CN110542639A - true triaxial gas seepage test device with CT real-time scanning and method - Google Patents
true triaxial gas seepage test device with CT real-time scanning and method Download PDFInfo
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- CN110542639A CN110542639A CN201910955551.6A CN201910955551A CN110542639A CN 110542639 A CN110542639 A CN 110542639A CN 201910955551 A CN201910955551 A CN 201910955551A CN 110542639 A CN110542639 A CN 110542639A
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- 238000002591 computed tomography Methods 0.000 claims abstract description 26
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- 238000002474 experimental method Methods 0.000 claims abstract description 18
- 239000011148 porous material Substances 0.000 claims abstract description 11
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
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- 229910002027 silica gel Inorganic materials 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 claims description 4
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- 239000010959 steel Substances 0.000 claims description 3
- 230000035699 permeability Effects 0.000 abstract description 10
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
- G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
- G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
Abstract
the invention provides a true triaxial gas seepage test device with CT real-time scanning and a method thereof. The true triaxial pressure chamber comprises a cover plate and a barrel body; the support comprises a top plate, a bottom plate and an upright post, and devices in the CT scanning area are all made of carbon fiber materials; the loading device comprises an axial pressure, a lateral pressure and a confining pressure loading device, and the axial pressure, the lateral pressure and the confining pressure required by the experiment are provided; the gas seepage device controls gas to pass through the coal body and obtains the flow of the discharged gas, and the change of the permeability is researched; the CT scanning device comprises a CT radioactive source and a CT detector and is used for observing the internal change of the test piece in real time. The real-time matching of true triaxial stress-strain-seepage and CT is realized, and the method has important significance for researching the expansion of the coal rock body pore crack and the permeability evolution rule in the true triaxial stress state.
Description
Technical Field
the invention relates to physical simulation experiment research, in particular to a true triaxial gas seepage test device with CT real-time scanning and a method thereof.
background
The research on the deformation and damage characteristics and permeability of the coal rock mass has important significance for preventing and treating various dynamic disasters of underground mining work. The gas-containing coal layer is in a stable equilibrium state under the combined action of overlying strata pressure, tectonic stress and gas pressure. Under the influence of mining activities, along with the pore communication and crack expansion of coal bodies, local energy is gathered, the coal bodies gradually enter an unstable equilibrium state, and complex dynamic disasters of coal mines can be promoted once the coal bodies are disturbed.
The stress has great influence on the mechanical property and the seepage rule of the coal containing gas, and the true triaxial fluid-solid coupling system can accurately simulate and analyze the stress condition of the coal and rock mass in engineering and analyze the change rule of the strength, the deformation property and the permeability of the coal and rock mass under the condition of three-dimensional different stresses. The true triaxial fluid-solid coupling system can apply stress meeting objective conditions on each surface of the coal rock test piece, monitor the strain and permeability of the test piece in real time, realize loading modes of various stresses and further systematically and comprehensively disclose the relationship between strain and seepage.
The damage of the coal rock mass is usually started from micro cracks and micro pores in the coal rock mass, and finally, the coal rock mass is communicated with each other to cause macroscopic damage, so that the permeability is influenced, and the key point is to clear the damage and damage condition in the coal rock mass. And the CT scanning technology can observe the structural change in the coal rock mass and comprehensively know the change in the coal rock mass. However, due to the limitation of equipment, the CT scanning is often performed after the coal rock mass is unloaded from the true triaxial gas seepage experiment table, and the observation cannot be realized.
Therefore, the CT scanning technology is combined with the true triaxial seepage experiment system, real-time scanning in the true sense is realized, the intensity and deformation conditions of the coal rock mass under the condition of three-dimensional stress are researched, the change condition of the internal pore cracks is observed by means of a CT scanning image, the deformation of the coal rock mass, the expansion of the internal pore cracks and the coal rock mass gas seepage rule can be comprehensively researched by combining the permeability change rule, and comprehensive and systematic research is realized.
relevant to the present application are:
1. chinese patent CN201510409976.9 discloses a true triaxial shear seepage experimental apparatus of hot fluid-solid coupling based on coal bed gas, including test box and the special construction rubber tray of components of a whole that can function independently structural formula, the structure is simple and convenient, and the precision is high, and the authenticity, the accuracy and the reliability of simulation are high.
2. Chinese patent CN201610120372.2 proposes a true triaxial fluid-solid coupling coal seepage experimental apparatus, which comprises a loading unit, a fluid unit and a control unit, and can accurately simulate and analyze the permeability change rule of coal under the condition of three-dimensional unequal stress.
above two patents mainly relate to the gas seepage flow condition of research coal body under the true triaxial condition, because test device whole frame, support and staving etc. are made by metal material, the ray that the CT machine sent can not pierce through, can't realize the real-time cooperation of true triaxial tester and CT scanning. In order to understand the development condition of the pore cracks in the coal body, the conventional method is to unload the test piece and then perform CT scanning, but the test piece is inevitably damaged in the operation process, so that the error of the experimental result is caused.
3. The three-axis pressure chamber with CT scanning disclosed in Chinese patent CN201310471580.8 is used for observing and researching the microscopic change of mechanical properties of a test piece under the conventional three-axis pressure by matching with Micro-focus CT.
4 chinese patent CN201510577392.2 relates to a true triaxial experimental apparatus with CT real-time scanning system and method, including pressure chamber, support, loading device and scanner, can realize real-time coordination of true triaxial and CT scanning experiment, and has important meaning for researching expansion and evolution of micro-cracks and micro-holes in coal rock mass under true triaxial stress state.
Although the experimental device that two above-mentioned patents proposed can realize the loaded CT real-time scanning of coal petrography body, what relate to all is mechanical properties, and research test piece damage deformation law does not consider the change trend of the permeability of the inside gas of coal petrography body in the experimentation, can not carry out gas seepage flow research, can not carry out comprehensive, systematic research to the coal petrography body.
The invention content is as follows:
the invention aims to provide a test device which can carry out real-time scanning and can carry out fluid-solid coupling experiments by using gas as a fluid medium, and simulate and analyze the development change rule of stress-deformation-seepage-pore cracks of coal rock mass under the condition of three-dimensional stress.
In order to realize the purpose, the technical scheme is as follows: a true triaxial gas seepage test device with CT real-time scanning comprises a true triaxial pressure chamber, a bracket for bearing the test device, a loading device for providing axial pressure, lateral pressure and confining pressure for a coal rock test piece, a gas seepage device for providing a seepage environment for the test piece, and a CT scanning system capable of observing the coal rock test piece in real time, wherein the CT scanning system comprises radioactive sources and detectors arranged at the front side and the rear side of a true triaxial test machine, and a control/acquisition monitoring device; the true triaxial pressure chamber comprises a barrel body and a cover plate, wherein the barrel body is provided with a liquid inlet/gas port, a liquid discharge/gas port and a loading system position port; the bracket comprises a top bottom plate with a loading device base and an upright post connected with the top bottom plate; the loading device comprises pressure chambers at four positions of an upper position, a lower position, a left position and a right position, and a confining pressure loading hydraulic pump of related accessories of the pressure chambers; in order to realize real-time scanning of the CT system, the true triaxial pressure chamber, the bracket and the loading system part fittings in the CT scanning area are all made of carbon fiber materials.
The top plate and the bottom plate of the support are made of rectangular thick steel plates because scanning is not needed, pressure chamber bases are arranged on the inner side surfaces of the top plate and the bottom plate, and the upper pressure chamber and the lower pressure chamber are fixed on the bases.
The upper part of the barrel body is open, a central hole is formed in the central position of the bottom of the barrel body, a central hole is also formed in the position, opposite to the bottom of the barrel body, of the cover plate, the cover plate is connected with the barrel body through a flange, and an O-shaped ring is arranged at the connecting position of the cover plate and the barrel body.
The pressure head that is located upper and lower pressure chamber and includes pneumatic cylinder, piston compression leg and compression leg front end constitutes, goes up pressure chamber and lower pressure chamber piston compression leg and stretches into in the pressure chamber from apron and barrel head centre bore to be connected with the pressure head, finally with the axle load pass to on the coal rock mass test piece, the centre bore edge is provided with O type circle, guarantees the seal.
The same high horizontal symmetry position of staving left and right sides be equipped with the hole to be connected with left and right pressure chamber, the pressure chamber welding is on the staving, has the piston compression leg to stretch out in the pressure chamber, the pressure head is connected to the compression leg front end, the pressure head links to each other with the briquetting, can pass to the required side pressure of experiment on the coal rock body test piece, has the gasket between each briquetting, prevents to take place rigid collision.
The cover plate is provided with a liquid inlet and a pressure sensor, the bottom of the barrel body is provided with an exhaust port, the lower part of the barrel body is provided with a liquid outlet, the liquid inlet is connected with an external hydraulic pump through a conduit and matched with the liquid outlet, and the pressure sensor provides confining pressure required by experimental conditions for a test piece according to the numerical value on the pressure sensor.
Go up the pressure head and all be equipped with gas seepage flow passageway with pressure head inside down, outside high-pressure gas cylinder passes through the wire and connects through the gas inlet and the gas channel that last pressure head was predetermine, and the gas channel that pressure head was predetermine down links to each other with outside gas flowmeter through the bottom gas vent, and whole seepage flow device provides required gas environment for the experiment, and gas flowmeter reads the gas flow of flowing through the coal rock mass test piece.
Temperature control device has been preset to staving inside, can control the temperature environment of experiment, keeps the invariant of temperature, prevents to appear experimental error.
And O-shaped rings are arranged around each hole on the barrel body and the cover plate for sealing.
in the true triaxial pressure chamber, displacement sensors are arranged in the upper, lower, left, right, front and back 6 directions around the position of the coal rock mass test piece, and are connected with an external control/monitoring device through leads to monitor the strain change of the coal rock mass test piece in real time.
The edge of each briquetting all is equipped with the chamfer about the upper and lower pressure head, prevents that the rigidity contact between each loading subassembly from appearing, prevents to influence the experimental result on the one hand, and on the other hand is in order to prolong the life of equipment accessories.
The CT scanning device comprises CT radioactive sources and CT detectors which are arranged on the front side and the rear side of the true triaxial apparatus, and all accessories located in a scanning area are made of carbon fiber materials.
The true triaxial gas seepage test method with the CT real-time scanning is characterized by comprising the following steps of:
1) Firstly, pretreating a prepared coal rock test piece, then coating silica gel on the surface of the test piece, after the silica gel is dried, firmly wrapping the coal rock test piece by using a heat-shrinkable tube, and fixing the coal rock test piece on an upper pressure head and a lower pressure head by using a clamp;
2) placing the well-prepared test piece, installing an axial pressure and lateral pressure loading system in place, connecting a gas seepage device, filling hydraulic oil into a pressure chamber, and assembling a cover plate;
3) Turning on a control/monitoring device, and setting the experiment temperature to be constant;
4) Opening a gas tank valve, observing a flow value and keeping the reading constant, closing an exhaust valve after the value is kept constant, keeping the opening state of the gas tank valve unchanged, and enabling the coal rock mass test piece to constantly adsorb gas for 48 hours;
5) And (3) opening the exhaust valve after the constant time is 48 hours, loading axial pressure, lateral pressure and confining pressure for testing after the reading of the flowmeter is stabilized again, simultaneously recording the stress-strain-seepage change of the coal rock mass test piece, carrying out CT scanning until the test piece is destroyed, and acquiring the pore crack development change in the whole process by using a CT scanning device.
In the whole test process, the control/monitoring system records pressure reading, displacement change of the test piece in each direction, gas pressure, flowmeter reading and other information in the whole test process, and the CT scanning device scans the test piece at a required moment to obtain the development degree of the internal hole crack of the test piece.
The invention has the following positive effects:
1) All accessories in the scanning area of the experimental device are made of carbon fibers, and radioactive rays can penetrate through the accessory, so that the defect that the traditional experiment cannot carry out CT scanning in real time is overcome;
2) The invention combines a true triaxial fluid-solid coupling gas seepage system with a CT scanner, can realize the synchronous research of stress-strain-seepage-hole crack coupling, and has undoubtedly richer and more comprehensive research on coal and rock sample test pieces;
3) The device has very important significance for researching permeability change, real-time development of pore cracks and mutual relation rules of the coal rock mass test piece in a true triaxial stress state;
4) The invention greatly enriches the research in the field of true triaxial visualization and seepage experiments.
Drawings
FIG. 1 is a general view of the overall apparatus of the present invention
FIG. 2 is a front view of the overall apparatus of the present invention (the line head direction in the figure indicates the data transmission direction)
FIG. 3 is a schematic view of the external structure of the CT radioactive source with the front side removed
FIG. 4 is a top view of the experimental apparatus of the present invention
FIG. 5 is a perspective view of a true triaxial cell of the experimental apparatus of the present invention
Wherein the content of the first and second substances,
0-experimental coal rock test piece, 1-true triaxial pressure chamber, 11-pressure chamber cover plate, 12-liquid inlet, 13-barrel body, 14-liquid outlet, 15-gas outlet, 16-gas inlet, 17-confining pressure sensor, 21-upright post, 22-top plate, 23-bottom plate, 310-upper pressure chamber, 311-upper pressure column, 312-axial displacement sensor 1, 313-axial pressure sensor 1, 314-upper pressure head, 320-lower pressure chamber, 321-lower pressure column, 322-axial displacement sensor 2, 323-axial pressure sensor 2, 324-lower pressure head, 410-right pressure chamber, 411-lateral pressure sensor 1, 412-lateral displacement sensor 1, 413-right pressure column, 414-right pressure head, 415-gasket, 416-pressing block, 420-left pressure chamber, 421-lateral pressure sensor 2, 422-lateral displacement sensor 2, 423-left pressing column, 424-left pressing head, 425-gasket, 426-pressing block, 5-high pressure gas cylinder, 51-seepage pipe, 52-wire netting, 53-flowmeter, 61-CT radioactive source, 62-CT detector and 7-monitoring control system
Detailed Description
The invention is described in further detail below with reference to the figures and the specific examples.
As shown in the figure, the true triaxial gas seepage test device with CT real-time scanning comprises a triaxial pressure chamber 1, a support 2, loading devices 3 and 4, a gas seepage device 5, a CT scanning system 6 and a control monitoring device 7. The true triaxial pressure chamber 1 comprises a cover plate 11 and a barrel body 13, wherein a liquid inlet 12 and a central hole are reserved on the cover plate, the upper part of the barrel body 13 is open, the central hole is reserved at the bottom part of the barrel body and is symmetrical to the cover plate 11, and a liquid outlet 14 is preset at the lower part of the barrel body 13.
The support consists of a vertical column 21, a top plate 22 and a bottom plate 23; the upright post penetrates through preset through holes on 4 corners of the top plate 22 and the bottom plate 23 to form a bracket 2; the top plate 22 and the bottom plate 23 are made of high-strength steel, and the upright posts are made of carbon fibers; the loading chamber base 31 is arranged at the center of the inner side of the top plate, the upper loading chamber 310 is fixed at the base 31 of the inner side of the top plate and assembled on the top plate 22, the piston pressure column 311 of the upper loading chamber extends into the barrel body 13 through the central hole of the cover plate 11 and is connected to the upper pressure head 314, and the pressure sensor 313 is arranged outside the upper loading chamber; a loading chamber base 32 is arranged at the central position of the inner side of the bottom plate, a lower loading chamber 320 is fixed on the bottom plate base 32 and assembled on the bottom plate 22, a lower loading chamber piston compression leg 321 extends into the barrel body 13 through the central hole of the barrel bottom and is connected with a lower pressure head 324, a pressure sensor 323 is arranged at the outer side of the lower loading chamber, and the axial pressure loading chamber transmits the axial pressure to a test piece 0 through the compression leg-pressure head; the contact parts of the compression columns 311 and 321, the barrel body 1 and the cover plate 11 are provided with O-shaped rings to ensure the sealing property; the cover plate 11 and the barrel body 13 are connected by flanges, and an O-shaped ring is also arranged at the joint.
holes are formed in the positions of two sides of the barrel body 13 of the true triaxial pressure chamber at the same horizontal height, the left and right pressure chambers 410 and 420 are welded on the outer sides of the holes, the front ends of the left and right piston pressure columns 413 and 423 are connected with left and right pressure heads 414 and 424, the pressure heads are connected with pressing blocks 415 and 425, and the pressing blocks are separated by gaskets 416 and 426 to prevent rigid collision; the pressing columns 413 and 423, the pressing heads 414 and 424 and the pressing blocks 415 and 425 are all made of carbon fiber materials; the side pressure force transmission sequence is pressure chamber-pressure column-pressure head-pressure block-coal rock test piece;
the cover plate is provided with a liquid inlet 12, an air inlet 16 and a pressure sensor 17, the bottom of the barrel body is provided with an air outlet 15, the lower part of the barrel body is provided with a liquid outlet 14, the liquid inlet 12 is connected with an external hydraulic pump through a guide pipe and matched with the liquid outlet 14, and the numerical value on the pressure sensor 17 provides confining pressure required by experimental conditions for a test piece.
The upper pressure head 314 and the lower pressure head 324 are internally provided with gas seepage channels 51, an external high-pressure gas bottle 5 is connected with a gas channel 52 preset by the upper pressure head through a gas inlet 16 by a lead, the gas channel preset by the lower pressure head is connected with an external gas flowmeter 53 through a bottom gas outlet 15, the whole seepage device provides a required gas environment for an experiment, and the gas flowmeter 53 reads the gas flow flowing through the coal rock mass test piece.
temperature control device has been preset to staving inside, can control the temperature environment of experiment, keeps the invariant of temperature, prevents to appear experimental error.
And O-shaped rings are arranged around each hole on the barrel body and the cover plate for sealing.
in the true triaxial pressure chamber, displacement sensors 312, 322, 422, 412, 112 and 122 are arranged in the upper, lower, left, right, front and rear 6 directions around the position of the coal rock mass test piece, and are connected with an external control/monitoring system 7 through data lines to monitor the strain change of the coal rock mass test piece in real time.
chamfers are arranged on the edges of the left pressing block and the right pressing block of the upper pressing head 314 and the lower pressing head 324, so that rigid contact among the loading components is prevented, on one hand, the experimental result is prevented from being influenced, and on the other hand, the service life of equipment accessories is prolonged;
The CT scanning device comprises a CT radioactive source 61 and a CT detector 62 which are arranged on the front side and the rear side of the true triaxial apparatus, and all accessories in a scanning area are made of carbon fiber materials.
In order to better understand the present invention, the following describes the true triaxial gas seepage test method with CT real-time scanning in detail.
the true triaxial gas seepage test method with the CT real-time scanning is characterized by comprising the following steps of:
1) Firstly, pretreating a prepared coal rock test piece, then coating silica gel on the surface of the test piece, after the silica gel is dried, firmly wrapping the coal rock test piece by using a heat-shrinkable tube, and fixing the coal rock test piece on an upper pressure head and a lower pressure head by using a clamp;
2) Placing the well-prepared test piece, installing an axial pressure and lateral pressure loading system in place, connecting a gas seepage device, filling hydraulic oil into a pressure chamber, and assembling a cover plate;
3) Turning on a control/monitoring device, and setting the experiment temperature to be constant;
4) Opening a gas tank valve, observing a flow value and keeping the reading constant, closing an exhaust valve after the value is kept constant, keeping the opening state of the gas tank valve unchanged, and enabling the coal rock mass test piece to constantly adsorb gas for 48 hours;
5) And (3) opening the exhaust valve after the constant time is 48 hours, loading axial pressure, lateral pressure and confining pressure for testing after the reading of the flowmeter is stabilized again, simultaneously recording the stress-strain-seepage change of the coal rock mass test piece, carrying out CT scanning until the test piece is destroyed, and acquiring the pore crack development change in the whole process by using a CT scanning device.
Claims (6)
1. the utility model provides a take CT real-time scanning's true triaxial gas seepage flow test device which mainly by: true triaxial pressure chamber, support, loading device, gas seepage flow device, CT scanning system and control/monitoring devices constitute, wherein:
The support comprises a top plate, a bottom plate and 4 stand columns, wherein a center hole is formed in the center of the bottom plate of the top plate, loading chamber bases are welded in the center positions of the inner side surfaces of the top plate and the bottom plate, and the top plate and the bottom plate are connected through the stand columns and fixed through bolts;
The true triaxial pressure chamber comprises a cover plate and a barrel body, round holes are formed in the barrel body at the same height and horizontal position on two sides of the barrel body, a side pressure loading device is connected to the outer side of each round hole, a central hole is formed in the bottom of each round hole, and a piston compression bar of the lower loading chamber extends into the barrel through the central hole; an air outlet is formed in the bottom of the barrel body, a liquid outlet is formed in the lower position of the barrel body, an O-shaped ring is arranged between the barrel body and the cover plate for sealing, bolt holes are formed in the periphery of the upper end of the barrel body, and the barrel body and the cover plate are connected;
a liquid inlet is preset on the cover plate and is matched with the liquid outlet for use to provide confining pressure required by experimental conditions, an air inlet is formed in the cover plate and is matched with an air outlet for use to connect air supply equipment and a sample seepage channel, a central hole is formed in the middle of the cover plate, and a piston compression bar of the upper loading chamber extends into the barrel through the central hole;
The loading device comprises an axial pressure loading chamber, a lateral pressure loading chamber and a confining pressure loading device; the axial loading chamber is arranged at a loading chamber base welded on a top plate and a bottom plate of the bracket; the axial pressure loading chamber comprises an upper pressure chamber, a lower pressure chamber, axial displacement sensors 1 and 2, axial pressure sensors 1 and 2, an upper pressure column, a lower pressure column, an upper pressure head and a lower pressure head, a left pressure chamber, a right pressure chamber, lateral displacement sensors 1 and 2, a left pressure column, a right pressure column, a left pressure head, a right pressure head, a plurality of pressing blocks and gaskets;
The upper (lower) pressure chamber and the left (right) pressure chamber are connected with piston compression columns, the front parts of the piston compression columns are connected with upper (lower) pressure heads and left (right) pressure heads, the pressure heads are connected with pressing blocks and are matched together to provide axial pressure and lateral pressure of a test piece under required experimental conditions, and gaskets are arranged among the pressing blocks to separate from each other so as to prevent rigid collision and influence on experimental results; the confining pressure loading mode is flexible loading, and the required confining pressure is provided for the experiment through a pressure pump through an upper liquid inlet;
The displacement sensors are arranged in 6 directions of the coal-rock test piece in the up, down, left, right, front and back directions respectively, and are used for monitoring the strain change of the test piece in the experimental process;
in the gas seepage device, gas in a high-pressure gas cylinder is connected to a seepage pipe at a gas inlet through a guide pipe, finally flows through a coal rock test piece from a gas inlet of an upper pressure head, and flows out through a gas outlet of a lower pressure head and a gas outlet reserved in a base through a gas flowmeter;
the CT scanning system comprises CT radioactive sources and CT detectors which are positioned on the front side and the rear side of the true triaxial experimental instrument, and can provide real-time scanning for a test piece.
2. The true triaxial gas seepage test device with CT real-time scanning according to claim 1, wherein: the CT radioactive sources and the CT detectors are arranged in the front side and the rear side of the true triaxial test instrument, so that real-time scanning can be performed while a true triaxial seepage test is performed.
3. the true triaxial gas seepage test device with CT real-time scanning according to claim 2, characterized in that: and gas flow channels are reserved at the upper pressure head and the lower pressure head, so that a gas seepage experiment is carried out while a mechanical strength test experiment is carried out.
4. the true triaxial gas seepage test device with CT real-time scanning according to claim 1 or 3, wherein: the experimental device accessories in the scanning area are all made of carbon fibers, and the rest parts are made of steel.
5. the true triaxial gas seepage test device with CT real-time scanning according to claim 4, wherein: the upper and lower pressure chambers for providing axial pressure for the experimental environment are fixed on the top plate and the bottom plate, and are stable.
6. the true triaxial gas seepage test method with CT real-time scanning according to claim 5, comprising the following experimental steps:
1) firstly, the prepared coal rock test piece is pretreated, then silica gel is smeared on the surface of the test piece, and after the silica gel is dried, the coal rock test piece is firmly wrapped by a heat-shrinkable tube and is fixed on an upper pressure head and a lower pressure head by utilizing a clamp.
2) Placing the well-prepared test piece, installing an axial pressure and lateral pressure loading system in place, connecting a gas seepage device, filling hydraulic oil into a pressure chamber, and assembling a cover plate;
3) turning on a control/monitoring device, and setting the experiment temperature to be constant;
4) opening a gas tank valve, observing a flow value and keeping the reading constant, closing an exhaust valve after the value is kept constant, keeping the opening state of the gas tank valve unchanged, and enabling the coal rock mass test piece to constantly adsorb gas for 48 hours;
5) and (3) opening the exhaust valve after the constant time is 48 hours, loading axial pressure, lateral pressure and confining pressure for testing after the reading of the flowmeter is stabilized again, simultaneously recording the stress-strain-seepage change of the coal rock mass test piece, carrying out CT scanning until the test piece is destroyed, and acquiring the pore crack development change in the whole process by using a CT scanning device.
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