True triaxial test method and device for reproducing time-delay rock burst occurrence process

Abstract

The invention relates to the technical field of indoor rockburst tests, and provides a true triaxial test method and a true triaxial test device for reproducing a time-delay rockburst occurrence process. The method comprises the following steps: firstly, determining damage stress and peak stress of a rock sample through a pre-test, and setting a critical interval for loading; multi-axial stress (including maximum principal stress, middle principal stress and minimum principal stress) is loaded according to a three-direction five-surface-single-surface air-free mode, acoustic emission signals are monitored synchronously, and loading stop conditions are accurately judged by synthesizing acoustic emission signal variation, damage stress and peak stress; and finally, the load is kept constant until rockburst occurs. According to the invention, through double quantitative criteria of stress and acoustic emission signals, accurate and controllable reproduction of time-delay rock burst is realized, limitation of a single criterion is effectively avoided, and reliability and efficiency of the test are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of indoor rockburst testing technology, and more specifically, to a true triaxial test method and apparatus for reproducing the time-delayed rockburst generation process. Background Technology

[0002] Rockburst is a dynamic phenomenon in which rock mass suddenly fractures and violently ejects rock during excavation or mining, accompanied by the release of a large amount of energy. Time-delayed rockburst refers to rockbursts that occur some time after excavation and unloading. Because the distance between the rockburst and the excavation face is unknown, and the time lag between the rockburst and the excavation at that location is unclear, on-site personnel can only rely on experience to assess potential rockburst risks and then wait for extended periods to avoid them. This poses a significant threat to the lives of on-site construction workers and severely impacts project progress. Therefore, simulating the occurrence process of time-delayed rockbursts through laboratory experiments to reveal its destructive characteristics and mechanisms is fundamental to the prevention and early warning of time-delayed rockbursts, and is also a prerequisite and key to safe construction in deep engineering projects.

[0003] Reproducing the occurrence process of time-delayed rockbursts in actual engineering through indoor experiments has always been a key focus of time-delayed rockburst research, yet it remains an unsolved problem. Currently, the time-delayed loading stress in time-delayed rockburst experiments... The judgment and selection are mainly based on two methods: one is based on damage stress. and peak stress The stress level was determined by judging the rock's damage stress and adjusting it based on the specific experimental results, and the determined stress level was between the damage stress and peak stress of the rock. However, this method is not suitable for selecting time-delayed loading stress. Not precise enough It may be damage stress. and peak stress Any point within the interval. Another approach is to determine the time-delayed loading stress based on acoustic emission signals. When the number of acoustic emission impacts rises rapidly, loading is stopped and the load is kept constant until a rock burst occurs in the rock sample. However, because acoustic emission signals are quite sensitive and easily affected by noise signals and the experimental environment, the acoustic emission signals fluctuate significantly during the stable phase of the rock sample. This makes it difficult to determine the time-delayed loading stress using acoustic emission parameters. There may be some misjudgments. If the loading is stopped and the load is kept constant, the rock sample will not experience time-delayed rockburst failure. A second loading is required, which reduces the reliability and efficiency of the test.

[0004] In summary, existing methods all suffer from a strong emphasis on qualitative judgment but a lack of quantitative standards, highlighting the need for precise stress control in experiments. Summary of the Invention

[0005] This invention addresses the technical problems existing in the prior art by providing a true triaxial test method and apparatus for reproducing the time-delayed rockburst generation process. It overcomes the shortcomings of the prior art, which relies solely on experience to select the time-delayed loading stress within the range of damage stress and peak stress, or on relying solely on easily interfered acoustic emission signals for judgment, resulting in high misjudgment rate, low test success rate, and the need for secondary loading.

[0006] According to a first aspect of the present invention, a true triaxial test method for reproducing time-delayed rock burst generation processes is provided, comprising: S1, providing a standard rock specimen and determining the damage stress of the rock specimen based on preliminary tests. and peak stress ; S2, according to a preset stress loading scheme, multiaxial stress is applied to the rock sample in a three-dimensional, five-faced-single-faced open manner, and the acoustic emission signal of the rock sample is monitored simultaneously. The multiaxial stress includes the maximum principal stresses that are perpendicular to each other. Intermediate principal stress and minimum principal stress The maximum principal stress The loading stop condition is based on the change in the acoustic emission signal and the damage stress. and peak stress Determined comprehensively; S3, maintaining maximum principal stress Intermediate principal stress and minimum principal stress The load remains constant until a rock eruption occurs.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Optionally, in step S1, providing a standard rock sample includes: At least one complete parent rock is taken from the engineering site, and the parent rock is processed into a cuboid rock sample with the end grinding error, height error, and vertical error between the end face and the central axis all within the preset range according to the test standard.

[0009] Optionally, in step S1, the damage stress of the rock sample is determined based on a preliminary test. and peak stress ,include: A time-delay rockburst pre-test was conducted on the rock sample under true triaxial conditions, and the damage stress was obtained through the volumetric strain curve of the rock crack. The peak stress was obtained through the rock stress-strain curve. .

[0010] Optionally, step S2 includes: The cuboid-shaped rock sample is installed in place such that the front of the rock sample is open, the other five faces are in effective contact with the stress control system, and the acoustic emission monitoring system is coupled to the rock sample. The direction in which the force is applied perpendicular to the upper and lower surfaces of the rock specimen is defined as the maximum principal stress. The direction of force application is defined as the direction perpendicular to the left and right end faces of the rock sample as the intermediate principal stress. The direction of force application is defined as the direction perpendicular to the rear end facing the rock specimen as the minimum principal stress. The direction of the applied force; The rock sample was subjected to the maximum principal stress according to the preset stress loading scheme. Intermediate principal stress and minimum principal stress The acoustic emission signal of the rock sample is monitored synchronously by an acoustic emission monitoring system. Determine the intermediate principal stress based on the preset threshold. and minimum principal stress The loading stopping condition; when the maximum principal stress Exceeding the damage stress Then, based on the change in the acoustic emission signal and the damage stress... and peak stress The maximum principal stress was determined comprehensively. The loading stop condition.

[0011] Optionally, the maximum principal stress is applied to the rock sample according to a preset stress loading scheme. Intermediate principal stress and minimum principal stress ,include: The maximum principal stress and intermediate principal stress Load at a preset rate to the preset value of intermediate principal stress Then, maintain the intermediate principal stress. The load remains unchanged, and the maximum principal stress continues to be applied at a preset rate. ; Minimum principal stress at a preset rate Loaded to minimum principal stress preset value Then, maintain the intermediate principal stress. and minimum principal stress The load remains unchanged; Continue to apply the maximum principal stress individually at the preset rate. until the maximum principal stress is reached. The loading stop condition maintains the maximum principal stress. Intermediate principal stress and minimum principal stress The load remains unchanged.

[0012] Optionally, the maximum principal stress The loading stop conditions include: When the maximum principal stress satisfy When the change in acoustic emission impact number ΔN exceeds the preset threshold c, the loading of the maximum principal stress is stopped. The preset threshold c is determined adaptively based on multiple factors.

[0013] Optionally, the preset threshold c is determined by the following formula:

[0014] in, The reference constant is determined through standard tests. The lithological influence coefficient is... This is a correction factor for the loading rate. This is the correction factor for the integrity of the rock sample. This is a correction factor for the equipment system. This is the environmental noise correction factor.

[0015] According to a second aspect of the present invention, a true triaxial test apparatus for reproducing time-delayed rockburst generation processes is provided, comprising the application of the above-described method, including: A true triaxial loading mechanism is used to apply and independently control the maximum principal stress on the five faces of a cuboid rock specimen. Intermediate principal stress and minimum principal stress And keep one face as an open face; An acoustic emission monitoring system is coupled to the rock sample and is used to monitor the acoustic emission signal of the rock sample in real time during the loading process, and to obtain the acoustic emission impact number based on the acoustic emission signal. The stress control system, signal-connected to the true triaxial loading mechanism, is configured to execute the stress loading path and automatically stop loading when a preset condition is met; the preset condition is: intermediate principal stress. and minimum principal stress Reaching the preset value; maximum principal stress Due to the damage stress of the rock sample With peak stress Between, and the change in the number of acoustic emission impacts detected by the acoustic emission monitoring system, ΔN, exceeds the adaptive threshold c; The data synchronization and processing unit is communicatively connected to the stress control system and the acoustic emission monitoring system, and is used to synchronously control stress loading and signal monitoring, and process data to determine the preset conditions.

[0016] Optionally, the device also includes: A high-speed camera system was configured to acquire video stream data during the experiment.

[0017] Optionally, the acoustic emission monitoring system is located at the bottom of the true triaxial loading mechanism, and the sensor probe of the acoustic emission monitoring system is coupled to the rock sample.

[0018] This invention provides a true triaxial testing method and apparatus for reproducing the time-delayed rockburst generation process. Preliminary tests determine two key critical parameters: damage stress and peak stress, thus defining a clear stress range. In the formal test, once the maximum principal stress among the multiaxial stresses applied to the rock sample enters this range, the changes in acoustic emission signals monitored in real time are used as a more sensitive criterion for microscopic damage. By combining stress control with acoustic emission activity, the optimal time to stop loading at the maximum principal stress is accurately determined, resulting in a more accurate time-delayed loading stress. This invention improves the success rate and reliability of time-delayed rockburst tests, effectively avoiding misjudgments or the need for secondary loading due to inaccurate single criteria, and provides stable and repeatable experimental conditions for in-depth research on rockburst mechanisms. Attached Figure Description

[0019] Figure 1 A flowchart of a true triaxial test method for reproducing time-delayed rock burst generation process provided by the present invention; Figure 2 A schematic diagram of the three-dimensional five-faced-single-faced air-filled force application method of a rock sample provided for a certain embodiment; Figure 3 A schematic diagram of a stress loading scheme provided for one embodiment; Figure 4 The present invention provides a block diagram of a true triaxial test apparatus for reproducing the time-delayed rock eruption process. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] Figure 1 A flowchart of a true triaxial test method for reproducing time-delayed rock eruption processes provided by this invention is shown below. Figure 1 As shown, the method includes steps S1 to S3: S1, providing a standard rock specimen and determining the damage stress of the rock specimen based on preliminary tests. and peak stress .

[0022] This step provides standard-compliant rock samples and obtains key material parameters for the subsequent main experiment.

[0023] For example, this step first requires obtaining representative, intact parent rock from the engineering site and processing it into cuboid specimens with controlled dimensions and geometric tolerances (such as end face parallelism and perpendicularity) strictly according to authoritative standards such as ISRM, to ensure the accuracy and repeatability of the test results. Then, through true triaxial pre-tests, the two core strength indicators of the rock are precisely determined: damage stress. The stress threshold at which internal cracks begin to propagate unstably; peak stress. These two strength indicators characterize the maximum stress that the rock can withstand. Together, they define the critical stress range of the rock specimen, providing a basis for accurately determining the time-delayed loading stress in subsequent main tests. It provides a scientific quantitative basis.

[0024] S2, according to a preset stress loading scheme, multiaxial stress is applied to the rock sample in a three-dimensional, five-faced-single-faced open manner, and the acoustic emission signal of the rock sample is monitored simultaneously. The multiaxial stress includes the maximum principal stresses that are perpendicular to each other. Intermediate principal stress and minimum principal stress The maximum principal stress The loading stop condition is based on the change in the acoustic emission signal and the damage stress. and peak stress Determined comprehensively.

[0025] This step is the core execution and decision-making stage of the entire method, dynamically controlling the experimental process based on the key parameters obtained in step S1. This step applies load to the specimen according to a carefully designed "three-dimensional five-plane - single-plane open" stress loading path to simulate the stress state after underground engineering excavation. During loading, the system synchronously monitors the acoustic emission signals of the rock in real time. This step also sets a comprehensive loading stop condition: requiring not only the maximum principal stress... It must be under the damage stress determined by step S1. and peak stress Within the critical range, the change in acoustic emission signal (such as the number of impacts ΔN) must reach or exceed a preset threshold. This step combines macroscopic stress control with microscopic acoustic emission activity monitoring as a dual criterion, realizing the transformation from qualitative judgment to quantitative control, improving the accuracy of the timing of stopping loading, and obtaining more accurate time-delayed loading stress, which is key to avoiding misjudgment and secondary loading.

[0026] S3, maintaining maximum principal stress Intermediate principal stress and minimum principal stress The load remains constant until a rock eruption occurs.

[0027] This step is the final stage for observing time-delayed rockburst phenomena. The operation involves maintaining a constant load in all directions immediately after the stopping condition is met in step S2. At this point, the sample is under a specific "three-dimensional, five-plane, single-plane unloaded" constant load stress state. This constant load maintenance stage is the core of reproducing the "time-delay" characteristic, simulating the process in engineering where stress redistribution is completed after excavation and unloading, but the rock mass still needs time to accumulate damage and eventually become unstable. Under this state, microcracks inside the rock will continue to slowly propagate and penetrate under constant high stress until the accumulated damage reaches a critical point, ultimately triggering a sudden and violent dynamic failure of the rock sample—i.e., a rockburst. This step successfully reproduced the complete process of time-delayed rockburst from stress preparation to delayed occurrence in laboratory tests, providing a crucial observation window for studying its mechanism.

[0028] Understandably, given the deficiencies in the background technology, this invention proposes a true triaxial test method to reproduce the time-delayed rockburst generation process. This method first scientifically determines the damage stress and peak stress of the rock through preliminary experiments, setting a clear critical range for subsequent loading. Then, in the main experiment, a "three-dimensional five-plane - single-plane open-circuit" loading path is used to simulate actual engineering conditions. Macroscopic stress control (requiring the maximum principal stress to be within the aforementioned critical range) is combined with microscopic damage monitoring (the change in acoustic emission signal exceeding a threshold) as a comprehensive criterion for stopping loading. Finally, by maintaining a constant load, necessary time is provided for the accumulation and penetration of damage within the rock, thereby triggering delayed rockburst failure.

[0029] The method of this invention accurately reproduces time-delay rockbursts through a three-stage continuous process, successfully elevating time-delay rockburst tests from qualitative and unreliable judgments that rely on empirical estimations or single sensitive signals to a precise control method based on dual quantitative criteria. This improves the success rate and repeatability of the test, providing a stable and reliable experimental foundation for in-depth research on rockburst mechanisms.

[0030] In one possible embodiment, step S1, providing the standard rock sample, includes: At least one complete parent rock is taken from the engineering site, and the parent rock is processed into a cuboid rock sample with the end grinding error, height error, and vertical error between the end face and the central axis all within the preset range according to the test standard.

[0031] For example, after obtaining a representative and complete parent rock at the engineering site, it must be processed strictly in accordance with the standards of the International Society for Rock Mechanics (ISRM) and the "Code for Rock Testing in Hydraulic and Hydropower Engineering" (SL264-2020). The processing parameters have clear quantitative indicators. For example, the grinding error at both ends of the sample must be controlled within ±0.02 mm, the height error within 1 mm, and the perpendicularity deviation between the upper and lower end faces of the sample and the central axis must be within ±0.25°. Finally, a cuboid rock sample with a size of 100 mm × 100 mm × 200 mm is prepared.

[0032] This embodiment eliminates systematic errors and non-uniform stress concentrations introduced by differences in specimen size, shape, and end-face flatness at the source, ensuring that all test rock specimens have highly consistent initial mechanical states and boundary conditions. This embodiment not only facilitates the subsequent accurate determination of damage stress... and peak stress This laid a reliable foundation and is a key prerequisite for ensuring that the entire time-delay rockburst reproduction test has good repeatability and comparability.

[0033] In one possible embodiment, in step S1, the damage stress of the rock sample is determined based on a preliminary test. and peak stress ,include: A time-delay rockburst pre-test was conducted on the rock sample under true triaxial conditions, and the damage stress was obtained through the volumetric strain curve of the rock crack. The peak stress was obtained through the rock stress-strain curve. .

[0034] It is understood that the aforementioned preliminary test is not a simple strength test, but a refined test conducted under true triaxial conditions specifically designed to capture the critical state of rocks. Specifically, the damage stress... It is determined by analyzing the volumetric strain curve of the rock crack during loading. This stress point marks the critical moment when numerous cracks begin to connect and penetrate within the rock, and the volumetric strain curve bends, i.e., the starting point of unstable crack propagation; while the peak stress... It is obtained directly from the stress-strain curve of the rock, that is, the stress corresponding to the maximum bearing capacity of the rock.

[0035] This embodiment sets a clear stress range for the subsequent main experiment. This not only avoids the arbitrariness and inaccuracy of relying solely on empirical estimation, but also ensures that the acquired parameters can truly reflect the damage evolution law of the rock, providing a basis for accurately determining the time-delayed loading stress in the main experiment. It provides a scientific and reliable basis.

[0036] In one possible embodiment, step S2 includes sub-steps S201-S203: S201, The cuboid-shaped rock sample is installed in place, such that the front of the rock sample is open, the other five faces are in effective contact with the stress control system, and the acoustic emission monitoring system is coupled to the rock sample.

[0037] like Figure 2 The stress loading path is shown. The cuboid-shaped rock sample has six rectangular faces. Figure 2 Taking the perspective of [example image], the rock sample with gray texture, with its front completely exposed and not in contact with any clamps, constitutes the "free face" of the simulated engineering excavation face. This face is the main direction for subsequent observation of rockburst fragment ejection. Meanwhile, the other five faces of the sample (top, bottom, left, right, and back) are tightly fitted with rigid clamps. These clamps are the actuators of the stress control system, through which the maximum principal stress can be independently and precisely applied to and controlled on the sample. Intermediate principal stress and minimum principal stress This allows for the simulation of realistic stress boundary conditions in a "three-dimensional, five-faced, single-faced open" environment indoors. Furthermore, the acoustic emission monitoring system utilizes red AE sensors (such as...) Figure 2 The sensor (shown as a dot at the bottom of the sample) is in direct contact with and coupled to the surface of the rock sample. The sensor is connected to the monitoring host via wires to ensure that it can capture and transmit the acoustic emission signals emitted by the generation and propagation of internal microcracks in the rock sample during loading in real time and with high sensitivity. Figure 2 The overall configuration shown is the physical basis for reproducing the time-delayed rock burst generation process.

[0038] S202 defines the direction perpendicular to the upper and lower surfaces facing the rock sample as the maximum principal stress. The direction of force application is defined as the direction perpendicular to the left and right end faces of the rock sample as the intermediate principal stress. The direction of force application is defined as the direction perpendicular to the rear end facing the rock specimen as the minimum principal stress. The direction of the applied force.

[0039] Understandably, the maximum principal stress The primary simulation focuses on the self-weight of the overlying strata in the vertical direction, i.e., the gravitational field of the strata, which is the most significant load leading to rock mass compression and energy accumulation. Intermediate principal stress. The simulation focuses on horizontal tectonic or constrained stresses, such as high-level stresses generated by tectonic movements (e.g., plate compression) and persistent within rock masses. These stresses significantly influence the failure mode and strength of rocks. Minimum principal stress. This simulates a relatively small confining pressure or constraint force in the horizontal direction. During the experiment, loading is stopped. And keep it constant, while making the corresponding rock surface a "free surface". This operation accurately simulates the formation process of a free surface in actual engineering (such as tunnel excavation) that causes the stress of the surrounding rock to be released instantaneously, which can easily induce rock bursts.

[0040] Then, the rock sample is subjected to the maximum principal stress according to the preset stress loading scheme. Intermediate principal stress and minimum principal stress The acoustic emission signal of the rock sample is monitored synchronously through an acoustic emission monitoring system.

[0041] S203, determine the intermediate principal stress according to the preset threshold. and minimum principal stress The loading stopping condition; when the maximum principal stress Exceeding the damage stress Then, based on the change in the acoustic emission signal and the damage stress... and peak stress The maximum principal stress was determined comprehensively. The loading stop condition.

[0042] More specifically, such as Figure 3 As shown, the stress loading scheme includes: The maximum principal stress and intermediate principal stress Load at a preset rate to the preset value of intermediate principal stress Then, maintain the intermediate principal stress. The load remains unchanged, and the maximum principal stress continues to be applied at a preset rate. ; Minimum principal stress at a preset rate Loaded to minimum principal stress preset value Then, maintain the intermediate principal stress. and minimum principal stress The load remains unchanged; Continue to apply the maximum principal stress individually at the preset rate. until the maximum principal stress is reached. The loading stop condition maintains the maximum principal stress. Intermediate principal stress and minimum principal stress The load remains unchanged.

[0043] It is understood that this embodiment first clearly defines, as follows: Figure 2 The physical boundary conditions shown, with the front side exposed and the other five sides in effective contact, accurately simulate the state of the free face formed by excavation and unloading in engineering; further specifying, for example... Figure 3 The stress loading path shown first involves simultaneously loading the maximum principal stress. and intermediate principal stress To the preset value of intermediate principal stress To stabilize the rock sample and prevent it from sliding towards the free surface, the minimum principal stress is then applied. And keep it constant to simulate confining pressure, and finally apply the maximum principal stress alone. The critical point is determined by the changes in damage stress, peak stress, and acoustic emission signal.

[0044] This embodiment reproduces the complete process of underground engineering from the initial geostress state to the stress redistribution after excavation, ensuring the similarity between the test and the actual engineering conditions. This is achieved by first establishing stable intermediate principal stresses. and minimum principal stress Constraints, and then finely control the critical maximum principal stress. This effectively prevents the sample from sliding or failing prematurely during the loading process, creating a stable mechanical environment for accurate observation of time-delayed rockbursts.

[0045] In one possible embodiment, combining Figure 3 As shown, the maximum principal stress The loading stop conditions include: When the maximum principal stress satisfy When the change in acoustic emission impact number ΔN exceeds the preset threshold c, the loading of the maximum principal stress is stopped. The preset threshold c is not determined by a fixed value, but by an adaptive determination based on multiple factors.

[0046] Maximum principal stress The loading stop condition is expressed as:

[0047] in, N represents the increase in the number of acoustic emission impacts. Let be the number of acoustic emission impacts obtained from the acoustic emission signal within the (i+1)th sampling interval. The number of acoustic emission impacts obtained from the acoustic emission signal within the i-th sampling interval.

[0048] The preset threshold c is determined by the following formula:

[0049] in, The reference constant is determined through standard tests. The lithological influence coefficient is... This is a correction factor for the loading rate. This is the correction factor for the integrity of the rock sample. This is a correction factor for the equipment system. This is the environmental noise correction factor.

[0050] This embodiment focuses on the most critical maximum principal stress in time-delay rockburst tests. The criteria for stopping loading have been elevated from traditional, principle-based qualitative descriptions to highly quantifiable, adaptively adjustable, and precise control rules, establishing the "maximum principal stress" as the basis for these rules. Under damage stress With peak stress The dual criteria of "within the interval" and "the change in the number of acoustic emission impacts ΔN exceeds the preset threshold c" must be met simultaneously, avoiding misjudgments that may occur if traditional schemes rely solely on stress or acoustic emission signals. The preset threshold c, as the core criterion, is based on multi-factor coupling analysis, comprehensively considering key variables such as lithology, loading rate, rock sample integrity, equipment system, and environmental noise. This embodiment can automatically calculate the most suitable preset threshold c by adjusting the corresponding coefficients for different lithologies (such as granite and marble) or under different test environments, thereby dynamically optimizing the judgment criteria, significantly reducing the risk of misjudgments caused by changes in test conditions or external interference, and improving test accuracy.

[0051] To achieve the true triaxial test method for reproducing time-delayed rock eruption processes provided in the above embodiments, Figure 4 A structural diagram of a true triaxial test apparatus for reproducing time-delayed rockburst generation processes is provided in an embodiment of the present invention, as shown below. Figure 4 As shown, a true triaxial test system for reproducing the time-delayed rockburst generation process includes a true triaxial loading mechanism, an acoustic emission monitoring system, a stress control system, and a data synchronization and processing unit, wherein: A true triaxial loading mechanism is used to apply and independently control the maximum principal stress on the five faces of a cuboid rock specimen. Intermediate principal stress and minimum principal stress And keep one face as an open face; An acoustic emission monitoring system is coupled to the rock sample and is used to monitor the acoustic emission signal of the rock sample in real time during the loading process, and to obtain the acoustic emission impact number based on the acoustic emission signal. The stress control system, signal-connected to the true triaxial loading mechanism, is configured to execute the stress loading path and automatically stop loading when a preset condition is met; the preset condition is: intermediate principal stress. and minimum principal stress Reaching the preset value; maximum principal stress Due to the damage stress of the rock sample With peak stress Between, and the change in the number of acoustic emission impacts detected by the acoustic emission monitoring system, ΔN, exceeds the adaptive threshold c; The data synchronization and processing unit is communicatively connected to the stress control system and the acoustic emission monitoring system, and is used to synchronously control stress loading and signal monitoring, and process data to determine the preset conditions.

[0052] It is understood that the true triaxial test device for reproducing time-delayed rock eruption process provided by the present invention corresponds to the true triaxial test method for reproducing time-delayed rock eruption process provided in the foregoing embodiments. The relevant technical features of the true triaxial test device for reproducing time-delayed rock eruption process can be referred to the relevant technical features of the true triaxial test method for reproducing time-delayed rock eruption process, and will not be repeated here.

[0053] In one possible embodiment, combining Figure 4 As shown, the device also includes: A high-speed camera system was configured to acquire video stream data during the experiment.

[0054] This embodiment introduces a high-speed camera system, adding visualization and dynamic process recording capabilities to the entire time-delay rockburst test device, enabling comprehensive and multi-dimensional data capture of the rockburst failure process. The high-speed camera system can record the entire dynamic process from the appearance of initial cracks on the rock surface, to flaking, and finally, the violent ejection of rock fragments, with extremely high temporal resolution. These intuitive image data, along with the internal micro-fracture signals (acoustic emission signals) recorded by the acoustic emission monitoring system, form a strong spatiotemporal correspondence and mutual verification relationship, reproducing to a certain extent the time-delay rockburst occurrence process in actual engineering.

[0055] This embodiment can accurately reveal key mechanisms such as the initiation point and energy release mode of rockbursts by correlating and comparing the surface damage morphology captured by vision with the internal damage evolution characterized by acoustic emission signals. This greatly enhances the richness and depth of experimental data and provides a more intuitive basis for in-depth research on the damage characteristics and triggering mechanism of time-delayed rockbursts.

[0056] In one possible embodiment, the acoustic emission monitoring system is located at the bottom of the true triaxial loading mechanism, and the sensor probe of the acoustic emission monitoring system is coupled to the rock sample.

[0057] In this embodiment, the bottom mounting method of the acoustic emission monitoring system effectively utilizes the stable support structure of the true triaxial loading mechanism, reducing the mechanical interference caused by stress fluctuations during stress loading on the sensor itself and ensuring the stability of the monitoring position. Secondly, acoustic coupling can be achieved through a coupling agent, while physical fixation is achieved through adhesive tape. This ensures a low-loss, high-fidelity transmission path for the acoustic emission signal from the rock sample to the fixture base and then to the sensor probe, effectively solving the problems of signal attenuation and distortion. This embodiment enables the system to continuously and stably capture the high-frequency weak signals generated by micro-fractures within the rock, providing a high-quality data foundation for accurate judgment based on the change in the number of acoustic emission impacts ΔN. This reduces the risk of misjudgment due to signal quality issues and enhances the data reliability of the entire experimental setup.

[0058] The present invention will now be illustrated with an example of a specific implementation scenario.

[0059] In this implementation scenario, a true triaxial test control method for a time-delayed rockburst generation process is provided, including the following steps: 1. Rock sample preparation Take a complete piece of parent rock from the engineering site and make multiple time-delay rockburst samples.

[0060] The specimen is a cube with dimensions of 100 mm × 100 mm × 200 mm. It is processed according to the ISRM standard and the requirements of the "Specifications for Rock Testing in Water Conservancy and Hydropower Engineering" (SL264-2020). The grinding error at both ends of the specimen should be within ±0.02 mm, and the height error should be within 1 mm. The upper and lower end faces of the specimen should be perpendicular to the central axis of the specimen, with an allowable deviation within ±0.25°.

[0061] 2. Preliminary tests to determine the damage stress of the rock specimens. and peak stress

[0062] A portion of the prepared rock samples under time-delay rockburst pre-tests were conducted to determine the damage stress of the rock. The peak stress is 297 MPa. The rock damage stress is 330 MPa. This indicates that numerous internal cracks in the rock have connected and permeated, causing a bend in the volumetric strain curve. Further crack propagation and completion no longer require additional external force; this is also known as the initiation point of unstable crack propagation. Existing research has shown that damage stress can be utilized... and peak stress Determine the critical state of the rock and select a time-delayed loading stress. This can reproduce the rockburst phenomenon.

[0063] 3. Conduct indoor true triaxial rockburst tests. Using an indoor true triaxial rockburst testing machine, combined with an acoustic emission monitoring system and a high-speed camera system, time-delay rockburst tests were conducted under true triaxial conditions, which to a certain extent reproduced the time-delay rockburst generation process in actual engineering.

[0064] Studies have shown a certain correlation between the propagation of internal cracks in rocks and acoustic emission phenomena. In acoustic emission monitoring of rock mass stability, a sharp increase followed by a sudden decrease or a relatively calm period in acoustic emission activity indicates potential rock mass failure. The acoustic emission impact number represents the cumulative number of acoustic emission signals exceeding a specific threshold per unit time, reflecting the frequency and total amount of acoustic emission signals. A rapid increase in the acoustic emission impact number indicates an increase in the number of micro-fractures within the rock sample, suggesting that the rock sample has entered an unstable state. If the rock sample continues under this stress state, a rockburst is likely to occur after a certain period. The specific steps are as follows: (1) Place the rock sample and use coupling agent to bond the AE sensor probe of the acoustic emission monitoring system to the base of the fixture. Secure the AE sensor probe with tape to ensure that the acoustic emission signal can be transmitted from the rock sample to the base of the fixture and received by the AE sensor probe, such as... Figure 2 As shown.

[0065] (2) Simultaneously start the stress control system and acoustic emission monitoring system of the rockburst test machine to ensure synchronous monitoring of acoustic emission signals with a time error of <1 ms.

[0066] (3) Apply stress according to the stress loading scheme, and make a judgment according to the following formula (1): When the maximum principal stress After exceeding the rock damage stress of 297 MPa, carefully observe the change in acoustic emission impact number. When the acoustic emission impact number increases... When N is greater than c, the stress loading system is stopped.

[0067] (1) In the formula, For rock damage stress, For peak rock stress, N represents the increase in the number of acoustic emission impacts. This represents the number of acoustic emission impacts within the (i+1)th sampling interval. Let be the number of acoustic emission impacts within the i-th sampling interval.

[0068] In this invention, the constant c is not determined by a fixed value, but rather by an adaptive process based on multi-factor coupling analysis. This strategy fully considers the complex conditions in actual engineering, ensuring the method has wide applicability and accuracy. The constant c is calculated according to formula (2): (2) in, These are reference constants determined through numerous standard tests. The lithological influence coefficient is... This is a correction factor for the loading rate. This is the correction factor for the integrity of the rock sample. This is a correction factor for the equipment system. This is the environmental noise correction factor.

[0069] In this implementation scenario, the reference constant The lithological influence coefficient is 80. The loading rate correction factor is 1.12. The correction factor for rock sample integrity is 1.08. The equipment system correction factor is 1.15. The environmental noise correction factor is 1.03. Since it is 0.92, we have: c = 80×1.12×1.08×1.15×1.03×0.92= 105.

[0070] In this implementation scenario, the stress loading scheme is as follows: To prevent the rock sample from sliding towards the free surface, the maximum principal stress is first applied. and intermediate principal stress The load is applied at a rate of 0.4 MPa / s to the preset intermediate principal stress value. Loading stops afterward. and maintain With the load unchanged, the maximum principal stress is continuously applied at a rate of 0.4 MPa / s. ; Then, the minimum principal stress is applied at a rate of 0.4 MPa / s. Loaded to minimum principal stress preset value Loading stops afterward. ; Maintain intermediate principal stress and minimum principal stress With constant load, the maximum principal stress under individual loading After exceeding the rock damage stress of 297 MPa, carefully observe the change in acoustic emission impact number. When the acoustic emission impact number increases... When N is greater than 105 (i.e., the value of c), Reaching 310 MPa (below peak stress) At this point, stop the stress loading system and maintain the current maximum principal stress. Intermediate principal stress and minimum principal stress The load remains unchanged.

[0071] (4) Maintain Figure 2 The three-dimensional five-faced-single-faced open-air constant stress state is shown until the rock eruption occurs.

[0072] This invention provides a true triaxial test method and apparatus for reproducing the time-delayed rockburst occurrence process, which can accurately reproduce the entire process of a time-delayed rockburst from stress accumulation to delayed occurrence indoors. It first determines the damage stress of the rock through rigorous pre-tests. With peak stress This establishes a clear critical range for subsequent loading; subsequently, in a loading device simulating the stress state of a real engineering project ("three-dimensional, five-plane - single-plane open"), a step-by-step stress loading path is executed. When the maximum principal stress... Once the critical range is reached, a threshold c for the change in acoustic emission impact number, calculated adaptively based on multiple factors, is introduced as a dual criterion to accurately determine the maximum principal stress at which loading stops. The timing; finally, by maintaining a constant load, the necessary conditions are provided for the time-delayed evolution of damage inside the rock until instability, and a high-speed camera system is used to record the dynamic details of the failure in its entirety.

[0073] This invention elevates the experimental research on time-delay rockbursts from qualitative judgments based on experience to precise control based on quantitative parameters. By using the linkage criterion of macroscopic stress and microscopic acoustic emission signals, it effectively solves the problems of misjudgment and the need for secondary loading caused by the inaccuracy of a single criterion in traditional methods. This effectively improves the success rate of the experiment and the reliability of the data, and provides a stable, repeatable, and data-rich advanced experimental platform for in-depth revelation of the mechanism of time-delay rockbursts.

[0074] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0075] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0076] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0077] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0078] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0079] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0080] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A true triaxial test method for reproducing time-delayed rock burst generation processes, characterized in that, include: S1, providing a standard rock specimen and determining the damage stress of the rock specimen based on preliminary tests. and peak stress ; S2, according to a preset stress loading scheme, multiaxial stress is applied to the rock sample in a three-dimensional, five-faced-single-faced open manner, and the acoustic emission signal of the rock sample is monitored simultaneously. The multiaxial stress includes the maximum principal stresses that are perpendicular to each other. Intermediate principal stress and minimum principal stress The maximum principal stress The loading stop condition is based on the change in the acoustic emission signal and the damage stress. and peak stress Determined comprehensively; S3, maintaining maximum principal stress Intermediate principal stress and minimum principal stress The load remains constant until a rock eruption occurs.

2. The true triaxial test method for reproducing time-delayed rock burst generation process according to claim 1, characterized in that, In step S1, providing a standard rock sample includes: At least one complete parent rock is taken from the engineering site, and the parent rock is processed into a cuboid rock sample with the end grinding error, height error, and vertical error between the end face and the central axis all within the preset range according to the test standard.

3. The true triaxial test method for reproducing time-delayed rock burst generation process according to claim 1, characterized in that, In step S1, the damage stress of the rock sample is determined based on preliminary tests. and peak stress ,include: A time-delay rockburst pre-test was conducted on the rock sample under true triaxial conditions, and the damage stress was obtained through the volumetric strain curve of the rock crack. The peak stress was obtained through the rock stress-strain curve. .

4. The true triaxial test method for reproducing time-delayed rock burst generation process according to claim 1, characterized in that, Step S2 includes: The cuboid-shaped rock sample is installed in place such that the front of the rock sample is open, the other five faces are in effective contact with the stress control system, and the acoustic emission monitoring system is coupled to the rock sample. The direction in which the force is applied perpendicular to the upper and lower surfaces of the rock specimen is defined as the maximum principal stress. The direction of force application is defined as the direction perpendicular to the left and right end faces of the rock sample as the intermediate principal stress. The direction of force application is defined as the direction perpendicular to the rear end facing the rock specimen as the minimum principal stress. The direction of the applied force; The rock sample was subjected to the maximum principal stress according to the preset stress loading scheme. Intermediate principal stress and minimum principal stress The acoustic emission signal of the rock sample is monitored synchronously by an acoustic emission monitoring system. Determine the intermediate principal stress based on the preset threshold. and minimum principal stress The loading stopping condition; when the maximum principal stress Exceeding the damage stress Then, based on the change in the acoustic emission signal and the damage stress... and peak stress The maximum principal stress was determined comprehensively. The loading stop condition.

5. The true triaxial test method for reproducing time-delayed rock burst generation process according to claim 4, characterized in that, The rock sample is subjected to the maximum principal stress according to the preset stress loading scheme. Intermediate principal stress and minimum principal stress ,include: The maximum principal stress and intermediate principal stress Load at a preset rate to the preset value of intermediate principal stress Then, maintain the intermediate principal stress. The load remains unchanged, and the maximum principal stress continues to be applied at a preset rate. ; Minimum principal stress at a preset rate Loaded to minimum principal stress preset value Then, maintain the intermediate principal stress. and minimum principal stress The load remains unchanged; Continue to apply the maximum principal stress individually at the preset rate. until the maximum principal stress is reached. The loading stop condition maintains the maximum principal stress. Intermediate principal stress and minimum principal stress The load remains unchanged.

6. A true triaxial test method for reproducing time-delayed rock eruption processes according to claim 1, 4, or 5, characterized in that, The maximum principal stress The loading stop conditions include: When the maximum principal stress satisfy When the change in acoustic emission impact number ΔN exceeds the preset threshold c, the loading of the maximum principal stress is stopped. The preset threshold c is determined adaptively based on multiple factors.

7. The true triaxial test method for reproducing time-delayed rock eruption processes according to claim 6, characterized in that, The preset threshold c is determined by the following formula: in, The reference constant is determined through standard tests. The lithological influence coefficient is... This is a correction factor for the loading rate. This is the correction factor for the integrity of the rock sample. This is a correction factor for the equipment system. This is the environmental noise correction factor.

8. A true triaxial test apparatus for reproducing time-delayed rock eruption processes, characterized in that, The method described by any one of claims 1 to 7 comprises: A true triaxial loading mechanism is used to apply and independently control the maximum principal stress on the five faces of a cuboid rock specimen. Intermediate principal stress and minimum principal stress And keep one face as an open face; An acoustic emission monitoring system is coupled to the rock sample and is used to monitor the acoustic emission signal of the rock sample in real time during the loading process, and to obtain the acoustic emission impact number based on the acoustic emission signal. The stress control system, signal-connected to the true triaxial loading mechanism, is configured to execute the stress loading path and automatically stop loading when a preset condition is met; the preset condition is: intermediate principal stress. and minimum principal stress Reaching the preset value; maximum principal stress Due to the damage stress of the rock sample With peak stress Between, and the change in the number of acoustic emission impacts detected by the acoustic emission monitoring system, ΔN, exceeds the adaptive threshold c; The data synchronization and processing unit is communicatively connected to the stress control system and the acoustic emission monitoring system, and is used to synchronously control stress loading and signal monitoring, and process data to determine the preset conditions.

9. A true triaxial test apparatus for reproducing time-delayed rock eruption processes according to claim 8, characterized in that, Also includes: A high-speed camera system was configured to acquire video stream data during the experiment.

10. A true triaxial test apparatus for reproducing time-delayed rock eruption processes according to claim 8, characterized in that, The acoustic emission monitoring system is located at the bottom of the true triaxial loading mechanism, and the sensor probe of the acoustic emission monitoring system is coupled to the rock sample.

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