Experimental device and test method for characterizing multi-stage surrounding rock fracture characteristics disturbed by tunnel drilling and blasting

Abstract

This application provides an experimental apparatus and testing method for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance. The experimental apparatus includes: a pressure assembly; and a rod assembly, wherein the rod assembly includes a first rod, at least one second rod, and a third rod, with the first rod and at least one second rod and the third rod arranged sequentially. The first rod and the second rod are flexible and adjustable; by adjusting the different lengths and numbers of the second rods, it is possible to simulate the fracture mode of fractured surrounding rock under multiple blasting disturbances, and also to simulate the damage characteristics of multi-stage surrounding rock joint surfaces caused by the propagation of a single blasting vibration wave. By controlling the initial fracture characteristics of the multi-stage fractured surrounding rock specimen, the damage evolution of the multi-stage fractured surrounding rock specimen under different occurrences and joint structures of real tunnel surrounding rock after being disturbed by multiple dynamic shock waves can be simulated.

Description

Technical Field

[0001] This application belongs to the technical field of modular vibration and impact test simulation of multi-level surrounding rock dynamic fracture damage test, specifically involving experimental device and test method for characterizing multi-level surrounding rock fracture characteristics under tunnel drilling and blasting disturbance. Background Technology

[0002] In the field of bridge and tunnel construction, when facing complex geological conditions such as large mountains, the drill-and-blast method is widely used because it can significantly shorten the tunneling period and improve construction efficiency. This technology effectively breaks and excavates rock by carrying out blasting operations within a pre-set excavation profile, meeting the project schedule requirements.

[0003] However, blasting inevitably triggers a series of impact and explosion-related problems, posing a serious threat to construction safety and the stability of the surrounding rock. Specifically, while blasting can achieve rock fragmentation as designed, it creates damaged zones in the surrounding rock mass. This damage is mainly caused by the combined effects of static unloading and dynamic disturbance. As the project progresses, the cumulative effects of continuous excavation and multiple blasts will further exacerbate the damage to the interlayer structure of the rock mass, directly affecting the stability of the tunnel structure during the operational phase.

[0004] Further research revealed that drilling and blasting operations cause a sudden release of strain energy stored within the mountain, leading to the violent ejection of surrounding rock blocks from the original rock mass, posing a significant threat to construction safety. Simultaneously, the rock blasting process triggers multiple consecutive impacts on the mountain's rock strata. The surrounding rock continuously endures these impacts, causing stress waves generated by the explosion to accumulate and damage the rock layers, further exacerbating internal rock damage and progressively expanding stress concentration areas. The dynamic loads generated by the blasting continuously affect the mutual resistance of the rock strata, causing stress redistribution, while repeated shock waves further expand the area of ​​damage. Compared to static excavation, the dynamic disturbances caused by blasting operations result in more severe damage to the structural surfaces and the connection areas of the working face, often leading to increased displacement and a greater degree of damage.

[0005] To gain a deeper understanding of the impact of blasting loads and the cumulative damage caused by repeated blasting, current construction operations have implemented measures to control wave velocity to avoid continuous impact damage to structures caused by vibrations. However, these measures are limited to seismic wave control and fail to effectively detect the dynamic development of geological rock structures. Therefore, in-depth research into the mechanism and laws of multi-stage fracture damage in surrounding rock under impact, especially the mechanism of repeated impact stress, is of great significance for optimizing blasting construction plans and ensuring project safety.

[0006] Currently, in the study of rock mass impact mechanics, the Hopkinson test apparatus, as a commonly used experimental device, can only perform single-impact studies. Its limited functionality makes it unable to simulate the stress state of fractured rock specimens under multiple continuous energy impacts, resulting in significant performance limitations. This makes it difficult to meet the research needs of practical engineering projects regarding the damage evolution of multi-stage relay structures and initial damage defects in rock masses under multiple blasting impacts. In actual engineering, detailed studies on the mechanical properties of fractured rock under multiple impacts have not yet been conducted, and the dynamic mechanics of multi-stage fractured rock differs significantly from the mechanical properties of conventional rocks under quasi-static loading conditions, rendering existing research results unusable. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0008] To address the aforementioned problems, the first aspect of this application provides an experimental apparatus for characterizing the multi-level surrounding rock fracture characteristics caused by tunnel drilling and blasting disturbance, comprising:

[0009] Pressurization components;

[0010] A rod assembly, the rod assembly comprising a first rod, at least one second rod, and a third rod, wherein the first rod and at least one second rod and the third rod are arranged sequentially;

[0011] A multi-stage fractured surrounding rock specimen, comprising a first fractured surrounding rock specimen and a second fractured surrounding rock specimen, wherein a first fractured surrounding rock specimen is placed between the first rod and the second rod, and between adjacent second rods, and a second fractured surrounding rock specimen is placed between the second rod and the third rod, and the pressurizing component is used to impact the first rod;

[0012] When the pressurizing component impacts the first rod, causing the first broken surrounding rock specimen to burst and the second broken surrounding rock specimen to undergo dynamic fracture damage, the first data acquisition component acquires the ejection velocity of the pressurizing component and records its impact process.

[0013] When the pressurizing component impacts the first rod, causing the first broken surrounding rock specimen to burst and the second broken surrounding rock specimen to undergo dynamic fracture damage, the second data acquisition component records the dynamic fracture damage process of the second broken surrounding rock specimen.

[0014] A control terminal is used to process the information collected by the first data acquisition component and the second data acquisition component.

[0015] Optionally, a pulse shaper is provided at the end of the first rod facing the pressurization assembly.

[0016] Optionally, it also includes strain gauges, a digital oscilloscope, an acoustic emission device, and an ultrasonic instrument. Several sets of strain gauges are provided in the first rod, the second rod, and the third rod. The control terminal is electrically connected to the strain gauges and the digital oscilloscope. The probe of the acoustic emission device is connected to the first fractured surrounding rock specimen and the second fractured surrounding rock specimen. The ultrasonic instrument is used to detect the dynamic fracture damage process of the first fractured surrounding rock specimen and the second fractured surrounding rock specimen.

[0017] Optionally, the pressurization component includes:

[0018] Nitrogen cylinder;

[0019] The nitrogen cylinder output end is connected to the launch tube;

[0020] An impact rod is disposed inside the launching tube, with its output end facing the pulse shaper.

[0021] Optionally, the first data acquisition component includes:

[0022] A speed detection device is used to collect the impact speed of the impact rod;

[0023] A first high-speed camera device is used to record the impact process of the impact rod.

[0024] Optionally, the second data acquisition component includes: a second high-speed camera device;

[0025] The second high-speed camera is located on one side of the second fractured surrounding rock specimen, and is used to record the dynamic fracture damage process of the second fractured surrounding rock specimen.

[0026] Optionally, the first rod, the second rod, and the third rod have the same axis.

[0027] Optionally, the third rod is provided with a fixing component for fixing the second broken surrounding rock specimen.

[0028] Optionally, the fixing member has protrusions on both sides of the second broken surrounding rock specimen.

[0029] The second aspect of this application also provides a test method for an experimental apparatus characterizing the fracture properties of surrounding rock disturbed by tunnel drilling and blasting, including:

[0030] S1. Initial conditions determination: Based on the actual geological conditions of the surrounding rock, determine the number of multi-stage fractured surrounding rock specimens, the initial fracture damage characteristics of the surrounding rock, and the number of rod components;

[0031] S2. Preparation of multi-stage fractured surrounding rock specimens: Prepare the first fractured surrounding rock specimen and the second fractured surrounding rock specimen;

[0032] S3. The placement, loading, and data acquisition of the first and second fractured rock mass specimens for the impact test of multi-stage fractured surrounding rock: The first fractured rock mass specimen is placed between the first and second rods and between pairs of the second rods. The second fractured rock mass specimen is placed between the second and third rods. Stress waves are generated by impacting the first rod through the pressurizing component. When the first fractured rock mass specimen undergoes explosive fracture and the second fractured rock mass specimen undergoes dynamic fracture damage, the first data acquisition component collects the ejection velocity of the pressurizing component and records its impact process. The second data acquisition component records the dynamic fracture damage process of the second fractured rock mass specimen. By adjusting the impact velocity of different first rods, the influence of vibration waves from different blasting construction scenarios on multi-stage surrounding rock fracture damage can be simulated.

[0033] S4. Strain monitoring and stress wave parameter analysis of the rod assembly under impact: When the first broken surrounding rock specimen bursts and the second broken surrounding rock specimen suffers dynamic fracture damage, the array of strain gauges on the first rod, the second rod, and the third rod converts the deformation within the first rod, the second rod, and the third rod into electrical signals and transmits them to the digital oscilloscope and the control terminal. The digital oscilloscope and the control terminal record and process these signals to form stress wave versus time curves, analyze the propagation law of dynamic stress waves, and calculate the wave velocity of the stress waves.

[0034] S5. Dynamic Damage Response Characteristics Analysis of Multi-stage Surrounding Rock: Based on the image information acquired by the first and second high-speed cameras, digital image correlation analysis is performed to analyze the dynamic damage evolution process and the distribution of dynamic stress and strain fields of the multi-stage fractured surrounding rock specimens. Based on the obtained dynamic stress-strain or stress-time history curves of the surrounding rock, the dynamic fracture strength, dynamic fracture strength growth factor, and dynamic fracture dissipation energy of the multi-stage fractured surrounding rock specimens are calculated. Based on the acquired ultrasonic signals and acoustic emission signals, dynamic fracture damage characteristic parameters such as ringing count and spatial distribution characteristics of tensile-shear damage of the multi-stage fractured surrounding rock are calculated.

[0035] Beneficial effects

[0036] The experimental apparatus and testing method for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance provided in the embodiments of the present invention are flexible and adjustable. By adjusting the different lengths and numbers of the second rods, it is possible to simulate the fracture mode of fractured surrounding rock under multiple blasting disturbances, and also to simulate the test of the fracture damage characteristics of multi-stage surrounding rock joint surfaces caused by the propagation of a single blasting vibration wave. By controlling the initial fracture characteristics of the multi-stage fractured surrounding rock specimens, the damage evolution of multi-stage fractured surrounding rock specimens under the joint structure conditions of surrounding rock with different occurrences in real tunnels after being disturbed by multiple dynamic shock waves can be simulated. The data acquisition of the first data acquisition component, the second data acquisition component, and the strain gauges can be used to accurately analyze the vibration response characteristics of the tunnel surrounding rock, such as the blasting vibration amplitude, duration and frequency, dynamic fracture strength growth factor, and dynamic fracture dissipation energy, providing a basis for blasting control in deep-buried tunnel drilling and blasting construction, which is of great significance for the efficient construction of deep underground engineering. Attached Figure Description

[0037] Figure 1 This is a structural diagram of the present invention;

[0038] Figure 2 This is a library of loading experimental specimen components for the present invention;

[0039] Figure 3 This is a flowchart of the testing method of the present invention.

[0040] The reference numerals in the attached figures are as follows:

[0041] 1. Pressurization assembly; 2. Rod assembly; 3. First rod; 4. Second rod; 5. Third rod; 6. First fractured surrounding rock specimen; 7. Second fractured surrounding rock specimen; 8. First data acquisition assembly; 9. Second data acquisition assembly; 10. Control terminal; 11. Pulse shaper; 12. Strain gauge; 13. Digital oscilloscope; 14. Acoustic emission device; 15. Ultrasonic instrument; 16. Nitrogen cylinder; 17. Launch tube; 18. Impact rod; 19. Velocity detection device; 20. First high-speed camera device; 21. Fixing component. Detailed Implementation

[0042] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", 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 the present invention 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 limiting the present invention.

[0043] 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 as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0046] See also Figure 1-2 As shown, according to an embodiment of this application, a first aspect provides an experimental apparatus for characterizing the fracture characteristics of multi-level surrounding rock under tunnel drilling and blasting disturbance, comprising:

[0047] Pressurization component 1;

[0048] The rod assembly 2 includes a first rod 3, at least one second rod 4, and a third rod 5, wherein the first rod 3 and at least one second rod 4 and the third rod 5 are arranged sequentially.

[0049] A multi-stage fractured surrounding rock specimen, comprising a first fractured surrounding rock specimen 6 and a second fractured surrounding rock specimen 7, wherein the first fractured surrounding rock specimen 6 is placed between the first rod 3 and the second rod 4 and between adjacent second rods 4, and the second fractured surrounding rock specimen 7 is arranged between the second rod 4 and the third rod 5, and the pressure assembly 1 is used to impact the first rod 3;

[0050] When the pressurizing component 1 impacts the first rod 3, causing the first broken surrounding rock specimen 6 to burst and the second broken surrounding rock specimen 7 to undergo dynamic fracture damage, the first data acquisition component 8 acquires the ejection speed of the pressurizing component 1 and records its impact process.

[0051] When the pressurizing component 1 impacts the first rod 3, causing the first broken surrounding rock specimen 6 to burst and the second broken surrounding rock specimen 7 to undergo dynamic fracture damage, the second data acquisition component 9 records the dynamic fracture damage process of the second broken surrounding rock specimen 7.

[0052] The control terminal 10 is used to process the information collected by the first data acquisition component 8 and the second data acquisition component 9.

[0053] Specifically, the pressurizing component 1 impacts the rod component 2, initially generating a stress wave upon contact with the first rod 3. This stress wave is transmitted through the first rod 3 to the first fractured surrounding rock specimen 6, causing it to burst and fracture under the impact. The stress wave continues to propagate along the second rod 4 to the second fractured surrounding rock specimen 7, resulting in dynamic fracture damage. The stress wave then propagates to the third rod 5. The experiment is considered successful when the first fractured surrounding rock specimen 6 bursts and the second fractured surrounding rock specimen 7 exhibits dynamic fracture damage. The first data acquisition component 8 collects the ejection velocity of the pressurizing component 1 and records its impact process with the first rod 3. The second data acquisition component 9 records the second fractured surrounding rock specimen... The dynamic fracture damage process of 7 is monitored by the control terminal 10, which receives data and images from the first data acquisition component 8 and the second data acquisition component 9. The data is integrated and analyzed in depth through algorithms. In the experiment, the length and number of the second rod 4 can be adjusted as needed, which has flexible controllability. By adjusting the different lengths and numbers of the second rod 4, multiple blasting modes can be simulated continuously at multiple levels to achieve blasting stress testing at different lengths. The second data acquisition component 9 can also be used to observe the crack changes of the second broken surrounding rock specimen 7 after multiple blasting at multiple distances. The relevant data can be compared with finite element analysis software to simulate the randomness of crack development and be applied to actual construction operations.

[0054] When sampling the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7, it is necessary to ensure the integrity of the collected specimens. At the same time, the length of the second rod 4 should be adjusted according to the distance between the collected specimens 6 and 7 in the actual rock stratum. The length of the second rod 4 should meet the 1:30 ratio requirement with the distance between the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 in the actual rock stratum.

[0055] Among them, the first fractured surrounding rock specimen 6 is the same as the dynamic fracturing and dynamic splitting specimens in the loading test specimen assembly library, and the second fractured surrounding rock specimen 7 is the same as the Type I fracture and Type II fractured surrounding rock specimens in the loading test specimen assembly library.

[0056] Depending on the actual engineering geological conditions, this device can also be equipped with a third data acquisition component, a fourth data acquisition component, etc.; correspondingly, the experimental device may include a third fractured surrounding rock specimen, a fourth fractured surrounding rock specimen, etc., and so on.

[0057] In addition, the initial fracture characteristics of each level of fractured surrounding rock specimen should be set with reference to the actual engineering geological conditions and divided into dynamic compression fracture, dynamic splitting fracture, and dynamic type I and type II fracture under different working conditions. The corresponding multi-level fractured surrounding rock specimens should be selected from the loading test specimen component library.

[0058] A pulse shaper 11 is provided at the end of the first rod 3 facing the pressure assembly 1.

[0059] Specifically, the pulse shaper 11, located at the end of the first rod 3 facing the pressurizing component 1, reshapes and modulates the initial stress wave generated by the impact of the pressurizing component 1, making the stress wave more consistent with the characteristics of the dynamic load on the surrounding rock during actual tunnel drilling and blasting construction. This provides more accurate load input conditions for simulation experiments. In traditional experiments, unshaped stress waves may cause localized stress concentration in the first fractured surrounding rock specimen 6, leading to a failure mode that deviates from the failure characteristics under actual working conditions. However, after installing the pulse shaper 11, the stress wave can act uniformly on the surface of the fractured surrounding rock specimen, causing the specimen to fail under a stress state that is more consistent with reality. For example, in experiments simulating the cumulative effect of multiple blasts on the surrounding rock, the shaped stress wave ensures that the stress state and failure process are consistent each time the stress wave acts on the fractured surrounding rock specimen. This facilitates researchers in comparing and analyzing the failure conditions of different fractured surrounding rock specimens and accurately obtaining the changes in the mechanical properties of the rock under multiple impacts. Furthermore, the pulse shaper 11 reduces the experimental requirements for the material uniformity of the fractured surrounding rock specimen. Because the stress wave is optimized, even if the fractured surrounding rock specimen has some material inhomogeneity, it can still fail under relatively uniform stress loading, reducing experimental errors caused by material differences in the fractured surrounding rock specimen.

[0060] It also includes strain gauges 12, digital oscilloscopes 13, acoustic emission devices 14, and ultrasonic instruments 15. Several sets of strain gauges 12 are provided in the first rod 3, the second rod 4, and the third rod 5. The control terminal 10 is electrically connected to the strain gauges 12 and the digital oscilloscope 13. The probe of the acoustic emission device 14 is connected to the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7. The ultrasonic instrument 15 is used to detect the dynamic fracture damage process of the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7.

[0061] Specifically, several sets of strain gauges 12 are arranged in the first rod 3, the second rod 4, and the third rod 5. Each set of strain gauges 12 is arranged according to actual needs. During the impact of the pressurizing component 1 on the first rod 3, the stress wave generated by the impact propagates in the first rod 3, the second rod 4, and the third rod 5. The strain gauges 12 measure the strain signal at that location and transmit it to the digital oscilloscope 13 and the control terminal 10. The digital oscilloscope 13 and the control terminal 10 convert it into a visualized strain waveform and process it to form a stress wave versus time curve, which can monitor the propagation process of stress waves at multiple locations.

[0062] During use, when the pressurizing component 1 impacts the first rod 3 to generate a stress wave, the strain gauge 12 converts the strain change into an electrical signal, which is then transmitted to the digital oscilloscope 13. The digital oscilloscope 13 processes and displays the signal, allowing researchers to observe the propagation process of the stress wave and the response of the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 in real time. After the experiment, the digital oscilloscope 13 can store the collected data and perform in-depth analysis using specialized software, plotting strain-time curves to visually present the mechanical behavior of the first rod 3, the second rod 4, the third rod 5, and the first fractured surrounding rock specimen 6 under the action of the stress wave. Furthermore, through comparative analysis of multiple experimental data, the differences in fracture characteristics of surrounding rock under different rock materials and loading conditions can be studied, providing a basis for the optimized design of tunnel drilling and blasting construction. The acoustic emission device 14 has four probes installed on each of the surfaces of the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 in a symmetrical, even, and tight arrangement. During the experiment, these probes convert the mechanical vibration of the material into electrical signals, which are then amplified, processed, and recorded. These signals are emitted from the acoustic emission source and propagate to the surface of the material, causing surface displacement that can be detected by the acoustic emission sensor. The method enables the localization of internal cracks in the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7. The experimental personnel can analyze and infer the mechanism of acoustic emission by observing the acoustic emission signals. The ultrasonic instrument 15 emits ultrasonic waves of a specific frequency into the specimen through the probe. When the specimen undergoes dynamic fracture damage, the continuity of the internal structure is disrupted, and the ultrasonic waves will generate signal changes due to reflection and scattering by the cracks during propagation. The ultrasonic instrument 15 receives and captures these changing signals in real time, analyzes the signal characteristics through the built-in algorithm, and then infers the crack initiation location, propagation path, propagation rate, and the range and degree of damage area, ultimately realizing real-time monitoring and quantitative characterization of the entire dynamic fracture damage process.

[0063] The digital oscilloscope 13 features wireless data transmission capabilities. In this implementation, this function enables experimental data to be transmitted in real-time to a remote computer or cloud server, allowing researchers to view, analyze, and share data anytime, anywhere. Simultaneously, wireless transmission reduces cable connections at the experimental site, resulting in a simpler experimental setup, reduced risk of data loss due to cable failures, and improved convenience and efficiency of experimental operations.

[0064] The pressurization component 1 includes:

[0065] Nitrogen cylinder 16;

[0066] The nitrogen cylinder 16 has its output end connected to the launch tube 17.

[0067] Impact rod 18 is disposed inside the launching tube 17, and the output end of the impact rod 18 faces the pulse shaper 11.

[0068] Specifically, the pressurization assembly 1 includes a nitrogen cylinder 16, a launch tube 17, and an impact rod 18, providing a stable and controllable power source for simulating the impact load during tunnel drilling and blasting. The nitrogen cylinder 16 precisely adjusts its output gas pressure, changing the initial velocity of the impact rod 18, thereby adjusting the intensity and waveform of the stress wave to simulate the impact load on the surrounding rock under different blasting conditions. The launch tube 17, serving as the interaction space between the nitrogen and the impact rod 18, can achieve high-speed, stable linear motion under the propulsion of high-pressure nitrogen. The impact rod 18 possesses high hardness and high toughness, capable of withstanding the enormous impact force generated during high-speed impacts without deformation or damage. L - the length of the first rod 3, Δt - the time required for the stress wave to enter the first fractured surrounding rock specimen 6 and for the first fractured surrounding rock specimen 6 to burst. By obtaining the length of the first rod 3 and the time required for the stress wave to enter the first fractured surrounding rock specimen 6 and for the first fractured surrounding rock specimen 6 to burst, the stress wave velocity C0 can be calculated.

[0069] When in use, after the nitrogen cylinder 16 releases high-pressure nitrogen into the launch tube 17, the impact rod 18 accelerates rapidly under the action of air pressure and impacts the pulse shaper 11 on the first rod body 3, generating a stress wave.

[0070] The first data acquisition component 8 includes:

[0071] Speed ​​detection device 19, the speed detection device 19 is used to collect the impact speed of the impact rod 18;

[0072] A first high-speed camera device 20 is used to record the impact process of the impact rod 18.

[0073] Specifically, the first data acquisition component 8 includes a velocity detection device 19 and a first high-speed camera device 20. The velocity detection device 19 can capture the ejection velocity of the impact rod 18, calculate the initial velocity and acceleration of the impact rod 18 through data processing, and output an acceleration waveform. The first high-speed camera device 20 uses high-speed photography technology to record the entire process of the impact rod 18 impacting the pulse shaper 11. In addition, the device supports multi-camera synchronous shooting, which can record the impact process from different angles. Through post-image analysis software, the stress distribution cloud map at the moment of impact can be reconstructed in three dimensions, providing intuitive visualization data for studying the propagation characteristics of stress waves.

[0074] In other examples, the velocity detection device 19 and the first high-speed camera device 20 are connected to the control terminal 10 via a wireless transmission protocol. This design eliminates the constraints of cables, facilitating flexible adjustment of the camera position, and is particularly suitable for complex experimental layouts involving multiple rods and fragmented surrounding rock specimens. Simultaneously, wireless transmission supports real-time data transmission and remote control, allowing researchers to preview the captured images and adjust parameters in a safe area, enhancing the convenience and safety of experimental operations.

[0075] Among them, the speed detection device 19 can be a speed measuring instrument.

[0076] The second data acquisition component 9 includes: a second high-speed camera device;

[0077] The second high-speed camera is located on one side of the second fractured surrounding rock specimen 7, and is used to record the dynamic fracture damage process of the second fractured surrounding rock specimen 7.

[0078] Specifically, the second data acquisition component 9 is a second high-speed camera device. This device uses a high-speed camera to record the dynamic changes in the fracture damage process of the second fractured surrounding rock specimen 7. It visually demonstrates the stress wave's destructive process on the rock.

[0079] The second high-speed camera is positioned to the side of the second fractured rock specimen 7 and maintains a perpendicular viewing angle to it, ensuring a complete record of the planar dynamic fracture damage of the fractured rock specimen under stress wave action. Furthermore, this device supports simultaneous multi-camera shooting, allowing for comprehensive recording of the three-dimensional failure morphology of the fractured rock specimen by adding shooting positions at different angles, such as the side and top. The image data acquired by the second high-speed camera can be fused with the stress wave data obtained by the strain gauge 12 and the digital oscilloscope 13. Using dedicated image analysis software, parameters such as crack length, width, and propagation angle in each frame of the image can be automatically measured and tracked, generating a curve showing the crack propagation over time.

[0080] The first rod 3, the second rod 4, and the third rod 5 have the same axis.

[0081] Specifically, before conducting the experiment, a linear guide rail needs to be laid. The pressure assembly 1, the first rod 3, the second rod 4, and the third rod 5 are all installed on the linear guide rail to ensure that the impact rod 18 in the pressure assembly 1 is aligned with the axis of the first rod 3, the second rod 4, and the third rod 5, thereby ensuring the stable propagation of stress waves in the experimental device and ensuring the uniformity of stress on the fractured surrounding rock specimen.

[0082] The impact rod 18 is aligned with the axes of the first rod 3, the second rod 4, and the third rod 5. This arrangement allows stress waves to propagate with minimal energy loss and waveform distortion when propagating through the coaxial rods. If the rod axes deviate, the stress waves will experience reflection and refraction due to abrupt changes in direction during propagation, leading to waveform disorder, uneven stress on the fractured rock specimens, and affecting the validity of the experimental data. With the axes aligned, the stress waves can be smoothly transmitted along the axes of the first rod 3, the second rod 4, and the third rod 5 to the first fractured rock specimen 6 and the second fractured rock specimen 7, causing them to fail under uniform stress. The failure modes of the first fractured rock specimen 6 and the second fractured rock specimen 7 are consistent with theoretical analysis, effectively improving the reliability of the experimental results.

[0083] In actual experiments, when studying the cumulative damage effect of fractured surrounding rock specimens with different lithologies under multiple blasting impacts, the impact rod 18 is aligned with the axes of the first rod 3, the second rod 4, and the third rod 5. This ensures a high degree of repeatability in the mode and intensity of stress wave action on the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 in each experiment, facilitating comparative analysis of different experimental data. Furthermore, it enhances the versatility of the experimental setup, ensuring stable propagation of stress waves whether conducting single-stage impact experiments or simulating multi-stage blasting conditions by increasing the number of second rods 4.

[0084] The third rod 5 is provided with a fixing member 21 for fixing the second broken surrounding rock specimen 7.

[0085] The fixing member 21 has protrusions on both sides of the second broken surrounding rock specimen 7.

[0086] Specifically, the fixing member 21 on the third rod 5 and the protrusions on both sides constitute the positioning and stable support of the second broken surrounding rock specimen 7, ensuring that the second broken surrounding rock specimen 7 remains in place under dynamic impact load, avoiding stress wave propagation deviation caused by displacement, and ensuring the accuracy of experimental data.

[0087] Combination Figure 1-3As shown, the second aspect of this application provides a test method for an experimental apparatus for characterizing the fracture characteristics of multi-level surrounding rock under tunnel drilling and blasting disturbance, comprising:

[0088] S1. Initial conditions determination: Based on the actual geological conditions of the surrounding rock, determine the number of multi-stage fractured surrounding rock specimens, the initial fracture damage characteristics of the surrounding rock, and the number of rod components 2;

[0089] S2. Preparation of multi-stage fractured surrounding rock specimens: Prepare the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7;

[0090] Specifically, the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 were prepared according to the loading test specimen component library. During the preparation, appropriate sampling points were selected according to the actual situation of the site topography and geomorphology. The first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 were sampled and prepared to ensure the integrity of the fractured surrounding rock specimens. The first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 were supported with the same components as those in the loading test specimen component library without damaging their inherent properties.

[0091] S3. The placement, loading, and data acquisition of the first and second fractured rock mass specimens 6 and 7 in the multi-stage fractured rock mass impact test: The first fractured rock mass specimen 6 is placed between the first rod 3 and the second rod 4, and between pairs of second rods 4. The second fractured rock mass specimen 7 is placed between the second rod 4 and the third rod 5. The first rod 3 is impacted by the pressurizing component 1 to generate stress waves. When the first fractured rock mass specimen 6 bursts and the second fractured rock mass specimen 7 experiences dynamic fracture damage, the first data acquisition component 8 acquires the ejection velocity of the pressurizing component 1 and records its impact process. The second data acquisition component 9 records the dynamic fracture damage process of the second fractured rock mass specimen 7. By adjusting different impact velocities of the first rod 3, the influence of vibration waves from different blasting construction scenarios on multi-stage rock mass fracture damage can be simulated.

[0092] Specifically, the first fractured surrounding rock specimen 6 is placed between the first rod 3 and the second rod 4, and the second fractured surrounding rock specimen 7 is placed between multiple second rods 4 and between the second rod 4 and the third rod 5. Driven by the nitrogen cylinder 16, the pressurization assembly 1 ejects the impact rod 18 from the launch tube 17, impacting the pulse shaper 11 at the front end of the first rod 3. The resulting stress wave propagates within the first rod 3, second rod 4, and third rod 5. The test is considered successful when the first fractured surrounding rock specimen 6 bursts and the second fractured surrounding rock specimen 7 experiences dynamic fracture damage in a single test. During the test, the velocity detection device 19 in the first data acquisition assembly 8 captures the ejection velocity of the impact rod 18, calculates its initial velocity and acceleration through data processing, and outputs an acceleration waveform. The first high-speed camera device 20 uses high-speed photography technology to record the entire process of the impact rod 18 impacting the pulse shaper 11. The second data acquisition assembly 9 records the dynamic changes in the dynamic fracture damage process of the second fractured surrounding rock specimen 7. It visually demonstrates the destructive process of stress waves on rocks.

[0093] S4. Strain monitoring and stress wave parameter analysis of rod assembly 2 under impact: When the first broken surrounding rock specimen 6 undergoes explosive fracture and the second broken surrounding rock specimen 7 undergoes dynamic fracture damage, the array of strain gauges 12 on the first rod 3, the second rod 4, and the third rod 5 converts the deformation within the first rod 3, the second rod 4, and the third rod 5 into electrical signals and transmits them to the digital oscilloscope 13 and the control terminal 10. The digital oscilloscope 13 and the control terminal 10 record and process these signals to form stress wave versus time curves, analyze the propagation law of dynamic stress waves, and calculate the wave velocity of stress waves.

[0094] S5. Dynamic Damage Response Characteristics Analysis of Multi-Stage Surrounding Rock: Based on image information acquired by the first high-speed camera device 20 and the second high-speed camera device, digital image correlation analysis is performed to analyze the dynamic damage evolution process and the distribution of dynamic stress and strain fields of the multi-stage fractured surrounding rock specimen. Based on the obtained dynamic stress-strain or stress-time history curves of the surrounding rock, the dynamic fracture strength, dynamic fracture strength growth factor, and dynamic fracture dissipation energy of the multi-stage fractured surrounding rock specimen are calculated. Based on the acquired ultrasonic signals and acoustic emission signals, dynamic fracture damage characteristic parameters such as ringing count and spatial distribution characteristics of tensile-shear damage are calculated for the multi-stage fractured surrounding rock.

[0095] Specifically, during the propagation of the stress wave through the first rod 3, the second rod 4, and the third rod 5, strain gauge 12 measures the strain signal at that location and transmits it to the digital oscilloscope 13 and control terminal 10. The digital oscilloscope 13 and control terminal 10 convert this into a visualized strain waveform, processing it to form a stress wave versus time curve. This allows for multi-location monitoring of the stress wave propagation process. Strain gauge 12 converts strain changes into electrical signals, which are then transmitted to the digital oscilloscope 13 for processing and display. Researchers can observe the propagation process of the stress wave and the response of the first fractured surrounding rock specimen 6 and the second fractured surrounding rock specimen 7 in real time. After the experiment, the digital oscilloscope 13 can store the collected data and perform in-depth analysis using specialized software, plotting the stress wave versus time curve to visually present the mechanical behavior of the first rod 3, the second rod 4, the third rod 5, and the first fractured surrounding rock specimen 6 under the action of the stress wave. Furthermore, by comparing and analyzing data from multiple experiments, the fracture characteristics under different fractured surrounding rocks and different impact rates can be studied. L - the length of the first rod 3, Δt - the time required for the stress wave to enter the first fractured surrounding rock specimen 6 and for the first fractured surrounding rock specimen 6 to fail. By obtaining the length of the first rod 3 and the time required for the stress wave to enter the first fractured surrounding rock specimen 6 and for the first fractured surrounding rock specimen 6 to burst, the stress wave velocity -C0 can be calculated.

[0096] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. An experimental device for characterizing multi-stage fracture properties of surrounding rock disturbed by tunnel drilling and blasting, characterized in that, include: Pressurization component (1); A rod assembly (2) includes a first rod (3), at least one second rod (4), and a third rod (5), wherein the first rod (3), at least one second rod (4), and a third rod (5) are arranged sequentially; A multi-stage fractured surrounding rock specimen, comprising a first fractured surrounding rock specimen (6) and a second fractured surrounding rock specimen (7), wherein a first fractured surrounding rock specimen (6) is placed between the first rod (3) and the first second rod (4) and between adjacent second rods (4), and a second fractured surrounding rock specimen (7) is provided between the last second rod (4) and the third rod (5), wherein the pressurizing component (1) is used to impact the first rod (3); The first data acquisition component (8) acquires the ejection speed of the pressurizing component (1) and records its impact process when the pressurizing component (1) impacts the first rod (3), causing the first broken surrounding rock specimen (6) to burst and the second broken surrounding rock specimen (7) to dynamically fracture and be damaged. The second data acquisition component (9) records the dynamic fracture damage process of the second broken rock specimen (7) when the pressurizing component (1) impacts the first rod (3), causing the first broken surrounding rock specimen (6) to burst and the second broken surrounding rock specimen (7) to suffer dynamic fracture damage. The control terminal (10) is used to process the information collected by the first data acquisition component (8) and the second data acquisition component (9).

2. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 1, characterized in that, The first rod (3) is provided with a pulse shaper (11) at the end facing the pressurizing assembly (1).

3. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 2, characterized in that, It also includes strain gauges (12), digital oscilloscopes (13), acoustic emission devices (14) and ultrasonic instruments (15). Several sets of strain gauges (12) are provided in the first rod (3), the second rod (4) and the third rod (5). The control terminal (10) is electrically connected to the strain gauges (12) and the digital oscilloscopes (13). The probe of the acoustic emission device (14) is connected to the first broken surrounding rock specimen (6) and the second broken surrounding rock specimen (7). The ultrasonic instrument (15) is used to detect the dynamic fracture damage process of the first broken surrounding rock specimen (6) and the second broken surrounding rock specimen (7).

4. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 3, characterized in that, The pressurization assembly (1) includes: Nitrogen cylinder (16); The output end of the nitrogen cylinder (16) is connected to the launch tube (17); Impact rod (18) is disposed inside the launching tube (17), and the output end of the impact rod (18) faces the pulse shaper (11).

5. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 4, characterized in that, The first data acquisition component (8) includes: Speed ​​detection device (19), the speed detection device (19) is used to collect the impact speed of the impact rod (18); A first high-speed camera device (20) is used to record the impact process of the impact rod (18).

6. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 5, characterized in that, The second data acquisition component (9) includes: a second high-speed camera device; The second high-speed camera is located on one side of the second fractured surrounding rock specimen (7), and the second high-speed camera is used to record the dynamic fracture damage process of the second fractured surrounding rock specimen (7).

7. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 6, characterized in that, The first rod (3), the second rod (4), and the third rod (5) have the same axis.

8. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 7, characterized in that, The third rod (5) is provided with a fixing member (21) for fixing the second broken surrounding rock specimen (7).

9. The experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance according to claim 8, characterized in that, The fixing member (21) has protrusions on both sides of the second broken surrounding rock specimen (7).

10. A test method for the experimental apparatus for characterizing the fracture characteristics of multi-stage surrounding rock under tunnel drilling and blasting disturbance as described in claim 9, characterized in that, include: S1. Initial conditions determination: Based on the actual geological conditions of the surrounding rock, determine the number of multi-stage fractured surrounding rock specimens, the initial fracture damage characteristics of the surrounding rock, and the number of rod components (2); S2. Preparation of multi-stage fractured surrounding rock specimens: Based on the loading test specimen component library, prepare the first fractured surrounding rock specimen (6) and the second fractured surrounding rock specimen (7); S3. The first broken rock specimen (6) and the second broken rock specimen (7) of the multi-stage broken rock impact test are arranged, loaded and data is collected: The first broken rock specimen (6) is placed between the first rod (3) and the first second rod (4) and between two pairs of second rods (4), and the second broken rock specimen (7) is placed between the last second rod (4) and the third rod (5). The first rod (3) is impacted by the pressurizing component (1) to generate stress waves. When the first broken rock specimen (6) bursts and the second broken rock specimen (7) suffers dynamic fracture damage, the first data acquisition component (8) collects the ejection speed of the pressurizing component (1) and records its impact process. The second data acquisition component (9) records the dynamic fracture damage process of the second broken rock specimen (7). By adjusting the impact speed of the first rod (3), the influence of vibration waves in different blasting construction scenarios on multi-stage rock fracture damage can be simulated. S4. Strain monitoring and stress wave parameter analysis of rod assembly (2) under impact: When the first broken surrounding rock specimen (6) bursts and the second broken surrounding rock specimen (7) suffers dynamic fracture damage, the array of strain gauges (12) on the first rod (3), the second rod (4) and the third rod (5) convert the deformation in the first rod (3), the second rod (4) and the third rod (5) into electrical signals and transmit them to the digital oscilloscope (13) and the control terminal (10). The digital oscilloscope (13) and the control terminal (10) record and process the signals to form a stress wave and time curve, analyze the propagation law of dynamic stress wave, and calculate the wave velocity of stress wave. S5. Dynamic damage response characteristics analysis of multi-stage surrounding rock: Based on the image information acquired by the first high-speed camera device (20) and the second high-speed camera device, digital image correlation analysis is performed to analyze the dynamic damage evolution process of the multi-stage fractured surrounding rock specimen and the distribution of dynamic stress and strain fields; based on the obtained dynamic stress-strain or stress-time history curves of the surrounding rock, the dynamic fracture strength, dynamic fracture strength growth factor and dynamic fracture dissipation energy of the multi-stage fractured surrounding rock specimen are calculated; based on the acquired ultrasonic signals and acoustic emission signals, the dynamic fracture damage characteristic parameters of the multi-stage fractured surrounding rock are calculated.

Images