitate the installation and fixation of the hollow connecting rods 14 and the hollow connecting blocks 18. Both the hollow connecting rods 14 and the hollow connecting blocks 18 are covered with a heat insulation layer 15. The heat insulation layer 15 protects the internal connecting wires from the temperature inside the test chamber, thus ensuring the stability of data transmission.

[0036] As an improvement of the present invention, the test system I further includes a top plate, which is installed at the upper opening of the test chamber to seal the interior of the test chamber; the top plate is removed when pressurization system II is required. The pressurization system II also includes multiple guide rods 6, one end of which is perpendicularly and fixedly connected to the upper surface of one of the pressure plates 8, and the other end of which is perpendicularly and fixedly connected to the upper surface of another pressure plate 8. All guide rods 6 pass through the support truss 5, and the movement of the guide rods 6 is limited by the support truss 5, thereby ensuring the uniformity of pressure applied at different positions when the two pressure plates 8 descend to apply pressure. The base plate 10 has threaded openings 9 for connecting wires to pass through, and is equipped with screws of the same diameter. When no connecting wire passes through, the screws are fixed in the screw holes for sealing. The heating element is a heating ball. Using this component ensures the stability of heating.

[0037] The components of the aforementioned test system I, pressurization system II, and temperature control and measurement system are all existing components.

[0038] The aforementioned experimental platform integrates functions such as pressure application, heating, grouting, data monitoring, and acquisition, enabling multiple experiments. This platform helps to understand the continuous development of internal fractures in coal pillars before and after they enter the goaf, the evolution mechanism of various parameters throughout the entire process of coal pillar crushing and spontaneous combustion, the seepage law of grout within the coal pillar during grouting reinforcement, and the synchronous response of resistivity to the above-mentioned coal crushing, spontaneous combustion, and grouting seepage processes using a resistivity detection system. This is of great help in studying coal spontaneous combustion detection and the seepage law of grout during grouting.

[0039] Before using this platform, first check whether the pressurization system II is operating normally. Then, raise the pressure plate 8 to its highest position, install the partition between coal pillar area A and goaf area B, assemble the sensor grid according to the sensor usage requirements of the test, and fix the required sensors. Then, fix the side plate 2 of test system I, fill coal pillar area A with large pieces of filler material that meet the test requirements, and after filling, remove the partition. Fill goaf area B with filler material that meets the requirements. At this point, the preparation work is complete. Next, conduct the pressure test by setting either the height of the pressure plate 8 of pressurization system II descending per minute or the magnitude of the applied force per minute. During the test, observe the changes in the filler material during the pressurization process using resistivity, electromagnetic methods, etc. After the pressure test is completed, raise the pressure plate 8 to its highest position. The test chamber is positioned higher than Test System I, with the top plate sealed above Test System I. Then, the steel plate 11 of the side plate 2 of Test System I is opened. A one-way valve is installed on the grouting hole 13 of the inner plate, creating a sealed environment. A heating ball is used to heat the test chamber, simulating the spontaneous combustion process. The temperature rise rate is set according to the test requirements. The entire process can be monitored and recorded using sensors, resistivity, electromagnetic methods, and ultrasound. After the spontaneous combustion requirement is met, a suitable grouting hole 13 is selected based on the test objective, and the grouting test is conducted. The entire grouting seepage process is observed using sensors, resistivity, electromagnetic methods, and ultrasound. The entire test process can simulate the entire process of real-time loading and pressure on the coal pillar in the goaf, leading to crack development and spontaneous combustion grouting, which is more realistic and meets practical needs.

[0040] The specific analysis process for data acquired using different monitoring methods is as follows:

[0041] 1. Application of resistivity method

[0042] Resistivity probing is a good method for monitoring changes in fracture pressure and evaluating the degree of filling. This method detects the conductivity between the grout and the coal / rock. Using a digitally controlled electrode converter and an electrical resistivity meter, data is rapidly measured, acquired, and stored along the measuring line. Resistivity contour maps reflecting changes in coal pillar fracture pressure and the diffusion of filling grout are plotted, allowing for comprehensive analysis of coal pillar fracture under pressure and evaluation of mine filling effectiveness. This method also allows for the study of the synchronous response patterns of coal body fracture, spontaneous combustion, and grouting seepage processes.

[0043] (1) Monitoring of fracture compression changes

[0044] The system first calculates the circuit impedance and the sample resistance, using the following formulas:

[0045] |Z|=U / I

[0046] R = |Z|cosθ

[0047] In the formula: |Z| is the circuit impedance; U is the voltage, V; I is the current, A; R is the resistance, Ω; θ is the phase angle.

[0048] Subsequently, the resistivity of the sample was determined based on its resistance:

[0049]

[0050] In the formula: ρ is resistivity, Ω; S is the measured cross-sectional area of ​​the sample, m²; L is the sample length, m.

[0051] The resistivity is higher when there are cracks between coal and rock, and lower when the coal and rock are denser. The coal body can be broken and spontaneously combusted by monitoring the resistivity changes when the coal pillar is crushed.

[0052] (2) Used for evaluation of filling degree

[0053] After the grout filling is completed, data is collected at regular intervals. During the test, the grout filling rate is analyzed when the grout has fully diffused. With the data acquisition device set up, the first step is to acquire the measured parameter files, interpret the data and remove outliers, then establish a coordinate system, conduct the detection, process the acquired resistivity data and perform inversion, and finally plot the resistivity change contour map.

[0054] The grout diffusion pattern exhibits a high-resistivity, low-resistivity, closed or semi-closed distribution, with the low-resistivity zone dynamically changing. This is because the grout and coal / rock have different electrical conductivity. The injection of the grout gradually alters the original electric field, leading to a gradual mixing of high-resistivity and low-resistivity zones. Low-resistivity zones contain a large amount of grout, while high-resistivity zones contain a small amount of grout or none at all. This means that the more low-resistivity zones there are, the better the grout diffusion effect; the more areas filled by the grout diffusion, the better the filling effect. Conversely, the opposite is true for high-resistivity zones.

[0055] 2. Application of Electromagnetic Method

[0056] Transient electromagnetic detection is a type of electromagnetic detection method. It involves emitting a single pulse electromagnetic field into the space of the medium being measured through a magnetic source in the form of an ungrounded loop or a current source in the form of a grounded electrode. During the off-state of the single pulse electromagnetic field, the secondary induced electromagnetic field excited by the single pulse electromagnetic field is observed through a coil or grounded electrode. The transient electromagnetic detection system consists of a transmitting device, a transmitting and receiving loop, a receiving device, and a data collection and processing system.

[0057] First, a pulsed electromagnetic field is emitted into the area to be measured. The induced current in the medium of the measured area generates varying heat losses, causing the secondary induced magnetic field obtained by the receiving loop to be not a stable, constant field, but rather a transient electromagnetic field with an exponential law that decays over time. The decay of the secondary field also varies to some extent due to different geological structures. Therefore, by analyzing and extracting data on the radiation, transmission, and scattering of the secondary magnetic field, combined with the electromagnetic characteristics and distribution of the target, the geological structure information of the measured spatial medium can be obtained. This allows for the discovery of anomalies in the geological structure, which can then be used to characterize the pressure exerted on the coal pillar and the continuous development of internal fractures. This helps to understand the evolution mechanism of various parameters in the entire process of coal pillar fracture from compression to spontaneous combustion, as well as the seepage law of grout inside the coal pillar during grouting reinforcement.

[0058] 3. Applications of ultrasound

[0059] Ultrasonic waves carry relevant information as they propagate through a medium. Ultrasonic testing technology is a non-destructive testing method, characterized by its convenience, speed, and cost-effectiveness. An ultrasonic detection system consists of a transmitting probe, a receiving probe, and data acquisition and analysis devices. The propagation of ultrasonic waves differs in various media, such as gas, heating elements, fissures, coal and rock, and slurry. Based on this, data obtained from ultrasonic detection can be systematically analyzed to examine the changes in coal pillars and goafs under pressure, from crushing to spontaneous combustion and then to grouting for fire extinguishing. This helps to observe and understand the characteristics of the entire coal spontaneous combustion process. Applying these characteristics to field practice can promptly identify potential spontaneous combustion hazards and provide a basis for taking effective prevention and control measures. The system characterizes the pressure on the coal pillar and the continuous development of internal fissures, helping to understand the evolution mechanism of various parameters in the entire process of coal pillar crushing to oxidative spontaneous combustion, as well as the seepage law of grout inside the coal pillar during grouting reinforcement. It also summarizes the synchronous response law of coal crushing, spontaneous combustion, and grouting seepage processes.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines, characterized in that, Includes a testing system, a pressurization system, and a temperature control and measurement system; The test system shown includes a base, columns, and a base plate. The base plate is fixed on the base to ensure that it is level with the ground and has a certain gap. Multiple columns are vertically fixed on the base plate, and the upper ends of each column are fixedly connected by a first connecting plate. Side plates are installed between adjacent columns to form a test chamber with multiple first connecting plates, multiple columns, multiple side plates, and the base plate, and to divide the interior of the test chamber into a coal pillar area and a goaf area. The pressurization system includes a support truss, two hydraulic cylinders, and two pressure plates. A second connecting plate is mounted on the lower part of the support truss. The support truss is mounted above the test system and fixed by the first and second connecting plates. The two hydraulic cylinders are mounted on the support truss and are positioned directly above the coal pillar area and the goaf area, respectively. The two pressure plates are mounted on the extended ends of the two hydraulic cylinders, with one pressure plate having an area equal to the opening area at the top of the coal pillar area, and the other pressure plate having an area equal to the opening area at the top of the goaf area. When the two hydraulic cylinders extend, they can move their corresponding pressure plates towards the coal pillar area or the goaf area to apply pressure. The temperature control and measurement system includes a sensor grid, heating elements, temperature sensors, gas concentration sensors, an ultrasonic transmitter and receiver, and a resistivity testing device. The sensor grid is installed inside the test chamber, and multiple heating elements, temperature sensors, and gas concentration sensors are mounted on the sensor grid. The heating elements are used to regulate the ambient temperature, while the temperature sensors and gas concentration sensors are used to collect ambient temperature and gas concentration data. The heating elements, temperature sensors, and gas concentration sensors are all connected to the outside of the test chamber through connecting lines inside the sensor grid for heating control and data transmission. The ultrasonic transmitter and receiver is used to perform ultrasonic detection on the coal pillar before and after pressure, and the resistivity testing device is used to test the resistivity of the coal pillar before and after grouting.

2. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The test system also includes a top plate. When the pressurization system is raised to its highest position, the top plate is installed at the upper opening of the test chamber to seal the inside of the test chamber. When the pressurization system is required to carry out a pressure test, the top plate is removed.

3. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The side plate consists of an inner plate and an outer plate arranged in parallel to each other. The inner plate is made of plexiglass, which facilitates ultrasonic testing. The outer plate is made of steel and can be detached and fixed. When it is detached, it is used for ultrasonic testing. Multiple grouting holes are opened on the inner plate in the goaf area for grouting testing.

4. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The pressurization system also includes multiple guide rods. One end of some guide rods is perpendicular to and fixedly connected to the upper surface of one of the pressure plates, and the other end of some guide rods is perpendicular to and fixedly connected to the upper surface of another pressure plate. All guide rods pass through the support truss and the movement of the guide rods is limited by the support truss, so as to ensure the uniformity of pressure applied at different positions when the two pressure plates descend to apply pressure.

5. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The base plate is provided with threaded openings for connecting wires to pass through.

6. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The sensor frame includes hollow connecting rods, hollow connecting blocks, and plugs. The hollow connecting blocks are rectangular with connection ports on each side. The hollow connecting rods have ports at both ends. The ports of the hollow connecting rods are inserted into one of the connection ports of the hollow connecting blocks, so that the hollow connecting rods communicate with the interior of the hollow connecting blocks. The required number of hollow connecting rods and hollow connecting blocks are selected to form the sensor frame. The plugs are installed on the connection ports where no hollow connecting rods are inserted to seal them.

7. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 1, characterized in that, The heating element is a heating ball.

8. The comprehensive test platform for detecting concealed fire sources of spontaneous combustion in deep coal mines according to claim 6, characterized in that, Both the hollow connecting rod and the hollow connecting block are wrapped with a heat insulation layer.

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