A laboratory coal and gas outburst simulation test system and method

Abstract

The application discloses a laboratory coal and gas outburst simulation test system and method, and relates to the technical field of coal mine safety dynamic disaster simulation test; the system comprises an outburst cavity, a rapid opening pressure relief assembly and a hydraulic shaft confining pressure loading assembly; a coal sample wrapped by a cylindrical rubber sleeve is arranged in the outburst cavity; the outburst cavity is assembled with the hydraulic shaft confining pressure loading assembly; the outburst cavity is connected with a hollow inflation channel; the coal sample is subjected to gas adsorption and inflation through the hollow inflation channel; the rapid opening pressure relief assembly can realize instantaneous release of the outburst port in the high-pressure outburst cavity; meanwhile, the pressure relief system can also be provided with an outburst weak surface, so that coal and gas outburst can be automatically induced to occur under the condition that the outburst threshold condition is reached; and the application solves the technical problems of poor stress simulation reality, single monitoring dimension and incapability of accurately quantifying the coupling rule of multiple factors of the outburst simulation test device.

Description

Technical Field

[0001] This invention relates to the field of coal mine safety dynamic disaster simulation test technology, specifically a laboratory coal and gas outburst simulation test system and method. Background Technology

[0002] Coal and gas outbursts are among the most destructive dynamic disasters in deep coal mining, characterized by their suddenness, intensity, and destructiveness. When this disaster occurs, the underground coal seam rapidly disintegrates and breaks apart within a very short time. Large amounts of gas, broken coal dust, and coal chunks erupt instantly from within the coal seam into the roadways and mining areas. This not only generates a strong impact force, damaging underground supports, mine cars, ventilation equipment, and other mining facilities, and distorting and destroying roadway support structures, but also causes large-scale coal dust accumulation in the roadways and disrupts the ventilation system, easily triggering secondary disasters such as gas explosions and asphyxiation. This seriously threatens the lives of underground workers and the safe production order of the mine. Currently, key operational scenarios such as coal seam exposure in high-gas mines and outburst-prone mines, coal roadway excavation, and longwall mining are all high-risk areas for coal and gas outbursts, making disaster prevention and control extremely difficult.

[0003] As the depth of coal mining in my country increases year by year, mines are gradually entering the stage of deep wells at depths of thousands of meters. Deep coal seams generally exhibit the characteristics of "three highs and one disturbance," namely high ground stress, high gas pressure, high gas content, and strong mining disturbance. Compared with shallow coal seams, the original stress level of deep coal bodies is significantly increased, the pore and fracture structures of the coal body are more complex, and the gas adsorption and desorption characteristics are more active. In addition, the continuous disturbance of the original stress balance of the coal and rock mass by underground mining operations makes it easy to induce stress concentration and abnormal gas accumulation, which greatly increases the probability and intensity of coal and gas outbursts. This also makes traditional disaster prevention and control technologies difficult to adapt to the safety requirements of deep mining.

[0004] The currently accepted mechanism of coal and gas outbursts in the industry is the comprehensive action hypothesis, which states that outburst disasters are the result of the coupled effects of three core factors: ground stress, gas pressure, and the physical and mechanical properties of the coal body. The dynamic matching relationship among these three factors directly determines whether an outburst occurs, its intensity, and the form of damage. To accurately reveal the outburst mechanism and formulate targeted prevention and control measures, conducting systematic simulation experiments is the core technical approach. However, due to the complex underground environment, experimental safety, and field conditions, in-situ outburst simulation experiments cannot be carried out. Indirect research can only be conducted based on underground monitoring data and post-disaster analysis, making it difficult to intuitively and completely reproduce the entire outburst process and accurately quantify the influence weight and action law of each core factor.

[0005] Therefore, laboratory physical simulation experiments have become the only reliable means to explore the mechanism of coal and gas outbursts and verify the effectiveness of prevention and control technologies. Although existing laboratory simulation devices can realize basic outburst simulation experiments, they have many technical shortcomings in practical applications, which seriously restrict the accuracy of experiments and research efficiency: First, most devices can only realize single axial compression loading and cannot simultaneously simulate the real stress environment of the three-dimensional confining pressure of the underground coal seam. The stress state of the coal body deviates greatly from the actual situation on site, and the simulation is not realistic enough. Second, existing devices have cumbersome structures, large equipment size, and are inconvenient to move. The amount of coal samples required for the experiment is large, the sample preparation process is complicated, and the cycle of a single test is long, making it impossible to realize batch comparative experiments with multiple working conditions and multiple variables. Third, the data monitoring system is imperfect. It can only monitor gas pressure or outburst coal powder quality, and cannot simultaneously collect multi-dimensional parameters such as stress, deformation, flow velocity, impact force, and acoustic emission, making it difficult to realize quantitative analysis of the outburst process. Fourth, the sealing performance of the device and the design of the piston guiding structure are unreasonable. During the experiment, problems such as air leakage, piston offset, and uneven stress on the coal sample are prone to occur, resulting in poor repeatability and reliability of the experiment. In summary, existing experimental devices cannot accurately quantify the coupling effect of the three factors of ground stress, gas pressure, and coal properties, making it difficult to meet the experimental needs of coal and gas outburst mechanism research and disaster prevention technology optimization under deep mining conditions. There is an urgent need to develop a high-precision, high-efficiency, and highly realistic coal and gas outburst simulation experimental device. Summary of the Invention

[0006] To address the technical shortcomings of existing coal and gas outburst simulation test devices, such as poor stress simulation realism, single monitoring dimensions, long test cycles, low operational flexibility, insufficient test reliability, and inability to accurately quantify the coupling effects of multiple factors, this invention provides a laboratory coal and gas outburst simulation test system and method.

[0007] This invention is achieved through the following technical solution: A laboratory coal and gas outburst simulation test system includes an outburst chamber, a quick-opening pressure relief assembly, and a hydraulic axial confining pressure loading assembly; The protruding cavity contains a coal sample wrapped in a cylindrical rubber sleeve. The annular space between the cylindrical rubber sleeve and the protruding cavity is a confining pressure chamber. The protruding cavity has a protrusion opening at its front end. The protruding cavity is equipped with a hydraulic axial confining pressure loading assembly, which applies axial pressure and confining pressure to the coal sample. The protruding cavity is connected to a hollow gas filling channel, through which the coal sample is gas-adsorbed and filled. The quick-opening pressure relief assembly is installed on the outside of the protrusion opening at the front end of the protrusion cavity. The protrusion opening is sealed by the quick-opening pressure relief assembly, and the transient process of downhole protrusion is simulated by opening the quick-opening pressure relief assembly.

[0008] Furthermore, a loading piston is assembled at the rear end of the protruding cavity. The loading piston has a hollow structure, and the hollow structure contains the aforementioned hollow inflation channel.

[0009] Furthermore, a mesh screen matching the piston diameter is fixed at the front end of the loading piston, and a porous loading plate is provided on the contact surface between the loading piston and the coal body. One end of the hollow gas filling channel is connected to the porous loading plate, and the other end is connected to a three-way valve. One end of the three-way valve is connected to a vacuum pump, and the other end of the three-way valve is connected to a gas cylinder. A gas pressure sensor is connected to the hollow gas filling channel.

[0010] Furthermore, a limiting groove is opened on the outside of the loading piston, and a guide strip is embedded therein. An O-ring is arranged in the middle of the guide strip and at the front end of the loading piston.

[0011] Furthermore, a cylindrical rubber sleeve is nested in the center of the protruding cavity, with the edge of the cylindrical rubber sleeve reserved. It is nested in a pre-set limiting groove inside the protruding cavity and is pressed and fixed by the limiting fixing block and the limiting nut.

[0012] Furthermore, the quick-opening pressure relief assembly includes an operating handle, a fixed plate, a sealing cover, a movable baffle, and a fixed shaft. The fixed plate is fixed to the front end face of the protruding cavity, and the fixed shaft is horizontally inserted and fixed in the pre-reserved shaft hole at the bottom of the fixed plate. The bottom of the movable baffle is hinged to the fixed shaft, and the upper end of the movable baffle is engaged and limited by the handle. A sealing cover is connected to the inner side of the middle of the movable baffle. The sealing cover is arranged between the movable baffle and the protruding opening of the cavity. In the locked state, the handle and the movable baffle are fastened and locked, and the sealing cover completely blocks the protruding opening.

[0013] Furthermore, the hydraulic axial confining pressure loading assembly includes a hydraulic cylinder, an axial pressure supply pump, a confining pressure supply pump, and a universal joint; the hydraulic cylinder is fixed on the reaction frame at the rear end of the protruding cavity, the cylinder piston of the hydraulic cylinder is connected to the loading piston through the universal joint, the axial pressure supply pump is connected to the oil inlet of the hydraulic cylinder, the protruding cavity is provided with a cavity confining pressure inlet, the cavity confining pressure inlet is connected to the cavity confining pressure filling cavity, and the confining pressure supply pump is connected to the cavity confining pressure inlet through a hydraulic oil circuit.

[0014] Furthermore, a disc-type pressure sensor is embedded between the cylinder piston and the universal joint, and a displacement sensor is connected to the outside of the hydraulic cylinder.

[0015] Furthermore, it also includes a coal powder collection and purification component, which includes multiple sections of acrylic pipes and an explosion-proof exhaust fan; the multiple sections of acrylic pipes are rigidly connected and fixed together by flange bolts, and the first section of the pipe is locked and connected to the protrusion at the front end of the protrusion cavity by a flange, and is arranged coaxially with the protrusion cavity; impact force sensors and acceleration sensors are fixedly installed at preset installation points on the acrylic pipe wall.

[0016] A laboratory coal and gas outburst simulation test method, based on the aforementioned test system, includes the following steps: Step 1: Coal sample preparation; Step 2, Equipment Assembly and Sealing Pretreatment: Place the prepared standard coal sample inside the cylindrical rubber sleeve, close the front quick-opening pressure relief component, and evacuate the internal cavity of the cylindrical rubber sleeve through the hollow air filling channel. Step 3, Saturated Adsorption of Gas in Coal Samples: After vacuuming is completed, the vacuuming pipeline is closed; gas is evenly introduced into the sealed cavity inside the cylindrical rubber sleeve through the hollow gas filling channel, and methane or carbon dioxide gas at a preset pressure is continuously introduced into the coal sample inside the cavity; so that the coal sample can be fully adsorbed under the preset pressure environment to achieve a state of saturated adsorption of gas. Step 4, Triaxial Stress Loading and Pressure Stabilization: First, apply initial axial prestress to the coal sample, then apply a preset radial confining pressure to the coal sample; after the confining pressure stabilizes, continuously supply hydraulic oil and gradually apply axial pressure until both axial pressure and confining pressure reach the test design parameters; after the parameters meet the standards, continue to maintain the pressure so that the coal stress and gas pressure are completely balanced, simulating the stable underground occurrence state; Step 5: Outburst test initiation and data acquisition: The pressure relief component is instantly unlocked and opened, the outburst outlet is instantly depressurized, the balance between coal stress and gas pressure is broken, and a coal and gas outburst occurs.

[0017] The beneficial effects of this invention compared to the prior art are as follows: 1. This invention employs a cylindrical rubber sleeve and a axial pressure and confining pressure co-loading system to accurately simulate the real three-dimensional stress state of deep coal seams, solving the problem of traditional devices only being able to load in one direction and resulting in distorted stress simulation. Through the coordinated operation of the axial pressure oil pump and the confining pressure oil pump, the magnitude of the in-situ stress on the coal body can be precisely controlled, reproducing the stress loading process under underground mining disturbances. Simultaneously, relying on the multi-hole surface loading plate design, uniform stress is achieved on the coal body end face, avoiding experimental errors caused by localized stress concentration. This allows for a realistic reproduction of the entire process of coal and gas outburst initiation, development, and outbreak under the coupled effects of high in-situ stress and high gas pressure, with experimental results highly consistent with actual field conditions.

[0018] 2. This invention integrates multi-dimensional monitoring units for gas pressure, gas flow rate, ground stress, coal body temperature, acoustic emission, coal powder flow impact force, and acceleration. Combined with a high-frequency data acquisition instrument and a high-speed camera, it can collect dynamic data in real-time and synchronously throughout the entire process of coal gas adsorption, stress loading, outburst outbreak, and coal powder migration. Compared to the single-parameter monitoring mode of traditional devices, this system can comprehensively acquire the stress evolution law, gas pressure attenuation characteristics, coal body deformation parameters, coal powder two-phase flow motion characteristics, and acoustic emission response law during the outburst process. It can accurately quantify the coupling mechanism and influence weight of the three core factors—ground stress, gas pressure, and coal mechanical properties—providing comprehensive and accurate data support for revealing the outburst mechanism.

[0019] 3. This invention features targeted optimization of the core motion and sealing structure. The piston area is equipped with double O-ring seals and a guide band. This multi-layered sealing structure completely eliminates gas leakage during the test, ensuring gas adsorption saturation and test pressure stability. The guide band precisely constrains the piston's movement trajectory, effectively preventing piston offset, top deviation, jamming, and other malfunctions, preventing damage to the cavity and coal sample, and ensuring consistent stress on the coal body in each test. Simultaneously, a mesh structure at the piston's front end ensures uniform gas penetration and adsorption while preventing broken coal powder from entering the hollow ventilation channel, protecting pipelines and monitoring equipment, significantly reducing equipment failure rates, ensuring consistency and repeatability across multiple comparative tests, and improving the reliability of test data.

[0020] 4. This invention adopts a compact modular structure with reasonably sized cylindrical coal samples, requiring less coal sample per test and significantly simplifying the coal sample preparation process. Utilizing a surface-type pressure-holding loading structure and a rapid adsorption and pressure-holding system, it effectively shortens the time for coal sample gas adsorption and stress pressure holding, enabling efficient single-variable and multi-variable orthogonal comparative experiments to meet the needs of batch testing under multiple conditions and parameters. Simultaneously, the device's overall structure is compact, allowing for rapid lifting via a high-strength screw at the base and free movement with a hydraulic trolley, making it adaptable to various laboratory testing scenarios.

[0021] 5. This invention can adapt to different test media and test scenarios without modifying the equipment structure. It can not only carry out conventional coal and gas outburst simulation tests to restore the characteristics of outburst disasters under different ground stress, gas pressure and coal mechanical properties, but also realize rock and carbon dioxide outburst simulation tests, thus expanding the test application range of the equipment. In addition, this invention can realize two outburst induction methods: one is manual rapid release of the outburst outlet, and the other is setting outburst weak surface to induce outburst occurrence, realizing the outburst simulation test process under the action of multiple induction methods.

[0022] 6. This invention, through working condition simulation and multi-parameter data acquisition, can quantitatively obtain the intensity, severity, and dynamic response characteristics of coal and gas outbursts under different working conditions, clarify the role law and critical threshold of each influencing factor, and provide precise experimental basis for optimizing gas disaster prevention and control technologies such as coal seam pre-drainage, stress release, and advanced support in deep outburst mines. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram highlighting the cavity and hydraulic cylinder structure; Figure 2 A schematic diagram of the quick-opening mechanism; Figure 3 A schematic diagram highlighting the piston joint inside the cavity; Figure 4 A schematic diagram showing the arrangement of the rubber sealing sleeve in the protruding cavity; Figure 5 A schematic diagram of the layout of a laboratory coal and gas outburst simulation test system; Figure 6 A cross-sectional schematic diagram of the pressure head and mold forming sleeve for preparing coal briquettes.

[0025] Reference numerals: 1. Protruding cavity; 2. Hydraulic cylinder; 3. Handle; 4. Fixing plate; 5. Sealing cover; 6. Movable baffle; 7. Fixed shaft; 8. Hollow inflation channel; 9. Universal joint; 10. Vacuum pump; 11. Three-way valve; 12. Axial displacement sensor; 13. Cylinder piston; 131. Loading piston; 14. Reaction frame; 15. Cavity confining pressure oil inlet; 16. Impact force sensor; 17. Acceleration sensor; 18. Flange; 19. Explosion-proof exhaust fan; 21. Axial pressure oil pump; 22. Long nut; 23. Cylindrical rubber sleeve; 24. Limiting and fixing block; 25. 26. Guide belt; 27. O-ring seal; 28. Limit nut; 29. ​​Mesh screen; 30. Limiting groove; 31. Rubber sleeve edge; 32. Confining pressure oil pump; 33. Gas cylinder; 34. Quick-opening pressure relief assembly; 35. Protrusion; 36. Acrylic pipe; 37. Multi-hole surface loading plate; 38. Gas pressure sensor; 39. Briquette preparation head; 30. Hollow position of briquette preparation head; 31. Main cavity of briquette pressing; 32. Chamfer position of main cavity of briquette pressing; 43. Hollow structure of main cavity of briquette pressing; 44. Brood release mold of main cavity of pressing; 45. Groove. Detailed Implementation

[0026] To make the technical problems to be solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The technical solutions of this invention are described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto. Example 1

[0027] like Figures 1-5 As shown, the present invention discloses a laboratory coal and gas outburst simulation test system, including an outburst chamber 1, a quick-opening pressure relief assembly 33, a hydraulic shaft confining pressure loading assembly, a coal powder collection and purification assembly, a mobile support base assembly, and a multi-dimensional data monitoring assembly; (a) Protruding cavity 1 The protruding cavity 1 serves as the load-bearing structure of the device. It is made of seamless steel pipe with a thickness of 35mm and has an overall dimension of 600mm in length, 160mm in inner diameter, and 230mm in outer diameter. The interior of the cavity is treated with an anti-rust and anti-corrosion coating to prevent rust from affecting the sealing performance and test accuracy. A cylindrical protrusion 34 with a diameter of 35mm is opened at the center of the front end of the protruding cavity 1 as a channel for the emission of pulverized coal and gas.

[0028] A cylindrical rubber sleeve 23 is nested inside the center of the protruding cavity 1. The sleeve has an inner diameter of 60mm, a length of 450mm, and a thickness of 6mm. A 30mm sealing edge (edge ​​30) is provided on the edge of the sleeve, which is precisely nested into the pre-set limiting groove 29 inside the cavity. It is then tightened and fixed by the limiting fixing block 24 and the limiting nut 27, completely eliminating the problems of hydraulic oil leakage and sleeve displacement. The interior of the cylindrical rubber sleeve 23 is a coal sample placement cavity, which can stably accommodate a cylindrical coal briquette sample with a length of 450mm and a diameter of 60mm.

[0029] The rear end of the protruding cavity 1 is equipped with a loading piston 131, which is the core force-bearing and force-transmitting component. The whole structure adopts a hollow structure, and a hollow gas filling channel 8 is set inside the hollow structure, which can realize the function of gas adsorption and filling of coal samples.

[0030] A 2mm thick mesh screen 28, matching the piston diameter, is fixed to the front end of the loading piston 131 and secured with screws. This ensures uniform gas penetration into the coal body while preventing coal dust from entering the hollow gas filling channel 8, thus protecting the pipeline. The contact surface between the loading piston 131 and the coal body uses a porous surface loading disk 36 to achieve uniform stress distribution across the entire coal sample, avoiding localized stress concentration. One end of the hollow gas filling channel 8 is connected to the porous surface loading disk 36, and the other end is connected to a three-way valve 11. One end of the three-way valve 11 is connected to the vacuum pump 10, and the other end is connected to the gas cylinder 32. A gas pressure sensor is connected to the hollow gas filling channel 8.

[0031] A limiting groove is formed on the outer side of the loading piston 131, and two guide strips 25, each 10mm wide and 8mm thick, are embedded inside. The guide strips 25 are positioned at the center of the groove to ensure precise alignment of the axial movement of the loading piston 131, preventing issues such as misalignment, jamming, and cavity damage. Double O-rings 26 are symmetrically arranged at 10mm and 1mm positions on both sides of the guide strips 25, achieving multiple seals between the piston and the cavity, completely solving the problems of air and oil leakage during the inflation and pressurization process, and ensuring the overall sealing performance of the device.

[0032] (ii) Quickly open the pressure relief component 33 The quick-opening pressure relief assembly 33 is mounted on the outside of the protruding opening 34 at the front end of the protruding cavity 1 and is fixed with M14 high-strength bolts. Combined with a sealing gasket, it achieves a complete seal at the interface. The quick-opening pressure relief assembly 33 includes an operating handle 3, a fixed plate 4, a sealing cover 5, a movable baffle 6, a fixed shaft 7, and an adjustable sealing block. The adjustable sealing block has a threaded structure inside, and the tightness of the seal can be precisely adjusted by turning the threads. A wear-resistant sealing gasket is attached to the surface of the sealing block to ensure an absolute seal when the protruding opening 34 is closed.

[0033] The fixed plate 4 serves as the base for the quick-opening pressure relief assembly 33. It is rigidly fixed to the front end face of the protruding cavity 1 with high-strength bolts, ensuring a stable position and serving as the mounting support for the entire quick-opening mechanism 33. The fixed shaft 7 is horizontally inserted and fixed in the pre-drilled shaft hole at the bottom of the fixed plate 4. The bottom of the movable baffle 6 is hinged to the fixed shaft 7, allowing it to rotate freely around the fixed shaft 7. The upper end of the movable baffle 6 engages with the handle 3 for a limiting position. The handle 3 is snapped onto the upper end of the movable baffle 6, locking it in place under normal conditions and preventing it from rotating, thus forming a mechanical lock. Upon impact, it quickly disengages, releasing the movable baffle 6. A sealing cover 5 is connected to the inner side of the middle of the movable baffle 6. The sealing cover 5 is positioned between the movable baffle 6 and the cavity protrusion 34, with a wear-resistant sealing gasket attached to the inner side of the cover, directly facing and completely covering the protrusion 34. In the locked state, tightening the threads at the end of the sealing cover 5 secures the sealing cover 5 to the protrusion 34, achieving a high-pressure seal in the cavity.

[0034] In the standby pressure-holding state of the device, the handle 3 is fastened and locked to the movable baffle 6, and the sealing cover 5 completely blocks the protrusion 34. When the test is started, the movable baffle 6 can be unlocked instantly by striking the handle 3 with external force. The sealing cover 5 is quickly released under the pressure of high-pressure gas and coal powder inside the cavity, realizing the millisecond-level pressure relief and opening of the protrusion 34, accurately simulating the real working condition of instantaneous pressure relief and power burst during an underground outburst.

[0035] (III) Hydraulic shaft confining pressure loading assembly The hydraulic axial confining pressure loading assembly is the core of the coal sample stress simulation, including a hydraulic cylinder 2, an axial pressure oil supply pump 21, a confining pressure oil supply pump 31, a universal joint 9, a disc pressure sensor, and a displacement sensor 12. The hydraulic cylinder 2 is fixed to the reaction frame 14 at the rear end of the protruding cavity 1. The cylinder extension arm, i.e., the cylinder piston 13, is connected to the loading piston 131 through the universal joint 9. The universal joint 9 can adaptively adjust the force transmission angle, completely avoiding piston movement jamming and force offset problems, and ensuring uniform and stable stress transmission.

[0036] A disc-type pressure sensor is embedded between the piston 13 of the hydraulic cylinder and the universal joint 9 to collect axial loading stress data in real time; a 150mm range displacement sensor 12 is fixed on the outside of the hydraulic cylinder 2 to monitor the axial deformation of the coal sample throughout the process. The axial pressure oil pump 21 is connected to the oil inlet of the hydraulic cylinder 2 to provide power to the hydraulic cylinder 2. The maximum axial loading force can reach 1000KN, and the maximum piston extension stroke is 100mm, which can meet the simulation requirements of different ground stress conditions.

[0037] The protruding cavity 1 is provided with a cavity confining pressure oil inlet 15, which is connected to the cavity confining pressure filling cavity. The confining pressure oil supply pump 31 is connected to the cavity confining pressure oil inlet 15 through a hydraulic oil circuit, which can fill hydraulic oil into the outer cavity of the cylindrical rubber sleeve 23 to apply radial confining pressure to the internal coal sample; realize the axial pressure loading of the coal sample; the confining pressure and axial pressure work together to accurately simulate the three-dimensional stress environment of the underground coal seam.

[0038] (iv) Pulverized coal collection and purification components The coal powder collection and purification assembly includes multiple acrylic pipes 35 and an explosion-proof exhaust fan 19; The acrylic pipe 35 has a segmented structure, with each segment being 1.5m long. Multiple pipe segments are rigidly connected and fixed together by flanges 18 and bolts. The end faces of adjacent pipes are sealed to ensure overall coaxiality and sealing, preventing coal dust and gas leakage. The first segment of the pipe is locked and connected to the protrusion 34 at the front end of the protrusion cavity 1 by flanges 18, and is arranged coaxially with the protrusion cavity 1, serving as a dedicated ejection and guiding channel for the coal dust-gas two-phase flow. The impact force sensor 16 and the acceleration sensor 17 are fixed to the preset installation points on the wall of the acrylic pipe 35 by clips, fitting tightly to the outer wall of the pipe without loosening or offset, and can accurately collect the impact dynamic parameters of the airflow inside the pipe.

[0039] The air inlet of the explosion-proof exhaust fan 19 is fixed to the end of the acrylic pipe 35 via a sealed adapter flange. A sealing gasket is installed at the interface to achieve a complete seal, ensuring a slightly negative pressure collection environment inside the pipe. The fan is horizontally fixed on the support frame at the rear of the equipment, maintaining horizontal and coaxial alignment with the acrylic pipe 35, ensuring stable and unwavering operation. The fan outlet is connected to a dust collection bag and purification device, forming a closed-loop structure of "outlet guidance - pipe transmission - fan suction - dust collection and purification".

[0040] (v) Support base assembly The mobile support base assembly consists of a base plate and support legs, which are the load-bearing support structure of the entire test device. Multiple support legs are connected to the bottom of the reaction frame 14, acrylic pipe 35 and protruding cavity 1. The bottom of multiple support legs are connected to the base plate. The base plate is connected to the fixed plane in the laboratory by multiple long nuts 22.

[0041] (vi) Multi-dimensional data monitoring components The multi-dimensional data monitoring component integrates multiple types of sensors and data acquisition instruments, with a data acquisition frequency of 2KHz. By connecting the data acquisition instrument to each sensor, it can simultaneously achieve real-time monitoring, recording, and storage of multiple parameters. The working principle of a laboratory coal and gas outburst simulation test system is as follows: This system is designed based on the hypothesis of the combined effects of coal and gas outbursts. It simulates the high ground stress environment of underground coal seams by simultaneously loading axial pressure and confining pressure, simulates the high gas content state of coal seams by high-pressure gas aeration and adsorption, and simulates the instantaneous release of stress induced by underground mining disturbances by rapidly opening and depressurizing. It fully reproduces the entire process of "stress accumulation - gas adsorption - fracture development - instability and outburst".

[0042] In the early stage of the experiment, the coal sample was brought to a preset gas saturation state through vacuum degassing and high-pressure gas adsorption. Then, the axial pressure and radial confining pressure were applied simultaneously through the hydraulic system to simulate the in-situ stress environment of the deep coal seam. The pressure was maintained to stabilize the stress and gas state of the coal body. Subsequently, the cavity pressure was released instantly by the rapid opening mechanism, which broke the balance between the stress of the coal body and the gas pressure. The internal cracks of the coal body expanded and connected rapidly, and the high-pressure gas carried the broken coal body and was ejected instantly, forming the dynamic phenomenon of coal and gas outburst.

[0043] Throughout the experiment, various monitoring sensors synchronously collect parameters such as stress, displacement, gas pressure, temperature, acoustic emission, and impact dynamics. Combined with the statistical results of coal dust collection, the influence of three major factors—ground stress, gas pressure, and coal properties—on outburst intensity, outburst velocity, and coal dust particle size distribution can be quantitatively analyzed, enabling multi-factor comparative experimental research. Furthermore, the device is compatible with both methane and carbon dioxide gases, allowing for rock and carbon dioxide outburst simulation experiments without modification, adapting to various experimental scenarios.

[0044] The assembly process of a laboratory coal and gas outburst simulation test system is as follows: 1. Main assembly: The protruding cavity 1 is horizontally fixed at the center of the reaction frame 14 to ensure that the central axis of the cavity is horizontal and without deviation; the hydraulic cylinder 2 is coaxially fixed to the rear reaction frame 14 of the cavity, and the cylinder telescopic arm is completely aligned with the central axis of the cavity piston, with a coaxiality error ≤0.5mm.

[0045] 2. Piston Assembly: The guide belt 25 and O-ring 26 are sequentially embedded into the pre-set grooves of the loading piston 131 to ensure a flat, smooth, and non-protruding installation; the mesh screen 28 is fastened to the front end of the piston with screws, ensuring a snug fit; the multi-hole loading disc 36 is coaxially fixed to the piston with a flat end face. The loading piston 131 is fully embedded in the rear end of the cavity and can slide freely along the central axis of the cavity without jamming or shifting.

[0046] 3. Rubber sleeve assembly: The cylindrical rubber sleeve 23 is inserted from the front end of the cavity, and the edge 30 of the sleeve is fully engaged in the cavity limiting groove 29. It is pressed by the limiting fixing block 24 and locked by the limiting nut 27 to ensure that the sleeve is not loose or wrinkled. The cylindrical rubber sleeve 23 cavity is fully aligned with the front end of the loading piston 131.

[0047] 4. Quick-opening system assembly: Fix the fixing plate 4 to the outside of the protrusion 34 at the front end of the cavity with M14 high-strength bolts, and the sealing gasket fits the interface end face without gap; the handle 3, movable baffle 6, and fixed shaft 7 are assembled in sequence to ensure flexible unlocking and firm locking; the adjustable sealing block is screwed until the sealing cover 5 fits completely with the protrusion 34 without any air leakage gap.

[0048] 5. Hydraulic system assembly: The universal joint 9 is fastened to the telescopic arm of the hydraulic cylinder 2 and the cavity loading piston 131 at both ends by bolts; the disc pressure sensor is clamped and fixed to the connection end face between the cylinder piston 13 and the universal joint 9; the displacement sensor 12 is horizontally fixed to the outside of the cylinder, with the detection end aligned with the piston movement end; the axial pressure oil supply pump 21 and the confining pressure oil supply pump 31 are respectively connected to the oil inlet of the hydraulic cylinder and the cavity confining pressure filling cavity through high-pressure oil circuits, and the oil circuit connection is sealed without leakage.

[0049] 6. Monitoring system assembly: Various sensors are fixed at preset points on the protruding cavity 1, the inflation pipeline, and the acrylic pipeline 35, respectively, and the sensor probes are in full contact with the measured medium; all sensor signal lines are connected to the data acquisition instrument to complete signal debugging and parameter calibration, ensuring accurate, real-time, and delay-free data acquisition.

[0050] 7. Auxiliary system assembly: Multiple acrylic pipes 35 are connected and fixed to the front end of the protrusion 34 via flanges 18. The pipe connections are securely sealed and coaxially straight. Explosion-proof exhaust fans 19 are connected to the end of the pipes, and the fan outlet is connected to an external dust collection device. The device base is fixed with long nuts to ensure that the equipment is placed horizontally without tilting or shaking.

[0051] This system can achieve the following: (1) Simulation of conventional coal and gas outburst: By adjusting the parameters of gas pressure, axial pressure and confining pressure, single-factor and multi-factor orthogonal tests can be carried out under different ground stress, gas conditions and coal mechanical properties to quantify the influence weight of each factor on outburst disaster.

[0052] (2) Rock and carbon dioxide outburst simulation: Rock and carbon dioxide outburst simulation test can be completed without modifying the equipment structure, changing the carbon dioxide gas source, and adjusting the stress loading parameters, thus expanding the equipment test scenario. Example 2

[0053] A laboratory coal and gas outburst simulation test method, based on the test system described in Example 1, includes the following steps: Step 1: Preparation of coal briquette samples (a) Coal powder pretreatment: After the raw coal is crushed by a crusher, qualified coal powder is screened out. About 6% water is added to the coal powder and stirred thoroughly to ensure that the coal powder has uniform moisture and no lumps.

[0054] (II) Pressing and molding of coal briquettes: The stirred coal powder is filled into the mold forming sleeve in batches, and the pressure shaft is used to vibrate and level it to eliminate the voids inside the coal powder; the whole set of molds is placed on a 200t press, and the pressing pressure is accurately calculated according to the cross-sectional area of ​​the coal sample. The briquetting head 38 on the press is used to press the coal sample with a force of 900KN on the 200t test machine for 1 hour to ensure that the coal sample is dense, uniform and structurally stable.

[0055] The mold forming sleeve includes a main cavity briquette demolding mold 40 and a briquette pressing main cavity 39. The briquette pressing main cavity 39 is a cylindrical hollow structure with a wall thickness of 30mm. The diameter of the hollow structure 392 of the briquette pressing main cavity is 60mm, used to hold coal powder or gypsum. The briquette pressing main cavity 39 is installed inside the main cavity briquette demolding mold 40. The briquette pressing main cavity 39 has a chamfer of about 5% at its lower part, i.e., the chamfer position point 391.

[0056] The main cavity briquette demolding mold 40 is a circular hollow structure with a groove 401. The outer wall of the briquette pressing main cavity 39 has a protrusion that can be embedded in the groove 401. After the briquette pressing main cavity 39 is placed in the main cavity briquette demolding mold 40, the outer wall of the briquette pressing main cavity 39 is stuck in the groove 401, making demolding easier.

[0057] The briquette preparation head 38 has a cylindrical structure, and the briquette preparation head 38 has a hollow position 381 inside, which is to reduce the weight during operation.

[0058] (III) Demolding: Place the mold stably on the demolding station of the press, slowly release the pressure, and demold smoothly to obtain a standard cylindrical briquette sample with a diameter of 60mm and a length of 450mm. Place it in a dry place for later use. During demolding, because the hollow structure 392 of the main cavity of the briquette pressing body is located below the middle and has a chamfer of about 5% at this position, demolding can be carried out smoothly without the need for additional release agent, and the integrity of the briquette sample is ensured during demolding. At the same time, the main cavity 39 of the briquette pressing body can be locked in the groove 401, ensuring the stability during demolding.

[0059] Step 2: Equipment Assembly and Sealing Pretreatment The prepared coal sample is placed stably inside the cylindrical rubber sleeve 23, ensuring that the sample is centered, without tilting or shifting. The front quick-opening mechanism 33 is closed, and the sealing cover bolts and adjustable sealing blocks are tightened step by step to compact the sealing gasket and ensure a complete seal at the protrusion. The pipeline connected to the vacuum pump 10 is used to evacuate the internal cavity of the cylindrical rubber sleeve 23 for at least 12 hours to thoroughly remove air and impurities from the coal sample and ensure the purity of gas adsorption.

[0060] Step 3: Saturated adsorption of coal gas After vacuuming is completed, vacuum pump 10 is turned off and the vacuuming pipeline is disconnected. Then, the valve of high-pressure gas cylinder 32 is opened. High-pressure gas cylinder 32 is sealed and connected to the hollow gas filling channel 8 inside the loading piston 131 through an external high-pressure gas pipeline. Gas can pass through the hollow gas filling channel 8 to the multi-porous loading disk 36 and the mesh screen 28 at the front end of the piston, and be evenly introduced into the sealed cavity inside the cylindrical rubber sleeve 23. Methane or carbon dioxide gas at a preset pressure is continuously introduced into the coal sample inside the cavity. The entire gas circuit is completely sealed to ensure that the gas can only penetrate the coal body and there is no external gas leakage. The gas pressure inside the cavity is kept constant, so that the coal sample can fully adsorb for 12 hours under the preset pressure environment to reach the gas saturation adsorption state. After adsorption is completed, the valve of high-pressure gas cylinder 32 is closed, the gas filling pipeline is sealed, and the coal sample gas filling and adsorption process is completed.

[0061] Step 4: Triaxial Stress Loading and Voltage Stabilization First, the axial pressure supply pump 21 is started, and the hydraulic cylinder 2 is controlled to advance at a low speed to apply initial axial prestress to the coal sample, ensuring that the coal sample is fixed and not loosened, without damaging the original mechanical structure of the coal body. Then, the confining pressure supply pump 31 is started to introduce hydraulic oil into the confining pressure filling cavity, applying a preset radial confining pressure to the rubber sleeve and the internal coal sample. After the confining pressure stabilizes, hydraulic oil is continuously supplied to gradually increase the axial pressure until both the axial pressure and the confining pressure reach the experimental design parameters. After the parameters are met, the pressure is maintained for 2 hours to allow the coal stress and gas pressure to completely reach equilibrium, simulating a stable underground storage state.

[0062] Step 5: Emphasizing Experiment Initiation and Data Acquisition Before the test, the explosion-proof exhaust fan 19 and data acquisition instrument were turned on, and all sensors were tested to ensure normal data acquisition. A hand hammer was used to strike the handle 3 of the quick-opening mechanism at a uniform speed, instantly unlocking the movable baffle 6. Under the high pressure inside the cavity, the sealing cover 5 quickly detached, instantly relieving pressure at the protrusion outlet 34. This disrupted the balance between coal stress and gas pressure, resulting in a coal and gas outburst. Throughout the outburst, the data acquisition instrument simultaneously recorded the gas pressure decay curve, axial deformation of the coal body, changes in loading stress, coal temperature, acoustic emission signals, and key parameters such as the impact acceleration and impact force of the pulverized coal two-phase flow. The explosion-proof exhaust fan 19 collected the ejected pulverized coal in real time, preventing dust diffusion.

[0063] Step Six: Post-Experiment Processing and Data Analysis After the test, all equipment power and pipeline valves were shut off, the axial pressure and confining pressure were smoothly released, and residual coal powder in the equipment cavity and pipelines was cleaned. During the process of expelling the crushed coal powder, the data acquisition instrument collected data on the gas pressure drop in the cylindrical rubber sleeve 23. The acceleration sensor 17 and impact force sensor 16 arranged on the acrylic pipe 35 monitored the acceleration and impact force of the two-phase flow of the crushed coal powder, and the data acquisition instrument effectively recorded the above acceleration and impact force data.

[0064] Outburst-prone coal dust was collected from acrylic pipe 35, and the total mass of the outburst-prone coal dust was weighed. The outburst-prone coal dust was then sieved using a standard coal sample sieve. The total mass of outburst-prone coal dust and the proportion of coal dust with different particle sizes were statistically analyzed, and the outburst intensity was calculated. Based on the monitored dynamic data, the influence of gas pressure, ground stress, and coal properties on the occurrence, development, and intensity of the outburst was analyzed, and the experimental data were compiled and analyzed. Example 3

[0065] A laboratory coal and gas outburst simulation test method, based on the test system described in Example 1, differs from Example 2 in that the outburst is not triggered by manually and rapidly releasing the outburst port 34, but rather by stimulating the outburst through the weak outburst surface; the specific difference is as follows: 1. Based on step one of Example 2, the preparation of the protruding weak surface is added: gypsum with a water content of 12% by mass is used as the protruding weak surface, and it is pressed into shape using the same method as briquette pressing. The diameter of the protruding weak surface is the same as the diameter of the briquette sample, which is 60mm.

[0066] 2. Step Two: Equipment Assembly and Sealing Pretreatment The prepared coal sample and the protruding weak surface are placed steadily inside the cylindrical rubber sleeve 23, with the protruding weak surface adjacent to the discharge port 34, ensuring that the coal sample is placed in the center without tilting or shifting; the rest is the same as step two of Example 2.

[0067] 3. Step Five: Emphasizing Experiment Start-up and Data Acquisition When different gas pressures and axial pressures are applied to the coal sample, when the conditions for destroying the outburst weak surface are met, the broken coal sample can be rapidly released from the outburst opening 34. The balance between coal stress and gas pressure is broken, and the outburst weak surface triggers coal and gas outburst. The data collection is the same as in Example 2.

[0068] The remaining steps are the same as in Example 2. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Without departing from the core principles of the present invention, those skilled in the art can reasonably optimize and improve the equipment structure and test parameters, all of which fall within the protection scope of the present invention.

Claims

1. A laboratory coal and gas outburst simulation test system, characterized in that, Includes a protruding cavity (1), a quick-opening pressure relief assembly (33), and a hydraulic shaft confining pressure loading assembly; The protruding cavity (1) contains a coal sample wrapped by a cylindrical rubber sleeve (23). The annular space between the cylindrical rubber sleeve (23) and the protruding cavity (1) is a confining pressure cavity. The protruding cavity (1) has a protruding opening (34) at the front end. The protruding cavity (1) is equipped with a hydraulic axial confining pressure loading assembly. The coal sample is subjected to axial pressure and confining pressure loading through the hydraulic axial confining pressure loading assembly. The protruding cavity (1) is connected to a hollow gas filling channel (8). The coal sample is gas-adsorbed and filled through the hollow gas filling channel (8). The quick-opening pressure relief assembly (33) is installed on the outside of the front protrusion (34) of the protrusion cavity (1). The protrusion (34) is sealed by the quick-opening pressure relief assembly (33), and the simulation of the downhole protrusion transient process is realized by opening the quick-opening pressure relief assembly (33).

2. The laboratory coal and gas outburst simulation test system according to claim 1, characterized in that, The rear end of the protruding cavity (1) is equipped with a loading piston (131), which is a hollow structure, and the hollow structure is provided with the hollow air filling channel (8).

3. The laboratory coal and gas outburst simulation test system according to claim 2, characterized in that, A mesh screen (28) matching the piston diameter is fixed at the front end of the loading piston (131). A porous loading disk (36) is provided on the contact surface between the loading piston (131) and the coal body. One end of the hollow gas filling channel (8) is connected to the porous loading disk (36), and the other end is connected to a three-way valve (11). One end of the three-way valve (11) is connected to the vacuum pump (10), and the other end of the three-way valve (11) is connected to the gas cylinder (32). A gas pressure sensor (37) is connected to the hollow gas filling channel (8).

4. The laboratory coal and gas outburst simulation test system according to claim 3, characterized in that, A limiting groove is provided on the outside of the loading piston (131), and a guide belt (25) is embedded therein. An O-ring (26) is arranged in the middle of the guide belt (25) and at the front end of the loading piston (131).

5. The laboratory coal and gas outburst simulation test system according to claim 1, characterized in that, A cylindrical rubber sleeve (23) is nested inside the center of the protruding cavity (1). The edge of the cylindrical rubber sleeve (23) is reserved with a rubber sleeve edge (30). It is nested in the preset limiting slot (29) inside the protruding cavity (1) and is pressed and fixed by the limiting fixing block (24) and the limiting nut (27).

6. The laboratory coal and gas outburst simulation test system according to claim 1, characterized in that, The quick-opening pressure relief assembly (33) includes an operating handle (3), a fixed plate (4), a sealing cover (5), a movable baffle (6), and a fixed shaft (7). The fixed plate (4) is fixed to the front end face of the protruding cavity (1). The fixed shaft (7) is horizontally inserted and fixed in the pre-reserved shaft hole at the bottom of the fixed plate (4). The bottom of the movable baffle (6) is hinged to the fixed shaft (7). The upper end of the movable baffle (6) is engaged and limited by the handle (3). The inner side of the middle of the movable baffle (6) is connected to the sealing cover (5). The sealing cover (5) is arranged between the movable baffle (6) and the protruding opening (34) of the cavity. In the locked state, the handle (3) and the movable baffle (6) are fastened and locked. The sealing cover (5) completely blocks the protruding opening (34).

7. The laboratory coal and gas outburst simulation test system according to claim 2, characterized in that, The hydraulic axial confining pressure loading assembly includes a hydraulic cylinder (2), an axial pressure supply pump (21), a confining pressure supply pump (31), and a universal joint (9). The hydraulic cylinder (2) is fixed on the reaction frame (14) at the rear end of the protruding cavity (1). The cylinder piston (13) of the hydraulic cylinder (2) is connected to the loading piston (131) through the universal joint (9). The axial pressure supply pump (21) is connected to the oil inlet of the hydraulic cylinder (2). The protruding cavity (1) is provided with a cavity confining pressure inlet (15). The cavity confining pressure inlet (15) is connected to the cavity confining pressure filling cavity. The confining pressure supply pump (31) is connected to the cavity confining pressure inlet (15) through a hydraulic oil circuit.

8. The laboratory coal and gas outburst simulation test system according to claim 7, characterized in that, A disc pressure sensor is installed between the cylinder piston (13) and the universal joint (9), and a displacement sensor (12) is connected to the outside of the hydraulic cylinder (2).

9. The laboratory coal and gas outburst simulation test system according to claim 1, characterized in that, It also includes a coal powder collection and purification component, which includes multiple acrylic pipes (35) and an explosion-proof exhaust fan (19); the multiple acrylic pipes (35) are rigidly connected and fixed by flanges (18) and bolts, and the first section of the pipe is locked and connected to the protrusion (34) at the front end of the protrusion cavity (1) by flanges (18), and is arranged coaxially with the protrusion cavity (1); an impact force sensor (16) and an acceleration sensor (17) are fixedly installed at the preset installation points on the acrylic pipe (35).

10. A laboratory method for simulating coal and gas outbursts, characterized in that, Based on the testing system according to any one of claims 1-9, and comprising the following steps: Step 1: Coal sample preparation; Step 2, Equipment assembly and sealing pretreatment: Place the prepared standard coal sample inside the cylindrical rubber sleeve (23), close the front end quick-opening pressure relief component (33), and vacuum the internal cavity of the cylindrical rubber sleeve (23) through the hollow air filling channel (8); Step 3, Saturated adsorption of coal sample gas: After vacuuming is completed, close the vacuuming pipeline; uniformly introduce gas into the sealed cavity inside the cylindrical rubber sleeve (23) through the hollow gas filling channel (8), and continuously introduce methane or carbon dioxide gas at a preset pressure into the coal sample inside the cavity; so that the coal sample can be fully adsorbed under the preset pressure environment and reach the state of saturated adsorption of gas. Step 4, Triaxial Stress Loading and Pressure Stabilization: First, apply initial axial prestress to the coal sample, then apply a preset radial confining pressure to the coal sample; after the confining pressure stabilizes, continuously supply hydraulic oil and gradually apply axial pressure until both axial pressure and confining pressure reach the test design parameters; after the parameters meet the standards, continue to maintain the pressure so that the coal stress and gas pressure are completely balanced, simulating the stable underground occurrence state; Step 5, Outburst test start and data acquisition: Instantly unlock and quickly open the pressure relief component (33), the outburst port (34) is instantly depressurized, the balance between coal stress and gas pressure is broken, and coal and gas outburst occurs.

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