In-situ rapid acquisition method and system for nonlinear static and dynamic parameters of surrounding rock

Abstract

This invention provides a method and system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock. The method includes: acquiring a three-dimensional apparent structural image of the surrounding rock at the tunnel excavation face or borehole wall; extracting features from cracks in the three-dimensional apparent structural image of the surrounding rock to obtain the true geometric feature parameters of the cracks; inputting the true geometric feature parameters into a modified compression-shear-slip crack propagation model, and calculating the nonlinear stress-strain response of the surrounding rock during loading and unloading, in conjunction with preset material parameters and stress loading conditions; the modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics when simulating crack bending propagation behavior; and determining the nonlinear static and dynamic parameters of the surrounding rock based on the nonlinear stress-strain response. This invention improves the accuracy and realism of nonlinear static and dynamic parameters.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics and geotechnical engineering numerical analysis technology, specifically to a method and system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock. Background Technology

[0002] In rock mass engineering construction and stability assessment of deep tunnels, mine roadways, and unconventional reservoir drilling, the nonlinear static and dynamic parameters of the surrounding rock (such as effective elastic modulus, crack initiation stress, and damage energy dissipation) are key inputs for numerical simulation, support design, and disaster early warning. Currently, these parameters are mainly obtained using the following two types of methods:

[0003] Category 1: Traditional indoor mechanical testing methods. This method involves drilling rock cores and conducting uniaxial compression, triaxial compression, and Brazilian splitting tests in a laboratory to determine the mechanical properties of the rock. While the results are relatively accurate, this method has the following inherent drawbacks: Long cycle and high cost: Core drilling, sample preparation, test loading, and data analysis are cumbersome and time-consuming, making it difficult to meet the rapid decision-making needs of engineering sites. Difficulty in reflecting in-situ conditions: The samples are removed from the engineering geological environment, altering their stress history, groundwater effects, and large-scale structural characteristics, leading to significant deviations between the test results and the actual mechanical behavior of the surrounding rock. Inability to characterize the structural characteristics of a specific excavation face: The test results are average properties of the rock mass material and cannot reflect the control effect of specific crack network structures formed on the mechanical behavior of a particular excavation face or well wall due to excavation disturbance and geological structures.

[0004] The second category: Numerical prediction methods based on compression-shear-slip crack theory models. To overcome the limitations of laboratory experiments, researchers have developed various compression-shear-slip crack models to predict the nonlinear mechanical behavior of rocks from the perspective of microscopic crack evolution. However, existing models generally have several limitations: First, their input parameters are usually based on idealized, statistically averaged crack system assumptions, such as assuming uniform crack size distribution, random orientation, or arrangement according to a fixed pattern. This idealization severs the direct connection between the model and the actual in-situ structure of the surrounding rock. Since the nonlinear mechanical behavior of the surrounding rock strongly depends on the real crack network with specific geometric shapes (length, dip angle, density) and spatial distribution, the prediction results of models based on idealized assumptions often fail to accurately reflect the actual response of the surrounding rock in a specific engineering location, and the prediction accuracy and reliability cannot be guaranteed. Second, existing models mostly use simplified wing crack propagation forms, failing to truly reflect the continuous evolution of wing cracks during growth, especially ignoring the inherent geometric relationship between wing crack length and deflection angle. This makes it difficult for models to accurately describe the actual geometric evolution path of cracks from initiation and deflection to penetration, thus limiting their ability to physically explain nonlinear deformation and damage evolution mechanisms. Furthermore, most models still rely on quasi-static loading as a basic assumption, insufficiently considering dynamic processes such as loading rate effects and stress wave disturbances, making it difficult to characterize the rapid evolution behavior of cracks under dynamic loading conditions. Therefore, the applicability and predictive ability of such models in engineering scenarios such as impact disturbances, blasting excavation, or rapid unloading remain significantly limited. Therefore, there is an urgent need to provide a method and system for the in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock, which can integrate the real geometric state into a new modified compression-shear-slip crack model to achieve rapid and accurate determination of nonlinear static and dynamic parameters. Summary of the Invention

[0005] In view of this, it is necessary to provide a method and system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, in order to solve the technical problems existing in the prior art. The input parameters of the existing models are usually based on idealized and statistically averaged crack system assumptions, which are difficult to accurately reflect the actual response of the surrounding rock in a specific engineering part. The crack propagation mechanism simplifies the growth and evolution of wing cracks and mostly uses quasi-static loading conditions as the basic assumptions, which fails to characterize the influence of dynamic processes on crack evolution and macroscopic response, resulting in low accuracy of the determined nonlinear static and dynamic parameters.

[0006] To address the aforementioned technical problems, in a first aspect, the present invention provides a method for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, comprising:

[0007] Acquire three-dimensional surface structure images of the surrounding rock at the tunnel excavation face or borehole wall;

[0008] Feature extraction is performed on the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks;

[0009] The actual geometric feature parameters are input into the modified compression-shear-slip crack propagation model. Combined with the preset material parameters and stress loading conditions, the nonlinear stress-strain response of the surrounding rock during loading and unloading is calculated. The modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics when simulating crack bending propagation behavior.

[0010] The nonlinear static-dynamic parameters of the surrounding rock are determined based on the nonlinear stress-strain response.

[0011] In one possible implementation, the step of extracting features from the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks includes:

[0012] The three-dimensional appearance structure image of the surrounding rock is sequentially processed by grayscale, filtering, enhancement and binarization to obtain a binarized three-dimensional appearance structure image.

[0013] The binary three-dimensional appearance structure image is subjected to spatial projection transformation to obtain a two-dimensional appearance structure image.

[0014] Cracks are extracted from the two-dimensional apparent structure image to obtain the true geometric feature parameters.

[0015] In one possible implementation, the true geometric feature parameters include crack half-length, crack orientation, and crack spatial distribution parameters, wherein the crack spatial distribution parameters include density per unit area and crack length density.

[0016] The half-length of the crack is:

[0017] ;

[0018] The crack orientation is:

[0019] ;

[0020] The density per unit area is:

[0021] ;

[0022] The crack length density is:

[0023] ;

[0024] In the formula, Let be the crack half-length of the i-th crack; The number of pixels in the i-th crack in the two-dimensional appearance structure image; Let j be the j-th pixel on the i-th crack; , () represents the two-dimensional coordinates of the j-th pixel in the two-dimensional appearance structure image; , (j+1) represents the two-dimensional coordinates of the (j+1)th pixel in the two-dimensional appearance structure image; The crack orientation of the i-th crack; , () represents the average of the two-dimensional coordinates of all cracks in the two-dimensional apparent structure image; Density per unit area; The total number of cracks in the two-dimensional apparent structure image; The area of ​​the two-dimensional appearance structure image; This represents the crack length density.

[0025] In one possible implementation, the stress loading conditions include confining pressure, maximum axial stress, and maximum loading time step; then, the actual geometric characteristic parameters are input into a modified compression-shear-slip crack propagation model, and combined with preset material parameters and stress loading conditions, the nonlinear stress-strain response of the surrounding rock during loading and unloading is calculated, including:

[0026] Obtain the current axial stress state of a single crack at the current loading time step;

[0027] When the current loading time step is less than the maximum loading time step, the crack is determined to be in the loading stage; when the current loading time step is greater than the maximum loading time step, the crack is determined to be in the unloading stage.

[0028] The current stress state of the crack is determined based on the current axial stress state, the confining pressure, and the crack orientation;

[0029] Determine the first critical stress during the loading stage to determine the stage in which the crack is located, and the second critical stress during the unloading stage to determine the stage in which the crack is located.

[0030] The additional compliance contribution value of the crack is determined based on the current axial stress state, the current stress state, the first critical stress, and the second critical stress.

[0031] The additional compliance contribution values ​​of each of the aforementioned cracks are summed to obtain the total additional compliance contribution value;

[0032] The strain at the current loading time step is determined based on the total additional compliance contribution value, the historical strain at the previous loading time step, and the historical axial stress state.

[0033] The calculation is iterated until the current loading time step reaches twice the maximum loading time step to obtain the nonlinear stress-strain response.

[0034] In one possible implementation, the current stress state includes the current normal stress and the current shear stress, wherein the current normal stress is:

[0035] ;

[0036] The current shear stress is:

[0037] ;

[0038] In the formula, This represents the current normal stress of a single crack; This represents the current axial stress state of a single crack. For confining pressure; The crack orientation of a single crack; This represents the current shear stress.

[0039] In one possible implementation, the first critical stress includes the crack closure critical stress, the crack friction slip critical stress, and the crack bending propagation critical stress, and the second critical stress includes the crack reverse slip critical stress.

[0040] The critical stress for crack closure is:

[0041] ;

[0042] The critical stress for crack friction slip is:

[0043] ;

[0044] The critical stress for crack propagation during bending is:

[0045] ;

[0046] The critical stress for the reverse slip of the crack is:

[0047]

[0048] ;

[0049] In the formula, The critical stress for crack closure is the stress at which the crack closes from the point of opening. The initial aperture of the crack; It is the equivalent elastic modulus under plane strain or plane stress conditions; The crack half-length of a single crack; The critical stress for frictional slip of a crack as it transitions from closed non-slip to frictional slip. This represents the initial cohesive force. The coefficient of friction; The critical stress for crack propagation from friction slip to bending propagation; The dynamic fracture toughness of the crack; The critical stress at which the crack transitions from jamming to reverse slip; For loading peak time ( = The normal stress of ) The unloading stress change represents the peak axial stress reached during the loading phase. Unloading to the current axial stress The difference.

[0050] In one possible implementation, determining the additional compliance contribution value of the crack based on the current axial stress state, the current stress state, the first critical stress, and the second critical stress includes:

[0051] During the loading phase, when the current axial stress state is less than or equal to the crack closure critical stress, the crack is determined to be in the open phase, and the additional compliance contribution value is determined based on the first additional compliance contribution formula. When the current axial stress state is greater than the crack closure critical stress but less than or equal to the crack friction slip critical stress, the crack is determined to be in the closed non-slip phase, and the additional compliance contribution value is zero. When the current axial stress state is greater than the crack friction slip critical stress but less than or equal to the crack bending propagation critical stress, the crack is determined to be in the closed slip phase, and the additional compliance contribution value is determined based on the second additional compliance contribution formula. When the current axial stress state is greater than the crack bending propagation critical stress but less than or equal to the peak axial stress, the crack is determined to be in the bending propagation phase, and the additional compliance contribution value is determined based on the third additional compliance contribution formula.

[0052] During the unloading phase, when the critical stress for crack reverse slip is less than or equal to zero, the crack is determined to be in the unloading and jamming phase, and the additional compliance contribution value is zero. When the critical stress for crack reverse slip is greater than zero, the crack is determined to be in the reverse slip phase, and the additional compliance contribution value is determined based on the fourth additional compliance contribution formula.

[0053] In one possible implementation, the formula for the first additional compliance contribution is:

[0054] ;

[0055] The formula for the second additional compliance contribution is:

[0056] ;

[0057] The formula for the third additional compliance contribution is:

[0058] ;

[0059] ;

[0060] ;

[0061] ;

[0062] ;

[0063] The formula for the fourth additional compliance contribution is:

[0064] ;

[0065] In the formula, Additional flexibility contribution value for the open phase; Additional compliance contribution value for the closed slip phase; This represents the current shear stress; For effective shear stress Additional flexibility contribution during the bending extension phase; This represents the current normal stress; For correction functions; The deflection angle of the wing crack relative to the original crack; It is the crack transition factor; Normalized wing crack length; The length of the wing crack; This is a correction term for the crack length of the wing. This is a function of the crack propagation rate; This refers to the crack propagation rate; The Rayleigh wave velocity of the material; It is a rate sensitivity index; This is the additional compliance contribution value for the reverse slip phase.

[0066] In one possible implementation, the nonlinear stress parameters include the effective elastic module, the initiation stress, and the damage energy dissipation.

[0067] Secondly, the present invention also provides a system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, comprising:

[0068] The image acquisition module is used to acquire three-dimensional surface structure images of the surrounding rock at the tunnel excavation face or borehole wall;

[0069] The image processing module is used to extract features from the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks.

[0070] The model calculation module is used to input the real geometric feature parameters into the modified compression-shear-slip crack propagation model, and calculate the nonlinear stress-strain response of the surrounding rock during loading and unloading by combining preset material parameters and stress loading conditions. The modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics when simulating crack bending propagation behavior.

[0071] The static and dynamic parameter output module is used to determine and output the nonlinear static and dynamic parameters of the surrounding rock based on the nonlinear stress-strain response.

[0072] The beneficial effects of this invention are as follows: The method for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock provided by this invention directly extracts the real geometric feature parameters from the three-dimensional apparent structure image of the surrounding rock as the input of the modified compression-shear-slip crack propagation model. It abandons the traditional model's reliance on idealized and averaged crack assumptions, simplified crack propagation mechanisms, and quasi-static loading assumptions, so that mechanical prediction is directly based on real data reflecting the specific geological structural characteristics of the engineering site, which greatly improves the accuracy and authenticity of the determined nonlinear static and dynamic parameters.

[0073] Furthermore, the modified compression-shear-slip crack propagation model in this invention reflects the evolution law of wing crack propagation morphology and the crack propagation rate dependence characteristics when simulating crack bending propagation behavior. This enables the model to more realistically describe the changes in wing crack propagation path with stress development. Compared with the traditional model with a fixed propagation direction, it significantly improves the physical rationality and accuracy of simulating the nonlinear deformation and damage accumulation process of surrounding rock.

[0074] Meanwhile, this invention eliminates the reliance on indoor rock sample tests. It only requires obtaining three-dimensional images of the surrounding rock's apparent structure at the tunnel excavation face or borehole wall. Subsequent image processing and model calculations allow for the rapid acquisition of the nonlinear static and dynamic parameters of the surrounding rock at that location within a short timeframe. The entire process is extremely short, low-cost, and causes no disturbance or damage to the rock mass, truly meeting the urgent need for real-time and rapid assessment of surrounding rock stability during engineering construction. Attached Figure Description

[0075] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0076] Figure 1 A schematic flowchart of an embodiment of the method for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock provided by the present invention;

[0077] Figure 2 For the present invention Figure 1 A schematic diagram of an embodiment of step S102;

[0078] Figure 3 A comparison image of the three-dimensional apparent structure of the surrounding rock provided by the present invention and the image after processing and feature extraction;

[0079] Figure 4 For the present invention Figure 1 A schematic flowchart of an embodiment of step S103;

[0080] Figure 5 A comparison diagram of the modified compression-shear-slip crack propagation model provided for this invention with the Kemeny-Cool model and the Ashby-Sammis model;

[0081] Figure 6 A comparison diagram of the modified compression-shear-slip crack propagation model provided by this invention with the classical model and experimental results;

[0082] Figure 7 A schematic diagram of the stress-strain response and the corresponding effective elastic modulus provided by the present invention;

[0083] Figure 8 This is a schematic diagram of an embodiment of the system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock provided by the present invention. Detailed Implementation

[0084] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0085] It should be understood that the illustrative drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the invention. It should be understood that the operations in the flowcharts may be implemented out of order, and steps without logical contextual relationships may be reversed or performed simultaneously. Furthermore, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor systems and / or microcontroller systems.

[0086] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0087] This invention provides a method and system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, which will be described below.

[0088] Surrounding rock refers to the rock mass behind and around the tunnel excavation face, or the rock mass around the well wall of a borehole (such as an oil and gas well or a geological exploration borehole). In other words, it is the portion of the rock mass around an artificially excavated or naturally formed underground engineering structure (such as a tunnel, roadway, chamber, mine, borehole, etc.) whose stress state and physical and mechanical properties have been significantly altered due to engineering activities.

[0089] Figure 1 This is a schematic flowchart of an embodiment of the method for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock provided by the present invention, as shown below. Figure 1 As shown, the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock includes:

[0090] S101. Obtain a three-dimensional surface structure image of the surrounding rock at the tunnel excavation face or borehole wall.

[0091] The method for acquiring the three-dimensional apparent structure image of the surrounding rock is based on visual imaging technology, such as cameras.

[0092] It should be noted that when the surrounding rock area is large but the camera's field of view is small, multiple images taken by the camera need to be stitched together to obtain a three-dimensional image of the surrounding rock's apparent structure. During this process, coordinate registration of the multiple images is necessary to ensure that the stitched result is consistent with a unified coordinate system.

[0093] S102. Extract features from cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks;

[0094] S103. Input the real geometric feature parameters into the modified compression-shear-slip crack propagation model, and calculate the nonlinear stress-strain response of the surrounding rock during loading and unloading by combining the preset material parameters and stress loading conditions. When simulating crack bending propagation behavior, the modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics.

[0095] S104. Determine the nonlinear static and dynamic parameters of the surrounding rock based on the nonlinear stress-strain response.

[0096] It should be understood that the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock in this embodiment of the invention can be implemented in any device based on the method, such as electronic devices like surrounding rock analysis equipment. Specifically, the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock is stored in the aforementioned device as a pre-programmed program. When the device is started, the program is invoked, and the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock is implemented.

[0097] Compared with existing technologies, the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock provided in this invention directly uses the real geometric feature parameters extracted from the three-dimensional apparent structure image of the surrounding rock as the input of the modified compression-shear-slip crack propagation model. It abandons the traditional model's reliance on idealized and averaged crack assumptions, simplified crack propagation mechanisms, and quasi-static loading assumptions, so that mechanical prediction is directly based on real data reflecting the specific geological structural characteristics of the engineering site, which greatly improves the accuracy and authenticity of the determined nonlinear static and dynamic parameters.

[0098] Furthermore, the modified compression-shear-slip crack propagation model in this embodiment reflects the evolution of the crack propagation morphology and the crack propagation rate dependence when simulating crack bending propagation behavior. This allows the model to more realistically describe the changes in the crack propagation path with stress development. Compared with the traditional model with a fixed propagation direction, it significantly improves the physical rationality and accuracy of simulating the nonlinear deformation and damage accumulation process of the surrounding rock.

[0099] Meanwhile, this invention eliminates the reliance on indoor rock sample tests. It only requires acquiring three-dimensional images of the surrounding rock's apparent structure at the tunnel excavation face or borehole wall. Subsequent image processing and model calculations allow for the rapid acquisition of nonlinear static and dynamic parameters of the surrounding rock at that location within a short timeframe. The entire process is extremely short, cost-effective, and causes no disturbance or damage to the rock mass, truly meeting the urgent need for real-time and rapid assessment of surrounding rock stability during engineering construction.

[0100] Because the modified compression-shear-slip crack propagation model uses two-dimensional geometric parameters of the crack, while the acquired three-dimensional apparent structure image of the surrounding rock is three-dimensional. Furthermore, to avoid image noise adversely affecting the extraction of true geometric feature parameters, in some embodiments of the present invention, such as... Figure 2 As shown, step S102 includes:

[0101] S201. The three-dimensional apparent structure image of the surrounding rock is sequentially processed by grayscale, filtering, enhancement and binarization to obtain a binarized three-dimensional apparent structure image.

[0102] Specifically, the image is processed to grayscale based on the following formula:

[0103] ;

[0104] In the formula, This is a grayscale processed image of the three-dimensional apparent structure of the surrounding rock. , , The three primary color components of the three-dimensional apparent structure image of the surrounding rock are red, green, and blue in the RGB color model.

[0105] Specifically, the filtering process is a Gaussian filtering process based on the Gaussian kernel function.

[0106] Enhancement processing is performed based on the following formula:

[0107] ;

[0108] In the formula, To enhance the processed image; The image after filtering; Opening operations for three-dimensional morphology; It is a three-dimensional structural element used to describe crack width characteristics.

[0109] Specifically, binarization is performed based on the following formula:

[0110] ;

[0111] In the formula, A binary three-dimensional appearance structure image; This is a locally adaptive threshold function.

[0112] S202. Perform spatial projection transformation on the binarized three-dimensional appearance structure image to obtain a two-dimensional appearance structure image.

[0113] Specifically, spatial projection transformation is performed based on the following formula:

[0114] ;

[0115] In the formula, represents the coordinate values ​​in the two-dimensional appearance structure image; represents the spatial projection operator.

[0116] S203. Extract cracks from the two-dimensional apparent structure image to obtain the true geometric feature parameters.

[0117] This invention, through sequential grayscale processing, filtering, enhancement, and binarization, effectively suppresses image noise, enhances the contrast between the crack and the background, and ultimately clearly segments the crack region, significantly improving the accuracy of crack identification. Furthermore, spatial projection transformation converts the three-dimensional crack data into a two-dimensional image, adapting it to the modified compression-shear-slip crack propagation model. Simultaneously, it significantly reduces the complexity of subsequent geometric parameter calculations and improves the efficiency of determining nonlinear static and dynamic parameters.

[0118] In some embodiments of the present invention, the true geometric feature parameters include crack half-length, crack orientation and crack spatial distribution parameters, and the crack spatial distribution parameters include density per unit area and crack length density.

[0119] The crack half-length is:

[0120] ;

[0121] The crack orientation is as follows:

[0122] ;

[0123] Density per unit area is:

[0124] ;

[0125] Crack length density is:

[0126] ;

[0127] In the formula, Let be the crack half-length of the i-th crack; The number of pixels in the i-th crack in the two-dimensional appearance structure image; Let j be the j-th pixel on the i-th crack; , () represents the two-dimensional coordinates of the j-th pixel in the two-dimensional appearance structure image; , (j+1) represents the two-dimensional coordinates of the (j+1)th pixel in the two-dimensional appearance structure image; The crack orientation of the i-th crack; , () represents the average of the two-dimensional coordinates of all cracks in the two-dimensional apparent structure image; Density per unit area; The total number of cracks in the two-dimensional apparent structure image; The area of ​​the two-dimensional appearance structure image; This represents the crack length density.

[0128] To illustrate the extraction process of real geometric feature parameters in embodiments of the present invention, in specific embodiments of the present invention, such as... Figure 3 As shown, Figure 3 The left side shows a three-dimensional apparent structure image of the surrounding rock. Figure 3 The right side shows the extraction results after extracting the true geometric feature parameters. Figure 3 The gradient from purple to yellow on the right side indicates a gradual increase in crack orientation. Figure 3 As can be seen, the embodiments of the present invention, based on multiple processing and crack extraction processes, can transform the original rock surface structure image obtained from the tunnel excavation face or well wall into clear crack and real geometric feature parameters, providing reliable input for subsequent models.

[0129] In some embodiments of the present invention, the stress loading conditions include confining pressure, maximum axial stress, and maximum loading time step; then, as follows... Figure 4 As shown, step S103 includes:

[0130] S401. Obtain the current axial stress state of a single crack at the current loading time step;

[0131] S402. When the current loading time step is less than the maximum loading time step, the crack is determined to be in the loading stage. When the current loading time step is greater than the maximum loading time step, the crack is determined to be in the unloading stage.

[0132] During the loading stage, the axial stress increases with the increase of the loading time step. During the unloading stage, the axial stress decreases with the increase of the loading time step. When the axial stress decreases to 0 MPa, the corresponding time step is twice the maximum loading time step.

[0133] S403. Determine the current stress state of the crack based on the current axial stress state, confining pressure, and crack orientation.

[0134] Specifically, the current stress state includes the current normal stress and the current shear stress, where the current normal stress is:

[0135] ;

[0136] The current shear stress is:

[0137] ;

[0138] In the formula, This represents the current normal stress of a single crack; This represents the current axial stress state of a single crack. For confining pressure; The crack orientation of a single crack; This represents the current shear stress.

[0139] S404. Determine the first critical stress in the loading stage to determine the stage in which the crack is located, and the second critical stress in the unloading stage to determine the stage in which the crack is located.

[0140] S405. Determine the additional compliance contribution value of the crack based on the current axial stress state, the current stress state, the first critical stress, and the second critical stress.

[0141] S406. The additional compliance contribution values ​​of each crack are summed to obtain the total additional compliance contribution value.

[0142] S407. Determine the strain of the current loading time step based on the total additional compliance contribution value, the historical strain of the previous loading time step, and the historical axial stress state.

[0143] Specifically, the strain at the current loading time step for:

[0144] ;

[0145] ;

[0146] In the formula, This is the historical strain from the previous loading time step; This represents the total additional flexibility contribution value. This represents the axial stress state at the current loading time step. This represents the historical axial stress state from the previous loading time step; The additional compliance contribution value for the i-th crack.

[0147] S408. Iterate the calculation until the current loading time step reaches twice the maximum loading time step to obtain the nonlinear stress-strain response.

[0148] Specifically, step S408 involves determining that when the current loading time step is less than twice the maximum loading time step, the current loading time step is taken as the previous loading time step, and steps S401-S407 are repeated until the current loading time step reaches twice the maximum loading time step. At this point, all time steps constitute a complete nonlinear stress-strain response.

[0149] It should be understood that the cracks in this step are not distinguished by quotation marks 'i', which can be interpreted as performing the same operation on each crack. In other words, the additional compliance contribution value is calculated for each crack to obtain the final total additional compliance contribution value. That is, the additional compliance contribution value of all cracks is calculated at each loading time step to obtain the total strain.

[0150] In some embodiments of the present invention, the loading stage is divided into an open stage, a closed non-slipping stage, a closed slipping stage, and a bending expansion stage, and the unloading stage includes an unloading stuck stage and a reverse slipping stage.

[0151] This invention constructs a refined mechanical analysis framework that comprehensively describes the entire crack propagation process from deformation, slip, propagation, and springback by dividing the loading process into four stages: open, closed non-slip, closed slip, and bending propagation, and clearly distinguishing the unloading process into two stages: unloading hysteresis and reverse slip. Compared to existing classical compression-shear-slip models that typically simplify unloading behavior and crack initiation and propagation mechanisms or focus on quasi-static loading conditions, this invention modifies the crack propagation model under dynamic loading conditions and achieves explicit modeling of the bending propagation stage and clear definition of the unloading hysteresis stage. This allows the model to more realistically reflect the key nonlinear behaviors of rock under cyclic loading or dynamic unloading, such as hysteresis, energy dissipation, and residual deformation. Furthermore, it can improve the accuracy of the nonlinear static and dynamic parameters determined based on the modified compression-shear-slip crack propagation model.

[0152] Based on the above stage division, in a specific embodiment of the present invention, the first critical stress includes the crack closure critical stress, the crack friction slip critical stress, and the crack bending propagation critical stress, and the second critical stress includes the crack reverse slip critical stress.

[0153] The critical stress for crack closure is:

[0154] ;

[0155] The critical stress for crack friction slip is:

[0156] ;

[0157] The critical stress for crack propagation at bend is:

[0158] ;

[0159] The critical stress for crack reverse slip is:

[0160] ;

[0161] ;

[0162] In the formula, The critical stress for crack closure is the stress at which the crack closes from the point of opening. The initial aperture of the crack; It is the equivalent elastic modulus under plane strain or plane stress conditions; The crack half-length of a single crack; The critical stress for frictional slip of a crack as it transitions from closed non-slip to frictional slip. This represents the initial cohesive force. The coefficient of friction; The critical stress for crack propagation from friction slip to bending propagation; The dynamic fracture toughness of the crack; The critical stress at which the crack transitions from jamming to reverse slip; For loading peak time ( = The normal stress of ) The unloading stress change represents the peak axial stress reached during the loading phase. Unloading to the current axial stress The difference.

[0163] Specifically, step S304 includes:

[0164] During the loading phase, when the current axial stress state is less than or equal to the crack closure critical stress, the crack is determined to be in the open stage, and the additional compliance contribution value is determined based on the first additional compliance contribution formula. When the current axial stress state is greater than the crack closure critical stress but less than or equal to the crack friction slip critical stress, the crack is determined to be in the closed non-slip stage, and the additional compliance contribution value is zero. When the current axial stress state is greater than the crack friction slip critical stress but less than or equal to the crack bending propagation critical stress, the crack is determined to be in the closed slip stage, and the additional compliance contribution value is determined based on the second additional compliance contribution formula. When the current axial stress state is greater than the crack bending propagation critical stress but less than or equal to the peak axial stress, the crack is determined to be in the bending propagation stage, and the additional compliance contribution value is determined based on the third additional compliance contribution formula.

[0165] During the unloading phase, when the critical stress for crack reverse slip is less than or equal to zero, the crack is determined to be in the unloading and jamming phase, and the additional compliance contribution is zero. When the critical stress for crack reverse slip is greater than zero, the crack is determined to be in the reverse slip phase, and the additional compliance contribution is determined based on the fourth additional compliance contribution formula.

[0166] Specifically, the formula for the first additional compliance contribution is:

[0167] ;

[0168] The formula for the second additional compliance contribution is:

[0169] ;

[0170] The formula for the third additional compliance contribution is:

[0171] ;

[0172] ;

[0173] ;

[0174] ;

[0175] ;

[0176] The formula for the fourth additional compliance contribution is:

[0177] ;

[0178] In the formula, Additional flexibility contribution value for the open phase; Additional compliance contribution value for the closed slip phase; This represents the current shear stress; For effective shear stress Additional flexibility contribution during the bending extension phase; This represents the current normal stress; For correction functions; The deflection angle of the wing crack relative to the original crack; It is the crack transition factor; Normalized wing crack length; The length of the wing crack; This is a correction term for the crack length of the wing. This is a function of the crack propagation rate; This refers to the crack propagation rate; The Rayleigh wave velocity of the material; It is a rate sensitivity index; This is the additional compliance contribution value for the reverse slip phase.

[0179] To verify the superiority of the modified compression-shear-slip crack propagation model of the present invention, the embodiments of the present invention are compared with existing models (Kemeny-Cool model and Ashby-Sammis model). The comparison results are as follows: Figure 5 As shown, by Figure 5 It is known that existing Kemeny-Cook and Ashby-Sammis models depict wing cracks as straight-line propagation from the original crack tip at a fixed angle, with a regular and uniform shape. However, the propagation path of the wing crack in the model proposed in this embodiment is either completely fixed or dynamically changing in direction, which is more consistent with the actual crack propagation trajectory observed in rock experiments.

[0180] Furthermore, the modified compression-shear-slip crack propagation model in this embodiment of the invention is compared with the classical model (Nemat-Horii model) and experimental results. The comparison results are as follows: Figure 6 As shown, by Figure 6 It can be seen that the modified compression-shear-slip crack propagation model proposed in this embodiment of the invention is closer to the experimental results, verifying its superiority.

[0181] In a specific embodiment of the present invention, the nonlinear stress parameters include the effective elastic modulus, the crack initiation stress, and the damage energy dissipation.

[0182] The effective elastic modulus refers to the ratio of the stress increment to the strain increment within a specific stress level or range in a nonlinear stress-strain relationship, used to describe the evolution of material stiffness (or flexibility). The process of determining the effective elastic modulus based on the nonlinear stress-strain response is as follows: a response curve is plotted based on the nonlinear stress-strain response, and the slope of the response curve is taken as the effective elastic modulus.

[0183] Initiation stress refers to the axial stress threshold corresponding to the start of macroscopic nonlinear deformation inside the rock and the entry of microcracks into a stable propagation stage, marking the formal start of damage accumulation.

[0184] In the model of this invention, the initiation stress is the minimum value of the critical stress for crack bending propagation corresponding to all cracks.

[0185] Damage energy dissipation refers to the energy dissipated due to irreversible damage (such as crack friction slip and propagation) within the rock during a complete loading and unloading cycle. On the stress-strain response curve, it is represented by the area of ​​the hysteresis loop enclosed by the loading and unloading curves.

[0186] Specifically, the formula for calculating damage energy consumption is as follows:

[0187] ;

[0188] In the formula, Energy consumption for damage ; represents the axial strain when loaded to the maximum axial stress. and Represents the axial stress and axial strain during the loading stage. This represents the axial strain at the point of unloading. and This represents the axial stress and axial strain during the unloading phase.

[0189] In a specific embodiment of the present invention, the obtained stress-strain response and the corresponding effective elastic modulus are as follows: Figure 7 As shown, by Figure 7 The stress-strain response curve shows that it has a clear hysteresis loop (the loading curve and the unloading curve do not coincide), and the existence of the hysteresis loop proves that the model has successfully simulated the unloading process.

[0190] In summary, the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock proposed in this invention directly introduces real geometric characteristic parameters into the modified compression-shear-slip crack propagation model. Without requiring additional mechanical tests, it can directly obtain the nonlinear stress-strain curve of the surrounding rock, achieving rapid conversion of crack structure information into macroscopic mechanical behavior. Simultaneously, based on the obtained nonlinear stress-strain curve, this invention can rapidly acquire key static and dynamic parameters of the surrounding rock during loading and unloading processes, such as the effective elastic modulus, crack initiation stress, and damage energy dissipation. Compared to traditional methods relying on indoor tests, this significantly shortens the parameter acquisition cycle and meets the needs of rapid mechanical assessment under engineering conditions. Furthermore, the modified compression-shear-slip crack propagation model proposed in this invention considers the influence of crack propagation rate and is applicable to the acquisition of nonlinear stress-strain curves and static and dynamic parameters under dynamic loading conditions. The wing crack propagation model has also been modified, and compared to existing models (such as Kemeny-Cook, Ashby-Sammis, and Nemat-Horii), it can more accurately reflect the true propagation morphology of the wing crack, thereby improving the physical rationality and prediction accuracy of the calculation results.

[0191] On the other hand, embodiments of the present invention also provide a system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, such as... Figure 8 As shown, the in-situ rapid acquisition system for nonlinear static and dynamic parameters of surrounding rock 800 includes:

[0192] Image acquisition module 801 is used to acquire three-dimensional surface structure images of the surrounding rock at the tunnel excavation face or borehole wall;

[0193] Image processing module 802 is used to extract features of cracks in the three-dimensional apparent structure image of surrounding rock and obtain the true geometric feature parameters of the cracks.

[0194] The model calculation module 803 is used to input the real geometric feature parameters into the modified compression-shear-slip crack propagation model, and calculate the nonlinear stress-strain response of the surrounding rock during loading and unloading by combining the preset material parameters and stress loading conditions. When simulating crack bending propagation behavior, the modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics.

[0195] The static and dynamic parameter output module 804 is used to determine and output the nonlinear static and dynamic parameters of the surrounding rock based on the nonlinear stress-strain response.

[0196] The in-situ rapid acquisition system 800 for nonlinear static dynamic parameters of surrounding rock provided in the above embodiments can realize the technical solutions described in the embodiments of the in-situ rapid acquisition method for nonlinear static dynamic parameters of surrounding rock. The specific implementation principles of each module or unit can be found in the corresponding content in the embodiments of the in-situ rapid acquisition method for nonlinear static dynamic parameters of surrounding rock, and will not be repeated here.

[0197] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware (such as a processor, controller, etc.), and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0198] The present invention provides a detailed description of a method and system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will know that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, characterized in that, include: Acquire three-dimensional surface structure images of the surrounding rock at the tunnel excavation face or borehole wall; Feature extraction is performed on the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks; The actual geometric feature parameters are input into the modified compression-shear-slip crack propagation model. Combined with the preset material parameters and stress loading conditions, the nonlinear stress-strain response of the surrounding rock during loading and unloading is calculated. The modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics when simulating crack bending propagation behavior. The nonlinear static-dynamic parameters of the surrounding rock are determined based on the nonlinear stress-strain response. The true geometric feature parameters include crack half-length, crack orientation, and crack spatial distribution parameters, wherein the crack spatial distribution parameters include density per unit area and crack length density; the stress loading conditions include confining pressure, maximum loading axial stress, and maximum loading time step; The actual geometric characteristic parameters are then input into the modified compression-shear-slip crack propagation model. Combined with preset material parameters and stress loading conditions, the nonlinear stress-strain response of the surrounding rock during loading and unloading is calculated, including: Obtain the current axial stress state of a single crack at the current loading time step; When the current loading time step is less than the maximum loading time step, the crack is determined to be in the loading stage; when the current loading time step is greater than the maximum loading time step, the crack is determined to be in the unloading stage. The current stress state of the crack is determined based on the current axial stress state, the confining pressure, and the crack orientation; Determine the first critical stress during the loading stage to determine the stage in which the crack is located, and the second critical stress during the unloading stage to determine the stage in which the crack is located. The additional compliance contribution value of the crack is determined based on the current axial stress state, the current stress state, the first critical stress, and the second critical stress. The additional compliance contribution values ​​of each of the aforementioned cracks are summed to obtain the total additional compliance contribution value; The strain at the current loading time step is determined based on the total additional compliance contribution value, the historical strain at the previous loading time step, and the historical axial stress state. Iterative calculations are performed until the current loading time step reaches twice the maximum loading time step to obtain the nonlinear stress-strain response; The first critical stress includes the crack closure critical stress, the crack friction slip critical stress, and the crack bending propagation critical stress; the second critical stress includes the crack reverse slip critical stress. The determination of the additional compliance contribution value of the crack based on the current axial stress state, the current stress state, the first critical stress, and the second critical stress includes: During the loading phase, when the current axial stress state is less than or equal to the crack closure critical stress, the crack is determined to be in the open phase, and the additional compliance contribution value is determined based on the first additional compliance contribution formula. When the current axial stress state is greater than the crack closure critical stress but less than or equal to the crack friction slip critical stress, the crack is determined to be in the closed non-slip phase, and the additional compliance contribution value is zero. When the current axial stress state is greater than the crack friction slip critical stress but less than or equal to the crack bending propagation critical stress, the crack is determined to be in the closed slip phase, and the additional compliance contribution value is determined based on the second additional compliance contribution formula. When the current axial stress state is greater than the crack bending propagation critical stress but less than or equal to the peak axial stress, the crack is determined to be in the bending propagation phase, and the additional compliance contribution value is determined based on the third additional compliance contribution formula. During the unloading phase, when the critical stress for crack reverse slip is less than or equal to zero, the crack is determined to be in the unloading and jamming phase, and the additional compliance contribution value is zero. When the critical stress for crack reverse slip is greater than zero, the crack is determined to be in the reverse slip phase, and the additional compliance contribution value is determined based on the fourth additional compliance contribution formula.

2. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 1, characterized in that, The step of extracting features from the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks includes: The three-dimensional appearance structure image of the surrounding rock is sequentially processed by grayscale, filtering, enhancement and binarization to obtain a binarized three-dimensional appearance structure image. The binary three-dimensional appearance structure image is subjected to spatial projection transformation to obtain a two-dimensional appearance structure image. Cracks are extracted from the two-dimensional apparent structure image to obtain the true geometric feature parameters.

3. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 1 or 2, characterized in that, The half-length of the crack is: The crack orientation is: The density per unit area is: The crack length density is: In the formula, Let be the crack half-length of the i-th crack; The number of pixels in the i-th crack in the two-dimensional appearance structure image; Let j be the j-th pixel on the i-th crack; , () represents the two-dimensional coordinates of the j-th pixel in the two-dimensional appearance structure image; , (j+1) represents the two-dimensional coordinates of the (j+1)th pixel in the two-dimensional appearance structure image; The crack orientation of the i-th crack; , () represents the average of the two-dimensional coordinates of all cracks in the two-dimensional apparent structure image; Density per unit area; The total number of cracks in the two-dimensional apparent structure image; The area of ​​the two-dimensional appearance structure image; This represents the crack length density.

4. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 3, characterized in that, The current stress state includes the current normal stress and the current shear stress. The current normal stress is: The current shear stress is: In the formula, This represents the current normal stress of a single crack; This represents the current axial stress state of a single crack. For confining pressure; The crack orientation of a single crack; This represents the current shear stress.

5. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 4, characterized in that, The critical stress for crack closure is: The critical stress for crack friction slip is: The critical stress for crack propagation during bending is: The critical stress for the reverse slip of the crack is: In the formula, The critical stress for crack closure is the stress at which the crack closes from the point of opening. The initial aperture of the crack; It is the equivalent elastic modulus under plane strain or plane stress conditions; The crack half-length of a single crack; The critical stress for frictional slip of a crack as it transitions from closed non-slip to frictional slip. This represents the initial cohesive force. The coefficient of friction; The critical stress for crack propagation from friction slip to bending propagation; The dynamic fracture toughness of the crack; The critical stress at which the crack transitions from jamming to reverse slip; For loading peak time ( = The normal stress of ) The unloading stress change represents the peak axial stress reached during the loading phase. Unloading to the current axial stress The difference.

6. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 5, characterized in that, The formula for the first additional compliance contribution is: The formula for the second additional compliance contribution is: The formula for the third additional compliance contribution is: The formula for the fourth additional compliance contribution is: In the formula, Additional flexibility contribution value for the open phase; Additional compliance contribution value for the closed slip phase; This represents the current shear stress; For effective shear stress Additional flexibility contribution during the bending extension phase; This represents the current normal stress; For correction functions; The deflection angle of the wing crack relative to the original crack; It is the crack transition factor; Normalized wing crack length; The length of the wing crack; This is a correction term for the crack length of the wing. This is a function of the crack propagation rate; This refers to the crack propagation rate; The Rayleigh wave velocity of the material; It is a rate sensitivity index; This is the additional compliance contribution value for the reverse slip phase.

7. The method for in-situ rapid acquisition of nonlinear static and dynamic parameters of surrounding rock according to claim 1, characterized in that, The nonlinear static-dynamic parameters include effective elastic modulus, crack initiation stress, and damage energy dissipation.

8. A system for rapid in-situ acquisition of nonlinear static and dynamic parameters of surrounding rock, characterized in that, The system is based on the in-situ rapid acquisition method for nonlinear static and dynamic parameters of surrounding rock according to any one of claims 1-7, and includes: The image acquisition module is used to acquire three-dimensional surface structure images of the surrounding rock at the tunnel excavation face or borehole wall; The image processing module is used to extract features from the cracks in the three-dimensional apparent structure image of the surrounding rock to obtain the true geometric feature parameters of the cracks. The model calculation module is used to input the real geometric feature parameters into the modified compression-shear-slip crack propagation model, and calculate the nonlinear stress-strain response of the surrounding rock during loading and unloading by combining preset material parameters and stress loading conditions. The modified compression-shear-slip crack propagation model reflects the evolution law of wing crack propagation morphology and crack propagation rate dependence characteristics when simulating crack bending propagation behavior. The static and dynamic parameter output module is used to determine and output the nonlinear static and dynamic parameters of the surrounding rock based on the nonlinear stress-strain response.

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