CN113281486A - Multi-field coupling dynamic characteristic experiment system and method for graded loading and unloading coal bodies - Google Patents
Multi-field coupling dynamic characteristic experiment system and method for graded loading and unloading coal bodies Download PDFInfo
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Abstract
The invention discloses a multi-field coupling dynamic characteristic experiment system for graded loading and unloading of coal bodies, which comprises an experiment device and a monitoring device, wherein the experiment device comprises a main body and a plurality of auxiliary bodies; the experimental device comprises an inflating device, a stress loading and unloading device, a seepage desorption device and a gas extraction device; the inflation device comprises a gas cylinder, a manual valve, a pressure reducing valve and a pneumatic valve; the seepage desorption device comprises a coal sample bin, and the stress loading and unloading device comprises a loading pump, a loading oil cylinder, a piston rod and a loading plate; the gas extraction device comprises a pneumatic valve, a stop valve and an extraction pump; the coal sample bin is of a cavity structure, a gas inlet and a gas outlet are arranged on the coal sample bin, a gas cylinder is communicated with the gas inlet of the coal sample bin through a gas pipeline, and a manual valve, a pressure reducing valve and a pneumatic valve are sequentially arranged on the gas pipeline; the gas outlet of the coal sample bin is communicated and connected with an extraction pump in the gas extraction device through a gas transmission pipeline. The method is used for simulating the strain and the damage characteristics of the coal body in the loading process under different stress environments, and the adsorption and desorption seepage conditions of the coal body under different conditions.
Description
Technical Field
The invention belongs to the technical field of development and utilization of coal bed gas and coal mine gas, and particularly belongs to a system and a method for a multi-field coupling dynamic characteristic experiment of graded loading and unloading coal bodies.
Background
Along with the gradual increase of the coal mining depth in China, the gas pressure and the gas content of a coal bed are obviously increased, and in addition, the gas permeability of the coal bed in most areas in China is low, the difficulty of gas extraction of a coal mine is increased more and more, and coal and gas outburst and gas explosion accidents are frequent. In order to improve the gas extraction efficiency and ensure the safe and efficient production operation of a coal mine, the analytic seepage rule of the loaded gas-containing coal body needs to be mastered more accurately.
At present, most of researchers develop experimental devices which cannot comprehensively consider original gas occurrence environments where coal bodies are located and different stress environments where coal bodies are subjected when researching the strain of the coal bodies in different stress environments and the damage characteristics of the coal bodies in a loading process and the adsorption-desorption-seepage conditions of the coal bodies under different conditions, and lack systematic monitoring and research on the stress strain of the coal bodies in a loading and unloading process and the desorption conditions of the gas seepage.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a system and a method for a multi-field coupling dynamic characteristic experiment of a graded loading and unloading coal body, which are used for simulating the strain and the damage characteristics of the coal body in the loading process under different stress environments and the adsorption-desorption-seepage conditions of gas of the coal body and the coal body under different conditions.
In order to achieve the purpose, the invention provides the following technical scheme:
a multi-field coupling dynamic characteristic experiment system for graded loading and unloading coal bodies comprises an experiment device and a monitoring device;
the experimental device comprises an inflating device, a stress loading and unloading device, a seepage desorption device and a gas extraction device;
the inflation device comprises a gas cylinder, a manual valve, a pressure reducing valve and a pneumatic valve; the seepage desorption device comprises a coal sample bin, and the stress loading and unloading device comprises a loading pump, a loading oil cylinder, a piston rod and a loading plate; the gas extraction device comprises a pneumatic valve, a stop valve and an extraction pump;
the coal sample bin is of a cavity structure, an air inlet and an air outlet are formed in the coal sample bin, the gas cylinder is communicated with the air inlet of the coal sample bin through a gas pipeline, and a manual valve, a pressure reducing valve and a pneumatic valve are sequentially arranged on the gas pipeline; the gas outlet of the coal sample bin is communicated and connected with an extraction pump in a gas extraction device through a gas transmission pipeline, and a pneumatic valve and a stop valve are sequentially arranged on the gas transmission pipeline along the gas flow direction;
the loading oil cylinder is arranged on the outer side wall of the coal sample bin and is in sealed connection, the loading pump is connected with an inner cavity of the loading oil cylinder, a piston rod is arranged in the inner cavity of the loading oil cylinder, a loading plate is arranged at the end part of the piston rod, and the loading plate is in sealed connection with the side wall of the coal sample bin;
the monitoring system comprises a non-contact full-field strain measuring device, an acoustic emission monitoring device and a multi-parameter measurement and control device;
the acoustic emission monitoring device comprises an acoustic emission probe and an acoustic emission amplifier; the multi-parameter measurement and control device comprises a first pressure gauge, a first flow sensor, a data acquisition instrument, a pressure gauge and a monitoring host;
the first flow sensor and the first pressure gauge are arranged on a gas pipeline of the gas cylinder, and the output ends of the first flow sensor and the first pressure gauge are connected with the input end of the data acquisition instrument; the acoustic emission probe is arranged on the side wall of the coal sample bin, the output end of the acoustic emission probe is connected with the input end of an acoustic emission amplifier, the output end of the acoustic emission amplifier is connected with the input end of a data acquisition instrument, and the output end of the data acquisition instrument is connected with a monitoring host;
the non-contact full-field strain measuring device is arranged on the outer side of the gas outlet of the coal sample bin, and the output end of the non-contact full-field strain measuring device is connected with the monitoring host.
Preferably, the inflation device further comprises a pressure reducing valve, a stop valve and a buffer tank, the buffer tank is connected with the gas outlet of the gas cylinder through a gas transmission pipeline, and the pressure reducing valve and the stop valve are sequentially arranged on the gas transmission pipeline; the other end of the buffer tank is connected with the inner cavity of the coal sample bin.
Preferably, the coal sample bin is machined by adopting a forged piece, a detachable upper end cover is arranged at the upper end of the coal sample bin, and a loading oil cylinder is arranged on the upper end cover.
Preferably, the side walls of the air inlet and the air outlet of the coal sample bin are provided with I-shaped radial grooves.
Preferably, a second pressure gauge and a second flow sensor are arranged on a gas transmission pipeline between the gas outlet of the coal sample bin and the extraction pump, and the second pressure gauge and the second flow sensor are connected with the input end of the data acquisition instrument.
Preferably, the extraction pump is a program-controlled adjustable extraction pump.
Preferably, the inner cavity of the coal sample bin is of a rectangular structure, the four side walls of the rectangular cavity are provided with acoustic emission probes, and the acoustic emission probes are in close contact with the coal sample.
Preferably, the acoustic emission probes in the coal sample bin are arranged in a cross manner.
A multi-field coupling dynamic characteristic experiment method for graded loading and unloading coal bodies is based on any one of the above mentioned experiment systems for multi-field coupling dynamic characteristics of graded loading and unloading coal bodies, and includes the following steps,
step 2, opening a valve of a gas cylinder, filling gas into the coal sample bin to enable the coal sample to be in a gas occurrence state meeting experimental conditions, and closing the manual valve after the gas filling is finished;
step 3, starting the loading pump again, applying pressure to the coal sample, and simultaneously pumping out gas in the coal sample bin by using the pumping pump to simulate the pumping out effect on the coal bed gas; the acoustic emission probe records internal damage data of the coal sample under the action of pressure, and transmits the internal damage data to the data acquisition instrument through the acoustic emission amplifier; after the stress loading is finished, the loading pump is closed;
step 4, the gas in the coal sample bin and the connecting pipeline is continuously pumped by the pumping pump, after the gas pumping is finished, the side panel of the gas outlet of the coal sample bin is opened, and the non-contact full-field strain measuring device measures the strain of the coal body in the coal sample bin;
step 5, the data acquisition instrument monitors and records data of the first pressure gauge, the first flow sensor, the loading pump and the coal sample bin, and uploads the data to the monitoring host;
and 6, after the experiment is finished, starting the loading pump, restoring the loading plate to the original position, opening the coal sample bin, taking out the coal sample, and cleaning residual coal in the coal sample bin.
Preferably, in the step 2, a valve of the gas cylinder is opened, and the high-pressure gas flows through the reducing valve and the stop valve and enters the buffer tank; after gas with certain pressure is filled into the buffer tank, the valve of the gas cylinder is closed, the manual valve is opened, gas is filled into the coal sample bin, so that the coal sample is in a gas occurrence state meeting experimental conditions, and after the gas filling is finished, the manual valve is closed.
Compared with the prior art, the invention has the following beneficial technical effects:
the invention provides a multi-field coupling dynamic characteristic experiment system for graded loading and unloading coal bodies, wherein the loading and unloading device can simulate different stress environments of the coal bodies; the extraction device can simulate seepage desorption of coal under different extraction negative pressure; the non-contact full-field strain measurement system can measure the strain field of the experimental coal wall with the opening on the side surface; the acoustic emission monitoring system can monitor the damage characteristics of the coal body in the loading process in real time; the multi-parameter measurement and control device can monitor and control parameters such as stress strain, extraction negative pressure, acoustic emission signals, gas pressure flow and the like in the experimental process in real time; the inflation device can simulate different gas occurrence states of the coal body; the coal sample gas surface diffusion seepage desorption device can realize the process of converting point diffusion into surface diffusion of gas, ensure the uniform adsorption of coal gas and reduce the actual seepage state of the coal gas.
The invention relates to a stress-damage-seepage multi-field coupling dynamic characteristic experiment system for graded loading and unloading of coal bodies, which consists of loading and unloading devices capable of simulating different stress environments where the coal bodies are located, a seepage desorption extraction device capable of simulating seepage of the coal bodies under the action of different extraction negative pressures and a data acquisition device for acquiring parameters such as stress strain, gas flow, gas pressure and the like of the coal bodies, and can monitor the stress and deformation of coal samples in real time and monitor monitoring data such as gas pressure, gas flow and the like. According to the method, different stresses are applied to the coal body, and the gas conditions of the coal sample are adjusted, so that different environments of the coal body containing gas underground are simulated more truly, and the method has important significance for more accurately mastering the mechanism and experimental research of seepage influence of the coal body containing gas.
Further, through setting up the buffer tank, treat that the gas in the buffer tank reaches certain pressure after, in the regulation entering coal sample storehouse of relief pressure valve and pneumatic valve again for output gas pressure is more stable, has enlarged the experimental pressure scope.
Furthermore, the coal sample bin is machined by adopting the forged piece, the machining is convenient, the upper end cover can be disassembled, the loading oil cylinder is conveniently installed above the upper end cover, the loading plate is installed at the lower end of the loading oil cylinder, the coal sample in the coal sample bin can be loaded and unloaded in a grading manner, and different stress effects on the coal sample in the coal bed can be simulated.
Furthermore, the radial grooves are formed in the side walls of the air inlet and the air outlet of the coal sample bin, so that the process of converting point diffusion into surface diffusion of gas is realized, and the environmental conditions of the coal sample are simulated more truly.
Furthermore, the acoustic emission probes are respectively arranged on the four side faces of the coal sample bin, the acoustic emission probes are in close contact with the coal sample, and the four holes are arranged in a cross mode, so that acoustic emission responses generated in the loading and unloading processes of the coal sample can be recorded, and the internal damage condition of the coal sample can be conveniently researched.
Furthermore, by using the program-controlled adjustable extraction pump in the gas extraction process, the extraction negative pressure can be adjusted, the seepage desorption process of gas in a coal body can be better simulated, and the program-controlled adjustable extraction pump can be remotely controlled by using the monitoring host.
Drawings
FIG. 1 is a schematic structural diagram of a multi-field coupling dynamic characteristic experiment system for graded loading and unloading coal bodies according to the present invention;
FIG. 2 is a schematic view of a radial groove on an end face of a side plate of a coal sample bin according to an embodiment of the invention;
FIG. 3 is a schematic diagram of arrangement holes of an acoustic emission sensor of a coal sample bin according to an embodiment of the invention;
in the drawings: 11-1: a gas cylinder; 11-2: a pressure reducing valve; 11-3: a stop valve; 11-4: a buffer tank; 11-5: a manual valve; 11-6: a pressure reducing valve; 11-7: a pneumatic valve; 12-1: a loading pump; 12-2: loading an oil cylinder; 12-3: a piston rod; 12-4: a loading plate; 13-1: a coal sample bin; 13-2: a radial type groove; 14-1: a pneumatic valve; 14-2: a stop valve; 14-3: a program-controlled adjustable extraction pump; 21: a non-contact full-field strain measurement device; 22-1: an acoustic emission probe; 22-2: an acoustic emission amplifier; 23-1: a first pressure gauge; 23-2: a first flow sensor; 23-3: a data acquisition instrument; 23-4: a second pressure gauge; 23-5: a second flow sensor; 23-6: and monitoring the host.
Detailed Description
The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The invention provides a graded loading and unloading coal body stress-damage-seepage multi-field coupling dynamic characteristic experiment system, wherein the loading and unloading device can simulate different stress environments of the coal body; the extraction device can simulate seepage desorption of coal under different extraction negative pressure; the non-contact full-field strain measurement system can measure the strain field of the experimental coal wall with the opening on the side surface; the acoustic emission monitoring system can monitor the damage characteristics of the coal body in the loading process in real time; the multi-parameter measurement and control device can monitor and control parameters such as stress strain, extraction negative pressure, acoustic emission signals, gas pressure flow and the like in the experimental process in real time; the inflation device can simulate different gas occurrence states of the coal body; the coal sample gas surface diffusion seepage desorption device can realize the process of converting point diffusion into surface diffusion of gas, ensure the uniform adsorption of coal gas and reduce the actual seepage state of the coal gas.
The multi-field coupling dynamic characteristic experiment system for the graded loading and unloading coal bodies can complete the following basic research experiments: 1. desorption rules of gas of loose and crushed coal bodies with different particle sizes; 2. simulation experiment of pressure relief coal wall/top coal gas emission rule; 3. a gas seepage desorption rule under the original coal extraction condition; 4. highlighting the gas desorption seepage rule in the whole process of coal load instability; 5. the law of influence of coal bed joint structure and physical and mechanical properties on gas seepage desorption; 6. influence rules of stress environment, mining disturbance, extraction effect and the like on coal gas seepage desorption.
The method applies different stresses to the coal body, adjusts the gas condition and the seepage desorption condition of the coal sample, more truly simulates different underground environments of the coal body containing gas, and has important significance for more accurately mastering the mechanism and experimental research of seepage influence of the coal body containing gas.
Examples
As shown in fig. 1, the multi-field coupling dynamic characteristic experiment system for stress-damage-seepage of graded loading and unloading coal in the embodiment includes an experiment system and a monitoring system, wherein the experiment device includes an inflation device, a stress loading and unloading device, a coal sample gas surface diffusion seepage desorption device and a gas extraction device, and the monitoring system includes a non-contact full-field strain measurement device 21, an acoustic emission monitoring device and a multi-parameter measurement and control device; wherein:
the gas charging device comprises a gas cylinder 11-1, a pressure reducing valve 11-2, a stop valve 11-3, a buffer tank 11-4, a manual valve 11-5, a pressure reducing valve 11-6 and a pneumatic valve 11-7; the stress loading and unloading device comprises a loading pump 12-1, a loading oil cylinder 12-2, a piston rod 12-3 and a loading plate 12-4; the coal sample gas surface diffusion seepage desorption device comprises a coal sample bin 13-1 and a radial groove 13-2 processed on the end faces of the side plates for air inlet and air outlet; the gas extraction device comprises a pneumatic valve 14-1, a stop valve 14-2 and a program-controlled adjustable extraction pump 14-3.
The acoustic emission monitoring device comprises an acoustic emission probe 22-1 and an acoustic emission amplifier 22-2; the multi-parameter measurement and control device comprises a pressure gauge 23-1, a flow sensor 23-2, a data acquisition instrument 23-3, a pressure gauge 23-4, a flow sensor 23-5 and a monitoring host 23-6;
when the gas cylinder is in use, high-pressure gas in the gas cylinder 11-1 flows through the pressure reducing valve 11-2 and the stop valve 11-3 to enter the buffer tank 11-4, and the valve of the gas cylinder 11-1 is closed after the gas in the buffer tank 11-4 reaches a certain pressure.
And opening the manual valve 11-5, and allowing the gas in the buffer tank 11-4 to flow through the pressure reducing valve 11-6, the flow sensor 23-2 and the pneumatic valve 11-7 to enter the coal sample bin 13-1, so that the coal in the coal sample bin 13-1 is in a gas occurrence state meeting experimental conditions.
After the loading pump 12-1 is started, the loading oil cylinder 12-2 applies pressure to the coal in the coal sample bin 13-1 through the piston rod 12-3 and the loading plate 12-4, at this time, the acoustic emission probes 22-1 installed on four side surfaces of the coal sample bin 13-1 record the internal damage condition of the coal sample, and the internal damage condition is uploaded to the data acquisition instrument 23-3 through the acoustic emission amplifier 22-2; meanwhile, gas in the coal sample bin 13-1 is pumped out under the action of the program-controlled adjustable extraction pump 14-3, and the extraction effect of coal bed gas is simulated.
In the whole experiment process, the data acquisition instrument 23-3 acquires and records data on a pressure gauge 23-1, a flow sensor 23-2, a loading pump 12-1, the pressure gauge 23-4 and a flow sensor 23-5 which are arranged between the coal sample bin 13-1 and the pneumatic valve 14-1 on the buffer tank 11-4. After the program-controlled adjustable extraction pump 14-3 pumps gas in the coal sample bin 13-1 and the connecting pipeline, the side panel of the gas outlet of the coal sample bin 13-1 is opened, and the non-contact full-field strain measurement system 21 measures the strain of the coal body in the coal sample bin 13-1. The monitoring host 23-6 analyzes and processes the data of the data acquisition instrument 23-3 and the non-contact full-field strain measurement device 21.
High-pressure gas in the gas cylinder 11-1 passes through a reducing valve 11-2 and a stop valve 11-3 and then enters a buffer tank 11-4. After the gas in the buffer tank 11-4 reaches a certain pressure, the gas enters the coal sample bin 13-1 through the regulation of the pressure reducing valve 11-6 and the pneumatic valve 11-7, the pressure of the output gas is more stable by adopting the gas pressure regulating device, and the experimental pressure range is expanded.
The coal sample bin 13-1 is machined by adopting a forged piece, the upper end cover is detachable, the loading oil cylinder 12-2 is arranged above the upper end cover, the loading plate 12-4 is arranged at the lower end of the loading oil cylinder 12-2, and the coal sample in the coal sample bin 13-1 can be loaded and unloaded in a grading manner to simulate different stress effects on the coal sample in a coal bed.
The radial grooves 13-2 are formed in the end faces of the side plates for air inlet and air outlet of the coal sample bin 13-1, so that the process of converting point diffusion into surface diffusion of gas is realized, and the environmental conditions of the coal sample are simulated more truly.
One side of the gas outlet of the coal sample bin 13-1 is a detachable opening which is used for measuring the surface strain of the loaded coal wall by the non-contact full-field strain measuring device 21.
An acoustic emission probe 22-1 is respectively arranged on four side surfaces of the coal sample bin 13-1, the acoustic emission probe 22-1 is tightly contacted with the coal sample, and four holes are arranged in a cross mode. The acoustic emission response generated in the loading and unloading process of the coal sample can be recorded, and the internal damage condition of the coal sample can be conveniently researched.
The gas in the coal sample bin 13-1 is extracted by using the program-controlled adjustable extraction pump 14-3, the extraction negative pressure can be adjusted, the seepage desorption process of the gas in the coal body can be better simulated, and the program-controlled adjustable extraction pump 14-3 can be remotely controlled by using the monitoring host 23-6.
A graded loading and unloading coal body stress-damage-seepage multi-field coupling dynamic characteristic experiment method comprises the following steps:
firstly, assembling an experimental system to ensure that the joints of the devices are in a sealed state and are airtight, and a manual valve 11-5 is in a closed state;
and secondly, selecting a coal body meeting experimental conditions to be prefabricated into the molded coal suitable for being placed in the coal sample bin 13-1, opening a side panel of an air outlet of the coal sample bin 13-1, placing the prefabricated coal sample in the coal sample bin 13-1, installing the side panel to the side surface of the coal sample bin 13-1, and sealing. Starting the loading pump 12-1 to enable the loading plate 12-4 to be tightly attached to the upper surface of the coal sample, and then closing the loading pump 12-1;
and thirdly, opening a valve of a gas cylinder 11-1, and allowing the high-pressure gas to flow through a pressure reducing valve 11-2 and a stop valve 11-3 and enter a buffer tank 11-4. After gas with certain pressure is filled into the buffer tank 11-4, closing a valve of a gas cylinder 11-1, opening a manual valve 11-5, filling gas into a coal sample bin 13-1 to enable the coal sample to be in a gas occurrence state meeting experimental conditions, and closing the manual valve 11-5 after the gas filling is finished;
and fourthly, the loading pump 12-1 is started again, certain pressure is applied to the coal sample, and meanwhile gas in the coal sample bin 13-1 is pumped out under the action of the program-controlled adjustable extraction pump 14-3, so that the extraction effect of the coal bed gas is simulated. In the process, the acoustic emission probe 22-1 records the internal damage condition of the coal sample under the action of pressure and uploads the internal damage condition to the data acquisition instrument 23-3 through the acoustic emission amplifier 22-2. After the stress loading is finished, the loading pump 12-1 is closed.
And fifthly, continuing pumping the gas in the coal sample bin 13-1 and the connecting pipeline by the program-controlled adjustable pumping pump 14-3, opening a side panel of an air outlet of the coal sample bin 13-1 after pumping the gas, and measuring the strain of the coal body in the coal sample bin 13-1 by the non-contact full-field strain measuring device 21.
Sixthly, in the whole experiment process, the data acquisition instrument 23-3 monitors and records data of a pressure gauge 23-1, a flow sensor 23-2, a loading pump 12-1, a pressure gauge 23-4 and a flow sensor 23-5 which are arranged between the coal sample bin 13-1 and the pneumatic valve 14-1 and uploads the data to the monitoring host 23-6.
Seventhly, after the experiment is finished, starting the loading pump 12-1, restoring the loading plate 12-4 to the original position, opening the coal sample bin 13-1, taking out the coal sample, and cleaning residual coal in the coal sample bin 13-1; and opening the manual valve 11-5 to discharge the gas in the buffer tank 11-4.
As shown in FIG. 2, FIG. 2 is a schematic view of a radial groove 13-2 on the end face of a side plate of a coal sample bin 13-1, the size of the side plate of the coal sample bin 13-1 is 200mm multiplied by 200mm, the pressure resistance is 20Mp, and the side plate is machined from a stainless steel forging. Radial grooves 13-2 are processed on the side panels of the left air inlet and the right air outlet of the coal sample bin 13-1, the groove lines are concentric circles, the distance is 15mm, and the groove depth is 0.5 mm. When gas enters the coal sample bin 13-1 from the left side panel and flows out of the coal sample bin 13-1 from the right side panel, the gas is firstly diffused in a groove line, the process that the gas is converted from point diffusion to surface diffusion is realized, the environmental conditions of the coal sample are more truly simulated, grooves are carved on a plane plate in a concentric circle mode on the side panel of the coal sample bin 13-1, two obliquely symmetrical grooves are used for communicating the grooves of the concentric circle, and the grooves of all the grooves are the same in depth and are on the same plane.
As shown in fig. 3, fig. 3 is a schematic diagram of arrangement holes of acoustic emission sensors in a coal sample bin 13-1, in order to accurately monitor the damage of a coal sample at different positions in each direction in the coal sample loading process, the arrangement holes of the acoustic emission sensors are respectively arranged on four side surfaces of the coal sample bin 13-1, and the arrangement holes of each side surface are arranged in a cross manner, so that the sensors are in close contact with the coal sample. The acoustic emission response generated in the loading and unloading process of the coal sample can be recorded, and the internal damage condition of the coal sample can be conveniently researched.
Claims (10)
1. A multi-field coupling dynamic characteristic experiment system for graded loading and unloading coal bodies is characterized by comprising an experiment device and a monitoring device;
the experimental device comprises an inflating device, a stress loading and unloading device, a seepage desorption device and a gas extraction device;
the gas charging device comprises a gas cylinder (11-1), a manual valve (11-5), a pressure reducing valve (11-6) and a pneumatic valve (11-7); the seepage desorption device comprises a coal sample bin (13-1), and the stress loading and unloading device comprises a loading pump (12-1), a loading oil cylinder (12-2), a piston rod (12-3) and a loading plate (12-4); the gas extraction device (14) comprises a pneumatic valve (14-1), a stop valve (14-2) and an extraction pump (14-3);
the coal sample bin (13-1) is of a cavity structure, a gas inlet and a gas outlet are arranged on the coal sample bin (13-1), the gas cylinder (11-1) is communicated with the gas inlet of the coal sample bin (13-1) through a gas pipeline, and a manual valve (11-5), a pressure reducing valve (11-6) and a pneumatic valve (11-7) are sequentially arranged on the gas pipeline; the gas outlet of the coal sample bin (13-1) is communicated and connected with a gas extraction pump (14-3) in a gas extraction device through a gas transmission pipeline, and a pneumatic valve (14-1) and a stop valve (14-2) are sequentially arranged on the gas transmission pipeline along the gas flow direction;
the loading oil cylinder (12-2) is arranged on the outer side wall of the coal sample bin (13-1) and is in sealing connection with the outer side wall of the coal sample bin, the loading pump (12-1) is connected with the inner cavity of the loading oil cylinder (12-2), a piston rod (12-3) is arranged in the inner cavity of the loading oil cylinder (12-2), a loading plate (12-4) is arranged at the end part of the piston rod (12-3), and the loading plate (12-4) is in sealing connection with the side wall of the coal sample bin (13-1);
the monitoring system comprises a non-contact full-field strain measuring device (21), an acoustic emission monitoring device and a multi-parameter measurement and control device;
the acoustic emission monitoring device (22) comprises an acoustic emission probe (22-1) and an acoustic emission amplifier (22-2); the multi-parameter measurement and control device (23) comprises a first pressure gauge (23-1), a first flow sensor (23-2), a data acquisition instrument (23-3), a pressure gauge (23-4) and a monitoring host (23-6);
the first flow sensor (23-2) and the first pressure gauge (23-1) are arranged on a gas pipeline of the gas cylinder (11-1), and the output ends of the first flow sensor (23-2) and the first pressure gauge (23-1) are connected with the input end of the data acquisition instrument (23-3); the acoustic emission probe (22-1) is arranged on the side wall of the coal sample bin (13-1), the output end of the acoustic emission probe (22-1) is connected with the input end of an acoustic emission amplifier (22-2), the output end of the acoustic emission amplifier (22-2) is connected with the input end of a data acquisition instrument (23-3), and the output end of the data acquisition instrument (23-3) is connected with a monitoring host computer (23-6);
the non-contact full-field strain measuring device (21) is arranged on the outer side of the air outlet of the coal sample bin (13-1), and the output end of the non-contact full-field strain measuring device (21) is connected with the monitoring host (23-6).
2. The system for the multi-field coupling dynamic characteristic experiment of the staged loading and unloading coal body according to claim 1, wherein the inflation device (11) further comprises a pressure reducing valve (11-2), a stop valve (11-3) and a buffer tank (11-4), the buffer tank (11-4) is connected with the gas outlet of the gas cylinder (11-1) through a gas transmission pipeline, and the pressure reducing valve (11-2) and the stop valve (11-3) are sequentially arranged on the gas transmission pipeline; the other end of the buffer tank (11-4) is connected with the inner cavity of the coal sample bin (13-1).
3. The system for the multi-field coupling dynamic characteristic experiment of the graded loading and unloading coal body according to claim 1, wherein the coal sample bin (13-1) is machined by adopting a forged piece, a detachable upper end cover is arranged at the upper end of the coal sample bin (13-1), and a loading oil cylinder (12-2) is arranged on the upper end cover.
4. The system for the multi-field coupling dynamic characteristic experiment of the graded loading and unloading coal body according to claim 1, wherein the side walls of the air inlet and the air outlet of the coal sample bin (13-1) are provided with I-shaped radial grooves (13-2).
5. The system for the multi-field coupling dynamic characteristic experiment of the graded loading and unloading coal body according to claim 1, wherein a second pressure gauge (23-4) and a second flow sensor (23-5) are arranged on a gas transmission pipeline between a gas outlet of the coal sample bin (13-1) and an extraction pump (14-3), and the second pressure gauge (23-4) and the second flow sensor (23-5) are connected with an input end of a data acquisition instrument (23-3).
6. The multi-field coupling dynamic characteristic experiment system for the graded loading and unloading coal body according to claim 1, wherein the extraction pump (14-3) is a program-controlled adjustable extraction pump.
7. The system for the multi-field coupling dynamic characteristic experiment of the graded loading and unloading coal body according to claim 1, wherein an internal cavity of the coal sample bin (13-1) is of a rectangular structure, the four side walls of the rectangular cavity are provided with acoustic emission probes (22-1), and the acoustic emission probes (22-1) are in close contact with the coal sample.
8. The system for the multi-field coupling dynamic characteristic experiment of the graded loading and unloading coal body according to claim 1, wherein the acoustic emission probes (22-1) in the coal sample bin (13-1) are arranged in a cross manner.
9. A multi-field coupling dynamic characteristic experiment method for graded loading and unloading coal bodies is characterized in that based on any one of claims 1 to 8, the multi-field coupling dynamic characteristic experiment system for graded loading and unloading coal bodies comprises the following steps,
step 1, prefabricating a coal body into a coal sample placed in a coal sample bin (13-1), opening a side panel of an air outlet of the coal sample bin (13-1), placing the prefabricated coal sample into the coal sample bin (13-1), installing the side panel to the side of the coal sample bin (13-1), and sealing; starting the loading pump (12-1), enabling the loading plate (12-4) to be tightly attached to the upper surface of the coal sample, and then closing the loading pump (12-1);
step 2, opening a valve of a gas cylinder (11-1), filling gas into a coal sample bin (13-1) to enable the coal sample to be in a gas occurrence state meeting experimental conditions, and closing a manual valve (11-5) after the gas filling is finished;
step 3, starting the loading pump (12-1) again, applying pressure to the coal sample, and simultaneously pumping out gas in the coal sample bin (13-1) by using the pumping out pump (14-3) to simulate the pumping out effect on the coal bed gas; the acoustic emission probe (22-1) records internal damage data of the coal sample under the action of pressure, and transmits the internal damage data to the data acquisition instrument (23-3) through the acoustic emission amplifier (22-2); after the stress loading is finished, the loading pump (12-1) is closed;
step 4, the gas in the coal sample bin (13-1) and the connecting pipeline is continuously pumped by the extraction pump (14-3), after the gas pumping is finished, a side panel of a gas outlet of the coal sample bin (13-1) is opened, and the non-contact full-field strain measuring device (21) measures the strain of the coal body in the coal sample bin (13-1);
step 5, the data acquisition instrument (23-3) monitors and records data of the first pressure gauge (23-1), the first flow sensor (23-2), the loading pump (12-1) and the coal sample bin (13-1) and uploads the data to the monitoring host (23-6);
and 6, after the experiment is finished, starting the loading pump (12-1), restoring the loading plate (12-4) to the original position, opening the coal sample bin (13-1), taking out the coal sample, and cleaning residual coal in the coal sample bin (13-1).
10. The experimental method for the multi-field coupling dynamic characteristics of the graded loading and unloading coal bodies as claimed in claim 9, wherein in the step 2, a valve of a gas cylinder (11-1) is opened, and high-pressure gas flows through a pressure reducing valve (11-2) and a stop valve (11-3) and enters a buffer tank (11-4); after gas with certain pressure is filled into the buffer tank (11-4), the valve of the gas cylinder (11-1) is closed, the manual valve (11-5) is opened, gas is filled into the coal sample bin (13-1), so that the coal sample is in a gas occurrence state meeting experimental conditions, and after the gas filling is finished, the manual valve (11-5) is closed.
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