CN110631937A - Testing arrangement that circulation absorption expansion deformation is anti-reflection to coal body fatigue damage - Google Patents
Testing arrangement that circulation absorption expansion deformation is anti-reflection to coal body fatigue damage Download PDFInfo
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Abstract
A testing device for fatigue damage and permeability increase of coal bodies by cyclic adsorption expansion deformation applies pressure to coal cores through an axial compression plunger loading pump and a ring compression plunger loading pump; the air pressure control system generates circulating air inlet end pressure with specific frequency, waveform and pressure at the front end of the coal core, and the monitoring system acquires the gas pressure at the front end and the rear end of the sample, the matrix strain of the sample and the axial displacement data; the invention has good sealing performance and can avoid the leakage of liquid and gas in the long-term test process; the pressure of the front-end air inlet end is controlled by a computer program, the pressure of the air inlet end with complex type and specific duration can be realized, the pressure control precision is high, manual operation is not needed, automatic measurement and recording of long-term tests are realized, and the permeability increasing rule of cyclic adsorption expansion deformation of different schemes on coal bodies is effectively measured; and the quantitative calculation of the sample damage degree caused by the cyclic adsorption expansion deformation is realized by measuring the matrix strain and the axial displacement of the sample in real time.
Description
Technical Field
The invention relates to a device for coal fatigue damage, in particular to a device for testing the permeability increase of coal fatigue damage through cyclic adsorption expansion deformation, and belongs to the technical field of coal rock mechanical testing.
Background
For the low gas extraction efficiency of most coal seams in China, increasing the gas permeability of the coal seams by adopting various technical means is the most effective method for improving the gas extraction efficiency. The current active measures for enhancing the permeability of coal seams are generally as follows: loosening blasting, hydraulic fracturing, hydraulic cave making, hydraulic slotting, hydraulic punching and the like. The loose blasting adopts the impact stress wave to cause the damage of the coal body, but the strength of the soft coal body is low, the propagation resistance of the impact stress wave is large, and therefore the anti-reflection range is small; the hydraulic fracturing mainly generates large-range expansion of cracks by means of the elastic brittleness characteristic of coal rock mass, and the ductility and toughness of the coal bed are strong, so that the hydraulic fracturing effect of the coal bed is determined to be poor essentially; the method for hydraulic cave-making, hydraulic seam-cutting and hydraulic punching adopts high-pressure water to destroy the coal body, generates pressure-relief space in the coal seam and generates a fracture zone in a certain range. Due to the development of a pore structure in the coal body, along with the adsorption and desorption of coal on gas, the expansion deformation of the gas adsorbed by the coal and the contraction deformation of the desorbed gas occur, and the cycle deformation can cause the microcrack expansion of the coal body and improve the permeability of the coal body.
At present, similar test equipment directly adopts gas cylinder pressure to carry out pulse fracturing on coal bodies, the pressure and the frequency of a gas inlet end cannot be quantitatively controlled, and complex operation is required to be carried out manually.
Disclosure of Invention
The invention aims to provide a testing device for testing the fatigue damage permeability increase of coal bodies by cyclic adsorption expansion deformation, which can realize automatic measurement and recording of long-term tests, can effectively measure the influence rule of different types of cyclic adsorption expansion deformation on the damage and permeability of the coal bodies, and quantitatively analyze the fatigue damage degree and permeability increase effect in the coal bodies.
In order to achieve the purpose, the invention provides a device for testing fatigue damage and permeability increase of a coal body by cyclic adsorption expansion deformation, which comprises a pressure-bearing cavity and a rubber sleeve, wherein the side surface of a coal core is wrapped by the rubber sleeve and then placed in the pressure-bearing cavity; one end of the pressure-bearing cavity is hermetically connected with a plug I matched with the thread on the inner wall of the pressure-bearing cavity, an axial piston matched with the inner wall of the plug I is hermetically and slidably connected inside the plug I, and the axial piston is tightly attached to one end of the coal core; the outer wall of the pressing cap I is in threaded fit connection with the inner wall of the plug I, and the inner wall of the pressing cap I is in sealed sliding connection with one end of the axial piston; the axial piston is connected with the axial compression plunger loading pump through a pipeline;
the other end of the pressure-bearing cavity is hermetically connected with a plug II matched with the thread on the inner wall of the pressure-bearing cavity to fix the axial displacement of the coal core; the outer wall of the pressing cap II is in threaded fit connection with the inner wall of the pressure-bearing cavity, and a sealing washer is arranged between the pressing cap II and the plug II to seal and fix the plug;
the gas cylinder is connected with the gas inlet end of the electronic pressure controller through a pipeline, and a valve II is arranged on the pipeline; an air outlet end pipeline of the electronic pressure controller penetrates through the axial piston and then is connected with one end of the coal core, and a vacuum pump provided with a valve I is connected to a pipeline connecting the air outlet end of the electronic pressure controller and the coal core;
the fluid channel at the other end of the coal core is connected with the standard container through a pipeline, and a valve III is arranged on the pipeline;
a strain gauge is pasted on the surface of the coal core, and a strain gauge lead penetrates through the surface of the plug II and then is connected to a strain acquisition instrument;
the pressure sensor I is arranged on a pipeline connecting the air outlet end of the electronic pressure controller with the coal core, and the pressure sensor II is arranged on a pipeline connecting the coal core with the standard container; the displacement sensor is axially arranged and fixed on the plug I, the probe is abutted against an extension rod of the axial piston, and the axial displacement of the coal core is obtained by measuring the moving distance of the axial piston;
the control computer is respectively connected with the electronic pressure controller, the pressure sensor I, the pressure sensor II, the strain acquisition instrument and the displacement sensor through cables and is used for controlling data signals of the electronic pressure controller, and acquiring data of the pressure sensor I, the pressure sensor II, the strain acquisition instrument and the displacement sensor.
In order to further increase the sealing effect of the axial piston and the rubber sleeve, the inner diameters of the two ends of the rubber sleeve are set to be larger than the inner diameter of the side wrapping position of the rubber sleeve and the coal rock core, and one end, connected with the bearing cavity, of the plug I can be embedded between the rubber sleeve and the axial piston.
In order to further increase the sealing effect and isolate the high-pressure liquid in the pressure-bearing cavity, a chuck is sleeved at the joint of the rubber sleeve and the plug II; in order to fix the plug II and fix the position of the right end of the coal core unchanged, an annular snap ring is sleeved at the joint of the bearing cavity and the plug II, and the joint of the annular snap ring and the chuck is connected by adopting a concave-convex structure.
In order to further enhance the testing precision of the device, the electronic pressure controller provided by the invention is selected to be composed of an electric pneumatic controller ER5000 and a pressure regulating valve 26-2065V24A181, the update rate of the pressure regulating valve is 25ms/s, the pressure rise time of 1 cubic foot volume from 0.7bar to 6.2bar is 350 milliseconds, the pressure range is 0.07-10 MPa, and the pressure precision is +/-0.05% FSO.
The strain gauge lead wire is of a flat sheet type, penetrates through the surface of the plug II and is extruded through the axial compression of the plug II, and therefore the sealing performance of the whole device is guaranteed.
The strain acquisition instrument adopts a TST3820 static signal testing system, has 16 channels, has the highest sampling frequency of 5Hz, the resolution of 1 mu epsilon and the null shift of less than or equal to 3 mu epsilon/24 h, and has small volume, convenient use and channel self-checking function.
The displacement sensor adopts an SPNL12A rebound type small-size LVDT displacement sensor, the measuring range is 0-10mm, the precision is 1 mu m, and the dynamic characteristic is 10 Hz.
The type of the strain gauge is BX120-0.5AA, the size of the substrate is 3.6X 3.6mm, the size of the silk screen is 0.5X 0.5mm, and the sensitivity coefficient is 2.0 +/-1%.
The pressure sensor I and the pressure sensor II are UNIK5000 series universal industrial pressure sensors, the model is PTX5072, the measuring range is 0.1-10 MPa, the measuring precision is 0.1% FS, and the pressure at the front end and the rear end of a sample can be accurately measured.
The metering pump is a common experimental device and can provide preset flow rate and pressure control, and the axial pressure plunger loading pump and the annular pressure plunger loading pump are both metering pumps; the gas cylinder is a methane gas storage container for testing; the vacuum pump is a common piston type gas vacuum pump; and the valve I, the valve II and the valve III are high-pressure gas needle valves.
Compared with the prior art, the coal core is wrapped by the rubber sleeve and then is loaded into the pressure-bearing cavity, and pressure is applied to the coal core through the axial pressure plunger loading pump and the annular pressure plunger loading pump; the system comprises an electronic pressure controller, a valve I, a valve II, a valve III, a vacuum pump and a gas cylinder, wherein a gas pressure control system which consists of the electronic pressure controller, the valve I, the valve II, the valve III, the vacuum pump and the gas cylinder generates circulating gas inlet end pressure with specific frequency, waveform and pressure on the front end of a coal core, and a monitoring system which consists of a pressure sensor I, a pressure sensor II, a standard container, a displacement sensor, a strain gauge lead and a strain acquisition instrument realizes the acquisition of gas pressure at the front end and the rear end of a sample, sample matrix; in the whole test process, firstly, the control computer sets the specific gas pressure generated at the outlet end of the electronic pressure controller, and after the pressures at the front end and the rear end are equal, the permeability of the coal core before permeability increase is calculated by a pulse attenuation method; then, the control computer sets the circulating gas pressure generated by the outlet end of the electronic pressure controller for a specific time to promote the coal core to circularly expand and contract to deform so as to generate fatigue damage; and setting the pressure of the air inlet end generated at the front end of the sample through the electronic pressure controller, and calculating by adopting a pulse attenuation method to obtain the permeability value of the coal body subjected to anti-reflection by cyclic adsorption expansion deformation. The invention has simple structure and good sealing performance, and can avoid the leakage of liquid and gas in the long-term test process; the pressure of the front-end air inlet end is controlled by a computer program, the pressure of the air inlet end with complex type and specific duration can be realized, the pressure control precision is high, manual operation is not needed, automatic measurement and recording of long-term tests are realized, and the permeability increasing rule of cyclic adsorption expansion deformation of different schemes on coal bodies is effectively measured; and the quantitative calculation of the sample damage degree caused by the cyclic adsorption expansion deformation is realized by measuring the matrix strain and the axial displacement of the sample in real time.
Drawings
Fig. 1 is a schematic diagram of the working principle of the present invention.
In the figure: 1. the axial compression plunger loading pump comprises an axial compression plunger loading pump body 2, an annular compression plunger loading pump body 3, a gas cylinder 4, a vacuum pump 5, valves I and 6, valves II and 7, an electronic pressure controller 8, pressure sensors I and 9, pressure sensors II and 10, valves III and 11, a standard container 12, a pressure-bearing cavity 13, a rubber sleeve 14, a strain gauge 15, a strain gauge lead wire 16, a clamping head 17, an annular clamping ring 18, plugs II and 19, a gasket 20, a compression cap II and 21, a strain acquisition instrument 22, a plug I and 23, an axial piston 24, a displacement sensor 25, compression caps I and 26 and a control computer.
Detailed Description
The invention will be further explained with reference to the drawings.
As shown in fig. 1, the device for testing fatigue damage and permeability increase of coal by cyclic adsorption expansion deformation comprises a pressure-bearing cavity 12 and a rubber sleeve 13, wherein the side surface of a coal core is wrapped by the rubber sleeve 13 and then placed in the pressure-bearing cavity 12, the rubber sleeve 13 isolates high-pressure liquid in the pressure-bearing cavity 12, the device also comprises an axial piston 23, an electronic pressure controller 7, a gas cylinder 3, a vacuum pump 4, a pressure sensor i 8, a pressure sensor ii 9, a standard container 11 and a displacement sensor 24, and the side surface of the pressure-bearing cavity 12 is connected with a ring pressure plunger loading pump 2 through a pipeline; one end of the pressure bearing cavity 12 is hermetically connected with a plug I22 matched with the thread of the inner wall of the pressure bearing cavity, the plug I22 is used for isolating high-pressure liquid in the pressure bearing cavity 12, an axial piston 23 matched with the inner wall of the plug I22 is hermetically and slidably connected inside the plug I22, the axial piston 23 is tightly attached to one end of the coal rock core, and the axial piston 23 can freely slide left and right; the outer wall of the pressing cap I25 is in threaded fit connection with the inner wall of the plug I22, and the inner wall of the pressing cap I25 is in sealed sliding connection with one end of the axial piston 23; the axial piston 23 is connected with the axial compression plunger loading pump 1 through a pipeline;
a plug II 18 matched with the inner wall thread of the pressure bearing cavity 12 is connected to the other end of the pressure bearing cavity in a sealing mode to fix the axial displacement of the coal core; the outer wall of the pressure cap II 20 is in threaded fit connection with the inner wall of the pressure bearing cavity 12, a sealing washer 19 is arranged between the pressure cap II 20 and the plug II 18, and the plug is sealed and fixed, so that the position of the right end of the coal rock core is guaranteed to be unchanged;
the gas cylinder 3 is connected with the gas inlet end of an electronic pressure controller 7 through a pipeline, and a valve II 6 is arranged on the pipeline; an air outlet end pipeline of the electronic pressure controller 7 penetrates through the axial piston 23 and then is connected with one end of the coal core, and a vacuum pump 4 provided with a valve I5 is connected to a pipeline connecting the air outlet end of the electronic pressure controller 7 with the coal core;
the fluid channel at the other end of the coal core is connected with a standard container 11 through a pipeline, and a valve III 10 is arranged on the pipeline;
a strain gauge 14 is attached to the surface of the coal core, and the strain gauge 14 penetrates through the surface of a plug II 18 through a strain gauge lead 15 and then is connected to a strain acquisition instrument 21;
the pressure sensor I8 is arranged on a pipeline connecting the air outlet end of the electronic pressure controller 7 with the coal core, and the pressure sensor II 9 is arranged on a pipeline connecting the coal core with the standard container 11; the displacement sensor 24 is axially arranged and fixed on the plug I22, the probe is abutted against an extension rod of the axial piston 23, and the axial displacement of the coal core is obtained by measuring the moving distance of the axial piston;
the control computer 26 is respectively connected with the electronic pressure controller 7, the pressure sensor I8, the pressure sensor II 9, the strain acquisition instrument 21 and the displacement sensor 24 through cables and is used for controlling data signals of the electronic pressure controller 7 and acquiring data of the pressure sensor I8, the pressure sensor II 9, the strain acquisition instrument 21 and the displacement sensor 24; the data signal of the electronic pressure controller 7 is controlled by the control computer 26 and is used for generating various required air inlet end pressures and generating circulating air inlet end pressures with specific frequency, pressure and waveform, and the coal core generates adsorption expansion deformation and desorption contraction deformation circularly under the action of adsorbed gas, so that the coal core is damaged in different degrees through different degrees of circulating loading and unloading.
The inner diameters of two ends of the rubber sleeve 13 are larger than the inner diameter of the side wrapping position of the rubber sleeve 13 and the coal core, and one end, connected with the pressure bearing cavity 12, of the plug I22 is embedded between the rubber sleeve 13 and the axial piston 23.
The joint of the rubber sleeve 13 and the plug II 18 is sleeved with a chuck 16, the joint of the pressure bearing cavity 12 and the plug II 18 is sleeved with an annular snap ring 17, and the joint of the annular snap ring 17 and the chuck 16 is connected by adopting a concave-convex structure.
The electronic pressure controller 7 consists of an electric pneumatic controller ER5000 and a pressure regulating valve 26-2065V24A181, the update rate of the pressure regulating valve is 25ms/s, the pressure rise time of 1 cubic foot from 0.7bar to 6.2bar is 350ms, the pressure range is 0.07-10 MPa, and the pressure precision is +/-0.05% FSO.
The strain gauge leads 15 are of a flat sheet type.
The strain acquisition instrument 21 adopts a TST3820 static signal test system, 16 channels are used in total, the highest sampling frequency is 5Hz, the resolution is 1 mu epsilon, and the null shift is less than or equal to 3 mu epsilon/24 h.
The displacement sensor 24 adopts an SPNL12A resilient type short-size LVDT displacement sensor, the measuring range is 0-10mm, the precision is 1 μm, and the dynamic characteristic is 10 Hz.
The strain gauge 14 has the model of BX120-0.5AA, the size of a substrate of 3.6X 3.6mm, the size of a wire grid of 0.5X 0.5mm and the sensitivity coefficient of 2.0 +/-1%.
The pressure sensor I8 and the pressure sensor II 9 are UNIK5000 series universal industrial pressure sensors, the model is PTX5072, the measuring range is 0.1-10 MPa, the measuring precision is 0.1% FS, and the pressure at the front end and the rear end of a sample can be accurately measured.
The axial pressure plunger loading pump 1 and the annular pressure plunger loading pump 2 are metering pumps; the gas cylinder 3 is a methane gas storage container for testing; the vacuum pump 4 is a common piston type gas vacuum pump; the valve I5, the valve II 6 and the valve III 10 are high-pressure gas needle valves.
Example 1
A testing device for permeability increase of coal fatigue damage by cyclic adsorption expansion deformation comprises the following steps:
filling a sample: firstly, drying a coal core, and putting the coal core in a 45 ℃ oven for drying for 24 hours; determining a complete area of the surface of the coal core, polishing the complete area by using abrasive paper, sticking the strain gauge 14 to the surface of the coal core along the axial direction by using an adhesive, sticking 4 groups in total, and welding a lead 15 of the strain gauge with a lead 14 of the strain gauge together; the coal core is wrapped by a rubber sleeve 13 and is arranged in the pressure bearing cavity 12, and the rubber sleeve 13 isolates high-pressure liquid in the pressure bearing cavity 12;
measuring initial permeability: checking the working states of a displacement sensor 24, a strain acquisition instrument 21, a pressure sensor I8, a pressure sensor II 9 and an electronic pressure controller 7; loading the coal core to 10MPa pressure at the speed of 1MPa/min through an axial pressure plunger loading pump 1 and a ring pressure plunger loading pump 2, and checking whether liquid leakage exists at each interface of the device; closing the valve II 6, opening the valve I5 and the valve III 10, opening the vacuum pump 4 after the confining pressure is stable, and vacuumizing the coal core for 24 hours; closing valve I5, opening valve II 6, valve III 10 and CH4The air pressure of the air outlet end of the electronic pressure controller 7 of the air bottle 3 is set to be 5MPa through the control computer 26, after the pressures of the pressure sensor I8 and the pressure sensor II 9 are equal, the air pressure of the air outlet end is set to be 5.1MPa through the electronic pressure controller 7, and the front-end pulse pressure is realized; after the measured pressure data of the pressure sensor II 9 is increased to 5.1MPa, fitting the data of the pressure sensor I8 and the pressure sensor II 9 through a formula (1) to obtain a pressure difference slope v, converting the formula (2) to obtain a formula (3), and calculating through the formula (3) to obtain the value of the permeability k before cyclic deformation fatigue damage;
in the formula: p is a radical ofup(t)-pdn(t) the pressure difference is measured by the pressure sensor I and the pressure sensor II;
Δ p is an initial differential pressure of 0.1 MPa;
t is the test elapsed time;
v is the pressure difference slope of the pressure sensor I and the pressure sensor II;
a is the cross-sectional area of the coal core;
mu is the gas viscosity coefficient;
beta is the gas compression coefficient;
l is the length of the coal core;
Vdnis the standard container volume, 50 mL;
k is the permeability;
③ absorbing, expanding, deforming and increasing the permeability: closing the valve III 10, setting the pressure at the air outlet end of the electronic pressure controller 7 to be 5MPa through the control computer 26, keeping for 2s, then reducing the pressure to be 1MPa through the electronic pressure controller 7, keeping for 2s, and then circularly adjusting the pressure at the air outlet end of the electronic pressure controller 7 to be changed between 5MPa and 1MPa for 1 h;
and fourthly, permeability determination after permeability increase: opening a valve III 10, repeatedly testing the permeability of the coal core according to the pulse attenuation method in the second step, and comparing the measurement results of the two times to obtain the permeability increasing effect of the adsorption expansion deformation on the coal core;
calculating damage degree: it is assumed that the difference in strain before and after the anti-reflection measured by the 4 sets of strain gauges 14 is Δ ∈ respectively1、Δε2、Δε3、Δε4The axial displacement difference before and after the permeability increase measured by the displacement sensor 24 is delta d, and the strain gauge position has no crack, so that the measured strain matrix is considered to be the strain generated by adsorption, and the matrix axial strain delta epsilon can be obtainedmComprises the following steps:
the deformation measured by the displacement sensor 24 gives the overall axial strain Δ ∈ of the sample:
since Delta epsilon is the deformation of the sample as a whole, including the fracture and the matrixThe axial strain delta epsilon generated by the crack can be obtained by the formula (4) and the formula (5) because of the same deformationfComprises the following steps:
the calculated fracture strain is the result of micro-fracture and fracture expansion of the coal body caused by cyclic expansion deformation;
sixthly, finishing the test: maintaining the data; closing the gas cylinder 3, reducing the gas pressure to 0 through the electronic pressure controller 7, and then reducing the axial pressure plunger loading pump 1 and the annular pressure plunger loading pump 2 to 0; and (5) disassembling the electronic pressure controller 7, the monitoring system and the confining pressure loading system, and taking out the coal core.
The device can generate the pressure of the circulating air inlet end with specific frequency, waveform and pressure, realize the circulating loading and unloading deformation of the coal core and increase the fatigue damage degree of the coal core; the electronic pressure controller 7 can automatically generate the front-end air pressure of a required waveform according to program setting to realize the anti-reflection test at a specific time, the air pressure change response speed is high, and the highest pulse frequency of the air inlet end can reach 50 Hz; the monitoring data is automatically recorded by the control computer, the whole test process is fully automatically carried out, and manual operation is not needed; the air pressure control system of the device can generate small pulse pressure on the coal core, the permeability of the core is calculated through the pressure difference between the pressure sensor I and the pressure sensor II, and the permeability increasing effect of cyclic adsorption expansion deformation is measured at any time; the strain gauge measures the strain of the coal matrix under the influence of pore pressure and adsorption deformation, and the LVDT displacement sensor measures the axial displacement of the whole sample fracture and the matrix under the influence of pore pressure and adsorption deformation; the cyclic adsorption expansion deformation only causes the new growth and expansion of the coal body fracture to cause the sample expansion deformation, and the measured matrix deformation is irrelevant to the damage caused by the cyclic adsorption expansion deformation, so that the deformation amount independently generated by the sample fracture can be calculated through the monitoring data of the device, and the qualitative calculation of the coal core damage degree under the action of the cyclic adsorption expansion deformation with different degrees is realized.
Claims (10)
1. A testing device for improving permeability of coal body fatigue damage by cyclic adsorption expansion deformation comprises a pressure-bearing cavity (12) and a rubber sleeve (13), wherein the side surface of a coal core is wrapped by the rubber sleeve (13) and then placed in the pressure-bearing cavity (12), and is characterized by further comprising an axial piston (23), an electronic pressure controller (7), a gas cylinder (3), a vacuum pump (4), a pressure sensor I (8), a pressure sensor II (9), a standard container (11) and a displacement sensor (24), wherein the side surface of the pressure-bearing cavity (12) is connected with an annular pressure plunger loading pump (2) through a pipeline; one end of the pressure bearing cavity (12) is hermetically connected with a plug I (22) matched with the inner wall of the pressure bearing cavity in a threaded manner, an axial piston (23) matched with the inner wall of the plug I (22) is hermetically and slidably connected inside the plug I, and the axial piston (23) is tightly attached to one end of the coal core; the outer wall of the pressing cap I (25) is in threaded fit connection with the inner wall of the plug I (22), and the inner wall of the pressing cap I (25) is in sealed sliding connection with one end of the axial piston (23); the axial piston (23) is connected with the axial compression plunger loading pump (1) through a pipeline;
the other end of the pressure bearing cavity (12) is hermetically connected with a plug II (18) matched with the inner wall thread of the pressure bearing cavity to fix the axial displacement of the coal core; the outer wall of the pressing cap II (20) is in threaded fit connection with the inner wall of the pressure-bearing cavity (12), and a sealing washer (19) is arranged between the pressing cap II (20) and the plug II (18) to seal and fix the plug;
the gas cylinder (3) is connected with the gas inlet end of the electronic pressure controller (7) through a pipeline, and a valve II (6) is arranged on the pipeline; an air outlet end pipeline of the electronic pressure controller (7) penetrates through the axial piston (23) and then is connected with one end of the coal core, and a vacuum pump (4) provided with a valve I (5) is connected to a pipeline connecting the air outlet end of the electronic pressure controller (7) with the coal core;
the fluid channel at the other end of the coal core is connected with a standard container (11) through a pipeline, and a valve III (10) is arranged on the pipeline;
a strain gauge (14) is attached to the surface of the coal core, and a strain gauge lead (15) of the strain gauge (14) penetrates through the surface of the plug II (18) and then is connected to a strain acquisition instrument (21);
the pressure sensor I (8) is arranged on a pipeline connecting the air outlet end of the electronic pressure controller (7) with the coal core, and the pressure sensor II (9) is arranged on a pipeline connecting the coal core with the standard container (11); the displacement sensor (24) is axially arranged and fixed on the plug I (22), the probe is abutted against an extension rod of the axial piston (23), and the axial displacement of the coal core is obtained by measuring the moving distance of the axial piston;
the control computer (26) is respectively connected with the electronic pressure controller (7), the pressure sensor I (8), the pressure sensor II (9), the strain acquisition instrument (21) and the displacement sensor (24) through cables and is used for controlling data signals of the electronic pressure controller (7) and acquiring data of the pressure sensor I (8), the pressure sensor II (9), the strain acquisition instrument (21) and the displacement sensor (24).
2. The device for testing the fatigue damage and permeability increase of the coal body through cyclic adsorption expansion deformation according to claim 1, wherein the inner diameter of the two ends of the rubber sleeve (13) is larger than the inner diameter of the side wrapping part of the rubber sleeve (13) and the coal core, and one end of the plug I (22) connected with the pressure bearing cavity (12) is embedded between the rubber sleeve (13) and the axial piston (23).
3. The device for testing the coal fatigue damage permeability improvement by cyclic adsorption expansion deformation according to claim 2, wherein a chuck (16) is sleeved at the joint of the rubber sleeve (13) and the plug II (18), an annular snap ring (17) is sleeved at the joint of the pressure-bearing cavity (12) and the plug II (18), and the joint of the annular snap ring (17) and the chuck (16) is connected by adopting a concave-convex structure.
4. The device for testing the fatigue damage permeability of coal bodies by cyclic adsorption, expansion and deformation according to claim 3, wherein the electronic pressure controller (7) comprises an electric pneumatic controller ER5000 and a pressure regulating valve 26-2065V24A181, the update rate of the pressure regulating valve is 25ms/s, the pressure rise time of 1 cubic foot volume from 0.7bar to 6.2bar is 350ms, the pressure range is 0.07-10 MPa, and the pressure precision is +/-0.05% FSO.
5. The device for testing the fatigue damage and permeability increase of coal bodies by cyclic absorption expansion deformation according to claim 3, wherein the strain gauge lead wire (15) is of a flat sheet type.
6. The device for testing the fatigue damage and permeability increase of the coal body through cyclic adsorption swelling deformation according to claim 3, wherein the strain acquisition instrument (21) adopts a TST3820 static signal testing system, 16 channels are adopted in total, the highest sampling frequency is 5Hz, the resolution is 1 mu epsilon, and the null shift is less than or equal to 3 mu epsilon/24 h.
7. The device for testing the permeability of the coal body to fatigue damage by cyclic adsorption swelling deformation according to claim 3, wherein the displacement sensor (24) is a SPNL12A resilient type short-sized LVDT displacement sensor with a measuring range of 0-10mm, a precision of 1 μm and a dynamic characteristic of 10 Hz.
8. The device for testing the anti-reflection of the fatigue damage of the coal body caused by cyclic adsorption expansion deformation according to claim 3, wherein the type of the strain gauge (14) is BX120-0.5AA, the substrate size is 3.6X 3.6mm, the wire grid size is 0.5X 0.5mm, and the sensitivity coefficient is 2.0 +/-1%.
9. The device for testing fatigue damage and permeability increase of coal bodies through cyclic adsorption expansion deformation according to claim 3, wherein the pressure sensor I (8) and the pressure sensor II (9) are UNIK5000 series universal industrial pressure sensors, the model is PTX5072, the range is 0.1-10 MPa, the measurement precision is 0.1% FS, and the pressure at the front end and the pressure at the rear end of a sample can be accurately measured.
10. The device for testing the fatigue damage and permeability increase of the coal body by cyclic adsorption expansion deformation according to claim 3, wherein the axial pressure plunger loading pump (1) and the annular pressure plunger loading pump (2) both adopt metering pumps; the gas cylinder (3) is a methane gas storage container for testing; the vacuum pump (4) is a common piston type gas vacuum pump; the valve I (5), the valve II (6) and the valve III (10) are high-pressure gas needle valves.
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| CN112525791A (en) * | 2020-11-04 | 2021-03-19 | 中国矿业大学(北京) | Device and method for measuring permeability, integral strain and fracture strain of coal rock |
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