A two-way adsorption preparation device for gas-bearing coal-rock assemblages

Abstract

This invention discloses a bidirectional adsorption preparation device for gas-bearing coal-rock assemblages. The device includes an integrated composite sample, a high-pressure sealed loading chamber, and a bidirectional fluid-structure coupling gas path. The integrated composite sample is formed by solidifying at least two coal body units and at least one barrier unit sandwiched between them into a single mechanical whole using a binder, with permeable structures at both ends. The high-pressure sealed loading chamber is equipped with a constraint device to provide radial centering and axial pre-tightening force. The bidirectional fluid-structure coupling gas path is connected to the permeable structures at both ends, respectively, for bidirectional symmetrical gas extraction and filling from both ends of the sample. This invention transforms a multi-layered structure into a single integrated whole, eliminating interfacial stress concentration and abrupt changes in wave impedance. It also overcomes the obstruction of gas migration by the barrier unit through bidirectional symmetrical adsorption, ensuring that the coal body units on both sides reach gas adsorption equilibrium simultaneously, thus meeting the testing requirements for refined physical simulation of multi-field coupling in deep coal-rock dynamic disasters.

Description

Technical Field

[0001] This invention relates to the field of gas-bearing coal and rock sample preparation and multi-field coupling test technology, specifically to a bidirectional adsorption preparation device for gas-bearing coal and rock assemblages. Background Technology

[0002] With the increasing depth of coal mining, deep coal and rock masses face a complex multi-field coupled environment of high ground stress and high gas pressure. Coal seams often share the effects of ground stress with the roof and floor strata or interbedded gangue layers. Their failure and instability are the result of the combined effects of the coal and rock system, often evolving into a complex dynamic disaster of coal and rock instability and gas outburst. Therefore, conducting laboratory studies on the mechanical and seepage characteristics of gas-bearing coal and rock assemblages is of significant engineering and scientific importance for revealing the mechanisms of complex dynamic disasters in deep coal and rock masses. In existing studies, gas-bearing coal-rock assemblages are usually prepared by processing raw coal and roof and floor rocks into standard cylindrical samples and then splicing them together. This involves key steps such as sample processing, bonding, gas adsorption saturation, and sealing. However, existing preparation methods and devices are mainly for binary coal-rock assemblages. For multi-layered assemblages such as coal-rock-coal (simulating coal seams with interbedded gangue or multi-coal seam structures), existing schemes generally use mechanical stacking or simple end-face bonding. Moreover, the gas adsorption process is mostly unidirectional gas filling. An integrated preparation device that combines interfacial mechanical continuity, symmetrical and uniform gas adsorption, and reliable sealing has not yet been developed.

[0003] The existing technologies have the following shortcomings: First, most existing preparation methods treat coal blocks and rock blocks as physically isolated independent components, relying solely on simple mechanical stacking or end-face bonding with ordinary glue. This piecemeal structure is prone to significant mechanically weak zones and abrupt changes in wave impedance at the interface, leading to unrealistic stress concentration or premature slippage and debonding under load. This severely interferes with the cross-interface transmission of energy release signals such as acoustic emission (AE), making it impossible to analyze the macroscopic failure law of the assembly as a real, single integrated whole. Second, existing preparation methods for gas-bearing coal-rock mass experimental samples often involve placing the coal-rock assembly into a sealed chamber and then performing unidirectional or unguided mixed gas filling. Because the rock strata in the coal-rock-coal structure are dense and have extremely low permeability, they act as gas barrier zones. Traditional aeration methods cause the coal body near the intake end to reach gas adsorption saturation first, while the gas pressure inside the coal body at the far end lags significantly. This asymmetric pore pressure distribution will create unexpected effective stress gradient errors inside the sample, seriously interfering with the accuracy of subsequent triaxial compression or seepage test data. Third, in the loading and unloading test of gas-bearing coal-rock assemblages, the sample needs to withstand high confining pressure, high gas pressure, and large axial deformation at the same time. Existing surface sealing methods mostly use silicone coating combined with ordinary heat shrink tubing. When the sample enters the yielding stage and undergoes significant lateral expansion or shear fracture, this rigid or semi-rigid seal is very likely to rupture at the deformation coordination difference at the coal-rock interface, causing high-pressure gas to leak into the confining oil, forcing the fluid-structure interaction experiment to be interrupted.

[0004] In summary, existing technologies struggle to prepare gas-bearing coal-rock-coal composites with continuous interfacial mechanical behavior, symmetrical and uniform gas adsorption, and reliable sealing performance. There is an urgent need for a preparation device that can transform multi-layered coal-rock structures into a single integrated whole, eliminate interfacial stress concentration and wave impedance abrupt changes caused by artificial assembly, and achieve symmetrical and uniform gas adsorption in the coal bodies on both sides of the gas-insulating rock layer. This device would meet the testing requirements for refined physical simulation of multi-field coupling in deep coal-rock dynamic disasters. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a bidirectional adsorption preparation device for gas-bearing coal-rock assemblages.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application provides a two-way adsorption preparation device for gas-bearing coal-rock assemblages, comprising: An integrated composite specimen, wherein the integrated composite specimen is formed by curing at least two coal body units and at least one barrier unit sandwiched between the coal body units into a single mechanical whole by a binder, and the upper and lower ends of the integrated composite specimen are respectively provided with air-permeable structures for allowing fluid to pass through. A high-pressure sealed loading chamber, in which the integrated composite specimen is housed, is provided with a constraint device for providing radial alignment and axial preload to the integrated composite specimen; and A bidirectional fluid-structure interaction gas path is provided, which is connected to the permeable structures at both ends of the integrated composite sample, and is used to perform bidirectional symmetrical gas extraction and gas filling from both ends of the integrated composite sample.

[0007] Furthermore, the integrated composite sample includes an upper coal seam unit, a rock layer unit, and a lower coal seam unit arranged sequentially from top to bottom; the adjacent contact surfaces of the upper coal seam unit, the rock layer unit, and the lower coal seam unit are respectively bonded by an impedance matching binder; the impedance matching binder is prepared by mixing an epoxy resin matrix with ultrafine rock powder particles incorporated into the epoxy resin matrix.

[0008] Furthermore, non-penetrating pre-crack units are provided at the cemented interface between the upper coal seam unit and the rock layer unit, and at the cemented interface between the rock layer unit and the lower coal seam unit, respectively. The pre-crack units are used to simulate the initial damage structure of the coal and rock mass.

[0009] Furthermore, the integrated composite sample is wrapped with a composite flexible sealing layer, which includes, from the inside out, a two-component addition-curing liquid silicone rubber layer and a fluororubber high-temperature and high-pressure heat-shrinkable tube layer; the two-component addition-curing liquid silicone rubber layer is attached to the side surface of the integrated composite sample, and the fluororubber high-temperature and high-pressure heat-shrinkable tube layer is sleeved on the outside of the two-component addition-curing liquid silicone rubber layer and heat-shrinkable and fastened.

[0010] Furthermore, the upper and lower ends of the fluororubber high-temperature and high-pressure heat shrink tubing layer are respectively wrapped with metal wires and tightened around the outer periphery of the breathable structure, and the area around the metal wires is coated with the two-component addition-curing liquid silicone rubber layer for secondary sealing and reinforcement.

[0011] Furthermore, the permeable structure is a permeable base plate, the bottom of the integrated composite sample is placed on a base with a gas outlet, and the permeable base plate is provided on the upper surface of the base with the gas outlet; the high-pressure sealing loading chamber is installed outside the integrated composite sample, and the lower end of the high-pressure sealing loading chamber is fastened to the base with the gas outlet by a flange; another permeable base plate is provided above the top of the integrated composite sample, and the constraint device includes an axial loading device, which passes through the top of the high-pressure sealing loading chamber and presses against the permeable base plate located at the top.

[0012] Furthermore, the high-pressure sealed loading chamber includes a high-pressure stainless steel sealed cavity, and the constraint device further includes a centering mold, which is disposed inside the high-pressure stainless steel sealed cavity and fitted onto the outside of the integrated composite sample; the bidirectional fluid-structure interaction gas path includes a methane gas inlet path, a methane gas outlet valve, a high-pressure methane cylinder, a vacuum pump, a vacuum extraction valve, a vacuum extraction path, a flow controller, and a pressure gauge; the high-pressure sealed loading chamber is provided with a vacuum port and a methane gas outlet, the vacuum port is connected to the vacuum pump through the vacuum extraction path, and the vacuum extraction valve is provided on the vacuum extraction path; the methane gas outlet is connected to the high-pressure methane cylinder through a methane flow path, and the pressure gauge and the flow controller are sequentially provided on the methane flow path.

[0013] Furthermore, the vacuum port and the methane gas outlet are respectively located at the flange of the high-pressure sealed loading chamber, and both the vacuum port and the methane gas outlet are connected to the gas channel inside the high-pressure stainless steel sealed cavity; the gas channel extends to the two permeable bottom plates located at the upper and lower ends of the integrated composite sample, so as to realize bidirectional symmetrical gas extraction and filling from both ends of the integrated composite sample.

[0014] Furthermore, the contact surfaces of each unit in the integrated composite specimen are all precision machined surfaces; the binder has a predetermined thickness; and during curing, the constraint device applies a predetermined axial preload to the integrated composite specimen.

[0015] Furthermore, the bidirectional fluid-structure interaction gas path is used to perform vacuuming treatment on the high-pressure sealed loading chamber and the interior of the integrated composite sample for a predetermined time; and, after vacuuming treatment, to fill the interior of the integrated composite sample with gas and perform constant pressure filling treatment for a predetermined time.

[0016] Compared with the prior art, this application has the following beneficial effects: This invention proposes a bidirectional adsorption preparation device for gas-bearing coal-rock assemblies, realizing the single integration of gas-bearing coal-rock assemblies, transforming multi-layered structures into a single mechanical whole, eliminating interfacial friction slip effects and abrupt changes in wave impedance, ensuring absolute continuity of stress transmission and cross-interface attenuation-free transmission of acoustic emission signals; simultaneously, the constraint device of the high-pressure sealed loading chamber provides radial alignment and axial pre-tightening for the integrated composite sample, and with the bidirectional fluid-structure interaction gas path simultaneously performing vacuuming and gas filling from both ends of the sample, it can overcome the obstruction effect of the barrier unit on gas transport, achieving symmetrical and uniform gas adsorption in the coal body units on both sides, providing reliable initial conditions for subsequent fluid-structure interaction experiments. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the overall structure of the bidirectional adsorption preparation device for gas-bearing coal-rock composites according to the present invention.

[0018] Figure label: 1000. Integrated composite sample; 1001. Upper coal seam unit; 1002. Impedance matching cement; 1003. Pre-cracked unit; 1004. Lower coal seam unit; 2000. High-pressure sealed loading chamber; 2001. Vacuum port; 2002. Axial loading device; 2003. Methane gas outlet; 2004. High-pressure stainless steel sealing cavity; 2005. Methane flow path; 2006. Gas channel; 2007. Centering mold; 2008. Two-component addition-curing liquid silicone rubber layer; 2009. Fluororubber high-temperature and high-pressure heat shrink tubing layer; 2010. Permeable base plate; 2011. Base with gas outlet; 3000. Two-way fluid-structure interaction gas path; 3001. Methane gas inlet path; 3002. Methane gas outlet valve; 3003. High-pressure methane cylinder; 3004. Vacuum pump; 3005. Vacuum extraction valve; 3006. Vacuum extraction path; 3007. Flow controller; 3008. Pressure gauge. Detailed Implementation

[0019] 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.

[0020] Furthermore, in this invention, an element referred to as fixed to or disposed on another element may be directly disposed on the other element, or there may be an intermediate element. When an element is considered to be connected to another element, it may be directly connected to the other element, or there may be an intermediate element present simultaneously. The terms vertical, horizontal, left, right, and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] like Figure 1As shown, the present invention provides a bidirectional adsorption preparation device for gas-bearing coal-rock assemblages, comprising three main modules: an integrated composite sample 1000, a high-pressure sealed loading chamber 2000, and a bidirectional fluid-solid coupling gas path 3000. The integrated composite sample 1000 is housed within the high-pressure sealed loading chamber 2000. The interior of the integrated composite sample 1000 is provided with a stacked structure consisting of at least two coal body units and at least one barrier unit sandwiched between the coal body units. This stacked structure is solidified into a single integrated whole by a binder. The high-pressure sealed loading chamber 2000... A constraint device is provided to provide radial centering and axial pre-tightening force for the integrated composite sample 1000. The bidirectional fluid-structure coupling gas path 3000 is connected to the ventilated structures at both ends of the integrated composite sample 1000, and is used to implement bidirectional symmetrical gas extraction and gas filling from both ends of the integrated composite sample 1000. In specific implementation, the ventilated structure is connected to the bidirectional fluid-structure coupling gas path 3000 through a gas channel set inside the high-pressure sealed loading chamber 2000, thereby realizing simultaneous vacuuming and gas filling from both ends of the sample.

[0022] In one specific embodiment, the integrated composite sample 1000 includes an upper coal seam unit 1001, a rock layer unit, and a lower coal seam unit 1004 arranged sequentially from top to bottom. The upper coal seam unit 1001 and the lower coal seam unit 1004 are coal body units, and the rock layer unit is a barrier unit. The barrier unit is not limited to rock strata but can also be other low-permeability interlayer materials, such as interbedded gangue layers, to simulate different geological conditions such as coal seams containing interbedded gangue or multi-coal seam structures. The phase composition of the upper coal seam unit 1001, the rock layer unit, and the lower coal seam unit 1004... The adjacent contact surfaces are bonded together using impedance matching adhesive 1002. In the specific preparation process, raw coal and roof and floor rocks from the same coal seam in the same mine are used. All contact surfaces are ultra-finely ground using a high-precision grinding machine, with flatness error controlled within ±0.01mm and perpendicularity deviation not exceeding 0.02mm, thus laying the physical foundation for deep interface bonding. The impedance matching adhesive 1002 is formulated with E-51 type two-component modified epoxy resin as the matrix, and mixed with 8% by mass of ultrafine rock powder particles. The ultrafine rock powder particles... With a diameter less than 10 μm, the incorporation of ultrafine rock powder particles in this invention ensures that the wave impedance and elastic modulus of the cemented layer are highly matched with those of the adjacent coal and rock units. This guarantees that stress waves and acoustic emission signals do not undergo distortion when passing through the interface during subsequent mechanical and acoustic tests, achieving deep mechanical and acoustic coupling at the interface. This completely transforms the coal-rock-coal structure into a single mechanical whole, effectively eliminating the frictional slip effect and abrupt changes in wave impedance at the interface in traditional mechanical stacking methods. It ensures the absolute continuity of stress transmission, enabling the acoustic emission (AE) signal to be transmitted across the interface without attenuation. The thickness of the binder layer was controlled between 0.1-0.2 mm. During curing, the axial loading device 2002 applied an axial pre-pressure of 0.5 MPa to the integrated composite sample 1000 and cured it at a constant temperature of 25°C for 48 hours. This enabled the three independent materials to achieve deep coupling at the interface. The coal-rock composite sample with a total height of 100 mm was prepared and, in all subsequent mechanical response tests and numerical simulations, it served as an inseparable single integrated whole to jointly bear the load and deformation, which greatly improved the accuracy of the study on the deterioration mechanism of gas-bearing coal and rock.

[0023] Based on the above embodiments, non-penetrating pre-fabricated crack units 1003 are respectively provided at the cementation interface between the upper coal seam unit 1001 and the rock layer unit, and at the cementation interface between the rock layer unit and the lower coal seam unit 1004. When the cementing agent is in the initial setting stage, non-penetrating irregular pre-fabricated micro-cracks are introduced at the interface using precision engraving or laser cutting technology as pre-fabricated crack units 1003. These pre-fabricated crack units 1003 effectively simulate the initial damage evolved by deep coal and rock masses under long-term geological stress, providing a real physical space for the migration and accumulation of gas at the interface, thereby more accurately restoring the adsorption and desorption environment under the influence of mining. In addition, the pre-fabricated crack units 1003 can also serve as stress concentration sources during the later mechanical loading process, truly reflecting the crack initiation and propagation law of coal and rock assemblies with initial damage under stress conditions.

[0024] The integrated composite specimen 1000 is externally wrapped with a composite flexible sealing layer, which consists of a two-component addition-curing liquid silicone rubber layer 2008 and a fluororubber high-temperature and high-pressure heat shrink tubing layer 2009, arranged from the inside out. The two-component addition-curing liquid silicone rubber layer 2008 is an RTV-2 type two-component addition-curing liquid silicone rubber, with a mass ratio of component A (base adhesive) to component B (curing agent) of 10:1. After curing, the Shore A hardness is only 18°-22°, and the elongation can reach over 500%. It adheres to the side surface of the integrated composite specimen 1000, ensuring airtightness and acting as a buffer medium. This effectively prevents excessive radial constraint from the external structure on the specimen when axial loads are applied or when gas adsorption and expansion occur, thus ensuring the accuracy of experimental data. The fluororubber high-temperature and high-pressure heat shrink tubing layer 2009 is a DR-25 type fluororubber Viton high-temperature and high-pressure heat shrink tubing with an initial wall thickness of... With a thickness of 0.8 mm and a shrinkage ratio of 2:1, it is fitted onto the outside of the two-component addition-cured liquid silicone rubber layer 2008 and uniformly heated with a hot air gun to shrink it tightly. This material has excellent resistance to methane permeation and high temperature and pressure, providing a robust external airtight barrier for the sample. In the specific encapsulation operation, RTV-2 type liquid silicone rubber is first uniformly applied to the side surface of the integrated composite sample 1000, and then DR-25 type fluororubber heat shrink tubing is inserted and uniformly heated with a hot air gun to shrink it tightly. This composite flexible sealing layer has a clear mechanical and sealing mechanism: the low-hardness inner silicone layer ensures airtightness and buffers radial constraints, while the outer fluororubber heat shrink tubing provides a high-strength airtight barrier. The overall flexible encapsulation layer can still adhere tightly to the substrate even when the sample enters the stage of large plastic deformation, preventing the leakage of internal high-pressure gas and significantly improving the reliability of fluid-structure interaction experiments.

[0025] The upper and lower ends of the fluororubber high-temperature and high-pressure heat shrink tubing layer 2009 are respectively tightened to the outer periphery of the ventilated structure by metal wires. A two-component addition-cured liquid silicone rubber layer 2008 is applied to the area around the metal wires for secondary sealing and reinforcement, further enhancing the sealing reliability of the ends and preventing high-pressure gas leakage from the junction of the ends and the ventilated structure. The ventilated structure is specifically a permeable base plate 2010, which has a mesh of pores inside to ensure that the injected gas can uniformly cover the integrated composite sample 1000. The integrated composite specimen 1000 has its bottom placed on a base 2011 with a gas outlet, and a permeable base plate 2010 is provided on the upper end face of the base 2011 with a gas outlet; a high-pressure sealed loading chamber 2000 is placed over the integrated composite specimen 1000, and the lower end of the high-pressure sealed loading chamber 2000 is fastened to the base 2011 with a gas outlet by a flange; another permeable base plate 2010 is provided above the top of the integrated composite specimen 1000, and the constraint device includes an axial loading device 20. 02. The axial loading device 2002 passes through the top of the high-pressure sealed loading chamber 2000 and presses against the permeable bottom plate 2010 located at the top. The high-pressure sealed loading chamber 2000 includes a high-pressure stainless steel sealing cavity 2004. The constraint device also includes a centering mold 2007, which is disposed inside the high-pressure stainless steel sealing cavity 2004 and sleeved on the outside of the integrated composite specimen 1000 to provide precise radial constraint for the specimen. During specific assembly, the encapsulated integrated composite specimen 1000 is vertically... The sample is placed directly on a base 2011 with an integrated exhaust pipe and gas outlet. A permeable base plate 2010 is fastened to the top of the sample, and then a high-pressure stainless steel sealing chamber 2004 is placed on top and the flange bolts are tightened. By adjusting the threaded column of the axial loading device 2002 at the top of the sealing chamber, an initial axial clamping force is applied to the sample, thereby stabilizing the internal structure and simulating the initial vertical stress state in the deep part. This structure ensures that the sample maintains good centering and stable axial constraint during the subsequent high-pressure gas filling and loading process.

[0026] The bidirectional fluid-structure interaction gas path 3000 includes a methane gas inlet path 3001, a methane gas outlet valve 3002, a high-pressure methane cylinder 3003, a vacuum pump 3004, a vacuum extraction valve 3005, a vacuum extraction path 3006, a flow controller 3007, and a pressure gauge 3008. The high-pressure sealed loading chamber 2000 is equipped with a vacuum port 2001 and a methane gas outlet 2003. The vacuum port 2001 is connected to the vacuum pump 3004 via the vacuum extraction path 3006. Vacuum extraction valve 3005 is provided on 3006; methane gas outlet 2003 is connected to high-pressure methane cylinder 3003 through methane flow path 2005, and pressure gauge 3008 and flow controller 3007 are sequentially provided on methane flow path 2005; the specific connection method is as follows: vacuum port 2001 and methane gas outlet 2003 are respectively set at the flange of high-pressure sealed loading chamber 2000, and both vacuum port 2001 and methane gas outlet 2003 are connected to high-pressure stainless steel sealed cavity. The gas channels 2006 inside the 2004 are connected; the gas channels 2006 extend to the two permeable bottom plates 2010 located at the upper and lower ends of the integrated composite sample 1000, so as to realize bidirectional symmetrical gas extraction and filling from both ends of the integrated composite sample 1000; it should be noted that the bidirectional symmetry in this invention is not limited to two completely independent gas pipelines, but rather the vacuum port 2001 and the methane gas outlet 2003 are connected to the permeable bottom plates 2010 at the upper and lower ends of the sample through the gas channels 2006, so that when vacuuming, the gas is extracted from both ends of the sample at the same time, and when filling with gas, the gas enters from both ends of the sample at the same time. With the help of the natural barrier effect of the intermediate low-permeability barrier unit, the gas is forced to form a symmetrical adsorption path that moves from both ends to the middle at the same time, overcoming the near-end saturation and far-end lag phenomenon caused by the traditional unidirectional gas filling method, so that the upper and lower coal body units separated by the barrier unit can reach a symmetrical gas adsorption equilibrium state synchronously.

[0027] The specific working process and preparation method of the device of the present invention are as follows: First, the integrated composite sample 1000 was prepared: coal blocks and top and bottom rock blocks from the same source were selected and processed into cylinders with a standard diameter of 50 mm. This ensured that the single-layer height of the upper coal seam unit 1001, the rock layer unit, and the lower coal seam unit 1004 was 33.3 mm. The contact surfaces were ultra-fine ground, with flatness error controlled within ±0.01 mm and verticality deviation not exceeding 0.02 mm. Impedance matching binder 1002 was prepared, using E-51 type two-component modified epoxy resin as the matrix, and incorporating 8% by mass of ultrafine... Rock powder with a particle size of less than 10μm; during the initial setting stage of the binder, non-penetrating pre-crack units 1003 are introduced at the interface using precision engraving or laser cutting technology; each unit is placed in the centering mold 2007 in sequence to ensure that the axes of the three are absolutely coincident; binder is evenly applied to the contact end face, and the thickness of the binder layer is controlled to be 0.1-0.2mm; axial pre-pressure of 0.5MPa is applied, and the material is cured at a constant temperature of 25℃ for 48 hours, so that the three independent materials achieve deep mechanical and acoustic coupling at the interface, forming a single integrated whole with a total height of 100mm.

[0028] Next, sample encapsulation and sealing chamber assembly are carried out: RTV-2 type two-component addition-type liquid silicone rubber layer 2008 is evenly coated on the side surface of the integrated composite sample 1000. After initial solidification, DR-25 type fluororubber high-temperature and high-pressure heat shrink tubing layer 2009 is sleeved on the outside and heated evenly with a hot air gun to make it shrink tightly; the integrated composite sample 1000 is placed on the permeable base plate 2010 on the base 2011 with gas outlet, another permeable base plate 2010 is placed on top, the high-pressure stainless steel sealing chamber 2004 is covered and the flange bolts are tightened, and the axial loading device 2002 is adjusted to apply the initial axial clamping force.

[0029] Finally, bidirectional symmetrical extraction and gas saturation are performed: the external vacuum pump 3004 is connected to the vacuum port 2001 on the flange of the sealed chamber, the vacuum extraction valve 3005 is opened, and the vacuum is continuously pumped along the vacuum extraction path 3006 to -0.1MPa and maintained for 24 hours to completely remove free air and moisture from the interior of the chamber and the pores of the integrated composite sample 1000; after degassing, the high-pressure methane cylinder 3003 is opened, and the gas enters the methane gas outlet 2003 after being monitored by the pressure gauge 3008 and stabilized by the flow controller 3007. Then, along the methane flow path 2005, it is simultaneously injected into the sample from the permeable bottom plate 2010 at the top and bottom of the integrated composite sample 1000 in both directions; after injecting methane gas at the target pressure such as 0.5MPa, 1MPa or 1.5MPa, the system maintains the set constant pressure for at least 48 hours, finally achieving a symmetrical methane adsorption equilibrium state between the upper and lower coal body units separated by the barrier unit.

[0030] Throughout the entire process described above, the low-hardness two-component addition-type liquid silicone rubber layer 2008 can absorb and adapt to the volume changes of the integrated composite sample 1000 during gas adsorption expansion and loading, preventing the external structure from exerting excessive radial constraints on the sample; while the outer fluororubber high-temperature and high-pressure heat-shrinkable tube layer 2009 provides a high-strength airtight barrier to prevent high-pressure gas leakage; the synergistic effect of the two enables the device of the present invention to maintain a sealed integrity even when the sample enters plastic yielding, undergoes significant expansion and large lateral deformation, ensuring the smooth monitoring of the entire stress-strain process.

[0031] The beneficial effects of this invention are as follows: By using an integrated composite specimen 1000 to solidify at least two coal body units and at least one barrier unit sandwiched between the coal body units into a single mechanical whole through a binder, the interfacial friction slip effect and wave impedance abrupt change are eliminated, ensuring the absolute continuity of stress transmission and the cross-interface attenuation-free transmission of acoustic emission signals, greatly improving the accuracy of the study on the deterioration mechanism of gas-bearing coal and rock; at the same time, the constraint device of the high-pressure sealed loading chamber 2000 provides radial centering positioning and axial pre-tightening force for the integrated composite specimen 1000, and in conjunction with the bidirectional fluid-structure coupling gas path 3000, the gas flows from both sides of the specimen... The bidirectional symmetrical gas extraction and gas injection overcomes the blocking effect of the barrier unit on gas transport and avoids the near-end saturation and far-end lag phenomenon caused by unidirectional gas injection. This allows the upper and lower coal body units separated by the barrier unit to reach a symmetrical gas adsorption equilibrium state simultaneously, providing highly reliable initial conditions for subsequent fluid-structure interaction experiments. In addition, the composite flexible sealing layer can still maintain a complete seal when the sample enters the stage of large plastic deformation, effectively solving the problem of easy leakage of existing rigid or semi-rigid seals during lateral expansion and shear rupture, and ensuring the smooth monitoring of the entire stress-strain process.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0033] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A two-way adsorption preparation device for gas-bearing coal-rock assemblages, characterized in that, include: An integrated composite specimen (1000) is formed by solidifying at least two coal body units and at least one barrier unit sandwiched between the coal body units into a single mechanical whole by a binder. The integrated composite specimen (1000) is provided with air-permeable structures at its upper and lower ends, which are used to allow fluid to pass through. A high-pressure sealed loading chamber (2000) is provided, in which the integrated composite specimen (1000) is housed. The high-pressure sealed loading chamber (2000) is equipped with a constraint device for providing radial centering and axial preload to the integrated composite specimen (1000). A bidirectional fluid-structure interaction gas path (3000) is provided, which is connected to the permeable structures at the upper and lower ends of the integrated composite sample (1000) respectively, for bidirectional symmetrical gas extraction and gas filling from both ends of the integrated composite sample (1000).

2. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 1, characterized in that, The integrated composite sample (1000) includes an upper coal seam unit (1001), a rock layer unit, and a lower coal seam unit (1004) arranged sequentially from top to bottom; the adjacent contact end faces of the upper coal seam unit (1001), the rock layer unit, and the lower coal seam unit (1004) are respectively bonded by an impedance matching binder (1002); the impedance matching binder (1002) is prepared by mixing an epoxy resin matrix with ultrafine rock powder particles incorporated into the epoxy resin matrix.

3. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 2, characterized in that, Non-penetrating pre-crack units (1003) are provided at the cemented interface between the upper coal seam unit (1001) and the rock layer unit, and at the cemented interface between the rock layer unit and the lower coal seam unit (1004). The pre-crack units (1003) are used to simulate the initial damage structure of the coal and rock mass.

4. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 3, characterized in that, The integrated composite sample (1000) is wrapped with a composite flexible sealing layer, which consists of a two-component addition-curing liquid silicone rubber layer (2008) and a fluororubber high-temperature and high-pressure heat-shrinkable tube layer (2009) from the inside out. The two-component addition-curing liquid silicone rubber layer (2008) is attached to the side surface of the integrated composite sample (1000), and the fluororubber high-temperature and high-pressure heat-shrinkable tube layer (2009) is sleeved on the outside of the two-component addition-curing liquid silicone rubber layer (2008) and heat-shrinkable and fastened.

5. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 4, characterized in that, The upper and lower ends of the fluororubber high-temperature and high-pressure heat shrink tubing layer (2009) are respectively wrapped with metal wires and tightened around the outer periphery of the breathable structure. The area around the metal wires is coated with the two-component addition-curing liquid silicone rubber layer (2008) for secondary sealing and reinforcement.

6. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 5, characterized in that, The permeable structure is a permeable base plate (2010). The bottom of the integrated composite sample (1000) is placed on a base (2011) with a gas outlet. The permeable base plate (2010) is provided on the upper surface of the base (2011) with a gas outlet. The high-pressure sealing loading chamber (2000) is covered outside the integrated composite sample (1000), and the lower end of the high-pressure sealing loading chamber (2000) is fastened to the base (2011) with a gas outlet by a flange. Another permeable base plate (2010) is provided above the top of the integrated composite sample (1000). The constraint device includes an axial loading device (2002). The axial loading device (2002) passes through the top of the high-pressure sealing loading chamber (2000) and presses against the permeable base plate (2010) located at the top.

7. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 6, characterized in that, The high-pressure sealed loading chamber (2000) includes a high-pressure stainless steel sealed cavity (2004), and the constraint device further includes a centering mold (2007), which is disposed inside the high-pressure stainless steel sealed cavity (2004) and fitted outside the integrated composite sample (1000); the bidirectional fluid-structure coupling gas path (3000) includes a methane gas inlet path (3001), a methane gas outlet valve (3002), a high-pressure methane cylinder (3003), a vacuum pump (3004), a vacuum extraction valve (3005), a vacuum extraction path (3006), a flow controller (3007), and a pressure... The pressure gauge (3008) is provided; the high-pressure sealed loading chamber (2000) is provided with a vacuum port (2001) and a methane gas outlet (2003). The vacuum port (2001) is connected to the vacuum pump (3004) through the vacuum extraction path (3006). The vacuum extraction path (3006) is provided with the vacuum extraction valve (3005); the methane gas outlet (2003) is connected to the high-pressure methane cylinder (3003) through the methane flow path (2005). The methane flow path (2005) is provided with the pressure gauge (3008) and the flow controller (3007) in sequence.

8. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 7, characterized in that, The vacuum port (2001) and the methane gas outlet (2003) are respectively located at the flange of the high-pressure sealed loading chamber (2000), and both the vacuum port (2001) and the methane gas outlet (2003) are connected to the gas channel (2006) inside the high-pressure stainless steel sealed cavity (2004); the gas channel (2006) extends to the two permeable bottom plates (2010) located at the upper and lower ends of the integrated composite sample (1000) to realize bidirectional symmetrical gas extraction and filling from both ends of the integrated composite sample (1000).

9. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 8, characterized in that, The contact surfaces of each unit in the integrated composite specimen (1000) are all precision machined surfaces; the adhesive has a predetermined thickness; during curing, the constraint device applies a predetermined axial preload to the integrated composite specimen (1000).

10. The bidirectional adsorption preparation device for gas-bearing coal-rock assemblages according to claim 9, characterized in that, The bidirectional fluid-structure interaction gas path (3000) is used to perform a vacuuming process on the high-pressure sealed loading chamber (2000) and the integrated composite sample (1000) for a predetermined time; and, after the vacuuming process, to fill the integrated composite sample (1000) with gas and perform a constant pressure filling process for a predetermined time.

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