Array type electric drive rock triaxial test device and rock test method

Abstract

The invention discloses an array type electric drive rock triaxial test device and a rock test method, and relates to the technical field of rock test equipment and methods, and the array type electric drive rock triaxial test device structurally comprises a confining pressure loading assembly, a lower axial pressure head base and an upper axial pressure head assembly. The confining pressure loading assembly comprises a rigid ring beam, a plurality of electromagnetic servo linear actuators on the rigid ring beam, a pressure applying tile and a pressure transmitting sleeve, and the electromagnetic servo linear actuators, the pressure applying tile and the pressure transmitting sleeve are jointly used for generating uniform confining pressure on the cylindrical surface of the rock sample core. The lower axial pressure head base and the upper axial pressure head assembly are jointly used for applying axial pressure to the rock sample core. The rock test method comprises the following steps: 1, mounting a cylindrical rock sample on the confining pressure loading assembly; 2, axially mounting a rock sample between an upper axial pressure head and a lower axial pressure head; 3, applying confining pressure; 4, applying axial pressure; 5, adjusting the pressure according to a plan; and 6, taking out the fragmented sample. According to the invention, the technical problems of low efficiency, large potential safety hazard, difficult maintenance and slow dynamic response of the existing test device can be solved.

Description

Technical Field

[0001] This invention relates to the field of rock testing equipment and methods, specifically to an array-type electrically driven triaxial rock testing device and a rock testing method. Background Technology

[0002] Triaxial testing of rocks is the most fundamental method for determining the strength and deformation characteristics of rocks. Existing conventional triaxial testing machines, such as the MTS and GDS systems, almost entirely rely on high-pressure hydraulic oil as the confining pressure medium. This traditional technique has significant drawbacks: 1. Low efficiency: The process of oil injection, venting, pressurization, oil unloading, and oil cleaning is cumbersome, and the cycle of a single test is long. 2. Significant safety hazards: High-pressure oil (usually 60-100MPa) contains enormous elasticity. Once the pipeline ages or the seal fails, it is very easy to cause injury or explosion. In addition, mineral oil is flammable and poses a fire risk under high temperature and pressure. 3. Difficult to maintain: The hydraulic system has a complex structure, and the pump station, valves, and seals are easily damaged. Oil leakage is common in the laboratory, resulting in a high equipment failure rate and expensive maintenance costs. 4. Unable to meet dynamic response requirements; the compressibility of hydraulic oil and pipeline damping cause lag in confining pressure control, making it difficult to simulate transient unloading processes such as rock bursts. Summary of the Invention

[0003] The purpose of this invention is to provide an array-type electrically driven triaxial rock testing device and a rock testing method, which can solve the technical problems of low efficiency, large safety hazards, difficult maintenance, and slow dynamic response of existing testing devices.

[0004] To achieve the above objectives, the present invention adopts the following technical solution.

[0005] An array-type electrically driven triaxial rock testing device includes a base, a reaction frame fixed on the base, a confining pressure loading assembly, a lower axial indenter base, an upper axial indenter assembly, and a control center.

[0006] The confining pressure loading assembly is adjustable and located in the middle of the reaction frame. The confining pressure loading assembly includes a rigid ring beam, multiple electromagnetic servo linear actuators evenly arranged circumferentially on the rigid ring beam, pressure pads located at the ends of the telescopic rods of the actuators, and a pressure transmission sleeve. The cylinder of the actuator is fixedly connected to the rigid ring beam. The telescopic rod of the actuator extends and retracts radially along the rigid ring beam. Multiple telescopic rods can push the corresponding pressure pads to extend or retract synchronously toward the center of the rigid ring beam. The pressure transmission sleeve is located inside the multiple pressure pads to uniformly transmit pressure to the cylindrical surface of the rock sample core to generate uniform confining pressure.

[0007] The lower axial pressure head base is fixed on the base, and the upper axial pressure head assembly is located on the top of the reaction frame. The upper axial pressure head assembly includes a drive motor, a telescopic shaft, an upper axial pressure head located at the bottom of the telescopic shaft, and a cover plate slidably located on the telescopic shaft. The drive motor can drive the telescopic shaft to extend and retract axially. The upper axial pressure head is used to press the rock sample core axially onto the lower axial pressure head base to apply axial force. The cover plate can slide axially along the telescopic shaft. The cover plate, together with the lower axial pressure head base, the upper axial pressure head, and multiple pressure pads, forms a sealed space so that the pressure transmission sleeve can transmit pressure to the rock sample core.

[0008] The control center can control the actuators and the upper axial pressure head assembly to extend or retract.

[0009] Furthermore, the pressure pad has an arc-shaped structure and is connected to the corresponding telescopic rod via a hinge. Multiple pressure pads can together form a retractable cylindrical inner cavity.

[0010] Furthermore, the number of actuators installed on the rigid ring beam is ≥6.

[0011] Furthermore, the actuator incorporates a high-precision grating ruler displacement sensor and a miniature spoke-type pressure sensor for real-time feedback of the telescopic rod's feed amount and contact force.

[0012] Furthermore, the pressure-transmitting sleeve is a hollow cylindrical sleeve, whose material has the characteristics of being incompressible in volume and having an arbitrary shape. It is used to fill the gaps between the pressure pads and between the pressure pads and the rock sample core, converting the discrete pressure of the pressure pads into a continuous and uniform static pressure acting on the sample surface.

[0013] Furthermore, the pressure transmission sleeve is made of modified polyurethane or silicone rubber composite material with a Shore hardness of 30A to 60A.

[0014] A rock testing method, based on the above-mentioned testing apparatus, includes the following steps: S1. Wrap the cylindrical rock core sample inside the pressure transmission sleeve, place the pressure transmission sleeve in the cylindrical inner cavity composed of multiple pressure pads, and use the actuator operated by the control center to synchronously push the telescopic rod towards the center so that the multiple pressure pads initially press the pressure transmission sleeve and the rock core sample together. S2. Adjust the position of the confining pressure loading component on the reaction frame so that the lower ends of the pressure pad and the rock core are placed on the lower axial pressure head base. Operate the upper axial pressure head component through the control center to push the telescopic shaft towards the lower axial pressure head base so that the upper axial pressure head and the cover plate contact the upper ends of the rock core and the pressure pad respectively, and fix the cover plate to the lower axial pressure head base. S3. The control center controls multiple actuators to push the telescopic rod towards the center in a synchronized manner. Multiple pressure pads simultaneously squeeze the pressure transmission sleeve to transmit pressure to the rock sample core. The Pascal effect of the pressure transmission sleeve is used to approximate the transmission principle so that the pressure in each radial direction of the cylindrical surface of the rock sample core is the same. S4. Control the upper axial pressure head assembly through the control center to push the telescopic shaft, and use the upper axial pressure head to apply axial pressure to the rock sample core; S5. The control center monitors radial deformation in real time based on the Poisson effect of the rock sample core, and maintains constant confining pressure through high-frequency fine adjustment of the actuator, or performs dynamic unloading of confining pressure according to a preset path. S6. After the sample is damaged, the telescopic rod of the actuator and the telescopic shaft of the upper axial pressure head assembly return to their initial positions, and the solid pressure transmission sleeve recovers its original shape by its own elasticity, and the broken sample is removed.

[0015] By adopting the above technical solution, the present invention has the following beneficial effects: 1. This invention completely eliminates hydraulic oil, oil pumps and pipelines, achieving zero leakage and zero pollution. The laboratory environment is clean and there is no need to treat waste oil, which meets the requirements of green and environmentally friendly laboratories. 2. This invention eliminates the accumulation of high-pressure fluid energy in a hydraulic system, and unloads immediately upon power failure, fundamentally eliminating the risks of high-pressure oil injection and container rupture, making the testing environment safer. 3. The present invention has a fast response speed. The response frequency of the electromagnetic servo drive can reach more than 1kHz, which is far superior to the hydraulic system. It can accurately simulate the violent fluctuations of confining pressure during seismic waves and rock bursts. 4. This invention adopts a fully electric structure, which can work as soon as it is powered on, enabling plug-and-play operation. It also has no easily damaged seals, which greatly improves the lifespan and reliability of the equipment and enables low maintenance. 5. This invention can not only perform conventional triaxial rock tests, but also achieve true triaxial loading by independently controlling the electric cylinder thrust in different directions and cooperating with the corresponding shape of the pressure transmission sleeve. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0017] Figure 2 This is a schematic diagram of the overall structure of the confining pressure loading component in this invention.

[0018] Figure 3 This is a schematic diagram of the method of applying confining pressure in Example 1.

[0019] Figure 4 This is a schematic diagram of the axial pressure application method in Example 1.

[0020] Figure 5This is a schematic diagram illustrating the application of different loads along two axially perpendicular axes in Embodiment 2.

[0021] Figure descriptions: 1. Base, 11. Reaction frame, 2. Confining pressure loading assembly, 21. Rigid ring beam, 22. Actuator, 221. Telescopic rod, 23. Pressure pad, 24. Pressure transmission sleeve, 3. Lower axial pressure head base, 4. Upper axial pressure head assembly, 41. Drive motor, 42. Telescopic shaft, 43. Upper axial pressure head, 44. Cover plate, 441. Cover plate connecting rod, 5. Rock sample core. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the features and performance of an array-type electrically driven triaxial rock testing device and rock testing method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Example 1 Please see the appendix Figures 1-4 An array-type electrically driven triaxial rock testing device includes a base 1, a reaction frame 11 fixed on the base 1, a confining pressure loading assembly 2, a lower axial pressure head base 3, an upper axial pressure head assembly 4, and a control center.

[0024] The confining pressure loading assembly 2 is adjustablely located in the middle of the reaction frame 11. The confining pressure loading assembly 2 includes a rigid ring beam 21, a plurality of electromagnetic servo linear actuators 22 evenly arranged circumferentially on the rigid ring beam 21, pressure bearings 23 located at the ends of the telescopic rods 221 of the actuators 22, and pressure transmission sleeves 24. In particular, in order to maintain uniform axial pressure, the number of actuators 22 provided on the rigid ring beam 21 is even and ≥6. Preferably, this embodiment provides 8 actuators 22.

[0025] The cylinder of actuator 22 is fixedly connected to rigid ring beam 21, and the telescopic rod 221 of actuator 22 extends and retracts radially along rigid ring beam 21. The pressure pads 23 have an arc-shaped structure and are connected to the corresponding telescopic rods 221 via hinges. Multiple pressure pads 23 can collectively form a retractable cylindrical cavity, and multiple telescopic rods 221 can push the corresponding pressure pads 23 to extend or retract synchronously toward the center of rigid ring beam 21. A pressure-transmitting sleeve 24 is located inside the multiple pressure pads 23 to uniformly transmit pressure to the cylindrical surface of the rock sample core 5, generating uniform confining pressure. Specifically, the pressure-transmitting sleeve 24 is a hollow cylindrical sleeve, made of a material with incompressible volume and arbitrarily changeable shape. In this embodiment, modified polyurethane or silicone rubber composite material with a Shore hardness of 30A to 60A is selected. It is used to fill the gaps between pressure pads 23 and between pressure pads 23 and rock sample core 5, converting the discrete pressure of the pressure pads 23 into continuous uniform static pressure acting on the sample surface.

[0026] The actuator 22 has a built-in high-precision grating ruler displacement sensor and a miniature spoke-type pressure sensor for real-time feedback of the feed amount and contact force of the telescopic rod 221. The control center corrects the position of each push rod in real time through a PID algorithm, which can compensate for the non-uniform radial expansion of the rock sample 5.

[0027] The lower axial pressure head base 3 is fixedly mounted on the base 1, and the upper axial pressure head assembly 4 is mounted on the top of the reaction frame 11. The upper axial pressure head assembly 4 includes a drive motor 41, a telescopic shaft 42, an upper axial pressure head 43 mounted at the bottom of the telescopic shaft 42, and a cover plate 44 slidably mounted on the telescopic shaft 42. The drive motor 41 can drive the telescopic shaft 42 to extend and retract axially. The upper axial pressure head 43 is used to press the rock sample core 5 axially onto the lower axial pressure head base 3 to apply axial force. The cover plate 44 can slide axially along the telescopic shaft 42. The cover plate 44, together with the lower axial pressure head base 3, the upper axial pressure head 43, and multiple pressure pads 23, forms a sealed space so that the pressure transmission sleeve 24 transmits pressure to the rock sample core 5.

[0028] The control center can control the actuator 22 and the upper axial pressure head assembly 4 to extend or retract.

[0029] A rock testing method, based on the above-described testing apparatus, includes the following steps.

[0030] S1. Wrap the cylindrical rock core 5 sample inside the pressure transmission sleeve 24, place the pressure transmission sleeve 24 in the cylindrical inner cavity composed of 8 pressure bearings 23, and push the telescopic rod 221 towards the center simultaneously through the actuator 22 operated by the control center so that the 8 pressure bearings 23 initially press the pressure transmission sleeve 24 and the rock core 5 together.

[0031] S2. Adjust the position of the confining pressure loading component 2 on the reaction frame 11 so that the lower ends of the pressure pad 23 and the rock sample core 5 are placed on the lower axial pressure head base 3. Operate the upper axial pressure head component 4 through the control center to push the telescopic shaft 42 towards the lower axial pressure head base 3 so that the upper axial pressure head 43 and the cover plate 44 contact the upper ends of the rock sample core 5 and the pressure pad 23 respectively. Fix the connecting cover plate 44 to the lower axial pressure head base 3 through the cover plate connecting rod 441.

[0032] S3. The control center controls 8 actuators 22 to push the telescopic rod 221 towards the center in a synchronized manner. The 8 pressure bearings 23 simultaneously squeeze the pressure transmission sleeve 24 to transmit the pressure to the rock sample core 5. The Pascal effect of the pressure transmission sleeve 24 is used to approximate the transmission principle so that the pressure in each radial direction of the cylindrical surface of the rock sample core 5 is the same.

[0033] S4. The upper axial pressure head assembly 4 is controlled by the control center to push the telescopic shaft 42, and the upper axial pressure head 43 is used to apply axial pressure to the rock sample core 5.

[0034] S5. The control center monitors the radial deformation in real time based on the Poisson effect of the rock sample core 5, and maintains the confining pressure constant through the high-frequency fine adjustment of the actuator 22, or performs dynamic unloading of the confining pressure according to the preset path.

[0035] S6. After the sample is damaged, the telescopic rod 221 of the actuator 22 and the telescopic shaft 42 of the upper axial pressure head assembly 4 return to their initial positions, and the solid pressure transmission sleeve 24 recovers its original shape by its own elasticity, and the broken sample is removed.

[0036] In practice, the purpose of this invention is to provide an array-type electrically driven triaxial rock testing device and a rock testing method, which completely replaces the hydraulic system by combining high-precision motor technology with materials science.

[0037] The core concept of this invention is to replace "hydraulic energy + liquid oil" with "electrical energy + solid soft medium". The main body of the experimental device consists of eight high-thrust electromagnetic servo linear actuators 22 arranged circumferentially along a rigid ring beam 21 to form a contraction ring. Between the steel pressure pad 23 and the rock sample 5, a specially made pressure-transmitting sleeve 24 made of a superelastic polymer material is set. This material can exhibit isotropic pressure transmission characteristics similar to a liquid when under pressure, converting the mechanical thrust of the surrounding actuators 22 into a uniform circumferential wrapping force (containment pressure) on the rock sample core 5.

[0038] The operating procedure is explained using a standard Φ50mm×100mm rock sample core 5 as an example.

[0039] First, the confining pressure loading component 2 is constructed. Eight heavy-duty planetary roller screw electromagnetic servo linear actuators 22 with a rated thrust of 50kN are selected and evenly distributed and fixed on the rigid ring beam 22 in the circumferential direction. The front end of the telescopic rod 221 of the actuator 22 is equipped with a pressure bearing 23 with an arc of 45 degrees.

[0040] Next, the pressure-transmitting medium is prepared. A pressure-transmitting sleeve 24 is cast using transparent polyurethane with a Shore hardness of 45A. This material has extremely high tear resistance and resilience. The inner diameter of the pressure-transmitting sleeve 24 is slightly larger than the cylindrical diameter of the rock sample core 5 for easy fitting. The outer diameter of the pressure-transmitting sleeve 24 is determined according to the diameter of the cylindrical cavity composed of multiple pressure pads 23, with the goal of completely filling the gap between the rock sample 5 and the pressure pads 23.

[0041] In the specific test: S1, the cylindrical rock sample core 5 is wrapped in the pressure transmission sleeve 24, and the pressure transmission sleeve 24 is placed in the cylindrical inner cavity composed of 8 pressure bearings 23. The actuator 22 is operated by the control center to push the telescopic rod 221 towards the center so that the 8 pressure bearings 23 initially press the pressure transmission sleeve 24 and the rock sample core 5.

[0042] S2. Adjust the position of the confining pressure loading component 2 on the reaction frame 11 so that the lower ends of the pressure pad 23 and the rock sample core 5 are placed on the lower axial pressure head base 3. Operate the upper axial pressure head component 4 through the control center to push the telescopic shaft 42 towards the lower axial pressure head base 3 using the drive motor 41, so that the upper axial pressure head 43 and the cover plate 44 contact the upper ends of the rock sample core 5 and the pressure pad 23 respectively. Use the cover plate connecting rod 441 to fix the cover plate 44 to the lower axial pressure head base 3.

[0043] S3. The control center controls eight actuators 22 to simultaneously push the telescopic rod 221 towards the center, and eight pressure bearings 23 to simultaneously compress the pressure-transmitting sleeve 24. The pressure-transmitting sleeve 24 undergoes elastic volume deformation under pressure, tightly wrapping the rock sample core 5 and transmitting pressure to it. Utilizing the Pascal effect of the pressure-transmitting sleeve 24, the pressure in all radial directions of the cylindrical surface of the rock sample core 5 is made uniform. Based on a pre-calibrated curve, the thrust value of the actuators 22 is converted into the confining pressure value (e.g., 20 MPa) experienced by the rock. Due to the pseudo-fluid properties of polyurethane, although there is an eight-point external loading, the rock sample core 5 experiences a uniform confining pressure.

[0044] S4. The upper axial pressure head assembly 4 is controlled by the control center to push the telescopic shaft 42, and the upper axial pressure head 43 is used to apply axial pressure to the rock sample core 5 for destructive testing.

[0045] S5. The control center monitors the radial deformation in real time based on the Poisson effect of the rock sample core 5. When the rock sample core 5 expands (volume expansion), the force sensor built into the actuator 22 detects the pressure surge. The control loop will instruct the actuator 22 to retreat slightly within 1ms to maintain a constant confining pressure setting value until the sample is destroyed.

[0046] S6. After the sample is damaged, the telescopic rod 221 of the actuator 22 and the telescopic shaft 42 of the upper axial pressure head assembly 4 return to their initial positions. The solid pressure transmission sleeve 24 recovers its original shape by its own elasticity, and the broken sample is removed. The whole process is oil-free, noiseless, and requires only one person to operate.

[0047] Example 2 The apparatus of this invention, in addition to enabling conventional triaxial rock tests as shown in Example 1, can also perform true triaxial rock tests. True triaxial testing requires a cubic rock core to apply different loads along three mutually perpendicular axes of the rock core.

[0048] like Figure 5 As shown, by using four specially shaped pressure-transmitting blocks, different loads can be applied to the square rock sample core in two mutually perpendicular axes in the horizontal direction through the confining pressure loading component 2, and the load can be applied in the vertical axial direction through the upper axial pressure head component 4, thus realizing a true triaxial test.

[0049] It should be noted that the parts not described in detail in this solution are all prior art. The above embodiments are only used to illustrate the present invention, but the present invention is not limited to the above embodiments. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An array-type electrically driven triaxial rock testing device, characterized in that: Includes a base (1), a reaction frame (11) fixed on the base (1), a confining pressure loading assembly (2), a lower axial pressure head base (3), an upper axial pressure head assembly (4), and a control center. The confining pressure loading assembly (2) is adjustablely located in the middle of the reaction frame (11). The confining pressure loading assembly (2) includes a rigid ring beam (21), multiple electromagnetic servo linear actuators (22) evenly arranged on the rigid ring beam (21) along the circumference, pressure pads (23) located at the ends of the telescopic rods (221) of the actuators (22), and pressure transmission sleeves (24). The cylinder of the actuator (22) is fixedly connected to the rigid ring beam (21). The telescopic rods (221) of the actuator (22) extend and retract radially along the rigid ring beam (21). Multiple telescopic rods (221) can push the corresponding pressure pads (23) to extend or retract synchronously toward the center of the rigid ring beam (21). The pressure transmission sleeves (24) are located inside the multiple pressure pads (23) to uniformly transmit pressure to the cylindrical surface of the rock sample core (5) to generate uniform confining pressure. The lower axial pressure head base (3) is fixedly mounted on the base (1), and the upper axial pressure head assembly (4) is mounted on the top of the reaction frame (11). The upper axial pressure head assembly (4) includes a drive motor (41), a telescopic shaft (42), an upper axial pressure head (43) mounted at the bottom of the telescopic shaft (42), and a cover plate (44) slidably mounted on the telescopic shaft (42). The drive motor (41) can drive the telescopic shaft (42) to extend and retract axially. The upper axial pressure head (43) is used to press the rock sample core (5) axially onto the lower axial pressure head base (3) to apply axial force. The cover plate (44) can slide axially along the telescopic shaft (42). The cover plate (44) is used to form a sealed space together with the lower axial pressure head base (3), the upper axial pressure head (43), and multiple pressure pads (23) so that the pressure transmission sleeve (24) can transmit pressure to the rock sample core (5). The control center can control the actuator (22) and the upper axial pressure head assembly (4) to extend or retract.

2. The array-type electrically driven triaxial rock testing device as described in claim 1, characterized in that: The pressure tile (23) has an arc-shaped structure. The pressure tile (23) is connected to the corresponding telescopic rod (221) through a hinge. Multiple pressure tiles (23) can jointly form a retractable cylindrical inner cavity.

3. The array-type electrically driven triaxial rock testing device as described in claim 1, characterized in that: The number of actuators (22) installed on the rigid ring beam (21) is ≥6.

4. The array-type electrically driven triaxial rock testing device as described in claim 1, characterized in that: The actuator (22) incorporates a high-precision grating ruler displacement sensor and a miniature spoke-type pressure sensor to provide real-time feedback on the feed amount and contact force of the telescopic rod (221).

5. The array-type electrically driven triaxial rock testing device as described in claim 1, characterized in that: The pressure transmission sleeve (24) is a hollow cylindrical sleeve. Its material has the characteristics of being incompressible in volume and having an arbitrary shape. It is used to fill the gaps between the pressure pads (23) and between the pressure pads (23) and the rock sample core (5), and to convert the discrete pressure of the pressure pads (23) into a continuous and uniform static pressure acting on the sample surface.

6. The array-type electrically driven triaxial rock testing device as described in claim 5, characterized in that: The pressure transmission sleeve (24) is made of modified polyurethane or silicone rubber composite material with a Shore hardness of 30A to 60A.

7. A rock testing method, based on the testing apparatus of claim 1, characterized in that: Includes the following steps, S1. Wrap the cylindrical rock core (5) sample in the pressure transmission sleeve (24), place the pressure transmission sleeve (24) in the cylindrical inner cavity composed of multiple pressure pads (23), and push the telescopic rod (221) towards the center simultaneously through the actuator (22) operated by the control center so that the multiple pressure pads (23) initially press the pressure transmission sleeve (24) and the rock core (5). S2. Adjust the position of the confining pressure loading component (2) in the reaction frame (11) row so that the lower ends of the pressure pad (23) and the rock core (5) are placed on the lower axial pressure head base (3). Through the control center, operate the upper axial pressure head component (4) to push the telescopic shaft (42) towards the lower axial pressure head base (3) so that the upper axial pressure head (43) and the cover plate (44) respectively contact the upper ends of the rock core (5) and the pressure pad (23) and fix the cover plate (44) to the lower axial pressure head base (3). S3. By controlling multiple actuators (22) through the control center to push the telescopic rod (221) towards the center simultaneously, multiple pressure pads (23) simultaneously squeeze the pressure transmission sleeve (24) to transmit the pressure to the rock sample core (5). By utilizing the Pascal effect of the pressure transmission sleeve (24) to approximate the transmission principle, the pressure in each radial direction of the cylindrical surface of the rock sample core (5) is the same. S4. The upper axial pressure head assembly (4) is controlled by the control center to push the telescopic shaft (42) and apply axial pressure to the rock sample core (5) using the upper axial pressure head (43); S5. The control center monitors the radial deformation in real time based on the Poisson effect of the rock core (5), and maintains the confining pressure constant by the high-frequency fine adjustment of the actuator (22), or performs dynamic confining pressure unloading according to the preset path. S6. After the sample is damaged, the telescopic rod (221) of the actuator (22) and the telescopic shaft (42) of the upper axial pressure head assembly (4) return to their initial positions, and the solid pressure transmission sleeve (24) recovers its original state by its own elasticity and removes the broken sample.

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