Rock true triaxial experiment acoustic emission sensor installation auxiliary device and using method

Abstract

The application discloses a rock true triaxial experiment acoustic emission sensor installation auxiliary device and a use method thereof, and relates to the field of rock true triaxial experiment acoustic emission sensor installation auxiliary devices.The device comprises telescopic pads, hollow long screw rods, rubber pad seats, flanges, hollow pad columns and bolts.The device can adapt to cubic rock samples of various sizes, can fully protect acoustic emission sensors and signal lines from being damaged due to the loading effect, and can make the acoustic emission sensors tightly coupled with each surface of the cubic rock sample.The device has the advantages of simple structure, convenient disassembly and assembly, wide application range and high practicability.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics experimental technology, and in particular to an auxiliary device for installing and using a true triaxial acoustic emission sensor for rock experiments. Background Technology

[0002] Acoustic emission (AE) is the phenomenon where rock materials release strain energy in the form of elastic waves when cracks form during stress. Acoustic emission technology is a dynamic non-destructive testing technique that uses an acoustic emission system to monitor acoustic emission signals during the rock fracturing process under load. The characteristics of these signals are then used to characterize the location and fracture state of cracks within the rock or rock mass. An acoustic emission system consists of an acoustic emission instrument, amplifier, acoustic emission sensors, and signal lines. Signals generated during rock fracturing are typically collected by multiple acoustic emission sensors, transmitted via signal lines to the amplifier, and then amplified before being transmitted to the acoustic emission instrument for storage and processing.

[0003] To effectively capture acoustic emission signals, the acoustic emission sensor needs to be in direct contact with the rock sample during acoustic emission monitoring, usually with the aid of a lubricating medium such as petroleum jelly to enhance coupling. For uniaxial compression tests, the cylindrical rock sample has exposed free surfaces, making it relatively easy to attach the acoustic emission sensor to the sample side. In conventional triaxial compression tests, the acoustic emission sensor is either attached to the side of the cylindrical rock sample or magnetically adsorbed onto the sides of the cylindrical pads at the top and bottom of the sample. The acoustic emission sensor and the sample are enclosed within the loading oil chamber, allowing for the arrangement of multiple acoustic emission sensors. However, for true triaxial tests, the six surfaces of the cubic rock sample need to be in full face-to-face contact with the loading modules in the three loading directions of the true triaxial test system during loading. The lack of space for safely placing the acoustic emission sensor directly on the sample surface makes it difficult to monitor the rock fracture process using acoustic emission technology in true triaxial tests. The published patent application CN105842343A prefabricated a T-shaped cavity for placing an acoustic emission sensor in a rock sample holder. A magnet and spring are used to press the acoustic emission sensor to achieve close contact with the sample. However, during installation, the signal line connecting the acoustic emission sensor is difficult to lead from the long slot of the cavity to the outlet of the short slot. Furthermore, the presence of a second spring washer between the sample holder and the hydraulic cylinder causes uneven loading stress. Patent CN110595909A places the acoustic emission sensor in a prefabricated through-hole in the loading plate, but the lack of a fixing or clamping device makes it difficult for the acoustic emission sensor to fully contact the rock sample during the experiment. It also does not explain how the data line led out from the guide groove passes through the sealed, heat-insulating, expandable flexible membrane assembly. Patent applications CN113959851A and CN213041649U both use springs to press the acoustic emission sensor in the prefabricated hole of the pressure plate, but even with a groove for the data line to be led out from the sealed loading device, it is still subject to compression. Therefore, there is an urgent need to invent an auxiliary device for installing acoustic emission sensors in true triaxial rock experiments, so as to provide sufficient assurance for the acoustic emission safety monitoring of rock damage behavior in true triaxial experiments. Summary of the Invention

[0004] This invention provides an auxiliary device for installing and using a true triaxial acoustic emission sensor for rock experiments, in order to solve the above-mentioned problems in the prior art.

[0005] The solution of the present invention is:

[0006] An auxiliary device for installing an acoustic emission sensor in a true triaxial rock test is disclosed. This device is positioned between the loading modules, the pressure plate, and the surfaces of the cubic rock sample in a true triaxial testing machine. It includes a retractable pad, a hollow long screw, a rubber pad, a flange, a hollow gasket, and bolts. The retractable pad is a cuboid, composed of several sub-pads of different sizes connected by interlocking. Each sub-pad has several pre-drilled circular through holes with internal threads. The acoustic emission sensor of the acoustic emission system is placed at the front end of each circular through hole. The rubber pad is an elastic cylindrical rubber pad. The acoustic emission sensor is positioned between the hollow long screw and the circular through-hole of the retractable pad. It serves primarily to mount the acoustic emission sensor and secondarily as a buffer element to transmit the preload force of the hollow long screw. The hollow screw is threaded to the circular through-hole of the retractable pad. The flange is a cuboid, with one side welded to the outer edge of the retractable pad. Circular flange holes are located at the four corners of the flange. Bolts pass through the circular flange holes and the hollow spacer to thread-connect and fix the flange to the loading module. The hollow spacer provides space between the flange and the loading module, creating conditions for manual tightening of the hollow long screw and routing of the acoustic emission probe signal lines.

[0007] The cylindrical rubber pad is an elastic cylindrical rubber pad;

[0008] As a preferred technical solution, the retractable pad is composed of several cuboid sub-pads connected by interlocking; between two adjacent sub-pads, the self-locking button of the inner sub-pad is tenoned with the reset hole or telescopic hole of the outer sub-pad to realize the telescopic movement of the inner sub-pad, so as to adapt to cubic rock samples of different sizes; a sub-pad reset hole is provided downstream of the telescopic hole of the outer sub-pad.

[0009] As a preferred technical solution, between two adjacent sub-pads, the reset hole and telescopic hole of the outer sub-pad match the self-locking button of the inner sub-pad. The upper inner surface and the lower inner surface of the outer sub-pad are respectively provided with reset holes and telescopic holes, and the upper outer surface and the lower outer surface of the inner sub-pad are respectively provided with self-locking buttons.

[0010] As a preferred technical solution, one end of the rubber pad is a sleeve base for mounting the acoustic emission sensor. The depth of the sleeve base is less than the thickness of the acoustic emission sensor. A small hole is opened at the bottom of the sleeve base to the other end, serving as a channel for the signal line.

[0011] As a preferred technical solution, the hollow long screw head is knurled. During the loading process, the hollow long screw is manually rotated, which in turn pushes the rubber pad with the acoustic emission sensor installed in the hole to move forward. The hollow long screw then compresses the rubber pad to make it come into close contact with the surface of the rock sample.

[0012] As a preferred technical solution, the true triaxial testing machine includes a crossbeam, a column, a base, a pressure plate, an extensometer, an X-direction loading module, a Y-direction loading module, and a Z-direction loading module; the X-direction loading module, the Y-direction loading module, the Z-direction loading module, and the pressure plate are prefabricated with four circular blind holes containing internal threads; the control system of the true triaxial testing machine controls the independent loading or unloading of the X and Y-direction loading modules and the Z-direction loading module through data lines, and collects the loads of the loading modules in each direction and the displacement parameters of the corresponding extensometers in real time during the experiment.

[0013] As a preferred technical solution, the cube rock sample is uniformly coated with Vaseline before the experiment to facilitate the coupling contact between the acoustic emission sensor and the surface of the cube sample. Then, the cube sample is placed on the pressure plate of a true triaxial testing machine for loading and unloading experiments and synchronous acoustic emission monitoring.

[0014] As a preferred technical solution, the acoustic emission system includes an acoustic emission instrument, an amplifier, an acoustic emission sensor, and a signal line. The acoustic emission sensor is placed in the sleeve base of the rubber pad at the front end of the circular through hole of the retractable pad. The signal line connecting the acoustic emission sensor passes through the rubber pad and is led out through the hollow long screw to be directly connected to the amplifier, and then connected to the acoustic emission instrument, thus realizing the acquisition and processing of acoustic emission signals during the true triaxial rock experiment.

[0015] This invention also discloses a method for using an auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment:

[0016] S1. Prepare a cubic sample of a certain size, and apply a layer of Vaseline evenly to the six surfaces of the cubic sample;

[0017] S2. Prepare auxiliary devices for installing acoustic emission sensors for six true triaxial rock experiments. Adjust the self-locking button of the sub-pad block and the tenon joint position of the adjacent sub-pad block according to the size of the cubic rock sample to make different sub-pad blocks expand and contract.

[0018] S3. Install several acoustic emission sensors with signal lines in the sleeve base at one end of the rubber pad, and then insert them into the pre-made circular through hole inside the telescopic pad. Then install the hollow screw. The signal lines of the acoustic emission sensors pass through the rubber pad and the hollow screw and are led out to connect to the amplifier, and then to the acoustic emission instrument.

[0019] S4. Use bolts to connect and fix the flange, hollow pad column, and loading module and pressure plate in the X, Y and Z directions of the true triaxial testing machine. Place the cubic rock sample on the acoustic emission sensor installation auxiliary device connected to the pressure plate, and align each retractable pad block with the corresponding surface of the cubic rock sample.

[0020] S5. Using the control system of the true triaxial rock testing machine, the loading modules of the true triaxial rock testing machine are driven to move, so that the acoustic emission sensor installation auxiliary device of the true triaxial rock test machine initially contacts each surface of the cubic rock sample.

[0021] S6. Manually tighten each hollow screw to move the rubber pad inside the circular through hole forward until the acoustic emission sensor is in close contact with the cubic rock sample.

[0022] S7. Set the loading and unloading parameters and acoustic emission parameters on the control system and acoustic emission host of the true triaxial testing machine according to the experimental plan. When the experiment starts, the acoustic emission system and the control system of the true triaxial testing machine are turned on synchronously. After the experiment, stop monitoring synchronously, store the real-time data of load, displacement and acoustic emission, disassemble the acoustic emission sensor and install the auxiliary device, clean the damaged rock sample, restore the true triaxial testing machine to its original state, and prepare for the next set of experiments.

[0023] A rock true triaxial experimental acoustic emission sensor installation auxiliary device and usage method, employing the above technical solution, includes a retractable pad, a hollow long screw, a rubber pad, a flange, a hollow gasket, and bolts. The retractable pad is a cuboid, composed of several sub-pads of different sizes connected by interlocking. Each sub-pad has several pre-fabricated circular through holes with internal threads, and the acoustic emission sensor of the acoustic emission system is placed at the front end of the circular through holes. The rubber pad is an elastic cylindrical rubber pad, placed between the acoustic emission sensor and the hollow long screw in the circular through holes of the retractable pad. The hollow screw is threadedly connected to the circular through holes of the retractable pad. The flange is a cuboid, with one side welded to the outer edge of the retractable pad, and circular flange holes are provided at the four corners of the flange. The bolts pass through the circular flange holes and the hollow gasket to thread-connect and fix the flange to the loading module.

[0024] Advantages of this invention:

[0025] This invention can accommodate cubic rock samples of various sizes, effectively protecting the acoustic emission sensor and signal lines from damage caused by loading, while ensuring tight coupling and contact between the acoustic emission sensor and each surface of the cubic rock sample. The device has a simple structure, is easy to assemble and disassemble, has a wide range of applications, and is highly practical.

[0026] (1) The acoustic emission sensor is embedded inside the acoustic emission sensor installation auxiliary device. By tightening the hollow long screw, the rubber pad is squeezed, which realizes the close contact between the acoustic emission sensor and the cubic sample, without interfering with the operation of the true triaxial testing machine and protecting the acoustic emission sensor from damage.

[0027] (2) The acoustic emission sensor installation auxiliary device is bolted to the loading module and the pressure plate through hollow pads, forming a large non-enclosed space. The acoustic emission signal line can be easily led out from the small hole of the rubber pad, the hollow screw, and the gap between the hollow pads without being crushed.

[0028] (3) The device contains multi-level sub-pads. By expanding and contracting different sub-pads, it can adapt to cubic samples of various sizes. The device has a simple structure and is easy to assemble and disassemble. It has multiple built-in circular through holes to install multiple acoustic emission sensors, which can realize three-dimensional positioning of the fracture location of rock samples. Attached Figure Description

[0029] Figure 1 This is a front view of the true triaxial acoustic emission experimental system for rocks according to the present invention.

[0030] Figure 2 This is a left view of the structure of the true triaxial acoustic emission experimental system for rocks according to the present invention;

[0031] Figure 3 This is a schematic diagram of the true triaxial rock experimental system of the present invention;

[0032] Figure 4 This is a schematic diagram of the acoustic emission system structure and the structure of the present invention.

[0033] Figure 5 This is a three-dimensional schematic diagram of the structure of the present invention;

[0034] Figure 6 This is a schematic diagram of the rubber pad structure of the present invention;

[0035] In the diagram: 1-True triaxial rock testing machine; 2-True triaxial experimental control system; 3-Acoustic emission system; 4-Auxiliary device for installing acoustic emission sensors in true triaxial rock testing; 5-Cube rock specimen; 101-Crossbeam; 102-Base; 103-Column; 104-Pressure plate; 105-Z-direction loading module; 106-X-direction loading module; 107-Y-direction loading module; 108-Extensometer; 109-Data cable; 110-Threaded hole; 301-Acoustic emission instrument; 302-Amplifier; 3 03-Acoustic emission sensor; 304-Signal line; 401-Retractable pad; 402-Circular through hole; 403-Rubber pad; 404-Hollow long screw; 405-Flange; 406-Flange hole; 407-Bolt; 408-Hollow pad; 40101-First pad; 40102-Second pad; 40103-Third pad; 40104-Reset hole; 40105-Self-locking button; 40106-Telescopic hole; 40301-Sleeve base; 40302-Lead wire hole. Detailed Implementation

[0036] To overcome the above deficiencies, the present invention provides an auxiliary device for installing and using a true triaxial acoustic emission sensor for rock experiments, thereby solving the problems in the background art.

[0037] An auxiliary device for installing an acoustic emission sensor in a true triaxial rock test is disclosed. This device is positioned between the loading modules, the pressure plate, and the surfaces of the cubic rock sample in a true triaxial testing machine. It includes a retractable pad, a hollow long screw, a rubber pad, a flange, a hollow gasket, and bolts. The retractable pad is a cuboid, composed of several sub-pads of different sizes connected by interlocking. Each sub-pad has several pre-drilled circular through holes with internal threads. The acoustic emission sensor of the acoustic emission system is placed at the front end of each circular through hole. The rubber pad is an elastic cylindrical rubber pad. The acoustic emission sensor is positioned between the hollow long screw and the circular through-hole of the retractable pad. It serves primarily to mount the acoustic emission sensor and secondarily as a buffer element to transmit the preload force of the hollow long screw. The hollow screw is threaded to the circular through-hole of the retractable pad. The flange is a cuboid, with one side welded to the outer edge of the retractable pad. Circular flange holes are located at the four corners of the flange. Bolts pass through the circular flange holes and the hollow spacer to thread-connect and fix the flange to the loading module. The hollow spacer provides space between the flange and the loading module, creating conditions for manual tightening of the hollow long screw and routing of the acoustic emission probe signal lines.

[0038] The cylindrical rubber pad is an elastic cylindrical rubber pad;

[0039] The retractable pad is composed of several cuboid sub-pads connected by interlocking; between two adjacent sub-pads, the self-locking button of the inner sub-pad is tenoned with the reset hole or telescopic hole of the outer sub-pad, which enables the inner sub-pad to expand and contract to accommodate cubic rock samples of different sizes; a sub-pad reset hole is provided downstream of the telescopic hole of the outer sub-pad.

[0040] Between two adjacent sub-pads, the reset hole and telescopic hole of the outer sub-pad match the self-locking button of the inner sub-pad. The upper inner surface and the lower inner surface of the outer sub-pad are respectively provided with reset holes and telescopic holes, and the upper outer surface and the lower outer surface of the inner sub-pad are respectively provided with self-locking buttons.

[0041] One end of the rubber pad is a sleeve base used to install the acoustic emission sensor. The depth of the sleeve base is less than the thickness of the acoustic emission sensor. A small hole is opened at the bottom of the sleeve base to the other end, serving as a channel for the signal line.

[0042] The hollow long screw has a knurled head. During loading, the hollow long screw is manually rotated, which in turn pushes the rubber pad with the acoustic emission sensor installed in the hole to move forward. The hollow long screw then compresses the rubber pad to make it come into close contact with the surface of the rock sample.

[0043] The true triaxial testing machine includes a crossbeam, column, base, pressure plate, extensometer, X-direction loading module, Y-direction loading module, and Z-direction loading module. The X-direction loading module, Y-direction loading module, Z-direction loading module, and pressure plate are prefabricated with four circular blind holes containing internal threads. The control system of the true triaxial testing machine controls the independent loading or unloading of the X and Y-direction loading modules and the Z-direction loading module through data lines, and collects the load of each loading module and the displacement parameters of the corresponding extensometer in real time during the experiment.

[0044] Before the experiment, the cube rock sample was uniformly coated with Vaseline to facilitate the coupling and contact between the acoustic emission sensor and the surface of the cube sample. Then, the cube sample was placed on the pressure plate of the true triaxial testing machine for loading and unloading experiments and synchronous acoustic emission monitoring.

[0045] The acoustic emission system includes an acoustic emission instrument, an amplifier, an acoustic emission sensor, and a signal line. The acoustic emission sensor is placed in the sleeve base of the rubber pad at the front end of the circular through hole of the retractable pad. The signal line connecting the acoustic emission sensor passes through the rubber pad and is led out through the hollow long screw to be directly connected to the amplifier, and then connected to the acoustic emission instrument, thus realizing the acquisition and processing of acoustic emission signals during the true triaxial rock experiment.

[0046] This invention also discloses a method for using an auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment:

[0047] S1. Prepare a cubic sample of a certain size, and apply a layer of Vaseline evenly to the six surfaces of the cubic sample;

[0048] S2. Prepare auxiliary devices for installing acoustic emission sensors for six true triaxial rock experiments. Adjust the self-locking button of the sub-pad block and the tenon joint position of the adjacent sub-pad block according to the size of the cubic rock sample to make different sub-pad blocks expand and contract.

[0049] S3. Install several acoustic emission sensors with signal lines in the sleeve base at one end of the rubber pad, and then insert them into the pre-made circular through hole inside the telescopic pad. Then install the hollow screw. The signal lines of the acoustic emission sensors pass through the rubber pad and the hollow screw and are led out to connect to the amplifier, and then to the acoustic emission instrument.

[0050] S4. Use bolts to connect and fix the flange, hollow pad column, and loading module and pressure plate in the X, Y and Z directions of the true triaxial testing machine. Place the cubic rock sample on the acoustic emission sensor installation auxiliary device connected to the pressure plate, and align each retractable pad block with the corresponding surface of the cubic rock sample.

[0051] S5. Using the control system of the true triaxial rock testing machine, the loading modules of the true triaxial rock testing machine are driven to move, so that the acoustic emission sensor installation auxiliary device of the true triaxial rock test machine initially contacts each surface of the cubic rock sample.

[0052] S6. Manually tighten each hollow screw to move the rubber pad inside the circular through hole forward until the acoustic emission sensor is in close contact with the cubic rock sample.

[0053] S7. Set the loading and unloading parameters and acoustic emission parameters on the control system and acoustic emission host of the true triaxial testing machine according to the experimental plan. When the experiment starts, the acoustic emission system and the control system of the true triaxial testing machine are turned on synchronously. After the experiment, stop monitoring synchronously, store the real-time data of load, displacement and acoustic emission, disassemble the acoustic emission sensor and install the auxiliary device, clean the damaged rock sample, restore the true triaxial testing machine to its original state, and prepare for the next set of experiments.

[0054] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0055] Example 1:

[0056] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6The present invention provides a true triaxial experimental acoustic emission sensor installation auxiliary device 4, which is placed between each loading module (Z-direction loading module 105, X-direction loading module 106, Y-direction loading module 107) / pressure plate 104 and each surface of the cubic rock sample 5 in the true triaxial testing machine 1. The true triaxial experimental acoustic emission sensor installation auxiliary device 4 includes a retractable pad 401, a circular through hole 402, a rubber pad 403, a hollow long screw 404, a flange 405, a flange hole 406, a bolt 407, and a hollow pad column 408. The retractable pad 401 is a cuboid, composed of several cuboid sub-pads of different sizes connected by interlocking. Each sub-pad has several pre-made circular through holes 402 with internal threads. The acoustic emission sensor 303 of the acoustic emission system 3 is placed at the front end of the circular through hole 402. The rubber pad 402 is a cylinder with a certain elasticity, placed between the acoustic emission sensor 303 and the hollow long screw 404 in the circular through hole of the retractable pad. It serves two purposes: first, to install the acoustic emission sensor 303, and second, to act as a buffer element for transmitting the preload force of the hollow long screw 404. The hollow screw 404 is connected to the circular through hole 402 of the telescopic pad by threads; the flange 405 is a cuboid, welded to the outer edge of the telescopic pad 401, and a circular flange hole 406 is arranged at each of the four corners of the flange; the bolt 407 passes through the flange circular hole 406 and the hollow pad 408 to thread the flange 405 and fix it to each loading module 105-107 and the pressure plate 104. The function of the hollow pad 408 is to create space between the flange 405 and the loading module 105-107 / pressure plate 104, so as to create conditions for manually tightening the hollow long screw 404 and the signal line 304 of the acoustic emission sensor 303.

[0057] The retractable pad 401 is composed of three sub-pads of different sizes (first pad 40101, second pad 40102, and third pad 40103) connected by interlocking. Each sub-pad has 3-8 pre-made circular through holes 402. Between two adjacent sub-pads, the self-locking button 40105 of the inner sub-pad is tenoned with the reset hole 40104 or the telescopic hole 40106 of the outer sub-pad, which enables the inner sub-pad to expand and contract to accommodate cubic rock samples of different sizes. The reset hole 40104 of the outer sub-pad is provided downstream of the telescopic hole 40106 of the outer sub-pad.

[0058] The retractable pad 401 is composed of three sub-pads of different sizes (first pad 40101, second pad 40102, and third pad 40103) connected by interlocking. Each sub-pad has 3-8 pre-drilled circular through holes 402 inside. The sub-pads are connected by tenon joints between the outer ring pad's reset hole 40104 or telescopic hole 40106 and the inner ring sub-pad's self-locking button 40105, enabling the inner ring pad to expand and contract to match cubic rock samples of different sizes. The reset hole 40104 or telescopic hole 40106 is a through hole with the same shape as the self-locking button 40105, and its shape can be circular or rectangular, etc. The reset hole 40104 or telescopic hole 40106 and the self-locking button 40105 can also appear symmetrically in pairs on the upper and lower surfaces of the sub-pad, see... Figure 4 and Figure 5 .

[0059] One end of the rubber pad 403 is a sleeve base 40301, used to mount the acoustic emission sensor 303. The depth of the sleeve base is less than the thickness of the acoustic emission sensor. A small lead hole 40302 is opened at the bottom of the base to lead to the other end, serving as a channel for the signal line 304. Figure 4 , Figure 5 and Figure 6 .

[0060] The hollow long screw 404 has a knurled head. During loading, the head of the hollow screw is manually rotated, which in turn pushes the rubber pad 403, on which the acoustic emission sensor 303 is installed, forward. The hollow screw 404 compresses the rubber pad 403, making it come into close contact with the surface of the rock sample 5. Figure 4 and Figure 5 .

[0061] The true triaxial testing machine 1 includes a crossbeam 101, a base 102, a column 103, a pressure plate 104, a Z-direction loading module 105, an X-direction loading module 106, a Y-direction loading module 107, an extensometer 108, and a data cable 109. Each of the Z-direction loading module 105, X-direction loading module 106, Y-direction loading module 107, and pressure plate 104 has four pre-drilled threaded holes 110 with internal threads for easy threaded connection to the flange 405. The true triaxial testing machine control system 2 controls the independent loading or unloading of the X and Y direction loading modules 106 and 107 and the Z-direction loading module 105 via the data cable 109, and collects the loads of each direction loading module and the corresponding displacement parameters monitored by the extensometer 108 in real time during the experiment.

[0062] The acoustic emission system 3 includes an acoustic emission instrument 301, an amplifier 302, an acoustic emission sensor 303, and a signal line 304. The acoustic emission sensor 303 is placed in the sleeve base 40301 at one end of the rubber pad at the front end of the circular through hole of the retractable pad. The signal line 304 connecting the acoustic emission sensor passes through the rubber pad 403 and the hollow screw 404 and is directly connected to the amplifier 302, and then connected to the acoustic emission instrument 301. This realizes the acquisition and processing of acoustic emission signals during the true triaxial rock experiment. See Figure 4 .

[0063] The cubic rock sample 5 has dimensions of (10-30) × (10-30) × (10-30) cm. Before the experiment, Vaseline was evenly applied to its surface to facilitate coupling contact between the acoustic emission sensor 303 and the surface of the cubic rock sample 5. Subsequently, the cubic rock sample 5 was placed on the pressure plate 104 of a true triaxial testing machine for loading and unloading experiments and synchronous acoustic emission monitoring. (See...) Figure 1 .

[0064] Example 2:

[0065] Specific applications are as follows:

[0066] In this design, the true triaxial rock testing machine 1 has external dimensions of 1200×1200×2000mm (length×width×height), the base 102 has dimensions of 500×500×500mm, the crossbeam 101 has dimensions of 1000×40×40mm (length×width×height), and the column 103 has a diameter of 10cm and a height of 0.8m. The maximum load of the Z-direction loading module 105, X-direction loading module 106, and Y-direction loading module 107 is 2000kN (error ±1%), and the displacement range is 200mm (error ±0.5%FS). The loading method can be displacement control or force control. The extensometer 108 is a LVDT model with a range of 10cm and an accuracy of 0.01mm. The Z-direction loading module 105, X-direction loading module 106, Y-direction loading module 107, and pressure plate 104 have a disc diameter of 30–40 mm. The pre-drilled threaded holes 110 have a diameter of 8–16 mm and a depth of 10–20 mm. The cubic rock sample 5 has dimensions of 150 × 150 × 150 mm.

[0067] The acoustic emission system 3 consists of a PCI-2 type acoustic emission instrument 301 manufactured by PAC (USA), two 2 / 4 / 6 preamplifiers 302 with a preamplifier gain of 40dB, and two PICO type piezoelectric ceramic acoustic emission sensors 303 with a center response frequency of 250kHz. In the acoustic emission sensor installation auxiliary device 4, the retractable pad 401 includes three sub-pads: the first pad 40101 has dimensions of 100×100×(50~100)mm (length, width, and thickness); the second pad 40102 has dimensions of 150×150×(50~100)mm (length, width, and thickness); and the third pad 40103 has dimensions of 200×200×(50~100)mm (length, width, and thickness). The first pad 40101 has a self-locking button 40105, and the second pad has a reset hole 40104. The mortise and tenon joint connects the self-locking button 40105 of the second pad (40102) to the telescopic hole 40106 of the third pad. The tenon joint allows the first and second sub-pads to extend as a whole, matching the surface dimensions of the cubic sample 5. The circular through-hole 402 has a full-length internal thread with an inner diameter of 12–15 mm. The built-in rubber pad 403 has an outer diameter of 8–10 mm and a length of 5–8 cm. The sleeve base 40301 has a wall thickness of 2 mm and a depth of 3–5 mm. The lead wire hole 40302 has a diameter of 3–5 mm. The hollow screw 404 has dimensions of M12×20 mm×Φ6.2 mm, with knurled head, allowing manual rotation to connect with the internal thread of the circular through-hole 402. The flange 405 has a thickness of 8–12 mm and is welded to the outer edge of the telescopic pad 401. The flange hole 406 has a diameter of 12 mm. The hollow pad 408 has an inner diameter of 12–15 mm, an outer diameter of 30–40 mm, and a length of 5–10 cm. The bolt 407 is an M10 type.

[0068] A method for using an auxiliary device for mounting a true triaxial experimental acoustic emission sensor includes the following steps:

[0069] (S1) Prepare a cubic rock sample 5 with dimensions of 150×150×150mm, and apply a layer of Vaseline evenly to the six surfaces of the cubic rock sample 5.

[0070] (S2) Prepare the auxiliary device 4 for installing six acoustic emission sensors in the true triaxial rock experiment. Adjust the position of the self-locking button 40105, reset hole 40104 and telescopic hole 40106 of each sub-pad so that the first sub-pad 40101 and the second sub-pad 40102 extend out.

[0071] (S3) Install several acoustic emission sensors 303 with signal lines 304 into the sleeve base 40301 at one end of the rubber pad 403, and then insert them together into the pre-made circular through hole 402 inside the telescopic pad 401. Then install the hollow long screw 404. The signal lines 304 of the acoustic emission sensors 303 pass through the rubber pad 403 and the hollow long screw 404 and are led out to connect to the amplifier 302, and then to the acoustic emission instrument 301;

[0072] (S4) The flange 405, hollow pad 408 of the rock true triaxial test acoustic emission sensor installation auxiliary device 4, the X-direction loading module 106, Y-direction loading module 107 and Z-direction loading module 105 of the rock true triaxial test machine 1 and the pressure plate 104 are screwed and fixed using bolts 407. The cubic rock sample 5 is placed on the rock true triaxial acoustic emission sensor installation auxiliary device 4 connected to the pressure plate 104, and the retractable pads 401 of each rock true triaxial acoustic emission sensor installation auxiliary device 4 are aligned with each surface of the cubic rock sample 5.

[0073] (S5) The rock true triaxial testing machine 1 is driven to move by the rock true triaxial testing machine control system, so that the rock true triaxial test acoustic emission sensor installation auxiliary device 4 initially contacts the surface of the cubic rock 5 sample.

[0074] (S6) Manually tighten each hollow long screw 404 to move the rubber pad 403 inside the circular through hole 402 forward until the acoustic emission sensor 303 is in close contact with the cubic rock sample 5.

[0075] (S7) Set the loading / unloading parameters and acoustic emission parameters on the true triaxial testing machine control system and acoustic emission instrument 301 according to the experimental plan. When the experiment starts, the acoustic emission system 3 and the true triaxial testing machine control system are turned on synchronously. After the experiment, stop monitoring synchronously, store the real-time data of load, displacement and acoustic emission, disassemble the acoustic emission sensor installation device, clean the damaged rock sample, restore the true triaxial testing machine of rock to its original state, and prepare for the next set of experiments.

[0076] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An auxiliary device for installing an acoustic emission sensor in a true triaxial rock test, wherein the auxiliary device is placed between each loading module, the pressure plate, and each surface of a cubic rock sample in a true triaxial testing machine, characterized in that: The system includes a retractable pad, a hollow long screw, a rubber pad, a flange, a hollow gasket, and bolts. The retractable pad is a cuboid, composed of several sub-pads of different sizes connected by interlocking. Each sub-pad has several pre-drilled circular through holes with internal threads, and the acoustic emission sensor of the acoustic emission system is placed at the front end of each circular through hole. The rubber pad is an elastic cylindrical rubber pad, positioned between the acoustic emission sensor and the hollow long screw in the circular through hole of the retractable pad. The hollow long screw is threadedly connected to the circular through hole of the retractable pad. The flange is a cuboid, with one side welded to the outer edge of the retractable pad, and circular flange holes at each of the four corners of the flange. Bolts pass through the circular flange holes and the hollow gasket to thread-connect and fix the flange to the loading module.

2. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: The retractable pad is composed of several cuboid sub-pads connected by interlocking; between two adjacent sub-pads, the self-locking button of the inner sub-pad is tenoned with the reset hole or telescopic hole of the outer sub-pad, and the reset hole of the outer sub-pad is provided downstream of the telescopic hole of the outer sub-pad.

3. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 2, characterized in that: Between two adjacent sub-pads, the reset hole and telescopic hole of the outer sub-pad match the self-locking button of the inner sub-pad. The upper inner surface and lower inner surface of the outer sub-pad are respectively provided with reset holes and telescopic holes, and the upper outer surface and lower outer surface of the inner sub-pad are respectively provided with self-locking buttons.

4. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: One end of the rubber pad is a sleeve base, which is used to install the acoustic emission sensor. The depth of the sleeve base is less than the thickness of the acoustic emission sensor. A small hole is opened at the bottom of the sleeve base to the other end, serving as a channel for the signal line.

5. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: The hollow long screw has a knurled head. During loading, the hollow long screw is manually rotated, which in turn pushes the rubber pad with the acoustic emission sensor installed in the hole to move forward. The hollow long screw squeezes the rubber pad to make it come into close contact with the surface of the rock sample.

6. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: The true triaxial testing machine includes a crossbeam, column, base, pressure plate, extensometer, X-direction loading module, Y-direction loading module, and Z-direction loading module. The X-direction loading module, Y-direction loading module, Z-direction loading module, and pressure plate are prefabricated with four circular blind holes containing internal threads. The control system of the true triaxial testing machine controls the independent loading or unloading of the X and Y-direction loading modules and the Z-direction loading module through data lines, and collects the load of each loading module and the displacement parameters of the corresponding extensometer in real time during the experiment.

7. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: Before the experiment, the cube rock sample was uniformly coated with Vaseline to facilitate the coupling and contact between the acoustic emission sensor and the surface of the cube sample. Then, the cube sample was placed on the bearing plate of the true triaxial testing machine for loading and unloading experiments and synchronous acoustic emission monitoring.

8. The auxiliary device for installing a true triaxial acoustic emission sensor in a rock experiment as described in claim 1, characterized in that: The acoustic emission system includes an acoustic emission instrument, an amplifier, an acoustic emission sensor, and a signal line. The acoustic emission sensor is placed in the sleeve base of the rubber pad at the front end of the circular through hole of the retractable pad. The signal line connecting the acoustic emission sensor passes through the rubber pad and is led out to the hollow long screw and directly connected to the amplifier, and then connected to the acoustic emission instrument, realizing the acquisition and processing of acoustic emission signals during the true triaxial rock experiment.

9. A method of using the auxiliary device for installing a true triaxial acoustic emission sensor in rock experiments as described in claim 1, characterized in that: S1. Prepare a cubic sample of a certain size, and apply a layer of Vaseline evenly to the six surfaces of the cubic sample; S2. Prepare auxiliary devices for installing acoustic emission sensors for six true triaxial rock experiments. Adjust the self-locking button of the sub-pad block and the tenon joint position of the adjacent sub-pad block according to the size of the cubic rock sample to make different sub-pad blocks expand and contract. S3. Install several acoustic emission sensors with signal lines in the sleeve base at one end of the rubber pad, and then insert them together into the pre-made circular through hole inside the telescopic pad. Then install the hollow long screw. The signal lines of the acoustic emission sensors pass through the rubber pad and the hollow long screw and are led out to connect to the amplifier, and then to the acoustic emission instrument. S4. Use bolts to screw and fix the flange, hollow pad column to the loading module and pressure plate in the X, Y and Z directions of the true triaxial testing machine. Place the cubic rock sample on the acoustic emission sensor installation auxiliary device connected to the pressure plate, and align each telescopic pad block with the corresponding surface of the cubic rock sample. S5. Using the control system of the true triaxial rock testing machine, the loading modules of the true triaxial rock testing machine are driven to move, so that the acoustic emission sensor installation auxiliary device of the true triaxial rock test initially contacts each surface of the cubic rock sample. S6. Manually tighten each hollow long screw to move the rubber pad inside the circular through hole forward until the acoustic emission sensor is in close contact with the cubic rock sample. S7. Set the loading and unloading parameters and acoustic emission parameters on the control system and acoustic emission host of the true triaxial testing machine according to the experimental plan. When the experiment starts, the acoustic emission system and the control system of the true triaxial testing machine are turned on synchronously. After the experiment, stop monitoring synchronously, store the real-time data of load, displacement and acoustic emission, disassemble the acoustic emission sensor and install the auxiliary device, clean the damaged rock sample, restore the true triaxial testing machine to its original state, and prepare for the next set of experiments.

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