Horizontal cutting joint carbon dioxide blasting similar coal body fracturing evaluation device and method

Abstract

The application discloses a horizontal cutting seam carbon dioxide blasting similar coal body cracking evaluation device and method, which comprises a transparent test box, the transparent test box comprises an outer frame and a plurality of transparent loading plates, a back plate is arranged on the back side of the transparent test box, and a hydraulic cracking mechanism can penetrate through the back plate and extend into the transparent test box; an ultrasonic CT is arranged adjacent to the transparent test box, the ultrasonic CT can scan the top of the transparent test box; a high-speed camera is arranged adjacent to the transparent test box, and the high-speed camera can shoot the coal sample in the transparent test box; the large-size coal seam pressure condition under the triaxial mining stress field condition can be simulated through the transparent loading plates on the upper side, the front side and the left side of the transparent test box, the large-size coal seam pressure condition is closer to the real and complex geological conditions on site, and the device is suitable for a large-size similar simulation coal body model.

Description

Technical Field

[0001] This invention relates to the field of coal fracturing detection, and in particular to a method for evaluating the fracturing effect of horizontally cut carbon dioxide blasting on similar coal bodies. Background Technology

[0002] my country's coal resources are characterized by complex and variable occurrences, with deep mines generally suffering from high gas content and low permeability, leading to poor gas extraction efficiency. Currently, domestic and international methods for depressurizing and enhancing coal seam permeability mainly include blasting fracturing, hydraulic fracturing (hydraulic hydraulic fracturing, hydraulic slotting, hydraulic perforation), and protective layer depressurization mining. Among these, synergistic fracturing combining hydraulic fracturing and CO2 blasting fracturing is an environmentally friendly and safe fracturing method. The combined fracturing creates a larger range of moving compensation space, effectively promoting coal seam fracturing, thereby increasing crack propagation and improving coal seam permeability.

[0003] To assess the fracturing effect of this method, existing approaches directly evaluate it by measuring the half-length, morphology, and orientation of fractures in the coal and rock mass after fracturing. Evaluation methods include microseismic methods, potential methods, well temperature methods, and radioactive tracer methods. Furthermore, artificial intelligence concepts and technologies are applied to fracturing engineering, such as using neural network technology combined with genetic algorithms, simulated annealing combined with genetic algorithms, or fuzzy comprehensive evaluation methods to predict and optimize fracturing construction parameters and analyze fracturing effects. However, most of these fracturing effect evaluation methods are designed for standard coal samples and are not suitable for similar simulations of slightly larger scales in the laboratory.

[0004] Therefore, how to provide a device that can detect the fracturing effect of coal seams in a similar simulation in the laboratory is a technical problem that urgently needs to be solved by those in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for evaluating the fracturing effect of horizontally cut carbon dioxide blasting on similar coal seams, in order to solve the problems existing in the prior art and to detect the fracturing effect of similar simulated coal seams in the laboratory.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides a horizontally slotted carbon dioxide explosion-induced fracturing evaluation device for similar coal bodies, comprising:

[0007] A transparent test chamber includes an outer frame and multiple transparent loading plates. The multiple transparent loading plates are respectively located on the upper side, front side, and left side of the transparent test chamber. The transparent loading plates are slidably connected to the outer frame and are always sealed to the outer frame during the sliding process relative to the outer frame. The transparent loading plates are connected to a drive mechanism, and the sliding paths of the multiple transparent loading plates do not intersect.

[0008] A back panel is provided on the rear side of the transparent test chamber. After the transparent test chamber is filled with a coal sample, a stress sensor and an acoustic emission sensor are installed in the coal sample. The connecting wires of the stress sensor and the acoustic emission sensor pass through the back panel and extend outside the transparent test chamber. The connecting wires are electrically connected to a computer.

[0009] A hydraulic fracturing mechanism, capable of penetrating the back plate and extending into the transparent test chamber;

[0010] An ultrasonic CT scanner is installed adjacent to the transparent test chamber, and the ultrasonic CT scanner is capable of scanning the top of the transparent test chamber.

[0011] A high-speed camera is provided, which is arranged adjacent to the transparent test chamber. The high-speed camera is capable of photographing the coal sample inside the transparent test chamber.

[0012] Furthermore, the driving mechanism includes a loading piston and a pressurizing cylinder. The loading piston is fixedly installed on the outer side of the transparent loading plate, and the output end of the pressurizing cylinder is fixedly connected to the loading piston.

[0013] Furthermore, it also includes:

[0014] A movable plate is disposed on the right side of the transparent test chamber. The movable plate is slidably connected to the transparent test chamber between a first position and a second position. When the movable plate is in the first position, the movable plate seals the transparent test chamber. When the movable plate is in the second position, the movable plate opens the transparent test chamber.

[0015] A feeding mechanism is provided near the movable plate and is capable of feeding material into the transparent test chamber when the movable plate is in the second position.

[0016] Furthermore, the feeding mechanism includes:

[0017] The first slide rail has one end located close to the moving plate and the other end extending outward along the left and right directions of the transparent test chamber.

[0018] A placement plate is slidably connected to the first slide rail, and the placement plate is capable of placing the coal sample on its upper surface and transporting it into the transparent test chamber.

[0019] Furthermore, the hydraulic fracturing mechanism includes:

[0020] The second slide rail has one end close to the back plate and the other end extending outward along the front-back direction of the transparent test chamber;

[0021] The drilling rig is slidably connected to the second slide rail. The output end of the drilling rig is connected to a drill rod. The drill rod can penetrate the back plate and the coal sample in the transparent test chamber. The drill rod drills a horizontal slit hole in the coal sample.

[0022] A hydraulic horizontal slit pipe is fixedly installed inside the horizontal slit borehole and sealed to the back plate. The hydraulic horizontal slit pipe is connected to the fracturing pump.

[0023] Furthermore, the hydraulically horizontally slotted pipe includes:

[0024] A fracturing section, which is located inside the transparent test chamber and close to the depth of the horizontally cut borehole;

[0025] A sealing section is connected to the fracturing section. The sealing section penetrates the back plate and extends to the outside. The sealing section is sealed to the inner wall of the back plate through a first sealing gasket and sealed to the outer wall of the back plate through a second sealing gasket.

[0026] An external connector is connected to the sealing section and is also connected to the fracturing pump.

[0027] Furthermore, it also includes a liquid carbon dioxide phase change blasting mechanism, which is connected to a liquid carbon dioxide phase change blasting tube. The drill rod penetrates the back plate and the coal sample in the transparent test chamber to drill a carbon dioxide blasting borehole in the coal sample. The liquid carbon dioxide phase change blasting tube is installed in the carbon dioxide blasting borehole.

[0028] This invention also discloses a method for evaluating the fracturing effect of coal bodies similar to those subjected to horizontally cut carbon dioxide explosions, comprising the following steps:

[0029] S1: Based on the parameters of the mining area to be tested, a similar coal body is prepared and sent into the transparent test chamber through the placement plate. The moving plate is closed and sealed. A stress sensor is buried at the bottom of the transparent test chamber. The connecting wire of the stress sensor extends from the sensor hole on the back plate and is electrically connected to the first computer.

[0030] S2: The pressurizing cylinder pushes each transparent loading plate inward from the X-axis, Y-axis and Z-axis directions through the loading piston, so that the similar coal body is shaped under a fixed loading pressure. After shaping, the pressure of each transparent loading plate on the similar coal body is released to obtain a similar simulated coal sample.

[0031] S3: Release the loading pressure on the transparent loading plate and remove all the similar simulated coal samples from S2;

[0032] S4: Lay a similar simulated coal sample from bottom to top in a transparent test chamber. After the laying is completed, embed an acoustic emission sensor at the front of the bottom of the transparent test chamber and at the rear of the similar simulated coal sample. The connecting wire of the acoustic emission sensor extends from the sensor hole on the back plate and is electrically connected to the second computer.

[0033] S5: Install and fix the ultrasound CT and high-speed camera, and start the high-speed camera to take pictures of the transparent test chamber;

[0034] S6: Triaxial stress is applied to a similar simulated coal sample inside the transparent test chamber using a pressurized hydraulic cylinder. After loading, the top of the transparent test chamber is scanned using ultrasonic CT to obtain the initial crack distribution.

[0035] S7: Drill horizontal slotting boreholes and carbon dioxide blasting boreholes in a similar simulated coal sample using a drilling rig, and install hydraulic horizontal slotting pipes and liquid carbon dioxide phase change blasting pipes; use a fracturing pump to transport water from the external joint of the hydraulic horizontal slotting pipes to the fracturing section, and inject water into the similar simulated coal sample.

[0036] S8: During the water injection process in step S7, the stress sensor and acoustic emission sensor will send the collected signals to the first computer and the second computer in real time. After the water injection is completed, the top of the transparent test chamber will be scanned by ultrasonic CT to obtain the secondary crack distribution.

[0037] S9: Relieve the triaxial stress on the similar simulated coal sample in S6, and use a liquid carbon dioxide phase change blasting mechanism and a liquid carbon dioxide phase change blasting tube to blast the similar simulated coal in the transparent test chamber with CO2. After the blasting is completed, turn off the high-speed camera and use ultrasonic CT to scan the top of the transparent test chamber to obtain the three-dimensional crack distribution.

[0038] S10: Upload similar simulated coal sample photos taken by a high-speed camera to a third computer, and use Photoshop to sketch the cracks in the coal sample in the photos; the second computer processes the signals transmitted by the acoustic emission sensor and forms an image.

[0039] The present invention discloses the following technical effects:

[0040] 1. The pressure of large coal seams under triaxial mining stress field conditions can be simulated through the transparent loading plates on the upper, front and left sides of the transparent test chamber, which is closer to the real and complex geological conditions on site and is suitable for large-sized similar simulated coal body models.

[0041] 2. The cracking process of coal is monitored in real time using acoustic emission sensors. A high-speed camera is used to monitor the crack propagation on the surface of coal in a transparent test chamber in real time. The crack distribution results of three scans using ultrasonic tomography (ultrasonic CT) technology, combined with the real-time stress detected by stress sensors and other experimental parameters, can be used to analyze the crack propagation of coal samples and finally obtain an overall evaluation result of the cracking effect. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0044] Figure 2 This is a schematic diagram of the backplate structure of the present invention;

[0045] Figure 3 Sensor distribution diagram;

[0046] Figure 4 A schematic diagram of a hydraulically horizontally slotted pipe installation;

[0047] Figure 5 This is a schematic diagram of the stress sensor installation (the installation method for the acoustic emission sensor is the same as that for the stress sensor);

[0048] The components include: 1. Transparent test chamber; 101. Transparent loading plate; 102. Outer frame; 2. Back plate; 201. Sensor hole; 202. Horizontal slotted drill hole; 203. Carbon dioxide blasting drill hole; 3. Stress sensor; 4. Acoustic emission sensor; 5. Loading piston; 6. Moving plate; 7. First slide rail; 8. Placement plate; 9. Second slide rail; 10. Drilling rig; 11. Hydraulic horizontal slotted pipe; 1101. Fracturing section; 1102. Sealing section; 1103. External connector; 12. First sealing gasket; 13. Second sealing gasket; 14. First computer; 15. Second computer; 16. Slide frame; 17. Conversion connector; 18. Fracturing pump; 19. Liquid carbon dioxide phase change blasting mechanism; 20. High-speed camera. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Reference Figures 1-5This invention provides a horizontally slit carbon dioxide explosion-induced coal body fracturing evaluation device, comprising: a transparent test chamber 1, the transparent test chamber 1 including an outer frame 102 and multiple transparent loading plates 101, the multiple transparent loading plates 101 being located on the upper side, front side and left side of the transparent test chamber 1 respectively, with six transparent loading plates 101 on each of the upper side and front side of the transparent test chamber 1 (the upper side is the position for applying X-axis loading force, and the front side is the position for applying Y-axis loading force), and one transparent loading plate 101 on the left side (the left side is the position for applying Z-axis loading force). (Force application position), the transparent loading plate 101 is slidably connected to the outer frame 102, and the transparent loading plate 101 remains sealed to the outer frame 102 during its sliding process relative to the outer frame 102. To achieve the above effect, the moving distance of each transparent loading plate 101 does not exceed the outer edge of the outer frame 102, and the outer edge of the transparent loading plate 101 remains sealed to the outer frame 102 during its movement; the transparent loading plate 101 is connected to the driving mechanism, and the sliding paths of the multiple transparent loading plates 101 do not intersect; back plate 2. The back plate 2 is located on the rear side of the transparent test chamber 1. After the transparent test chamber 1 is filled with a coal sample, a stress sensor 3 and an acoustic emission sensor 4 are installed inside the coal sample. The connecting wires of the stress sensor 3 and the acoustic emission sensor 4 pass through the back plate 2 and extend outside the transparent test chamber 1. The connecting wires are electrically connected to a computer. The connecting wire of the stress sensor 3 is led from the sensor hole 201 to the outside of the transparent test chamber 1 and sequentially connected to the adapter 17, the data acquisition box, and the first computer 14. The connecting wire of the acoustic emission sensor 4 is led from the sensor hole 201 to the back side of the transparent test chamber 1. 01 leads to the outside of the transparent test chamber 1 and is sequentially connected to a conversion connector 17, an amplifier, a signal acquisition and processing device, and a second computer 15; a hydraulic fracturing mechanism, which can penetrate the back plate 2 and extend into the transparent test chamber 1; an ultrasonic CT, which is arranged adjacent to the transparent test chamber 1 and can scan the top of the transparent test chamber 1; and a high-speed camera 20, which is arranged adjacent to the transparent test chamber 1 and can photograph the coal sample inside the transparent test chamber 1.

[0052] In this embodiment, the driving mechanism includes a loading piston 5 and a pressurizing cylinder. The loading piston 5 is fixedly installed on the outer side of the transparent loading plate 101, and the output end of the pressurizing cylinder is fixedly connected to the loading piston 5.

[0053] like Figure 1As shown, in this embodiment, it further includes: a movable plate 6, which is disposed on the right side of the transparent test chamber 1. The movable plate 6 is slidably connected to the transparent test chamber 1 between a first position and a second position. When the movable plate 6 is in the first position, it seals the transparent test chamber 1; when the movable plate 6 is in the second position, it opens the transparent test chamber 1. A feeding mechanism is disposed near the movable plate 6 and is capable of feeding material into the transparent test chamber 1 when the movable plate 6 is in the second position. In this embodiment, a slide 16 is provided on the front and right sides of the transparent test chamber 1. The slide 16 has a sliding groove, and the movable plate 6 extends towards the slide 16 to form a slide rail, which is slidably connected to the sliding groove.

[0054] like Figure 1 As shown, in this embodiment, the feeding mechanism includes: a first slide rail 7, one end of which is disposed near the moving plate 6, and the other end of which extends outward along the left and right direction of the transparent test chamber 1; and a placement plate 8, which is slidably connected to the first slide rail 7, and the placement plate 8 is capable of placing the coal sample on its upper surface and conveying it into the transparent test chamber 1.

[0055] like Figure 1 and Figure 4 As shown, the hydraulic fracturing mechanism includes: a second slide rail 9, one end of which is close to the back plate 2, and the other end which extends outward along the front-rear direction of the transparent test chamber 1; a drill rig 10, which is slidably connected to the second slide rail 9, and the output end of the drill rig 10 is connected to a drill rod, which can penetrate the back plate 2 and the coal sample in the transparent test chamber 1, and the drill rod drills a horizontal slit borehole 202 in the coal sample; and a hydraulic horizontal slit pipe 11, which is fixedly installed in the horizontal slit borehole 202 and sealed to the back plate 2, and the hydraulic horizontal slit pipe 11 is connected to the fracturing pump 18. The hydraulic horizontal slotted pipe 11 includes: a fracturing section 1101, located inside the transparent test chamber 1 and close to the depth of the horizontal slotted borehole 202; a sealing section 1102, connected to the fracturing section 1101, penetrating the back plate 2 and extending outwards, sealed to the inner wall of the back plate 2 via a first sealing gasket 12 and sealed to the outer wall of the back plate 2 via a second sealing gasket 13; and an external connector 1103, connected to the sealing section 1102 and communicating with the fracturing pump 18. The hydraulic horizontal slotted pipe 11 is 0.5m long, the fracturing section 1101 is 0.36m long, and the sealing section 1102 is 0.14m long.

[0056] In this embodiment, a liquid carbon dioxide phase change blasting mechanism 19 is also included. The liquid carbon dioxide phase change blasting mechanism 19 is connected to a liquid carbon dioxide phase change blasting tube. The drill rod penetrates the back plate 2 and the coal sample in the transparent test chamber 1 to drill a carbon dioxide blasting borehole 203 in the coal sample. The liquid carbon dioxide phase change blasting tube is installed in the carbon dioxide blasting borehole 203.

[0057] The following describes a method for evaluating the fracturing of similar coal bodies induced by horizontally cut carbon dioxide explosions, using specific embodiments, including the following steps:

[0058] S1: According to the parameters of the mining area to be tested, similar coal bodies are prepared and sent into the transparent test chamber 1 through the placement plate 8. The moving plate 6 is closed and sealed. A stress sensor 3 is buried at the bottom of the transparent test chamber 1. The connecting wire of the stress sensor 3 extends from the sensor hole 201 on the back plate 2 and is electrically connected to the first computer 14.

[0059] S2: The pressurizing cylinder pushes each transparent loading plate 101 inward from the X-axis, Y-axis and Z-axis directions through the loading piston 5, so that the similar coal body is shaped under a fixed loading pressure, wherein the fixed air pressure is 18MPa and the shaping time is 1h. After shaping, the pressure of each transparent loading plate 101 on the similar coal body is released to obtain a similar simulated coal sample.

[0060] S3: Release the loading pressure on the transparent loading plate 101 and remove all the similar simulated coal samples from S2;

[0061] S4: A similar simulated coal sample is laid from bottom to top in the transparent test chamber 1. After the laying is completed, an acoustic emission sensor 4 is buried at the front of the bottom of the transparent test chamber 1 and at the rear of the similar simulated coal sample. The connecting wire of the acoustic emission sensor 4 extends from the sensor hole 201 on the back plate 2 and is electrically connected to the second computer 15.

[0062] S5: Install and fix the ultrasound CT and high-speed camera 20, and start the high-speed camera 20 to take pictures of the transparent test chamber 1;

[0063] S6: Triaxial stress loading is applied to the similar simulated coal sample in the transparent test chamber 1 by pressurizing the hydraulic cylinder. The loading stress of the six transparent loading plates 101 in the X-axis direction is 6MPa, the loading stress of the six transparent loading plates 101 in the Y-axis direction is 8MPa, and the loading stress of one transparent loading plate 101 in the Z-axis direction is 10MPa. After loading, the top of the transparent test chamber 1 is scanned by ultrasonic CT to obtain the initial crack distribution.

[0064] S7: Drill horizontal slotting boreholes 202 and carbon dioxide blasting boreholes 203 in a similar simulated coal sample using a drilling rig, and install a hydraulic horizontal slotting pipe 11 and a liquid carbon dioxide phase change blasting pipe; use a fracturing pump 18 to transport water from the external joint 1103 of the hydraulic horizontal slotting pipe 11 to the fracturing section 1101, and inject water into the similar simulated coal sample; the water injection rate is 12 mL / s;

[0065] S8: During the water injection process in step S7, the stress sensor 3 and the acoustic emission sensor 4 send the collected signals to the first computer 14 and the second computer 15 in real time. After the water injection is completed, the top of the transparent test chamber 1 is scanned by ultrasonic CT to obtain the secondary crack distribution.

[0066] S9: Relieve the triaxial stress on the similar simulated coal sample in S6, and use the liquid carbon dioxide phase change blasting mechanism 19 and the liquid carbon dioxide phase change blasting tube to blast the similar simulated coal in the transparent test chamber 1 with CO2. After the blasting is completed, turn off the high-speed camera 20, and use ultrasonic CT to scan the top of the transparent test chamber 1 to obtain the three-dimensional crack distribution.

[0067] S10: Upload similar simulated coal sample photos captured by high-speed camera 20 to a third computer, and use Photoshop to sketch the cracks in the coal sample photos; the second computer 15 processes the signals transmitted by acoustic emission sensor 4 and forms an image; based on the coal body photos captured by high-speed camera 20, analyze the growth and propagation laws of surface cracks in the coal body during horizontal slit hydraulic fracturing under different conditions, and use Photoshop to sketch the final crack morphology, analyze the relationship between different fracturing parameters such as the location of horizontal slit borehole 202, water injection rate, and CO2 charge after synergistic fracturing and the number, area, and initiation pressure of fracturing cracks; based on the acoustic emission... Sensor 4 monitors acoustic emission signals during the simulated coal body fracturing process. Acoustic emission sensor 4 detects elastic waves propagating to the surrounding area and converts the elastic wave information into electrical signals. An amplifier amplifies the electrical signals, and the information is processed by a signal acquisition and processing device. An image is generated on a computer terminal for manual analysis. Ultrasonic CT scanning is performed on the top of the transparent test chamber 1 multiple times. The measured ultrasonic travel time data is used to calculate the image. The imaging results can accurately and intuitively represent the crack situation of the coal body on the entire cross-section. Based on the crack distribution results of the three scans, crack propagation analysis is performed, and finally an overall evaluation of the fracturing effect is obtained.

[0068] This invention provides a method for evaluating the fracturing effect of horizontally slotted carbon dioxide blasting on similar coal seams. It simulates the pressure conditions of a large-size coal seam under triaxial mining stress field conditions using transparent loading plates 101 on the upper, front, and left sides of a transparent test chamber 1. This method more closely approximates the complex geological conditions in real-world environments and is suitable for large-size similar simulated coal seam models. A acoustic emission sensor 4 is used to monitor the coal seam fracturing process in real time. A high-speed camera is used to monitor the crack propagation on the coal surface in the transparent test chamber 1 in real time. The crack distribution results obtained from three scans using ultrasonic tomography (ultrasonic CT), combined with real-time stress detected by a stress sensor 3 and other experimental parameters, allow for analysis of the crack propagation in the coal sample, ultimately yielding an overall evaluation result of the fracturing effect.

[0069] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0070] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for evaluating the fracturing effect of horizontally slitted carbon dioxide blasting-induced coal seams, characterized in that, An evaluation device for evaluating the fracturing of coal seams similar to those produced by horizontally slit carbon dioxide blasting includes: A transparent test chamber (1) includes an outer frame (102) and multiple transparent loading plates (101). The multiple transparent loading plates (101) are located on the upper side, front side and left side of the transparent test chamber (1), respectively. The transparent loading plates (101) are slidably connected to the outer frame (102) and are always sealed to the outer frame (102) during the sliding process of the transparent loading plates (101) relative to the outer frame (102). The transparent loading plates (101) are connected to the driving mechanism, and the sliding paths of the multiple transparent loading plates (101) do not intersect. Back plate (2), the back plate (2) is set on the rear side of the transparent test chamber (1). After the transparent test chamber (1) is filled with coal sample, stress sensor (3) and acoustic emission sensor (4) are set in the coal sample. The connecting wires of the stress sensor (3) and acoustic emission sensor (4) pass through the back plate (2) and extend to the outside of the transparent test chamber (1). The connecting wires are electrically connected to the computer. A hydraulic fracturing mechanism that can penetrate the back plate (2) and extend into the transparent test chamber (1); Ultrasonic CT, wherein the ultrasonic CT is arranged adjacent to the transparent test chamber (1), and the ultrasonic CT is capable of scanning the top of the transparent test chamber (1); A high-speed camera (20) is arranged adjacent to the transparent test chamber (1). The high-speed camera (20) is capable of taking pictures of the coal sample inside the transparent test chamber (1). The driving mechanism includes a loading piston (5) and a pressurizing cylinder. The loading piston (5) is fixedly installed on the outer side of the transparent loading plate (101), and the output end of the pressurizing cylinder is fixedly connected to the loading piston (5). Also includes: A movable plate (6) is disposed on the right side of the transparent test chamber (1). The movable plate (6) is slidably connected to the transparent test chamber (1) between a first position and a second position. When the movable plate (6) is in the first position, the movable plate (6) seals the transparent test chamber (1). When the movable plate (6) is in the second position, the movable plate (6) opens the transparent test chamber (1). A feeding mechanism is provided close to the movable plate (6) and is capable of feeding material into the transparent test chamber (1) when the movable plate (6) is in the second position; The feeding mechanism includes: The first slide rail (7) is located near the moving plate (6) at one end and extends outward along the left and right directions of the transparent test chamber (1) at the other end. Placement plate (8), which is slidably connected to the first slide rail (7), is capable of placing coal samples on the upper surface and transporting them into the transparent test chamber (1); The hydraulic fracturing mechanism includes: The second slide rail (9) has one end close to the back plate (2) and the other end extends outward along the front and rear direction of the transparent test chamber (1); The drilling rig (10) is slidably connected to the second slide rail (9). The output end of the drilling rig (10) is connected to a drill rod. The drill rod can penetrate the back plate (2) and the coal sample in the transparent test chamber (1). The drill rod drills a horizontal slit borehole (202) in the coal sample. A hydraulic horizontal slit pipe (11) is fixedly installed in the horizontal slit borehole (202) and sealed to the back plate (2). The hydraulic horizontal slit pipe (11) is connected to the fracturing pump (18). The hydraulically horizontally slotted pipe (11) includes: The fracturing section (1101) is located inside the transparent test chamber (1) and close to the depth of the horizontal slotted borehole (202); A sealing section (1102) is connected to the fracturing section (1101). The sealing section (1102) penetrates the back plate (2) and extends outward. The sealing section (1102) is sealed to the inner wall of the back plate (2) through a first sealing gasket (12) and sealed to the outer wall of the back plate (2) through a second sealing gasket (13). An external connector (1103) is connected to the sealing section (1102) and is connected to the fracturing pump (18). It also includes a liquid carbon dioxide phase change blasting mechanism (19), which is connected to a liquid carbon dioxide phase change blasting tube. The drill rod penetrates the back plate (2) and the coal sample in the transparent test chamber (1) to drill a carbon dioxide blasting borehole (203) in the coal sample. The liquid carbon dioxide phase change blasting tube is installed in the carbon dioxide blasting borehole (203). Includes the following steps: S1: According to the parameters of the mining area to be tested, similar coal bodies are prepared and sent into the transparent test chamber (1) through the placement plate (8). The moving plate (6) is closed and sealed. A stress sensor (3) is buried at the bottom of the transparent test chamber (1). The connecting wire of the stress sensor (3) extends from the sensor hole (201) on the back plate (2) and is electrically connected to the first computer (14). S2: The pressurizing cylinder pushes each transparent loading plate (101) inward from the X-axis, Y-axis and Z-axis directions through the loading piston (5) so that the similar coal body is shaped under a fixed loading pressure. After shaping, the pressure of each transparent loading plate (101) on the similar coal body is released to obtain a similar simulated coal sample. S3: Release the loading pressure on the transparent loading plate (101) and remove all the similar simulated coal samples in S2; S4: Lay a similar simulated coal sample from bottom to top in the transparent test chamber (1). After the laying is completed, a sound emission sensor (4) is buried at the front of the bottom of the transparent test chamber (1) and at the rear of the similar simulated coal sample. The wire of the sound emission sensor (4) extends from the sensor hole (201) on the back plate (2) and is electrically connected to the second computer (15). S5: Install and fix the ultrasonic CT and high-speed camera (20), and start the high-speed camera (20) to take pictures of the transparent test chamber (1); S6: Triaxial stress loading is applied to a similar simulated coal sample in the transparent test chamber (1) by a pressurized oil cylinder. After loading, the top of the transparent test chamber (1) is scanned by ultrasonic CT to obtain the initial crack distribution. S7: Drill horizontal slotting boreholes (202) and carbon dioxide blasting boreholes (203) in a similar simulated coal sample using a drilling rig, and install hydraulic horizontal slotting pipes (11) and liquid carbon dioxide phase change blasting pipes; use fracturing pumps (18) to transport water from the external joint (1103) of the hydraulic horizontal slotting pipes (11) to the fracturing section (1101), and inject water into the similar simulated coal sample; S8: During the water injection process in step S7, the stress sensor (3) and the acoustic emission sensor (4) will send the collected signals to the first computer (14) and the second computer (15) in real time. After the water injection is completed, the top of the transparent test chamber (1) will be scanned by ultrasonic CT to obtain the secondary crack distribution. S9: Relieve the triaxial stress on the similar simulated coal sample in S6, and use the liquid carbon dioxide phase change blasting mechanism (19) and liquid carbon dioxide phase change blasting tube to blast the similar simulated coal in the transparent test chamber (1) with CO2. After the blasting is completed, turn off the high-speed camera (20) and use ultrasonic CT to scan the top of the transparent test chamber (1) to obtain the three-dimensional crack distribution. S10: Upload the similar simulated coal sample photos captured by the high-speed camera (20) to the third computer, and use PS to sketch the coal sample cracks in the photos; the second computer (15) processes the signal transmitted by the acoustic emission sensor (4) and forms an image.

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