A device and method for indoor experiment impact loading and acoustic emission cooperative monitoring of a roadway structure

Abstract

The application provides a kind of indoor experiment impact loading and acoustic emission cooperative monitoring device and method for roadway structure, the device of the application includes true triaxial electromagnetic hopkinson bar system, acoustic emission monitoring system, rock burst loading module and data monitoring and control system, the rock burst loading module includes loading plate, loading rod, wherein the cross section of the loading rod is circular, the loading plate is arranged between loading rod and roadway surrounding rock model sample, for changing the cross section of loading rod and connecting roadway surrounding rock model sample, acoustic emission probe fixing hole is provided on the side wall of the loading plate, the acoustic emission probe of the acoustic emission monitoring system is installed on the side wall of the loading plate through the acoustic emission probe fixing hole, and can be contacted with roadway surrounding rock model sample.The application can use true triaxial electromagnetic hopkinson bar to simulate roadway structure impact loading, and realize acoustic emission cooperative monitoring in the process of roadway structure impact loading.

Description

Technical Field

[0001] This invention relates to the field of tunnel surrounding rock simulation research technology, specifically to an indoor experimental impact loading and acoustic emission co-monitoring device and method for tunnel structures. Background Technology

[0002] Coal mining has entered deep-level operations. Deep coal and rock masses are not only subjected to high static stresses such as the weight of the overlying strata and tectonic stress, but also to dynamic disturbances such as mine vibrations, blasting, and coal cutting. As mining depth increases, the stress environment of the coal and rock mass becomes increasingly complex, leading to frequent dynamic disasters such as rock bursts, which seriously threaten mine safety. Under the coupled effects of high static loads and strong disturbances, the response mechanism of the coal and rock mass becomes more complex, significantly increasing the risk of disasters. Therefore, in-depth research on the mechanisms of disaster incubation and instability failure in deep coal and rock masses is of great significance for improving the ability to prevent and control dynamic disasters and ensuring safe and efficient coal mining.

[0003] In terms of disturbance patterns, the surrounding rock of the roadway may be subjected to vertical dynamic disturbances such as overlying strata fracturing and roof blasting, as well as horizontal dynamic disturbances such as coal blasting and coal cutting. These dynamic load disturbances may occur simultaneously or be asynchronously superimposed, causing the surrounding rock to be in a multi-axis, multi-directional coupled disturbance state.

[0004] In engineering practice, geophysical field monitoring technology is an important means of early warning of rockbursts. In coal mines, microseismic monitoring systems are often used to monitor low-frequency elastic wave signals generated by large-scale fracture rupture, while in laboratories, acoustic emission monitoring systems are often used to monitor high-frequency elastic wave signals in coal and rock samples during the initiation and propagation of microfractures. Essentially, both are monitoring elastic wave signals generated by the release of elastic strain energy during fracture evolution.

[0005] Currently, true triaxial electromagnetic Hopkinson bars can achieve multi-axis, multi-directional synchronous or asynchronous dynamic load disturbance effects, providing a basis for simulating complex stress environments in deep coal and rock masses. However, the following shortcomings and defects still exist: (1) It is difficult to achieve impact loading on the tunnel structure.

[0006] Existing Hopkinson bar experiments often use small-sized cylindrical (Φ50*50mm) or cubic (50*50*50mm) specimens. However, actual roadway surrounding rock often exhibits structural-scale coordinated response and non-uniform failure characteristics under deep impact disturbance. Existing small-sized specimens cannot meet the structural characteristics of roadway surrounding rock.

[0007] Furthermore, existing true triaxial electromagnetic Hopkinson bars use titanium square bars as loading rods. If a variable cross-section design is used, the presence of sharp corners in the square bar cross-section leads to uneven stress wave distribution, making it difficult to satisfy the one-dimensional stress wave propagation assumption. In the transition region of the variable cross-section, local stress concentration is easily formed at the sharp corners, resulting in additional reflections and waveform distortion, which weakens the stability and regularity of energy transfer.

[0008] (2) It is difficult to achieve coordinated monitoring of acoustic emission.

[0009] In true triaxial electromagnetic Hopkinson bars, the six-directional loading rods form a fully covered structure over the sample, limiting the space on the sample's outer surface and making it difficult to directly place acoustic emission sensors on the sample surface or critical stress areas. Furthermore, due to the significant spatial directionality and temporal differences in crack propagation, and the structural limitations hindering multi-channel, omnidirectional placement, spatial localization of acoustic emission events and source mechanism inversion are difficult to conduct, making it impossible to achieve precise matching between loading information and fracture response.

[0010] (3) The signal monitoring process is severely interfered with.

[0011] In true triaxial electromagnetic Hopkinson bar experiments, strong transient electromagnetic radiation is generated during electromagnetic acceleration, which severely affects the accurate acquisition of acoustic emission (AE) signals by the probe. On one hand, electromagnetic waves may enter the acoustic emission system through the loading rod, creating strong background noise that drowns out the weak AE signal, leading to waveform distortion, triggering errors, or missed signal detection. On the other hand, strong electromagnetic pulses may also interfere with sensitive electronic components such as preamplifiers, affecting the system's gain stability and frequency response, thereby reducing the signal-to-noise ratio and spatiotemporal resolution of the acoustic emission signal. Furthermore, collisions at the loading rod end and clamp vibrations can also generate secondary noise.

[0012] Therefore, in order to address the above shortcomings, a rockburst loading device based on a true triaxial electromagnetic Hopkinson bar was developed, aiming to solve the problem of accurately monitoring the failure process of coal and rock mass in existing rockburst tests. Summary of the Invention

[0013] To address the problems in the prior art, this invention provides an indoor experimental impact loading and acoustic emission co-monitoring device and method for roadway structures, which can improve the accuracy of monitoring the simulated coal and rock mass failure process based on impact ground pressure loading of a true triaxial electromagnetic Hopkinson rod.

[0014] This invention relates to an indoor experimental impact loading and acoustic emission coordinated monitoring device for tunnel structures, comprising a true triaxial electromagnetic Hopkinson bar system, an acoustic emission monitoring system, an impact ground pressure loading module, and a data monitoring and control system. The rockburst loading module includes a loading plate and a loading rod. The loading rod has a circular cross-section. The loading plate is positioned between the loading rod and the roadway surrounding rock model sample to change the cross-section of the loading rod and connect the roadway surrounding rock model sample. The loading plate is a variable cross-section plate with a thickness of T mm, wherein the bottom is... × The cross-section is mm, and the top is... × A cross-section of mm, with the bottom and top separated by... × mm cross section × The section transitions at mm, with the bottom contacting the roadway surrounding rock model sample, and the top center has a loading rod assembly hole matching the loading rod. , Both T and T are positive numbers, and ; The true triaxial electromagnetic Hopkinson bar system includes a loading frame, an electromagnetic pulse emission system and a confining pressure servo control system mounted on the loading frame. The electromagnetic pulse emission system and the confining pressure servo control system are used to apply static loads and impact load disturbances to the roadway surrounding rock model sample in six directions through the triaxial six-axis loading bar. The acoustic emission monitoring system is used to monitor the crack evolution and energy release law of the roadway surrounding rock model sample during impact loading, as well as to reduce the influence of electromagnetic radiation during data acquisition. The loading plate has an acoustic emission probe fixing hole on one or more side walls between the bottom and top. The acoustic emission probe of the acoustic emission monitoring system is installed on the side wall of the loading plate through the acoustic emission probe fixing hole and can contact the roadway surrounding rock model sample. The data monitoring and control system is used to control the true triaxial electromagnetic Hopkinson bar system and the acoustic emission monitoring system, and to record and store stress and acoustic emission signal data.

[0015] Furthermore, the loading rod is mounted on the loading frame via one or more leveling supports, with one end of the loading rod in contact with the electromagnetic pulse emission system and the other end positioned in the mounting hole at the top of the loading plate.

[0016] Furthermore, the leveling support includes a base and a support rod. The support rod has an arc-shaped limiting groove in the middle that is adapted to the outer surface of the loading rod. It also includes a bracket on the base, a longitudinal adjustment mechanism on the bracket that drives the support rod to move longitudinally relative to the bracket, and a lateral adjustment mechanism that drives the arc-shaped limiting groove in the middle of the support rod to adjust laterally. Through the longitudinal adjustment mechanism and the lateral adjustment mechanism, the loading rod is stably supported and leveled during the installation process.

[0017] Furthermore, the acoustic emission monitoring system includes an acoustic emission probe, which is fixed to the loading plate by an acoustic emission probe holder. The acoustic emission probe holder includes a fixing frame, a gasket, and a bolt. The outer surface of the fixing frame is provided with external threads, and the inner wall of the acoustic emission probe fixing hole is provided with internal threads. The fixing frame has a receiving cavity inside and a bolt hole at the top. The acoustic emission probe is placed in the receiving cavity, and its lower surface can contact and connect with the outer surface of the roadway surrounding rock model sample. The bolt passes through the bolt hole, and the acoustic emission probe is fixed in the receiving cavity by the gasket.

[0018] Furthermore, the fixing frame is made of ferrite, and the gasket is made of silicone.

[0019] Furthermore, when the bottom and top cross-sections of the loading plate end face change, the taper angle of the variable cross-section... The angle is 15°, and the design size range of the loading plate is 100mm-250mm. The formula for calculating the size of the loading plate is: in, This refers to the side length of the bottom section of the loading plate; This refers to the side length of the top section of the loading plate; The impedance ratio of the loading plate; The transmission coefficient of the loading plate is . ; The thickness of the transition section; The thickness is the loading plate thickness.

[0020] This invention also provides a method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures, based on the aforementioned indoor experimental impact loading and acoustic emission coordinated monitoring device for tunnel structures, comprising the following steps: S1: Prepare a roadway surrounding rock model specimen. Select a cubic specimen, make a hole in the middle of the cubic specimen to simulate the roadway, form the final roadway surrounding rock model specimen, and calculate the in-situ stress of the deep roadway to provide initial stress parameters for subsequent static load loading. S2: Assemble a true triaxial electromagnetic Hopkinson bar system, an acoustic emission monitoring system, an impact ground pressure loading module, and a data monitoring and control system. The acoustic emission probe of the acoustic emission monitoring system is placed in a fixed frame that can shield electromagnetic interference, and the preamplifier at the signal output end is placed in an electromagnetic shielding box. S3: Conduct preliminary experiments using standard samples, collect noise data from the laboratory environment, and calculate the noise identification threshold using a data denoising algorithm. The noise identification threshold includes a time consistency threshold. Similarity threshold ; S4: Assemble the tunnel surrounding rock model specimen, fix the tunnel surrounding rock model specimen and apply lubricant to the loading end face, and center the loading rod in six degrees of freedom in the three orthogonal directions of X, Y and Z; S5: The true triaxial electromagnetic Hopkinson bar system applies static load to the roadway surrounding rock model sample, uniformly loads it to the calculated initial stress state, and holds it for a set time to stabilize the fracture structure. Then, according to the experimental conditions, it releases electromagnetic pulses to realize synchronous or asynchronous loading of stress fluctuation disturbance in uniaxial unidirectional, biaxial four-directional, or triaxial six-directional directions. S6: During the loading process, the data monitoring and control system synchronously records stress wave and acoustic emission signals, and uses an acoustic emission signal data noise reduction algorithm to remove noise from the collected acoustic emission data; S7: Save and organize the data, analyze the fracture signal characteristics of the roadway surrounding rock model sample through multi-angle and multi-channel acoustic emission monitoring results, and then reveal the disaster-causing process of the roadway.

[0021] Furthermore, in step S3, the standard sample is made of the same material as the loading rod, and its dimensions are consistent with those of the roadway surrounding rock model sample. The method for calculating the noise recognition threshold is as follows: S301: Construct a multi-channel event set: based on the first arrival time of the channel that received the signal first. As a reference time, within a fixed time window If the signals from other channels arrive first... satisfy Then the set of events is: S302: Parameter normalization: based on the median of the amplitude A, ring count N, and energy E for each channel. Based on the parameter reference, normalized parameters for amplitude, ring count, and energy are constructed. , and ; S303: Constructing the event intensity function: using amplitude, ring count, and energy normalization parameters. , and Calculate the signal strength index ; S304: Preliminary Noise Identification: Calculating the First Arrival Range of Event e And the strength standard deviation, and calculate the strength similarity index based on the strength standard deviation; S305: Calculate the time consistency threshold based on the first arrival time range Calculate the intensity similarity threshold based on the intensity similarity index. .

[0022] Further, in step S6, a consistency criterion is constructed using the event arrival time range and intensity similarity index; when an event satisfies both intensity similarity and time consistency, it is determined to be a systematic noise event and eliminated. The judgment formula is as follows: , in, This is an intensity similarity index for event e. The first time event e arrives, the extreme difference is reached.

[0023] Furthermore, in step S303, the signal strength index The calculation formula is: Where e represents the acoustic emission event; i represents the channel number; This is the weighting coefficient of amplitude in the intensity index, representing the degree of contribution of amplitude to the intensity index; The imaginary unit; Signal strength index; The magnitude of the signal strength index.

[0024] Furthermore, in step S305, the time consistency threshold... Similarity threshold The calculation method is as follows: in, For event e, the first arrival time range of each channel The 95th percentile; The intensity similarity index for event e The 95th percentile.

[0025] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention enables the simulation of deep tunnel structures in true triaxial electromagnetic Hopkinson bar tests. Through the self-designed impact pressure loading module, especially the variable cross-section loading plate, the cross-section of the loading bar is enlarged, which can adapt to the size of the tunnel surrounding rock model sample to simulate large-scale tunnel structures and monitor the cooperative response and non-uniform failure characteristics of the tunnel structure. At the same time, the bar part of the electromagnetic Hopkinson bar is redesigned to make this invention meet the requirements of using a true triaxial electromagnetic Hopkinson bar to simulate impact loading of tunnel structures.

[0026] (2) The present invention can realize acoustic emission monitoring of coal and rock mass failure process during the impact pressure simulation experiment of true triaxial electromagnetic Hopkinson rod. Through the self-designed acoustic emission monitoring system and loading plate, the acoustic emission probe can be conveniently placed directly on the sample surface or key stress area, and the influence of electromagnetic radiation on stress wave and acoustic emission signal data acquisition during the experiment can be reduced, realizing acoustic emission collaborative monitoring during the impact loading of roadway structure.

[0027] (3) This invention significantly improves the recognition accuracy of AE signals in complex electromagnetic environments through data denoising methods, providing strong support for the extraction of acoustic emission features in the impact failure process of coal and rock masses. By using an acoustic emission signal data denoising algorithm based on signal source distance and signal source type, it can remove signal noise generated by electromagnetic drive pulses, electromagnetic interference, loading rod end collisions, clamp vibrations, etc., accurately identify coal and rock mass failure signals, and effectively improve the accuracy of monitoring the coal and rock mass failure process. Attached Figure Description

[0028] To more clearly illustrate the solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a structural block diagram of the indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to the present invention; Figure 2 This is a schematic diagram of the overall structure of the device of the present invention; Figure 3 This is a schematic diagram of the true triaxial electromagnetic Hopkinson rod system of the present invention; Figure 4 for Figure 3 Enlarged view of part A; Figure 5 This is a schematic diagram of the loading plate structure of the present invention; Figure 6 This is a schematic diagram of the leveling support structure of the present invention; Figure 7 This is a schematic diagram of the electromagnetic shielding box structure of the present invention; Figure 8 This is a schematic diagram of the acoustic emission probe holder structure of the present invention.

[0030] Reference numerals: 1-Loading frame; 11-Central support platform; 12-Base box; 2-Electromagnetic pulse emission system; 21-Electromagnetic pulse emission cavity; 22-Electromagnetic pulse emission cavity support frame; 3-Confining pressure servo control system; 31-Loading cylinder; 32-Actuator; 33-Fixed baffle; 4-Impact pressure loading module; 41-Loading plate; 411-Acoustic emission probe fixing hole; 412-Loading rod assembly hole; 413-Internal thread; 42-Loading rod; 43-Leveling support; 431-Base; 432-Support 433-Horizontal adjustment mechanism; 434-Longitudinal adjustment mechanism; 5-Acoustic emission monitoring system; 51-Acoustic emission monitoring host; 52-Preamplifier; 53-Acoustic emission probe; 54-Electromagnetic shielding box; 541-BNC coaxial interface; 542-Grounding terminal; 543-Cover plate; 55-Acoustic emission probe holder; 551-Fixing frame; 552-Bolt; 5521-Screw; 5522-Washer; 5523-Bolt head; 56-BNC electromagnetic shielding wire; 6-Data monitoring and control system. Detailed Implementation

[0031] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects, not to describe a particular order.

[0032] In this invention, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment to other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0034] like Figure 1As shown, this invention relates to an indoor experimental impact loading and acoustic emission coordinated monitoring device for tunnel structures. It includes a true triaxial electromagnetic Hopkinson bar system, an acoustic emission monitoring system, an impact pressure loading module, and a data monitoring and control system. The true triaxial electromagnetic Hopkinson bar system comprises a loading frame, an electromagnetic pulse emission system mounted on the loading frame, and a confining pressure servo control system. The electromagnetic pulse emission system and the confining pressure servo control system are used to apply static loads and impact load disturbances to a tunnel surrounding rock model specimen (hereinafter referred to as the specimen) in six directions via a triaxial, six-axis loading bar. The impact pressure loading module is used to change the cross-section of the loading bar and connect it to the tunnel surrounding rock model specimen, realizing the force transmission between the true triaxial electromagnetic Hopkinson bar system and the tunnel surrounding rock model specimen. It is also used to install the acoustic emission probe of the acoustic emission monitoring system. The acoustic emission monitoring system is used to monitor crack evolution and energy release patterns of the tunnel surrounding rock model specimen during impact loading, as well as to reduce the influence of electromagnetic radiation during data acquisition. The data monitoring and control system is used to control the true triaxial electromagnetic Hopkinson bar system and the acoustic emission monitoring system, and to record and store stress and acoustic emission signal data.

[0035] like Figures 2-5 As shown, the rockburst loading module of the present invention includes a loading plate 41 and a loading rod 42, wherein the loading rod 42 has a circular cross-section, and the loading plate 41 is disposed between the loading rod 42 and the roadway surrounding rock model sample, for changing the cross-section of the loading rod and connecting the roadway surrounding rock model sample. The loading plate 41 is a variable cross-section plate with a thickness of T mm, wherein the bottom is... × The cross-section is mm, and the top is... × A cross-section of mm, with the bottom and top separated by... × mm cross section × The section transitions at mm, with the bottom contacting the roadway surrounding rock model sample, and the top center has a loading rod assembly hole 412 that matches the loading rod 42. , Both T and T are positive numbers, and To ensure that the experiment satisfies the one-dimensional stress wave propagation theory and stress balance, both the loading plate 41 and the loading rod 42 are made of titanium metal to reduce the impact of changes in wave impedance and stress wave dispersion on stress wave propagation.

[0036] Preferably, the transition thickness between the bottom and top in this example is... mm, vertical thickness is mm. The loading rod mounting hole 412 at the top has a diameter of 50 mm and a depth of 5 mm. One or more side walls between the bottom and top of the loading plate 41 are provided with acoustic emission probe fixing holes 411, each with a diameter of 14 mm. These holes penetrate the loading plate 41, allowing the acoustic emission probe 53 to directly contact the sample. The inner wall of the acoustic emission probe fixing hole 411 is provided with an internal thread 413, which connects to the acoustic emission probe holder 55 via a thread. The loading plate 41 is a replaceable assembly; the bottom size of the loading plate can be selected according to the size of the roadway surrounding rock model sample. Due to the limitation of the reference box 12, the design size range of the loading plate in this example is 100 mm to 250 mm. To maintain stress wave reflection at the variable cross-section and reduce dispersion, the taper angle of the variable cross-section is adjusted when the bottom and top cross-sections of the loading plate end face change. The angle remains constant at 15°. To ensure that this rockburst loading module satisfies the one-dimensional stress wave propagation assumption, the loading plate dimensions are calculated according to the following formula: In the formula: This refers to the side length of the bottom section of the loading plate; This refers to the side length of the top section of the loading plate; The impedance ratio of the loading plate; Transmission coefficient of the loading plate ( Selected according to experimental requirements; The thickness of the transition section; For the thickness of the loading plate; In this example, the loading rod is a round rod with a length of 2740mm and a diameter of 50mm, and a boss is provided at the end of the round rod; the outer diameter of the boss is 90mm and the thickness is 80mm. The three pairs of round rods are arranged on both sides of the reference square box 12 in the X, Y, and Z directions through one or more leveling supports 43, and are placed on the central support platform 11.

[0037] like Figure 6The leveling support 43 in this example includes a base 431, a support rod 432, a lateral adjustment mechanism 433, and a longitudinal adjustment mechanism 434. Bolt holes are pre-drilled in the base 431, and the leveling support 43 is fixed to the loading frame 1 by bolts. The support rod 432 has an arc-shaped limiting groove in its middle that matches the outer surface of the loading rod, used for axial positioning of the rod. The leveling support 43 also includes brackets mounted on the base 431. Two brackets are vertically fixed to the base 431, and the support rod 432 is laterally positioned between the two brackets. The longitudinal adjustment mechanism 434 is located on the upper part of the brackets and is used for height adjustment of the loading rod. The lateral adjustment mechanism 433 is located on both sides of the brackets and includes an adjusting screw threaded to the bracket. The end of the adjusting screw abuts against the support rod 432. By rotating the adjusting screw, a small displacement and angle adjustment of the support rod 432 can be achieved, thereby ensuring stable support and precise leveling of the loading rod above the support rod 432 during installation.

[0038] like Figures 2-4 As shown, the loading frame 1 consists of a central support platform 11 and a reference box 12. The reference box 12 is located in the center of the central support platform 11. Six sides along the X, Y, and Z directions are provided with connecting holes that are connected to the loading rod 42, and the corresponding connecting holes are arranged in a continuous manner. The loading frame 1 mainly serves as a test platform and guides the alignment of multi-axis and multi-directional rods.

[0039] The electromagnetic pulse emission system 2 includes an electromagnetic pulse emission cavity 21 and an electromagnetic pulse emission cavity support frame 22. The electromagnetic pulse emission cavity 21 is directly connected to the loading rod 42. A guide rail is provided on the bottom support frame of the central support platform 11. The electromagnetic pulse emission cavity 21 can move on the guide rail to achieve buffering, so as to realize multi-axis and multi-directional synchronous loading of stress waves.

[0040] The confining pressure servo control system 3 consists of a loading cylinder 31, an actuator 32, and a fixed baffle 33. The loading cylinder 31 is fixed on the fixed baffle 33 and is used to drive the actuator 32 to apply confining pressure and to apply static load.

[0041] The data monitoring and control system 6 includes a multi-channel high-speed synchronous recorder, strain gauges, a Wheatstone bridge, a strain signal amplifier, and a time-delay transmitter. It can ensure that the test data is recorded and stored completely and effectively, control the impact pressure loading system and acoustic emission monitoring module, and record and store the test data.

[0042] In this example, the acoustic emission monitoring system 5 is used to monitor the crack evolution and energy release patterns of the tunnel model during impact loading, as well as to reduce the impact of electromagnetic radiation during data acquisition. It includes an acoustic emission monitoring host 51, a preamplifier 52, an acoustic emission probe 53, an electromagnetic shielding box 54, and an acoustic emission probe holder 55. The acoustic emission monitoring host 51, the preamplifier 52, and the acoustic emission probe 53 are connected by a BNC electromagnetic shielding cable 56. At the same time, the acoustic emission monitoring host 51 is connected to the data monitoring and control system using a BNC electromagnetic shielding cable 56.

[0043] The preamplifier 52 is connected to the acoustic emission monitoring host 51 and the acoustic emission probe 53. It is used to amplify the weak electrical signal output by the acoustic emission probe 53 with low noise, perform impedance matching, and perform primary filtering and protection.

[0044] like Figure 7 As shown, the electromagnetic shielding box 54 in this example is a metal cuboid shell with a sealed cover plate 543. The two ends of the side panel are provided with BNC coaxial interface 541 and grounding terminal 542, and the preamplifier 52 is placed inside to allow the signal to enter and exit over a short distance. Its function is to isolate external electromagnetic interference, suppress cable conduction noise and stabilize grounding, thereby improving the signal-to-noise ratio and reliability of acoustic emission measurement.

[0045] like Figure 8 As shown, the acoustic emission probe holder 55 in this example includes a fixing frame 551 and a bolt 552. The outer surface of the fixing frame 551 is threaded, and it is threadedly connected to the internal thread of the acoustic emission fixing hole at the variable cross-section of the loading plate 41. Preferably, the fixing frame 551 in this example uses ferrite as the material to shield high-intensity electromagnetic interference. The acoustic emission probe holder 55 in this example has an outer diameter of 14 mm, the top is in direct contact with the sample, the inner diameter is 10 mm, and the thickness is 2 mm; the bottom is connected to the bolt 552, the inner diameter is 6 mm, the thickness is 5 mm, and the inner wall of the bottom is threaded. The bolt 552 includes a screw 5521, a washer 5522, and a bolt head 5523. The washer 5522 has a diameter of 6 mm and a thickness of 2 mm, and the material is preferably silicone. The two ends of the washer 5522 contact the acoustic emission probe 53 and the screw 5521 respectively, and generate a buffering effect when an impact occurs to prevent the probe from being damaged due to the impact. In this example, the screw 5521 has a diameter of 6mm and a length of 10mm; the nut has a diameter of 8mm and a thickness of 4mm.

[0046] The assembly method of each part of the device of the present invention is as follows: The leveling support 43 is bolted to a preset position on the loading frame 1. It has a support rod 432 that matches the shape of the round rod, used to support and position the loading rod 42. The loading rod 42 is placed inside the support rod 432, with its lower surface fitting against the arc-shaped limiting groove, thus achieving stable support. The leveling support 43 has a lateral adjustment mechanism 433 on both sides and a longitudinal adjustment mechanism 434 on the top. These two mechanisms work together, and by fine-tuning the adjustment screw 5521, precise adjustment and centering of the loading rod 42 in six degrees of freedom—horizontal, vertical, front-back, left-right, and up-down—can be achieved. This structure ensures that multiple loading rods 42 are consistently aligned and fixed in six directions during installation, avoiding uneven loading caused by eccentricity or misalignment, thereby improving the stability and testing accuracy of the loading system.

[0047] The loading rod 42 and the loading plate 41 are fixed together via loading rod assembly holes. The contact end of the loading plate 41 has loading rod assembly holes with a diameter of 50mm and a depth of 5mm, for insertion and engagement with the round rod portion at the end of the loading rod 42. Through this structure, the loading rod 42 can be stably embedded within the loading plate 41, effectively reducing reflection and maintaining waveform stability during stress wave transmission across the variable cross-section. Furthermore, three pairs of loading rods 42 are arranged along the X, Y, and Z orthogonal directions and placed on the central support platforms 11 on both sides of the reference box 12. With the assembly structure of the loading plate 41 and the loading rod 42, loading forces in six directions can be applied simultaneously or independently to the tunnel model sample, thereby ensuring the overall stability and loading accuracy of the loading system.

[0048] The prepared roadway surrounding rock model sample is placed inside the reference box 12, and leveled and fixed by the positioning device to ensure the stability and coaxiality of the sample during the loading process.

[0049] The external thread of the acoustic emission probe holder 55 is screwed into the acoustic emission probe fixing hole 411 at the variable cross-section of the loading plate 41, so that the thread is tightened and connected. Its top end face is in direct contact with the tunnel model sample to ensure the effectiveness of signal acquisition.

[0050] Insert the acoustic emission probe into the 10mm inner diameter cavity of the acoustic emission probe holder 55, ensuring direct contact between the probe tip and the sample surface. The tip of the acoustic emission probe abuts against the screw 5521 via a silicone gasket 5522. The silicone gasket 5522 provides elastic cushioning, absorbing some impact energy during impact loading to prevent damage to the acoustic emission probe. Then, connect the 6mm diameter screw 5521 to the threaded connection, tighten the nut to press the gasket 5522, and complete the fixation of the acoustic emission probe.

[0051] The electromagnetic shielding box 54 has a removable cover plate 543 on its top. The preamplifier 52 is placed inside the electromagnetic shielding box 54, with its input interface connected to the first BNC internal interface on the inside of the shielding box and its output interface connected to the second BNC internal interface on the inside of the shielding box. The first and second BNC internal interfaces are respectively connected to the BNC coaxial interface 541 on the outside of the side wall of the shielding box, so that the input signal enters the interior through the first BNC coaxial interface of the electromagnetic shielding box 54, is amplified by the preamplifier 52, and is then output through the second BNC coaxial interface. Through this assembly structure, the preamplifier 52 is completely encapsulated in the shielding box, and the electromagnetic shielding box 54 plays the role of isolating external electromagnetic interference and providing stable grounding, thereby enabling short-distance entry and exit and low-noise transmission of acoustic emission signals.

[0052] The input interface of the acoustic emission monitoring host 51 is connected to the second BNC coaxial interface of the electromagnetic shielding box 54, and the output of the acoustic emission monitoring host 51 is further electrically connected to the data monitoring and control system via a BNC electromagnetic shielding cable 56. Through this connection, the weak electrical signal collected by the acoustic emission probe is amplified by the preamplifier 52 with low noise and then input to the acoustic emission monitoring host 51. The acoustic emission monitoring host then processes and transmits the signal, ultimately sending it to the data monitoring and control system for real-time acquisition and storage, thus forming a complete acoustic emission signal amplification, transmission, and acquisition chain.

[0053] The device of the present invention has the following innovative features: (1) Optimize the impact pressure loading of the tunnel structure simulation.

[0054] This invention enables the simulation of deep tunnel structures in true triaxial electromagnetic Hopkinson bar tests. Through a self-designed variable cross-section impact pressure module, the cross-section of the loading rod (42mm) is enlarged, allowing for adaptive simulation of large-scale tunnel structures based on the tunnel model's dimensions, and monitoring of the cooperative response and non-uniform failure characteristics of the tunnel structure. Simultaneously, the rod components of the electromagnetic Hopkinson bar are redesigned to meet the requirements for simulating impact loading of tunnel structures using a true triaxial electromagnetic Hopkinson bar.

[0055] (2) Acoustic emission monitoring module with integrated collaborative monitoring.

[0056] This invention enables acoustic emission monitoring of coal and rock mass failure during impact pressure simulation experiments using a true triaxial electromagnetic Hopkinson bar. Through a self-designed acoustic emission monitoring system, the impact of electromagnetic radiation on stress wave and acoustic emission signal data acquisition during the experiment is reduced, achieving coordinated acoustic emission monitoring during roadway structure impact loading.

[0057] The present invention also provides a method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures, comprising the following steps: S1: Prepare a roadway surrounding rock model specimen. Select a cubic specimen, make a hole in the middle of the cubic specimen to simulate the roadway, form the final roadway surrounding rock model specimen, and calculate the in-situ stress of the deep roadway to provide initial stress parameters for subsequent static load loading.

[0058] Based on the actual working conditions of the coal mine roadway, the model size is determined to be 100-250mm. In this example, a roadway model of 250×250×250mm is selected. The roadway openings are based on: That is, the model size is 250×250×250mm, the tunnel size is 50×50×250mm, and the final tunnel surrounding rock model sample is obtained. In this example, the bottom section of the loading plate 41 is selected as 250×250mm according to the size of the tunnel surrounding rock model sample.

[0059] The initial stress of the tunnel is obtained from on-site measurements or by using the in-situ stress calculation formula. The in-situ stress calculation formula is as follows: Where H represents the tunnel depth; For vertical stress in the tunnel; This represents the maximum horizontal stress in the tunnel. This represents the minimum horizontal stress in the tunnel.

[0060] S2: Assemble a true triaxial electromagnetic Hopkinson bar system, acoustic emission monitoring system, impact pressure loading module, and data monitoring and control system.

[0061] The fixing frame 551 of the acoustic emission probe holder is screwed into the fixing hole of the acoustic emission probe at the variable cross-section position of the loading plate 41. The external thread of the acoustic emission probe holder 55 mates with the internal thread 413 of the acoustic emission probe fixing hole and is tightened to ensure stable installation. After uniformly applying coupling agent to the surface of the acoustic emission probe, it is inserted into the receiving cavity of the acoustic emission probe holder, so that its front end is in close contact with the sample surface. The tail end of the acoustic emission probe abuts against the gasket 5522. The gasket 5522 absorbs impact energy through elastic deformation, playing a buffering and protective role. Then, the 6mm diameter screw 5521 is screwed into the internal thread of the fixing frame 551 and tightened with the nut, so that the gasket 5522 presses against the probe, completing the fixation.

[0062] The preamplifier 52 is placed inside the electromagnetic shielding box 54 to isolate external electromagnetic interference and stabilize the signal environment. The output of the preamplifier 52 is connected to the acoustic emission monitoring host 51 via a BNC electromagnetic shielded cable 56, and the output of the acoustic emission monitoring host is then connected to the data monitoring and control system via the BNC electromagnetic shielded cable 56, forming a complete signal link.

[0063] S3: Conduct preliminary experiments using standard samples, collect noise data from the laboratory environment, and calculate the noise identification threshold using a data denoising algorithm. The noise identification threshold includes a time consistency threshold. Similarity threshold .

[0064] In this example, the standard specimen is a 250mm × 250mm × 250mm cube. The static stress of the standard specimen is applied to the design level. Before noise reduction of the acoustic emission data, the noise data is first classified: (1) Electromagnetic pulse: high amplitude but extremely short duration; (2) Clamp collision: High ring count but low energy; (3) Rod resonance: high energy but narrow bandwidth and slow attenuation; (4) Far-field vibration: The magnitudes of each parameter are relatively small and multiple channels are synchronized.

[0065] The method for calculating the noise recognition threshold in this example is as follows: S301: Construct a multi-channel event set: based on the first arrival time of the channel that received the signal first. As a reference time, within a fixed time window If the signals from other channels arrive first... satisfy Then the set of events is: S302: Parameter normalization: based on the median of the amplitude A, ring count N, and energy E for each channel. Based on the parameter reference, normalized parameters for amplitude, ring count, and energy are constructed. , and : S303: Constructing the event intensity function: using amplitude, ring count, and energy normalization parameters. , and Calculate the signal strength index The calculation formula is: S304: Preliminary Noise Identification: Calculating the First Arrival Range of Event e The strength standard deviation is calculated, and the strength similarity index is calculated based on the strength standard deviation.

[0066] Calculate the first-arrival range of event e. The calculation formula is: Calculate the average intensity of event e : Calculate the standard deviation of the intensity of event e : Calculate the intensity similarity index: S305: Calculate the time consistency threshold based on the first arrival time range Calculate the intensity similarity threshold based on the intensity similarity index. The calculation formula is: in, For event e, the first arrival time range of each channel The 95th percentile; The intensity similarity index for event e The 95th percentile.

[0067] S4: Assemble the tunnel surrounding rock model specimen, fix the tunnel surrounding rock model specimen and apply lubricant to the loading end face, and center the loading rod in six degrees of freedom in the three orthogonal directions of X, Y and Z.

[0068] Specifically, the processed tunnel model sample is placed inside the reference box 12. The sample is leveled and fixed using a positioning device to ensure coaxiality between the sample and the true triaxial electromagnetic Hopkinson rod system. Vaseline is applied to the loading end face to reduce end face friction. Then, the loading plate 41 is installed, and the loading rod 42 is supported by the support frame of the leveling support 43. Fine adjustments are made using the lateral adjustment mechanism 433 and the longitudinal adjustment mechanism 434 to achieve centering of the loading rod 42 in six degrees of freedom in the three orthogonal directions of X, Y, and Z, avoiding loading eccentricity.

[0069] S5: The true triaxial electromagnetic Hopkinson bar system applies a static load to the roadway surrounding rock model sample, uniformly loading it to the calculated initial stress state, and holding it for a set time to stabilize the fracture structure; in this example, it is set to 0.5 minutes. Then, depending on the experimental conditions, electromagnetic pulses are released to achieve uniaxial unidirectional, biaxial four-directional, or triaxial six-directional stress wave loading. In this example, the disturbance mode can be switched synchronously or asynchronously.

[0070] S6: During the loading process, the data monitoring and control system synchronously records stress wave and acoustic emission signals, and uses an acoustic emission signal data noise reduction algorithm to remove noise from the collected acoustic emission data.

[0071] Since noise sources such as electromagnetic pulses, rod resonance, and far-field vibrations are far-field or systematically excited relative to the sample, they exhibit highly synchronized arrival times and high intensity consistency in multi-channel analysis. Based on this, a consistency criterion is constructed using the event arrival time range and intensity similarity index. When an event satisfies both intensity similarity and time consistency, it is determined to be a systematic noise event and eliminated. The method for judging systematic noise is as follows: S7: Save and organize the data.

[0072] After the experiment, the data was saved and organized. The rupture signal characteristics of the tunnel model were analyzed through multi-angle and multi-channel acoustic emission monitoring results, thereby revealing the disaster-causing process of the tunnel. This will help to better analyze the mechanism of rockburst induced by dynamic disturbance and provide experimental basis for the mechanism research and risk assessment of rockburst induced by dynamic disturbance in tunnels.

[0073] This invention not only improves the accuracy of data acquisition by shielding electromagnetic interference through structural improvements, but also significantly enhances the recognition accuracy of acoustic emission (AE) signals in complex electromagnetic environments through data denoising methods, providing strong support for the extraction of acoustic emission features in the impact failure process of coal and rock masses. By employing an acoustic emission signal data denoising algorithm based on signal source distance and signal source type, it can remove signal noise generated by electromagnetic drive pulses, electromagnetic interference, loading rod end collisions, and clamp vibrations, accurately identifying coal and rock mass failure signals and effectively improving the accuracy of monitoring the coal and rock mass failure process.

[0074] The specific embodiments described above are preferred embodiments of the present invention and are not intended to limit the specific scope of the present invention. The scope of the present invention includes, but is not limited to, these specific embodiments. All equivalent changes made in accordance with the present invention are within the protection scope of the present invention.

Claims

1. A device for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures, characterized in that: It includes a true triaxial electromagnetic Hopkinson bar system, an acoustic emission monitoring system, a rockburst loading module, and a data monitoring and control system, among which, The rockburst loading module includes a loading plate and a loading rod. The loading rod has a circular cross-section. The loading plate is positioned between the loading rod and the roadway surrounding rock model sample to change the cross-section of the loading rod and connect the roadway surrounding rock model sample. The loading plate is a variable cross-section plate with a thickness of T mm, wherein the bottom is... × The cross-section is mm, and the top is... × A cross-section of mm, with the bottom and top separated by... × mm cross section × The section transitions at mm, with the bottom contacting the roadway surrounding rock model sample, and the top center has a loading rod assembly hole matching the loading rod. , Both T and T are positive numbers, and ; The true triaxial electromagnetic Hopkinson bar system includes a loading frame, an electromagnetic pulse emission system and a confining pressure servo control system mounted on the loading frame. The electromagnetic pulse emission system and the confining pressure servo control system are used to apply static loads and impact load disturbances to the roadway surrounding rock model sample in six directions through the triaxial six-axis loading bar. The acoustic emission monitoring system is used to monitor the crack evolution and energy release law of the roadway surrounding rock model sample during impact loading, as well as to reduce the influence of electromagnetic radiation during data acquisition. The loading plate has an acoustic emission probe fixing hole on one or more side walls between the bottom and top. The acoustic emission probe of the acoustic emission monitoring system is installed on the side wall of the loading plate through the acoustic emission probe fixing hole and can contact the roadway surrounding rock model sample. The data monitoring and control system is used to control the true triaxial electromagnetic Hopkinson bar system and the acoustic emission monitoring system, and to record and store stress and acoustic emission signal data.

2. The indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to claim 1, characterized in that: The loading rod is mounted on the loading frame via one or more leveling supports. One end of the loading rod is in contact with the electromagnetic pulse emission system, and the other end is located in the mounting hole at the top of the loading plate.

3. The indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to claim 2, characterized in that: The leveling support includes a base and a support rod. The support rod has an arc-shaped limiting groove in the middle that is adapted to the outer surface of the loading rod. It also includes a bracket on the base, a longitudinal adjustment mechanism on the bracket that drives the support rod to move longitudinally relative to the bracket, and a lateral adjustment mechanism that drives the arc-shaped limiting groove in the middle of the support rod to adjust laterally. Through the longitudinal adjustment mechanism and the lateral adjustment mechanism, the loading rod is stably supported and leveled during the installation process.

4. The indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to claim 1, characterized in that: The acoustic emission monitoring system includes an acoustic emission probe, which is fixed to a loading plate by an acoustic emission probe holder. The acoustic emission probe holder includes a fixing frame, a gasket, and a bolt. The outer surface of the fixing frame is provided with external threads, and the inner wall of the acoustic emission probe fixing hole is provided with internal threads. The fixing frame has a receiving cavity inside and a bolt hole at the top. The acoustic emission probe is placed in the receiving cavity, and its lower surface can contact and connect with the outer surface of the roadway surrounding rock model sample. The bolt passes through the bolt hole, and the acoustic emission probe is fixed in the receiving cavity by the gasket.

5. The indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to claim 4, characterized in that: The fixing frame is made of ferrite, and the gasket is made of silicone.

6. The indoor experimental impact loading and acoustic emission co-monitoring device for tunnel structures according to claim 1, characterized in that: When the bottom and top sections of the loading plate end face change, the taper angle of the variable section... The angle is 15°, and the design size range of the loading plate is 100mm-250mm. The formula for calculating the size of the loading plate is: in, This refers to the side length of the bottom section of the loading plate; This refers to the side length of the top section of the loading plate; The impedance ratio of the loading plate; The transmission coefficient of the loading plate is . ; The thickness of the transition section; The thickness is the loading plate thickness.

7. A method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures, implemented based on the indoor experimental impact loading and acoustic emission coordinated monitoring device for tunnel structures according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Prepare a roadway surrounding rock model specimen. Select a cubic specimen, make a hole in the middle of the cubic specimen to simulate the roadway, form the final roadway surrounding rock model specimen, and calculate the in-situ stress of the deep roadway to provide initial stress parameters for subsequent static load loading. S2: Assemble a true triaxial electromagnetic Hopkinson bar system, an acoustic emission monitoring system, an impact ground pressure loading module, and a data monitoring and control system. The acoustic emission probe of the acoustic emission monitoring system is placed in a fixed frame that can shield electromagnetic interference, and the preamplifier at the signal output end is placed in an electromagnetic shielding box. S3: Conduct preliminary experiments using standard samples, collect noise data from the laboratory environment, and calculate the noise identification threshold using a data denoising algorithm. The noise identification threshold includes a time consistency threshold. Similarity threshold ; S4: Assemble the tunnel surrounding rock model specimen, fix the tunnel surrounding rock model specimen and apply lubricant to the loading end face, and center the loading rod in six degrees of freedom in the three orthogonal directions of X, Y and Z; S5: The true triaxial electromagnetic Hopkinson bar system applies static load to the roadway surrounding rock model sample, uniformly loads it to the calculated initial stress state, and holds it for a set time to stabilize the fracture structure. Then, according to the experimental conditions, it releases electromagnetic pulses to realize synchronous or asynchronous loading of stress fluctuation disturbance in uniaxial unidirectional, biaxial four-directional, or triaxial six-directional directions. S6: During the loading process, the data monitoring and control system synchronously records stress wave and acoustic emission signals, and uses an acoustic emission signal data noise reduction algorithm to remove noise from the collected acoustic emission data; S7: Save and organize the data, analyze the fracture signal characteristics of the roadway surrounding rock model sample through multi-angle and multi-channel acoustic emission monitoring results, and then reveal the disaster-causing process of the roadway.

8. The method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures according to claim 7, characterized in that: In step S3, the standard sample is made of the same material as the loading rod, and its dimensions are consistent with those of the roadway surrounding rock model sample. The method for calculating the noise recognition threshold is as follows: S301: Construct a multi-channel event set: based on the first arrival time of the channel that received the signal first. As a reference time, within a fixed time window If the signals from other channels arrive first... satisfy Then the set of events is: S302: Parameter normalization: based on the median of the amplitude A, ring count N, and energy E for each channel. Based on the parameter reference, normalized parameters for amplitude, ring count, and energy are constructed. , and ; S303: Constructing the event intensity function: using amplitude, ring count, and energy normalization parameters. , and Calculate the signal strength index ; S304: Preliminary Noise Identification: Calculating the First Arrival Range of Event e And the strength standard deviation, and calculate the strength similarity index based on the strength standard deviation; S305: Calculate the time consistency threshold based on the first arrival time range Calculate the intensity similarity threshold based on the intensity similarity index. .

9. The method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures according to claim 8, characterized in that: In step S6, a consistency criterion is constructed using the event arrival time range and intensity similarity index. When an event satisfies both intensity similarity and time consistency, it is determined to be a systematic noise event and removed. The judgment formula is as follows: ， in, This is an intensity similarity index for event e. The first time event e arrives, the extreme difference is reached.

10. The method for indoor experimental impact loading and acoustic emission coordinated monitoring of tunnel structures according to claim 8, characterized in that: In step S303, the signal strength index The calculation formula is: Where e represents the acoustic emission event; i represents the channel number; This is the weighting coefficient of amplitude in the intensity index, representing the degree of contribution of amplitude to the intensity index; The imaginary unit; Signal strength index; The magnitude of the signal strength index. In step S305, the time consistency threshold Similarity threshold The calculation method is as follows: in, For event e, the first arrival time range of each channel The 95th percentile; The intensity similarity index for event e The 95th percentile.

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