A hierarchical true triaxial indenter with an acoustic emission system based on a laminated design

Abstract

The present invention discloses a graded true triaxial pressure head with an acoustic emission system based on a lamination design, which relates to the technical field of rock mechanics testing, and includes a plurality of graded loading pressure heads arranged in a true triaxial loading frame, wherein the plurality of graded loading pressure heads are symmetrically arranged in the XYZ direction and are used to load rock samples; the graded loading pressure head includes a primary pressure head and a secondary pressure head, wherein one end of the primary pressure head is fixedly connected to the secondary pressure head, and the other end is used to contact the rock sample; an acoustic emission monitoring system is arranged in the primary pressure head. While protecting the acoustic emission monitoring system from damage, the present invention realizes close contact between the acoustic emission monitoring system and the rock sample, shortens the path of the fracture signal generated inside the rock sample to propagate to the acoustic emission monitoring system, reduces stress wave loss, receives the fracture signal inside the rock sample to the maximum extent, and ensures the accuracy of fracture position positioning.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanics testing, and in particular to a hierarchical true triaxial indenter with an acoustic emission system based on a lamination design. Background Art

[0002] The deformation of rocks and the process of crack initiation and expansion under stress can be detected, recorded and analyzed by acoustic emission sensors. This technology is called acoustic emission monitoring technology. Acoustic emission monitoring technology is currently widely used in indoor tests. It can monitor the generation and development of cracks inside rock samples, the formation of fracture surfaces, sliding and other destructive phenomena. Its monitoring results are of great significance for studying the stability of rocks. Acoustic emission monitoring technology can not only be used to monitor the changes in acoustic emission signals of rocks during different loading and unloading processes, but also to monitor the generation, development and penetration of cracks inside rocks to form fracture surfaces in real time and perform three-dimensional positioning. This is different from other monitoring methods, so it has become an important means of studying the mechanism of rock fracture. In addition to being used in rock materials, it is also widely used in materials such as concrete and ceramics.

[0003] At present, when using acoustic emission monitoring technology to conduct monitoring tests during indoor true triaxial tests, the acoustic emission probe is often unable to directly contact the rock sample, but is attached to the loading arm, which results in more noise signals in the final data. The reasons include two aspects. First, since the acoustic emission probe is not in direct contact with the rock sample, the propagation of the stress wave generated inside the rock sample during the test cannot be directly received by the acoustic emission probe, but needs to pass through several contact surfaces before being received by the acoustic emission probe. During the propagation process, stress wave loss will occur, thereby reducing the effective signal obtained; second, during the true triaxial test, the loading arm needs to perform continuous loading and unloading actions, and the true triaxial testing machine generally uses servo control, which will result in a large number of noise signals.

[0004] In order to solve the above problem, some technicians have tried to fix the acoustic emission probe in a loading pressure head in contact with the rock sample. This method still has some disadvantages. That is, when the rock is crushed, the debris generated may enter the acoustic emission probe, which may seriously cause the acoustic emission probe to be crushed. Summary of the invention

[0005] In view of this, the present invention provides a hierarchical true triaxial indenter with an acoustic emission system based on a laminate design to solve the problems raised in the above background technology.

[0006] A hierarchical true triaxial indenter with an acoustic emission system based on a laminated design, comprising a plurality of hierarchical loading indenters arranged in a true triaxial loading frame, wherein the plurality of hierarchical loading indenters are symmetrically arranged in the XYZ directions and are used to load a rock sample;

[0007] The graded loading head comprises a primary head and a secondary head. One end of the primary head is fixedly connected to the secondary head, and the other end is used to contact the rock sample. An acoustic emission monitoring system is arranged in the primary head.

[0008] Furthermore, the acoustic emission monitoring system includes multiple waveguides and multiple acoustic emission probes, and multiple probe mounting holes are evenly arranged in the first-level pressure head. The probe mounting holes include a first-level countersunk hole and a second-level countersunk hole that are interconnected. The first-level countersunk hole is adapted to the front section of the waveguide, and the second-level countersunk hole is adapted to the middle and rear sections of the waveguide. The front end of the waveguide is flush with the outer wall of the first-level pressure head and is used to contact the rock sample. The rear end of the waveguide is provided with a receiving groove adapted to the acoustic emission probe; a bolt is provided at one end of the secondary countersunk hole away from the waveguide, and the bolt is fixedly connected to the rear end of the waveguide through an annular gasket for fixing the acoustic emission probe.

[0009] Furthermore, a plurality of isolation gaskets are provided between the outer wall of the waveguide and the inner wall of the secondary countersunk hole.

[0010] Furthermore, a plurality of lead grooves communicating with the secondary countersunk holes are provided in the secondary pressure head, and the wires of the acoustic emission probe pass through the lead grooves and are connected to an external acoustic emission connector.

[0011] Furthermore, a coupling agent is filled between the outer wall of the acoustic emission probe and the inner wall of the containing groove.

[0012] Furthermore, the maximum temperature resistance of the acoustic emission probe is 150° C., and the maximum pressure resistance is 100 MPa.

[0013] Furthermore, a coupling agent is applied on the contact surface between the first-stage pressure head and the rock sample.

[0014] The beneficial effects of the present invention are:

[0015] The present invention protects the acoustic emission monitoring system from being damaged, realizes the close contact between the acoustic emission monitoring system and the rock sample, shortens the path of the fracture signal generated inside the rock sample to propagate to the acoustic emission monitoring system, reduces the stress wave loss, receives the fracture signal inside the rock sample to the maximum extent, and ensures the accuracy of the fracture position positioning; the bolts, the acoustic emission probe and the waveguide form a stacked structure, and the acoustic emission probe is in the middle position, which can prevent the acoustic emission probe from being damaged; the isolation gasket is used to isolate the signal generated by the first-stage pressure head that interferes with the acoustic emission probe, and is also used to increase the friction between the waveguide and the second-stage counterbore; the outer wall of the acoustic emission probe and the inner wall of the accommodating groove are filled with a coupling agent to ensure the transmission quality of the acoustic emission signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of the graded loading pressure head in the present invention.

[0018] Figure 2 It is a structural schematic diagram of the wave velocity measurement system in the present invention.

[0019] Figure 3 It is a bottom view of the graded loading pressure head in the present invention.

[0020] Figure 4 It is a structural schematic diagram of the acoustic emission monitoring system in the present invention.

[0021] Among them, in the figure:

[0022] 1. Stepped loading pressure head; 11. First-stage pressure head; 111. Probe mounting hole; 1111. First-stage countersunk hole; 1112. Second-stage countersunk hole; 12. Second-stage pressure head; 121. Open cavity; 122. Lead groove; 2. Wave velocity measurement system; 21. Signal generator; 22. Shear wave and longitudinal wave transducers; 23. Longitudinal and shear wave receivers; 3. Rock sample; 4. Acoustic emission monitoring system; 41. Waveguide; 42. Acoustic emission probe; 43. Ring gasket; 44. Bolt; 45. Wire. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0026] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0027] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0028] See attached Figure 1-4The present invention discloses a hierarchical true triaxial indenter with an acoustic emission system based on a laminated design, comprising a plurality of hierarchical loading indenters 1 arranged in a true triaxial loading frame, wherein the plurality of hierarchical loading indenters 1 are symmetrically arranged in the XYZ direction and are used to load a rock sample 3;

[0029] The graded loading head 1 comprises a primary head 11 and a secondary head 12. One end of the primary head 11 is fixedly connected to the secondary head 12, and the other end is used to contact the rock sample 3. The primary head 11 is provided with an acoustic emission monitoring system 4, and the secondary head 12 is provided with a wave velocity measurement system 2.

[0030] In this embodiment, the wave velocity measurement system 2 is arranged in the secondary pressure head 12, which can not only ensure that the wave velocity measurement system 2 will not be damaged, but also ensure the propagation of the sound wave signal and the integrity of the sound wave signal, thereby greatly improving the accuracy of the test results.

[0031] In this embodiment, the distance between the central axis of the wave velocity measurement system 2 and the central axis of the acoustic emission monitoring system 4 is 30 mm, and the two do not affect each other.

[0032] The wave velocity measurement systems 2 symmetrically arranged in the XYZ directions serve as signal transmitting sources and signal receiving sources for each other.

[0033] The wave velocity measurement system 2 can sequentially excite P-wave, S1-wave, and S2-wave signals to achieve real-time measurement of the anisotropic wave velocity of the rock sample 3 during loading and unloading, and can better analyze the anisotropic properties of the rock sample 3.

[0034] The wave velocity measurement system 2 includes a signal generator 21, a shear wave and longitudinal wave transducer 22, and a longitudinal and shear wave receiver 23 connected in sequence. The secondary pressure head 12 is provided with an open cavity 121 at one end away from the primary pressure head 11, and the longitudinal and shear wave receiver 23 is fixedly connected to the center position of the bottom wall of the open cavity 121.

[0035] In this embodiment, the distance between the center position and the side wall of the secondary pressure head 12 is 47 mm.

[0036] In this embodiment, a wire embedding space is reserved in the secondary pressure head 12, so as to realize the real-time measurement of anisotropic wave velocity during the loading process without interfering with the loading of the rock sample.

[0037] In this embodiment, while protecting the acoustic emission monitoring system 4 from damage, close contact between the acoustic emission monitoring system 4 and the rock sample 3 is achieved, shortening the path for the fracture signal generated inside the rock sample 3 to propagate to the acoustic emission monitoring system 4, reducing stress wave losses, and maximizing the reception of the fracture signal inside the rock sample 3, thereby ensuring the accuracy of the fracture position positioning.

[0038] The acoustic emission monitoring system 4 includes multiple waveguides 41 and multiple acoustic emission probes 42. A plurality of probe mounting holes 111 are evenly arranged in the first-stage pressure head 11. The probe mounting holes 111 include a first-stage countersunk hole 1111 and a second-stage countersunk hole 1112 that are interconnected. The first-stage countersunk hole 1111 is adapted to the front section of the waveguide 41, and the second-stage countersunk hole 1112 is adapted to the middle and rear sections of the waveguide 41. The front end of the waveguide 41 is flush with the outer wall of the first-stage pressure head 11 and is used to contact the rock sample 3. The rear end of the waveguide 41 is provided with a receiving groove adapted to the acoustic emission probe 42; a bolt 44 is provided at one end of the second-stage countersunk hole 1112 away from the waveguide 41, and the bolt 44 is fixedly connected to the rear end of the waveguide 41 through an annular gasket 43 for fixing the acoustic emission probe 42.

[0039] In this embodiment, the first-stage pressure head 11 is provided with three probe mounting holes 111, which are distributed in a triangular shape, and the specific arrangement positions are as follows: the center of the probe mounting hole 111 on the right side is 16.5 mm away from the right boundary of the bottom wall of the first-stage pressure head 11, and is 46.5 mm away from the upper and lower boundaries of the bottom wall of the first-stage pressure head 11; the center of the probe mounting hole 111 on the upper left side is 20.52 mm away from the upper boundary of the bottom wall of the first-stage pressure head 11, and is 31.5 mm away from the left boundary of the bottom wall of the first-stage pressure head 11; the center of the probe mounting hole 111 on the lower left side is 20.52 mm away from the lower boundary of the bottom wall of the first-stage pressure head 11, and is 31.5 mm away from the left boundary of the bottom wall of the first-stage pressure head 11.

[0040] In this embodiment, the bolt 44, the acoustic emission probe 42 and the waveguide 41 form a stacked structure, and the acoustic emission probe 42 is in the middle position, which can prevent the acoustic emission probe 42 from being damaged. At the same time, the acoustic emission probe 42 is in close contact with the rock sample 3, shortening the path of the fracture signal generated inside the rock sample 3 to propagate to the acoustic emission probe 42, reducing stress wave losses, maximizing the reception of the fracture signal inside the rock sample, and ensuring the accuracy of the fracture position positioning.

[0041] A plurality of isolation washers are provided between the outer wall of the waveguide 41 and the inner wall of the secondary countersunk hole 1112 for isolating the signal generated by the primary pressure head 11 that interferes with the acoustic emission probe 42 and for increasing the friction between the waveguide 41 and the secondary countersunk hole 1112 .

[0042] A plurality of lead grooves 122 communicating with the secondary countersunk holes 1112 are provided in the secondary pressure head 12 . The wires 45 of the acoustic emission probe 42 pass through the lead grooves 122 and are connected to an external acoustic emission connector.

[0043] A coupling agent is filled between the outer wall of the acoustic emission probe 42 and the inner wall of the receiving groove to ensure the transmission quality of the acoustic emission signal.

[0044] The maximum temperature resistance of the acoustic emission probe 42 is 150° C., and the maximum pressure resistance is 100 MPa.

[0045] In this embodiment, the acoustic emission probe 42 is temperature-resistant, pressure-resistant, and oil-resistant.

[0046] The contact surface between the first-stage pressure head 11 and the rock sample 3 is coated with a coupling agent.

[0047] In this embodiment, the coupling agent is butter or vaseline.

[0048] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A hierarchical true triaxial indenter with an acoustic emission system based on a laminate design, characterized in that: It comprises a plurality of graded loading pressure heads (1) arranged in a true triaxial loading frame, wherein the plurality of graded loading pressure heads (1) are symmetrically arranged in the XYZ directions and are used to load a rock sample (3); The step-type loading head (1) comprises a primary head (11) and a secondary head (12); one end of the primary head (11) is fixedly connected to the secondary head (12), and the other end is used to contact the rock sample (3); an acoustic emission monitoring system (4) is provided in the primary head (11), and a wave velocity measurement system (2) is provided in the secondary head (12); The acoustic emission monitoring system (4) comprises a plurality of waveguides (41) and a plurality of acoustic emission probes (42); a plurality of probe mounting holes (111) are evenly arranged in the first-stage pressure head (11); the probe mounting holes (111) comprise a first-stage countersunk hole (1111) and a second-stage countersunk hole (1112) which are interconnected; the first-stage countersunk hole (1111) is adapted to the front section of the waveguide (41); the second-stage countersunk hole (1112) is adapted to the middle and rear sections of the waveguide (41). The front end of the waveguide (41) is flush with the outer wall of the first-stage pressure head (11) and is used to contact the rock sample (3). The rear end of the waveguide (41) is provided with a receiving groove adapted to the acoustic emission probe (42). The second-stage counterbore (1112) is provided with a bolt (44) at one end away from the waveguide (41). The bolt (44) is fixedly connected to the rear end of the waveguide (41) through an annular gasket (43) and is used to fix the acoustic emission probe (42). The first-stage pressure head (11) is provided with three probe mounting holes (111) which are arranged in a triangular shape. The specific arrangement positions are as follows: the center of the probe mounting hole (111) located on the right side is 16.5 mm away from the right boundary of the bottom wall of the first-stage pressure head (11), and is 46.5 mm away from the upper and lower boundaries of the bottom wall of the first-stage pressure head (11); the center of the probe mounting hole (111) located on the upper left side is 20.52 mm away from the upper boundary of the bottom wall of the first-stage pressure head (11), and is 31.5 mm away from the left boundary of the bottom wall of the first-stage pressure head (11); the center of the probe mounting hole (111) located on the lower left side is 20.52 mm away from the lower boundary of the bottom wall of the first-stage pressure head (11), and is 31.5 mm away from the left boundary of the bottom wall of the first-stage pressure head (11); The distance between the central axis of the wave velocity measurement system (2) and the central axis of the acoustic emission monitoring system (4) is 30 mm, and the two do not affect each other; The wave velocity measurement systems (2) symmetrically arranged in the XYZ directions are mutually a signal transmitting source and a signal receiving source; The wave velocity measurement system (2) can sequentially excite P wave, S1 wave, and S2 wave signals, thereby achieving real-time measurement of the anisotropic wave velocity of the rock sample (3) during loading and unloading, and better analyzing the anisotropic properties of the rock sample (3); The wave velocity measurement system (2) comprises a signal generator (21), a transverse wave and longitudinal wave transducer (22), and a longitudinal and transverse wave receiver (23) which are connected in sequence; an open cavity (121) is provided at one end of the secondary pressure head (12) away from the primary pressure head (11); and the longitudinal and transverse wave receiver (23) is fixedly connected to the center position of the bottom wall of the open cavity (121).

2. A hierarchical true triaxial indenter with an acoustic emission system based on a laminated design according to claim 1, characterized in that: A plurality of isolation gaskets are provided between the outer wall of the waveguide (41) and the inner wall of the secondary countersunk hole (1112).

3. The hierarchical true triaxial indenter with an acoustic emission system based on a laminated design according to claim 1, characterized in that: A plurality of lead grooves (122) in communication with the secondary countersunk holes (1112) are provided in the secondary pressure head (12); the lead wires (45) of the acoustic emission probe (42) pass through the lead grooves (122) and are connected to an external acoustic emission connector.

4. The hierarchical true triaxial indenter with an acoustic emission system based on a laminated design according to claim 1, characterized in that: A coupling agent is filled between the outer wall of the acoustic emission probe (42) and the inner wall of the accommodating groove.

5. The hierarchical true triaxial indenter with an acoustic emission system based on a laminated design according to claim 1, characterized in that: The acoustic emission probe (42) has a maximum temperature resistance of 150° C. and a maximum pressure resistance of 100 MPa.

6. A hierarchical true triaxial indenter with an acoustic emission system based on a laminated design according to claim 1, characterized in that: A coupling agent is applied on the contact surface between the first-stage pressure head (11) and the rock sample (3).

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