Self-stress anchor rod damage evolution simulation method for jointed rock mass bolting-grouting reinforcement

Abstract

The invention relates to the field of geotechnical engineering, and discloses a self-stress anchor rod failure evolution simulation method for jointed rock mass bolting-grouting reinforcement, which comprises the following steps: S1, constructing a three-dimensional rock mass model containing a joint structure in an FLAC3D platform, and defining joint surface space distribution and geometric parameters; s2, a bolting-grouting structure is introduced into the three-dimensional rock mass model, an anchor rod, a grouting body and the contact relation between the anchor rod and the grouting body and the rock mass are set, and an anchor rod load transfer model is established; s3, a loading path is set, displacement control is adopted as a loading mode, and a certain included angle is formed between the loading direction and the joint surface; and S4, establishing a numerical model in FLAC3D, performing grid division, and setting a rock mass material constitutive model and contact surface parameters. By accurately controlling the loading direction and the loading angle in simulation and analyzing the change influence of different loading paths on the failure mode of the bolting-grouting structure, the problem that the traditional simulation method neglects the change of the failure mode under different loading conditions is solved.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering, and specifically to a method for simulating the failure evolution of self-stressing anchor bolts for grouting reinforcement of jointed rock masses. Background Art

[0002] During the design and construction of geotechnical engineering, the mechanical behavior analysis of grouted jointed rock masses is a crucial part. Especially in underground engineering, tunnels, underground gas storage facilities and other projects, the design of grouting structures requires accurate simulation of the interaction between rock masses and grouting systems to ensure the safety and stability of the structures. However, due to the complexity and inhomogeneity of rock masses, especially the special properties of jointed rock masses, traditional analysis methods face many challenges when dealing with grouted jointed rock masses.

[0003] Most existing technologies adopt simplified assumptions and models to simulate the mechanical behavior of grouted jointed rock masses, but these methods fail to fully consider the complexity of rock mass joints and the real response under load. For example, many traditional models rely on idealized constitutive models of rock mass materials, ignoring the shear failure and slip characteristics of jointed rock masses, and unable to accurately simulate the changes in bond strength and friction force on the contact surface. Therefore, the numerical results of these models often deviate greatly from the actual engineering test results and are difficult to provide accurate theoretical support for engineering design.

[0004] In addition, the setting of material parameters has always been a technical problem in geotechnical engineering. The mechanical properties of jointed rock masses and grouting structures usually show large spatial variability, and the characteristics of rock materials and grouting bodies in different regions are significantly different. Existing experimental methods and data usually cannot effectively cover all possible working conditions and material characteristics, which makes the selection and setting of material parameters often have great uncertainties when establishing numerical models. Many existing methods estimate these parameters through empirical formulas or theoretical assumptions, but these methods often cannot truly reflect the actual mechanical behavior of rock masses.

[0005] Furthermore, when studying failure modes, most existing technologies focus on the analysis of single failure modes, such as shear failure or pull-out failure, but the grouted jointed rock masses in actual engineering often show complex composite failure behaviors. Due to changes in factors such as loading direction and load level, the failure mode may change, and existing technologies fail to fully identify and quantitatively describe the mechanisms of these changes. Therefore, traditional failure mode analysis can often only capture local failure characteristics and cannot comprehensively reveal the failure process under complex working conditions. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a method for simulating the failure evolution of self-stressing anchor bolts for grouting reinforcement of jointed rock masses, which solves the problem of poor ability to simulate, identify and quantitatively describe failure modes in the existing technology.

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for simulating the failure evolution of self-stressing anchor bolts for grouting reinforcement of jointed rock masses, comprising the following steps:

[0008] S1. Construct a three-dimensional rock mass model containing joint structures in the FLAC3D platform, and define the spatial distribution and geometric parameters of the joint surfaces;

[0009] S2. Introduce a grouting and anchoring structure into the three-dimensional rock mass model, set the contact relationships between the anchor bolts, grout bodies and the rock mass, and establish an anchor bolt load transfer model;

[0010] S3. Set the loading path, adopt displacement control for the loading method, and the loading direction forms a certain angle with the joint surface;

[0011] S4. Establish a numerical model in FLAC3D and conduct mesh division, and set the constitutive model of the rock mass material and the contact surface parameters;

[0012] S5. Conduct three-dimensional numerical simulation, obtain the mechanical response process of the grouting and anchoring structure, and extract the load-displacement curve;

[0013] S6. Verify the deviation of the numerical model by comparing with the physical test results, and adjust the three-dimensional rock mass model if it meets the correction conditions;

[0014] S7. Based on the comparison between the numerical simulation results and the physical test results, deduce and correct the theoretical formula for the ultimate bearing capacity of the grouted jointed rock mass, and finally obtain the accurate structural failure characteristics and deformation instability laws.

[0015] Preferably, the spatial distribution and geometric parameters of the joint surfaces in S1 include joint dip angle, joint spacing and joint length. The joint surfaces are simulated by introducing a contact surface or a weak surface model into the three-dimensional rock mass model, and the contact friction angle and cohesion are set.

[0016] Preferably, the anchor bolt load transfer model in S2 is simulated through the contact mechanical behavior between the anchor bolt and the rock mass;

[0017] The grouting and anchoring structure consists of steel anchor bolts, grout bodies and free sections. The contact force model between the anchor bolts and the rock mass is described by the interaction of adhesive force and slip force. A line-plane bonding model is adopted between the grout body and the rock mass, and the bonding strength τ of the grout body g and the axial force F of the anchor bolt satisfy the relationship:

[0018]

[0019] where d a is the diameter of the anchor bolt, and l is the length of the bonded section.

[0020] Preferably, the loading path in S3 is a one-way displacement boundary applied along the direction of the angle θ with the normal of the joint plane, the loading speed is constant, and the loading angle θ is adjusted within the range of 0° to 90°. By controlling θ, the influence of different loading directions on the failure mode is analyzed.

[0021] Preferably, in S4, the shear failure behavior of the rock mass material is described by the Mohr-Coulomb constitutive model, and the specific manifestation is:

[0022] τ = c + σ·tanφ;

[0023] where τ is the shear stress, c is the cohesion of the rock mass, σ is the normal stress, and φ is the internal friction angle.

[0024] Preferably, in S5, the load-displacement curve is obtained by using the measuring point extraction function in FLAC3D. Multiple measuring points are arranged along the loading direction, and the displacement changes at the head, joint plane, and tail of the bolt are extracted and the full-process bearing curve is plotted.

[0025] Preferably, the correction condition in S6 is: after comparing the physical test results, when the deviation from the simulation results is large, the material parameters, contact parameters, and load path are adjusted.

[0026] Preferably, in S7, combining the numerical simulation results with the physical test data, the expression of the ultimate bearing capacity of the grouted jointed rock mass is corrected, and the formula is:

[0027]

[0028] where A is the fitting constant, n, m, k are the fitting exponents, α is the joint dip angle, d a is the bolt diameter, l is the bonded section length, τ g is the bond strength, P u is the ultimate bearing capacity.

[0029] Preferably, based on the simulation results, the failure characteristics and instability laws of the grouted jointed rock mass anchor structure are extracted, and the structure failure characteristics and instability laws include:

[0030] Identifying and classifying shear failure, pull-out failure, and composite failure modes according to the loading angle and load level;

[0031] Analyzing the transformation mechanism of different loading paths on the failure mode, and clarifying the triggering conditions for the transformation from shear to pull-out or composite mode;

[0032] Determining the instability critical load of the joint plane or the bolt-rock mass system, and extracting the corresponding displacement mutation characteristics;

[0033] Establishing a quantitative correlation between the mechanical response and failure mode of the grouted structure, including the axial force and displacement response characteristics under various failure modes.

[0034] Self-stress anchor failure evolution simulation system for grouting reinforcement of jointed rock mass, comprising:

[0035] A modeling module for constructing a three-dimensional model of jointed rock mass and grouting structure;

[0036] A parameter setting module for defining joint parameters, grouting parameters and material constitutive models;

[0037] A loading control module for setting loading direction, loading speed and boundary conditions;

[0038] A numerical simulation module for performing simulation calculations based on the FLAC3D platform;

[0039] A verification and correction module for correcting parameters and assumptions in the numerical model by comparing with physical test data;

[0040] A result analysis module for extracting load-displacement curves, identifying failure modes and establishing theoretical bearing capacity expressions.

[0041] The present invention provides a self-stress anchor failure evolution simulation method and system for grouting reinforcement of jointed rock mass. It has the following beneficial effects:

[0042] 1. By precisely controlling the loading direction and loading angle in the simulation, the present invention analyzes the influence of different loading paths on the transformation of the failure mode of the grouting structure, solves the problem that traditional simulation methods ignore the change of the failure mode under different loading conditions, realizes a comprehensive analysis of the influence of the loading angle on the failure mode, and obtains the effect of accurately predicting the transformation of the failure mode under different loading paths.

[0043] 2. By constructing a three-dimensional numerical model including jointed rock mass and grouting structure in the FLAC3D platform, the present invention accurately describes the load transfer process between the anchor and the rock mass, considers the influence of the joint surface on the failure mode, realizes the accurate simulation of the failure evolution of the grouting structure of jointed rock mass, and obtains the effect of accurately reflecting the actual failure process.

[0044] 3. By combining the numerical simulation results with the physical test data, the present invention deduces and corrects the theoretical formula of the ultimate bearing capacity of grouted jointed rock mass, overcomes the problem that traditional methods are difficult to accurately evaluate the ultimate bearing capacity of the structure, realizes the accurate deduction and correction of the theoretical formula, and obtains the effect of providing a reliable bearing capacity evaluation for actual engineering.

[0045] 4. By extracting the load-displacement curve and systematically analyzing the mechanical responses under various failure modes, the present invention clarifies the critical load for instability and the characteristics of displacement mutation of the grouted bolt structure in jointed rock masses, solves the problem that traditional methods are insensitive to the transformation of failure modes, realizes the comprehensive extraction of failure modes and instability laws, and achieves a profound understanding and efficient prediction of the instability behavior of the grouted bolt structure. Description of the Drawings

[0046] Figure 1 It is a schematic diagram of the method steps of the present invention;

[0047] Figure 2 It is a schematic diagram of the system architecture of the present invention;

[0048] Figure 3 It is a flow chart of the indoor test of the present invention;

[0049] Figure 4 It is a schematic diagram of the shear failure test of the present invention;

[0050] Figure 5 It is a schematic diagram of the grouted joint pull-out test of the present invention. Detailed Embodiments

[0051] Next, in combination with the drawings of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] Please refer to the attached Figure 1 , the embodiment of the present invention provides a self-stress bolt failure evolution simulation method for grouting reinforcement of jointed rock masses, including the following steps:

[0053] S1. Construct a three-dimensional rock mass model containing joint structures in the FLAC3D platform, and define the spatial distribution and geometric parameters of the joint surfaces;

[0054] Specifically, the FLAC3D platform is used to first construct a three-dimensional rock mass model, where the rock mass is composed of multiple cells. These cells represent different rock materials, and different types of rock masses (such as granite, shale, etc.) can be simulated by setting their material properties. When constructing the rock mass model, special attention should be paid to the accurate setting of the joint planes (such as inclination angle, spacing, etc.). The joint planes should be set according to the distribution of fractures, fissures or discontinuity planes in the actual rock mass. Specifically, in FLAC3D, the joint plane is defined as a crack or discontinuity plane, and by setting anisotropic mechanical properties, the spatial distribution and geometric shape (such as the parallelism of joints, concavo-convex shape, etc.) of the joint plane can be ensured to conform to the actual situation. According to the actual engineering data, input the geometric parameters of the joints, such as length, width, spacing, fracture angle, etc.

[0055] The geometric parameters of the joint plane include the shape, azimuth angle, porosity of the joint and its relationship with the rest of the rock mass. The accuracy of the geometric parameters is the basis for ensuring the accuracy of numerical simulation. Simulate the distribution of these joint planes in FLAC3D through a three-dimensional modeling tool and ensure that their positions and sizes in the entire rock mass are consistent with the actual situation.

[0056] By accurately modeling the spatial distribution and geometric parameters of the joint plane, the non-uniformity of the rock mass in numerical simulation can be effectively considered, thus laying a foundation for subsequent loading and analysis and being able to better reflect the complexity in actual engineering.

[0057] S2. Introduce the grouting and bolting structure into the three-dimensional rock mass model, set the bolts, grout bodies and their contact relationships with the rock mass, and establish a bolt load transfer model;

[0058] The bolt load transfer model in S2 is simulated through the contact mechanical behavior between the bolt and the rock mass;

[0059] The grouting and bolting structure consists of steel bolts, grout bodies and free segments. The contact force model between the bolt and the rock mass is described by the interaction of adhesive force and slip force. A line-plane bonding model is adopted between the grout body and the rock mass, and the bonding strength τ of the grout body g and the axial force F of the bolt satisfy the relationship:

[0060]

[0061] where d a is the bolt diameter and l is the length of the bonded section.

[0062] Specifically, in this embodiment, we introduce the grouting and bolting structure into the three-dimensional rock mass model and set the contact relationships between the rock bolts, grout bodies, and rock mass. The grouting and bolting structure consists of steel rock bolts, grout bodies, and free segments. The contact mechanical behavior between the rock bolts and the rock mass is described by the interaction of adhesive force and slip force. Specifically, the contact force model between the rock bolts and the rock mass adopts the bond-slip model, where the adhesive force represents the adhesion between the rock bolts and the rock mass, and the slip force describes the slip phenomenon that occurs between the rock bolts and the rock mass under the action of load.

[0063] Next, the contact force between the grout body and the rock mass adopts the line-plane bond model. This model can better simulate the bonding characteristics between the grout body and the rock mass. The bonding strength of the grout body is not only affected by the properties of the grouting material but also related to the axial force of the rock bolts.

[0064] Through this model, we can more accurately depict the mechanical behavior of the grouting and bolting structure in numerical simulations. During the loading process, the adhesive force between the rock bolts and the rock mass plays a major role in load transfer, while the slip force simulates the relative sliding phenomenon when the load increases. The bonding strength between the grout body and the rock mass further enhances the overall stability of the structure. When the load exceeds a certain critical value, the adhesive force begins to weaken, and the slip phenomenon gradually intensifies, thus affecting the stability of the entire grouting and bolting structure.

[0065] This model provides us with a very intuitive and accurate load transfer process. Through careful parameter settings, the model can effectively predict the behavior of the grouting and bolting structure under actual working conditions, especially the ultimate bearing capacity and failure modes of the grouting and bolting structure under different conditions such as different grouting materials, rock bolt diameters, and bond segment lengths. This provides very reliable data support for engineering design, which can help designers conduct reasonable structural optimization in different application scenarios, thereby improving the overall safety and stability.

[0066] S3. Set the loading path. The loading method adopts displacement control, and the loading direction forms a certain angle with the joint plane; the loading path in S3 is a one-way displacement boundary applied along the direction of the angle θ with the normal of the joint plane, the loading speed is constant, and the loading angle θ is adjusted within the range of 0° to 90°. By controlling θ, the influence of different loading directions on the failure mode is analyzed.

[0067] Specifically, in this embodiment, the setting of the loading path is crucial. The loading method adopts displacement control, which means that we apply the load by controlling the displacement rather than directly increasing the load to control the deformation. This method can more accurately simulate the response of the structure under external deformation constraints in actual engineering. The angle between the loading direction and the joint plane is set as θ, and the loading path applies a one-way displacement boundary along the direction of the angle θ with the normal of the joint plane.

[0068] Specifically, we apply a one-way displacement boundary by setting the loading path along the direction of the angle θ with respect to the normal of the joint plane. This means that the loading direction is not completely perpendicular to the joint plane but is loaded at a certain angle. The loading speed is kept constant to ensure that the rate of structural deformation is consistent during each loading process, facilitating subsequent data analysis and comparison. In this embodiment, the range of the loading angle θ is set between 0° and 90°, and the value of θ can be adjusted to analyze the influence of different loading directions on the failure mode.

[0069] As the angle θ changes, different loading directions will have a significant impact on the failure mode of the structure. For example, when θ is 0°, the loading direction coincides exactly with the normal of the joint plane, and at this time, the load is mainly transmitted along the joint plane. When θ gradually increases to 90°, the loading direction gradually becomes perpendicular to the normal of the joint plane, the load transfer path and failure mechanism change, and the failure mode of the structure will also change accordingly. In this way, we can deeply study the response behavior of jointed rock masses under different loading conditions and accurately capture the failure mode caused by the load.

[0070] This setting of the loading path enables us to flexibly analyze the mechanical response and failure characteristics of grouted jointed rock masses under different loading directions.

[0071] S4. Establish a numerical model in FLAC3D, conduct mesh generation, and set the constitutive model of the rock mass material and the contact surface parameters;

[0072] Specifically, the purpose of mesh generation is to discretize the complex three-dimensional rock mass model so that each small element can be independently calculated according to its physical properties and behavior. The fineness of the mesh directly affects the accuracy of the simulation results. Therefore, during the modeling process, we ensure that the mesh generation can fully reflect the mechanical properties of the rock mass.

[0073] The constitutive model of the rock mass material adopts the Mohr-Coulomb constitutive model, which is commonly used to describe the shear failure behavior of rock materials. In practical applications, the Mohr-Coulomb constitutive model can well capture the failure mechanism of the rock mass under different stress conditions.

[0074] The relationship between the shear stress and the normal stress in the model is described by the following formula:

[0075] τ = c + σ·tanφ;

[0076] Where τ is the shear stress, c is the cohesion of the rock mass, σ is the normal stress, and φ is the internal friction angle.

[0077] Through this formula, we can see that when the rock mass is subjected to normal stress, its shear strength is not only related to the magnitude of the normal stress, but also closely related to the internal friction angle and cohesion. The internal friction angle describes the shear resistance of the rock mass, and cohesion is an important parameter for the rock mass to maintain its structural integrity without external forces.

[0078] Through this constitutive model, we can simulate in FLAC3D how the rock mass fails during the loading process as the load increases. When the normal stress increases, the shear stress of the rock mass also increases until it reaches the failure limit of the rock mass. At this time, cracks or slips will occur in the rock mass, and the model can accurately reflect the failure process of the rock mass through these behaviors.

[0079] Setting the contact surface parameters is also an important part of this step. The contact behaviors between the rock mass, grouting body, and anchor bolts are crucial for load transfer. The setting of the contact surface parameters directly affects the simulation accuracy, especially when simulating the failure evolution process. We set the bond strength and friction coefficient on the contact surface according to the Mohr-Coulomb model to ensure that the frictional force and slip force on the contact surface can accurately reflect the actual situation under the action of the load.

[0080] In this way, FLAC3D can not only accurately simulate the failure behavior of the rock mass, but also further enhance the reliability of the model through the detailed constitutive model and the setting of contact surface parameters.

[0081] S5. Conduct three-dimensional numerical simulation to obtain the mechanical response process of the grouted and bolted structure, and extract the load-displacement curve; the load-displacement curve in S5 is obtained by using the measuring point extraction function in FLAC3D. Multiple measuring points are arranged along the loading direction, and the displacement changes at the head, joint surface, and tail of the anchor bolt are extracted and the full-load process curve is plotted.

[0082] Specifically, the core task of this step is to analyze the bearing characteristics and failure process of the structure by simulating the behavior of the grouted and bolted structure under the action of the load, extracting the displacement changes of the anchor bolt, and plotting the load-displacement curve.

[0083] To obtain an accurate load-displacement curve, we used the measuring point extraction function in FLAC3D. In the numerical model, we arranged multiple measuring points along the loading direction at different positions. The main measuring points are located at the head, joint surface, and tail of the anchor bolt respectively. By extracting the displacement data at these key positions, we can comprehensively reflect the deformation of the grouted and bolted structure during the loading process.

[0084] Specifically, the loading process starts from the initial stage. As the load gradually increases, the grouted anchor structure will go through different deformation stages. During this process, we monitor the displacement changes of each measuring point. For example, the displacement of the bolt head mainly reflects the overall response of the structure, while the displacement at the joint surface can reveal the deformation and failure conditions on the contact surface. The displacement at the tail reflects the force transmission characteristics of the grouted anchor structure during the loading process.

[0085] Through the functions provided by FLAC3D, we can summarize the displacement change data of these measuring points and plot the load-displacement curve. This curve shows the relationship between the load and displacement during the entire process from the start of loading to the occurrence of failure. The load-displacement curve can help us identify the response characteristics of the structure under different loads, especially the ultimate bearing capacity of the structure, as well as the change rate of displacement and the failure mode when the load reaches the limit.

[0086] S6. By comparing with the physical test results, verify the deviation of the numerical model. If it meets the correction conditions, the three-dimensional rock mass model can be adjusted; the correction conditions in S6 are: after comparing the physical test results, when the deviation from the simulation results is large, adjust the material parameters, contact parameters and load path.

[0087] Specifically, according to the principle of similarity test, the physical test simulates the common shear and pull-out mechanical behaviors in the grouted joint project, and conducts the shear and pull-out tests of the grouted joint respectively. The indoor test process is as Figure 3 shown. In order to determine the ultimate bearing capacity of the grouted joint under different structural composition conditions, hard rocks and soft rocks with relatively high and low strengths are selected for the rock, such as granite and shale; the size of the rock specimen is 300×200×50. Ordinary Portland cement commonly used in engineering is selected for the cement. Mortar is used to simulate the grouting material, and two mortar strength standards of C20 and C10 are selected. The mortar thicknesses are selected as 5 cm, 10 cm, 15 cm and 20 cm. The strength of the bolt steel bars is selected as HPB235 and HRB335, and the diameter is selected as φ8. The implantation angles of the bolts are 900 and 450 respectively. The two ends of the bolts are threaded and anchored. Fine sand with a particle size range of 0.1-0.25 mm is selected as the aggregate. Each specimen is made strictly in accordance with the rock mechanics test regulations.

[0088] Direct shear test of grouted joint:

[0089] The failure of the grouted joint rock mass project often occurs in the shear stress area. Therefore, in order to simulate the actual working conditions, this project plans to conduct a shear failure test of the grouted joint (the schematic diagram of the shear test is as Figure 4As shown, it reveals the shear failure characteristics and their evolution laws of grouted joints. The possible locations of shear failure of grouted joints are: the jointed rock mass, the interface between the grout body and the rock mass, the grout body, and the interface between the bolt body and the grout cementation body. The failure characteristics of grouted joints are controlled by the composition and structural form of the grouted structure, and different failure characteristics of grouted joints correspond to different ultimate bearing capacity formulas of grouted joints. Therefore, in this experiment, a series of physical test models of grouted joints will be constructed. The selected joints are representative. Plane joint surfaces and uniformly concave-convex joint surfaces are used as representatives. Different strengths and grouting thicknesses will be used for the grout body. Different strengths, stiffnesses, diameters, and bolt inclination angles will be used for the grouted steel bars. Strain gauges will be pasted at corresponding parts of the shear surface, and stress gauges will be buried at the steel bar parts. Shear loads will be applied parallel to the joint surface to conduct a destructive shear test on the grouted joints. The stress and strain evolution processes during the shear process of the grouted joints will be monitored throughout the process. Image photography and speckle techniques will be used to observe the shear failure characteristics of the grouted joints, and the structural shear ultimate bearing capacity will be obtained.

[0090] Pull-out test of grouted joints:

[0091] The failure of the anchor root part of the prestressed bolt is also the main reason for the failure of the grouted joint rock mass project. Therefore, in this experiment, a pull-out test model of grouted joints will be established (the schematic diagram of the pull-out test is as Figure 5 shown), so as to simulate the whole process of the failure response of the anchor root structure of the prestressed bolt. The anchorage section of the ordinary prestressed bolt is often set in the intact and firm rock mass, and the anchoring force often depends on the bonding strength between the grout body and the rock surface of the hole wall. For the grouted joint rock mass under the action of the pull-out load, the bearing capacity of its anchorage section must consider the anti-shear contribution of the grouting wedge. There will be great differences in their bearing characteristics and stress distribution characteristics. Therefore, for the convenience of parameter testing and theoretical calculation in the experiment, the joint surface of the pull-out test model is assumed to be multiple groups of parallel and penetrating joint surfaces; steel bar stress gauges and strain gauges will be buried at different parts of the anchor pull steel bar and the side wall of the rock block to test the change law of stress and strain parameters during the pull-out test process, trace the key links of structural failure along the stress transmission path, observe the failure characteristics and evolution laws of the grouted structure under the action of the pull-out, and then judge the influencing factors of structural failure, and measure the anti-pull ultimate bearing capacity of the grouted structure.

[0092] Compare the results obtained from the above physical tests with the simulation results. If there are significant deviations between the simulation results and the actual test data, make adjustments according to the correction conditions. First, compare the load-displacement curves, deformation processes, etc. in the tests with the numerical simulation results. If the deviations are obvious, we will consider adjusting the material parameters, contact parameters, and load paths in the model. Material parameters, such as the elastic modulus, shear strength, and cohesion of the rock mass, may need to be fine-tuned according to the test data to better match the mechanical properties of the actual material. The contact surface parameters may also need to be reset, especially the friction coefficient and bond strength. If the test data shows different contact behaviors, adjusting these parameters will help improve the simulation results. In addition, the setting of the load path may also be the cause of the deviation. If the loading method or direction does not match the actual working conditions, we will adjust the load path to ensure that the simulation process is consistent with the actual loading situation.

[0093] S7. Based on the comparison between the numerical simulation results and the physical test results, deduce and correct the theoretical formula for the ultimate bearing capacity of grouted jointed rock masses, and finally obtain the accurate structural failure characteristics and deformation instability laws. In S7, combine the numerical simulation results with the physical test data to correct the expression for the ultimate bearing capacity of grouted jointed rock masses. The formula is:

[0094]

[0095] where A is the fitting constant, n, m, and k are the fitting exponents, α is the joint dip angle, d a is the bolt diameter, l is the bonded section length, τ g is the bond strength, and P u is the ultimate bearing capacity.

[0096] Extract the failure characteristics and instability laws of the grouted structure of jointed rock masses based on the simulation results. The failure characteristics and instability laws of the structure include:

[0097] Identify and classify shear failure, pull-out failure, and combined failure modes according to the loading angle and load level;

[0098] Analyze the transformation mechanism of different loading paths on the failure mode, and clarify the triggering conditions for the transformation from shear to pull-out or combined mode;

[0099] Determine the critical load for the instability of the joint surface or the bolt-rock mass system, and extract the corresponding displacement mutation characteristics;

[0100] Establish a quantitative relationship between the mechanical response and failure mode of the grouted structure, including the axial force and displacement response characteristics under various failure modes.

[0101] Specifically, by combining numerical simulation results and physical test data, the theoretical formula for the ultimate bearing capacity of grouted jointed rock mass was derived and corrected. By comparing the results of numerical simulation and physical test, the mechanical responses and failure modes of the grouting structure were extracted, and finally a set of accurate theoretical formulas and analysis methods for failure characteristics were obtained.

[0102] First, through the data comparison between numerical simulation and physical test, the expression of the ultimate bearing capacity of grouted jointed rock mass was corrected.

[0103] The formula is:

[0104] where A is the fitting constant, n, m, k are the fitting exponents, α is the joint dip angle, d a is the bolt diameter, l is the bonded section length, τ g is the bond strength, and P u is the ultimate bearing capacity.

[0105] These parameters extracted through numerical simulation were matched with the results of physical tests, thus correcting the theoretical formula to ensure its higher accuracy and reliability.

[0106] Based on the simulation results, we further extracted the failure characteristics and instability laws of the grouting structure of jointed rock mass. First, according to different loading angles and load levels, several main failure modes were identified and classified, including shear failure, pull-out failure and composite failure modes. The classification of these failure modes helped us understand how the grouting structure fails under different working conditions and the specific characteristics of the failure.

[0107] Secondly, we analyzed the influence of different loading paths on the transformation of failure modes and clarified the triggering conditions for the transformation from shear failure to pull-out or composite failure modes. For example, under certain conditions, the change of loading angle will cause the transformation of the failure mode of the structure, and this transformation is crucial for engineering design because it determines the bearing capacity and stability of the structure under different loads.

[0108] Furthermore, we determined the instability critical load of the joint surface or the bolt-rock mass system and extracted the displacement mutation characteristics at the time of instability. Through the study of the instability critical load and displacement mutation characteristics, we can predict the possible deformation and failure of the grouting structure under the action of the critical load, providing an important basis for the safety assessment of the structure.

[0109] Finally, we established a quantitative relationship between the mechanical responses and failure modes of the grouting structure, including the axial force and displacement response characteristics under various failure modes. This quantitative relationship can not only help us understand the deformation process of the grouting structure, but also provide data support for optimizing the design and improving the stability and safety of the structure in practical engineering.

[0110] Please refer to the attached Figure 2 , the self-stress bolt failure evolution simulation system for grouting reinforcement of jointed rock mass, includes:

[0111] A modeling module, used to construct a three-dimensional model of jointed rock mass and grouting structure;

[0112] A parameter setting module, used to define joint parameters, grouting parameters and material constitutive models;

[0113] A loading control module, used to set the loading direction, loading speed and boundary conditions;

[0114] A numerical simulation module, which performs simulation calculations based on the FLAC3D platform;

[0115] A verification and correction module, used to correct the parameters and assumptions in the numerical model by comparing with physical test data;

[0116] A result analysis module, used to extract the load-displacement curve, identify the failure mode and establish the theoretical bearing capacity expression.

[0117] Specifically, the modeling module is the starting point of the entire analysis process, mainly used to construct a three-dimensional model containing jointed rock mass and grouting structure. According to the actual engineering requirements, this module first defines the geometric shape and physical properties of the jointed rock mass, and adds the grouting structure on this basis. The geometric information, material properties, contact relationships, etc. of the model are set at this stage and used by other modules in the subsequent steps. The modeling module ensures the authenticity and rationality of the entire numerical model and provides basic data for subsequent simulation calculations and result analysis.

[0118] The parameter setting module follows the modeling module, mainly responsible for defining the physical parameters of the jointed rock mass and grouting structure. This includes the shape of the joint, the strength of the grouting body, the diameter and length of the bolt, the material constitutive model, etc. The material constitutive models used here, such as the Mohr-Coulomb model and the elastoplastic model, define key parameters such as the compressive strength, friction coefficient, and bonding strength of different materials based on the mechanical behavior of the rock mass. This module not only defines the properties of the materials, but also provides the necessary parameter support for the loading conditions and contact surface settings. All the set parameters will be called and applied in the numerical simulation stage.

[0119] The loading control module plays a crucial role throughout the simulation process. It is used to define the loading direction, loading rate, and the way of load application. The selection of the loading direction, especially the loading angle (such as the angle with the joint plane normal), directly affects the mechanical response of the structure. The loading rate is usually set to be constant to ensure a smooth and repeatable load application process. The setting of boundary conditions ensures that the model can simulate the actual stress state during the simulation, avoiding boundary effects or unrealistic free deformations. The output information of this module directly affects the calculation results of the numerical simulation module.

[0120] The numerical simulation module is the core part that performs the entire numerical simulation calculation, and it is calculated based on the FLAC3D platform. This module utilizes all the data input during the previous modeling and parameter setting stages, and calculates the mechanical response of the grouted jointed rock mass under different loading conditions according to numerical methods (such as the finite difference method). During this process, loads are applied to the model, and the model evolves step by step according to the mechanical state during the loading process, generating deformations, stress distributions, and the final failure modes. After this module is executed, the output includes mechanical response data such as stress fields, displacement fields, and load-displacement curves, providing support for subsequent analysis.

[0121] The verification and correction module is used to verify by comparing with physical test data after obtaining the preliminary results of the numerical simulation to ensure the accuracy of the numerical model. When there are significant deviations between the numerical simulation results and the experimental results, this module will adjust the key parameters in the model (such as material parameters, contact parameters, load paths, etc.) according to the actual situation. By comparing with the physical test data, it can be found whether the assumptions in the model are reasonable and whether the setting of certain parameters deviates from the actual situation. This module ensures that the numerical model can better fit the actual working conditions, improves the accuracy of the simulation results, and thus provides reliable data support for subsequent analysis.

[0122] The result analysis module is a key link for the final analysis after completing the numerical simulation and verifying the accuracy of the model. It extracts the load-displacement curves from the numerical simulation results, analyzes the mechanical response of the grouted structure, and identifies and discriminates the failure modes under different loading conditions (such as shear failure, pull-out failure, and composite failure modes). In addition, the result analysis module will also help to establish a theoretical bearing capacity formula through the analysis of the failure modes. This formula comprehensively considers the ultimate bearing capacity and deformation instability law of the grouted structure under different loading conditions and can be provided to engineering designers for structural optimization design.

[0123] Each module is interconnected through data flow and information transfer to form a closed loop. The modeling module and the parameter setting module first provide the model and the required physical data. The loading control module sets the loading conditions based on this data. Then, the numerical simulation module performs simulation calculations through FLAC3D. The simulation results are subsequently checked by the verification and correction module, and the model parameters are corrected by comparing with the physical test data to ensure the reliability of the results. Finally, the result analysis module analyzes the failure mode based on the corrected model, proposes the theoretical bearing capacity formula, and provides suggestions for the design.

[0124] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A simulation method for the failure evolution of self-stressing anchor bolts for grouting reinforcement of jointed rock masses, characterized in that, It includes the following steps: S1. Construct a three-dimensional rock mass model containing joint structures in the FLAC3D platform, and define the spatial distribution and geometric parameters of the joint surfaces; S2. Introduce the grouting and bolting structure into the three-dimensional rock mass model, set the contact relationships between bolts, grout bodies and the rock mass, and establish a bolt load transfer model; S3. Set the loading path, adopt displacement control for the loading method, and the loading direction forms a certain angle with the joint surface; S4. Establish a numerical model in FLAC3D and conduct mesh division, and set the constitutive model of the rock mass material and the contact surface parameters; S5. Conduct three-dimensional numerical simulation, obtain the mechanical response process of the grouting and bolting structure, and extract the load-displacement curve; S6. By comparing with the physical test results, verify the deviation of the numerical model. If it meets the correction conditions, the three-dimensional rock mass model can be adjusted; S7. Based on the comparison between the numerical simulation results and the physical test results, deduce and correct the theoretical formula for the ultimate bearing capacity of the grouted and bolted jointed rock mass, and finally obtain the accurate structural failure characteristics and deformation and instability laws.

2. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that In the S1, the spatial distribution and geometric parameters of the joint surface include joint dip angle, joint spacing and joint length. The joint surface is simulated by introducing a contact surface or a weak surface model in the three-dimensional rock mass model, and the contact friction angle and cohesion are set.

3. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that In the S2, the bolt load transfer model is simulated by the contact mechanical behavior between the bolt and the rock mass; The anchor injection structure consists of a steel anchor rod, a grouting body and a free section. The contact force model between the anchor rod and the rock mass is described by the interaction between the bonding force and the slip force. A line-plane bonding model is adopted between the grouting body and the rock mass, and the bonding strength τ of the grouting body g and the axial force F of the anchor rod satisfy the relationship: Among them, d a is the diameter of the anchor rod, and l is the length of the bonded section.

4. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that, In the S3, the loading path is a one-way displacement boundary applied along the direction of the angle θ with the normal of the joint surface. The loading speed is constant, and the loading angle θ is adjusted within the range of 0° to 90°. By controlling θ, the influence of different loading directions on the failure mode is analyzed.

5. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that, In the S4, the shear failure behavior of the rock mass material is described by the Mohr-Coulomb constitutive model, and the specific manifestation is: τ = c + σ·tanφ; where τ is the shear stress, c is the cohesion of the rock mass, σ is the normal stress, and φ is the internal friction angle.

6. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that In the S5, the load-displacement curve is obtained by using the measuring point extraction function in FLAC3D. A plurality of measuring points are arranged along the loading direction, and the displacement changes at the bolt head, joint surface and tail are extracted and the full-process bearing curve is drawn.

7. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that In the S6, the correction condition is: after comparing with the physical test results, when the deviation from the simulation results is large, the material parameters, contact parameters and load path are adjusted.

8. The self-stress bolt failure evolution simulation method for jointed rock mass grouting reinforcement according to claim 1, characterized in that, In the S7, combining the numerical simulation results and the physical test data, correct the expression of the ultimate bearing capacity of the grouted and bolted jointed rock mass. The formula is: where A is a fitting constant, n, m, and k are fitting exponents, α is the joint dip angle, d a is the bolt diameter, l is the bond length, and τ g is the bond strength.

9. The self-stress bolt failure evolution simulation method for jointed rock mass anchor grouting reinforcement according to claim 1, characterized in that Based on the simulation results, extract the failure characteristics and instability laws of the grouted and bolted jointed rock mass structure. The structural failure characteristics and instability laws include: Identify and divide the shear failure, pull-out failure and composite failure modes according to the loading angle and load level; Analyze the transformation mechanism of different loading paths on the failure mode, and clarify the triggering conditions for the transformation from shear to pull-out or composite mode; Determine the instability critical load of the joint surface or the bolt-rock mass system, and extract the corresponding displacement mutation characteristics; Establish a quantitative correlation between the mechanical response and the failure mode of the grouting and bolting structure, including the axial force and displacement response characteristics under various failure modes.

10. A self-stress bolt failure evolution simulation system for grouting reinforcement of jointed rock masses, according to the method for simulating the failure evolution of self-stress bolts for grouting reinforcement of jointed rock masses described in any one of claims 1-9, characterized in that, It includes: A modeling module for constructing a three-dimensional model of jointed rock mass and grouting and bolting structure; A parameter setting module for defining joint parameters, grouting parameters, and material constitutive models; A loading control module for setting the loading direction, loading speed, and boundary conditions; A numerical simulation module for performing simulation calculations based on the FLAC3D platform; A verification and correction module for correcting the parameters and assumptions in the numerical model by comparing with physical test data; A result analysis module for extracting load-displacement curves, identifying failure modes, and establishing theoretical bearing capacity expressions.

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