Device for obtaining water-immersed gas-containing coal body under loaded condition and application method

Abstract

The invention discloses a device for obtaining a water-immersed gas-containing coal body under a loaded condition and an application method. The device for obtaining the water-immersed gas-containing coal body under the loaded condition comprises a mechanical loading system, a sample mounting and testing system and a gas injection and water injection system. Through efficient cooperation of the mechanical loading system, the sample mounting and testing system and the gas injection and water injection system, water can be injected into a coal sample after a load is applied to the coal sample and methane gas is injected, so that the process that a loaded gas-containing coal body is influenced by a hydraulic measure in a coal mine engineering site can be effectively simulated; and when mechanical loading and seepage experiments are carried out after the water-containing coal sample is obtained, vacuum does not need to be pumped again, so that extra loss of water is avoided, and the mechanical and seepage rules of the water-immersed loaded gas-containing coal body can be accurately obtained to guide the hydraulic permeability-increasing extraction engineering design of the on-site coal seam.

Description

Technical Field

[0001] The invention relates to the research field of mine gas prevention and control technology, and in particular to a device for obtaining a water-immersed gas-containing coal body under load conditions and an application method thereof. Background Art

[0002] Coal has always been the dominant energy source in my country, supporting the sustained and rapid development of my country's economy and society for a long time. With the continuous reduction of shallow coal resource reserves, the depth of coal mining has continued to increase. After entering deep mining, the characteristics of high ground stress, high gas pressure, and low permeability have become more and more obvious, making coal and gas outburst disasters increasingly serious; on the other hand, mine gas is also a clean and efficient energy resource. If it can be scientifically and efficiently extracted, it can also provide a strong driving force for the progress of the national economy.

[0003] At present, strengthening deep coal seam gas extraction is the most important means to eliminate the danger of coal and gas outbursts in coal seams and promote the clean use of gas resources. However, due to the generally low permeability of deep coal seams, low-permeability coal seam gas control technology represented by hydraulic permeability enhancement extraction has gradually become the main technical method for preventing and controlling gas dynamic disasters in deep coal seams.

[0004] After the hydraulic measures are implemented in the deep low-permeability coal seam, a large amount of external water flows into the coal body, which greatly affects the mechanical strength and deformation characteristics of the coal body and the seepage characteristics of the gas in the coal. In order to quantitatively characterize the effect of external water intrusion on the coal body characteristics, it is necessary to prepare coal samples with specific moisture content in combination with engineering practice. At present, some methods for preparing water-containing coal samples have been proposed, such as immersion method, steam curing method, etc., but these methods have many prominent problems, such as uneven wetting of coal samples, inability to accurately obtain the moisture content of coal samples, etc. More importantly, in the process of obtaining water-containing coal samples by the above methods, it is impossible to apply loads to coal samples, and it is impossible to inject gas into coal samples in advance. Therefore, it is impossible to simulate the process of hydraulic measures on site affecting the loaded gas-containing coal body. Moreover, after obtaining the water-containing coal sample, it is necessary to re-evacuate when conducting mechanical loading and seepage experiments. This process will remove part of the water, resulting in unpredictable changes in the moisture content of the coal, which ultimately affects the accuracy of the results of laboratory quantitative research on the mechanics and seepage laws of water-containing coal samples. Summary of the invention

[0005] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0006] To this end, the purpose of the present invention is to provide a device and application method for obtaining water-immersed gas-containing coal under loaded conditions, which can accurately obtain coal with a specific water content under loaded conditions.

[0007] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0008] A device for obtaining gas-containing coal bodies in water under load conditions, comprising:

[0009] The mechanical loading system comprises a computer, a servo meter, a signal transmission line, a confining pressure loading pump, an axial pressure loading pump, a data collector and a high-pressure injection pipe; the computer sends instructions to the servo meter through the signal transmission line; the servo meter can control the confining pressure loading pump and the axial pressure loading pump through the signal transmission line according to the instructions sent by the computer; the confining pressure loading pump and the axial pressure loading pump are filled with hydraulic oil; the data collector can transmit the collected data to the computer through the signal transmission line;

[0010] The sample installation and testing system includes an experimental platform bracket, a sealed cavity, a high-pressure aviation plug, a coal sample, a circumferential strain monitor, an axial strain monitor, a top clamping pad, a bottom clamping pad, a loading cylinder and a signal transmission line; the experimental platform bracket is made of stainless steel and is cut as a whole; the sealed cavity is a cylindrical structure with a size of φ200×400mm; the base of the high-pressure aviation plug is embedded in the outer wall of the sealed cavity; the free end of the high-pressure aviation plug is connected to the data collector through a signal transmission line; the coal sample is a φ50×10 0mm cylindrical coal block; the circumferential strain monitor and the axial strain monitor are used to monitor the circumferential deformation and axial deformation of the coal body sample during the experiment, and are connected to the base of the high-pressure aviation plug through the signal transmission line; the data collected by the circumferential strain monitor and the axial strain monitor can be transmitted to the computer for analysis through the signal transmission line, the high-pressure aviation plug and the data acquisition device; the top clamping pad and the bottom clamping pad are used to fix the coal body sample on the loading cylinder in the sealed cavity; the coal body sample is wrapped with a heat shrink tube to prevent hydraulic oil from penetrating into the coal body sample;

[0011] The gas injection and water injection system comprises a methane gas cylinder, a vacuum pump, a high-pressure advection pump, a high-precision flow meter, a gas injection port metering pump, a gas outlet metering pump, a water injection pipeline, a gas injection pipeline, a gas outlet pipeline, a gas-water separator and a valve; the methane gas cylinder is filled with high-pressure methane gas, and methane gas can be injected into the gas injection port metering pump and the gas outlet metering pump; the vacuum pump is used to remove impurity gases in the entire system; the high-pressure advection pump can inject liquid water into the coal body sample through the water injection pipeline; the high-precision flow meter can accurately test the flow rate of water injected by the high-pressure advection pump; the gas injection port metering pump can inject methane gas into the coal body sample through the gas injection pipeline, and record the flow rate and total injection amount of the injected methane gas in real time; the gas outlet metering pump can record the flow rate and total discharge amount of methane gas discharged from the gas outlet pipeline in real time; the gas-water separator is used to monitor whether there is water flowing out of the coal body sample and prevent water from entering the gas outlet metering pump;

[0012] The confining pressure loading pump can inject hydraulic oil into the sealed cavity through the high-pressure injection pipe, and can apply a confining load to the coal body sample through the hydraulic oil;

[0013] The axial pressure loading pump can control the rising and falling action of the loading cylinder through the high-pressure injection pipe, thereby realizing the action of applying axial load to the coal body sample and unloading axial load;

[0014] The top clamping pad and the bottom clamping pad are provided with holes, and are respectively connected to the water injection pipeline, the air injection pipeline and the air outlet pipeline.

[0015] In addition, the present invention also proposes an application method of a device for obtaining a gas-containing coal body by water immersion under load conditions, which comprises the following working steps:

[0016] Phase 1: Prepare the standard coal sample. First, wrap it with heat shrink tubing. Then use the top clamping pad and the bottom clamping pad to fix it on the loading cylinder. Then install the circumferential strain monitor and the axial strain monitor at the appropriate position of the coal sample, and connect the signal transmission line. Finally, close the sealed cavity and connect the high-pressure aviation plug, data acquisition device, servo instrument, confining pressure loading pump, and axial pressure loading pump to the computer through the signal transmission line.

[0017] The second stage: open valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), close valve (b) and valve (i), start the vacuum pump, and evacuate the entire system to discharge the impurity gas in the system; after the vacuum evacuation is completed, first close valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), and then turn off the vacuum pump;

[0018] The third stage: inject hydraulic oil into the sealed cavity through the confining pressure loading pump, and then send instructions to the servo instrument through the computer according to the preset initial experimental conditions, and the servo instrument controls the confining pressure loading pump and the axial pressure loading pump to apply a circumferential load of x MPa and an axial load of y MPa to the coal sample; open valve (d), valve (h), valve (i) and the methane gas cylinder cock in turn, inject a certain amount of methane gas into the gas injection port metering pump and the gas outlet metering pump, and then close the methane gas cylinder cock, valve (i), valve (h) and valve (d) in turn; adjust the gas flow parameters of the gas injection port metering pump and the gas outlet metering pump to the preset values, and open valves (c), valves (g) and valves (e) to inject z into the coal sample. MPa methane gas, and always keep x>z in this process; when the gas pressure and gas volume in the gas injection port metering pump and the gas outlet metering pump are kept constant, it is considered that the methane gas in the coal sample has reached the adsorption equilibrium state, and at this time, valves (c), (g) and (e) are closed;

[0019] The fourth stage: open valve (b), the high-pressure advection pump switch and valve (e) in sequence, inject liquid water into the coal sample, and record the water injection flow rate and injection time in combination with a high-precision flow meter, and then calculate the water injection volume; when the water injection volume reaches the preset value, close valve (b) and the high-pressure advection pump switch in sequence; when the gas-water separator detects that water flows out of the coal sample, it indicates that the water has fully wetted the coal sample, and at this time, immediately close valve (e), and the water-immersed gas-containing coal sample under load conditions can be obtained;

[0020] The fifth stage: Based on the water-immersed gas-containing coal samples under the loaded conditions obtained above, the circumferential load and axial load applied to the coal samples can be adjusted by controlling the confining pressure loading pump and the axial pressure loading pump, so as to carry out the mechanical strength and deformation characteristics experiments of the water-immersed gas-containing coal samples under loaded conditions; through the mutual cooperation of the gas injection port metering pump and the gas outlet metering pump, the parameters such as the gas injection pipeline flow rate, the gas outlet pipeline flow rate, the gas injection pipeline pressure and the gas outlet pipeline pressure can be obtained, thereby calculating the permeability of the water-immersed gas-containing coal samples under loaded conditions, and then studying its seepage evolution law.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] In the embodiments of the present invention, the device and application method for obtaining water-immersed gas-containing coal under load conditions provided can inject water into the coal sample after applying a load to the coal sample and injecting methane gas, effectively simulating the process of hydraulic measures at the coal mine engineering site affecting the loaded gas-containing coal body, and after obtaining the water-containing coal sample, when mechanical loading and seepage experiments are carried out, there is no need to re-vacuum, thus avoiding additional loss of water, and thus the mechanical and seepage laws of the water-immersed loaded gas-containing coal body can be accurately obtained to guide the design of on-site coal seam hydraulic permeability enhancement and extraction engineering.

[0023] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of a device for obtaining a gas-containing coal body in water under load conditions in an embodiment of the present invention.

[0025] In the figure, 1 is a computer; 2 is a servo instrument; 3 is a signal transmission line; 4 is a confining pressure loading pump; 5 is an axial pressure loading pump; 6 is a data acquisition device; 7 is an experimental platform bracket; 8 is a sealed cavity; 9 is a high-pressure aviation plug; 10 is a hydraulic oil; 11 is a coal body sample; 12 is a circumferential strain monitor; 13 is an axial strain monitor; 14 is a top clamping pad; 15 is a bottom clamping pad; 16 is a high-pressure liquid injection pipe; 17 is a loading cylinder; 18 is a water injection pipeline; 19 is a gas injection pipeline; 20 is a gas outlet pipeline; 21 is a gas-water separator; 22 is a high-pressure horizontal flow pump; 23 is a high-precision flow meter; 24 is a gas injection port metering pump; 25 is a gas outlet metering pump; 26 is a vacuum pump; 27 is a methane gas cylinder; a~i are valves. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0027] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios in conjunction with the accompanying drawings.

[0028] like Figure 1 As shown, a device for obtaining gas-containing coal body in water under load conditions comprises:

[0029] A mechanical loading system comprises a computer (1), a servo instrument (2), a signal transmission line (3), a confining pressure loading pump (4), an axial pressure loading pump (5), a data acquisition device (6) and a high-pressure injection pipe (16); the computer (1) sends instructions to the servo instrument (2) through the signal transmission line (3); the servo instrument (2) can control the confining pressure loading pump (4) and the axial pressure loading pump (5) through the signal transmission line (3) according to the instructions sent by the computer (1); the confining pressure loading pump (4) and the axial pressure loading pump (5) are filled with hydraulic oil (10); the data acquisition device (6) can transmit the collected data to the computer (1) through the signal transmission line (3);

[0030] A sample installation and testing system comprises an experimental platform bracket (7), a sealed cavity (8), a high-pressure aviation plug (9), a coal sample (11), a circumferential strain monitor (12), an axial strain monitor (13), a top clamping pad (14), a bottom clamping pad (15), a loading cylinder (17) and a signal transmission line (3); the experimental platform bracket (7) is made of stainless steel and is cut as a whole; the sealed cavity (8) is a cylindrical structure with a size of φ200×400mm; the base of the high-pressure aviation plug (9) is embedded in the outer wall of the sealed cavity (8); the free end of the high-pressure aviation plug (9) is connected to a data acquisition device (6) through a signal transmission line (3); the coal sample (11) is a cylindrical structure with a size of φ50×100mm. A cylindrical coal block; the circumferential strain monitor (12) and the axial strain monitor (13) are used to monitor the circumferential deformation and axial deformation of the coal sample (11) during the experiment, and are connected to the base of the high-pressure aviation plug (9) through a signal transmission line (3); the data collected by the circumferential strain monitor (12) and the axial strain monitor (13) can be transmitted to a computer (1) for analysis through the signal transmission line (3), the high-pressure aviation plug (9) and the data acquisition device (6); the top clamping pad (14) and the bottom clamping pad (15) are used to fix the coal sample (11) on the loading cylinder (17) in the sealed cavity (9); the coal sample (11) is wrapped with a heat shrink tube to prevent the hydraulic oil (10) from penetrating into the coal sample (11);

[0031] The gas injection and water injection system comprises a methane gas cylinder (27), a vacuum pump (26), a high-pressure advection pump (22), a high-precision flow meter (23), a gas injection port metering pump (24), a gas outlet metering pump (25), a water injection pipeline (18), a gas injection pipeline (19), a gas outlet pipeline (20), a gas-water separator (21) and valves (a) to (i); the methane gas cylinder (27) is filled with high-pressure methane gas, and methane gas can be injected into the gas injection port metering pump (24) and the gas outlet metering pump (25); the vacuum pump (26) is used to remove impurity gases in the entire system; the high-pressure advection pump (22) can be ... The water injection pipeline (18) injects liquid water into the coal sample (11); the high-precision flow meter (23) can accurately test the flow rate of water injected by the high-pressure horizontal flow pump (22); the gas injection port metering pump (24) can inject methane gas into the coal sample (11) through the gas injection pipeline (19), and record the flow rate and total amount of injected methane gas in real time; the gas outlet metering pump (25) can record the flow rate and total amount of methane gas discharged from the gas outlet pipeline (20) in real time; the gas-water separator (21) is used to monitor whether there is water flowing out of the coal sample (11) and prevent water from entering the gas outlet metering pump (25);

[0032] The confining pressure loading pump (4) can inject hydraulic oil (10) into the sealed cavity (8) through a high-pressure liquid injection pipe (16), and can apply a confining load to the coal sample (11) through the hydraulic oil (10);

[0033] The axial pressure loading pump (5) can control the rising and falling movements of the loading oil cylinder (17) through the high-pressure liquid injection pipe (16), thereby realizing the actions of applying an axial load to the coal body sample (11) and unloading the axial load;

[0034] The top clamping pad (14) and the bottom clamping pad (15) are provided with holes, and are respectively connected to a water injection pipeline (18), an air injection pipeline (19) and an air outlet pipeline (20).

[0035] In addition, the present invention also proposes an application method of a device for obtaining a gas-containing coal body by water immersion under load conditions, which comprises the following working steps:

[0036] The first stage: prepare the standard coal sample (11), first wrap it with heat shrink tube, then use the top clamping pad (14) and the bottom clamping pad (15) to fix it on the loading cylinder (17), then install the circumferential strain monitor (12) and the axial strain monitor (13) at the appropriate position of the coal sample (11), and connect the signal transmission line (3), finally close the sealing cavity (8), and connect the high-pressure aviation plug (9), data acquisition device (6), servo instrument (2), confining pressure loading pump (4), axial pressure loading pump (5) to the computer (1) through the signal transmission line (3);

[0037] The second stage: open valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), close valve (b) and valve (i), start vacuum pump (26), and evacuate the entire system to discharge impurity gases in the system; after the evacuation is completed, first close valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), and then turn off vacuum pump (26);

[0038] The third stage: inject hydraulic oil (10) into the sealed cavity (8) through the confining pressure loading pump (4), and then send instructions to the servo instrument (2) through the computer (1) according to the preset initial experimental conditions, and the servo instrument (2) controls the confining pressure loading pump (4) and the axial pressure loading pump (5) to apply a circumferential load of x MPa and an axial load of y MPa to the coal sample (11); open valve (d), valve (h), valve (i) and the stopcock of the methane gas cylinder (27) in turn, inject a certain amount of methane gas into the gas injection port metering pump (24) and the gas outlet metering pump (25), and then close the stopcock of the methane gas cylinder (27), valve (i), valve (h) and valve (d) in turn; adjust the gas flow parameters of the gas injection port metering pump (24) and the gas outlet metering pump (25) to the preset values, and open valve (c), valve (g) and valve (e) to inject z into the coal sample (11). MPa methane gas, and x>z is always maintained during this process; when the gas pressure and gas volume in the gas injection port metering pump (24) and the gas outlet metering pump (25) are kept constant, it is considered that the methane gas in the coal sample (11) has reached an adsorption equilibrium state, and valves (c), (g) and (e) are closed at this time;

[0039] The fourth stage: open the valve (b), the high-pressure horizontal flow pump (22) switch and the valve (e) in sequence, inject liquid water into the coal sample (11), and record the water injection flow rate and injection time in combination with the high-precision flow meter (23), and then calculate the water injection amount; when the water injection amount reaches a preset value, close the valve (b) and the high-pressure horizontal flow pump (22) switch in sequence; when the gas-water separator (21) detects that water flows out of the coal sample (11), it indicates that the water has fully wetted the coal sample (11), and at this time, immediately close the valve (e), and the water-immersed gas-containing coal sample (11) under load conditions can be obtained;

[0040] The fifth stage: Based on the water-immersed gas-containing coal body sample (11) under the load condition obtained above, the circumferential load and axial load applied to the coal body sample (11) can be adjusted by controlling the confining pressure loading pump (4) and the axial pressure loading pump (5) to carry out the mechanical strength and deformation characteristics experiment of the water-immersed gas-containing coal body sample (11) under the load condition; through the mutual cooperation of the gas injection port metering pump (24) and the gas outlet metering pump (25), the parameters such as the gas injection pipeline (19) flow rate, the gas outlet pipeline (20) flow rate, the gas injection pipeline (19) pressure and the gas outlet pipeline (20) pressure can be obtained, thereby calculating the permeability of the water-immersed gas-containing coal body sample (11) under the load condition, and then studying its seepage evolution law.

[0041] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0042] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A device for obtaining gas-containing coal bodies under water immersion under load conditions and an application method, characterized in that: The device for obtaining the water-immersed gas-containing coal body under load conditions comprises: The mechanical loading system comprises a computer, a servo meter, a signal transmission line, a confining pressure loading pump, an axial pressure loading pump, a data collector and a high-pressure injection pipe; the computer sends instructions to the servo meter through the signal transmission line; the servo meter can control the confining pressure loading pump and the axial pressure loading pump through the signal transmission line according to the instructions sent by the computer; the confining pressure loading pump and the axial pressure loading pump are filled with hydraulic oil; the data collector can transmit the collected data to the computer through the signal transmission line; The sample installation and testing system includes an experimental platform bracket, a sealed cavity, a high-pressure aviation plug, a coal sample, a circumferential strain monitor, an axial strain monitor, a top clamping pad, a bottom clamping pad, a loading cylinder and a signal transmission line; the experimental platform bracket is made of stainless steel and is cut as a whole; the sealed cavity is a cylindrical structure with a size of φ200×400mm; the base of the high-pressure aviation plug is embedded in the outer wall of the sealed cavity; the free end of the high-pressure aviation plug is connected to the data collector through a signal transmission line; the coal sample is a φ50×10 0mm cylindrical coal block; the circumferential strain monitor and the axial strain monitor are used to monitor the circumferential deformation and axial deformation of the coal body sample during the experiment, and are connected to the base of the high-pressure aviation plug through the signal transmission line; the data collected by the circumferential strain monitor and the axial strain monitor can be transmitted to the computer for analysis through the signal transmission line, the high-pressure aviation plug and the data acquisition device; the top clamping pad and the bottom clamping pad are used to fix the coal body sample on the loading cylinder in the sealed cavity; the coal body sample is wrapped with a heat shrink tube to prevent hydraulic oil from penetrating into the coal body sample; The gas injection and water injection system comprises a methane gas cylinder, a vacuum pump, a high-pressure advection pump, a high-precision flow meter, a gas injection port metering pump, a gas outlet metering pump, a water injection pipeline, a gas injection pipeline, a gas outlet pipeline, a gas-water separator and a valve; the methane gas cylinder is filled with high-pressure methane gas, and methane gas can be injected into the gas injection port metering pump and the gas outlet metering pump; the vacuum pump is used to remove impurity gases in the entire system; the high-pressure advection pump can inject liquid water into the coal body sample through the water injection pipeline; the high-precision flow meter can accurately test the flow rate of water injected by the high-pressure advection pump; the gas injection port metering pump can inject methane gas into the coal body sample through the gas injection pipeline, and record the flow rate and total injection amount of the injected methane gas in real time; the gas outlet metering pump can record the flow rate and total discharge amount of methane gas discharged from the gas outlet pipeline in real time; the gas-water separator is used to monitor whether there is water flowing out of the coal body sample and prevent water from entering the gas outlet metering pump; The confining pressure loading pump can inject hydraulic oil into the sealed cavity through the high-pressure injection pipe, and can apply a confining load to the coal body sample through the hydraulic oil; The axial pressure loading pump can control the rising and falling action of the loading cylinder through the high-pressure injection pipe, thereby realizing the action of applying axial load to the coal body sample and unloading axial load; The top clamping pad and the bottom clamping pad are provided with holes, and are respectively connected to the water injection pipeline, the air injection pipeline and the air outlet pipeline.

2. The device and application method for obtaining gas-containing coal bodies under load conditions according to claim 1, characterized in that: The device for obtaining gas-containing coal body by water immersion under load conditions as claimed in claim 1 comprises the following steps: Phase 1: Prepare the standard coal sample. First, wrap it with heat shrink tubing. Then use the top clamping pad and the bottom clamping pad to fix it on the loading cylinder. Then install the circumferential strain monitor and the axial strain monitor at the appropriate position of the coal sample, and connect the signal transmission line. Finally, close the sealed cavity and connect the high-pressure aviation plug, data acquisition device, servo instrument, confining pressure loading pump, and axial pressure loading pump to the computer through the signal transmission line. The second stage: open valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), close valve (b) and valve (i), start the vacuum pump, and evacuate the entire system to discharge the impurity gas in the system; after the vacuum evacuation is completed, first close valve (a), valve (c), valve (d), valve (e), valve (f), valve (g) and valve (h), and then turn off the vacuum pump; The third stage: inject hydraulic oil into the sealed cavity through the confining pressure loading pump, and then send instructions to the servo instrument through the computer according to the preset initial experimental conditions, and the servo instrument controls the confining pressure loading pump and the axial pressure loading pump to apply a circumferential load of x MPa and an axial load of y MPa to the coal sample; open valve (d), valve (h), valve (i) and the methane gas cylinder cock in turn, inject a certain amount of methane gas into the gas injection port metering pump and the gas outlet metering pump, and then close the methane gas cylinder cock, valve (i), valve (h) and valve (d) in turn; adjust the gas flow parameters of the gas injection port metering pump and the gas outlet metering pump to the preset values, and open valves (c), valves (g) and valves (e) to inject z into the coal sample. MPa methane gas, and always keep x>z in this process; when the gas pressure and gas volume in the gas injection port metering pump and the gas outlet metering pump are kept constant, it is considered that the methane gas in the coal sample has reached the adsorption equilibrium state, and at this time, valves (c), (g) and (e) are closed; The fourth stage: open valve (b), the high-pressure advection pump switch and valve (e) in sequence, inject liquid water into the coal sample, and record the water injection flow rate and injection time in combination with a high-precision flow meter, and then calculate the water injection volume; when the water injection volume reaches the preset value, close valve (b) and the high-pressure advection pump switch in sequence; when the gas-water separator detects that water flows out of the coal sample, it indicates that the water has fully wetted the coal sample, and at this time, immediately close valve (e), and the water-immersed gas-containing coal sample under load conditions can be obtained; The fifth stage: Based on the water-immersed gas-containing coal samples under the loaded conditions obtained above, the circumferential load and axial load applied to the coal samples can be adjusted by controlling the confining pressure loading pump and the axial pressure loading pump, so as to carry out the mechanical strength and deformation characteristics experiments of the water-immersed gas-containing coal samples under loaded conditions; through the mutual cooperation of the gas injection port metering pump and the gas outlet metering pump, the parameters such as the gas injection pipeline flow rate, the gas outlet pipeline flow rate, the gas injection pipeline pressure and the gas outlet pipeline pressure can be obtained, thereby calculating the permeability of the water-immersed gas-containing coal samples under loaded conditions, and then studying its seepage evolution law.

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