Rock mass post-peak rheological test method, device, electronic equipment and storage medium

Abstract

The application discloses a rock mass post-peak rheological test method and device, electronic equipment and a storage medium, relates to the technical field of rock engineering, and can improve the test precision of the post-peak rheological behavior of deep broken rock mass. The method comprises the following steps: applying a lateral constraint stress to a rock sample to a target level; in a displacement control mode, loading the rock sample in the axial direction, and calculating an initial damage variable; continuing to load the rock sample in the displacement control mode to make the rock sample pass through the peak strength, and under the condition that the axial stress relaxation of the rock sample is detected to be stable, extracting a special residual strength; keeping the target lateral constraint stress constant, determining a target unloading stress based on the special residual strength, switching the testing machine to a force control mode, and unloading the axial stress to a safety threshold range lower than the special residual strength; and in the force control mode, taking the special residual strength as a benchmark, and performing a double-path rheological test.

Description

Technical Field

[0001] This application relates to the field of rock engineering technology, and in particular to a method, apparatus, electronic device and storage medium for post-peak rheological testing of rock mass. Background Technology

[0002] With the depletion of shallow mineral resources, deep resource extraction has become the norm. Deep engineering rock masses are often situated in a complex environment characterized by high ground stress, high osmotic pressure, high temperature, and intense mining disturbance—a "three-highs-one-disturbance" environment. The surrounding rock accumulates varying degrees of initial damage before excavation. Under the combined effects of high stress differentials and the free face, the surrounding rock near the excavation face rapidly evolves into a post-peak fragmentation and fracture zone, exhibiting strong nonlinear rheological characteristics. This rheological behavior is essentially the result of the coupling of lateral constraint stress effects and structural effects. Therefore, quantifying initial damage and elucidating the time-dependent deformation patterns under post-peak unloading and compensation constraints have become key scientific issues for the long-term stability control of deep tunnels.

[0003] In related technologies, rock rheological testing techniques typically employ a split approach. Specifically, a batch of samples is first subjected to conventional compression tests to estimate peak or residual strength, and then a rheological stress level is set for another batch of samples. In terms of fracture surface reconstruction, artificially straight prefabricated joints are used to replace the actual fracture surface. In terms of test control, conventional loading methods are typically used to load the samples to a predetermined stress or deformation level before conducting rheological tests. However, there is a lack of stable control and smooth transition methods for the post-peak fragmentation state. In terms of test path, constant lateral constraint stress and axial graded loading methods are often used.

[0004] In the process of implementing the relevant technology, the applicant recognized that the relevant technology has at least the following technical problems: Stress settings based on analog estimation are prone to inaccuracy due to the large dispersion of rock masses, making it difficult to accurately reflect the true rheological response of the sample in the post-peak state. Artificially prefabricated joints cannot reproduce the true rough interlocking structure formed after post-peak failure, making it difficult to characterize the actual stress and deformation characteristics of the post-peak fractured rock mass. If the control mode is switched directly after the sample enters the post-peak residual stage, servo response lag and frictional abrupt changes can easily induce brittle instability and secondary failure of the sample, threatening equipment safety. Furthermore, a single loading path cannot simulate the excavation unloading process, making it difficult to reveal the time-dependent deformation law of the post-peak fractured rock mass under different stress paths and the critical conditions for its transformation from "stress-dominated" to "structure-dominated." Therefore, existing technologies struggle to achieve stable, realistic, and controllable rheological testing of post-peak fractured rock masses. Summary of the Invention

[0005] In view of this, this application provides a method, apparatus, electronic device and storage medium for post-peak rheological testing of rock mass. The main purpose is to solve the problems that the existing technology is difficult to achieve stable, realistic and controllable rheological testing for post-peak fractured rock mass, and difficult to accurately reveal the time deformation law under different stress paths.

[0006] According to a first aspect of this application, a post-peak rheological test method for rock mass is provided, the method comprising: Lateral constraint stress was applied to the rock sample to the target level; In displacement control mode, the rock sample is loaded along the axial direction, the elastic modulus of the linear elastic compression stage after the compaction section is extracted, and the initial damage variable is calculated based on the elastic modulus. Continue loading in the displacement control mode to make the rock sample exceed the peak strength, stop the displacement loading and let the rock sample stand still, and extract the exclusive residual strength of the rock sample when the axial stress relaxation of the rock sample is detected. Keeping the lateral constraint stress constant, after determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a safe threshold ratio range below the exclusive residual strength; In the force control mode, the rock sample is subjected to a dual-path rheological test based on the exclusive residual strength. During the execution of the dual-path rheological test, data fusion is performed by combining multi-source monitoring data before and after the test to define the critical boundary of secondary failure of the fractured rock mass. The test of the rock sample is completed when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes post-peak constant lateral constraint stress axial graded loading rheological test and post-peak constant axial stress lateral graded unloading rheological test.

[0007] According to a second aspect of this application, a post-peak rheological testing apparatus for rock masses is provided, the apparatus comprising: Lateral constraint stress application module, used to apply lateral constraint stress to rock samples to the target level; The initial damage calculation module is used to load the rock sample along the axial direction in displacement control mode, extract the elastic modulus of the linear elastic compression stage after the compaction section, and calculate the initial damage variable based on the elastic modulus. A dedicated residual strength determination module is used to continue loading the rock sample under the displacement control mode to make the rock sample exceed the peak strength, stop the displacement loading to let the rock sample stand still, and extract the dedicated residual strength of the rock sample when the axial stress of the rock sample is detected to be relaxed and stable. The mode switching module is used to keep the lateral constraint stress constant, and after determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a safe threshold ratio range lower than the exclusive residual strength. The testing module is used to perform a dual-path rheological test on the rock sample under the force control mode, based on the exclusive residual strength. During the execution of the dual-path rheological test, it combines multi-source monitoring data before and after the test to perform data fusion to define the critical boundary of secondary failure of the fractured rock mass, realize the test of the rock sample, and end the test of the rock sample when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes post-peak constant lateral constraint stress axial graded loading rheological test and post-peak constant axial stress lateral graded unloading rheological test.

[0008] According to a third aspect of this application, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described in any of the first aspects above.

[0009] According to a fourth aspect of this application, a storage medium is provided that stores a computer program thereon, which, when executed by a processor, implements the steps of the method described in any one of the first aspects above.

[0010] By employing the aforementioned technical solutions, this application provides a method and apparatus for post-peak rheological testing of rock masses. This method overcomes the problem of inaccurate stress level setting caused by the large discreteness of rock masses in traditional separate testing by sequentially performing initial damage calibration, in-situ reconstruction of the actual post-peak fracture surface, and extraction of specific residual strength on the same rock sample. Furthermore, by determining the target unloading stress based on the specific residual strength in the post-peak state and then switching to force control mode to implement unloading, the risk of brittle instability and secondary damage caused by servo response lag and frictional abrupt changes is reduced, ensuring equipment safety and testing continuity. Additionally, a dual-path rheological test is conducted using the measured residual strength as a benchmark, involving axial graded loading of constant lateral constraint stress and lateral graded unloading of constant axial stress after the peak. This can simulate excavation unloading and stress concentration conditions respectively. Combined with multi-source monitoring data fusion analysis, it provides a basis for determining the critical conditions for the transformation of fractured rock masses from stress-dominated compaction stability to structure-dominated slip failure, thereby significantly improving the testing accuracy and engineering applicability of post-peak rheological behavior in deep fractured rock masses.

[0011] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0012] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This paper illustrates a schematic flowchart of a post-peak rheological test method for rock mass provided in an embodiment of this application. Figure 2 This paper presents a schematic diagram of another post-peak rheological test method for rock mass provided in an embodiment of this application. Figure 3 This paper shows a schematic diagram of the structure of a rock mass post-peak rheological testing device provided in an embodiment of this application; Figure 4 A schematic diagram of the device structure of an electronic device provided in an embodiment of this application is shown. Detailed Implementation

[0013] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0014] This application provides a method for post-peak rheological testing of rock mass, such as... Figure 1 As shown, the method includes: S10: Apply lateral constraint stress to the rock sample to the target level; in displacement control mode, load the rock sample along the axial direction, extract the elastic modulus of the linear elastic compression stage after the compaction section, and calculate the initial damage variable based on the elastic modulus.

[0015] In this embodiment of the application, rock samples taken from the deep engineering site are placed in a triaxial testing machine beforehand. The rock samples can be standard cylindrical or cubic samples. Then, a set hydrostatic pressure is applied to simulate the lateral constraint stress environment at the target burial depth. In the displacement control mode, the rock samples are loaded axially at a low rate such as 0.01 to 0.02 mm / min, so that the rock samples are subjected to axial stress and axial compressive deformation. The displacement control mode applies the load by controlling the movement rate of the loading piston, rather than directly controlling the magnitude of the force.

[0016] In the initial loading stage, the rock sample undergoes a micro-fracture compaction phase before entering the linear elastic deformation stage. At this point, it is necessary to extract the elastic modulus of the linear elastic compression stage after the compaction phase. Based on the elastic modulus reduction principle, this elastic modulus is compared with the reference elastic modulus of intact, undisturbed rock in the same region to determine the initial damage variable. The initial damage variable characterizes the degree to which the implicit initial damage accumulated during core sampling, processing, or in-situ excavation disturbance weakens the initial stiffness of the rock sample.

[0017] In this way, by integrating the quantitative evaluation of initial damage directly into the testing process of the same rock sample through the above process, the cognitive bias of traditional methods that regard seemingly intact rock cores as undamaged rocks can be eliminated. This provides a unique damage benchmark for each rock sample, thus laying the foundation for the accurate setting of subsequent rheological stress levels. For example, a standard cylindrical sample processed from deep hard rock in a mining area is loaded at a displacement rate of 0.02 mm / min under a target lateral constraint stress of 15 MPa. The linear elastic modulus is measured to be 32 GPa. Assuming that the benchmark elastic modulus of intact, undisturbed rock in the same region as the rock sample is 40 GPa, the initial damage variable calculated according to the elastic modulus reduction relationship is 0.2, indicating that the rock sample has already experienced 20% stiffness degradation.

[0018] S20: Continue loading in displacement control mode to allow the rock sample to pass the peak strength, stop displacement loading and allow the rock sample to stand still, and extract the exclusive residual strength of the rock sample when the axial stress of the rock sample is detected to be relaxed and stable.

[0019] In this embodiment, after calculating the initial damage variables, the displacement control mode and loading rate are kept constant, and the axial piston continues to advance, causing the axial stress on the rock sample to continuously increase, allowing the rock sample to surpass the peak strength and enter the post-peak softening stage. As the rock sample surpasses the peak strength, its internal fractures continue to develop, and the stress-strain curve enters the post-peak softening stage, with the axial stress gradually decreasing as deformation increases. When the curve becomes flat, indicating a significant slowdown in the stress drop rate, this embodiment stops the active loading of axial displacement and maintains the current deformation state of the rock sample, allowing the rock sample to remain stationary under approximately constant deformation conditions for a period of time, for example, more than 20 minutes. During the stationary period, the internal stress of the rock sample relaxes and redistributes, and the axial stress naturally adjusts and gradually tends to a stable value. When the rate of change of axial stress is detected to be close to zero, it indicates that stress relaxation has ended. The average axial stress within this stable stage is extracted and defined as the exclusive residual strength of the rock sample.

[0020] In this way, through the above process, a macroscopic fracture surface with a natural rough undulation and real spatial interlocking characteristics is formed in situ under lateral constraint stress, which helps to reduce the distortion in physical morphology of artificially prefabricated straight joints. At the same time, the obtained residual strength is a unique benchmark value of the rock sample itself, which can eliminate the dispersion error caused by analogy estimation using rock samples from other groups. Continuing with the above example, assuming that the rock sample from a certain mining area stopped displacement loading during the post-peak softening stage and was left to stand for 25 minutes, the axial stress dropped from the peak value of 210 MPa and stabilized at 48 MPa, then 48 MPa is the unique residual strength of the rock sample.

[0021] S30: Keep the lateral constraint stress constant. After determining the target unloading stress based on the exclusive residual strength, switch the testing machine to force control mode and unload the axial stress to a safe threshold range below the exclusive residual strength.

[0022] In this embodiment, after determining the specific residual strength, without changing the current lateral constraint stress setting, a safety threshold range lower than the specific residual strength is first determined. This safety threshold range is preferably 80%–90% of the specific residual strength, for example, set to 85%, meaning the target unloading stress is 0.85 times the specific residual strength. Subsequently, after determining the target unloading stress based on the specific residual strength, the testing machine is switched to force control mode, and the axial stress is actively and smoothly unloaded to the safety threshold range. At this point, the rock sample is in a subcritical safety zone far from the limit equilibrium state. Then, the axial and radial deformation of the rock sample under this low stress level is continuously monitored. When the changes in axial and radial deformation of the rock sample are detected to be less than the instrument accuracy threshold for several consecutive minutes, the rock sample is determined to be in a stable subcritical state. In this state, the testing machine maintains the force control mode, providing stable control conditions for subsequent rheological testing.

[0023] In this way, by constructing a mechanical buffer through active unloading during the above process, secondary brittle instability and eccentric impact loads induced by servo system response lag or sudden drop in frictional force on the fracture surface when directly switching control modes in the danger zone after the peak can be avoided. This ensures the safety of expensive high-pressure sensors and rigid indenters, and creates stable control conditions for subsequent rheological tests. For example, based on the exclusive residual strength of 48 MPa, the target lateral constraint stress is kept constant at 15 MPa. After determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to 85% of 48 MPa, i.e., 40.8 MPa. After monitoring for 5 minutes, the sample deformation tends to stabilize. Subsequently, subsequent rheological tests are carried out under this force control state, during which no stress abrupt changes or abnormal sounds occur.

[0024] S40: In force control mode, based on the exclusive residual strength, a dual-path rheological test is performed on the rock sample. During the dual-path rheological test, data fusion is performed by combining multi-source monitoring data before and after the test to define the critical boundary of secondary failure of the fractured rock mass. The test of the rock sample is completed when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes post-peak constant lateral constraint stress axial grade loading rheological test and post-peak constant axial stress lateral grade unloading rheological test.

[0025] In this embodiment, after successfully switching to force control mode, the previously measured residual strength is used as the absolute reference benchmark, and two comparative rheological test paths are performed on the same rock sample. The first path is a post-peak constant lateral constraint stress axial graded loading rheological test, and the second path is a post-peak constant axial stress lateral graded unloading rheological test. Multi-source monitoring data is collected, including but not limited to axial strain, radial strain, acoustic emission signals, and pre- and post-test industrial CT (Computed Tomography) 3D reconstructed images. Data fusion analysis is performed by combining the online monitoring data collected during the test and the monitoring data before and after the test. For example, a curve showing the relationship between steady-state creep rate and stress level is plotted, and stress inflection points where radial or axial strain abnormally accelerate are identified. This quantitatively defines the critical lateral constraint stress value or critical stress threshold at which the fractured rock mass transforms from "stress-dominated" to "structure-dominated."

[0026] Thus, through the above dual-path comparison test, the time-dependent deformation characteristics of deep surrounding rock under different excavation disturbance conditions can be revealed. The fusion analysis of online monitoring data collected during the test and monitoring data before and after the test can provide a basis for determining the minimum support resistance required to prevent secondary time-dependent instability of fractured rock mass, and provide a reference for the excavation compensation and long-term stability design of deep roadways.

[0027] In this embodiment of the application, optionally, in the displacement control mode, the rock sample is loaded along the axial direction, the elastic modulus of the linear elastic compression stage after the compaction section is extracted, and the initial damage variable is calculated based on the elastic modulus, including: applying an initial hydrostatic pressure to the rock sample placed in the triaxial pressure chamber to the target lateral constraint stress. In this system, acoustic emission probes are coupled to the walls of the triaxial pressure chamber or both ends of the rock sample. In displacement control mode, the rock sample is loaded at a preset low rate to subject it to axial stress. In the initial stage of loading, the elastic modulus of the rock sample during the linear elastic compression stage after passing through the compaction section is extracted. Simultaneously, the reference elastic modulus of the intact, undisturbed rock in the same region as the rock sample was obtained. The initial damage variable is obtained by calculating the elastic modulus and the reference elastic modulus using the following formula. Formula 1: , in, This represents the initial damage variable obtained from the calculation.

[0028] In this embodiment, standard rock samples, either cored from the engineering site or processed from raw blocks, are placed in a triaxial pressure chamber beforehand. The rock samples can be cylindrical or cubic, and high-precision axial and radial displacement sensors (LVDT, Linear Variable Differential Transformer) are used to monitor the axial and radial deformation of the samples in real time during the loading process. Simultaneously, acoustic emission (AE) probes are coupled to the chamber wall of the triaxial pressure chamber or both ends of the rock samples to record the acoustic background noise and microcrack evolution characteristics during the initial loading phase. Subsequently, an initial hydrostatic pressure is applied to the pressure chamber until the target lateral constraint stress is reached. Target lateral constraint stress It represents the lateral constraint stress of the simulated deep rock mass in the geostress environment. Its value can be set according to the measured geostress at the engineering site or the simulated burial depth, so that the rock sample is in an initial stress state of isotropic pressure.

[0029] Under this target lateral constraint stress condition, the system switches to displacement control mode. The load is applied by controlling the movement rate of the loading piston, rather than directly controlling the magnitude of the force. This allows the rock sample to be loaded at a preset low rate, such as 0.01–0.02 mm / min, thus subjecting the rock sample to axial stress. axial stress This represents the maximum principal stress applied along the axial direction of the specimen, or deviatoric stress. This is the net driving force that causes shear failure in the rock sample. In this embodiment, during the initial loading stage, the rock sample first undergoes a microcrack compaction stage, followed by a linear elastic deformation stage. At this time, this embodiment extracts the slope of the stress-strain curve during the linear elastic stage and records it as the initial compressive elastic modulus. Initial compressive modulus This reflects the stiffness of the rock sample under initial loading and without extensive plastic deformation. Furthermore, in this embodiment, a baseline elastic modulus is obtained by drilling completely intact, undisturbed rock cores from the same area and conducting standard compression tests. Reference elastic modulus This represents the inherent elastic stiffness of the rock in the undisturbed state. Finally, based on the principle of elastic modulus degradation, the initial damage variable is calculated using Equation 1. : Formula 1: , Among them, the initial damage variable Dimensionless, with values ​​between 0 and 1, it is used to quantitatively characterize the degree to which latent initial damage accumulated in a specimen due to core sampling, processing, or in-situ excavation disturbance weakens its initial stiffness. The larger the value, the more severe the initial damage.

[0030] Thus, in the above process, through the synchronous deployment of multi-source sensors and the quantitative calculation of elastic modulus reduction, not only is a unique damage benchmark provided for each rock sample, eliminating the cognitive bias of equating seemingly intact rock cores with undamaged rocks in traditional methods, but also the AE background noise at the initial stage of loading is recorded, establishing acoustic baseline data for subsequent early warning of fracture and instability.

[0031] The above process will be illustrated below with reference to two typical embodiments: Example 1, based on conventional triaxial conditions, specifically assesses the time-dependent stability of the sidewalls of a deep, straight-walled, semi-circular arch roadway in a certain mining area. Deep hard rock samples taken from this mining area are processed into standard cylindrical specimens, with a diameter of 50 mm and a height of 100 mm. In a conventional triaxial testing machine, initial hydrostatic pressure is applied until the target lateral constraint stress is reached. To simulate the geostress level at a specific burial depth in the mining area, a displacement-controlled mode was then employed, applying a low-rate axial loading (0.02 mm / min) to subject the rock sample to axial stress. In the initial stage of loading, the elastic modulus of the rock sample during the linear elastic compression stage after the compaction section is extracted and recorded as the initial compressive elastic modulus. Meanwhile, the reference elastic modulus of intact, undisturbed rock in the same region as the rock sample is known. Substituting into Formula 1, the initial damage variable of the rock sample was calculated to be 0.2, indicating that the rock sample had accumulated about 20% stiffness degradation during core taking and processing.

[0032] Example 2, based on true triaxial conditions, specifically targets deep, high-level tectonic stress zones. Hard rock blocks are processed into standard 50 mm × 50 mm × 50 mm cube rock specimens, ensuring that the perpendicularity error between adjacent end faces is less than 0.02 mm and the parallelism error between relative end faces is less than 0.02 mm. Furthermore, to eliminate the interference of true triaxial rigid indenter end-face friction effect on the specimen's fracture mode, molybdenum disulfide grease is evenly applied to the four sides of the rock specimen, and a polytetrafluoroethylene (PTFE) film is used for double friction reduction. The four sides correspond to the central principal stress. With minimum principal stress Loading end face. Furthermore, a miniature triaxial displacement gauge (LVDT) needs to be installed at the free corner of the rock specimen not completely obscured by the indenter or at a pre-reserved channel inside the indenter to independently collect deformation data of the specimen in the X, Y, and Z principal stress directions. Simultaneously, multiple broadband acoustic emission sensors are uniformly attached to the triaxial chamber wall or the corners of the specimen to achieve three-dimensional spatial positioning and feature capture of internal microcracks during aging deformation. Relying on a true triaxial testing system with three-way independent servo control, preload is first applied synchronously in the three principal stress directions, and then the minimum principal stress is increased at a force-controlled rate of 0.1 MPa / s. Applying 15 MPa, intermediate principal stress A pressure of 25 MPa was applied to simulate high-level structural deviatoric stress; subsequently, along the maximum principal stress... The loading was performed using a displacement control mode of 0.02 mm / min. In the initial stage of loading, the elastic modulus of the rock sample during the linear elastic compression stage after the compaction section was extracted and recorded as the initial compressive elastic modulus. And obtain the reference elastic modulus of the intact, undisturbed rock in the same region as the rock sample. By comparison, the initial damage variable of the rock sample was calculated using Formula 1. .

[0033] In this embodiment, optionally, the rock sample is loaded in displacement control mode until it surpasses the peak strength, then the displacement loading is stopped and the rock sample is allowed to rest. When the axial stress of the rock sample is detected to have relaxed and stabilized, the specific residual strength of the rock sample is extracted. This includes: maintaining the displacement control mode unchanged, continuing to advance the axial piston at a constant speed until the rock sample surpasses the peak strength under lateral constraint stress; continuously monitoring the stress-deformation relationship curve of the rock sample, and stopping the displacement loading and allowing the rock sample to rest when the stress-deformation relationship curve enters the post-peak softening stage and tends to stabilize; recording the resting time of the rock sample during the resting process, and determining that the axial stress of the rock sample has relaxed and stabilized when the resting time reaches a preset resting time, and extracting the current stable average axial stress of the rock sample, defining the average axial stress as the specific residual strength of the rock sample. During the static setting process, the axial stress of the rock sample is adjusted and relaxed, and the rate of change of the axial stress of the rock sample tends to zero.

[0034] In this embodiment, after the initial damage variable calibration is completed, the displacement control mode needs to be kept unchanged, and the axial piston needs to be advanced at the same low rate to keep the rock sample under lateral constraint stress. Under lateral constraints created by the combined action of axial stress and lateral stress, the load is gradually increased until it exceeds the peak strength. As the deviatoric stress surpasses the peak value, one or more macroscopic shear fracture surfaces begin to emerge and develop within the rock specimen. This process occurs in situ under real high lateral constraints, resulting in fracture surfaces with naturally rough, undulating morphology and genuine spatial interlocking characteristics, significantly different from artificially cut, straight, pre-formed joints. During this process, the test system continuously monitors the stress-deformation curve of the specimen. When the curve is observed to enter the post-peak softening stage, i.e., the axial stress gradually decreases with increasing deformation and tends to stabilize (i.e., the stress drop rate slows significantly and the curve slope approaches zero), the active loading of axial displacement is immediately stopped, but the current approximately constant deformation state of the rock specimen is maintained, allowing the specimen to remain stationary in the pressure chamber. During this stationary period, the axial stress of the rock specimen undergoes natural adjustment and relaxation, and local stress redistribution occurs on the micro-protrusions on the internal fracture surfaces.

[0035] In this embodiment, a settling time is preset, for example, more than 20 minutes. When the settling time reaches the preset value and the axial stress change rate approaches zero, the stress relaxation is considered stable. At this time, the average axial stress during the current stable stage of the rock sample is extracted and defined as the exclusive residual strength of the rock sample. The exclusive residual strength represents the long-term stable stress level that the rock sample can still withstand after experiencing post-peak failure and forming a macroscopic fracture surface, and is the absolute benchmark for the stress level of subsequent rheological tests. In this way, through the above process, on the one hand, the macroscopic fracture surface formed by in-situ compression under lateral constraint truly restores the fragmentation and fracturing structure of deep hard rock after excavation disturbance, which can reduce the distortion of the physical morphology of artificial prefabricated joints; on the other hand, the exclusive residual strength obtained by settling and relaxing on the same sample can eliminate the rock mass dispersion error caused by the use of other sets of samples for analog estimation in traditional separate tests, and provide a reliable basis for the accurate setting of subsequent rheological stress levels.

[0036] The above process will be further illustrated below with reference to two typical embodiments mentioned above: Example 1 is based on conventional triaxial conditions and is a test conducted on deep hard rock in a mining area. Specifically, after the initial damage calibration was completed, the displacement control mode and loading rate of 0.02 mm / min were maintained, and the axial piston was continued to advance. Assuming the peak strength of the rock sample is approximately 210 MPa, after the axial stress exceeds the peak strength, the stress-strain curve enters the post-peak softening phase, and the axial stress gradually decreases. When the curve flattens, the displacement loading is immediately stopped, allowing the sample to rest for at least 20 minutes under approximately constant deformation. During the resting period, the axial stress further relaxes from approximately 52 MPa after the initial drop and eventually stabilizes at 48 MPa, with the stress change rate approaching zero. At this point, the average stress of 48 MPa within this stable phase is extracted as the exclusive residual strength of the rock sample. Subsequent graded unconstrained lateral stress-rheological tests are all set based on this 48 MPa.

[0037] Example 2 is based on true triaxial conditions and is conducted on a deep, high-level structural stress zone. Specifically, after initial damage calibration, the test continues along... Loading the rock sample with the same displacement rate in the same direction causes it to exceed the peak strength under a triaxial unequal compressive stress field, resulting in the in-situ formation of a complex shear fracture zone controlled by a true three-dimensional stress field. (To be continued) The stress-strain curve in the direction enters the softening phase after the peak and tends to stabilize, then stops. Displacement loading in the direction, while maintaining and Under constant conditions that maintain the deformation constraint of the specimen, allow it to stand for 30 minutes. When the rate of change of axial stress approaches zero, the average axial stress during the steady-state phase at this point is extracted and defined as the exclusive residual strength of the specimen under true three-dimensional stress. This provides an accurate stress reference for subsequent minimum principal stress graded unloading rheological tests.

[0038] Optionally, in this embodiment, keeping the lateral constraint stress constant, after determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a safe threshold ratio range lower than the exclusive residual strength. This includes: determining a preset safe threshold ratio range; calculating a safe stress range based on the exclusive residual strength and the safe threshold ratio range; and determining the target unloading stress with reference to the safe stress range; keeping the lateral constraint stress constant, switching the testing machine to force control mode, and unloading the axial stress to the target unloading stress so that the axial stress decreases to within the safe stress range.

[0039] In this embodiment, after extracting the specific residual strength of the rock sample, a preset safety threshold ratio range needs to be determined first. This safety threshold ratio range is optimized based on numerous pre-tests and equipment response characteristics. In this embodiment, it is taken as 80% to 90% of the specific residual strength, for example, a recommended value is 85%. Based on this, the target unloading stress value is calculated, such as 0.85 times the specific residual strength. Subsequently, the target lateral constraint stress set in the current test is maintained. With the test machine switched to force control mode, the axial stress is actively and smoothly unloaded, gradually reducing it from the current residual strength level to within the pre-calculated target unloading stress, for example, to 85% of the specific residual strength. This unloading operation utilizes the local release of elastic potential energy within the fractured rock block and the weak self-locking effect between micro-protrusions on the macroscopic fracture surface to actively construct a subcritical safety buffer zone far from the ultimate equilibrium state.

[0040] At this subcritical stress level, the testing system continuously monitors the axial and radial deformation of the specimen, specifically through surface-mounted high-precision LVDT displacement sensors. When the deformation in both directions is detected to be less than the instrument's accuracy threshold for several consecutive minutes (e.g., the axial and radial deformation rates are both below 0.001 mm / min), it is determined that the rock specimen deformation has completely stabilized and the specimen structure has moved out of the danger zone of post-peak instability. At this point, the testing machine continues to maintain force control mode, providing a stable control basis for subsequent rheological testing.

[0041] In this way, by actively unloading to a safe threshold range during the above process, the rebound effect and secondary brittle instability induced by the response lag of the electro-hydraulic servo system and the sudden change in friction force on the fracture surface in the traditional method can be completely cut off from the physical operation. This can eliminate the risk of huge eccentric impact load generated at the moment of mode switching, thereby protecting the expensive high-pressure sensor and rigid pressure head in all aspects and providing a stable control environment for subsequent rheological testing.

[0042] The above process will be further illustrated below with reference to two typical embodiments mentioned above: Example 1 is based on conventional triaxial conditions and is a test conducted on deep hard rock in a certain mining area. The specific residual strength of the cylindrical sample has been measured in the preceding steps. The safety threshold ratio is determined to be 85% of the residual strength, and the target unloading stress value is calculated to be 40.8 MPa. Lateral constraint stress is maintained. The axial stress was steadily unloaded from 48 MPa to 40.8 MPa after the testing machine was switched to force control mode. At this subcritical stress level, the axial and radial deformation of the specimen was continuously monitored. After approximately 5 minutes, the rate of displacement change in both directions decreased to below 0.0005 mm / min, confirming deformation stability. Subsequently, while maintaining the force control mode, subsequent staged unloading lateral constraint stress rheological tests were conducted, during which no stress abrupt changes or abnormal impacts occurred.

[0043] Example 2, based on true triaxial conditions and testing in a deep, high-level structural stress zone, involved post-peak fracture and residual strength extraction of a 50 mm × 50 mm × 50 mm cubic specimen on a true triaxial testing machine. The specific residual strength under true three-dimensional stress was obtained, assumed to be 65 MPa. The intermediate principal stress was maintained. Minimum principal stress Constant and unchanging, in the future After the directional loading system switches to force control mode, the maximum principal stress is smoothly unloaded to a subcritical safety state, with the target value set at 0.85 times the exclusive residual strength. The test system will continuously monitor for 10 minutes to confirm that the displacement changes of the specimen in the three principal stress directions (X, Y, and Z) are all less than the instrument accuracy threshold. If the displacement change rate in each direction is less than 0.001 mm / min, subsequent minimum principal stress graded unloading rheological tests will continue under this force control state.

[0044] Optionally, in the force control mode, using the specific residual strength as a benchmark, a dual-path rheological test is performed on the rock sample. During the dual-path rheological test, data fusion is performed by combining multi-source monitoring data before and after the test to define the critical boundary for secondary failure of the fractured rock mass. This includes: in the force control mode, using the specific residual strength as a reference benchmark, performing two rheological tests included in the dual-path rheological test on the rock sample, wherein the dual-path rheological test includes a post-peak constant lateral constraint stress axial graded loading rheological test and a post-peak constant axial stress lateral graded unloading rheological test. The post-peak constant lateral constraint stress axial graded loading rheological test is an axial stress incrementing rheological test that maintains a constant lateral constraint stress and gradually increases the axial stress from an initial value lower than the exclusive residual strength. The post-peak constant axial stress lateral graded unloading rheological test is a lateral constraint stress decrementing rheological test that maintains a constant current axial stress and gradually decreases the lateral constraint stress. Throughout the dual-path rheological test, data fusion analysis is performed by combining multi-source monitoring data before and after the test to determine the critical boundary. The multi-source monitoring data includes steady-state creep rate, radial strain, acoustic emission signal, and three-dimensional reconstructed image.

[0045] In this embodiment, after successfully switching to the force control mode, using the previously extracted proprietary residual strength as a reference benchmark, two comparative tests in the dual-path rheological test are performed on the same rock sample. The first test is a post-peak constant lateral constraint stress axial graded loading rheological test, which keeps the lateral constraint stress constant and gradually increases the axial stress from a starting value lower than the proprietary residual strength, holding each stress level for a sufficient time to simulate the axial load increase caused by adjacent mining area excavation or stress concentration. The second test is a post-peak constant axial stress lateral graded unloading rheological test, which keeps the current axial stress absolutely constant and gradually decreases the lateral constraint stress downwards, holding each level for the same duration to simulate the radial unloading or support resistance reduction caused by deep tunnel excavation.

[0046] Throughout the aforementioned dual-path rheological test, the experimental system integrates online monitoring data collected during the test with monitoring data before and after the test for data fusion analysis. This multi-source monitoring data includes, but is not limited to, steady-state creep rate, radial strain, acoustic emission signals, and 3D reconstructed images before and after the test under various stress levels. The steady-state creep rate characterizes the change in strain per unit time and is used to determine the creep stage; radial strain reflects the lateral expansion characteristics of the sample; acoustic emission signals involve ringing counts and b-value evolution, used to capture internal microcrack activity; and the 3D reconstructed images can be industrial CT scan results used to observe the evolution of the fracture network. By fusing and analyzing this multi-source data, such as plotting the relationship between steady-state creep rate and stress level, and identifying inflection points where radial strain accelerates abnormally or acoustic emission signals increase sharply, the critical boundary for the transformation of fractured rock mass from a stress-dominated compaction stability state to a structure-dominated accelerated slip failure state can be quantitatively defined, such as the critical lateral constraint stress threshold or critical stress value, thus completing the test of the rock sample.

[0047] In this way, through the above process, the dual-path test realistically reproduces the time-dependent deformation mechanism of deep surrounding rock under different excavation disturbance conditions, overcoming the limitation that the traditional single loading path cannot simulate the unloading process. Moreover, by combining the online monitoring data collected during the test with the monitoring data before and after the test for integrated analysis, it can provide a basis for determining the minimum support resistance required to prevent secondary time-dependent instability of fractured rock mass, and provide a direct mechanical basis for the excavation compensation and long-term stability design of deep roadways.

[0048] In this embodiment, optionally, using the specific residual strength as a reference benchmark, the rock sample is subjected to two rheological tests included in the dual-path rheological test, including: when performing the post-peak constant lateral constraint stress axial graded loading rheological test, the lateral constraint stress is kept constant, a preset loading graded strategy is determined, and the axial stress is applied upward step by step according to the loading graded strategy, wherein the loading graded strategy is used to limit the holding time of each stress level to not less than a preset duration threshold, and the deformation data of the rock sample is continuously collected after each loading, and when it is determined that the deformation of the rock sample tends to stabilize, the next loading test is continued; when performing the post-peak constant axial stress lateral graded unloading rheological test, the current axial stress is kept constant, a preset unloading graded strategy is determined, and the lateral constraint stress is unloaded downward step by step according to the unloading graded strategy, wherein the unloading graded strategy is used to limit the holding time of each stress level to not less than the duration threshold.

[0049] In this embodiment, for the post-peak constant lateral constraint stress axial graded loading rheological test, to maintain a constant target lateral constraint stress, a preset loading graded strategy is first determined, using a subcritical safety starting point, such as 0.85 times the specific residual strength, as the initial stress, and then increasing the load level progressively upwards according to the loading graded strategy. In this embodiment, the loading graded strategy can be set to 0.90 times, 0.95 times, 0.975 times the specific residual strength, etc. The holding time of each stress level is not less than a preset duration threshold, for example, the preset duration threshold can be 8 hours, and deformation data of the rock sample is continuously collected after each loading level. The next loading level test can only continue when the deformation of the rock sample tends to stabilize, for example, when the difference in strain increment between adjacent time periods is less than a set threshold or the strain change rate is less than a preset threshold. This test path aims to simulate the axial load increase condition caused by adjacent mining area tunneling or stress concentration. In practical applications, during post-peak constant lateral constraint axial graded loading rheological tests, the stress gradually increases with loading time during the initial loading and failure stage. Subsequently, the specimen experiences a primary failure, causing a sudden drop in stress, entering the post-peak stress adjustment stage. Afterward, the stress gradually stabilizes, entering the residual stress stabilization stage, at which point a fractured rock mass with multiple loading fracture surfaces forms inside the specimen. Furthermore, in graded loading creep tests, the axial strain increases stepwise with time, and the strain rate decreases from fast to slow during each loading stage, exhibiting typical decaying creep characteristics.

[0050] For post-peak constant axial stress lateral graded unloading rheological testing, the current axial stress needs to be kept absolutely constant, specifically fixed at a subcritical safety value, such as 0.85 times the specific residual strength. A preset unloading graded strategy is determined, and the lateral constraint stress is gradually reduced downward according to this strategy. The holding time of each stress level is also not less than a preset duration threshold. The path of post-peak constant axial stress lateral graded unloading rheological testing aims to accurately reproduce the unloading and support resistance aging conditions of deep excavation. In practical application, in post-peak constant axial stress lateral graded unloading rheological testing, the stress first rises rapidly to the peak value, then enters the graded unloading stage. Each stress level is kept constant for a period of time before decreasing stepwise, forming multiple plateaus and steep drop sections, reflecting the stepwise unloading process under post-peak stress control. Under each constant stress level, the axial strain gradually increases with time. At the moment of stress unloading, the axial strain exhibits instantaneous elastic recovery, and then continues to creep under the new stress level, showing an overall stepwise upward trend. Radial strain continuously increases during each load holding period, and its increment is usually greater than that of axial strain, reflecting a significant expansion phenomenon. During unloading, instantaneous rebound also occurs, but the accumulation of radial strain is more significant, ultimately exhibiting radial deformation that continues to expand over time. Actual testing shows that in the initial unloading stage, the rock mass is strongly laterally constrained, limiting micro-protrusion shear and microcrack propagation. The samples mainly exhibit decelerating creep and low-rate steady-state creep, at which point the rock mass mechanical behavior is "stress-dominated," with a significant compaction effect. As the lateral constraint stress gradually decreases, when the lateral constraint stress drops to a certain critical threshold, such as 8.75 MPa, the radial strain exhibits significant anomalous accelerated expansion, and the acoustic emission signal increases sharply. At this point, the sample's mechanical behavior shifts to "structure-dominated," with accelerated aging slip on the macroscopic fracture surface leading to eventual failure. This critical lateral constraint stress threshold reflects the minimum support resistance required to maintain the long-term stability of the fractured surrounding rock, thus providing direct mechanical basis for on-site excavation compensation and anchor-mesh cable support design.

[0051] The above describes the detailed process and examples of the two path tests. It should be noted that in actual applications, multiple sets of specimens with different initial constant lateral constraint stresses can be set up to conduct comparative tests in order to evaluate the long-term effectiveness of excavation compensation at different burial depths.

[0052] Through the comparative tests of the aforementioned dual paths, combined with multi-source data such as synchronously acquired macroscopic creep curves and acoustic emission, the critical boundary of the transformation of fractured rock mass from a "stress-dominated" compaction stability state to a "structure-dominated" accelerated slip failure state can be quantitatively defined, revealing the complex coupling mechanism of structural and stress effects in large-scale deformation over time. Furthermore, the dual-path tests simulated two typical engineering conditions: stress concentration and excavation unloading. This overcomes the limitation of traditional single-loading paths in simulating the unloading process. By setting clear holding times and stability criteria, the tests ensure the full development of the rheological response at each stage, providing a reliable experimental data foundation for accurately determining the critical boundary.

[0053] In this embodiment of the application, optionally, data fusion analysis is performed by combining multi-source monitoring data before and after the test to determine the critical boundary, including: drawing a first nonlinear relationship curve based on the steady-state creep rate and the corresponding stress level, and drawing a second nonlinear relationship curve based on the change of radial strain with lateral constraint stress or axial stress; combining the ringing count and b-value evolution characteristics of the acoustic emission signal and the distribution pattern of the fracture network in the three-dimensional reconstruction image, identifying the stress inflection point where the radial strain or axial strain is abnormally accelerated in the first nonlinear relationship curve and the second nonlinear relationship curve, and determining the stress value or lateral constraint stress value corresponding to the stress inflection point as the critical boundary for secondary failure of the fractured rock mass.

[0054] In this embodiment, during the entire process of dual-path rheological testing, it is necessary to collect data on the strain variation of the rock sample over time at various stress levels, and extract the steady-state creep rate at each stress level accordingly. steady-state creep rate This represents the change in strain of a rock sample per unit time, reflecting the deformation rate during the creep stage. Its unit is typically 1. or Simultaneously, the aging expansion characteristics of radial strain are extracted. Radial strain reflects the expansion deformation of the specimen under changes in lateral constraint, and expansion characteristics refer to the critical behavior of volume shifting from compression to expansion. In this embodiment, a first nonlinear relationship curve is plotted based on the steady-state creep rate and the corresponding stress level; simultaneously, a second nonlinear relationship curve is plotted based on the change in radial strain with lateral constraint stress or axial stress.

[0055] Based on this, acoustic emission (AE) signals are acquired synchronously, and ring count and b-value evolution features are extracted based on the acquired AE signals. The b-value is the slope parameter in the relationship between the amplitude and frequency of acoustic emission events. A decrease in the b-value usually indicates a precursor to large-scale rupture. In addition, the distribution morphology of the fracture network in the three-dimensional reconstructed images obtained from industrial CT scans before and after the experiment is also acquired.

[0056] Next, these multi-source data are fused and analyzed. Specifically, stress inflection points where radial or axial strain accelerates abnormally are identified in the first and second nonlinear relationship curves. For example, the radial strain curve changes from flat to steep, and the steady-state creep rate suddenly deviates from the linear trend. The stress value corresponding to the stress inflection point, such as the axial stress value, or the lateral constraint stress value, such as the lateral constraint stress threshold, is determined as the critical boundary for secondary failure of the fractured rock mass.

[0057] In this way, by integrating macroscopic mechanical curves with microscopic acoustic and imaging information, we can not only accurately determine the long-term strength threshold of fractured rock masses and the critical compensating lateral constraint stress to prevent time-dependent slip, but also identify the physical mechanism of the rheological acceleration stage at the microscopic level. That is, we can determine whether it is caused by the deterioration and shearing of rough micro-protrusions or by the initiation of secondary cracks and macroscopic slip, thus providing microscopic evidence to support the design of erosion protection and strong support for deep engineering.

[0058] In summary, the logical process of the technical solution in the embodiments of this application is as follows: Figure 2 As shown, it includes five core steps: Step S1 involves preparing the sample for multi-source monitoring and quantitatively calibrating the initial damage. Specifically, this involves extracting the elastic modulus at the initial loading stage and quantitatively calculating the latent initial damage. Step S2 involves in-situ reconstruction of the true fracture surface after the peak and extraction of residual strength, i.e., in-situ compression to induce fracture at the peak value, followed by static extraction of the sample's unique residual strength. Step S3 involves subcritical stress retreat and smooth, undisturbed switching of the control mode. Operationally, after determining the target unloading stress based on the unique residual strength, the testing machine is switched to force control mode for smooth unloading. Step S4 involves in-situ testing of multi-condition dual-path aging deformation, conducting dual-path rheological tests based on the unique residual strength, including axial graded loading and lateral graded unloading. Step S5 involves multi-source monitoring data fusion analysis and critical condition determination. The entire process is completed continuously on the same sample, achieving integrated testing from initial damage quantification, post-peak fracture reconstruction, safe mode switching, dual-path rheological testing to critical boundary determination.

[0059] As can be seen from the above analysis of the technical solution of this application, the technical solution proposed in this application extracts the linear elastic compressive modulus of the rock sample at the initial stage of axial loading and calculates the ratio with the reference elastic modulus of the intact rock in the region to calibrate the initial mechanical damage degree accumulated by the sample during core sampling or in-situ disturbance. Simultaneously, the technical solution of this application loads the sample beyond the peak strength under a set lateral constraint. After the sample enters the post-peak strain softening stage and tends to level off, the deformation state of the sample remains unchanged, and the internal stress is allowed to relax and stabilize. The axial stress at this point is then extracted as the reference residual strength for subsequent rheological tests of the sample. Furthermore, after the sample enters the post-peak residual stage, the technical solution of this application maintains a constant target lateral constraint. After determining the target unloading stress based on the measured residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a subcritical safety level lower than the measured residual strength, preferably 80% to 90% of the residual strength. Based on this, the technical solution of this application also constructs an implementation method for post-peak rheological testing of fractured rock mass based on a multi-axis servo control system. Specifically, in force control mode, a loading rheological path is constructed by maintaining constant lateral constraints while progressively increasing the maximum principal stress; and an unloading rheological path is constructed by maintaining constant maximum principal stress while progressively unloading lateral constraint stress or minimum principal stress. Finally, the technical solution of this application identifies the stress inflection point where the radial expansion strain or axial strain of the sample abnormally accelerates during progressive unloading of lateral constraints or progressive loading of maximum principal stress, and quantitatively determines the critical stress threshold or critical lateral support force for secondary aging instability failure of the post-peak fractured rock mass.

[0060] The method provided in this application overcomes the problem of inaccurate stress level setting caused by the large discreteness of rock mass in traditional separate testing by sequentially completing initial damage calibration, in-situ reconstruction of the actual fracture surface after peak, and extraction of specific residual strength on the same rock sample. It also reduces the risk of brittle instability and secondary damage caused by servo response lag and frictional mutation by determining the target unloading stress based on specific residual strength in the post-peak state and switching to force control mode to implement unloading, thus ensuring equipment safety and testing continuity. Furthermore, it conducts dual-path rheological testing based on measured residual strength, performing axial graded loading of constant lateral constraint stress after peak and lateral graded unloading of constant axial stress after peak. This can simulate excavation unloading and stress concentration conditions respectively. Combined with multi-source monitoring data fusion analysis, it provides a basis for determining the critical conditions for the transformation of fractured rock mass from stress-dominated compaction stability to structure-dominated slip failure, thereby significantly improving the testing accuracy and engineering applicability of post-peak rheological behavior of deep fractured rock mass.

[0061] Furthermore, as Figure 1 To specifically implement the method, this application provides a post-peak rheological testing device for rock masses, such as... Figure 3As shown, the device includes: a lateral constraint stress application module 301, an initial damage calculation module 302, a dedicated residual strength determination module 303, a mode switching module 304, and a testing module 305.

[0062] Lateral constraint stress application module 301 is used to apply lateral constraint stress to the rock sample to the target level; The initial damage calculation module 302 is used to load the rock sample along the axial direction in the displacement control mode, extract the elastic modulus of the linear elastic compression stage after the compaction section, and calculate the initial damage variable based on the elastic modulus. The dedicated residual strength determination module 303 is used to continue loading the rock sample in the displacement control mode to make the rock sample exceed the peak strength, stop the displacement loading to let the rock sample stand still, and extract the dedicated residual strength of the rock sample when the axial stress of the rock sample is detected to be relaxed and stable. The mode switching module 304 is used to keep the lateral constraint stress constant, and after determining the target unloading stress based on the exclusive residual strength, switch the testing machine to force control mode and unload the axial stress to a safe threshold ratio range lower than the exclusive residual strength. The testing module 305 is used to perform a dual-path rheological test on the rock sample under the force control mode, based on the exclusive residual strength. During the execution of the dual-path rheological test, it combines multi-source monitoring data before and after the test to perform data fusion to define the critical boundary of secondary failure of the fractured rock mass, realize the test of the rock sample, and end the test of the rock sample when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes a post-peak constant lateral constraint stress axial graded loading rheological test and a post-peak constant axial stress lateral graded unloading rheological test.

[0063] In a specific application scenario, the initial damage calculation module 302 is used to apply an initial hydrostatic pressure to the rock sample placed in the triaxial pressure chamber until the target lateral constraint stress is reached. Acoustic emission probes are coupled to the walls of the triaxial pressure chamber or both ends of the rock sample; in the displacement control mode, the rock sample is loaded at a preset low rate, causing the rock sample to bear axial stress. In the initial stage of loading, the elastic modulus of the rock sample during the linear elastic compression stage after passing through the compaction section is extracted. Simultaneously, the reference elastic modulus of the intact, undisturbed rock in the same region as the rock sample was obtained. The initial damage variable is obtained by calculating the elastic modulus and the reference elastic modulus using the following formula. Formula 1: , in, This represents the calculated initial damage variable.

[0064] In a specific application scenario, the dedicated residual strength determination module 303 is used to maintain the displacement control mode unchanged and continue to advance the axial piston at a constant speed, so that the rock sample exceeds the peak strength under the lateral constraint stress; continuously monitor the stress-deformation relationship curve of the rock sample, and when the stress-deformation relationship curve is detected to enter the post-peak softening stage and tend to stabilize, stop the displacement loading and let the rock sample rest; record the resting time of the rock sample during the resting process, and when the resting time is detected to reach the preset resting time, determine that the axial stress of the rock sample is relaxed and stable, and extract the current stable average axial stress of the rock sample, defining the average axial stress as the dedicated residual strength of the rock sample. During the static setting process, the axial stress of the rock sample is adjusted and relaxed, and the rate of change of the axial stress of the rock sample tends to zero.

[0065] In a specific application scenario, the mode switching module 304 is used to determine the preset safety threshold ratio range, calculate the safety stress range based on the exclusive residual strength and the safety threshold ratio range, and determine the target unloading stress by referring to the safety stress range; keep the lateral constraint stress constant, switch the testing machine to the force control mode, and unload the axial stress to the target unloading stress so that the axial stress drops to within the safety stress range.

[0066] In specific application scenarios, the testing module 305 is used to perform two rheological tests included in the dual-path rheological test on the rock sample under the force control mode, using the exclusive residual strength as a reference benchmark. The dual-path rheological test includes a post-peak constant lateral constraint stress axial graded loading rheological test and a post-peak constant axial stress lateral graded unloading rheological test. The post-peak constant lateral constraint stress axial graded loading rheological test is an axial stress increment rheological test that maintains the lateral constraint stress constant and gradually increases the axial stress from a starting value lower than the exclusive residual strength. The post-peak constant axial stress lateral graded unloading rheological test is a lateral constraint stress decrement rheological test that maintains the current axial stress constant and gradually decreases the lateral constraint stress. Throughout the dual-path rheological test, data fusion analysis is performed using multi-source monitoring data before and after the test to determine the critical boundary. The multi-source monitoring data includes steady-state creep rate, radial strain, acoustic emission signal, and three-dimensional reconstructed image.

[0067] In specific application scenarios, the test module 305 is used to maintain a constant lateral constraint stress during the post-peak constant lateral constraint stress axial graded loading rheological test, determine a preset loading graded strategy, and apply the axial stress upwards step by step according to the loading graded strategy. The loading graded strategy limits the holding time of each stress level to no less than a preset duration threshold, and continuously collects deformation data of the rock sample after each loading level. When the deformation of the rock sample is determined to be stable, the next loading test is continued. During the post-peak constant axial stress lateral graded unloading rheological test, the module maintains a constant axial stress, determines a preset unloading graded strategy, and unloads the lateral constraint stress downwards step by step according to the unloading graded strategy. The unloading graded strategy limits the holding time of each stress level to no less than the duration threshold.

[0068] In specific application scenarios, the test module 305 is used to plot a first nonlinear relationship curve based on the steady-state creep rate and the corresponding stress level, and simultaneously plot a second nonlinear relationship curve based on the change of radial strain with lateral constraint stress or axial stress. Combining the ringing count and b-value evolution characteristics of the acoustic emission signal and the distribution pattern of the fracture network in the three-dimensional reconstructed image, the module identifies stress inflection points where radial strain or axial strain is abnormally accelerated in the first and second nonlinear relationship curves, and determines the stress value or lateral constraint stress value corresponding to the stress inflection point as the critical boundary where the fractured rock mass undergoes secondary failure.

[0069] The device provided in this application overcomes the problem of inaccurate stress level setting caused by the large discreteness of rock mass in traditional separate testing by sequentially completing initial damage calibration, in-situ reconstruction of the actual fracture surface after peak, and extraction of specific residual strength on the same rock sample. It also reduces the risk of brittle instability and secondary damage caused by servo response lag and frictional mutation by determining the target unloading stress based on specific residual strength in the post-peak state and switching to force control mode to implement unloading, thus ensuring equipment safety and testing continuity. Furthermore, it conducts dual-path rheological testing based on measured residual strength, performing axial graded loading of constant lateral constraint stress after peak and lateral graded unloading of constant axial stress after peak. This can simulate excavation unloading and stress concentration conditions respectively. Combined with multi-source monitoring data fusion analysis, it provides a basis for determining the critical conditions for the transformation of fractured rock mass from stress-dominated compaction stability to structure-dominated slip failure, thereby significantly improving the testing accuracy and engineering applicability of post-peak rheological behavior of deep fractured rock mass.

[0070] It should be noted that other corresponding descriptions of the functional units involved in the rock mass post-peak rheological testing device provided in this application embodiment can be found in the following references. Figures 1 to 2 The corresponding descriptions in [the document] will not be repeated here.

[0071] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0072] The above embodiments and the technical features in the embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0073] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

[0074] In an exemplary embodiment, see Figure 4Furthermore, an electronic device is provided, comprising a bus, a processor, a memory, and a communication interface. It may also include input / output interfaces and a display device, wherein the various functional units can communicate with each other via the bus. The memory stores a computer program, and the processor executes the program stored in the memory to perform the rock mass post-peak rheological test method described in the above embodiments.

[0075] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the post-peak rheological test method for rock mass.

[0076] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented in hardware or by using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium and includes several instructions to cause an electronic device to execute the methods described in the various embodiments of this application.

[0077] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of a preferred embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing this application.

[0078] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules in the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0079] The above-disclosed embodiments are merely a few specific examples of this application. However, this application is not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of this application.

Claims

1. A post-peak rheological test method for rock mass, characterized in that, include: Lateral constraint stress was applied to the rock sample to the target level; In displacement control mode, the rock sample is loaded along the axial direction, the elastic modulus of the linear elastic compression stage after the compaction section is extracted, and the initial damage variable is calculated based on the elastic modulus. Continue loading in the displacement control mode to make the rock sample exceed the peak strength, stop the displacement loading and let the rock sample stand still, and extract the exclusive residual strength of the rock sample when the axial stress relaxation of the rock sample is detected. Keeping the lateral constraint stress constant, after determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a safe threshold ratio range below the exclusive residual strength. In the force control mode, the rock sample is subjected to a dual-path rheological test based on the exclusive residual strength. During the execution of the dual-path rheological test, data fusion is performed by combining multi-source monitoring data before and after the test to define the critical boundary of secondary failure of the fractured rock mass. The test of the rock sample is completed when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes post-peak constant lateral constraint stress axial graded loading rheological test and post-peak constant axial stress lateral graded unloading rheological test.

2. The post-peak rheological test method for rock mass according to claim 1, characterized in that, In the displacement control mode, the rock sample is loaded along the axial direction, the elastic modulus of the linear elastic compression stage after the compaction section is extracted, and the initial damage variable is calculated based on the elastic modulus, including: An initial hydrostatic pressure is applied to the rock sample placed in a triaxial pressure chamber until the target lateral constraint stress is reached. Acoustic emission probes are coupled to the walls of the triaxial pressure chamber or to both ends of the rock sample. In the displacement control mode, the rock sample is loaded at a preset low rate to subject it to axial stress. ; In the initial stage of loading, the elastic modulus of the rock sample during the linear elastic compression stage after passing through the compaction section is extracted. Simultaneously, the reference elastic modulus of the intact, undisturbed rock in the same region as the rock sample was obtained. ; The initial damage variable is obtained by calculating the elastic modulus and the reference elastic modulus using the following formula. ， in, This represents the calculated initial damage variable.

3. The post-peak rheological test method for rock mass according to claim 1, characterized in that, The process of continuing to load the rock sample under the displacement control mode until it surpasses its peak strength, stopping the displacement loading and allowing the rock sample to rest, and extracting the specific residual strength of the rock sample after detecting that the axial stress of the rock sample has relaxed and stabilized, includes: While maintaining the displacement control mode, continue to advance the axial piston at a constant speed, so that the rock sample can exceed the peak strength under the action of the lateral constraint stress; The stress-deformation relationship curve of the rock sample is continuously monitored. When the stress-deformation relationship curve is detected to enter the post-peak softening stage and tend to stabilize, the displacement loading is stopped and the rock sample is allowed to stand still. During the settling process of the rock sample, the settling time is recorded. When the settling time reaches a preset settling time, the axial stress of the rock sample is determined to be relaxed and stable. The average axial stress of the rock sample at the current stable state is extracted and defined as the exclusive residual strength of the rock sample. During the static setting process, the axial stress of the rock sample is adjusted and relaxed, and the rate of change of the axial stress of the rock sample tends to zero.

4. The method for post-peak rheological testing of rock mass according to claim 1, characterized in that, Maintaining the lateral constraint stress constant, and after determining the target unloading stress based on the specific residual strength, switching the testing machine to force control mode and unloading the axial stress to a safe threshold range below the specific residual strength, includes: A preset safety threshold ratio range is determined; based on the specific residual strength and the safety threshold ratio range, a safety stress range is calculated; and with reference to the safety stress range, the target unloading stress is determined. To maintain the lateral constraint stress constant, the testing machine is switched to the force control mode to unload the axial stress to the target unloading stress, so that the axial stress decreases to within the safe stress range.

5. The post-peak rheological test method for rock mass according to claim 1, characterized in that, In the force control mode, using the specific residual strength as a benchmark, a dual-path rheological test is performed on the rock sample. During the dual-path rheological test, data fusion is performed by combining multi-source monitoring data before and after the test to define the critical boundary for secondary failure of the fractured rock mass, including: In the force control mode, using the exclusive residual strength as a reference benchmark, the rock sample is subjected to two rheological tests included in the dual-path rheological test. The dual-path rheological test includes a post-peak constant lateral constraint stress axial graded loading rheological test and a post-peak constant axial stress lateral graded unloading rheological test. The post-peak constant lateral constraint stress axial graded loading rheological test is an axial stress increment rheological test that keeps the lateral constraint stress constant and increases the axial stress stepwise from a starting value lower than the exclusive residual strength. The post-peak constant axial stress lateral graded unloading rheological test is a lateral constraint stress decrement rheological test that keeps the current axial stress constant and decreases the lateral constraint stress stepwise. Throughout the dual-path rheological test, data fusion analysis is performed by combining the multi-source monitoring data before and after the test to determine the critical boundary. The multi-source monitoring data includes steady-state creep rate, radial strain, acoustic emission signal, and three-dimensional reconstructed image.

6. The method for post-peak rheological testing of rock mass according to claim 5, characterized in that, Using the specific residual strength as a reference, the rock sample is subjected to two rheological tests included in the dual-path rheological test, including: When performing the post-peak constant lateral constraint stress axial graded loading rheological test, the lateral constraint stress is kept constant, a preset loading graded strategy is determined, and the axial stress is applied upward step by step according to the loading graded strategy. The loading graded strategy is used to limit the holding time of each stress level to not less than a preset duration threshold, and the deformation data of the rock sample is continuously collected after each loading. When it is determined that the deformation of the rock sample tends to be stable, the next loading test is continued. When performing the post-peak constant axial stress lateral graded unloading rheological test, the current axial stress is kept constant, a preset unloading graded strategy is determined, and the lateral constraint stress is unloaded step by step downward according to the unloading graded strategy. The unloading graded strategy is used to limit the holding time of each stress level to not be less than the duration threshold.

7. The method for post-peak rheological testing of rock mass according to claim 5, characterized in that, The process of combining the multi-source monitoring data before and after the test to perform data fusion analysis to determine the critical boundary includes: Based on the steady-state creep rate and the corresponding stress level, a first nonlinear relationship curve is plotted, and a second nonlinear relationship curve is plotted based on the change of radial strain with lateral constraint stress or axial stress. Combining the ringing count and b-value evolution characteristics of the acoustic emission signal with the distribution pattern of the fracture network in the three-dimensional reconstructed image, stress inflection points where radial or axial strains accelerate abnormally are identified in the first and second nonlinear relationship curves, and the stress value or lateral constraint stress value corresponding to the stress inflection point is determined as the critical boundary where the fractured rock mass undergoes secondary failure.

8. A post-peak rheological testing device for rock masses, characterized in that, include: Lateral constraint stress application module, used to apply lateral constraint stress to rock samples to the target level; The initial damage calculation module is used to load the rock sample along the axial direction in displacement control mode, extract the elastic modulus of the linear elastic compression stage after the compaction section, and calculate the initial damage variable based on the elastic modulus. A dedicated residual strength determination module is used to continue loading the rock sample under the displacement control mode to make the rock sample exceed the peak strength, stop the displacement loading to let the rock sample stand still, and extract the dedicated residual strength of the rock sample when the axial stress of the rock sample is detected to be relaxed and stable. The mode switching module is used to keep the lateral constraint stress constant, and after determining the target unloading stress based on the exclusive residual strength, the testing machine is switched to force control mode, and the axial stress is unloaded to a safe threshold ratio range lower than the exclusive residual strength. The testing module is used to perform a dual-path rheological test on the rock sample under the force control mode, based on the exclusive residual strength. During the execution of the dual-path rheological test, it combines multi-source monitoring data before and after the test to perform data fusion to define the critical boundary of secondary failure of the fractured rock mass, realize the test of the rock sample, and end the test of the rock sample when secondary failure occurs, radial expansion or abnormal acceleration of axial deformation occurs, the preset maximum deformation / strain is reached, the preset holding time is reached, or the preset grade endpoint is reached. The dual-path rheological test includes post-peak constant lateral constraint stress axial graded loading rheological test and post-peak constant axial stress lateral graded unloading rheological test.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the rock mass post-peak rheological test method according to any one of claims 1 to 7.

10. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the rock mass post-peak rheological test method according to any one of claims 1 to 7.

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