Low-temperature Rock Mass Variable-frequency and Variable-amplitude Dynamic Shear Acoustic Physics Test System and Test Method

Abstract

The present invention discloses a low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system and a test method. The test system includes a low-temperature control subsystem, a dynamic shear subsystem, an acoustic physics test subsystem, and a measurement and control subsystem. This testing machine realizes fatigue cyclic shear tests with variable frequencies and variable amplitudes through a frame system and an environmental chamber, and simultaneously conducts acoustic emission and ultrasonic tests. It can invert the source mechanism during the shear fracture process of the rock mass, and can also perform acoustic wave imaging on the degradation of the mesoscopic structure during the deformation and fracture process of the rock mass. It has the characteristics of adjustable frequency and amplitude, can simultaneously conduct acoustic emission and ultrasonic tests, invert the source mechanism during the shear fracture process of the rock mass, and perform acoustic wave imaging on the degradation of the mesoscopic structure during the deformation and fracture process of the rock mass.

Description

Technical Field

[0001] The present invention belongs to the field of testing the mechanical properties of rocks, and particularly relates to a low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system and a test method. Background Art

[0002] Open-pit mine engineering slopes are often subjected to the disturbance of excavation and frequent blasting stress waves. When the bench slope is far from the blasting source, the blasting stress waves evolve into seismic waves, which promotes the deterioration of the mechanical properties of rock masses. Therefore, the deterioration of the rock mass structure of mine slopes is a typical dynamic problem. According to incomplete statistics, more than 60% of the total number of landslides in open-pit mines are caused by the penetration of rock bridges. Typical open-pit landslides include the landslide in Zhujiabao Iron Mine of Pangang, the east slope landslide in Bayan Obo Iron Mine of Inner Mongolia, the landslide in Grasberg Open-pit Mine in Indonesia, and the landslide in Bingham Canyon Open-pit Copper Mine in the United States, etc. The continuous occurrence of landslides in the bedding rock slopes of open-pit mines not only seriously threatens the normal operation of mining enterprises, but also poses a great threat to the lives and safety of employees. Compared with the plain mines in low-altitude areas, in addition to dynamic disturbances such as excavation and far-field blasting, the frequent freeze-thaw action is another factor that cannot be ignored in causing the deterioration of the rock bridge structure of slopes in cold regions. The frost heaving force generated during the water-ice phase change process and the moisture migration accelerate the deterioration and variation of rock bridges. China is rich in mineral resources in cold regions. In high-altitude and cold regions, in the face of the harsh natural environment, the understanding of the disaster-causing mechanism of slope environmental geological disasters is not deep enough, and effective prevention and control measures have not been provided. Therefore, the freeze-thaw deterioration of the rock mass structure has triggered a large number of catastrophic events.

[0003] Literature research shows that a large number of domestic and foreign scholars have systematically studied the fracture and penetration of key rock bridges with locking sections by means of in-situ tests, laboratory tests, numerical calculations, etc. The scale of rock bridges in the rock considered in the model develops from one to multiple and multiple groups. The model tests consider the influence of joint roughness, spatial distribution, arrangement form, rock bridge width and normal stress, and focus on discussing the mechanical properties, failure mechanism, strength and penetration mode of rock bridges in fractured rock masses. Almost all the studies are under the static loading environment at normal temperature, without considering the influence of freeze-thaw. However, due to the frequent disturbance of engineering rock masses by environmental factors, excavation unloading, blasting vibration and seismic waves, the dynamic characteristics of rock bridge fracture are different from the previous static loading fracture, which is a typical dynamic (medium strain rate) problem. At present, there are many studies on the dynamic loading mechanical tests of rock joints under complex stress disturbances. There are sporadic reports on the mechanical tests of rock bridges under normal temperature and normal direction unloading conditions. However, there are few studies on the shear fracture mechanism of freeze-thaw rock bridges, and the coupling mechanism between rock bridges and joints caused by volume expansion during the rock bridge fracture process is not studied deeply enough.

[0004] When a porous medium such as rock is in a low temperature environment, the water in the pores and cracks inside the rock undergoes a phase change and freezes, resulting in the physical and mechanical properties of the rock not only being related to its own physical structure, but also being affected by the water, temperature, and stress state inside it. When the rock is subjected to low temperature, it will produce very high tensile stress through contraction. Joints and cracks, as initial defects in the rock, will further expand due to the uneven contraction between particles. The temperature stress in the rock will also lead to the generation of tensile stress. The pore or crack water in the rock undergoes a phase change at low temperature, changing from liquid water to Solid ice, the expansion of volume produces frost heave effect, which aggravates the development of cracks, and then causes the cracks to expand and break, and the physical and mechanical properties to drop sharply; in engineering construction, rock excavation causes rock stress redistribution, accompanied by deformation and destruction of the rock mass, and its mechanical properties also change. The shear failure has the greatest impact on engineering safety, and the rock mass is often subjected to dynamic disturbances of different frequencies and amplitudes caused by mechanical excavation, blasting or seismic loads. Therefore, exploring the damage and fracture mechanism of low-temperature rock mass under dynamic shear disturbances of variable frequency and amplitude is of great significance to ensure the safe construction of cold region projects;

[0005] At present, acoustic physical testing technologies including ultrasonic imaging and acoustic emission positioning provide means to realize the characteristics of internal structural changes of rock mass during dynamic shear fracture. Rock ultrasonic imaging is a method of obtaining data from the inside of the rock mass through ultrasonic testing and reconstructing the internal image of the rock mass with this data, and interpreting the internal situation based on the difference in sound velocity values ​​on this image; the acoustic emission signal inverts the characteristics of the internal structural changes of the rock mass through multiple parameters such as acoustic emission counts, signal energy, acoustic emission amplitude, and waveform characteristics, and locates the initiation of rock cracks. Through theoretical research and related mathematical analysis methods, it can describe rich information such as acoustic emission parameters and waveforms, and derive the essence of rock fracture;

[0006] At present, most of the existing rock dynamic shear equipment are static or quasi-static experimental equipment for direct shearing. A few rock dynamic shear equipment are impact shearing, which cannot realize the loading of variable frequency and variable amplitude cyclic loads. Moreover, most of the equipment does not take into account the influence of low temperature on the shear failure characteristics of rock and use acoustic physics means to realize acoustic physics imaging in the process of rock shear fracture. It cannot simulate the dynamic shear characteristics of jointed rocks under various working conditions in actual testing projects and reveal the internal crack propagation mechanism in the process of rock damage and fracture. Therefore, it is very important to develop a low-temperature rock variable frequency and variable amplitude dynamic shear acoustic physics testing machine. Summary of the invention

[0007] Aiming at the above problems, the present invention aims to provide a low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system and test method. Through the frame system and environmental chamber, this testing machine can achieve fatigue cyclic shear tests with variable frequencies and variable amplitudes, and simultaneously conduct acoustic emission and ultrasonic tests. It can invert the source mechanism during the shear failure process of the rock mass and perform acoustic wave imaging on the deterioration of the mesoscopic structure during the deformation and failure process of the rock mass. It has the characteristics of adjustable frequency and amplitude, can simultaneously conduct acoustic emission and ultrasonic tests, invert the source mechanism during the shear failure process of the rock mass, and perform acoustic wave imaging on the deterioration of the mesoscopic structure during the deformation and failure process of the rock mass.

[0008] To achieve the above objectives, the technical solutions adopted by the present invention are as follows:

[0009] A low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system, comprising a low-temperature control subsystem, a dynamic shear subsystem, an acoustic physical test subsystem, and a measurement and control subsystem;

[0010] The low-temperature control subsystem includes an environmental chamber, a refrigeration pipe, and a temperature control and acquisition box. The environmental chamber is arranged within the main machine frame and is connected to the temperature control and acquisition box through the refrigeration pipe;

[0011] The dynamic shear subsystem is arranged within the environmental chamber and includes an oil source, a vertical loading mechanism, a horizontal shear mechanism, a shear box, and a rock mass specimen. The oil source is respectively connected to the vertical loading mechanism and the horizontal shear mechanism through oil pipes, and the shear box is arranged between the vertical loading mechanism and the horizontal shear mechanism;

[0012] The dynamic shear subsystem adopts a combination of a vertical loading mechanism and a horizontal shear mechanism to achieve dynamic loading of complex disturbance stress waveforms on the rock mass specimen in the shear box under variable-frequency variable-amplitude conditions;

[0013] The acoustic physical test subsystem includes an ultrasonic imaging system and an acoustic emission positioning system arranged on the shear box;

[0014] The measurement and control subsystem includes a displacement measurement system and a data control, acquisition, calculation, and imaging system.

[0015] Preferably, the vertical loading mechanism includes a vertical connection disk, a vertical pressure head, a piston, and a cylinder barrel. The cylinder barrel is installed on the main machine frame through a vertical oil cylinder support ring and is connected to the oil pipe. The piston is movably installed in the inner cavity of the cylinder barrel through a vertical oil cylinder cylinder head, and the vertical pressure plate installed at the lower end of the piston is connected to the vertical pressure head through a vertical connection disk and a vertical connection column. A upper pressure plate is arranged at the lower end of the vertical pressure head, and the upper pressure plate is used in cooperation with the rock mass specimen.

[0016] Preferably, the transverse shearing mechanism includes a horizontal oil cylinder support ring, a horizontal oil cylinder head, a horizontal connecting column, a horizontal pressure head, and a horizontal reaction force assembly. The cylinder barrel is installed on the mainframe frame through the horizontal oil cylinder support ring and is connected to the oil pipe. The piston is movably installed in the inner cavity of the cylinder barrel through the horizontal oil cylinder head, and the horizontal pressure plate installed at the end of the piston is connected to the horizontal pressure head through a horizontal connecting plate and a horizontal connecting column. The horizontal pressure head is used in cooperation with the shearing box. The horizontal reaction force assembly includes a horizontal by-bar, a by-bar pressure head, and a reaction bar. The horizontal by-bar is connected to the mainframe frame through a round nut. The reaction bar is connected to the horizontal by-bar. The by-bar pressure head is arranged at the end of the reaction bar and is used in cooperation with the shearing box.

[0017] Preferably, the shearing box includes an upper shearing box and a lower shearing box that are used in cooperation with each other, and a guiding strip is arranged between the upper shearing box and the lower shearing box. Both the upper shearing box and the lower shearing box include a connecting plate, side plates, shearing jaws, and a main pushing plate. The side plates are symmetrically arranged on both sides of the connecting plate and the main pushing plate and are connected to the connecting plate and the main pushing plate through connecting bolts. The shearing jaws are arranged inside the main pushing plate, and a cavity for placing the rock sample is formed inside the shearing jaws. The main pushing plate is used in cooperation with the transverse shearing mechanism. The guiding strip is arranged in the guiding groove on the side plate. A sliding mechanism is also arranged on the lower side of the lower shearing box. And mounting round holes with fixed sizes are provided on the connecting plate, side plates, shearing jaws, and main pushing plate.

[0018] Preferably, the sliding mechanism includes a bottom plate, a roller frame, a roller frame connecting cushion block, and several cushion blocks. The bottom plate is arranged on the lower side of the lower shearing box and is movably clamped on the upper side of the roller frame and slides along the rollers arranged on the roller frame. The roller frame is connected to the upper cushion block through the roller frame connecting cushion block. There are several cushion blocks, and all the cushion blocks are pinned to each other through pin bolts. The bottom cushion block is connected to the mainframe frame through a small round cushion plate.

[0019] Preferably, the ultrasonic imaging system includes several ultrasonic probes and an acoustic wave controller. The ultrasonic probes are installed in the middle of the side plates and the connecting plates on both sides of the upper shearing box and the lower shearing box, and the ultrasonic probes are connected to the sensors in the acoustic wave controller. The acoustic wave controller can receive ultrasonic signals and realize the ultrasonic imaging of the internal structure of the rock mass in the computer through calculation software.

[0020] Preferably, the acoustic emission positioning system includes an acoustic emission probe and an acoustic emission controller. The acoustic emission probe is located on the side plates on both sides of the upper shearing box and the lower shearing box, and the acoustic emission probe is connected to the sensors in the acoustic emission controller. The acoustic emission controller can receive acoustic emission signals and realize the acoustic emission positioning imaging of the internal structure of the rock mass in the computer through calculation software.

[0021] Preferably, the data control acquisition and calculation imaging system includes a loading oil source controller and a computer. The sensors in the loading oil source controller, the acoustic wave controller, and the acoustic emission controller are all connected to the computer, enabling automatic control of the loading system and data reading. After being processed by analysis software, ultrasonic imaging and acoustic emission positioning imaging can be achieved.

[0022] Preferably, the displacement measurement system includes a horizontal shear displacement measurement mechanism and a vertical compression displacement measurement mechanism. Both the horizontal shear displacement measurement mechanism and the vertical compression displacement measurement mechanism include a grating scale, a sensor bracket, a bracket, an adjusting rod, and a contact piece. The bracket of the vertical compression displacement measurement mechanism is connected to the upper pressure plate through a connecting bolt, and the bracket of the horizontal shear displacement measurement mechanism is connected to the connecting plate of the lower shear box through a connecting bolt. The adjusting rod is threadedly connected to the bracket, and a knob is provided at the end of the adjusting rod. The contact piece is arranged on the adjusting rod. The grating scale of the vertical compression displacement measurement mechanism is connected to the roller frame through the sensor bracket and the connecting bolt and is used in cooperation with the contact piece of the corresponding vertical compression displacement measurement mechanism. The grating scale of the horizontal shear displacement measurement mechanism is connected to the rod press head through the sensor bracket and the connecting bolt and is used in cooperation with the contact piece of the corresponding horizontal shear displacement measurement mechanism.

[0023] The beneficial effects of the present invention are as follows: The present invention discloses a low-temperature rock mass variable-frequency and variable-amplitude dynamic shear acoustic physics testing machine and a testing method. Compared with the prior art, the improvements of the present invention are as follows:

[0024] (1) The present invention designs a low-temperature rock mass variable-frequency and variable-amplitude dynamic shear acoustic physics testing machine and a testing method. Through the design of the frame system and the environmental chamber, the present testing machine realizes the dynamic loading, servo control, and response of complex disturbance stress waveforms under variable-frequency and variable-amplitude conditions, and can perform precise servo control and high-speed servo response on the two servo valves of the main oil cylinder and the shear oil cylinder during the fatigue shear process.

[0025] (2) At the same time, the low-temperature control system can simulate the complex environments such as low temperature and freeze-thaw cycles of the rock mass, truly restoring the dynamic shear mechanical properties of the rock mass under the actual engineering situation. The transparent and high-strength environmental chamber door can not only maintain the closed state of the environmental chamber but also observe the morphology of the rock mass sample during the shear process in real time and safely.

[0026] (3) The design of the acoustic physics test system can achieve ultrasonic imaging and acoustic emission positioning imaging, and can reveal the characteristics of the internal structure change of the rock mass during the dynamic shear fracture process.

[0027] (4) This testing machine uses a grating displacement sensor to solve the problem of high-resolution dynamic measurement of rock sample deformation during the dynamic load process. At the same time, the grating displacement sensor has the advantages of a large measuring range and high accuracy, can achieve dynamic measurement, is easy to realize the automation of measurement and data processing. During the experiment, it has the advantages that the frequency and amplitude can be adjusted, acoustic emission and ultrasonic tests can be carried out simultaneously, the source mechanism during the shear failure process of the rock mass can be inverted, and acoustic wave imaging can be performed on the deterioration of the mesoscopic structure during the deformation and failure process of the rock mass. Description of the Drawings

[0028] Figure 1 It is a schematic structural diagram of the whole system of the low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system of the present invention.

[0029] Figure 2 It is a front view of the whole system structure of the low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system of the present invention.

[0030] Figure 3 It is a front view of the structure of the dynamic shear testing machine of the present invention.

[0031] Figure 4 It is a sectional view of the structure of the dynamic shear testing machine of the present invention.

[0032] Figure 5 It is a schematic structural diagram of the shear box of the present invention.

[0033] Figure 6 It is a schematic structural diagram of the acoustic physics test subsystem of the present invention.

[0034] Figure 7 It is a schematic structural diagram of the sliding mechanism of the present invention.

[0035] Figure 8 It is a front view of the displacement measurement system of the present invention.

[0036] Figure 9 It is a side view of the displacement measurement system of the present invention.

[0037] Figure 10 It is a top view of the displacement measurement system of the present invention.

[0038] Among them: 1. Oil source; 2. Oil source control line; 3. Oil pipe; 4. Mainframe frame; 5. Vertical cylinder head; 6. Vertical cylinder support ring; 7. Vertical pressing plate; 8. Vertical connection plate; 9. Vertical pressing head; 10. Upper pressing plate; 11. Upper shear box; 12. Lower shear box; 13. Environmental chamber; 14. Upper roller; 15. Roller frame connection pad; 16. Pad; 17. Small round backing plate; 18. Grating scale; 19. Horizontal pressing head; 20. Horizontal connection plate; 21. Horizontal pressing plate; 22. Refrigeration pipe; 23. Horizontal rod; 24. Temperature control acquisition box; 25. Computer; 26. Loading oil source controller; 27. Acoustic wave controller; 28. Acoustic emission controller; 29. Acoustic wave control line; 30. Acoustic emission control line; 31. Rod pressing head; 32. Reaction rod; 33. Knob; 34. Contact piece; 35. Adjusting rod; 36. Bracket; 37. Acoustic emission probe; 38. Ultrasonic probe; 39. Base plate; 40. Guide bar; 41. Sensor bracket; 42. Horizontal cylinder head; 43. Horizontal cylinder support ring; 44. Piston; 45. Roll; 46. Roller frame; 47. Horizontal connection column; 48. Cylinder barrel; 49. Vertical connection column; 50. Shearing jaw; 51. Main push plate; 52. Rock mass sample; 53. Side plate; 54. Connection plate. Detailed implementation manners

[0039] In order to enable ordinary technicians in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

[0040] Refer to the Figures 1-10 Low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system shown in the figure, including a low-temperature control subsystem, a dynamic shear subsystem, an acoustic physics test subsystem, and a measurement and control subsystem;

[0041] The low-temperature control subsystem includes an environmental chamber 13, a refrigeration pipe 22, and a temperature control acquisition box 24. The environmental chamber 13 is arranged in the mainframe frame 4 and is connected to the temperature control acquisition box 24 through the refrigeration pipe 22. When in use, the temperature control acquisition box 24 transmits cold air flow through the refrigeration pipe 22 to control the temperature in the environmental chamber 13;

[0042] The dynamic shear subsystem is arranged in the environmental chamber 13 and includes an oil source 1, a vertical loading mechanism, a horizontal shearing mechanism, a shear box, and a rock mass sample 52. The oil source 1 is respectively connected to the vertical loading mechanism and the horizontal shearing mechanism through an oil pipe 3 to provide loading pressure for the vertical loading mechanism and the horizontal shearing mechanism. The shear box is arranged between the vertical loading mechanism and the horizontal shearing mechanism and is used for fixing the rock mass sample 52;

[0043] The acoustic physics test subsystem includes an ultrasonic imaging system and an acoustic emission positioning system arranged on the shear box;

[0044] The measurement and control subsystem includes a displacement measurement system and a data control acquisition and computational imaging system.

[0045] Preferably, as Figures 3-4 shown, the dynamic shear subsystem realizes the dynamic loading of the complex disturbance stress waveform under variable frequency and variable amplitude conditions on the rock mass sample 52 in the shear box by combining a vertical loading mechanism and a horizontal shear mechanism; wherein the vertical loading mechanism includes a vertical connection plate 8, a vertical pressure head 9, a piston 44 and a cylinder barrel 48. The cylinder barrel 48 is installed on the main frame 4 through a vertical oil cylinder support ring 6 and is connected to the oil pipe 3. The piston 44 is movably installed in the inner cavity of the cylinder barrel 48 through a vertical oil cylinder head 5. The vertical pressure plate 7 installed at the lower end of the piston 44 is connected to the vertical pressure head 9 through the vertical connection plate 8, a vertical connection column 49 and a hexagonal bolt. A upper pressure plate 10 is arranged at the lower end of the vertical pressure head 9. The upper pressure plate 10 is used in cooperation with the rock mass sample 52. That is, during the axial pressurization of the rock mass sample 52, the oil source 1 pumps hydraulic oil into the cylinder barrel 48 through the oil pipe 3. As the oil pressure in the cylinder barrel 48 increases, the piston 44 is pushed downward to transmit the axial pressure. The axial load is conducted to the vertical pressure head 9 through the vertical pressure plate 7 and then conducted downward onto the upper pressure plate 10, and the upper pressure plate 10 is used to apply axial pressure to the rock mass sample 52.

[0046] The horizontal shear mechanism includes a horizontal oil cylinder support ring 43, a horizontal oil cylinder head 42, a horizontal connection column 47, a horizontal pressure head 19 and a horizontal reaction force assembly. The cylinder barrel 48 is installed on the main frame 4 through the horizontal oil cylinder support ring 43 and is connected to the oil pipe 3. The piston 44 is movably installed in the inner cavity of the cylinder barrel 48 through the horizontal oil cylinder head 42. The horizontal pressure plate 21 installed at the end of the piston 44 is connected to the horizontal pressure head 19 through a horizontal connection plate 20, a horizontal connection column 47 and a hexagonal bolt. The horizontal pressure head 19 is used in cooperation with the shear box. That is, during use, the oil source 1 pumps hydraulic oil into the cylinder barrel 48 through the oil pipe 3. As the oil pressure in the cylinder barrel 48 increases, the piston 44 is pushed horizontally to apply a shear load. The horizontal load is conducted to the horizontal pressure head 19 through the horizontal pressure plate 21, and the horizontal pressure head 19 is used to apply a horizontal shear load to the lower shear box 12 of the shear box. The horizontal reaction force assembly includes a horizontal tie rod 23, a tie rod pressure head 31 and a reaction rod 32. The horizontal tie rod 23 is connected to the main frame 4 through a round nut. The reaction rod 32 is connected to the horizontal tie rod 23. The tie rod pressure head 31 is arranged at the end of the reaction rod 32 and is used in cooperation with the upper shear box 11 of the shear box to apply a reverse acting force to the upper shear box 11.

[0047] Preferably, as Figure 5As shown in the figure, the shear box includes an upper shear box 11 and a lower shear box 12 that are used in cooperation, and a guide bar 40 is provided between the upper shear box 11 and the lower shear box 12. Both the upper shear box 11 and the lower shear box 12 include a connecting plate 54, side plates 53, shear jaws 50, and a main pushing plate 51. The side plates 53 are symmetrically arranged on both sides of the connecting plate 54 and the main pushing plate 51, and are connected to the connecting plate 54 and the main pushing plate 51 through connecting bolts to form a square box structure. The shear jaws 50 are arranged inside the main pushing plate 51, and a cavity for placing the rock mass specimen 52 is formed inside the shear jaws 50. The main pushing plate 51 is used in cooperation with the horizontal shear mechanism. That is, during use, the horizontal press head 19 applies a horizontal shear load to the lower shear box 12, and the rod press head 31 applies a reaction force to the upper shear box 11; and to reduce the frictional resistance between the upper shear box 11 and the lower shear box 12 when applying external forces, the guide bar 40 is arranged in the guide groove on the side plate 53. During use, the horizontal shear force and the reaction force acting on the lower shear box 12 and the upper shear box 11 are used to shear the rock mass specimen 52. To avoid the frictional force at the lower part of the lower shear box 12 affecting the shear accuracy during the shear process, a sliding mechanism is also provided on the lower side of the lower shear box 12.

[0048] Preferably, the sliding mechanism includes a bottom plate 39, a roller frame 46, a roller frame connecting pad 15, and a plurality of pads 16. The bottom plate 39 is arranged on the lower side of the lower shear box 12 and is movably clamped on the upper side of the roller frame 46 by means of clamping in a slide rail slot. A stick 45 is rotatably installed on the roller frame 46 through an upper stick 14. The lower side of the bottom plate 39 is also in close contact with the stick 45 and slides left and right along the stick 45 under the action of the shear force. The roller frame 46 is connected to the upper layer of pads 16 through the roller frame connecting pad 15 to fix the roller frame 46. A plurality of pads 16 are provided, and all the pads 16 are pinned to each other through bolt pins. The bottom layer of pads 16 is connected to the mainframe frame 4 through small round pads 17 to support the upper loading mechanism.

[0049] Preferably, the connecting plate 54, the side plates 53, the shear jaws 50, and the main pushing plate 51 are all provided with mounting round holes of fixed sizes, which is beneficial to realizing ultrasonic imaging and acoustic emission positioning of rock mass rupture during the dynamic shear process; the ultrasonic imaging system includes six ultrasonic probes 38 and an acoustic wave controller 27. The six ultrasonic probes 38 are installed in the middle of the side plates 53 and the connecting plates 54 on both sides of the upper shear box 11 and the lower shear box 12, and the ultrasonic probes 38 are connected to the sensors in the acoustic wave controller 27. The acoustic wave controller 27 can receive ultrasonic signals and realize ultrasonic imaging of the internal structure of the rock mass in the computer through calculation software.

[0050] Preferably, the acoustic emission positioning system includes twelve acoustic emission probes 37 and an acoustic emission controller 28. The acoustic emission probes 37 are located on the side plates 53 on both sides of the upper shear box 11 and the lower shear box 12, and the acoustic emission probes 37 are connected to the sensors in the acoustic emission controller 28. The acoustic emission controller 28 can receive acoustic emission signals and realize the acoustic emission positioning imaging of the internal structure of the rock mass through calculation software in a computer.

[0051] Preferably, the data control acquisition and calculation imaging system includes a loading oil source controller 26 and a computer 25. The sensors in the loading oil source controller 26, the acoustic wave controller 27, and the acoustic emission controller 28 are all connected to the computer 25. Through the control of the computer 25, the automatic control of the loading system and the reading of data can be realized, and ultrasonic imaging and acoustic emission positioning imaging can be realized after being processed by analysis software.

[0052] Preferably, the displacement measurement system includes a horizontal shear displacement measurement mechanism and a vertical compression displacement measurement mechanism. Both the horizontal shear displacement measurement mechanism and the vertical compression displacement measurement mechanism include a grating scale 18, a sensor bracket 41, a bracket 36, an adjusting rod 35, a knob 33, and a contact piece 34. The bracket 36 of the vertical compression displacement measurement mechanism is connected to the upper pressure plate 10 through a connecting bolt, and the bracket 36 of the horizontal shear displacement measurement mechanism is connected to the connecting plate 54 of the lower shear box 12 through a connecting bolt. The adjusting rod 35 is threadedly connected to the bracket 36, and a knob 33 is provided at the end of the adjusting rod 35 for adjusting the relative distance between the adjusting rod 35 and the bracket 36. The contact piece 34 is arranged on the adjusting rod 35. At the same time, the grating scale 18 of the vertical compression displacement measurement mechanism is connected to the roller bracket 46 through the sensor bracket 41 and a connecting bolt and is used in cooperation with the contact piece 34 of the corresponding vertical compression displacement measurement mechanism. The grating scale 18 of the horizontal shear displacement measurement mechanism is connected to the rod pressure head 31 through the sensor bracket 41 and a connecting bolt and is used in cooperation with the contact piece 34 of the corresponding horizontal shear displacement measurement mechanism. That is, when in use, when measuring the vertical compression displacement of the rock mass specimen 52, the grating scale 18 on the sensor bracket 41 of the vertical compression displacement measurement mechanism first contacts the contact piece 34 and is in a compressed state. The bracket 36 is fixed on the upper pressure plate 10. When the rock mass specimen 52 is compressed, the upper pressure plate 10 drives the adjusting rod 35 and the contact piece 34 to move downward, so that the reading head of the grating scale 18 is relaxed to measure the vertical displacement. When measuring the horizontal shear displacement, the grating scale 18 on the sensor bracket 41 of the horizontal shear displacement measurement mechanism first contacts the contact piece 34 and is in a compressed state. When the rock mass specimen 52 undergoes shear slip, the lower shear box 12 drives the adjusting rod 35 and the contact piece 34 to move in the direction of the reaction rod 32, and the reading head of the grating scale 18 is relaxed as the contact piece 34 moves to measure the horizontal shear displacement.

[0053] Preferably, in the technical solution provided by the embodiments of the present invention, for easy observation, the environmental chamber door is made of a transparent material with a certain strength, which can observe the test process inside the dynamic shear testing machine while realizing the closed cooling cycle of the environmental chamber 13. Selecting a suitable coolant can ensure that the lowest temperature inside the environmental chamber 13 reaches -65°C when the testing machine is working properly.

[0054] Preferably, the rock mass specimen 52 can be a complete rock mass, a non-penetrating fractured rock mass or a penetrating fractured rock mass.

[0055] Preferably, the loading frequency range of the dynamic shear testing machine is 0 - 10 HZ, and the loadable range of the vertical load and the horizontal load is 0 - 1000 t.

[0056] Preferably, the size of the shear box can be 100 mm × 100 mm × 100 mm or 100 mm × 100 mm × 200 mm; when switching shear boxes of different sizes, the loading height of the rock mass specimen 52 can be adjusted by adjusting the number of spacer blocks 16.

[0057] The test method of the low-temperature rock mass variable-frequency and variable-amplitude dynamic shear acoustic physics test system of the present invention includes the following steps:

[0058] S1. Place the rock mass specimen 52 into the shear box, adjust the knob 33 to make the grating scale 18 contact the contact piece 34 and apply appropriate pressure to the grating scale 18, and then close the environmental chamber door;

[0059] S2. Connect the acoustic emission probe and the ultrasonic probe, and closely attach them to the rock specimen. Start the acoustic wave controller 27, the acoustic emission controller 28 and the computer 25, and test the smoothness and effective signals of the lines;

[0060] S3. Start the temperature control acquisition box 24, set a certain low temperature in the environmental chamber and then start the refrigeration cycle; realize the real-time freeze-thaw, freezing and melting treatment of the rock. The temperature inside the environmental chamber and the number of freeze-thaw cycles can be automatically controlled;

[0061] S4. Start the dynamic shear testing machine and the loading oil source controller 26, and test the disturbing force signal;

[0062] S5. Set the loading frequency, loading amplitude and number of cycles for the testing machine through the loading control software of the computer 25, and clear the displacement data measured by the grating scale 18. After the temperature inside the environmental chamber 13 reaches the set value, emit ultrasonic waves and start loading;

[0063] S6. During the loading process, collect data on the load, displacement, ultrasonic signal and acoustic emission signal through the measurement and control system, and observe the change of the shear stress-strain curve during the loading process;

[0064] S7. When the rock mass specimen 52 fails, stop loading;

[0065] S8. Close the temperature control acquisition box 24, open the door of the environmental chamber. After the temperature in the environmental chamber 13 reaches room temperature, take out the damaged rock mass specimen 52 and turn off the low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system.

[0066] The above-mentioned low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system of the present invention has the following advantages:

[0067] 1. The test system described in the present invention can not only meet the requirements of most test scales, but also realize variable-frequency variable-amplitude loading through the dynamic shear system, low-temperature control system, acoustic physics test system, measurement and control system. It can consider the influence of low temperature on the shear failure characteristics of rock mass and use acoustic physics means to realize the acoustic physics imaging during the shear fracture process of rock mass. It can simulate and test the dynamic shear characteristics of jointed rocks under various working conditions in engineering practice and reveal the internal crack propagation mechanism during the damage and fracture process of rock mass, enriching the test data and improving the test quality;

[0068] 2. The test system described in the present invention uses the ultrasonic imaging technology and acoustic emission location imaging technology in the acoustic physics test system to locate the initiation of internal cracks in the rock mass specimen during the loading process, and can reveal the characteristics of the internal structure change of the rock mass during the dynamic shear fracture process;

[0069] 3. According to the above specific implementation manners, the testing machine of the test system described in the present invention uses strain gauges and strain gauges to measure the deformation of the specimen under dynamic disturbance. The methods of measuring deformation by strain gauges are all the averages of the deformations at points or on the surfaces of the rock samples, and the measurement results are closely related to the strain measurement positions. The volumetric strain calculated in turn is also local. At the same time, under the action of dynamic shear, the deformation of the specimen is large and the accuracy will be poor. Our invention uses a grating displacement sensor to measure the deformation of the rock mass specimen during the dynamic shear process, solves the problem of high-resolution dynamic measurement of the deformation of the rock sample during the dynamic load process, and at the same time, the grating displacement sensor has the advantages of a large range and high accuracy, can realize dynamic measurement, and is easy to realize the automation of measurement and data processing.

[0070] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system, Characterized in that: It includes a low-temperature control subsystem, a dynamic shear subsystem, an acoustic physics test subsystem, and a measurement and control subsystem; The low-temperature control subsystem includes an environmental chamber (13), a refrigeration pipe (22), and a temperature control acquisition box (24). The environmental chamber (13) is arranged inside the mainframe frame (4) and is connected to the temperature control acquisition box (24) through the refrigeration pipe (22); The dynamic shear subsystem is arranged inside the environmental chamber (13) and includes an oil source (1), a vertical loading mechanism, a horizontal shear mechanism, a shear box, and a rock mass specimen (52). The oil source (1) is connected to the vertical loading mechanism and the horizontal shear mechanism respectively through oil pipes (3), and the shear box is arranged between the vertical loading mechanism and the horizontal shear mechanism; The dynamic shear subsystem realizes the dynamic loading of the complex disturbance stress waveform under variable-frequency variable-amplitude conditions on the rock mass specimen (52) in the shear box by combining the vertical loading mechanism and the horizontal shear mechanism; The acoustic physics test subsystem includes an ultrasonic imaging system and an acoustic emission positioning system arranged on the shear box; The measurement and control subsystem includes a displacement measurement system and a data control acquisition calculation imaging system; The shear box includes an upper shear box (11) and a lower shear box (12) that are used in cooperation, and a guiding strip (40) is arranged between the upper shear box (11) and the lower shear box (12). The upper shear box (11) and the lower shear box (12) both include a connecting plate (54), a side plate (53), a shear jaw (50), and a main pushing plate (51). The side plates (53) are symmetrically arranged on both sides of the connecting plate (54) and the main pushing plate (51), and are connected to the connecting plate (54) and the main pushing plate (51) through connecting bolts. The shear jaw (50) is arranged inside the main pushing plate (51), and a cavity for placing the rock mass specimen (52) is formed inside the shear jaw (50). The main pushing plate (51) is used in cooperation with the horizontal shear mechanism. The guiding strip (40) is arranged in a guiding groove on the side plate (53), and a sliding mechanism is also arranged on the lower side of the lower shear box (12); and mounting round holes with fixed sizes are opened on the connecting plate (54), the side plate (53), the shear jaw (50), and the main pushing plate (51); The sliding mechanism includes a bottom plate (39), a roller frame (46), a roller frame connecting pad (15), and several pads (16). The bottom plate (39) is arranged on the lower side of the lower shear box (12) and is movably clamped on the upper side of the roller frame (46) and slides along a rod (45) arranged on the roller frame (46). The rod (45) is rotationally installed on the roller frame (46) through an upper rod (14). The roller frame (46) is connected to the pads (16) through the roller frame connecting pad (15). Several pads (16) are stacked, and the pads (16) are connected to the mainframe frame (4) through small round pads (17).

2. The low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physics test system according to claim 1, Characterized in that: The vertical loading mechanism described above includes a vertical connection plate (8), a vertical indenter (9), a piston (44), and a cylinder barrel (48). The cylinder barrel (48) is installed on the mainframe (4) through a vertical oil cylinder support ring (6) and is connected to an oil pipe (3). The piston (44) is movably installed in the inner cavity of the cylinder barrel (48) through a vertical oil cylinder head (5). A vertical pressure plate (7) installed at the lower end of the piston (44) is connected to the vertical indenter (9) through a vertical connection plate (8) and a vertical connecting column (49). A upper pressure plate (10) is provided at the lower end of the vertical indenter (9), and the upper pressure plate (10) is used in cooperation with a rock mass specimen (52).

3. The low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system according to claim 2, characterized in that: The lateral shear mechanism described above includes a horizontal oil cylinder support ring (43), a horizontal oil cylinder head (42), a horizontal connecting column (47), a horizontal indenter (19), and a horizontal reaction force assembly. The cylinder barrel (48) is installed on the mainframe (4) through a horizontal oil cylinder support ring (43) and is connected to an oil pipe (3). The piston (44) is movably installed in the inner cavity of the cylinder barrel (48) through a horizontal oil cylinder head (42). A horizontal pressure plate (21) installed at the end of the piston (44) is connected to the horizontal indenter (19) through a horizontal connection plate (20) and a horizontal connecting column (47). The horizontal indenter (19) is used in cooperation with a shear box; The horizontal reaction force assembly includes a horizontal passive rod (23), a passive rod indenter (31), and a reaction rod (32). The horizontal passive rod (23) is connected to the mainframe (4) through a round nut. The reaction rod (32) is connected to the horizontal passive rod (23). The passive rod indenter (31) is provided at the end of the reaction rod (32) and is used in cooperation with the shear box.

4. The low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system according to claim 1, characterized in that: The ultrasonic imaging system described above includes a number of ultrasonic probes (38) and an acoustic wave controller (27). The ultrasonic probes (38) are installed in the middle of the side plates (53) and connecting plates (54) on both sides of the upper shear box (11) and the lower shear box (12). The ultrasonic probes (38) are connected to sensors in the acoustic wave controller (27). The acoustic wave controller (27) can receive ultrasonic signals and realize ultrasonic imaging of the internal structure of the rock mass in a computer through calculation software.

5. The low-temperature rock mass variable-frequency variable-amplitude dynamic shear acoustic physical test system according to claim 4, characterized in that: The acoustic emission positioning system described above includes an acoustic emission probe (37) and an acoustic emission controller (28). The acoustic emission probe (37) is located on the side plates (53) on both sides of the upper shear box (11) and the lower shear box (12). The acoustic emission probe (37) is connected to sensors in the acoustic emission controller (28). The acoustic emission controller (28) can receive acoustic emission signals and realize acoustic emission positioning imaging of the internal structure of the rock mass in a computer through calculation software.

6. The low-temperature rock mass variable-frequency and variable-amplitude dynamic shear acoustic physical test system according to claim 5, characterized in that: the data control acquisition calculation imaging system includes a loading oil source controller (26) and a computer (25). The sensors in the loading oil source controller (26), the acoustic wave controller (27) and the acoustic emission controller (28) are all connected to the computer (25), capable of realizing the automatic control of the loading system and the reading of data, and ultrasonic imaging and acoustic emission positioning imaging can be realized after being processed by analysis software.

7. The low-temperature rock mass variable-frequency and variable-amplitude dynamic shear acoustic physical test system according to claim 1, characterized in that: the displacement measurement system includes a horizontal shear displacement measurement mechanism and a vertical compression displacement measurement mechanism. Both the horizontal shear displacement measurement mechanism and the vertical compression displacement measurement mechanism include a grating scale (18), a sensor bracket (41), a bracket (36), an adjusting rod (35) and a contact piece (34). The bracket (36) of the vertical compression displacement measurement mechanism is connected to the upper pressure plate (10) through a connecting bolt. The bracket (36) of the horizontal shear displacement measurement mechanism is connected to the connecting plate (54) of the lower shear box (12) through a connecting bolt. The adjusting rod (35) is threadedly connected to the bracket (36), and a knob (33) is arranged at the end of the adjusting rod (35). The contact piece (34) is arranged on the adjusting rod (35). The grating scale (18) of the vertical compression displacement measurement mechanism is connected to the roller bracket (46) through the sensor bracket (41) and a connecting bolt and is used in cooperation with the contact piece (34) of the corresponding vertical compression displacement measurement mechanism. The grating scale (18) of the horizontal shear displacement measurement mechanism is connected to the rod pressing head (31) through the sensor bracket (41) and a connecting bolt and is used in cooperation with the contact piece (34) of the corresponding horizontal shear displacement measurement mechanism.

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