A method and system for distinguishing static damage from dynamic damage

Abstract

The present invention relates to a method and system for distinguishing static damage from dynamic damage, the method comprising: establishing a PFC 3D Discrete element model; PFC using trial and error method 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model; Determine multiple stress combinations based on indoor test results; Adjust the PFC based on multiple stress combinations 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results; determines the critical stress combination range according to the simulation results; determines the critical stress equation according to the critical stress combination range; determines the critical stress of the true triaxial sudden unloading failure process of granite according to the critical stress equation; determines whether the true triaxial sudden unloading failure process of granite has static failure or dynamic failure according to the critical stress. The present invention can accurately determine whether the true triaxial sudden unloading failure process of granite has static failure or dynamic failure.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanics, and in particular to a method and system for distinguishing static failure from dynamic failure. Background Art

[0002] Rockburst is a dynamic phenomenon in which the elastic energy accumulated in the rock mass is suddenly released due to unloading during excavation in high-altitude stress areas, resulting in the explosion and ejection of surrounding rocks. It is highly sudden, random and harmful. Rockburst disasters affect the progress of engineering construction and threaten the lives of construction workers. In order to study the conditions and failure mechanisms of rockbursts, scholars have carried out many true triaxial loading and unloading failure experiments. Jiang MZ et al. found that under low-rate unloading, the failure process of marble samples is more stable and dynamic ejection is not easy to occur. Feng XT et al. found that under the same stress state as when the sample was destroyed, the bearing capacity and deformation of the unloading stress path are greater than those of the loading stress path. Suo GS et al. used acoustic emission technology to study the characteristics and laws of the rockburst ejection failure process and obtained the acoustic emission precursors of static and dynamic instability of hard rock. Zhu GA et al. found that under certain confining pressure conditions, when the axial stress is greater than 3 times the uniaxial compressive strength of the coal sample, the coal sample will undergo rockburst failure.

[0003] Indoor true triaxial test equipment is expensive, and the stress paths that can be carried out in the test are limited, and it cannot simulate the complex and changeable rock burst stress conditions. Numerical simulation methods can take into account the nonlinear deformation characteristics of the rock mass and the changeable stress paths. Scholars use finite element, finite difference and discrete element methods to simulate the failure process of true triaxial unloading tests. Limited by the unit grid problem, most finite element and finite difference programs cannot simulate the rock crack propagation process well. Some scholars have written their own programs to simulate the true triaxial loading and unloading failure process of rocks, but their versatility is limited and they are often only applicable to certain specific stress paths.

[0004] Particle Flow Program PFC 3D It is developed based on discrete element theory, PFC 3D The model is composed of granular materials and can better simulate the initiation and expansion process of cracks in heterogeneous rock masses and the dynamic phenomena of particle ejection. Ma Chunchi et al. established a mechanical model of hard and brittle rock at the microscopic level and used PFC 3D The rockburst effect of triaxial unloading with different confining pressures was simulated, indicating that high confining pressure unloading has more obvious brittle fracture properties. Cong Yi et al. conducted conventional triaxial loading and unloading test simulations to explore the fracture properties and failure mechanisms of marble at different unloading rates. It was shown that the faster the unloading rate, the more likely the marble is to undergo brittle failure. When the unloading rate exceeds 6 MPa / s, the damage degree and failure form of the marble gradually become consistent. Wu Shunchuan et al. conducted an indoor unloading rockburst test of gray dolomite, using PFC 3DNumerical simulation of rock burst was carried out to explore the mesoscopic fracture phenomenon of rock samples in rock burst under different stress states. 3D The mesoscopic fracture process of rocks in true triaxial unloading tests was reproduced, and the evolution law of mesoscopic cracks was explored, indicating that the number of cracks increased rapidly during unloading. Zhang Y.J. et al. studied the mechanical and failure characteristics of marble specimens with prefabricated cracks under conventional triaxial unloading conditions by using the three-dimensional particle flow discrete element method (PB-DEM), indicating that as the initial confining pressure increases or the unloading rate decreases, the peak strength gradually increases, and the unloading stress path has a significant effect on the crack penetration type and final failure mode of marble specimens with prefabricated cracks. Bai QS et al. studied the failure behavior of anisotropic rock mass during true triaxial stress path loading through numerical simulation, indicating that the unloading of the intermediate principal stress σ2 and the minimum principal stress σ3 triggered microcracks in the early damage stage of the specimen, revealing the role of unloading in rock failure.

[0005] The true triaxial simulation test of rockburst focuses on analyzing the rock failure process and failure characteristics, while the rockburst particle flow simulation focuses on reproducing the particle ejection process. It is not clear whether the rock particle ejection completely corresponds to the rockburst, and the static-dynamic conversion mechanism and conversion conditions when the rockburst occurs are still unclear. It is impossible to distinguish between static and dynamic damage, which leads to inaccurate prediction of rockburst and unsatisfactory prevention and control effects. Summary of the invention

[0006] The purpose of the present invention is to provide a method and system for distinguishing static damage from dynamic damage, so as to solve the problems of inaccurate prediction of rock burst and unsatisfactory prevention and control effect in the prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A method for distinguishing static damage from dynamic damage includes:

[0009] Building PFC 3D Discrete Element Model;

[0010] The PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model; the microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation;

[0011] Determine multiple groups of stress combinations according to indoor test results; the indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite; the stress combinations include minimum principal stress and intermediate principal stress;

[0012] The adjusted PFC is adjusted according to a plurality of stress combinations 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results; the simulation results are the failure form, energy change, particle displacement and particle velocity under any of the stress combinations;

[0013] Determining a critical stress combination range according to the simulation results;

[0014] Determining a critical stress equation according to the critical stress combination range;

[0015] Determine the critical stress of granite true triaxial sudden unloading failure process according to the critical stress equation;

[0016] According to the critical stress, it is determined whether the granite true triaxial sudden unloading failure process will cause static failure or dynamic failure.

[0017] Optionally, the PFC is tested using a trial and error method. 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model, including:

[0018] According to the PFC 3D The macro parameters of the discrete element model are selected as 3D Mesoscopic parameters of the discrete element model; the macroscopic parameters include peak strength, elastic modulus and Poisson's ratio;

[0019] adjusting the mesoscopic parameters using a trial and error method;

[0020] When the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model are consistent with the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

[0021] Optionally, determining the critical stress combination range according to the simulation results specifically includes:

[0022] Determining the evolution process of particle displacement and particle velocity during the true triaxial sudden unloading failure simulation process according to the simulation results;

[0023] According to the evolution process, the failure form of true triaxial sudden unloading failure and the change law of instantaneous kinetic energy during the unloading failure process are determined;

[0024] Determining whether the simulation result is static failure or dynamic failure according to the failure form and the change rule of the instantaneous kinetic energy;

[0025] Determine the critical stress combination according to the stress combination that causes static failure and the stress combination that causes dynamic failure;

[0026] The critical stress combination range is determined according to the critical stress combination.

[0027] Optionally, determining the critical stress combination range according to the critical stress combination specifically includes:

[0028] The minimum principal stress remains unchanged, the intermediate principal stress is increased by 1 MPa as an increment, and the initial critical stress combination range is determined;

[0029] According to the initial critical stress combination range, the intermediate principal stress is increased in increments of 0.1 MPa to determine the critical stress combination range.

[0030] Optionally, determining the critical stress equation according to the critical stress combination range specifically includes:

[0031] Fitting the critical stress combination range to determine the critical stress equation;

[0032] The critical stress equation is: σ1-σ2=109.41+6.84σ3-0.146σ3 2 ; Among them, σ1 represents axial stress; σ2 represents intermediate principal stress; σ3 represents minimum principal stress.

[0033] A static damage and dynamic damage discrimination system, comprising:

[0034] Model building module for building PFC 3D Discrete Element Model;

[0035] The parameter adjustment module is used to adjust the PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model; the microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation;

[0036] A stress combination determination module is used to determine multiple groups of stress combinations according to indoor test results; the indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite; the stress combinations include minimum principal stress and intermediate principal stress;

[0037] A simulation module is used to simulate the adjusted PFC according to multiple groups of stress combinations. 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results; the simulation results are the failure form, energy change, particle displacement and particle velocity under any of the stress combinations;

[0038] A critical stress combination range determination module, used to determine the critical stress combination range according to the simulation results;

[0039] A critical stress equation determination module, used to determine the critical stress equation according to the critical stress combination range;

[0040] A critical stress determination module, used to determine the critical stress of the true triaxial sudden unloading failure process of granite according to the critical stress equation;

[0041] The discrimination module is used to discriminate whether static destruction or dynamic destruction occurs in the true triaxial sudden unloading destruction process of granite according to the critical stress.

[0042] Optionally, the parameter adjustment module specifically includes:

[0043] A parameter determination unit is used to determine the PFC 3D The macro parameters of the discrete element model are selected as 3D Mesoscopic parameters of the discrete element model; the macroscopic parameters include peak strength, elastic modulus and Poisson's ratio;

[0044] an adjustment unit, for adjusting the mesoscopic parameters by trial and error;

[0045] The model determines the unit for when the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model are consistent with the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

[0046] Optionally, the critical stress combination range determination module specifically includes:

[0047] An evolution process determination unit, used to determine the evolution process of particle displacement and particle velocity in the true triaxial sudden unloading failure simulation process according to the simulation results;

[0048] According to the evolution process, the failure form of true triaxial sudden unloading failure and the change law of instantaneous kinetic energy during the unloading failure process are determined;

[0049] A determination unit, configured to determine whether the simulation result is static failure or dynamic failure according to the failure form and the change rule of the instantaneous kinetic energy;

[0050] A critical stress combination determination unit is used to determine a critical stress combination according to a stress combination causing static failure and a stress combination causing dynamic failure;

[0051] The critical stress combination range determining unit is used to determine the critical stress combination range according to the critical stress combination.

[0052] Optionally, the critical stress combination range determining unit specifically includes:

[0053] An initial range determination subunit is used to keep the minimum principal stress unchanged, increase the intermediate principal stress by 1 MPa as an increment, and determine the initial critical stress combination range;

[0054] The refinement subunit is used to increase the intermediate principal stress by 0.1 MPa as an increment according to the initial critical stress combination range to determine the critical stress combination range.

[0055] Optionally, the critical stress equation determination module specifically includes:

[0056] The critical stress equation determination unit is used to fit the critical stress combination range to determine the critical stress equation; the critical stress equation is σ1-σ2=109.41+6.84σ3-0.146σ3 2 ; Among them, σ1 represents axial stress; σ2 represents intermediate principal stress; σ3 represents minimum principal stress.

[0057] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0058] The present invention establishes PFC 3D Discrete element model; PFC using trial and error method 3D The microscopic parameters of the discrete element model are adjusted; multiple stress combinations are determined based on the indoor test results; the adjusted PFC is 3D The discrete element model is used to simulate the true triaxial loading failure and the true triaxial sudden unloading failure to obtain simulation results; the critical stress equation is determined according to the simulation results, and then the critical stress is determined; according to the critical stress, it is determined whether the granite true triaxial sudden unloading failure process occurs static failure or dynamic failure. Based on the indoor test results, the present invention uses the particle flow program PFC 3D Establish a discrete element model and analyze the PFC3D The discrete element model is used to perform damage simulation to determine the critical stress equation, thereby judging whether the true triaxial sudden unloading damage process of granite occurs static damage or dynamic damage, which improves the accuracy of rock burst prediction and achieves a good effect in rock burst prevention and control. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0060] Figure 1 A flowchart of a method for distinguishing static damage from dynamic damage provided by the present invention;

[0061] Figure 2 Indoor test and PFC in the specific implementation mode of the present invention 3D Discrete element model simulation specimen diagram; among them, Figure 2 (a) is a schematic diagram of the granite sample for indoor testing; Figure 2 (b) PFC 3D Schematic diagram of discrete element model;

[0062] Figure 3 Indoor test and PFC in the specific implementation mode of the present invention 3D Comparison of stress-strain curves simulated by discrete element model;

[0063] Figure 4 It is a schematic diagram of the sudden unloading direction in a specific embodiment of the present invention;

[0064] Figure 5 This is a schematic diagram of the true triaxial sudden unloading failure form of granite in a specific embodiment of the present invention; wherein: Figure 5 (a) is a schematic diagram of the first failure form; Figure 5 (b) is a schematic diagram of the second damage form; Figure 5 (c) is a schematic diagram of the third damage form;

[0065] Figure 6 This is a graph of instantaneous kinetic energy-axial strain curve of numerical simulation scheme I in a specific implementation manner of the present invention; wherein, Figure 6 (a) is the instantaneous kinetic energy-axial strain curve when the minimum principal stress σ3 = 10 MPa; Figure 6 (b) is the instantaneous kinetic energy-axial strain curve when the minimum principal stress σ3 = 20 MPa; Figure 6 (c) is the instantaneous kinetic energy-axial strain curve when the minimum principal stress σ3 = 30 MPa;

[0066] Figure 7 It is a comparison diagram of static-dynamic destruction instantaneous kinetic energy curves in a specific embodiment of the present invention;

[0067] Figure 8 It is a stress combination relationship curve diagram of dynamic failure critical state in a specific implementation mode of the present invention;

[0068] Fig. 9 This is a structural diagram of a static damage and dynamic damage discrimination system provided by the present invention. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] The purpose of the present invention is to provide a method and system for distinguishing static damage from dynamic damage, so as to solve the problems of inaccurate prediction of rock burst and unsatisfactory prevention and control effect in the prior art.

[0071] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] Figure 1 A flow chart of a method for distinguishing static damage from dynamic damage provided by the present invention is shown in FIG. Figure 1 As shown, a method for distinguishing static damage from dynamic damage includes:

[0073] Step 101: Build PFC 3D Discrete element model. In practical applications, PFC 3D The discrete element model is a cuboid. In order to make the simulation results more realistic, PFC 3D The size of the discrete element model is the same as that of the indoor test specimen, which is 50 mm × 50 mm × 100 mm. Figure 2 As shown in (a), the boundary conditions are determined by generating a wall, and particles with a diameter of 2.5 to 3.75 mm are randomly generated within the boundary. The total number of particles is 9761, PFC 3D Discrete element model Figure 2 (b) as shown.

[0074] Step 102: Use trial and error to test the PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC3D Discrete element model. The microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation. In practical applications, the adjusted PFC 3D The discrete element model can accurately describe the physical and mechanical properties of rock mass.

[0075] In a specific implementation, the step 102 specifically includes:

[0076] According to the PFC 3D The macro parameters of the discrete element model are selected as 3D The microscopic parameters of the discrete element model; the macroscopic parameters include peak strength, elastic modulus and Poisson's ratio.

[0077] The mesoscopic parameters were adjusted using a trial and error method.

[0078] When the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model are consistent with the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

[0079] In practical applications, due to PFC 3D The macroscopic parameters of the discrete element model are mainly affected by the microscopic parameters of the contact between particles. Parallel bonding that can transmit force and torque is selected to better reflect the mechanical properties of rock. First, based on the macroscopic parameters (peak strength, elastic modulus and Poisson's ratio, etc.), the microscopic parameters (particle-particle contact modulus, particle stiffness ratio, parallel bonding elastic modulus, parallel bonding stiffness ratio, particle friction coefficient, parallel bonding radius multiplier, parallel bonding normal strength mean, parallel bonding normal strength standard deviation, parallel bonding tangential strength mean and parallel bonding tangential strength standard deviation, etc.) are preliminarily selected, and then the various microscopic parameters are adjusted by trial and error to make PFC 3D The stress-strain curve, peak strength value, peak strain value, and failure mode of granite simulated by the discrete element model are consistent with the indoor test results, such as Figure 3 As shown (Numercial simulation test for PFC 3D Numerical simulation, Laboratory test is indoor test, ordinate σ1 is the first principal stress, abscissa ε1 is the axial stress), which shows that the microscopic parameters can better reflect the mechanical properties and failure characteristics of granite under true triaxial stress state. The PFC finally selected 3DThe microscopic parameters of the discrete element model are shown in Table 1.

[0080] Table 1 Final selected PFC 3D Discrete element model micro-parameter table

[0081]

[0082]

[0083] Step 103: Determine multiple groups of stress combinations according to the indoor test results. The indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite. The stress combinations include minimum principal stress and intermediate principal stress.

[0084] In practical applications, based on the results of indoor tests, by supplementing more simulation schemes and conducting simulations, we find more stress combinations of static-dynamic failure in the true triaxial sudden unloading failure process, and determine the critical stress combination based on the stress combination. When the stress combination is greater than the critical stress combination, dynamic failure occurs in the true triaxial sudden unloading failure process; when the stress combination is less than the critical stress combination, static failure occurs in the true triaxial sudden unloading failure process.

[0085] The results of the true triaxial unloading failure test of granite were carried out at three unloading confining pressure rates. In order to study the influence of unloading rate on the rock failure mechanism, the indoor test was supplemented by numerical simulation. The test scheme to supplement the indoor test is shown in Table 2.

[0086] Table 2 Test plan to supplement indoor test

[0087]

[0088]

[0089] According to the test results, in order to find the critical stress combination of static-dynamic failure in the true triaxial sudden unloading failure process, more simulation schemes need to be added. Table 3 shows the simulation schemes added for the particle flow simulation test, with a total of 66 stress combinations, as shown in Table 3.

[0090] Table 3 Additional simulation schemes for particle flow simulation test

[0091]

[0092] Step 104: Regulate the adjusted PFC according to the plurality of stress combinations. 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results, which are the failure form, energy change, particle displacement and particle velocity under any of the stress combinations.

[0093] True triaxial loading failure simulation: Use servo control to move the surrounding "walls" and simultaneously increase the compressive stresses σ2 and σ3 in two directions to the set confining pressure (σ2 = 40MPa, σ3 = 30MPa); keep σ2 and σ3 unchanged, load axial stress σ1 at the target speed until the rock sample fails, and obtain the peak strength σ of the rock sample p . Among them, σ1 represents the axial stress; σ2 represents the intermediate principal stress; σ3 represents the minimum principal stress; here, the target speed is set to 0.001MPa / step. In other embodiments, the target speed can also be other values, which need to be determined according to the actual simulated working conditions.

[0094] True triaxial sudden unloading simulation: Figure 4 As shown in the figure, the compressive stresses σ2 and σ3 in the two directions are increased synchronously to the set value and then remain unchanged. The upper and lower "walls" are moved by servo control to increase the axial stress σ1 to the target value σ u (80% of the peak intensity) and then remain unchanged; keep σ1 and σ2 unchanged, delete a "wall" in the direction of σ3, and realize the simulation of a sudden unloading process.

[0095] Step 105: Determine the critical stress combination range according to the simulation results.

[0096] In a specific implementation, the step 105 specifically includes:

[0097] The evolution process of the particle displacement and particle velocity during the true triaxial sudden unloading failure simulation is determined according to the simulation results.

[0098] The failure form of sudden unloading failure and the changing law of instantaneous kinetic energy during the unloading failure process are determined according to the evolution process.

[0099] The simulation result is determined to be static failure or dynamic failure according to the failure form and the changing rule of the instantaneous kinetic energy.

[0100] The critical stress combination is determined based on the stress combination that causes static failure and the stress combination that causes dynamic failure.

[0101] The critical stress combination range is determined according to the critical stress combination.

[0102] In a specific embodiment, determining the critical stress combination range according to the critical stress combination specifically includes:

[0103] The minimum principal stress value remains unchanged, and the intermediate principal stress is increased in increments of 1 MPa to determine the initial critical stress combination range.

[0104] According to the initial critical stress combination range, the intermediate principal stress is increased in increments of 0.1 MPa to determine the critical stress combination range.

[0105] In practical applications, as the axial stress continues to increase during the simulation, the displacement and velocity of the particles also change continuously. By recording the particle velocity cloud map and particle displacement cloud map under different axial stresses, the particle displacement and velocity evolution process of the true triaxial sudden unloading simulation is obtained. u When the stress level is low, the inclined "interlaced plane" formed by the particle displacement corresponds to the position of the macroscopic shear failure surface. The true triaxial sudden unloading failure forms of granite are classified by analyzing the number of particles ejected from the unloading free surface and the crack penetration. The failure forms are divided into three categories: ① A small number of particles are ejected near the unloading free surface, and no obvious through cracks appear, such as Figure 5 (a) As shown; ② Some particles are ejected at the end of the unloading free surface, and the internal cracks penetrate to form a main fracture surface, such as Figure 5 (b) As shown; ③ A large number of particles are ejected from the end and middle of the unloading free surface, forming an obvious "V" shape on the surface of the rock sample, and the internal cracks penetrate to form a main fracture surface and a secondary fracture surface, as shown in Figure 5 (c) as shown.

[0106] During the simulation, the energy value, stress and strain value are recorded, and finally the instantaneous kinetic energy-axial strain curve is obtained, such as Figure 6 As shown in the figure (the ordinate transient kinetic energy is the instantaneous kinetic energy, and the abscissa ε1 is the axial stress), according to the change law of the instantaneous kinetic energy-axial strain curve during the unloading failure process, it can be divided into two categories: one is that the instantaneous kinetic energy suddenly increases during the unloading failure process, and then decreases rapidly and stabilizes at a lower value, and then the instantaneous kinetic energy has only a small number of sporadic jumps, which is considered to be static failure, such as Figure 6 (a) As shown; the second is that the instantaneous kinetic energy suddenly increases during the unloading destruction process, and then decreases rapidly. After a short "quiet period", the instantaneous kinetic energy gradually increases, forming a dense area with high instantaneous kinetic energy values, which is considered to be dynamic destruction. Figure 6 (b) Figure 6 By judging whether there is a short "quiet period" in the change of instantaneous kinetic energy (i.e., the instantaneous kinetic energy is basically zero for a period of time), and whether a second large increase occurs to form a dense area with high instantaneous kinetic energy values, the static damage and dynamic damage in the true triaxial sudden unloading process can be distinguished, such as Figure 7 As shown (Dynamic failure is dynamic failure, Static failure is static failure), Figure 7The solid line is the instantaneous kinetic energy-axial strain curve of the stress combination σ3 = 10MPa, σ2 = 20MPa, and the dotted line is the instantaneous kinetic energy-axial strain curve of the stress combination σ3 = 30MPa, σ2 = 240MPa. It can be seen that the instantaneous kinetic energy characteristics of static failure are: sudden jump-low value fluctuation. This type of failure characteristics is similar to Figure 5 (a) Corresponding to the type ① damage form; the instantaneous kinetic energy characteristics of dynamic damage are: sudden jump-quiet period-slow increase. This type of damage characteristics is similar to Figure 5 (b) Figure 5 (c) Types ② and ③ have broken correspondence.

[0107] According to the failure form and the changing law of instantaneous kinetic energy during the unloading failure process, the static failure and dynamic failure of the particle flow simulation results of true triaxial sudden unloading failure of granite are distinguished, and the critical stress of true triaxial sudden unloading static-dynamic failure is found. The critical value means that when the minimum principal stress is the same, dynamic failure occurs when the intermediate principal stress ≥ the critical value, and static failure occurs when the intermediate principal stress < the critical value.

[0108] In practical applications, the simulation results of granite true triaxial sudden unloading failure are shown in Table 4. When σ3 ≥ 20 MPa, the granite specimens all suffered dynamic failure; when σ3 = 10 MPa, the granite specimens all suffered static failure. It is inferred that the critical stress of true triaxial sudden unloading static-dynamic failure is in the combination of 10 MPa < σ3 < 20 MPa. When σ2 = σ3 is set and gradually reduced from σ2 = σ3 = 20 MPa, it is found that when σ2 = σ3 ≥ 17.3 MPa, the granite specimens all suffered dynamic failure.

[0109] Table 4 Simulation results of true triaxial sudden unloading failure of granite

[0110]

[0111] In order to determine the critical stress combination of static-dynamic failure, the stress combination with the minimum principal stress σ3 < 17.3MPa is taken for simulation based on the above, and the process is as follows:

[0112] (1) The minimum principal stress σ3 is fixed (respectively 17, 16, 15, 14, and 13 MPa), the intermediate principal stress σ2 is equal to the minimum principal stress σ3, and then the intermediate principal stress is increased in increments of 1 MPa to preliminarily determine the critical stress combination range.

[0113] (2) Refine the results of the previous step, take the intermediate principal stress at intervals of 0.1 MPa, and determine the critical value of the intermediate principal stress σ2.

[0114] The statistical table of simulation results of the refined scheme for true triaxial sudden unloading failure of granite is shown in Table 5. The bold numbers in the table are the critical values ​​of the intermediate principal stress σ2 when dynamic failure occurs.

[0115] Table 5 Statistics of simulation results of granite true triaxial sudden unloading refinement scheme

[0116]

[0117]

[0118] According to Table 5, five groups of critical stress combinations for dynamic failure are determined:

[0119] (1)σ3=17MPa, σ2=17.9MPa;

[0120] (2)σ3=16MPa, σ2=19.8MPa;

[0121] (3)σ3=15MPa, σ2=24.0MPa;

[0122] (4)σ3=14MPa, σ2=27.4MPa;

[0123] (5)σ3=13MPa, σ2=30.2MPa.

[0124] The above five groups of critical stress combinations are fitted, such as Figure 8 As shown in the figure (Fitted curve is the fitting curve, Correlation coefficient is the correlation coefficient), the critical stress equation that needs to be satisfied for the dynamic failure of granite under true triaxial sudden unloading is:

[0125] σ1-σ2=109.41+6.84σ3-0.146σ3 2

[0126] In order to verify the correctness of the criterion, the three principal stress values ​​of the true triaxial unloading failure test were substituted into the above formula for verification, and the predicted results were basically consistent with the actual results.

[0127] Step 106: Determine a critical stress equation according to the critical stress combination range.

[0128] In a specific implementation, the step 106 specifically includes:

[0129] The critical stress combination range is fitted to determine the critical stress equation. The critical stress equation is σ1-σ2=109.41+6.84σ3-0.146σ3 2 .

[0130] Step 107: Determine the critical stress of the true triaxial sudden unloading failure process of granite according to the critical stress equation.

[0131] Step 108: Determine whether static failure or dynamic failure occurs in the true triaxial sudden unloading failure process of the granite according to the critical stress.

[0132] The purpose of the present invention is to study the conditions and destruction mechanism of rock burst, distinguish static destruction from dynamic destruction, and judge the static-dynamic conversion mechanism and conversion conditions when rock burst occurs.

[0133] The beneficial effects of the present invention are as follows: (1) The present invention is based on the results of true triaxial loading and unloading failure tests of granite to develop a particle flow program PFC 3D Numerical simulation overcomes the problems of expensive indoor true triaxial test equipment and limited stress paths that can be tested.

[0134] (2) Compared with the experiment, the rockburst particle flow simulation focuses on reproducing the particle ejection process, better simulating the initiation and expansion process of cracks in heterogeneous rock masses and the dynamic phenomenon of particle ejection, and exploring the static-dynamic conversion mechanism and conversion conditions of true triaxial unloading failure of granite.

[0135] Fig. 9 A structural diagram of a static damage and dynamic damage discrimination system provided by the present invention, such as Fig. 9 As shown, a static damage and dynamic damage discrimination system includes:

[0136] Model building module 901, used to build PFC 3D Discrete element model.

[0137] The parameter adjustment module 902 is used to adjust the PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model. The microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation.

[0138] In a specific implementation, the parameter adjustment module 902 specifically includes:

[0139] A parameter determination unit is used to determine the PFC 3D The macro parameters of the discrete element model are selected as 3D The microscopic parameters of the discrete element model include peak strength, elastic modulus and Poisson's ratio.

[0140] An adjustment unit is used to adjust the microscopic parameters using a trial and error method.

[0141] The model determines the unit for when the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model under true triaxial loading correspond to the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

[0142] The stress combination determination module 903 is used to determine multiple groups of stress combinations according to indoor test results. The indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite. The stress combinations include minimum principal stress and intermediate principal stress.

[0143] The simulation module 904 is used to simulate the adjusted PFC according to the multiple stress combinations. 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results, which are the failure mode, energy change, particle displacement and particle velocity under any of the stress combinations.

[0144] The critical stress combination range determination module 905 is used to determine the critical stress combination range according to the simulation results.

[0145] In a specific implementation, the critical stress combination range determination module 905 specifically includes:

[0146] The evolution process determination unit is used to determine the evolution process of particle displacement and particle velocity in the true triaxial sudden unloading failure simulation process according to the simulation results.

[0147] According to the evolution process, the failure form of true triaxial sudden unloading failure and the change law of instantaneous kinetic energy during the unloading failure process are determined.

[0148] A distinguishing unit is used to determine whether the simulation result is static damage or dynamic damage according to the damage form and the changing rule of the instantaneous kinetic energy.

[0149] The critical stress combination determination unit is used to determine the critical stress combination according to the stress combination causing static failure and the stress combination causing dynamic failure.

[0150] The critical stress combination range determining unit is used to determine the critical stress combination range according to the critical stress combination.

[0151] In a specific embodiment, the critical stress combination range determining unit specifically includes:

[0152] The initial range determination subunit is used to keep the minimum principal stress unchanged, increase the intermediate principal stress by 1 MPa as an increment, and determine the initial critical stress combination range.

[0153] The refinement subunit is used to increase the intermediate principal stress by 0.1 MPa as an increment according to the initial critical stress combination range to determine the critical stress combination range.

[0154] The critical stress equation determination module 906 is used to determine the critical stress equation according to the critical stress combination range.

[0155] In a specific implementation, the critical stress equation determination module 906 specifically includes:

[0156] The critical stress equation determination unit is used to fit the critical stress combination range to determine the critical stress equation. The critical stress equation is σ1-σ2=109.41+6.84σ3-0.146σ3 2 .

[0157] The critical stress determination module 907 is used to determine the critical stress of the true triaxial sudden unloading failure process of granite according to the critical stress equation.

[0158] The determination module 908 is used to determine whether static failure or dynamic failure occurs in the true triaxial sudden unloading failure process of granite according to the critical stress.

[0159] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0160] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for distinguishing static damage from dynamic damage, characterized in that: include: Building PFC 3D Discrete Element Model; The PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model; the microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation; Determine multiple groups of stress combinations according to indoor test results; the indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite; the stress combinations include minimum principal stress and intermediate principal stress; The adjusted PFC is adjusted according to a plurality of stress combinations 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results; the simulation results are the failure mode, energy change, particle displacement and particle velocity under any of the stress combinations; Determining a critical stress combination range according to the simulation results; Determining a critical stress equation according to the critical stress combination range; Determine the critical stress of granite true triaxial sudden unloading failure process according to the critical stress equation; According to the critical stress, it is determined whether the granite true triaxial sudden unloading failure process will cause static failure or dynamic failure.

2. The method for distinguishing static damage from dynamic damage according to claim 1, characterized in that: The PFC is tested by trial and error. 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model, including: According to the PFC 3D The macro parameters of the discrete element model are selected as 3D Mesoscopic parameters of the discrete element model; the macroscopic parameters include peak strength, elastic modulus and Poisson's ratio; adjusting the mesoscopic parameters using a trial and error method; When the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model are consistent with the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

3. The method for distinguishing static damage from dynamic damage according to claim 1, characterized in that: Determining the critical stress combination range according to the simulation results specifically includes: Determining the evolution process of particle displacement and particle velocity during the true triaxial sudden unloading failure simulation process according to the simulation results; According to the evolution process, the failure form of true triaxial sudden unloading failure and the change law of instantaneous kinetic energy during the unloading failure process are determined; Determining whether the simulation result is static failure or dynamic failure according to the failure form and the change rule of the instantaneous kinetic energy; Determine the critical stress combination according to the stress combination that causes static failure and the stress combination that causes dynamic failure; The critical stress combination range is determined according to the critical stress combination.

4. The method for distinguishing static damage from dynamic damage according to claim 3, characterized in that: Determining the critical stress combination range according to the critical stress combination specifically includes: The minimum principal stress remains unchanged, the intermediate principal stress is increased by 1 MPa as an increment, and the initial critical stress combination range is determined; According to the initial critical stress combination range, the intermediate principal stress is increased in increments of 0.1 MPa to determine the critical stress combination range.

5. The method for distinguishing static damage from dynamic damage according to claim 1, characterized in that: Determining the critical stress equation according to the critical stress combination range specifically includes: The critical stress combination range is fitted to determine the critical stress equation; the critical stress equation is σ1-σ2=109.41+6.84σ3-0.146σ3 2 ; Among them, σ1 represents axial stress; σ2 represents intermediate principal stress; σ3 represents minimum principal stress.

6. A static damage and dynamic damage discrimination system, characterized in that: include: Model building module for building PFC 3D Discrete Element Model; The parameter adjustment module is used to adjust the PFC 3D The microscopic parameters of the discrete element model are adjusted to obtain the adjusted PFC 3D Discrete element model; the microscopic parameters include particle-particle contact modulus, particle stiffness ratio, parallel bond elastic modulus, parallel bond stiffness ratio, particle friction coefficient, parallel bond radius multiplier, parallel bond normal strength mean, parallel bond normal strength standard deviation, parallel bond tangential strength mean and parallel bond tangential strength standard deviation; A stress combination determination module is used to determine multiple groups of stress combinations according to indoor test results; the indoor test results are test results of indoor true triaxial loading and unloading failure tests of granite; the stress combination includes a minimum principal stress value and an intermediate principal stress value; A simulation module is used to simulate the adjusted PFC according to multiple groups of stress combinations. 3D The discrete element model performs true triaxial loading failure simulation and true triaxial sudden unloading failure simulation to obtain simulation results; the simulation results are the failure form, energy change, particle displacement and particle velocity under any of the stress combinations; A critical stress combination range determination module, used to determine the critical stress combination range according to the simulation results; A critical stress equation determination module, used to determine the critical stress equation according to the critical stress combination range; A critical stress determination module, used to determine the critical stress of the true triaxial sudden unloading failure process of granite according to the critical stress equation; The discrimination module is used to discriminate whether static destruction or dynamic destruction occurs in the true triaxial sudden unloading destruction process of granite according to the critical stress.

7. The static damage and dynamic damage discrimination system according to claim 6, characterized in that: The parameter adjustment module specifically includes: A parameter determination unit is used to determine the PFC 3D The macro parameters of the discrete element model are selected as 3D Mesoscopic parameters of the discrete element model; the macroscopic parameters include peak strength, elastic modulus and Poisson's ratio; an adjustment unit, for adjusting the mesoscopic parameters by trial and error; The model determines the unit for when the PFC 3D When the stress-strain curve, peak strength value, peak strain value and failure form of granite simulated by discrete element model are consistent with the indoor test results, the adjusted PFC is obtained. 3D Discrete element model.

8. The static damage and dynamic damage discrimination system according to claim 6, characterized in that: The critical stress combination range determination module specifically includes: An evolution process determination unit, used to determine the evolution process of particle displacement and particle velocity in the true triaxial sudden unloading failure simulation process according to the simulation results; According to the evolution process, the failure form of sudden unloading failure and the change law of instantaneous kinetic energy during the unloading failure process are determined; A determination unit, configured to determine whether the simulation result is static failure or dynamic failure according to the failure form and the change rule of the instantaneous kinetic energy; A critical stress combination determination unit is used to determine a critical stress combination according to a stress combination causing static failure and a stress combination causing dynamic failure; The critical stress combination range determining unit is used to determine the critical stress combination range according to the critical stress combination.

9. The static damage and dynamic damage discrimination system according to claim 8, characterized in that: The critical stress combination range determination unit specifically includes: An initial range determination subunit is used to keep the minimum principal stress unchanged, increase the intermediate principal stress by 1 MPa as an increment, and determine the initial critical stress combination range; The refinement subunit is used to increase the intermediate principal stress by 0.1 MPa as an increment according to the initial critical stress combination range to determine the critical stress combination range.

10. The static damage and dynamic damage discrimination system according to claim 6, characterized in that: The critical stress equation determination module specifically includes: The critical stress equation determination unit is used to fit the critical stress combination range to determine the critical stress equation; the critical stress equation is σ1-σ2=109.41+6.84σ3-0.146σ3 2 ; Among them, σ1 represents axial stress; σ2 represents intermediate principal stress; σ3 represents minimum principal stress.

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