Charge signal monitoring device and monitoring method based on true triaxial hopkinson pressure bar

Abstract

The present application relates to a kind of charge signal monitoring devices based on true triaxial hopkinson pressure bar, including three groups of loading rods for clamping rock sample and being three-dimensional spatial distribution and perpendicular to each other, two loading faces of one group of loading rods are respectively provided with mounting pad, mounting groove is opened on mounting pad, corresponding in the two opposite faces of rock sample respectively is provided with charge sensing unit for monitoring rock sample charge signal, the installation position of charge sensing unit corresponds with mounting groove, mounting groove can accommodate wrapped charge sensing unit, charge sensing unit is electrically connected with controller.The present application sets up eight charge sensing units of rectangular array distribution on true triaxial hopkinson pressure bar test system, and combines mounting pad, buffer pad and external electromagnetic shield cover and other structures, realizes the high-precision, multidimensional monitoring of internal damage evolution of rock sample under the loading environment of full-closed, no temporary air face.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics and impact dynamics test monitoring technology, specifically to a charge signal monitoring device and method based on a true triaxial Hopkinson pressure bar. Background Technology

[0002] As shallow resources are gradually depleted, underground engineering projects in mining, transportation, water conservancy, and national defense are continuously expanding into deeper areas. The geostress environment of deep rocks is extremely complex, typically exhibiting a true triaxial stress state with high stress levels. Under these true triaxial stress conditions, the mechanical response, deformation characteristics, and failure mechanisms of rocks differ significantly from those under uniaxial or conventional triaxial conditions. Simultaneously, deep underground engineering projects frequently encounter dynamic impact loads during construction and operation, such as rockbursts, blasting excavation, mechanical impacts, and seismic wave disturbances. These dynamic disturbances, superimposed on the existing high static stress field, can easily induce sudden instability and failure of the surrounding rock, causing serious safety accidents and economic losses. Therefore, studying the failure characteristics of rocks under dynamic impact loads under true triaxial stress states is of significant theoretical and engineering value for revealing the mechanisms of deep rock mass disasters and optimizing engineering design and disaster prevention.

[0003] Currently, the true triaxial Hopkinson bar (SHPB) test system is the primary means of simulating the mechanical behavior of deep rocks under coupled triaxial static stress and dynamic impact loading conditions. In this system, the six faces of a cubic rock specimen are tightly surrounded by six rigid bars to achieve independent triaxial stress loading. However, this fully enclosed loading method results in the specimen being completely in a closed space during the impact process, with no free surfaces. Traditional optical observation methods (such as high-speed photography and digital image correlation (DIC)) and conventional acoustic emission (AE) sensors are greatly limited, making it difficult to monitor the initiation, propagation, and penetration evolution of microcracks inside the specimen in real time. In addition, the electromagnetic / charge signals generated by rock failure have attracted attention in the field of rock mechanics monitoring due to their fast response speed and sensitivity to crack propagation. However, existing research is mostly focused on static or quasi-static loading conditions, lacking devices and methods for monitoring charge signals under true triaxial dynamic impact in a closed space.

[0004] Therefore, developing a charge signal monitoring device suitable for true triaxial impact tests, capable of reliably capturing the charge signals generated by the internal damage evolution of rock samples under extreme loading conditions with six non-free surfaces and in a fully enclosed environment, is of urgent need and significant value for breaking through the current monitoring technology bottleneck and gaining a deeper understanding of the failure mechanism of deep rocks under true triaxial dynamic impact. Summary of the Invention

[0005] The purpose of this invention is to provide a charge signal monitoring device based on a true triaxial Hopkinson bar to address the shortcomings of existing technologies. By setting up eight charge sensing units in a rectangular array on a true triaxial Hopkinson bar test system, and combining them with structures such as mounting blocks, buffer pads, and external electromagnetic shielding covers, high-precision, multi-dimensional monitoring of the internal damage evolution of rock samples is achieved in a fully enclosed loading environment without free surfaces. This aims to solve the technical problem that in existing true triaxial Hopkinson bar impact tests, the rock samples are in a fully enclosed state without free surfaces, making it difficult for traditional monitoring methods to effectively capture the internal damage evolution signals of the rock.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A charge signal monitoring device based on a true triaxial Hopkinson bar includes three sets of loading rods arranged in three-dimensional space and perpendicular to each other for clamping rock samples. One set of loading rods has mounting blocks on two loading surfaces. Multiple mounting slots are formed on the mounting blocks. Multiple charge sensing units for monitoring the charge signal of the rock sample are uniformly distributed on two opposite surfaces of the rock sample. The installation position of the charge sensing unit corresponds to the mounting slot. Each mounting slot can only accommodate one charge sensing unit. The charge sensing unit is electrically connected to a controller.

[0007] Furthermore, it also includes a buffer pad disposed between the bottom of the mounting slot and the charge sensing unit to separate the mounting slot from the charge sensing unit.

[0008] Furthermore, four charge sensing units are respectively provided on two opposite surfaces of the rock sample. The four charge sensing units located on the same side are arranged in a rectangular pattern, and four mounting slots are provided on a corresponding mounting pad.

[0009] Furthermore, loading pads are provided on the four loading surfaces of the other two sets of loading rods.

[0010] Furthermore, it also includes an electromagnetic shielding cover that encloses the rock sample and the loading surfaces of all loading rods.

[0011] Furthermore, the electromagnetic shielding cover includes multiple shields that are detachably connected to each other in the horizontal direction.

[0012] A method for monitoring charge signals based on a true triaxial Hopkinson bar includes the following steps: Step 1: Prepare the rock sample and determine the loading surface to be monitored according to the test plan. Install the charge sensing unit on the opposite two surfaces of the rock sample. Step 2: Install the mounting pads onto the loading surfaces of a set of loading rods, assemble the six-direction loading rods of the true triaxial SHPB system, make the mounting slot accommodate and enclose the charge sensing unit, and connect the charge sensing unit to the controller; Step 3: Apply true triaxial static stress to the predetermined value. After the static stress stabilizes, trigger the SHPB system to apply dynamic impact load. During the entire dynamic impact process, the charge sensing unit records the charge signal inside the rock sample in real time and transmits it to the controller. Step 4: Analyze and process the acquired raw charge signals, record the arrival time of each channel signal through the controller, invert the three-dimensional spatial coordinates of the crack source, and analyze the damage evolution law, fracture precursor characteristics and failure mechanism of the rock under true triaxial dynamic loading.

[0013] Furthermore, in step four, the process of retrieving the three-dimensional spatial coordinates of the crack source includes: speed of electromagnetic waves in rock samples The calculation formula is as follows:

[0014] in, The speed of light in a vacuum. is the relative permittivity of the rock sample; Let the three-dimensional spatial coordinates of the crack initiation be... , No. The known coordinates of each charge sensing unit are The crack source is then connected to the charge sensing unit. straight-line distance The calculation formula is as follows:

[0015] Set charge sensing unit The absolute arrival time of the recorded signal is Reference sensing unit The absolute arrival time of the recorded signal is Then the signal arrival time difference The calculation formula is as follows:

[0016] Then the signal arrival distance difference The calculation formula is as follows:

[0017] in, From crack source to reference sensing unit The distance is calculated using the following formula:

[0018] Then Substitute the calculation formula The calculation formula yields the three-dimensional spatial coordinates of the crack initiation. The equation of the hyperboloid with unknowns is as follows:

[0019] Solving the above equation yields the three-dimensional coordinates of the crack initiation. .

[0020] Compared with existing technologies, this invention, for the first time, achieves charge signal monitoring based on an eight-sensor rectangular array under true triaxial SHPB fully enclosed loading conditions. It possesses comprehensive capabilities such as crack spatial localization and propagation trajectory reconstruction and identification. This device fills the gap in existing technologies for real-time monitoring of internal damage evolution in the field of true triaxial dynamic impact. It provides a novel, high-resolution monitoring method for studying the failure mechanism of deep rock masses under the coupled action of true triaxial static stress and dynamic disturbance. It can be widely applied to fundamental rock dynamics research in fields such as deep mining, tunnel blasting excavation, and underground protection engineering. Specific beneficial effects are as follows: ① Achieving in-situ monitoring in a fully enclosed environment: Addressing the technical challenge of cubic specimens being surrounded by loading rods and pads on all six sides in true triaxial SHPB tests, with no free face and the inability to install traditional sensors, this invention creates mounting grooves on the mounting pads, allowing the charge sensing unit to be attached to the surface of the rock sample and embedded inside the mounting pads. This enables in-situ real-time acquisition of charge signals from rock samples during dynamic impact without altering the original true triaxial loading structure.

[0021] ② Effectively suppresses impact interference and improves signal-to-noise ratio: The present invention sets a flexible buffer pad between the bottom of the groove and the sensor. The buffer pad can absorb part of the mechanical energy generated by the impact load, avoid rigid collision between the pad and the sensor, and significantly reduce the false charge signals introduced by mechanical noise such as the impact of the loading rod and the vibration of the pad. At the same time, the external overall electromagnetic shielding cover isolates the environmental electromagnetic radiation interference, ensuring that the collected signals are mainly the real charge signals generated by the initiation, expansion and friction of internal rock cracks, which greatly improves the reliability and signal-to-noise ratio of the monitoring data.

[0022] ③ Precise positioning and reconstruction of crack initiation and propagation process in three-dimensional space: This invention arranges eight charge sensors on a Y-direction pad according to a rectangular geometric relationship to form a spatial three-dimensional array. When microcracks initiate or propagate inside the rock sample, the charge signal generated by charge separation and friction at the crack tip will propagate in the form of electromagnetic waves. Since the coordinate positions of each sensor in space are different, there is a certain time difference in the time when the signal generated by the same fracture event arrives at different sensors. This invention records the arrival time of each channel signal through a high-precision synchronous acquisition system (sampling rate ≥ 1MHz), and combines the propagation speed of electromagnetic waves in the rock medium. Using the hyperbolic positioning algorithm or the least squares optimization algorithm, the three-dimensional spatial coordinates of the fracture source can be inverted. The rectangular array of eight sensors provides redundant spatial constraints, significantly improving positioning accuracy and reliability, and enabling accurate identification of the initiation location of cracks. In addition, the eight sensors, distributed in a rectangular array, can continuously record the spatial location and occurrence time of each fracture event with a microsecond-level temporal resolution. By sequentially labeling each fracture event in a three-dimensional spatial coordinate system in chronological order, the complete evolution trajectory of the crack from initiation, propagation, bifurcation, convergence to the final formation of a macroscopic fracture surface can be reconstructed.

[0023] ④ Good compatibility with existing true triaxial SHPB systems and low modification cost: This invention only adds a structure to the original system without modifying the loading host, six cuboid loading rods, impact bullets and static load application device of the true triaxial SHPB system. The rectangular size of the added pad is consistent with the standard pad, and the installation method is the same, which has good plug-and-play characteristics. This design makes it easy to integrate this device into the existing true triaxial SHPB test platform, with low modification cost and high promotion value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the electromagnetic shielding cover in this invention; Figure 3 This is an overall sectional view of the present invention; Figure 4 for Figure 3 A magnified view of a section at point A in the middle; Figure 5 This is a perspective view of the rock sample after six pads are installed on the outside of the rock sample in this invention; Figure 6 This is a schematic diagram of the mounting pad structure in this invention; Figure 7 This is a schematic diagram of the structure of the cover in this invention.

[0025] The attached figures are labeled as follows: 1. Loading rod; 2. Rock sample; 3. Charge sensing unit; 4. Mounting pad; 41. Mounting groove; 42. Lead wire channel; 5. Buffer pad; 6. Loading pad; 7. Cover; 71. Flange; 72. Groove. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0027] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0028] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0030] For easier understanding, please refer to Figures 1 to 7This embodiment provides a charge signal monitoring device based on a true triaxial Hopkinson bar, including three sets of loading rods 1 arranged in three-dimensional space and perpendicular to each other for clamping rock sample 2. Specifically, the loading rods 1 are six cuboid loading rods 1 corresponding to the three directions of the spatial rectangular coordinate system X, Y, and Z, namely, loading rod 1 in the positive X direction, loading rod 1 in the negative X direction, loading rod 1 in the positive Y direction, loading rod 1 in the negative Y direction, loading rod 1 in the positive Z direction, and loading rod 1 in the negative Z direction. Each loading rod 1 can independently apply an initial static load to the cubic rock sample before dynamic impact loading to simulate the true triaxial static stress state. The rear end of the loading rod 1 in the positive X direction is also equipped with a dynamic impact loading device (such as an impact bullet) to apply a dynamic impact load to the sample along the positive X direction after the static stress has stabilized, so as to simulate the process of deep rock being subjected to dynamic disturbance under true triaxial stress conditions. A mounting pad 4 is fixedly installed on the loading surface (contact surface with rock sample 2) of the two Y-direction loading rods 1. The mounting pad 4 has a mounting groove 41. A charge sensing unit 3 is provided on the two Y-direction surfaces of the rock sample 2. The charge sensing unit 3 is used to monitor and sense the charge signal generated by the rock sample under dynamic impact in real time. The installation position of the charge sensing unit 3 corresponds to the mounting groove 41. The depth of the mounting groove 41 is greater than the thickness of the charge sensing unit 3. That is, the mounting groove 41 can accommodate and wrap the charge sensing unit 3, preventing the mounting pad 4 from directly squeezing the charge sensing unit 3 during the impact. Furthermore, multiple uniformly distributed charge sensing units 3 are provided on both sides of the rock sample 2 in the Y direction. The charge sensing units 3 on each side are uniformly distributed. The number of mounting grooves 41 and buffer pads 5 is the same as the number of charge sensing units 3. Each mounting groove 41 can only accommodate one charge sensing unit 3, avoiding the mounting groove 41 from occupying too much surface area, thus ensuring the direct contact area between the mounting pad 4 and the rock sample 2, thereby ensuring the transmission effect of stress waves. Specifically, four charge sensing units 3 are provided on each side of the Y direction. The four charge sensing units 3 on the same side are arranged in a rectangular shape, corresponding to four rectangular mounting grooves 41 opened on a mounting pad 4. The charge sensing unit 3 is electrically connected to a controller, which includes a preamplifier, a data acquisition card, and a signal processing computer. The charge sensor can be connected to the controller via signal leads for amplifying, filtering, analog-to-digital conversion, and storing and analyzing the acquired charge signals. Furthermore, each mounting slot 41 has a lead channel 42 for the signal leads to pass through, connecting the charge sensing unit 3 and the controller via the lead channel 42. Preferably, the charge sensing unit 3 is a PVDF piezoelectric thin film sensor; if a charge sensing unit 3 with wireless data transmission capability is used, it is not necessary to have a lead channel 42 in the mounting slot 41.

[0031] Loading pads 6 are fixedly installed on the four loading surfaces of the other two sets (X-direction and Z-direction) of loading rods 1. Furthermore, the loading pads 6 and mounting pads 4 are made of the same material as the loading rods 1, but the loading pads 6 have fewer mounting grooves 41 compared to the mounting pads 4. Since the surface of rocks (especially natural rocks) after being cut into rock samples 2 has microscopic unevenness, the loading pads 6 and mounting pads 4 can improve the uniformity of contact between the loading rods 1 and the rock sample 2, ensuring uniform force distribution. At the same time, the rock sample 2 is very hard and rough, and under the high-speed impact of a true triaxial Hopkinson bar test, it is prone to localized damage to the loading surface of the loading rods 1 (especially the loading rods 1 in the positive X direction). In this case, the loading pads 6 and mounting pads 4 can act as sacrificial layers to absorb and transfer impact energy, avoiding direct contact between the loading rods 1 and the rock sample 2, thus protecting the loading rods 1 from direct damage and extending the service life of the experimental apparatus. Therefore, users should conduct external inspections of the installation pad 4 and loading pad 6 before and after the experiment. If unevenness or damage is found, the pads should be replaced in time.

[0032] A flexible buffer pad 5 is installed at the bottom of the mounting groove 41. The buffer pad 5, positioned between the bottom of the mounting groove 41 and the charge sensing unit 3, separates the mounting groove 41 from the charge sensing unit 3. This buffer pad 5 absorbs some energy under impact loads and further prevents rigid contact between the mounting pad 4 and the charge sensing unit 3, thereby suppressing false interference signals caused by mechanical impact. Furthermore, the depth of the mounting groove 41 is slightly greater than the thickness of the charge sensing unit 3 plus the buffer pad 5. That is, in the initial state, the buffer pad 5 is attached to the bottom of the mounting groove 41, with a certain gap between the buffer pad 5 and the charge sensing unit 3.

[0033] The electromagnetic shielding cover is located on the outside of the entire device and is used to enclose the rock sample 2 and all loading surfaces to isolate electromagnetic radiation interference from the external environment. The electromagnetic shielding cover includes four L-shaped covers 7 that are detachably connected to each other in the horizontal direction. The four covers 7 have identical structures and are designed to prevent mistaken identity in the vertical direction. Specifically, the upper horizontal ends of the covers 7 are provided with corresponding flanges 71 and grooves 72, and the lower horizontal ends of the covers 7 are also provided with the same flanges 71 and grooves 72. The two flanges 71 or grooves 72 must be located on opposite sides in the horizontal direction, that is, the two flanges 71 or grooves 72 cannot be located in the same vertical direction. Preferably, the material of the electromagnetic shielding cover can be metallic copper or aluminum, or non-metallic conductive plastic / coating and conductive cloth padding.

[0034] The method for monitoring charge signals in a true triaxial impact test using the above-mentioned device includes the following steps: Step 1: Sample preparation and sensor installation: Prepare a cubic rock sample and determine the loading surface to be monitored according to the test plan. Attach the charge sensing unit 3 to the opposite two surfaces of the rock sample 2. Then, install the buffer pad 5 in the mounting groove 41 and lead out the signal lead of the charge sensing unit 3 along the lead channel 42 of the mounting pad block 4 (this can be ignored if a charge sensing unit 3 with wireless data transmission function is used).

[0035] Step 2: Device Assembly Install two mounting pads 4 with charge sensing units 3 installed on the loading surface of one set of loading rods 1 respectively. Install four loading pads 6 on the loading surfaces of the other two sets of loading rods 1 respectively. Assemble the six-direction loading rods 1 of the true triaxial SHPB system, so that each pad is in close contact with the surface of the rock sample 2 to form a fully enclosed loading space. Connect all signal leads to the controller, install and close the external electromagnetic shielding cover, and ensure good grounding.

[0036] Step 3: Loading and Signal Acquisition A true triaxial static stress is applied to a predetermined value to simulate the original rock stress state of deep rocks. After the static stress is stabilized, the SHPB system is triggered to apply a dynamic impact load in the X direction. During the entire dynamic impact process, the charge sensing unit 3 records the charge signals generated by the initiation, propagation and friction of microcracks inside the rock sample 2 in real time, and transmits them to the controller through the signal lead.

[0037] Step 4: Signal Processing and Analysis The acquired raw charge signals are subjected to necessary filtering (such as low-pass filtering and band-stop filtering) to remove noise caused by impact vibration, electromagnetic radiation, etc., and the damage evolution law, fracture precursor characteristics and failure mechanism of rocks under true triaxial dynamic loading are analyzed in combination with stress wave data and charge signal characteristics.

[0038] It should be noted that in this embodiment, eight charge sensing units 3 are arranged in a rectangular geometric relationship on the mounting block 4 in the Y direction to form a spatial three-dimensional array. When microcracks initiate or propagate inside the rock sample 2, the charge signal generated by charge separation and friction at the crack tip will propagate in the form of electromagnetic waves. Since the coordinate positions of each charge sensing unit 3 in space are different, there is a certain time difference in the arrival time of the signal generated by the same fracture event at different sensors. The arrival time of the signal of each channel is recorded by the high-precision synchronous acquisition system (sampling rate ≥1MHz) in the controller. Combined with the propagation speed of electromagnetic waves in the rock medium, the three-dimensional spatial coordinates of the fracture source can be deduced using the hyperbolic positioning algorithm or the least squares optimization algorithm. Specifically, the three-dimensional crack location method is as follows: (1) Calibration of electromagnetic wave propagation speed speed of electromagnetic waves in rocks This can be obtained through theoretical calculations or on-site calibration:

[0039] in, The speed of light in a vacuum. The relative permittivity of the rock; or through a known distance Time difference of arrival of direct waves between two sensing units It can be obtained through direct calculation.

[0040] (2) Spatial distance relationship between crack source and sensor Let the three-dimensional spatial coordinates of the crack initiation be... , No. The known coordinates of each charge sensing unit are The straight-line distance from the crack source to the charge sensing unit is... Determined by the following formula:

[0041] This formula forms the basis of the geometric relationship for all subsequent positioning calculations.

[0042] (3) Direct measurement expression for arrival time difference Set charge sensing unit The absolute arrival time of the recorded signal is Reference sensing unit The absolute arrival time of the recorded signal is Then the time difference The calculation formula is as follows:

[0043] Due to the exact moment when the crack occurred Unknown, time difference This can eliminate the unknown quantity, making the location problem solvable.

[0044] (4) Core positioning equation based on Time Difference of Arrival (TDOA) Let the speed of electromagnetic wave propagation in rock medium be... (Obtained in advance through calibration tests), the crack source signal reaches the charge sensing unit. and reference sensing unit The time difference is The corresponding distance difference Determined by the following formula:

[0045] in, The distance from the crack source to the reference sensing unit is calculated using the following formula:

[0046] Then Substitution That is, to obtain The equation of the hyperboloid with unknowns is as follows:

[0047] This equation geometrically represents a charge sensing unit and reference sensing unit A hyperboloid with focal point .

[0048] Furthermore, for any two different charge sensing units and charge sensing unit Alternatively, you can write it directly:

[0049] When using 8 charge sensing units, one of them is selected as a reference (e.g., a reference sensing unit). The above equations can be established separately for the other 7 charge sensing units, forming the following system of equations:

[0050] This system of equations contains 7 equations, with the only unknown being the crack initiation point. There are 3 in total, therefore it is an overdetermined system of equations.

[0051] The optimal three-dimensional coordinates of the crack initiation can be obtained by using the least squares method. In practice, the calculation can be performed directly using conventional mathematical software (such as MATLAB) without the need for iteration or complex filtering.

[0052] (5) Positioning error estimation Positioning accuracy is affected by both the geometric layout of the sensor unit and the time difference measurement error. The standard deviation of the positioning error can be approximately expressed as:

[0053] in, The number of independent time differences. The standard deviation of the time difference measurement error for each channel. This represents the sensitivity coefficient (error propagation factor) of the positioning algorithm to time difference. The rectangular array layout in this embodiment has good spatial symmetry, which can effectively reduce this error.

[0054] The above formulas together constitute a complete calculation process from charge signal acquisition, time delay estimation, spatial positioning to time-frequency verification, realizing three-dimensional dynamic positioning and reconstruction of the entire process of crack initiation, propagation and penetration inside rocks under true triaxial SHPB closed conditions.

[0055] Although the present invention has been described using the above preferred embodiments, it is not intended to limit the scope of protection of the present invention. Any changes and modifications made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. A charge signal monitoring device based on a true triaxial Hopkinson bar, comprising three sets of loading rods (1) arranged in three-dimensional space and perpendicular to each other for clamping a rock sample (2), characterized in that, One of the loading rods (1) has two loading surfaces with mounting pads (4) and multiple mounting slots (41) on the mounting pads (4). On the two opposite surfaces of the rock sample (2), multiple charge sensing units (3) for monitoring the charge signal of the rock sample (2) are provided in a uniform distribution. The installation position of the charge sensing unit (3) corresponds to the mounting slot (41). Each mounting slot (41) can only accommodate one charge sensing unit (3). The charge sensing unit (3) is electrically connected to a controller.

2. The charge signal monitoring device based on a true triaxial Hopkinson bar according to claim 1, characterized in that, It also includes a buffer pad (5) disposed between the bottom of the mounting slot (41) and the charge sensing unit (3) to separate the mounting slot (41) and the charge sensing unit (3).

3. The charge signal monitoring device based on a true triaxial Hopkinson bar according to claim 1, characterized in that, The rock sample (2) has four charge sensing units (3) on its two opposite surfaces. The four charge sensing units (3) on the same side are arranged in a rectangular shape, and four mounting slots (41) are opened on a mounting pad (4).

4. The charge signal monitoring device based on a true triaxial Hopkinson bar according to claim 1, characterized in that, The other two sets of loading rods (1) are provided with loading pads (6) on their four loading surfaces.

5. The charge signal monitoring device based on a true triaxial Hopkinson bar according to claim 1, characterized in that, It also includes an electromagnetic shielding cover for the rock sample (2) and all loading surfaces.

6. The charge signal monitoring device based on a true triaxial Hopkinson bar according to claim 5, characterized in that, The electromagnetic shielding cover includes multiple shield bodies (7) that are detachably connected to each other in the horizontal direction.

7. A monitoring method based on the charge signal monitoring device of claim 1, characterized in that, Includes the following steps: Step 1: Prepare rock samples and determine the loading surfaces to be monitored according to the test plan. Install the charge sensing unit (3) on the opposite two sides of the rock sample (2). Step 2: Install the mounting pads (4) on the loading surfaces of a set of loading rods (1), and assemble the six-direction loading rods (1) of the true triaxial SHPB system, so that the mounting slot (41) can accommodate the charge sensing unit (3), and connect the charge sensing unit (3) to the controller. Step 3: Apply true triaxial static stress to the predetermined value, and after the static stress is stabilized, trigger the SHPB system to apply dynamic impact load. During the entire dynamic impact process, the charge sensing unit (3) records the charge signal inside the rock sample (2) in real time and transmits it to the controller. Step 4: Analyze and process the acquired raw charge signals, record the arrival time of each channel signal through the controller, invert the three-dimensional spatial coordinates of the crack source, and analyze the damage evolution law, fracture precursor characteristics and failure mechanism of the rock under true triaxial dynamic loading.

8. The monitoring method according to claim 7, characterized in that, Step four, the process of retrieving the three-dimensional spatial coordinates of the crack source, includes: speed of electromagnetic waves in rock samples The calculation formula is as follows: , in, The speed of light in a vacuum. is the relative permittivity of the rock sample; Let the three-dimensional spatial coordinates of the crack initiation be... , No. The known coordinates of each charge sensing unit are The crack source is then connected to the charge sensing unit. straight-line distance The calculation formula is as follows: ， Set charge sensing unit The absolute arrival time of the recorded signal is Reference sensing unit The absolute arrival time of the recorded signal is Then the signal arrival time difference The calculation formula is as follows: , Then the signal arrival distance difference The calculation formula is as follows: , in, From crack source to reference sensing unit The distance is calculated using the following formula: ， Then Substitute the calculation formula The calculation formula yields the three-dimensional spatial coordinates of the crack initiation. The equation of the hyperboloid with unknowns is as follows: ， Solving the above equation yields the three-dimensional coordinates of the crack initiation. .

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