Discrete element simulation method and device for self-healing characteristics of salt rock

Abstract

The application relates to the technical field of salt rock damage self-healing, in particular to a salt rock self-healing characteristic discrete element simulation method and device.The method comprises the following steps: based on a pre-constructed healing starting criterion of target salt rock, in the case that the preset healing condition is met among the particles of the damage interface of the target salt rock, reconstructing the broken contact among the particles into a rebonding contact, giving new parallel bonding force among the particles, determining the equivalent healing stress of the damage interface of the target salt rock after healing, further quantifying the strain evolution of the volume before healing and the volume after healing, and in the case that the strain evolution result meets the preset healing termination condition, generating a discrete element simulation result of the self-healing characteristic of the target salt rock. Thus, the problem that in the related art, after the contact among the particles is broken, the bonding with strength cannot be re-established, and the microscopic mechanics recovery process of the self-healing of the salt rock after damage cannot be truly reflected is solved.

Description

Technical Field

[0001] This application relates to the field of salt rock damage self-healing technology, and in particular to a discrete element simulation method and apparatus for salt rock self-healing characteristics. Background Technology

[0002] Salt rock is widely used for underground energy storage and nuclear waste disposal. One of the most prominent characteristics of its mechanical behavior is the self-healing phenomenon of microcracks under certain conditions, meaning that cracks can close again after damage, restoring a certain strength. Mainstream salt rock mechanical simulations often employ continuum methods, such as FEM (Finite Element Method) and FDM (Finite Difference Method). These methods treat the material as a continuum, based on stress-strain equivalent fields, making it difficult to accurately characterize the entire process of crack formation, evolution, and closure, especially given the discrete and nonlinear nature of crack regeneration and self-healing processes. Therefore, the Discrete Element Method (DEM) can be used to analyze the damage development process of salt rock.

[0003] However, while the discrete element method in related technologies can simulate the occurrence and closure of cracks, it cannot re-establish strong adhesion once the contact between particles breaks. It lacks physical modeling of the restoration of mechanical connection between particles during the healing process and cannot truly reflect the microscopic mechanical restoration process of self-healing after salt rock damage. This reduces the physical realism and engineering prediction reliability of salt rock self-healing behavior in discrete element simulation, which urgently needs to be solved. Summary of the Invention

[0004] This application is based on the inventor's understanding and insights into the following issues:

[0005] First, the damage-self-healing mechanism of salt rock mainly manifests as microcrack initiation, i.e., the propagation of microcracks between crystals under tensile or shear stress; damage propagation, i.e., the increase and connection of cracks, resulting in deterioration of mechanical properties and volume expansion; crack closure, i.e., under high pressure, low temperature, and other conditions, the crack surfaces re-contact, and the cracks are filled due to ion migration, creep, etc.; and performance recovery, i.e., the closed area gradually bears the load again, macroscopically manifested as enhanced mechanical properties and volume compression. This process is dynamic, time-varying, and state-dependent, requiring simulation methods with the capabilities of time-series control, crack identification, contact renewal, and strength reconstruction.

[0006] Among them, such as Figure 1As shown, the shortcomings of the conventional PFC (Particle Flow Code) discrete element model in simulating the self-healing of salt rock are as follows: Crack formation can be simulated, but healing cannot be represented: In the traditional model, once particles break, contact disappears; they can re-establish contact later, but they will not bond again. Secondly, the recovery of mechanical properties cannot be reconstructed: Even if contact is reformed, there will be no new parallel bonding force; and there is no healing criterion: the model cannot determine "whether the crack can heal, when it will heal, and how it will heal."

[0007] Therefore, relying solely on traditional DEM models cannot simulate the actual damage-healing process of salt rock and urgently needs improvement.

[0008] This application provides a discrete element method and apparatus for simulating the self-healing properties of salt rock, in order to solve the problems in the discrete element method of related technologies, such as the inability to re-establish strong adhesion after contact fracture between particles, the inability to truly reflect the micromechanical recovery process of self-healing of salt rock after damage, and the reduction of the physical authenticity and engineering prediction reliability of salt rock self-healing behavior in discrete element simulation.

[0009] The first aspect of this application provides a discrete element method for simulating the self-healing properties of salt rock, comprising the following steps: based on a pre-constructed healing initiation criterion for the target salt rock, detecting whether the interparticles at the damaged interface of the target salt rock meet a preset healing condition; if the interparticles meet the preset healing condition, reconstructing the fracture contact between the particles into a re-bonding contact to impart a new parallel bonding force to the particles, and determining the equivalent healing stress after the damaged interface of the target salt rock is healed based on the new parallel bonding force between the particles; based on the equivalent healing stress after the damaged interface is healed, quantifying the strain evolution of the volume of the damaged interface before and after healing to obtain a strain evolution result, and generating a discrete element simulation result of the self-healing properties of the target salt rock if the strain evolution result meets a preset healing termination condition.

[0010] Optionally, in one embodiment of this application, the step of detecting whether the interparticles of the damaged interface of the target salt rock meet the preset healing conditions based on the pre-constructed healing initiation criterion of the target salt rock includes: constructing the healing initiation criterion of the target salt rock based on the minimum principal stress and the Mises stress; and detecting whether the interparticles of the damaged interface of the target salt rock meet the preset healing conditions based on the target flow potential function in the healing initiation criterion of the target salt rock.

[0011] Optionally, in one embodiment of this application, determining the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between the particles includes: calculating the macroscopic stress state of the target salt rock after the damage interface has healed according to a preset equivalent healing stress formula, and converting the macroscopic stress state into the microscopic contact force between the particles of the damage interface; using the microscopic contact force to determine the new parallel bonding force between the particles, so as to determine the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between the particles.

[0012] Optionally, in one embodiment of this application, generating the discrete element simulation result of the self-healing characteristics of the target salt rock when the strain evolution result is detected to meet the preset healing termination condition includes: determining whether the increment of the volumetric strain after the damage interface heals in the strain evolution result is less than a first preset threshold, whether the number of cracks remains unchanged in the target time step, and whether the target unbalanced force is less than a second preset threshold; if the increment of the volumetric strain is less than the first preset threshold, the number of cracks remains unchanged in the target time step, and the target unbalanced force is less than the second preset threshold, then generating the discrete element simulation result of the self-healing characteristics of the salt rock; if the increment of the volumetric strain is greater than or equal to the first preset threshold in the target time step, the number of cracks does not remain unchanged in the target time step, or the target unbalanced force is greater than or equal to the second preset threshold, then continuing the discrete element simulation of the self-healing characteristics of the salt rock.

[0013] Optionally, in one embodiment of this application, the healing initiation criterion of the target salt rock is expressed as:

[0014]

[0015] Among them, F h Let σ3 be the target flow potential function, a6 and a5 be the minimum principal stresses, and σ be the model parameters. v For von Mises stress.

[0016] Optionally, in one embodiment of this application, the target healing equivalent stress formula is expressed as:

[0017]

[0018] Where I1 is the first invariant of stress, x 10 σ1 is the equivalent healing parameter, and σ1 is the maximum principal stress.

[0019] A second aspect of this application provides a discrete element method (DEM) simulation device for the self-healing characteristics of salt rock, comprising: a detection module, configured to detect whether the interparticles at the damaged interface of the target salt rock meet a preset healing condition based on a pre-constructed healing initiation criterion for the target salt rock; a determination module, configured to, when the preset healing condition is met, reconstruct the fracture contact between the particles into a re-bonding contact to impart a new parallel bonding force between the particles, and determine the equivalent healing stress after the damaged interface of the target salt rock is healed based on the new parallel bonding force between the particles; and a simulation module, configured to, based on the equivalent healing stress after the damaged interface is healed, quantify the strain evolution of the volume of the damaged interface before and after healing to obtain a strain evolution result, and generate a discrete element method simulation result for the self-healing characteristics of the target salt rock when the strain evolution result meets a preset healing termination condition.

[0020] Optionally, in one embodiment of this application, the detection module includes: a construction unit, configured to construct a healing initiation criterion for the target salt rock based on the minimum principal stress and the Mises stress; and a detection unit, configured to detect whether the interparticles at the damage interface of the target salt rock meet the preset healing conditions based on the target flow potential function in the healing initiation criterion for the target salt rock.

[0021] Optionally, in one embodiment of this application, the determining module includes: a calculation unit, configured to calculate the macroscopic stress state of the damaged interface of the target salt rock after healing according to a preset equivalent healing stress formula, and convert the macroscopic stress state into the microscopic contact force between the particles of the damaged interface; and a determining unit, configured to determine the new parallel bonding force between the particles using the microscopic contact force, so as to determine the equivalent healing stress of the damaged interface of the target salt rock after healing based on the new parallel bonding force between the particles.

[0022] Optionally, in one embodiment of this application, the simulation module includes: a judgment unit, configured to judge whether the increment of volumetric strain after the damage interface heals in the strain evolution result is less than a first preset threshold, whether the number of cracks remains unchanged in the target time step, and whether the target unbalanced force is less than a second preset threshold; a first processing unit, configured to generate the discrete element simulation result of the salt rock self-healing characteristics if the increment of volumetric strain is less than the first preset threshold in the target time step, the number of cracks remains unchanged in the target time step, and the target unbalanced force is less than the second preset threshold; and a second processing unit, configured to continue the discrete element simulation of the salt rock self-healing characteristics if the increment of volumetric strain is greater than or equal to the first preset threshold in the target time step, the number of cracks does not remain unchanged in the target time step, or the target unbalanced force is greater than or equal to the second preset threshold.

[0023] Optionally, in one embodiment of this application, the healing initiation criterion of the target salt rock is expressed as:

[0024]

[0025] Among them, F h Let σ3 be the target flow potential function, a6 and a5 be the minimum principal stresses, and σ be the model parameters. v For von Mises stress.

[0026] Optionally, in one embodiment of this application, the target healing equivalent stress formula is expressed as:

[0027]

[0028] Where I1 is the first invariant of stress, x 10 σ1 is the equivalent healing parameter, and σ1 is the maximum principal stress.

[0029] A third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the discrete element simulation method for the self-healing characteristics of salt rock as described in the above embodiments.

[0030] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the discrete element simulation method for the self-healing properties of salt rock as described above.

[0031] A fifth aspect of this application provides a computer program product, including a computer program that, when executed, is used to implement the discrete element simulation method for the self-healing properties of salt rock as described above.

[0032] This application's embodiments can, based on a pre-constructed healing initiation criterion for the target salt rock, reconstruct the fractured contact between particles into a re-bonded contact when the healing conditions are met at the damaged interface of the target salt rock. This imparts a new parallel bonding force to the particles, thereby determining the equivalent healing stress after the damaged interface heals. Furthermore, it quantifies the strain evolution of the volume before and after healing at the damaged interface. When the strain evolution result meets the healing termination condition, it generates discrete element simulation results of the target salt rock's self-healing characteristics. This realistically reflects the micromechanical recovery process of salt rock self-healing after damage, effectively improving the physical realism and engineering prediction reliability of salt rock self-healing behavior in discrete element simulations. Therefore, it solves the problem in related technologies where the discrete element method cannot re-establish strong bonding after contact fracture between particles, thus failing to realistically reflect the micromechanical recovery process of salt rock self-healing after damage.

[0033] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0034] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0035] Figure 1 This is a schematic diagram comparing general re-contact and healing re-contact in PFC in related technologies;

[0036] Figure 2 This is a flowchart of a discrete element simulation method for the self-healing properties of salt rock provided in an embodiment of this application;

[0037] Figure 3 This is a schematic diagram of the short-term strength (A), expansion boundary (B), and healing boundary (C) of salt rock according to a specific embodiment of this application;

[0038] Figure 4 This is a schematic diagram of particles after damage and after healing, according to a specific embodiment of this application.

[0039] Figure 5 This is a schematic diagram showing the number of cracks and changes in volumetric strain during the healing process of a specific embodiment of this application.

[0040] Figure 6 This is a schematic diagram of a discrete element simulation device for the self-healing properties of salt rock provided in an embodiment of this application;

[0041] Figure 7 This is a schematic diagram of the structure of an electronic device provided according to an embodiment of this application. Detailed Implementation

[0042] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0043] The following describes a discrete element method and apparatus for simulating the self-healing characteristics of salt rock according to embodiments of this application, with reference to the accompanying drawings. Addressing the issues mentioned in the background section regarding the inability of discrete element methods to re-establish strong adhesion after contact fracture between particles, thus failing to accurately reflect the micromechanical recovery process of self-healing in salt rock damage and reducing the physical realism and engineering prediction reliability of salt rock self-healing behavior in discrete element simulations, this application provides a discrete element method for simulating the self-healing characteristics of salt rock. In this method, based on a pre-constructed healing initiation criterion for the target salt rock, when the healing conditions are met between particles at the damaged interface of the target salt rock, the fractured contact between particles is reconstructed into a re-adhesive contact to impart new parallel adhesion forces between particles. This determines the equivalent healing stress after the damaged interface heals, quantifies the strain evolution of the volume before and after healing, and generates discrete element simulation results of the self-healing characteristics of the target salt rock when the strain evolution results meet the healing termination conditions. This accurately reflects the micromechanical recovery process of self-healing in salt rock damage, effectively improving the physical realism and engineering prediction reliability of salt rock self-healing behavior in discrete element simulations. This solves the problem in related technologies where the discrete element method cannot re-establish strong adhesion after contact fracture between particles, and cannot truly reflect the micromechanical recovery process of self-healing after salt rock damage.

[0044] Specifically, Figure 1 This is a schematic flowchart of a discrete element simulation method for the self-healing properties of salt rock provided in an embodiment of this application.

[0045] like Figure 1 As shown, the discrete element method for simulating the self-healing properties of salt rock includes the following steps:

[0046] In step S101, based on the pre-constructed healing initiation criterion for the target salt rock, it is detected whether the intergranular space at the damaged interface of the target salt rock meets the preset healing conditions.

[0047] In this embodiment of the application, the target salt rock is the salt rock currently being simulated using discrete element method (DEM) simulation of its self-healing properties.

[0048] It is understood that the embodiments of this application can pre-construct the healing initiation criterion of the target salt rock based on the minimum principal stress and Mises stress in the following steps. This allows for the detection of whether the interparticles at the damage interface of the target salt rock meet certain healing conditions based on the healing initiation criterion. For example, the flow potential function can be used to determine whether the damage has healed, effectively improving the executability of discrete element simulation of the self-healing characteristics of salt rock.

[0049] In one embodiment of this application, the detection of whether the interparticles of the damaged interface of the target salt rock meet the preset healing conditions is based on a pre-constructed healing initiation criterion for the target salt rock, including: constructing a healing initiation criterion for the target salt rock based on the minimum principal stress and the von Mises stress; and detecting whether the interparticles of the damaged interface of the target salt rock meet the preset healing conditions based on the target flow potential function in the healing initiation criterion for the target salt rock.

[0050] In practical application, the Huo / Lux model, incorporating damage theory from continuum mechanics and based on the Lobby 2 rheological model, phenomenologically integrates diffusion and displacement, damage and damage healing, and strain hardening and recovery in salt rock deformation. Therefore, in the Huo / Lux model, the total strain rate... From the elastic part Inelastic part Right now:

[0051]

[0052] The strain rate of the elastic component is given by Hooke's law:

[0053]

[0054] Among them, s ij Let I1 be the first invariant stress, K be the bulk modulus, D be the damage parameter, defined as D = damage area / total area, G be the shear modulus, and δ be the deviatoric stress. ij For Kronecker product.

[0055] The inelastic strain rate includes: viscoplastic volumetric strain rate, damage expansion, and healing contraction, i.e.:

[0056]

[0057] in, For viscoplastic volumetric strain rate, To expand the volume of the damage, To promote healing and reduce volume.

[0058] Since the components are linearly superimposed, this embodiment only focuses on the volume reduction caused by healing:

[0059]

[0060] Where, ε Vol For shear dilatation strain, F h Let F be the flow potential function. * For stress reference value, F is taken here. * =1MPa, Q h σ is the plastic potential function caused by damage healing. ij Let ε be the stress tensor. Vol For shear dilatation strain, a 11 a 12 a 13 These are the model parameters.

[0061] In the above formula, <x>It is a switching function, that is:

[0062]

[0063] The flow potential function F in the above formula h The flow potential function determines whether the strain rate induced by healing is activated; therefore, this flow potential function is considered as a criterion for damage healing in PFC, i.e.:

[0064]

[0065] Where σ3 is the minimum principal stress, a6 and a5 are model parameters, and σ v For von Mises stress.

[0066] When F h A value greater than 0 indicates that the damage has healed, when F h A value less than 0 indicates that damage healing cannot occur. In the formula, σ3 is the minimum principal stress, and a6 and a5 are model parameters; here, a6 = 67.0 MPa and a5 = 0.055 MPa are taken. -1 , σ v For von Mises stress, that is:

[0067]

[0068] Among them, σ1, σ2, and σ3 are the first, second, and third principal stresses, respectively.

[0069] Since PFC is a discrete particle system, the stress state of the particle assembly as a continuous medium needs to be redefined. Therefore, the stress state of the particle system can be represented by the REV (Representative Elementary Volume) method, which uses the averaging approach, and expressed in tensor product form, i.e.:

[0070]

[0071] Where V is the size of REV. For the set of contacts within REV, For contact reaction force, This is the branch vector. This method is implemented in PFC by measuring a circle, and the calculation formula is:

[0072]

[0073] in, For the average stress, F (c) L is the contact force vector. (c) N is the branch vector connecting the centroids of two contacting objects. c This represents the number of contacts within the measurement area.

[0074] Therefore, the embodiments of this application can use the stress state calculated by the representative element volume (REV) method as a basis, combine the minimum principal stress and von Mises stress to construct the healing initiation criterion, and use the target flow potential function to further refine the detection of healing conditions, thereby realizing the accurate simulation and control of the self-healing behavior of salt rock.

[0075] In step S102, when it is detected that the preset healing conditions between particles are met, the fracture contact between particles is reconstructed into a re-bonding contact to give the particles a new parallel bonding force, and based on the new parallel bonding force between particles, the equivalent healing stress after the damage interface of the target salt rock is determined.

[0076] It is understood that, in the embodiments of this application, when the healing conditions in the above steps are met, the fracture contact between particles can be reconstructed into a re-bonded contact to impart new parallel bonding forces to the particles. Then, drawing on the MDCF (Multimechanism Deformation Coupled Fracture) model, an equivalent healing stress can be introduced to describe the strength change in the healing region. For example, after the damage to salt rock heals, its mechanical properties will also change. Therefore, MDCF can be proposed based on MD (Multimechanism Deformation). In the MDCF model, the equivalent healing stress formula is used to evaluate the material strength and stress state after damage healing. This formula, by considering the first invariant of the stress tensor and the influence of the principal stresses, can more accurately describe the material behavior after damage healing, i.e.:

[0077]

[0078] in, For the healing equivalent stress, I1 is the first invariant of stress, x 10 Let x be the equivalent healing parameter. This formula shows that the equivalent healing stress depends not only on the first invariant of the stress tensor but also on the principal stresses. This is achieved by introducing the coefficient x. 10 This formula can describe the healing behavior of materials under different stress states. In simulating the self-healing process of salt rock damage, this formula can be used to calculate the equivalent stress after healing, thereby evaluating the damage healing effect and mechanical properties of the material.

[0079] In one embodiment of this application, determining the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between particles includes: calculating the macroscopic stress state of the target salt rock after the damage interface has healed according to a preset equivalent healing stress formula, and converting the macroscopic stress state into the microscopic contact force between particles at the damage interface; using the microscopic contact force to determine the new parallel bonding force between particles, so as to determine the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between particles.

[0080] As one possible approach, in PFC simulations using the granular flow code, force transmission is achieved through microscopic contact forces between particles. However, the healing equivalent stress formula in the MDCF model is based on a description of a continuous macroscopic stress state. The principal stresses and other parameters involved in the healing equivalent stress formula are derived from the calculation of the macroscopic stress tensor. Therefore, to apply the healing equivalent stress from the MDCF model to PFC simulations, the macroscopic stress state must be linked to the microscopic contact forces.

[0081] Assume that the two spheres pass through a radius of at their contact point. If the circular, flat contact areas interact microscopically, the adhesive normal force after healing can be expressed as:

[0082]

[0083] in, For normal healing equivalent force, Let be the area of ​​the contact region in the two-dimensional case. Substituting equation (1.10) into the equation, we get:

[0084]

[0085] Therefore, the total parallel adhesion force after healing is:

[0086]

[0087] in, For parallel bond tangential stiffness, δ s This is the tangential displacement.

[0088] In step S103, based on the equivalent healing stress after the damaged interface heals, the strain evolution of the volume before and after the damaged interface heals is quantified to obtain the strain evolution results. If the strain evolution results are found to meet the preset healing termination condition, discrete element simulation results of the self-healing characteristics of the target salt rock are generated.

[0089] It is understood that the embodiments of this application can use the boundary particle method to track the strain behavior of the sample based on the equivalent healing stress after the damage interface heals, quantify the strain evolution of the volume before and after the damage interface heals, and obtain the strain evolution results. When the strain evolution results are detected to meet the healing termination conditions, for example, when the strain evolution results are detected to meet the triple healing termination criteria of strain stability, crack number stability, and unbalanced force less than a certain threshold, adaptive healing termination control can be performed to generate discrete element simulation results of the self-healing characteristics of the target salt rock. This can realistically reflect the micromechanical recovery process of self-healing after salt rock damage, effectively improving the physical reality and engineering prediction reliability of the self-healing behavior of salt rock in discrete element simulation.

[0090] Optionally, in one embodiment of this application, when the strain evolution result is detected to meet the preset healing termination condition, a discrete element simulation result of the self-healing characteristics of the target salt rock is generated, including: determining whether the increment of volumetric strain after the damage interface is healed in the strain evolution result is less than a first preset threshold, whether the number of cracks remains unchanged in the target time step, and whether the target unbalanced force is less than a second preset threshold; if the increment of volumetric strain is less than the first preset threshold, the number of cracks remains unchanged in the target time step, and the target unbalanced force is less than the second preset threshold, then a discrete element simulation result of the self-healing characteristics of the salt rock is generated; if the increment of volumetric strain is greater than or equal to the first preset threshold in the target time step, the number of cracks does not remain unchanged in the target time step, or the target unbalanced force is greater than or equal to the second preset threshold, then the discrete element simulation of the self-healing characteristics of the salt rock continues.

[0091] It should be noted that the self-healing of salt rock damage is a complex process involving many factors such as time, stress, temperature, and chemical potential energy. However, current numerical simulation techniques cannot adequately consider all these factors in the research process. Therefore, this application draws on phenomenological thinking to focus on the differences in mechanical properties before and after healing. Furthermore, from the perspectives of mechanical equilibrium, damage stability, and energy dissipation, the following healing termination conditions suitable for discrete element numerical simulation methods are proposed:

[0092] First, the volumetric strain does not change significantly within the 1e5 time step, i.e., |ε (t+1) -ε t ≤0.1%;

[0093] Since volume expansion is a result of damage, while healing results in a reduction of volume expansion, such as... Figure 3 As shown, when the damage stress exceeds the expansion strength, the volume expansion will increase under the action of shear stress and tensile stress.

[0094] This process can be described using the capacity expansion recovery rate. This means, that is:

[0095]

[0096] Where, ε Vol For volume expansion, ε Vol <0, a 11 a 12 a 13 a 14 These are the model parameters.

[0097] ε v =ε x +ε y (1.15)

[0098] Where, ε v For volumetric strain, ε x For radial strain, ε y For axial strain.

[0099] In PFC2D, the boundary particle method is used to calculate strain. That is:

[0100]

[0101] Where, d r ,d l ,d t ,d b These represent the displacements of the right, left, top, and bottom boundaries of the specimen, respectively, while L and H represent the width and height of the specimen, respectively (the center point of the specimen is located at the origin).

[0102] Although volumetric strain is not equivalent to dilatancy strain, this application considers the difficulty in directly obtaining shear strain variables from the PFC model and uses the trend of volumetric strain change as an approximate indicator of the dilatancy trend. Furthermore, during the healing process of salt rock, fracture closure is accompanied by volumetric shrinkage, a characteristic consistent with the dilatancy suppression process. Therefore, if the increment is less than 0.1% within 1e5 consecutive time steps, the volumetric deformation is considered stable, and this can be approximated as the termination of dilatancy behavior.

[0103] Secondly, in a continuous 1×10 5 Within a given time step, the number of cracks no longer changes;

[0104] like Figure 4 As shown, whether it's damage or healing, the most intuitive change is the generation and closure of microcracks, i.e., the change in the number of cracks. As damage progresses, the microcracks inside the sample undergo stages such as initiation, development, and penetration, further increasing the number of cracks until final failure. Taking the parallel bond contact model in PFC as an example: when the parallel bond normal force at contact... Tensile failure occurs when the parallel bond tensile strength is greater than the tensile strength of the contact; when the parallel bond tangential force is greater than the tensile strength of the contact, tensile failure occurs. Shear failure occurs when its parallel bond shear strength is exceeded.

[0105] Conversely, when previously damaged particles come into contact again and meet certain healing criteria (Equation (1.17)), the crack can be considered closed, i.e.:

[0106]

[0107] Among them, R c R represents the interparticle spacing. h For healing interval.

[0108] This application refers to a rebonded contact after fracture as a rebonded contact. The biggest difference between a rebonded contact and a normally regenerated contact after fracture is that its parallel bond state (pb_state) is a bonded state and has a parallel bond force (pb_force). Therefore, a rebonded contact can withstand tensile force and bending moment. The magnitude of the parallel bond force of the rebonded contact is given according to (1.13) equivalently.

[0109] Furthermore, the average unbalanced force ratio of the particle system is <1e-4;

[0110] Since the average force ratio (AFR) of a system is an important indicator for measuring whether the overall model has reached quasi-static equilibrium, in PFC, it is defined as the ratio of the sum of the unbalanced force components on all particles to the sum of the total applied forces, expressed as:

[0111]

[0112] Among them, f i For each particle force component, <v i >=|v x |+|v y |+|v z | represents the Manhattan norm, and n represents the total number of particles.

[0113] This metric is a reliable method for measuring the overall convergence of a system. The AFR directly quantifies the degree of force imbalance between particles in the system, reflecting the current "non-equilibrium" state of the system, which is consistent with the natural trend of the salt body healing process towards static equilibrium.

[0114] Therefore, as Figure 5 As shown, when the increment of volumetric strain is less than the corresponding threshold within the target time step, the number of cracks remains unchanged within the target time step, and the target unbalanced force is less than the corresponding threshold, the embodiments of this application can write the above three conditions as a healing termination function and solve it using the fish-halt keyword until all conditions are met and healing terminates; when one of the above three conditions is not met, the discrete element simulation of the self-healing characteristics of salt rock continues, so that this application can completely reproduce the full-cycle mechanical evolution process of salt rock cracks from "initiation-development-connection-closure", effectively making up for the defects of existing continuous and traditional discrete methods in "self-healing mechanism simulation", accurately capturing the mechanical stability state of the salt rock self-healing process, and improving the physical authenticity and engineering application reliability of the simulation results.

[0115] The discrete element method for simulating the self-healing characteristics of salt rock proposed in this application can reconstruct the fracture contact between particles into a re-bonded contact based on a pre-constructed healing initiation criterion for the target salt rock. This reconstructs the contact to give the particles a new parallel bonding force, thereby determining the equivalent healing stress after the damaged interface heals. Furthermore, it quantifies the strain evolution of the volume before and after healing. Finally, when the strain evolution result meets the healing termination condition, it generates the discrete element simulation results of the target salt rock's self-healing characteristics. This method can realistically reflect the micromechanical recovery process of salt rock self-healing after damage, effectively improving the physical realism and engineering prediction reliability of salt rock self-healing behavior in discrete element simulations. Therefore, it solves the problem in related technologies where discrete element methods cannot re-establish strong bonding after particle contact fracture, thus failing to realistically reflect the micromechanical recovery process of salt rock self-healing after damage.

[0116] Next, referring to the accompanying drawings, a discrete element simulation device for the self-healing characteristics of salt rock proposed according to an embodiment of this application is described.

[0117] Figure 6 This is a block diagram of a discrete element simulation device for the self-healing characteristics of salt rock according to an embodiment of this application.

[0118] like Figure 6 As shown, the discrete element simulation device 10 for the self-healing properties of salt rock includes: a detection module 100, a determination module 200, and a simulation module 300.

[0119] Specifically, the detection module 100 is used to detect whether the interparticles at the damage interface of the target salt rock meet the preset healing conditions based on the pre-constructed healing initiation criteria of the target salt rock.

[0120] The determination module 200 is used to reconstruct the fracture contact between particles into a re-bonding contact when the preset healing conditions between particles are detected, so as to give the particles a new parallel bonding force, and determine the equivalent healing stress after the damage interface of the target salt rock is healed based on the new parallel bonding force between particles.

[0121] The simulation module 300 is used to quantify the strain evolution of the volume of the damaged interface before and after healing based on the equivalent healing stress after the damaged interface heals, so as to obtain the strain evolution results. When the strain evolution results are detected to meet the preset healing termination conditions, the discrete element simulation results of the self-healing characteristics of the target salt rock are generated.

[0122] Optionally, in one embodiment of this application, the detection module 100 includes a construction unit and a detection unit.

[0123] Among them, the building unit is used to construct the healing initiation criterion of the target salt rock based on the minimum principal stress and the Mises von Mises stress.

[0124] The detection unit is used to detect whether the interparticles at the damaged interface of the target salt rock meet the preset healing conditions based on the target flow potential function in the healing initiation criterion of the target salt rock.

[0125] Optionally, in one embodiment of this application, the determining module 200 includes a calculation unit and a determining unit.

[0126] The calculation unit is used to calculate the macroscopic stress state of the target salt rock after the damage interface is healed according to the preset healing equivalent stress formula, and convert the macroscopic stress state into the microscopic contact force between the particles of the damage interface.

[0127] A defined element is used to determine the new parallel bond force between particles using microscopic contact forces, and based on the new parallel bond force between particles, the equivalent healing stress after the damage interface of the target salt rock is healed is determined.

[0128] Optionally, in one embodiment of this application, the simulation module 300 includes: a judgment unit, a first processing unit, and a second processing unit.

[0129] The judgment unit is used to determine whether the increase in volumetric strain after the damage interface heals in the strain evolution result is less than a first preset threshold within the target time step, whether the number of cracks remains unchanged within the target time step, and whether the target unbalanced force is less than a second preset threshold.

[0130] The first processing unit is used to generate discrete element simulation results of salt rock self-healing characteristics if the increment of volumetric strain is less than a first preset threshold within the target time step, the number of cracks remains unchanged within the target time step, and the target unbalanced force is less than a second preset threshold.

[0131] The second processing unit is used to continue the discrete element simulation of the self-healing characteristics of salt rock if the increment of volumetric strain is greater than or equal to the first preset threshold within the target time step, the number of cracks does not remain unchanged within the target time step, or the target unbalanced force is greater than or equal to the second preset threshold.

[0132] Optionally, in one embodiment of this application, the healing initiation criterion for the target salt rock is expressed as:

[0133]

[0134] Among them, F h Let σ be the target flow potential function, σ3 be the minimum principal stress, and a6 and a5 be model parameters. v For von Mises stress.

[0135] Optionally, in one embodiment of this application, the target healing equivalent stress formula is expressed as:

[0136]

[0137] Where I1 is the first invariant of stress, x 10 σ1 is the equivalent healing parameter, and σ1 is the maximum principal stress.

[0138] It should be noted that the foregoing explanation of the discrete element simulation method for the self-healing characteristics of salt rock also applies to the discrete element simulation device for the self-healing characteristics of salt rock in this embodiment, and will not be repeated here.

[0139] The discrete element method (DEM) simulation device for the self-healing characteristics of salt rock proposed in this application can, based on a pre-constructed healing initiation criterion for the target salt rock, reconstruct the fracture contact between particles into a re-bonding contact when the healing conditions are met at the damaged interface of the target salt rock. This imparts a new parallel bonding force to the particles, thereby determining the equivalent healing stress after the damaged interface heals. Furthermore, it quantifies the strain evolution of the volume before and after healing at the damaged interface. When the strain evolution result meets the healing termination condition, it generates the DEM simulation results for the self-healing characteristics of the target salt rock. This allows for a realistic reflection of the micromechanical recovery process of self-healing after salt rock damage, effectively improving the physical realism and engineering prediction reliability of salt rock self-healing behavior in DEM simulation. Therefore, it solves the problem in related technologies where the DEM method cannot re-establish strong bonding after the contact fracture between particles, thus failing to realistically reflect the micromechanical recovery process of self-healing after salt rock damage.

[0140] Figure 7 A schematic diagram of the structure of an electronic device provided in an embodiment of this application. The electronic device may include:

[0141] The memory 701, the processor 702, and the computer program stored on the memory 701 and executable on the processor 702.

[0142] When the processor 702 executes the program, it implements the discrete element simulation method for the self-healing characteristics of salt rock provided in the above embodiments.

[0143] Furthermore, electronic devices also include:

[0144] Communication interface 703 is used for communication between memory 701 and processor 702.

[0145] The memory 701 is used to store computer programs that can run on the processor 702.

[0146] The memory 701 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0147] If the memory 701, processor 702, and communication interface 703 are implemented independently, then the communication interface 703, memory 701, and processor 702 can be interconnected via a bus to complete communication between them. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, 7... Figure 7 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0148] Optionally, in a specific implementation, if the memory 701, processor 702, and communication interface 703 are integrated on a single chip, then the memory 701, processor 702, and communication interface 703 can communicate with each other through an internal interface.

[0149] The processor 702 may be a central processing unit (CPU), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0150] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the discrete element simulation method for the self-healing properties of salt rock as described above.

[0151] This embodiment also provides a computer program product, including a computer program that, when executed, is used to implement the discrete element simulation method for the self-healing properties of salt rock as described above.

[0152] In the description of this specification, the references to "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0153] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0154] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or N executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0155] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0156] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0157] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0158] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0159] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.< / x>

Claims

1. A discrete element method for simulating the self-healing properties of salt rock, characterized in that, Includes the following steps: Based on the pre-constructed healing initiation criteria for the target salt rock, it is detected whether the interparticles at the damage interface of the target salt rock meet the preset healing conditions. When the preset healing conditions are met between the particles, the fracture contact between the particles is reconstructed into a re-bonding contact to impart a new parallel bonding force between the particles. Based on the new parallel bonding force between the particles, the equivalent healing stress of the target salt rock after the damage interface is healed is determined. The determination of the equivalent healing stress of the target salt rock after the damage interface is healed based on the new parallel bonding force between the particles includes: calculating the macroscopic stress state of the target salt rock after the damage interface is healed according to a preset equivalent healing stress formula, and converting the macroscopic stress state into the microscopic contact force between the particles at the damage interface; using the microscopic contact force to determine the new parallel bonding force between the particles, and then determining the equivalent healing stress of the target salt rock after the damage interface is healed based on the new parallel bonding force between the particles. The equivalent healing stress formula is expressed as follows: in, As the first invariant of stress, x 10 For equivalent healing parameters, This is the maximum principal stress; The new formula for parallel adhesion force is expressed as follows: in, For parallel bond tangential stiffness, For tangential displacement, The radius is ; Based on the equivalent healing stress after the damaged interface heals, the strain evolution of the volume of the damaged interface before and after healing is quantified to obtain the strain evolution result. When the strain evolution result is detected to meet the preset healing termination condition, the discrete element simulation result of the self-healing characteristics of the target salt rock is generated.

2. The method according to claim 1, characterized in that, The method based on a pre-constructed healing initiation criterion for the target salt rock, which detects whether the intergranular surfaces of the damaged interface of the target salt rock meet preset healing conditions, includes: Based on the minimum principal stress and the Mises von Mises stress, a healing initiation criterion for the target salt rock is constructed. Based on the target flow potential function in the healing initiation criterion of the target salt rock, it is detected whether the interparticles at the damaged interface of the target salt rock meet the preset healing conditions.

3. The method according to claim 1, characterized in that, When the strain evolution result is detected to meet the preset healing termination condition, the discrete element simulation result of the self-healing characteristics of the target salt rock is generated, including: Determine whether the increase in volumetric strain after the damage interface heals in the strain evolution result is less than a first preset threshold within the target time step, whether the number of cracks remains unchanged within the target time step, and whether the target unbalanced force is less than a second preset threshold. If the increment of the volumetric strain is less than the first preset threshold within the target time step, the number of cracks remains unchanged within the target time step, and the target unbalanced force is less than the second preset threshold, then the discrete element simulation results of the salt rock self-healing characteristics are generated. If the increment of the volumetric strain is greater than or equal to the first preset threshold within the target time step, the number of cracks does not remain constant within the target time step, or the target unbalanced force is greater than or equal to the second preset threshold, then the discrete element simulation of the salt rock self-healing characteristics continues.

4. The method according to claim 2, characterized in that, The healing initiation criterion for the target salt rock is expressed as follows: in, Let be the target flow potential function. For the minimum principal stress, For model parameters, For von Mises stress.

5. A discrete element simulation device for the self-healing properties of salt rock, characterized in that, include: The detection module is used to detect whether the interparticles at the damage interface of the target salt rock meet the preset healing conditions based on the pre-constructed healing initiation criteria of the target salt rock. A determination module is configured to, upon detecting that the particles meet the preset healing conditions, reconstruct the fracture contact between the particles into a re-bonding contact to impart a new parallel bonding force between the particles, and determine the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between the particles. The determination of the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between the particles includes: calculating the macroscopic stress state of the target salt rock after the damage interface has healed according to a preset equivalent healing stress formula, and converting the macroscopic stress state into a microscopic contact force between the particles at the damage interface; using the microscopic contact force to determine the new parallel bonding force between the particles, and then determining the equivalent healing stress of the target salt rock after the damage interface has healed based on the new parallel bonding force between the particles. The equivalent healing stress formula is expressed as follows: in, As the first invariant of stress, x 10 For equivalent healing parameters, This is the maximum principal stress; The new formula for parallel adhesion force is expressed as follows: in, For parallel bond tangential stiffness, For tangential displacement, The radius is ; The simulation module is used to quantify the strain evolution of the volume of the damaged interface before healing and after healing based on the equivalent healing stress after the damaged interface heals, so as to obtain the strain evolution result, and generate the discrete element simulation result of the self-healing characteristics of the target salt rock when the strain evolution result is detected to meet the preset healing termination condition.

6. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the discrete element simulation method for the self-healing properties of salt rock as described in any one of claims 1-4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by the processor to implement the discrete element simulation method for the self-healing properties of salt rock as described in any one of claims 1-4.

8. A computer program product, comprising a computer program, characterized in that, The computer program is executed by a processor to implement the discrete element simulation method for the self-healing properties of salt rock as described in any one of claims 1-4.

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