High-temperature and high-pressure rock multifunctional CT triaxial experiment device and method

Abstract

The invention discloses a multifunctional CT triaxial experiment device and method for high-temperature and high-pressure rock, and belongs to the technical field of rock engineering measurement devices. The device comprises a device body, a confining pressure pump, an electric heater, a fluid outflow container, a fluid injection container and a CT radiation device, and the device body can enter an inner cavity of the CT radiation device along a sliding way. The device main body mainly comprises a reaction kettle cover, a reaction kettle barrel, a reaction kettle base, a tip cone type force sensor, a sample assembly and a stepping motor. According to the invention, on the premise that a triaxial compression test can be carried out, the force balance stability, the split-flow infiltration capacity, the scanning sample stability and the test detection means in the shearing process of the triaxial apparatus test device are improved, and the research is beneficial to deeply understanding the mechanical properties and behaviors of rocks under geological conditions; and technical support is provided for exploring deep geological resource development and engineering construction.

Description

Technical Field

[0001] The invention belongs to the technical field of rock engineering measurement devices, and in particular relates to a high-temperature and high-pressure rock multifunctional CT triaxial experimental device and method. Background Art

[0002] The study of rock mechanics usually targets high temperature and high pressure conditions in deep geological areas, including the deformation characteristics, crack evolution laws, seepage characteristics and mesoscopic structure of rocks under high temperature and high pressure. The device combines CT scanning technology to obtain real-time internal structural information of rock samples under triaxial loading conditions, including crack development, deformation evolution, etc. By conducting triaxial experiments on rock samples under high temperature and high pressure conditions, the mechanical response laws of rocks in deep geological environments can be revealed.

[0003] The triaxial apparatus is a common geotechnical testing instrument designed to simulate the mechanical behavior of rocks under stratum stress conditions. However, ordinary triaxial devices can only analyze stress-strain curves, temperature, pressure, flow, etc. after uniaxial compression studies. They cannot detect changes in internal microstructures, and few test equipment set up pore pressure for seepage experiments. Therefore, the researchers modified the ordinary triaxial apparatus, organically combined the triaxial apparatus with an X-ray CT scanner, and proposed a high-temperature and high-pressure rock triaxial experimental device CN112229739A that cooperates with CT online scanning. However, this device has certain problems during actual use: 1. The top cone force sensor connects the pressure head and the upper reactor to provide force balance when the triaxial apparatus is axially loaded. However, the loading device does not have a top cone force sensor on the upper part of the triaxial apparatus mainframe, which makes it easy for the triaxial apparatus to "deviate" and "excessive deflection of the center axis" during axial loading of the specimen. 1. The device is heated by high-temperature thermal oil, which can reach a temperature control range of 0-600°. However, in actual operation, if the sample is temperature-controlled by injecting pre-cooled hydraulic oil, the temperature of the hydraulic oil is greatly affected by the environment, and it is not necessarily possible to ensure that the test temperature can reach a high temperature close to 600°. The accuracy of the test data is questionable. 2. The seepage system of the device adopts an integrated design, which does not fully consider the effect of the introduction and diversion of the seepage fluid (evenly passing the seepage fluid through the sample). If upper and lower permeable stones are added, better seepage test results can be obtained. Chinese patent CN102778464B discloses a high-temperature and high-pressure industrial CT scanning system and its use method. The system uses hydraulic pressure to apply temperature and pressure to the sample to explore the mechanical response law of rock in geological environment, but the temperature control range of the device is small and does not meet the high temperature requirements that may be required for rock tests.

[0004] Aiming at the shortcomings of the Chinese invention patent "A high-temperature and high-pressure rock triaxial experimental device in conjunction with CT online scanning" CN112229739A, the present invention redesigned and optimized the high-temperature and high-pressure rock multifunctional CT triaxial experimental device. On the premise of being able to carry out triaxial compression tests, the triaxial test device has improved the shear process force balance stability, diversion penetration capacity, scanning sample stability performance and test detection methods. This research is helpful to deeply understand the mechanical properties and behaviors of rocks under geological conditions, and provide technical support for exploring deep geological resource development and engineering construction. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and provide a high temperature and high pressure rock multifunctional CT triaxial experimental device and method. The present invention is helpful to study the fracture mechanism and deformation characteristics of samples under high temperature and high pressure conditions and obtain relevant mechanical parameters, and realize comprehensive testing and analysis of triaxial mechanical properties under high temperature and high pressure conditions.

[0006] The specific technical solutions adopted by the present invention are as follows:

[0007] In a first aspect, the present invention provides a high-temperature and high-pressure rock multifunctional CT triaxial experimental device, comprising a device body, a confining pressure pump, an electric heater, a fluid outflow container, a fluid injection container and a CT radiation device, wherein the device body can enter the inner cavity of the CT radiation device along a slideway;

[0008] The device body comprises a reactor cover, a reactor cylinder and a reactor base which are detachably connected from top to bottom and together form a reaction cavity; a top cone force sensor is installed on the reactor cover, and the action end of the top cone force sensor is located in the reaction cavity; a stepper motor is installed on the reactor base, and the output end of the stepper motor is connected to a loading rod; the top of the loading rod passes through the reactor base and extends into the reaction cavity, and can move in a vertical direction under the driving force of the stepper motor, and the loading rod is sealed and slidably connected to the reactor base; a sample assembly is fixed on the top of the loading rod, and the sample assembly comprises an upper reaction pressure head, an upper A permeable stone, a sample, a lower permeable stone and a lower reaction pressure head; an optical fiber sensor is spirally wound around the periphery of the sample, and a rubber film wraps the outside of the sample assembly to achieve integrated fixation; the upper reaction pressure head can contact the action end of the top cone force sensor, and the loading rod is driven up and down by a stepper motor to perform axial shear on the sample; a spiral heat coil is arranged in the reaction cavity outside the sample assembly, and the spiral heat coil is connected to the electric heater through a third channel; the top of the upper permeable stone is connected to the fluid outflow container through a pipeline, the bottom of the lower permeable stone is connected to the fluid injection container through a pipeline, and the reaction cavity is connected to the confining pressure pump through a pipeline.

[0009] Preferably, the action end of the top cone force sensor, the sample assembly, the loading rod and the output end of the stepper motor are coaxially arranged.

[0010] Preferably, a plurality of acoustic wave probes are symmetrically arranged on the lower surface of the upper reaction pressure head and the upper surface of the lower reaction pressure head, respectively. Wiring grooves are also respectively opened on the lower surface of the upper reaction pressure head and the upper surface of the lower reaction pressure head, and each group of acoustic wave probes are connected by a signal line fixed in the wiring groove.

[0011] Preferably, a support column frame is provided at the bottom of the device body, and the support column frame can move axially along the slide; one end of the slide is located inside the CT radiation device, and the other end is located outside the CT radiation device.

[0012] Preferably, the reactor cover is fixed to the reactor cylinder by a plurality of screws, a protrusion is provided in the middle of the upper part of the reactor base, and the bottom of the reactor cylinder can be covered on the reactor base and cooperate with the protrusion to achieve sealing of the reaction cavity.

[0013] Preferably, the optical fiber sensor is connected to an external optical fiber strain gauge via a third channel.

[0014] Preferably, the upper reaction pressure head is provided with a seepage outlet connected to the upper permeable stone, and the reactor base is provided with a second channel having one end connected to the reaction cavity and the other end connected to the outside; the seepage outlet is connected to one end of the second channel through a first seepage outlet pipeline located in the reaction cavity, and the other end of the second channel is connected to the fluid outflow container through a second seepage outlet pipeline located outside the device body.

[0015] Preferably, the lower reaction pressure head is provided with a seepage inlet connected to the lower permeable stone, and the reactor base is provided with a first channel with one end connected to the reaction cavity and the other end connected to the outside; the seepage inlet is connected to one end of the first channel through a first seepage inlet pipeline located in the reaction cavity, and the other end of the first channel is connected to the fluid injection container through a second seepage inlet pipeline located outside the device body.

[0016] Preferably, a confining pressure channel is provided on the reactor base, one end of the channel being connected to the reaction cavity and the other end being connected to the outside, and the confining pressure channel is connected to the confining pressure pump via a motor connecting pipeline located outside the device body.

[0017] In a second aspect, the present invention provides a test method using any high-temperature and high-pressure rock multifunctional CT triaxial test device described in the first aspect, which is as follows:

[0018] S1: polish the surface of the cylindrical sample to make it smooth, coaxially stack the upper reaction head, the upper permeable stone, the sample, the lower permeable stone and the lower reaction head in the order of vertical stacking, and then wrap the whole in a rubber film to obtain a sample assembly; open the reaction cavity, coaxially fix the sample assembly on the top of the loading rod, and then seal the reaction cavity;

[0019] S2: Connect the spiral heat coil to the electric heater through the third channel for sample heating; connect the top of the upper permeable stone to the fluid outflow container through a pipeline, connect the bottom of the lower permeable stone to the fluid injection container through a pipeline, connect the reaction cavity to the confining pressure pump through a pipeline, and connect the acoustic wave probe and the optical fiber sensor to the data collector; the acoustic wave probe is used to collect acoustic wave data, and the optical fiber sensor is attached to the sample surface to collect surface strain data;

[0020] S3: Set the parameters of the CT radiation device according to experimental requirements;

[0021] S4: Send the device body into the inner cavity of the CT radiation device along the slide; turn on the confining pressure pump and inject hydraulic oil into the reaction cavity to achieve confining pressure control of the sample;

[0022] S5: Turn on the electric heater, and the spiral heat coil is connected to the electric heater through the third channel to control the temperature of the sample to a specified temperature;

[0023] S6: Set and maintain the axial shear rate of the stepper motor, and push the loading rod to move vertically to shear the sample; in this process, the pressure change of the stepper motor and the displacement change of the top cone force sensor are collected by the data acquisition device to obtain the stress-strain curve of the sample during the axial loading process;

[0024] S7: Open the fluid injection container and the fluid outflow container, inject the seepage fluid into the sample from the bottom of the lower permeable stone to test the permeability of the sample after shearing, and the seepage fluid finally enters the fluid outflow container from the top of the upper permeable stone through the pipeline;

[0025] S8: When the sample needs to be CT scanned by the CT radiation device, the axial loading of the stepper motor is suspended; the CT radiation device records the radiation data transmitted from different angles by rotating the X-ray source for subsequent image reconstruction;

[0026] S9: After the test is completed, stop the axial loading of the sample by the stepper motor, and when the temperature of the device body and the sample returns to room temperature, unload the stress; take out the sample wrapped in the rubber film, obtain the three-dimensional image reconstructed by CT, collect the acoustic wave data collected by the acoustic wave probe and the strain data collected by the optical fiber sensor, and perform data analysis and image processing; according to the results of the data analysis, interpret the strength characteristics and mechanical properties of the sample.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The mainframe of the entire three-axis experimental device adopts a sliding CT radiation device. The mainframe remains stationary during CT scanning, and the external X-ray penetrating source scans. The installation and test operation process is simple, avoiding the "winding" and "coil shielding" problems that may be caused by the rotation of the mainframe during CT scanning, and has good stability.

[0029] (2) A top cone force sensor is added between the upper reactor cover and the sample. A fixing bolt is installed on the top of the top cone force sensor to enhance the stability of the entire sample during axial compression and prevent the sample from being excessively "tilted" or "excessively deflected" due to axial compression during the experiment, which would affect the normal progress of the experiment.

[0030] (3) The present invention designs an acoustic emission probe and a spiral-rising optical fiber sensor in the high-temperature and high-pressure rock multifunctional CT triaxial experimental device, thereby improving the traditional triaxial instrument pressure head. The acoustic emission probe is arranged at "four corners" to better collect the acoustic emission signal of the sample deformation. The optical fiber sensor is used as a new measurement method to measure the temperature and strain information of the sample with high precision, thereby diversifying the measurement methods of the high-temperature and high-pressure rock multifunctional CT triaxial experimental device and better collecting the mechanical behavior information of the sample during the deformation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a structural diagram of the device body.

[0032] Figure 2 It is a system diagram of a high-temperature and high-pressure rock multifunctional CT triaxial experimental device.

[0033] Figure 3 It is a schematic diagram of the sample structure and stress action in the central chamber of the reactor.

[0034] Figure 4 It is a schematic diagram of the installation position and structure of the pressure head of the sonic probe.

[0035] In the figure: 1—reactor cover; 2—screws; 3—upper reaction pressure head; 41—upper permeable stone; 42—lower permeable stone; 5—rubber membrane; 6—optical fiber sensor; 7—sample; 8—lower reaction pressure head; 9—first channel; 10—stepping motor; 11—second channel; 12—reactor base; 13—third channel; 14—spiral heat coil; 15—first seepage outlet pipeline; 16—reactor cylinder; 17—seepage outlet; 18—top cone force sensor; 19—device body; 20—second seepage inlet pipeline; 21—motor connecting pipeline; 22—confining pressure pump; 23—slideway; 24—support column frame; 25—electric heater; 26—second seepage outlet pipeline; 27—fluid outflow container; 28—fluid injection container; 30—CT radiation device; 31—sound wave probe; 32—wiring groove; 33—confining pressure channel. DETAILED DESCRIPTION

[0036] The present invention is further described and illustrated below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0037] like Figure 2 As shown, a high-temperature and high-pressure rock multifunctional CT triaxial experimental device provided by the present invention mainly includes a device body 19, a confining pressure pump 22, an electric heater 25, a fluid outflow container 27, a fluid injection container 28 and a CT radiation device 30. Among them, the device body 19 can enter and exit the inner cavity of the CT radiation device 30 along the slide 23, and the confining pressure pump 22, the electric heater 25, the fluid outflow container 27, and the fluid injection container 28 are located outside the device body 19.

[0038] As a preferred embodiment of the present invention, a support column frame 24 is further provided at the bottom of the device body 19, and the device body 19 and the support column frame 24 are detachably connected, and the support column frame 24 can move axially along the slide 23. One end of the slide 23 is located inside the CT radiation device 30, and the other end is located outside the CT radiation device 30, thereby achieving the effect of the device body 19 entering and exiting the inner cavity of the CT radiation device 30.

[0039] The structure and connection method of each component will be described in detail below.

[0040] In the present invention, if Figure 1 As shown, the device body 19 mainly includes a reactor cover 1, a reactor cylinder 16, a reactor base 12, a top cone force sensor 18, a sample assembly, a stepper motor 10, etc. The reactor cover 1, the reactor cylinder 16 and the reactor base 12 are detachably connected from top to bottom, and the three together form a reaction cavity with a certain sealing performance.

[0041] As a preferred embodiment of the present invention, the reactor cover 1 is a top cover structure, and the reactor cylinder 16 is a cylindrical structure that is open at the top and bottom. The reactor cover 1 and the reactor cylinder 16 can be fixed and connected to form an "n"-shaped integrated structure by multiple screws 2. In order to ensure a better sealing effect, a sealing ring can be provided at the connection between the reactor cover 1 and the reactor cylinder 16. A cylindrical protrusion is provided in the middle of the upper part of the reactor base 12, and the bottom of the reactor cylinder 16 can be covered on the reactor base 12 and cooperate with the protrusion of the reactor base 12 to achieve the sealing of the reaction cavity. In actual use, when it is necessary to assemble or disassemble the sample assembly, the integrated structure of the reactor cover 1 and the reactor cylinder 16 can be removed for easy operation.

[0042] In the present invention, a top cone force sensor 18 is installed on the reactor cover 1, and the action end of the top cone force sensor 18 is located in the reaction cavity. In actual use, a hole can be drilled in the lower center of the reactor cover 1, and the top cone force sensor 18 can be installed through a threaded connection. The bottom action end of the top cone force sensor 18 can contact the upper reaction pressure head 3 on the top of the sample assembly. The top cone force sensor 18 is used to record the axial displacement of the sample and provide real-time feedback of the axial displacement.

[0043] In the present invention, a stepper motor 10 is installed on the reactor base 12, and the output end of the stepper motor 10 is connected to the loading rod. The stepper motor 10 and the lower reactor base 12 can be connected by bolt nesting. The top of the loading rod passes through the reactor base 12 and extends into the reaction cavity. The loading rod can move up and down in the vertical direction under the driving force of the stepper motor 10, and the loading rod is sealed and slidably connected to the reactor base 12. A sample assembly is fixed to the top of the loading rod.

[0044] As a preferred embodiment of the present invention, in order to ensure that the sample is provided with better axial stress (such as Figure 3 As shown in σ1 in the figure, the action end of the top cone force sensor 18, the sample assembly, the loading rod and the output end of the stepper motor 10 should be arranged vertically coaxially. In order to better fix the sample assembly between the loading rods, the loading rod can be set to a "T" structure, that is, the horizontal platform at the top can be used to place the sample assembly.

[0045] In the present invention, if Figure 3 and 4 As shown, the sample assembly mainly includes an upper reaction pressure head 3, an upper permeable stone 41, a sample 7, a lower permeable stone 42, a lower reaction pressure head 8, and an optical fiber sensor 6, wherein the upper reaction pressure head 3, the upper permeable stone 41, the sample 7, the lower permeable stone 42, and the lower reaction pressure head 8 are coaxially placed in sequence from top to bottom. In actual use, the permeable stone is installed between the sample and the pressure head to prevent the pressure head from being "scratched" or "squeezed" during the axial compression process, and plays a "diverting" role in the process of the seepage liquid entering the sample. An optical fiber sensor 6 is spirally wound in the vertical direction around the periphery of the sample 7, and the optical fiber sensor 6 is attached to the sample surface for collecting surface strain data. The rubber film 5 wraps the upper reaction head 3, the upper permeable stone 41, the sample 7, the lower permeable stone 42, the lower reaction head 8, and the optical fiber sensor 6 to achieve integrated fixation of the components. Specifically, the rubber film 5 wraps the lower half of the upper reaction head 3, the upper permeable stone 41, the sample 7, the lower permeable stone 42, and the upper half of the lower reaction head 8. The upper reaction head 3 can contact the action end of the top cone force sensor 18, and the loading rod is driven up and down by the stepping motor 10 to perform axial shear on the sample 7.

[0046] As a preferred embodiment of the present invention, Figure 4 As shown, a plurality of (four in this embodiment) acoustic wave probes 31 are symmetrically arranged on the lower surface of the upper reaction head 3 and the upper surface of the lower reaction head 8, and the acoustic wave probes 31 are used to collect acoustic emission signals of sample deformation. A wiring groove 32 is also provided on the lower surface of the upper reaction head 3 and the upper surface of the lower reaction head 8, and each group of acoustic wave probes 31 is connected by a signal line fixed in the wiring groove 32.

[0047] As a preferred embodiment of the present invention, the optical fiber sensor 6 is connected to the optical fiber strain gauge located outside through the third channel 13 to collect temperature and strain signals. The third channel 13 is opened on the reactor base 12, one end of which is connected to the reaction cavity and the other end is connected to the outside.

[0048] In the present invention, a spiral heat coil 14 is provided in the reaction cavity outside the sample assembly, and the spiral heat coil 14 is connected to the electric heater 25 through the third channel 13. The top of the upper permeable stone 41 is connected to the fluid outflow container 27 through a pipeline, the bottom of the lower permeable stone 42 is connected to the fluid injection container 28 through a pipeline, and the reaction cavity is connected to the confining pressure pump 22 through a pipeline.

[0049] As a preferred embodiment of the present invention, the spiral heat coil 14 can be installed only in the lower part of the reaction cavity, that is, the spiral heat coil 14 is fixed on the inner wall of the reactor cylinder 16 located below the sample 7.

[0050] As a preferred embodiment of the present invention, a seepage outlet 17 connected to the upper permeable stone 41 is provided on the upper reaction head 3, and a second channel 11 is provided on the reactor base 12. One end of the second channel 11 is connected to the reaction cavity, and the other end is connected to the outside. The seepage outlet 17 is connected to one end of the second channel 11 located in the reaction cavity through a first seepage outlet pipeline 15 located in the reaction cavity, and the other end of the second channel 11 located outside the reaction cavity is connected to a fluid outflow container 27 through a second seepage outlet pipeline 26 located outside the device body 19.

[0051] As a preferred embodiment of the present invention, a seepage inlet connected to the lower permeable stone 42 is provided on the lower reaction head 8, and a first channel 9 is provided on the reactor base 12. One end of the first channel 9 is connected to the reaction cavity, and the other end is connected to the outside. The seepage inlet is connected to one end of the first channel 9 located in the reaction cavity through a first seepage inlet pipeline located in the reaction cavity, and the other end of the first channel 9 located outside the reaction cavity is connected to the fluid injection container 28 through a second seepage inlet pipeline 20 located outside the device body 19.

[0052] As a preferred embodiment of the present invention, a confining pressure channel 33 is provided on the reactor base 12. One end of the confining pressure channel 33 is connected to the reaction chamber, and the other end is connected to the outside. The confining pressure channel 33 is connected to the confining pressure pump 22 through the motor connecting pipeline 21 located outside the device body 19 to provide confining pressure (such as Figure 3 (shown in σ3) control.

[0053] Using the high temperature and high pressure rock multifunctional CT triaxial experimental device, the present invention also provides a test method, which is specifically as follows:

[0054] S1: Sample preparation and installation:

[0055] The surface of the cylindrical sample 7 is polished smooth, and the upper reaction head 3, the upper permeable stone 41, the sample 7, the lower permeable stone 42 and the lower reaction head 8 are coaxially stacked in sequence, and then the whole is wrapped in a rubber film 5 to obtain a sample assembly. The reaction cavity is opened, and the sample assembly is coaxially fixed to the top of the loading rod, and then the reaction cavity is sealed.

[0056] In this embodiment, the steps are as follows:

[0057] According to the required sample size, the sample 7 is processed into a diameter matching the reaction cavity, the surface of the cylindrical sample is polished smooth, the upper permeable stone 41, the sample 7, and the lower permeable stone 42 are wrapped in the rubber film 5 in turn, the reactor cover 1 and the reactor cylinder 16 are opened, the upper permeable stone 41, the sample 7, and the lower permeable stone 42 wrapped in the rubber film 5 are placed in the device body 19, and then the rubber film 5 continues to wrap the lower half of the upper reaction pressure head 3 and the upper half of the lower reaction pressure head 8, and the reactor cover 1 and the reactor cylinder 16 are covered.

[0058] S2: Connecting pipe:

[0059] The spiral heat coil 14 is connected to the electric heater 25 through the third channel 13, the top of the upper permeable stone 41 is connected to the fluid outflow container 27 through a pipeline, the bottom of the lower permeable stone 42 is connected to the fluid injection container 28 through a pipeline, the reaction cavity is connected to the confining pressure pump 22 through a pipeline, the acoustic wave probe 31 and the optical fiber sensor 6 are connected to the data acquisition device, the acoustic wave probe 31 is used to collect acoustic wave data, and the optical fiber sensor 6 is attached to the sample surface to collect surface strain data.

[0060] In this embodiment, the steps are as follows:

[0061] The lower reaction kettle base 12 of the device body 19 is fixed on the support column frame 24. Figure 2, connect the first channel 9 of the device body 19 to the fluid injection container 28 through the second seepage inlet pipeline 20 to realize the injection function of the seepage fluid. Connect the second channel 11 of the device body 19 to the fluid outflow container 27 through the second seepage outlet pipeline 26 to realize the outlet function of the seepage fluid. Connect the spiral heat coil 14 of the device body 19 to the electric heater 25 through the third channel 13 using a pipeline to realize sample temperature control. Connect the confining pressure pump 22 to the confining pressure channel 33 through the motor connecting pipeline 21 to realize confining pressure control. Connect the acoustic wave probe 31 and the optical fiber sensor 6 of the device body 19 to the data acquisition device to realize data acquisition of the device body 19 during the experiment.

[0062] S3: CT instrument settings:

[0063] According to the experimental requirements, the parameters of the CT radiation device 30 (eg, X-ray source intensity, rotation speed, scanning range, etc.) are set.

[0064] S4: Apply confining pressure:

[0065] Push the support column 24 and send the device body 19 along the slide 23 into the inner cavity of the CT radiation device 30. Turn on the confining pressure pump 22 and inject the hydraulic oil into the reaction cavity through the confining pressure channel 33 to achieve the confining pressure control of the sample 7. Figure 3 shown.

[0066] S5: Temperature Control:

[0067] The electric heater 25 is turned on, and the spiral heat coil 14 is connected to the electric heater 25 through the third channel 13 to control the sample to a specified temperature.

[0068] S6: Shear specimen:

[0069] According to the shear rate required by the experiment, the axial shear rate of the stepper motor 10 is set and maintained to push the loading rod to move vertically to shear the sample 7, such as Figure 3 In this process, the pressure change of the stepper motor 10 and the displacement change of the top cone force sensor 18 are collected by the data acquisition device to obtain the stress-strain curve of the sample 7 during the axial loading process.

[0070] S7: Fluid injection:

[0071] Open the fluid injection container 28 and the fluid outflow container 27, and inject the seepage fluid into the sample 7 from the bottom of the lower permeable stone 42 to perform a permeability test on the sample 7 after shearing. The seepage fluid eventually enters the fluid outflow container 27 from the top of the upper permeable stone 41 through the pipeline.

[0072] S8: When the sample 7 needs to be CT scanned by the CT radiation device 30, the axial loading of the stepper motor 10 is suspended. The CT radiation device 30 records the radiation data transmitted from different angles by rotating the X-ray source for subsequent image reconstruction.

[0073] S9: Stress unloading and equipment and data collection:

[0074] After the test is completed, stop the axial loading of the stepper motor 10 on the sample 7, and when the temperature of the device body 19 and the sample 7 returns to room temperature, unload the stress. Take out the sample 7 wrapped in the rubber film 5, obtain the three-dimensional image reconstructed by CT, collect the acoustic wave data collected by the acoustic wave probe and the strain data collected by the optical fiber sensor, and perform data analysis and image processing, specifically including measuring parameters such as porosity, particle distribution, displacement deformation, etc. According to the results of the data analysis, interpret the strength characteristics and mechanical properties of the sample 7.

[0075] Under the premise of being able to carry out triaxial compression tests, the present invention improves the shear process force balance stability, diversion permeability, scanning sample stability performance and test detection means of the triaxial test device. This research is helpful to deeply understand the mechanical properties and behaviors of rocks under geological conditions, and provide technical support for exploring deep geological resource development and engineering construction.

[0076] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A high temperature and high pressure rock multifunctional CT triaxial experimental device, characterized in that: The device comprises a device body (19), a confining pressure pump (22), an electric heater (25), a fluid outflow container (27), a fluid injection container (28) and a CT radiation device (30), wherein the device body (19) can enter the inner cavity of the CT radiation device (30) along a slideway (23); The device body (19) comprises a reactor cover (1), a reactor cylinder (16) and a reactor base (12) which are detachably connected from top to bottom and together enclose a reaction chamber; a top cone force sensor (18) is installed on the reactor cover (1), and the action end of the top cone force sensor (18) is located in the reaction chamber; a stepper motor (10) is installed on the reactor base (12), and the output end of the stepper motor (10) is connected to a loading rod; the top of the loading rod passes through the reactor base (12) and extends into the reaction chamber, and can move in a vertical direction under the driving force of the stepper motor (10), and the loading rod is sealed and slidably connected to the reactor base (12); a sample assembly is fixed on the top of the loading rod, and the sample assembly comprises an upper reaction pressure head (3), an upper permeable stone (41), and a sample pressure gauge (42) which are placed in sequence from top to bottom. (7), a lower permeable stone (42) and a lower reaction pressure head (8); an optical fiber sensor (6) is spirally wound around the periphery of the sample (7), and a rubber film (5) wraps the outside of the sample assembly to achieve integrated fixation; the upper reaction pressure head (3) can contact the action end of the top cone force sensor (18), and the loading rod is driven up and down by a stepping motor (10) to perform axial shear on the sample (7); a spiral heat coil (14) is provided in the reaction cavity outside the sample assembly, and the spiral heat coil (14) is connected to the electric heater (25) through a third channel (13); the top of the upper permeable stone (41) is connected to the fluid outflow container (27) through a pipeline, the bottom of the lower permeable stone (42) is connected to the fluid injection container (28) through a pipeline, and the reaction cavity is connected to the confining pressure pump (22) through a pipeline.

2. A high temperature and high pressure rock multifunctional CT triaxial experimental device according to claim 1, characterized in that: The action end of the top cone force sensor (18), the sample assembly, the loading rod and the output end of the stepping motor (10) are coaxially arranged.

3. The high-temperature and high-pressure rock multifunctional CT triaxial experimental device according to claim 1 is characterized in that: A plurality of acoustic wave probes (31) are symmetrically arranged on the lower surface of the upper reaction pressure head (3) and the upper surface of the lower reaction pressure head (8), respectively. Wiring grooves (32) are also respectively provided on the lower surface of the upper reaction pressure head (3) and the upper surface of the lower reaction pressure head (8), and each group of acoustic wave probes (31) are connected via a signal line fixed in the wiring groove (32).

4. The high-temperature and high-pressure rock multifunctional CT triaxial experimental device according to claim 1 is characterized in that: A support column frame (24) is provided at the bottom of the device body (19), and the support column frame (24) can move axially along the slideway (23); one end of the slideway (23) is located inside the CT radiation device (30), and the other end is located outside the CT radiation device (30).

5. The high temperature and high pressure rock multifunctional CT triaxial test device according to claim 1 is characterized in that: The reactor cover (1) is fixed to the reactor cylinder (16) by a plurality of screws (2); a protrusion is provided in the middle of the upper part of the reactor base (12); the bottom of the reactor cylinder (16) can be covered on the reactor base (12) and cooperate with the protrusion to achieve sealing of the reaction cavity.

6. The high temperature and high pressure rock multifunctional CT triaxial test device according to claim 1 is characterized in that: The optical fiber sensor (6) is connected to an external optical fiber strain gauge via a third channel (13).

7. The high temperature and high pressure rock multifunctional CT triaxial test device according to claim 1 is characterized in that: The upper reaction pressure head (3) is provided with a seepage outlet (17) connected to the upper permeable stone (41); the reactor base (12) is provided with a second channel (11) having one end connected to the reaction cavity and the other end connected to the outside; the seepage outlet (17) is connected to one end of the second channel (11) through a first seepage outlet pipeline (15) located in the reaction cavity, and the other end of the second channel (11) is connected to a fluid outflow container (27) through a second seepage outlet pipeline (26) located outside the device body (19).

8. The high-temperature and high-pressure rock multifunctional CT triaxial experimental device according to claim 1 is characterized in that: The lower reaction pressure head (8) is provided with a seepage inlet connected to the lower permeable stone (42); the reactor base (12) is provided with a first channel (9) having one end connected to the reaction cavity and the other end connected to the outside; the seepage inlet is connected to one end of the first channel (9) through a first seepage inlet pipeline located in the reaction cavity, and the other end of the first channel (9) is connected to a fluid injection container (28) through a second seepage inlet pipeline (20) located outside the device body (19).

9. The high temperature and high pressure rock multifunctional CT triaxial test device according to claim 1 is characterized in that: The reactor base (12) is provided with a confining pressure channel (33) with one end connected to the reaction chamber and the other end connected to the outside. The confining pressure channel (33) is connected to a confining pressure pump (22) via a motor connecting pipeline (21) located outside the device body (19).

10. A test method using the high temperature and high pressure rock multifunctional CT triaxial test device according to any one of claims 1 to 9, characterized in that: The details are as follows: S1: polish the surface of the cylindrical sample (7) to make it smooth, coaxially stack the upper reaction head (3), the upper permeable stone (41), the sample (7), the lower permeable stone (42) and the lower reaction head (8) in this order, and then wrap the whole in a rubber film (5) to obtain a sample assembly; open the reaction cavity, coaxially fix the sample assembly on the top of the loading rod, and then seal the reaction cavity; S2: The spiral heat coil (14) is connected to the electric heater (25) through the third channel (13) to heat the sample (7); the top of the upper permeable stone (41) is connected to the fluid outflow container (27) through a pipeline, the bottom of the lower permeable stone (42) is connected to the fluid injection container (28) through a pipeline, the reaction cavity is connected to the confining pressure pump (22) through a pipeline, and the acoustic wave probe (31) and the optical fiber sensor (6) are connected to the data acquisition device; the acoustic wave probe (31) is used to collect acoustic wave data, and the optical fiber sensor (6) is attached to the surface of the sample (7) to collect surface strain data; S3: setting parameters of the CT radiation device (30) according to experimental requirements; S4: The device body (19) is sent into the inner cavity of the CT radiation device (30) along the slideway (23); the confining pressure pump (22) is turned on to inject hydraulic oil into the reaction cavity to achieve confining pressure control of the sample (7); S5: turning on the electric heater (25), the spiral heat coil (14) is connected to the electric heater (25) through the third channel (13), and is used to control the temperature of the sample (7) to a specified temperature; S6: setting and maintaining the axial shear rate of the stepper motor (10), pushing the loading rod to move vertically to shear the sample (7); in this process, collecting the pressure change of the stepper motor (10) and the displacement change of the top cone force sensor (18) through the data acquisition device, and obtaining the stress-strain curve of the sample (7) during the axial loading process; S7: Open the fluid injection container (28) and the fluid outflow container (27), and inject the seepage fluid into the sample (7) from the bottom of the lower permeable stone (42) to test the permeability of the sample (7) after shearing. The seepage fluid finally enters the fluid outflow container (27) from the top of the upper permeable stone (41) through the pipeline; S8: When it is necessary to perform CT scanning on the sample (7) through the CT radiation device (30), the axial loading of the stepper motor (10) is suspended; the CT radiation device (30) records the radiation data transmitted from different angles by rotating the X-ray source for subsequent image reconstruction; S9: After the test is completed, the axial loading of the sample (7) by the stepper motor (10) is stopped, and when the temperature of the device body (19) and the sample (7) returns to room temperature, the stress is unloaded; the sample (7) wrapped in the rubber film (5) is taken out, a three-dimensional image reconstructed by CT is obtained, the acoustic wave data collected by the acoustic wave probe (31) and the strain data collected by the optical fiber sensor (6) are collected, and data analysis and image processing are performed; based on the results of the data analysis, the strength characteristics and mechanical properties of the sample (7) are interpreted.

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