A test device and method for testing the energy storage and release of rock mass with variable stiffness

Abstract

This invention relates to the field of geotechnical physical property testing, specifically to a rock mass energy storage and release variable stiffness testing device, comprising an axial compression stiffness adjustment device, a confining pressure variable stiffness adjustment device, a deformation measurement system, and a measurement and control system. The measurement and control system is correspondingly connected to the deformation measurement system to control the axial stiffness adjustment actuator, axial loading actuator, horizontal stiffness adjustment actuator, and horizontal loading actuator based on the detection results of the deformation measurement system. Through the coordinated control of the measurement and control system, the axial compression stiffness adjustment device, the confining pressure variable stiffness adjustment device, and the deformation measurement system, the test is first set up by the measurement and control system. The axial compression stiffness adjustment device realizes axial loading and stiffness change control and real-time feedback. The confining pressure device realizes confining pressure loading and variable stiffness control and real-time feedback. The deformation measurement system realizes effective output and feedback of the test data, effectively measuring and controlling changes in stiffness and strength and collecting accurate data.

Description

Technical Field

[0001] This invention belongs to the field of rock and soil physical property testing technology, specifically relating to a rock mass energy storage and release variable stiffness testing device and method. Background Technology

[0002] The storage limit energy of rocks is an important research topic in rock engineering, such as mining, as the magnitude of energy accumulation in a rock mass is a fundamental factor determining whether rockbursts will occur. In actual underground environments such as caverns, the stored strain energy of rock masses varies under different stress states. When the original rock stress is under a triaxial unequal pressure state, local stress reduction zones will appear in the surrounding rock of underground engineering projects, and the strain energy in the elastic deformation zone will decrease. The variable stiffness testing device for rock mass energy storage and release enables the control and acquisition of stiffness and strength changes during the test, more closely approximating the failure mode under natural conditions, and providing more accurate measurements of the storage limit energy of different rock masses under different conditions.

[0003] For rocks in underground engineering environments, current MTS and RMT are rigid testing machines. When testing the properties of the rock mass itself, the loading stiffness is mostly a constant value. They mainly test the basic properties of the rock mass, such as compressive strength, tensile strength, and shear strength. This has certain limitations for studying the energy storage and release phenomenon during the loading and unloading of the rock mass. As the mining depth increases, the state and location of the surrounding rock in deep tunnels are different. The testing device needs to be able to further realize the function of simulating the variable stiffness test of rock mass energy storage and release.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art. This invention provides a test device and method for testing the variable stiffness of rock mass energy storage and release.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A rock mass energy storage and release variable stiffness testing device includes an axial compression stiffness adjustment device, a confining pressure variable stiffness adjustment device, a deformation measurement system, and a measurement and control system; The axial compression stiffness adjustment device includes: An axial stiffness adjustment actuator is mounted on a frame and can adjust its own stiffness; an axial stiffness adjustment sensor is provided at one end of the axial stiffness adjustment actuator corresponding to the rock sample. An axial loading actuator is provided, which is located directly below the axial stiffness adjustment actuator, and an axial loading sensor is provided at one end of the axial loading actuator corresponding to the rock mass sample. The axial stiffness adjustment actuator and the axial loading actuator squeeze the rock mass sample relative to each other to apply a force to the rock mass sample in the axial direction. The confining pressure stiffness adjustment device includes: A horizontal guide rail assembly that extends horizontally and passes between the axial stiffness adjustment actuator and the axial loading actuator; A horizontal variable stiffness adjustment actuator is provided at one end of the horizontal guide rail assembly, which can adjust its own stiffness. A horizontal variable stiffness adjustment sensor is provided at one end of the horizontal variable stiffness adjustment actuator corresponding to the rock mass sample. A horizontal loading actuator is provided at the other end of the horizontal guide rail assembly, and a horizontal loading sensor is provided between the horizontal loading actuator and the rock mass sample. The horizontal variable stiffness adjustment actuator and the horizontal variable stiffness adjustment actuator squeeze the rock mass sample relative to each other to apply a force to the rock mass sample in the horizontal direction. The deformation measurement system is correspondingly connected to the axial stiffness adjustment sensor, the axial loading sensor, the horizontal stiffness adjustment sensor, and the horizontal loading sensor. The measurement and control system is connected to the deformation measurement system to control the axial stiffness adjustment actuator, axial loading actuator, horizontal stiffness adjustment actuator, and horizontal loading actuator based on the detection results of the deformation measurement system.

[0007] Preferably, a first axial elastic pressure plate ring is provided between the axial stiffness adjustment sensor and the rock mass sample, and a second axial elastic pressure plate ring is provided between the axial loading sensor and the rock mass sample. A first horizontal elastic pressure plate ring is provided between the horizontal variable stiffness adjustment sensor and the rock mass sample, and a second horizontal elastic pressure plate ring is provided between the variable stiffness loading sensor and the rock mass sample. An axially loaded steel column is provided between the first axially elastic pressure plate ring and the rock mass sample. A first sliding sleeve corresponding to the axially loaded steel column is provided on the frame. The first sliding sleeve is provided with a waist-shaped hole corresponding to the axially loaded steel column. The waist-shaped hole extends along the load direction of the horizontal loading actuator. A first horizontal loading steel column is provided between the first horizontal elastic pressure plate ring and the rock mass sample. A second sliding sleeve corresponding to the first horizontal loading steel column is provided on the frame. The second sliding sleeve is provided with a waist-shaped hole corresponding to the axial loading steel column. The waist-shaped hole extends along the load direction of the axial loading actuator. A second horizontal loading steel column is provided between the second horizontal elastic pressure plate ring and the rock mass sample. A third sliding sleeve corresponding to the second horizontal loading steel column is provided on the frame. The third sliding sleeve is provided with a waist-shaped hole corresponding to the axial loading steel column. The waist-shaped hole extends along the load direction of the axial loading actuator.

[0008] Preferably, the deformation measurement system further includes an axial displacement sensor and a horizontal displacement sensor; wherein, the axial displacement sensor is disposed between the axial elastic pressure plate ring and the axially loaded steel column; and the horizontal displacement sensor is disposed between the second horizontally loaded steel column and the second horizontal elastic pressure plate ring.

[0009] Preferably, the frame is equipped with columns corresponding to the axial compression stiffness adjustment device; A first axial loading frame is provided at the upper end of the column, and the axial stiffness adjustment actuator is correspondingly assembled on the first axial loading frame. A second axial loading frame is provided at the lower end of the column, and the axial loading actuator is correspondingly assembled on the second axial loading frame.

[0010] Preferably, the first axial loading frame is provided with a plurality of guide posts evenly distributed around the axial stiffness adjustment actuator, and the axial stiffness adjustment sensor is slidably mounted on the guide posts.

[0011] Beneficial effects: The testing device provided by this invention coordinates and controls the axial compression stiffness adjustment device, the confining pressure variable stiffness adjustment device, and the deformation measurement system through a measurement and control system. First, the measurement and control system sets up the test. The axial compression variable stiffness adjustment device realizes the control and real-time feedback of axial loading and stiffness change. The confining pressure device realizes the control and real-time feedback of confining pressure loading and variable stiffness. The deformation measurement system realizes the effective output and feedback of the test data, effectively measuring and controlling the changes in stiffness and strength and collecting accurate data.

[0012] The testing device can adjust the stiffness of rock tests according to the testing method, and proposes an easy-to-operate method for using the testing device to study the energy release and accumulation phenomena of rock masses during loading and unloading. Then, by observing the energy accumulation phenomenon during the loading process, the storage limit energy of the test rock mass under simulated underground confining pressure is determined, providing a theoretical basis for the prevention and control of rockburst dynamic disasters in coal mines. Attached Figure Description

[0013] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Wherein: Figure 1 This is a front view of the entire invention; Figure 2 This is a side view of the present invention.

[0014] In the figure: 101, first axial loading frame; 102, guide column; 103, axial stiffness adjustment actuator; 104, axial stiffness adjustment sensor; 105, axial elastic pressure plate ring; 106, axial loading steel column; 107, axial loading sensor; 108, axial loading actuator; 109, second axial loading frame. 201. First horizontal loading frame; 202. Horizontal guide rail assembly; 203. Horizontal variable stiffness adjustment actuator; 204. Horizontal variable stiffness adjustment sensor; 205. First horizontal elastic pressure plate ring; 206. First horizontal loading steel column; 207. Horizontal loading sensor; 208. Horizontal loading actuator; 209. Second horizontal loading frame; 210. Second horizontal elastic pressure plate ring; 211. Second horizontal loading steel column; 301. Axial displacement sensor; 302. Horizontal displacement sensor. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0016] In the description of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. The terms "connected" and "linked" used in this invention should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through intermediate components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0017] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0018] like Figure 1-2As shown, a rock mass energy storage and release variable stiffness testing device includes an axial pressure stiffness adjustment device, a confining pressure variable stiffness adjustment device, a deformation measurement system, and a measurement and control system. The axial pressure stiffness adjustment device can apply loads to the two axial sides of the rock mass sample, including an axial stiffness adjustment actuator 103 and an axial loading actuator (servo hydraulic cylinder). The axial stiffness adjustment actuator 103 is mounted on a frame, and an axial stiffness adjustment sensor 104 is provided at one end of the axial stiffness adjustment actuator 103 (servo hydraulic cylinder) corresponding to the rock sample to adjust the variable stiffness stress in real time through telescopic control. The frame is provided with multiple columns, and an axial loading frame is set above the columns. The axial stiffness adjustment actuator 103 is fixed in the middle of the loading frame. The axial loading actuator is located directly below the axial stiffness adjustment actuator, and an axial loading sensor 107 is provided at one end of the axial loading actuator corresponding to the rock mass sample. The axial stiffness adjustment actuator and the axial loading actuator compress the rock mass sample relative to each other to apply force to the rock mass sample in the axial direction. The axial stiffness adjustment actuator is equivalent to a spring, and its own stiffness can be adjusted according to the sensing of the axial stiffness adjustment sensor 104 (pressure sensor). Specifically, the axial stiffness adjustment actuator can be a servo cylinder, which determines its own stiffness according to the pressure of the supplied gas, thereby adjusting its own stiffness according to actual needs, thus adjusting the axial stiffness of the device. The axial loading actuator can apply a load to the rock mass sample, which controls the force applied to the spring. The confining pressure stiffness adjustment device includes a horizontal guide rail assembly 202, a horizontal stiffness adjustment actuator 203 (servo hydraulic cylinder), and a horizontal loading actuator: the horizontal guide rail assembly 202 extends horizontally and passes between the axial stiffness adjustment actuator and the axial loading actuator; the horizontal stiffness adjustment actuator... The actuator 203 is located at one end of the horizontal guide rail assembly 202. A horizontal stiffness adjustment sensor 204 (pressure sensor) is located at the end of the horizontal stiffness adjustment actuator 203 corresponding to the rock mass sample. The horizontal stiffness adjustment actuator 203 is equivalent to a spring and can adjust its own stiffness according to the sensing of the horizontal stiffness adjustment sensor 204. It can adjust the load on the horizontal stiffness adjustment actuator 203 in the horizontal direction. The horizontal loading actuator is located at the other end of the horizontal guide rail assembly 202 to adjust the variable stiffness stress in real time through telescopic control. A horizontal loading sensor 207 is provided between the horizontal loading actuator and the rock mass sample. The horizontal loading sensor 207 is a pressure sensor used to detect the stiffness of the rock mass sample and thus change the stiffness of the press itself.

[0019] The deformation measurement system is connected to the axial stiffness adjustment sensor 104, the axial loading sensor 107, the horizontal stiffness adjustment sensor 204, and the horizontal loading sensor 207. The measurement and control system is connected to the deformation measurement system to control the axial stiffness adjustment actuator 103, the axial loading actuator, the horizontal stiffness adjustment actuator 203, and the horizontal loading actuator based on the detection results of the deformation measurement system. The test load and stiffness can be set according to the rock mass sample or test requirements, so that the device can operate automatically according to the preset load. This realizes the effective acquisition of real-time feedback and measurement and control outputs for axial loading and stiffness adjustment, horizontal confining pressure loading and stiffness adjustment, and effective acquisition of real-time feedback. In this embodiment, the main contents measured by the testing machine include load force and displacement deformation of the rock mass sample. The axial stiffness adjustment actuator 103 and the horizontal stiffness adjustment actuator 203 are equivalent to adding an elastic ring under the stiffness testing machine, which can control and change the stiffness of the equipment, thereby simulating the actual rock mass force field. This embodiment sets up four forces and four displacements in two directions. A change in any displacement or loading force will affect the others, enabling comprehensive recording and analysis of the actual changes in the rock mass sample. This achieves effective output and feedback of the test data, effectively measuring and controlling changes in stiffness and strength, and acquiring accurate data. The deformation measurement system is connected to an axial variable stiffness deformation sensor, an axial stress loading sensor, a horizontal variable stiffness deformation sensor, and a horizontal stress loading sensor. Both the axial and horizontal stress loading sensors are pressure sensors. The axial variable stiffness is adjusted in real time through displacement and deformation control.

[0020] Specifically, a first axial elastic pressure plate ring 105 is provided between the axial variable stiffness adjustment sensor 104 and the rock mass sample, and a second axial elastic pressure plate ring 105 is provided between the axial loading sensor 107 and the rock mass sample; a first horizontal elastic pressure plate ring 205 is provided between the horizontal variable stiffness adjustment sensor 204 and the rock mass sample, and a second horizontal elastic pressure plate ring 210 is provided between the variable stiffness loading sensor and the rock mass sample; the first axial elastic pressure plate ring 105, the second axial elastic pressure plate, the first horizontal elastic pressure plate ring 205, and the second horizontal elastic pressure plate are all made of elastic materials, such as rubber or elastic steel fiberboard, which can play a role in deceleration during load loading. An elliptical perforation is provided in the middle of the elastic pressure plate. When the preload is applied, the elastic pressure plate ring is equivalent to a spring, which can store the load energy. The elastic pressure plate relies on its own elasticity to perform elastic loading. During the test, the rock mass sample will undergo relative displacement. At this time, the two sides of the elliptical perforation can be staggered, so as to buffer and make way when the rock mass sample is displaced under force, and ensure the force during the displacement process.

[0021] In this embodiment, an axially loaded steel column 106 is provided between the first axially elastic pressure plate ring 105 and the rock mass sample. A first sliding sleeve corresponding to the axially loaded steel column 106 is provided on the frame. The first sliding sleeve has a waist-shaped hole corresponding to the axially loaded steel column 106, and the waist-shaped hole extends along the driving direction of the horizontal loading actuator. A first horizontally loaded steel column 206 is provided between the first horizontally elastic pressure plate ring 205 and the rock mass sample. A second sliding sleeve corresponding to the first horizontally loaded steel column 206 is provided on the frame. The second sliding sleeve has a waist-shaped hole corresponding to the axially loaded steel column 106, and the waist-shaped hole extends along the driving direction of the axial loading actuator. A second horizontally loaded steel column 211 is provided between the second horizontally elastic pressure plate ring 210 and the rock mass sample. A third sliding sleeve corresponding to the second horizontally loaded steel column 211 is provided on the frame. The third sliding sleeve has a waist-shaped hole corresponding to the axially loaded steel column 106, and the waist-shaped hole extends along the driving direction of the axial loading actuator. The axial loading steel column 106, the first horizontal loading steel column 206, and the second horizontal loading steel column 211 are all slidably mounted on the frame, and can slide accordingly on the frame as the rock mass sample moves. In this embodiment, no loading steel column is set below the rock mass sample; the rock mass sample is placed directly above the axial loading sensor 107, and the rock mass sample is supported by the axial loading sensor 107 and the axial loading actuator.

[0022] In this embodiment, a loading block is provided at one end of the axial loading steel column 106 corresponding to the rock mass sample. Loading plates corresponding to the first horizontal loading steel column 206 and the second horizontal loading steel column 211 are provided on both sides of the loading block. The two loading plates are respectively assembled onto the loading block via pins. A strip-shaped hole extending along the load direction of the horizontal loading actuator is provided on the loading frame, allowing the loading plate to slide along the strip-shaped hole on the loading block under load during the test. A pad is provided above the axial loading sensor 107, facing the lower end face of the loading block. Multiple pads are provided, and they can be added or removed according to actual needs and the height of the rock mass sample, thereby ensuring that the rock mass sample is directly facing the confining pressure stiffness adjustment device. The bottom of the axial loading frame is fixedly connected to the horizontal loading frame. The bottom of the axial loading frame has a lower structural beam, forming a narrow U-shape, which ensures stable test performance. The axial loading actuator 108 is mounted on the bottom crossbeam of the axial loading frame. The axial loading actuator 108 can realize axial compression loading and move in conjunction with the stiffness adjustment actuator to realize axial stiffness adjustment and loading.

[0023] In another optional embodiment, the deformation measurement system further includes an axial displacement sensor 301 and a horizontal displacement sensor 302. The axial displacement sensor 301 is disposed between the axial elastic pressure plate ring 105 and the axially loaded steel column 106, and can monitor the axial displacement of the rock mass sample. The horizontal displacement sensor 302 is disposed between the second horizontally loaded steel column 211 and the second horizontal elastic pressure plate ring 210. The horizontal displacement sensor can monitor the axial displacement of the rock mass sample. During dynamic overload adjustment, the axial elastic pressure plate ring 105 does not deform after being loaded with a certain load (or the elastic variable is pre-determined based on the elastic coefficient), thereby avoiding affecting the test results.

[0024] In another optional embodiment, the frame is provided with four columns corresponding to the axial stiffness adjustment device. A first axial loading frame 101 is provided at the upper end of the columns, and an axial stiffness adjustment actuator 103 is correspondingly mounted on the first axial loading frame 101. A second axial loading frame 109 is provided at the lower end of the columns, and an axial loading actuator is correspondingly mounted on the second axial loading frame 109. The first axial loading frame 101 is provided with a plurality of guide posts 102 evenly distributed around the axial stiffness adjustment actuator 103, and an axial stiffness adjustment sensor 104 is slidably mounted on the guide posts 102. When a load is applied in the longitudinal direction, an axial guide rail assembly is provided on the axial stiffness adjustment sensor 104. The axial guide rail assembly includes a guide plate fixed to the axial stiffness adjustment sensor 104, and a plurality of through holes evenly distributed around the axial stiffness adjustment sensor 104 are provided on the guide plate. The axial loading frame is provided with guide posts 102 corresponding to the through holes. The axially loaded frame has a controllable stiffness ≥20GN / m. An axial stiffness adjustment actuator 103 is connected to the top of the guide plate, with an adjustment range of 0 to 1000kN and a stroke of 100mm. A stiffness adjustment sensor is connected to the lower end of the axial stiffness adjustment actuator 103. A nut at the lower end of the stiffness adjustment sensor is connected to an axial elastic pressure plate ring 105. This axial loading actuator 108 has a loading adjustment range of 0 to 600KN and a stroke of 100mm.

[0025] In another optional embodiment, the horizontal guide rail assembly 202 includes two guide rails disposed on both sides of the rock mass sample, with both ends of the two guide rails fixed to the frame; a first horizontal loading frame 201 corresponding to the horizontal variable stiffness adjustment actuator 203 is fixed to one end of each of the two guide rails; and a second horizontal loading frame 209 corresponding to the horizontal loading actuator is fixed to the other end of each of the two guide rails. The horizontal guide rail assembly 202 is composed of electrically controlled wheel systems on both the horizontal variable stiffness adjustment actuator 203 and the horizontal loading actuator, each equipped with a corresponding guide rail, enabling horizontal movement between the first horizontal loading frame 201 and the second horizontal loading frame 209. A horizontal guide rail assembly 202 is installed on the flat loading frame. The horizontal loading frame is required to withstand 600KN. The horizontal variable stiffness adjustment actuator 203 can adjust the variable stiffness to 0.6, 0.8, 1.0, and 2GN / m. The horizontal variable stiffness adjustment actuator 203 is connected to a horizontal variable stiffness adjustment sensor 204, which is a deformation sensor used to detect horizontal deformation and perform stress control based on the deformation.

[0026] During testing, a certain longitudinal displacement can be provided through the horizontal elastic pressure plate ring to ensure the test results. The horizontal loading actuator 208 can control the confining pressure range from 0 to 30 MPa.

[0027] The lower end of the axial stiffness adjustment actuator is connected to the axial stiffness adjustment sensor 104 via a nut. The lower movable end of the axial stiffness adjustment sensor 104 is a high-strength steel structure, and the nut also has compressive and tensile strength to ensure that it will not break or be crushed during stiffness adjustment. A pair of axial guide rail assemblies are connected to the two outer ends of the stiffness adjustment sensor to realize axial testing activities. This ensures that after loading during the test, the stiffness adjustment will not deviate in the axial direction. The axial guide rail assemblies have elasticity and memory properties, allowing for slow correction of any deviation.

[0028] In another optional embodiment, the deformation measurement system includes a control center and an output module. The control center can be a computer or a PLC controller, capable of controlling the axial stiffness adjustment actuator 103, the axial loading actuator, the horizontal stiffness adjustment actuator 203, and the horizontal loading actuator based on the detection results of the deformation measurement system. It further controls the moving parts of the stiffness adjustment actuator to adjust the stiffness. The stiffness adjustment sensor 104 feeds the measured data back to the measurement and control system for hydraulic steady-state adjustment of adding and unloading. Stiffness adjustment is achieved by changing the horizontal stiffness adjustment actuator 203. The horizontal loading hydraulic control device is controlled, further controlling the loading component of the horizontal loading actuator 208 to act on the left-side horizontal loading sensor 207. The horizontal loading sensor 207 then causes the horizontal loading steel column connected to the left to act on the specimen, and feeds the measured data back to the measurement and control system for hydraulic steady-state adjustment of adding and unloading, achieving horizontal confining pressure control. Axial data acquisition is achieved by the axial displacement sensor 301 and the axial loading sensor 107 feeding back information to the measurement and control system. Horizontal data acquisition is achieved by the horizontal displacement sensor 302 feeding back information to the measurement and control system. The output module is connected to the control center and is used to convert the output displacement and load function relationship, which can further analyze the relationship between load and displacement during the test.

[0029] In another optional embodiment, the present invention provides a method for testing the variable stiffness of rock mass energy storage and release, comprising the following steps: Step S1: First, the parameters for stiffness and strength operation of the testing device are set through the measurement and control system. The parameter settings include loading time, loading speed, loading grade unit value, etc., to ensure the real natural condition of the surrounding rock of the simulated pore structure under a certain state in the corresponding test scheme. This enables the study of the rock's ultimate energy storage under different processes and states of time-series energy storage and release, and the study of the changes in the rock's ultimate energy storage under different loading paths.

[0030] Step S2: Place the rock sample and preload it using a loading steel column. Unload the load after ensuring the steel column is in close contact with the rock. Trim the contact surface of the rock. If a smooth contact surface cannot be guaranteed, slightly fill the contact surface and the loading steel column with rock powder. Start the measurement and control system to control the deformation measurement system to preload the loading steel column, ensuring close contact with the rock in all directions. This prevents localized compression of protruding rock sections during loading and unloading, which could lead to structural differences in the test setup due to localized stress. After confirmation, unload the load to zero the negative pressure sensor reading. Control the stiffness and strength changes of the axial pressure stiffness adjustment device and the confining pressure variable stiffness adjustment device to reach the set parameters, and initialize the test device displacement as the initial value for displacement recording. Simultaneously, control the stiffness and strength changes of the axial pressure stiffness adjustment device and the confining pressure variable stiffness adjustment device to reach the set values, and initialize the displacement sensor to start recording as the initial value.

[0031] Step S3: The measurement and control system controls loading and unloading according to the set parameters. The deformation measurement system collects data through the displacement sensor and converts the displacement and load function relationship into an output through the measurement and control system. The measurement and control system controls loading and unloading according to the operating parameters. The displacement sensor and load sensor of the deformation measurement system collect data and convert the displacement and load function relationship into an output through the measurement and control system. The stiffness adjustment sensor and axial loading sensor 107 on the axial compression stiffness adjustment device provide real-time feedback to the measurement and control system for steady-state adjustment. The variable stiffness adjustment sensor 104 and horizontal loading sensor 207 on the variable stiffness adjustment device provide real-time feedback to the measurement and control system for steady-state adjustment.

[0032] Step S4: After the measurement and control system controls the test device to run until the rock becomes unstable and fails, the experiment stops.

[0033] In another optional embodiment, in step S3, during the loading and unloading process, the stiffness adjustment sensor and axial loading sensor 107 of the axial pressure stiffness adjustment device feed the detection data back to the measurement and control system in real time for steady-state adjustment. The variable stiffness adjustment sensor 104 and horizontal loading sensor 207 of the confining pressure variable stiffness adjustment device also feed the data back to the measurement and control system in real time for steady-state adjustment, ensuring that the stiffness value is always controlled within the preset value. Steady-state adjustment through displacement control and deformation control primarily controls and stabilizes the rock sample at the preset variable stiffness value, keeping it in the center position, thereby achieving the variable stiffness loading test.

[0034] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A rock mass energy storage and release variable stiffness testing device, characterized in that, It includes an axial compression stiffness adjustment device, a confining pressure variable stiffness adjustment device, a deformation measurement system, and a measurement and control system; The axial compression stiffness adjustment device includes: An axial stiffness adjustment actuator is mounted on a frame and can adjust its own stiffness; an axial stiffness adjustment sensor is provided at one end of the axial stiffness adjustment actuator corresponding to the rock sample. An axial loading actuator is provided, which is located directly below the axial stiffness adjustment actuator, and an axial loading sensor is provided at one end of the axial loading actuator corresponding to the rock mass sample. The axial stiffness adjustment actuator and the axial loading actuator squeeze the rock mass sample relative to each other to apply a force to the rock mass sample in the axial direction. The confining pressure stiffness adjustment device includes: A horizontal guide rail assembly that extends horizontally and passes between the axial stiffness adjustment actuator and the axial loading actuator; A horizontal variable stiffness adjustment actuator is provided at one end of the horizontal guide rail assembly, which can adjust its own stiffness. A horizontal variable stiffness adjustment sensor is provided at one end of the horizontal variable stiffness adjustment actuator corresponding to the rock mass sample. A horizontal loading actuator is provided at the other end of the horizontal guide rail assembly, and a horizontal loading sensor is provided between the horizontal loading actuator and the rock mass sample. The horizontal variable stiffness adjustment actuator and the horizontal variable stiffness adjustment actuator squeeze the rock mass sample relative to each other to apply a force to the rock mass sample in the horizontal direction. The deformation measurement system is correspondingly connected to the axial stiffness adjustment sensor, the axial loading sensor, the horizontal stiffness adjustment sensor, and the horizontal loading sensor. The measurement and control system is connected to the deformation measurement system to control the axial stiffness adjustment actuator, axial loading actuator, horizontal stiffness adjustment actuator and horizontal loading actuator based on the detection results of the deformation measurement system. A first axial elastic pressure plate ring is provided between the axial stiffness adjustment sensor and the rock mass sample, and a second axial elastic pressure plate ring is provided between the axial loading sensor and the rock mass sample. A first horizontal elastic pressure plate ring is provided between the horizontal variable stiffness adjustment sensor and the rock mass sample, and a second horizontal elastic pressure plate ring is provided between the variable stiffness loading sensor and the rock mass sample. An axially loaded steel column is provided between the first axially elastic pressure plate ring and the rock mass sample. A first sliding sleeve corresponding to the axially loaded steel column is provided on the frame. The first sliding sleeve is provided with a waist-shaped hole corresponding to the axially loaded steel column. The waist-shaped hole extends along the load direction of the horizontal loading actuator. A first horizontal loading steel column is provided between the first horizontal elastic pressure plate ring and the rock mass sample. A second sliding sleeve corresponding to the first horizontal loading steel column is provided on the frame. The second sliding sleeve is provided with a waist-shaped hole corresponding to the axial loading steel column. The waist-shaped hole extends along the load direction of the axial loading actuator. A second horizontal loading steel column is provided between the second horizontal elastic pressure plate ring and the rock mass sample. A third sliding sleeve corresponding to the second horizontal loading steel column is provided on the frame. The third sliding sleeve has a waist-shaped hole corresponding to the axial loading steel column. The waist-shaped hole extends along the load direction of the axial loading actuator. The deformation measurement system also includes an axial displacement sensor and a horizontal displacement sensor. The axial displacement sensor is located between the axial elastic pressure plate ring and the axial loading steel column. The horizontal displacement sensor is located between the second horizontal loading steel column and the second horizontal elastic pressure plate ring.

2. The rock mass energy storage and release variable stiffness testing device according to claim 1, characterized in that, The frame is equipped with columns that have corresponding axial compression stiffness adjustment devices; A first axial loading frame is provided at the upper end of the column, and the axial stiffness adjustment actuator is correspondingly assembled on the first axial loading frame. A second axial loading frame is provided at the lower end of the column, and the axial loading actuator is correspondingly assembled on the second axial loading frame.

3. The rock mass energy storage and release variable stiffness testing device according to claim 2, characterized in that, The first axial loading frame is provided with a plurality of guide posts evenly distributed around the axial stiffness adjustment actuator, and the axial stiffness adjustment sensor is slidably mounted on the guide posts.

4. The rock mass energy storage and release variable stiffness testing device according to claim 1, characterized in that, The horizontal guide rail assembly includes two guide rails disposed on both sides of the rock mass sample, with the two ends of the two guide rails respectively fixed on the frame; One end of each of the two guide rails is fixed with a first horizontal loading frame corresponding to the horizontal variable stiffness adjustment actuator. The other end of the two guide rails is fixed with a second horizontal loading frame corresponding to the horizontal loading actuator.

5. The rock mass energy storage and release variable stiffness testing device according to claim 1, characterized in that, The deformation measurement system includes: The control center controls the axial stiffness adjustment actuator, axial loading actuator, horizontal stiffness adjustment actuator, and horizontal loading actuator based on the detection results of the deformation measurement system. The output module is connected to the control center and is used to convert the output displacement and load function relationship.

6. A method for testing the variable stiffness of rock mass energy storage and release, wherein the test is conducted using the variable stiffness testing device described in any one of claims 1-5, characterized in that... Includes the following steps: Step S1: First, set the parameters for the stiffness and strength operation of the testing device; Step S2: Place the rock mass sample and preload the rock mass sample circumferentially by loading a steel column. Unload the load after ensuring that the loading steel column is in close contact with the rock. The stiffness and strength changes of the axial compression stiffness adjustment device and the confining pressure variable stiffness adjustment device are controlled and adjusted to reach the set parameters, and the displacement of the test device is initialized as the initial value for displacement recording. In step S3, the measurement and control system controls the loading and unloading according to the set parameters. The deformation measurement system collects data through displacement sensors and load sensors, and then converts and outputs the displacement and load function relationship through the measurement and control system. Step S4: After the measurement and control system controls the test device to run until the rock becomes unstable and fails, the experiment stops.

7. The method for testing the variable stiffness of rock mass energy storage and release according to claim 6, characterized in that, In step S3, during the loading and unloading process, the stiffness adjustment sensor and axial loading sensor of the axial pressure stiffness adjustment device will feed back the detection data to the measurement and control system in real time for steady-state adjustment. The variable stiffness adjustment sensor and horizontal loading sensor of the confining pressure variable stiffness adjustment device provide real-time feedback to the measurement and control system for steady-state adjustment.

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