Coal measure stratum gas migration visualization test system and method based on transparent soil

Abstract

The application provides a coal measure stratum gas migration visualization test system and method based on transparent soil, and the system realizes direct visualization observation of the migration process of gas in the coal measure stratum through cooperation of a transparent model box and a layered transparent soil stratum, and overcomes the invisible technical defect; a field coal seam area with different particle sizes and a weak tectonic coal seam area are arranged in the coal seam simulation layer to simulate the non-homogeneous geological conditions of obvious tectonic development and weak coal seam distribution, and the problem that the existing device is difficult to truly express the complex tectonic coal seam is solved; through controllable switching of the closed state and the open state of the boundary component, the dynamic change of the boundary from closed to exposed in the process of uncovering the coal seam in the tunnel can be simulated, and in combination with the loading device and the optical observation processing component, the multi-factor coupling simulation of the layered coal measure stratum, the weak tectonic coal seam, the tunnel boundary and the loading condition is realized, and a more real and more comprehensive test platform is provided for studying the gas migration law and the disaster response mechanism.

Description

Technical Field

[0001] This application relates to the field of coal and rock gas migration testing technology, and in particular to a visualization test system and method for gas migration in coal-bearing strata based on transparent soil. Background Technology

[0002] In coal-bearing strata and related underground engineering, the migration process of gas in coal seams, roof and floor, and structurally weakened zones is closely related to the coal seam occurrence state, stratigraphic structure, boundary disturbance, and engineering excavation conditions. In particular, during coal seam exposure, near-coal seam tunneling, and as the tunnel working space gradually approaches the coal seam, the original closed boundary gradually transforms into an exposed boundary, and the gas pressure field and migration path within the coal seam undergo significant changes.

[0003] In practical engineering, abnormal migration and local accumulation of gas in coal-bearing strata can easily induce disasters such as gas outbursts, gas accumulation, dynamic manifestations, and coal and gas outbursts. In severe cases, these can adversely affect the safety of construction personnel, equipment operation, and tunnel stability. Especially under conditions of well-developed geological structures, significant distribution of weak coal seams, and constantly changing boundary relationships between coal seams and tunnels, the gas migration process becomes more complex, and the disaster risk is more prominent. Therefore, it is necessary to establish an experimental system that can realistically reflect the layered structure, structural differences, and boundary variation characteristics of coal-bearing strata in order to study the gas migration patterns and disaster response mechanisms.

[0004] Existing research methods on gas migration mainly include field testing, numerical simulation, and indoor model experiments. Field testing is greatly limited by engineering environment, safety conditions, and construction schedule, making it difficult to directly observe the gas migration process inside the coal seam. Although numerical simulation is convenient for analyzing different working conditions, it still has limitations in accurately representing complex coal seams, local weak surfaces, and boundary opening processes. In existing indoor experimental devices, the interior of some samples is not visible, making it difficult to identify gas migration paths, frontal positions, and the evolution of dominant channels. Some devices also focus more on the adsorption and desorption of single coal bodies or local point source gas injection studies, making it difficult to simultaneously simulate the coupling effects between layered coal-bearing strata, weak structural coal seams, tunnel boundaries, and loading conditions. Summary of the Invention

[0005] In view of this, this application provides a visualization test system for gas migration in coal-bearing strata based on transparent soil. It realizes the visualization observation of the gas migration process through transparent soil layers, constructs a heterogeneous coal seam simulation layer through particle size differences, and simulates the dynamic boundary conditions of the coal seam by switching the state of boundary components. It overcomes the technical defects of existing technologies that are not visible and difficult to simulate complex structures and dynamic boundaries.

[0006] To achieve the above objectives, this application provides the following technical solution: A visualization test system for gas migration in coal-bearing strata based on transparent soil includes: a transparent model box; a layered transparent soil stratum, set inside the transparent model box and formed by layering transparent soil material, and including at least a coal seam simulation layer for simulating coal seams, wherein the coal seam simulation layer includes a undisturbed coal seam region and a weak structural coal seam region along a first direction, the undisturbed coal seam region being formed by filling transparent soil particles with a first particle size, and the weak structural coal seam region having at least one coarse-grained band or coarse-grained surface inside, the coarse-grained band or coarse-grained surface being composed of transparent soil particles with a particle size larger than the first particle size, for simulating structural fracture surfaces or weak zones within the coal seam; and a gas injection component for injecting simulated gas into the coal seam simulation layer to simulate a gas pressure field. The tunnel simulation cavity has an inner opening facing the coal seam simulation layer. A boundary component is provided at the inner opening. The boundary component has a closed state for isolating the coal seam simulation layer from the interior of the tunnel simulation cavity, or an open state for connecting the coal seam simulation layer and the tunnel simulation cavity. The boundary assembly includes a boundary element and a sealing membrane for separating the boundary element from the coal seam simulation layer; The boundary element is configured as one of a rigid grid plate, a flexible mesh, and an open frame, wherein: When the boundary element is the rigid grid plate, the size of the gaps or through holes opened on the rigid grid plate is smaller than the particle size of the transparent soil material, so as to prevent the transparent soil material particles from passing through and allow gas migration. When the boundary element is the flexible mesh, the flexible mesh is used to constrain the spillage of the simulated coal seam layer and allow simulated gas to pass through; When the boundary element is the open frame, the open frame allows the coal seam simulation layer to pour down, in order to simulate the rapid leakage of coal inrush conditions; A loading device is disposed on the top of the transparent model box and is used to apply a vertical load to the layered transparent soil layer; An optical observation and processing component is used to visualize and record the simulated gas migration process inside the coal seam simulation layer through the transparent model box and the layered transparent soil layer.

[0007] Optionally, in the above-mentioned visual experimental system for gas migration in coal-bearing strata based on transparent soil, the sealing membrane is fixed to the simulated tunnel cavity by fasteners or adhesive bonding; or, The sealing membrane is adhered to the boundary element to form a closed boundary between the coal seam simulation layer and the tunnel simulation cavity.

[0008] Optionally, in the above-mentioned transparent soil-based coal-bearing strata gas migration visualization test system, a partition plate is detachably installed inside the transparent model box. The partition plate is used to divide the transparent model box into the original coal seam area and the weak structural coal seam area along a first direction during the transparent soil filling stage.

[0009] Optionally, in the above-mentioned visualization test system for gas migration in coal-bearing strata based on transparent soil, the gas injection component includes: The main intake pipe is used to introduce simulated gas and allow it to enter the simulated coal seam layer; The branch air pipe is provided with multiple branches and is connected to the main air inlet pipe, and each branch air pipe has multiple air holes in its circumferential direction.

[0010] Optionally, in the above-mentioned visual test system for gas migration in coal-bearing strata based on transparent soil, a sealing structure is provided at the connection between the main air intake pipe and the transparent model box to ensure a sealed connection between the main air intake pipe and the transparent model box.

[0011] Optionally, in the above-mentioned visualization test system for gas migration in coal-bearing strata based on transparent soil, the optical observation and processing component includes: A laser sheet irradiation device is used to irradiate a sheet-like beam of light onto the transparent model box to form an optical slice; Image acquisition device, used to acquire images of simulated gas migration inside the transparent model box; Information processors are used to display, store, and process optical slices and images.

[0012] Optionally, in the above-mentioned visualization test system for gas migration in coal-bearing strata based on transparent soil, the transparent model box includes: A rigid frame is composed of multiple rigid components; A transparent panel is disposed between adjacent rigid members and encloses the rigid frame to form the transparent model box.

[0013] Optionally, the above-mentioned visualization test system for gas migration in coal-bearing strata based on transparent soil further includes a support for supporting the transparent model box, the support comprising: Support plate; The limiting member provided on the support plate is used to limit the position of the transparent model box; Support feet are installed at the bottom of the support plate.

[0014] A method for visualizing gas migration in coal-bearing strata based on transparent soil, applicable to the aforementioned visualizing gas migration test system for coal-bearing strata based on transparent soil, the method comprising: S1: Insert a partition plate into the transparent model box, and fill the transparent model box with transparent soil material in layers. The component includes at least the layered transparent soil layer of the coal seam simulation layer. The partition plate divides the coal seam simulation layer into the original coal seam area and the weak structural coal seam area along the first direction. The original coal seam area is formed by filling transparent soil particles with a first particle size. The weak structural coal seam area has at least one coarse particle band or coarse particle surface inside. The coarse particle band or coarse particle surface is composed of transparent soil particles with a particle size larger than the first particle size. S2: Pull out the partition plate to form a continuous coal seam interface between the original coal seam area and the weak structural coal seam area; S3: Run the optical observation processing component; S4: Activate the loading device to apply a vertical load from the top of the transparent model box; S5: Inject simulated gas into the gas injection component, and adjust the gas injection pressure and flow rate to make the internal pressure of the simulated coal seam reach the set value and maintain it basically constant. S6: Select the composition and state of the boundary components based on the simulation purpose; S7: Compare the response characteristics of simulated gas migration into the simulated tunnel cavity under different boundary component conditions.

[0015] This application provides a visualization test system for gas migration in coal-bearing strata based on transparent soil. By combining a transparent model box with layered transparent soil strata, it enables direct visualization of the gas migration process in coal-bearing strata, and can identify the gas migration path, frontal position and dominant channel evolution, overcoming the technical defects of existing devices that are not visible.

[0016] Meanwhile, by setting up undisturbed coal seam regions with different particle sizes and weak structural coal seam regions in the coal seam simulation layer, this application can simulate heterogeneous geological conditions with well-developed structures and obvious distribution of weak coal seams, thus solving the problem that existing devices cannot realistically represent complex structural coal seams.

[0017] Furthermore, this application, through the controllable switching between the closed and open states of the tunnel simulation cavity boundary components, can simulate the dynamic transformation of the boundary from closed to exposed during the exposure of coal seams in the tunnel. Combined with the vertical load of the loading device and the optical observation and processing components, it realizes the simulation of the multi-factor coupling effect of layered coal-bearing strata, weak structural coal seams, tunnel boundaries and loading conditions, providing a more realistic and comprehensive experimental platform for studying the gas migration law and its disaster response mechanism. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 A schematic diagram of the structure of the model box provided in this application; Figure 2 A schematic diagram of the structure of a visualization test system provided in this application; Figure 3 A first-view structural schematic diagram of the gas injection assembly provided in this application; Figure 4 A second-view structural schematic diagram of the gas injection assembly provided in this application; Figure 5 A structural schematic diagram of the support component provided in this application; Figure 6 This is a schematic diagram of the structure of the tunnel simulation cavity provided in this application.

[0020] icon: 1. Transparent model box; 2. Coal seam simulation layer; 3. Gas injection assembly; 4. Tunnel simulation cavity; 5. Loading device; 6. Optical observation and processing assembly; 7. Separator; 8. Support components; 11. Rigid frame; 12. Transparent panel; 21. Undeveloped coal seam area; 22. Coal seam area with weak structure; 31. Main intake pipe; 32. Branch intake pipe; 33. Sealing structure; 41. Boundary components; 42. Sealing membrane; 43. Short cylindrical cavity; 61. Laser sheet illumination device; 62. Image acquisition device; 63. Information processor; 81. Support plate; 82. Limiting component; 83. Support foot. Detailed Implementation

[0021] This application provides a visualization test system for gas migration in coal-bearing strata based on transparent soil. It enables the visualization observation of the gas migration process through transparent soil layers, constructs a heterogeneous coal seam simulation layer through particle size differences, and simulates the dynamic boundary conditions of the coal seam by switching the state of boundary components. This overcomes the technical defects of existing technologies, such as the inability to visualize and simulate complex structures and dynamic boundaries.

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] like Figures 1-6 As shown, this application provides a visualization test system for gas migration in coal-bearing strata based on transparent soil, including a transparent model box 1, a layered transparent soil stratum, a gas injection component 3, a tunnel simulation cavity 4, a loading device 5, and an optical observation and processing component 6.

[0024] In one example, the transparent model box 1 is a cuboid structure. Layered transparent soil strata are set inside the transparent model box 1, comprising multiple layers stacked vertically. Gas injection assembly 3 is located within the coal seam simulation layer 2 of the layered transparent soil strata; more specifically, gas injection assembly 3 is located in the undisturbed coal seam area 21 of the coal seam simulation layer 2. A tunnel simulation cavity 4 is located in the weak structural coal seam area 22 of the coal seam simulation layer 2. A loading device 5 is located at the top of the transparent model box 1, applying a vertical load to the layered transparent soil strata from the top. An optical observation and processing assembly 6 is located on the periphery of the side wall of the transparent model box 1, used to visualize and record the simulated gas migration process inside the coal seam simulation layer 2 through the transparent model box 1 and the layered transparent soil strata.

[0025] It should be noted that the loading device 5 is implemented using existing conventional loading equipment, such as hydraulic loading device 5, mechanical loading device 5, or other equipment capable of providing stable vertical loads.

[0026] It should also be noted that the simulated gas is used to replace methane, preferably one of nitrogen, carbon dioxide, compressed air, or helium. To improve the visualization of the methane migration process in the transparent soil model, smoke tracer media, fine aerosol particles, fluorescent tracer particles, or other scattering tracer media that can be identified by laser sheet illumination are mixed into the simulated gas. The simulated gas contains smoke, aerosols, or fluorescent tracer particles, which scatter light in the light sheet, allowing the gas flow pattern, boundaries, and velocity to be captured and visualized.

[0027] Fine aerosol particles, such as visible colored aerosols or fluorescent aerosols, preferably colored smoke aerosols such as red, yellow, and blue, or fluorescent aerosols that have a color-developing effect under laser sheet irradiation, are carried into the coal seam simulation layer 2 by nitrogen gas to improve the visualization of the gas migration process.

[0028] The layered transparent soil layer is located inside the transparent model box 1 and is formed by filling transparent soil material in layers. The layered transparent soil layer includes, from bottom to top, the underlying rock stratum simulation layer, the bottom plate simulation layer, the coal seam simulation layer 2, the roof plate simulation layer, and the overlying rock stratum simulation layer. The coal seam simulation layer 2 includes the original coal seam area 21 and the weak structural coal seam area 22 along the length direction (first direction) of the transparent model box 1. The original coal seam area 21 is formed by filling transparent soil particles with a first particle size. The weak structural coal seam area 22 has at least one coarse particle band or coarse particle surface inside. The coarse particle band or coarse particle surface is composed of transparent soil particles with a particle size greater than the first particle size, so as to simulate the structural fracture surface or weak band in the coal seam.

[0029] The inner opening of the tunnel simulation cavity 4 faces the coal seam simulation layer 2. A boundary component is provided at the inner opening. The boundary component has a closed state for isolating the coal seam simulation layer 2 from the interior of the tunnel simulation cavity 4, or an open state for connecting the coal seam simulation layer 2 and the tunnel simulation cavity 4, so as to simulate the dynamic transformation process of the boundary conditions between the tunnel and the coal seam from closed to partially exposed, completely exposed or suddenly exposed.

[0030] In summary, firstly, the use of transparent soil layers filled from bottom to top fully reproduces the actual occurrence state of the underlying rock strata, floor, coal seam, roof, and overlying rock strata; the coal seam is divided into the original coal seam zone 21 and the weak structural coal seam zone 22, and coarse-grained zones / faces are set in the weak zone to accurately simulate geological structures such as coal seam fractures and weak zones, making the gas migration test more consistent with the complex geological conditions on site; secondly, the boundary components of the tunnel simulation cavity 4 can flexibly switch between closed and open states, simulating the entire process of the tunnel and coal seam boundary transformation from closed to partially exposed, fully exposed, and suddenly exposed, realistically reproducing gas under boundary disturbances during coal uncovering, tunneling, and other engineering projects. The system exhibits several advantages: First, it can detect and record dynamic conditions that are difficult to achieve with conventional experiments. Second, in conjunction with the optical observation and processing component 6, it can conduct high-definition observation and recording of the migration path, diffusion front, and dominant channel evolution of simulated gas within the coal seam through the transparent model box 1 and the layered transparent soil strata, solving the technical problem that traditional experiments cannot directly capture the internal gas migration patterns. Third, the loading device 5 can stably apply vertical loads to simulate ground stress, and the gas injection component 3 controls the gas pressure field within the coal seam. The experimental parameters are adjustable and the process is repeatable, enabling both conventional gas migration pattern research and analysis of disaster response characteristics under boundary disturbances. The experimental conclusions are highly reliable and have strong engineering guidance value.

[0031] It should be noted that different forms of boundary components are selected based on different experimental purposes. The boundary components include boundary element 41 and sealing membrane 42 for separating boundary element 41 and coal seam simulation layer 2. Boundary element 41 is configured as one of rigid grid plate, flexible mesh and open frame. In the initial stage of the experiment, coal seam simulation layer 2 and tunnel simulation cavity 4 are isolated by sealing membrane 42. When simulation is required, the sealing membrane 42 is cut, punctured, torn, pulled out or partially opened to change the coal seam boundary from closed state to exposed state. Boundary element 41 remains in place and plays a certain role in restricting the leading edge of coal seam.

[0032] When the boundary element 41 is a rigid grid plate, the size of the gaps or through holes opened on the rigid grid plate is smaller than the particle size of the transparent soil material, so as to prevent the transparent soil material particles from passing through as a whole and allow gas migration. It is suitable for conducting gas slow migration condition tests.

[0033] Alternatively, when the boundary element 41 is a flexible mesh, the flexible mesh is tensioned and fixed at the inner end opening of the short cylindrical cavity 43 of the tunnel simulation cavity 4 to constrain the spillage of the coal seam simulation layer 2 while allowing simulated gas to pass through. That is, after the sealing membrane 42 is removed, the flexible mesh can constrain the large-scale spillage of the coal seam simulation layer 2 into the tunnel simulation cavity 4, while allowing gas to pass through the tunnel simulation cavity 4 and allowing limited deformation of the local boundary, which is suitable for conducting gas outburst coal disaster initiation condition tests.

[0034] Alternatively, when the boundary element 41 is an open frame, the open frame allows the coal seam simulation layer 2 to pour out, simulating a rapid coal outburst. In this case, the inner end of the short cylindrical cavity 43 of the tunnel simulation cavity 4 forms an unobstructed exposed boundary. After the sealing membrane 42 is opened, there is no longer a significant barrier between the coal seam and the tunnel simulation cavity 4, thus it can be used to simulate a rapid coal outburst.

[0035] In summary, the boundary component 41 can be flexibly selected from three forms: rigid grating, flexible mesh, and open frame. Combined with the sealing membrane 42, it can achieve various boundary states such as closed, partially open, fully open, and sudden opening, satisfying all engineering conditions including slow gas migration, coal and gas outburst initiation, and rapid leakage, significantly improving the versatility and efficiency of the test. Furthermore, by changing the boundary component 41 and adjusting the opening method of the sealing membrane 42, various disaster simulations, such as conventional gas migration and coal and gas outbursts, can be completed, simplifying the device structure and reducing test costs.

[0036] The sealing membrane 42 is fixed to the tunnel simulation cavity 4 by a fastener or by adhesive; or, the sealing membrane 42 is adhesively bonded to the boundary member 41 to form a closed boundary between the coal seam simulation layer 2 and the tunnel simulation cavity 4. The fastener may be, but is not limited to, one or more of a clamping ring, a pressing ring, and a pressure plate.

[0037] The sealing membrane 42 can be fixed by one or more combinations of methods such as bonding, clamping ring, pressing ring, and pressure plate. The fixing method is flexible and adaptable to different test scenarios, and can firmly form a complete closed boundary between the coal seam simulation layer 2 and the tunnel simulation cavity 4, effectively avoiding gas leakage in the initial stage of the test and ensuring stable gas injection pressure.

[0038] The sealing membrane 42 and the fastener can be disassembled and resealed multiple times. The same set of tunnel simulation cavity 4 can be used to conduct multiple sets of boundary opening tests repeatedly without replacing the entire component, reducing test consumables and costs, and improving the utilization rate of the device.

[0039] In a preferred embodiment, a partition plate 7 is detachably provided inside the transparent model box 1. The partition plate 7 is used to divide the transparent model box 1 into an original coal seam area 21 and a weak structural coal seam area 22 along a first direction during the transparent soil filling stage.

[0040] Specifically, the transparent model box 1 includes a transparent plate 12 arranged opposite to each other, and a slot is provided on the transparent plate 12 arranged opposite to each other. The slot can be U-shaped, L-shaped, etc. In this way, the partition plate 7 is inserted into or removed from the transparent model box 1 along the slot. It can be understood that the slot can not only limit the partition plate 7, but also guide the partition plate 7.

[0041] By using the detachable partition plate 7 in conjunction with the guide slot, the transparent model box 1 can be divided into the original coal seam area 21 and the weak structural coal seam area 22 during the filling stage. The materials in the two areas are filled independently and do not interfere with each other, which significantly improves the accuracy of model preparation. In addition, after the coal seam is formed, the partition plate 7 can be pulled out along the slot, so that the original coal seam area 21 and the weak structural coal seam area 22 form a continuous and realistic coal seam interface without any separation, avoiding permanent partitions from interfering with the gas migration path and maximizing the restoration of the continuous occurrence state of the coal seam on site.

[0042] In a preferred embodiment, the gas injection assembly 3 includes: a main intake pipe 31 for introducing simulated gas and allowing it to enter the simulated coal seam layer 2; and multiple branch pipes 32 connected to the main intake pipe 31, with each branch pipe 32 having multiple vents in its circumferential direction. Specifically, each branch pipe 32 has vents in both its length and circumferential directions, thus preventing the gas from concentrating at a single point and instead creating a more uniform, stable, and adjustable gas pressure field within the coal seam. This makes it more suitable for studying gas migration paths, frontal advances, and local accumulation behaviors.

[0043] It should be noted that the pressure of the simulated gas entering the main intake pipe 31 can be adjusted by regulating the pressure or flow rate of the equipment that inputs the simulated gas to achieve the pressure of the simulated coal seam 2.

[0044] The connection between the main air intake pipe and the transparent model box 1 is equipped with a sealing structure to ensure a sealed connection between the main air intake pipe 31 and the transparent model box 1.

[0045] The sealing structure can use existing commercially available through-plate seals, such as compression through-plate joints, threaded locking through-plate joints, flange compression through-plate joints, through-plate joint assemblies or combinations thereof, as long as they can meet the sealing requirements of the through-plate position on the side wall of the transparent model box 1.

[0046] By setting up a sealing structure, a stable and reliable airtight connection can be achieved between the main air inlet pipe 31 and the transparent model box 1, meeting the sealing requirements under different air injection pressures, effectively preventing air leakage and pressure loss during the test, improving the stability of the internal pressure field of the coal seam, and improving the accuracy of the test data.

[0047] In a preferred embodiment, the optical observation and processing component 6 includes: a laser sheet illumination device 61 for illuminating a sheet-like beam of light onto the transparent model box 1 to form an optical slice; an image acquisition device 62 for acquiring images of simulated gas migration within the transparent model box 1; and an information processor 63 for displaying, storing, and processing the optical slice and images. The image acquisition device 62 is a CCD image acquisition device.

[0048] The laser sheet irradiation device 61 irradiates a sheet-like beam into the interior of the transparent model box 1 along a first direction (the length direction of the transparent model box 1) to form an optical slice. The laser sheet irradiation forms a two-dimensional optical slice along the length direction of the model box, which can highlight the position and movement of simulated gas in the transparent soil layer, such as flow velocity. The image acquisition device 62 acquires images of the optical slice along a second direction (the width direction of the transparent model box 1). The information processor 63 is connected to the image acquisition device 62 and is used to display, store and analyze these images, thereby quantitatively observing gas migration, including flow velocity, direction and channel evolution.

[0049] This application uses a laser sheet illumination device 61 to illuminate a sheet-like beam of light into the interior of the transparent model box 1 along a first direction (the length direction of the transparent model box 1) to form an optical slice, which can create a high-brightness two-dimensional observation plane inside the layered transparent soil layer. When the simulated gas migrates in the transparent soil layer, the refractive index difference between the tracer medium in the simulated gas or between the gas and the transparent soil particles will scatter the sheet light, allowing the morphology, boundary, and velocity of the gas migration to be clearly captured. Combined with image acquisition device 62 acquiring images along a second direction (the width direction of the transparent model box 1, i.e., the direction perpendicular to the optical slice plane), an image of the gas distribution on the entire optical slice plane can be obtained. Compared with the existing technology that uses discrete sensor point measurement or indirect boundary inference, this application realizes full-section, spatially continuous, and quantitative observation of the gas migration process.

[0050] This application, through the laser sheet irradiation device 61 and the image acquisition device 62, can intuitively observe the propagation of the gas wavefront, the formation of the dominant channel, and the gas flow around low-permeability areas, providing a brand-new technical means for studying the non-uniform migration law of gas in coal-bearing strata.

[0051] In a preferred embodiment, the transparent model box 1 includes: a rigid frame 11 composed of multiple rigid members; and a transparent plate 12 disposed between adjacent rigid members and enclosing the transparent model box 1 with the rigid frame 11. The transparent model box 1 has a cuboid structure, the rigid frame 11 can be regarded as the edge of the cuboid structure, and the transparent plate 12 is the face of the cuboid structure.

[0052] A support plate is installed at the bottom of the transparent model box 1, forming the base plate of the transparent model box 1, and is used to support the transparent soil material, embedded components and other parts inside the box. A clamping plate is installed at the top of the transparent model box 1, forming the top plate of the transparent model box 1, and is used to limit and seal the upper part of the transparent soil material after filling, and at the same time serves as the force interface when the loading device 5 transmits the load downwards. The front, rear, left and right transparent plates 12 form the side walls of the transparent model box 1.

[0053] The rigid frame 11 not only fixes the transparent plate 12, but also provides overall constraint for the transparent model box 1, thereby reducing the outward bulging deformation of the transparent plate 12 during the filling of transparent soil, air injection and pressurization and top loading, thus improving the overall rigidity of the model box and the stability of the test.

[0054] The system also includes a support component 8 for supporting the transparent model box 1. The support component 8 includes: a support plate 81; limiting components 82 disposed on the support plate 81 to limit the movement of the transparent model box 1; and support feet disposed at the bottom of the support plate 81. The limiting components 82 are L-shaped limiting blocks, four in number, used to laterally limit the movement of the transparent model box 1 around its bottom perimeter, preventing in-plane displacement of the model box during loading, installation, or testing. The support feet 83 are disposed below the support plate, eight in number, used to support the entire system and can be leveled as needed.

[0055] In addition, this application provides a method for visualizing gas migration in coal-bearing strata based on transparent soil. This method is applicable to the aforementioned visualizing gas migration test system for coal-bearing strata based on transparent soil. The method includes: S1: Insert a partition plate 7 into the transparent model box 1, and fill the transparent model box 1 with transparent soil material in layers. The component includes at least a layered transparent soil layer of the coal seam simulation layer 2. The partition plate 7 divides the coal seam simulation layer 2 into an original coal seam area 21 and a weak structure coal seam area 22 along a first direction. The original coal seam area 21 is formed by filling transparent soil particles with a first particle size. The weak structure coal seam area 22 has at least one coarse particle band or coarse particle surface inside. The coarse particle band or coarse particle surface is composed of transparent soil particles with a particle size greater than the first particle size.

[0056] It should be noted that the air injection component 3, the tunnel simulation cavity 4 and the partition plate 7 are pre-installed inside the transparent model box 1. The tunnel simulation cavity 4 has a boundary component set at its inner end during installation.

[0057] S2: Pull out the partition plate 7 to form a continuous coal seam interface between the original coal seam zone 21 and the weak structural coal seam zone 22; S3: Run the optical observation and processing component 6; S4: Start the loading device 5 to apply a vertical load from the top of the transparent model box 1; S5: Inject simulated gas into the gas injection component 3, and adjust the gas injection pressure and flow rate to make the internal pressure of the simulated coal seam layer 2 reach the set value and maintain it basically constant; S6: Select the composition and state of the boundary components based on the simulation purpose; S7: Compare the response characteristics of the simulated gas migrating into the tunnel simulation cavity 4 under different boundary component conditions.

[0058] Depending on the experimental purpose, different forms of boundary components are selected. The boundary components include a boundary element 41 and a sealing membrane 42 for separating the boundary element 41 and the coal seam simulation layer 2. The boundary element 41 is configured as one of a rigid grid plate, a flexible mesh, and an open frame. In the initial stage of the experiment, the coal seam simulation layer 2 and the tunnel simulation cavity 4 are isolated by the sealing membrane 42. When simulation is required, the sealing membrane 42 is cut, punctured, torn, pulled out, or partially opened to change the coal seam boundary from a closed state to a revealed or exposed state. The boundary element 41 remains in place and plays a certain role in restricting the leading edge of the coal seam.

[0059] When the boundary element 41 is a rigid grid plate, the size of the gaps or through holes opened on the rigid grid plate is smaller than the particle size of the transparent soil material, so as to prevent the transparent soil material particles from passing through as a whole and allow gas migration. This is suitable for conducting gas slow migration test. Under the gas slow migration condition, the boundary element 41 adopts a rigid grid plate, and the sealing membrane 42 forms a restricted ventilation boundary by partially opening or cutting. At this time, the transparent soil material will not enter the short cylindrical cavity 43 as a whole, and the gas mainly migrates slowly along the interior of the coal seam and the weak structural surface and dissipates towards the tunnel simulation cavity 4. This condition is mainly used to study the migration path, front advancement and dominant channel evolution of gas in the undisturbed coal seam area 21 and the weak structural coal seam area 22.

[0060] Alternatively, when the boundary element 41 is a flexible mesh, the flexible mesh is tensioned and fixed at the inner end opening of the short cylindrical cavity 43 of the tunnel simulation cavity 4 to constrain the spillage of the coal seam simulation layer 2 while allowing simulated gas to pass through. That is, after the sealing membrane 42 is removed, the flexible mesh can constrain the large-scale spillage of the coal seam simulation layer 2 into the tunnel simulation cavity 4, while allowing gas to pass through the tunnel simulation cavity 4 and allowing limited deformation of the local boundary, which is suitable for studying the confined exposure response characteristics of the coal seam boundary in the initial stage of a gas outburst coal disaster.

[0061] Alternatively, when the boundary element 41 is an open frame, the open frame allows the coal seam simulation layer 2 to pour out, simulating a rapid coal outburst. In this case, the inner end of the short cylindrical cavity 43 of the tunnel simulation cavity 4 forms an unobstructed exposed boundary. After the sealing membrane 42 is opened, there is no longer a significant barrier between the coal seam and the tunnel simulation cavity 4, thus it can be used to simulate a rapid coal outburst.

[0062] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0063] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0064] It should also be noted that in the apparatus, equipment, and housing of this application, the components or steps can be disassembled and / or reassembled. These disassemblies and / or reassemblies should be considered as equivalent solutions of this application.

[0065] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0066] It should be understood that the qualifiers “first,” “second,” “third,” “fourth,” “fifth,” and “sixth” used in the description of the embodiments of this application are only used to more clearly illustrate the technical solutions and are not intended to limit the scope of protection of this application.

[0067] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A visualization test system for gas migration in coal-bearing strata based on transparent soil, characterized in that, include: Transparent model box; A layered transparent soil stratum is set inside the transparent model box and is formed by layering transparent soil material. It includes at least a coal seam simulation layer for simulating coal seams. The coal seam simulation layer includes an original coal seam area and a weak structural coal seam area along a first direction. The original coal seam area is formed by filling transparent soil particles with a first particle size. The weak structural coal seam area has at least one coarse particle band or coarse particle surface inside. The coarse particle band or coarse particle surface is composed of transparent soil particles with a particle size larger than the first particle size, so as to simulate the structural fracture surface or weak band in the coal seam. The gas injection component is used to inject simulated gas into the simulated coal seam layer to simulate the gas pressure field. The tunnel simulation cavity has an inner opening facing the coal seam simulation layer. A boundary component is provided at the inner opening. The boundary component has a closed state for isolating the coal seam simulation layer from the interior of the tunnel simulation cavity, or an open state for connecting the coal seam simulation layer and the tunnel simulation cavity. The boundary assembly includes a boundary element and a sealing membrane for separating the boundary element from the coal seam simulation layer; The boundary element is configured as one of a rigid grid plate, a flexible mesh, and an open frame, wherein: When the boundary element is the rigid grid plate, the size of the gaps or through holes opened on the rigid grid plate is smaller than the particle size of the transparent soil material, so as to prevent the transparent soil material particles from passing through and allow gas migration. When the boundary element is the flexible mesh, the flexible mesh is used to constrain the spillage of the simulated coal seam layer and allow simulated gas to pass through; When the boundary element is the open frame, the open frame allows the coal seam simulation layer to pour down, in order to simulate the rapid leakage of coal inrush conditions; A loading device is disposed on the top of the transparent model box and is used to apply a vertical load to the layered transparent soil layer; An optical observation and processing component is used to visualize and record the simulated gas migration process inside the coal seam simulation layer through the transparent model box and the layered transparent soil layer.

2. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, The sealing membrane is fixed to the simulated tunnel cavity by fasteners or adhesive bonding; or... The sealing membrane is adhered to the boundary element to form a closed boundary between the coal seam simulation layer and the tunnel simulation cavity.

3. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, The transparent model box is detachably equipped with a partition plate, which is used to divide the transparent model box into the original coal seam area and the weak structural coal seam area along a first direction during the transparent soil filling stage.

4. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, The gas injection assembly includes: The main intake pipe is used to introduce simulated gas and allow it to enter the simulated coal seam layer; The branch air pipe is provided with multiple branches and is connected to the main air inlet pipe, and each branch air pipe has multiple air holes in its circumferential direction.

5. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 4, characterized in that, A sealing structure is provided at the connection between the main air intake pipe and the transparent model box for sealing the connection between the main air intake pipe and the transparent model box.

6. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, The optical observation processing component includes: A laser sheet irradiation device is used to irradiate a sheet-like beam of light onto the transparent model box to form an optical slice; Image acquisition device, used to acquire images of simulated gas migration inside the transparent model box; Information processors are used to display, store, and process optical slices and images.

7. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, The transparent model box includes: A rigid frame is composed of multiple rigid components; A transparent panel is disposed between adjacent rigid members and encloses the rigid frame to form the transparent model box.

8. The visualization test system for gas migration in coal-bearing strata based on transparent soil according to claim 1, characterized in that, It also includes a support member for supporting the transparent model box, the support member comprising: Support plate; The limiting member provided on the support plate is used to limit the position of the transparent model box; Support feet are installed at the bottom of the support plate.

9. A visual experimental method for gas migration in coal-bearing strata based on transparent soil, characterized in that, The method applicable to the visual experimental system for gas migration in coal-bearing strata based on transparent soil as described in any one of claims 1-8, comprises: S1: Insert a partition plate into the transparent model box, and fill the transparent model box with transparent soil material in layers. The component includes at least the layered transparent soil layer of the coal seam simulation layer. The partition plate divides the coal seam simulation layer into the original coal seam area and the weak structural coal seam area along the first direction. The original coal seam area is formed by filling transparent soil particles with a first particle size. The weak structural coal seam area has at least one coarse particle band or coarse particle surface inside. The coarse particle band or coarse particle surface is composed of transparent soil particles with a particle size larger than the first particle size. S2: Pull out the partition plate to form a continuous coal seam interface between the original coal seam area and the weak structural coal seam area; S3: Run the optical observation processing component; S4: Activate the loading device to apply a vertical load from the top of the transparent model box; S5: Inject simulated gas into the gas injection component, and adjust the gas injection pressure and flow rate to make the internal pressure of the simulated coal seam reach the set value and maintain it basically constant. S6: Select the composition and state of the boundary components based on the simulation purpose; S7: Compare the response characteristics of simulated gas migration into the simulated tunnel cavity under different boundary component conditions.

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