Multi-shear end surface damage seepage dynamic test system

Abstract

A multi-shear end surface damage seepage dynamic test system, comprising a clamping chamber (4), the clamping chamber (4) being used for containing a coal sample (16); shear end surface assemblies (12) are located at both ends of a rubber sleeve (5), the rubber sleeve (5) being located inside the clamping chamber (4); the left end of the clamping chamber (4) is connected to a left pressing cap (3), the left pressing cap (3) being connected to a fixed piston (10), and the fixed piston (10) being provided with a gas inlet hole (2) and an axial pressure liquid injection hole (1); the right end of the clamping chamber (4) is connected to a right pressing cap (7), the right pressing cap (7) being connected to a combined piston (8), and the combined piston (8) being provided with a gas outlet hole (9); and the surface of the clamping chamber (4) is provided with a confining pressure injection hole (6). The test system injects gas into the clamping chamber (4), applies shear stress and presses the chamber respectively by means of the gas inlet hole (2), the axial pressure liquid injection hole (1) and the confining pressure injection hole (6), and, by means of the gas outlet hole (9) arranged at the right end of the clamping chamber (4), monitors the gas flow, thus achieving coal and rock mass stress-fracture-seepage testing at different shear end surfaces and different shear degrees; and the present invention has the advantages of convenient disassembly, practicability and effectiveness.

Description

A dynamic test system for multi-shear end-face damage seepage Technical Field

[0001] The invention discloses a multi-shear end-face damage seepage dynamic testing system, belonging to the technical field of seepage mechanics experimental devices. Background Art

[0002] Coal dominates my country's primary energy consumption structure. Gas occurrence in coal seams is complex, with high-gas coal seams accounting for approximately 50%-70%. As coal mining depths increase and geological conditions become increasingly complex, the threat of coal mine gas disasters cannot be underestimated. In recent years, gas accidents have consistently accounted for a high proportion of coal mine accidents in my country, causing significant casualties and property losses, while also significantly limiting mine production capacity. Therefore, preventing gas accidents is a pressing challenge in coal mine safety production. Gas is also a greenhouse gas that can damage the ozone layer and impact the human living environment. Therefore, gas extraction is of great significance to both economic development and environmental protection.

[0003] The gas extraction effect is significantly affected by permeability. Permeability is an important parameter that characterizes the ability of gas to flow in coal, and is mainly determined by the opening, number, and continuity of coal fissures and matrix properties. Coal mining involves drilling, tunnel excavation, and protective layer mining, which will cause damage to the coal body. The damaged coal body will expand and its permeability will increase sharply, and the increase can be hundreds or thousands of times. Therefore, compared with the opening, number, and matrix properties of coal fissures, the impact of coal damage on permeability is the most significant. In the existing technology, there are few detection devices for the permeability of coal in a damaged state, and the test results are not accurate enough.

[0004] Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention discloses a multi-shear end-face damage seepage dynamic testing system, which can accurately reflect the permeability of the coal body under the damaged state.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A multi-shear end face damage seepage dynamic testing system, the system includes a shear end face assembly, the shear end face assembly is located at both ends of a rubber sleeve, the rubber sleeve is located inside a clamping cavity, the left end of the clamping cavity is connected to a left pressure cap, the left pressure cap is connected to a fixed piston, the fixed piston is provided with a gas inlet hole and an axial pressure liquid inlet hole; the right end of the clamping cavity is connected to a right pressure cap, the right pressure cap is connected to a combined piston, the combined piston is provided with a gas outlet hole; the surface of the clamping cavity is provided with a confining pressure injection hole.

[0008] Furthermore, the rubber sleeve wraps the coal sample.

[0009] Furthermore, the shear end face assembly is provided with a gas inlet hole and a disassembly hole.

[0010] Furthermore, a shear end face assembly with a fixed plug and a combined plug is installed on the left and right ends of the rubber sleeve respectively.

[0011] Furthermore, the shear end face assembly comprises a combination of one or more of a steel block and a soft plastic block.

[0012] Furthermore, the clamping cavity is equipped with a separate heating jacket.

[0013] Furthermore, the gas inlet hole is connected to the gas cylinder through a pipeline provided with a gas inlet valve.

[0014] Furthermore, the axial injection hole and the confining pressure injection hole are connected to the axial pressure servo loading device and the confining pressure servo loading device respectively through pipelines.

[0015] Furthermore, the gas outlet hole is connected to a gas flow meter through a pipeline provided with a gas outlet valve.

[0016] Furthermore, the shear end face assembly is provided with a gas inlet hole and a disassembly hole.

[0017] The present invention includes the following beneficial effects:

[0018] A shear end face assembly composed of steel blocks and soft plastic blocks in different proportions is set up to realize the permeability test of damaged coal bodies with different proportions of shear end faces and different shear degrees.

[0019] It is easy to install and disassemble, has a reliable structure, low modification cost and uniform loading force distribution.

[0020] The use of a detachable rubber sleeve can prevent the rubber sleeve from deformation, thereby ensuring the accuracy of the experiment.

[0021] A dedicated servo loading device is set up to achieve independent control and visual monitoring of axial pressure and confining pressure, ensure the stability of experimental data recording, and realize real-time feedback of experimental data through computer terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the structure of the multi-shear end-face damage seepage dynamic testing system.

[0023] Figure 2 is a schematic diagram of six sets of shear end face assemblies with different proportions.

[0024] The meanings of the markings shown in the figure are: 1-axial pressure liquid injection hole, 2-gas inlet hole, 3-left pressure cap, 4-clamping cavity, 5-rubber sleeve, 6-confining pressure injection hole, 7-right pressure cap, 8-combination piston, 9-gas outlet hole, 10-fixed piston, 11-fixed plug, 12-combination plug, 13-confining pressure servo loading device, 14-fixed steel block, 15-fixed soft plastic block, 16-coal sample, 17-movable soft plastic block, 18-movable steel block, 19-gas outlet valve, 20-gas flowmeter, 21-gas inlet valve, 22-gas cylinder, 23-axial pressure servo loading device, 24-disassembly hole. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making innovative efforts are within the scope of protection of the present invention.

[0026] Example:

[0027] A multi-shear end-face damage seepage dynamic testing system comprises the following steps:

[0028] First, the coal sample 16 is placed into the rubber sleeve 5 within the clamping cavity 4. The rubber sleeve 5 wraps around the coal sample 16. The gas cylinder 22 and the gas inlet valve 21 are opened, and gas is introduced into the coal sample 16 in the rubber sleeve 5 through the gas inlet hole 2. The axial pressure liquid injection hole 1 is connected to the axial pressure servo loading device 23. The fixed piston 10 connected to the left pressure cap 3 is driven to apply a predetermined shear stress to the fixed plug 11 composed of a fixed steel block 14 and a fixed soft plastic block 15. The confining pressure injection hole 6 is connected to the confining pressure servo loading device 13 and confining pressure is applied. The shear failure operation is carried out, and the fixed plug 11 is continuously pushed to squeeze the coal sample 16. The combined plug 12 at the other end is composed of a movable steel block 18 and a movable soft plastic block 17. Since the hardness and rigidity of the movable soft plastic block 17 are both lower than those of the movable steel block 18, a weak surface is formed in the end face area of ​​the movable soft plastic block 17. The coal sample 16 is pushed by the end of the fixed plug 11, resulting in a large displacement at this location, while the displacement in the end face area of ​​the movable steel block 18 is small, thereby causing shear damage to the coal sample 16. During the entire process of pushing and shearing the coal sample 16, gas passes through the coal sample 16, driving the combined piston 8 connected to the right pressure cap 7 to pass the gas through the gas outlet 9 and the gas outlet valve 19 to the gas flowmeter 20. The gas flowmeter monitors the amount of gas passing through the coal sample 16 in real time and calculates the permeability. By sequentially replacing six sets of removable shear face assemblies with different proportions at the combined plug 12, each equipped with a gas inlet port 2 and a disassembly port 24, namely, 50% semicircular steel blocks and 50% semicircular soft plastic blocks, 40% arc-shaped steel blocks and 60% arc-shaped soft plastic blocks, 30% arc-shaped steel blocks and 70% arc-shaped soft plastic blocks, 20% arc-shaped steel blocks and 80% arc-shaped soft plastic blocks, 10% arc-shaped steel blocks and 90% arc-shaped soft plastic blocks, and 100% circular steel blocks, permeability testing of damaged coal bodies with different shear face and different shear degrees was achieved. The permeability changes of coal sample 16 during the shear failure process under different shear face assemblies were recorded in real time, the data was exported, and the experiment was concluded. The experimental data are shown in Table 1 below.

[0029] Table 1

[0030] Combining the data in the table, we can see that:

[0031] (1) The present invention can monitor in real time the permeability of damaged coal bodies at different ratios of shear end faces and different shear degrees after the coal sample 16 is damaged under different stress levels, and the results are accurate and reliable;

[0032] (2) The shear end face assembly is easy to disassemble and replace, has a simple structure, and has uniform stress loading distribution.

[0033] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements, and equivalent substitutions made within the scope of the principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A multi-shear end surface damage seepage dynamic test system, characterized in that: The system includes a shear end face assembly, which is located at both ends of the rubber sleeve, and the rubber sleeve is located inside the clamping cavity. The left end of the clamping cavity is connected to the left pressure cap, and the left pressure cap is connected to the fixed piston. The fixed piston is provided with a gas inlet hole and an axial pressure liquid inlet hole; the right end of the clamping cavity is connected to the right pressure cap, and the right pressure cap is connected to the combined piston, and the combined piston is provided with a gas outlet hole; the surface of the clamping cavity is provided with a confining pressure injection hole.

2. The test system according to claim 1, characterized in that: The rubber sleeve wraps the coal sample.

3. The test system according to claim 2, characterized in that: The shear end face assembly is provided with a gas inlet hole and a disassembly hole.

4. The test system according to claim 3, characterized in that: The shear end face assembly includes a combination of one or more of a steel block and a soft plastic block.

5. The test system according to claim 1, characterized in that: The clamping cavity is equipped with a separate heating jacket.

6. The test system according to claim 1, characterized in that: The gas inlet hole is connected to the gas cylinder through a pipeline provided with a valve.

7. The test system according to claim 1, characterized in that: The gas outlet hole is connected to a gas flow meter through a pipeline provided with a gas outlet valve.

8. The test system according to claim 1, characterized in that: The axial pressure liquid injection hole is connected to the axial pressure servo loading device through a pipeline, and the confining pressure injection hole is connected to the confining pressure servo loading device through a pipeline.

9. The test system according to claim 1, characterized in that: The gas outlet hole is connected to a gas flow meter through a pipeline provided with a gas outlet valve.

10. Application of the testing system described in any one of claims 1 to 9 to the technical problem of dynamic changes in permeability caused by coal body damage under different shear end surfaces.

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